X-ray absorption spectroscopy study of CuO at high pressure: Unveiling the correlation between local, vibrational and electronic structure. Dr Vera Cuartero1,2,3, Dr. Virginia Monteseguro4, Dr Alberto Otero-de-la-Roza5, Dr Andrea Sanson6 1Centro Universitario De La Defensa, Zaragoza, Spain, 2ESRF - The European Synchrotron, Grenoble, Francia, 3Instituto de Nanociencia y Materiales de Aragón, Zaragoza, Spain, 4DCITIMAC, Universidad de Cantabria, , Spain, 5Universidad de Oviedo, , Spain, 6University of Padova, Padova, Italy T3.24: X-ray absorption spectroscopy study of CuO at high pressure: Unveiling the correlation between local, vibrational and electronic structure. July 13, 2021, 19:20 - 19:30

CuO has been the subject of extensive investigation as understanding the nature of Cu-O bonds is key for the comprehension of cuprate-based high Tc superconductors. More recently, CuO itself has seen renewed interest due to the discovery of multiferroicity (MF) at relatively high temperature TN = 230 K and ambient pressure [1].

CuO presents type II MF, where ferroelectricity is magnetically driven by an antiferromagnetic (AFM) spiral ground state. These findings motivated theoretical [2,3] and experimental studies considering the application of high pressure to promote a room temperature MF state in this material [4]. These studies predicted stable MF at room temperature (RT) in the P~20-40 GPa range due to large super-exchange correlations in an incommensurate AFM ground state [3]. Subsequently, Jana and coworkers [4] found an anomaly in the dielectric constant and a drop in DC resistance by three orders of magnitude at ~ 4 GPa and RT, that were proposed to be correlated with strong dynamic O-ion displacements along the b-axis in monoclinic CuO. In parallel, neutron diffraction experiments under pressure combined with Monte Carlo simulations found that TN is far from RT at 38 GPa. [5]

The electronic and local structural properties of CuO under pressure have been investigated by means of X- ray absorption spectroscopy (XAS) at Cu K edge, multiple scattering and ab-initio calculations, up to 17 GPa. The crystal structure of CuO consists of Cu motifs within CuO4 square planar units and two elongated apical Cu-O bonds. The CuO4 square planar units are stable in the studied pressure range, with Cu-O distances that are approximately constant up to 5 GPa, and then decrease slightly up to 17 GPa. An anomalous increase of the mean square relative displacement (EXAFS Debye Waller, DW) of the elongated Cu-O path is observed from 5 GPa up to 13 GPa, when a drastic reduction takes place in DW. This is interpreted in terms of configurational local dynamic disorder along the apical Cu-O path. At higher pressures (P >13 GPa), the local structure of Cu2+ changes from a 4-fold square planar to a 4+2 Jahn-Teller distorted octahedral ion. On the other hand, the near edge features in our XAS experiment show a discontinuity and a change of tendency at Pc ~ 5 GPa. For P < Pc the evolution of the edge shoulde is ascribed to purely electronic effects which also affect the charge transfer integral. In summary, the combination of EXAFS, XANES and ab-initio calculations allowed us to probe the correlation between the local structural, vibrational and electronic properties on CuO under pressure.[6]

[1] T. Kimura et al, Nat. Mat. 7, 291 (2008). [2] X. Rocquefelte et al. Sci. Rep. 2, 759 (2012). [3] X. Rocquefelte et al., Nat. Commun. 4, 2511 (2013). [4] R. Jana et al., Sci. Rep. 6, 31610 (2016). [5] D. P. Kozlenko et al. Phys Rev B 95, 054115 (2017). [6] V. Cuartero et al, Phys. Chem. Chem. Phys. 22, 24299 (2020).

In situ monitoring of Pd NPs growth in UiO-66: FTIR and XAS study Mr Andrei Tereshchenko1, Dr. Vera Butova1, Dr Alexander Guda1, Ms Olga Burachevskaya1, Dr Aram Bugaev1, Mr Alexey Bulgakov1, Ms Alina Skorynina1, Mr Yury Rusalev1, Prof. Alexander Soldatov1 1The Smart Materials Research Institute, Southern Federal University, Rostov-on-Don, Russian Federation

T2.6: In situ monitoring of Pd NPs growth in UiO-66: FTIR and XAS study, July 13, 2021, 15:50 - 16:00

Rational functionalization of metal-organic frameworks (MOFs) by noble metal nanoparticles (NPs) for designing novel heterogeneous catalysts is a challenging task. Also, the development of novel techniques to study the kinetics of active center formation and growth of particles is still required.

In this work, we created nucleation centers of Pd in the pores of UiO-66 by introducing defects using benzoic acid as a modulator that was post-synthetically exchanged for amino-benzoic acid. As a result, the defect pores were decorated by amino groups that attracted ions of the Pd precursor after impregnation. Further, Pd NPs were grown by the reduction in H2 flow at 200 °C.

The interaction of metal precursor with amino groups and rates of NPs growth were further monitored in situ by laboratory infrared spectroscopy of adsorbed probing molecules. Three processes were distinguished during the reduction in H2 atmosphere – the gaseous HCl release, NH2 linker activation, and growth of extended Pd surfaces. This experiment was repeated using synchrotron-based XAS to compare the 2– results of the kinetic study. It also revealed the initial state of the precursor as hydrolyzed species PdCl2OH2 and confirmed a high dispersion of Pd.

Thus, we demonstrated a method that allows obtaining well-dispersed Pd NPs in MOF. Suggested advanced application of laboratory-scale FTIR spectroscopy for in situ kinetic studies of nucleation and growth could be a complementary method for synchrotron-based techniques.

This research was financially supported by the Ministry of Science and Higher Education of the Russian Federation (State assignment in the field of scientific activity, № 0852-2020-0019)

XANES analysis of the nickel phosphide catalysts by theoretical approaches Mr MdHarunAl Rashid1, Professor Kiyotaka Asakura1 1Hokkaido University, Sapporo, Japan T1.13: XANES analysis of the nickel phosphide catalysts by theoretical approaches, July 13, 2021, 09:30 - 09:40

Introduction: Transition metal nickel phosphides have seven different phases, which show a variety of electronic, magnetic, optical, and catalytic properties. Recently, Yamanaka et al. reported that the SiO2- supported Ni phosphides had a high activity for Non-Oxidative Coupling of Methane (NOCM) reactions which were strongly depending on the Ni and P ratio. We need to know the structures of the nickel phosphides with various Ni and P ratios to understand the relation between their catalytic activity and structure. X-ray absorption near-edge structure (XANES) is a powerful technique to investigate the local structure of inorganic- oxide-supported catalysts, which is more sensitive to the electronic effects and nearest-neighbor effects than EXAFS spectroscopy. The lack of a suitable reference compound hindered XANES analysis because it is difficult to compare XANES of the reference and unknown as a fingerprint. The recent development of XANES calculations like FEFF has enabled us to use theoretical references. In this research, we calculated the theoretical XANES spectra of seven different nickel phosphides by FEFF to identify the unknown local structure of nickel phosphide catalysts.

Experimental methods: X-ray absorption fine structure (XAFS) measurements were carried out at BL9A of the photon factory in Institute for structure Materials Science, High Energy Accelerator Organization (KEK-IMSS- PF), using a Si (111) double crystal monochromator. The XANES data reductions were carried out by the REX2000 (Rigaku Co), and the theoretical XANES spectra were calculated by FEFF8.

Results and discussion: The measured XANES spectrum of reference Ni2P was compared with the theoretical one calculated by FEFF. The experimental and theoretical XANES spectra of Ni2P both showed the same three peak features with a little deviation of peak position energies. Thus the theoretical XANES could reproduce the observed XANES of Ni2P. The XANES of the Ni phosphide catalysts were compared with those of seven different nickel phosphides obtained by FEFF. We could explain the nickel phosphides with Ni:P =1:1, 2:1, and 3:1 as Ni2P, Ni12P5, and Ni3P, respectively. The nickel phosphide catalyst with Ni:P =1:1 was the most active so that Ni2P was determined to be the active structure for NOCM.

Conclusions: In this work, we have revealed the structures of the SiO2-supported nickel phosphide NOCM catalysts using XANES. We have successfully demonstrated the Ni2P was the active phase for NOCM by theoretical approaches.

Acknowledgment: We thank to Prof. I.Yamanaka and S.Iguchi in Tokyo Institute of Technology for their kind supply of the catalyst samples and Prof. Y. Nitani, Prof. H.Abe in Photon Factory for their technical help. The work was supported by the CREST project “ Innovative Catalyst.”

Temperature driven self-doping of magnetic polarons in magnetite Dr Hebatalla Elnaggar1,2, Mr Silvester Graas2, Dr Sara Lafuerza3, Dr Blanka Detlefs3, Prof. Wojciech Tabiś4,5, Mr. M. Gala4, Mr. A. Ismail2, Mr. Ad Eerden2, Prof. Marcin Sikora6, Prof. Jurgen Honig7, Dr. Pieter Glatzel3, Prof. Frank de Groot1 1Institute of Mineralogy, Physics of Materials and Cosmochemistry, Sorbonne University, Paris, France, 2Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, Netherlands, 3European Synchrotron Radiation Facility, Grenoble , France, 4Faculty of Physics and Applied Computer Science, AGH University of Science Science and Technology, Krakow, Poland, 5Institute of Solid State Physics, TU Wien, Vienna, Austria, 6Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, Krakow, Poland, 7Department of Chemistry, Purdue University, West Lafayette, USA T3.17: Temperature driven self-doping of magnetic polarons in magnetite, July 13, 2021, 18:50 - 19:00

Introduction: Magnetite (Fe3O4) is one of the most fascinating strongly correlated systems exhibiting the enigmatic first-order metal to insulator Verwey transition. Several decades of experimental and theoretical research revealed that an intricate long-range network of Fe3+-Fe2+-Fe3+ linear magnetic molecules (called trimerons) form in the insulative phase of Fe3O4. Short-range structural fluctuations linked to the presence of trimerons were shown to exist in the high temperature metallic phase up to the Curie temperature, however the role of these short-range trimerons and the mechanism behind their collapse remains an unsolved puzzle. Here we disclose the missing pieces, providing a novel view of the temperature evolution of trimerons in Fe3O4.

Experimental methods: We measured Fe Kα1 high-energy resolved fluorescence-detected x-ray absorption spectroscopy (HERFD-XAS) on an Fe3O4 single crystal over a wide temperature range (10K-1200K) spanning both the Verwey (TV ≈ 123K) and the Curie transitions (TC ≈ 840K). HERFD-XAS measurements at the Fe K pre-edge offers a rigorous route to determine the local symmetry of Fe cations as a function of temperature because it acts as a "magnifying glass" enhancing the signal of Fe cations residing selectively in the A-sites nearly four times the B-sites.

Results and discussion: We discovered a new cation reordering occurs starting from 330K leading to a hole self-doping effect at the Fe octahedral sublattice. We found that the level of self-doping can be continuously (and reversibly) tuned by controlling the temperature and we identified four regimes of self- doping that describe the temperature dependence of key physical properties such as the electrical conductivity and magnetism. Our results provide an elegant analogy between the effect of chemical doping and temperature-driven self-doping on trimerons in magnetite. For example, we find a change in the cation ordering regime at T = 500K which is triggered by a critical hole self-doping level of c ~ 0.023 mirroring the effect of chemical doping that changes the Verwey transition from a first to second order transition at the same level.

Conclusion: This demonstrates that temperature driven self-doping provides a unique adjustable experimental handle intimately connected to chemical doping. Beyond these results, we envision using the combination of K pre-edge HERFD-XAS and theoretical calculations to solve open questions in palaeomagnetism where understanding correlations in iron minerals under high pressure and temperatures is essential.

Acknowledgements: We are also thankful to M. van der Linden and P. Zimmermann for their assistance during the beamtime. A. Juhin, D. Cabaret, Ph. Sainctavit and F. Meirer are thanked for the fruitful discussions. This work was financed by the ERC advanced Grant XRAYonACTIVE No. 340279 and NWO Rubicon Fellowship (project number 019.201EN.010).

Simulating x-ray optical activity in quartz using first principle calculations Mr SOLAL Lellouche1 1Impmc, 75005 Paris, France M3.5: Simulating x-ray optical activity in quartz using first principle calculations, July 12, 2021, 17:50 - 18:00

Dichroism is observed when the absorption spectrum of a material is influenced by the polarisation of incident photons. X-ray Natural circular dichroism of a given sample is the difference of absorption spectra recorded with right and left circularly polarized X-rays in the absence of a net magnetization of the sample.

Natural circular dichroism, first observed in 1895 by Aimé Cotton, is one of the most powerful tools for obtaining stereochemical information, and is the only method outside of X-ray crystallography capable of revealing the absolute configuration of a chiral system. Circular dichroism measurements have first been developed in the UV-Visible range and have recently been extended to X-ray absorption spectroscopy (XAS), where it received the name of X-ray Natural Circular Dichroism (XNCD). Up to now, XNCD has only been observed in crystals. Due to the intrinsic chemical selectivity of XAS, XNCD mixes information from the local environment of the absorbing atom to the symmetry of the crystal itself. XNCD can only be observed for crystals for which the point group of the space group belongs to a family of 13 point groups [1]. Although the theoretical basis seems rather straightforward, there are few examples of XNCD calculations and so far, there is not much understanding on how the observed shape of XNCD signals relate to the local point group of the absorbing atom or the point group of the crystal space group. Following previous work by Nadejda Bouldi [2], we have performed a theoretical investigation of the XNCD signals in the chiral crystal of -quartz.

One of the structures for SiO2 is -quartz that crystallizes in one of the two chiral space groups P3121 and P3221. These two space groups are compatible with the observation of XNCD. -quartz has no magnetic ion so that its net magnetization is zero and the XNCD signal cannot be polluted by an XMCD (X-ray Magnetic Circular Dichroism) signal. For both and enantiomers, we have calculated XNCD at both O and Si K-edges and their angular dependence by using the code Quantum Espresso. It is based on Density Functional Theory (DFT) and uses pseudo-potentials expanded on a plane wave basis. The ultimate target of the calculation is to apply the XNCD sum rule that make connection between the integral of the XNCD signal with the average value of some operator, the pseudo-deviator whose intensity depends on the p-d hybridization of the absorbing site.

REFERENCES 1. C.R. Natoli et al., Eur. Phys. J. B, 4 1 (1998) 1-11 2. N. Bouldi et al., Phys. Rev. B, 96, 085123 (2017) 3. C Brouder ,1990 J. Phys.: Condens. Matter 2 701

X-ray absorption spectroscopy of (3,4,5)p element hydrides Assistant Professor Robert Hauko1, Professor Jana Padežnik Gomilšek1, Professor Alojz Kodre2,3, Professor Iztok Arčon4,3 1University of Maribor, Faculty of Mechanical Engineering, Maribor, Slovenia, 2University of Ljubljana, Faculty of Mathematics and Physics, Ljubljana, Slovenia, 3J. Stefan Institute, Ljubljana, Slovenia, 4University of Nova Gorica, Nova Gorica, Slovenia

M3.21: X-ray absorption spectroscopy of (3,4,5)p element hydrides, July 12, 2021, 19:10 - 19:20

Tiny multielectron photoexcitation (MEPE) features in X-ray absorption spectra (XAS) in the energy region of K and L edges, accessible at bright synchrotron sources, reveal fine details of mechanisms of inner- shell photoexcitation, in particular the correlated motion of electrons, offering the possibility to test the state- of-art calculations of the photoeffect cross-section beyond standard quasi-single electron approximations [1- 9]. In the purest form, the electron correlation effects in XAS spectra can be studied on monatomic species, i.e. the noble gases and some volatile metals. Yet, for most other elements the free-atom state is practically inaccessible for the XAS experiment [1-4]. In the np regions of the periodic system, gaseous hydride can serve as a good substitute to the free-atom state [5]. The weak and simple structural signal (EXAFS) from hydrogen neighbours, overlapping the intra-atomic effects, can be reliably modelled and removed, to approximate the atomic absorption spectrum. In the standard EXAFS analysis the atomic absorption spectrum as background is typically substituted by a smooth spline function, neglecting MEPE features, whereby systematic errors can be introduced [9-10]. Here we present a systematic study of the valence MEPE in the K- and L- edge absorption spectra of 3p, 4p and 5p hydrides [5-9]. We have developed new experimental procedures for the measurement of the absorption spectra of chemically less stable gaseous 5p hydrides (SnH4, SbH3, TeH2, HI): these include on-site synthesis of commercially unavailable samples and an adaptation of the x-ray absorption cell [8]. The effect of electron correlation is deduced from the evolution of individual absorption features along the p series and their similarity in the XAS spectra of homologous elements [6-7]. Theoretical calculations of individual multi- electron photo-excitation channels are compared with the experiment [7]. The data from 5p K and L edges reveal the complementary information regarding the symmetry of the initial core hole. With the known K- edge spectrum of atomic iodine, the iodine hydride spectra can help explain the effect of the weak molecular bond in the absorption process [9].

References. [1] R. D. Deslattes et al, Phys. Rev. A 27, 923 (1983). [2] S. J. Schaphorst et al, Phys. Rev. A 47, 1953 (1993). [3] M. Kavcic et al, Phys. Rev. Lett. 102, 143001 (2009). [4] A. Kodre et al, Phys. Rev. A 82, 022513 (2010). [5] R. Prešeren et al, J. Sinchrotron Rad. 8, 279 (2001). [6] R. Hauko et al, Phys. Rad. Phys. Chem. 139, 66 (2017). [7] R. Hauko et al, Phys. Rev. A 99, 062501 (2019). [8] R. Hauko et al, Phys. Rad. Phys. Chem. 171, 108743 (2020). [9] J. Padežnik Gomilšek et al, Phys. Rev. A 79, 032514 (2009). [10] I. Arčon, et al, Physica Scripta. Vol, T115, 235 (2005). Acknowledgement. The research was supported by the Slovenian Research Agency [P1-0112] and CALIPSOplus from the EU Framework Programme for Research and Innovation “HORIZON 2020” [730872]. We acknowledge access to the SR facilities of ELETTRA (beamline XAFS, Proposals No. 20185165), and DESY, a member of the Helmholtz Association (HGF) (beamline P65-PETRA III Proposals No. I-20180356 EC). The authors are grateful to Giuliana Aquilanti, Luca Olivi, Simone Pollastri, and Ricardo Grisonich from XAFS beamline of ELETTRA and Edmund Welter, Ruidy Nemausat, and Mathias Herrmann from P65 beamline of DESY for expert advice and assistance on beamline operation.

Towards advanced data acquisition strategies for high-resolution spectroscopic needs at the ISS beamline Dr Denis Leshchev1, Dr Maksim Rakitin1, Dr Eli Stavitski1 1Brookhaven National Lab, Upton, United States M1.5: Towards advanced data acquisition strategies for high-resolution spectroscopic needs at the ISS beamline, July 12, 2021, 08:50 - 09:00

High-resolution (HR) spectroscopy is a family of methods that encompass high energy-resolution fluorescence detection (HERFD) x-ray absorption spectroscopy (XAS), x-ray emission spectroscopy (XES), and resonant inelastic x-ray scattering (RIXS), which provide deep insights into the electronic structure of species under study. To work effectively with diluted samples, these methods have stringent requirements on x-ray beam delivery system, which includes high fluxes (>10^12 ph/s) and tight focusing (~100 of um). With the high x- ray fluency, the radiation-induced sample degradation becomes one of the biggest challenges of experimental high-resolution spectroscopy. A number of strategies are typically employed to mitigate these effects, which include reducing the flux on the sample, shortening the exposure time for each energy step, and installation of additional fast shutters to block the x-ray beam during mechanical motions between energy steps. While helpful, these strategies severely reduce the number of useful photons and effectively slow down the measurement.

Inner Shell Spectroscopy (ISS) beamline at the National Synchrotron Light Source II (Brookhaven National Lab) is currently developing HR spectroscopy capabilities. To mitigate the effects of radiation damage and optimize the beamtime efficiency we leverage our data acquisition (DAQ) system. The ISS DAQ system is based on asynchronous operation of two modules recording time-stamped data continuously during incident energy scans. One module records monochromator encoder output and the other one records analog output from the ionization chambers and photodiodes. The second module emits trigger for consecutive fast exposures of spectrometer detector, such as Pilatus or silicon drift diode. The time stamped data streams are then correlated in the post-processing to reconstruct spectra. This approach allows to perform scans in as fast as 10s, allowing effective beamtime usage. In this presentation we discuss the ISS DAQ implementation and demonstrate the approach in real experiments.

This research used beamline 8 ID (ISS) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704.

Revisiting the FEFF-based EXAFS fit through a Supervised Machine Learning Approach Dr Andrea Martini1,2, Dr Aram Bugaev2, Dr Alexander Guda2, Dr Sergey Guda2, Dr Elisa Borfecchia1, Prof Alexander Soldatov2 1University Of Turin, Turin, Italy, 2The Smart Materials Research Institute, Rostov-on-Don, Russian Federation M3.15: Revisiting the FEFF-based EXAFS fit through a Supervised Machine Learning Approach, July 12, 2021, 18:40 - 18:50

Although being well developed and successfully applied over decades, the standard EXAFS fitting procedure exhibits some drawbacks. First, the paths scattering amplitudes and phases depend on the local atomic structure and they become unreliable for big variations of the bond distances with respect to the initial guess structure. In addition, the multiple scattering (MS) processes of these functions show a strong non-linear angular dependence.1 The second problem is related to the choice of the variables appearing in the EXAFS equation which can be properly refined through the fitting procedure. As the number of parameters involved in the fit increase, the correlation among all the fitting variables becomes higher. These facts lead to express some fitting variables, especially those linked to MS paths, as a function of parameters already involved in the EXAFS fit within the simpler single scattering (SS) models.2 Apart from technical complications, the conversion of the fitting parameters into the exact 3D representation of the atomic structure is not straightforward. Herein, we propose to fit the EXAFS data by means of a machine learning (ML) based approach3. A theoretical training set is used to construct a series of signal functions approximating each scattering path composing the total theoretical EXAFS signal under the variation of a set of user-defined structural parameters. The EXAFS equation is then generalised to account for any kind of deformations (e.g. bond distances and angles). The effective path lengths associated to each scattering process are obtained directly as a function of the molecular deformations without recurring to any elaborated formula acting to describe them. The proposed approach is successfully applied to analyse, in the Fourier and Wavelet Transform space, the experimental 2+ EXAFS data of the KAu(CN)2, [RuCl2(CO)3]2 and [Cu2(NH3)4O2] molecular complexes, in which the advantages over the FEFF based EXAFS fit are demonstrated.

References 1. A. Kuzmin and J. Chaboy, IUCrJ, 2014, 1, 571-589. 2. B. Ravel and M. Newville, J. Synchrot. Radiat., 2005, 12, 537-541. 3. A. Martini, S. Guda, A. Guda, G. Smolentsev, A. Algasov, O. Usoltsev, M. A. Soldatov, A. Bugaev, Y. Rusalev and C. Lamberti, Comput. Phys. Commun., 2020, 250, 107064.

Chemical composition dependent local lattice distortions in high entropy alloys by a combination of XAFS and XRD Dr Yuanyuan Tan1, Mr Ming-Yao Su1,2, Mr Zhou-Can Xie1,2, Prof. Zhong-Jun Chen3, Dr. Yu Gong3, Prof. Li- Rong Zheng3, Prof. Zhan Shi3, Prof. Guang Mo3, Prof. Yong Li4, Prof. Ling-Wei Li4, Prof. Hai-Ying Wang1,2, Prof. Lan-Hong Dai1,2,5 1Institute Of Mechanics, Beijing, China, 2School of Engineering Science, University of Chinese Academy of Sciences, Beijing, P R China, 3Institute of High Energy Physics, Chinese Academy of Sciences & Graduate, University of Chinese Academy of Sciences, Beijing, P R China, 4Institute of Advanced Magnetic Materials, School of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou, P R China, 5State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing, P R China M1.14: Chemical composition dependent local lattice distortions in high entropy alloys by a combination of XAFS and XRD, July 12, 2021, 09:30 - 09:40

Dedicate characterizations of local lattice distortion is key on profound understandings of structure- property correlations in alloys. However, the reports on local lattice distortions centered around specified alloying element in high entropy alloys (HEAs) are very limited. Meanwhile, local lattice distortion in HEAs is still a crucial issue under passionate debate. Since the incipient hypothesis of local lattice distortion in HEAs is severe, however, numerous reports based on experiments and simulations have demonstrated disputing results.

Here, we present our work on local lattice distortion in CrCoNi MEA, CrFeCoNi and CrMnFeCoNi HEAs using key experimental technologies. We reported that averaged lattice distortion and local lattice distortion in the studied alloys are not serious but enhanced with chemical complexity increase. In general, the local lattice distortion in HEAs relates strongly to their chemical compositions. Standard deviation of atom pair distance centered around each element has been calculated as a quantitative factor to evaluate element specified local lattice distortion. The results show that the distortion magnitude centered around certain alloying element keeps in the same order of Ni>Co>Fe>Cr>Mn. The observed positive strain would counteract negative strains and thus leading to subtle averaged lattice distortion. The XANES results suggested that local electron structure flexibility of element should be one factor that contributes to local lattice distortions. These findings provide important clues on local lattice distortion for tailoring advanced HEAs and other multicomponent alloys.

This work is supported by the National Key Research and Development Program of China (No. 2017YFB0702003), the NSFC (Nos. 11790292, 11672316, 12002341), the NSFC Basic Science Center Program for “Multiscale Problems in Nonlinear Mechanics” (No.11988102), the Strategic Priority Research Program (Nos. XDB22040302, XDB22040303), the Key Research Program of Frontier Sciences (Grant No. QYZDJSSW- JSC011), Science Challenge Project (No. TZ2016001).

Application of machine learning algorithms for quantitative analysis of XANES spectra Dr Alexander Guda1, Dr Sergey Guda1, Dr Andrea Martini2, Dr Aram Bugaev1, Dr., Prof. Alexander Soldatov1 1The Smart Materials Research Institute, Southern Federal University, Rostov-on-don, Russian Federation, 2Department of Chemistry, INSTM Reference Center and NIS and CrisDi Interdepartmental Centers, University of Turin, Turin, Italy

T2.5: Application of machine learning algorithms for quantitative analysis of XANES spectra, July 13, 2021, 15:50 - 16:00

X-ray absorption near-edge structure (XANES) spectra are the fingerprint of the local atomic and electronic structure around the absorbing atom. However, the quantitative analysis of these spectra is not straightforward. Even with the most recent advances in this area, for a given spectrum, it is not clear a priori which structural parameters can be refined and how uncertainties should be estimated. Here, we present a novel concept for the analysis of XANES spectra which is based on using machine learning (ML) algorithms and establishes the relationships between intuitive descriptors of spectra (such as edge position, intensities, positions and curvatures of minima and maxima) and the descriptors of the local atomic and electronic structure (i.e. coordination numbers, bond distances and angles, oxidation state). This approach allows overcoming the problem of the systematic difference between theoretical and experimental spectra. Furthermore, the obtained numerical relations can be expressed in the analytical formulas providing a simple and fast tool for a researcher to extract structural parameters based on the spectral shape. The methodology was successfully applied to the experimental data of the multicomponent Fe:SiO2 system and reference iron compounds, demonstrating a high prediction quality for both theoretical validation sets and experimental data.

This work was financially supported by the Russian Foundation for Basic Research (project number 20-32- 70227)

Parallel and Serial Reduction Pathways in Complex Oxide Lithium-ion Battery Anodes Dr Kent Griffith1, Professor Kenneth Poeppelmeier1 1Northwestern University, Evanston, United States M1.6: Parallel and Serial Reduction Pathways in Complex Oxide Lithium-ion Battery Anodes, July 12, 2021, 08:50 - 09:00

Complex early transition metal oxides have emerged as leading candidates for fast charging lithium- ion battery anode materials. Framework crystal structures with frustrated topologies are good electrode candidates because they may intercalate large quantities of guest ions with minimal structural response. Starting from the empty perovskite (ReO3) framework, shear planes and filled pentagonal columns are examples of motifs that decrease the structural degrees of freedom. As a consequence, many early transition metal oxide shear and bronze structures do not readily undergo the tilts and distortions that lead to phase transitions and/or the clamping of lithium diffusion pathways that occur in a purely corner-shared polyhedral network.

In this work, we explore the relationship between composition, crystal structure, and reduction pathway in a variety of mixed transition metal and main group oxides. Operando and ex situ X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) data are collected at Ga K-edge, Nb K-edge, W LI,II,III-edges, Bi LIII-edge, and Ti K-edges to track the evolution of electronic and local atomic structure of the complex oxides during lithium insertion and extraction. Early transition metals in their fully oxidized d0 electronic states (Ti4+, Nb5+, W6+) undergo inversion-breaking local distortions. When these oxides are reduced, such as in lithiation in a lithium-ion battery, their local symmetry increases. The symmetry dependence of XANES makes it uniquely sensitive to this phenomenon, known as the second-order Jahn– Teller effect. In mixed metal oxides, XANES and EXAFS differentiate the redox centers and reveal that the transition metals proceed along parallel reduction pathways while the main group elements react in a stepwise conversion-type mechanism. X-ray absorption spectroscopy is complemented by 6/7Li and 23Na solid- state NMR spectroscopy, synchrotron and neutron diffraction, and DFT to gain a comprehensive picture of the charge storage mechanisms. Prospects for tunability and implications for charge rate and structural stability will be discussed.

This work was supported by the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility, operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02- 06CH11357. Extraordinary facility operations were supported in part by the DOE Office of Science through the National Virtual Biotechnology Laboratory, a consortium of DOE national laboratories focused on the response to COVID-19, with funding provided by the Coronavirus CARES Act. We acknowledge Diamond Light Source for time on beamline B18.

Oxygen vacancy driven orbital reconstruction at the surface of TiO2 core-shell nanocrystals Dr Vinod K. Paidi1 1Pohang Accelerator Laboratory, Pohang, South Korea T3.28: Oxygen vacancy driven orbital reconstruction at the surface of TiO2 core-shell nanocrystals, July 13, 2021, 19:40 - 19:50

Oxygen vacancies and its correlation with the electronic structure are crucial to understanding the functionality of transition-metal-oxide based nanocrystals in materials design applications. Here, I report the fundamental physics of engineering the electronic structure with selective oxygen vacancies in core-shell anatase TiO2 nanocrystals. By employing hard and soft x-ray absorption spectroscopy measurements, along with the corresponding model calculations I show that the oxygen vacancies significantly transform the Ti local symmetry by modulating the covalency of titanium–oxygen bonds. Most strikingly, the results suggest that the altered Ti local symmetry is similar to the C3v, which implies that the Ti exists in two local symmetries (D2d and C3v) at the surface. The findings also indicate that the Ti distortion is a short-range order effect and presumably confined to the second nearest neighbors. Such distortions are responsible for the orbital reconstruction and provide a promising strategy to structural design of the TiO2 nanocrystals.

Funding Information:

This work was supported by Research Center Program of the IBS – IBS-R006-D1 (T.H.), Basic Science Research Program through the National Research Foundation of Korea (NRF) grants funded by 2018R1D1A1B07046980 (Y.H.K.) and 2018R1D1A1B07041997 (K.-S.L.).

XANES Studies of Brain Zinc Homeostasis and Its Role During Cognitive Decline and Ageing Miss Ashley Hollings1,2,3, Mr Nicholas Fimognari2,4, Dr Virginie Lam2,5, Dr Cameron Kewish6, Dr Martin de Jonge6, Dr Peter Kappen6, Associate Professor Ryu Takechi2,5, Professor John Mamo2,5, Dr Mark Hackett1,2,3 1Curtin Institute for Functional Molecules and Interfaces, Curtin University, Bentley, Australia, 2Curtin Health Innovation Research Institute, Curtin University, Bentley, Australia, 3School of Molecular and Life Sciences, Curtin University , Bentley, Australia, 4School of Biomedical Sciences, Curtin University, Bentley, Australia, 5School of Public Health, Curtin University, Bentley , Australia, 6Australian Nuclear Science and Technology Organisation, Clayton, Australia T1.14: XANES Studies of Brain Zinc Homeostasis and Its Role During Cognitive Decline and Ageing, July 13, 2021, 09:30 - 09:40

The greatest risk factor for dementia is ageing. With no cure or effective therapies to slow progression, and with an ageing population, dementia has reached crisis levels in Australia. The content and distribution of metals such as Fe, Cu, Zn is known to change in the ageing brain (metal dis-homeostasis), and thus, increased understanding of the mechanistic role of metal dis-homeostasis may illuminate new therapeutic strategies. Specifically, Zn homeostasis and dis-homeostasis appear to be a potent modulator of memory function, yet, the exact chemical form(s) of Zn that are vital to memory function are unknown. Development of new spectroscopic methods to image different chemical forms of Zn may help increase understanding of Zn- modulated memory function and dysfunction. There are currently no available imaging protocols to differentiate between different chemical forms of Zn, however, substantive evidence supports that X-ray absorption techniques could provide such capability. Recently, our group has utilised X-ray absorption spectroscopy (XAS) to build a spectroscopic library of Zn standard solutions that reflects the chemical forms of Zn likely to be present in the brain. Preliminary analysis has revealed that XAS is able to differentiate between multiple Zn compounds localized within specific brain regions. Critically, we have investigated the effect that sample preparation has on brain-Zn speciation, and observed that the process of air-drying tissue can significantly influence Zn coordination in the tissue. Our future experiments now hope to use the chemically specific Zn imaging protocols, to determine how Zn speciation changes in specific brain regions during ageing or neuorodegenerative disease. Such insights into whether specific types of zinc are affected with ageing may reveal mechanisms contributing to cognitive decline, in turn presenting potential pathways for targeted therapeutic interventions.

This research funded by an Australian Government Research Training Program (RTP) Scholarship, an Australian Institute of Nuclear Science and Engineering Post Graduate Research Award (AINSE PGRA), and an ARC Future Fellowship.

Effect of interfacial structure on catalytic properties of bimetallic nanoparticles Dr Akhil Tayal1, Dr. Okkyun Seo2, Dr. Jaemyung Kim2, Dr. Kohei Kusada3, Dr. Hirokazu Kobayashi3, Prof. Hiroshi Kitagawa3, Dr. Osami Sakata2 1Deutsches Elektronen Synchrotron, Hamburg, Germany, 2National Institute for material science, Sayo-gun, Japan, 3Kyoto University, Sakyo-ku, Japan T3.7: Effect of interfacial structure on catalytic properties of bimetallic nanoparticles, July 13, 2021, 18:00 - 18:10

Platinum group elements show remarkable catalytic properties and are widely used for the chemical storage of hydrogen.[1] However, their economic viability is limited due to depleted natural reserves. It is known that the various catalytic activity occurs on the surface; therefore, nanoparticles (NPs) of these elements provide an optimum surface to volume ratio, thus reducing their consumption. However, to further minimize the usage of these expensive elements, numerous investigations were devoted to probing the catalytic properties in the bimetallic alloy systems. Various studies on the bimetallic NPs such as Pd-Ru, Ru- Cu, Pt-Ru, Au-Pt, and Ag-Ru show a substantial improvement in the catalytic properties, hydrogen storage capacity, and stability relative to the monometallic NPs.[1] Interestingly, many bimetallic systems show catalytic properties that are not observed in the individual NPs. [1] Moreover, many of the above bimetallic systems are immiscible in bulk but can only form in the solid solution alloy in the form of NPs. It suggests that the new state of NPs solid-solution shows distinct behavior from the individual NPs. Therefore, a systematic investigation must be required to understand their local structure and explore these bimetallic systems' exciting catalytic properties. The local structure in the proximity of alloy mixing sites strongly correlates with the electronic structure that gives rise to the novel catalytic properties in these bimetallic systems. In this regard, we have studied various bimetallic systems such as Pd-Pt and Ag-Rh NPs alloys for the chemical storage of hydrogen. Our finding reveals that the local structure around the interfacial region strongly governs the hydrogen storage properties in these systems. The bimetallic NPs are prepared via the conventional chemical reduction method. The samples were characterized by various techniques to investigate their catalytic performance. X-ray absorption spectroscopy (XAFS) at metal K-edge and L3-edge was used to probe the element-specific local structure. In the Pd-Pt bimetallic core(Pd)-shell(Pt) (CS) NPs, we observed that after the process of hydrogen absorption and desorption, the CS structure is transformed to the solid-solution (SS) structure. Interestingly it was observed that the SS Pd-Pt NPs show remarkable improvement in the H2 absorption properties. The XAFS findings reveal that interfacial structure served as highly active sites for the H2 absorption. In the SS phase alloy phase gets distributed homogenously, increasing the coverage area of active sites, resulting in enhanced H2 absorption. [2-3] The Ag-Rh is the immiscible system, and neither Ag nor Rh shows any hydrogen absorption properties.[4] However, it was demonstrated that in the NPs alloy form, they do offer the H2 absorption properties. Our recent investigation reveals that the catalysis sites having Rh linked to Ag are responsible for the unexpected H2 absorption properties. Reference: 1. Kusada et al., Chem. - Eur. J. 26, 5105−5130 (2020). 2. Tayal et al., J. Alloys Compds. 791, 1263-1269 (2019). 3. Tayal et al., ACS Appl. Inter. Sci. https://doi.org/10.1021/acsami.0c22432 (2021). 4. Tayal et al., J. Alloys Compds. 869, 159268 (2021).

Dimerization of nickel ions in ZnWO4-NiWO4 solid solutions as-evidenced by EXAFS spectroscopy Dr Georgijs Bakradze1, Dr Aleksandr Kalinko1, Dr Alexei Kuzmin1 1Institute of Solid State Physics, University of Latvia, Riga, Latvia M2.1: Dimerization of nickel ions in ZnWO4-NiWO4 solid solutions as-evidenced by EXAFS spectroscopy, July 12, 2021, 15:30 - 15:40

X-ray absorption spectroscopy has evidenced the existence of nickel dimers in wolframite-type NiWO4 and ZnWO4-NiWO4 solid solutions. Temperature- (10-300 K) and composition-dependent X-ray absorption spectra were recorded at the W L3-edge, Ni and Zn K-edges of microcrystalline NiWO4, ZnWO4-NiWO4 and ZnWO4 to study the influence of thermal disorder and static distortions on the local atomic structure. Structural models were obtained by analyzing the experimental extended X-ray absorption fine structure (EXAFS) spectra simultaneously at three metal absorption edges using reverse Monte Carlo simulations. The reconstructed radial distribution functions allowed us to trace in detail the influence of temperature and composition on the local environment around metal ions. Dimerization of Ni2+ ions in quasi-one-dimensional zigzag chains of [NiO6] octahedra was observed in NiWO4 at all temperatures. It manifests itself as the splitting of the Ni-Ni radial distribution function in the second coordination shell of nickel atoms.

G.B. acknowledges the financial support provided by the State Education Development Agency for project No. 1.1.1.2/VIAA/3/19/444 (agreement No. 1.1.1.2/16/I/001) realized at the Institute of Solid State Physics, University of Latvia. A.K. and A.K. would like to thank the support of the Latvian Council of Science project No. lzp-2019/1-0071.

Selective Deoxygenation of Biomass Volatiles into Light Oxygenates Catalysed by S- Doped, Nanosized Zinc-Rich Scrap Tyre Char with In-situ Formed Multiple Acidic Sites Ms Qiaoqiao Zhou1, Ms Sasha Yang1, Prof Huanting Wang1, Prof Zhenyu Liu2, A/Prof Lian Zhang1 1Chemical Engineering, Monash University, Melbourne, Australia, 2State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, China T1.18: Selective Deoxygenation of Biomass Volatiles into Light Oxygenates Catalysed by S-Doped, Nanosized Zinc-Rich Scrap Tyre Char with In-situ Formed Multiple Acidic Sites, July 13, 2021, 09:50 - 10:00

Abstract

In this paper, we report the unique properties and catalytic performance of scrap tyre char, an otherwise low- value waste derivative on the selective deoxygenation of biomass volatiles (derived from flash pyrolysis of lignocellulosic biomass at 500oC) into value-added light oxygenates including furfural and phenol. Due to the inclusion of sulphur (S) and zinc oxide (ZnO) as additives during the prior tyre manufacturing process, the pyrolysis-derived tyre char is rich in both organically bound S and nano-sized zinc sulphide (ZnS) that are highly dispersed within the carbonaceous matrix. Detailed characterisations of the fresh and spent catalysts have been conducted to elaborate the unique mechanisms, upon the use of XPS, TEM-SAED, XAS, NEXAFS, Pyridine- FTIR, and NH3-TPD. As has been confirmed, multiple acidic sites are present in tyre char, including organically bound S serving as a weak Brønsted acid and nano-sized ZnS being a strong Lewis acid. The former acid is active for dehydration, whilst the latter one mainly catalyses the decarboxylation and decarbonylation reactions. Upon the interaction with adsorbed oxygen-bearing species and water molecules, the ZnS-centered active acid site can in-situ transform into a ZnSOx-centered super strong acid site, which is a Brønsted acid that is able to enhance the deoxygenation extent remarkably. More interestingly, the organic S enables an in- situ sulphidation of the less active ZnO on the catalyst surface, thereby enabling a continuous exposure of bio-oil vapour to the highly active ZnS and its sulphate derivative. This in turn enlarges the lifetime of the catalyst and its strong stability upon cyclic tests.

Keywords: Bio-oil selective deoxygenation; Waste scrap tyre char; Nano-sized ZnS; Organic sulphur; In-situ acidity transformation

[This work was funded by Australian Research Council (ARC) Industrial Hub (170100009) and Linkage Project (180100128). The first author would like to acknowledge China Scholarship Council (CSC) for the PhD living allowance support.]

Structural characterization of deep eutectic solvents and their mixtures with water and methanol Dr Matteo Busato1, Dr Alessandra Del Giudice1, Dr Valerio Di Lisio1, Dr Pierpaolo Tomai1, Dr Valentina Migliorati1, Prof Alessandra Gentili1, Prof Andrea Martinelli1, Prof Paola D'Angelo1 1Università di Roma “La Sapienza”, Roma, Italy M3.14: Structural characterization of deep eutectic solvents and their mixtures with water and methanol, July 12, 2021, 18:30 - 18:40

Deep eutectic solvents (DESs) are formed by the combination of a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA), solid starting materials that liquefy upon contact producing a eutectic with a melting point significantly lower than those of the individual components. DESs have been proposed as a sustainable alternative to traditional solvents owing to some outstanding properties, such as negligible vapor pressure, non-flammability, high conductivity, and low toxicity [1]. They are also “designer solvents”, since their constituents can be tailored to meet desired physicochemical requirements.

Here we present a study about the structural characterization of some DESs and of their mixtures obtained upon addition of water and methanol (MeOH) as co-solvents. The introduction of a co-solvent can dramatically affect several DESs key-properties providing a further designing strategy [2]. In this project, small- and wide-angle X-ray scattering (SWAXS), ATR-FTIR spectroscopy and molecular dynamics (MD) simulations have been employed to study the changes in the nanostructure of the archetypal DES “reline” (choline chloride (ChCl):urea 1:2) and of the eutectic formed by ChCl and sesamol in 1:3 ratio [3] upon co- solvent addition. For high water contents, segregation between sesamol- and water-rich regions occurs, up to the formation of water pores of 70 Å diameter able to confine most of the ChCl and disrupt the DES internal structure [4]. Differently, segregation was not displayed by MeOH mixtures. The formation of pseudo-phase domains was also observed in metal-based DES (MDESs) formed by iron(III), cobalt(II) and nickel(II) chloride salts with urea. MD simulations were carried out and showed that the metal salt is segregated from urea to form cage-like structures. The analysis of the X-ray absorption (XAS) data collected on these MDESs, and on their mixtures with water, was able to shed light on the local coordination of the metal ions in these media.

[1] E. L. Smith, A. P. Abbott and K. S. Ryder, Chem. Rev. 2014, 114, 11060. [2] Y. Dai, G.-J. Witkamp, R. Verpoorte and Y. H. Choi, Food Chem. 2015, 187, 14. [3] P. Tomai, A. Gentili, R. Curini, R. Gottardo, Franco Tagliaro and S. Fanali, J. Pharm. Anal. 2020, in press. [4] M. Busato, V. Di Lisio, A. Del Giudice, P. Tomai, V. Migliorati, L. Galantini, A. Gentili, A. Martinelli and P. D’Angelo, J. Mol. Liq. 2021, 331, 115747.

Principal Component Analysis as the key for the XANES Spectral Decomposition problem: when the Transformation Matrix is better than the MCR-ALS approach Dr Andrea Martini1,2, Dr Alexander Guda2, Prof Sergey Guda2, Mr Francesco Tavani3, Dr Elisa Borfecchia1, Prof Paola D'Angelo3, Prof Alexander Soldatov2 1University of Turin, Turin, Italy, 2The Smart Materials Research Institute, Rostov-on-Don, Italy, 3Università degli Studi di Roma, La Sapienza, Roma, Italy T3.13: Principal Component Analysis as the key for the XANES Spectral Decomposition problem: when the Transformation Matrix is better than the MCR-ALS approach, July 13, 2021, 18:30 - 18:40

X-ray absorption spectroscopy (XAS) today represents a widespread and powerful technique, able to monitor complex systems under in situ and operando conditions, while external variables, such as sampling time, sample temperature or even beam position over the analyzed sample, are varied. X-ray absorption spectroscopy is an element-selective but bulk-averaging technique. Each measured XAS spectrum can be seen as an average signal arising from all the absorber-containing species/configurations present in the sample under study.1 The acquired XAS data are thus represented by a spectroscopic mixture composed of superimposed spectral profiles associated to well-defined components characterized by concentration values evolving during the experiment. Herein we show how the classic principal component analysis (PCA) can be properly employed in the solution of the XANES spectral decomposition problem, proposing an approach, currently implemented in the PyFitIt code2, in which an experimental XANES dataset is decomposed in a set of pure spectral and concentration profiles. The potentiality of this methodology, based on the application of a transformation matrix, stands in the possibility to manipulate directly every single principal component and combine them in order to obtain a set of physical/chemical interpretable spectra even when the dataset variance is very low where, usually, the multivariate curve resolution alternating least-squares (MCR-ALS) algorithm3 fails. Moreover, it is possible also to visualize the range of variation of each element of the transformation matrix able to recover a set of spectroscopic meaningful profiles. Finally the PCA derived spectra can be compared directly with the theoretical XANES approximations derived through the Machine Learning indirect approach4 (provided always by the PyFitIt code). Herein the elements of the transformation matrix, as well as the structural parameters from whom the theoretical XANES depends, can be refined in one turn together, reducing drastically the level of uncertainty associated to the results of the spectral decomposition.

References 1. A. Martini and E. Borfecchia, Crystals, 2020, 10, 46. 2. A. Martini, S. A. Guda, A. A. Guda, G. Smolentsev, A. Algasov, O. Usoltsev, M. A. Soldatov, A. Bugaev, Y. Rusalev, C. Lamberti and A. V. Soldatov, Comput. Phys. Commun., 2019, DOI: https://doi.org/10.1016/j.cpc.2019.107064, 107064. 3. J. Jaumot, R. Gargallo, A. de Juan and R. Tauler, Chemometr. Intell. Lab., 2005, 76, 101-110. 4. A. A. Guda, S. A. Guda, K. A. Lomachenko, M. A. Soldatov, I. A. Pankin, A. V. Soldatov, L. Braglia, A. L. Bugaev, A. Martini, M. Signorile, E. Groppo, A. Piovano, E. Borfecchia and C. Lamberti, Catal. Today, 2019, 336, 3-21.

Nonadiabatic small polarons produced by Ti ions in Cr1.8Ti0.2O3+z particles: A study by XANES Dr Martín E. Saleta1,2, MS Daniela P. Valdés1,2, Dr Liliana Mogni1,2, Dr. Dina Tobia1, Dr. Santiago Figueroa3, BSc Júnior Mauricio3, Dr. Enio Lima Jr1, Dr. Guillermo Zampieri1,2, Dr. Rodolfo D. Sánchez1,2 1Instituto Nanociencia y Nanotecnología (CNEA-CONICET), S.C. de Bariloche, Argentina, 2Instituto Balseiro, S.C. de Bariloche, Argentina, 3azilian Synchrotron Light Laboratory (LNLS), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil M1.2: Nonadiabatic small polarons produced by Ti ions in Cr1.8Ti0.2O3+z particles: A study by XANES, July 12, 2021, 08:30 - 08:40

Metal-oxide semiconductors have been studied for their potential technological applications due to their interesting physical and chemical properties. In particular the solid solution of Cr oxide substituted with Ti (Cr2−xTixO3+z) has been studied due to its technological application as a gas or volatile organic compound detector. In particular the electrical properties of the extremes of the solid solution are very different. The Ti2O3 has been widely studied due to the metal-to-insulator transition that this sesquioxide exhibits, without a change in its crystalline symmetry. Meanwhile, Cr2O3 is a semiconductor. Theoretical and experimental results suggest that the conduction mechanism of Cr2O3 can be explained by the small polaron model. The solid solution Cr2−xTixO3+z presents p- type conductivity predominantly determined by the Cr defects and it was reported that its conduction is not affected significantly by the incorporation of Ti ions, except for a gradual decrease of the conductivity with respect to that of pure Cr2O3.

In this work, we present magnetic and electrical conduction characterizations of Cr1.8Ti0.2O3+z (CTO) synthesized by a sol-gel method followed by two thermal treatments at 1273 K. Magnetic susceptibility studies showed a para- to antiferromagnetic transition at around 305-310 K, which is confirmed by electron spin resonance spectroscopy. X-ray photoemission spectra (XPS) and X-ray absorption spectroscopy studies confirm that the Cr ions are only present in the +3 state. Meanwhile, in the Ti K-edge, it is observed that inside the Cr2O3 structure, a fraction of the Ti ions is in the +4 oxidation state and a minor part in the +3 state. By XPS, we confirmed that the Ti ions located on the surface are all practically in the +4 oxidation state, meaning that the core of the CTO particles is constituted by ions in both oxidation states, +3 and +4, and those on the surface are in the +4 state. The electric conduction of CTO is described by the nonadiabatic small polaron hopping (NA-SPH) model. The mixed valence in the Ti3+/Ti4+ system improves notably the mobility of the electrons. On the other hand, in the temperature range of 750-790 K, the characteristic parameters of the NA-SPH model (exponential hopping energy and pre-exponential conductivity factor) change. Both parameters are lower at high temperatures than their respective values at low temperatures. It is important to mention that no changes, in this temperature range, are observed in the thermal evolution of the cell parameters (or volume) studied by X-ray diffraction, which discards any possible structural rearrangement or transition. However, the thermal evolution of the intensity of some selected peaks of the Ti K-edge of the XANES spectra presents a break at the same temperature range. The changes observed in both experiments strongly suggest that these are associated with a variation in the electron-phonon interaction in the CTO system. This is a novel effect, and this result opens new perspectives for understanding the physical phenomena of the electron-phonon interaction, which could be complemented with further theoretical calculations.

M.E. Saleta, et al. J. Phys. Chem. C. (2021) DOI: 10.1021/acs.jpcc.1c00366.

Microliter-stirred sample setup for X-ray spectroscopy analysis of nanomaterials in suspension Mr Rafał Fanselow1, Associate Professor Jakub Szlachetko1 1Institute of Nuclear Physics Polish Academy of Sciences, Kraków, Poland

M3.19: Microliter-stirred sample setup for X-ray spectroscopy analysis of nanomaterials in suspension, July 12, 2021, 19:00 - 19:10 Analysis of samples in the liquid environment using X-ray spectroscopy techniques is a very attractive approach as it provides specimen characterization in its native conditions. However, very often due to challenging synthesis procedures and the expensive cost of specimens it is difficult to obtain a sample in quantities for optimal measurement. Additionally, nanomaterial suspensions often undergo agglomeration and sedimentation processes that can be avoided either by sonication or sample stirring. Relatively small sample volumes and intrinsic agglomeration processes make X-ray spectroscopy measurements challenging especially when long periods are needed for the collection of high-quality data. To address both issues we report a newly developed special sample holder that allows the measurement of up to 100 µL of the liquid sample with continuous stirring of the suspension. The device was equipped with an electrically driven stirrer that mixed nanoparticle suspension during signal acquisition preventing their sedimentation. Capabilities of the designed holder were tested using a laboratory X-ray spectrometer with simultaneous X-ray absorption and X-ray emission spectroscopy measurement. The microliter-stirred sample system was tested with 150 µL zinc oxide nanoparticle suspension at 200 mM concentration. The experiments showed a stable signal from the sample solution over 1,5 h acquisition time. If no stirring was applied agglomeration and subsequent sedimentation processes were visible already within few minutes making any quantitative or qualitative sample analysis impossible.

Acknowledgements: This work was supported by the National Science Centre (Poland) under grant number 2020/37/B/ST3/00555

In situ XAS investigation for the working structure of stable Ni catalyst in CO2 dry reforming of CH4 Mr Wenjie Yang1, Prof Jun Huang1 1The University Of Sydney, Sydney, Australia T1.11: In situ XAS investigation for the working structure of stable Ni catalyst in CO2 dry reforming of CH4, July 13, 2021, 09:20 - 09:30

[Introduction] Hydrogen has long been considered the most environmentally friendly energy carrier. To produce hydrogen in a large scale, methane has attracted much attention since it is the major component of petroleum reserves and landfill gas, upgrading it into higher value products is an extremely promising way to offer renewable energy. In this work, we report confined single-site Ni/SiO2 catalysts that can produce hydrogen and carbon monoxide syngas via dry methane reforming (DRM). Under the help of ex situ and in situ X-ray absorption spectroscopy (XAS) characterization, the superior stability of the catalyst highlights the essential roles of confined sites during the catalytic processes.

[Results and discussion] In ex-situ XAS study, the x-ray absorption near edge structure (XANES) showed that all fresh Ni/SiO2 samples possessed an intense while line reminiscent of nickel oxide rather than metallic nickel. In the extended X-ray absorption fine structure (EXAFS) spectrum, the Ni-Ni scattering (~2.1Å) cannot be identified for 2.5% Ni/SiO2 catalyst, but weakly observable for 5% and 12.5% Ni/SiO2 catalysts. In all EXAFS spectra, the Ni-O bond (~2.0 Å) and a Ni-(O)-Ni bond (~2.6Å) played predominate roles. This observation suggests that the 2.5% Ni/SiO2 are single atom catalyst (SAC) while 5% and 12.5% Ni/SiO2 are single sites catalysts (SSC). These assignments have also been confirmed by transmission electron microscopy (TEM) and atomic probe tomography (APT). For DRM reaction, the SSC catalyst showed an excellent activity and superior stability. Further In-situ EXAFS analysis shows that the Ni single-site cannot be fully reduced under even 800oC. However, after the introduction of reactant methane and carbon dioxide, the Ni-Ni scattering (~2.1Å) became predominant and a new Ni-O-Si bond can be observed. The existence of the bond was also confirmed by cluster analysis of APT. The observation of Ni-O-Si bond in SSC suggests the site confinement of nickel single-site maybe the key for the proceeding of the DRM.

[No grant]

In-situ / operando XAS characterization of ZSM-5 supported Mo catalysts to identify the pathway to the active species for methane dehydroaromatization Dr Nirmalendu Patra1, Dr. Adam Hoffman1, Dr. Sheima Khatib2, Dr. Mustafizur Rahman3, Dr. Simon Bare1 1SLAC National Accelerator Laboratory, Menlo Park, United States, 2Texas Tech University, Lubbock, United States, 3Pacific Northwest National Laboratory, Richland, United States T1.4: In-situ / operando XAS characterization of ZSM-5 supported Mo catalysts to identify the pathway to the active species for methane dehydroaromatization, July 13, 2021, 08:40 - 08:50

Methane dehydroaromatization (MDA) is a chemical reaction that directly converts methane to benzene and hydrogen. We used zeolite (ZSM-5) supported MoOx catalyst with 3% and 10% Mo loading and Si/Al 15 and

40 for activating the methane conversion by a direct reduction process from RT to 700°C with H2 flow followed by carburization with CH4. Our study identifies the chemical species during the reduction process and shows how the local surrounding around the Mo atom evolves within the zeolite support. The XANES study shows that in the reduction process the catalyst transform from Mo6+ to Mo0 species with an intermediate Mo4+ species. Multivariate analysis was carried out using PCA and k-mean clustering to represent the reduction mechanism. This indicated that the whole reduction process can be represented by 6 unique clusters which represents a relative variation of Mo6+, Mo4+ and Mo0 species.

Additionally, full EXAFS modeling was performed on three stages during the catalyst activation. At 200°C the tetrahedral Mo-oxo species is anchored to the zeolite support via two Mo – O bonds and other two Mo = O bonds act as the terminal oxygens within the zeolite pore. With increasing temperature to ~450°C the MoOx reduces, and a metallic Mo cluster starts forming. Finally, at 700°C the catalyst was fully reduced to metallic

Mo nanoparticles. These metallic Mo NPs were directly carburized in a CH4 flow at 700°C. Thus, the reduced catalyst was carburized to a MoCx cluster without forming an intermediate Mo oxycarbide intermediate. These directly carburized Mo carbide species are active and selective for MDA and show only slow deactivation [1]. After cooling to room temperature, the EXAFS modeling is consistent with a α-MoC1-x species.

Reference:[1] Rahman, M., Infantes-Molina, A., Hoffman, A., Bare, S., Emerson, K.L., Khatib*, S.J., Effect of Si/Al ratio of ZSM-5 support on structure and activity of Mo species in methane dehydroaromatization, Fuel, 278, 118290 (2020)

Structure investigation of Pt nanoclusters deposited on flat carbon support – A model catalyst for fuel cell electrode by operando BCLA / HERFD+BI-XAFS method Miss Kaiyue Dong1, Dr. Bing Hu2, Mr Bang Lu1, Mr M.H.Al Rashid1, Dr. Satoru Takakusagi2, Dr. Keiko Miyabayashi3, Dr Kotaro Higashi4,5, Dr Tomoya Uruga4, Dr Yasuhiro Iwasawa4, Dr Kiyotaka Asakura2 1Graduate School of Engineering, Hokkaido University, Sapporo, Japan, 2Institute for Catalysis, Hokkaido University, Hokkaido University, Japan, 3Graduate School of Integrated Science and Technology, Shizuoka University., Shizuoka, Japan, 4Innovation Research Center for Fuel Cell, The University of Electro-Communications, Tokyo, Japan, 5Japan Synchrotron Radiation Research Institute., Hyogo, Japan T1.15: Structure investigation of Pt nanoclusters deposited on flat carbon support – A model catalyst for fuel cell electrode by operando BCLA / HERFD+BI-XAFS method, July 13, 2021, 09:40 - 09:50

Introduction: Polymer electrolyte membrane fuel cells (PEMFCs) is one of the most promising clean power sources. In order to understand the interaction between Pt and carbon support and further improve of catalytic activities of Pt, we fabricated a model catalyst system, where PtNPs were deposited on a flat carbon support – highly oriented pyrolytic graphite (HOPG), which is suitable for applications of the modern surface science techniques such as Atomic Force Microscopy (AFM), X-ray Photon Spectroscopy (XPS). Operando XAFS technique, as a powerful technique for characterization on PtNPs on flat support, was also applied to determine the PtNPs structure under electrochemical conditions. Experimental: A small amount of well-dispersed PtNPs (~ 1015 Pt atom/cm2) was deposited on a HOPG surface by a spin- coating method, which was firstly studied by Cyclic Voltammetry (CV) in the range of (+ 0.1 ~ + 1.0) VRHE in 0.1 M HClO4. Later, operando Bent Crystal Laue Analyzer-enhanced / High Energy Resolution Fluorescence Detected XAFS (BCLA/HERFD+BI-XAFS) technique was applied to the PtNPs/HOPG system to reveal the in-situ structure and surface adsorbates of Pt under electrochemical conditions. All XAFS measurements were conducted at BL36XU, SPring 8, Japan. Results and Discussions: The EXAFS analysis by REX 2000 and Feff 8 suggested the PtNPs possessed a stable framework over potentials, which was well explained by a cuboctahedron model with 509 Pt atoms, with a bond distance of 2.76 0.01 Å. HERFD-XANES results showed the potential-dependent adsorption/desorption of -H, -OH, and -O species. Hydrogen was adsorbed at the 0.1 VRHE, then desorbed at 0.4 VRHE with the increasement of potential and - OH species was found at (+0.6 ~ +0.8) VRHE. The characteristic XANES peak appeared at 11568 eV, indicating that the surface species were converted to -O species finally. The HERFD+BI-XANES is a promising technique to distinguish adsorbates at electrochemical surfaces.

Acknowledgement: This work was supported by JSPS Grant-in-Aids for Scientific Research 20H00367 and NEDO Fuel cell project.

Determination of the magnetism in spinel ferrites by site occupancy and valence

Julia Lumetzberger1, Verena Ney1, Anna Zakharova2, Andreas Ney1

1Johannes Kepler University Linz, Linz, Austria, 2Paul Scherrer Institut, Villigen, Switzerland

M3.3: Determination of the magnetism in spinel ferrites by site occupancy and valence, July 12, 2021, 17:40 - 17:50

In this work the origin of the magnetic properties of Zn/Al doped nickel ferrites are investigated as a magnetic insulator for applications in spintronic [1, 2]. XAS, XLD and XMCD spectra of Zn/Al doped nickel ferrites with varying doping concentrations at 300K have been recorded. By measuring at the Fe and Ni L3, 2 edges information about the cation distribution in this material can be extracted. Unexpectedly, Zn was found to influence not only the lattice site occupancy of Ni2+, but also controls the amount of Oh Fe2+, while keeping the strain constant by an unchanged Al concentration. This was evidenced by a careful analysis of the measured XMCD spectra by multiplet ligand field theory simulations [1]. Due to the vital role of Td Ni2+ and Oh Fe2+ for controlling the anisotropy and magnetic damping, a sample series with systemically varied Zn and Al concentration was grown and measured by XRD, SQUID magnetometry and FMR to obtain information about the structure and magnetism. However, the main focus in this contribution is the analysis of the XMCD spectra at the Ni and Fe L3, 2 edge as well as XLD at the Al K edge and its impact on the magnetic properties.

Additionally, the sample system of zinc ferrites thin films, which is known for its struggle to accurately determine the predominant type of magnetism ranging from an antiferromagnet to a spin glass, is investigated [3]. The XMCD spectra at the Fe and Zn L3, 2 edge in combination with multiplet ligand field simulations probe the site occupancy and therefore give information about a possible A/B disorder, which has been determined to be the key component to confirm the magnetic order. Furthermore, a detailed analysis of the integral magnetic properties has been done with SQUID magnetometry, complementing the findings from x-ray absorption spectroscopy.

[1] J. Lumetzberger et. al., Phys. Rev. B 102, 054402 (2020) [2] S. Emori et. al., Adv. Mater. 29, 1701130 (2017) [3] V. Zviagin, M. Grundmann and R. Schmidt-Grund, Physica Status Solidi (b) 257, 1900630 (2020)

Caught while dissolving: interfacial solvation properties of the Mg2+ ion revealed by Operando soft X-ray absorption spectroscopy at ambient pressure Mr Francesco Tavani1, Dr Matteo Busato1, Dr Luca Braglia2, Dr Piero Torelli2, Prof Paola D'Angelo1 1Dipartimento di Chimica, Università di Roma “La Sapienza”, P.le A. Moro 5, 00185 Rome, Italy, Rome, Italy, 2Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science Park, S.S. 14 km 163.5, Trieste I-34149, Italy, Trieste, Italy M3.16: Caught while dissolving: interfacial solvation properties of the Mg2+ ion revealed by Operando soft X-ray absorption spectroscopy at ambient pressure, July 12, 2021, 18:40 - 18:50

Understanding the structural and dynamic properties of the Mg2+ ion would represent an important step forward towards the mechanistic comprehension of relevant biological and technological processes. Mg2+ plays in fact vital roles in all forms of life, many of which are not understood as yet, activating enzymes and nucleic acids, promoting their conformational transitions and behaving as a Lewis acid in ATP hydrolysis and RNA folding1,2. Further, rechargeable Mg-ion batteries, where common electrolytes such as acetonitrile are employed, are gaining considerable interest as promising candidates for future energy storage systems3. However, to date, the use of X-ray Absorption Spectroscopy (XAS) to probe the structural and electronic properties of the Mg2+ ion in aqueous and non-aqueous solutions has been severely hampered by the requirement of soft X-rays, that need tailored beamline experimental set-ups (such as vacuum conditions and windowless beamlines) and special systems of detection4.

In this presentation, I will summarize our group’s recent efforts to address the need of innovative methods that may uncover the solvation properties of the Mg2+ ion. Specifically, by combining operando near edge X- ray absorption fine structure at ambient pressure with multivariate curve resolution5-7, density functional theory and molecular dynamics analyses, we present a method to monitor in real time the chemical changes that take place at the surface of a Mg-containing solid system upon exposure to a series of solvating media, such as water, methanol and acetonitrile. Within the employed work-flow, quantitative structural and electronic information is retrieved for the reversibly dissolved Mg2+ ions in each of the investigated solvents. Our results pave the way for the application of operando soft XAS to access the often elusive properties of low-Z number metal ions involved in processes of chemical and biological interest.

References 1. N. S. Poonia, A. V. Bajaj, Chem. Rev., 1979, 79, 389-445. 2. D. Klein, P. Moore, T. Steitz, RNA, 2004, 10, 1366-79. 3. S. Tepavcevic, Y. Liu, D. Zhou, B. Lai, J. Maser, X. Zuo, H. Chan, P. Krl, C. S. Johnson, V. Stamenkovic, N. M. Markovic, T. Rajh, ACS Nano, 2015, 9, 8194–8205. 4. B. Akabayov, C. J. Doonan, I. J. Pickering, G. N. George, I. Sagi, J. Synchr. Rad., 2005, 12, 392–401. 5. F. Tavani, A. Martini, G. Capocasa, S. Di Stefano, O. Lanzalunga, P. D’Angelo, Inorg. Chem., 2020, 59, 9979– 9989. 6. F. Tavani, G. Capocasa, A. Martini, F. Sessa, S. Di Stefano, O. Lanzalunga, P. D’Angelo, Dalton Trans., 2021, 50, 131-142. 7. F. Tavani, M. Fracchia, N. Pianta, P. Ghigna, E. Quartarone, P. D’Angelo, Chem. Phys. Lett., 2020, 760, 13796

Soft XAS as a tool for locating protons in organic crystal structures: A Classical Electrostatic model of Hydrogen Bonding and Brønsted Proton Transfer Mr Paul Edwards1,2, Dr Joanna Stevens3, Dr Elizabeth Shotton2, Prof. Sven Schroeder1 1University Of Leeds, Leeds, United Kingdom, 2Diamond Light Source, Harwell, United Kingdom, 3Cambridge Crystallographic Data Centre, Cambridge, United Kingdom M3.27: Soft XAS as a tool for locating protons in organic crystal structures: A Classical Electrostatic model of Hydrogen Bonding and Brønsted Proton Transfer, July 12, 2021, 19:40 - 19:50

Using standard X-ray diffraction (XRD) techniques for crystal structure refinement often leaves the precise location of protons ambiguous. Core level spectroscopies can be used as a tool for proton location refinement due to the direct sensitivity of the core electron binding energy to the acceptor-proton distance. We have demonstrated how both Near Edge X-ray Absorption Fine Structure (NEXAFS) and X-ray Photoelectron Spectroscopy (XPS) can be used as a diagnostic tool for proton transfer in hydrogen bonds through a consistent core level shift of +2 eV in the nitrogen acceptor 1s emission where proton transfer is observed.1,2 We have studied a range of organic crystals consisting of both salts and cocrystals, where the core level shift appears to be a universal effect.1,2 This core level shift can be linked directly to the electrostatic effect of a shorter N-H distance.

Using a model based entirely on classical electrostatics, we have modelled the effect of the proton position on the 1s -> π* transition of N 1s electrons, to understand the contribution of the electrostatic interaction to the core level shift observed with changing proton position. From this classical electrostatic model, we observe a continuous change in core electron binding energy with change in proton position. A shift of +2 eV is observed between N-H distances of 1 Å - 2 Å, as observed experimentally 1,2, with structures containing centred protons resulting in an intermediate shift, fully in keeping with a continuum.1 This indicates that the primary interaction involved is electrostatic, further suggesting that the effect observed in XPS and NEXAFS is direct electrostatic sensitivity to the proton position. Future work will investigate the use of NEXAFS spectroscopy with additional information from Density Functional Theory calculations to more accurately refine proton positions in organic crystals than the current standard methods used in XRD.

References 1 J. S. Stevens, S. Coultas, C. Jaye, D. A. Fischer and S. L. M. Schroeder, Core level spectroscopies locate hydrogen in the proton transfer pathway-identifying quasi-symmetrical hydrogen bonds in the solid state, Physical Chemistry Chemical Physics, 2020, 22, 4916–4923. 2 P. Edwards, L. K. Saunders, A. R. Pallipurath, A. Britton, E. A. Willneff, E. J. Shotton and S. L. M. Schroeder, How to Locate Protons Correctly in Organic Brønsted Donor/Acceptor Pairs by XPS: A Step-by-Step Analysis of Three Isonicotinamide complexes, Paper to be submitted.

Acknowledgments We acknowledge funding from the Engineering and Physical Sciences Research Council and Diamond Light Source for the studentship.

3D structure determination of active Pt clusters on an α-Al2O3(0001) surface during CO oxidation by operando PTRF-XAFS technique Mr Bang Lu1, Dr Satoru Takakusagi1, Dr Daiki Kido1, Mr Haoran Xu1, Prof Kiyotaka Asakura1 1Hokkaido University, Sapporo, Japan M1.10: 3D structure determination of active Pt clusters on an α-Al2O3(0001) surface during CO oxidation by operando PTRF-XAFS technique, July 12, 2021, 09:10 - 09:20

Oxide-supported metal catalysts play an essential role in many industrial processes because of their high activity and/or selectivity. Since catalytic performances of the oxide-supported metal catalysts largely depend on the size, shape of the metal species and their interaction with the supports, it is highly demanded to determine them at the atomic-level for elucidating precise structure-activity relationship and developing further active catalysts. We have previously developed the ultra-high vacuum (UHV) polarization-dependent total reflection fluorescence (PTRF)-XAFS technique which can determine valence state (XANES) and 3D [1-5] structure (EXAFS) of metal species dispersed on single-crystal surfaces, such as TiO2(110) and Al2O3(0001). Recently we have constructed a new apparatus which enables us to measure the PTRF-XAFS and catalytic activity of metal catalyst dispersed on a single-crystal oxide surface simultaneously under working conditions.[6] We call this method “operando PTRF-XAFS” technique. In this study, the operando PTRF-XAFS technique was applied to a Pt/-Al2O3(0001) model catalyst surface during the CO oxidation reaction. The Pt/-Al2O3(0001) model catalyst surface was prepared by vacuum evaporation of Pt on an atomically flat - Al2O3(0001) surface at room temperature (RT) in an UHV chamber. The coverage of the Pt atoms was determined to be 0.96 ML (1ML: 5.1×1014 /cm2) by the XPS measurements. The sample was then transferred to the operando PTRF-XAFS cell under the UHV condition. The Pt L3-edge PTRF-XAFS measurements were carried at BL9A of the Photon Factory at the Institute of Materials Structure Science (KEK-IMSS-PF, Tsukuba, Japan) after the cell was attached to the 6-axis goniometer in the hutch and optimizing total-reflection conditions for the incident X-rays. REX2000 and FEFF8.04 were used to analyze XAFS spectra. We found that icosahedral Pt55 clusters were formed on the -Al2O3(0001) surface after the Pt deposition at room temperature, while they were converted to larger cuboctahedral clusters (Pt147) under the CO oxidation reaction at 493 K. The CO oxidation reaction rates were measured simultaneously, and its turnover frequency (TOF) was estimated to be 0.06 s-1 based on the structure of the Pt clusters. Thus, the relationship between the 3D structure of a metal species on a well-defined oxide surface and its catalytic activity has been determined successfully by the operando PTRF XAFS technique.

(References) [1] S. Takakusagi et al., Chem. Rec. 19 (2019) 1244. [2] S. Takakusagi et al., J. Phys. Chem. C 120 (2016) 15785. [3] S. Takakusagi et al., Phys. Chem. Chem. Phys. 15 (2013) 14080. [4] S. Takakusagi et al., Top. Catal. 56 (2013) 1477. [5] K. Asakura in Catalysis (Eds.: J. J. Spivey and M. Gupta), RSC publishing, Cambridge, 2012, pp. 281– 322. [6] B.Lu et al, J. Phys. Chem. C, accepted for publication (2021).

Grant information: KAKENHI Grant No. JP18H01864, Asahi Glass Foundation, Japan Science and Technology Agency (JST)-CREST project (No. JPMJCR19R3)

The interaction of plutonium with iron storage protein, ferritin Mr Cyril Zurita1 1Institut De Chimie Nice, Nice, France M3.4: The interaction of plutonium with iron storage protein, ferritin, July 12, 2021, 17:40 - 17:50

The impact of the contamination of living organisms by actinide elements has been a constant subject of attention since the early steps of the atomic era, just after the end of WWII. But to date, surprisingly little is understood about the bioinorganic chemistry of actinides. Ferritin is the major storage and regulation protein of iron in many organisms, it consists of a protein ring of about 474 kDa and a ferrihydric core at the center with flexible size. Our work sheds light on the interactions of early actinides (Pu as a main interest, Th as a surrogate) at oxidation state +IV with ferritin and its ability to store those elements at physiological pH compared to Fe. The ferritin - thorium load curve suggests that Th(IV) saturates the protein (2840 Th atoms per ferritin) in a similar way that Fe(III) does on the protein ring. To further understand the mechanisms of interaction of Th(IV) and Pu(IV) with ferritin, complementary spectroscopic techniques (Spectrophotometry, Infrared Spectroscopy and X-ray Absorption Spectroscopy) were combined with Molecular Dynamics. Comparison of those spectroscopic data together with MD calculations suggested that Th(IV) and Pu(IV) are complexed mainly on the protein ring and not on the ferrihydric core. Indeed from XAS data at the actinide and iron edges, there is no evidence of Fe neighbors in the Th and Pu environments. On the other hand, carboxylates from amino acids of the protein ring and a possible additional carbonate anion from the medium are shaping the cation coordination spheres. This thorough description from a molecular view point of Th(IV) and Pu(IV) interaction with ferritin, an essential iron storage protein, is a cornerstone in comprehensive nuclear toxicology.

PhD fellowship of C. Zurita was provided by the Ministry of Higher Education and Research, France.

An algorithm for deglitching XAS data Mr Samuel Wallace1, Dr Marco Alsina2, Dr Jean-François Gaillard1 1Northwestern University, Evanston, United States, 2University of Talca, Curicó, Chile T1.5: An algorithm for deglitching XAS data, July 13, 2021, 08:50 - 09:00

X-ray absorption spectroscopy (XAS) spectra occasionally contain glitches, which are spurious data points generated by unintended diffraction events either within the monochromator or the sample itself. These points are removed in a process known as deglitching, which is a necessary step prior to data analysis. Deglitching is generally performed manually on a per-spectrum basis by the analyst, which is tedious and ill- suited for large datasets.

Here, we present an algorithm for high-throughput identification and removal of glitches from XAS spectra. It is implemented as a Python program designed to be compatible with Larch and Araucaria. First, a Savitzky- Golay filter is used to smooth the data. Residuals between the original data and the filtered data are then normalized using a rolling median absolute deviation. Outliers in these normalized residuals are identified using a generalized extreme Studentized deviate test. As a safeguard against false-positive glitch identification, outlying points are removed and replaced in a copy of the data with interpolated points, and the deglitching process is essentially repeated. The spectrum with interpolated points is then filtered, and the residuals between the newly filtered data and the original absorption data are found and normalized. Outliers identified in these residuals are identified as glitches and removed.

Through this algorithm, we achieve repeatable and statistically robust removal of glitches from full-spectrum XAS data, including the x-ray absorption near edge structure (XANES) region. Analysts may tune the parameters of the deglitching algorithm to fit the needs of their data. Once these parameters are optimized, large datasets can be deglitched rapidly and automatically.

Support for this research was provided by the Strategic Environmental Research and Development Program (SERDP) (project ER18-1428) and the Institute for Sustainability and Energy at Northwestern (Interdisciplinary Graduate Cluster Fellowship in Energy and Sustainability).

Determining a Robust Long- and Short-Range Order Structural Model for ‘Stuffed’ Pyrochlores as Solid Electrolytes Mr Bryce Mullens1, Dr Zhaoming Zhang2, Dr Maxim Avdeev1,2, Dr Helen Brand3, Dr Bruce Cowie3, Dr Matilde Saura Muzquiz1, Professor Brendan Kennedy1 1The University Of Sydney, Sydney, Australia, 2Australian Nuclear Science and Technology Organisation, Lucas Heights, Australia, 3Australian Synchrotron, Clayton, Australia M2.9: Determining a Robust Long- and Short-Range Order Structural Model for ‘Stuffed’ Pyrochlores as Solid Electrolytes, July 12, 2021, 16:10 - 16:20

The development of carbon-neutral energy-generation is critical to combatting climate change. One such technology is the development of next-generation ion conductors for solid-oxide fuel cells (SOFCs). SOFCs offer a much more efficient method to extract energy from hydrogen or hydrocarbon fuels than current combustion engines due to their one-step chemical process. However, a bottleneck to the large-scale uptake of SOFCs is the poor performance of the conducting electrolytes that separate the anode from the cathode.

Pyrochlores of the structure A2B2O7 have been proposed as solid electrolyte candidates in SOFCs due to their high oxygen-defect concentration and the mobility of their oxygen vacancies[1-2]. Previous work has demonstrated an increase of bulk oxygen ionic conductivity of these structures by increasing the amount of disorder across the cationic and anionic lattices of these materials [3-4]. Despite this, debate still exists in the literature as to the exact structural models of these pyrochlore structures and how different types of disorder enhance their conductivity [5].

We are investigating the oxygen-vacancy disorder, and ‘tailoring’ it to improve the applications of pyrochlores. We have done this by looking at ‘stuffed’ pyrochlores of the form A2(AxB2-x)O7-x/2. We wish to determine whether controlling the disorder in both the anion and cation sublattices will allow us to tailor- make stuffed pyrochlores as solid electrolytes for SOFCs.

Two series of stuffed pyrochlores have been synthesised using conventional solid-state methods and their long-range average structures characterised by Rietveld refinement against synchrotron X-ray and neutron diffraction data. The local short-range order has been characterised by X-ray absorption near-edge structure (XANES) by observing the crystal field splitting of Ti4+. This is the first time this data has been used to provide a detailed structural model of stuffed pyrochlores for both their long-range average and short-range local structure. These insights can be used in the development and engineering of novel and advanced electrolyte materials for SOFCs.

[1] Moon et al.; Solid State Ionics, 1988, 28-30, 470-474. [2] Anantharaman et al.; Ceram. Int., 2021, 47 (4), 4367-4388. [3] Mandal et al.; J. Mater. Res., 2008, 23 (4), 911-916. [4] Abrantes et al.; J. Cryst. Growth, 2011, 318 (1), 966-970. [5] Mullens et al.; Inorg. Chem., 2021, 60 (7), 4517-4530.

Assessing the accuracy of Reverse Monte Carlo method for EXAFS data analysis Dr Fabio Iesari1, Dr Angela Trapananti2, Prof Andrea Di Cicco2 1Aichi Synchrotron Radiation Center, Seto (Aichi), Japan, 2University of Camerino, Camerino (MC), Italy T1.23: Assessing the accuracy of Reverse Monte Carlo method for EXAFS data analysis, July 13, 2021, 10:20 - 10:30

Reverse Monte Carlo is a structural modeling process where atoms, instead of being driven by a theoretical interatomic potential, are set to reproduce one or more experimental data. While initially applied to the analysis of the structure factor from x-ray or neutron scattering data, the method can be used with any experimental signal that can be calculated starting from atomic coordinates, such as Extended X-ray Absorption Fine Structure (EXAFS) data. While the standard ‘peak-fitting’ approach used in EXAFS analysis provides a set of average structural parameters (average distance, variance, coordination numbers) related to Gaussian or even non-Gaussian distance distributions, the output of RMC are sets of atomic positions allowing full structural analysis. This approach has many advantages, allowing to overcome pre-selected shapes of the interatomic distance distributions and giving additional information on bond-angle distributions and occurring local symmetries.

Since about 20 years, we have developed and applied to molecules and liquid metals a RMC program based on the GNXAS package, called RMC-GNXAS [1,2,3,4]. One interesting issue that is rarely discussed in the literature is the accuracy of the structural results which obviously depends on many factors including the noise and energy range of the experimental data. This is particularly important for EXAFS refinements, for which the structural information content is usually limited by the short photoelectron mean-free-path as well as by the available wave vector (k) range.

In this communication, we put to a test RMC EXAFS refinements of selected molecular and crystalline systems, exploring the effect of statistical noise and energy (wave vector) range on the structural refinements. Results will be directly compared with those available in literature and of standard EXAFS peak-fitting methods, and are thought to help clarifying potential and limits of the RMC refinements.

[1] A. Di Cicco, A. Trapananti, S. Faggioni and A. Filipponi, Phys. Rev. Letters 91, 135505 (2003) [2] A. Di Cicco and A. Trapananti, J. Phys. Condens. Matter 17 S135 (2005) [3] A. Di Cicco, F. Iesari, S. De Panfilis, M. Celino, S. Giusepponi and A. Filipponi, Phys. Rev. B 89, 060102 (2014) [4] A. Di Cicco, F. Iesari, A. Trapananti, P. D'Angelo and A. Filipponi, J. Chem. Phys. 148, 094307 (2018)

[F. I. acknowledges support from JST CREST JPMJCR1861]

Crystallization of transition-metal oxides in aqueous solution studied using in-situ XAFS Dr. Eun-Suk Jeong1, Dr. In-Hui Hwang1,2, Professor Sang-wook Han1 1Jeonbuk National University, Jeonju, South Korea, 2Argonne National Laboratory, Argonne, USA T3.2: Crystallization of transition-metal oxides in aqueous solution studied using in-situ XAFS, July 13, 2021, 17:30 - 17:40

The crystallization mechanism of transition-metal oxides (TMOs) in a solution was examined based on ZnO crystallization using in-situ x-ray absorption fine structure (XAFS) measurements at Zn K edge and semi- empirical quantum chemistry (SEQC) simulations. The XAFS results quantitatively determine the local structural and chemical properties around a zinc atom at successive stages from Zn(NO3)2 to ZnO in an aqueous solution. The results also show that a zinc atom in Zn(NO3)2 ions dissolves in a solution and bonds with approximately three oxygen atoms at room temperature (RT). When hexamethylenetetramine (C6H12N4) is added to the solution at RT, a stable Zn-O complex consisting of six Zn(OH)2s is formed, which is a seed of ZnO crystals. The Zn-O complexes partially and fully form into a wurtzite ZnO at 60oC and 80oC, respectively. Based on the structural properties of Zn-O complexes determined by extended-XAFS (EXAFS), SEQC simulations clarify that Zn-O complexes consecutively develop from a linear structure to a polyhedral complex structure under the assistance of hydroxyls(OH-s) in an aqueous solution. In a solution with a sufficient

- concentration of OH s, ZnO spontaneously grows through the merging of ZnO seeds (6Zn(OH)2s), reducing the total energy by the reactions of OH-s. ZnO crystallization suggests that the crystal growth of TMO can only be ascribed to Ostwald ripening when it exactly corresponds to the size growth of TMO particles.

The work was conducted under the auspices of the Basic Science Research Program through the National Research Foundation of Korea government grant funded by the Ministry of Science and ICT (No. 2017K1A3A7A09016390, 2020K1A3A7A09080403). The XAFS data were collected at the 8C beamline of PLS in Korea and the 20BM beamline of APS in USA. APS is a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE- AC02-06CH11357.

Monitoring and quantifying morphological and structural changes in electrode materials under operando conditions Dr Marcus Fehse1 1Cicenergigune, Vitoria-gasteiz, Spain T3.22: Monitoring and quantifying morphological and structural changes in electrode materials under operando conditions, July 13, 2021, 19:10 - 19:20

Small-angle x-ray scattering (SAXS) can be used in an elegant way to gain reliable and quantifiable information on the bulk morphology of battery electrodes under operando conditions. By coupling the SAXS with simultaneous x-ray absorption spectroscopy (XAS) of the redox active element, the observed morphological changes can be directly linked to the state of the electrochemical reaction. Hence, this approach allows one to closely follow the electronic and local structure evolution, as well as monitor and quantify the morphological and nanostructural changes occurring during electrochemical cycling. On the example of the conversion reaction of doped and non-doped Fe2O3 anode material vs. Li the assets and feasibility under operando conditions of joining these two complementary techniques are highlighted. Our results reveal that upon discharge Fe3+ is gradually reduced to the metallic state and segregated as nanoparticles. For the relithiation reaction, upon subsequent charge, we observe improved reversibility for the Sr-doped compared to non-doped and Ca-doped Fe2O3. [1] We accentuate that this combined technique approach is a reliable, facile and powerful tool to investigate electrode materials under realistic cycling condition. It provides an unbiased and holistic picture of the morphological and structural changes occurring during operation, which foster our understanding of the cycling mechanism and degradation processes and allow for adequate material tailoring.

Ref: [1] M. Fehse et al., “Monitoring and quantifying morphological and structural changes in electrode materials under operando conditions,” J. Power Sources, vol. 478, p. 228685, Dec. 2020, doi: 10.1016/j.jpowsour.2020.228685.

Structural insight into the electroactivity of a CuS-based composite electrode material for all-solid-state lithium battery Dr. Angelo Mullaliu1,2, Mr. Milad Hosseini1,2, Prof. Paolo Conti3, Dr. Giuliana Aquilanti4, Prof. Marco Giorgetti5, Dr. Alberto Varzi1,2, Prof. Stefano Passerini1,2 1Helmholtz Institute Ulm (HIU), Ulm, Germany, 2Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany, 3University of Camerino, Camerino, Italy, 4Elettra Sincrotrone Trieste, Basovizza, Italy, 5University of Bologna, Bologna, Italy M3.8: Structural insight into the electroactivity of a CuS-based composite electrode material for all-solid- state lithium battery, July 12, 2021, 18:00 - 18:10

All-solid-state (SS) lithium batteries have recently re-gained attention due to their intrinsic safety, higher power capability, and, in some cases, wider electrochemical stability window than conventional liquid electrolytes. Copper sulfide (CuS), characterized by high electronic conductivity and theoretical specific capacity, was investigated by our group in SS cells with the LiI-Li3PS4 sulfidic electrolyte. Two different datasets with and without conductive additive were studied, namely CuS and CuS-C.[5] Cells featured specific capacities above 850 mAh g-1 for more than 800 cycles using lithium metal as an anode at 20 °C and an 18% energy density increase to a conventional carbon-sulfur cathode. X-ray diffraction resulted inadequate for investigating the structural modifications upon cycling due to the low crystallinity of the material. Therefore, ex situ and operando x-ray fine structure (XAFS) spectroscopy was performed at the Cu K-edge to shed light on the CuS electroactivity and reaction mechanism. The operando XANES spectra, recorded in fluorescence mode for the high absorption of the SS cell, were analyzed by multivariate curve resolution refined by alternating least squares (MCR-ALS) to identify the pure spectral components and their concentration range. The datasets under investigation display different reaction kinetics, being Cu converted to CuS upon charge faster in the CuS-C set. The extended XAFS (EXAFS) spectra highlighted a high defectivity and low dimensionality of the in situ formed metallic copper. The MCR-ALS chemometric technique proved to be essential in clarifying the reaction mechanism and excluding the formation of Li-intercalated CuS. While CuS and metallic Cu mainly co-exist below 2V, the Cu K-edge does not significantly evolve in the upper voltage window, where sulfur is believed to be electroactive. The joint XAFS-MCR approach demonstrated to be crucial in studying the CuS composite electrode material, also under challenging conditions such as the SS cell format.

Acknowledgments. Measurements at the Elettra Sincrotrone Trieste were supported by in-house research (G.A.) and Project number 20195449 (A.M. as P.I.). The research leading to this result has been supported by the project CALIPSOplus under Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020. A.M. would like to acknowledge the SILS society for the additional financial support to carry out the experiments. The HIU authors acknowledge the basic funding of the Helmholtz Association.

Operando synchrotron studies of high-capacity Mn-hexacyanoferrate for energy storage applications Dr Angelo Mullaliu1,2, Dr. Mattia Gaboardi3, Prof. Paolo Conti4, Dr. Jasper Plaisier3, Dr. Giuliana Aquilanti3, Prof. Stefano Passerini1,2, Prof. Marco Giorgetti5 1Helmholtz Institute Ulm (HIU), Ulm, Germany, 2Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany, 3Elettra Sincrotrone Trieste, Basovizza, Italy, 4University of Camerino, Camerino, Italy, 5University of Bologna, Bologna, Italy T3.9: Operando synchrotron studies of high-capacity Mn-hexacyanoferrate for energy storage applications, July 13, 2021, 18:10 - 18:20

Affordable energy is a crucial factor for enabling sustainable economic growth. For this reason, new battery chemistries employing abundant, safe, and environmentally friendly electrode materials, possibly avoiding strategic elements, are actively investigated. Manganese-hexacyanoferrate (MnHCF) is made of earth- abundant elements by a safe and easy route and offers high specific capacities at a higher potential than other Prussian blue analogs (PBAs). In this work, Na-rich MnHCF was tested in both Li- and Na-ion organic electrolytes in a post-Li strategy perspective and investigated using x-ray absorption fine structure (XAFS) spectroscopy and synchrotron x-ray diffraction (XRD). Both Fe and Mn sites are involved in the electrochemical process, and the high delivered capacity (>130 mAh g-1) results from a reversible evolution in the metallic centers’ oxidation states (Fe3+/Fe2+ and Mn2+/Mn3+). Along with the Mn2+/Mn3+ oxidation, the Mn local environment experiences a substantial, yet reversible, Jahn–Teller (JT) effect. In Mn-active compounds, such as lithium metal oxides, the JT-active Mn3+ generally undergoes a disproportionation into Mn2+ and Mn4+, and the initial specific capacity is irreversible. Here, the cyanide first-shell environment around the Mn site hinders the capacity fade and promotes a reversible Mn2+/Mn3+ redox, in contrast to other Mn-containing compounds. EXAFS shows a substantial and reversible basal contraction (10%) in the charged states due to the equatorial Mn-N bonds’ shortening (2.18 Å → 1.96 Å). Furthermore, operando XRD highlights a non-cooperative JT (NCJT) distortion. The lattice volume expands only by 2% upon electrochemical alkali-ion removal and insertion, which contrasts with EXAFS-retrieved Mn−N distances. This apparent disagreement underlines the capability of the PBA open framework to mitigate and disperse the pronounced variation of the JT-active Mn3+, granting overall stability to the structure. The electroactivity of both metals and the NCJT distortion are critical advantages in employing MnHCF as an electrochemical host in energy storage.

Acknowledgments. Measurements at the Elettra Sincrotrone Trieste were supported by in-house research (G.A.) and Projects 2018022, 20180360 (M.G. as P.I.). M.G. acknowledges the support Initiative and Networking Fund of the Helmholtz Association within the Network of Excellence on post-Lithium batteries (ExNet-0035) for the visiting professor scholarship at the Helmholtz Institute Ulm. The HIU authors acknowledge the basic funding of the Helmholtz Association.

Energy Dispersive X-ray Absorption Spectroscopy with an Inverse-Compton X-ray Source Ms Juanjuan Huang1, Benedikt Günther1, Dr. Klaus Achterhold1, Dr. Martin Dierolf1, Prof. Dr. Franz Pfeiffer1,2 1Chair of Biomedical Physics, Department of Physics and Munich School of BioEngineering, Technical University of Munich, 85748 Garching, Germany, Garching Bei München, Germany, 2Department of Diagnostic and Interventional Radiology, School of Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany, Garching Bei München, Germany T3.8: Energy Dispersive X-ray Absorption Spectroscopy with an Inverse-Compton X-ray Source, July 13, 2021, 18:00 - 18:10

X-ray absorption spectroscopy (XAS) is one of the most frequently used synchrotron techniques. However, it is typically conducted at large facilities, there the available beamtime is constantly oversubscribed. Recent years have witnessed the intensive development of laboratory XAS. An essential parameter for improving the efficiency of laboratory XAS is the spectral brightness of the source. Therefore, compact x-ray sources that can generate high spectral-brightness x-rays provide new opportunities for laboratory XAS. Over the last decade, inverse Compton scattering (ICS) sources have emerged as one of the most promising types of compact x-ray sources. The ICS sources produce x-rays through the collision of MeV electrons with infrared photons. The Munich Compact Light Source (MuCLS), located at the Technical University of Munich, is the first application-centered ICS facility. The MuCLS consists of a commercial ICS source (Lyncean Technologies Inc., Fremont, USA) and two experimental endstations developed in-house, dedicated to transferring synchrotron techniques to a laboratory framework. Multiple techniques in the areas of x-ray imaging, scattering, and spectroscopy have been successfully implemented [1]. We started the XAS project at the MuCLS in 2018 and published the first results in 2020 [2], which was also the first XAS demonstration with an ICS source. The XAS setup is based on an energy-dispersive Laue geometry using a slightly bent silicon crystal. The x-ray properties of the MuCLS make it well-suited for XAS: a photon flux of > 1010 photons/s in < 5% bandwidth, energy tunability in the range 15 – 35 keV, a low divergence as well as relatively small source size — make it well-suited for the XAS technique. In this oral presentation, we would like to introduce the MuCLS facility and present the XAS implementations and results at the MuCLS.

Reference [1] Günther B, Gradl R, Jud C, Eggl E, Huang J, Kulpe S, Achterhold K, Gleich B, Dierolf M, Pfeiffer F. The versatile X-ray beamline of the Munich Compact Light Source: design, instrumentation and applications. J Synchrotron Radiat 27, 5 (2020). [2] Huang J, Günther B, Achterhold K, Cui YT, Gleich B, Dierolf M, Pfeiffer F. Energy-Dispersive X-ray Absorption Spectroscopy with an Inverse Compton Source. Sci Rep 10, 8772 (2020).

Acknowledgment We acknowledge financial support through the Center for Advanced Laser Applications (CALA). Further, the authors would like to thank the staff of Lyncean Technologies Inc. for their technical support.

Time resolved in situ monitoring of mechanochemical transformations by X-ray spectroscopy (XAS) Dr Paulo de Oliveira1, Dr Adam Michalchuk2, MSc Cafer Tufan Cakir2, Dr Kirill Yusenko2, Dr Martin Radtke2, Dr Uwe Reinholz2, Dr Franziska Emmerling2, Dr Ana Buzanich2 1Instituto De Química - Universidade De São Paulo, São Paulo, Brazil, 2Federal Institute for Materials Research and Testing (BAM), Berlin, Germany M1.3: Time resolved in situ monitoring of mechanochemical transformations by X-ray spectroscopy (XAS), July 12, 2021, 08:40 - 08:50

Mechanochemical reactions promise a new direction for environmentally benign preparation of materials, and has been dubbed by IUPAC as one of the 10 chemical innovations that will change our world [1]. Despite this significant promise, very little is known about the mechanisms that drive mechanochemical transformations, posing significant barriers to realizing their full potential. To this end, there is growing need to follow mechanochemical reactions in situ and in real time. We here describe advances in the development and application of XAS methods to monitor material synthesis in real time under mechanochemical conditions. We demonstrate the generality of our approaches by describing mechanochemical syntheses of materials by both vibratory ball milling and by Resonant Acoustic Mixing (RAM), with a temporal resolution of up to 1 second per XAS spectrum. Moreover, we describe how spectroscopic methods can be coupled to diffraction-based approaches (Figure 1), thereby providing new dimensions in understanding mechanochemical synthesis [2].

Figure 1 Time-resolved-XANES (Au-LIII edge) (top) and time-resolved-XRD patterns (bottom) for the synthesis of Au NPs under ball milling conditions using hydroquinone (HQ) (A and B), ascorbic acid (AA) (C and D) and NaBH4 (E and F) as reducing agents. The black spectra in A, C and E correspond to the AuIII (HAuCl4·3H2O) and Au0 (foil) standards. The XRD patterns shown as the black traces in B, D, and F are data from ex situ measurements after the milling period.

1 F. Gomollón-Bel Chem. Int., 2019, 41 , 12 —17 2 P. F. M. de Oliveira et al. Chem. Commun., 2020,56, 10329-10332

Migration and speciation of anthropogenic uranium in natural soils Mr Simon Bayle1 1Université Côte D'azur, Orsay, France M3.1: Migration and speciation of anthropogenic uranium in natural soils, July 12, 2021, 17:30 - 17:40

Uranium is an actinide that is naturally present in rocks, soils and groundwaters. Anthropogenic activities such as mining and activities of the nuclear and the military industries can increase locally its concentration in these matrices. Anthropogenic sources of uranium in environment are a concern because of its potential radiological and chemical effects, and the associated risks to human and environmental health. As with other metals, the mobility of uranium depends on its physicochemical properties and distribution: understanding the initial mechanisms governing its mobilization and the speciation in natural matrices is thus essential for predicting its long-term behavior. In this framework, two approaches have been undertaken in parallel: a field study with natural samples containing anthropogenic uranium related to soil pollution, and a laboratory scale study. In the first one, bulk EXAFS of natural samples have been recorded at the U LII edge to pinpoint the uranium speciation as a function of depth. In the second approach we have reproduced, using model columns, the natural weathering of uranium in an environment similar to that of the natural field. X-Ray Fluorescence micro-Mapping coupled with spatial resolved EXAFS allowed to analyze at micrometer scale the migration and the speciation of uranium the underlying first millimeters away from the source term. The most important question in this approach is to assess if the mechanisms governing the behavior of uranium on short time scales (a few months to a year) within the column is representative of the field observations. Results highlight the evolution of uranium speciation as a function of migration depth (involving the key role of organic matter), the migration of uranium microparticles through soil from the deposit source term, and the leading role of soil composition in controlling both solid-phase and aqueous uranium speciation.

Kondo effect and crystal field properties of rare earths explored by XMCD measurements at ultra-low temperature Mr Weibin Li1,2, Dr Jean-Paul Kappler3, Dr Edwige Otero2, Dr Guy Schmerber3, Dr Fabrice Scheurer3, Prof Wolfgang Felsch4, Dr Philippe Sainctavit1,2 1Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Paris, France, 2SOLEIL Synchrotron, Gif-sur-Yvette, France, 3Institut de Physique et Chimie des Matériaux de Strasbourg, Strasbourg, France, 4Georg-August-Universität Göttingen, Göttingen, Germany M3.6: Kondo effect and crystal field properties of rare earths explored by XMCD measurements at ultra-low temperature, July 12, 2021, 17:50 - 18:00

In metals with magnetic impurities, one generally observes a minimum of electronical resistivity at low temperature, i.e., the resistivity diverges from the expected behavior for a pure metal. This is indeed what is observed for gold with impurities of ytterbium. With decreasing temperature below 10 K, the resistivity decreases by a power of 5 of T then reaches a minimum and then presents a logarithmic divergence. This behavior stems from the magnetic coupling of Yb spin magnetic moment with Au conduction electron, yielding a singlet because of an antiferromagnetic coupling. We study this phenomenon thanks to XAS (X-ray Absorption Spectroscopy) and XMCD (X-ray Magnetic Circular Dichroism) measurements at Yb M4,5 edges. Our sample contains 0.5% of Yb atoms in a Au matrix.

In order to perform this study, the first part of my work was the participation to the development of a 200 mK 3He-4He dilution cryogenic insert on the DEIMOS beamline of the synchrotron SOLEIL. This instrument allows to perform XAS and XMCD between 300 K and 200 mK, with an external magnetic field of up to 7 Tesla and for a sample in ultra-high vacuum ( mbar).

By recording the XAS and XMCD signals and developing an appropriate atomic model, we have been able to compute the experimental variation of the spin and orbit magnetic moments of Yb as a function of temperature and the external magnetic field. In addition, we have applied the magneto-optical sum rules and found that they nicely follow our model. On the other hand, crystal field calculations including multi-electronic Coulomb repulsions, spin-orbit coupling, and Zeeman interaction allow to compute the theoretical spin and orbit magnetic moments. From the comparison of the theoretical magnetic moments with the experimental ones, one detects the existence of the singlet state, consequence of the Kondo effect.

Temperature and time-resolved XANES studies of novel valence tautomeric cobalt complex Ms Svetlana Shapovalova1, Mr Alexander Guda1, Mr Michael Bubnov2, Mr Grigory Smolentsev3, Mr Yuri Rusalev1, Mr Viktor Shapovalov1, Mr Alexey Zolotukhin2, Mr Vladimir Cherkasov2, Mr Andrey Starikov4, Mr Valery Vlasenko5, Mr Alexander Soldatov1 1The Smart Materials Research Institute at the Southern Federal University, Rostov-on-Don, Russian Federation, 2G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, Nizhny Novgorod, Russian Federation, 3Paul Scherrer Institute, Villigen, Switzerland, 4Institute of Physical and Organic Chemistry, Southern Federal University, Rostov-on-Don, Russian Federation, 5Institute of Physics, Southern Federal University, Rostov-on-Don, Russian Federation M2.2: Temperature and time-resolved XANES studies of novel valence tautomeric cobalt complex, July 12, 2021, 15:30 - 15:40

Valence tautomers are characterized by different electron density distributions, where metal-to- ligand electron transfer accomplishes interconversion between tautomers [1]. These compounds are unique model systems that can help study electron transfer mechanisms and find applications as sensors and displays or storage and fast optical switching devices. Wherein the valence tautomeric (VT) interconversion can be thermally, magnetically or radiatively driven. Among transition metal complexes cobalt complexes with redox-active ligands have been shown to undergo a VT interconversion between high-spin (HS) and low-spin (LS) forms [2, 3]. This study is devoted to optical and x-ray structure characterization of novel (N-cyclohexyl-2- iminopyridine)(3,6-di-tert-butyl-o-benzosemiquinonato)(3,6-di-tert-butyl-catecholato) (Co2) cobalt complex. We have monitored the transition induced both by temperature and laser stimuli. Complexes were dissolved in toluene. X-ray pump-probe study was performed at the Super-XAS beamline of the Swiss Light Source, Villigen, PSI. A green nanosecond laser with 532 nm wavelength was operated at 150 kHz repetition mode. We accumulated an X-ray fluorescence signal for different delays after laser excitation pulse with 20 ns time resolution for each energy point. Then principal component analysis was applied for the whole data set. According to XANES, change in the cobalt oxidation and spin state can be observed when temperature decreases below 240 K. The time-resolved transient difference shown can be compared to the static difference obtained at low and high temperatures. Kinetics of the transient signal decay for 213 K can be approximated by a monotonic exponential decay with a characteristic time of 250±50 ns Theoretical characterisation showed decreasing Co-O, N bonds lengths during HS CoII to LS CoIII transition. The optical absorption spectra in the toluene solution with a VT transition from the HS CoII to LS CoIII state during cooling showed that VT transition temperatures for liquid lower than that in solid. The appearance of isosbestic points during cooling is strong evidence that only two different species are present in the solution [2]. Obtained results confirm the presence of a VT transition in the cobalt complex under study. Our measurements indicate that CoII is transformed into CoIII under temperature decrease while reverse transition can be induced both under the influence of temperatures and laser radiation.

[1] Pierpont, C. G. (2001). Coord. Chem. Rev. 216, 99. [2] Adams D.M., Hendrickson D.N. (1996). J. Am. Chem. Soc. 118, 11515. [3] Ash R., Zhang K., Vura-Weis J. (2019) J. Chem. Phys. 151, 104201.

This work was supported by Russian Foundation for Basic Research, project 18-02-40029. S.O. Shapovalova acknowledges her PhD support from Russian Foundation for Basic Research (RFBR #20-32-90046) for a travel opportunity.

The new beamline SOLABS for X-ray spectroscopy in the tender energy range at SOLARIS Dr Alexey Maximenko1, Prof Josef Hormes2,3, Dr Wantana Klysubun4, Dr Tonya Vitova5, Dr Piotr Ciochoń1, Prof Jost Göttert6, Dr Henning Lichtenberg6, Kevin Morris3, Dr Paweł Paweł1, Prof Alexander Prange3,6, Prof Jacek Szade1, Pongjakr Tarawarakarn4, M.Eng. Lasse Wagner6, Dr Marcin Zając1 1National Synchrotron Radiation Centre SOLARIS, Jagiellonian University , Kraków, Polska, 2Institute of Physics, Rheinische Friedrich- Wilhelm-University, Bonn, Germany, 3Center for Advanced Microstructures and Devices, Louisiana State University, Baton Rouge, USA, 4Synchrotron Light Research Institute, Nakhon Ratchasima, Thailand, 5Institute for Nuclear Waste Disposal, Karlsruhe Institute of Technology, Karlsruhe, Germany, 6Hochschule Niederrhein University of Applied Sciences, Krefeld, Germany T3.19: The new beamline SOLABS for X-ray spectroscopy in the tender energy range at SOLARIS, July 13, 2021, 19:00 - 19:10

At a bending magnet of the National Synchrotron Radiation Centre SOLARIS a new X-ray absorption spectroscopy (XAS) beamline called SOLABS (XAS-HN) is currently in the last phase of construction. Commissioning will start in summer 2021. The beamline is built by Hochschule Niederrhein University of Applied Sciences in collaboration with the Synchrotron Light Research Institute, the Physics Institute of Bonn University and SOLARIS. SOLABS will be a compact beamline optimized for the tender X-ray range without any windows between the source point and the monochromator in order to minimize absorption of low energy photons. The fixed exit beam Lemmonier type double crystal vacuum monochromator covers photon energies from ~1 to ~15 keV. Thus, among others the K-edges of important elements such as P, S, Si, Al and Mg will be accessible for measurements. Due to its straightforward and user-friendly concept SOLABS can be quickly aligned and easily operated. Motorized sample positioning will allow partly automated experiments, which can be easily handled by both experienced and new beamline users, even remotely. After commissioning, XAS spectra will be recorded in transmission mode, and implementation of fluorescence mode measurements using a SDD detector will follow till the end of 2021. As future upgrades surface-sensitive Electron Yield (TEY, CEY) measurements, in situ experiments and combinations of XAS with complementary techniques (e.g. IR) are planned. In summer 2022 a spectrometer for high energy resolution fluorescence detection will be installed in the framework of the EU project SYLINDA. SOLABS has a high potential to attract both academic and industrial users from various fields. We would like to thank the directors/president of the involved institutions – K. Desch, H.-H. von Grünberg, M. Stankiewicz, S. Sujitjorn. This project was partly supported within the grant 03-IHS-084 by the BMBF, Germany and within the EU Horizon2020 program (952148-Sylinda).

Newly established X-ray spectroscopy user endstation at ELI-Beamlines Dr Anna Zymaková1, Dr. Wojciech Błachucki2, Dr. Hab. Jakub Szlachetko2, Assoc. Prof. Jens Uhlig3, Dr. Jakob Andreasson1 1ELI Beamlines, 252 41 Dolní Břežany , Czech Republic, 2Institute of Nuclear Physics, Polish Academy of Sciences, 31-342 Kraków, Poland, 3Lund University, 221 00 Lund, Sweden M3.2: Newly established X-ray spectroscopy user endstation at ELI-Beamlines, July 12, 2021, 17:30 - 17:40

ELI-Beamlines is an intensely developing research facility located near Prague in the Czech Republic. The core idea of the facility is the development of ultra-high power lasers and technologies that utilize laser radiation to drive secondary sources for user applications. Ultrashort laser pulses, with a duration of only a few fs, allow researchers to trace and study ultrafast processes with high time resolution. A new X-ray spectroscopy end station, built in the E1 experimental hall, has recently delivered first scientific results (Zymaková et al., 2020), (Zymaková et al.). The station employs a Mo-anode X-ray tube for sample pre-characterization and steady-state experiments, and complementary Cu-tape (Zamponi et al., 2009) and water-jet plasma X-ray sources (PXS) (Miaja-Avila et al., 2018) for upcoming time-resolved experiments. The station is built in a von Hamos geometry (Szlachetko et al., 2012) and can be used for X-ray absorption and emission experiments. Implementation of a parallel XAS/XES operation scheme is ongoing. An optical spectroscopy end station with a TOPAS-prime parametric amplifier is prudently located in close vicinity allowing flexible tuning of the pump beam in a wide wavelength range. The talk will focus on the current state and give an overview of planned developments of the X-ray spectroscopy end-station. The development and results obtained using the water-jet PXS will be particularly emphasized. Recent progress in X-ray emission spectroscopy measurements on a number of relevant sample types, including liquid samples calibrated using calibration foils, will also be reported.

Miaja-Avila, L., O’Neil, G. C., Uhlig, J., Cromer, C. L., Dowell, M. L., Jimenez, R., Hoover, A. S., Silverman, K. L. & Ullom, J. N. (2018). Nat. Chem. 10, 355–362. Szlachetko, J., Nachtegaal, M., De Boni, E., Willimann, M., Safonova, O., Sa, J., Smolentsev, G., Szlachetko, M., Van Bokhoven, J. A., Dousse, J. C., Hoszowska, J., Kayser, Y., Jagodzinski, P., Bergamaschi, A., Schmitt, B., David, C. & Lücke, A. (2012). Rev. Sci. Instrum. 83, 103105. Zamponi, F., Ansari, Z., Korff Schmising, C. V, Rothhardt, S. P., Zhavoronkov, N., Woerner, M., Elsaesser, T., Bargheer, M., Trobitzsch-Ryll, T. & Haschke, M. (2009). Appl Phys A. 96, 51–58. Zymaková, A., Albrecht, M., Antipenkov, R., Špaček, A., Karatodorov, S., Hort, O., Andreasson, J. & Uhlig, J. To Be Publ. Zymaková, A., Khakurel, K., Picchiotti, A., Błachucki, W., Szlachetko, J., Rebarz, M., Uhlig, J. & Andreasson, J. (2020). J. Synchrotron Radiat. 27, 27.

Acknowledgements: This work was supported by the European Regional Development Fund [project No. CZ.02.1.01/0.0/0.0/16_019/0000789 (Adonis)], Project PAN-20-20 “Development of multipurpose liquid sample delivery system for X-ray spectroscopy applications” and Visegrad fund [project ID 22020037]

XAS and RXES studies of phase transitions in CuMo1-xWxO4 solid solutions Mrs Inga Pudza1, Dr. Aleksandr Kalinko2, Mr. Arturs Cintins1, Dr. Alexei Kuzmin1 1Institute of Solid State Physics, University of Latvia, Riga, Latvia, 2Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany T2.1: XAS and RXES studies of phase transitions in CuMo1-xWxO4 solid solutions, July 13, 2021, 15:30 - 15:40

CuMo1−xWxO4 solid solutions are multifunctional materials demonstrating remarkable properties, including thermochromic, piezochromic, halochromic, thermosalient and catalytic. Therefore, the structure-property relationship must be understood to learn how to control their functionality. At atmospheric pressure, pure CuMoO4 exists in two phases – low-temperature γ-phase with dark brown colour and high-temperature α-phase with green colour. The phase transition has a hysteretic behaviour. Furthermore, it is possible to tailor the properties of the molybdate by applying external pressure or by modifying its composition. Depending on the tungsten content, CuMo1−xWxO4 solid solutions can be obtained in phases isostructural to high-pressure CuMoO4. To understand the relationship between structural and thermochromic properties in CuMo1−xWxO4 solid solutions, we performed temperature and composition-dependent X-ray absorption spectroscopy study at the Cu and Mo K-edges and W L3-edge. Analysis of the Mo K-edge X-ray absorption near-edge structure (XANES) allowed us to determine the hysteresis of the phase transitions. Extended X-ray absorption fine structure (EXAFS) spectra were interpreted using reverse Monte Carlo modelling. The sensitivity of the resonant X-ray emission spectroscopy (RXES) was further used to study the α-to-γ phase transition in CuMo1- xWxO4 from a tungsten perspective. We extracted information on the crystal-field-induced splitting of the 5d(W) states from the W 2p3d RXES plane by analysing the high-energy resolution fluorescence detected X- ray absorption near-edge structure and off-resonant X-ray emission spectra. The experimental results were interpreted using ab initio calculations. It was found that an increase of tungsten content promotes the coordination change of molybdenum atoms from tetrahedral to octahedral which is accompanied by the material’s colour change from greenish to brownish. This study demonstrates the possibilities of the XAS and RXES techniques to probe coordination changes in functional thermochromic materials with controllable properties on the example of CuMo1−xWxO4.

The financial support provided by the Latvian Council of Science project No. lzp-2019/1-0071 is acknowledged.

Visualization of Structural Heterogeneities in Spinel Lithium Nickel Manganese Oxide Particle by Ptychography-XAFS Mr Hideshi Uematsu1,2,3, Assistant Professor Nozomu Ishiguro2,3,4, Mr Masaki Abe1,2,3, Mr Shutaro Takazawa1,2,3, Assistant Professor Jungmin Kang2,3,4, Assistant Professor Nguyen Duong Nguyen5, Professor Hien Chi Dam5, Dr Eiji Hosono6, Professor Masashi Okubo7, Professor Yukio Takahashi2,3,4 1Graduate School of Engineering, Tohoku University, Sendai, Miyagi, Japan, 2Riken SPring-8 Center, Sayo, Hyogo, Japan, 3International Center for Synchrotron Radiation Innovation Smart, Tohoku University, Sendai, Miyagi, Japan, 4Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, Japan, 5Japan Advanced Institute of Science and Technology, Nomi, Ishikawa, Japan, 6The National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan, 7Department of Electrical Engineering and Bioscience, School of Advanced Science and Engineering, Waseda University, Shinjuku-ku, Tokyo, Japan M2.8: Visualization of Structural Heterogeneities in Spinel Lithium Nickel Manganese Oxide Particle by Ptychography-XAFS, July 12, 2021, 16:00 - 16:10

Ptychography-XAFS, a combination of ptychography imaging using coherent X-ray and XAFS spectroscopy, is powerful tool for visualizing internal structures and distribution of chemical states of bulk materials on 10 nm scale [1, 2]. In this study, we visualize the chemical state and the heterogeneities in spinel lithium nickel-manganese oxide (LNMO) particles which are expected as the next-generation 5 V Li-ion battery cathode material. Furthermore, we discuss its distribution and domains with data mining, which affect the battery performance. Ptychography-XAFS measurements were performed at BL29XUL in SPring-8 (Hyogo, Japan). LNMO particles (1-5 µm size) were dispersed on a SiN membrane and mounted on piezo stages in a vacuum chamber. Incident X-ray beams were monochromatized by Si(111) monochromator and focused into 300 nm in size by KB mirrors on the sample position. Diffraction patterns were collected at X-ray energies between 6520 and 6589 eV (Mn K-edge), and between 8300 eV and 8381 eV (Ni K-edge), respectively. The absorption and phase images were reconstructed from the collected diffraction data at each energy by using an iterative phase retrieval calculation. The spatially-resolved XAFS of the LNMO sample at the Mn and Ni K-edge were successfully derived with the spatial resolution better than 80 nm. Then, the atomic density and the valence of Mn, them of Ni, and the electron density were estimated by the curve-fitting analysis of the spatially-resolved XAFS and the phase spectra. Data mining of the chemical maps was also performed and clarified the existence of three type of domains, which have different elemental compositions and chemical states. References [1] M. Hirose et al., Angew. Chem. Int. Ed. 130 (2018) 1490–1495. [2] M. Hirose et al., Communs. Chem. 2 (2020) 50.

Acknowledgement This work was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI (Grant Nos. JP17J01673, JP18H05253, JP19H05814 and JP20K15375). This work was also supported in part by “Dynamic Alliance for Open Innovation Bridging Human, Environment and Materials” from the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT).

How temperature impacts the multipole transitions probed in XAS and XRS Mr Steven delhommaye1, Mr Guillaume Radtke1, Mr Christian Brouder1, Mr Steve Collins2, Mr Simo Huotari3, Mr Cristoph Sahle4, Ms Delphine Cabaret 1Sorbonne Université, IMPMC UMR CNRS 7590, Paris, France, 2Diamond light source, Harwell Science and Innovation campus, Didcot, United Kingdom, 3Department of Physics, University of Helsinki, Helsinki, Finland, 4European Synchrotron Radiation Facility, Grenoble, France T3.4: How temperature impacts the multipole transitions probed in XAS and XRS, July 13, 2021, 17:40 - 17:50

This study aims to assess the thermal nuclei motion effects on the multipole transition channels involved in two core-level spectroscopies, X-ray Absorption Spectroscopy (XAS) and X-ray Raman Scattering (XRS). Nuclear thermal fluctuations are explicitly included in the spectra calculation using a method based on density functional theory that consists of averaging non-equilibrium configurations of the material at finite temperatures, which are determined from phonon calculations [1]. First, temperature effects on dipole 1s → p and monopole 1s → s transitions will be examined through the case of the Al K edge recorded at room temperature in α-Al2O3 using X-ray Raman scattering spectroscopy. Second, the temperature dependence of dipole 1s → p and quadrupole 1s → d contributions will be investigated through the XAS Ti K pre-edge structures in rutile TiO2. In that case, we will show how to circumvent difficulties that arise when calculating the natural dichroic signals at finite temperatures, when using methods based on averaging non-equilibrium atomic configurations such as the one used in this work. We will present a method to cancel the spurious contributions to the calculated dichroic signals that actually are related to the loss of symmetry inherent to this type of approach. These two cases allow to draw general conclusions regarding the effect of nuclear quantum fluctuations on the different transition channels available to both core-level spectroscopies.

[1] R. Nemausat, D. Cabaret, C. Gervais, C. Brouder, N. Trcera, A. Bordage, I. Errea and F. Mauri, Phys. Rev. B 92, 144310 (2015).

Unraveling the evolution of the local-coordination environment and metal oxidation state in a Mn-Mo bimetallic catalyst during exposure to a reactive atmosphere by temperature-resolved XAS Mr Wilson Henao1, Ms Maria Elena Martínez-Monje1, Prof. Gonzalo Prieto1, Dr Giovanni Agostini2 1Instituto de Tecnología Química (ITQ), CSIC-UPV, Valencia, Spain, 2ALBA-CELLS Synchrotron Light Facility, Cerdanyola del Vallès, Spain M3.22: Unraveling the evolution of the local-coordination environment and metal oxidation state in a Mn- Mo bimetallic catalyst during exposure to a reactive atmosphere by temperature-resolved XAS, July 12, 2021, 19:10 - 19:20

Understanding changes in the local structure and redox behavior of bimetallic materials during their exposure to aggressive gas atmospheres is essential in fields such as corrosion, batteries, and catalysis. Recently, we have developed an innovative bimetallic material based on molybdenum and manganese by using ammonium manganomolybdate complex NH4[Mn2Mo2O8(OH)(H2O)] as a starting precursor. The crystalline nature of this bimetallic complex allows the integration of both Mo and Mn within the same structure, which in some cases is difficult to achieve due to constrains imposed by their different chemical properties. X-ray diffraction shows that the crystalline structure (monoclinic C12/m1) of this solid evolves progressively into a rather amorphous material via other crystalline intermediates (oxides, nitrides, carbides) upon exposure to a reactive gas mixture containing CO, NH3 and H2 at increasingly high temperatures ranging from 100 ºC to 600 ºC. Further ex situ XAS experiments at the Mo and Mn K edges, performed at the ALBA-CELLS Synchrotron Light Facility (Spain), proved that the temperature-dependent transition in the local coordination symmetry around the Mo and Mn atoms, followed by the loose of long-range atomic order, took place alongside changes in the metal formal oxidation states (OS). The latter were quantified from the Mo-K and Mn-K absorption edge position in comparison to those in well-known standard materials by analysis of the first derivative of the XANES spectra. Nonetheless, OS-dependent differences in the monotony of the spectra at the absorption edge, as well as differences in the coordination sphere around the metals occurring in a carb-/nitr-idizing chemical environment, compared to oxidic standard compounds, shall be addressed. This study contributes towards the disentanglement of the relationship between the structural development of bimetallic centers and their redox properties in catalysis, and additionally underscores the obstacles in the classical assignment of oxidation states through XANES by this analytical method.

This work is funded by the Spanish Ministry of Innovation through project RTI2018-096399-A-100 (including PhD fellowship to W.H.) and the European Research Council (ERC-CoG- 864195, TANDEng).

In situ HERFD-XANES and X-ray scattering studies on the non-classical formation of CoO nano-assemblies in solution Mr. Lukas Grote1,2, Ms. Cecilia A. Zito1,3, Mr. Kilian Frank4, Dr. Ann-Christin Dippel2, Mr. Patrick Reisbeck4, Mr. Krzysztof Pitala5,6, Prof. Dr. Kristina O. Kvashnina7,8, Dr. Stephen Bauters7,8, Dr. Blanka Detlefs9, Dr. Oleh Ivashko2, Dr. Pallavi Pandit2, Mr. Matthias Rebber1, Mr. Sani Y. Harouna-Mayer1, PD Dr. Bert Nickel4, Prof. Dr. Dorota Koziej1 1University of Hamburg, Center for Hybrid Nanostructures, 22761 Hamburg, Germany, 2Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany, 3São Paulo State University UNESP, 15054000 São José do Rio Preto, Brazil, 4Ludwig-Maximilians- Universität München, Fakultät für Physik, 80539 Munich, Germany, 5AGH, University of Science and Technology, Faculty of Physics and Applied Computer Science, 30-059 Krakow, Poland, 6Academic Center for Materials and Nanotechnology, AGH University of Science and Technology, 30-055 Krakow, Poland, 7The Rossendorf Beamline at the European Synchrotron Radiation Facility ESRF, 38043 Grenoble, France, 8Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Resource Ecology, 01328 Dresden, Germany, 9European Synchrotron Radiation Facility ESRF, 38043 Grenoble, France M3.12: In situ HERFD-XANES and X-ray scattering studies on the non-classical formation of CoO nano- assemblies in solution, July 12, 2021, 18:20 - 18:30

Introduction The fabrication of complex nanomaterials requires the control of chemical reactions at various length scales. For this purpose, the classical crystallization theory is insufficient to properly describe the chemical reaction leading to monomer formation, the evolution of small primary particles, and how they assemble into superstructures. Here, we illustrate how the combination of advanced X-ray spectroscopic and scattering in situ studies probe length scales all the way from atomic to macroscopic, and shed light on the formation mechanism of CoO nanocrystal assemblies in solution under solvothermal conditions. Experimental methods and results High energy-resolution fluorescence-detected X-ray absorption near edge structure (HERFD-XANES) measurements are sensitive to subtle changes in the local chemical environment of the absorbing atom. We extend the in situ spectroscopic studies with FEFF simulations, which allows us to access straight to the molecular level of the reaction. The methods reveal that initially the organo-metallic cobalt precursor rapidly reduces and coordinates to oxygen atoms of two solvent molecules, forming a bis-adduct of the square-planar complex with octahedral coordination. Furthermore, we track subsequent structural changes with in situ total X-ray scattering and atomic pair distribution function (PDF) analysis, pinning down the transition from the dissolved Co complex to crystalline CoO. Ultimately, small-angle X-ray scattering (SAXS) uncovers the assembly process of the crystallites into distinct spherical superstructures. Discussion and Conclusion The concomitant growth and assembly of crystallites into a superstructure differentiates the investigated pathway from a classical mechanism. We find that small nuclei a few nanometers in size assemble into larger spheres. Nanocrystals and assemblies continue growing simultaneously. While the individual crystals develop various shapes, the polycrystalline assemblies retain a spherical morphology throughout the growth process. Thus, with the versatile combination of X-ray spectroscopy and scattering, we elucidate the emergence of nano-assemblies in solution with a broad perspective.

Recognition of bimetallic PtCu nanaparticles architecture using EXAFS Mrs Daria Tolchina1, Mr Leon Avakyan1, Mr Sergey Belenov2, Mrs Anastasia Alekseenko2, Ms Anaida Shaginyan1, Mr Vladimir Guterman2, Mr Lusegen Bugaev1 1Southern Federal University, Faculty of Physics, Rostov-on-Don, Russian Federation, 2Southern Federal University,Faculty of Chemistry, Rostov-on-Don, Russian Federation M2.6: Recognition of bimetallic PtCu nanaparticles architecture using EXAFS, July 12, 2021, 15:50 - 16:00

Current state of nanotechnology manufacturing allows to construct nanocomposites containing layered nanoparticles, in particular, core-shell nanoparticles. The properties of such particles may outreach the single-component ones. In particular, the usage of iron-core cementite shell nanoparticles allows to tweak their magnetic properties, and the application of silver-gold bimetallic nanopartilcles allows to control shape and wavelength of surface plasmon resonance. The considered bimetallic Pt-shell Cu-core nanoparticles show catalytic activity in the oxygen reduction reaction (ORR), comparable with that achieved using single-metal Pt particles. Also, the core-shell particles are more cheap comparing to pure-platinum particles, with higher durability characteristics. Further improvement of durability can be achieved in so called “gradient” nanoparticles with smooth component change in shell-to-core region [A. Alekseenko, V. Guterman, S. Belenov, et. al. International Journal of Hydrogen Energy, 43, 3676, 2018]. The identification of the structure (or “architecture”) of bimetallic nanoparticles is not a simple task. It can vary from mixture of independent particles, random solid solution (alloy), core-shell and gradient particles. The difference in the architectures should be reflected in pair radial distribution function of atoms (RDF), which, in turn, can be efficiently measured by EXAFS. In the present study we apply machine learning (ML) algorithms fitted on a wide range of synthetic RDF data, obtained from molecular dynamics simulations of 3D atomic models of nanoparticles with different size, composition and architecture. We showed high sensitivity of RDF towards the nanoparticles architecture: the correct recognition can be achieved in 99% test cases. The sensitivity towards composition and size is lower, giving ~50% and ~30% correct identifications. The application of ML to EXAFS derived RDFs provided expected answers for core-shell and gradient particles, but show high degree of Pt aggregation in PtCu alloy particles. The study is supported by Russian Science Foundation grant # 20-79-10211.

A laboratory-based X-ray absorption system with synchrotron-like performance Dr Yiyao Tian1, Dr Ruimin Qiao1, Dr Yi-Sheng Liu1, Ms Sylvia Lewis1, Mr S. H. Lau1, Dr Wenbing Yun1, Dr Srivatsan Seshadri1 1Sigray, Inc., Concord, United States M1.11: A laboratory-based X-ray absorption system with synchrotron-like performance, July 12, 2021, 09:20 - 09:30

X-ray absorption Spectroscopy (XAS) is predominantly performed at synchrotron facilities due to their high brightness and tunable energy x-ray beams [1]. However, difficulty in timely access, limited beamtime and challenging logistic issues limit the scope of their use and preclude the possibility of using them for routine measurements. Hence, there is significant need for a high throughput and high-performance laboratory based XAS system that enables academic and industrial researchers to perform routine XAS measurements and analyses on various samples. We have developed a compact, laboratory based, vacuum compatible XAS system operating in the ~4-10 KeV energy range that can be extended down to ~1.7KeV with synchrotron-like performance such as sub eV energy resolution in XANES and short data acquisition time (several minutes for concentrated samples). This performance is achieved by using 1) internally developed ultrahigh brightness, microfocus x- ray source with multiple targets, 2) highly efficient double paraboloid x-ray optics with a sharp high energy cutoff which allows for reduction of higher order harmonics, 3) single crystal x-ray crystal analyzers based on a) Johansson geometry for XANES which requires high energy resolution and b) HOPG mosaic crystal for EXAFS which can tolerate a more relaxed energy resolution (5-10 eV), and 4) an advanced high detection quantum efficiency (DQE) direct detection detector with high spatial resolution and multiframe readout capabilities. In this presentation, we will introduce recent developments in system design and innovations in greater detail and present data collected using this laboratory-based system comparing with synchrotron data.

References: [1] J. Yano, and V.K. Yachandra, X-ray absorption spectroscopy. Photosynth. Res. 102, 241 (2009)

Acknowledgment: The authors gratefully acknowledge funding from the NIH, National Cancer Institute for the development of the XANES system (R44CA228912).

Chemically Mapping Uranium Oxide Stoichiometry in Spent Nuclear Fuel Focused Ion Beam Sections using Oxygen K-edge Spectromicroscopy Dr Alexander Ditter1, Dr Danil Smiles1, Dr. Jason Harp2, Mr. Daniel Lussier1, Dr Michael Mara2, Dr Mitchell Meyer2, Dr Claude Delguedre3, Dr Lingfeng He2, Dr David Shuh1 1Lawrence Berkeley National Laboratory, Berkeley, United States, 2Idaho National Laboratory, Idaho Falls, United States, 3Lancaster University, Lancaster, United Kingdom T1.6: Chemically Mapping Uranium Oxide Stoichiometry in Spent Nuclear Fuel Focused Ion Beam Sections using Oxygen K-edge Spectromicroscopy, July 13, 2021, 08:50 - 09:00

[Abstract body] Spent nuclear fuel offers a unique window into the extreme chemical and thermal environment of nuclear fuel in the reactor. The oxidation of uranium in UO2 is particularly important because it results in volumetric expansion, creating cracks through which short-lived fission products can escape, and it affects the solubility and uptake of uranium in the environment. Oxygen K-edge spectroscopy is a highly sensitive probe of oxygen chemistry but requires samples thinner than 1 µm. This limitation was overcome by using a focused ion beam (FIB) to create thin lamellae of a spent nuclear fuel pellet. These FIB sections were then measured at the Scanning Transmission X-ray Microscope (STXM) at Beamline 11.0.2 of the Advanced Light Source (ALS). Results show that the bulk of the fuel is UO2, but U3O7 is concentrated around defects and intergranular cracks in the fuel, which is made clear through comparison with transmission electron microscopy. Spectra at the uranium N4,5 and cerium M4,5 edges were also measured. This work shows the value in coupling FIB sectioning with soft x-ray spectroscopy for chemical speciation imaging, particularly for spent nuclear fuel.

This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences (CSGB) Heavy Elements Chemistry program of the U.S. Department of Energy (DOE) under Contract Number DE-AC02-05CH11231 at LBNL.

The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 at LBNL.

A new HERFD-XAS imaging spectrometer at SSRL beam line 6-2 Dr Nicholas Edwards1, Dr Samuel Webb1, Dr. John Bargar1 1SLAC National Accelerator Laboratory, Pebble Beach, United States T1.9: A new HERFD-XAS imaging spectrometer at SSRL beam line 6-2, July 13, 2021, 09:10 - 09:20

A newly developed x-ray microprobe beamline at the Stanford Synchrotron Radiation Lightsource at the SLAC National Acceleratory Laboratory will be presented. This instrument combines micro SR-XRF and XAS, integrated with a high energy resolution fluorescence detection (HERFD) crystal analyzer. The combination of these techniques with the highly energy sensitive detector allows for the rapid location and imaging of particles and provides non-destructive analysis that gives chemical and structural information, as well as the distribution of phases across different particles at the micro-scale. This instrument has been developed primarily for application in the field of nuclear forensics, but is compatible with SSRL’s library of analyzer crystals, allowing for HERFD/imaging of a wide range of elements and absorption edges. We have used this instrument to develop detailed chemical signatures to provide links between the determination of molecular composition, morphological distribution, and nuclear fuel cycle processes.

Electrochemical Reaction Mechanism of High-Entropy Oxides in Li-ion Batteries Mr Otavio Marques1, Associate Professor Elena Timofeeva1, Professor Carlo Segre1 1Illinois Institute of Technology, Chicago, United States M1.8: Electrochemical Reaction Mechanism of High-Entropy Oxides in Li-ion Batteries, July 12, 2021, 09:00 - 09:10

High-entropy oxides (HEOs) have emerged as an alternative conversion electrode material for next- generation Li-ion batteries. The concept of entropy stabilization of numerous transition metal oxides (TMOs) in a single disordered solid solution opens new boundaries of materials design, providing the possibility of overcoming individual TMOs limitations by tailorable properties. Although conversion anode TMOs deliver high capacity due to multi-electron redox processes, they still suffer from large volume variation and severe structural changes, leading to electrode pulverization and drastic capacity fading. The contribution of each transition metal (TM) in the HEO structure to the electrochemical reaction and its structural stability is not yet well understood and prevents the rational design of HEOs. In this work, (MgCoNiCuZn)O anode materials were synthesized by solid state reaction and subsequent high energy ball milling. The system consists of five component bivalent ions sharing the same TM site in a rock-salt structure. Extended x-ray absorption fine structure (EXAFS) was used to investigate the change in the local structure around each TM in the pristine and galvanostatically cycled electrodes. The 1st, 2nd and 100th cycles in lithiated and delithiated states were studied, showing an initial capacity of ~550 mAh/g at a current density of 50 mA/g for the first couple of cycles, and ~650 mAh/g at100 mA/g after 100 cycles. Our preliminary data reveal significant changes from the initially octahedral coordination of each TM, giving us insights about the electrochemical and structural role of each component. In the lithiated state, Co, Cu and Ni are reduced to a metallic state. Subsequent delithiation shows that Co and Ni are re-oxidized to some degree while Cu remains unchanged. In this presentation we will discuss the structural analysis of the local environment of each TM with a focus on their individual roles in the electrochemical performance of the HEO anode.

Unraveling the depths of complex alloys with grazing exit XANES Mr Cafer Tufan Cakir1, Dr. A. Guilherme Buzanich1, Dr. Uwe Reinholz1, Prof. Dr. Christina Streli2, Dr. Martin Radtke1 1Bundesanstalt für Materialforschung und -prüfung, Unter Den Eichen 87, Germany, 2Vienna University of Technology, Vienna, Austria M3.11: Unraveling the depths of complex alloys with grazing exit XANES, July 12, 2021, 18:20 - 18:30

High entropy alloys (HEAs) are considered as a new class of alloys containing at least 5 elements with concentrations between 5 and 35 atomic percent. There has been a growing interest in HEAs in the material research field in recent years. Due to their adjustable composition, which enables the modifications of mechanical properties (such as hardness, strength and ductility etc) and their stability at high temperatures, HEAs have been the focus of various studies [1,2].

Especially the corrosion behavior of HEAs has been a wide research interest. Since the grazing exit X-ray fluorescence (GEXRF) offers a non-destructive way to collect notable information regarding the high temperature oxidation, we consider it as a useful method to investigate how HEAs behave in corrosive environments.

The main idea of grazing geometry is to enhance the fluorescence signal of the surface. This enables highly sensitive surface analyses of thin protective film on surface in sub-micrometer scale [3]. Position-sensitive area detectors provide information regarding the signal emitted from the sample as a function of emission angle and thus allow depth-sensitive analysis. Furthermore, the data collected from samples of an incidence energy which lays within a specific energy range provides XANES data to determine oxidation states. Moreover, since GEXRF profiles can also be simulated through physical models (Urbach 1999), they enable us to determine the layer thickness of a given sample in a non-destructive way.

Figure 1 The GEXRF profile (CrCoNi) Figure 2 The XANES of surface and bulk (CrCoNi)

In this contribution, we present the preliminary results of a conceptual study regarding layer properties of CrCoNi medium entropy alloy. The successful implementation of such methodological concept will pave the way for the investigation of more complex alloys with multiple layers, which is planned for the later phases of the project.

1) R. Kozak, A. Sologubenko,W. Steurer (2015). Zeitschrift für Kristallographie. 230. 2) M.Tsai & J. Yeh (2014). Materials Research Letters. 2:3. 107-123. 3) Y. Kayser, J. Szlachetko, D. Banaś, W. Cao, J.-Cl. Dousse, J. Hoszowska, A. Kubala-Kukuś, M. Pajek (2013). Spectrochimica Acta Part B: Atomic Spectroscopy. 88.

Araucaria: A Python library to analyze XAFS spectra Dr Marco Alsina1, Mr Samuel Wallace2, Dr Morgane Desmau3, Professor Jean-François Gaillard2 1University Of Talca, Curicó, Chile, 2Northwestern Univeristy, Evanston, USA, 3Deutsches Elektronen-Synchrotron, Hamburg, Germany M1.4: Araucaria: A Python library to analyze XAFS spectra, July 12, 2021, 08:40 - 08:50

Meaningful interpretation of x-ray absorption fine structure (XAFS) spectra requires a series of steps ranging from data pre-processing and spectral normalization to analysis using a given set of numerical techniques. Although several commercial and open-source software are available to perform XAFS spectral analysis, most of them focus on graphical user interfaces (GUI) to manipulate data. While convenient for upcoming users, such approaches are ill-suited for systematic processing of large datasets, including spectra produced by continuous/quick scanning modes. In addition, GUI-based software is not readily extensible without proper knowledge of its inner workings.

Here we introduce Araucaria, a library written in the Python language and designed to be light-weight, modular, robust, and readily extensible. The library includes functions to read/write spectra in plain file formats, accessing and storing data in binary format, produce publication-ready plots, and perform routine tasks on XAFS spectra, including calibration, alignment, merge, normalization, and background removal. In addition, araucaria offers classes and functions to perform exploratory data analysis, linear algebra operations, and state of the art routines such as automatic deglitching of spectra.

The library is well suited for researchers requiring systematic analysis of large XAFS datasets. In addition, it allows communication of fully reproducible results through Python code and web-based formats such as Jupyter notebooks. This last feature has also been used for production of enriched documentation and tutorials, which should prove valuable for researchers interested in using the library.

Araucaria also supports integration with advanced Python libraries for machine learning and interactive visualization, allowing researchers to extend functionality and develop their own routines within a single programming ecosystem. Future work is aimed at allowing spectral analysis through ab-initio methods.

Support for this research was provided by the Chilean Agency of Research and Development (ANID) through a Research Grant (Fondecyt Project N° 11190622).

Evidence of Irreversible Dynamic Changes of Mixed Metal Oxides During Oxygen Evolution Reaction from X-ray Absorption Spectroscopy Dr Jiyun Hong1, Samji Samara2, John Carl A. Camayang2, Eranda Nikolla2, Simon R. Bare1 1SLAC National Accelerator Laboratory, Stanford, United States, 2Wayne State University, Detroit, United States T1.7: Evidence of Irreversible Dynamic Changes of Mixed Metal Oxides During Oxygen Evolution Reaction from X-ray Absorption Spectroscopy, July 13, 2021, 09:00 - 09:10

Systematic development of electrocatalysts for the anodic oxygen evolution reaction (OER) remains critical for sustainable energy conversion and storage technologies including electrochemical water splitting, 1,2 CO2 electro-reduction and metal-O2 batteries. Non-stoichiometric mixed metal oxides belonging to the perovskite family of the general form An+1BnO3n+1 (A=alkali/rare earth metal; B=transition metal; n=1 ) remain attractive due to their high crystallinity, as well as their ability to accommodate >90% of all metals.3,4 In this presentation, we show that dynamic changes of the surface structure of these oxides occur during OER. This is demonstrated through a series of oxides with varying A and B-site cationic compositions and global crystal symmetries. Changes in the electronic structure and local coordination environment of the metal cations in the oxides with electrochemical cycling were measured using X-ray absorption spectroscopy (XAS). The catalytically active B-site cations on the surface were found to undergo irreversible structural changes as identified by extended X-ray absorption fine structures and X-ray absorption near edge structure analyses. The extent of change in the surface layers of the oxide electrocatalysts was quantified as a function of electrochemical testing. These structural insights gained from XAS were supported by cation leaching experiments using inductively coupled plasma mass spectrometry and oxide surface characterization via scanning transmission electron microscopy. These findings from advanced characterization of these complex oxide electrocatalysts provide important insights into their dynamic nature under OER conditions – knowledge that can play a pivotal role in guiding their design and application.

References: 1. Gu, X., Samira, S., Nikolla, E., Chem. Mater., 2018, 30, 2860-2872. 2. Samira, S., Deshpande, S., Greeley, J., Nikolla, E., et al., ACS Energy Lett., 2021, 6, 665-674. 3. Samira S., Gu, X., Nikolla, E., et al., ACS Catal., 2019, 9, 10575-10586. 4. Gu, X., Camayang, J.C.A., Samira, S., Nikolla, E., J. Catal., 2020, 388, 130-140.

We gratefully acknowledge the primary financial support from the United States Department of Energy (DOE), Basic Energy Science (BES), Chemical Sciences, Geosciences, and Bio- sciences Division, under award number DE-SC0020953.

Unsupervised Machine Learning and Chemical Classification in X-ray Absorption Spectroscopies Ms Samantha Tetef1, Mr Niranjan Govind2, Mr Gerald Seidler1 1University Of Washington, Seattle, United States, 2Pacific Northwest National Laboratory, Richland, United States T1.20: Unsupervised Machine Learning and Chemical Classification in X-ray Absorption Spectroscopies, July 13, 2021, 10:00 - 10:10

We report a comprehensive computational study of unsupervised machine learning (ML) for extraction of chemically relevant classification from X-ray absorption near edge structure (XANES) and valence-to-core X-ray emission spectra (VtC-XES) of a broad survey of sulforganic compounds.1 Specifically, we introduce a variational autoencoder (VAE) neural network and t-distributed stochastic neighbor embedding (t-SNE) to the field. Although there is previous work in the XAFS community using supervised ML1, unsupervised ML has not been used to extract the chemically relevant information. Unsupervised ML removes preconceived biases about information content and facilitates direct comparison of information encoded in XANES versus that encoded in VtC-XES. Unsupervised dimensionality reduction routines extract the most relevant information encoded in datasets. Thus, we trained dimensionality reduction algorithms on both XANES and VtC-XES spectra of sulforganic compounds, simulated using time-dependent density functional theory (TD-DFT) with NWChem. By progressively decreasing the constraints of the algorithm, moving from a linear mapping, i.e., principal component analysis (PCA), to VAE (a nonlinear mapping), to finally t-SNE (a nonlinear embedding), we find improved sensitivity to steadily more refined chemical information. The chemical classification sensitivity of these methods was obtained by applying supervised ML to the three reduced spaces to partition the space and thus acquire classification accuracies. Surprisingly, when representing spectra in merely two dimensions, t-SNE distinguishes not just oxidation state and general sulfur bonding environment but also the aromaticity of the bonding radical group with 83% accuracy. We find a strong similarity between the chemical information encoded in XANES versus VtC-XES. However, VtC-XES yields slightly stronger encoding due to its larger variation in spectral features. Our results suggest t-SNE as a promising model for unbiased classification, not only for X-ray absorption spectroscopy, but for other one-dimensional spectroscopy methods. Moreover, this study exemplifies the value of unsupervised ML as a precursor to supervised ML.

1. Tetef, S; Govind, N.; Seidler, G.T.; Unsupervised Machine Learning and Chemical Classification in X- ray Absorption Spectroscopies. Submitted 2021. 2. Timoshenko, J.; Lu, D. Y.; Lin, Y. W.; Frenkel, A. I., Supervised Machine-Learning-Based Determination of Three-Dimensional Structure of Metallic Nanoparticles. Journal of Physical Chemistry Letters 2017, 8 (20), 5091-5098.

We acknowledge funding from NRT-DESE: Data Intensive Research Enabling Clean Technologies (DIRECT) under grant no. NSF #1633216. This research benefitted from computational resources (Cascade) provided by the Environmental Molecular Sciences Laboratory (EMSL), a DOE Office of Science User Facility sponsored by the Office of Biological and Environmental Research and located at PNNL.

Expanding the working range of actinide M5-edge HR-XANES spectroscopy: Speciation of 1 ppm-140 ppm neptunium adsorbed on clay Ms Bianca Schacherl1, Dr. Claudia Joseph1, Mr Aaron Beck1, Dr. Tim Prüssmann1, Dr. David Fellhauer1, Dr. Jun-Yoep Lee1, Dr. Kathy Dardenne1, Dr. Jörg Rothe1, Prof. Dr. Horst Geckeis1, Dr. Tonya Vitova1 1Karlsruhe Institute Of Technology (KIT) - Insitute For Nuclear Waste Disposal (INE), P.O. Box 3640, D-76021 Karlsruhe, Germany M3.10: Expanding the working range of actinide M5-edge HR-XANES spectroscopy: Speciation of 1 ppm-140 ppm neptunium adsorbed on clay, July 12, 2021, 18:10 - 18:20

A deep geological disposal within a multi-barrier system is proposed to safely isolate the high-level radioactive waste from the biosphere. Clays are considered as potential host rock and backfill materials. The focus of this work is understanding the interaction between illite, a clay mineral present in several clay host rocks, and Np-237, a radionuclide present in high-level waste. X-ray absorption spectroscopy (XAS), especially the recently emerged actinide (An) M4,5-edge high-energy resolution X-ray absorption near edge structure (HR-XANES) technique [1], are very powerful experimental tools for characterization of the Np speciation on mineral surfaces. This study investigates the redox-speciation and the atomic environment of Np sorbed onto -6 illite (Illite du Puy [2], 6.94 wt.% Fe2O3) for samples from batch sorption (c0(Np(V)) = 1×10 mol/L to 1×10-8 mol/L, pH 5, 7, and 9, I = 0.1 mol/L NaCl, S/L = 2 g/L, contact time 11 to 811 days) and diffusion -5 experiments (I = 0.1 mol/L NaCl, pH 5, source reservoir c0(Np(V)) = 1.4·10 mol/L, L = 11.5 mm, Ø = 25.6 mm, 3 ρbulk = 1700 kg/m , t = 1060 days). Different spectroscopic (Np M5–edge HR-XANES, Np L3–edge extended X- ray absorption fine structure, Fe K-edge XANES and Mößbauer) and microscopic techniques (scanning electron (SEM), transmission electron (TEM) and fluorescence microscopy) were applied. For the first time, Np M5-edge HR-XANES spectroscopy was applied to study Np sorbed onto illite. By improving the experimental conditions, it was possible to achieve spectra of samples with ≈ 1 µg Np/g illite (1 ppm) at the CAT-ACT beamline for catalysis and actinide science at the Karlsruhe research accelerator (KARA) at KIT, Karlsruhe [3]. This is 50 to 1000 times lower than loadings usually studied by conventional XANES. A newly designed cryogenic set-up allowed suppressing beam-induced changes of the Np oxidation state. By the application of the above described complementary spectroscopic and microscopic techniques a partial reduction of Np(V) to Np(IV) and Np coordinated to Fe-OH groups was found. Potential mechanisms of Np(IV) formation in the system will be discussed. Reduction of Np(V) to Np(IV) could be caused by structural

Fe(II), organic matter or thermodynamic stability of a Np(IV) sorption species depending on pH and Eh. The described innovative approach paves the way for efficient An M4,5-edge HR-XANES studies on samples from actinide contaminated sites or representative for safety case scenarios in the context of nuclear waste repositories in deep geological formations.

Acknowledgements: We thank the Institute for Beam Physics and Technology (IBPT), KIT for the operation of the storage ring, the Karlsruhe Research Accelerator (KARA). This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 847593.

References [1] T. Vitova, I. Pidchenko, D. Fellhauer et al., Nat. Commun. 8, (2017). [2] M. A. Glaus, M. Aertsens, C. A. J. Appelo et al. Geochim. Cosmochim. Acta 165: 376–88 (2015). [3] A. Zimina, K. Dardenne, M. A. Denecke et al., Rev. Sci. Instrum. 88, 1 (2017).

Important role of open copper sites on adsorption of various molecules in Cu-BTC metal organic framework Dr Iuliia Mikulska1, Dr Roberto Boada1,2, Dr Shusaku Hayama1, Dr Matteo Aramini1, Dr Luke Keenan1, Dr Monica Amboage1, Dr Sofia Diaz-Moreno1 1Diamond Light Source Ltd., Didcot, United Kingdom, 2Chemistry Department, Faculty of Science, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Barcelona, Spain M3.26: Important role of open copper sites on adsorption of various molecules in Cu-BTC metal organic framework, July 12, 2021, 19:30 - 19:40

Cu-BTC metal-organic framework (MOF) has been found to be a promising candidate for removing hazardous substances from air via adsorption1. To understand the role that the copper sites in Cu-BTC play in the adsorption process, we have performed a detailed X-ray absorption spectroscopy (XAS) study. Conventional XAS and high energy resolution fluorescence detection XAS (HERFD-XAS) were collected on degassed Cu-BTC, and after being exposed to CO2, water and benzene. The EXAFS analysis reveals that, although the local environment around the copper centers in all samples is similar, differences can be found in the first and second coordination shells. We have found that the Cu-O distance in the first coordination shell is slightly larger when the sample is immersed in water and benzene than in the degassed sample, while it does not change for the sample exposed to CO2. Small differences are also observed in the Cu-Cu distance, gradually increasing from 2.49 Å in the degassed sample, to 2.52 Å, 2.58 Å and 2.63 Å upon adsorption of CO2, benzene and water, respectively. HERFD-XAS has been used to obtain information about the electronic and geometric structure around the copper metal centers, as the use of high energy resolution enhances the features in the XANES spectrum enabling the detection of subtle changes2. We have observed differences in the intensity and the energy position of some of the XANES spectral features upon adsorption of different adsorbates that can be attributed to changes in the local environment around the copper centers, as detected in the EXAFS analysis. In this study we show that XAS is a powerful and very sensitive tool for studying host-guest interactions in MOFs, providing atomic-level insights into adsorption mechanisms.

1. V.Chevalier et al., J. Env.Chem. Eng. (2019), 7, 103131. 2. P.Glatzel and U.Bergmann, Coord. Chem. Rev. (2005), 249, 65.

Femtosecond energy transfer in Fe(II)-Co(III) photocatalyst directly observed with X- ray emission spectroscopy Mr Tae-Kyu Choi1, Mrs Marina Huber-Gedert2, Dr Michał Nowakowski2, Dr Ahmet Kertmen3, Prof. Dr. Jacek Kubicki3, Prof. Dr. Matthias Bauer2, Prof. Dr. Wojciech Gawelda4,5,3 1European XFEL, Schenefeld, Germany, 2Universität Paderborn, Paderborn, Germany, 3Adam Mickiewicz University, Poznań, Poland, 4Universidad Autónoma de Madrid, Madrid, Spain, 5Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Madrid, Spain T3.11: Femtosecond energy transfer in Fe(II)-Co(III) photocatalyst directly observed with X-ray emission spectroscopy, July 13, 2021, 18:20 - 18:30

Modeling the bimetallic photocatalyst especially without any noble-metal element demands a clear understanding of how the incident photon energy transforms efficiently into useful chemical energy. An excited electron in the photoactive moiety could be transferred to the catalytic moiety, or activate it via an energy transfer, on the so-called ultrafast timescale. Herein we show and discuss our recent results of femtosecond-resolved X-ray emission spectroscopy measurements on the Fe(II)-Co(III) photocatalyst at SACLA. Upon 515 nm photoexcitation, both Fe Kα1 and Co Kα1 transient emission signal kinetics revealed the same 110 fs arising time constant, indicating that both moieties are coupled. Subsequently, the 8 ps (3MLCT/MC; the triplet Metal-to-Ligand Charge Transfer/Metal- Centered state) and 2.5 ps (S=1/2; the doublet Co(II) excited state) decay dynamics appeared in the Fe Kα1 and Co Kα1 transient signal kinetics respectively, unveiling that the excited electron in the MLCT state of the Fe(II) moiety spontaneously perturbed the Co(III) moiety by the energy transfer, letting an excessive electron from its dimethylglyoxime (dmgH) ligand be transferred on the Co(III) metal ion. The resulting Co(II) photoactivated complex leads to the twice faster photocatalytic proton reduction compared to the corresponding two-component system.

T.-K.C. acknowledges support from the International Max Planck Research School for Ultrafast Imaging and Structural Dynamics (IMPRS-UFAST) and the European XFEL. M.H.-G. thanks the Fonds der Chemischen Industrie for a Kekulé grant. A.K. and W.G. acknowledge funding from Narodowe Centrum Nauki through SONATA BIS 6 grant (2016/22/E/ST4/00543). W.G. further acknowledges funding from Comunidad de Madrid and Universidad Autónoma de Madrid through Proyecto de I+D para Investigadores del Programa Beatriz Galindo (SI2/PBG/2020-00003), Spanish MICIU through Proyecto de I+D+i 2019 (PID2019-108678GB- I00) and IMDEA-Nanociencia through Severo Ochoa Programme in R&D (SEV-2016-0686).

57Fe nuclear resonance scattering on the H-cluster of [FeFe]-hydrogenase Dr Michael Haumann1 1Freie Universität Berlin, Berlin, Germany

The H-cluster of [FeFe]-hydrogenase enzymes is nature´s blueprint for efficient hydrogen formation catalysis. It consists of a [4Fe-4S]-cluster linked to a unique diiron complex, which is the active site of H2 formation. We used nuclear resonance vibrational spectroscopy (NRVS) and nuclear forward scattering (NFS) to study the H- cluster in purified [FeFe]-hydrogenase protein. The cofactor was selectively labeled with 57Fe at the [4Fe-4S] cluster, the diiron site, or at both sub-complexes, which facilitated site-selective nuclear resonance experiments. Clear attribution of vibrational bands was achieved, using quantum-mechanics/molecular- mechanics (QM/MM), as well as statistical approaches to compare experimental and computational data. Thereby, assignment of redox and protonation patterns, as well as binding of hydride species at the iron centers in various cofactor species was achieved.1,2,4 The results aid to the formulation of mechanistic schemes for catalysis and potential regulatory reactions at the H-cluster, thereby improving our understanding of biological hydrogen production.3

[1] S. T. Stripp, S. Mebs, M. Haumann, Temperature dependence of structural dynamics at the catalytic cofactor of [FeFe]-hydrogenase. Inorg. Chem. 59, 16474–16488 (2020) [2] S. Mebs, J. Duan, F. Wittkamp, S. T. Stripp, T. Happe, U.-P. Apfel, M. Winkler, M. Haumann. Differential protonation at the catalytic six-iron cofactor of [FeFe]-hydrogenases revealed by 57Fe nuclear resonance scattering and QM/MM analysis. Inorg. Chem. 58, 4000-4013 (2019) [3] M. Haumann, S. T. Stripp. The molecular proceedings of biological hydrogen turnover. Acc. Chem. Res. 51, 1755-1763 (2018) [4] S. Mebs, R. Kositzki, J. Duan, L. Kertess, M. Senger, F. Wittkamp, U.-P. Apfel, T. Happe, S. T. Stripp, M. Winkler, M. Haumann. Hydrogen and oxygen trapping at the H-cluster of [FeFe]-hydrogenase revealed by site-selective spectroscopy and QM/MM calculations. Biochim. Biophys. Acta 1859, 28-41 (2017)

Magnetic properties of binary ferrofluids investigated by RIXS-MCD spectroscopy Miss Malika Khelfallah1, Mrs Sophie Neveu2, Mr James Ablett3, Mr Vincent Dupuis2, Ms Niéli Daffé1,2,3, Mr Guillaume Gouget1,2, Mr Marcin Sikora4, Mr Philippe Sainctavit1,3, Ms Hebatalla Elnaggar1, Mrs Claire Carvallo1, Mr Dario Taverna1, Mrs Amélie Juhin1 1IMPMC, Paris, France, 2PHENIX, Paris, France, 3Synchrotron SOLEIL, Saint-Aubin, France, 4AGH University of Science and Technology, Kraków, Poland T3.5: Magnetic properties of binary ferrofluids investigated by RIXS-MCD spectroscopy, July 13, 2021, 17:50 - 18:00

Ferrofluids are suspensions of magnetic nanoparticles in a liquid, which have found numerous applications in biomedicine (magnetic hyperthermia, improved MRI agents…), technology (magnetic recording, permanent magnets…) or fine arts. Intriguing macroscopic properties of ferrofluids arise from their nanoscale structuring: when the magnetic dipolar interparticle interaction are large enough, particles assemble in chains and rings even in the absence of a magnetic field (Fig. 1). These assemblies turn into microsized chains when an external magnetic field is applied. Variation of the nanoparticle size, shape and composition (e.g., hard or soft magnetic material) changes the magnetic anisotropy, which plays a crucial role in magnetic dipole interactions. This results in a modification of the structuring of ferrofluids as well as their collective magnetic properties like coercivity, magnetic saturation or remanence. Understanding and controlling interparticle interactions could lead to improving the efficiency of known ferrofluids for applications and the discovery of novel magnetic responsive materials. Magnetic binary ferrofluids, i.e. those composed of two types of nanoparticles with different magnetic anisotropy, are particularly appealing because they offer an unprecedented interplay of magnetic dipole interactions. However, bulk magnetometry only allows to probe the average magnetic properties of the ferrofluid, which preventing from selectively measuring the contribution of each component. There is therefore a need for chemically selective magnetic measurements, which can be realized using Resonant Inelastic X-ray Scattering spectroscopy combined with X-ray Magnetic Circular Dichroism with hard x-rays (RIXS-MCD, [1]). Element selective magnetization curves detected by RIXS-MCD have been measured at the GALAXIES beamline of the SOLEIL synchrotron on binary ferrofluids with different particle size, shape and composition (Fig 2.). Zero Field Cooled and Field Cooled magnetic measurements have been performed to investigate how the structuring induced by an external magnetic field modifies the measured collective properties. Ferrofluid samples have been measured in the frozen state using a dedicated cryo liquid cell [2] which is inserted between the poles of an electromagnet. RIXS-MCD experiments are complementary to bulk magnetometry and First Order Reversal Curve diagram measurements of collective magnetic properties. Combined with the information obtained from Cryogenic Transmission Electron Microscopy and Electron Holography regarding the structuring, our results pave the way for a better understanding of the relationship between magnetic properties and structuring of binary ferrofluids.

Figure 3: Cryo-Transmission Electron Microscopy image of CoFe2O4 nanoflowers in Figure 2: RIXS-MCD hysteresis loop and spectra for a water binary ferrofluid composed of CoFe2O4 and MnFe2O4 nanoflowers.

References: [1] M. Sikora, A. Juhin, T.-C. Weng, P. Sainctavit, C. Detlefs, F. de Groot and P. Glatzel Physical Review Letters, 105,037202 (2010). [2] N. Daffé, J. Zečević, K. N. Trohidou, M. Sikora, M. Rovezzi, C. Carvallo, M. Vasilakaki, S. Neveu, H. Meeldijk, N. Bouldi, V. Gavrilov, Y. Guyodo, F. Choueikani, V. Dupuis, D. Taverna, Ph. Sainctavit, and A. Juhin. Nanoscale 12, 11222-11231 (2020).

[We acknowledge funding from Agence Nationale de la Recherche under grant number ANR- 17-CE30-0010- 01.]

Laboratory-XAFS and its application fields at the Technische Universität Berlin Mr Sebastian Praetz1, Dr. Christopher Schlesiger1, Dr. Wolfgang Malzer1, Prof. Dr. Birgit Kanngießer1 1Technische Universität Berlin, Berlin, Deutschland T3.12: Laboratory-XAFS and its application fields at the Technische Universität Berlin, July 13, 2021, 18:20 - 18:30

High resolution X-ray absorption fine structure spectroscopy (XAFS) is a frequently used method for chemical speciation, such as the oxidation state or coordination of functionalized materials or biomolecules. This technique is usually performed at synchrotron radiation sources because of the need of a brilliant X-ray source and a high spectral resolving power. Compared to the well-established synchrotron based XAFS, a laboratory setup has the advantage of higher accessibility and flexibility, which open this technique for routine analysis e.g. in catalysis and environmental research or industrial applications.

We have successfully developed an X-ray tube based von Hámos spectrometer using a graphite mosaic crystal, called Highly Annealed Pyrolytic Graphite (HAPG), as dispersive element. With this HAPG it is possible to perform X-ray absorption spectroscopy in a laboratory setup without the need of a high brilliant synchrotron radiation source and with a wide energy range of 4 keV to 15 keV [1,2]. Even with the limited spectral resolving power up to E/ΔE=4000 in the first order of reflection, the method is attractive for everyday analysis for material, chemical and biomedical science such as the determination of the composition of amorphous materials, like minerals and catalysts, or liquids like contrast agents for medical use.

Within this contribution we will present an overview of the current laboratory setup as well as present and possible future applications. The applications vary from determination of oxidation states in the field of catalysis research [3,4,5] over the determination of chromium species in filter materials for wastewater treatment to the quantitative chemical speciation in minerals via linear combination of references spectra. The emphasis will be on the specific scientific question, circumstances and approaches with the laboratory spectrometer and evaluation schemes.

References: [1] C. Schlesiger et al., J. Anal. At. Spectrom. (30), 2015, 1080-1085. [2] C. Schlesiger et al., J. Anal. At. Spectrom. (35), 2020, 2298-2304. [3] M. Dimitrakopoulou et al., Faraday Discuss., 2017. [4] X. Zhao et al., J. Am. Chem. Soc. 141, 2019, 6623–6630. [5] P. W. Menezes et al., Angew. Chem. Int. Ed. 2019, 58, 16569.

X-ray absorption spectroscopy at SOLARIS for industrial applications dr Piotr Ciochoń1, dr Marta Avila2, prof. Josef Hormes3,4, dr Henning Lichtenberg5, dr Alexey Maximenko1, prof Alexander Prange3,5, dr Alejandro Sanchez2 1National Synchrotron Radiation Centre SOLARIS, Jagiellonian University, Kraków, Poland, 2ALBA Synchrotron Light Source, Cerdanyola del Vallès, Barcelona, Spain, 3Institute of Physics, Rheinische Friedrich-Wilhelm-Universit, Bonn, Germany, 4Center for Advanced Microstructures and Devices, Louisiana State University, Baton Rouge, United States of America, 5Hochschule Niederrhein University of Applied Sciences, Krefeld, Germany M3.20: X-ray absorption spectroscopy at SOLARIS for industrial applications, July 12, 2021, 19:00 - 19:10

Despite a large number of X-ray absorption spectroscopic studies conducted in collaboration with industrial partners, successful operation of synchrotron beamlines dedicated to applied science and various concepts developed to address specific demands of commercial users, XAS is still not considered a standard, routine method for industrial research. While, the possibilities of applying XAS to solving various technological problems and developing new products and processes seem very wide, only few facilities offer access to a full service, encompassing both measurements and advanced data analysis, with the goal of actually answering questions from industrial clients. In the framework of the EU project Sylinda (Synchrotron Light Industry Applications), researchers at the light sources SOLARIS (Poland) and ALBA (Spain), Hochschule Niederrhein University of Applied Sciences (Germany), and Rheinische Friedrichs-Wilhelms-Universität Bonn (Germany), are aiming at establishing a full industrial service for high-resolution X-ray absorption spectroscopy, which will include the possibility of studying low-Z elements such as P, S, Si, Al and Mg. With a new, user-friendly X-ray beamline, which can be quickly aligned, easily operated and which is equipped with a fluorescence spectrometer with high energy resolution, SOLARIS can become a favored synchrotron facility for cooperation with commercial companies, especially SMEs. Here, we present several applications of X-ray absorption spectroscopy of low-Z elements, with industrial relevance, specifically in the field of biotechnology, environmental engineering, energy, oil&gas and rubber industries from the perspective of an Industry Liaison Officer from SOLARIS synchrotron. Combining the experience of the project partners, we show that solving problems from industrial users requires often different solutions and approaches, than the ones applied for basic science research. The toolbox, being now developed in the Sylinda project, can be used to offer tailored services for industrial users, boosting innovation, as well as societal and economic impact of large research facilities.

Sylinda project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 952148.

New developments at the MARS beamline of Synchrotron SOLEIL Dr Denis Menut1, Dr Myrtille O.J.Y. Hunault1, Dr Pier Lorenzo Solari1, Mr Hervé Hermange1 1Synchrotron SOLEIL, Gif-Sur-Yvette, France T3.6: New developments at the MARS beamline of Synchrotron SOLEIL, July 13, 2021, 17:50 - 18:00

MARS (Multi-Analyses on Radioactive Samples) beamline at the French synchrotron SOLEIL is devoted to advanced structural and chemical characterizations of radioactive matter (solid or liquid) using hard X-rays (3-35keV). Since its commissioning in 2010, capabilities for synchrotron-based radionuclides and actinides sciences have been continuously expanded, driven by users’ need. Since 2019, the beamline is licensed to accept sample holders with radio-activities up to 18.5 GBq for experiments at ambient pressure and temperature. For experiments at high pressures, high temperatures, low temperatures or with in situ chemical reactions, a licensing for activities up to 200 times the exemption limit is expected for 2022. Two experimental stations are available: a 4-circle High-Resolution diffractometer allowing powder diffraction, surface analyses with combined texture and residual-stress analysis, reflectometry and reciprocal space mapping; and a multimodal station allowing to perform combined analyses with X-ray absorption and emission spectroscopies (XANES, EXAFS, HERFD-XANES, XRF) as well as diffraction and scattering measurements (SAXS/WAXS) using a Pilatus 2M detector, and equivalent X-ray microbeam techniques. Concomitantly, a dedicated motorized stage for 2D detectors and specific instrumentation has been developed. Both end stations are equipped with removable shieldings designed in collaboration with CEA for the study of highly irradiating samples ( , X, and neutron emitters). In this contribution we will describe the most recent instrumental developments of the beamline and illustrate their application with experiments on a selection of topics related to the nuclear or radiochemical fields.

Strontium and Cesium Geochemistry in Clayey Soils, and the Impacts of Silica Grout Dr Pieter Bots1, Dr Josick Comarmond2, Dr Timothy Payne2, Dr Alexandra Schellenger1, Prof Rebecca Lunn1, Dr Joanna Renshaw1 1University of Strathclyde, Glasgow, United Kingdom, 2Australian Nuclear Science and Technology Organisation, Lucas Heights, Australia M3.25: Strontium and Cesium Geochemistry in Clayey Soils, and the Impacts of Silica Grout, July 12, 2021, 19:30 - 19:40

Abstract During the early years of Australia’s nuclear energy research program, low-level radioactive wastes were disposed between 1960 – 1968 in unlined trenches in low permeability clays at a site now known as the Little Forest Legacy Site (LFLS) in New South Wales, Australia. The disposal of lower activity wastes in such trenches was commonly used in the early days of nuclear energy research and the location was often chosen based on the local geology and soil composition. The Little Forest Legacy Site was selected based on the clayey nature of the soils and rocks present (~50 % kaolinite and illite-smectite), limiting water movement and migration of radioactive contaminants [1,2]. These trenches contain complex wastes, including radioactive contaminants, beryllium, steel, and organic materials, and were backfilled with soil materials [1]. Radioactive contaminants itemized in historical records include relatively short-lived fission products (e.g. Sr-90, Cs-137) and long-lived actinides (e.g. Pu, U and Th) [1]. Despite the clay-rich environment, radioactive contaminants (including fission products and actinides) have been detected in sediments, groundwater, surface runoff and vegetation at the Little Forest Legacy Site [2,3]. Thus, a long-term management strategy is required. In-situ immobilization of radioactive toxic wastes is being considered to reduce possible migration of contaminants. Colloidal silica- based grouts have beneficial properties to immobilize radioactive wastes [4, 5], such as low-toxicity, low viscosity for on-site injection, low permeability, and high level of control over in-situ gelling (through varying the accelerant (e.g., NaCl, CaCl2) and its concentration [5]). However, the effects of colloidal silica-based grouts on the geochemistry, speciation and fate of radionuclides present in soils and wastes are largely unknown. Furthermore, in order to ensure continued safe management of the site, as well as to develop new engineering strategies for their containment and / or cleanup, an improved understanding of the geochemistry of radioactive contaminants is required [6]. We will present results from adsorption and leaching experiments using trace concentrations of Cs-137 and Sr-85 combined with Sr and Cs XAS in analogous experiments with elevated concentrations. The detailed experimental study, and comprehensive interpretation of the X-ray absorption spectra (including developing a holistic approach to fitting EXAFS spectra) provides detailed information on the geochemistry of Sr and Cs in clayey soils and the effects of colloidal silica-based grouts. This will provide evidence that utilizing such grouts have the potential to enhance radionuclide retention in addition to providing hydraulic containment of the legacy wastes. References [1] Payne. Background Report on the Little Forest Burial Ground Legacy Waste Site. (ANSTO, 2012). [2] Cendón et al. Aust J Earth Sci 62, 123-141, (2015). [3] Payne et al. Environ Sci Technol 47, 13284-13293, (2013). [4] Hakem, N., et al., Radiochim. Acta., 2004. 92(7): p. 419-432. [5] Pedrotti, M., et al., Tunn. Undergr. Sp. Tech., 2017. 70: p. 105-113. [6] Upgrading of near surface repositories for radioactive waste, (IAEA, Vienna, 2005).

The XAS Resource Workbook (XAS-RW): An Open-Source Instructional Guide for New XAS Users Mr Charles Cardot1, Professory Jerry Seidler1 1University Of Washington, Seattle, United States M1.12: The XAS Resource Workbook (XAS-RW): An Open-Source Instructional Guide for New XAS Users, July 12, 2021, 09:20 - 09:30

Each year, an increasing number of new users enter the larger XAS community. Despite the growing reach of XAS methods across multiple fields of science and the new opportunities provided by upgraded synchrotrons and new lab-based instruments, formal educational opportunities in University curricula on XAS are still relatively rare. Self-study of XAS texts and review articles, supported by beamline scientists and research group members, remains the most common road to initial expertise. Here we report the development of the first edition of the XAS Resource Workbook (XAS-RW): a 16-lesson package for new XAS users. Each lesson begins with suggested reading from texts and review articles, followed by a high-level overview description and citations of classic and representative papers related to the lesson topic, before proceeding to scripted exercises in a worksheet format. The XAS-RW starts with a review of the photoelectric effect and progressively builds through the fundamentals of EXAFS, XANES, basic data analysis, and different experimental techniques and variations thereof, including XES and x-ray Raman scattering. The lesson worksheets make heavy use of qualitative examples and visual exercises, with minimal focus on derivations, to give a rapid, initial introduction. We are in the process of seeking feedback on the lessons from members of the XAS community and will soon begin posting the lessons on GitHub [1] where PDF files will be freely available. We hope that this new resource will make it easier for new users to develop early expertise, while also lowering the barrier to including XAS in regular undergraduate and graduate education in Inorganic Chemistry, Spectroscopy, and related topics. Finally, this will be an open-source living project, and we are actively seeking collaborators to help improve our current lessons and add new ones.

[1] XASResourceWorkbook. GitHub, 27 Apr. 2021 https://github.com/XASResourceWorkbook.

Acknowledgements: This work was supported by subcontract to the University of Washington under a National Science Foundation Small business Technology Transfer (STTR) award, Grant No.1937879, made to easyXAFS LLC.

An In-situ XAFS Study of Olefin Oxidation on Titanium Silicalite Dr Luke Harvey1, Professor Eric Kennedy, Professor Michael Stockenhuber 1The University Of Newcastle, Callaghan, Australia M1.13: An In-situ XAFS Study of Olefin Oxidation on Titanium Silicalite, July 12, 2021, 09:30 - 09:40

Introduction XANES spectra of calcined TS-1 shows a pre-edge at 4967 eV, attributed to Ti(IV) in Td framework positions. Changes to coordination number result in decreasing the XANES pre-edge. In-situ FTIR suggests a reaction path for allyl alcohol to carbonyl over TS-1 after treatment with hydrogen peroxide and re-heated in vacuo. The FTIR spectra demonstrate that the allyl vinyl functionality is oxidised to carbonyl, instead of epoxide. Similar reactions occur in the absence of hydrogen via an isomerisation- tautomerisation mechanism. In-situ XAFS was used to identify framework changes to the TS-1 catalyst giving rise to this reaction mechanism. Methodology TS-1 was synthesised per the original method. A TS-1 wafer was heated to 500°C under vacuum, after which H2O2 was added and the vacuum reapplied. Allyl alcohol was dosed one minute. XAFS measurements were taken between 4966 and 6200 eV, with an edge step of 0.1 and k-step of 0.03. Results The addition of peroxide results in a decrease of the pre-edge, accompanied by a doubling in the XANES edge, indicating the formation of the TiOO- species. Re-heating the sample in-vacuo returns the XANES edge to its initial state, indicating complete removal of the TiOO- species. The pre-edge remains lower in intensity, indicating a decrease in Td symmetry in the framework titanium. EXAFS fitting of the re-calcined sample converges on a model with four oxygen atoms in the first shell with an additional oxygen atom at a slightly greater distance from the Ti centre for a total Ti coordination number of approximately 5.3. This and the presence of a hydroxyl stretching vibration in the FTIR spectrum of the re-calcined sample lead us to propose the structure giving rise to the tautomerisation mechanism is a conventional framework Ti species with an additional coordinated hydroxide.

Tracing the fate of metals during passive and accelerated mineral carbonation of mine tailings. Dr Jessica Hamilton1 1ANSTO - Australian Synchrotron, Clayton, Australia T1.22: Tracing the fate of metals during passive and accelerated mineral carbonation of mine tailings., July 13, 2021, 10:10 - 10:20

The mineral wastes produced by ultramafic mines (i.e. Cu–Ni–PGE, podiform chromite, diamondiferous kimberlite and historical chrysotile deposits) are ideal materials for sequestering CO2 via mineral carbonation, which is a natural process that involves weathering of Mg or Ca-rich silicate and hydroxide minerals to form Mg-carbonate. This is known to occur passively in mine tailings via reaction with the atmosphere, but if geochemical treatments such as acid leaching were applied to these materials, reaction rates could be further accelerated such that a mine could potentially achieve carbon neutrality. However, leaching treatments may inadvertently mobilize potentially toxic trace metals as well as Mg2+ and Ca2+ cations. Here, we report the results of laboratory and synchrotron X-ray Fluorescence Microscopy (XFM) and X-ray Absorption Near Edge Spectroscopy (XANES) experiments that were undertaken to better understand the mobility and fate of first row transition metals during passive and accelerated weathering and carbonation. We find that transition metals are immobilized on a scale of micrometers to centimeters, which is consistent with observations of concentrations below detection in mine pit waters. In accelerated experiments, pH strongly controls the mobilization and immobilization of metals, and we identify an opportunity for value adding by coupling carbonation with enhanced trace metal recovery from mine wastes.

Electrochemical Redox Couples: A Combined XAS and Modulation excitation study Mr Armando Ibraliu1,2,3, Dr Xiaolei Fan1, Dr Luke Keenan2, Dr Daniel Bowron3, Dr Sofia Diaz-Moreno2, Prof Chris Hardacre1 1Department of Chemical Engineering and Analytical Science, The University of Manchester, Manchester, United Kingdom, 2Diamond Light Source Ltd., Oxford, United Kingdom, 3STFC ISIS Facility, Oxford, United Kingdom T3.27: Electrochemical Redox Couples: A Combined XAS and Modulation excitation study, July 13, 2021, 19:40 - 19:50

The use of X-ray absorption spectroscopy (XAS) to follow liquid phase catalysed reactions is widely used. However, in catalysis, small quantities of active species are usually present, complicating the differentiation of spectator and active species. In these cases, the use of Modulation Excitation (ME) techniques can be used to achieve a better signal-to-noise ratio by cycle averaging. ME coupled with phase-sensitive detection can significantly improve the sensitivity of the spectroscopic technique by filtering out contributions of spectator species that are unaltered by the external stimulation. This has been used in combined XAS/DRIFTS studies of gas phase reactions, successfully identifying surface intermediates present in small concentration. [1] In this study, ME assisted by phase-sensitive detection analysis has been applied to the study of liquid-phase reactions using XAS. This methodology has been successfully applied to the study of the electrochemical

II oxidation of Na4Fe (CN)6. The experiment was undertaken in a newly three-electrode designed electrochemical cell at the I20-EDE beamline at Diamond Light Source. 30, 50, and 75 mM aqueous solutions of the iron complex in 1 M NaF/NaCl electrolytes were investigated. Cyclic voltammograms were measured during potential cycling with potential limits ± 1.5 V, at 200 and 300 mV/s scan rates, for 100 cycles. This perturbed the system reversibly allowing the cycle averaging of the XAS data. This study shows that ME assisted by phase-sensitive detection analysis can be successfully applied to XAS for the study of liquid-phase reactions. Signal-to-noise ratios were improved significantly through cycle averaging, and additional information were extracted from the phase-resolved FT-EXAFS spectra demonstrating the enhanced sensitivity. [1] D. Ferri, M.S. Kumar, R. Wirz, A. Eyssler, O. Korsak, P. Hug, A. Weidenkaff, M.A. Newton, Phys. Chem. Chem. Phys., 12 (2010) 5634.

Speciation analysis in selenium biofortified wheat plants exposed to cadmium pollution

Ms Nithyapriya Manivannan1,2, Dr. Roberto Boada1,2, Dr. Carlo Marini1, Dr. Mercè Llugany3, Dr. Manuel Valiente2, Dr. Laura Simonelli1 1Alba Synchrotron, Barcelona, Spain, 2GTS-UAB, Department of chemistry, Barcelona, Spain, 3Plant Physiology Group (BABVE), Faculty of biosciences, Barcelona, Spain

T3.21: Speciation analysis in selenium biofortified wheat plants exposed to cadmium pollution, July 13, 2021, 19:10 - 19:20

Humans need ca. 40 µg/day of selenium (Se) in their diet for proper functioning of immune, reproduction, cardiovascular and thyroid systems. Se biofortication of crops helps in overcoming Se-deficient diets due to food produced in Se-poor regions. A careful design of the biofortification processes is crucial to produce the desired bioavailable Se species within a safe concentration range to eliminate any possible toxicity issues. Unfortunately, heavy metal pollutants present in agricultural soils could interfere with the biofortification process. Therefore, it is of great importance to understand how heavy metals affect the transformation of Se in the plants. In this work, we have focused on cadmium (Cd) since it is a pollutant originated by different anthropogenic activities (e.g., mining industries, phosphate fertilizers) that gets biomagnified in the food chain. Wheat (T. Aestivum) plants were grown in hydroponic systems and exposed to 10 µM of different inorganic Se species (sodium salts of selenite and/or selenate) for the biofortication process and 1 µM of CdCl2. Different parts of the plant were analysed to understand the plant metabolism and bioavailable Se species. Our ICP-MS analysis shows that the presence of Cd decreases the Se concentration in the grain. Besides, there is a reduction of the Cd uptake upon exposing the plants to Se. Se K-edge XAS studies revealed that the formation of methyl-selenocysteine in the grains is enhanced in the Se biofortified plants when exposed to Cd. This could be due to changes in the Se breakdown mechanism induced by the heavy metal pollutant. μXRF mapping of wheat grain sections allowed us to get the spatial distribution of Se. μXANES measurements showed that selenomethionine is mainly found in the pigment strand and eye regions, whereas methyl-selenocysteine and selenocystine are distributed along the endosperm. Hence, the presence of Cd affects the biofortication process.

[We would like to acknowledge the DOC-FAM funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 754397]

Relativistic corrections to phase shift calculation in the GNXAS package Dr. Nodoka Hara2, Professor Andrea Di Cicco1, Dr. Georghii Tchoudinov1, Prof. Keisuke Hatada2, Dr. Calogero Natoli3 1University Of Camerino, Camerino, Italy, 2Faculty of Science, Academic Assembly, University of Toyama, Gofuku 3190, Toyama 930- 8555, Japan, 3INFN Laboratori Nazionali di Frascati, c.p. 13, I-00044 Frascati,, Italy T3.18: Relativistic corrections to phase shift calculation in the GNXAS package, July 13, 2021, 18:50 - 19:00

Modern XAFS (X-ray Absorption Fine Structure) data-analysis is based on accurate multiple-scattering (MS) calculations [1] of the x-ray absorption cross-section. In this communication, we present the inclusion and test of relativistic corrections for the multiple-scattering calculations within the GnXAS suite of programs[2,3], which is relevant to the treatment of the XAFS signals [4] when atoms with high atomic number are contained into the system. We present a suitable strategy for introducing relativistic corrections without altering the basic structure of the suite of programs. In particular, this is realized modifying only the Phagen program calculating the atomic absorption cross sections and scattering t-matrices for the selected cluster. The modification incorporates a pseudo-Schroedinger Equation (SE) replacing the Dirac relativistic form. The phase-shift calculations have been put to a test in two known molecular and crystalline cases: molecular bromine and crystalline Pb[5,6]. Calculations have been shown to be very close to the non-relativistic case for bromine while corrections for amplitude and phases of the XAFS multiple-scattering signals have been found to be larger than 10% for Pb.

[1] C. R. Natoli and D. Sébilleau, in Multiple Scattering Theory for Spectroscopies , Springer Proceedings in Physics, Vol. 204, edited by D. Sébilleau, K. Hatada, and H. Ebert (Springer International Publishing, 2018) pp. 221#256. [2] A. Filipponi, A. Di Cicco, and C. R. Natoli, Phys. Rev. B 52 , 15122 (1995). [3] F. Iesari, K. Hatada, A. Trapananti, M. Minicucci, and A. Di Cicco, in Multiple Scattering Theory for Spectroscopies , Springer Proceedings in Physics, Vol. 204, edited by D. Sébilleau, K. Hatada, and H. Ebert (Springer International Publishing, 2018) pp. 221-256. [4] T. A. Tyson, Phys. Rev. B 49, 12578 (1994). [5] A. Filipponi and P. D' Angelo, J. Chem. Phys. 109 , 5356 (1998). [6] A. Di Cicco, M. Minicucci, E. Principi, A. Witkowska, J. Rybicki, and R. Laskowski, J. Phys.: Condens. Matter 14 , 3365 (2002).

[Please include the grant or other support information for your research on a separate line at the bottom of your abstract. If yes, then the support acknowledgment also should be included on your poster.]

A software-based solution for continuous scan measurements at XAFS beamline at Elettra Dr Danilo Oliveira De Souza1 1Elettra-sincrotrone Trieste S.c.p.a., Trieste, Italy T3.14: A software-based solution for continuous scan measurements at XAFS beamline at Elettra, July 13, 2021, 18:30 - 18:40

On the last decades, XAS has been popularized as a powerful technique of atomic-level characterization of materials. Particularly, in the hard x-ray regime, it has been largely using to perform time-resolved in situ and operando experiments able to unravel mechanisms of chemical reactions, catalytic kinetics and electrochemical processes with unprecedent details. For that purpose, dedicated beamlines have been setting up to achieve timescale on the order of sub second resolution, which is now known as Quick-EXAFS.

XAFS at Elettra is a multi-purpose beamline installed on a bending magnet source, operating since 2003 and designed to cover a wide energy range (2.1 to 27 keV) to serve a large number of researches in the area of conventional XAS, from catalysis to material and environmental science. It uses a high-resolution double crystal monochromator in the standard step-by-step mode of acquisition. Currently, the XAFS beamline suffers from a high demand issue, being one of the most required beamlines at Elettra, the ratio of success for a submitted proposal is just 37% on average during the last decade. Indeed, one of the main reasons of long-lasting scans is the large fraction of time spent waiting for the monochromator mechanics to move, settle of mechanical vibrations and the readout time of motor encoders. As result, the time devoted to photon- detection is just a portion of the total scanning time.

In order to change this panorama, we developed a continuous scan acquisition mode allowing us to collect EXAFS spectra within tens of seconds keeping the features of high-quality data that characterize the XAFS beamline. In continuous scan mode, ionization chambers signals are registered on-the-fly as monochromator sweep the energy of the beam. The synchronization among all data recorded is an essential point on this kind of acquisition to avoid autocorrelation between spectrum acquisition time and energy resolution. In our setup we conceived and implemented a software-based system that correlates energy and photon intensities in a quite unique solution to set down XAS spectra in a fraction of the time when compared to step-by-step mode and with an equivalent quality concerning signal-to-noise ratio. Thus, on this work we describe the logic of our piece of software, the statistical analysis, a comparison with a metallic foil and the first results of a measurement on a real experiment.

X-ray Absorption Fine Structure as an in situ method of nanothermometry for intracellular hyperthermia Dr Alvaro Munoz Noval1,2, Mrs Rosalia López Méndez2,3, Dr Alexandre Fromain4,5, Dr Emiliano Fonda6, Dr Javier Reguera7, Dra Claire Wilhelm4,5, Dr. Miguel Angel Garcia7, Dra Ana Espinosa2,3 1University Complutense De Madrid, Madrid, Spain, 2IMDEA Nanociencia, c/ Faraday 9, 28049 Madrid, Spain, , Spain, 3Nanobiotecnología (IMDEA-Nanociencia), Unidad Asociada al Centro Nacional de Biotecnología (CSIC), 28049 Madrid, Spain., , Spain, 4Laboratoire Matière et Systèmes Complexes MSC, UMR 7057, CNRS & University of Paris, 75205 Paris Cedex 13, France, , France, 5Institut Curie, Université PSL, Sorbonne Université, CNRS UMR 168, Laboratoire Physico Chimie Curie, 75005 Paris, France, , France, 6Synchrotron SOLEIL, L’Orme des Meisiers–BP48,91192 Saint-Aubin, France, , France, 7BCMaterials, Basque Center Centre for Materials, Applications and Nanostructures, UPV/EHU Science Park, 48940 Leioa, Spain, , Spain, 8Institute of Ceramics and Glass-CSIC, 28049, Madrid, Spain, , Spain M3.23: X-ray Absorption Fine Structure as an in situ method of nanothermometry for intracellular hyperthermia, July 12, 2021, 19:20 - 19:30

Treatments based on multifunctional thermal-activated nanomaterials have emerged as a promising biomedical strategy to fight cancer [1]. Temperature increments above 42°C were shown to kill cancer cells which has led to the development of nanoparticle- mediates thermo-therapeutic strategies in the fight of oncological diseases. However, these therapeutic effects have been also observed by localized nanoparticle heating without a detectable macroscopic temperature rise. However, the precise determination of the local temperature reached in the tumour tissue is necessary to evaluate the onset of thermal doses and quantify possible side effects on healthy tissues [2]. In this study, we investigate the capabilities of XAFS to determine in situ the temperature reached in double-faced Au-FexOy Janus nanoparticles [3] under photoactivated hyperthermia. Experiments were performed in inorganic and cell matrices in Au L3-edge and Fe K-edge at BM25-SpLine@ESRF and SAMBA@SOLEIL. We will discuss the capabilities and limitations of the technique [4] and shortly introduce the heat transfer mechanisms at the nanoscale. Finally, we will discuss the results of experiments carried out on cell tissues.

[1] A. Curcio, A. K. Silva, S. Cabana et al., Theranostics 9, 1288 (2019). [2] S. Wilhelm, A. J. Tavares, Q. Dai et al., Nature Reviews Materials 1, 16014 (2016). [4] A. Espinosa, J. Reguera, A. Curcio et al., Small, 1904960 (2020). [5] A. Espinosa, G.R. Castro et al. Nano Lett. (2021)

Acknowledgments: This work was supported by the Comunidad de Madrid (2018-T1/IND-10360 Talento, 2018-T1/IND-1005 Talento, 2018/NMT-4321), AECC project Ideas Semilla 2019, Spanish Ministry of Economy and Competitiveness (RTI2018-095303-A-C52). IMDEA Nanociencia acknowledges support from the 'Severo Ochoa' Programme for Centres of Excellence (MINECO, SEV-2016-0686).

Prospective copper(II) anticancer compounds’ examination with the X-ray Absorption Spectroscopy M.Sc.Eng. Wiktoria Stańczyk1, Ph.D. Eng. Joanna Czapla-Masztafiak1, Ph.D. Anna Wach1, Ph.D. Wojciech Błachucki1, M.Sc. Rafał Fanselow1, Associate Professor Jakub Szlachetko1, Professor Wojciech Maria Kwiatek1 1Institute of Nuclear Physics PAN, Kraków, Poland T3.16: Prospective copper(II) anticancer compounds’ examination with the X-ray Absorption Spectroscopy, July 13, 2021, 18:40 - 18:50

The number of reported cases of cancer is still tremendously growing, due to late diagnosis or inefficient treatment. This fact leads to developing new ways of therapy, including searching for new drugs that could be implemented in chemotherapy. Some copper compounds could replace commonly used platinum drugs such as cis-platinum and reduce a number of side effects, since copper belongs to micronutrients [1]. Recently, copper complexes with phenanthroline are in the area of interest, because their geometry enables fitting between DNA strands and their reactivity leads to the generation of free radicals that can damage DNA and biomolecule’s structures [2]. This kind of twin-track action could result in better anticancer properties. However, before introducing such drugs into clinical applications, their detailed characterization should be performed. In the presented research, we focused on the X-ray Absorption Spectroscopy (XAS) examinations of chosen copper(II) compounds: CuO, CuSO4 and Cu(1,10-phenanthroline)Cl2. Powder samples were pressed into pellets or were dissolved in water and were subsequently characterized with the use of laboratory XAS setup, build in the Institute of Nuclear Physics PAN, Cracow, Poland [3]. In addition, the measurements were done with the use of synchrotron radiation source at Paul Scherrer Institut, Villigen, Switzerland. Since different X-ray sources and samples’ form were used, the goal of the experiment was to establish proper experimental conditions in order to obtain good quality spectra. The XAS spectra analysis provided information about the oxidation state of copper and electronic structure of compounds. The results were in a good agreement with the data obtained with the FEFF program [4], showing that the main spectra contributions are arising from Cu p,d- orbitals and N,Cl p-orbitals at around edge energies. These examinations were with the aim to characterize copper(II) phenanthroline complex, before checking its interaction with other biomolecules such as DNA.

[1] S.Tabassum, et al., European journal of medicinal chemistry 58 (2012): 308-316. [2] G.Barone, et al., Coordination Chemistry Reviews 257.19-20 (2013): 2848-2862. [3] W.Błachucki, et al. Journal of Analytical Atomic Spectrometry 34.7 (2019): 1409-1415. [4] W.Stańczyk, J.Czapla-Masztafiak, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 497 (2021): 65-69.

Authors would like to acknowledge National Science Centre, Poland (NCN) for partial support under grant no. 2016/21/D/ST4/00378.

Metal nodes of Ni-MOFs as catalytic precursors for olefin oligomerization Dr Christian Wittee Lopes1, Dr Yuri Miguel Variani1, Dr Giovanni Agostini2, Dr Carlo Marini2, Dra Katia Bernardo-Gusmão1 1Federal University of Rio Grande do Sul, Porto Alegre , Brazil, 2ALBA synchrotron, Cerdanyola del Vallès, Spain M1.1: Metal nodes of Ni-MOFs as catalytic precursors for olefin oligomerization, July 12, 2021, 08:30 - 08:40

In the last years, much attention has been paid to the development of new heterogeneous catalysts for ethylene oligomerization. Among different catalysts for olefins oligomerization, those based on Ni are the most studied, e.g., Ni-aluminosilicates or Ni-MOFs. In the latter, Ni is commonly found attached to functionalized walls of the metal-organic framework. Alternatively, the Kaskel group[1] reported the employment of different Ni-MOFs as catalysts for olefin oligomerization. The use of secondary building units of MOFs as the catalytic precursor is an attractive alternative once several post-synthesis steps could be avoided. In this work, we synthesized the Ni2(BDC)2(DABCO) and studied its application as a catalyst in ethylene oligomerization using EASC as co-catalyst. Ni-MOF was highly active, reaching 132821 h-1 at optimum Al/Ni molar ratio with 100% selectivity to C4. Recycling tests show that the material can be used for at least two more reactions with some activity loss. XANES indicate that Ni atoms are present as Ni2+ in the as- prepared material and after reaction. However, the post-catalysis spectrum suggests that Ni local environment is affected during/after reaction conditions. Indeed, EXAFS spectra show that Ni local order is affected after reaction once the first shell contribution is flattened compared with that of the as-prepared sample, indicating ligand losses. The coordination number of the post-reaction sample decreases while an enlargement of the Ni-ligand distance take place. Linear combination fit performed between the as-made sample and bulk NiO suggests the sample after reaction is composed by approximately 80% of MOF and 20% of NiO. These results suggest that some MOF secondary units are most likely unattached, forming NiO or Ni0. These results demonstrate that metal nodes of MOFs can act as catalysts for olefin oligomerization and more studies on catalyst stability should be carried out.

[1] Arrozi, et al. Dalton Trans., 2019, 48, 3415.

Local atomic structures of borate glasses: X-ray absorption analysis and computer modeling Miss Alexandra Ermakova1, Miss Galina Sukharina1, Mr Roman Alekseev2, Mr Alexander Trigub3, Mr Alexey Veligzhanin3, Mr George Shakhgildyan2, Mr Leon Avakyan1, Mr Lusegen Bugaev1, Mr Vladimir Sigaev2 1Southern Federal University, Rostov-on-Don, Russian Federation, 2Mendeleev University of Chemical Technology , Moscow, Russian Federation, 3National Research Centre “Kurchatov Institute”, Moscow, Russian Federation M2.4: Local atomic structures of borate glasses: X-ray absorption analysis and computer modeling, July 12, 2021, 15:40 - 15:50

The borate glass La2O3-Nb2O5-B3O2 (LNB) systems are promising materials for optical applications. The study of the structure of borate glasses will make it possible to establish its effect on the optical properties of the material and to develop a composition with the required refractive indices and density [1]. In this work we have studied the local structure of La in borate glass La2O3-Nb2O5-B3O2 and the dependence of this structure upon the changing of concentrations of Nb2O5 and B2O3. Structural analysis was performed using X-ray absorption near edge structure (XANES) spectroscopy since this method allows determining local atomic structure in materials without long range atomic order. The experimental XANES spectra of the La L3 absorption edge were measured at the "Structural Materials Science" station of the Kurchatov synchrotron radiation source (Moscow, RF). Simulations of XANES were performed using multiple scattering and finite different methods realized in FDMNES program code [2], considering various, most plausible structures for La atomic surrounding in the considered glass samples. By using such approach, we have revealed the probable model of local atomic structure around La atom in borate glasses of LNB system and determined the dependence of this structure upon the concentrations of Nb2O5 component, which was increased in the studied glass samples from 5 to 30 mol.% under simultaneous decreasing of B2O3 component.

[1] Bengisu M., Journal of materials science. 51(5), pp. 2199-2242 (2016) [2] Joly Y., Physical Review B. 63, 125120 (2001)

In-situ slot-die coating platform at the Balder beamline Dr Matteo Ciambezi1, Dr Eva Unger2, Dr Justus Just1 1MaxIV Laboratory, Lund University, Lund, Sweden, 2Lund University, Lund, Sweden M3.24: In-situ slot-die coating platform at the Balder beamline, July 12, 2021, 19:20 - 19:30

Solution processable functional materials for photovoltaics, batteries, sensors and other opto- electronic devices are increasing their relevance because of their high performances, production flexibility and low cost.[1-3] Nevertheless, a deeper understanding of the film formation mechanisms during deposition is key for upscaling and to obtain high-quality functional layers for these devices. For this purpose we developed* a platform for in-situ analysis of these solution-processed materials, which is integrated into the Balder beamline at MAX IV. It consists of a small footprint roll-to-roll slot die coater with thermal annealing and a gas-quenching stages. It allows for in-situ, multimodal measurements during various coating and annealing procedures. The platform is fully remotely operated and permits to perform automated high-throughput experiments, which is crucial in synchrotron facilities experiment- environments. Moreover, the platform is designed modular to enable high versatility to carry out different possible experiments and future upgrades. This instrumentation allows for a real-time and in-situ combination of X-ray spectroscopy (XAS and XRF), X-ray diffraction (XRD) and X-ray excited optical spectroscopy (XEOL), all measured simultaneously and at the same spot from the same incident X-ray beam. This permits a complementary investigation of the local structure, crystalline phase, chemical composition, oxidation state, and opto-electronic properties, unraveling formation and other time-dependent processes during and after slot-die ink deposition. Furthermore, the coating process is controllable remotely, giving precise control of ink mixing, processing parameters like slot- die height and substrate speed, thermal (RT-250 °C) annealing and air-blade based gas quenching. Currently, the project is in a mid-term stage: the setup has been build and first coating processes have been tested at the Balder beamline. We will present the capabilities and technical details of the system as well as first exemplary measurements.

* SSF ITM-170276 granted project in-FORM (In-situ multi-parameter Analysis Platform for Formation of Energy Materials) Info: http://just.science/in-form/

References: 1Nishide, Hiroyuki, and Kenichi Oyaizu. "Toward flexible batteries." Science 319.5864 (2008): 737-738. 2 Burschka, Julian, et al. "Sequential deposition as a route to high-performance perovskite-sensitized solar cells." Nature 499.7458 (2013): 316-319. 3Li, Jinzhao, et al. "20.8% slot-die coated MAPbI3 perovskite solar cells by optimal DMSO-content and age of 2-ME based precursor inks." (2020).

In situ size- and temperature-dependent formation and decomposition of surface and bulk palladium oxides Mr Oleg Usoltsev1, Mr Aram Bugaev1,2, Mrs Alina Skorynina1, Mrs Elizaveta Kozyr1, Mrs Anna Pnevskaya1, Mr Dragos Stoyan3, Mr Riccardo Pellegrini4, Mr Jeroen van Bokhoven5, Mr Alexander Soldatov1 1Southern Federal University, Rostov-on-Don, Russian Federation, 2Federal State Budgetary Institution of Science "Federal Research Centre The Southern Scientific Centre of The Russian Academy of Sciences", Rostov-on-Don, Russian Federation, 3ESRF, Grenoble, France, 4Chimet S.p.A., Arezzo, Italy, 5Paul Sherrer Institute , Villigen, and ETH Zurich, Switzerland T2.4: In situ size- and temperature-dependent formation and decomposition of surface and bulk palladium oxides, July 13, 2021, 15:40 - 15:50

Supported palladium nanoparticles (Pd NPs) are extensively used in important catalytic reactions such as oxidation of alcohols or methane combustion. It is known that presence of oxygen in the reaction results in the formation of palladium oxide phase which affects the catalytic activity of the material. Here, we investigate the type of oxide phase, the rate of the phase formation and decomposition and the stability of surface and bulk oxides for differently sized supported Pd NPs by in situ X-ray absorption spectroscopy (XAS). The experiments were performed at the BM31 beamline of the ESRF using commercial Pd catalysts provided by Chimet S.p.A. (Pd@Al2O3 with NP size of 3 nm, and Pd@P4VP with NPs size of 1 nm, and Pd microparticles). The treatment procedure included alternate switching of hydrogen and oxygen streams at various temperatures (50, 100, 150, 180, 220, 260, 300, 400 °C). XAS spectra were collected every 10 s and were analysed in both XANES and EXAFS region providing the evolution of Pd oxidation state and changes in the local structure from 12-coordinated metallic Pd to 4-coordinated surrounding in Pd oxide. The following results were obtained: i. Surface palladium oxides are formed immediately upon exposure to molecular oxygen in the temperature interval 50 – 400 °C ii. Core-shell structures with metallic core and 4-coordinated palladium oxide shell are formed. iii. Above 200 °C palladium oxide phase extends from surface to bulk resulting in the formation of full palladium oxide particles. iv. Particles with smaller size demonstrate higher degree of oxidation due to higher surface-to-bulk ratio. v. Both surface and bulk oxides are easily reduced in hydrogen at all studies temperatures.

The work was supported by the President's Grant of Russian Federation for young scientists МК- 5853.2021.1.2.

Mo4Ce4Al7C3 nanolamellar ferromagnetic Kondo lattice studied with XANES and XMCD Mr Maxime Barbier2 1ESRF (European Synchrotron Radiation Facility), 38000 Grenoble , France, 2Université Grenoble Alpes, CNRS, Grenoble INP, LMGP, 38000 Grenoble, France T3.3: Mo4Ce4Al7C3 nanolamellar ferromagnetic Kondo lattice studied with XANES and XMCD, July 13, 2021, 17:40 - 17:50

The study of Rare-Earth (RE) based compounds has been at the forefront of condensed matter physics for decades, due to the variety of magnetic and electronic ground states that they display. Recently, rare- earth-based nanolaminates have attracted attention because of their rich magnetism and their potential as precursors for strongly correlated two-dimensional materials, opening the door to exciting fundamental science as well as technological applications. We report on the Mo4Ce4Al7C3 phase, which belongs to a recently discovered family of nanolaminates with Mo4RE4Al7C3 stoichiometry in which the RE order within planes, and featuring 2 non-equivalent lattice sites for the RE to sit on [1]. Single crystals of this compound were grown using high temperature solution growth. Bulk magnetization revealed a transition to a ferromagnetic (FM) order below TC=10.5K, with the easy magnetisation axis in the out-of-plane direction. X-ray absorption near edge structure (XANES) performed at the Ce L3-edge revealed that Ce is in a mixed-valence state [1]. X-ray Circular Magnetic Dichroism (XMCD) carried out at the edges of the Mo, Al and C elements of the compound allowed us to conclude that one of the 2 non-equivalent Ce sites is in a 4f1 configuration and is responsible for the FM, while the other one is in a mixed-valence state and does not participate to the FM [1,2]. Thanks to XANES and XMCD measurements, we were able to establish which of the two Ce lattice sites is FM, and which one is in a mixed-valence state. High-pressure XANES showed an evolution of the initially mixed-valent Ce site, up to a fully 4f0 configuration at around 20GPa. This measurement, together with high pressure magnetoresistance measurements across the ferromagnetic transition unveiled a clear Kondo behaviour.

References: [1] Q. Tao, T. Ouisse, D. Pinek, O. Chaix-Pluchery, F. Wilhelm, A. Rogalev, C. Opagiste, L. Jouffret, A. Champagne, J.-C. Charlier, J. Lu, L. Hultman, M. W. Barsoum, and J. Rosen, Phys. Rev. Mater. 2, 114401 (2018) [2] M. Barbier, F. Wilhelm, D. Pinek, K. Furuta, T. Ito, Y. Kim, M. Magnier, D. Braithwaite , M.Vališka, C. Opagiste, M. W. Barsoum, P. Ohresser, E. Otero, P. Le Fèvre, F. Bertran, G. Garbarino, A. Rogalev, and Thierry Ouisse, Phys. Rev. B 102, 155121 (2020)

Evolution of Ru-sites in homogenous hydrodeoxygenation catalyst by Ru K-edge XANES analysis using machine learning approaches Mrs Elizaveta Kozyr1, Mr Aram Bugaev1, Mr Sergey Guda1, Mr Alexander Guda1, Mr Kirill Lomachenko2, Mr Koen Janssens3, Mr Smolders3, Mr Dirk De Vos3, Mr Alexander Soldatov1 1Southern Federal University, Rostov-on-don, Russian Federation, 2European Synchrotron Radiation Facility, Grenoble , France , 34Centre for Membrane separations, Adsorption, Catalysis and Spectroscopy for Sustainable Solutions , Leuven, Belgium T2.2: Evolution of Ru-sites in homogenous hydrodeoxygenation catalyst by Ru K-edge XANES analysis using machine learning approaches, July 13, 2021, 15:30 - 15:40

The project aims to investigate the structure of the active sites of ruthenium-based homogenous catalytic systems, which converts sugar alcohols to alkenes. Recently, simple RuBr3 salt dissolved in the tetrabutylphosphonium bromide (Bu4PBr) ionic liquid was demonstrated as a promising catalyst [ссылка на ACS catalysis]. Here, we track the evolution of the catalytic system using the EXAFS and XANES analysis (involving machine learning-based approaches) complemented by DFT calculations.

Ru(m)Cl(x)Br(y)(CO)(z) structures and RuXn clusters (X = Cl, Br) were taken as the initial ones. The latter group was divided into two large series according to the number of ruthenium centers: m = 1 and m = 2, for monomeric and dimeric species, respectively. For each structure, more than 10,000 different structural deformations were introduced and ab initio XANES spectra were calculated for each geometry. The calculated theoretical spectra were then used for training the machine learning algorithms implemented in the PyFitIt code.1 We applied an inverse approach to predict interatomic distance around Ru sites to CO, Br and Cl ligands from XANES spectra, which were found in excellent agreement for the reference’s spectra. We showed that initial RuX3 salts are dissolved in IL resulting in RuBr4 ions, which are then converted to Ru2Br2x(CO)10-2x (x = 3..4) in presence of CO and remained stable under reaction conditions. These methodological advances have been successfully used to establish important structural patterns for ruthenium-based catalytic systems and have enabled us to predict both geometry and ligand surrounding of ruthenium-based catalysts using machine learning. The work was supported by Russian Science Foundation grant 20-43-01015. 1. Martini, A.; Guda, S. A.; Guda, A. A.; Smolentsev, G.; Algasov, A.; Usoltsev, O.; Soldatov, M. A.; Bugaev, A.; Rusalev, Y.; Lamberti, C.; Soldatov, A. V., PyFitit: the software for quantitative analysis of XANES spectra using machine-learning algorithms. Comput. Phys. Commun 2020, 250, 107064.

Study of the mechanism of nucleation of platinum nanoparticles through X-ray absorption spectroscopy using a continuous flow microfluidic device Dr Sylvia Britto1, Dr. Christopher M. A. Parlett1,2, Dr. Stuart Bartlett1, Dr Konstantin Ignatyev1, Prof. Sven L. M. Schroeder1,3 1Diamond Light Source Ltd, Didcot, United Kingdom, 2The University of Manchester at Harwell, Diamond Light Source, Didcot, United Kingdom, 3School of Chemical and Process Engineering, University of Leeds, Leeds, United Kingdom T3.25: Study of the mechanism of nucleation of platinum nanoparticles through X-ray absorption spectroscopy using a continuous flow microfluidic device, July 13, 2021, 19:30 - 19:40

Platinum nanoparticles exhibit unique catalytic properties and have a number of important applications: as an industrial catalyst for fuel cells, in the synthesis of nitric acid, as well as in the reduction of exhaust gases from vehicles. While there have been many studies demonstrating size and morphology control of platinum nanoparticles, a molecular level understanding of the nucleation and growth mechanisms underlying nanoparticle formation, which is crucial for efficient optimization of size controlled synthesis, is lacking in the literature. Structurally incisive experimental in situ probes with enough spatial and temporal resolution are needed to monitor nucleation and growth processes. Here we use operando X-ray Absorption Spectroscopy (XAS) coupled with continuous flow microfluidics to study the mechanisms of platinum nanoparticle formation by reduction of H2PtCl6 using ethylene glycol as a reducing agent. In contrast to a batch synthesis, a continuous flow device allows for rapid and efficient mixing of precursors and fine control over the synthesis parameters such as concentration, flow rate and temperature. The XAS results capture the intermediate stages of nanoparticle formation through to complete reduction to Pt nanoparticles. The setup described here can, in principle, be used to study nanoparticle nucleation and growth mechanisms of a wide range of nanoparticles that occur at fast (microsecond) timescales.

[Please include the grant or other support information for your research on a separate line at the bottom of your abstract. If yes, then the support acknowledgment also should be included on your poster.]

Machine Learning application for XANES analysis of Pd nanocatalysts based on experimental training set. Mr Oleg Usoltsev1, Mr Aram Bugaev1,2, Mrs Anna Pnevskaya1, Mr Alexander Guda1, Mr Sergey Guda1, Mr Alexander Soldatov1 1Southern Federal University, Rostov-on-Don, Russian Federation, 2Federal State Budgetary Institution of Science "Federal Research Centre The Southern Scientific Centre of The Russian Academy of Sciences", Rostov-on-Don, Russian Federation T2.7: Machine Learning application for XANES analysis of Pd nanocatalysts based on experimental training set., July 13, 2021, 16:00 - 16:10

Machine learning (ML) algorithms are widely used methods for data analysis in materials science. Here we applied ML to predict interatomic distances, the Debye-Waller parameter and coordination number of the Pd nanoparticles (NPs) by X-ray Absorption Near-Edge Structure (XANES) spectra. Since there are still no direct unambiguous method to extract structural information from XANES data, we used results of standard first- shell Fourier analysis of Extended X-Ray Absorption Fine Structure (EXAFS) of the same X-ray absorption spectra (XAS) to construct the training set. We fitted more than 1000 experimental EXAFS spectra, collected output parameters, and combine them with respective XANES spectra. We compared different approaches (such as Regression methods, Trees and Neural Networks). Now we demonstrate step by step how prediction accuracy (or possibility) depends on training set size, processes occurred in sample during synchrotron experiment, particles size and spectra collection source.

The work was supported by the grant of Russian Foundation for Basic Research № 19-32-60083.

Local atomic structure of porous InxGa1-xSb films modified by ion irradiation Mr Charles Bolzan1, Dr Bernt Johannessen, Mr Zhibin Wu, Dr Raquel Giulian 1Ufrgs, Porto Alegre, Brazil, 2Australian Synchrotron, Clayton, Australia, 3Institute for Superconducting & Electronic Materials, University of Wollongong, , Australia, 4UFRGS, Porto Alegre, Brazil T1.3: Local atomic structure of porous InxGa1-xSb films modified by ion irradiation, July 13, 2021, 08:40 - 08:50

III–V ternary alloy systems can be applied in many high-speed electronic and optoelectronic devices because they provide a natural means of tuning the magnitude of the band gaps so as to optimize and widen the range of applications of semiconductor devices. The properties of this compound can be extended by making them porous due to the exclusive combination of their crystalline structures and large internal surface areas, which allows higher adsorbate effects and consequently, an enhancement in the activity of their surface chemical reactions, making them very attractive for sensor applications. Understanding the structural modifications induced by ion irradiation in these compounds is essential to better exploit their capabilities. Based on this, InxGa1-xSb films with x values equal 0, 0.2, 0.4, 0.5 and 1 were deposited using magnetron +6 sputtering onto SiO2/Si substrate and subsequently irradiated with 16 MeV Au ions with fluences in the order of 1 × 1013 cm−2 to 1 × 1014 cm−2 . The structure of all films were investigated by scanning electron microscopy (SEM), Rutherford backscattering spectrometry (RBS), grazing incidence x-ray diffraction (GIXRD) and extended x-ray absorption fine structure (EXAFS) spectroscopy. GIXRD analysis showed the formation of a polycrystalline compound structure with a zincblende phase for all of the InxGa1-xSb films (as-deposited). From EXAFS technique around In and Ga atoms, it was observed a bimodal distribution for the first nearest neighbor interatomic distance in InxGa1-xSb with the lattice mismatch being accommodated favorably through bond bending over bond stretching similar to other III-V ternary alloys. When irradiated, via a combination of SEM, RBS and GIXRD results, it was observed the occurrence of a continuous-to-porous transition, similar to binary antimonides, accompanied by layer swelling and amorphization with a stoichiometry-dependent porosity by ion irradiation. However, through EXAFS analysis, it was shown that the local structural 14 −2 parameters were unaffected by ion irradiation up to 5 × 10 cm in InxGa1-xSb films.

This work was sponsored by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Coordenadoria de Aperfeiçoamento de Pessoal do Ensino Superior (CAPES) and Fundação de Amparo a Pesquisa do Estado do Rio Grande do Sul (FAPERGS). Part of this research was undertaken on the XAS Beamline, part of ANSTO.

Multimodal in-situ real-time XAS/XRD/UV-vis on energy materials Dr. Justus Just1, Dr. Matteo Ciambezi1, Prof. Dr. Per-Anders Carlsson2 1MAX IV Laboratory, Lund, Sweden, 2Chalmers University, Göteborg, Sweden T3.23: Multimodal in-situ real-time XAS/XRD/UV-vis on energy materials, July 13, 2021, 19:20 - 19:30

Meeting the raising demand for in-situ and operando studies on material systems especially for energy applications we develop an in-situ investigation platform at the Balder beamline: In-FORM. It consists of specialized sample environments, real-time and multimodal measurements as well as data analysis tools. The Balder beamline at the MAX IV Synchrotron is dedicated to X-ray absorption and emission spectroscopy in the energy range of 2-45 keV, exhibiting a beamsize down to 50 x 50 µm with a flux of ~1012 ph/s. Our specialized quick scanning fixed exit monochromator together with a closed loop fine adjustment of the beam position allows for relatively quick (1-10 s) energy scans while keeping the beam position constant within several micrometers. This stability and small focal size enable for X-ray diffraction and scattering measurements, complementing X-ray absorption spectroscopy. With a recently developed X-ray diffraction end-station based on an EIGER 1M 2D-detector we perform simultaneous measurements of X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD). A trigger controller synchronizes all experimental read outs with the monochromator energy motion. We therefore collect diffraction images as well as the X-ray absorption in transmission or fluorescence, exactly synchronous for every point during a quick energy scan. An effective time resolution of about 1-10 ms is achieved for diffraction measurements, being 1-10 s for XAS. We will present results from combined XAS, XRD and optical spectroscopy measurements on 1) the crystallization of perovskite semiconductors for photovoltaic applications and 2) the evolution of active structures of realistic bimetallic Pt-Pd supported catalysts during methane oxidation. Both real-time in situ investigations emphasize the importance of multimodal approaches to understand process kinetics and intermediate states.

A Laboratory-Based Double Spectrometer for Simultaneous Measurements of P Kα and Kβ for Air-Sensitive Samples Mr Jared Abramson1 1University Of Washington, Seattle, United States M1.9: A Laboratory-Based Double Spectrometer for Simultaneous Measurements of P Kα and Kβ for Air- Sensitive Samples, July 12, 2021, 09:10 - 09:20

X-ray emission spectroscopy (XES) has a steadily growing footprint in the broader XAS community thanks to its sensitivity to oxidation and spin state (core-to-core transitions) and its explicit mapping of the occupied density of states involved in chemical bonding (valence-to-core transitions). While much of this work continues at synchrotron light sources, recent years have seen a rapid growth of laboratory-based instrumentation and application of XES due to high core-hole generation rates of laboratory x-ray sources. [1- 6] We report here a laboratory-based XES spectrometer that has been specialized for the problem of phosphorus XES for air-sensitive samples in the context of a user facility supporting non-experts for analytical applications. The spectrometer simultaneously operates two 10-cm Rowland circles using the Dispersive Rowland Refocusing (DRR) geometry [2], one for the P Kα energy range and the other in the P Kβ (valence-to- core) energy range. The Rowland planes are tilted and rotated with respect to one another for clearance, and both use Si (111) cylindrical Johann analyzers and CMOS x-ray cameras. The resulting instrument will soon be installed in a research-grade glove box for optimal accommodation of air-sensitive samples. Commissioning studies show very high energy resolution, rapid data collection, and good ease of use. We will report measurements of InP quantum dots, NiP electrocatalysts, and functionalized black phosphorus. Multiplexing spectrometers in the lab environment have thus proven to be a beneficial approach to simplifying operations.

Acknowledgements: This project is supported by the United States National Science Foundation through the UW Molecular Engineering Materials Center, a Materials Research Science and Engineering Center (Grant No. DMR-1719797) and also through Grant No. CHE-1904437.

[1] Evan P. Jahrman, et al., Review of Scientific Instruments 90, 024106 (2019) https://doi.org/10.1063/1.5049383 [2] William M. Holden, et al., Review of Scientific Instruments 88, 073904 (2017) https://doi.org/10.1063/1.4994739 [3] Wolfgang Malzer, et al., Review of Scientific Instruments 89, 113111 (2018) https://doi.org/10.1063/1.5035171 [4] William M. Holden, et al., The Journal of Physical Chemistry A 2020 124 (26), 5415-5434 https://doi.org/10.1021/acs.jpca.0c04195 [5] Evan P. Jahrman, et al., Analytical Chemistry 2018 90 (11), 6587-6593 https://doi.org/10.1021/acs.analchem.8b00302 [6] Jennifer L. Stein, et al., Chemistry of Materials 2018 30 (18), 6377-6388 https://doi.org/10.1021/acs.chemmater.8b02590

Machine-learning assisted identification of atomic properties from X-ray spectroscopies Ms. Yiming Chen1, Dr. Chi Chen1, Dr. Chengjun Sun2, Dr. Steve Heald2, Dr. Maria K. Y. Chan2, Prof. Shyue Ping Ong1 1University of California San Diego, La Jolla, United States, 2Argonne National Laboratory, Lemont, United States M1.18: Machine-learning assisted identification of atomic properties from X-ray spectroscopies, July 12, 2021, 09:50 - 10:00

The determination of atomic properties such as local environment and spin states of functional materials is of great importance to materials science. Characterization techniques such as X-ray absorption and emission spectroscopies are sensitive to these properties, but the interpretation of these spectra pose challenges due to subtleties in the relationship between desired properties and spectroscopic features. Machine learning approaches may provide a way to aide these interpretation efforts. In this talk, we will discuss examples of machine learning models, trained on computational spectra, that can determine those properties from X-ray spectroscopies. The first example is to use random forest models for local environment prediction from X-ray absorption spectroscopy (XAS). In this multi-label classification task, a high accuracy of 85.4% was achieved over 33 cation species for models trained on ~200,000 spectra in XASdb1,2. In the second example, we tackle the atomic structure change of one specific material, LiNixMnyCozO2 (NMC). NMC is a well-known cathode for Li-ion battery because of its high energy density, long-term cyclability and relatively low cost. We will describe the determination of the complex atomic structure change in NMC during electrochemical cycling. Additional information about electronic structures available from X-ray emission spectra will also be discussed. In summary, these findings indicate that the combination of the computational spectroscopy and machine learning techniques will be an invaluable resource to the materials research community by significantly enhancing the efficiency at which experimental X-ray spectra can be analyzed.

References (1) Mathew, K.; Zheng, C.; Winston, D.; Chen, C.; Dozier, A.; Rehr, J. J.; Ong, S. P.; Persson, K. A. High- Throughput Computational X-Ray Absorption Spectroscopy. Sci Data 2018, 5 (1), 180151. https://doi.org/10.1038/sdata.2018.151. (2) Zheng, C.; Chen, C.; Chen, Y.; Ong, S. P. Random Forest Models for Accurate Identification of Coordination Environments from X-Ray Absorption Near-Edge Structure. Patterns 2020, 1 (2), 100013. https://doi.org/10.1016/j.patter.2020.100013.

This work was supported, in part, by the Data Infrastructure Building Blocks (DIBBs) Local Spectroscopy Data Infrastructure (LSDI) project funded by National Science Foundation (NSF), under award name 1640899. This work was supported, in part, by the Scientific User Facilities project titled “Integrated Platform for Multimodal Data Capture, Exploration and Discovery Driven by AI Tools” and by Laboratory Directed Research and Development (LDRD) funding from Argonne National Laboratory, both funded by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-06CH11357.

Rearrangement of the electronic structure induced by oxidation of titanium probed by means of X-ray spectroscopy methods Mrs Klaudia Wojtaszek1, Ph.D. Anna Wach1, Ph.D. Wojciech Błachucki1, Ph.D. Eng. Joanna Czapla- Masztafiak1, Professor Wojciech M. Kwiatek1, Professor Jakub Szlachetko1 1Institute of Nuclear Physics Polish Academy of Sciences, 31-342 Krakow, Poland, 31-342 Krakow, Poland M3.18: Rearrangement of the electronic structure induced by oxidation of titanium probed by means of X-ray spectroscopy methods, July 12, 2021, 18:50 - 19:00

Titanium dioxide (TiO2) is of great interest as a potential photocatalyst in visible light due to its efficient photoactivity, high stability and low cost. Numerous studies have shown that structure modification of titanium compounds can improve the photocatalytic activity, which is attributed to change in the electronic structure [1]. Subtle differences and changes in the molecular structure are reflected in the electronic structure of the studied material [2]. Thus, knowledge about the electronic structure, especially orbital contribution and the relative energy position of the highest occupied (valence band) and the lowest unoccupied states (conduction band) is crucial. In this context, methods such as X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS), allowing for detailed investigation of the electronic structure of the matter, with element selectivity, are of great importance to design materials with improved properties [3].

In the present study, a high energy resolution XAS and XES spectra were used to determine changes in the electronic structure during temperature-induced oxidation of titanium metallic substrate at ambient atmosphere in a custom-made cell [4]. In situ measurements for Kβ emission lines and absorption on Ti K- edge were carried out at the SuperXAS beamline at the Swiss Light Source Synchrotron (Villigen, Switzerland). Application of surface sensitive X-ray spectroscopy techniques allowed us to track the formation of oxides on metal surface at various annealing stages and to observe formation of valence and conduction electronic states. The experimental data were compared with theoretical calculations of the density of states (DOS) performed with the FEFF9.0 program. Understanding the kinetics and dynamics of the metal-to-oxide transformation is of great importance for TiO2 applications.

[1] S. J. Baloyi and J. Moma, Modified Titanum Dioxide for Photocatalytic Applications, Photocatalysts - Applications and Attributes, Sher Bahadar Khan Eds., IntechOpen: London (2019). [2] K.Wojtaszek, et al. The influence of nitrogen doping on the electronic structure of the valence and conduction band in TiO2, J. Synchrotron Rad. 26, 145–151(2019). [3] J. Szlachetko and J. Sá, Rational design of oxynitride materials: From theory to experiment, CrystEngComm 14 (2013). [4] K. Wojtaszek, K. Tyrała, A. Wach, Custom-Made Cell Designed for Thermal Studies and In Situ X-Ray Spectroscopy Experiments, Acta Physica Polonica A 137, 54 (2020).

Acknowledgements: Authors would like to acknowledge National Science Centre, Poland (NCN) for partial support under grant no. 2015/18/E/ST3/00444.

Inducing Synergy in Bimetallic RhNi Catalysts for CO2 Methanation Dr Yuan (Helena) Wang1, Dr Hamid Arandiyan1, A/Prof Jason Scott2, Prof Karen Wilson1, Prof Adam F Lee1, Prof Rose Amal2 1School of Science, Royal Melbourne Institute of Technology University, Melbourne, Australia, 2Particles and Catalysis Research Group, School of Chemical Engineering, The University of New South Wales, Sydney, Australia M1.17: Inducing Synergy in Bimetallic RhNi Catalysts for CO2 Methanation, July 12, 2021, 09:50 - 10:00

With the emergence of abundant, low cost H2 from electrolysis using renewable energy, catalytic hydrogenation of CO2 into chemical products and fuels now offers an economically viable non-fossil route to hydrocarbons, and opportunity to mitigate anthropogenic CO2 emissions. Thermochemical CO2 reduction by H2 to methane may be catalysed by precious and/or Earth abundant transition metal nanoparticles.[1] Bimetallic variants may offer unique nanoparticle morphologies, surface terminations and active site ensembles (geometric effects), and be accompanied by unique electronic properties arising from charge transfer between constituent metals or metal-support interactions (electronic effects).[2] We recently investigated galvanic replacement (GR) as a catalyst synthesis strategy to induce intimate contact between Rh and Ni, while avoiding their alloying, employing X-ray absorption spectroscopy (XAS) and operando infrared (IR) spectroscopy to elucidate the roles of metal and support in CO2 hydrogenation to methane.[3] A bimetallic Ni@Rh core-shell catalyst exhibits a 3.5-fold rate enhancement for CO2 methanation relative to an analogue prepared by chemical reduction (CR), and is twice as active as monometallic Rh/Al2O3 (Fig. 1a-b). Superior performance of RhNi/Al2O3(GR) is attributed to Rh dispersion as an atomically thin RhOx shell encapsulating Ni nanoparticles, stabilised by a strong Rh-Ni interaction evidenced by XAS (Fig. 1c). Operando IR spectroscopy identifies reactively-formed CO from the dissociative chemisorption of CO2 over Rh as the key intermediate for methane production. Surface formate from the dissociative chemisorption of CO2 and subsequent hydrogenation (via spillover from Rh sites) over alumina is a catalytic spectator. This mechanistic insight paves the way to high activity nanostructured catalysts for CO2 methanation.

3 Figure 1. (a) Catalytic activity for CO2 methanation, (b) Rh K-edge XAS spectra, and (c) k -weighted Fourier transforms (radial distribution functions) Reference: [1] Y. Wang et al. Nat Commun 8, 2017, 15553 [2] Y. Wang et al. ACS Catal. 6, 2016, 6935-6947 [3] Y. Wang et al. Appl. Catal. B 277, 2020, 119029

Acknowledgement: The infrared spectroscopy experiments were conducted under the supervision of Dr. AnnetteTrunschke and Prof. Robert Schlöglat at Fritz Haber Institute in Germany.

Study of the electronic structure of Pt-based bimetallic systems by HERFD-XAS and XES Dr Jiatang Chen1 1Keio University, Yokohama, Japan, 2Western University, London, Canada T1.17: Study of the electronic structure of Pt-based bimetallic systems by HERFD-XAS and XES, July 13, 2021, 09:50 - 10:00

Pt is one of the best catalysts for a wide range of chemical reactions such as oxygen reduction reaction because of its unique 5d electron configuration. The high price and limited supply, however, have become an obstacle in the wide application of Pt-based catalysts. Introducing a 3d transition metal into Pt has been demonstrated to be an effective means to reduce the usage of Pt and raise the catalytic performance at the same time. The underlying mechanism of the improvement in catalytic activity associated with the lattice control upon alloying is yet fully explained. This study aims at elucidating the change of electronic structure of Pt upon alloying with 3d metals. Pt-Ni bulk alloys, Pt-Ni nanoparticles, and Pt-Cu nanoparticles as different forms of Pt-based bimetallic systems have been synthesized. XRD, XPS, XAS, and VTC-XES have been used to study the local and electronic structures of these bimetallic systems. A general trend of the charge transfer between Pt and 3d metals (Ni, Cu) in fcc bimetallic systems has been summarized regarding the L3,2-edge whiteline areas of HERFD-XAS, revealing a linear correlation between the unoccupied 5d5/2 and 5d3/2 states of Pt upon alloying. The subtle change of Pt valence band has been experimentally observed as a result of the competition between the strain effect and ligand effect accompanying the lattice control in Pt-Ni alloys, exhibiting varying valence bandwidths as well as band shifts. Synchrotron-based HERFD-XAS and XES have been demonstrated to be powerful tools to study the electronic structure of Pt-based materials because of the high resolution and elemental sensitivity, which reveals the origin of high chemical reactivity and provides guidance for materials design.

Research at the University of Western Ontario (UWO) is supported by NSERC (RGPIN-2019-05926), CFI, OIT, OMRI and CRC (TKS). This research used resources of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory and was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357, and the Canadian Light Source and its funding partners.

Carbon Supported Rhodium and Iridium Hybrid Catalysts for Selective Hydrosilylation of Alkynes Dr Max Roemer1, Dr Sinead T. Keaveney2, A/Prof James Downes2, Prof Barbara A. Messerle3 1The University Of Sydney, Sydney, Australia, 2Macquarie University, Sydney, Australia, 3University of New South Wales, Sydney, Australia M1.15: Carbon Supported Rhodium and Iridium Hybrid Catalysts for Selective Hydrosilylation of Alkynes, July 12, 2021, 09:40 - 09:50

Transition-metal catalysis is ubiquitous in synthetic chemistry and among the most important processes in the chemical industry. Surface immobilized transition metal catalysts, viz. hybrid catalysts, combine the efficiency of heterogeneous- and the selectivity of homogenous catalysts. Advantages over traditional homogeneous analogues are stability and simplified removal of the catalyst from the reaction mixture, which provides access to urgently needed more efficient and greener processes.1 Here, a series of new hybrid rhodium- and iridium based pyrazole-triazole complexes, attached to carbon black (CB) with varying tether lengths, is described.2 The syntheses of the complexes was accomplished by tin mediated acylation of aromatic systems3, Click-chemistry and metal coordination, affording the Rh- and Ir-complexes. The complexes are anchored to CB via a radical methodology, which affords the hybrid catalysts. The catalytically active metal complex as head group is connected to the surface via an alkyl linker. Initially, we optimised grafting conditions to gain control over the metal loading on the surface. We have prepared different hybrid catalysts with varying chain lengths. The hybrid catalysts were analysed using a number of techniques, including X-ray absorption spectroscopy. EXAFS spectra were recorded on the Rh K edge for the Rh containing catalysts and on the Ir L3 edge for the Ir containing catalysts. The hybrid catalysts are efficient catalysts that are robust and recyclable. In particular, they promote the hydrosilylation of terminal alkynes, generating a mixture of the and isomers of silylated alkenes. Interestingly, our series of homogeneous Rh complexes gives a mixture of all isomers, while the same Rh complexes immobilized on CB are selective. EXAFS in combination with control experiments helped to unravel the origin of the observed selectivity: a chemical modification of the head-group during the surface immobilization.2 Furthermore, the Ir catalysts are highly selective.

References 1. Valkenberg, M. H.; Hölderich, W. F., Catal. Rev. 2002, 44 (2), 321-374. 2. Roemer, M.; Gonçales, V. R.; Keaveney, S. T.; Pernik, I.; Lian, J.; Downes, J.; Gooding, J. J.; Messerle, B., Catal. Sci. Technol. 2021, 11, 1888-1898. 3. Chen, X.; Roemer, M.; Yuan, L.; Du, W.; Thompson, D.; del Barco, E.; Nijhuis, C. A., Nat. Nanotechnol. 2017, 12 (8), 797-803.

Acknowledgement Beamtime at the Australian Synchrotron at the XAS beamline is gratefully acknowledged (Projects 14297 and 15780).

Laboratory operando XAS study of iron(II) fluoride based conversion cathode material for Li-ion batteries Mr. Viktor Shapovalov1, Dr. Alexander Guda Guda1, Mrs. Vera Butova1, Mr. Abdelaziz Aboraia1, Dr. Alexander Soldatov1 1The Smart Materials Institute, Southern Federal University, Rostov-on-Don, Russian Federation M2.7: Laboratory operando XAS study of iron(II) fluoride based conversion cathode material for Li-ion batteries, July 12, 2021, 16:00 - 16:10

Li-ion conversion cathode material based on FeF2 was produced by calcination of MIL-88a-PVDF composite. Dynamics of its local atomic and electronic structure during charge-discharge was investigated by means of Fe K-edge operando XANES using a laboratory XAS spectrometer and a home-built electrochemical cell. The cell design allows for adjustment of the sample thickness to achieve an optimal value of the total sample absorption and signal-to-noise ratio. Over 300 Fe K-edge XANES spectra were collected in operando regime during initial discharge and 3 consecutive cycles. The prominent changes related to the redox processes were clearly observed. Principal component analysis (PCA) was employed to mathematically decompose a series of spectra for electrochemically-induced phase transition process to extract the pure spectra and concentrations of involved phases. Two components were successfully identified, one showing very good agreement with the spectrum of + - 0 metallic Fe (assuming FeF2 + 2Li + 2e => 2LiF + Fe conversion mechanism). Despite the other component shows good agreement with the sample before cycling, it is quite different from pure FeF2, closely resembling 2+ the spectrum of FeSO4, which indicates the octahedral coordination of Fe and possible presence of oxygen in the structure. The resulting concentrations of these components have artefacts in several regions. Introduction of the 3rd component for PCA analysis results in a more reasonable behavior of Fe0 rd component. The 3 component shows very good agreement with the experimental spectrum of pure FeF2. Two other components keep good agreement with metallic Fe and sample before cycling, respectively. Concentration analysis suggests rapid interchange between two Fe2+ phases at the beginning of each discharge. The sum of the concentrations of 2 different Fe2+ phases shows much more reasonable dependency on the cell SOC than the single Fe2+ phase in case of a PCA for 2 components.

Research was financially supported by the Ministry of Science and Higher Education of the Russian Federation (State assignment in the field of scientific activity, № 0852-2020-0019)

Dielectric response of BaTiO3 electronic states under AC fields via microsecond time- resolved X-ray absorption spectroscopy Mr Seiya Kato1 1Hiroshima University, Higashi-hiroshima-shi, Japan T1.19: Dielectric response of BaTiO3 electronic states under AC fields via microsecond time-resolved X-ray absorption spectroscopy, July 13, 2021, 10:00 - 10:10

Ferroelectric materials are widely used in various practical applications such as multilayer ceramic capacitors, actuators, and memory cells. Dielectric properties of a typical dielectric materials ATiO3 are affected significantly by A-site cations: For example, BaTiO3 and PbTiO3 have spontaneous electric polarizations, while SrTiO3 and CaTiO3 do not. However, previous related literature is primarily focused on the Ti off-center displacement. Therefore, we investigated electronic states of BaTiO3 under application of electric fields. It reveals that a correlated effect between Ti and Ba atoms is closely linked to the dielectric properties. Microsecond time-resolved X-ray absorption spectroscopy was employed because tiny changes in spectra are expected. It is essential to exclude any undesired influences caused by a DC measurement such as Joule heating and fatigues. The sample is an BaTiO3 thin film with a thickness of 650 nm prepared by pulsed laser deposition. It was confirmed by X-ray diffraction that the film had a preferred (001) orientation normal to the surface. Intensities of the pre-edge eg peak and shoulder structure just below the main Ti-K edge increase with an increase in the amplitude of the applied electric field, whereas that of the main peak decreases. The eg peak corresponds to excitation from the Ti 1s to the Ti 3d unoccupied states hybridized with O 2p states, while the shoulder structure is caused by the transition to the unoccupied Ba states, revealed by comparing Ti-K spectra of various ATiO3. Based on the multiple scattering theory, the increase and decrease of the eg and main peaks are simulated for different Ti off-center displacements. In contrast, the shoulder structure is not affected by changes in the Ti off-center displacement but is susceptible to the effect of the corner site Ba ions. This is the first experimental verification of electronic contribution of Ba to polarization reversal.

This research was performed under the approval of the Photon Factory Program Advisory Committee (PF-PAC; Contract Numbers 2015G580, 2017G587, and 2019G614) and was financially supported by JSPS KAKENHI Grant Numbers 18H01153, 19H02426, and 18K19126.

Molar Normalization and the Emergence of Isosbestic Points in Solution Phase Valence-to-Core X-ray Emission Spectroscopy of Battery Electrolytes Mr Diwash Dhakal1, Dr. Timothy T Fister2, Prof. Dr. Gerald T Seidler3 1Department of Materials Science and Engineering, University of Washington, Seattle, USA, 2Argonne National Laboratory, Lemont, USA, 3Department of Physics, University of Washington, Seattle, USA T1.10: Molar Normalization and the Emergence of Isosbestic Points in Solution Phase Valence-to-Core X-ray Emission Spectroscopy of Battery Electrolytes, July 13, 2021, 09:10 - 09:20

Valence-to-core x-ray emission spectroscopy (VTC-XES) is emerging as a powerful diagnostic for the electronic structure of chemical bonding. While much prior work has focused on molecular or crystalline systems, we report a detailed VTC-XES study of ion pairing in ZnCl2 and ZnBr2 aqueous solutions that are model electrolytes for aqueous Zn ion batteries (ZIB). Ion pairing in battery electrolytes strongly influences transport properties and also electrolyte stability. Unsurprisingly, x-ray absorption fine structure (XAFS) has proven powerful for characterizing ion pairing.[1] We show here, on a complementary note, that the strongly local nature of the VTC-XES gives a particularly clean signature of different local coordinations for metal ions in solution and can be used to quantify the degree of ion pairing. The combination of the two techniques in the future has clear benefits. Making use of the 3d10 configuration of the Zn2+ ion, we normalize the spectra via the main Kβ emission line integral intensity to achieve a consistent mole-normalized intensity scale. We find isosbestic points in VTC-XES as a function of ion activity and use a one-parameter linear superposition of octahedral and tetrahedral endpoint spectra with good performance. Our methods open avenues for future studies of ion- pairing in more complex and commercially relevant ZIB electrolytes and other ionic liquids. It has occasionally been argued that oxidation state is more simply determined from K energy shifts (when they occur) than from linear superposition analysis of XAFS due to the difficulty in creating reference standards that correctly encompass second shell structure for disordered materials.[2] The present work suggests extending this ‘less is more’ concept to the assessment of coordination geometries. Finally, we note that the VTC-XES study was performed with a lab-based spectrometer, providing another example of how the emerging availability of laboratory XAS empowers entire research projects and research programs.[3]

Acknowledgements: This research was supported by the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, and Basic Energy Sciences. [1] J.L. Fulton, et al., J. Phys. Chem. A 107, 4688 (2003), https://doi.org/10.1021/jp0272264 [2] W.M. Holden, et al., J. Phys. Chem. A 122, 5153 (2018), https://doi.org/10.1021/acs.jpca.8b02816 [3] E.P. Jahrman, et al., Rev. Sci. Instrum. 90, 024106 (2019), https://doi.org/10.1063/1.5049383

A new internally heated diamond anvil cell system for time resolved optical and x-ray measurements. Dr Yimin Mijiti1, Dr Marco Perri1, Mr Jean Coquet2, Dr Lucie Nataf2, Dr Marco Minicucci1, Dr Angela Trapananti1, Dr Tetsuo Irifune3, Dr Francois Baudelet2, Dr Andrea Di Cicicco1 1Physics Division, University Of Camerino, Camerino, Italy, 2Synchrotron SOLEIL, Saint-Aubin, France, 3Geodynamics Research Center, Ehime University, Matsuyama, Japan T3.15: A new internally heated diamond anvil cell system for time resolved optical and x-ray measurements., July 13, 2021, 18:40 - 18:50

We have developed and tested a new internally heated diamond anvil cell (DAC) as reported in a recent paper published in Review of Scientific Instruments [1]. The system includes a portable vacuum chamber and was designed for routine performance of x-ray and optical experiments. We have adopted a self-heating W/Re gasket design allowing for both sample confinement and heating. This solution proved to be very efficient to improve heating and cooling rates in a temperature regime up to 1500 K. The system has been widely tested and calibrated under high-temperature conditions. The temperature distribution was measured by in situ optical measurements and resulted to be uniform within the typical uncertainty of the measurements (5% at 1000 K). XAS (x-ray absorption spectroscopy) of pure Ge at 3.5 GPa were easily obtained in the 300 K–1300 K range, studying the melting transition and nucleation to the crystal phase. An original XAS-based dynamical temperature calibration procedure was developed and used to monitor the sample and diamond temperatures, indicating that heating and cooling rates in the 100 K/s range can be easily achieved using this device.

Figure 1. (a): 2D plot of the time resolved Ge K-edge XAS data presenting the absorption as function of photon energy and acquisition time (t). For clarity, the supplied electric power as function of time (square wave) is given at the left side of the figure. The Ge K-edge XAS spectrum at room temperature (t=0 s) is shown at the bottom. (b): 3D visualization of time dependent evolution of the near-edge XAS and the first diamond glitch (G1). The whole set of data was measured under nearly constant pressure at P=3.5 GPa.

[1] Y. Mijiti, M. Perri, J. Coquet, L. Nataf, M. Minicucci, T. Irifune, A. Trapananti, F. Baudelet, A. Di Cicco, Rev. Sci. Instrum. 91, 085114 (2020)

A novel multimodal probe for optical fluorescence, vibrational spectroscopy and XFM imaging Ms Jiarun Lin1,2, Dr David Paterson3, Prof Elizabeth New1,2,4, Prof Peter Lay1,2 1The University of Sydney, School of Chemistry, Sydney, Australia, 2The University of Sydney Nano Institute, Sydney, Australia, 3Australian Synchrotron, Clayton, Australia, 4Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, Sydney, Australia T2.9: A novel multimodal probe for optical fluorescence, vibrational spectroscopy and XFM imaging, July 13, 2021, 16:10 - 16:20

Understanding changes in biochemical processes on the cellular and subcellular level is a pivotal part of understanding disease processes. Cellular structure and function can be studied with a variety of imaging techniques, with varying capabilities dependent on mode of action, specific sensitivity and spatial and temporal resolution. Optical fluorescence techniques provide high specificity and spatial resolution, but probes are limited to one or two analytes. On the other hand, vibrational spectroscopy and synchrotron x-ray fluorescence microscopy (XFM) techniques map the spatial distribution of multiple analytes throughout the cell; the former is useful for organic biomolecules including lipids, proteins, carbohydrates and nucleic acids whilst the latter maps metals and other elements. In both cases, this information cannot be easily linked to subcellular localisation without further correlative techniques. To overcome the disadvantages of existing techniques, it is necessary to develop new tools. Multimodal imaging with two or more modalities can overcome the intrinsic limitations of each modality alone, providing complementary information for improved sensitivity and accuracy.

We have developed a novel multimodal probe for optical fluorescence, vibrational spectroscopy and XFM techniques. To our knowledge, this is the first small molecule probe of its kind. Initial optical fluorescence studies of our probe in multiple cell lines showed selective staining for lipid droplets, the major organelles for the storage of neutral lipids. Localisation was correlated with vibrational techniques performed separately, with the signal of the probe overlapping with lipid peaks. XFM mapping provided additional correlation, and XANES studies provided further insight on the localisation of our probe. This new multimodal approach provides complementary, orthogonal information on the chemical environment of the cell and its organelles.

This research was funded by the Australian Research Council. JL acknowledges the Australian Government for Research Training Program Scholarships. This research was undertaken on the X-ray fluorescence microscopy beamline at the Australian Synchrotron, part of ANSTO.

Exploration of sub-fs dynamics in matter with the concept of X-ray chronoscopy Dr Wojciech Błachucki1, Dr Anna Wach1, Dr Joanna Czapla-Masztafiak1, Dr Christopher Arrell2, Dr Pavle Juranić2, Dr Christopher Milne3, Prof Jacinto Sá4, Prof Jakub Szlachetko1 1Institute Of Nuclear Physics, Polish Academy Of Sciences, Kraków, Poland, 2Paul Scherrer Institute, Villigen, Switzerland, 3European XFEL GmbH, Schenefeld, Germany, 4Uppsala University, Uppsala, Sweden T3.20: Exploration of sub-fs dynamics in matter with the concept of X-ray chronoscopy, July 13, 2021, 19:00 - 19:10

The researchers of different disciplines are nowadays able to study matter with unprecedented temporal and spatial resolutions using the X-ray free electron lasers (XFELs) [1]. However, access to the attosecond domain remains elusive. This work reports on an innovative experimental approach to study sub- femtosecond processes in matter. It is based on the X-ray chronoscopy concept [2] and explores the time distribution of an ultra-short X-ray pulse before and after interaction with a medium. The pulse’s time structure can be measured using the state-of-the-art terahertz streaking cameras at XFELs [3] arranged in the camera-sample-camera sequence. The present work demonstrates capabilities of the THz streaking method and explores the X-ray chronoscopy approach for investigation of nonlinear processes at ultra-short time scales. The rate equation model used in this work confirms that the X-ray-induced dynamics leading to the target’s X-ray transparency can be probed through measurement of X-ray pulses’ time structure.

[1] B. W. J. McNeil, N. R. Thompson, Nature Photonics 4, 814 (2010). [2] D. J. Bradley et al., Optics Communications 15, 231 (1975). [3] U. Frühling et al., Nature Photonics 3, 523 (2009).

This work was supported by the National Science Centre (Poland) under Grant No. 2017/27/B/ST2/01890.

Full-potential multiple scattering calculations in EXAFS regime Mr Yoshiaki Tamura1, Mr. Kazuki Yoshikawa1, Dr. Fabio Iesari2, Dr. Toshihiro Okajima2,3, Prof. Keisuke Hatada1 1University of Toyam, Gofuku, Japan, 2Aichi Synchrotron Radiation Center, Seto, Japan, 3Kyushu Synchrotron Light Research Center, Tosu, Japan T1.21: Full-potential multiple scattering calculations in EXAFS regime, July 13, 2021, 10:10 - 10:20

1. Introduction In the calculation of X-ray absorption spectra using multiple scattering theory, the spherical approximation to the potential (Muffin-Tin approximation) has been widely used, but in the XANES region where the kinetic energy of photoelectrons is low, it is important to treat the potential beyond this (Full potential method) [1]. On the other hand, the spectra in the high energy regime (EXAFS) have been considered to be well analyzed in the framework of the Muffin-Tin approximation, since the backscattering which plays an important role in EXAFS is mainly due to the strong potential near the nucleus which is almost centrosymmetric. In Full-potential multiple scattering theory (FPMS) [1], the system of interest is divided into Voronoi cells for the calculation. The Voronoi cells are arranged in such a way that they fill the space and do not overlap with each other. Therefore, FPMS theory can handle clusters of large size and can calculate in the region of high photoelectron energy. In this work, we use the FPMS cords based FPMS theory from XANES to EXAFS regime. 2. Theory The theoretical expression for the X-ray absorption spectrum can be expressed as follows, . Photoelectrons excited from the core orbital with energy by the optical field created by incident X- rays with frequency propagate through the system which is described by the Green's function . In XANES and EXAFS, the photoelectrons are mainly in a continuum state, so the scattering theory can provide a correct physical picture for the Green’s function, , where and are matrix representations of the local numerical solutions when the system of interest is divided into scattering sites and are solutions of the local Schrödinger equation that are regular or divergent at the origin, respectively. The subscripts < and > denote solutions close to or far from the origin, respectively. The -matrix describes the scattering at a site, and is the multiple scattering matrix. 3. Results and Discussion We have calculated and compared the K-edge XANES and EXAFS spectra of Cu Foil for the Muffin-Tin approximation and the Full-potential method. And since the temperature dependence is important in the EXAFS regime, we developed FPMS incorporating thermal fluctuations.

References [1] K. Hatada, K. Hayakawa, M. Benfatto and C. R Natoli, J. Phys.: Condens. Matter 22, (2010) 185501-1-24.

Acknowledgment This work is supported by JST CREST (JPMJCR1861) and JSPS KAKENHI (19KK0139)

Speciation studies of Ru(II) anticancer complexes in biological systems with infrared and x-ray absorption spectroscopies Mr Thomas Stewart1, Dr Aviva Levina1, Dr Valerie Mitchell2, Dr Olga Antipova3, Dr Barry Lai3, Prof Peter Lay1 1School of Chemistry, University Of Sydney, Australia, 2Australian Synchrotron, Clayton, Australia, 3Advanced Photon Source, Lemont, United States of America T1.16: Speciation studies of Ru(II) anticancer complexes in biological systems with infrared and x-ray absorption spectroscopies, July 13, 2021, 09:40 - 09:50

Ruthenium complexes have emerged as promising alternatives to existing platinum chemotherapeutics, with Ru(II) arene complexes being particularly attractive owing to the number of properties and antitumour effects they can possess with different ligands.[1] However these effects, along with mechanisms of action and biological targets, are not fully understood. The behaviour of Ru complexes in all biological environments they encounter must be considered to ensure any observed effect is attributed to the appropriate species, which may differ from the administered complex.[2] X-ray spectroscopic techniques are particularly useful for such studies, providing information on both metal complex biotransformations in various biological media and localisation within target cells.[3] Infrared spectroscopy has been successfully applied to studying cellular biochemistry, including in response to treatments and other stimuli.[4] In this project, x-ray and infrared spectroscopies were used to examine the speciation and localisation of two leading Ru(II) arene drug candidates with differing anticancer effects – the antimetastatic RAPTA-C and cytotoxic RAED-C.[5] Speciation in bulk cells, buffer, cell culture medium and human serum were studied using x-ray absorption spectroscopy and localisation and biochemical impact in individual cells were examined using x-ray fluorescence and infrared spectroscopic mapping. This comprehensive investigation of the biochemical impact and transformations of the complexes in fluids and cancer cells provides new insights into their respective mechanisms of action and possible pathways through which they exert anticancer effects. References [1] Renfrew, A. Chimia 2009, 63, 217-219. [2] Levina, A.; Crans, D. C.; Lay, P. A. Coord. Chem. Rev. 2017, 352, 473-498. [3] Markham, J.; Liang, J.; Levina, A.; Mak, R.; Johannessen, B.; Kappen, P.; Glover, C. J.; Lai, B.; Vogt, S.; Lay, P. A. Eur. J. Inorg. Chem. 2017, 2017, 1812-1823. [4] Heidari, A. Glob. Imaging Insights 2018, 3(6), 1-8. [5] Janoš, P.; Spinello, A.; Magistrato, A. Curr. Opin. Chem. Biol. 2021, 61, 1-8.

[This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Part of this research was undertaken on the x-ray absorption spectroscopy beamline at the Australian Synchrotron, part of ANSTO. Support from the Australian Research Council is gratefully acknowledged

X-Ray Absorption Spectroscopic study of the interactions of new phosphorescent dyes under biological conditions Miss Kartika Wardhani1, Dr. Aviva Levina1, Prof. Georges E. R. Grau2,3, Prof. F. Richard Keene4,5, Prof. J. Grant Collins6, Prof. Peter A. Lay1,2,7 1School Of Chemistry, The University Of Sydney, Sydney, Australia, 2Sydney Nano, Sydney Cancer Network, Marie Bashir Institute, The University of Sydney, Sydney, Australia, 3Vascular Immunology Unit, Department of Pathology, School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, Australia, 4Department of Chemistry, School of Physical Sciences, The University of Adelaide, Adelaide, Australia, 5Australian Institute of Tropical Health and Medicine/Centre for Molecular Therapeutics, James Cook University, Townsville, Australia, 6School of Science, The University of New South Wales, Australian Defence Force Academy, Canberra, Australia, 7Sydney Analytical, The University of Sydney, Sydney, Australia M3.28: X-Ray Absorption Spectroscopic study of the interactions of new phosphorescent dyes under biological conditions, July 12, 2021, 19:40 - 19:50

Microvesicles (MVs) released by all living cells are crucial to all lifeforms, from single-cell organisms and how they respond to their environment, to higher lifeforms, such as humans, for normal physiological responses and progression of disease pathogenesis. However, the lack of MV-specific phosphorescent dyes and analytical technologies for MVs poses a barrier to clinical translation. In this work, new phosphorescent dyes are shown to be highly selective for detection of MVs released from immune system THP-1 monocytic leukemia cells, which have many advantages over standard staining technologies. X-ray Absorption Spectroscopy (XAS) analysis has demonstrated that the dyes remain intact in biological media, which provides information on their preferred biomolecular targets with the MVs. The high stability of the phosphorescent dyes will open up unprecedented opportunities to study MV biology with selective dyes that make major contributions to understanding disease pathologies, such as cancer and degenerative- and pathogen-induced brain damage, as well as changes in MV signaling in response to treatments with anti-cancer drug.

P.A.L. is grateful for financial support from the Australian Research Council (ARC) including an ARC Senior Research Associate position for A.L. (DP180102741). K.W. thanks the Indonesia Endowment Fund for Education Scholarship (LPDP). G.E.G. was supported by the National Health & Medical Research Council of Australia (APP1099920). This research was undertaken on the XAS beamline at the Australian Synchrotron, part of ANSTO.

Operando Laboratory-based XANES analysis at Multiple K edges of CO2 Hydrogenation Catalysts Dr. Nina S. Genz1, M.Sc. Antti-Jussi Kal•lio2, Dr. Ramon Oord1, Dr. Florian Meirer1, Prof. Simo Huotari2, Prof. Dr. ir. Bert M. Weckhuysen1 1Utrecht University, Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht, Netherlands, 2University of Helsinki, Department of Physics, Helsinki, Finland M3.17: Operando Laboratory-based XANES analysis at Multiple K edges of CO2 Hydrogenation Catalysts, July 12, 2021, 18:50 - 19:00

Deducing a fundamental understanding of structure-performance correlations of solid catalysts via operando experiments is indispensable for a rational design of improved catalyst formulations.[1] Inherent to such a fundamental understanding is the use of appropriate characterization techniques of solid catalysts at work. This ambition also drives the continuous development of advanced X-ray characterization techniques for catalysis research. Amongst those, laboratory-based X-ray absorption spectroscopy (XAS), especially X-ray absorption near-edge structure (XANES) analysis, emerged as highly promising approach for a fundamental characterization of catalysts, including supported metal nanoparticles, which lack long-range ordering.[2] Lab- XAS offers new opportunities in advanced catalyst characterization and presents a real alternative and complement to precious beamtime at synchrotron facilities, which has become even more important during times of travel restrictions as those of COVID-19.

We successfully designed a setup for performing in situ XANES experiments on solid catalysts at relevant reaction conditions in the laboratory.[2, 3] By upgrading this setup, we are now able to perform operando, quasi-simultaneous XANES measurements at multiple K edges, allowing for operando XANES studies of mono- , bi-, and trimetallic CO2 hydrogenation catalysts.

Here, we focus on the study of supported bi- and trimetallic catalysts consisting of Ni, Fe, Cu, and corresponding monometallic counterparts. Detailed operando XANES studies provided new insights into synergistical effects through metal alloy formation during catalyst reduction and their influence on catalytic performance in CO2 hydrogenation. Hereby, we were able to unravel metal-dependent differences in reducibility and re-oxidation behavior of the multi-element catalysts. The applicability of operando lab-based XANES experiments performed quasi-simultaneously at multiple K edges paves the way for advanced multi- element catalyst characterization complementing such studies at synchrotron facilities.

[1] B.M. Weckhuysen, Phys. Chem. Phys. Chem.,5, 2003, doi: 10.1039/B309654H. [2] J.G. Moya-Cancino et al., ChemCatChem 11, 2019, 1039–1044. [3] A.-P. Honkanen et al., Rev. Sci. Instrum. 90, 2019, 033107.

N.S. Genz is funded by German Research Foundation (DFG) – 452243354.

Virtual Laboratory at European XFEL: teaching, training and experimental planning Dr Alexander Guda1, K. Kubicek2, A. Britz2, K Ebbesen2, V. Myalkina3, M. Soldatov1, D. Vlasenko1, V. Popuzin3, K. Namavir1, A.V. Soldatov1, Ch. Bressler2,4 1The Smart Materials Research Institute, Southern Federal University, , Russia, 2European XFEL GmbH, , Germany, 3Institute of mathematics, mechanics and computer science, Southern Federal University, , Russia, 4Universität Hamburg, , Germany M2.5: Virtual Laboratory at European XFEL: teaching, training and experimental planning, July 12, 2021, 15:50 - 16:00

Experiments at large scale facilities require the presence of a large team due to their complexity. These teams perform various highly specialized tasks, such as experiment setup, execution and data evaluation, which complement each other. The specialization of the scientists ensures the success of the measurements, but it also means that each individual team member usually does not get a detailed insight into the other specialties. The beamtime planning, teaching and team communication is complicated due to very limited time period available for each group for the onsite experiment. A virtually set up practical has the potential to teach students and users about the technical details of a given experiment without the need of using the physical instrumentation right away. We have created a virtual model of FXE beamline at European XFEL, which has been programmed to operate according to physical laws of interaction of X-rays with matter. The software can be executed on PC and VR headset and provides the means to get training on equipment. The entire 20 m long scientific instrument is packed with diagnostic and other equipment, each of which is accessible from the software package. The lab practical gives users the full power to operate such a virtual instrument, and observe and learn, what such complex instrumentation really does in detail. They are also able to extract “real” data, with a signal quality defined by the students ability to set up the experiment accordingly.

Figure 1. The screenshots from the virtual FXE software demonstrating the interface of interaction with a Spectrum analyzer and animation of X-ray scattering towards LPD detector.

This work was carried out in cooperation with Univirlab Ltd and supported by European XFEL and Joachim Herz Stiftung.

Laboratory optical pump soft X-ray probe NEXAFS spectroscopy on organic thin films Mr Adrian Jonas1, R. Gnewkow2, B. Kanngießer1, H. Stiel3, I. Mantouvalou1,2 1Technical University Berlin, , Germany, 2Helmholtz-Zentrum Berlin, , Germany, 3Max-Born-Institute, , Germany T3.10: Laboratory optical pump soft X-ray probe NEXAFS spectroscopy on organic thin films, July 13, 2021, 18:10 - 18:20

Optical pump soft X-ray probe near edge X-ray absorption fine structure (pp-NEXAFS) spectroscopy is a method to measure the photoinduced dynamics of the electronic structure of a given sample. Pp-NEXAFS is commonly carried out at synchrotron radiation facilities or free electron laser were beamtime is limited. For laboratory soft X-ray pp-NEXAFS experiments high harmonic generation (HHG) sources or laser produced plasma (LPP) sources can be used. While HHG sources produces coherent light with ultrashort pulse length LPP sources work at larger timescales and reach much higher photon flux especially at energies higher than 500 eV. Most studies are widely focused on the investigation of processes in the gas or liquid phase but often scientific questions deal with dynamics in the solid phase. Especially the field of organic electronics or photovoltaics can profit from new experimental possibilities for the investigation of thin organic films.

We present a soft X-ray pp-NEXAFS spectrometer that is based on a laser-produced plasma source and operates with photon energies for the probe pulse up to 1303 eV with a resolving power of > 1000 and a time resolution of 500 ps [1,2]. Pp-NEXAFS spectra at the C K-edge and N K-edge at different delay times after laser excitation on various organic thin films will be shown [3]. The ground state NEXAFS is compared to time dependent density functional theory calculations (TDDFT) in order to assign the characteristic NEXAFS features and gain further insights into the dynamical processes. Also the possibility for Quick NEXAFS with 10 ms time resolution using a soft X-ray CMOS detector is discussed [4].

1. I. Mantouvalou et al., Rev. Sci. Instrum., 2015, 86, 35116. [1] A. Jonas et al., Optics Express, 2019, 27:25, 36525. [2] A. Jonas et al., Anal. Chem. 2020, 92:23, 15611–15615. [3] A. Jonas et al., Rev. of Sci. Instr. 2021 92, 023102.

Advances In Time-Resolved Laser Pump X-ray Multi-probe Absorption Spectroscopy at the APS Dr Eli Kinigstein1, Guy Jennings1, Charles Kurtz1, Anne Marie March2, Xiaobing Zuo1, Christopher Otolski2, Gilles Doumy2, Xiaoyi Zhang1 1X-ray Science Division, Argonne National Lab, , , 2Chemical Science and Engineering Division, Argonne National Lab, , T1.12: Advances In Time-Resolved Laser Pump X-ray Multi-probe Absorption Spectroscopy at the APS, July 13, 2021, 09:20 - 09:30

Synchrotron based X-ray Transient Absorption Spectroscopy (XTA) combines the insights of hard x- ray spectroscopy with synchronized laser excitation, in a time resolved pump-probe scheme. X-ray multiprobe data acquisition (XMP DAQ) generates XTA data from every available x-ray pulse, and generates a highly consistent set of time resolved x-ray absorption spectra at thousands of pump-probe time delays simultaneously. XMP DAQ therefore enables an extremely efficient and self-consistent route to XTA characterization of photochemical and photophysical phenomena. Presently I describe a qualitatively new XMP DAQ technique called X-ray Multi-Probe with Asynchronous Acquisition (XMP-AA). XMP-AA utilizes a frequency mismatch between the pump laser oscillator and the synchrotron x-ray pulses to simultaneously collect XTA spectra every 1.4 nanoseconds in a variable time window. I present XTA data of the Fe K-edge, obtained by exciting FeCN6 at 257nm, and acquired with XMP-AA. This data set illustrates utility of XMP-AA for analyzing in-situ photochemical reactions. I describe some of the hardware which make XMP-AA possible, including the new generation of x-ray photon detectors developed at the APS. These new detectors enable XTA data acquisition in APS 324 bunch mode (11.36ns pulse spacing) for the first time.

This material is based upon work supported by Laboratory Directed Research and Development (LDRD) funding from Argonne National Laboratory, provided by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-06CH11357.

Impact of Al and Si ions on the structural organization of Fe-OM nanoaggregates Dr Anthony Beauvois1, D. Vantelon2, J. Jestin3, M. Davranche4 1Sorbonne Université, , France, 2Synchrotron SOLEIL, , , 3Grenoble Cedex, , , 4Géosciences Rennes, , T3.1: Impact of Al and Si ions on the structural organization of Fe-OM nanoaggregates, July 13, 2021, 17:30 - 17:40

Natural colloids composed of iron (Fe) and organic matter (OM) are a key factor controlling the mobility of metallic pollutants due to their high adsorption capacity. The physico-chemical conditions under which Fe- OM nano-aggregates are formed influence their structural organization and the Fe speciation. In this study, we probed the influence of two major elements of natural systems, aluminum (Al) and silicon (Si), expected to influence the Fe-OM nano-aggregates organization and to have an impact on the Fe speciation. Fe-OM-Al/Si nano-aggregates, mimicking environmental ones, have been synthesized with different Fe/OM and oxyanion/Fe ratios. Their multiscale structural organization has been characterized combining XAS and SAXS measurements and cryo-TEM observations. In these systems, the Fe speciation is complex and variable, depending on the Fe and oxyanion content relative to OM. The Fe phases are composed of oligomers and ferrihydrite-like nanoparticles (Fh-Np), both integrated in the OM matrix. The Fh-Np form a fractal network whose organization is controlled by the OM. As Fe/OM increases, the oligomer content decreases in favor of the Fh-Np, which increases in size. By adding Al or Si, this phenomenon may strongly differ. Al, forming oligomers and bound to both Fe and OM, clearly allows the growth of the Fh-Np/oligomer ratio, the Fh-Np size and the whole nano-aggregates structure. On the contrary, Si, bound to Fe, has the exact opposite effect. These differences result from the different interactions between Al and Si and the components of the Fe-OM nano-aggregates. These results clearly highlight the antagonist effect of the major elements, Al and Si, on the structural organization of Fe-OM colloids. They impact all the levels of organization: the Fe speciation and the OM and Fe phases arrangement. This structural variability has a direct consequence on the ability of Fe-OM nano- aggregates to trap and transport pollutants in the hydrographic network.

[This study is part of a thesis project funded by the French administrative region Brittany and by the SOLEIL- LLB through the ‘ORPHREA’ project. It was funded by the French “Institut national des sciences de l'Univers” (INSU) through the “Initiative Structurante EC2CO – BIOHEFECT”.]

Combined EXAFS and XPDF analysis of calcium methoxide short-range structure Dr Thokozile Kathyola1, Dr Elizabeth Willneff1, Professor Sven Schroeder1,2, Dr Giannantonio Cibin2, Dr Philip Chater2 1University Of Leeds, Leeds, United Kingdom, 2Diamond Light Source, Didcot, United Kingdom T3.26: Combined EXAFS and XPDF analysis of calcium methoxide short-range structure, July 13, 2021, 19:30 - 19:40

Extended X-ray absorption fine structure (EXAFS) and X-ray Pair Distribution Function (XPDF) analysis are versatile complementary techniques that provide information about local structure and bonding in crystalline and non-crystalline materials. Both techniques provide information about the coordination number of neighbouring atoms, bond distances and the degree of static/thermal disorder. EXAFS is a well-established element-specific method that provides short-range order information around the X-ray absorber of interest. XPDF is not element-specific, but provides short-range order information similar to EXAFS, alongside long- range structure.

Calcium methoxide (Ca(OCH3)2) is one of the prominent heterogeneous catalysts that are being used in the formation of sustainable biolubricants and biodiesel from natural/synthetic oils via transesterification. Other compounds that have been considered as viable catalysts include calcium oxide (CaO) and calcium hydroxide (Ca(OH)2). Unlike these two bases, which have been comprehensively characterised using EXAFS, the short-range crystalline structure of Ca(OCH3)2 is yet to be fully determined. Not much is known about its structure beyond the indication that it has the same hexagonal space group (P-3m1) as Ca(OH)2. This was determined over 40 years ago, using powder X-ray diffraction and mid infrared spectroscopy, and has not been investigated since. Hence, we present a comparative study on the local structure of CaO, Ca(OH)2 and Ca(OCH3)2 using EXAFS and XPDF analysis. Our results demonstrate how a new/refined model crystal Ca(OCH3)2 structure was obtained using XPDF data, crystal symmetry and unit cell dimensions. This model was subsequently used in EXAFS simulations to determine atom coordination numbers, bond distances and static disorder in Ca(OCH3)2. To the best of our knowledge, this is the first time EXAFS and XPDF data has been presented on a calcium alkoxide. The structural information obtained from this study could benefit development of more sophisticated alkoxide-based heterogenous catalysts. This multi-technique ex situ analysis of the three basic calcium catalysts could also inform operando studies of alkaline-earth metal catalysis with these techniques.

This research was supported by EPSRC Centre for Doctoral Training in Complex Particulate Products and Processes (Grant: EP/L015285/1). The authors are grateful to Diamond Light Source for the EXAFS beamtime awards SP14673 and SP17686 at beamline B18 and XPDF beamtime award EE17391 at beamline I15-1. TAK gratefully acknowledges financial support from Infineum UK Ltd and the EPSRC CMAC Research Hub. SLMS acknowledges support of the Bragg Centenary Chair by the Royal Academy of Engineering, Infineum UK Ltd and Diamond Light Source.

Multivariate Curve Resolution for in situ XAS: general strategy and constraint selection Eli Stavitski1, Dr Denis Leshchev1 1National Synchrotron Light Source II, Brookhaven National Laboratory, , USA T1.8: Multivariate Curve Resolution for in situ XAS: general strategy and constraint selection, July 13, 2021, 09:00 - 09:10

Modern synchrotron in situ X-ray Absorption Spectroscopy (XAS) experiments typically record tens to hundreds of spectra, making the analysis of individual spectra tedious and time-consuming. To take full advantage of these large datasets, novel approaches based on data factorization must be employed. A typical analysis focuses on the following: (1) number of independent components (or spectra) present in a dataset; (2) the length of transformation stages, e.g. time scales, range of temperatures or potentials; (3) retrieval of the “pure” spectra of species present in the process. The first two questions can be addressed with principle component analysis (PCA) performed by means of singular value decomposition (SVD), where components are inspected for significance and used for data interpretation. The final step, retrieval of the pure spectra, requires employing a priori knowledge about the system. Multivariate Curve Resolution (MCR) method presents a convenient framework for such retrieval as it relies on utilization of a set of constraints that ensure that the retrieved spectra are physically meaningful. While recent years saw growth of MCR popularity, the applications remain limited due to the complexity associated with selection of constraints and starting solutions. Here we demonstrate two cases where data factorization and careful constraint curation delivers insights into reaction dynamics. First, we consider a Co catalyst where we use MCR to characterize its reduction process and are able to observe the formation of an intermediate Co oxide species [1]. Second, we investigate the dynamics of titania growth using atomic layer deposition over ZnO nanowires [2]. Here, MCR allows us to track the relative contributions from interface/surface and bulk of the film as a function of time providing insight into the film growth process. We further find that the pure spectrum of the interface component corresponds to tetrahedral Ti motifs that contrast with octahedral Ti in bulk TiO2. These examples showcase the possible strategies for application of MCR and point towards streamlining of MCR application in XAS experiments.

[1] R. Liu et al, Appl. Catal. B, 284 (2021), 119787 [2] X. Qu et al, Chem. Mater. (2021) DOI: 10.1021/acs.chemmater.0c04547

This research used beamline 8 ID (ISS) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704.

A chemist view of electronic structure: Lessons from laboratory and synchrotron x-ray spectroscopy Professor Serena DeBeer

M: Plenary 2 | Serena DeBeer | A chemist view of electronic structure: Lessons from laboratory and synchrotron x-ray spectroscopy, July 12, 2021, 16:25 - 17:15

In recent years, there has been increasing interest in the development and application of in-house X- ray spectrometers. In this talk, I will provide a historical perspective on these developments. Recent research conducted using in-house X-ray spectrometers in our own laboratories will be presented, with a focus on the electronic structure information that can be obtained and an emphasis on how such studies complement synchrotron-based research. The relative advantages and disadvantages of in-house setups will be highlighted. Further, the experiments that still require synchrotrons will be discussed. Focus will be placed on X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES), and resonant XES (RIXS). Future possibilities for in-house setups will be highlighted.

How X-ray spectroscopy in heterogeneous catalysis will benefit from the new generation synchrotron sources? Dr Amélie Rochet

M: Opening & Plenary 1 | Amélie Rochet | How X-ray spectroscopy in heterogeneous catalysis will benefit from the new generation synchrotron sources?, July 12, 2021, 07:30 - 08:15

Brazilian Synchrotron Light Laboratory (LNLS), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-970, Campinas, São Paulo, Brazil

Among the different techniques available in synchrotron facilities, X-ray absorption spectroscopy (XAS) has become an indispensable method for probing the local structure and composition of heterogeneous catalysts. Due to the high penetration of hard X-rays and the non-destructive nature of the analysis, XAS is perfectly suited for in situ and operando studies, revealing the active sites and establishing relationships between local structure and catalytic performances. Moreover, the high time-resolution available on dedicated XAS beamlines in combination with the use of efficient chemometric tools, such as the multivariate curve regression with alternating least square (MCR-ALS) method shed light on transient species formed upon reaction. I will present studies on hydrodesulphurisation catalysts where complementary information obtained by time-resolved XAS and Raman spectroscopy enabled the identification of intermediate species leading to detailed reactional mechanisms [1-2]. These experiments performed at 3rd generation synchrotrons will be put in perspective with the 4th generation synchrotron radiation facilities, such as the recently built Brazilian synchrotron source Sirius [3]. The exploration of catalytic reactions should directly benefit of the huge improvement of brilliance and coherence properties opening new ways towards catalysts characterisation, with faster measurements for time-resolved studies, better spatial resolution with nano-spectroscopy, higher sensitivity to various chemical and physical properties with emerging X-ray spectro-imaging methodologies.

[1] Rochet, A.; Ribeiro Passos, A.; Legens, C.; Briois, V. Catal. Struct. React. 2017, 3, 33. [2] Rochet, A.; Baubet, B.; Moizan, V.; Devers, E.; Hugon, A.; Pichon, C.; Payen, E.; Briois, V. J. Phys. Chem. C 2017, 121, 18544. [3] Lin, L., Milas, N., Mukai, A. H. C., Resende, X. R., De Sá, F. H. (2014) J. Sync. Rad. 2014, 21, 904.

Taking Roads Less Traveled to Uncover the Structure of Rust Minerals: Ferrihydrite Michel Sassi1, Anxu Sheng2, Odeta Qafoku1, Mark E. Bowden1, Alpha T. N’Diaye3, Carolyn I. Pearce1, Richard N. Collins4, Juan Liu2, Kevin M. Rosso1,*

1Pacific Northwest National Laboratory, Richland, Washington, U.S.A. 2Peking University, Beijing, China 3Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, U.S.A. 4University of New South Wales, Sydney, Australia

T: Plenary 3 | Kevin Rosso | Taking Roads Less Traveled to Uncover the Structure of Rust Minerals: Ferrihydrite, July 13, 2021, 07:30 - 08:15

Fe(III)-(oxyhydr)oxides are critical secondary minerals in soils and sediments that control iron bioavailability and the cycling of coupled elements. The nanomineral ferrihydrite is a poorly crystalline and metastable initial form, typically resulting from aqueous Fe(II) oxidation during meteoric recharge of otherwise stagnant suboxic pore water. Because it is metastable, ferrihydrite will spontaneously transform into more crystalline and persistent bulk phases such as goethite or hematite. However, in the absence of a redox catalyst such as Fe(II), this transformation tends to be kinetically hindered, consistent with both 1) the extremely low aqueous solubility of Fe(III), which restricts the dissolution/reprecipitation pathway, and 2) the extremely low solid- state diffusivity of lattice iron expected at room temperature, which restricts the topotactic transformation pathway. Particle-based recrystallization to goethite has been proposed, but this cannot transform ferrihydrite without recruiting one or both of these two slow pathways. Furthermore, in the presence of millimolar aqueous Fe(II), the goethite product and its physical characteristics are essentially unchanged, but the kinetics are, intriguingly, about 1000x faster. We report a comprehensive experimental/computational investigation into this transformation at suboxic conditions and circumneutral pH, resolved at the iron site occupancy level. In the absence of added Fe(II), two-line ferrihydrite aged over two years was periodically characterized using in situ XRD with detailed line shape analysis, electron microscopy, and synchrotron Fe L-edge and O K-edge XAS/XMCD spectroscopy quantitatively analyzed using MRCI ab initio calculations. The results are compared to DFT calculations of the relative thermodynamic stabilities of several possible ferrihydrite structure models as a function of hydration state, and goethite, along with activation energies for solid-state diffusion of iron along hypothetical topotactic channels. Tetrahedral Fe(III) is clearly resolved in 2 d ferrihydrite, diminishing concomitantly with increasing octahedral Fe(III) and decreasing net magnetic moment until the first appearance of goethite at ~ 100 d. Calculated iron diffusion activation energies are as low as 1 eV per unit cell. In the presence of Fe(II), the accelerated transformation kinetics appear to involve facile mass transfer of a labile Fe(III) pool created on ferrihydrite surfaces during oxidative adsorption of Fe(II). The findings are being assembled into transformation kinetics models that will help resolve the relative importance of dissolution/reprecipitation vs. solid-state pathways, to lay out the first atomically-resolved mechanism of this important Fe(III)- (oxyhydr)oxide mineral transformation.

Unveiling the Nature of Active Site in Heterogeneous Metal Catalysis Professor Junling Lu

T: Plenary 4 | Junling Lu | Unveiling the Nature of Active Site in Heterogeneous Metal Catalysis, July 13, 2021, 16:30 - 17:15

Heterogeneous catalysts possess very complex structures. Identification of the nature of catalytic active site as well as tracing their dynamic structure changes under different environments is of great importance but challenging. In many catalytic reactions, the question of the nature of the active sites has been debated for decades, which significantly impedes atomic-level understanding of the structure-activity relationships and developments of advanced catalysts with high efficiency. X-ray adsorption spectroscopy (XAS) is a powerful tool for determining the electronic structure and the local geometry around the absorbing atom. The feature of X-ray in and out enables it to be an ideal tool for in-situ/operando characterization of the structure of catalytic active sites under reaction conditions without any limitation of reaction pressures.

In this presentation, three examples of metal-oxide interfaces, bimetallic nanoparticles (NPs), and single-atom catalysts (SACs) characterized by XAS will be discussed. Firstly, in situ XAS was employed to unveil the structure evaluation of atomically-dispersed Fe1 species on Pt NPs under different environments. We showed that the Fe1 species changed from Fe1O4 to Fe1(OH)2 and to Fe1(OH)3 at room temperature in oxidizing, reducing and reaction conditions of preferential CO oxidation in H2, respectively. Moreover, in situ X-ray absorption near-edge structure (XANES) further demonstrated that atomically dispersed Fe1(OH)x species had a much higher reducibility than Fen(OH)x clusters, confirming the high intrinsic activity of Fe1(OH)x-Pt single interfacial sites [1]. Secondly, in situ XAS demonstrated that remarkable improvements in both activity and selectivity in benzonitrile hydrogenation were attributed to the formation of a Pd1Ni single-atom surface alloy structure, where Pd is atomic-dispersed of within the outermost layer of Ni NPs [2]. Thirdly, XAS revealed the electronic properties of metal single atoms (Pd1, and Pt1) in SACs as governed by the local coordination atoms, have an enormous impact on the activity and stability of SACs [3-5]. In brief, these studies suggest that in situ XAS is a powerful tool for unveiling the nature of catalytic active site in the real heterogeneous catalyst under reaction conditions, thus greatly facilitating the atomic-level understanding of the structure-activity relationships.

References [1] L.N. Cao, W. Liu, Q.Q. Luo, S.Q. Wei, J.L. Yang, J.L. Lu, et al., Nature, 565 (2019) 631-635. [2] H.W. Wang, Q.Q. Luo, W. Liu, Y. Lin, Q.Q. Guan, X.S. Zheng, H.B. Pan, J.F. Zhu, Z.H. Sun, S.Q. Wei, J.L. Yang, J.L. Lu, Nat. Commun, 10 (2019) 4998. [3] H. Yan, H. Cheng, H. Yi, Y. Lin, T. Yao, C.L. Wang, J.J. Li, S.Q. Wei, J.L. Lu, J. Am. Chem. Soc., 137 (2015) 10484-10487. [4] J.J. Li, Q.Q. Guan, H. Wu, W. Liu, Y. Lin, Z.H. Sun, X.X. Ye, X.S. Zheng, H.B. Pan, J.F. Zhu, S. Chen, W.H. Zhang, S.Q. Wei, J.L. Lu, J. Am. Chem. Soc., 141 (2019) 14515-14519. [5] H. Yan, Y. Lin, H. Wu, W.H. Zhang, Z.H. Sun, H. Cheng, W. Liu, C.L. Wang, J.J. Li, X.H. Huang, T. Yao, J.L. Yang, S.Q. Wei, J.L. Lu, Nat. Commun., 8 (2017) 1070.

New on the Physics Menu: Superconducting Sandwiches! Mr Andrew Chan M1.16: New on the Physics Menu: Superconducting Sandwiches!, July 12, 2021, 09:40 - 09:50

Our cuprate-manganite ‘superconducting sandwich’ multilayers exhibit a highly unusual magnetic-field induced insulating-to-superconducting transition, contrary to the commonly held understanding that magnetic fields are detrimental to superconductivity [1, 2]. This new phenomenon is unequivocally a result of the specific magnetic and electronic properties of the manganite (Pr0.5La0.2Ca0.3MnO3 (PLCMO) or Nd0.65(Ca0.7Sr0.3)0.35MnO3 (NCSMO)) coupling with the cuprate (YBa2Cu3O7-δ, YBCO) [3, 4]. We hypothesize this new behaviour has origins at the YBCO-manganite interfaces. Using linearly polarized soft X-rays resonant to the Cu and Mn L-edges, we resolved the interfacial electronic and orbital structure in our sandwiches.

In this talk, we highlight the X-ray linear dichroism (XLD) technique (analogous to the ‘search light’ effect) specific to epitaxially grown thin film multilayers to determine orbital occupation and orientation. Importantly, we identify interfacial orbital reconstruction effects as one key piece of the puzzle in the ongoing goal of understanding the coupling between the cuprate and manganite that leads to these intriguing new properties.

References: [1] Bert et al. Direct imaging of the coexistence of ferromagnetism and superconductivity at the LaAlO3/SrTiO3 interface. Nat. Phys. (2011) 7, 767-771. [2] Gray et al. Superconductor to Mott insulator transition in YBa2Cu3O7/LaCaMnO3 heterostructures. Sci. Rep. (2016) 6:33184, 1-9. [3] Mallett et al. Granular superconductivity and magnetic-field-driven recovery of macroscopic coherence in a cuprate/manganite multilayer. Phys. Rev. B (2016) 94, 180503(R). [4] Perret et al. Coupled Cu and Mn charge and orbital orders in YBa2Cu3O7/Nd0.65(Ca1-ySry)0.35MnO3 multilayers. Comms. Phys. (2018) 1:45, 1-9.

Application of machine learning methods for analysis of pre-edge XANES spectra of Fe:SiO4 system Mr Danil Pashkov1, Dr Alexander A. Guda1, Dr Sergey A. Guda1, Prof Alexander V. Soldatov1 1Southern Federal University, Rostov-on-Don, Russian Federation Poster Session

Advanced quantitative analysis of the local atomic geometry around active catalytic sites requires novel experimental method e.g. the pre-edge structure of X-ray absorption near edge spectra (XANES) measured in the high-energy resolution fluorescence detected mode. However, there is no widely used ab initio theoretical method which could be routinely applied to the analysis of such experimental data except parametric multiplet calculations. To overcome the parameter tuning procedure, the local Hamiltonian DFT, built on the basis of Wannier orbitals, is used - the so-called multiplet ligand field theory (MLFT). Using the XTLS code in the framework of MLFT using maximally localized Wannier functions (MLWF) it is possible to calculate pre- edge region of X-ray absorption spectra.

However the process of pre-edge XANES spectra computation according to MLFT approach is a complicated procedure, which requires using a lot of software, such as: Wien2k, XTLS code, Wannier90 and several additional programs. We developed «w2auto» program, which automates the whole process of pre-edge XANES computation. «w2auto» emulates work in w2web interface of Wien2k software and provides opportunity to run all necessary programs without any user operations.

In recent years machine learning has become a powerful instrument for solving numerous scientific problems. In this work we have used machine learning methods for analysis of the Fe:SiO4 pre-edge XANES spectra. As recently shown, machine learning methods have been successfully applied to the quantitative analysis of spectroscopic data of X-ray near edge spectroscopy (XANES). In the present work we show applicability of machine learning methods to extract structural information of the Fe:SiO4 system. During this work we have collected 60 pre-edge XANES spectra in differrent coordination (from 2-fold to 6-fold) and oxidation states (Fe2+ and Fe3+) using «w2auto» program.

We used this dataset to train and validate several machine learning methods such as SVM, Logistic regression, Decision Tree, ExtraTrees and artificial neural network to determine both coordination number and oxidation state by spectrum.

Acknowledgment The study was carried out with the financial support of the Russian Foundation for Basic Research (RFBR) in the framework of the scientific project №20-32-70227

Electronic state of surface adsorbed molecules in photocatalytic reaction Mr Kohei Shibuya1, Mr Ryosuke Yamamoto1, Prof. Kenta Amemiya1,2 1Graduate School of Science, The University of Tokyo, Bunkyo City, Japan, 2Institute of Materials Structure Science, KEK, Tsukuba City, Japan Poster Session

- Superoxide anion (O2 ) works as a part of the bactericidal mechanism in the immune system and phagocytic cells in the living body. Superoxide anion is also produced in the photocatalytic oxidation reaction and plays an important role in the reaction. It has been shown that superoxide anion stably presents on the catalyst surface in the photocatalytic reaction of titanium oxide under oxygen gas [1], but it is not known why superoxide anion exists so stably. In order to investigate the reason for the stability of superoxide anion from the electronic state, we have performed in-situ XAFS measurements using the fluorescence yield method under several Pa oxygen. Anatase titanium oxide thin films were prepared on a quartz substrate by the spin coating method. The obtained spectrum was dominated by water, oxygen, and SiO2, but we found a spectral feature that can be attributed to superoxide anion from the difference spectrum between the light-on and light-off conditions. We further plan to perform operando XAFS measurements of the photocatalytic oxidation reaction on titanium oxide in a similar way, using calcium fluoride as a substrate to eliminate the oxygen signal from the substrate. We choose oxygen and isopropanol as the inflow gases under the condition of 1 Pa. We will discuss the result with the DFT calculation in the presentation.

[1] Keniti Ishibashi et al., J. Pys. Chem.B, 2000, 104.

The new electrical energy induced by electromagnetic resonance in the transformer Mr Osamu Ide1 1Not Company or Organization, but private., Hongo-cho, Funabashi-shi, Japan Poster Session

Introduction The author started to research the electromagnetic resonance of the transformer, and found electromagnetic resonance amplifies the input energy to the transformer in 2017. The author has presented the early result by a poster at 14th International Conference on Materials Chemistry (MC14), July 2019 in Aston University, Birmingham, UK. In early August 2020, the author has succeeded to make an inverter of which the output DC power is larger than input DC power.

Experimental method and result The transformer applied the electromagnetic resonance has unexpected structure compared with common transformer. The magnetic core is divided. The capacitors are connected to the each coils to induce resonance. The input coil is connected to sine wave oscillator. By subtle tuning of the input voltage, frequency and the location of the magnetic cores, the rectified output power exceeds the input DC power of the transformer.

Discussion The author started to test the electromagnetic resonator between two or three resonance circuits. The author found the total resonating electromagnetic energy is much larger than the input energy to the system. The author succeeded to make an inverter of which the output DC power is larger than the input DC power. But the self-sustaining experiment was failed because of the load was not connected to the system. The voltage of the capacitor for power source suddenly rose high up and the system was broken. The author tried to replicate the system. However, on the course of replicating the experiment above, the author found another method.

Conclusion The author found new method to induce electricity by electromagnetic resonance. The energy problem should be solved by the technology in near future.

The author is grateful to Mr. Tsutomu Uchida for his financial support.

In situ Molten Salt Studies in a Laboratory X-ray Absorption Spectrometer Equipped with a Vacuum Furnace Dr Daria Boglaienko1, Dr Gerald Seidler2, Dawson Dean-Hill2, Dr Tatiana Levitskaia1 1Pacific Northwest National Laboratory, Richland, United States, 2University of Washington, Seattle, United States Poster Session

Molten salts have seen growing interest in the XAS community because of their importance for potential next- generation nuclear reactors. That being said, the pace of research could be accelerated if the necessary high- temperature studies could be performed in the laboratory, rather than waiting for synchrotron access. To this end, we have constructed and installed a miniature vacuum furnace into a commercial laboratory scale XAFS system. We show that in situ measurements of molten lanthanide salts are feasible in the lab setting. The new furnace is small enough to be integrated into the Rowland circle design of an easyXAFS300 spectrometer and can be transferred via standard loadlock into a glovebox filled with an inert gas. This allows anaerobic sample preparation and loading, after which the furnace vacuum chamber is sealed, reinstalled in the spectrometer, and then connected to a pre-pumped foreline to establish and maintain low pressures before heating. We use trivalent europium chloride, EuCl3 6H2O, as a starting material that is oven-dried to remove water, then mixed with potassium chloride and processed into a pellet under argon atmosphere. The resulting EuCl3-KCl system was studied by XANES up to temperatures reaching the melting point and higher. We find Eu3+/Eu2+ reduction processes occurring with the increasing temperature, and the ability to measure the reduction-oxidation profile demonstrates the success of our approach.

Acknowledgements: Laboratory Directed Research and Development Program (CheMSR Agile Initiative) at the Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle Memorial Institute for the United States Department of Energy under Contract No. DE-AC05-76RL1830. Devon R. Mortensen, easyXAFS LLC, Renton, WA, USA.

THORONDOR: a software for fast treatment and analysis of low energy XAS data Dr Andrea Martini1, Mr David Simonne3, Dr Matteo Signorile1, Dr Alessandro Piovano1, Dr Luca Braglia4, Dr Piero Torelli4, Dr Elisa Borfecchia1, Prof Gabriele Ricchiardi1 1University Of Turin, Turin, Italy, 2The Smart Materials Research Institute, Rostov-on-Don, Russian Federation, 3Synchrotron SOLEIL, Paris, France, 4CNR-IOM, TASC Laboratory, Triest, Italy Poster Session

We developed a new software, named THORONDOR, for the quick treatment and analysis of low energy XAS data.1 The latter is a graphic user interface (GUI), written in Python, accessible via the browser-based Jupyter notebook framework.2, 3 It aims to provide an interactive and user-friendly tool for the analysis of NEXAFS spectra collected during in situ experiments.4, 5 The program allows the on-the-fly representation, the quick visualization and correction of large datasets coming from single or multiple experiments. In particular, it includes the possibility to align the spectra in energy on the basis of user-defined references and treat the X-ray absorption phenomena which involve the gas-mixture feed inside a reactor cell during an ambient pressure experiment. Various techniques regarding the signal background subtraction and normalization are made available. In this context, an innovation of this GUI consists in the usage of a slider-based approach that gives the user the possibility to instantly manipulate and view the processed data. Finally, the program is characterized by an advanced fitting toolbox based on the lmfit package.6 It offers a large selection of fitting routines as well as different peak distributions and empirical ionization potential step edges, which can be used for the fit of the NEXAFS rising edge peaks. Statistical parameters describing the goodness of a fit such as the chi-square or the R-factor7 together with the parameter uncertainties distributions and the related correlations can be extracted for each chosen model.

Acknowledgements This work has received support from project PRIN-2017 MOSCATo (Cutting-edge X-ray methods and models for the understanding of surface site reactivity in heterogeneous catalysts and sensors).

References 1. D. H. Simonne, A. Martini, M. Signorile, A. Piovano, L. Braglia, P. Torelli, E. Borfecchia and G. Ricchiardi, J. Synchrot. Radiat., 2020, 27, 1741-1752. 2. T. Kluyver, 2016. 3. F. a. G. Perez, B. E., Computing in Science Engineering, 2007, 9, 21-27. 4. A. J. Atkins, M. Bauer and C. R. Jacob, Phys. Chem. Chem. Phys., 2013, 15, 8095-8105. 5. C. Castan-Guerrero, D. Krizmancic, V. Bonanni, R. Edla, A. Deluisa, F. Salvador, G. Rossi, G. Panaccione and P. Torelli, Rev. Sci. Instrum., 2018, 89, 8. 6. M. Newville, Stensitzki, Till, Allen, Daniel B., & Ingargiola, Antonino., Zenodo, 2014, DOI: http://doi.org/10.5281/zenodo.11813. 7. I. S. a. C. Committee, Error Reporting Recommendations: A Report of the Standards and Criteria Committee, 2000.

Core-level x-ray spectroscopy of infinite-layer nickelate : DFT+DMFT analysis Mr Keisuke Higashi1, Dr Winder Mathias2, Dr Takayuki Uozumi1, Docter Jan Kunes2, Dr Atsushi Hariki1 1Department of Physics and Electronics, Osaka Prefecture University, Sakai , Japan, 2Institute for Solid Physics, TU Wien, Vienna, Austria Poster Session

Recently superconductivity was discovered in infinite-layered nickelate (Nd0.8Sr0.2NiO2) [1], whose microscopic origin is currently being actively studied. To understand differences and similarities with high- temperature superconducting cuprates, it is important to study the valence states of Ni ions as well as the character of the first ionization state where doped holes reside. Motivated by recent experimental studies [2,3,4], we theoretically investigate Ni 2p core-level x-ray photoemission spectroscopy (XPS), Ni 2p core-level x-ray absorption spectroscopy (XAS) and Ni 2p-3d resonant inelastic x-ray scattering (RIXS). We employ density functional theory (DFT) + dynamical mean-field theory (DMFT) framework which was developed recently [5]. This method describes both realistic bands (Ni 3d, O 2p and Nd 5d bands) with the strong electronic correlation and a local core-valence interaction in the XPS, XAS and RIXS processes accurately. Thus, it enables us to take into account realistic hybridization effect with the valence band in these spectroscopies beyond a conventional impurity-model analysis using e.g. the cluster model or atomic model. Besides, our approach describes the reconstruction of the valence band due to hole doping and associates it with the low-energy RIXS features. From the Ni 2p XPS analysis for the experimental data for NdNiO2 [2], we find that Ni ion is close to the monovalent, i.e. 3d9 configuration in the ground state, which is reminiscent of cuprates. However, the charge-transfer energy Δ, that is the key parameter for determining the character of the doped hole, is larger (about 2~3 eV) than typical values for cuprates. Therefore, NdNiO2 is more Mott-Hubbard like in the Zaanen- Sawatzky-Allen classification for transition metal oxides. The Ni 2p (L3-edge) XAS and RIXS analysis for the experimental data [3,4] supports the conclusion. The RIXS analysis reveals a signature of a self-doping from the Nd 5d bands to the NiO2 plane, which we show in this talk is the origin for the metal-like behavior reported in the parent compound (NdNiO2) of infinite-layered nickelate in contrast to the Mott-insulating ground sate in undoped cuprates.

[1] D. Li et al., Nature 572 624 (2019) [2] Y. Fu et al., arXiv:1911. 03177 (2019) [3] M. Hepting et al., Nat. Mat. 19, 381 (2019) [4] M Rossi et al., arXiv:2011: 00595 (2020) [5] A Hariki et al., Phys. Rev. B 96, 045111 (2017)

High-resolution spectromicroscopy of silicon compounds in integrated circuits Mrs Kristina Kutukova1, Dr. Stephan Werner2, Dr. Peter Guttmann2, Prof. Gerd Schneider2, Prof. Ehrenfried Zschech1 1Fraunhofer Institute for Ceramic Technologies and Systems, Dresden, Germany, 2Helmholtz Zentrum Berlin, Berlin, Germany Poster Session

The on-chip copper interconnects of state-of-the-art microelectronic products are embedded in different types of dielectrics: interlayer dielectrics (ILD) and dielectric capping layers. Leading-edge products use porous organosilicate glass (OSG) ILDs, processed using chemical vapour deposition (CVD) and subsequent UV curing, and SiCN capping layers that act as etch-stop layers within the manufacturing process. Spectromicroscopy studies performed at the full-field transmission X-ray microscope at the U41-PGM1-XM beamline at BESSY II allow to differentiate between SiCN and OSG dielectrics based on the photon energies of the Si-K absorption edges and the shape of the resonance peaks. A cross-section lamella with a thickness of 400 nm was extracted from a commercial product manufactured in 14 nm CMOS technology node using focused ion beam (FIB) milling. X-ray microscopy images of the cross-sectioned interconnect stack consisting of 12 layers of copper were taken with high spatial resolution. Si-K NEXAFS spectra were acquired from two marked regions of interest: SiCN and OSG. The Si-K absorption edges of SiCN and OSG are located at 1842.5 eV and 1847.0 eV, respectively. The energy difference between the Si-K absorption edges of SiCN and OSG of 4.5 eV can be explained with different Si-X bindings (X=C,N in the case of SiCN and X=C,O in the case of OSG). It is consistent with the expected shift of the Si-K absorption edge to higher photon energies for increasing O coordination and decreasing C coordination. In addition, the broadened resonance peak in the Si-K NEXAFS spectrum for SiCN is explained with antibonding Si 3p – N 2p and Si 3p – C 2sp hybridized states that form a characteristic double peak with an energy difference of 2.9 eV.

Study on Formation of Weak Interaction of Tryptophan in Biomimetic Complexes: Approach by Structural Analysis Using X-ray Dr Hiromi Oshita1, Prof Hitoshi Abe1,2, Prof Yuichi Shimazaki2 1High Energy Accelerator Research Organization, Tsukuba, Japan, 2Ibaraki University, Mito, Japan Poster Session

Understanding the construction principle of proteins provides us crucial insights into their functionalities. X- ray techniques has been one of the necessary tools to analyze the structures in detail. We have focused on weak interactions formed by amino acids in protein, especially those by tryptophan. Tryptophan has an electron rich aromatic ring, indole, which is a hetero ring of pyrrol and benzene. The indole of tryptophan prefers forming a π-π stacking interaction and a hydrogen bond with other amino acids in protein. These are common interactions but play important roles in protein: (1) to maintain the steric structure of protein, (2) to stabilize and regulate the active state of protein, and sometimes (3) to transfer an electron. These functions are often found near the proximity of the metal center and/or reactive site, but their mechanism is not fully clarified. To understand the mechanisms of above three functions, we investigated the electronic contribution of weak interaction by indole to its structure. In this study, we used a bio-mimetic metal complex to discuss the fine structure and its reaction mechanism of a particular part of a protein. As a model of galactose oxidase, SALEN-type complexes with an indole side chain, Ni-SALEN and Cu-SALEN, were synthesized in the same manner as the previous reports.[1] The structures for all of the complexes and their oxidized complexes were analyzed by single crystal x-ray diffraction. The electronic states of the nickel and copper ion in the complexes were determined by XAFS. The indole side chain of the neutral Ni- and Cu-SALEN complexes showed no intra- and inter-molecular stacking interaction with the aromatic ring of SALEN ligand (phenolate). Meanwhile, all oxidized complexes gave an intra- molecular stacking structure. The structural difference with redox reaction were observed in the XANES spectra. The white line of the oxidized complex was smoother than that of the neutral complex indicating that the coordination number of the central metal ions changed from 4 to 5 by the formation of interaction between indole and metal ion. From these results, the stacking interaction of indole is selective and prefers an electron-poor site as an interactive partner. In the poster, the more detailed results and discussion will be presented.

1. H. Oshita, Y. Shimazaki, Chem. Eur. J. 2020, 26, 8324- 8340. Figure. The structure of neutral and oxidized Cu-SALEN complexes and their Cu K-edge XANES spectra.

A hydrothermal apparatus for X-ray absorption spectroscopy of hydrothermal fluids at DESY Dr Manuela Borchert1,2, Mr Michael Feldhaus1, Dr Vasily Potapkin1, Prof Max Wilke3, Dr Marion Louvel1, Dr Anselm Loges5, Dr Arno Rohrbach1, Peter Weitkamp1, Dr Edmund Welter2, Dr Maria Kokh3, Dr Christian Schmidt4, Dr Denis Testemale6 1WWU Münster, Germany, Münster, Germany, 2Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany, 3Universität Potsdam, Potsdam, Germany, 4GeoForschungsZentrum Potsdam, Potsdam, Germany, 5Freie Universität , Berlin, Germany, 6Institut Néel, Grenoble, France Poster Session

Hydrothermal fluids play an important role during the formation of most economic ore deposits. While cycling through the crust these supercritical fluids efficiently dissolve and transport metals from the source rocks and metal-rich minerals precipitate on their way towards the Earth’s surface. In general, compositions of hydrothermal ore fluids are well known e.g., by analyzing fluid inclusions (FI) in ore minerals. However, because sources and physiochemical characteristics of hydrothermal fluids vary widely complexation and speciation of metals in the fluid and precipitation mechanisms of ore minerals are still matter of controversial debates. Statements on metal complexation and speciation in the fluids are usually based on analysis of quench experiments that do not consider the probably non-quenchable nature of hydrothermal metal complexes e.g., as previously reported for gold (Pokrovski et al. (2015)). Thus, reliable information on metal complexation and speciation during ore deposit formation can only be obtained using in-situ data.

Here, we present a new autoclave dedicated to in-situ characterization of hydrothermal fluids at high pressures and temperatures at Deutsches Elektronen-Synchrotron (DESY). The design of the autoclave follows the one from Testemale et al. (2005) but with some significant adjustments. This type of autoclave can be used for X-ray absorption and Raman spectroscopy. Besides discussing further details of the hydrothermal apparatus we will also present results of first experiments at PETRAIII spectroscopy beamlines P64 and P65. On the one hand, we will show in-situ data on tungsten speciation and complexation in hydrothermal fluids and on the other hand we hope to report first in-situ valence to core spectroscopy data on Ge in hydrothermal fluids. The latter experiments are planned for early June.

G. Pokrovski, et al., Sulfur radical species form gold deposits on Earth, PNAS 112 (44), (2015)

D. Testemale et al., High pressure/high temperature cell for x-ray absorption and scattering techniques, Rev Sci Instr, 76, (2005).

Funding: Bundesministerium für Bildung und Forschung (BMBF) grant FKZ 05K16PMA, DESY Center for Molecular Water Science - Early Science Project.

In situ XAFS studies of Cobalt Oxide phases on Pt(111) during CO and O2 exposures Miss Dorotea Gajdek1, Mr Pär A. T. Olsson1, Ms Sara Blomberg2, Mr Johan Gustafson2, Mr Per-Anders Carlsson3, Ms Dörthe Haase4, Mr Edvin Lundgren2, Mr Lindsay Richard Merte1 1Malmö University, Malmö, Sweden, 2Lund University, Lund, Sweden, 3Chalmers University of Technology, Göteborg, Sweden, 4MAX IV Laboratory, Lund, Sweden Poster Session

Noble metals such as platinum and iridium are proven as highly efficient catalysts for many processes, especially for low temperature CO oxidation and oxygen evolution reaction. As an alternative due to the high cost and potential environmental and health hazard, cobalt oxides have shown increasing potential as earth- abundant heterogeneous catalysts. To study interface effects, reaction mechanisms and fundamental properties in heterogeneous catalysis, ultra-thin oxide films supported on metal surfaces showed to be worthy model systems. This study was performed on ultra-high vacuum (UHV) grown CoOx thin films deposited on Pt(111) single crystal. The film growth was confirmed with LEED and STM analysis. Environmental cell (MAX IV Laboratory, Lund, Sweden) was used to preserve desired sample atmosphere during in-situ measurements. Three different gases/gas mixtures (O2, CO, CO+O2) were flown through the environmental cell at four different temperatures (RT, 50°C, 100°C and150°C) with a total pressure of 1 bar. To follow the composition of the outlet gas mixture, a quadruple mass spectrometer (QMS) was installed at the end of the gas line. Simultaneously, XAFS spectra was recorded (DESY, Germany) at the Co K-edge (7709 eV) with the out-of-plane polarization relevant to the beam. XANES spectra shows changes between Co2+ and Co3+ depending on the gas composition. EXAFS analysis showed that CoO bilayer is not present at any conditions due to the constant absence of Co-Pt scattering paths and a constant presence of Co-Co scattering paths. Furthermore, low temperature data shows possible consistency with the transformation between Co(OH)2 and CoO2, while higher temperature data indicated dewetting and a formation of Co3O4 under O2 and CO + O2 flows. We have used grazing incidence geometry to probe only the structure of the thin film and shown that in-situ XAFS analysis can be successfully used on thin metal-supported oxide films under catalytic conditions.

The valency of chromium and copper ions in manganese doping CuCr2Se4 spinel Dr Jerzy Kubacki1, Dr Izabela Jendrzejewska1 1University Of Silesia, Katowice, Poland Poster Session

CuCr2Se4 compound is intensively study because its specific combinations of magnetic and electric properties and its potential applications in magneto-optical and spin-based electronic properties. The investigated material crystallize in a spinel structure Fd 3m and exhibit ferromagnetic state at room temperature with Curie temperature 430 K. In our studies we analysed impact of manganese doping on sublattice and charges of Cu and Cr atoms. Polycrystalline samples with a general formula of CuCr2–xMnxSe4 (x = 0.1, 0.2) were synthesized using the standard solid-state reaction method. Stoichiometric amounts of high purity Cu, Mn, Cr and Se (Sigma Aldrich, 5N purity) were weighted and mixed using a mortar and pestle. The mixtures were sintered two times in evacuated quartz ampoules at 850 C for 240 hours. Grinding of the materials was repeated after each sintering. The obtained samples were tested to be a single phase by XRD method. The occupied and un-occupied electronic states were investigated by x-ray absorption (XAS) and x- ray photoelectron (XPS) methods. XANES and EXAFS spectra of the K-edge of Cu, Cr and Se were obtained at the A1 beamline at Hasylab/DESY synchrotron in Hamburg, Germany. Photoemission measurements of Cr2p, Cu2p and Se3d lines were collected using Alk -monochromatized X-ray source (h =1486.6eV) in a PHI5700/660 Physical Electronics spectrometer. The positions of absorption peaks of Cr at 6000 eV, Se at 12,662 eV, and Cu at 8998 eV remained independent from Mn substitution. The position of Mn K-edge were observed at 6556 eV. XPS position of the following peaks exists: 54.2 eV for Se3d, 575.3 eV for Cr2p3/2 and 932.7 eV for Cu2p3/2. XAS and XPS studied shows that copper exists mainly on 2+ oxidation state while and chromium exists on 3+ oxidation state. The mixed valency of manganese ions (Mn3+ and Mn4+) were concluded can suggesting a change in copper ions valency from divalency to monovalency.

Freeze Quenching of Short-Lived LPMO Intermediates for XAS Characterisation Miss Abbey Telfer1,2, Dr Daniel E Diaz1, Professor Paul H Walton1, Dr Sofia Diaz-Moreno2 1University Of York, York, United Kingdom, 2Diamond Light Source Ltd., Didcot, United Kingdom Poster Session

Lytic Polysaccharide Monooxygenases (LPMOs) are a family of naturally occurring copper enzymes which have the unique ability to be able to perform saccharification of cellulose. Cellulose is the most abundant natural polymer on Earth and is therefore an ideal feedstock for the production of biofuels. The ability of LPMOs to oxidatively activate C-H bonds (> 100 kcal/mol) gives a 100-fold increase in the rate of release of useful bioproducts over current methods of enzymatic hydrolysis1. Understanding if the LPMO catalytic mechanism is fundamental in developing biofuels as an attractive source of renewable energy.

Stopped-flow spectrophotometry has shown that the catalytic mechanism of LPMOs includes the formation of short-lived intermediate species when reacted with O2. A LPMO species with indefinite stability has been characterised as an unusual copper(II)-tyrosyl complex through the use of XAS, UV–vis, CD, MCD, resonance Raman, EPR spectroscopy2. In order to characterise the short-lived intermediate species a new approach is required. The combination of freeze quenching and X-ray Absorption Spectroscopy (XAS) will be employed to gain insights into the structure and mechanism of LPMOs on a millisecond timescale.

The preparation of LPMO samples for XAS has many challenges, but the collected data will have profound applications in the production of biofuels as well as in copper chemistry.

1. L. Lo Leggio, T. J. Simmons, J.-C. N. Poulsen, K. E. H. Frandsen, G. R. Hemsworth, M. A. Stringer, P. von Freiesleben, M. Tovborg, K. S. Johansen, L. De Maria, P. V. Harris, C.-L. Soong, P. Dupree, T. Tryfona, N. Lenfant, B. Henrissat, G. J. Davies and P. H. Walton, Nat. Commun., 2015, 6, 5961. 1. A. Paradisi, E. M. Johnston, M. Tovborg, C. R. Nicoll, L. Ciano, A. Dowle, J. McMaster, Y. Hancock, G. J. Davies and P. H. Walton, J. Am. Chem. Soc., 2019, 141, 18585–18599.

XAFS study of copper complexes of aspartic and glutamic acids Ms Monica Bairagi1 1Ujjain Engineering College, Ujjain, 456010, India, Indore, India Poster Session

Introduction: Copper (II) complexes, in which an amino acid is a ligand, have been found to be good models to study metal-protein interactions. Aspartic acid is a naturally occurring α-amino acid with two carboxylic groups in side chains. Copper (II) complexes of aspartic acid have received considerable attention. In the present work, we have investigated X-ray absorption fine structure (XAFS) of copper (II) complexes of aspartic acid and glutamic acid. Through, the crystal structure of both of these complexes have been studied using X-ray crystallography, it was considered worthwhile to study the local structures around copper ion using XAFS.

Experimental: The complexes [Cu(L-Asp)H2O].H2O [Asp = aspartic acid (CO2CH2CHNH2CO2)] (1) and [Cu(L- glu)H2O].H2O [glu = glutamatic acid (CO2(CH2)2CHNH2CO2)] (2) have been prepared and characterized by following standard methods [1-3]. The X-ray absorption spectra of the complexes have been recorded at the K-edge of copper on BL-8 dispersive EXAFS beamline at 2.5 GeV Indus-2 synchrotron source at Raja Ramanna Centre for Advanced Technology (RRCAT), Indore, India. The data has been analysed using software Athena and Artemis. Results and discussion: X-ray crystallographic study of 1, done by Calvo et al. [1], has shown it to be in distorted tetragonal pyramidal coordination. At the four corners of the pyramidal base are an α-carboxylic oxygen, an amino nitrogen of one aspartic molecule, a β-carboxylic oxygen of another aspartic molecule and an oxygen of water molecule. The Cu(II) ion is at the center of the squares plane. The oxygen of another water molecule is at the top of pyramid. X-ray crystallographic study of 2 has been done by Gramaccioli and Marsh [2] using Weissenberg photographs. The study was again done by Mizultani et al. [3] with greater precision. These authors have found the complex to have approximately square planer geometry with the amino nitrogen and the carboxylate oxygen of L-glu, a side chain carboxylate oxygen of the neighboring L-glu, and a water molecule oxygen. The distorted octahedral is completed by two L-glu oxygen weakly coordinating to both axial positions of the distorted octahedral. EXAFS analysis of the experimental data has been performed to extract the structural parameters of the complexes. The crystallographic data from the previous studies [1,2] were used to generate the theoretical models, which have been fitted to the experimental data of the complexes in k-space and R-space. The bond lengths determined from the analysis of EXAFS data are in good agreement with crystallography data. Also, the crystal structures of the complexes obtained from EXAFS analysis are the same as those obtained from crystallography. References: [1] R. Calvo et al., Inorg. Chem., 32, 1993, 6016 [2] C. M. Gramaccioli and R.E. Marsh, Acta Cryst., 21,1965, 594 [3] M. Mizutani et al., Inorganica Chimica Acta, 283, 1998, 105

Synthesis, structural and magnetic characteristics of few-layer nanographene clusters in carbon micro- and nano-spheres Mrs Daria Tolchina1, Mr Leon Avakyan1, Mr Ratibor Chumakov2, Mr Andrey Emelyanov2, Mr Narek Sysakyan3, Mr Harutyun Gyulasaryan3, Mr Aram Manukyan3, Mr Lusegen Bugaev1 1Southern Federal University, Rostov-on-Don, Russian Federation, 2National Research Center “Kurchatov Institute”, Moscow, Russian Federation, 3 Institute for Physical Research, National Academy of Sciences of Armenia, Ashtarak , Armenia Poster Session

Synthesis of the room temperature ferromagnetic carbon micro- and nano-spheres consisting of few- layer nanographene clusters was performed by the method of solid-phase pyrolysis of organic compounds. Powders of metal-free phthalocyanine were used as precursors of synthesized carbon micro- and nano- spheres. Pyrolysis products of metal-free phthalocyanine contained 4 – 1 at.% nitrogen, replacing carbon in the graphene lattice in pyrrolic and pyridinic coordinations. Sample, containing 4 at.% nitrogen, demonstrates a strong paramagnetism with the concentration of paramagnetic centers ~5×1019 spin g-1. At the same time, for this sample, ferromagnetism was revealed in the temperature range of 5–300 K, with a temperature dependence similar to ferromagnetic cluster spin-glass. The values of saturation magnetization and coercive force were obtained. To reveal the origin of these ferromagnetic properties, atomic structure of the synthesized carbon spheres was studied and determined using transmission electron microscopy, X-ray diffraction, X-ray photoelectron and absorption spectroscopy (C and N K-edge XAFS) in combination with cluster simulations by the method of Reax Force Field (ReaxFF) of Molecular Dynamics. By this approach, the relationships between the pyrolysis conditions (temperature, pressure, duration of pyrolysis, as well as the choice of the reagent for pyrolysis) – atomic structure of the N-species, their type and concentrations in the mean carbon’s sphere – and the observed magnetic characteristics of the sample were established. This will allow to improve the magnetic characteristics of carbon spheres by governing and optimizing the concentration of impurity nitrogen atoms and carbon edge states with zigzag type in graphene clusters by changing parameters of pyrolysis. The study is supported by RFBR grant # 20-52-05011.

In-situ observation of ZnO nanoparticle growth by a combination of time-resolved EXAFS and XRD Mr Franz Eckelt1, Prof. Dr. Dirk Lützenkirchen-Hecht1, Mr. Ralph Wagner1, Dr. Ankica Saric2, Dr Martina Vrankic2 1Bergische Universität Wuppertal, Wuppertal, Germany, 2Division of Materials Physics, Zagreb, Croatia Poster Session

Due to their photo-, thermal- and chemical stability, low toxicity, biocompatibility and low cost, zinc oxide nanoparticles are widely used materials with applications in quite different fields such as catalysis, electronics, energy harvesting, cosmetics and biomedicals. Several experimental works have shown that all the details of the different available synthesis routes have a strong impact on the resulting morphology and the physico-chemical properties of the prepared ZnO nanomaterials, indicating that many details of the ZnO growth processes are not yet understood. We have therefore conducted time-resolved in-situ EXAFS and XRD studies during the hydrothermal preparation of ZnO nanoparticles in the liquid phase.

We have employed Zinc acetylacetonate monohydrate (Zn(acac), Zn(C5H7O2)2·H2O), sodium hydroxide (NaOH), 1-octanol (CH3(CH2)7OH) and triply distilled water as starting materials for the synthesis, which were heated to 90°C under continuous stirring. The preparation was performed in a dedicated cell made of carbon- reinforced PTFE, which is equipped with a heater suited for temperatures of up to ca. 300°C, temperature sensors and a magnetic stirrer. Two Kapton X-ray windows allow to properly adjust the X-ray beam path within the solution and to measure the growth process of the ZnO nanoparticles in the solution in-situ with transmission mode EXAFS at the Zn K-edge. Simultaneously, XRD patterns on a Pilatus 100K detector were continuously recorded during ZnO preparation. The measurements were carried out at the P64 beamline at the Petra III storage ring at DESY (Hamburg, Germany), employing the QEXAFS monochromator and gas-filled ionization chambers as detectors. The obtained results show that distinct changes of the XANES and EXAFS occur during the heating of the pristine, slightly alkaline Zn(acac), with substantial modifications in the first Zn-O and Zn-Zn coordination shells during ZnO formation. Simultaneously, diffraction peaks characteristic for the hexagonal wurtzite ZnO were observed, the details of which will be discussed.

Angular dependence of multi-atom resonant X-ray Raman scattering Mr Junya Kogo1, Mr Ryusaku Sato1, Dr Kaori Niki1 1Chiba University, Chiba, Japan Poster Session

1. Introduction Multi-atom resonant X-ray Raman (MARX-Raman) scattering is a kind of inelastic X-ray scattering involving a deep core on the target atom and a shallow core on another. Experimental evidence has been reported [1], and a theoretical study has shown that MARX-Raman is related to XAFS from an atom with a shallow core [2]. We can expect that MARX-Raman depends on the polarization of the incident X-ray because an interaction between the target atom and surrounding atom contributes to MARX-Raman. This can be important to separate MARX-Raman and resonant X-ray Raman scattering inside the target atom, both of which can be measured in the same time. In this work, we study the relationship between the polarization of the X-ray and rotation angle of the sample.

2. Theory We focus on the structure factor , which reflects the local structure around an atom with a shallow core [2]. is defined by where corresponds to the polarization of incident photon, is the position of the site .

3. Results and discussion The calculations for the GaN structure show that the structure factor is related to , where is the rotating angle. The calculations for the SnO2 structure also show similar results. We find that a key factor is a bond between the atom with a shallow core and a surrounding atom in the different environment from the other atoms.

4. Conclusion The calculations demonstrate the importance of a particular bond that destroys the symmetry around the shallow core site: The structure factor is maximized when the bond is parallel to the linear polarization vector or the bond is perpendicular to the circular polarization vector.

References [1] N. Sirisit et al., e-J. Surf. Sci. Nanotech. 16, 387 (2018). [2] T. Fujikawa et al., J. Elec. Spec. Relat. Phenom. 233, 57 (2019).

XAFS analysis of supported Pd and Pt catalyst for dehydrogenative coupling of benzene and alkane with solid acid co-catalyst Ms Moe Takabatake1, Prof. Chun Wang-Jae2, Prof. Yuichi Manaka1,3, Prof. Ken Motokura1,4 1Tokyo Institute of Technology, Yokohama, Japan, 2International Christian University, Tokyo, Japan, 3National Institute of Advanced Industrial Science and Technology, Fukushima, Japan, 4Yokohama National University, Yokohama, Japan Poster Session

Carbon-carbon bond formation through activation of alkane C-H bond is an important reaction from the viewpoint of effective utilization of resources. Our group has reported that a solid acid, aluminum-exchanged montmorillonite (Al-mont), is active in the alkylation of benzene with alkanes at 150 °C 2). Recently, we found that the addition of hydrotalcite-supported metal catalysts (M/HT) to Al-mont greatly enhanced the dehydrogenative coupling reaction between benzene and alkane. Here, the active metal species in the reaction was investigated by structural analysis before and after the reaction using XAFS and other techniques, and the reaction mechanism was estimated. The reaction of n-heptane with benzene was carried out using Al-mont and supported Pd catalysts. When only Pd/HT was used, only biphenyl was formed and the desired alkylation reaction did not proceed. On the other hand, when Pd/HT was added to Al-mont, the activity significantly increased: the benzene conversion improved from 1.8% to 6.8%. In the case of Pt/HT, the benzene conversion of 9.7% was achieved. Pd K-edge XANES measurements of Pd/HT before and after the catalytic reaction Pd K-edge XANES 1.2 showed that the Pd species reduced during the reaction, suggesting that the zero-valent Pd particles produced during the reaction 1.0 were the active species (Figure).3) On the other hand, in the case of Pt/HT, since Pt was 0.8 Pd/HT used not reduced during the reaction, the target product was obtained in higher yield using 0.6 Pd foil (0) the pre-reduced zero-valent Pt/HT. χµ (E) PdO (II) Dehydrogenation coupling of simple 0.4 alkanes and benzenes was successfully Pd/HT achieved by a simple approach of physical 0.2 mixing of Al-mont and Pd/HT or Pt/HT. In the presentation, we will also report on the 0.0 detailed reaction mechanism, structural 24320 24340 24360 24380 analysis of the catalyst, and substrate scope. Energy (eV)

1. M. Takabatake, M. Nambo, Y. Figure Manaka, K. Motokura, ChemPlusChem, 2020, 85, 450–453. 1) M. Takabatake, A. Hashimoto, W. Chun, M. Nambo, Y. Manaka, K. Motokura, JACS Au, 2021, 1, 119-123.

Anti-corrosion properties of biosynthesized Zinc Oxide nanoparticles from Nypa fruticans (Nipa) biocomposites Mr Flyndon Mark Dagalea1, Dr. Karina Milagros Lim1, Ms. Janet Agresor1 1University Of Eastern Philippines, Catarman, Northern Samar, Philippines Poster Session

Abstract

Recent researches involves natural resource in the biosynthesis of nanoparticles. This poses less toxicity outcome to the environment rather than the chemical based synthesis of nanoparticles. In this research, an underutilized natural resource found in the coastal areas of Northern Samar, Philippines – Nypa fruticans (Nipa) was used as reducing and capping agent for the biosynthesis of zinc oxide nanoparticles (ZnOnps). Isolation of starch was done to the fruit of the nipa palm; it was used in the biosynthesis. Thereafter, the biosynthesized nanoparticles was used as an anti-corrosion substance. Results showed that after several day submerge in a 25% ZnOnps anti-corrosion solution the metals rods was seen to inhibit the growth of rust and other corrosion traits. With this result, ZnOnps biosynthesized from nipa palm can be an alternative to the commercially available products against corrosion.

Keywords – Nypa fruticans, zinc oxide nanoparticles, biosynthesis, anti-corrosion

In-Situ EXAFS and XRD Investigations on Nb-Treatments in N2 at elevated Temperatures Mr. Patrick Rothweiler1, Dr. Benjamin Bornmann1, Mr. Ralph Wagner1, Mr. Franz Eckelt1, Prof. Dr. Dirk Lützenkirchen-Hecht1 1University Of Wuppertal, 42119 Wuppertal, Germany Poster Session

Smooth polycrystalline Nb metal foils were treated in dilute N2 atmospheres at elevated temperatures of 800 °C and 1200 °C. The foils were investigated using time-resolved X-ray absorption spectroscopy (EXAFS) at the Nb K-edge to access the structural changes of the materials during nitrogen exposure. Parallel to the EXAFS studies, X-ray diffraction (XRD) data were measured in transmission mode on a 2D X-ray detector. A dedicated high-vacuum cell allowing treatments under a controlled influence of dilute gases, temperatures of up to 1200 °C and pressures down to 10-6 mbar was employed for the experiments. The treatments consist of (a) a pre-heating phase at 800 °C under high-vacuum for 1 h, (b) a phase of gas exposure at temperatures between 800 °C and 1200 °C (typically 1 h) and (c) the cooldown phase back to room temperature under high-vacuum. EXAFS and XRD data were collected during all of the three phases with a time resolution of 1 s. In general, only small modifications of the X-ray absorption fine structure of the pristine Nb-material were observed in the XANES and the EXAFS at 800°C, indicating low levels of nitrogen uptake, and bulk formation of Nb-nitrides (NbxNy) can be excluded. In contrast, more pronounced changes of the XANES/EXAFS as well as the appearance of additional Bragg peaks were observed at a more elevated temperature of 1200°C, presumably indicating the presence of NbxNy phases on the surface of the Nb. A more detailed analysis of the data will be presented at the conference.

We gratefully acknowledge financial support by the German Federal Ministry of Education and Research (BMBF) under project No. 05H18PXRB1. We would further like to thank F. Brockner and M. Weiss for their manifold help at the beamlines.

Investigating the role of Zn in glucose regulation using X-ray Fluorescence Microscopy and X-ray absorption near-edge structure spectroscopy Dr Gae Ellison1,2, Ms Ashley Hollings1, Ms Arazu Sharif2,3, A/Prof Ryusuke Takechi2,3, Dr Daryl Howard4, Dr Keith Bambery4, Dr Mark Hackett1,2 1School of Molecular and Life Sciences, Curtin University, Bentley, Australia, 2Curtin Health Innovation Research Institute (CHIRI), Curtin University, Bentley, Australia, 3Curtin School of Population Health, Curtin University, Bentley, Australia, 4Australia's Nuclear Science and Technology Organisation (ANSTO), Clayton, Australia Poster Session

Zinc plays an important function in glucose regulation via its roles in signalling and hormone production, particularly within pancreatic islets, which are the anatomical home of the glucose regulating hormones insulin and glucagon. Glucose dysregulation is a significant contributor to the epidemic of ‘diseases of affluence’ such as diabetes and metabolic syndrome that are experienced by an increasingly large portion of the population. Zn is found in very high (mM) concentrations in islets; more specifically, within insulin- secreting β-cells. Zn is known to facilitate insulin storage within β-cells, and is co-secreted with insulin, subsequently acting as a signalling molecule. Zn dysregulation can be coincident with impairment of insulin secretion, but little is known about the nature of the changes. Since a subset of the pool of Zn in islets is labile, it is difficult to image in its in vivo situation using conventional techniques such as histochemistry, or the use of probes or fluorophores. Not only do preparation steps such as washing displace Zn, but it exists in several forms, some of which are not readily or accurately discernible using conventional microscopy techniques. X- ray fluorescence microscopy (XFM) and X-ray absorption near-edge structure spectroscopy (XANES) offer several advantages in that tissue preparation is minimal, facilitating the conservation of native states, and all forms of Zn are not only detectable, but also able to be discriminated by matching spectra against an existing library of Zn forms. Here we report the preliminary results from our study of Zn speciation and elemental mapping in murine islets from healthy or diabetes-prone animals in two age groups, 14 (denoted young) or 28 (old) weeks. This work uses a library of biologically relevant Zn forms created in our laboratory, and contributes to our understanding of the role of Zn in glucose regulation in health and disease, including aging.

The authors would like to thank AINSE Limited for providing financial assistance (Award – AINSE ECRG 2020 – Ref: ALNGRA2003) to enable this work. Funding was also provided through an ARC Future Fellowship – FT190100017.

Investigation into the solvent effect aimed at the time-resolved experiments Dr Shota Tsuru1, Dr Bikramjit Sharma1, Dr Masanari Nagasaka2, Prof. Dr. Christof Hättig1 1Ruhr-universität Bochum, Bochum, Germany, 2Institute for Molecular Science, Okazaki, Japan Poster Session

Development of electronic-structure theories has enabled quantitative discussion of the pre-edge region in the X-ray absorption spectra. Since the excitations to the virtual orbitals are discrete, the pre-edge region sensitively reflects electronic structure of the initial state. Added to this, main features of X-ray absorption spectroscopy (XAS) such as locality and element selectivity are also advantages for tracking photo-induced or chemical reaction dynamics in pump–probe scheme experiments. Our present work is aimed at extending application of time-resolved (TR) XAS to solution systems.

We chose pyridazine as the solute of interest. We performed ab initio molecular dynamics (AIMD) simulations of pyridazine in water using CP2K [1], to generate solvent configurations. For ultraviolet (UV) and X-ray absorption in the gas phase, we calculated the excitation energies at the Franck-Condon (FC) geometry. For these absorption in aqueous solution, we did excitation-energy calculations for 100 snapshots extracted from the AIMD trajectory every 1 ps. In the calculations for the ensemble of the snapshots, water molecules in the first solvent shell of both the pyridazine nitrogen atoms were explicitly taken into account, whereas the long range solvation was expressed with the conductor-like screening model (COSMO) [2]. We also performed the nitrogen K-edge XAS experiment for pyridazine gas and 0.5 M aqueous solution at the soft X-ray undulator beamline BL3U at the UVSOR-III Synchrotron [3].

The lowest nπ* excitation energy is 0.5 eV higher in the aqueous solution than in gas phase [4, 5]. This energy difference was reproduced well, and we confirmed that this difference is due to stabilization of the lone pairs at the nitrogen atoms by hydrogen bonds. The XAS spectrum for the aqueous solution in the experiment exhibits broadening of the peaks due to fluctuation of the solvent, and this broadening was reproduced as well.

We conclude that calculation for ensemble of the AIMD snapshots expressed with the model consisted of the solute, the explicit first solvent shell and COSMO generally gives the most accurate valence and core- excitation energies.

We acknowledge Prof. D. Marx at RUB for fruitful discussion. This research was funded by Alexander von Humboldt Foundation and the Deutsche Forschungsgemeinschaft.

References 1. T. D. Kühne et al., J. Chem. Phys. 152, 194103 (2020). [1] S. K. Khani, A. M. Khah, and C. Hättig, Phys. Chem. Chem. Phys. 20, 16354 (2018). [2] M. Nagasaka et al., Anal. Sci. 36, 95 (2020). [3] F. Peral and E. Gallego, Spectrochim. Acta Part A 59, 1223 (2003). [4] B. Samir et al., Chem. Phys. Lett. 751, 137469 (2020).

Applications of Energy Dispersive X-ray Absorption Spectroscopy at the Munich Compact Light Source Juanjuan Huang1, Benedikt Günther1, Fuli Deng2, Dr. Klaus Achterhold1, Dr. Martin Dierolf1, Prof. Dr. Franz Pfeiffer1,3 1Chair of Biomedical Physics, Department of Physics and Munich School of BioEngineering, Technical University of Munich, 85748 Garching, Germany, , , 2Department of Chemistry and Catalysis Research Center, Technical University of Munich, 84747 Garching, Germany, , , 3Department of Diagnostic and Interventional Radiology, School of Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany, , Poster Session

X-ray absorption spectroscopy (XAS) is a well-established synchrotron technique and provides an in- depth characterization of materials. However, this technique is typically conducted at large facilities with limited access. Consequently, there is a global interest in developing laboratory XAS. Among laboratory x-ray sources, inverse Compton scattering (ICS) sources have emerged as one of the most promising types, with significantly reduced spatial and financial requirement compared to synchrotrons. The Munich Compact Light Source (MuCLS), located at the Technical University of Munich, is the first application-centered ICS facility. The facility consists of a commercial ICS source (Lyncean Technologies Inc., Fremont, USA) and two experimental endstations developed in-house, dedicated to transferring synchrotron techniques to a laboratory framework. We have implemented XAS at the MuCLS in recent years [1]. The XAS setup is based on an energy- dispersive Laue geometry, composed of a slightly bent silicon crystal and a CCD camera. The crystal combined with the 4 mrad divergence of the x-ray source results in an energy gradient across the detector. In the poster presentation, we would like to present recent applications of the energy-dispersive setup, e.g., an in-situ XAS measurement of a Pd catalyst at a time resolution of < 5 min [2]. Furthermore, the image captured on the CCD camera has both energy-resolved and spatially resolved information, meaning the setup also has the potential for spectral imaging. A proof-of-principle spectral imaging result will be presented in the poster.

Reference [1] Huang J, Günther B, Achterhold K, Cui YT, Gleich B, Dierolf M, Pfeiffer F. Energy-Dispersive X-ray Absorption Spectroscopy with an Inverse Compton Source. Sci Rep 10, 8772 (2020). [2] Huang J, Deng F at al., Laboratory-Scale in situ X-Ray Absorption Spectroscopy of a Palladium Catalyst at a Compact Inverse-Compton Scattering X-Ray Beamline In preparation

Acknowledgment We acknowledge financial support through the Center for Advanced Laser Applications (CALA). Further, the authors would like to thank the staff of Lyncean Technologies Inc. for their technical support.

XAS diagnostic of the photoactive state in Co(II) azobenzene complex in organic solutions Ms Svetlana Shapovalova1, Mr Valery Vlasenko2, Mr Alexander Guda1, Mr Anatoly Chernyshev3, Mr Andrey Starikov3, Mr Grigory Smolentsev4, Mr Anatolii Burlov3, Mr Sergei Mashchenko3, Mr Alexander Soldatov1 1The Smart Materials Research Institute at the Southern Federal University, Rostov-on-Don, Russian Federation, 2Research Institute of Physics, Southern Federal University, Rostov-on-Don, Russian Federation, 3Institute of Physical and Organic Chemistry, Southern Federal University, Rostov-on-Don, Russian Federation, 4Paul Scherrer Institute, Villigen, Switzerland Poster Session

Materials whose magnetic properties can be controlled by external influences can become the basis for creating high-capacity nonvolatile molecular memory, molecular switches, pressure sensors, contrast agents for magnetic resonance imaging [1]. Among the effects leading to the switching of the magnetic states of transition metal complexes is the spin-crossover [2], a ligand-driven light-induced spin change [3] and light- driven coordination-induced spin-state switching [4]. The first step in understanding which of these mechanisms is realized for a given material is understanding the structure of complex in the photoactive form, which can be significantly different from the crystal structure of the initial material. In the present work, the optical properties of bis{1-phenyl-3-methyl-4-[4-methyl-2-(4- methylphenylazo)-phenylamino-methylene]pyrazol-5-onate}cobalt(II) (I) containing a photochemically active azobenzene group are studied. This study aims to analyze the Co complex's local atomic and electronic structure after its dissolution to address its photochemical behaviour. The complex I reveals photoinduced transformations only in the dimethylformamide (DMF) but not in acetonitrile. While being inactive upon irradiation, the optical absorption spectrum's shape in acetonitrile was similar to the photoaccumulated state in DMF. Therefore, we conclude that the structure of the complex changes both upon light stimuli and the interaction with DMF solvent molecules. X-ray absorption spectroscopy (XAS) used to characterize the photoactive structure of the complex I were measured at Super- XAS beamline, Swiss Light Source. After dissolution in DMF and acetonitrile, Co K-edge XANES indicated pseudo-octahedral coordination of complex I. XANES spectra does not change into acetonitrile, indicating any bond dissociation or complex coordination by solvent molecules. In contrast, dissolution in DMF induces gradual changes in the complex spectra. The number of spectra recorded in the series has isosbestic points, indicating the transition between two states. In DMF, an activation process occurs related to the decrease of coordination number, bond shortening and absorption edge shift to higher energies. To address the structural transition of the complex in DMF, we have performed DFT simulations for the set of models with and without coordinating solvent molecules. For each structure then the theoretical Co K-edge XANES spectrum was calculated and compared to the experimental data. We attribute observed changes to the reduction in coordination number from 6 to 5. The final state can be described by a mixture of low-spin Co(II) isomers with possible DMF molecule coordination. Photo activity of the complex in DMF is attributed to the E/Z isomerization of the azobenzene group dissociated from the Co atom.

1. M.A. Halcrow in Spin-Crossover Materials: Properties and Applications, John Wiley & Sons: Chichester, 2013, 564 p. [1] P. Gutlich, H.A. Goodwin, Top. Curr. Chem., Springer, Berlin, 2004, pp. 233-235. [2] C. Roux, J. Zarembowitch, B. Gallois, T. Granier, R. Claude, Inorg. Chem. 1994, 33, 2273-2279. [3] S. Venkataramani, U. Jana, M. Dommaschk, F.D. Sonnichsen, F. Tuczek, R. Herges, Science 2011, 331, 445-448.

S.O. Shapovalova acknowledge her PhD support from Russian Foundation for Basic Research (RFBR #20- 32-90046).

In-situ XANES of non-stoichiometric vanadium oxide during electrochemical cycling of aqueous Zn-ion battery Associate Professor Christopher Patridge1 1D'youville College, Buffalo, United States Poster Session

Multivalent ion batteries represent a unique approach to increasing energy capacity for electrochemical storage. While Li-ion batteries (LIB) are the dominant technology that continues to advance with novel architectures and engineering, there still exists serious issues of thermal sensitivity and runaway. Aqueous systems would significantly reduce these thermal concerns and also drop the economic costs associated with the organic solvents that compose the electrolytes in LIBs. The Zn ion (+2) gives twice the capacity and the ionic radii (0.78 Å) matches closely to the Li ion. The increased electronic/structural disruption imposed by intercalating a +2 ion finds some relief by co-intercalation of H2O along with sandwich layered structures often associated with the multitude of vanadium oxide polymorphs. Synchrotron work* at NSLS-II BM-6 looked at the XANES and EXAFS dependence on voltage. Using crystal structure data for the material, theoretical XAFS scattering was compared to the experimental data to establish possible local site occupancy for the intercalated Zn ion. Further in-situ experiments on both Zn0.25V2O5 and Ca0.25V2O5 were performed using a novel electrochemical cell. Both materials exhibit a clear change in the local geometry and oxidation state of the vanadium in the active material with early cycle reversibility. Integrated XANES difference spectra are correlated with the approximate shift of vanadium from a nominal oxidation state of +4.75 → +4.00 if assuming an approximate fully discharged state stoichiometry of Zn1V2O5 or Ca0.25Zn0.75V2O5.

* - This work was supported by internal support from the Office of Vice President of Academic Affairs at D’Youville College, Buffalo, NY 14210. The author wishes to thank Dr. Ravel for assistance in data collection

Custom-built 4 K closed-cycle cryostat for XAS and XES experiments at MAX IV

Susan Nehzati1, Johan Selberg, Staffan Benedictsson, Svetolik Ivanovic, Mathieu Leme, Stuart Ansell, Konstantin Klementiev, Kajsa GV Sigfridsson Clauss 1MAX IV, Lund, Sweden Poster Session

We introduce our new, custom-built 4 K closed-cycle cryostat designed and developed at MAX IV Laboratory operable at the Balder beamline – conducting XAS and XES experiments in the range 5-40 keV. The cryostat accommodates a sample plate of w x h, 22 x 75 mm2 (thickness 0.5-2 mm, 2-16 multiple samples) with broad- range translations (x and y) and rotational movements in the cold zone. The cryostat is accompanied with temperature ramping capabilities using a Lakeshore PID controller for examining experiments from 4-300 K. The cryostat is incorporated with a microscope camera for live point-and-click sample positioning during measurements. Data acquisition is compatible with both transmission and fluorescence measurements using an integrated SDD or Germanium detectors. In addition, a slot shaped exit window makes it compatible with diffraction measurements in the beam direction. We will present a series of measurements showcasing these experimental proficiencies that are important for a variety of experiments and sample types – molecular and natural biological and environmental composite samples. Lastly, with the emergence of highly brilliant 4th generation lightsources, the issues with X-ray induced photochemistry of sensitive samples could be increasingly problematic. We will revisit the use of cryoprotectants in mitigating X-ray induced photodamage. What is the cold, hard truth about cryoprotectants? Do they really cause more harm than good?

Metal coordination in ALD/MLD deposited Fe and Ni metal-organic thin films Dr. Sami Vasala1, Dr. Anish Philip2, Prof. Maarit Karppinen2, Dr. Pieter Glatzel1 1European Synchrotron Radiation Facility, Grenoble, France, 2Aalto University, Espoo, Finland Poster Session

In this work, we study the local structure of metal-organic thin films grown by a combined atomic/molecular layer deposition (ALD/MLD) approach. Metal–organic frameworks (MOFs), a class of porous materials having metal nodes and organic linker molecules, have been widely used for a range of applications such as gas storage, capture or release of molecules, and sensors. From the application point of view, it is often beneficial to produce the MOFs in thin-film form, and the uniqueness of the ALD/MLD technology is the possibility to obtain continuous, homogeneous, conformal and high-quality pinhole-free thin films with precise thickness control on various substrate materials of interest. For the development of the ALD/MLD process and for the applications of the MOF films, it is important to know the coordination environment around the metal ion. Here we use 1s2p resonant inelastic x-ray scattering (RIXS) to study the local metal coordination of thin films with Fe or Ni nodes linked by azobenzenedicarboxylic acid or terephthalic acid molecules. We examine the K-absorption pre-edge region and use crystal field multiplet calculations to explain features of the RIXS spectra.

Thoughts about the optimization of the photon collection efficiency and energy resolution of lab-based XAS spectrometers

Mr Antti-jussi Kallio1 1University Of Helsinki, Helsinki, Finland

Poster Session

We present some practical and useful tips to 1) enhance the energy resolution of a laboratory-based XAS instrumentation using spherically bent analyzer crystals (SBCA) as well as 2) the utility of spherical astigmatism of SBCA’s to collect efficiently signal when the sample is in a form of a thin capillary or a liquid flow stream.

The finite x-ray source size in the dispersive plane of a wavelength dispersive spectrometer causes normally a contribution to the energy resolution and it can become dominant in the case of Bragg angles not close enough to 90 deg. With position sensitive detector (PSD) the broadening can be detected as an energy dispersion within the focus of the SBCA. Following earlier recipes of dispersion compensation shown using synchrotron radiation [1, 2] we show how this contribution to the energy resolution of SBCA-based laboratory-scale XAS instruments can be removed. Some challenges arise, however, due to glitches that originate from simultaneous other reflections, and from the required precise detector tracking.

In certain cases the shape of a specimen can pose challenges owing to the complex nature of, e.g., in-situ flow reactors based on a capillary design [3], or if the sample is a liquid flow column. Here, the spherical astigmatism of an SBCA can be in fact used for the benefit of detection efficiency, since the shape of the focal spot of an SBCA can be chosen between vertical line focus, round spot focus, and a horizontal line focus. These focalisation conditions can be matched to the shape and size of the sample. In order to reach the latter option of a horizontal line focus, the detector must be moved away from the Rowland circle. Here the efficiency gain of optimally shaped beam is discussed in the case of a capillary flow reactor in combination of an automized SBCA exchanger and capillary height adjustment.

[1] Improving the performance of high-resolution X-ray spectrometers with position-sensitive pixel detectors, Journal of Synchrotron Radiation, August 2005, 12 (Pt4):467-72

[2] Honkanen et al., General method to calculate the elastic deformation and X-ray diffraction properties of bent crystal wafers, IUCrJ, Volume 8, Part 1, January 2021, p. 102-115

[3] Moya-Cancino et al., In-situ X-ray Absorption Near Edge Structure Spectroscopy of Solid Catalysts using a Laboratory-Based Set-up, ChemCatChem, Volume 11, Issue 3, p. 1039-1044

Nitrate (NO3-) chemodenitrification by Fe(II)/Fe(III) iron (oxyhydr)oxides and its stable N isotope fractionation signature

Mr Xin Wang1, Dr Naomi Wells2, Dr Adele Jones1, Dr Richard Collins1

1University of New South Wales, Kingsford, Australia, 2Southern Cross University, Lismore, Australia

Poster Session

Abstract The co-occurrence of iron oxide and oxyhydroxide minerals with Fe(II) is common in the natural environment, especially in subsoils, sludges of surface water and at the groundwater-sediment interface. In this study, the kinetics of nitrate reduction in Fe(II)/Fe(III) heterogeneous systems were investigated at neutral pH (from pH 6.5 to 7.5) and ambient temperature (at 25℃). Of all of the iron (oxyhydr)oxides examined, abiotic nitrate reduction by Fe(II) was only facilitated in the presence of green rust (GR). Comparison of type 1 and type 2 GRs demonstrated that type 1 (GR(Cl-)) had the strongest nitrate reducing ability, with a first-order kinetic

- -1 -6 -6 2- constant of Kobs (NO3 ) (s ) = 1.88 X 10 , compared to 0.73 X 10 for green rust type 2 (GR(SO4 )). In both cases, ammonium was the dominant reaction product and accounted for ~92 % of the nitrate reduced. In this paper, we use Fe K-edge X-ray absorption spectroscopy (XAS) to investigate purity of type 1 and type 2 GRs synthesized from ferrihydrite transformation. Type 2 has more purity than type 1. We also confirmed that the two types of GRs were transferred to magnetite once abiotic nitrate reduction occurred.

15 18 N and O isotope effects for chemodenitrification ( εcDNF and εcDNF) when catalyzed by green rust ranged from 2 to 8 ‰. N isotope fractionation of ammonium were consistently high (+20.3‰ 1.5‰), especially relative to bacterial denitrification (~0‰). This study contributes to the deeper understanding of the specific relevance for mineral-derived Fe(II) to promote the reduction of nitrate and consequent production of ammonium at neutral pH and ambient temperature.

Dispersion improvement of Pt nanoparticles using a hydrogen peroxide treatment Dr Eun-Suk Jeong1, Dr In-Hui Hwang2, Dr Mi-Young Kim3, Dr Sang-Wook Han1 1Department of Physics Education and Institute of Fusion Science, Jeonbuk National University, Jeonju 54869, South Korea, 2X-ray Science Division, Advanced Photon Source Argonne National Laboratory, Lemont 60439, USA, 3Corporate Research and Technology, Cummins Inc., 1900 McKinley Avenue, Columbus, USA Poster Session

The influence of hydrogen peroxide (H2O2) on the dispersion of Pt nanoparticles on titania-incorporated fumed silica (Pt/Ti-FS) was examined using X-ray absorption fine structure (XAFS) measurements at Pt L3- and Ti K-edges and density functional theory (DFT) calculations. The heterogeneous catalysts of Pt/transition- metal oxides are typically synthesized by calcining at 500℃ and Pt nanoparticles are uniformly and highly dispersed when H2O2 is applied before calcination. Local structural and chemical properties around Pt and Ti atoms of Pt/Ti-FS with and without an H2O2 treatment were monitored using in-situ XAFS at different temperatures during heating from room temperature to 500℃. XAFS revealed that the size and the local structural properties of Pt nanoparticles showed a lack change up to 500℃ once Pt atoms strongly bonded with H2O2-Ti-FS supports and Ti atoms formed a distorted anatase TiO2 structure at 250℃. DFT calculations demonstrated that the binding energy of Pt to oxidized-TiO2 is larger than those of Pt to reduced-TiO2 and intact-TiO2. XAFS measurements and DFT calculations clarified that oxygen atoms due to the H2O2 treatment seizing interface between Pt nanoparticles and Ti-FS supports play a critical role in a strong bond of Pt on TiO2. An H2O2 treatment can be widely used to synthesize stable and uniform metal nanoparticles with a high dispersion.

The work was conducted under the auspices of the Basic Science Research Program through the National Research Foundation of Korea government grant funded by the Ministry of Science and ICT (No. 2017K1A3A7A09016390, 2020K1A3A7A09080403). The XAFS data were collected at the 8C beamline of PLS in Korea and the 20BM beamline of APS in USA.

Advanced X-ray Spectroscopic Monitoring of Surface and Interfaces Mr James M. Bucag1, Ms Saphora B. Dabo1, Dr. Thokozile A. Kathyola1, Dr. Elizabeth A. Willneff1, Prof. Sven L. M. Schroeder1, Dr. Anna B. Kroner2 1University Of Leeds, Leeds, United Kingdom, 2Diamond Light Source, Harwell, United Kingdom Poster Session

The latest generation of advanced X-ray characterisation techniques allows a seamless multi- technique approach to in situ monitoring of molecular level transformations and interactions through all stages of homogenous and heterogeneous processes. X-ray absorption spectroscopy (XAS) techniques identify molecular species including their intra- and intermolecular bonding. It is the most established advanced characterization technique in the suite of techniques used in our studies and can be used to monitor interfaces. We have recently developed a cell for spatially resolved mapping and monitoring of interfacial chemistry on solid surfaces by XAS with a microfocus X-ray beam in combination with X-ray diffraction (XRD). It is based on standard laboratory glassware where laboratory conditions can be replicated while performing in situ XAS. The design of the cell accommodates simultaneous XAS measurements of the (i) overall sample, (ii) near-surface region (top 1-10 μm) and (iii) surfaces (1-10 nm). XAS can thus be applied to solutions, interfaces in one experimental setup, allowing us to follow molecules seamlessly from the solution state through the products formed on the interface. Simultaneous XRD identifies crystalline phases. XAS requires synchrotron radiation for its operation and is therefore not always readily available. However, similar information about the chemical nature of interfacial and surface composition can now be obtained through the latest generation of near-ambient pressure (NAP) X-ray photoelectron spectroscopy (XPS) techniques in the home laboratory. High throughput measurements on NAP-XPS with a localized 300 um beam spot complements micro-focused XAS experiments. Similar to XAS, NAP-XPS is sensitive to variations in the chemical environment around atoms and molecules, and thus provides quantitative information about chemical composition, environment and transformations. In this study, we use this multi-technique approach to investigate the surface and interface of metals. Through time-resolved experiments, we track chemical adsorption leading to overlayer formation and changes in its chemical composition.

This project is supported by EPSRC (EP/P006965/1) and Infineum UK Ltd.

Development of reaction cells for XAS and HERFD-XAS operando characterization of catalysts at high-pressure and high-temperature Dr Antonio Aguilar Tapia1,2, Dr Samy Ould-Chikh2, Ing Eric Lahera3, Ing. Alain Prat1, Professor Jorge Gascon2, Dr Jean-Louis Hazemann1 1Neel Institut, CNRS, Grenoble, France, 2KAUST Catalysis Center, , Saudi Arabia, 3OSUG, Grenoble, France Poster Session

Heterogeneous catalysts commonly exhibit a variety of different surface sites that are difficult to identify. Identification of the active sites is critical for the design and development of improved catalytic materials. Ideally, characterization of a catalyst involves the measurement of its corresponding properties during the catalytic reaction, i.e., operando conditions. However, performing analytic measurements of the reaction process under realistic conditions is highly challenging. Currently, X-ray absorption spectroscopy (XAS) is one of the most widely used techniques for analysis of catalysts under reaction conditions due to the penetration depth of the high-energy X-rays, enabling adequate analysis of the electronic and structural properties of heterogeneous catalysts. We present the development of various reaction cells for XAS operando characterization of catalysts. Our setup is derived from the previous high-pressure/high-temperature cell available on the FAME beamline.1 Therefore, it is possible to operate at high temperatures (up to 1000 °C). The design offers the capability of using fluorescence and transmission detection modes. The reaction cell includes a plug-flow reactor made from glassy carbon which allows almost all of the X-rays to be transmitted to the sample2 (Figure 1 left). The cell is available in BM30 beamline. Further modifications of the reaction cell resulted in a new cell with a 70° aperture, which allows irradiation of the 14-crystal analyzer spectrometer (CAS) available in BM16. This HT cell allow the collection of HERFD-XANES and XES spectra in operando conditions (Figure 1 middle). Our more recent development consists in a reaction cell for high-pressure (up to 1000 bar) and high –temperature reaction cell (Figure 1 right). All the reaction cells are provided with a completely automated gas distribution system dedicated for each cell, which is used to deliver a mixture of gases through the reaction cell, and the venting. The gas composition from the reactor is monitored on-line by an EcoCat-P portable mass spectrometer system operated remotely. The system is equipped with two identical capillary inlets for the on-line analysis of the reactor outlet and a bypass line. The system also allows quantitative analysis and has the capability to monitor up to 64 species in real time. It offers detection levels down to ppb levels.

Figure 1: HT operando reaction cells available in BM30 (left) and BM16 (middle) and HP/HT (right).

References [1] D. Testemale, R. Argoud, O. Geaymond, and J.L. Hazemann,

Rev. Sci. Instrum. 76, 1 (2005). [2] A. Aguilar-Tapia, S. Ould-Chikh, E. Lahera, A. Prat, W. Delnet, O. Proux, I. Kieffer, I. J.M. Basset, K. Takanabe and J.L. Hazemann, Rev. Sci. Instrum. 89, 1 (2018).

Valence transition in Eu2Pt6Al15 studied by high-energy resolution fluorescence detected x-ray absorption spectroscopy and hard x-ray photoemission spectroscopy Mr Masafumi Gotoda1 1Osaka Prefecture University, Sakai, Japan Poster Session

Electronic structure of a new valence transition compound Eu2Pt6Al15 [1, 2] has been investigated by means of high-energy resolution fluorescence detected x-ray absorption spectroscopy (HERFD-XAS) and hard x-ray photoemission spectroscopy (HAXPES). The HERFD-XAS experiments for polished sample surface and the HAXPES experiments for in situ fractured one were carried out at BL39XU and BL15XU of SPring-8, respectively. The temperature dependence of the observed Eu L3 HERFD-XAS and Eu 3d HAXPES spectra clearly shows the first-order valence transition: the spectral intensity ratio of Eu3+ component to Eu2+ one drastically changes beyond the valence transition temperature Tv ~ 45 K. From each spectrum, the Eu mean valence v was evaluated using a profile function. The v-value evaluated from the HERFD-XAS spectra shows the almost constant value of 2.12 – 2.17 at 300 – 60 K, and increases rapidly from 50 to 40 K, reaches to 2.48 at 3 K. This result is consistent with that from the HAXPES spectra at the temperatures from 20 to 300 K. However, the absolute v-values at all the measured temperatures are ~0.2 smaller than those from the transmission-mode XAS experiments using powder sample [2]. This difference might be influenced by the fact that the Eu element for the synthesis of Eu2Pt6Al15 in this study was weighed more than that reported before [2].

[1] M. Radzieowski et al., J. Am. Chem. Soc. 140, 8950 (2018). [2] K. Oyama et al., J. Phys. Soc. Jpn. 89, 114713 (2020).

*The HERFD-XAS and RXES experiments were performed at BL39XU of SPring-8 with the approval of JASRI (Proposal No. 2020A0706). The HAXPES experiments were performed at BL15XU of SPring-8 with the approval of the Synchrotron X-ray Station (Proposals No. 2020A4907 and No. 2020A4800). This work was partly supported by Grant-in-Aid for Scientific Researches “KAKENHI” (grant No. 15K05195) from JSPS and the NIMS microstructural characterization platform as a program of “Nanotechnology Platform” (Project No. 12024046) of MEXT, Japan.

Thermal excitation of trivalent Eu 4f electrons in EuBe13 revealed by high-energy resolution fluorescence detected x-ray absorption and resonant x-ray emission spectroscopies Mr Kenta Hamahara1, Mr Gen Isumi1, Mr Kotaro Tamura1, Mr Naomi Kawamura2, Mr Masaichiro Mizumaki2, Mr Hiroyuki Hidaka3, Mr Hiroshi Amitsuka3, Mr Kojiro Mimura1 1Department of Physics and Electronics, Osaka Prefecture University, Sakai, Japan, 2Japan Synchrotron Radiation Research Institute, Sayo, Japan, 3Graduate School of Science, Hokkaido University, Sapporo, Japan Poster Session

3+ EuBe13, that crystallizes in a cubic NaZn13-type structure, is one of the typical trivalent Eu (Eu ) compounds that its magnetic susceptibility can be well explained by the Van Vleck paramagnetism [1, 2]. In this study, the electronic structure in EuBe13 has been investigated by high-energy resolution fluorescence detected x-ray absorption spectroscopy (HERFD-XAS) and resonant x-ray emission spectroscopy (RXES) in order to discuss the thermal excitation process of Eu3+ 4f electrons among the multiplet structures from a spectroscopic viewpoint. The HERFD-XAS and RXES experiments in the Eu L3 absorption region (incident photon energy: hν = 6.95–7.05 keV) were performed at BL39XU of SPring-8 [3]. All the spectra were acquired from 3 to 300 K. The Eu L3 HERFD-XAS spectra show the significant single-peak ascribed to the electric dipole transition at hν = 6.9834 keV. This result is consistent with the previous ones that the Eu ion in EuBe13 is in the pure trivalent state [1, 2]. In addition, one can find two fine structures close to the Eu L3 absorption edge. Intensity of these structures, attributed to the electric quadrupole transition reflecting the Eu3+ 4f state, increases with increasing temperature. This trend is found more clearly in the Eu Lα1,2 RXES spectra. To quantitatively evaluate the temperature and hν dependence of the intensities of fine structures, we precisely extracted the fine structure components from the RXES spectrum by the line-shape analysis. This analysis reveals that the intensity variation of the fine structures is in accordance with the temperature dependence of the Boltzmann distribution function and the intensity variation of each fine structure shows the different hν dependence. The former result suggests that some of Eu3+ 4f electrons are thermally excited to J = 1 above 200 K even if the J = 1 excited state is located at 460 K above the J = 0 ground state in the Eu3+ ion. The later result may reflect that the transition process of fine structure differs each other.

[1] E. Bucher et al., Phys. Rev. B 11, 440 (1975). [2] H. Hidaka et al., J. Phys. Soc. Jpn. 88, 034708 (2019). [3] N. Kawamura et al., J. Phys. Soc. Jpn. 86, 014711 (2017).

*The HERFD-XAS and RXES experiments were performed at BL39XU of SPring-8 with the approval of JASRI (Proposal No. 2020A1225). This work was partly supported by Grant-in-Aid for Scientific Researches “KAKENHI” (grant No. 15K05195) from JSPS.

Eu valence state of valence fluctuating heavy fermion system EuNi2(P1–xGex)2 studied by Eu L3 high-energy resolution fluorescence detected x-ray absorption spectroscopy Mr Kotaro Tamura1,2, Mr Ryohei Shimokasa1,2, Mr Gen Isumi1, Mr Kenta Inoue1, Mr Kenta Hamahara1, Dr Naomi Kawamura2, Dr Norimasa Sasabe2, Dr Masaichiro Mizumaki2, Dr Akihiro Mitsuda3, Dr Hirofumi Wada, Dr Takayuki Uozumi1, Dr Kojiro Mimura1 1Osaka Prefecture University, Sakai, Japan, 2Japan Synchrotron Radiation Research Institute, Sayo, Japan, 3 Kyushu University, Fukuoka, Japan Poster Session

EuNi2(P1–xGex)2 changes from a valence-fluctuating heavy fermion state to a magnetically ordered state with increasing Ge concentration x [1]. In order to explore correlation of Eu mean valence and Eu 4f-5d Coulomb interaction (Ufd) which is much important to understand the quantum critical phenomena ascribed to the valence fluctuation [2], we have performed Eu L3 high-energy resolution fluorescence detected x-ray absorption spectroscopy (HERFD-XAS) experiment at BL39XU of SPring-8. At all the measured temperatures from 3 to 300 K, the Eu2+ and Eu3+ components are clearly recognized in the HERFD-XAS spectra for x = 0 and 0.1. This result reflects that EuNi2(P1–xGex)2 with x = 0 and 0.1 are in the valence fluctuation states at 3–300 K. With increasing temperature, the Eu2+ component gradually increases, while the Eu3+ one decreases. We evaluated the Eu mean valence (v) and the energy difference between the 2+ 3+ Eu and Eu peaks (δE) which contains the information on Ufd, through the least square fitting of HERFD-XAS spectra. For x = 0 and 0.1, v gradually changes from 2.58 and 2.56 at 3 K to 2.42 and 2.41 at 300 K, respectively. Furthermore, δE increases gradually as v decreases, which means that the relation between the temperature dependences of v and δE shows a good linear scaling. This suggests that the valence fluctuation and Ufd in this system are closely related, considering that the difference between a core-hole potential and a charge transfer energy is almost unchanged at all the measurement temperatures. In addition, we find that for x = 0 the temperature dependence of the 4f-electron contribution of volume expansion and the evaluated v value also shows a good linear scaling. Compared with the typical heavy- fermion compound CeRu2Si2, a maximum of linear thermal expansion coefficient α = d(∆l/l)dT gives a half value of the Kondo temperature [3]. The valence variation rate (dv/dT) evaluated for x = 0 has an extremal value at 43 K just like α. The extremal value of dv/dT for x = 0.1 is reached at 40 K. This result suggests that the Kondo temperature for x = 0 is higher than that for x = 0.1, corresponding that c-f hybridization of x = 0 is stronger than that of x = 0.1, as shown in the Doniach phase diagram.

[1] U. B. Paramanik et al., J. Phys.: Condens. Matter 28, 166001 (2016). [2] S. Watanabe and K. Miyake, J. Phys.: Condens. Matter 23, 094217 (2011). [3] Y. Hiranaka et al., J. Phys. Soc. Jpn. 82, 083708 (2013).

*The HERFD-XAS experiments were performed at BL39XU of SPring-8 with the approval of JASRI (Proposal Nos. 2019A1399, 2019B1119 and 2020A1225). This work was partly supported by Grant-in-Aid for Scientific Researches “KAKENHI” (grant No. 15K05195) from JSPS.

CORAL: a toolbox for statistical XAS data analysis in Jupyter Notebook Mr Igor Torquato1, Dr. Amélie Rochet1, Mr Alexey Espindola1, Dr. Carlos Pérez1, Dr. Santiago Figueroa1 1 Brazilian Synchrotron Light Laboratory (LNLS), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil Poster Session

CORAL (Curve ResOlution foR dAta anaLysis) is a new set of chemometric tools built in Python to perform multivariate spectral decomposition of large amount of XAS data. Jupyter Notebook permits to overcome difficulties related to the huge amount of data coming from fast data acquisition during time- resolved XAS studies. On beamlines controlled by Jupyter environment, such as the XAS beamline at SIRIUS [1], it also allows the creation of a complete experimental Notebook that allows to get on track the data analysis [2]. Principal Component Analysis (PCA) and Iterative Target Transformation Factor Analysis (ITTFA) from Prestopronto [3] are implemented and optimized to deal with larger datasets. This new implementation follows the evolution of a time-resolved experiment in the same experimental Jupyter Notebook and reduces the use of Random-access memory (RAM) by a considerable amount. Multivariate curve resolution with alternating least-squares (MCR-ALS) fitting analysis is a powerful tool for isolating pure spectra of intermediate species involved in kinetic studies [4]. This method is becoming commonly used for XAS studies, as for example in catalysis [5]. Our new implementation can be easily extended to parallel processing (using GPU or CPU) and has the advantage to be easily integrated to other applications thanks to the use of the freely usable Python language.

[1] Liu, L., N. Milas, N., Mukai, A. H. C., Resende, X. R. Sá F. H., (2014) J. Synch. Rad., 21, 904. [2] Randles, B. M., Pasquetto, I. V., Golshan, M. S., & Borgman, C. L. (2017) ACM/IEEE Joint Conference on Digital Libraries (JCDL) 1-2, doi: 10.1109/JCDL.2017.7991618. [3] Figueroa, S. J. A., & Prestipino, C. (2016) J. Phys.: Conf. Ser. 712, 012012. [4] Jaumot, J., Juan, A., Tauler, R., (2015) Chem. and Intel. Lab. Syst., 140, 1. [5] Rochet, A., Baubet, B., Moizan, V., Pichon, C., Briois, V., (2016)Comptes Rendus Chimie, 19, 1337.

Metabolism of Se+4 in the mycelium of Phycomyces blakesleeanus Dr Milan Žižić1 1Institute For Multidisciplinary Research, University Of Belgrade, 11000, Serbia Poster Session

Selenium can exist in several oxidation states that determine its beneficial or detrimental effects in biosystems. Unlike selenite (Se+4), elemental selenium (Se0) is water insoluble and non-toxic for human and animals in low concentration. Beside detoxification, reduction of Se in some microbial species results in production of SeNPs with extraordinary biological effects. Capacity for removing Se+4 from environmental medium and its metabolic pathway in the fungus of Phycomyces blakesleeanus has been examined by XANES spectroscopy. Spectra of sample were collected in fluorescence mode. Two physiologically relevant concentration of Se+4 have been used for mycelium treatment. XANES of the mycelium incubated 24h in 0.5 mM Se+4 reveal its metabolic transformation. Although reduction of Se occurred and the first inflection point coincides with those of metallic Se0, their spectral features are different, indicated by position of second peak at 1267 eV, typical for XANES of R-Se-R containing organic molecules. The derivative spectrum and the first EXAFS peak in the Fourier transformed spectrum indicates S as the atom in the first coordination sphere of Se. Treatment with 10 mM Se+4 leads to mycelial color change to red suggesting production of Se nanoparticles. XANES spectrum of 10 mM treated sample is characterized by the appearance of the shoulder at 1258 eV together with main peak at 1265 eV which point to changed form of Se in regard with 0.5 mM Se+4 samples and gray Se0 reference standard. The identical XANES features have been earlier documented to stem from CysSe- functional group, indicating protein involvement in reduction process of 10 mM Se+4. Results indicate that metabolic transformation and detoxification from Se+4 are concentration- dependent and occur intracellularly, while the reduction process in the fungus incubated in high Se+4 concentration is completed by excretion of biogenic SeNPs.

This document is an abstract template for the International Conference on X-ray Absorption Fine Structure XAFS2021, 11–13 July 2021. All of the specific formatting requirements for abstracts are online at https://xafs2021.org/call-for-abstracts.php.

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Analysis of liquid metals EXAFS data using deep neural networks Dr Fabio Iesari1, Dr Hiroyuki Setoyama2, Prof Toshihiro Okajima1 1Aichi Synchrotron Radiation Center, Seto-shi, Japan, 2Kyushu Synchrotron Light Research Center, Tosu-shi, Japan Poster Session

Over the last decade, the use of neural networks (NNs) for scientific applications has been steadily increasing. Consisting of numerous “neurons” stacked into layers, they are able to distinguish patterns or understand relationships between different quantities after appropriate training. They have been applied to the analysis of EXAFS data to obtain radial distribution function and probe phase transitions [1]. We wanted to investigate whether the same methodology could be applied to disordered phases and whether it would be possible to obtain information beyond the pair distribution function.

The critical point of any NN is the dataset used for the training process, that should be sufficiently large and heterogeneous. For this purpose, we used MD simulations of mono-atomic nickel in different structural configurations and at various temperature. The temperature was increased past the melting point to also include liquid configurations. From each configuration, we calculated the radial distribution function, bond- angle distribution of the nearest neighbours and the EXAFS signal, using GNXAS suite of programs [2]. The created dataset was then used to optimize and train a set of deep NNs to estimate radial and bond-angle distribution functions from a given EXAFS signal.

We used the NNs to analyse data of nickel at different temperatures. Obtained results show that the NNs are able to distinguish between ordered and disordered configurations and are also able to detect small changes in the local ordering of liquid structure, comparable with previously published results [3].

[1] J. Timoshenko, A. Anspoks, et al., Phys. Rev. Lett. 120, 225502 (2018) [2] A. Filipponi and A. Di Cicco, Phys. Rev. B 52, 15135 (1995) [3] A. Di Cicco, F. Iesari, et al., Phys. Rev. B 89, 060102 (2014)

[This work is supported by JST CREST JPMJCR1861.]

Simulation of Potassium K-edge XANES standards with applications in energy storage and catalysis Mr Alexander Mayer1,2, Dr Simon Kondrat1, Dr Giannantonio Cibin2, Dr Matteo Aramini2, Dr Diego Gianolio2 1Loughborough University, Loughborough, United Kingdom, 2Diamond Light Source, Didcot, United Kingdom Poster Session

Potassium is the eighth most abundant element on earth and is commonly present in minerals and functional materials. Potassium has many practical applications, such as an alternative to lithium-ion batteries1,2 or as a promotor in catalytic materials increasing activity and selectivity.3,4 Research into alkali metals via X- ray absorption techniques are limited due to their low atomic number. However, potassium K-edge excitation at 3609 eV, though still low in energy, is appropriate for analysis. Cibin et al. studied the potassium environment and coordination within the layers of trioctahedral micas and layered silicates.5–7 Despite this, there is still a low number of potassium K-edge studies. Therefore, it is important to create a portfolio of known standards that can be used as a reference for unknown materials.

Potassium K-edge spectra of a number of standards have been measured experimentally and calculated by Green’s function multiple-scattering method (FEFF)8–10 and DFT plane-wave pseudopotential method (CASTEP)11. Experimentally samples have been measured using total electron yield (TEY) in a vacuum chamber. Experimental results showed that potassium K-edge XANES are often rich in features and calculated spectra from both methods show success and are comparable to the experimental spectra. The largest discrepancies encountered within the simulated spectra were the intensities of the peaks compared to experimental. However, there is high agreement between the absolute peak positions of both calculated and experimental spectra. From further calculations of density of states (DOS), we hope to understand the transitions to unoccupied states. This work provides the foundations for experimental and simulated K- edge XANES for potassium standards demonstrating that simulation codes are available to successfully calculate spectra. Therefore, leading to greater understanding to the nature of potassium and to provide a resource to predict potassium coordination within an unknown structure or how potassium affects an environment during a reaction. Bibliography

1. A. V, B. John and M. TD, ACS Appl. Energy Mater., 2020, 3, 9478–9492. 1 T. Hosaka, K. Kubota, A. S. Hameed and S. Komaba, Chem. Rev., 2020, 120, 6358–6466. 2 Z. Tian, C. Wang, J. Yue, X. Zhang and L. Ma, Catal. Sci. Technol., 2019, 9, 2728–2741. 3 C. J. Davies, A. Mayer, J. Gabb, J. M. Walls, V. Degirmenci, P. B. J. Thompson, G. Cibin, S. Golunski and S. A. Kondrat, Phys. Chem. Chem. Phys., 2020, 22, 18976–18988. 4 G. Cibin, A. Mottana, A. Marcelli and M. F. Brigatti, Mineral. Petrol., 2005, 85, 67–87. 6 G. Cibin, Am. Mineral., 2006, 91, 1150–1162. 7 A. Marcelli, G. Cibin, G. Cinque, A. Mottana and M. F. Brigatti, Radiat. Phys. Chem., 2006, 75, 1596– 1607. 8 K. Jorissen and J. J. Rehr, J. Phys. Conf. Ser., 2013, 430, 012001. 9 J. J. Rehr, J. J. Kas, F. D. Vila, M. P. Prange and K. Jorissen, Phys. Chem. Chem. Phys., 2010, 12, 5503. 10 J. J. Rehr, J. J. Kas, M. P. Prange, A. P. Sorini, Y. Takimoto and F. Vila, Comptes Rendus Phys., 2009, 10, 548–559. 11 S. J. Clark, M. D. Segall, C. J. Pickard, P. J. Hasnip, M. I. J. Probert, K. Refson and M. C. Payne, Zeitschrift für Krist. - Cryst. Mater., 2005, 220, 567–570

Ultrafast solution chemistry capabilities at the Femtosecond X-ray Experiments instrument of the European XFEL Mr Florian Otte1,2, Dr Frederico Alves Lima1, Mr Paul Frankenberger1, Dr Dmitry Khakhulin1, Mr. Tae-Kyu Choi1, Dr Peter Zalden1, Dr Mykola Biednov1, Mr Martin Knoll1, Dr Yifeng Jiang1, Dr Fernando Ardana- Lamas1, Dr Vandana Tiwari1, Dr Chris Milne1 1European XFEL, Schenefeld, Germany, 2Technische Universität Dortmund, Dortmund, Germany Poster Session

The investigation of photo-induced femtosecond dynamics in liquid chemistry samples at the Femtosecond X-ray Experiments (FXE) instrument at the European Free Electron Laser facility (XFEL) has been of key interest from the very beginning of operation1. The past year has seen several technical and methodological advancements at the instrument, which have significantly enhanced the capabilities to handle samples with demanding chemical environments, such as volatile (organic) solvents, or samples that require a specific atmosphere. We report on a new sample chamber system for liquid chemistry experiments, which is at the heart of an improved sample environment at the instrument, designed to enable the acquisition of high- quality multi-spectroscopy data for demanding chemical samples. On the detection side, the collection of X-ray emission spectroscopy (XES), a sensitive probe for the electronic state of samples2,3, has been further developed. The simultaneous energy-dispersive detection of multiple XES lines (e.g. the 2p→1s (Kα) or 3p→1s (Kβ) fluorescence decay) is now accomplished regularly during user experiments (if required by multiple fully integrated PSI JUNGFRAU4 detectors), allowing for (X- ray pulse)-correlated data acquisition. We demonstrate how the flexible nature of the new sample environment aids the collection of multiple spectroscopies at once. Due to the immense FEL photon-flux, most samples are required to be jetted through the X-ray beam with a nozzle. For this configuration, an improved high-pressure pump setup and solutions for online optical spectroscopy capabilities (UV/Vis spectroscopy) have been developed and successfully used during user experiments. Examples will be presented.

[1] Khakhulin, D. et al. Appl. Sci. 10, 995 (2020). doi:10.3390/app10030995 [2] Vankó, G. et al. J. Electron Spectros. Relat. Phenomena 188, 166–171 (2013). doi:10.1016/j.elspec.2012.09.012 [3] Pollock, C. J., Delgado-Jaime, M. U., Atanasov, M., Neese, F. & DeBeer, S. J. Am. Chem. Soc 136, 9453 (2014). doi:10.1021/ja504182n [4] Mozzanica, A. et al. Synchrotron Radiat. News 31, 16–20 (2018). doi:10.1080/08940886.2018.1528429

Florian Otte gratefully acknowledges financial support via the BMBF fund 05K16PE1 and the CUI/AIM excellence cluster in Hamburg.

XAFS study of local atomic surrounding of silver in different structural states forming in silicate glasses by UV laser radiation Miss Sofia Bazovaya1, Mr Vasiliy Srabionyan1, Mr Leon Avakyan1, Mr Ivan Viklenko1, Miss Galina Sukharina1, Mr Juergen Ihlemann2, Mr Lusegen Bugaev1 1Southern Federal University, Rostov-on-Don, Russian Federation, 2Institute for Nanophotonics Göttingen, Göttingen, Germany Poster Session

Formation of defect centers of silver and of silver nanoparticles (NPs) in dielectric matrices has been extensively studied because these materials exhibit valuable linear and non-linear optical properties, including the localized surface plasmon resonance (SPR) of silver NPs [1]. Silver NPs in glasses are attracting particular attention since the wavelength of their SPR is distinctively separated from the wavelengths of interband absorption, making such materials promising candidates for applications in optoelectronics and nanoplasmonics. In this work, silver NPs in sodium silicate glasses were prepared by Ag+↔Na+ ion exchange and subsequent UV laser irradiation (193 nm) below the ablation threshold. However, depending on the laser parameters, UV-radiation can lead to the reduction of size or dissolution of NPs and to their instability even at room temperature. Therefore, to obtain stable NPs with required characteristics of SPR it is necessary to examine the dependences of these characteristics upon the parameters of the laser irradiation and to obtain irradiation conditions that provide stability of the forming NPs in glasses. Characteristics of NPs SPR depend in turn of the size, form, atomic structure of NPs and dielectric properties of the surrounding matrix. Besides, the hole- trap centers (HTC) containing one or two silver atoms are also forming in glass, which affects the optical absorption spectra of material, and complicates significantly determination of Ag NPs structure and their contribution in the features of SPR, simultaneously with determination of the atomic structure of such HTC defect centers. In this study X-ray absorption spectroscopy (XAFS) together with DFT modeling of HTC were used to obtain information on structural states of silver in glass matrix and the obtained structural models were verified by experimental SPR. The used approach enabled to reveal the most plausible models of local structure of silver atoms in the samples, which in turn enabled to suggest the structural models for HTC and to examine the relative changes of contributions from HTC and silver NPs under the variations of laser irradiation parameters.

[1] M. Heinz, V. V. Srabionyan, L.A. Avakyan, A.L. Bugaev, A. V. Skidanenko, S.Y. Kaptelinin, et al., Formation of bimetallic gold-silver nanoparticles in glass by UV laser irradiation, J. Alloys Compd. 767 (2018) 1253–1263. doi:10.1016/j.jallcom.2018.07.183.

Ion association in hydrothermal aqueous NaCl solutions: Implications for the microscopic structure of supercritical water Mr Mirko Elbers1 1University Potsdam, Potsdam, Germany Poster Session

We present a combined in situ x-ray Raman scattering (XRS) and ab initio molecular dynamics simulations study of aqueous sodium chloride solutions at high pressure and temperature to reveal the microscopic structure of this relevant fluid and to investigate the influence of the alkali halide on the hydrogen-bond network up to supercritical conditions. Hydrothermal fluids are of crucial importance for various industrial applications and for material and heat transport processes in the Earth's crust, especially for the formation of magma and the genesis of ore deposits. By probing the oxygen K-edge of the salt solution, unique information is obtained about the oxygen’s local coordination, e.g., solvation-shell structure and ion pairing. The measured XRS spectra exhibit systematic temperature dependence, the relative course of which is nicely reproduced by the spectral calculations based on structural snapshots obtained by ab initio molecular dynamics simulations. Therefore, we utilize detailed structural information extracted from the simulated trajectories for our analysis. This combined analysis reveals a net destabilizing effect of the dissolved ions, which is reduced with rising temperature. The observed increased formation of contact ion pairs and occurrence of larger polyatomic clusters at higher temperatures can be identified as a driving force behind the increasing similarities of the aqueous sodium chloride solution and pure water in terms of spectral and structural differences. These findings are of significant importance for geochemical processes that are involved during the formation of ore deposits and comprehend the understanding of ion-solvent interaction. We thank for financial support: BMBF (05KP16PE1), DFG via STE 1079/2-1, STE 1079/4-1 (FOR2125, CarboPaT), STE 1079/6-1, WI 2000/22-1 and EXC 2033 - 390677874 – RESOLV. The authors gratefully acknowledge PETRA III (beamline P01, proposal number 20180388) and the ESRF (beamline ID20, proposal number ES-863) for providing synchrotron radiation and beamline support. We also thank the Gauss Centre for Supercomputing e.V. for providing computing time (project ID CHPO15) as well as the Linux HPC cluster at TU Dortmund (partially funded by DFG project 271512359).

Balder beamline at MAX IV: Hard X-ray Spectroscopy at a 4th Generation Storage Ring Dr. Justus Just1, Dr. Kajsa Sigfridsson-Clauss1, Dr. Konstantin Klementiev1 1MAX IV Laboratory, Lund, Sweden Poster Session

Balder is a wiggler beamline dedicated to X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) in medium and hard X-ray energy range 2.4–40 keV [1]. Our aim is to reach a high repetition rate down to 1s for full EXAFS in order to preserve the sample (reduce radiation damage) and attain redox dynamics in in-situ reactions. The beamline is in the user operation and under expansion of the instrumentation portfolio.

In this poster, we describe the beamline and demonstrate the achieved XAS data. We show the presence of undulator features in the wiggler spectrum, characteristic of low emittance storage rings, and point at sample- related difficulties arising from the intense X-ray beam. We also present the XES spectrometer of the 1D Johansson type [2]: its design, crystal technology, detector features and a few measured emission spectra. Our available sample infrastructures are exemplified by (i) an in-house developed 2D mapping closed cycle He cryostat, (ii) a micro-fluidic setup and (iii) a capillary based in-situ reactor

References [1] - Klementiev K, Norén K, Carlson S, Sigfridsson Clauss K and Persson I 2016 The BALDER Beamline at the MAX IV Laboratory, J. Phys.: Conf. Ser. 712 012018. [2] - Klementiev K, Preda I, Carlson S, Sigfridsson K and Norén K 2015 High performance emission spectrometer at Balder/MAXIV beamline, J. Phys.: Conf. Ser. 712 012018.

Crystal and electronic structure of Co3O4 spinel under pressure probed by XANES and Raman spectroscopy. Dr Yimin Mijiti1,2, Dr Kai Chen2, Dr Joao Elias F. S. Rodrigues4, Dr Lucie Nataf2, Dr Angela Trapananti1, Dr Zhiwei Hu5, Dr Francois Baudelet2, Dr Andrea Di Cicco1 1Physics Division, University Of Camerino, Camerino, Italy, 2Synchrotron SOLEIL, Saint-Aubin, France, 3Helmholtz-Zentrum Berlin fur Materialien und Energie,, Berlin, Germany, 4Instituto de Ciencia de Materiales de Madrid, Cantoblanco, Spain, 5Max Planck Institute for Chemical Physics of Solids, Dresden, Germany Poster Session

Crystal and electronic structure of Co3O4 spinel have been investigated by x-ray absorption near edge structure (XANES) at the Co K edge up to 58.5 GPa and Raman scattering up to 65 GPa [1]. Several transitions have been observed upon pressurization, and the original structure was recovered on decompression. Experimental and theoretical XANES and Raman data are compatible with the occurrence of a monoclinic P21/c phase above ∼52.7 GPa [2,3]. Vibrational modes analyzed in details by Raman scattering indicate that two other subtle transitions take place above ∼21.9 GPa (orthorhombic Fddd) and ∼43.0 GPa (monoclinic C2/m), in agreement with the previous x-ray diffraction experiments [2]. Our combined experimental XANES and multiple scattering calculations indicate clear evidence of a tetrahedral to octahedral coordination crossover at the Co2+ sites, being completed upon transition to the monoclinic P21/c phase. The valence and spin states at two different Co sites remained unchanged at least up to the transition onset to the monoclinic P21/c phase ruling out the possibility of charge transfer and spin crossover in the intermediate phases as proposed previously [4,5].

Figure 1. XANES data (b) and their first derivative (d) upon pressure increase up to 58.5 GPa and decrease down to 2.3 GPa. For the sake of clarity, pre-edge ranges (7702~7714 eV) in XANES and first derivative spectra are shown with magnifications in (a) and (c) respectively.

[1] Y. Mijiti, K. Chen, J. E. F. S. Rodrigues, Z. Hu, L. Nataf, A. Trapananti, A. Di Cicco, and F. Baudelet, Phys. Rev. B 103, 024105 (2021). [2] F. Cova, M. V. Blanco, M. Hanfland, and G. Garbarino, Phys. Rev. B 100, 054111 (2019). [3] S. Hirai and W. L. Mao, Appl. Phys. Lett. 102, 041912 (2013). [4] L. Bai, M. Pravia, Y. Zhao, C. Park, Y. Meng, S. V. Sinogeikin, and G. Shen, J. Phys.: Condes. Matter 24, 435401 (2012). [5] T. Kaewmaraya, W. Luo, X. Yang, P. Panigrahi, and R. Ahuja, Phys. Chem. Chem. Phys. 17, 19957 (2015)

An open access XAS spectra database at SOLARIS Dr Pawel Nita1, Dr Alexey Maximenko1, Prof Josef Hormes2,3, Dr Henning Lichtenberg4, Prof. dr hab. Jacek Szade1, Dr Marcin Zając1 1National Synchrotron Radiation Centre Solaris, Kraków, Poland, 2Institute of Physics, Rheinische Friedrich-Wilhelm-University, Bonn, Germany, 3Center for Advanced Microstructures and Devices, Louisiana State University, Baton Rouge, USA, 4Hochschule Niederrhein University of Applied Sciences, Krefeld, Germany Poster Session

SOLABS (XAS-HN), a new X-ray absorption spectroscopy (XAS) beamline in the tender energy range at the SOLARIS synchrotron, is at the final stage of construction. Commissioning will take place during summer 2021. In parallel, the beamline team is developing a database framework dedicated to hosting XAS spectra to be collected during routine operation of the beamline. Recently, Asakura et al. (J. Synchrotron Rad. 25, 967, 2018) and Cibin et al. (Radiation Physics and Chemistry 175, 108479, 2020) submitted a postulate for creating an international XAFS database as an essential element for the further development of XAFS spectroscopy, pointing out that, an open- access repository of XAS spectra is of great importance for beamline users as well as the entire XAS community- since reliable and reproducible reference spectra in a standardized format play a crucial role in a data analysis. The main objective of our project is to provide a comprehensive information about the investigated materials and measurements, such as preparation conditions, experimental details and bibliographic references, along with the respective spectra in a modern and user-friendly format. The database will be available in a form of website, which is being built using the Python micro web framework Flask (https://flask.palletsprojects.com/en/1.1.x/) and the SQLite database engine (https://www.sqlite.org/). Raw data will be stored in XDI (XAS Data Interchange) format (Ravel et al. J. Phys. Conf. Ser. 712, 012148, 2016). We wish to introduce our concept at the XAFS2021 conference and appreciate feedback from the XAFS community in order to tailor the database to the specific demands of future users.

Identifying Signatures of Charge Transfer in the Time-Resolved N K-edge XAS of an Ru Photocatalyst using Time-Dependent Density Functional Theory Ms Nahid Ghodrati1, Ms. Hana Cho2, Mr. Kiryong Hong2, Dr. Robert W. Schoenlein3, Prof. Dr. Tae Kyu Kim4, Prof. Dr. Nils Huse5, Dr. Benjamin E. Van Kuiken1 1European XFEL, Schenefeld, Germany, 2Korea Research Institute of Standards and Science, Daejeon, Republic of Korea, 3SLAC National Accelerator Laboratory, California, United States, 4Yonsei University, Seoul, Republic of Korea, 5University of Hamburg, Hamburg, Germany Poster Session

Ruthenium polypyridyl complexes have many photochemical applications including solar energy conversion, photo-redox catalysis, and photodynamic therapy. The activity of these complexes is due to the long-lived triplet metal-to-ligand charge transfer (3MLCT) excited states. Understanding how the electron density evolves following photoexcitation of these molecules remains a challenge. This is particularly true of Ru(II) complexes possessing the dppp2 (pyrido [2ʹ,3ʹ:5,6] pyrazino[2,3-f] [1,10] phenanthroline) ligand because they exhibit multiple low-lying 3MLCT states where the electron is predicted to be either localized proximally (3MLCTprox) or distally (3MLCTdis) to the Ru atom. Ultrafast optical studies have shown that timescale for the 3 prox 3 dis interconversion between MLCT and MLCT and the overall lifetime are both strongly solvent dependent. 2+ We have used picosecond time-resolved N K-edge XAS to investigate the MCLT reaction in [Ru(bpy)2(dppp2)] and track the evolution of charge density across the nitrogen atoms of the ligands. In this contribution, we focus on the use of time-dependent density functional theory (TDDFT) to assess the spectral content of the time-resolved N K-edge data. TDDFT is used to calculate the N K-edge XAS spectra of the ground state and 3MLCT states of 2+ [Ru(bpy)2(dppp2)] . The intense pre-edge 1s → π* feature in the N K-edge spectra is seen to provide information about the charge distribution across the dppp2 ligand, and the XAS spectrum is decomposed into contributions from each N atom. The TDDFT calculations reproduce the spectral changes observed in the synchrotron-based picosecond time-resolved measurements and identify the long-lived MLCT excited state as 3MLCTdis, which is consistent with the previous optical measurements. The solvent dependence of the excited state dynamics is investigated using continuum solvation models and multiple density functional are tested. Finally, we assess the ability of the N K-edge XAS and RIXS to differentiate 3MLCTprox and 3MLCTdis which may be observed in future femtosecond experiments at XFEL sources.

X-ray emission scanning imaging setup to study electronic structure of iron bearing compounds in-situ at conditions of the Earth’s mantle Mr Christian Albers1, Georg Spiekermann2, Lélia Libon3, Robin Sakrowski1, Max Wilke3, Johannes Kaa5, Nicola Thiering1, Hlynur Gretarsson4, Martin Sundermann4, Metin Tolan1, Christian Sternemann1 1Fakultät Physik/DELTA, Technische Universität Dortmund, , Germany, 2Institut für Geochemie und Petrologie, , Switzerland, 3Institut für Geowissenschaften, Universität Potsdam, , Germany, 4Deutschen-Elektronen-Synchrotron DESY, , Germany, 5HED Group, European XFEL GmbH, , Germany Poster Session

The determination of the electronic structure in iron-bearing compounds under high pressure and high temperature (HPHT) conditions is of crucial importance for the understanding of the Earths’ interior and planetary matter. (Magnesio)siderite (Mg,Fe)CO3 is in focus of recent research as it is a candidate for the carbon storage in the deep Earth. (Magnesio)siderite exhibits a complex chemistry at pressures above 50 GPa and temperatures above 1400 K resulting in the formation of tetracarbonates featuring tetrahedrally coordinated CO4-groups instead of the typical triangular-planar CO3-coordination. These tetracarbonates are well understood on a structural level but information on their electronic structure is scarce [1-3]. We present a setup to investigate the electronic structure of iron-bearing compounds in-situ at HPHT conditions using X-ray emission spectroscopy (XES) and show first results for the study of tetracarbonate phases at about 80 GPa and 3000 K. The HPHT conditions are accomplished by diamond anvil cells (DACs) in combination with a portable laser heating setup [4]. Information on the spin state of the pressurized and heated samples are obtained by in-situ XES of the iron’s Kβ-emission utilizing an energy dispersive von Hamos spectrometer in combination with a Pilatus 100K area detector [5]. This setup provides a full emission spectrum including valence-to-core (vtc) emission in a single shot fashion. In combination with a dedicated sample preparation together with highly intense synchrotron radiation of beamline P01 at Petra III, the duration of the measurements is shortened to an extent that in-situ XES, including vtc, as well as in-situ spin state imaging becomes feasible. Furthermore, the use of miniature diamonds enables resonant XES measurements at the Fe-K edge and provides insights into the iron's oxidation state. Adding X-ray diffraction and Raman spectroscopy imaging after temperature quenching the samples, the results on the electronic structure are linked to the occurring phases.

Acknowledgments: We thank PETRA III (beamlines P01 and P02.2) for providing synchrotron radiation. We also thank S. Chariton, C. McCammon and L. Dubrovinsky for the synthesis of FeCO3 single crystals at Bayerisches Geoinstitut. This work was supported by the DFG via STE 1079/4-1 (FOR2125, CarboPaT) and STE 1079/4-2. The FXE-group of XFEL is kindly acknowledged for providing a set of analyzer crystals for use with the von Hamos spectrometer. We thank C. Schmidt for support with the Raman imaging at Deutsche GeoForschungsZentrum. We are grateful for the support of Hanns-Peter Liermann, Konstantin Glazyrin, Nico Giordano and Rachel Husband for the support with the XRD imaging.

[1] J. Liu, J-F. Lin, T. Mao, V. B. Prakapenka, Scientific Reports, 5, 7640 (2015) [2] M. Merlini, M. Hanfland, A. Salamat, S. Petitgirard and H. Müller, American Mineralogist, 100, 2001, (2015) [3] V. Cerantola, E. Bykova, I. Kupenko , M. Merlini, L. Ismailova, C. McCammon, M. Bykov, A. Chumakov, S. Petitgirard, I. Kantor, V. Svitlyk, J. Jacobs, M. Hanfland , M. Mezouar , C. Prescher, R. Rüffer, V. Prakapenka and L. Dubrovinsky, Nature Communications 8, 15960 (2017) [4] G. Spiekermann, I. Kupenko, S. Petitgirard, M. Harder, A. Nyrow, C. Weis, C. Albers, N. Biedermann, L. Libon, C. J. Sahle, V. Cerantola, K. Glazyrin, Z. Konôpková, R. Sinmyo, W. Morgenroth, I. Sergueev, H. Yavaş, L. Dubrovinsky, M. Tolan, C. Sternemann, M. Wilke, Journal of Synchroton Radiation, 27, 414 (2020) [5] C. Weis, G. Spiekermann, C. Sternemann, M. Harder, G. Vankó, V. Cerantola, C.J. Sahle, Y. Forov, R. Sakrowski, I. Kupenko, S. Petitgirard, H. Yavaş, C. Bressler, W. Gawelda, M. Tolan and M. Wilke, Journal of Analytical Atomic Spectroscopy 34, 384 (2019)

Investigation of the Electronic Structure of Iron in Bridgmanite at Deep Mantle Pressure Conditions by (Resonant) X-ray Emission Spectroscopy Mr. Robin Sakrowski1, G. Spiekermann2, C. Albers1, N. Thiering1, L. Libon5, H. Gretarsson3, M. Sundermann3, J.P. Rueff4, M. Tolan1, M. Wilke5, C. Sternemann1 1Faculty of Physics/DELTA, TU Dortmund University, , , 2Institute of Geochemistry and Petrology, , , 3Deutsches-Elektronen-Synchrotron DESY, , , 4Synchrotron SOLEIL, , , 5Institute of Geosciences, University of Potsdam, , Poster Session

We report tracking changes in the controversial discussed iron spin state in bridgmanite, as well as coordination state and oxidation state. For that, we use a combination of novel approaches like in situ resonant X-ray emission (RXES) at the iron K-pre-edge region, iron Kβ- and valence-to-core (vtc) X-ray emission spectroscopy (XES). In the case of the Fe-bearing magnesium silicate perovskite (Mg,Fe)SiO3, recently named as bridgmanite, the Fe spin transition is complicated by the crystal chemistry, because Fe may occupy the A and B-site of the lattice and the Fe oxidation state may vary. Here, our recent results on the spin-state of ferrous (Fe2+) and ferric (Fe3+) iron in bridgmanite will be presented and discussed in in context to the results obtained by Badro et al. [1]. Preliminary analysis of the ferrous iron data implies that the results there [1] cannot be explained by a combination of our ferrous data and results obtained by Liu et al. [2] on ferric iron. Tracking changes in the coordination state and oxidation state we evaluate the Fe K pre-edge feature position and intensity [3] from HERFD XANES. The XES experiments were performed using an energy dispersive von Hamos type spectrometer in combination with a Pilatus area detector and nano-polycrystalline miniature diamonds for simultaneous acquisition of Fe Kβ and vtc XES [4] in combination with RXES measurements giving M-/L-edge like information [5]. Consequently, the combination of these methods helps to further constrain the observed gradual (ferrous) or sharp (ferric) change in spin state, local coordination and oxidation state of iron in ferrous- (up to 140 GPa) and ferric- (up to 75 GPa) bridgmanite, aiming to solve the controversy on the iron’s spin state in bridgmanite.

[1] J. Badro, J.P. Rueff, G. Vanko, G. Monaco, G. Fiquet., F. Guyot, Science 2004, 305, 383. [2] J. Liu, S.M. Dorfmann, F. Zhu, J. Li, Y. Wang. D. Zhang, Y. Xiao, W. Bi and E.E. Alp, Science 2018, 9, 1284. [3] M. Wilke, G.M. Partzsch, R. Bernhardt, D. Lattard, Chem. Geo. 2004, 213, 71. [4] C.Weis, G. Spiekermann, C. Sternemann, M. Harder, G. Vanko, V. Cerantola, C.J. Sahle, Y. Forov, R. Sakrowski, I. Kupenko, S. Petitgirad, H. Yavas, C. Bressler, W. Gawelda, M. Tolan, M. Wilke, J. Anal. At. Spectrom.2019, 34, 384. [5] P. Glatzel and U. Bergmann, Coord. Chem. Rev. 2005,249, 65-95

Acknowledgments: We thank PETRA III (beamlines P01, P06) and Soleil (GALAXIES) for providing synchrotron radiation. This work was supported by DFG projects STE 1079/2-1, STE 1079/4-1, and WI 200/8-1 (latter two within research unit FOR 2125, CarboPaT) and the BMBF project 05KP16PE1. The FXE-group of XFEL is kindly acknowledged for providing the von Hamos spectrometer crystals. We thank L.Ziberna, C. McCammon and L. Dubrovinksy for synthesis of Bridgmanite single crystals at Bayrisches Geoinstitut.

Determining the composition of magnetic iron oxide-silica nanoparticles for use in Australian COVID-19 test kits Dr Valerie Mitchell1, Nicholas Kirkwood2, Jessica Hamilton1, Bernt Johannessen1, Siobhan Bradley2, Jiho Han2, Dingchen Wen2, Trent Ralph2, Paul Mulvaney2 1Australian Synchrotron, ANSTO, , , 2University of Melbourne, , Poster Session

Silica-coated magnetic nanoparticles (MNPs) are often used in diagnostic tests to separate DNA and RNA from other biological material for analysis. These MNPs are a crucial component of COVID-19 testing, but Australia lacks a domestic producer. Working with local industry, the Mulvaney group at the University of Melbourne has been developing synthetic strategies for the production of these MNPs for use in viral testing kits. The ideal particles must have a high (reversible) magnetic response, long shelf-life and reproducible response in relevant clinical testing conditions, all factors which can vary with particle composition which in turn is controlled by the synthetic methodology. At the X-Ray Absorption beamline of the Australian Synchrotron, we have analysed the iron oxide compositions of MNPs produced via various techniques in order to understand the factors contributing to MNP performance and the synthetic strategies best able to produce these optimized particles. The information gained will be used to inform the Australian production of MNPs for COVID-19 test kits.

This work was supported by the Australian Research Council Centre of Excellence in Exciton Science.

New on the Physics Menu: Superconducting Sandwiches! Mr Andrew Chan

Poster Session

Between two pieces of bread is a world of unlimited possibilities to discover exciting new flavours. As scientists with access to advanced layering technologies, we procure our own sandwiches with atomic-level precision - combining mutually exclusive phenomenon such as superconductivity and magnetism to study their interplay [1]. Superconductors carry electrical current with zero resistance when cooled below its critical temperature (Tc).

Near-universally, however, superconductivity is degraded by large magnetic fields or electric currents – a key performance limitation bottlenecking emerging superconductor technologies. Recently, we discovered novel emergent properties in thin-film multilayers of a cuprate high-temperature superconductor (YBa2Cu3O7, YBCO) and magnetic manganite (Pr0.5La0.2Ca0.3MnO3, PLCMO). At low temperatures, this ‘superconductor sandwich’ hosts an exotic granular superconducting state characterized by a phase-pinned superconducting condensate and an unusually high resistance [2]. Surprisingly, the customary superconducting state is recovered in a large magnetic field and/or current, making our sandwiches one of just four systems exhibiting magnetic field and electric current induced superconductivity. As interesting as these sandwiches are, they are unfortunately unsuitable for human consumption. Rather, once we gain a better understanding of their novel physics, they may be destined as components in future electronic devices.

References: [1] Malik et al. Pulsed laser deposition growth of heteroepitaxial YBa2Cu3O7/La0.67Ca0.33MnO3 superlattices on NdGaO3 and Sr0.7La0.3Al0.65Ta0.35O3 substrates. Phys. Rev. B. (2012), 85, 054514. [2] Mallett et al. Granular superconductivity and magnetic-field-driven recovery of macroscopic coherence in a cuprate/manganite multilayer. Phys. Rev. B (2016) 94, 180503(R).