kth royal institute of technology Doctoral Thesis in Chemistry Y-Radiation Induced Synthesis of Metal Oxides Control of Particle Size, Composition, and Morphology ZHUOFENG LI Stockholm, Sweden 2021 Y-Radiation Induced Synthesis of Metal Oxides Control of Particle Size, Composition, and Morphology ZHUOFENG LI Academic Dissertation which, with due permission of the KTH Royal Institute of Technology, is submitted for public defence for the Degree of Doctor of Philosophy on 17 September 2021 at 10:00 in room Kollegiesalen, KTH, Brinellvägen 8, SE-11428, Stockholm. Doctoral Thesis in Chemistry KTH Royal Institute of Technology Stockholm, Sweden 2021 © ZHUOFENG LI © RSC, Paper I © Elsevier, Paper II © Elsevier, Paper III ISBN 978-91-7873-946-2 TRITA-CBH-FOU-2021:30 Printed by: Universitetsservice US-AB, Sweden 2021 “Science and technology constitute a primary productive force.” Xiaoping Deng Abstract Nanomaterials show a significant difference in chemical, mechanical, electronic, magnetic and optical properties compared with bulk counterparts. The synthesis is a key-step to achieve the unique properties of nanomaterials. As an efficient, clean and straightforward approach, the γ- radiation induced synthesis has been extensively applied to fabricate metal nanoparticles. However, with regard to production of metal oxide nanoparticles via γ-radiation induced synthesis, the knowledge is still insufficient. The following metal oxides have been selected as synthesis substances in this thesis: Cu2O, MnO2, Mn3O4 and CeO2. A prerequisite for utilization of the radiation-induced approach to engineer metal oxide nanomaterials is to optimize the reaction conditions for each specific nanofabrication case. The current study aims to understand the effects of different reaction conditions, i.e., pH, scavenger concentration, precursors, dose, and support materials, on the structural, and physico-chemical properties of the fabricated metal oxide nanomaterials. The pH of the reaction plays an important role in determining the thermodynamically stable metal oxide products in radiation-induced synthesis. (Paper I). When using high concentration of solutes, i.e., isopropanol (used as a hydroxyl radical scavenger), the solvent effects must be considered (Paper I). It is found that different metal cation precursors (same element but different oxidation state) can result in metal oxides differing in composition and morphology under different radiation-induced redox conditions (Paper II). By gradually increasing the dose, ceria nanoparticles in different growth stages can be captured, and their morphological development is studied by TEM (Paper IV). Based on this, a mechanism for nucleation of ceria nanoparticles and mesocrystal growth is proposed as a function of the dose. Support materials, i.e., carbon black and PVP nanogel, are used to engineer supported metal oxides. The reactivity of carbon black towards water radiolysis products (Paper III), and the size-controlling effect of nanogel on produced metal/metal oxide nanoparticles (Paper V) are investigated in this thesis. In addition, for the view of application, the primary electrochemical properties of radiation- induced synthesized carbon black supported samples are studied (Paper II). Keywords: γ-radiation induced synthesis, Metal oxide nanoparticles, Metal oxide nucleation, Mesocrystal formation, Carbon black reactivity towards radical, PVP nanogel. I Sammanfattning Nanomaterial uppvisar en signifikant skillnad i kemiska, mekaniska, elektroniska, magnetiska och optiska egenskaper jämfört med motsvarande bulkmaterial. Syntesprocessen är ett av de viktigaste stegen för att åstadkomma nanomaterialens unika egenskaper. Som ett effektivt, rent och enkelt tillvägagångssätt har γ-strålningsinducerad syntes använts i stor utsträckning för att tillverka metallnanopartiklar. När det gäller produktion av metalloxid-nanopartiklar via γ- strålningsinducerad syntes är kunskaperna fortfarande otillräckliga. Följande material har valts som syntesämnen i denna avhandling: Cu2O, MnO2, Mn3O4 och CeO2. En förutsättning för att använda strålningsinducerad syntes för att producera metalloxid- nanomaterial är att optimera reaktionsförhållandena för varje specifikt nanofabrikationsfall. Den aktuella studien syftar till att förstå effekterna av olika reaktionsförhållanden, d.v.s. pH, reaktantkoncentration, startmaterial, stråldos och eventuellt templatmaterial, på de tillverkade metalloxid-nanomaterialens strukturella och fysikalisk-kemiska egenskaper. Reaktionens pH spelar en viktig roll för att bestämma de termodynamiskt stabila metalloxidprodukterna vid strålningsinducerad syntes (Artikel I). Vid användning av höga koncentrationer av lösta ämnen, t.ex. isopropanol som används som hydroxylradikalinfångare, måste även lösningsmedelseffekter betraktas (Artikel I). Olika startmaterial (samma grundämne men olika oxidationstal) kan ge produkter som skiljer sig åt i fråga om sammansättning och morfologi under olika strålningsinducerade redoxförhållanden (Artikel II). Genom att gradvis öka stråldosen kan CeO2-nanopartiklar i olika tillväxtstadier fångas in och deras morfologiska utveckling studeras med TEM (Artikel IV). Utifrån detta föreslås en mekanism för kärnbildning av CeO2-nanopartiklar och mesokristalltillväxt som en funktion av stråldosen. Templatmaterialen kimrök och PVP-nanogel har använts vid syntes av metalloxider. Kimrökens reaktivitet mot vattenradiolysprodukter (Artikel III) och den storleksreglerande effekten av nanogel på syntetiserade metall/metalloxid-nanopartiklar (Artikel V) undersöks i denna avhandling. Dessutom studeras de primära elektrokemiska egenskaperna hos strålningsinducerade syntetiserade kimröksbaserade prover (Artikel II). Nyckelord: γ-strålningsinducerad syntes, Metalloxidnanopartiklar, Metalloxid kärnbildning, Mesokristallbildning, Kimröks reaktivitet mot radikal, PVP nanogel. II List of Papers I. pH-Control as a way to fine-tune the Cu/Cu2O ratio in radiation induced synthesis of Cu2O particles Zhuofeng Li, Inna L. Soroka, Fanyi Min, Mats Jonsson Dalton Transactions, 2018, 47, 16139-16144 DOI: 10.1039/C8DT02916D II. Tuning morphology, composition and oxygen reduction reaction (ORR) catalytic performance of manganese oxide particles fabricated by γ-radiation induced synthesis Zhuofeng Li, Yi Yang, Axel Relefors, Xiangyang Kong, Gerard Montserrat Siso, Björn Wickman, Yohannes Kiros, Inna L. Soroka Journal of Colloid and Interface Science, 2021, 583, 71-79 DOI: 10.1016/j.jcis.2020.09.011 III. On the reactivity of aqueous radiolysis products towards carbon black used in in- situ radiation-synthesis of catalytic nanoparticles in graphite electrodes Zhuofeng Li, Mats Jonsson Carbon, 2021, 173, 61-68 DOI: 10.1016/j.carbon.2020.10.094 IV. Nanoscopic insights on different stages of CeO2 mesocrystals formation in aqueous solutions explored using radiation chemistry Zhuofeng Li, Diana Piankova, Yi Yang, Yuta Kumagai, Hannes Zschiesche, Mats Jonsson, Markus Antonietti, Nadezda V. Tarakina and Inna L. Soroka Manuscript. V. Inorganic/organic hybrid nanoparticles synthesized in a two-step radiation- driven process Zhuofeng Li, Inna L. Soroka, Nadezda V. Tarakina, Maria Antonietta Sabatino, Emanuela Muscolino, Marta Walo, Mats Jonsson, Clelia Dispenza Manuscript. III Contribution to the papers I. I participated in designing the experiments, performed all the experiments, wrote the original draft. II. I participated in part of experimental design, performed part of the experiments, wrote part of the original draft and did the editing work. III. I participated in the experimental design, performed all the experiments, wrote the original draft and did the editing work. IV. I participated in the experimental design, performed synthesis, analyzed solutions and did XRD study of the precipitate, wrote a draft of radiation chemistry part, and did the editing work. V. I participated in the experimental design, performed and wrote the experimental part, and did the editing work. IV Contents Abstract ........................................................................................................................ I Sammanfattning ......................................................................................................... II List of Papers ............................................................................................................. III Contribution to the papers ....................................................................................... IV 1 Introduction ............................................................................................................ 1 1.1 Background .................................................................................................................... 1 1.2 Interactions between ionizing radiation and matter ......................................................... 4 1.3 Water radiolysis .............................................................................................................. 5 1.4 Metal oxide formation in irradiated aqueous solution ...................................................... 6 1.4.1 Radiolytic oxidation of metal ions ............................................................................... 7 1.4.2 Radiolytic reduction of metal ions .............................................................................. 7 1.5 Hydrolysis and condensation reactions of metal ions in aqueous solution ...................... 8 1.6 Supported metal oxide formation in irradiated aqueous system ...................................