Adsorption of Sarin and Chlorosarin Onto the Al12n12 and Al12p12 Nanoclusters: DFT and TDDFT Calculations

Received: 26 March 2020 Revised: 29 May 2020 Accepted: 24 June 2020 DOI: 10.1002/sia.6861

RESEARCH ARTICLE

Adsorption of sarin and chlorosarin onto the Al12N12 and Al12P12 nanoclusters: DFT and TDDFT calculations

1Golestan Rheumatology Research Center, Golestan University of Medical Science, This study provides details of the electronic and optical structures and binding ener- Gorgan, Iran gies of sarin (SF) and chlorosarin (SC) with Al–N and Al–P surfaces of Al12N12 and 2Department of Chemistry, Azadshahr Branch, Islamic Azad University, Azadshahr, Iran Al12P12 nanoclusters in the gas phase. The adsorption mechanism of SF and SC on 3+ 3Department of Physics, Faculty of Sciences, these nanoclusters containing the Al central cation was studied. Optimized geome- Golestan University, Gorgan, Iran tries and thermodynamic parameters of SF and SC adsorption complexes were calcu- 4Department of Chemistry and Biotechnology, lated. SF and SC are chemisorbed on these nanoclusters because of the formation of Swinburne University of Technology, Hawthorn, VIC, Australia P OAl bonds. The chemical bond is formed between an oxygen atom of SF and SC and an aluminum atom of fullerene-likes (chemisorption). However, the binding ener- Correspondence

Alireza Soltani and Mohammad Hassan Jokar, gies of the complexes with the Al12N12 nanocluster are larger than these values for Golestan Rheumatology Research Center, the Al P nanocluster. The interaction enthalpy and Gibbs free energy of all studied Golestan University of Medical Science, 12 12 Gorgan, Iran. systems were found to be negative. We can conclude that SF and SC will be Email: [email protected]; adsorbed preferably on Al N nanocluster. [email protected]; 12 12 [email protected] KEYWORDS Funding information adsorption, Al12N12,Al12P12, electronic structure, optical effect Golestan University of Medical Sciences

1 | INTRODUCTION outstanding performance in hydrogen storage15 with a gravimetric

density of hydrogen of 4.7 wt%. In conjunction with this, Al12N12 Aluminum nitride (AlN) is one of an important semiconducting mate- nanocluster has reported applications as a potential NO sensor device rials in groups III and V of the periodic table with many promising for the sake of the high electronic sensitivity on the adsorption of the applications in the microelectronic and optical industry.1–4 Under NO molecule.16 ambient conditions, the bulk AlN, as a semiconductor, has a wide band Sarin (SF) nerve agent or isopropyl methylphosphonoflouridate is gap about 6.2 eV and large exciton binding energy about 70 meV and one of important toxic agents in both vapor and liquid forms and can indicates a wurtzite structure where each Al ion is fourfold be considered as a class of organophosphate nerve agents that differ coordinated.5–7 It is found that the AlN nanosheet8 and AlN nano- in ester linkage and substituent groups. Exposure to SF can be fatal tube9 have band gap energies about 2.96 and 4.11 eV, respectively, within minutes to hours. In vapor or liquid form, SF can be inhaled or 10,11 compared with Al12N12 (3.93 eV) fullerene-like. Currently, theo- absorbed, respectively, across the skin, eyes, or mucous mem- retical studies stand for the high and eye-catching stability of AlN branes.17,18 The indiscriminate use of toxic nerve agents by terrorist nanostructures through density functional theory (DFT) calculations groups has attracted attention of the scientific communities toward among which fullerene-like-like clusters of (AlN)n (n =2–41) are ener- the development of novel design of adsorbents and decontamination getically considered to be the most stable cluster in this family that strategies for these deadly chemicals. Exposure to this toxic agent can be a promising inorganic fullerene like cage.5,12 Because of the may cause increase in acetylcholine through the inhibition of acetyl- electronic and optical properties, AlN nanostructures have been cholinesterase, which therefore results in hyperstimulation at cholin- reported as suitable candidates for detection and removal of the toxic ergic synapses.19,20 It generally causes different kinds of disease and 13,14 gases. For instance, the pure Al12N12 fullerene-like indicates disorders in the body's functions with exposure most commonly

Surf Interface Anal. 2020;1–10. wileyonlinelibrary.com/journal/sia © 2020 John Wiley & Sons, Ltd. 1 2 SEDIGHI ET AL. occurring via inhalation or dermal exposures. The method of expo- nerve agents and in comparing observed and calculated infrared sure, in conjunction with the quantity of SF in which the organism is (IR) and ultraviolet–visible (UV–vis) spectra. exposed to, determines how the degree of exposure is classed. The degree of exposure ranges from low to intermediate and high exposures. Upon inhalation, exposure may cause the following symptoms: 2 | METHODOLOGIES miosis, ocular pain, tearing, rhinorrhea, bronchospasm, slight dyspnea, respiratory secretions, salivation, and diaphoresis (at low degree of In the presented work, DFT computations for the adsorption of toxic exposure); moderate dyspnea, nausea, vomiting, and diarrhea agents SF and chlorosarin, over pure Al12N12 and Al12P12 nanoclusters (at intermediate degree of exposure); and loss of consciousness, con- in gas phase, have been performed using GAMESS program pack- vulsions, muscle fasciculations, flaccid paralysis, copious secretions, age.35 Subsequently, all the structures have been optimized using the apnea, and death (at high degree of exposure). Regarding dermal M06-2X functional36,37 in conjunction with the 6-311++G** standard exposure, in a time frame of 10 min to 18 h, localized sweating at site basis set. The M06-2X density functional has been previously of contact, muscular fasciculations, and weakness at the site of con- reported to calculate interaction energies, metallic and nonmetallic tact can occur (at low degree of exposure), whereas intermediate and compounds, kinetics, and stability of noncovalent interactions on the high degree of dermal exposure results in similar symptoms to those different nanostructures.38–42 Natural bond orbital analysis, vibration of inhalation exposure.21,22 Sharma and Kakkar investigated the role frequencies, and thermodynamic parameters were also calculated at of doped and defect sites on the adsorption of SF onto MgO nan- the same level. Molecular electrostatic potential, highest occupied otubes by means of DFT.23 They found that the adsorption of SF is molecular orbital (HOMO) and lowest unoccupied molecular orbital exothermic on both perfect and Ti-doped MgO nanotubes. Fallahi and (LUMO), and spin density plots of molecular configurations were gen- 43 coworkers evaluated adsorption effect of Tabun molecule on Al12N12, erated with the GaussView program (Gaussian, Inc. Pittsburgh, PA).

Al12P12,B12N12,Be12O12,C12Si12,Mg12O12, and C24 nanocages using To calculate total energies, self-consistent field and electron density DFT calculations.24 They found that the Tabun molecule has a strong calculations are performed with a convergence criterion of 1.0 * 10−6 chemical bond with Al12N12 nanocage in comparison with other nan- Hartree. In geometry optimizations, the cut-off values for force and ocages mentioned above. Adsorption of cyclosarin nerve agent on the displacement were 0.00045 Hartree/Bohr and 0.0018 Bohr, respec- surfaces of the pristine, Stone–Wales defected, and Si-doped BN tively. The corresponding binding energies (Eb) of the mentioned sys- nanosheets were studied using DFT calculations.25 In previous report, tems were determined through the following equation: we theoretically evaluated the adsorptions of soman, chlorosoman, −ðÞ SF, and chlorosarin (SC) upon the pure and cobalt-decorated C24 Eb = Eadsorbate – adsorbent Eadsorbate + Eadsorbent +EBSSE, nanoclusters by means of PBE/6-311++G** level of theory.26 ð1Þ We found that the energy interaction between the toxic agents and the cobalt-decorated C24 nanocluster is energetically more favorable where Eadsorbate-Al12N12 and Eadsorbate-Al12P12 are the total energies of than that of the pure C24 fullerene-like and leading to alter of the SF and SC as adsorbates over the pure Al12N12 and Al12P12 structural and electronic properties. Yan and coworkers experimen- nanoclusters as adsorbent. Eadsorbate is the total energies of the SF and tally reported a photonic crystal (PhC) hydrogel immobilized with but- SC molecules. Eadsorbent is the total energy of the pure Al12N12 and yrylcholinesterase for the sensing of SF agents. They found that the Al12P12 nanoclusters. The basis set superposition error (BSSE) for the functionalized hydrogel recognized the SF agent and then shrunk; binding energy was computed by implementing the counterpoise thus, the diffraction of PhC hydrogel blue shifted significantly, and a method. The electron localization function (ELF), total density of state limit of detection of 10−15 mol L−1 was achieved.27 In another study, (TDOS), and projected density of states (PDOS) analyses were per- the adsorption of SF on three model solid surfaces consisting of ali- formed using the Multiwfn software package.44 phatic (graphane), aromatic (graphene), and ionic (CaO) surfaces was studied using DFT and time-dependent DFT (TDDFT) calculations. Based on DFT calculations, the values of binding energy for the SF on 3 | RESULTS AND DISCUSSION graphane, graphene, and CaO surfaces were found to be 6.4, 4.8, and 18 18.8 kcal/mol, respectively. Moreover, the adsorption of some mol- 3.1 | Optimized Al12N12 and Al12P12 nanoclusters ecules such as phosgene, H2,H2O and H2S, O3 and SO2, dimethyl 28–32 ether, Cl2 and O2, and so forth and the adsorption of common The optimized structures of Al12N12 and Al12P12 nanoclusters accom- biomolecules including vitamin C and 4-aminopyridine have also been panied by TDOS and ELF plots are shown in Figure 1. The investigated on the surface of B12N12,B12P12,Ca12O12,Al12P12, and nanoclusters have two different types of bonds: The shorter of the 33,34 Al12N12 nanoclusters in earlier reports. The objective of this work two Al–N/P bonds has a length of 1.784 (2.271) Å in eight is to describe surface interactions at high accuracy using theory in 6-membered rings (6MRs), and the longer one has a length of 1.849 order to understand the details of the removal of toxic agents such as (2.326) Å in six 4-membered rings (4MRs). The calculated results show

SF and SC by the Al12N12 and Al12P12 nanoclusters. The interest here that the bond lengths of the 4MRs are somewhat longer than those of has been in determining the structure and energetics of the SF and SC the 6MRs.45 Wang et al. theoretically calculated the Al–N bond in SEDIGHI ET AL. 3

FIGURE 1 Plots of TDOS and ELF for the pure Al12N12 and Al12P12 fullerene-likes

48–51 Al12N12 nanocluster with a length of 1.855 Å in 4MRs and 1.792 Å in Al12N12 and Al12P12 nanoclusters. Therefore, the characteristic 15 6MRs. Saeedi et al. reported the optimized structure of Al12N12 semiconducting behavior of Al12N12 and Al12P12 fullerene-likes makes nanocluster with a length of 1.874 Å in 4MRs and 1.808 Å in 6MRs.46 them appropriate candidates to their specific applications in nanoscale

Peyghan and coworkers reported the length of Al–P bond in Al12P12 devices. ELF plots for both the Al12N12 and Al12P12 nanoclusters, nanocluster with a values of 2.30 Å in the 6MRs and 2.34 Å in depicted in Figure 1, reflect the probability of finding two electrons at the 4MRs.47 the same location at any given moment while also showing the type The electronic property analysis based on TDOS at the M06-2X of bonding involved in the interaction.52 Scaling runs from 0 (very low functional shows an energy band gap (Eg) of 6.32 and 4.77 eV for the charge density, blue) to 1.0 (full localization, red) refers to the jellium- 53 Al12N12 and Al12P12 fullerene-likes, respectively. Eg values of the like homogeneous electron gas and renormalizes. A reference value

Al12N12 and Al12P12 nanoclusters are close to the reported results by of 0.5 (green) corresponds to a homogeneous electron gas (metallic Silaghi–Dumitrescu and Niu.12,45 A comparison of the calculated bonding), whereas covalent bonds appear red color because of the energy band gaps indicates more semiconducting behavior of the electron pairing. 4 SEDIGHI ET AL.

3.2 | SF and SC adsorption over pure Al12N12 and Table 1 demonstrate the relaxed models of SF and SC molecularly

Al12P12 nanoclusters adsorbed toward the Al12N12 and Al12P12 nanoclusters through the formation of a chemical bond (chemisorption). In contrast to our First, the optimized structures of the individual SF and SC molecules results, the binding energy value of cyclosarin, when adsorbing onto and the Al12N12 and Al12P12 nanoclusters are computed. Then, for the pristine and Stone-Wales-defected BN sheets (0.315 kcal/mol), investigation of SF and SC adsorption on the out surface of the was found to be very weak and did not indicate any remarkable ener- nanoclusters, several possible initial adsorption geometries of SF and getic properties.21 Papas et al. investigated the binding energy SF, SC molecules close to the surface of the nanoclusters are considered. adsorbed on the surfaces of graphane, graphene, and calcium oxide, After full structural optimization without any limitation, Figure 2 and and reported values of 6.4, 4.8, and 18.8 kcal/mol, respectively.24 For

FIGURE 2 Geometries and projected density of states of molecular adsorption of SF and SC on the surface of Al12N12 and

Al12P12 nanoclusters SEDIGHI ET AL. 5

TABLE 1 Computed bond length, angle, adsorption energy (Eb/kcal/mol), charge transfer (Q/e), distance (D/Å), HOMO energies (EHOMO/eV),

LUMO energies (ELUMO/eV), HOMO–LUMO energy gap (Eg/eV), Fermi level energy (EF/eV), and dipole moment (μD/Debye) for all the systems at M06-2X functional

Property Al12N12 SF/Al12N12 SC/Al12N12 Al12P12 SF/Al12P12 SC/Al12P12 Al–N/Å 1.849 1.939 1.904 - - - Al–P/Å - - - 2.33 2.384 2.387 O/Å - 1.522 1.521 - 1.521 1.522 P–F/Å - 1.606 - - 1.605 - P–Cl/Å - - 2.059 - - 2.056 O–P–F/ - 106.59 - - 106.23 - O–P–Cl/ - - 110.13 - - 109.51 N–Al–N/ 94.83 92.53 92.80 - - - P–Al–P/ - - - 98.81 97.74 98.04

E HOMO/eV −8.03 −7.51 −7.30 −7.80 −7.28 −7.25

E LUMO/eV −1.71 −1.49 −1.37 −3.03 −2.59 −2.55

E g/eV 6.32 6.02 5.93 4.77 4.69 4.70

ΔEg/% - 4.75 6.17 - 1.68 1.47

E F/eV −4.87 −4.50 −4.34 −5.42 −4.94 −4.90 DM/Debye 0.0 6.74 9.22 - 9.44 11.23

E ad/kcal/mol - −33.14 −31.39 - −27.70 −26.97 D/Å - 1.871 1.913 - 1.922 1.918 Q/e - 0.312 0.116 - 0.366 0.182 ΔG/eV - −20.51 −19.82 - −15.21 −13.60 ΔH/eV - −33.65 −25.36 - −28.81 −26.51 I/eV 8.03 7.51 7.30 7.80 7.28 7.25 A/eV 1.71 1.49 1.37 3.03 2.59 2.55 η/eV 3.16 3.01 2.97 2.39 2.35 2.35 μ/eV −4.87 −4.50 −4.34 −5.42 −4.94 −4.90 S/eV−1 0.16 0.17 0.17 0.21 0.21 0.21 ω/eV 3.75 3.63 3.17 6.15 5.19 5.11

ΔNmax 1.54 1.50 1.52 2.04 1.92 1.91

Abbreviations: SC, chlorosarin; SF, sarin.

the interaction models, the binding energy values of SF (A) and SC (B) charges of approximately 0.312 and 0.116 |e| are transferred from SF molecules on the Al12N12 fullerene-like were −33.14 and and SC to Al12N12 nanocluster, whereas charges of approximately

−31.39 kcal/mol and on the Al12P12 nanocluster were −27.70 and 0.366 and 0.182 |e| are transferred to Al12P12 nanocluster during −26.97 kcal/mol (chemisorption process), respectively. Cross- adsorption, respectively. The increase in the Al–N and Al–P bond examinations of both the Al12N12 and Al12P12 nanoclusters binding lengths from 1.849 and 2.33 Å in pristine model to 1.939 and 2.384 Å energy values, interacting with SF and SC molecules, show a signifi- (SF) and 1.904 and 2.387 Å (SC) models represents that sp2 hybridiza- cantly large energy difference between the two nanoclusters of about tion of the free fullerene-like has altered to sp3 hybridization. 4–6 kcal/mol, depending on the sort of fullerene-like. The Al … O P The binding energy values and the structural parameters of the interaction distances are reported to be 1.871 and 1.913 Å for configurations upon the adsorption process showed that the configu-

Al12N12 fullerene-like and 1.922 and 1.918 Å for Al12P12 nanoclusters. rations have a fair interaction between the SF and SC molecules and

It should be noted that this great binding energy suggests that the the fullerene-likes. The binding energy of SC on Al12N12 nanocluster recovery of the SF and SC on Al12N12 and Al12P12 nanoclusters will is greater than the rest of the models. These results indicate that the be a hard task; however, the main potential application of these SF and SC molecules can be adsorb on the AlN fullerene-likes, and the fullerene-likes is focused around the removal of the toxic nerve agent AlN nanocluster can be used in many catalytic processes for formation in the state of emergency and war; therefore, energetically expensive of a variety of useful compounds or as a potential efficient adsorbent recovery is not suspected to be an issue. The Al … O P bond angle is for adsorption of SF and SC molecules. The large electron localization found to be 134.70 (SF) and 128.97 (SC). Based on MPA analysis, area distributed around the toxic agent adsorbates on the 6 SEDIGHI ET AL.

FIGURE 3 FMO and ELF plots of molecular adsorption of SF and SC on Al12N12 and Al12P12 fullerene-likes nanoclusters is depicted in Figure 3. The observed presence of a vertical lines in Figure 2 indicate the Fermi level position and edge of new covalent bond between the aluminum atom located on the the valence band. PDOS plots show that the 2p orbital of oxygen in nanocluster (blue color) and the oxygen atom located on the adsor- the SC and SF molecules overlap with the 3p orbitals of aluminum in bates (red color) is also depicted in Figure 3 displaying and ELF value the Al12N12 and Al12P12 nanoclusters. Adsorptions of SC and SF have close to 1.0. However, the perturbations of the electrons surrounding some minor effects in the electronic properties of the Al12N12 and the SC and SF molecules (with the high charge density) are consider- Al12P12 nanoclusters, and Eg values are slightly dropped during the able during the adsorption process. In order to investigate the thermo- adsorption process (see Figure 2). dynamic feasibility of SF and SC adsorption on the out surface of the nanoclusters, changes in enthalpies (ΔH) and free energies (ΔG) of the structures at 298.15 K and 1 atmosphere are calculated from the fre- 3.3 | Quantum molecular descriptors quency calculations and are summarized in Table 1. Calculated frequencies are positive, showing that the structures are stable. Quantum molecular descriptors (QMDs) for the studied structures Calculated negative values of ΔH and ΔG for the structures show a were also computed with the M06-2X functional (See Table 1). The strong interaction between SF and SC molecules on the out surface of Al12N12 and Al12P12 nanoclusters interacting with SC molecule have the fullerene-likes and indicate that the interaction process can hap- low electron affinity (A) and ionization potential (I) in comparison with pen spontaneously at room temperature and 1 atm.54,55 Also, the SF molecule. These are directly linked to the alteration of HOMO and results again show that SF and SC adsorptions on the Al12N12 LUMO energies. When SC molecule reacts with Al12N12 nanocluster, nanocluster are larger than these values for the Al12P12 nanocluster. the global hardness (η) has the lowest amount of hardness, whereas

The PDOS plots of first (adsorbent) and second (adsorbate) fragments the change in Al12P12 nanocluster was insufficient. The ionization represent with the red and blue colors of specified complexes. The potential of the Al12N12 and Al12P12 adsorbents were decreased SEDIGHI ET AL. 7 because of the decrease in the electronegativity of the systems after 4000 cm−1 as illustrated in Figure S1. A scaling factor of 0.969 was their interactions with SF and SC.56,57 This may be because of the dis- used for evaluating the harmonic frequencies for M06-2X functional tortion of the geometry structure of the adsorbents after interacting and 6–311++G** basis set. As seen in Figure S1, the Al12N12 with the toxic agents which consequently affects the HOMO–LUMO fullerene-like demonstrates Al–N stretching vibration at around orbital localizations on the adsorbents (see Table 1 and Figure 3). Elec- 308, 385, 510, 655, 708, 862, and 893 cm−1, whereas the Al–P tron affinity values were decreased as the electron transfers from the stretching vibration for Al12P12 was appeared at 330, 449, 496, and toxic molecule adsorbates to the adsorbents reducing the adsorbents 522 cm−1 by the M06-2X functional. Angappan et al.60 experimentally willingness to attract more electrons (see Table 1).58 Softness and calculated Al–N stretching vibration of AlN films deposited by RMS at hardness of the adsorbents have also decreased and increased due to 500 and 600C with a peak near 670 cm−1. Kim and coworkers found the interactions happening between the adsorbents and adsorbates. that AlN particles show the appearance of a broad peak in the spec- −1 Al12N12 was found to be more capable of interacting with the toxic SF trum near 720 cm because of stretching and bending of the Al–N and SC agents. The higher changes observed in the hardness and soft- bond by Fourier-transform infrared spectroscopy (FT-IR) analysis.61 ness values provides evidence for this claim. Generally, there are more For the SF molecule adsorbed onto the Al12N12 and Al12P12 −1 changes in the values of QMDs for the Al12N12 than the Al12P12 nanoclusters, the P O vibrational frequency reduced from 1252 cm −1 nanocluster which indicates higher capability of Al12N12 to adsorb the to 1149 and 1151 cm , respectively, leading to the corresponding SF and SC toxic agents. red shifts of 103 and 101 cm−1. Whereas for the SC molecule

adsorbed on the Al12N12 and Al12P12 nanoclusters, the P O vibrational frequency changed62 from 1251 cm−1 to 1155 and 1152 cm−1, 3.4 | IR spectra respectively. The experimentally observed IR fundamental frequency for the P O vibration has been reported to be between 1277 cm−1 The theoretical infrared (IR) spectra of SF and SC adsorbed on (liquid)4 and 1280 cm−1,63 or at 1240 cm−1 for dilute aqueous solu- 59 64 Al12N12 and Al12P12 nanoclusters are ranged from 400 to tions of SF. These red shifts for SC are slightly stronger than the

FIGURE 4 UV–vis spectra of molecular adsorption of SF and SC on Al12N12 and Al12P12 fullerene-likes 8 SEDIGHI ET AL.

P O bond perturbation observed for the SF complexes, where are depicted in Figure S2. The implied UV–vis absorption spectra of −1 16 a − 21 cm change was reported theoretically. both the Al12N12 and Al12P12 nanoclusters had sharp absorption peaks in the regions of 232 and 329 nm, respectively. The

corresponding optical gap energies were (Eog) of 5.32 and 3.77 eV. 3.5 | UV–vis spectra Angappan et al. experimentally showed the AlN nanoparticle has an optical gap of 5.08 eV,65 which is comparable with our calculations. The UV–vis absorption spectra of the ground and low-lying excited The calculated absorption spectra of the ground state are depicted states in gas phase were predicted by using TDDFT calculations in Figure 4. An obvious blue shift of the absorption peak of the gro- with M06-2X functional and 6–311++G** basis set. The UV–vis und state for Al12N12 is seen from the gas phase (λmax = 232 nm absorption spectra for both the Al12N12 and Al12P12 nanoclusters and Eog = 5.32 eV) to the red-shift region of the absorption peak in

the SF/Al12N12 (λmax = 314 nm and Eog = 3.94 eV) and SC/Al12N12

(λmax = 366 nm and Eog = 3.38 eV). All these low-lying excitations TABLE 2 Optoelectronic properties of the SF and SC adsorbed are featured almost particularly H-13 ! L and H-9 ! L transitions, on Al N and Al P fullerene-likes 12 12 12 12 being characterized as the π ! π* and n ! π* types (see Figure 3).

Eg/ λmax/ The values of λmax of Al12N12 indicate changes of about 80 and Systems eV nm f Assignment 90 nm to longer wavelength in the presence of the SF and SC mol-

Al12N12 5.32 232 0.0513 H-4 ! L + 3 (25%), ecules, respectively. By contrast, the maximum absorption peak of H-1 ! L + 11 (20%), SC/Al12N12 represents a relatively weak red shift with an f value of HOMO!L + 8 (10%) about 0.0052. The difference between SF/Al12N12 and SC/Al12N12 5.12 241 0.0026 H-5 ! L + 3 (22%), is reflected from the distinct variation of the backbone and charge H-2 ! L + 8 (35%), H-15 ! LUMO (5%) distribution from both molecules, as displayed by the values of bond length variation and dipole moment, μ , in Table 2. 4.04 306 0.0011 H-2 ! LUMO (84%), D H-5 ! L + 3 (8%)

Al12N12/ 3.94 314 0.0615 H-13 ! L (90%) SF 4 | CONCLUSION 3.78 327 0.0016 H-1 ! L + 11 (12%), H-1 ! L + 2 (85%) We have performed a theoretical study on the adsorption of SF and

3.43 361 0.0033 H-9 ! L (98%) SC with Al–N and Al–P surfaces of Al12N12 and Al12P12 nanoclusters. 2.51 494 0.0012 H-1 ! L (100%) The results demonstrate that SF and SC molecules can be

Al12N12/ 3.84 322 0.0010 H-9 ! L (61%), H-3 ! L+1 chemisorbed upon the nanoclusters because of the formation of SC (−30%) P OAl bonds. In addition, the adsorption of the molecules on the

3.72 333 0.0027 H ! L + 4 (98%) surface of Al12N12 fullerene-likes is larger than that of the Al12P12 3.38 366 0.0052 H-9 ! L (61%), H-3 ! L+1 nanoclusters. The important results can be useful in predicting the (30%) synthesis of new molecules and to better understand the mechanism 2.97 416 0.0017 H ! L + 1 (100%) of formation of the molecules and also design further molecules with

Al12P12 2.81 312 0.0050 H-18 ! LUMO (62%), better reactivity. The TDDFT calculations demonstrated that except in H-2 ! L + 3 (6%) the case of Al12N12 and Al12P12, all the four main peaks of complexes 3.77 329 0.0054 H-13 ! LUMO (60%), happen at higher wavelengths (red shifted) because of the interaction ! H-12 LUMO (4%) with toxic molecules with the main electron transitions from the first 3.96 441 0.0010 H-1 ! LUMO (94%) HOMO orbital of nanoclusters (donor) to the LUMO orbitals of toxic

Al12P12/ 3.26 380 0.0017 H-2 ! L + 2 (98%), H-21 ! L agent (acceptor) molecules. The comparison between the calculated SF (4%) vibrational frequencies and the experimental FT-IR spectra supports 3.05 406 0.0012 H-13 ! L (98%) each other. 2.89 428 0.0031 H-11 ! L (98%) 2.23 556 0.0010 H-4 ! L 94%), H-1 ! L (2%) ACKNOWLEDGMENTS

Al12P12/ 3.22 385 0.0005 H-4 ! L (54%), H-3 ! L We gratefully acknowledge financial support from Golestan University SC (43%) of Medical Sciences. We also thank the Clinical Research Develop- 3.08 402 0.0018 H-1 ! L + 1 (99%) ment Unit (CRDU), Sayad Shirazi Hospital, Golestan University of 2.88 432 0.0030 H-11 ! L (98%) Medical Sciences, Gorgan, Iran. 2.20 563 0.0010 H-4 ! L (54%), H-3 ! L (43%)

Abbreviations: HOMO, highest occupied molecular orbital; LUMO, lowest ORCID unoccupied molecular orbital; SC, chlorosarin; SF, sarin. Alireza Soltani https://orcid.org/0000-0002-4739-636X SEDIGHI ET AL. 9

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