Publication Date: 2007
PHYSICAL REVIEW A (10502947)76(6)
In response to the preceding Comment, results of our research show that rate is not necessarily linearly time-dependent and it is possible to define and calculate instantaneous ionization rate. We show that a negative ionization rate and the quiver motion in strong laser field are not necessarily correlated and may occur independently. Furthermore, a negative ionization rate is not identical to recombination. Details of the instantaneous ionization rate and photoelectron kinetic energy release are calculated and analyzed for the evolution of the electron wave packet of H-2(+) in a 25-cycle ultrashort intense linearly polarized laser pulse of I=1.0 x 1014 W/cm(2) intensity and lambda=1064 nm wavelength with a sin(2)-shaped envelope.
Publication Date: 2005
JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM (01661280)731(1-3)pp. 239-239
Publication Date: 2016
COMPUTATIONAL AND THEORETICAL CHEMISTRY (2210271X)1093pp. 9-19
Density functional theory at the B3LY13/6-31++G(d,p) level was applied to study structural, electronic and bonding characteristics of various 5-unsubstituted 4,6-diaryl-2-oxo-1,2,3,4-tetrahydropyrimidines (THPMs). To elucidate the steric and electronic effects of the substituents on the characteristic parameters obtained from the optimized structures, additional electron-donating and electron-withdrawing substituents were considered to be at different aryl positions, which are already located on the C-4 and C-6 positions of the heterocyclic ring. Results of this study show that the six-membered heterocyclic ring in half of these compounds adopts a pseudo-boat conformation with a pseudo-axial orientation of the C-4-aryl substituent; in other cases a twisted chair conformation is observed. The extent of deviation of the N-1 and C-4 atoms from the boat plane depends on the type and position of the additional substituent on both aryl rings. Dihedral angle scanning elucidates the intramolecular interaction regarding the steric and electronic effects of the additional substituent, and its location on the aryl groups at the C-4 and C-6 positions on the total energy content of the molecule. (C) 2016 Elsevier B.V. All rights reserved.
Publication Date: 2016
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH (08885885)55(22)pp. 6517-6529
Proton nuclear magnetic resonance (H-1 NMR), diffusion-ordered NMR spectroscopy (DOSY-NMR), and ultraviolet-visible (UV-vis) spectroscopy techniques were used to study the specific intermolecular interactions within the binary mixtures of 1-butyl-3-methylimidazolium tetrafluoroburate, [bmim]BF4, and poly(ethylene glycol), PEG, with different average molecular weights (i.e., 200, 400, 600, and 1000) in the whole composition range. Also, the electrical conductivity and the viscosity of these four mixtures were measured at different compositions and temperatures. The results of 1H NMR spectra show that the change in proton chemical shifts of ionic liquid (IL) and PEG molecules in the mixtures is more than that of the pure ones. DOSY-NMR was used to measure the diffusion coefficients of the ionic species in the mixtures. Also, the other parameters such as hydrodynamic radii, transport numbers of anions and cations, and dissociation and association degrees of IL molecules were calculated from the diffusion coefficient and viscosity data. The overall results show that the behavior of the mixtures of [bmim]BF4 + PEG400, PEG600, and PEG1000 which show the synergistic effect on their viscosity is completely different from the IL + PEG200 mixture, and this difference can be interpreted well according to the special interactions occurring at the molecular level in these mixtures. Accordingly, in these mixtures, larger hydrodynamic radii and lower transport numbers of anions with respect to the cations may be attributed to the trapping of small anions in the polymeric clusters. Increasing the chain length and the concentration of PEG increases the association degree of the IL molecules due to increasing intermolecular interactions. The continuous decrement of electrical conductivity with increasing PEG concentration in these three mixtures confirms the cluster formation in the mixtures. The UV-vis spectra showed more hydrogen bonding interactions between unlike molecules in the mixtures containing higher molecular weight PEGs with respect to the lower ones.
Publication Date: 2023
Journal of Molecular Liquids (01677322)384
Based on the recently synthesized triphenylamine-based organic dyes [https://doi.org/10.1021/acsami.1c11547], several small molecules that can be considered as organic semiconducting materials in photovoltaic devices were theoretically modeled. It is found that these designed dyes with the donor-π conjugated bridge-acceptor (D-π-A) framework show high charge transport properties in the dye-synthesized solar cells (DSSCs). Divers types of π-bridges are explored and the structural, electronic, optical, and charge transport characteristics of considered organic small molecules are studied. Our results revealed the effect of π-bridge in tuning the charge transport properties of the studied dyes. Especially, it is found that the thiazole-based moieties as the most favorable candidate for π-bridges, can be used in the D-π-A backbone of the synthesized dye to improve the photovoltaic performance of the organic semiconductors. For designed organic dyes, the low electron reorganization energies and high intra-molecular coupling created by π-stacking give rise to improved electron and hole mobilities. This approach can be used for improving the semiconducting character of organic dyes in photovoltaic devices. © 2023 Elsevier B.V.
Publication Date: 2023
Synthetic Metals (03796779)297
Motivated by the synthesis of a covalent organic framework by condensation procedure of phenyl diboronic acid (denoted as COF-1), and the other theoretical studies of an energetically favorable (BO)18C36H24 unit cell, we investigate its potential as an anode material in the Li-ion battery (LIB). Using density functional theory method, we found that the COF-1 is a promising anode whose specific capacity of 513.98 mAhg-1 is higher than that of graphite, ψ-graphene and boron nanolayers (∼370 mAhg-1). Furthermore, energy diffusion barrier of Li-ions and the average voltage along the COF-1 anode are 0.34 eV and 0.85 V, respectively, which can deliver high operating voltage when linked to the cathode. These findings can pave the route for application of COFs with promising performance as the LIB anode. © 2023 Elsevier B.V.
Publication Date: 2023
Journal of Molecular Liquids (01677322)383
Increasing the greenhouse gases in the atmosphere, mainly from human activities leads to the global warming phenomenon and poses a serious threat to life on the earth. Hence, there is a pressing need to mitigate greenhouse gases emission and overcome global warming. It is proven that Ionic liquids (ILs) and deep eutectic solvents (DESs) are fruitful materials to capture gases and reduce their emission. Here, we investigate the environmentally friendly and cost-effective cholinium geranate ([Cho][Ger]) IL and cholinium geranate:geranic acid ([Cho][Ger]:Ger acid) DES, for carbon dioxide (CO2) capture. To this end, the density functional theory (DFT) and molecular dynamics (MD) simulation approaches are employed to provide quantitative microscopic insight into the interactions between CO2 and IL/DES. The adsorption energies of IL…CO2 and DES…CO2 are explored through the DFT calculations and show stronger interaction between the IL…CO2 than DES…CO2. The MD simulation analyses including density profile, non-bonded energy, radial distribution function (RDF), and spatial distribution function (SDF) affirm the stronger interaction between the IL…CO2 than DES…CO2. Meanwhile, the DFT and MD simulation results reveal the strongest interaction between CO2 and [Ger] - anion of both IL and DES. Furthermore, the minimum potential of mean force (PMF) of CO2 at the IL-air interface represents the favorable adsorption of CO2 on IL. Overall, our molecular level findings which are not accessible through the experimental approaches could help experimentalists find high-efficient solvents for CO2 capture. © 2023 Elsevier B.V.
Publication Date: 2022
Physical Chemistry Chemical Physics (14639076)24(22)pp. 13988-13998
Rechargeable Li-ion batteries (LIBs) are one of the green energy storage devices that have been utilized in large-scale devices. Hence, improving the LIBs performance plays a crucial role in many industrial sectors. Herein, we introduce a novel electrode and electrolytes for improving the LIBs efficiency. The deep eutectic solvents (DESs) electrolytes based on lithium bis[(trifluoromethyl)sulfonyl] imide (Li[TFSI]) and two different ratios of 2,2,2-trifluoroacetamide (TFA): (Li[TFSI] : 2TFA and Li[TFSI] : 4TFA), and the calcium carbide monolayer (Ca2C-ML) MXene were used as an anode in the LIBs. The molecular dynamics (MD) simulation and density functional theory (DFT) calculations are performed to evaluate the interaction and orientation of DESs on Ca2C-ML. The density profiles, pair correlation functions, mean square displacement (MSD), diffusion coefficient, ionic conductivity, molecular orientation, and charge density profiles analyses are performed to determine the behavior of DESs on Ca2C-ML. The results indicate that in both DESs, the adsorption of Li+ cations and TFA species on the Ca2C surface is more than that of the [TFSI]− anions. However, the interaction of Li+ cations on the Ca2C surface in Li[TFSI]:2TFA is stronger than in Li[TFSI]:4TFA. Because the adsorption of Li+ on the Ca2C occurs favorably, the low intercalation potential of Li+ on the Ca2C anode can be predicted. Additionally, the simulations are carried out at higher temperatures (333.15 K, 353.15 K, and 373.15 K), and the enhancement in MSD, diffusion coefficient, and ionic conductivity is observed by increasing the temperature. Meanwhile, the low open-circuit voltage (0.30 V) during the Li-ion intercalation processes further shows the advantages of Ca2C MXene as a potential candidate for LIB anodes. Overall, it is hoped that these findings will provide guidance for the future design of high efficiency LIBs using the Li-based DESs electrolytes and novel MXene anodes. © 2022 The Royal Society of Chemistry
Publication Date: 2022
Molecular Physics (00268976)120(7)
Carbon/boron nitride heteronanotubes are now at the centre of experimental and theoretical studies because of their tunable properties and diverse applications. Herein, we investigate the charge transport and optical properties of carbon/boron nitride hybrid single- and double-walled nanotubes on the basis of first-principles calculations. Our results reveal that the C/BN heterojunctions with radial junctions parallel (horizontal) to the tube axis have more effects than the perpendicular (vertical) junctions on the charge transport properties of heteronanotubes. Furthermore, we find that the nonlinear optical response can be meaningfully controlled by altering the C/BN content and junction arrangement. In double-walled coaxial heteronanotubes, the interwall interaction is also found to increase the electron and hole transport rates noticeably and to have a major effect on the first hyperpolarizabilities of C/BN heteronanotubes. In contrast with coaxial carbon nanotubes, where the inner constituent is totally shielded by the outer tube, in our studied C/BN coaxial heteronanotubes, the inner shell is only partially shielded by the outer constituent. This study suggests a strategy to high-efficient design heteronanotubes with high charge transport properties and tunable nonlinear optical responses. Moreover, the designed C/BN heteronanotubes can discrete electrons and holes, suggesting their application in solar cell materials. © 2022 Informa UK Limited, trading as Taylor & Francis Group.
Publication Date: 2021
Computational and Theoretical Chemistry (2210271X)1198
Using density functional theory calculations, we design the novel materials with high nonlinear optical responses via linking the Li atom and Li3O superalkali to the [Rh2B18], [Ir2B18], [RhPdB18]+, [IrPtB18]+, [Pd2B18] 2+, and [Pt2B18] 2+ teetotum boron clusters. Our results reveal that the first static hyperpolarizability of the Li3O@M2B18, as a microscopic criterion of the nonlinear optical materials, are higher than the Li@M2B18 materials due to the higher electron-donating ability of the Li3O compared to the Li atom. Besides, the hyperpolarizability of the designed materials significantly increases along with the imposed external electric fields, representing that the nonlinear optical responses of the considered materials can be enhanced by applying the electric files parallel to the charge transfer direction. © 2021 Elsevier B.V.
Publication Date: 2021
Journal of Environmental Chemical Engineering (22133437)9(2)
One of the most exciting events in chemistry is the stable assemblies of atoms, denoted by superatoms, that could mimic the behaviors of elements in the periodic table. For the first time by Jena et al., a novel type of di-anions superchalcogens (BeAl122- and TiAu122-) has been introduced based on the various electron-counting rules. Inspired by the fascinating finding of these superatoms and guided by density functional theory calculations, we propose a novel and efficient strategy to capture pollutants from waste water via adsorbing the toxic heavy metal cations (Cd2+, Hg2+, and Pb2+) by the BeAl122- and TiAu122- superchalcogens. Our results reveal that the BeAl122- and TiAu122- superchalcogens were powerful to adsorb the Pb2+, Hg2+, and Cd2+ cations in the aqueous solution. Furthermore, by investigating the hydrated cations, the adsorption of hydrated [Pb(H2O)4]2+ on the BeAl122- and TiAu122- superatoms was found thermodynamically more favorable than the [Cd(H2O)4]2+ and [Hg(H2O)4]2+. Our calculations also showed that the adsorbing heavy metal cations can considerably narrow the wide HOMO-LUMO gap and remarkably enhance the first hyperpolarizability of the pristine BeAl122- and TiAu122- superchalcogens, due to electron transfer in this type of superatoms. Moreover, the results highlight the systems with higher electron transport rates, show the larger first hyperpolarizability as well as the higher nonlinear optical response. Time-dependent density functional calculations also revealed "ligand to metal charge transfer"vertical excitations for the cation/superchalcogen systems. However, these theoretical findings might be helpful for experimental scientists toward designing high-efficient adsorbents based on superatoms for eliminating water pollutants. © 2020 Elsevier Ltd.
Publication Date: 2020
ACS Applied Energy Materials (25740962)3(11)pp. 11463-11469
The performance of Li-ion batteries (LIBs) depends upon anode materials with high capacity. Motivated by the recent synthesis of a carbon nanocone (CNC), which includes a pentagon encircled by 30 hexagons using a palladium-catalyzed cross-coupling reaction, we investigate its potential for a LIB anode material. Density functional theory (DFT) calculations are performed to examine the potential application of the CNC layer with topological defects as an anode material in the LIBs. The Stone−Wales (SW)-defect-filled CNC (CNC-SW) layer exhibits a more negative Li binding energy than the pristine CNC (CNC-PR). We found that the Li atom exhibits fast diffusion on the surface of both the CNC-PR and CNC-SW layers with the low energy barriers of 0.38 and 0.32 eV, respectively. Also, both the CNC-PR and CNC-SW layers show high storage capacities of 843 and 893 mAh g−1, which are standing among the largest storage capacities of the carbon-based anodes for LIBs. Moreover, the Li atoms intercalated CNC-SW layer show a low open-circuit voltage (VOCV) of 0.59 V. Thus, our results reveal that the CNC is a promising material for application as an anode in the LIBs. As the existence of the CNC layer is experimentally confirmed, the results reported in this study can be helpful for further improving the performance of anode materials in the LIBs. © 2020 American Chemical Society
Publication Date: 2020
Journal of Molecular Liquids (01677322)312
To address the enhancing request of appropriate photovoltaic materials for application in renewable energy resources, an attempt has been made herein to design and investigate the novel porphyrin-based donors with higher transport properties. The interesting furan-linked porphyrin donor (FPD) and thiophene-linked porphyrin donor (TPD) containing Zn metal atom have been previously synthesized and applied into the organic solar cell. Inspired by this fascinating finding, we suggest a new set of porphyrin-based donors with high charge transport properties via designing molecular scaffolds with different numbers of coordinated nitrogen atoms (FPD-Nx and TPD-Nx, x = 0–4) and various types of metal atoms (FPD-M and TPD-M, M = Fe, Co, Ni, Cu, and Zn). Then, the structural, electronic, optical, and charge transport properties of the designed donors have been studied and compared with the available experimental results. Our calculations reveal that the FPD-N2, TPD-N2, FPD-Co, and TPD-Co porphyrins possess the planar structures, proper energy levels in reference to the PCBM acceptor, high open-circuit voltage (VOC), and excellent charge transport properties which make them ideal donors that are used in organic solar cells. Accordingly, our predicted donors represented the improvement in the structural and transport properties which may lead to organic solar cells with high power conversion efficiency. Consequently, this approach can be useful for further improving the efficiency of porphyrin donors in organic solar cells. © 2020 Elsevier B.V.
Publication Date: 2019
Journal of Chemical Information and Modeling (15499596)59(5)pp. 1930-1945
On the basis of the newly synthesized banana-shaped thieno[3,2-b] pyrrole building block [Bulumulla, C.; Gunawardhana, R.; Kularatne, R. N.; Hill, M. E.; McCandless, G. T.; Biewer, M. C.; Stefan, M. C. Thieno[3,2-b] pyrrole-Benzothiadiazole Banana-Shaped Small Molecules for Organic Field Effect Transistors. ACS Appl. Mater. Interfaces 2018, 10, 11818-11825], several small molecules that can be used as organic semiconducting materials were theoretically designed. We have shown that these novel molecules with the donor-πconjugated bridge-acceptor-πconjugated bridge-donor (D-π-A-π-D) building block exhibit superior charge transport properties in organic field-effect transistors (OFETs). A variety of donors, π-bridges, and acceptors are examined, and the structural, electronic, optical, and charge transport properties of designed semiconductors are systematically investigated. The results highlight the impact of the core acceptor in improving the transport properties of the designed molecules. In particular, this work points toward the benzo-bis(1,2,5-thiadiazole) as the most promising acceptor that can be combined with thiophene π-bridge and flanked benzo-thiadiazole terminal units to produce a reasonable candidate for synthesis and for incorporating into OFET materials. For the suggested semiconductor, the small electron reorganization energy and large intramolecular coupling originating from dense π-stacking gave rise to enhanced electron mobility. This strategy can be helpful for further improving the performance of curved small molecules in field-effect devices. © 2018 American Chemical Society.
Publication Date: 2018
Inorganic Chemistry (00201669)57(15)pp. 9335-9347
Presently, many researches are directed toward the design of novel superatoms with high nonlinear optical responses. Inspired by a fascinating finding of superatoms which were designed by bonding superhalogen (Al13 nanocluster) with superalkalis (M3O, M = Na and K), we suggest an effective strategy to form a series of typical donor-acceptor frameworks with high nonlinear optical responses via bonding the superalkalis M3O (Li3O, Na3O, K3O, Li2NaO, Li2KO, Na2LiO, Na2KO, K2LiO, K2NaO, and LiNaKO) with low ionization potential to the superhalogen Al13 with large electron affinity. The ionization potential, electronic spatial extent, electric field gradient tensors of 17O nuclei, and natural bond orbital charge values of the superalkalis M3O were also calculated. We found that the M ligands have the remarkable effect on the ionization potential as well as 17O nuclear quadrupole resonance parameters of the superalkalis M3O. Our results also represented that the bonding superalkalis can efficiently narrow wide HOMO-LUMO gap and considerably enhance first hyperpolarizability of the pristine Al13, due to electron transfer in this type of superatom. Also, the effect of oriented external electric fields on the nonlinear optical responses of the superatoms M3O-Al13 has been systematically explored. We found that the first hyperpolarizability of the superatom compounds can be gradually increased by increasing the imposed oriented external electric field from zero to the critical external electric field along the charge transfer direction (M3O → Al13). In this respect, this work reveals an effective approach to gradually enhance the nonlinear optical responses of the superatoms through applying oriented external electric fields. © 2018 American Chemical Society.
Publication Date: 2018
Synthetic Metals (03796779)241pp. 39-46
Increasing concerns about capture and separation of CO2 and its impact on the global warming are motivating researchers to discover new materials and strategies for efficient CO2 capture. Here, we explored the possibility of conductive Fe/Nx clusters embedded in graphene (Fe/Nx/G) as an adsorbent for electrocatalytically switchable CO2 capture. Using density functional theory including long-range dispersion corrections, we investigated the adsorption process of CO2 on Fe/Nx/G (x = 0, 2, and 4) systems with various charge states. We found that CO2 molecule - forms weak interaction with the neutral Fe/Nx/G systems. On the contrary, the adsorption behavior of CO2 molecule on the Fe/Nx/G systems can be significantly enhanced by adding extra charges into the Fe/Nx/G. Our results show that by removing the charges, CO2 molecule automatically desorbs from Fe/N4/G. Thus, by switching on/off the charges carried by Fe/Nx/G systems the CO2 capture/release procedures can be easily controlled without any energy barrier. Moreover, these Fe/Nx/G systems are highly selective for separating CO2 from its mixtures with methane, hydrogen, and nitrogen. These predictions open the route for the further studies of charge-modulated systems with switchable capture/release capabilities that present high selectivity for CO2. © 2018 Elsevier B.V.
Publication Date: 2018
Applied Surface Science (01694332)434pp. 1239-1247
Metal particles supported on metal oxides (MMO) are promising materials with versatile applications such as catalyst in fuel cell technologies. As one of the transition metal oxides, niobium oxide (NbO) demonstrates a wide interesting properties that make it a potentially applicable in MMO materials. Here, the catalytic activity for the O 2 activation of transition metals (Fe, Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au) supported on the NbO has been studied theoretically using density functional theory (DFT). The activation of O 2 molecule and yielding two separated O atoms is an essential step for the oxygen reduction reaction. Our study demonstrates that the transition metals supported on the NbO can act as driving force for O 2 dissociation. Consistent with the prediction of reactivity descriptors, the maximum catalytic activity toward O 2 activation is related to the Pt-supported on the NbO metal oxide. © 2017 Elsevier B.V.
Publication Date: 2018
Surface Science (00396028)668pp. 117-124
Electrical charging of an FeN4 cluster embedded in graphene (FeN4G) is proposed as an approach for electrocatalytically switchable carbon monoxide (CO) adsorption. Using density functional theory (DFT), we found that the CO molecule is strongly adsorbed on the uncharged FeN4G cluster. Our results show that the adsorption energy of a CO molecule on the FeN4G cluster is dramatically decreased by introducing extra electrons into the cluster. Once the charges are removed, the CO molecule is spontaneously adsorbed on the FeN4G absorbent. In the framework of frontier molecular orbital (FMO) analysis, the enhanced sensitivity and reactivity of the FeN4G cluster towards the CO molecule can be interpreted in terms of interaction between the HOMO of CO molecule and the LUMO of FeN4G cluster. Therefore, this approach promises both facile reversibility and tunable kinetics without the need of specific catalysts. Our study indicates that the FeN4G nanomaterial is an excellent absorbent for controllable and reversible capture and release of the CO. © 2017 Elsevier B.V.
Publication Date: 2018
Vacuum (0042207X)147pp. 126-133
Indium-doped ZnO nanoparticle has been recently synthesized using a modified sol-gel technique. This study has revealed that the In-doped ZnO nanoparticles represent a higher sensitivity than the pristine ZnO nanoparticles to the carbon monoxide gas and can detect it at sub-ppm concentrations. Motivated by this study, in the present work using first-principles calculations, we study the effect of In-doping on the sensing properties of a ZnO nanocluster. In our survey, we have explored the sensitivity of pristine as well as In-doped ZnO nanoclusters towards CO detection. In contrast to the pristine form, the In-doped ZnO nanocluster can detect the CO molecule due to significant decrease in the HOMO-LUMO energy gap and thereby in the resistivity. As a secondary objective of the present study, electrical charging of the ZnO nanocluster is proposed as an approach for electrocatalytically switchable CO adsorption. We found that the CO molecule is weekly adsorbed on the neutral ZnO nanocluster. Our results show that the interaction between CO molecule and ZnO nanocluster is dramatically increased by introducing extra positive charges into the nanocluster. Once the charges are removed, the CO molecule spontaneously desorbed from the ZnO absorbent. Therefore, this approach promises both facile reversibility and tunable kinetics without the need of specific catalysts. © 2017 Elsevier Ltd
Publication Date: 2017
Materials Chemistry and Physics (02540584)202pp. 258-265
Opening a bandgap in graphene is one of the most important subjects in the graphene research currently, since most of the suggested applications for graphene in field-effect transistors and optoelectronic devices require the ability to adjust its bandgap. To solve this problem, a novel graphene-like nanomaterials, i.e. a nitrogenated holey graphene has been recently synthesized using a simple wet-chemical reaction (Nat. Commun. 2015, 6, 6486). Motivated by this experimental work, in the present study, the structural and electronic properties of the zero dimensional (0D) holey graphene flake are investigated using first-principles calculations. In the framework of density functional theory, we analyze the effects of number of doped atoms (nitrogen and boron) on the structure, stability, and electronic properties of the holey graphene flake. In our survey, we have explored the stability of pristine as well as doped and co-doped holey graphene flake by studding of band gap energy as well as cohesive energy, chemical hardness, hyper-hardness, electrophilicity index, and dipole moment values of the considered flakes. The present study opens the way for manipulating holey graphene and developing promising materials for applications in field-effect transistors and optoelectronic devices. © 2017 Elsevier B.V.
Publication Date: 2017
Synthetic Metals (03796779)234pp. 38-46
The O2 dissociation and yielding two separated O atoms is an essential step for the oxygen reduction reaction. Dissociation of the strong bond in the O2 often involves large activation barriers on metal particles used as catalysts. Here, the O2 dissociation on the Fe/Nx clusters embedded in the fullerene C60, carbon nanotube, and graphene nanomaterials have been studied theoretically using density functional theory. The following outcomes can be derived from our calculations: (1) The Fe/Nx clusters embedded in the C60, carbon nanotube, and graphene enhance the reactivity of these nanomaterials, however, it is more effective in the case of Fe/Nx clusters embedded in the graphene. (2) Consistent with the prediction of the reactivity descriptors, the maximum catalytic activity toward the O2 dissociation is related to the Fe/N4 cluster embedded in graphene. (3) The adsorption energies of the O2 adsorbed on the Fe/Nx clusters embedded in the C60, carbon nanotube and graphene increase with the increase Fe transition metal positive charges. (4) Our study demonstrates that the Fe/N4 cluster embedded in graphene can act as driving force for the O2 dissociation. (5) The energy barrier of the O2 dissociation process shows that the O2 dissociation on the Fe/N4 cluster embedded in the graphene will be kinetically preferable. These predictions open the route for the experimental studies of catalysts that offer high activity for oxygen reduction reaction processes. © 2017 Elsevier B.V.
Publication Date: 2017
Journal of Molecular Graphics and Modelling (10933263)77pp. 218-224
The activation of the O2 molecule and yielding two separated O atoms is an essential step for the oxygen reduction reaction processes. Dissociation of the strong bond in the O2 often involves large activation barriers on metal particles used as catalysts. Here, the catalytic activity for the O2 dissociation of the transition metals (Fe, Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au) deposited on the BN nanocluster have been studied theoretically using density functional theory. The following outcomes can be derived from our calculations: (1) The strong interaction between the Fe and Ni metal atoms and boron atom in BN nanocluster suggests that these transition metals deposited on BN nanocluster should be stable under high temperatures. (2) Transition metal deposition enhances the reactivity of BN nanocluster, however, it is more effective in the case of Fe-deposited on BN nanocluster. (3) Consistent with the prediction of reactivity descriptors, the maximum catalytic activity toward O2 dissociation is related to the Fe-deposited on BN nanoclusters. (4) The adsorption energies of the O2 adsorbed on the metal-deposited BN nanoclusters increase with the increase transition metals positive charges. (5) The energy barrier of the O2 dissociation is significantly decreased by introducing extra positive charges into the metal deposited on the BN nanocluster. Our study demonstrates that the transition metals-deposited on the BN nanoclusters can act as driving force for O2 dissociation. These predictions open the route for the experimental studies of catalysts that offer high activity for oxygen reduction reaction processes. © 2017 Elsevier Inc.
Publication Date: 2017
Computational and Theoretical Chemistry (2210271X)1115pp. 179-184
Elemental boron is electron-deficient and cannot form graphene-like structures. Instead, triangular boron lattices with hexagonal vacancies have been predicted to be stable. Recently, experimental and theoretical studies showed that the B36 sheet has a planar C6V structure with a central hexagonal hole, providing the first experimental evidence for the viability of atom-thin boron sheets with hexagonal vacancies, dubbed borophene. Herein, the sensitivity of the B36 borophene toward HCN molecule is theoretically investigated. The electronic properties of HCN/borophene adducts are strongly dependent on the molecular adsorption configuration. Owing to strong interactions between HCN and the B36 borophene, dramatic changes in the electronic properties of the sheet together with large HOMO-LUMO gap variations were observed. We found that the adsorption of HCN molecule can significantly influence the electronic structure of B36 borophene. Our results demonstrate that the B36 nanosheet is sensitive to the concentration (or pressure) of HCN gas. Our predictions can serve a guideline for further theoretical and experimental researches in investigating the electronic properties of the B36 borophene nanosheet. © 2017 Elsevier B.V.
Publication Date: 2017
Chemical Physics (03010104)493pp. 85-90
Electrical charging of Co/N4 cluster embedded in graphene (Co/N4/G) is proposed as an approach for electrocatalytically switchable hydrogen adsorption. Using density functional theory, we found that the H2 molecule is weakly adsorbed on the uncharged Co/N4/G cluster. Our results show that the adsorption energy of hydrogen molecule on Co/N4/G cluster is significantly increased by introducing extra positive charges into the cluster. Once the charges are removed, H2 molecule spontaneously desorb from the Co/N4/G absorbent. Therefore, this approach promises both facile reversibility and tunable kinetics without the need of specific catalysts. Our study indicates that the Co/N4/G nanomaterial is excellent absorbent for controllable and reversible adsorption and release of H2. © 2017 Elsevier B.V.
Mohammadpour, Z.,
Safavi, A.,
Omidvar, A.,
Mohajeri, A.,
Mobaraki, N.,
Shamsipur, M. Publication Date: 2016
Journal of Fluorine Chemistry (00221139)190pp. 12-22
In this work, a new type of water soluble fluorescent assay was designed for fluoride ion based on the inner filter effect (IFE) of simple para-substituted arylboronic acids. Carbon nanodots (CDs) as the green and nontoxic carnbonic nanomaterials were used as the fluorophores and arylboronic acids as the absorbers. The reaction of fluoride ion with boron center of arylboronic acids tuned the absorption profiles toward longer or shorter wavelengths. In case of an increase in the spectral overlap between absorber and fluorophore, a decrease in fluorescence intensity of CDs was observed and considered as a response for quantitative fluoride measurement. The minimum detectable value of fluoride by these assays fulfilled the Environmental Protection Agency (EPA) requirement for water safety. The simple design of this assay together with avoidance of any covalent linkage between fluorophore and absorbers offers a cost effective, selective and sensitive fluoride sensor in aqueous environments. Furthermore, we have carried out density functional theory calculations to study the electronic structures and optical absorption spectra of the arylboronic acids before and after reaction with fluoride. Excellent agreement between the experimental result and theoretical calculations enables for prediction of spectral change of aryl boronic acids upon reaction with fluoride. In particular, the effect of fluoridation reaction on the excitation spectrum of CDs through IFE could be simply predicted by the theoretical calculation. Therefore, by using the present system, design of even more successful probes would be feasible for fluoride recognition in aqueous media. © 2016
