Solvent effects on the photoinduced charge separation dynamics of directly linked zinc phthalocyanine-perylenediimide dyads: a nonadiabatic dynamics simulation with an optimally tuned screened range-separated hybrid functional.

Herein, we have employed a combination of the optimally tuned screened range-separated hybrid (OT-SRSH) functional, the polarizable continuum model (PCM), and nonadiabatic dynamics (NAMD) simulations to investigate the photoinduced dynamics of directly linked donor-acceptor dyads formed using zinc phthalocyanine (ZnPc) and perylenediimide (PDI), in which ZnPc is the donor while PDI is the acceptor. Our simulations aim to analyze the behavior of these dyads upon local excitation of the ZnPc moiety in the gas phase and in benzonitrile. Our findings indicate that the presence of a solvent can significantly influence the excited state dynamics of ZnPc-PDI dyads. Specifically, the polar solvent benzonitrile effectively lowers the vertical excitation energies of the charge transfer (CT) state from ZnPc to PDI. As a result, the energetic order of the locally excited (LE) states of ZnPc and the CT states is reversed compared to the gas phase. Consequently, the photoinduced electron transfer (PET) dynamics from ZnPc to PDI, which is absent in the gas phase, takes place in benzonitrile with a time constant of 10.4 ps. Importantly, our present work not only qualitatively agrees with experimental results but also provides in-depth insights into the underlying mechanisms responsible for the photoinduced dynamics of ZnPc-PDI. Moreover, this study emphasizes the importance of appropriately considering solvent effects in NAMD simulation of organic donor-acceptor systems, taking into account the distinct excited state dynamics observed in the gas phase and benzonitrile. Furthermore, the combination of the OT-SRSH functional, the PCM solvent model, and nonadiabatic dynamics simulations shows promise as a strategy for investigating the complex excited state dynamics of organic donor-acceptor systems in solvents. These findings will be valuable for the future design of novel organic donor-acceptor structures with improved performance.

Non-negligible roles of charge transfer excitons in ultrafast excitation energy transfer dynamics of a double-walled carbon nanotube.

Herein, we employed a developed linear response time dependent density functional theory-based nonadiabatic dynamics simulation method that explicitly takes into account the excitonic effects to investigate photoinduced excitation energy transfer dynamics of a double-walled carbon nanotube (CNT) model with different excitation energies. The E11 excitation of the outer CNT will generate a local excitation (LE) |out*〉 exciton due to its low energy, which does not induce any charge separation. In contrast, the E11 excitation of the inner CNT can generate four kinds of excitons with the LE exciton |in*〉 dominates. In the 500-fs dynamics simulation, the LE exciton |in*〉 and charge transfer (CT) excitons |out-in+〉 and |out+in-〉 are all gradually converted to the |out*〉 exciton, corresponding to a photoinduced excitation energy transfer, which is consistent with experimental studies. Finally, when the excitation energy is close to the E22 state of the outer CNT (∼1.05 eV), a mixed population of different excitons, with the |out*〉 exciton dominated, is generated. Then, photoinduced energy transfer from the outer to inner CNTs occurs in the first 50 fs, which is followed by an inner to outer excitation energy transfer that is completed in 400 fs. The present work not only sheds important light on the mechanistic details of wavelength-dependent excitation energy transfer of a double-walled CNT model but also demonstrates the roles and importance of CT excitons in photoinduced excitation energy transfer. It also emphasized that explicitly including the excitonic effects in electronic structure calculations and nonadiabatic dynamics simulations is significant for correct understanding/rational design of optoelectronic properties of periodically extended systems.

Ultrafast charge transfer in a nonfullerene all-small-molecule organic solar cell: a nonadiabatic dynamics simulation with optimally tuned range-separated functional.

Herein, we have employed linear-response time dependent density functional theory (LR-TDDFT)-based nonadiabatic dynamics simulations to investigate the ultrafast charge transfer in a nonfullerene all-small-molecule donor-acceptor (D-A) system formed by a porphyrin small-molecule donor ZnP and a recently developed nonfullerene small-molecule acceptor 6TIC, during which the optimally tuned range-separated hybrid (OT-RSH) functional was adopted. In combination with static electronic structure calculations, several important conclusions were drawn. Firstly, the ZnP and 6TIC are more likely combined together non-covalently in parallel rather than in perpendicular to form ZnP-6TIC due to the much larger adsorption energies, i.e. -44.6 kcal mol-1vs. -25.2 kcal mol-1. Secondly, the excited state properties obtained by OT-RSH functionals seem more consistent with the experimental results compared to their untuned versions. Specifically, the energy of the lowest charge transfer (CT) state was predicted to be smaller than the lowest lying local excitation (LE) states using the OT-RSH functional-based LR-TDDFT calculations, which is beneficial for the charge transfer process that might be crucial for the high power conversion efficiency (PCE) achieved experimentally. In contrast, the untuned RS functionals all predict higher CT state energies, which is contradictory to the high PCE obtained in the experiment. Moreover, strong hybridization upon excitation between these states was revealed, which might be one of the reasons responsible for the high PCE observed in the experiment. Finally, ultrafast excited state relaxation can be completed within 500 fs due to the small energy gaps and the strong nonadiabatic couplings between these states, which is accompanied by ultrafast photoinduced electron transfer from ZnP to 6TIC and photoinduced hole transfer the other way around. The efficient charge transfer processes and the involvement of two charge generation channels might be another cause resulting in the excellent photovoltaic performance of ZnP-6TIC based OSCs. Our present work not only provides solid evidence for elucidating the underlying mechanism observed in previous experiments, but also suggests that the combination of OT-RSH functionals and LR-TDDFT-based nonadiabatic dynamics simulations might be a powerful tool for investigating the excited state dynamics of organic D-A systems, which is crucial for the theoretical design of novel OSCs with better performances in the future.

Ultrafast exciton delocalization and localization dynamics of a perylene bisimide quadruple π-stack: a nonadiabatic dynamics simulation.

Unraveling the photogenerated exciton dynamics of π-stacked molecular aggregates is of great importance for both fundamental studies and industrial applications. Among various π-stacked molecular aggregates, perylene tetracarboxylic acid bisimide (PBI) based aggregates are regarded as one of the prototypes due to their inherent high fluorescence quantum yield and excellent photostability and flexibility in controlling intermolecular forces via chemical modifications. However, the exciton dynamics of these PBI based aggregates remain elusive up to now. In this work, we have first employed LR-TDDFT-based nonadiabatic dynamics simulations and static electronic structure calculations to investigate the ultrafast exciton dynamics of a newly synthesized perylene bisimide quadruple (PBQ) π-stack. Upon photoexcitation, the S6 to S10 states are the most likely populated excited states, which can be regarded as a combination of local excited (LE) excitons and charge transfer (CT) excitons of those four PBI chromophores. Then, the excited PBQ π-stack relaxes ultrafast to the lowest lying excited S1 state within 500 fs, which is accompanied by the complicated exciton conversion as well as exciton localization/delocalization dynamics. In short, the initially populated hybrid LE and CT excitons convert to the LE excitons of B/C and A/D, in which the LE excitons of B/C contribute the most (∼0.44) while the LE excitons of A/D also have minor contributions (0.21), indicating the formation of the localized excimer state. We use the notations A/B/C/D here to represent the four PBI fragments of PBQ π-stacks along the direction perpendicular to the PBI molecular plane. Additionally, using a recently defined root mean square deviation (RMSD) of electron and hole spatial distributions along three Cartesian coordinates, we could investigate the exciton localization/delocalization dynamics in a quantitative way. Our simulation results indicate that the photoinduced electrons and holes of the PBQ π-stack exhibit an ultrafast localization(∼10 fs)-delocalization(∼60 fs)-localization(∼200 fs) dynamics, during which both LE and CT excitons play crucial roles. Our present work is not only consistent with previous experimental studies, but also provides more detailed insights into the relevant processes, which might be useful for the future design of PBI based optoelectronic devices with improved performances.

Theoretical Study of Hydrogen Production from Ammonia Borane Catalyzed by Metal and Non-Metal Diatom-Doped Cobalt Phosphide.

The decomposition of ammonia borane (NH3BH3) to produce hydrogen has developed a promising technology to alleviate the energy crisis. In this paper, metal and non-metal diatom-doped CoP as catalyst was applied to study hydrogen evolution from NH3BH3 by density functional theory (DFT) calculations. Herein, five catalysts were investigated in detail: pristine CoP, Ni- and N-doped CoP (CoPNi-N), Ga- and N-doped CoP (CoPGa-N), Ni- and S-doped CoP (CoPNi-S), and Zn- and S-doped CoP (CoPZn-S). Firstly, the stable adsorption structure and adsorption energy of NH3BH3 on each catalytic slab were obtained. Additionally, the charge density differences (CDD) between NH3BH3 and the five different catalysts were calculated, which revealed the interaction between the NH3BH3 and the catalytic slab. Then, four different reaction pathways were designed for the five catalysts to discuss the catalytic mechanism of hydrogen evolution. By calculating the activation energies of the control steps of the four reaction pathways, the optimal reaction pathways of each catalyst were found. For the five catalysts, the optimal reaction pathways and activation energies are different from each other. Compared with undoped CoP, it can be seen that CoPGa-N, CoPNi-S, and CoPZn-S can better contribute hydrogen evolution from NH3BH3. Finally, the band structures and density of states of the five catalysts were obtained, which manifests that CoPGa-N, CoPNi-S, and CoPZn-S have high-achieving catalytic activity and further verifies our conclusions. These results can provide theoretical references for the future study of highly active CoP catalytic materials.

"On-The-Fly" Non-Adiabatic Dynamics Simulations on Photoinduced Ring-Closing Reaction of a Nucleoside-Based Diarylethene Photoswitch.

Nucleoside-based diarylethenes are emerging as an especial class of photochromic compounds that have potential applications in regulating biological systems using noninvasive light with high spatio-temporal resolution. However, relevant microscopic photochromic mechanisms at atomic level of these novel diarylethenes remain to be explored. Herein, we have employed static electronic structure calculations (MS-CASPT2//M06-2X, MS-CASPT2//SA-CASSCF) in combination with non-adiabatic dynamics simulations to explore the related photoinduced ring-closing reaction of a typical nucleoside-based diarylethene photoswitch, namely, PS-IV. Upon excitation with UV light, the open form PS-IV can be excited to a spectroscopically bright S1 state. After that, the molecule relaxes to the conical intersection region within 150 fs according to the barrierless relaxed scan of the C1-C6 bond, which is followed by an immediate deactivation to the ground state. The conical intersection structure is very similar to the ground state transition state structure which connects the open and closed forms of PS-IV, and therefore plays a crucial role in the photochromism of PS-IV. Besides, after analyzing the hopping structures, we conclude that the ring closing reaction cannot complete in the S1 state alone since all the C1-C6 distances of the hopping structures are larger than 2.00 Å. Once hopping to the ground state, the molecules either return to the original open form of PS-IV or produce the closed form of PS-IV within 100 fs, and the ring closing quantum yield is estimated to be 56%. Our present work not only elucidates the ultrafast photoinduced pericyclic reaction of the nucleoside-based diarylethene PS-IV, but can also be helpful for the future design of novel nucleoside-based diarylethenes with better performance.

T7 RNA Polymerase Discriminates Correct and Incorrect Nucleoside Triphosphates by Free Energy.

RNA polymerase (RNAP) is the primary machine responsible for transcription. Its ability to distinguish between correct (cognate) and incorrect (noncognate) nucleoside triphosphates (NTPs) is important for fidelity control in transcription. In this work, we investigated the substrate selection mechanism of T7 RNAP from the perspective of energetics. The dissociation free energies were determined for matched and unmatched base pairs in the preinsertion complex using the umbrella sampling method. A clear hydrogen-bond-rupture peak is observed in the potential of mean force curve for a matched base pair, whereas no such peaks are present in the position of mean force profiles for unmatched ones. The free-energy barrier could prevent correct substrates from being separated from the active site. Therefore, when NTPs diffuse into the active site, correct ones will stay for chemistry once they establish effective base pairing contacts with the template nucleotide, whereas incorrect ones will be withdrawn from the active site and rejected back to solution. This result provides an important energy evidence for the substrate selection mechanism of RNAP. Then we elucidated energetics and molecular details for correct NTP binding to the active site of the insertion complex. Our observations reveal that strong interactions act on the triphosphate of NTP to constrain its movement, whereas relatively weak interactions serve to position the base in the correct conformation. Triple interactions, hydrophobic contacts from residues M635 and Y639, base stacking from the 3' RNA terminal nucleotide, and base pairing from the template nucleotide act together to position the NTP base in a catalytically competent conformation. At last, we observed that incorrect NTPs cannot be as well-stabilized as the correct one in the active site when they are misincorporated in the insertion site. It is expected that our work can be helpful for comprehensively understanding details of this basic step in genetic transcription.

Mechanism of NTP Binding to the Active Site of T7 RNA Polymerase Revealed by Free-Energy Simulation.

In genetic transcription, molecular dynamic details and energetics of NTP binding to the active site of RNA polymerase (RNAP) are poorly understood. In this article, we investigated the NTP binding process in T7 RNAP using all-atom MD simulation combined with the umbrella sampling technique. Based on our simulations, a two-step mechanism was proposed to explain NTP binding: first, substrate NTP in aqueous solution, which carries a magnesium ion, diffuses through a secondary channel of RNAP to attain a pore region, where it undergoes conformational changes to give a correct orientation; next, the NTP establishes initial basepairing contacts with the template nucleoside (TN). Our free-energy calculations suggest that both steps are spontaneous. This mechanism can easily explain the problem of NTP binding with different orientations. Moreover, it is found that the nascent NTP:TN basepair is fragile and easily broken by thermal disturbance. Therefore, we speculate that the fingers domain will be triggered to close, so as to create a steady environment for the next chemical step. The observations from the work provide valuable information for comprehensively understanding the mechanism of the basic step in genetic transcription.

Polarizability as a tool to determine the electrostatic shielding effect of nanocarbon cages: a polarizability distribution study on noble gas endohedral fullerenes.

Shielding effects of a nanocage can be determined by the field felt by an encapsulated noble gas (NG) atom. Using the polarizability distributions about NG endohedral fullerenes (NGEFs), a new scheme based on the local polarizability of the NG is introduced to detect the shielding effects of fullerenes, using density functional theory calculations and Hirshfeld population analysis. For large cage sizes, this scheme can provide reliable results. Further analysis reveals that the shielding effect is dependent on the shape of the cage, and a shielding zone can be found around the center of the cavity in which the electric field can be considered to be uniform and of lower strength than that of an applied external field. For small cages, intermolecular interactions between the cage and the endoatom contribute to the overestimation of the shielding effects.

Theoretical insights into the photophysics of an unnatural base Z: A MS-CASPT2 investigation.

We have employed the highly accurate multistate complete active space second-order perturbation theory (MS-CASPT2) method to investigate the photoinduced excited state relaxation properties of one unnatural base, namely Z. Upon excitation to the S2 state of Z, the internal conversion to the S1 state would be dominant. From the S1 state, two intersystem crossing paths leading to the T2 and T1 states and one internal conversion path to the S0 state are possible. However, considering the large barrier to access the S1 /S0 conical intersection and the strong spin-orbit coupling between S1 and T2 states (>40 cm-1 ), the intersystem crossing to the triplet manifolds is predicted to be more preferred. Arriving at the T2 state, the internal conversion to the T1 state and the intersystem crossing back to the S1 state are both possible considering the S1 /T2 /T1 three-state intersection near the T2 minimum. Upon arrival at the T1 state, the deactivation to S0 can be efficient after overcoming a small barrier to access T1 /S0 crossing point, where the spin-orbit coupling (SOC) is as large as 39.7 cm-1 . Our present work not only provides in-depth insights into the photoinduced process of unnatural base Z, but can also help the future design of novel unnatural bases with better photostability.

Adsorption characteristics of sulfonamide antibiotic molecules on carbon nanotube and the effects of environment.

CONTEXT: In this paper, the adsorption characteristics of five sulfonamide antibiotic molecules on carbon nanotubes were investigated using density functional theory (DFT) calculations. The adsorption configurations of different adsorption sites were optimized, and the most stable adsorption configuration of each sulfonamide molecule was determined by adsorption energy comparison, and the relative adsorption stability of five sulfonamide molecules on carbon nanotubes was determined by comparing their adsorption energies, i.e., sulfamethazine > sulfadiazine > sulfamerazine > sulfamethoxazole > sulfanilamide. The electron densities of the adsorption configurations were then calculated to confirm that the adsorption of five sulfonamide drug molecules on carbon nanotubes should be physical adsorption. Moreover, the adsorption energy of five sulfonamide molecules on carbon nanotubes in the aqueous environment was larger than that in the vacuum even though the adsorption process remain to be physical adsorption. The adsorption characteristics of the five sulfonamide molecules in various acid-base environments were finally investigated. In contrast, the adsorption energies of the five drug molecules in acid-base environments were significantly reduced, indicating that carbon nanotubes may need to have a suitable pH range to achieve the optimal adsorption effect when they are used for the treatment of sulfonamide antibiotics. METHODS: In this paper, we use density functional theory (DFT) with PBE functional to study the adsorption properties of five sulfonamides on carbon nanotubes. The structural optimization and the calculation of electronic structural properties are carried out by CP2K package (version 7.1), adopting the DZVP-MOLOPT-SR-GTH basis set and Goedeck-Teter-Hutter (GTH) pseudo potential. Grimme's D3 correction is used to during all the calculations to correctly capture the influence of the van der Waals interactions.

Properties at the interface of the pristine CdSe and core-shell CdSe-ZnS quantum dots with ultrathin monolayers of two-dimensional MX2 (M: Mo, W; X: S, Se, Te) heterostructures from density functional theory.

In this work, eight van der Waals heterojunctions based on CdSe or CdSe-ZnS quantum dots (QDs) and four commonly used two-dimensional transition metal dichalcogenides (2D-TMDs) are theoretically designed. On the basis of the constructed structures, density functional theory (DFT) method is employed to investigate the structural and optoelectronic related properties of these heterojunctions in detail. Specifically, their electronic properties including charge density differences, density of states, and band offsets are calculated, based on which band alignment types as well as their potentials as novel photovoltaic materials are discussed. According to these calculations, we proposed that several van der Waals heterostructures including MoS2/CdSe, MoTe2/CdSe, WSe2/CdSe, MoTe2/CdSe-ZnS, and WSe2/CdSe-ZnS might be used as potential photovoltaic materials due to their type II band alignment characteristics. Moreover, the WSe2/CdSe-ZnS heterostructure is expected to have optimal photovoltaic performance attributed to their large bond offsets and band gaps, which could not only facilitate charge separation processes, but also slow down charge recombination. Our present theoretical work could be helpful for the future experimental design of novel CdSe QDs and 2D-TMD based van der Waals heterostructures with excellent photovoltaic performances.

Theoretical investigation complexation characteristics and UV-Vis absorption spectral properties of CdTe QDs with four capping agents.

In this paper, density functional theory (DFT) and time-dependent density functional theory (TDDFT) are used to study the complexation characteristics CdTe QDs with four different capping agents, i.e. 3-mercaptopropionic acid (MPA), reduced glutathione (GSH), 1-thioglycerol (TG) and 2-mercaptoethanesulfonate (MES). The properties of these complexes are analyzed by the complexation free energies, bond lengths, LOL, ADCH charges, frontier molecular orbitals and the UV-Vis absorption spectra. The results indicate that the four capping agents could form stable complexes with CdTe QDs. Whether the four capping agents interact with (CdTe)6 or (CdTe)9, MES has the strongest complexation ability with CdTe QDs and the MES-complexes are the most stable. For (CdTe)6, A2-MES is the most stable configuration. The complexation free energy and bond length of A2-MES are - 74.50 kcal/mol and 2.461 Å, respectively. When (CdTe)9 as substrate, A4-MES is the most stable configuration and corresponding complexation free energy is - 100.97 kcal/mol, which is followed by A4-MPA (- 57.75 kcal/mol) and A3-TG (- 60.20 kcal/mol), while A4-GSH (- 44.47 kcal/mol) is the weakest. Moreover, the electron amount transferred from MES to CdTe QDs is the most, and the ADCH charge value is 1.47 e. The absorption intensity of UV-visible light after complexation is also the largest. This is consistent with the result of the complexation free energy. Thus, it can be seen that the complexation abilities of four capping agents are in order of MES > MPA≈TG > GSH.

Theoretical study on the ring-opening isomerization reaction mechanism of the ring isomers of N8H8.

Ring-opening isomerization from ring-shaped isomers to chain-shaped isomers of N(8)H(8) has been studied by a density function B3LYP method at 6-311+ +G** level. 20 ring-shaped isomers have been found to be able to transform into chain-shaped isomers, with 20 possible transition states got by ring-opening structure optimization. Furthermore, the ring-openings have been found in the longer N-N single bond by analyzing the length change of N-N bond of ring-shaped isomers in ring-opening processes. In addition, with the activation energies in ring-opening processes, the differences of the activation energies in isomerization between the isomers have been found according to the classification of rings. The activation energies in ring-opening isomerization of six-membered ring-shaped isomers are higher than that of the four-membered ring-shaped isomers. It indicates that six-membered ring-shaped isomers difficult in ring-opening in the isomerization are the steadiest ring-shaped isomers of N(8)H(8) while four-membered ring-shaped isomers easy in ring-opening are the most unstable.

A novel strategy for sequential reduction of nitrate into nitrogen by CO2 anion radical: Experimental study and DFT calculation.

In order to expand the application of CO2 anion radical (CO2-), as a novel green reductant in the control of environmental pollution, CO2- radical was induced into the reduction of nitrate. The reduction efficiency, products and mechanism of nitrate or nitrite by CO2- radical were investigated based on the results of batch experiments and theoretical calculation using density functional theory (DFT) methods, respectively. It was found that: (1) the efficiency of nitrate reduction by CO2- radical from the HCOOH/UV system was far lower than that of nitrite under the same reaction conditions, (2) the rate-control step of nitrate reduction by CO2- radical was the transformation process of nitrate into nitrite with an activation energy of 23.9 kcal/mol, (3) the final products of nitrate reduction were mainly composed of nitrogen (N2). On this basis, a novel strategy of rapid reduction of nitrate into N2 using CO2- radical was proposed. Specifically, nitrate was firstly reduced into nitrite with the assistance of Zn/Ag bimetal, and then nitrite was further reduced into N2 by CO2- radical. In this way, the removal efficiency of nitrate was all achieved nearly 100% in the initial nitrate concentration ranging from 25 to 100 mg (N)/L, while the highest N2 selectivity could reach 97.5%. This work provided a promising approach for the reduction of nitrate into nitrogen with high efficiency and high N2 selectivity by CO2- radical.

Microscopic mechanism of light-induced tetrazole-quinone 1,3-dipolar cycloaddition: a MS-CASPT2 theoretical investigation.

Recently, experimentalists have developed a green and efficient method to synthesize pyrazole-fused quinones through light-induced tetrazole-quinone 1,3-dipole cycloadditions. However, the underlying microscopic mechanisms remain to be clarified. In this work, we have employed several electronic structure calculation methods (MS-CASPT2, CASSCF, DFT) to systematically explore the microscopic mechanism of related light-induced reactions and deactivation pathways. Upon excitation with ultraviolet light, one of the original reactants 2-(4-fluorophenyl)-5-phenyl-2H-tetrazole (FPT) reaches its S1 excited state. After that, due to the ultrahigh energy and the small energy barrier, the FPT molecule breaks the N2-N3 and N4-C5 bonds sequentially, removing the nitrogen atom finally in the S1 state. Combined with the cleavage of the second N4-C5 bond, the system reaches its conical intersection region and deactivates ultrafast to the ground state, generating the active intermediate ((4-fluorophenyl)diazen-1-ium-1-ylidene) (phenyl)methanide (FPNI). Subsequently, the active intermediate FPIN can react with naphthoquinone in the ground state by overcoming an energy barrier of about 5.7 kcal mol-1, after which the 1-(4-fluorophenyl)-3-phenyl-1H-benzo[f]indazole-4,9(3aH, 9aH)-dione (FP2HQ) is formed. The FP2HQ can be oxidized to obtain the 1-(4-fluorophenyl)-3-phenyl-1H-benzo[f]indazole-4,9-dione (PFQ). Due to the high energy and small barrier, the entire reaction process can easily take place, which ultimately leads to the efficient reaction. Our present work not only explains the experimental mechanism in detail but can also be helpful for the future design of related photoinduced reactions with the aid of theoretical calculations.

Rational design of monolayer transition metal dichalcogenide@fullerene van der Waals photovoltaic heterojunctions with time-domain density functional theory simulations.

van der Waals heterojunctions formed by transition metal dichalcogenides (TMDs) and fullerenes are promising candidates for novel photovoltaic devices due to the excellent optoelectronic properties of both TMDs and fullerenes. However, relevant experimental and theoretical investigations remain scarce to the best of our knowledge. Herein, we have first employed static density functional theory (DFT) calculations in combination with time-domain density functional theory (TDDFT) based nonadiabatic dynamics simulations to rationally evaluate the photovoltaic performances of four TMD@fullerene heterostructures, i.e. WSe2@C60, WSe2@C70, MoTe2@C60 and MoTe2@C70, respectively. Our simulation results indicate that the C70-based heterostructures overall have better photoinduced electron transfer efficiencies than their C60-based counterparts, among which the performance of the WSe2@C70 heterostructure is the best and the electron transfer from WSe2 to C70 almost accomplishes within 1 ps. In addition, the large build-in potential of about 0.75 eV of WSe2@C70 is beneficial for the charge separation processes. Our present work not only selects the van der Waals TMD@fullerene heterojunctions that might have excellent photovoltaic properties, but also paves the way for the rational design of novel heterojunctions with better optoelectronic performances with DFT and TDDFT simulations in the future.

Effect of molecular structure on the adsorption affinity of sulfonamides onto CNTs: Batch experiments and DFT calculations.

In order to investigate the adsorption behaviors of sulfonamides onto hydroxylated multi - walled carbon nanotubes (CNTs) with a porous structure and large specific surface area, six typical sulfonamides including sulfanilamide (SAM), sulfamerazine (SMR), sulfadimethoxine (SMX), sulfadiazine (SDZ), sulfamethazine (SMT) and sulfametoxydiazine (SMD) were selected to be adsorbed respectively on CNTs, and in the same time the structural parameters of the six sulfonamides molecules were calculated according to the density functional theory (DFT). Based upon above mentioned experiments and the structural parameters, the quantitative correlation between the structural parameters of sulfonamides molecules and their adsorption affinity (e.g. adsorption capacity and adsorption rate constant) onto CNTs was established, respectively. The adsorption data of sulfonamides fitted well with the pseudo - second - order kinetic model and the Langmuir isotherm model. The order of both pseudo - second - order kinetic constant and maximum adsorption capacity of the six sulfonamides were SAM < SMR < SMX < SDZ < SMT < SMD. The frontier molecular orbital energy (EHOMO) and dipole moment (µ) could be used as indicators for the adsorption affinity of sulfonamides onto CNTs. Accordingly, the possible adsorption mechanism was proposed.

The adsorption characteristics and degradation mechanism of tinidazole on an anatase TiO2 surface: a DFT study.

The adsorption characteristics and degradation mechanism of tinidazole on TiO2(101) and (001) surfaces under vacuum and aqueous solution conditions were studied by density functional theory (DFT). The results show that tinidazole can adsorb on the surfaces of TiO2(101) and (001) under different conditions. The hydrogen bond generated during the adsorption process can enhance the stability of the adsorption configuration, which makes the bond length of C-N of tinidazole longer and finally facilitates the ring-opening degradation reaction. As for the mechanism of the ring-opening degradation reaction, it was found that ring-opening can be carried out along reaction route II on both crystal surfaces, and the reaction activation energy is lower on (101) surface. Under the conditions of aqueous solution, the decrease of the activation energy of the ring-opening degradation reaction indicates that the solvent conditions can promote the degradation reaction.

Theoretical study of the adsorption characteristics and the environmental influence of ornidazole on the surface of photocatalyst TiO2.

In this paper, density functional theory (DFT) was performed to study the adsorption properties of ornidazole on anatase TiO2(101) and (001) crystal facets under vacuum, neutral and acid-base conditions. We calculated the adsorption structure of ornidaozle on the anatase TiO2 surface, optimal adsorption sites, adsorption energy, density of states, electronic density and Milliken atomic charge under different conditions. The results show that when the N(3) atom on the imidazole ring is adsorbed on the Ti(5) atom, the largest adsorption energy and the most stable adsorption configuration could be achieved. According to the analysis of the adsorption configuration, we found that the stability of C(2)-N(3) bond showed a weakening trend. The adsorption wavelengths of the electronic transition between the valence band and conduction band of ornidazole on the TiO2 surface were in the visible light wavelengths range, showing that the TiO2 crystal plane can effectively make use of visible light under different conditions. We speculate the possibility of ornidazole degradation on the surface of TiO2 and found that the reactive site is the C-N bond on the imidazole ring. These discoveries explain the photocatalytic degradation of ornidazole by TiO2 and reveal the microscopic nature of catalytic degradation.