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Through multiscale modeling, it is predicted that TSSSSI is a potential candidate for NIR-II FLI-guided PDT–PTT therapy.

Acceptors in organic solar cells (OSCs) are of paramount importance. On the basis of the well-known non-fullerene acceptor Y6, six acceptors (Y6-COH, Y6-COOH, Y6-CN, Y6-SO

Sulfinyl radicals (R-SO˙) play important roles in lots of reactions, while the isomer oxathiyl radicals (R-OS˙) and the isomerization between them are rarely observed due to the poor stability of R-OS˙. In this work, the complete active space self-consistent field (CASSCF) and its multi-state second order perturbation (MS-CASPT2) methods were employed to study the photo-induced reaction mechanisms of phenylsulfinyl radical PhSO˙ 1 and its isomer phenoxathiyl radical PhOS˙ 2. Our results show that 1 and 2 have similar singly occupied molecular orbitals in the ground state but different properties in the excited state, which determine their diverse behaviors after irradiation. Radical 1 can generate 2 by light irradiation, but 2 produces isomerization product 3 (2-hydroxyphenylthiyl radical) and ring-opening product 4 (acyclic thioketoketene radical) in two paths

The heteroatoms could play a critical role in improving the hole transport and interfacial charge transfer of triphenylamine-based HTM.

Molecular engineering has been demonstrated to be a predominant strategy for augmenting the long-term stability and passivating adverse defects for perovskite solar cells (PSCs). Here, using density functional theory calculations combined with

This article investigates the combined impact of fiscal and credit policies on green‐firm investment opportunities using firm‐level panel data of green industries in China. Our empirical results demonstrate that subsidies, tax rebates, and green credit loans have significantly U‐shaped nexuses with green‐firm investment opportunities: Subsidies, tax rebates, and green credit policies generate significant interactions on green‐firm investment opportunities. External financing constraints may weaken the incentive of subsidies, tax rebates, and green credit loans on green‐firm investment opportunities.

The design of active cathode catalysts, with abundant active sites and outstanding catalytic activity for CO2 electroreduction, is important to promote the development of solid oxide electrolysis cells (SOECs). Herein, A-site-deficient perovskite oxide (La0.2Sr0.8)0.9Ti0.5Mn0.4Cu0.1O3-δ (LSTMC) is synthesized and studied as a promising cathode for SOECs. Cu nanoparticles can be rapidly and uniformly in situ-exsolved under reducing conditions. The heterostructure formed by the exsoluted Cu and LSTMC provides abundant active sites for the catalytic conversion of CO2 to CO. Combined with the remarkable oxygen-ion transport capacity of the LSTMC substrate, the specially designed Cu@LSTMC cathode exhibits a dramatically improved electrochemical performance. Furthermore, first-principles calculations proposed a mechanism for the adsorption and activation of CO2 by the heterostructure. Electrochemically, the Cu@LSTMC presents a high current density of 2.82 A cm-2 at 1.8 V and 800 °C, which is about 2.5 times higher than that of LSTM (1.09A cm-2).

Sequence-selective recognition of cationic amphipathic peptides by synthetic receptors is significant to biological applications, but it is still a great challenging task. Here we first study the binding characteristics of receptor cucurbit[7]uril (CB[7]) to the smallest aromatic tripeptides X1GG (X1 = tryptophan (W), phenylalanine (F), and tyrosine (Y)) and basic tripeptides X2GG (X2 = arginine (R), lysine (K), and histidine (H)) by molecular dynamics simulations. The study indicates that the sidechains of aromatic X1 residues can be encapsulated into the CB[7] cavity, while the sidechains of basic X2 residues prefer to locate at the CB[7] portal. Based on that, we consider hydrophobic aromatic residues as the N-terminus, the smallest glycine (G) as the 2nd-residue and basic residues as the C-terminus, and design nine tripeptides X1GX2 (X1 = F, Y, W and X2 = H, K, R). We found that there is a great influence of the C-terminal basic residue of X1GX2 on binding with CB[7] due to the introduction of a new binding site between CB[7] and the sidechain of the C-terminal residue. Interestingly, CB[7] can differentiate WGR and WGK with similar structures efficiently because of their eight orders of magnitude difference in the association constant (Ka). Besides, for WGR, YGR, and YGK with a nanomolar binding affinity (Ka > 109 M−1), on reversing the sequence order of the 2nd-residue and 3rd-residue, their Ka reduces by about at least 1000-fold, implying the sequence dependence of CB[7] on recognizing these tripeptides. These results predict the potential applications of CB[7] in recognizing cationic amphipathic peptides.

To achieve the efficient and precise regulation of aggregation-induced emission in supramolecular systems, revealing the role of host–guest interactions in AIEgens is of vital importance. Using the theoretical protocol that combines molecular dynamics simulations and the hybrid quantum mechanics/molecular mechanics calculations, we explored the mechanism of host–guest interaction-induced emission enhancement of amphiphilic guest molecules (AIEgens) as both dispersed monomers and assembled aggregates. We confirmed that the binding pattern of host–guest inclusions between α-cyclodextrin (CD) and three amphiphilic guest molecules is that the interior hydrophobic cavity of CD hosts one phenyl ring of the TPE moiety and part of PEG chain of the guest; simultaneously, the exterior hydrophilic surfaces of CD fasten the PEG chain and adjacent phenyl rings of the TPE moiety of guest molecules by intermolecular hydrogen bonds and O–H⋯π interactions, respectively. The packing density of the assembled aggregates decreases as the CD concentration increases. The analysis of the radiative decay rate constants and the reorganization energy indicate that the monomer emission is enhanced after host–guest complexation; meanwhile, combining host–guest interactions and aggregation effects could further increase the fluorescence efficiency, because both host–guest interactions and the aggregation effect can effectively retard the low-frequency intramolecular phenyl ring rotational motions and CC double bond plane twisting, thus suppressing the nonradiative decay channels. The fluorescence emission spectra are also blue-shifted after complexation. Our theoretical protocol is general and applicable to other AIEgens in the supramolecular field, thus laying a solid foundation for the rational design of advanced AIE materials.

The acceptor in organic solar cells (OSCs) is of paramount importance for achieving a high photovoltaic performance. Based on the well-known non-fullerene acceptor Y6, we designed a set of asymmetric A–D1A′D2–A type new acceptors Y6–C, Y6–N, Y6–O, Y6–Se, and Y6–Si by substituting the two S atoms of one thieno[3,2-b]thiophene unit with C, N, O, Se, and Si atoms, respectively. The electronic, optical, and crystal properties of Y6 and the designed acceptors, as well as the interfacial charge-transfer (CT) mechanisms between the donor PM6 and the investigated acceptors have been systematically studied. It is found that the newly designed asymmetric acceptors possess suitable energy levels and strong interactions with the donor PM6. Importantly, the newly designed acceptors exhibit enhanced light harvesting ability and more CT states with larger oscillator strengths in the 40 lowest excited states. Among the multiple CT mechanisms, the direct excitation of CT states is found to be more favored in the case of PM6/newly designed acceptors than that of PM6/Y6. This work not only offers a set of promising acceptors superior to Y6, but also demonstrates that designing acceptors with asymmetric structure could be an effective strategy to improve the performance of OSCs.

Photocatalytic water splitting to produce hydrogen is a potential means of achieving scalable and economically feasible solar hydrogen production. Two-dimensional (2D) triphosphides are 2D materials with potential applications in photovoltaics and optoelectronics. Here, we theoretically investigated 56 systems in total, including seven monolayer XP3 (X = Al, Ga, Ge, As, In, Sn, and Sb) and their combined vertical and lateral heterostructures. We found that the lateral heterostructure AlP3-GaP3 should be a promising photocatalyst for water splitting, through a quadruple screening process combining free energy calculations. It is fascinating that AlP3-GaP3 ingeniously combines all the desired features for photocatalytic water-splitting reactions, including a nearly direct band gap (1.43 eV), perfect band edge position, high STH efficiency (16.89%), broad light absorption region of sunlight, ultrahigh carrier mobility (20,000 cm2 V-1 s-1), low exciton binding energy (0.33 eV), and excellent stability in a water environment. Moreover, through Gibbs free energy calculations, the active sites and possible reaction pathways of the overall water-splitting reaction by AlP3-GaP3 were also confirmed. Our work offers a strategy for the design and fabrication of novel lateral heterostructures for a high-performance photocatalyst in water-splitting reactions.

The electron-transporting material (ETM) in inverted perovskite solar cells (PSCs) plays important role in reducing hysteresis and realizing simple processing procedures, while the improvement of power conversion efficiency is limited by low electron mobility and weak perovskite/ETM interface interaction. In this work, three new ETMs (HAT-1, HAT-2, and HAT-3) were designed by introducing methoxyphenyl, imide, and naphthalene groups into the hexaazatriphenylene (HAT) skeleton, based on the ETM HATNASOC7 synthesized experimentally [Jen

Organic-inorganic halide perovskite solar cells (PSCs) have attracted much attention due to their rapid increase in power conversion efficiencies (PCEs), and many efforts are devoted to further improving the PCEs. Designing highly efficient hole transport materials (HTMs) for PSCs may be one of the effective ways. Herein we theoretically designed three new HTMs (FDT-N, FDT-O, and FDT-S) by introducing a nitrogen-phenyl group, an oxygen atom, and a sulfur atom into the spiro core of an experimentally synthesized HTM (FDT), respectively. And then we performed quantum chemical calculation to study their application potential. The results show that the devices with FDT-O and FDT-S instead of FDT may have higher open circuit voltages owing to their lower highest occupied molecular orbital (HOMO) energy levels. Moreover, FDT-S exhibits the best hole transport performance among the studied HTMs, which may be due to the significant HOMO-HOMO overlap in the hole hopping path with the largest transfer integral. Furthermore, the results on interface properties indicate that introducing oxygen and sulfur atoms can enhance the MAPbI3 /HTM interface interaction. The present work not only offers two promising HTMs (FDT-O and FDT-S) for PSCs but also provides theoretical help for subsequent research on HTMs.

Intramolecular charge transfer (ICT) is a fundamental process in photochemistry, during which charge flows from a donor (D) to an acceptor (A). In (probably) most dyes, ICT is enhanced upon photoex...

As the key component of organic solar cells (OSCs), the acceptor plays key roles in determining the power conversion efficiency (PCE). Based on the famous non-fullerene acceptor ITIC, a series of acceptors (A1-A5) were designed by introducing fused-ring units (phenanthrene, pyrene, benzopyrazine, dibenzo[a,c]phenazine, and phenanthro[4,5-abc]phenazine) as the end groups. Theoretical calculations showed that A1-A5 display improved solubility and redshifted absorption spectra compared with ITIC. More importantly, the newly designed acceptors exhibit much higher electron mobility, where the electron mobility of A5_h (similar to A5 but with the same hexyl side chain as ITIC) is about four orders of magnitude larger than that of ITIC. The computed binding energies of the donor PBDB-TF with the acceptor ITIC and A5_h are -2.52 eV and -3.75 eV, indicating much stronger interface interactions in PBDB-TF/A5_h. In terms of charge-transfer (CT) mechanism, we found that both PBDB-TF/ITIC and PBDB-TF/A5_h can generate CT states through direct excitation and hot excitons, meanwhile there exist more opportunities of producing CT states via the intermolecular electric field (IEF) mechanism in PBDB-TF/A5_h. Our results not only offer a set of promising ITIC-based acceptors, but also provide new insights into the donor/acceptor interface properties, which are closely related to the PCE of OSCs.

Black phosphorus (BP) is a promising two-dimensional (2D) semiconductor, because of its tunable band gap and high hole mobility; however, its easy degradation under atmospheric conditions largely limits its application in photocatalytic water-splitting reactions. To overcome this disadvantage, we proposed a strategy for designing sandwiched P4O2-encapsulated BP (P4O2/BP) 2D materials, considering the automatic formation and high stability of P4O2 in air. We systematically considered five different packing models involving twenty sandwiched P4O2/BP systems using first-principles calculations. Through the triple screening process of 20 sandwiched P4O2/BP systems, we found that the O-1-P system with intrinsic electric field ingeniously combines all the desired features for photocatalytic water-splitting reactions, including small direct band gap (1.34 eV), low exciton binding energy, high hole mobility and ultrahigh solar-to-hydrogen efficiency as high as 22.77%. Through Gibbs free energy calculations, the active sites and possible reaction pathways of full water-splitting reactions were also confirmed. Our work offers useful guidance for designing and fabricating stable 2D materials with high performance for application in photocatalytic water-splitting reactions.

Hybrid organic-inorganic perovskite solar cells (PSCs) have shown significant potential for use in the energy field. Typically, hole-transporting materials (HTMs) play an important role in affecting the power conversion efficiency (PCE) of PSCs. A deep understanding of the structure-property relationship plays a vital role in developing efficient HTMs. Herein, the relationship between the structure and properties of two small organic HTMs H2,5 and H3,4 were systematically investigated in terms of the electronic and optical properties, the hole-transporting behavior by using density functional theory (DFT) and Marcus electron transfer theory. The results demonstrated that the high power conversion efficiency of the H2,5-based PSC was caused by strong interactions with the perovskite material on the interface and an enhanced hole mobility in H2,5 compared with H3,4. The strong interaction derives from the short bond length of O atom of HTM and Pb atom of perovskite material, and the highly hole mobility derives from the quasi-planar conjugated conformation and tight packing model of neighboring molecules in H2,5. In addition, we found that the planar structure enhances the intermolecular interaction between HTM and perovskite materials compared with the 'V'-shaped molecule. Importantly, we also note that the HOMO level of the isolated molecule is not always proportional to the open-circuit voltages of PSCs since the HOMO level might move toward a higher level when the interaction between HTM and interface of perovskite was included. The work gives essential information for rational designing efficient HTMs.

Electronic structure calculations and nonadiabatic dynamics simulations were carried out on the excited state decay mechanism of a typical aggregation-induced emission (AIE)-active molecule, 10,10 ',11,11 '-tetrahydro-5,5 '-bidibenzo[a,d][7]annulenylidene (THBDBA), which was experimentally found to be almost non-emissive in THF solution but highly luminescent as an aggregate. At the MS-CASPT2//CASSCF level, the decay path from S-1 leads to a conical intersection (CI) seam with the ground state (S-0) via a cyclization process of two neighboring phenyl groups. Nonadiabatic dynamics simulations of 367 surface hopping trajectories show that all the structures of hopping points resemble those of the S-1/S-0 CI seam with cyclized geometry. The final structures of trajectories hopping to S-0 belong to either Franck-Condon (FC) like structures (66.8 %) or cyclized conformers (33.2 %), which agrees well with the experimental result of 23 % cyclization product (Y. Cai et al. Chem. Sci., 2011, 2, 2029-2034). Our results also indicate that long-time irradiation leads to a photostationary state where the open and cyclized forms interconvert photochemically. The preference for photocyclization over double bond isomerization is due to the rigidity of the dihydrofulvene rings. From the point of view of AIE, the calculations suggest that THBDBA follows our restricted access to a CI (RACI) model because the photocyclization requires large displacements of the phenyl rings. These displacements must be blocked in the aggregate phase, inhibiting the decay and leading to luminescence. Our study contributes to understand the AIE and switch behavior of THBDBA and will be useful to support the design of new molecules with these features.

Photocatalytic water splitting by a two-dimensional material is a promising technology for producing clean and renewable energy. Development of this field requires candidate materials with desirabl...

In inverted perovskite solar cells (PSCs), electron transfer materials (ETMs) have a significant effect on the efficiency and stability, because they can reduce the energy barrier between the perovskite film and electrode materials and suppress the potential interfacial charge recombination. Herein we designed a series of ETMs (o-PDTP, m-PDTP, and p-PDTP) through introducing pyridyl as the side chain of the experimentally synthesized ETM 10,14-bis(5-(2-ethylhexyl)thiophen-2-yl)-dipyrido-[3,2-a:2′,3′-c][1,2,5]-thiadiazolo-[3,4-i]-phenazine (TDTP) based on quantum chemical calculations. Our results showed that introducing pyridyl changes the molecular packing mode from the herringbone packing motif in TDTP to two-dimensional π–π stacking in p-PDTP due to the strong interactions between the added nitrogen atoms and the hydrogen atoms of the molecular skeleton. Therefore, the average electron mobility of p-PDTP (1.65 cm2 V−1 s−1) is 34 times higher than that of TDTP. Our results also indicated that the additional N⋯Pb interface interaction between the nitrogen atoms in the ETMs and the lead atom in MAPbI3 leads to stronger binding energies and easier electron injection. The present results not only offer two promising ETMs (m-PDTP and p-PDTP), but also propose a new design strategy of introducing pyridyl into ETMs for more efficient PSCs.

Herein, the complete active space self-consistent field (CASSCF) and its second-order perturbation (CASPT2) methods combined with time-dependent density functional theory (TD-DFT) calculations were employed to investigate the isomerization reaction mechanisms of an asymmetric N,C-chelate organoboron compound, B(ppy)MesPh, in the ground (S0) state and the first singlet excited (S1) state. Our calculations show that isomerizations proceed via different pathways in the S0 and S1 states,; however, the energy barriers for mesityl isomerization are higher than those for phenyl isomerization in both states; this is in good agreement with the experimentally observed regioselectivity (S. Wang, et al. Angew. Chem., Int. Ed., 2017, 56, 6093-6097). Photoisomerization is motivated by charge transfer from two phenyl rings to the pyridyl moiety and initiated by the cleavage of the B-Cppy bond, followed by the formation of a boracyclopropane ring via an (S1/S0)X conical intersection and a biradical intermediate. Both steric and electronic features were found to be important for regioselective photoisomerization. Our results not only shed light on the experimental observations, but also provide valuable details on the excited state dynamics of organoboron compounds and can facilitate further syntheses and applications.

Acceptor-π-donor-π-acceptor (A-π-D-π-A) type small molecule acceptors have made significant progress in organic solar cells (OSCs). To achieve high performance acceptors, three novel acceptors (s4-s6) are designed and investigated based on small molecule acceptors (s1-s3) via introduction of different end-capped groups. The quantum chemistry and Marcus theory approaches are used to calculate the electronic structures and crucial parameters dramatically related to the short-circuit current density (JSC), involving the absorption spectrum, electron-hole correlation, driving force, and electron mobility. Compared with s1-s3, s4-s6 not only yield greater red-shift and stronger and broader absorption spectra, but also exhibit much higher electron mobility, easier exciton dissociation abilities, and much better electron transfer efficiencies in active layer. Our results will offer theoretical guidelines for further design and synthesis of acceptors to enhance the performance of OSCs.

A theoretical study on the multi-channel hydrogen addition of maleimide containing 2-hydroxy-benzophenone onto polyethylene in ultra-violet (UV) radiation cross-linking process was carried out using density functional theory (DFT) method at the B3LYP/6–311 + G(d,p) level. The energetic information and the minimum energy path (MEP) are calculated for nine reaction channels. The electrophilic addition reactions at two positions in the target molecule (maleimide containing 2-hydroxy-benzophenone) were investigated, which are on the C atom of C = C groups and on the O atom of C = O groups. Frontier molecular orbitals (MOs) and natural bond orbital (NBO) charge population of the target molecule have been analyzed in detail. As a result, the reaction site of C in C = C group is more active than the site of O in C = O groups. The target molecule can be used as a multi-functional additive candidate. The predicted mechanism may provide a theoretical basis for the real application of cross-linked polyethylene (XLPE) high-voltage insulation cables.

5-diazo Meldrum’s acid (DMA) undergoes the photo-induced Wolff rearrangement (WR). Recent gas-phase experiments have identified three photochemical products formed in a sub-ps scale after irradiation, a carbene formed after nitrogen loss, the ketene formed after WR and a second carbene formed after nitrogen and CO elimination (Steinbacher, A., et al. Phys. Chem. Chem. Phys., 2014, 16, 7290-7298). In this work the ground- and excited-state potential energy surfaces (PES) have been investigated at the MS-CASPT2//CASSCF level. The key element of the PES is an extended S0/S1 conical intersection seam along the C-N dissociation coordinate. The C-N predissociated region of the seam is accessed after excitation to the bright S2 state, and decay paths from the seam to the three primary products have been characterized. For the ketene and carbene II products, we suggest two possible formation pathways, a direct and a stepwise one, which suggests that these products may be formed in a bimodal fashion. We have also characterized two possible mechanisms for triplet formation, one ocurring before C-N dissociation involving a (S1/T2/T1) crossing region, and another one through the carbene. In contrast, excitation to S1 leads to a C-N bound region of the seam from where DMA regeneration or diazirine formation are possible, with a preference for the first case. The results are in good agreement with experimental data. Together with our previous work on diazonaphthoquinone, they show the importance of an extended seam in the photochemistry of α-diazoketones This work is financially supported by the National Natural Science Foundation of China (21303007); the Excellent Young Scholars Research Fund of Beijing Institute of Technology (2013YR1917); the Spanish Ministerio de Economía y Competitividad (RYC-2011-09582,CTQ2015-69363-P, FIS2012-37549-C05-02, and UNGI-10-4E-801) together with the European Fonds for Regional Development (FEDER); and the Generalitat de Catalunya (2014-SGR-301,2014-SGR-1202, and Xarxa de Referència en Química Teòrica i Computacional)

Organic azides are an efficient source of nitrenes, which serve as vigorous intermediates in many useful organic reactions. In this work, the complete active space self-consistent field (CASSCF) and its second-order perturbation (CASPT2) methods were employed to study the photochemistry of 2-furoylazide 1 and 3-furoylazide 5, including the Curtius rearrangement to two furylisocyanates (3 and 7) and subsequent reactions to the final product cyanoacrolein 9. Our calculations show that the photoinduced Curtius rearrangement of the two furoylazides takes place through similar stepwise mechanisms via two bistable furoylnitrenes 2 and 6. However, the decarbonylation and ring-opening process of 7 to 9 prefers a stepwise mechanism involving the 3-furoylnitrene intermediate 8, while 3 to 9 goes in a concerted asynchronous way without the corresponding 2-furoylnitrene intermediate 4. Importantly, we revealed that several conical intersections play key roles in the photochemistry of furoylazides. Our results are not only consistent and also make clear the experimental observations (X. Zeng, et al., J. Am. Chem. Soc., 2018, 140, 10-13), but additionally provide important information on the chemistry of furoylazides and nitrenes.

We systematically investigate the binding nature of CB[7] towards 20 amino acids in both neutral (AAs) and protonated (AAs+) states by quantum chemistry methods. The result indicates molecular recognition process are enthalpy-driven. Among AAs, Arg and Asn shows the largest binding strength to CB[7], and for AAs+, Gln+ and Asn+ bind to CB[7] the strongest. The binding strength of protonated CB[7]/AA+ is much stronger than that of neutral CB[7]/AA counterpart, due to the introduction of ion-dipole interaction and the increase number and strength of hydrogen bonds. Energy decomposition analysis (EDA) indicates that electrostatic interactions play major roles in both CB[7]/AAs and CB[7]/AAs+ complexes. Moreover, we analyzed the dependence of binding strength on single AA volume and dipole moment. This study is benefit for providing valuable information in predicting the recognition sites for sequence-based peptide or protein by CB[7] and rationally designing synthetic host molecule for specific peptide or protein recognition.

Multiple absorbers that function in different absorption regions (near infra-red (NIR) and UV-Visible (UV-Vis)) have been widely used in solar cell applications to enhance the light-harvesting. Herein, two special co-sensitizing Models 1 and 2, which feature either saturated dye IQ21 or saturated co-sensitizer S2, have been added to a TiO2 surface to explore the effect of the altered sensitizing sequence, namely the co-sensitizing ratio of IQ21/S2 and S2/IQ21 on the electrostatic potential variation (ΔV), electron injection efficiency (ηinj′), and Forster resonance energy transfer (FRET), using density functional theory and first-principle molecular dynamics simulations. The ΔV related to the open-circuit voltage (Voc) is insensitive in both Models 1 and 2. However, the absorption (λabs) and ηinj′ associated with the short-circuit density (Jsc) display a significant deviation (the λabs for 1 is red-shifted compared to that of 2, and the ηinj′ for 1 is improved by 56%). Meanwhile, Model 1 manifests a suppressed FRET and potentially favors co-sensitizer S2 functioning as the electron-injector and not the energy-donor. Another two possible Models 3 and 4 that feature a reduced adsorption of IQ21 and S2 relative to 1 and 2 were considered further, and the result mirrors the main trend in 1 and 2, except for the ηinj′. Overall, it implies that sensitizing a larger absorber with NIR features to saturate it first, then introducing a smaller absorber with UV-Vis features, can potentially improve the electron injection and diminish electron–hole recombination considerably. Our results provide a comprehensive analysis of the active role of an optimized sensitizing sequence to improve the conversion efficiency.

Organosulfur compounds are being of increasing interest in the atmospheric environment and climate because of their profound impacts on the formation of secondary organic aerosol. However, their role in the initial step of new particle formation (NPF) is still unclear. Here, using Density Functional Theory (DFT) calculation combined with the Atmospheric Clusters Dynamic Code (ACDC) model, we study the enhancement effect of hydroxymethanesulfonic acid (HMSA) - one of the most important organosulfur compounds - on sulfuric acid (SA) - dimethylamine (DMA) molecular clustering and the underlying mechanism. The results show that HMSA can enhance cluster formation rates at room temperature with the enhancement strength ranging from zero to four orders of magnitude. The comparison of the enhancement effect between HMSA and MSA shows that the enhancement strength of HMSA could be up to 3.97 times stronger than that of MSA, indicating that HMSA may be a more potential stabilizer. Meanwhile, different from the “bridge” role of α-hydroxyl acids, HMSA acts as “stabilizer” directly participating in NPF. Both of its enhancement strength on cluster formation rate and the corresponding contribution to the growth pathway present a negative dependence on SA concentration. All those could, to some extent, help to explain the missing sources of NPF between field observation and currently cognition, as well as to assist us to better understand atmospheric organosulfur chemistry.

The molecular dynamics (MD) simulation method was used to simulate the aggregation of four types of surfactants at the oil/water interface. The effect of different cations such as Na+, Mg2+...

Recently, mixed cation/anion perovskite solar cells (PSCs) have attracted considerable attention due to their higher stability and better photovoltage performance than pure ABX3 perovskite solar cells. However, the fundamental mechanism of such an improvement has not yet been fully investigated. In this paper, substituting cesium cation for methylammonium cation of the (1 0 0) surface of CH3NH3PbI3 perovskites was made to study the improvement of stability and electronic properties of MAPbI3 perovskite. The results show that the decomposition energies of perovskite increase with the increased concentration of doping Cs+, which indicates that the thermodynamic stability can be enhanced. By analyzing the Bader charge and charge density difference of the perovskite/TiO2 heterostructures, we find that the system of doping Cs+ transfers more electrons to TiO2 since the distance between I and Ti reduces. Doping Cs+ can make the PbI6 octahedral frame tilt and the tilting orientation is different for different concentration of Cs+. Meanwhile, the band gap increases with the increased concentration of Cs+, which leads to the increase in open circuit voltage VOC. This study can give some guidance for improving stability and PCE of the perovskite solar cells.

The prominent roles of organofluorine compounds in various fields have aroused considerable interest in the development of new methods for carbon-fluorine bond formation. Electrophilic fluorination receives much attention. Density functional theory (DFT) was used to theoretically explore the fluorination activity of 12 N-Fluoropyridinium salts on the substrate of benzene in acetonitrile solution. Geometry optimizations and frequency calculations of the reactants, transition states, and products were performed at B3LYP/6-311G(d,p) level for the 12 fluorination reaction channels. Based on the optimized structure, all the stationary points have been corrected by the single point energy at a high-level of M06-2x/6-311++G (d,p). Four substituents were considered in this paper, they are nitro-, cyano-, chloro-, methoxy-, respectively. Three substituted sites (ortho-, meso-, para-) were also concluded. Based on the obtained potential energy surfaces information and analysis of substituent effect, the fluorination reaction channel of oNO2NFpyr is most efficient due to the lowest reaction energy barrier; therefore, oNO2NFpyr is a promising optimum fluorinating reagent among the studied 12 N-Fluoropyridinium salts.

Sulfate is one of the most important components in the aerosol due to its key role in air pollution and global climate change. Recent work has suggested that reactive nitrogen chemistry in aqueous water can explain the missing source of sulfate in the aqueous water. Herein, we have mapped out the energy profile of the oxidization process of SO2 leading from NO2 and two feasible three-step mechanisms have been proposed. For the oxidation of HOSO2− and HSO3− by the dissolved NO2 in weakly acidic and neutral aerosol (pH ≤ 7), the main contribution to the missing sulfate production comes from the oxidation of HOSO2−. The whole process is a self-sustaining process. For the oxidation of SO32− in alkaline aerosol (pH > 7), the third step - decomposition step of H2O or hydrolysis of SO3 step which are two parallel processes are the rate-limiting steps. The present results are of avail to better understand the missing source of sulfate in the aerosol and hence may lead to better science-based solutions for resolving the severe haze problems in China.

In this study, using coconut fibers as raw material, activated carbon fibers were prepared via carbonization and KOH activation processes. The morphology, composition, specific surface area, pore structure and thermal stability of the resulting activated carbon fibers were systematically characterized. It was found that the activation process increases the specific surface area of carbon fibers to a greater extent via formation of a large number of micropores (0.7–1.8 nm) and a certain amount of slit-shaped mesopores (2–9 nm). The specific surface area and the pore volume of the activated carbon fibers reach 1556 m2 g−1 and 0.72 cm3 g−1, respectively. The activation process can also decompose the tar deposits formed after the carbonization process by pyrolysis, making the surface of the activated carbon fibers smoother. To study the adsorption properties of the as-prepared activated carbon fibers, the adsorption capacities and adsorption kinetics of various organic dyes including methylene blue, Congo red and neutral red were investigated. The adsorption capacities of the dyes increased with the increasing initial dye concentrations, and varied greatly with the pH value of the system. In methylene blue and neutral red systems, the adsorption capacities reach the maximum at pH 9, and in the Congo red system, it reaches the maximum at pH 3. The adsorption capacities of the activated carbon fibers in methylene blue, Congo red and neutral red systems reached equilibrium at 150, 120, and 120 min, and the maximum adsorption capacities were 21.3, 22.1, and 20.7 mg g−1, respectively. The kinetics of the adsorption process was investigated using three models including pseudo-first-order, pseudo-second-order and intraparticle diffusion models. The results indicated that the dynamic adsorption processes of coconut-based activated carbon fibers to methylene blue, Congo red and neutral red were all in accordance with the second-order kinetic model, and the equations are as follows: t/Qt = 0.1028 + t/21.3220, t/Qt = 0.1128 + t/21.5982 and t/Qt = 0.0210 + t/20.6612.

Oxygen molecule has a negative effect on perovskite solar cells, which has been investigated experimentally. However, detailed theoretical research is still rare. This study presents a microscopic view to reveal the interaction mechanism between O 2 and perovskite based on the first-principles calculation. The results show that O 2 is adsorbed on the (100) surface of MAPbI 3 perovskite mainly by Van der Waals force. O 2 adsorption makes the MAPbI 3 surface generate a small number of positive charges, which leads to the increase of the work function of the MAPbI 3 surface. This is in agreement with the experimental measurement. And increased work function of MAPbI 3 surface is not beneficial to electron transfer from perovskite to electronic extraction layer (such as TiO 2 ). Comparison of the density of states (DOS) of the clean (100) surface and the adsorbed system shows that an in-gap state belonging to O 2 appears, which can explain the phenomenon observed from experiments that electron transfers from the surface of perovskite to O 2 to form superoxide. The theoretical power conversion efficiency of the system with and without O 2 adsorption is evaluated, and it turns out that the power conversion efficiency of the system with O 2 adsorption is slightly lower than that of the system without O 2 adsorption. This result indicates that avoiding the introduction of O 2 molecules between perovskite and electronic extraction layer is beneficial to the perovskite solar cell.

Nitric acid, an air pollutant with strong acidity and oxidizability, can be found in considerable quantities in the gas and aerosol phase. Understanding the role of nitric acid in atmospheric new particle formation is essential to study the complicated nucleation mechanism. Using density functional theory combined with the Atmospheric Clusters Dynamic Code (ACDC), the role of nitric acid in the formation of new particles has been investigated under different atmospheric conditions (different precursor concentrations and temperatures). The results show that nitric acid can form clusters with sulfuric acid and ammonia by hydrogen bond or even proton-transfer interactions. The concentrations of clusters involving nitric acid can be comparable with those of sulfuric acid-ammonia-based clusters, considering the thermodynamic stability combined with the realistic atmospheric concentrations of precursors. Within the atmospheric concentration range, nitric acid can enhance the formation rates of sulfuric acid-ammonia clusters, especially at low temperature, low sulfuric acid concentration and high ammonia concentration. In addition, the new particle formation mechanism indicates that nitric acid can contribute to the cluster formation and the role of nitric acid in the cluster formation pathway is as a "bridge" connecting the smaller and larger clusters.

Theoretical investigation on the reaction of maleic anhydride (MAH) in the UV radiation cross-linking process of polyethylene as high voltage cable insulation materials is accomplished at B3LYP/6-311 + G(d,p) level. The reaction potential energy information of 10 reaction channels is identified. The results show that the UV radiation cross-linking reaction of polyethylene is initiated by benzophenone, and the multi-functional crosslinker triallyl isocyanurate (TAIC) is needed to take part in the cross-linking process. The behavior of grafting the polar group MAH onto the polyethylene is explored in detail at atomic and molecular levels during UV radiation cross-linking process. The investigation is expected to provide reliable information for optimizing polyethylene UV radiation cross-linking process and for the development of the insulation material of high-voltage cable exceed 500 kV in real applications.

Chemical passivation implemented by Lewis base has been demonstrated as an effective method to overcome the water vulnerability of perovskite solar cells (PSCs) along with better performance. Comprehensive understanding of the surface passivation effects is crucial to future improve the PSCs efficiency and stability. Herein, we utilized first-principles to simulate the structure and electronic properties of the passivated perovskite, and carried out ab initio molecular dynamics (AIMD) to understand the effectiveness of the experimental passivation molecules, 2-MP, Py, and PTT, on the classical perovskite (Zhu et al., 2019). Calculations show that introducing both -SH and the N atom of 2-MP enhances the electric dipole moment, the binding strength, the adsorption probability and the carrier transfer rate compared to these of Py and PTT. Moreover, the efficient separation of electrons and holes at the interface and the large bandgap can be achieved by the 2-MP treatment, which is beneficial to improve the photovoltaic performance. AIMD simulations indicate that the interactions of N⋯Pb, S⋯Pb, and H⋯I between 2-MP and the MAPbI3 surface lead to a stronger passivation effect than that of Py and PTT, which is in agreement with the experimental observations. Our results are expected to provide new ideas for developing more distinguished passivation molecules to endow the PSCs stability against water.