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Biomolecule carrier systems based on metal–organic frameworks (MOFs) are highly promising owing to a high degree of structural tunability, high surface area, porosity, and higher chemical/thermal stability. UiO-66, one of the most stable Zr(IV)-based MOFs, has a pore aperture of 0.6 nm and a theoretical pore volume of 0.77 cm3 g−1, ideal for high storage capacity of biomolecule cargo; however, its potential to be implemented as an efficient carrier for fosfomycin is yet to be investigated. The UiO-66 nanocrystal, synthesized at room temperature, as a fosfomycin carrier was reported. Drug modulated synthesis (in situ encapsulation) and post-synthesis (adsorption/impregnation) were applied to incorporate fosfomycin in and/or on UiO-66 nanocrystals. We determined the effect of room temperature synthesis conditions on the structural properties of the UiO-66 nanocrystals as a functional carrier for fosfomycin. The incorporation of fosfomycin either by encapsulation or adsorption did not change the inherent crystal structure and UiO-66 nanocrystals retained their morphology. The addition of fosfomycin into the reaction medium led to an increase in the particle size from 127 ± 45 nm to 203 ± 52 nm. Our FTIR results indicated the development of a Zr–O–P connection due to the capture of drug molecules by adsorption. Antibacterial activity studies unveiled the drug concentration dependent bactericidal and bacteriostatic activities towards S. aureus and E. coli for fosfomycin loaded UiO-66 nanocrystals. Investigations with the help of density functional theory were performed to reveal the interaction mechanism between fosfomycin and UiO-66. Our theoretical findings indicated that fosfomycin strongly interacts with the metal center in the defected UiO-66 through its oxygen atom in the phosphite group with a Zr–O distance of 2.087 Å. Additionally, the energy of interaction for the adsorption process was found to have a large negative value of −74.3 kcal mol−1, which supports the strong interaction between the two systems. [ABSTRACT FROM AUTHOR]

The development of substantial, environment-friendly and low-cost electrocatalysts for an efficient oxygen reduction reaction (ORR) is essentially important for the production and storage of green energy which has sparked the curiosity of researchers for scalable production of metal-free electrocatalysts from biowaste. We report an easy transformation of chestnut-derived biowaste into reduced graphene oxide (rGO) and pyridinic-N-dominated nitrogen-doped rGO (NCS-rGO). The synthesized catalyst exhibits better ORR activity with an onset and half-wave potential of 0.93 V and 0.86 V, respectively, along with a high diffusion-limiting current density of 5.05 mA cm−2. Under alkaline conditions, we found that NCS-rGO shows an unusually high electrocatalytic activity that is superior to that of the commercial 20% Pt/C catalyst. More notably, the NCS-rGO-based ORR electrocatalyst manifests higher methanol tolerance, without deterioration in catalytic activity even in the presence of significant amount of methanol, outperforming the current state-of-the-art Pt electrocatalyst. Density functional theory (DFT) studies illustrate that pyridinic N is a decisive part of NCS-rGO to achieve the best ORR performance. [ABSTRACT FROM AUTHOR]

Cocatalysts are usually applied in the photocatalytic water splitting process to accelerate the kinetics of the hydrogen evolution reaction (HER). Specifically, the transition metal nitride (Mo2N) featuring a unique local surface plasmon resonance (LSPR) effect has exhibited great potential to function as a HER cocatalyst. However, the low metallicity of Mo2N hampers its ability to improve charge separation. To address this issue, transition metal atom doping (Co and Cu) engineering was used to modulate the electronic structure of Mo2N nanosheets to achieve a higher electrical conductivity and a lower hydrogen adsorption free energy (‖ΔGH*‖), thereby favoring the HER kinetics. Density functional theory (DFT) calculations and experimental results showed that Co-doping and Cu-doping mainly take place at Mo sites in the crystal structure of Mo2N to form stable structures of Co doped Mo2N (Co–Mo2N) and Cu doped Mo2N (Cu–Mo2N). Compared with pristine Mo2N, both Cu–Mo2N and Co–Mo2N demonstrated a much improved cocatalytic effect over g-C3N4 in promoting charge separation, accelerating HER kinetics and enhancing light absorption. The Co–Mo2N with the highest conductivity and lowest ‖ΔGH*‖ illustrated the best cocatalytic effect, and the H2 production performance (367.8 μmol g−1 h−1) of Co–Mo2N/g-C3N4 achieved was 10 and 5 times higher than those of Mo2N/g-C3N4 and Cu–Mo2N/g-C3N4. This paper provides significant guidance in the design and development of efficient cocatalysts for the HER application. [ABSTRACT FROM AUTHOR]

FOX-7 represents a class of promising candidates for the replacement of RDX because of its good sensitivity and comparable detonation properties to RDX. The design and synthesis of novel FOX-7 derivatives remains a focus. Herein, ten novel FOX-7-like energetic compounds were designed. The molecular structures, electronic properties, detonation properties and stabilities of the designed compounds were extensively evaluated based on density functional theory. Most of the designed compounds show superior detonation performance to that of FOX-7 or RDX. Compounds 2b (ρ = 1.872 g cm−3, D = 9113 m s−1, P = 37.3 GPa) and 2c (ρ = 1.895 g cm−3, D = 9054 m s−1, P = 36.7 GPa) are predicted to be the most promising energetic compounds among the designed compounds. The higher nitrogen content in the heterocyclic rings and more nitro groups in the designed molecules are the key factors for their enhanced detonation performance, while their intramolecular or intermolecular hydrogen bonds and better molecular planarity play an important role in stabilizing the structures. These results are expected to facilitate the experimental synthesis of these novel FOX-7-like energetic compounds. [ABSTRACT FROM AUTHOR]

In this study, oxidative degradation of Orange G (OG) and Eosin Y (EY) dyes with TiO2 as the catalyst was explored in air-equilibrated aqueous dispersions under UV light irradiation. To determine the optimal operating conditions for degradation, various effects were investigated, such as the pH of the dye dispersion, the addition of cationic surfactants and the specific additive. The photodegradation efficiency of both dyes was significantly enhanced at alkaline pH, particularly in the presence of tetraalkylammonium bromide surfactants, as they promote a mutual interaction between the dye and TiO2 surface, otherwise prevented due to their negative charge under basic conditions. The surfactant concentration also played an important role, because it influences the state of surfactant aggregation on the semiconductor surface. The kinetic trend of the fragmentation process was strongly affected by different hydrophobic and electrostatic interactions that OG and EY and their derivative intermediates are able to establish with surfactant/TiO2 in various forms of aggregation, as well as by their redox properties. Density functional theory (DFT) calculations of charge distribution and Gibbs free energy changes of solvation, performed on optimized molecular geometry, were useful to support and rationalize the surfactant involvement in the degradation process. [ABSTRACT FROM AUTHOR]

The magnetic properties of Zintl phase barium vanadium selenide (BaVSe3) were investigated experimentally and theoretically. BaVSe3, synthesized through a solid-state route, crystallized into a hexagonal structure with the space group p63/mmc. A secondary phase of barium selenide (BaSe3) was also formed during the synthesis along with BaVSe3. The BaVSe3 crystal system exhibited a Curie temperature (TC) of 40.81 K. Exotic magnetic phenomena like the glassy nature and the Griffiths-like phase were observed in BaVSe3 for the first time. The experimentally observed effective magnetic moment was less than the spin-only moment due to the nonmagnetic secondary phase. The crystal structure, lattice parameters, DOS, spin-polarized charge density calculations, TC and effective magnetic moment were theoretically studied using density functional theory (DFT) as implemented in Quantum ESPRESSO and via the atomistic simulation code VAMPIRE. DFT and atomistic simulations give an insight into the localization of magnetic moment on the V4+ ions, the metallic nature, and the occurrence of ferromagnetism in BaVSe3 which has been observed experimentally. [ABSTRACT FROM AUTHOR]

The oxidation of CO by N2O over M–porphyrin (M = Ti, Fe, Co, Ni, Cu, and Zn) catalysts has been investigated via density functional theory calculations. The whole reaction process is divided into two steps: the catalytic decomposition of N2O that breaks the N–O bond resulting in O–M active species, and the carbon atoms of the CO molecule reaction with O–M to form CO2. For the rate-controlled step of the reaction, the porphyrins of different metal centers appear in different positions. The barrier height of N2O decomposition on Ti–porphyrin is 3.8 kcal mol−1, and the barrier height of CO oxidation is 21.9 kcal mol−1. The rate-controlled step appears in the process of oxidation of CO. However, for Fe–porphyrin, the barrier height of N2O decomposition is 24.2 kcal mol−1, and the barrier height of CO oxidation is 11.4 kcal mol−1. The rate-controlled step appears in the process of N2O decomposition. For the catalytic decomposition of N2O, the Ti–porphyrin has a low activation energy barrier, which may be due to the smaller gap between the highest occupied molecular orbital (HOMO) of the metal porphyrin and the lowest unoccupied molecular orbital (LUMO) of N2O for Ti–porphyrin compared to Fe–porphyrin. [ABSTRACT FROM AUTHOR]

Real-time monitoring of intracellular pH is urgently required for studying cell metabolism and apoptosis. Carbon dot-based fluorescence probes are the most likely candidates to fulfil such an application, as they possess excellent chemical inertness, low cytotoxicity, high resistance to photobleaching, good biocompatibility, and tuneable emission wavelength. Our research program aims to develop tailor-designed red emissive carbon dots (r-CDs) using technology innovations in synthetic strategies. The r-CDs showing responses to pH were prepared through direct calcination of 1,2,4-triaminobenzene as the only carbon source. Measurements of fluorescent emission wavelength and quantum yield were carried out to optimize the carbonized temperature and heating time. The obtained r-CDs can sensitively respond to pH both in colorimetric and fluorometric modes, namely, with the increase of pH from 4.0 to 8.0, the color of the r-CD solution under ambient light changed from red to orange and then to yellow, and the corresponding fluorescence varied from purple to orange then to yellow under UV irradiation, which can be easily observed by the naked eye. Experimental characterization along with density functional theory (DFT) simulation study reveal that the pH response originates from the reversible transformation between azo and quinone structures during the protonation process. This solid-state preparation is not only simple in procedures and ready to scale up production, more significantly the resulting r-CDs exhibit a number of distinct advantages, and have great potential for biological sensing applications. [ABSTRACT FROM AUTHOR]

Dimethyldichlorosilane, which is the most important organic silicon monomer, can be prepared using a novel core–shell catalyst. However, the debate continues regarding its redistribution mechanism. In the current study, the redistribution mechanism catalyzed by the ZSM-5(5T)@MIL-53(Al) catalyst was theoretically studied via density functional theory on the level of M06-2X/def2-TZVP. Then, the catalytic performances of different active centers modified with AlCl3 were evaluated. The results showed that the active center of the former was Brønsted acid, while that of the latter modified by AlCl3 was Lewis acid. In addition, Lewis acid increased the catalytic activity in comparison with Brønsted acid. The calculations of activation energy, frequency vibrational analysis, bond order analysis, frontier molecular orbital theory, electronic localization function, and localized orbital locator analyses were in agreement with the said mechanism and results. [ABSTRACT FROM AUTHOR]

The electronic and nonlinear optical (NLO) properties of Al13-TCNQ/F4-TCNQ were systematically investigated using density functional theory methods. The Al13-TCNQ/F4-TCNQ complex has a high ionization potential of 7.51/6.71 eV and a strong binding energy of 1.93/2.39 eV, indicating its high structural stability. The stability of the complexes is confirmed through atom-centered density matrix propagation simulation at different temperatures up to 2000 fs. TCNQ/F4-TCNQ (electron donor) interacts with Al13 to form a charge-transfer framework, and F4-TCNQ is a stronger electron acceptor. A113-TCNQ and A113-F4-TCNQ complexes exhibit excellent NLO responses [static first and second hyperpolarizability (β0 and γ0), hyper-Rayleigh scattering coefficient (βHRS), frequency-dependent first hyperpolarizability β(−2ω; ω, ω) and β(−ω; ω, 0)], which are crucial evaluation indexes for designing NLO materials. The static and dynamic hyperpolarizability increases with the enhancement of the electron-acceptor capacity, for example, the β0 value of Al13-F4-TCNQ (92 275 au) is larger than that of Al13-TCNQ (76 720 au). The absorption spectrum reveals that these molecules have deep ultraviolet (UV) and infrared (IR) transparent regions, and hence are new UV and IR NLO molecules. Therefore, linking an Al13 cluster with TCNQ/F4-TCNQ is an effective strategy to design stable potential candidates for high-performance NLO molecules. [ABSTRACT FROM AUTHOR]

Hybridized local and charge-transfer (HLCT) is an attractive strategy for achieving efficient electroluminescence (EL) in electro-fluorescent devices, owing to the transformation of the triplet excited state (T) to the singlet excited state (S) via a reverse intersystem crossing that gives rise to a high exciton utilization efficiency exceeding the spin statistical limit. However, most efficient HLCT-based OLED devices are fabricated by high-cost vacuum deposition of the HLCT emitters. Herein, two new solution-processable HLCT fluorophores (CBFPhC and CBFTPA) based on benzothiadiazole (Bz) derivatives are designed and synthesized. The photoluminescence emissions of these two HLCT luminogens are experimentally and theoretically investigated using the solvatochromic effect and density functional theory calculations. Both molecules exhibit a high solubility, HLCT characteristics, and an intense yellow-green fluorescence with solid-state photoluminescence quantum yields of 77–79%. They are successfully employed as non-doped emissive layers in solution-processed double-layered OLEDs, which produce intense yellow-green emission colors with low turn-on voltages (3.0–3.2 V), high maximum luminescence (31 920 cd m−2), high maximum efficiencies (EQEmax = of 5.91%, PEmax = 13.29 lm W−1, and CEmax = 13.18 cd A−1), and decent efficiency low-off. [ABSTRACT FROM AUTHOR]

A heterochiral diphenylalanine auxin derivative has exhibited remarkable mechanical strength and antimicrobial propensities at room temperature (N. Khan, A. Gupta, V. Shivhare, R. Ahuja, M. Varshney, A. Basu, and A. Dutt Konar New J. Chem., 2022, Just Accepted) (hydrogelators I–II). To explore the impact of stereogenicity on the aromatic/non-aromatic amino acid residues on these dimensions, herein we report the design and development of hydrogelators III–V, with varied chiral centers, that immobilized physiological buffer at room temperature, in a fashion akin to that of hydrogelators I–II. Interestingly, our rheological experiments demonstrated that the mechanical integrity of the heterochiral hydrogelator III, containing hydrophobic amino acid Leu, as a replacement residue in diphenylalanines, is much higher in comparison to that of the homochiral diphenylalanine analogs (hydrogelators IV–V). To reinforce this observation, we performed density functional theory (DFT) calculations with the hydrogelators. Our investigations illustrated that the cause of such high mechanical integrity might be due to the antiparallel orientation of naphthyl units and the Leu(1) sidechain of hydrogelator III, unlike other homochiral hydrogelators IV–V, where the phenylalanine(1)/naphthyl rings are perpendicularly organized. Overall, studies indicate that the inclusion of appropriate chiral residue at a relevant position in the sequence enlightens a rational strategy towards regulating the mechanical strength of the hydrogels, optimized for need-based applications. The conformational and morphological analysis suggested the presence of β-sheet-like structures stabilized by intermolecular hydrogen bonding. Surprisingly hydrogelator III was found to be selective towards Gram-positive microorganisms, namely Staphylococcus aureus and S. mutans, and inactive against Gram-negative Escherichia coli and Klebsiella pneumoniae. However, the homochiral derivatives showed no particular preference for exhibiting antibacterial action. Also, the anti-fungal behavior towards C. albicans and A. niger and the anti-inflammatory response in matrix metalloproteinase receptors were found to be significantly affected by chirality. Thus, our efforts focus on how chirality in the peptide sequence has a profound impact on gelation strength, potency, and selectivity. Indeed, this work establishes innovative design principles for the development of efficient therapeutics with the ability to address the challenges arising due to microbial infections as well as inflammations collectively in one shot. [ABSTRACT FROM AUTHOR]

Herein, density functional theory was used to study the isomerization mechanism of azobenzenesulfonamide at the ωB97XD/6-31G(d) level. The similarities and differences among the isomerization of single- and bi-molecular azobenzenesulfonamide derivatives with silicon substrates are discussed. The calculated results show that azobenzenesulfonamide (PhN1＝N2SO2NH2Ph) has two rotation-assisted inversion isomerism modes: N1 inversion and N2 inversion. These two isomerization pathways are closely related to the substituents on the benzene ring connected to the N1 atom. The stronger the electron-withdrawing ability of the substituent, the easier it is for the N1 inversion to occur. In addition, the cis–trans isomerization mechanism of a single molecular azobenzenesulfonamide derivative with a silicon substrate is similar to that without a silicon substrate. However, the isomerization pathway of a bi-molecular azobenzenesulfonamide derivative on a silicon substrate is different from that of single-molecule isomerization. Among them, the first molecular functional group of azobenzenesulfonamide undergoes N2 inversion, the second molecular functional group then adopts the N1 inversion mode, and the free energy barriers of isomerization of the two molecular functional groups are 26.88 and 13.99 kcal mol−1, respectively. This may be related to the steric hindrance of the groups in the conversion isomers. Interestingly, compared to the isomerization of the first and second azobenzenesulfonamide molecular functional groups, the energy barrier of the second group is significantly reduced. This will provide theoretical insights into the design of azobenzene and the action of its derivatives as molecular switches in polymerization systems. [ABSTRACT FROM AUTHOR]

A highly sensitive, reversible, reusable and fluorogenic "turn-on" probe (HBTC) is fabricated for the sole detection of Al3+. On incremental addition of Al3+ in a solution of HBTC in ACN : H2O (4 : 1), a sharp "turn-on" emission enhancement is observed at 480 nm. The reversibility of the probe (HBTC) was displayed on the addition of F− solution. The detection limit is found to be of the order of 10−9 M which suggests that HBTC can detect Al3+ at a very minute level. The mechanism for Al3+ detection in ACN : H2O (4 : 1) is attributed to forbidding C＝N isomerization and ESIPT process simultaneously turning on the chelation-enhanced fluorescence process. The reusability and real-time application of the probe are also studied. Bioimaging study reveals that HBTC can detect Al3+ in human breast cancer cells (MDA-MB-231). Electronic structure of the probe is explained by density functional theory. [ABSTRACT FROM AUTHOR]

In order to elucidate a detection mechanism of a photo-induced electron transfer (PET)-type fluorescent sensor for water, we have synthesized anthracene-(aminomethyl)-4-cyanophenylboronic acid (AminoMeCNPhenylB(OH)2) TF-2 by the deprotection of pinacol ester (Pin) of anthracene-AminoMeCNPhenylBPin OF-2. For OF-2, the PET takes place from the nitrogen atom of the amino moiety to the photoexcited fluorophore (anthracene) skeleton in the absence of water, leading to fluorescence quenching (PET active state). When water was added to the OF-2 solution, a drastic enhancement of the fluorescence emission is observed due to the formation of the PET inactive (fluorescent) species OF-2W or OF-2WH by interaction with water molecules which has been determined by 1H NMR spectral measurements. On the other hand, even in the absence of water TF-2 exhibits intense fluorescence emission and addition of water to the TF-2 solution shows a negligible change in the fluorescence intensity. The 1H NMR spectra of the TF-2 solution without the addition of water clearly indicated the formation of the PET inactive (fluorescent) species TF-2H by the intramolecular OH⋯N hydrogen bonding between the hydroxyl group of the B(OH)2 moiety and the nitrogen atom of the amino moiety. For TF-2, single-crystal X-ray structural analysis as well as density functional theory (DFT) calculations revealed the existence of the intramolecular OH⋯N hydrogen bonding, that is, the formation of TF-2H. Interestingly, the 1H NMR spectra of the TF-2 solution with the addition of water showed the existence of the PET inactive (fluorescent) species TF-2W or TF-2WH by interaction with water molecules, as with the case of OF-2. Consequently, it was found that for the PET-type fluorescent sensor based on the anthracene-AminoMeCNPhenylBPin structure, the BPin moiety is essential not only to activate the PET in the absence of water, leading to fluorescence quenching, but also to form the PET inactive (fluorescent) species upon the addition of water. This work provides a direction in molecular design toward creating an effective PET-type fluorescent sensor for water as well as a conclusive detection mechanism of the anthracene-AminoMeCNPhenylBPin structure for water. [ABSTRACT FROM AUTHOR]

Li–CO2 batteries have attracted close attention due to their ability to simultaneously store energy and capture CO2. The development of suitable catalytic cathodes plays a decisive role in promoting the electrochemical performance of Li–CO2 batteries. Herein, an electrocatalytic cathode material based on oxygen-decorated CoP nanosheets is reported. Benefiting from the enhanced electrical conductivity brought about by the presence of P element, the construction of catalytically active sites brought about by the presence of Co–O bonds, and the full exposure of catalytically active sites brought about by the two-dimensional morphology, Li–CO2 batteries exhibit good cycling characteristics (>1000 h) and excellent discharge capacity (13 200 mA h g−1). Density functional theory (DFT) calculations demonstrate that the efficient construction of O–Co–P bonds is the key to improving the performance of electrocatalytic cathodes. This provides an effective reference for the subsequent development of efficient catalytic cathodes. [ABSTRACT FROM AUTHOR]

This work presents a theoretical study of the interaction between carbon nanotubes (CNTs), boron nitride nanotubes (BNNTs) and gallium nitride nanotubes (GaNNTs) with the pollutant diamines cadaverine and putrescine, using density functional theory (DFT) as implemented using SIESTA. For this purpose, we analyzed the structural, energetic and electronic properties of (10,0) nanotubes with cadaverine and putrescine adsorbed, respectively, on their external surfaces. From the results, two important conclusions were inferred: (i) the CNTs and BNNTs interacted with both molecules through a moderate adsorption process, making spontaneous desorption not so difficult; (ii) the GaNNTs interacted very strongly with both molecules through a chemical adsorption process, which makes the desorption process difficult. Overall, our results are promising for the use of BNNTs in environmental applications, such as pollutant sensors for detecting selectively cadaverine in the presence of putrescine molecules. [ABSTRACT FROM AUTHOR]

Two-dimensional nanomaterials of Ni–Al layered double hydroxide nanosheets (Ni–Al-LDH-NS) were fabricated using an exfoliation process with formamide as the pillaring agent. XRD, FT-IR, LRS, N2 adsorption–desorption, XPS, and SEM were used to study their structure and morphology. The adsorption of ethyl mercaptan (EM) on Ni–Al-LDH-NS was investigated by an adsorption experiment on a fixed bed adsorption apparatus and density functional theory calculations (DFT). The characterization analysis indicates that Ni–Al-LDH-NS presents a uniform sheet structure with a specific surface area of 266.94 m2 g−1. An EM breakthrough adsorption capacity up to 229.95 mg g−1 was found in the absorption experiment using the Ni–Al-LDH-NS. DFT calculations indicate that EM is mainly adsorbed on Ni–Al-LDH-NS through coordination bonds, in which the S → Ni coordination bond plays a major role, and its coordination bonds interact with the Ni 3d orbital through the S 3p orbital. In addition, differences in adsorption performance between Ni–Ti-LDH-NS and Ni–Al-LDH-NS were investigated via studying host–guest interactions and structural properties. [ABSTRACT FROM AUTHOR]

Dicalcium phosphate dihydrate (DCPD) and octacalcium phosphate (OCP) particles have been widely recognized as precursors for synthesizing hydroxyapatite (HAp), the main mineral found in bone tissues. In this regard, we demonstrated a novel approach for biomimicking DCPD and OCP biocomposite particles in the hydroxylpropyl methylcellulose (HPMC) biopolymer using single and double diffusion gel techniques. Hybrid biocomposite aggregates were collected and characterized by infrared spectroscopy (IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and scanning pyroelectric microscopy (SPEM). We also conducted density functional theory (DFT) calculations to unravel interactions among HPMC and ionic species by determining the optimized structures, bond lengths and sigma. SEM showed different morphologies of DCPD/HPMC and OCP/HPMC biocomposite particles from highly porous spheres and nano-platelets to plate-shaped biocomposites. We also demonstrated that the HPMC biopolymer was entrapped within the biocomposite particles after the demineralization process. We found that different parameters influenced the generation of calcium phosphate/HPMC biocomposites including ion concentration and the type of diffusion method. In addition, HPMC was able to change the morphology of particles from crystal shapes to porous aggregates and spheres of DCPD/HPMC and OCP/HPMC biocomposites. This study may suggest that HPMC, as a high molecular-weight polysaccharide, is a potential candidate for bone tissue regeneration. [ABSTRACT FROM AUTHOR]

Molecular engineering of high-performance non-fullerene acceptors (NFAs) is critical to enhance the power conversion efficiencies (PCEs) of bulk heterojunction organic solar cells (BHJ OSCs). In this work, density functional theory (DFT) and time-dependent DFT are employed to investigate the effects of π-bridge engineering on the photoelectric performance of high-performance NFA Y6. This π-bridge engineering principally involves (1) inserting different types of π-bridge units between the fused-ring core and the terminal unit of Y6, and then the π-bridge unit with better performance is screened for the next study, (2) inserting different numbers of screened π-bridge units between the fused-ring core and the terminal unit of Y6, and (3) modifying the side chains of the screened π-bridge unit with halogen atoms. Theoretical results predict that the selenophene π-bridge has superior properties in terms of dipole moment, exciton binding energy, and light absorption compared with other π-bridge units. In addition, studies on different numbers of selenophene π-bridges suggest that increasing the number of selenophene π-bridges has significant advantages in enhancing light absorption and electron transport capabilities for enhancing the short circuit current density (JSC). Meanwhile, the study of π-bridged side chains substituted with different halogen atoms indicates that the substitution of halogen atoms can play a significant role in reducing the exciton binding energy and raising the transferred charge amounts. The results obtained in this work are expected to be used to design new Y6 derivatives. [ABSTRACT FROM AUTHOR]

A novel luminescent isoreticular metal–organic framework Zn4O(ECMTDC)3·10DMF (Cz-MOF-1), where ECMTDC denotes 3-(9-ethyl-9H-carbazol-3-yl)-4-methylthieno[2,3-b]thiophene-2,5-dicarboxylate and DMF denotes N,N-dimethylformamide, was successfully synthesized via solvothermal methods from Zn(NO3)2·6H2O and H2ECMTDC in DMF. Powder X-ray diffraction experiments along with scanning electron microscopy images indicate that Cz-MOF-1 has excellent water stability compared with other Zn4O-based MOFs, which can be attributed to the hydrophobic surroundings around the Zn4O clusters formed from N-ethylcarbazolyl and methyl groups. Cz-MOF-1 displays a strong deep blue light emission (452 nm) and a quantum efficiency of 3.74%, and has high selectivity and sensitivity for the detection of Fe3+, Cr2O72− and DCN. Furthermore, the possible luminescence sensing mechanisms have been discussed in detail, which are supported by PXRD analysis, UV-vis spectroscopy and density functional theory (DFT). [ABSTRACT FROM AUTHOR]

Triplet potential energy surfaces, for phosphorescent materials, play a predominant role in determining the radiative and non-radiative decay processes. It is significant and meaningful to explore a promising strategy to control the triplet potential energy surface. In this article, the influence of substituents on the triplet potential energy surface was investigated with the help of density functional theory. In addition, the triplet potential energy surfaces of bimetallic Pt(II) complexes were also explored. The investigated results indicate that for the monometallic Pt(II) complexes, the adiabatic triplet energies of T bent1 are located at near 68.66 kcal mol−1. That is, when the adiabatic triplet energy is lower than 68.66 kcal mol−1, by at least 7.22 kcal mol−1, the triplet potential energy surface is constructed with the T planar1 configuration. In contrast, the triplet potential energy surface consists of T planar1 and T bent1 configurations. Thus, it can be regarded as a criterion used to judge the composition of the triplet potential energy surface. In addition, because the HOMO–LUMO energy gaps can be controlled by adding various substituents, the corresponding adiabatic triplet energies can also be tuned. Compared with monometallic Pt(II) complexes, both the T1A and T1B excited states of bimetallic Pt(II) complexes exhibit the planar configuration and the energy differences between T1A and T1B are 12.42 and 12.56 kcal mol−1, facilitating high phosphorescence quantum yields. Moreover, the large energy barrier of the temperature-dependent non-radiative decay process and small spin–orbit coupling matrix elements between T1 and S0 lead to a small non-radiative rate for the bimetallic Pt(II) complex. The results presented here are helpful in addressing the designed strategies as they show that the properties of the triplet potential energy surfaces for mono- and bimetallic Pt(II) complexes can be appropriately tuned. [ABSTRACT FROM AUTHOR]

In order to exploit novel light-driven molecular switches, a series of pyrazolyazoindole photoswitches was designed and synthesized via modifying the nitrogen atoms of indole, and three typical title compounds were characterized via single crystal X-ray diffraction. Herein, UV-vis and NMR spectroscopy studies were used to confirm that the photostationary state (PSS) proportions of the desired conformations were in the ranges of 59–95% and 74–92% for PSStrans and PSScis, respectively. The thermal half-lives of the photoswitches ranged from a quarter of a day (6 h) to more than a week (231 h) depending on differences in the substituents at the R1 position. Density functional theory (DFT) calculations were applied to further explain the experimentally observed photochemical properties, such as differences in the spatial structures of the trans and cis isomers of azo switches and the relationships to thermal relaxation in the dark and the photoisomerization yields of pyrazolyazoindoles. Finally, the potential use of pyrazolyazoindole photoswitches for biological applications was verified. A bifunctional model photoswitch (C1) was successfully synthesized and it almost entirely inherited the photoswitching properties of these excellent azo switches. [ABSTRACT FROM AUTHOR]

Coronene-based quantum dots have theoretically been investigated as potential carriers for the loading and controlled release of the doxorubicin (DOX) drug. Density functional theory calculations were performed to explore the role of oxygen and amine functional groups, as well as the effect of the size on the drug delivery performance of quantum dot carriers. To this end, five coronene-based carriers with different sizes and functional groups were selected for the delivery of the DOX drug. The enthalpy changes indicate that the adsorption of DOX over the examined coronenes is energetically favorable. The mechanistic details and the nature of the DOX–carrier interactions have been surveyed by non-covalent interactions and energy decomposition analyses. Moreover, charge decomposition analysis has also been utilized to investigate the electron transfer among the fragments during complex formation. After the DOX adsorption, simultaneous quenching and a red-shift in the fluorescence spectrum of the carriers imply that the designed drug delivery systems can be tracked by fluorescence imaging. We have also studied the release of the drug by a stimulus such as pH gradient or negative charge injection. The sensitivity of the DOX/carrier toward charge and pH is promising for developing efficient tumor-targeting drug delivery. [ABSTRACT FROM AUTHOR]

4-(3,5-Di-tert-butyl-2-hydroxyphenylamino)-N-(6-methoxypyridazin-3-yl)benzenesulfonamide (LSOAPH2) is an 2-aminophenol-appended, redox-non-innocent molecule. It was characterized structurally by spectroscopy and its structure was confirmed by single-crystal X-ray diffraction. The o-iminosemiquinonate monoanion (LSOISQ) was obtained by one electron-oxidation and confirmed by electron paramagnetic resonance (EPR) spectroscopy and UV-vis spectroscopy. Cyclic voltammetry showed two consecutive redox couples: o-amidophenolate/o-iminosemiquinonate monoanion (LSOAPH2/LSOISQ) and o-iminosemiquinonate monoanion/o-benoquinone (LSOISQ/LSOIQ). The radical features of LSOISQ in air were supported by EPR spectroscopy (g = 2.005) in a solution at room temperature. Computation based on density functional theory revealed the spin density to be localized on LSOISQ due to formation of the o-iminosemiquinonatemonoanion radical. The in vitro toxicity of LSOAPH2 and LSOISQ was estimated against human cancer cell lines (HepG2, MDA-MB 231, HeLa) and a human normal cell line (WI-38). The cellular metabolic activity of LSOAPH2 and LSOISQ were determined using the MTT assay using the cell lines stated above. LSOAPH2 and LSOISQ enhanced cellular levels of reactive oxygen species in human cancer cell lines, which culminated in the inactivation/death of cancer cells. LSOISQ was more effective than LSOAPH2 as an anticancer agent. [ABSTRACT FROM AUTHOR]

In this paper, a series of stable Sn-containing heteroaromatic conjugated oligomers, dialkyl dithieno[3,2-b:2′,3′-d]stannole (DTSn) and stannafluorene (SnF) derivatives, were designed and synthesized employing a new synthetic route. The distinctive feature of this route is that terminal groups are linked to the backbone before the stannole cycle closed, which can avoid the cleavage of stannole in the Stille reaction. Three Sn-heteroaromatic small molecules, DTSn-1, SnF-1 and SnF-3, have been obtained and characterized. The density functional theory (DFT) calculations show that the alkyl groups are further displaced from the conjugated backbone due to the larger atomic radius of Sn, which allows a stronger π-stacking interaction to occur. Interestingly, the fluorescence intensity of DTSn-1 is increased in the presence of Al3+ due to interaction between Al3+ and Sn. However, the emissions of the three Sn-containing oligomers can be quenched by Ru3+, which renders these compounds potential candidates as fluorescence detectors for Ru3+. [ABSTRACT FROM AUTHOR]

In this paper, the excited-state proton transfer (ESPT) of 7-hydroxyquinoline (7HQ) in hydrogen-donating methanol (MeOH) was investigated theoretically. The change in the calculated primary bond lengths and the infrared spectra of the 7HQ–(CH3OH)3 configuration from the S0 state to the S1 state testify that the intermolecular hydrogen bonds were strengthened in the S1 state. Therefore, we propose two proton transfer (PT) types in which the ESPT reaction occurs along the hydrogen-bonded bridge O7…H8–O9 (Type-A) or N1…H2–O3 (Type-B). The normal Stokes shift and the large Stokes shift suggest the existence of the enol form 7HQ–(CH3OH)3 and the keto form 7HQ–(CH3OH)3-PT, respectively, and thus that the proton transfer can occur in the excited-state. In order to further study the details of the complicated multiple proton transfer of the 7HQ–(CH3OH)3 cluster, we scanned the potential energy curves for the ground state (S0) and the excited state (S1) of the hydrogen-bonded 7HQ–(CH3OH)3 complex along with the hydrogen-bonding coordinate (distance of the H2–O3 and H8–O9 bonds). The results show the close barrier height between Type-A (5.35 kcal mol−1) and Type-B (6.65 kcal mol−1), which indicates that the two possible PT types may co-exist and have competition between themselves. [ABSTRACT FROM AUTHOR]

This paper describes the synthesis, properties and crystal structure of a new phosphonium-1-indenylide ligand, 4,7-dimethyl-1-C9H4PMePh2, and the syntheses of complexes of rhodium(i) and iridium(i) containing both the parent PHIN ligand, 1-C9H6PMePh2 (I) and 4,7-dimethyl-1-C9H4PMePh2 (II). The complexes [M(η4-COD)(η5-PHIN)]X (M = Rh, Ir; PHIN = I, II; COD = 1,5-cyclooctadiene; X = Cl, BF4) and [Rh(η5-I)(PPh3)2]BF4 have been prepared and characterized by HR-ESM, elemental analyses and NMR spectroscopy. While [Ir(η4-COD)(η5-I)]Cl undergoes one or more chloride-induced exchange processes involving the COD ligand, the analogous complexes of rhodium and iridium with the more weakly coordinating BF4− counter anion exhibit no exchange processes. In contrast, [Rh(η5-I)(PPh3)2]BF4 undergoes an exchange process involving the inequivalent PPh3 phosphorus atoms and which is rationalized using DFT calculations. [ABSTRACT FROM AUTHOR]

Nickel cobalt selenide presents a typical Faraday charge storage mechanism, but its electrochemical performance is limited due to its poor reaction kinetics. As a common defect type, vacancy defects can eliminate the limitations of intrinsic chemical and structural characteristics, thereby improving the reaction kinetics of the electrode. Herein, we report a Va-NiCo2Sex nanomaterial with adjustable Se vacancy concentrations achieved by NaBH4 induction, realizing an enhancement of the performance of the supercapacitor. This adjustment of vacancy concentrations can not only essentially regulate the adsorption site and ion valence state and enhance the adsorption capacity and redox activity of ions, but also reveal the significant improvement of vacancy modification on the surface reaction kinetics of electrode materials through density functional theory (DFT) calculation. The electrochemical results show that the V2-NiCo2Sex electrode material with optimal vacancy concentrations has the highest specific capacity of 310.8 mA h g−1 at 1 A g−1. The assembled hybrid supercapacitor V2-NiCo2Sex//AC-HSC can provide a high energy density of 76.5 W h kg−1 at a power density of 800.1 W kg−1. This work provides an effective strategy for exploring the structure–function relationship between vacancy concentrations and electrochemical performance. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitride (h-BN) has received extensive attention due to its potential applications in electronic devices, but the growth mechanism of h-BN remains unclear. Here, the stability of various h-BN edges terminated by isolated Ni atoms on the Ni(111) surface was investigated by density functional theory (DFT) calculations. Our results show that most edges terminated by isolated Ni atoms have lower energies than those passivated by the Ni(111) surface, and that the zigzag edge terminated with nitrogen atoms (ZZN) is the most stable one. Combined with Wulff construction theory, we predict that the equilibrium morphology of h-BN domains is likely to be triangles enclosed by ZZN edges in N-rich environments, while the triangles are enclosed by ZZB edges in B-rich environments. An in-depth understanding of the stability of h-BN edges terminated by isolated Ni atoms on the Ni(111) surface is crucial to reveal the growth mechanism. Therefore, it should provide valuable information for controlling the morphology of h-BN domains in experiments and provide useful perspectives for the synthesis of other two-dimensional binary materials. [ABSTRACT FROM AUTHOR]

In this work, a first-principles study of Na2O and K2O monolayers and their Janus structure has been carried out using density functional theory calculations based on the projector-augmented plane wave method. Good structural stability is confirmed by phonon dispersion curves and formation enthalpy. The formation of the NaKO monolayer starting from either Na2O or K2O is analyzed via the surface formation energy method. The experimental feasibility with the exothermic synthesis process is demonstrated, mostly in Na-poor or K-poor conditions. Na2O and NaKO monolayers are direct gap semiconductors with band gaps of 0.97 (1.97) and 0.51 (1.21) eV, respectively, as calculated using the PBE (HSE06) functional. Meanwhile, the K2O monolayer exhibits an indirect gap semiconductor character with an energy gap of 0.52 (1.28) eV. The ionic nature is also confirmed by means of the projected density of states and charge density difference. In addition, the 2D materials studied herein exhibit good absorption in a wide energy range from the visible to ultraviolet region with large absorption coefficients of the order of 105 (cm−1), indicating their potential to be applied in optoelectronic devices. [ABSTRACT FROM AUTHOR]

The Overman rearrangement is a very useful C–N bond forming reaction described for the first time in 1974. This transformation allows a chirality transfer with an excellent predictible induction, starting from a configurationally pure allylic alcohol, yielding in only one step an amide moiety, via a [3,3]-sigmatropic rearrangement of an intermediate imidate. A recent valuable extension was developed by Chida and co-workers on orthoamide structures starting from allylic vicinal diols, avoiding time consuming protections. However, this attractive modified approach suffers generally from elevated temperatures, long reaction times and sometimes disappointing yields. To bridge this gap, we have carried out a combined experimental and theoretical study with the aim of elucidating the structures and the reactivities of these orthoamides. In order to rationalize the experimental results, it was first fundamental to identify the actual reactive species. The reactivity of these orthoamides was then investigated. Theoretical calculations using density functional theory (wB97X-D/Def2TZVP method) were then performed in the gas phase at 453 K to characterize the relevant chemical species (conformers of orthoamide diastereoisomers, prereactive complexes, and transition states structures) and to estimate the free energies of activation. The role of temperature has also been taken into consideration at 298 K and 373 K in comparison with 453 K. A major contribution of the theoretical part of this study has been to show that the reactivity of orthoamides in the Overman rearrangement crucially depends on diastereoisomers present in the reaction media. Molecular simulation has allowed us to clarify the reasons behind the temperature requirements and the reaction time, tentatively helping chemists to understand their troubles in orthoamide Overman rearrangement. [ABSTRACT FROM AUTHOR]

The possible mechanisms and the origin of regioselectivity of the N-heterocyclic carbene (NHC)-catalyzed double acylation reaction of aromatic 1,2-diketones with α,β-unsaturated ketones have been theoretically studied using density functional theory. Two regioselective pathways associated with the attack on the acetyl carbon or benzoyl carbon by NHC have been discovered, and the attack pathway to the acetyl carbon has been identified as the main pathway. The most energetically favorable pathway has been confirmed to contain several steps: nucleophilic addition of NHC, intramolecular migration of the p-chlorobenzaldehyde group, Michael addition of functional enamine to ketene, the formation of a five membered ring, and dissociation of NHC. The Michael addition forming a C–C bond is the rate-determining step. Moreover, the origin of regioselectivity has also been explored based on the detailed mechanistic cycle and the analyses of local electrophilic and nucleophilic indexes. [ABSTRACT FROM AUTHOR]

Low-dimensional organic–inorganic metal halides have shown great application potential and new opportunities for use in solid-state lighting due to their excellent optical and electronic properties. However, the most studied hybrid compounds contain lead, which limits their application environments. The preparation of organic–inorganic metal halides with high luminous efficiency, long-term stability, and a lead-free composition for environmental protection has become an important goal for the design of materials. Here, novel Sb3+-doped indium-based metal halides, (CH3NH3)4InCl6·Cl, have been designed and synthesized via a simple mechanical ball milling method; in the lead-free zero-dimensional (0D) halide (CH3NH3)4InCl6·Cl, isolated [InCl6]3− octahedra are separated by methylamine cations. Under UV excitation, the bulk-phase powder exhibits broadband orange-yellow emission peaking at 607 nm with a full width at half-maximum of ∼160 nm upon incorporating Sb3+ into the (CH3NH3)4InCl6·Cl matrix. The photoluminescence quantum yield (PLQY) of Sb3+-doped (CH3NH3)4InCl6·Cl is as high as 67.72%. The effects of the Sb3+-doping concentration on the crystal structure and optical characteristic have been investigated. The indirect band gap characteristics of (CH3NH3)4InCl6·Cl were demonstrated via density functional theory (DFT) calculations, and the relatively wide band gaps of 3.83 eV and 2.99 eV of (CH3NH3)4InCl6·Cl and (CH3NH3)4ClInCl6:Sb3+ were experimentally determined. These experimental results suggest that the as-prepared Sb3+-doped (CH3NH3)4InCl6·Cl has potential applications in solid-state lighting devices. [ABSTRACT FROM AUTHOR]

Density functional theory calculations were performed to investigate the mechanism, regioselectivity, and resonance and inductive effects in methylation of nitronate reactions in the gas-phase and in solutions (water, DMF, and CCl4). The vinylogue extrapolation (VE) approach calculates the resonance effect contributions (ΔEres) to be −21.79 and −48.53 kJ mol−1 for C-methylation and O-methylation in the gas-phase, respectively, while the inductive effect (ΔEind) was calculated to increase the reaction energy barrier (E‡) by −33.41 and −44.86 kJ mol−1 for the C-methylation and O-methylation pathways, respectively. The larger values of ΔEres and ΔEind for O-methylation suggest that both of these effects serve to increase the E‡ for O-methylation more than they do for C-methylation, therefore explaining the regioselectivity towards C-methylation. The polar solvents reduce the E‡ for O-methylation; however, they do not reverse the regioselectivity. [ABSTRACT FROM AUTHOR]

A novel bismuth/cerium oxide/reduced graphene oxide (Bi/CeO2/rGO) platform was prepared on an FTO electrode via an in situ electrochemical deposition method, which was employed for the detection of Pb2+. The differential pulse anodic stripping voltammetry (DPASV) results demonstrated that the Bi/CeO2/rGO/FTO sensing platform exhibited good electroanalytical performance. The linear calibration curve for Pb2+ ranged from 0.001 to 2 μM with a detection limit of 0.00045 μM (S/N = 3). The resulting data were compared with some other reported sensors. The present electrochemical sensor possessed high sensitivity, anti-interference ability, stability and reproducibility for the detection of Pb2+. The improved Pb2+ sensing performance was attributed to the synergetic effect, where rGO was employed as a supporter to improve electron transport and CeO2 was used to increase the stability of rGO and prevent the re-stacking of rGO. Calculations based on density functional theory (DFT) revealed that the Bi/CeO2/rGO/FTO possessed lower Gibbs free energy for the detection of Pb2+ in comparison with the rGO/FTO and CeO2/rGO/FTO, which might further explain the improved sensitivity of the Bi/CeO2/rGO/FTO electrode. The proposed Bi/CeO2/rGO/FTO sensing platform was relatively facile, nontoxic and low-cost. Consequently, it was successfully applied for the analysis of Pb2+ in actual water samples. [ABSTRACT FROM AUTHOR]

A comprehensive density functional theory study has been performed on the mechanism of Cp*Rh(III)-catalyzed C–H activation of N-(pivaloyloxy)acrylamide with alkynyl triazene. The calculated results reveal that a concerted Lossen rearrangement/OPiv migration from N to Rh is the most favorable pathway to afford an isocyanate intermediate, where a redox-neutral process is involved without the involvement of a Rh(V)-nitrenoid species. Subsequently, the annulation of a rearranged six-membered ring intermediate is realized through a nucleophilic attack of Rh-bonded carbon on the isocyanate carbon, and this process is likely to be the rate-determining step for the entire catalytic cycle, with an overall energy barrier of 20.5 kcal mol−1. In addition, the stepwise OPiv migration from N to Rh and C–N reductive elimination, and vice versa, are competitive to yield a non-rearranged byproduct, which experiences a Rh(III)–Rh(V)–Rh(III) transformation of oxidation state. [ABSTRACT FROM AUTHOR]

A distinct S-scheme heterojunction 0D/3D CeO2/Bi2O2CO3 photocatalyst was successfully synthesized by a hydrothermal method for the photocatalytic degradation of methylene blue (MB), tetracycline (TC) and aureomycin (AM). Compared with bare Bi2O2CO3 and CeO2, CeO2/Bi2O2CO3 possesses admirable photodegradation capacity. Additionally, the influence of the molar ratio of CeO2 in the compounds was also discussed, and the optimal molar ratio was identified as 15% (nCe/nBi), for which the photodegradation of MB reaches 98% in 120 min with light irradiation. Favorable retrogradation effects were achieved in the photodegradation of TC and AM. Furthermore, UV–vis diffuse reflectance spectroscopy revealed that the absorption range of solar illumination was successfully expanded to the visible light range for the CeO2/Bi2O2CO3 composites (with a molar ratio of 15%). Besides, based on photoelectrochemical detection, active species capture experiment and density functional theory (DFT), the constructed catalyst conforms to a step-scheme (S-scheme) heterojunction charge transfer mechanism. The satisfactory degradation activity and the outstanding solar light response performance benefit from the driving force in the space separation of photogenerated carriers, optimized energy band structure and high-quality redox capacity. It is speculated that the novel CeO2/Bi2O2CO3 composite would have broad application prospects in the degradation of organic contaminants. [ABSTRACT FROM AUTHOR]

In this work, we have manually constructed several single-walled carbon nanotube supported single metal atom (Al, Zn, Fe) catalysts (Al-SWCNTs, Zn-SWCNTs, Fe-SWCNTs) and employed them to catalyse the synthesis of hydrogen peroxide with the aid of density functional theory calculations, in which several water and oxygen molecules are included as reactants. Specifically, three different possible reaction pathways are studied in detail and relevant reactants, transition states, and products are optimized. Their activation energies are compared with each other, based on which the optimal reaction path is selected and the possible side products are also discussed. In addition, we have also calculated the relevant electron densities and densities of states of these three catalysts to help reveal the different effects after introducing different metal atoms. These physical properties are possibly related to their catalytic performances. Our results are not only consistent with previous experiments investigating the catalyzing reaction using Zn-SWCNTs, but also predict the catalytic properties of Al-SWCNTs and Fe-SWCNTs in comparison with Zn-SWCNTs. [ABSTRACT FROM AUTHOR]

We report the relative stabilities, structural properties and ferroelectric properties of different polymorphs of BiMO3 (M = Al, Ga, In) in the framework of density functional theory (DFT). We compared several exchange–correlation functionals at different levels of DFT. This includes a local density approximation (LDA), different forms of a generalized gradient approximation (GGA) and a meta-generalized gradient approximation (meta-GGA), as well as hybrid functionals. First, we calculated the structural, electronic, and ferroelectric properties of the ground state phases of BiMO3. We compared our results with the experimental data. We found that AM05, MS0, and SCAN functionals improved the values of structural parameters at a same level of accuracy as the hybrid HSE functional. Next, we analyzed the relative stabilities of 16 BiMO3 polymorphs. We found that only two meta-GGA functionals, MS2 and SCAN, described correctly the crystallographic ground states of BiMO3. As a result, these functionals are most suitable to study polymorphism in BiMO3 compounds. We also found that most of the low-energy phases of BiAlO3 and BiGaO3 were polar structures with large values of ferroelectric polarization. This suggests that these materials could be an alternative to the widely used toxic Pb-based ferroelectrics. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS2)-based transition-metal chalcogenides are considered to be cost-efficient, environmentally-friendly, and stable materials in the application of electrocatalytic hydrogen production. However, the low density and poor reactivity of active sites within the basal plane of MoS2 hinder hydrogen evolution reaction (HER). Herein, we reported that N, P co-doped in the basal plane of MoS2 (N, P-MoS2) can convert the parts of 2H MoS2 to 1T MoS2 and enlarge interlayer spacing for an efficient HER. Subsequently, electrochemical tests revealed that N, P-MoS2 showed an overpotential of 179 mV at 10 mA cm−2, a corresponding Tafel slope of 143 mV dec−1, and remarkable long-term stability over 20 h. In addition, we combined these findings with theoretical results from density functional theory (DFT) simulations. The results confirmed that the synergistic effect of N and P activated the HER catalytic activity at the edge of N-MoS2. In short, the synergy improved the conductivity of N-MoS2 and promoted the rapid transfer of charge to achieve high-performance HER activity. The work provides new insight into the synergistic effect of N and P co-doped in the basal plane of MoS2, as well as a new pathway for the rational design of efficient HER electrocatalysts. [ABSTRACT FROM AUTHOR]

π-Conjugated nanohoops containing porphyrins, a long desirable target, have become synthetically accessible thus far. Exploring their origin of photophysical properties at the electronic microstructure level is rather important for performance improvement and application. Herein, we investigated the photophysical properties of a series of π-conjugated nanohoops, consisting of two porphyrins linked by terphenyl bridges, via density functional theory calculations. Compound 1 exhibits a π–π* electron transition character within the porphyrins, and intrinsic chirality primarily originating from exciton-coupling between the porphyrin moieties and terphenyls. Based on the parent compound 1, seven cyclic porphyrin-based compounds 2–8 with various central metals and electron donor/acceptor substituents were designed. These subtle structural modifications have significant impact on the photophysical properties such as UV-vis absorption intensity, electron transition properties, and second-order nonlinear optical (NLO) responses, indicating an obvious adjustability of electron properties. Notably, the second-order polarization value of compound 8 is up to 76.6 × 10−30 esu, which is about 14 times that (cal. 5.30 × 10−30 esu) of the typical organic molecule p-nitroaniline. Thus, the studied compounds would be potential candidates for second-order NLO materials. [ABSTRACT FROM AUTHOR]

The visible-light water splitting enhancement of B in ZnO/CdS was systematically studied and the B-doped ZnO/CdS rods (B-ZnO/CdS) showed an excellent H2 generation rate of 13 100 μmol h−1 g−1, mostly 2 times higher than that of ZnO/CdS (ca. 5249 μmol h−1 g−1, λ > 420 nm), indicating that due to the introduction of the B element, the electron separation efficiency in ZnO/CdS was improved significantly. Through various characterization methods (e.g., PL spectroscopy, UV-Diffuse reflection spectroscopy and photoelectric response), the enhanced electron separation efficiency in the B-ZnO/CdS system was directly demonstrated. In addition, according to the density functional theory (DFT) calculation results, B-ZnO/CdS exhibited a negative adsorption energy of water (EH2O* = −1.22 eV), and the d-band center of the Cd atom had a positive shift from −8.46 to −8.45 eV, which was favorable for water absorption and dissociation. From the charge density difference and density of states, it could be found that electrons tend to transfer from ZnO to H2O at the Cd active sites. The accumulated electrons in H2O could extend the H–OH bond length from 0.975 Å to 0.983 Å, thereby facilitating the dissociation of H2O. [ABSTRACT FROM AUTHOR]

We apply high resolution inelastic neutron scattering techniques, at cryogenic temperatures and up to near ambient temperatures, to study the microscopic dynamics of dihydrogen molecules, chemically bound in a RuH2(H2)2[P(C5H9)3)]2 high-hydrogen content complex. At the lowest temperatures we first observe the quantum tunneling spectrum of the ground ortho-para hydrogen states. At slightly elevated and near ambient temperatures we observe the corresponding quasi-elastic scattering due to rapid proton exchange between the dihydrogen ligands and the hydrides. The overall energetics of the hydrides and the possible reaction paths for proton exchange are modelled with the use of hybrid density functional theory calculations. [ABSTRACT FROM AUTHOR]

In this study, in order to compare the energetic performance of poly-nitrogen compounds with different structures, N6 was taken as an example, and three bi-ring structures of N6 were presented and calculated by using density functional theory (DFT) methods. N6-1 with 3D caged structures exhibits the highest density (1.64 g cm−3), highest heat of formation (1262.2 kJ mol−1), best detonation performance (D: 10 899 m s−1; P: 50.7 GPa) and best specific impulse (422.7 s) among the three N6 isomers. V-shaped N6-2 (d: 1.58 g cm−3; D: 10 093 m s−1; P: 41.3 GPa) has higher density and detonation performance than N6-3 (d: 1.50 g cm−3; D: 9714 m s−1; and P: 44.6 GPa) with a chair-like structure. All three designed materials show a better precited detonation performance and specific impulses (387.2–422.7 s) than CL-20 (D: 9406 m s−1; P: 44.6 GPa; and Isp: 272.6 s), and the detonation properties of N6-1 can be compared to those of octanitrocubane (ONC, D: 10 100 m s−1; and P: 50.0 GPa). The surface electrostatic potentials, frontier molecular orbitals, and weak interactions were also analyzed to further understand the structure–performance relationship. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) Si-based materials are very attractive for use in electronic devices due to their main advantages, such as hardness, stability and non-toxicity. In this work, we study the electronic and optical properties of the penta-siligraphene (p-Si2C4) monolayer with/without effects of biaxial strain (εb) and external electric field (E) using density functional theory (DFT). The structural, dynamic and thermal stabilities of the p-Si2C4 monolayer were confirmed by its negative formation energy, absence of soft modes in the phonon dispersion curve and small drift in the total energy at standard temperature, respectively. Our results showed that the p-Si2C4 monolayer is an indirect semiconductor with a bandgap of 1.39 eV. We found that under the effect of biaxial strain and electric field, a semiconductor-to-metal phase transition occurs and the bandgap depends on both εb and E. Indeed, the bandgap decreases under compressive strain and both negative and positive electric fields, while the bandgap increases slightly with a tensile strain of up to 2%. For the optical properties, the p-Si2C4 monolayer has a high optical absorption of the order of ∼105/106 cm−1 in both visible/UV ranges and it can be enhanced by biaxial strain. This improvement in optical absorption can increase the range of applicability of p-Si2C4 in optoelectronics. [ABSTRACT FROM AUTHOR]

The precursor 3,5-dinitro-4-chloro-1-(dinitromethyl)pyrazole (A) was synthesized by a two-step reaction with a yield of 81.5%. Nitrate ester, amino and diazo-oxide groups were introduced to A by the one-step substitution of the chlorine group in water. This method provides the possibility for large-scale preparation due to its simplicity and efficiency. The reaction mechanisms were explained by density functional theory. Among these compounds, the hydroxylamine salt B2 exhibits high detonation performance (P = 35.5 GPa; vD = 8842 m s−1) and oxygen balance (OBCO = 27%), superior to those of ADN (P = 23.6 GPa; vD = 7860 m s−1; OBCO = 25.7%), and has a promising future as an energetic oxidant. The diazo-oxide zwitterion C1 possesses good detonation performance (P = 37.7 GPa; vD = 9159 m s−1), higher than that of RDX (P = 34.9 GPa; vD = 8795 m s−1), and features a comparable impact sensitivity with DDNP (IS = 1 J), which make it a promising candidate for green primary explosives. Based on the good reactivity towards nucleophiles of the chlorine group, this is a simple method to introduce substituents into dinitromethylpyrazoles to tune their oxygen balance and detonation performance. [ABSTRACT FROM AUTHOR]

ZnCo2O4/Ag3PO4 heterostructure nanoparticles were prepared via a facile ultrasonic method and characterized using various techniques. The photocatalytic activity of ZnCo2O4/Ag3PO4 nanoparticles was investigated for the degradation of organic pollutants (methyl orange and bisphenol A) under visible-light irradiation. An enhanced photocatalytic efficiency was observed within 75 minutes compared with the individual constituents. A mechanism of the enhanced photocatalytic activity of the heterojunction is proposed based on density functional theory (DFT) calculations. The cytotoxicity of the ZnCo2O4/Ag3PO4 nanoparticles was tested against the breast cancer cell line (MCF-7), the human colorectal cancer cell line (HCT116) and the normal human foreskin fibroblast cell line (HFF). More cytotoxicity was observed against the fibroblast cell line. The antimicrobial and antifungal activities of the ZnCo2O4/Ag3PO4 nanoparticles were also examined against methicillin-resistant Staphylococcus aureus (MRSA), multidrug-resistant Pseudomonas aeruginosa (MDR-PA) and the yeast Candida albicans. It was observed that MDR-PA was more susceptible to ZnCo2O4/Ag3PO4 nanoparticles than MRSA and Candida albicans. Furthermore, the effect of the ZnCo2O4/Ag3PO4 nanoparticles on biofilm formation by MDR-PA, MRSA and Candida albicans was also studied. The results indicated that the inhibition of biofilm production by MDR-PA was higher than for MRSA and yeast under similar conditions. [ABSTRACT FROM AUTHOR]

Two new isostructural halogenated dihydroquinolinones were synthesized and characterized by single crystal X-ray diffraction. A detailed isostructural analysis of the electronic and optical properties is presented using density functional theory models with emphasis on the structure–property relationship in the solid phase. The physicochemical properties such as molecular electrostatic potential, frontier molecular orbitals as well as the nature of intermolecular interactions and the interaction energy of dimeric structures are almost unaffected by the replacement of the bromine atom by the chlorine atom. Starting from the embedded unit cells, the third-order nonlinear susceptibility (χ(3)) of the newly synthesized crystals has been estimated using an iterative electrostatic scheme, in which the surrounding molecules are represented by point charges. Theoretical results illustrate the role played by the environment polarization effect and halogenated substituents on χ(3) which has the same order of magnitude as those observed in other organic crystals. Our findings suggest that the dihydroquinolinone derivative crystals are very promising NLO materials. [ABSTRACT FROM AUTHOR]

The generalized gradient approximation (GGA) density functional theory (DFT), Perdew–Burke–Ernzerh (PBE), and long-range corrected DFT (ωB97XD) were used to investigate the interaction between lithium polysulfides (Li2Sx, x = 2–8) and N-doped graphene to understand the adsorption mechanism and effect of catalytic conversion, including the reduction from S8 to Li2S and Li2S decomposition. The binding of Li2Sx to N-doped graphene was significantly stronger than that to solvents, such as 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME), approximately by 0.5–3.0 eV, indicating that N-doped graphenes possessed the ability to trap soluble Li2Sx. The binding of Li2Sx to N-doped graphenes followed the order of pyrrolic N > pyridinic N > graphene > graphitic N. Among them, pyrrolic N exhibited the strongest anchoring effect mainly via forming the coordination bond of LiN3. In addition, in all the investigated systems, the van der Waals force also played an important role in binding. We comprehensively analyzed the micro-nano-scale theoretical data, including charge, bond distance, bond order, electron density difference, the electron localization function (ELF), and the independent gradient model (IGM) of the Li ion and N atom. The strength of the Li–N bond confirmed that the strongest anchoring occurred when the Li ion was trapped above the vacancy-forming coordination bond rather than a regular covalent bond. Although the strength of Li–N binding had a direct effect on the binding energy, other thermodynamic parameters (free energy and dissociation energy) of catalytic conversion and the energy barrier of Li2S phase transformation also showed a similar capacity. [ABSTRACT FROM AUTHOR]