Quantum spin Hall states in MX (M = Ru, Os; X = As, Sb) monolayers.

The quantum spin Hall (QSH) effect has attracted extensive research interest due to its great promise in topological quantum computing and novel low-energy electronic devices. Here, using first-principles calculations, we find that MX (M = Ru and Os; X = As and Sb) monolayers are 2D topological insulators (TIs). The spin-orbit coupling (SOC) band gaps for RuAs, RuSb, OsAs, and OsSb monolayers are predicted to be 80, 131, 118, and 221 meV, respectively.

The Configuration Identification of Guanine Molecules Adsorbed on the Si(100) Surface by Using XPS Shake-up Satellites and NEXAFS.

Bioelectronic devices can be manufactured by organic-inorganic hybrid systems based on biomolecules and silicon semiconductors. The performance of the hybrid systems is largely determined by the adsorption manners of biomolecules on the silicon surface. In this paper, we demonstrated that the X-ray photoelectron spectroscopy (XPS) shake-up satellites and near-edge X-ray absorption fine-structure (NEXAFS) spectra at the carbon K-edges can be used to distinguish the interface of guanine molecules anchored on Si(100) surface.

Effect of Bridging Manner on the Transport Behaviors of Dimethyldihydropyrene/Cyclophanediene Molecular Devices.

A molecule-electrode interface with different coupling strengths is one of the greatest challenges in fabricating reliable molecular switches. In this paper, the effects of bridging manner on the transport behaviors of a dimethyldihydropyrene/cyclophanediene (DHP/CPD) molecule connected to two graphene nanoribbon (GNR) electrodes have been investigated by using the non-equilibrium Green's function combined with density functional theory. The results show that both current values and ON/OFF ratios can be modulated to more than three orders of magnitude by changing bridging manner.

Core-Hole Excitation Spectra of the Oxides and Hydrates of Fullerene C and Azafullerene CN.

The interaction of fullerenes and their derivatives with environmental molecules such as oxygen or water was crucial for the rational design of low-dimensional materials and devices. In this paper, the near-edge X-ray absorption fine structure (NEXAFS), X-ray emission spectroscopy (XES) and X-ray photoelectron spectroscopy (XPS) shake-up satellites were employed to distinguish the oxides and hydrates of the fullerene C and azafullerene CN families. The study includes various isomers, such as the open [5,6] and closed [6,6] isomers of CO, CH(OH), C-O-C, CH-O-CH, CN(OH) and CN-O-CN, based on density functional theory.

Rational Design of Photocontrolled Rectifier Switches in Single-Molecule Junctions Based on Diarylethene.

The construction of multifunctional, single-molecule nanocircuits to achieve the miniaturization of active electronic devices is a challenging goal in molecular electronics. In this paper, we present an effective strategy for enhancing the multifunctionality and switching performance of diarylethene-based molecular devices, which exhibit photoswitchable rectification properties. Through a molecular engineering design, we systematically investigate a series of electron donor/acceptor-substituted diarylethene molecules to modulate the electronic properties and investigate the transport behaviors of the molecular junctions using the non-equilibrium Green's function combined with the density functional theory.

Controlling the electrochemical activity of dahlia-like β-NiS@rGO by interface polarization.

Transition metal sulfides have become more and more important in the field of energy storage due to their superior chemical and physical properties. Herein, dahlia β-NiS with a rough surface and β-NiS@reduced graphene oxide (rGO) have been green synthesized by a one-step hydrothermal method. The interface characteristics of β-NiS@ rGO composites have been systematically studied by XPS, Raman, and first-principles calculations.

A non-heat-source process for preparing graphene oxide with low energy consumption.

As the most widely used method for preparing graphene oxide (GO), Hummers' method always involves a key step, that is adding water to concentrated sulfuric acid. We found that if this process is cancelled, the oxidation degree of GO will be significantly reduced. This means that the heat released during concentrated sulfuric acid dilution will promote further oxidation of GO.

An intramolecular-locked strategy for designing nonlinear optical materials with remarkable first hyperpolarizability.

To meet the expanding demands of high performance nonlinear optical (NLO) materials, an unprecedented intramolecular-locked strategy is proposed to design NLO materials with remarkable static first hyperpolarizability (). This strategy means that importing a large steric hindrance group diphenylmethane (DPM) decreases the torsion angles () between the donor {triphenylamine (TPA)} and acceptor {9--thioxanthen-9-one-10,10-dioxide (TXO)} units, as well as between the donor (TPA) and π-bridge (benzene) fragments. The decrease of can accelerate the intramolecular charge transfer and enhance the contributions of the TPA, TXO and quinoxaline-6,7-dicarbo-nitrile (QCN) fragments to the axial component of the value, and then the values of TPA-TXO ( = 10 762 au) and TPA-QCN ( = 22 495 au) are increased by 14.

Effects of Fluorination and Molybdenum Codoping on Monoclinic BiVO Photocatalyst by HSE Calculations.

Monoclinic phase bismuth vanadate (BiVO) is one of the most promising photoelectrochemical materials used in water-splitting photoelectrochemical cells. It could be even better if its band gap and charge transport characteristics were optimized. Although codoping of BiVO has proven to be an effective strategy, its effects are remarkably poorly understood.

Sc/C codoping effect on the electronic and optical properties of the TiO (101) surface: a first-principles study.

Extension of the light absorption range and a reduction of the possibility of the photo-generated electron-hole pair recombination are the main tasks to break the bottleneck of the photocatalytic application of TiO. In this paper, we systematically investigate the electronic and optical properties of Sc-doped, C-doped, and Sc/C-codoped TiO (101) surfaces using spin-polarized DFT+U calculations. The absorption coefficient of the Sc/C-codoped TiO (101) surfaces were enhanced the most compared with the other two doped systems in the high energy region of visible light, which can be attributed to the shallow impurity states.

Corrosion-controlled surface engineering improves the adhesion of materials for stable free-standing electrodes.

Directly anchoring active materials on porous conductive substrates is considered an effective strategy to obtain a high-activity electrode since the direct contact between active materials and substrates benefits charge transfer, and the presence of porous structures provides more active sites. However, due to the presence of strong stress and weak adhesion, active materials loaded on the substrate are very easy to peel off during assembly and use, which can greatly shorten the lifetime of use. Herein, an ultrasonic corrosion strategy is proposed to regulate the surface of a metal substrate.

Second-Order Nonlinear Optics Response of the Boron-Dipyrromethenes-Based Mislinked Expanded Porphyrins: Revealing the Role of the -BF Group.

Here, the mislinked expanded porphyrins singly (labeled ) and doubly (labeled ) neo-confused [22]smaragdyrin, the boron-dipyrromethenes-based mislinked expanded porphyrins singly (labeled ) and doubly (labeled ) neo-confused [22]smaragdyrin, where both and include a -BF group, are chosen to serve as the study objects, and theoretical calculations are carried out to study the role of the -BF group in the second-order nonlinear optics (NLO) behaviors. Results highlighted that the -BF group plays an important role for the second-order behaviors in mislinked expanded porphyrins; namely, embedding the -BF group well enhanced the hyper-Rayleigh scattering (HRS) value {β(0;0,0)}, = 2.0 and = 2.

Two-dimensional ZrC as a novel anode material with high capacity for sodium ion battery.

Rational design of high-performance anode materials is of paramount importance for developing rechargeable lithium ion batteries (LIBs) and sodium ion batteries (SIBs). In this work, a ZrC monolayer is predicted by performing the particle swarm optimization (PSO) algorithm. The high energetic, dynamic, and thermal stabilities of the ZrC monolayer are confirmed by cohesive energy, phonon dispersion, and molecular dynamics simulations, respectively.

Adsorption of Organic Molecules and Surfactants on Graphene: A Coarse-Grained Study.

The research studies on the adsorption of surfactants on graphene help us to know how to use surfactants to exfoliate graphene from graphite or functionalize the graphene surface. Among them, molecular dynamics (MD) simulation has been widely used to investigate the adsorption of organic molecules and surfactants on graphene. In particular, coarse-grained (CG) MD simulation greatly improves the computational efficiency by simplifying the complexity of the studied systems, allowing us to explore the structure and dynamics of complex systems on larger spatial scales and longer time scales.

Two-dimensional ScN with high carrier mobility and unexpected mechanical properties.

Two-dimensional (2D) semiconductors with desirable bandgaps and high carrier mobility have great potential in electronic and optoelectronic applications. In the present work, 2D M-ScN, H-ScN, and O-ScN are predicted by the swarm-intelligent global structure search method. The low formation energies and high dynamical and thermal stabilities indicate the high feasibility of experimental synthesis of these ScN monolayers.

Hybrid Density Functional Theory Study of Native Defects and Nonmetal (C, N, S, and P) Doping in a BiWO Photocatalyst.

Native defects and nonmetal doping have been shown to be an effective way to optimize the photocatalytic properties of BiWO. However, a detailed understanding of defect physics in BiWO has been lacking. Here, using the Heyd-Scuseria-Ernzerhof hybrid functional defect calculations, we study the formation energies, electronic structures, and optical properties of native defects and nonmetal element (C, N, S, and P) doping into BiWO.

Effects of native defects and cerium impurity on the monoclinic BiVO photocatalyst obtained via PBE+U calculations.

In this article, we report a periodic density functional theory (DFT) investigation on the formation of the native defects and cerium doping in monoclinic BiVO (m-BiVO) and their effect on the electronic structures, using the Perdew-Burke-Ernzerhof functionals corrected for on-site Coulombic interactions (PBE+U). From the point defect formation energies and transition levels, the Bi (Bi vacancy), V (V vacancy), O (O interstitial) and Ce (Ce doping on V site) defects in m-BiVO are identified as shallow acceptors. For Ce doping in m-BiVO, the substitution of Bi by Ce is energetically favorable in the single positively charged state (Ce) under Bi/V-poor conditions, while the substitution of V by Ce is in the single negatively charged state (Ce) under O-rich conditions.

Atom-Pair Catalysts Supported by N-Doped Graphene for the Nitrogen Reduction Reaction: -Band Center-Based Descriptor.

Achieving an effective nitrogen reduction reaction (NRR) under mild conditions is a great challenge for industrial ammonia synthesis. NRR is often accompanied by a competing hydrogen evolution reaction (HER), which causes an extremely low Faraday efficiency. We systematically investigated the NRR reactivity of atom-pair catalysts (APCs) formed by 20 transition metal (TM) elements supported by N-doped graphene via three reaction pathways.

Electron-Phonon Scattering Is Much Weaker in Carbon Nanotubes than in Graphene Nanoribbons.

Carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) are lower-dimensional derivatives of graphene. Similar to graphene, they exhibit high charge mobilities; however, in contrast to graphene, they are semiconducting and thus are suitable for electronics, optics, solar energy devices, and other applications. Charge carrier mobilities, energies, and lifetimes are governed by scattering with phonons, and we demonstrate, using ab initio nonadiabatic molecular dynamics, that charge-phonon scattering is much stronger in GNRs.

Effect of Cholesterol and 6-Ketocholestanol on Membrane Dipole Potential and Sterol Flip-Flop Motion in Bilayer Membranes.

A variety of experimental and theoretical approaches have been employed to investigate the sterol flip-flop motion in lipid bilayer membranes. However, the sterol effect on the dipole potential of lipid bilayer membranes is less well studied and the influence of dipole potential on sterol flip-flop motion in lipid bilayer membranes is less well understood. In our previous works, we have demonstrated the performance of our coarse-grained (CG) model in the computation of the dipole potential.

Single Pt atoms stabilized on MoTiCO for hydrogen evolution: A first-principles investigation.

Single-atom catalysis offers an effective way to reduce the amount of used noble metals and maximizes their catalytic activity. We systematically explore electrocatalytic performances of Pt doped MoTiCO monolayer by the first principles calculations. Our results show that the presence of donor defects in MoTiCO can always increase the reaction free energy of hydrogen adsorption and further promotes the performance in hydrogen evolution reaction (HER).

Interface Schottky barrier in HfNT/MSSe (T = F, O, OH; M = Mo, W) heterostructures.

The Schottky barrier height (SBH) is a critical parameter that determines the carrier transfer at metal/semiconductor interfaces. In this work, the interfacial properties of Hf2NT2/MSSe (T = F, O, OH; M = Mo, W) heterostructures are systematically investigated using first-principles calculations. It is found that, for MoSSe and WSSe, the use of S or Se atomic layers in contact with Hf2NT2 can give significantly different SBHs.

Molecular Dynamics Simulations of Ether- and Ester-Linked Phospholipid Bilayers: A Comparative Study of Water Models.

Membrane dipole potential influences a variety of important biological processes involving cell membranes. Because it is quite challenging to directly measure the membrane dipole potential in experiments, molecular dynamics (MD) simulation has emerged as a powerful tool for a reasonable prediction of the dipole potential. Although MD predictions agree well with experiments about the sign of the dipole potential, the magnitude of the dipole potential varies significantly with the force field parameters.

Effect of Cholesterol on Membrane Dipole Potential: Atomistic and Coarse-Grained Molecular Dynamics Simulations.

The effect of cholesterol on membrane dipole potential has been the subject of a great number of experimental and theoretical investigations, but these studies have yielded different findings and interpretations at high cholesterol concentrations. This suggests that the underlying mechanism of the cholesterol effect is not well addressed. Moreover, as far as we know, none of the previously proposed coarse-grained (CG) models (including MARTINI and its improved versions) have been successfully used to probe the effect of cholesterol on membrane dipole potential, owing to either an inaccurate description of water-cholesterol electrostatics or the neglect of the contribution of cholesterol to membrane dipole potential.

CO oxidation on Ru-Pt bimetallic nanoclusters supported on TiO(101): The effect of charge polarization.

Pt-based catalyst is widely used in CO oxidation, while its catalytic activity is often undermined because of the CO poisoning effect. Here, using density functional theory, we propose the use of a Ru-Pt bimetallic cluster supported on TiO for CO oxidation, to achieve both high activity and low CO poisoning effect. Excellent catalytic activity is obtained in a RuPt/TiO(101) system, which is ascribed to strong electric fields induced by charge polarization between one Ru atom and its neighboring Pt atoms.