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Fabrication cobalt-doped indium oxide/molybdenum disulfide ternary nanocomposite toward carbon monoxide gas sensing
摘要： This paper demonstrated a high-performance carbon monoxide (CO) gas sensor based on cobalt (Co)-doped indium oxide (In2O3) nanoparticles/molybdenum disulfide (MoS2) nanoflowers nanocomposite. Co-In2O3 nanoparticles were synthesized by a co-precipitation method, and flower-like MoS2 was prepared by one-step hydrothermal route. Layer-by-layer self-assembly technique was employed to fabricate Co-In2O3/MoS2 film sensor on an epoxy substrate with interdigital electrodes. Scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) were carried out to fully examine the morphology, microstructure, and elementary composition of the as-prepared samples. The CO-sensing characteristics of the Co-In2O3/MoS2 film sensor were systematically investigated under room temperature through exposing the sensor to various concentration of CO gas. The Co-In2O3/MoS2 sensor achieved high sensitivity, fast response/recovery speed, excellent repeatability and stable long-term stability. An approach of combining gas-sensing experiments with density-functional theory (DFT) simulation based on first-principle was used to further explore the CO-sensing mechanism of the Co-In2O3/MoS2 sensor. The Co2+ ion doping, and heterojunctions created at interfaces of Co-In2O3 and MoS2 were attributed to the high-performance CO sensing.
关键词： CO gas sensor,LbL self-assembly,molybdenum disulfide,first-principle theory,Co-doped indium oxide
更新于2025-09-23 15:21:01
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Single-layer planar penta-X2N4 (X= Ni, Pd and Pt) as direct-bandgap semiconductors from first principle calculations
摘要： Using first principle calculations we have investigated the structure stabilities, electronic and optical properties of single layer planar penta-X2N4 (X=Ni, Pd and Pt). According to the calculated phonon dispersion relation and elastic constants, as well as ab initio molecular dynamics simulation results, monolayers of planar penta-X2N4 are dynamically, mechanically, and thermally stable. In addition, these monolayers are direct-gap semiconductors with sizeable bandgaps ranging from 0.92 eV to 1.11 eV, which can be further tuned by external strains. Besides, the bonding characteristics and the optical properties in these monolayers are investigated based on HSE06 calculations, where strong in-plane optical absorption with wide spectral range has been revealed. Our results indicate that planar penta-X2N4 monolayers possess excellent electrical and optical properties, and may find potential applications in solar cells and nanoelectronics.
关键词： Electronic properties,First principle calculations,Optical properties,Direct-bandgap semiconductors,Planar penta-X2N4
更新于2025-09-23 15:21:01
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Theoretical and experimental study on the electronic and optical properties of K <sub/>0.5</sub> Rb <sub/>0.5</sub> Pb <sub/>2</sub> Br <sub/>5</sub> : a promising laser host material
摘要： The data on the electronic structure and optical properties of bromide K0.5Rb0.5Pb2Br5 achieved by first-principle calculations and verified by X-ray spectroscopy measurements are reported. The kinetic energy, the Coulomb potential induced by the exchange hole, spin-orbital effects, and Coulomb repulsion were taken into account by applying the Tran and Blaha modified Becke–Johnson function (TB-mBJ), Hubbard U parameter, and spin-orbital coupling effect (SOC) in the TB-mBJ + U + SOC technique. The band gap was for the first time defined to be 3.23 eV. The partial density of state (PDOS) curves of K0.5Rb0.5Pb2Br5 agree well with XES K Ll and Br Kb2, and XPS spectra. The valence band (VB) is characterized by the Pb-5d3/2 and Pb-5d5/2 sub-states locating in the vicinities of ~20 eV and ~18 eV, respectively. The VB middle part is mainly formed by K-3p, Rb-4p and Br-4s states, in which the separation of Rb-4p3/2 and Rb-4p1/2 was also observed. The strong hybridization of Br-p and Pb-s/p states near ~6.5 eV reveals a major covalent part in the Br–Pb bonding. With a large band gap of 3.23 eV, and the remarkably high possibility of inter-band transition in energy ranges of 4–7 eV, and 10–12 eV, the bromide K0.5Rb0.5Pb2Br5 is expected to be a very promising active host material for core valence luminescence and mid-infrared rare-earth doped laser materials. The anisotropy of optical properties in K0.5Rb0.5Pb2Br5 is not significant, and it occurs at the extrema in the optical spectra. The absorption coefficient a(u) is in the order of magnitude of 106 cm?1 for an energy range of 5–25 eV.
关键词： electronic structure,X-ray spectroscopy,optical properties,laser host material,first-principle calculations,K0.5Rb0.5Pb2Br5
更新于2025-09-23 15:19:57
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Tantalum disulfide quantum dots: preparation, structure, and properties
摘要： Tantalum disulfide (TaS2) two-dimensional film material has attracted wide attention due to its unique optical and electrical properties. In this work, we report the preparation of 1 T-TaS2 quantum dots (1 T-TaS2 QDs) by top-down method. Herein, we prepared the TaS2 QDs having a monodisperse grain size of around 3 nm by an effective ultrasonic liquid phase exfoliation method. Optical studies using UV-Vis, PL, and PLE techniques on the as-prepared TaS2 QDs exhibited ultraviolet absorption at 283 nm. Furthermore, we found that dimension reduction of TaS2 has led to a modification of the band gap, namely a transition from indirect to direct band gap, which is explained using first-principle calculations. By using quinine as reference, the fluorescence quantum yield is 45.6%. Therefore, our results suggest TaS2 QDs have unique and extraordinary optical properties. Moreover, the low-cost, facile method of producing high quality TaS2 QDs in this work is ideal for mass production to ensure commercial viability of devices based on this material.
关键词： Transition metal dichalcogenides,First-principle,Quantum dots,Ultrasonic method,Modulating bandgap
更新于2025-09-16 10:30:52
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Roles of spin-orbit coupling in tetragonal hybrid halide perovskite for photovoltaics light-absorber
摘要： Hybrid halide perovskite has been gain appropriate attraction because of their relatively high efficiency in most recently solid-state solar cell development. In this work, A first-principle calculation based on non-local van der Waals-corrected Density Functional Theory (vdW-DFT) is performed to investigate high accuracy atomic structures of a tetragonal structure methyl ammonium (CH3NH3) metal (Pb, Sn) halide (Br3, Cl3, I3). The calculated electronic structures were systematically studied using semi-local exchange-correlation functional (GGA-PBE), non-local functional (hybrid HSE06) and post-DFT approximation (GW). A relativistic effect in metal ion was taken into account by incorporating spin-orbit coupling (SOC) effect to obtain more accurate band gap properties of these materials. Our results shown that SOC corrected the electronic structures about 0.92 eV and 0.19 eV in case of lead ion and tin ion, respectively. The combination between GW approximation and spin-orbit coupling show a good agreement between DFT calculations and experimental studies. This computational scheme is necessary for high accuracy organic-inorganic solar cell design.
关键词： Spin-Orbit Coupling,Hybrid perovskite solar cell,Methyl ammonium metal halide,First-principle calculation
更新于2025-09-12 10:27:22
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Highly-efficient overall water splitting in 2D Janus group-III chalcogenide multilayers: the roles of intrinsic electric filed and vacancy defects
摘要： Two-dimensional (2D) van der Waals materials have been widely adopted as photocatalysts for water splitting, but the energy conversion efficiency remains low. On the basis of first-principles calculations, we demonstrate that the 2D Janus group-III chalcogenide multilayers: InGaXY, M2XY and InGaX2 (M = In/Ga; X, Y = S/Se/Te), are promising photocatalysts for highly-efficient overall water splitting. The intrinsic electric field enhances the spatial separations of photogenerated carriers and alters the band alignment, which is more pronounced compared with the Janus monolayers. High solar-to-hydrogen (STH) efficiency with the upper limit of 38.5% was predicted in the Janus multilayers. More excitingly, the Ga vacancy of InGaSSe bilayer effectively lowers the overpotentials of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) to the levels provided solely by the photogenerated carriers. Our theoretical results suggest that the 2D Janus group-III chalcogenide multilayers could be utilized as highly efficient photocatalysts for overall water splitting without the needs of sacrificial reagents.
关键词： Photocatalytic water splitting,Janus group-III chalcogenides,Intrinsic electric fields,First-principle calculation,Solar-to-hydrogen efficiency
更新于2025-09-11 14:15:04
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Interfacial properties of Hg <sub/>2</sub> CuTi-type Heusler alloy Ti <sub/>2</sub> NiAl/GaAs(100) heterojunction
摘要： For Hg2CuTi-type Inverse-Heusler alloy Ti2NiAl/GaAs(100) tunnel heterojunction, the magnetism, density of states and spin polarization of atoms at the interface were investigated systematically based on the first-principle calculation within the density functional theory (DFT). The calculated results reveal that the interface states seriously destroy the structural half-metallicity and lead to the spin polarization less than 60%. Among all of calculational hetero-structures, only the heterojunction with TA-ATⅡ structure still retains nearly 60% spin polarization, which is expected for further application in Tunnel Magneto resistance (TMR) devices.
关键词： first-principle calculation,Hg2CuTi-type Heusler alloy,TMR devices,Ti2NiAl/GaAs(100) heterojunction,spin polarization
更新于2025-09-11 14:15:04
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First-principle calculation of the electronic structures and optical properties of the metallic and nonmetallic elements-doped ZnO on the basis of photocatalysis
摘要： In the present paper, the electronic structure and the optical properties of metallic and nonmetallic elements-doped ZnO were investigated based on the principle of photocatalysis by first-principle density functional theory. Element doping shortens the band gap of ZnO. Due to the p-type characteristics, Fe, Cu, B and N doping brings impurity states over the Fermi level of ZnO, resulting in the shortening of the band gap, extending the absorption and utilization of solar light and thus enhancing the photocatalytic properties of ZnO. However, no impurity states appear in the band gap of Cd- and S-doped ZnO due to the intrinsic doping of Cd and S. Further investigations indicate that different doping atoms can indeed alter the near-Fermi level density of states (DOS) of ZnO and their electronic structures via substitution of zinc and oxygen atoms. In addition, the optical properties of ZnO are improved after doped with different atoms by comparing with those of pure ZnO. Due to the difference of their outer shell electrons of the doped atoms, the optical absorption properties of the investigated materials are followed as the following order: Fe-/B-doped ZnO>Cu-/N-doped ZnO>Cd-/S-doped ZnO>pure ZnO.
关键词： Doped ZnO,Density functional theory (DFT),Photocatalysis,First principle calculation
更新于2025-09-11 14:15:04
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Influence of Pressure on the Mechanical and Electronic Properties of Wurtzite and Zinc-Blende GaN Crystals
摘要： The mechanical and electronic properties of two GaN crystals, wurtzite and zinc-blende GaN, under various hydrostatic pressures were investigated using first principles calculations. The results show that the lattice constants of the two GaN crystals calculated in this study are close to previous experimental results, and the two GaN crystals are stable under hydrostatic pressures up to 40 GPa. The pressure presents extremely similar trend effect on the volumes of unit cells and average Ga-N bond lengths of the two GaN crystals. The bulk modulus increases while the shear modulus decreases with the increase in pressure, resulting in the significant increase of the ratios of bulk moduli to shear moduli for the two GaN polycrystals. Different with the monotonic changes of bulk and shear moduli, the elastic moduli of the two GaN polycrystals may increase at first and then decrease with increasing pressure. The two GaN crystals are brittle materials at zero pressure, while they may exhibit ductile behaviour under high pressures. Moreover, the increase in pressure raises the elastic anisotropy of GaN crystals, and the anisotropy factors of the two GaN single crystals are quite different. Different with the obvious directional dependences of elastic modulus, shear modulus and Poisson’s ratio of the two GaN single crystals, there is no anisotropy for bulk modulus, especially for that of zinc-blende GaN. Furthermore, the band gaps of GaN crystals increase with increasing pressure, and zinc-blende GaN has a larger pressure coefficient. To further understand the pressure effect on the band gap, the band structure and density of states (DOSs) of GaN crystals were also analysed in this study.
关键词： first principle,electronic property,GaN,pressure,mechanical property
更新于2025-09-10 09:29:36
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The effects of point defects on the electronic and magnetic properties of GaN/ZnO heterojunction polar interface
摘要： The potential use of GaN/ZnO heterojunction as a magnetic material has been neglected because its magnetic properties are rarely studied. In this study, the magnetic properties of GaN/ZnO heterojunction interface are systematically calculated, and the effect of electric polarization intensity on the spin-electron was analyzed. Results showed that GaN/ZnO heterojunction interface exhibits a semiconducting feature. The magnetism of GaN/ZnO heterojunction interface is mainly affected by two factors. The first factor is the number of unpaired p-state electrons induced by cation vacancies, and the magnetism in the heterojunction interface originated from the spin polarization of these p-state electrons. The second factor is the electric polarization intensity in the heterojunction interface. If the electric polarization intensity is too low, then the unpaired p-electrons cannot be spin-polarized to produce a net magnetic moment. The spin polarization of p-state electrons increases with the increase in electric polarization intensity. Excessive electric polarization intensity inverts the spin direction of a part of p-state electrons, and ferromagnetic–ferrimagnetic–antiferromagnetic transition occurs in the heterojunction interface. Therefore, the magnetic property of GaN/ZnO heterojunction interface can be controlled by varying the electric polarization intensity.
关键词： First-principle,Magnetism,Point defects,GaN/ZnO heterojunction
更新于2025-09-10 09:29:36