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Defective ZnS nanoparticles anchored in situ on N-doped carbon as a superior oxygen reduction reaction catalyst
摘要： Defect engineering has been used to develop low-cost and effective catalysts to boost oxygen reduction reactions. However, the development of catalysts that use metal cation vacancies as the active sites for oxygen reduction reaction is lacking. In this study, ZnS nanoparticles on N-doped carbon serve as an oxygen reduction reaction catalyst. These catalysts were prepared via a one-step method at 900 °C. Amazingly, the high-resolution transmission electron microscope image revealed obvious defects in the ZnS nanoparticles. These facilitated the catalyst synthesis, and the product displayed good electrocatalytic performance for the oxygen reduction reaction in an alkaline medium, including a lower onset potential, lower mid-wave potential, four electron transfer process, and better durability compared with 20 wt% Pt/C. More importantly, the density functional theory results indicated that using the Zn vacancies in the prepared catalyst as active sites required a lower reaction energy to produce OOH ? from ?OO toward oxygen reduction reaction. Therefore, the proposed catalyst with Zn vacancies can be used as a potential electrocatalyst and may be substitutes for Pt-based catalysts in fuel cells, given the novel catalyst’s resulting performance.
关键词： Density functional theory calculations,Oxygen reduction reaction,Zn vacancy,Electrocatalyst,Defective ZnS nanoparticle
更新于2025-11-14 17:03:37
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Cobalt doping-induced strong electromagnetic wave absorption in SiC nanowires
摘要： Understanding the electronic structure-property relationship in doped systems is a prerequisite to designing functional materials. We fabricated Co-doped SiC nanowires with different Co contents by a facile carbothermal reduction approach. The nanowires were characterized in terms of microstructure, electronic structure, and electromagnetic (EM) parameters to uncover the effect of Co dopants on enhancing the EM wave absorption ability. Microstructure analysis and density functional theory calculations verified that the doped Co species inhibited the formation of stacking faults and point defects and increased the conductivity of Co-doped SiC nanowires, which indicated the dominant role of conductivity in enhancing dielectric loss. The Co dopants also imparted the Co-doped SiC nanowires with distinct room-temperature ferromagnetic property, which led to enhanced magnetic loss and impedance matching. The induced synergism among SiC nanowires and Co dopants endowed Co-doped SiC nanowires with strong EM wave absorption ability. The minimum reflection loss of Co-doped SiC nanowires reaches (cid:1)50 dB, and the effective absorption bandwidth is 4.0 GHz with only 1.5 mm sample thickness. Thus, Co-doped SiC nanowires can be used as effective EM wave absorption materials. This study also provided a guideline for designing high-performance EM wave absorbers.
关键词： Dielectric loss,Doping,Density functional theory calculations,Electromagnetic wave absorption,Magnetic property
更新于2025-09-23 15:23:52
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From pentagonal geometries to two-dimensional materials
摘要： Hexagons are dominating building blocks in the atomic structures of existing and predicted two-dimensional (2D) materials. A wealth of properties possessed by numerous 2D materials are attributed to their hexagonal, structural units. Although many review articles exist for 2D hexagonal materials, this review focus on a less common building block, pentagon, of 2D materials. We start with introducing 15 types of convex pentagons that can tile an infinite plane without creating a gap. We connect one of these pentagonal geometries (type 2 pentagon) with 2D materials via density functional theory (DFT) calculations, resulting in predictions of 2D pentagonal materials that could be synthesized in experiments. We summarize the experimental and theoretical efforts in this burgeoning subfield of 2D materials research. We also suggest several issues that DFT calculations can continue to address to develop the subfield. We expect this brief review to stimulate further experimental and computational interests in synthesizing and designing new 2D pentagonal materials.
关键词： Density functional theory calculations,Pentagonal geometries,Two-dimensional materials
更新于2025-09-23 15:22:29
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Superior Sensing Properties of Black Phosphorus as Gas Sensors: A Case Study on the Volatile Organic Compounds
摘要： The unique structure and prominent properties of black phosphorus (BP) and its monolayer and multilayers in device applications have attracted significant attention to this elemental 2D material. In this study, a comprehensive evaluation of the candidacy of monolayer BP as a channel material for high-performance volatile organic compound (VOC) sensors is conducted combining first-principles density functional theory calculations and non-equilibrium Green’s function formalism. The adsorption configurations and energetics of several typical VOCs (ethanol, propionaldehyde, acetone, toluene, and hexane) on monolayer BP are examined and it is demonstrated that VOCs generally exhibit stronger interaction with monolayer BP than with the widely studied monolayer MoS2, indicative of monolayer BP potentially being a more sensitive VOC sensor. Monolayer BP is shown to exhibit highly anisotropic transport behaviors, whereas the absolute modification of current–voltage responses due to VOCs is found to show a trend that is direction independent. Moreover, the adsorption of VOCs on monolayer BP is strong enough to resist thermal disturbance, yet allows fast recovery time. The results suggest that BP is a compelling and feasible candidate for sensing applications of VOCs.
关键词： density functional theory calculations,gas sensors,black phosphorus,volatile organic compounds,non-equilibrium Green’s function formalism
更新于2025-09-23 15:22:29
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Unusual Electronic States and Superconducting Proximity Effect of Bi Films Modulated by NbSe2 Substrate
摘要： Heterostructures of two-dimensional layered materials can be functionalized with exotic phenomena that are unpresented with each constituting component. The interface effect plays a key role in determining the electronic properties of the heterostructure, whose characterization requires a correlation with the morphology with atomic-scale precision. Here, we report an investigation on the electronic properties of few-layer Bi(110) films mediated by NbSe2 substrate. By utilizing scanning tunneling microscopy and spectroscopy, we show a significant variation of the density of states at different Bi film thicknesses, resulting in an unusual superconducting proximity effect that deviates from the conventional monotonous decay behavior. Moreover, the electronic states of the Bi films are also prominently modulated by the Moiré pattern spatially. With first-principles calculations, we illuminate these findings as the results of covalent-like quasi-bonds formed at the Bi/NbSe2 interface, which profoundly alter the charge distributions in the Bi films. Our study indicates a viable way of modulating the electronic properties of ultrathin films by quasi-covalent interfacial couplings beyond conventional van der Waals interactions.
关键词： few-layers bismuth(110),two-dimensional heterostructures,thickness dependence,scanning tunneling microscopy,density functional theory calculations,covalent-like quasi-bonds,proximity effect
更新于2025-09-23 15:22:29
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Mixing Thermodynamics and Photocatalytic Properties of GaP-ZnS solid solutions
摘要： Preparation of solid solutions represents an effective means to improve the photocatalytic properties of semiconductor-based materials. Nevertheless, the effects of site-occupancy disorder on the functional properties of materials are difficult to predict and consequently many experimental trials may be required before achieving enhanced photocatalytic activity. Here, first-principles methods are employed to estimate the mixing free energy and the structural and electronic properties of (GaP)x(ZnS)1?x solid solutions. The method relies on a multi-configurational supercell approach that takes into account the configurational and vibrational contributions to the free energy. Phase competition among the zinc-blende and wurtzite polymorphs is also considered. Overall excellent agreement with the available experimental data is demonstrated, namely: 1) zinc-blende is energetically most favorable, 2) the solid solution energy band gap lies within the 2–3 eV range, and 3) the energy band gap of the solid solution is direct for compositions x ≤ 75%. It is found that at ambient conditions, (GaP)x(ZnS)1?x solid solutions with x ≈ 25%, 50% and 75% render promising hydrogen evolution photocatalysts for water splitting under visible light, owing to their favorable energy band gaps and band levels relative to vacuum.
关键词： multiconfigurational supercell approach,semiconductor solid solutions,density functional theory calculations,photocatalytic materials
更新于2025-09-23 15:22:29
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Strongly inhomogeneous distribution of spectral properties of silicon-vacancy color centers in nanodiamonds
摘要： The silicon-vacancy (SiV) color center in diamond is a solid-state single photon emitter and spin quantum bit suited as a component in quantum devices. Here, we show that SiV centers in nanodiamonds exhibit a strongly inhomogeneous distribution with regard to the center wavelengths and linewidths of the zero-phonon-line (ZPL) emission at room temperature. We find that the SiV centers separate in two clusters: one group exhibits ZPLs with center wavelengths within a narrow range ≈730–742 nm and broad linewidths between 5 and 17 nm, whereas the second group comprises a very broad distribution of center wavelengths between 715 and 835 nm, but narrow linewidths from below 1 up to 4 nm. Supported by ab initio Kohn–Sham density functional theory calculations we show that the ZPL shifts of the first group are consistently explained by strain in the diamond lattice. Further, we suggest, that the second group showing the strongly inhomogeneous distribution of center wavelengths might be comprised of a new class of silicon-related defects. Whereas single photon emission is demonstrated for defect centers of both clusters, we show that emitters from different clusters show different spectroscopic features such as variations of the phonon sideband spectra and different blinking dynamics.
关键词： diamond,single photons,density functional theory calculations,color centers,optical emission,nanodiamond
更新于2025-09-19 17:15:36
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Intrinsic defects in and electronic properties of <i>θ</i> -Al <sub/>13</sub> Fe <sub/>4</sub> : an <i>ab initio</i> DFT study
摘要： θ-Al13Fe4 exhibits a rich variety of crystal physics. It contains twenty crystallographically different atomic species with a diversity of chemical coordination. An understanding of its structural and physical properties is a prerequisite for controlling its formation and its use. Here we investigate systematically the intrinsic defects in θ-Al13Fe4 using a ?rst-principles density-functional theory method. The calculations reveal that among the various intrinsic defects it is energetically favourable for Fe substitution of Al but on just three of the ?fteen Al sites. This results in a new structural model, Al68Fe24(Al, Fe)4(Al, Fe)2(Al, Fe)4 (the Roman numerals represent the Al sites) which updates the thermodynamic model, currently in use, which is associated with the formation of vacancies on some of the Al sites. The calculations demonstrate that the addition of Fe induces magnetism which gives rise to clustering. The calculations provide the dependence of the lattice parameters on Fe concentration and explain the experimental data in the literature. The information obtained here provides insight into the formation and properties of θ-Al13Fe4 and its role in the solidi?cation of Al alloys, in determination of the microstructure and related mechanical properties of the products, and in catalysis for organic reactions.
关键词： magnetic properties,density-functional theory calculations,intrinsic defects,θ-Al13Fe4,phase stability
更新于2025-09-19 17:15:36
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A novel and simple imidazo[1,2-a]pyridin fluorescent probe for the sensitive and selective imaging of cysteine in living cells and zebrafish
摘要： Cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) play many crucial physiological roles in organisms. Their abnormal levels can cause and indicate various diseases. In the present study, a small-molecule fluorescent probe 2-(imidazo[1,2-a]pyridin-2-yl)phenyl acrylate (IPPA) was designed, synthesized and characterized by NMR, FT-IR and HRMS. IPPA can selectively detect Cys over other analytes because of an approximately 76 times enhancement in fluorescence intensity. The limit of detection of IPPA for Cys was 0.33 μM. The pseudo-first-order rate constant of the reaction between IPPA and Cys was approximately 10 times that of the reaction between IPPA and Hcy (KCys 3.18 × 10?? S?1 vs KHcy 4.92 × 10?? S?1), indicating that Cys can be distinguished from Hcy. In addition, IPPA exhibits strong anti-interference ability, small molecular weight, high efficiency, low toxicity and good cell permeability. It was successfully used in imaging HepG2 cells and zebrafish. The fluorescence response of IPPA for calf serum are powerful proofs for practical application. Therefore, IPPA has high potential for bioassay applications.
关键词： Fluorescent probe,Imaging,Cysteine,Cellular detection,Density functional theory calculations
更新于2025-09-19 17:15:36
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Theoretical, spectroscopical, and experimental investigations of small azomethine molecules for organic solar cells
摘要： Small azomethine molecules (4,4′-bis((2-hydroxy-4-octyloxyphenyl)methylimino)diphenylmethane (BP-DPM) and 4,4′-bis((2-hydroxy-4-octyloxyphenyl)methylimino)diphenyl ether (BP-DPE)) for photovoltaic applications were synthesized by condensation of appropriate arylaldehydes and arylendiamines and characterized using Fourier-transform infrared spectroscopy, 1H NMR, 13C NMR, and liquid chromatography–mass spectrometry. Azomethine molecules are additives in organic solar cells. The effect of a possible energy transfer between BP-DPE and P3HT on the photovoltaic performance of devices employing ternary blends of BP-DPE:P3HT: phenyl-C61-butyric acid methyl ester (PCBM) was investigated by absorption and emission spectra. The devices employing BP-DPE:P3HT:PCBM with 1:4 ratio exhibited a Jsc of 4.2 mA cm?2, Voc of 575 mV, and FF of 0.27 which led to a power conversion efficiency (PCE) of 0.65%. In addition, density functional theory calculations (DFT/B3LYP/6-31G(d)) were used to determine the optimized molecular geometry, highest occupied molecular orbital–lowest unoccupied molecular orbital energies, electronic structures, and the molecular electrostatic potential surfaces of the molecules.
关键词： density functional theory calculations,organic solar cell,azomethines,fluorescence
更新于2025-09-19 17:13:59