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1.
WS2由于其优异的物理和光电性质引起了广泛关注。本研究基于第一性原理计算方法,探索了本征单层WS2及不同浓度W原子替位钇(Y)掺杂WS2的电子结构和光学特性。结果表明本征单层WS2为带隙1.814 eV的直接带隙半导体。进行4%浓度(原子数分数)的Y原子掺杂后,带隙减小为1.508 eV,依旧保持着直接带隙的特性,随着Y掺杂浓度的不断增大,掺杂WS2带隙进一步减小,当浓度达到25%时,能带结构转变为0.658 eV的间接带隙,WS2表现出磁性。适量浓度的掺杂可以提高材料的导电性能,且掺杂浓度增大时,体系依旧保持着透明性并且在红外光和可见光区对光子的吸收能力、材料的介电性能都有着显著提高。本文为WS2二维材料相关光电器件的研究提供了理论依据。 相似文献
2.
Dr. Ming-Hui Sun Prof. Dr. Li-Hua Chen Shen Yu Prof. Dr. Yu Li Xian-Gang Zhou Dr. Zhi-Yi Hu Prof. Dr. Yu-Han Sun Prof. Dr. Yan Xu Prof. Dr. Bao-Lian Su 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(44):19750-19759
Zeolite Beta single crystals with intracrystalline hierarchical porosity at macro-, meso-, and micro-length scales can effectively overcome the diffusion limitations in the conversion of bulky molecules. However, the construction of large zeolite Beta single crystals with such porosity is a challenge. We report herein the synthesis of hierarchically ordered macro-mesoporous single-crystalline zeolite Beta (OMMS-Beta) with a rare micron-scale crystal size by an in situ bottom-up confined zeolite crystallization strategy. The fully interconnected intracrystalline macro-meso-microporous hierarchy and the micron-sized single-crystalline nature of OMMS-Beta lead to improved accessibility to active sites and outstanding (hydro)thermal stability. Higher catalytic performances in gas-phase and liquid-phase acid-catalyzed reactions involving bulky molecules are obtained compared to commercial Beta and nanosized Beta zeolites. The strategy has been extended to the synthesis of other zeolitic materials, including ZSM-5, TS-1, and SAPO-34. 相似文献
3.
A zinc coordination polymer derived from pyridine-2,6-dicarboxylate (PDC), {[Zn2(PDC)2]}n, was successfully prepared via conventional, sonication and microwave-irradiation methods. The composition and characteristics of the obtained coordination polymers (CPs) were investigated by elemental analysis, TGA/DTA, X-ray diffraction and spectroscopic techniques. The so obtained CPs were heat-treated in the air at 600 °C for 2 h to produce ZnO of nanosized particles (NPs). It is of interest to note that the synthesis approach of the precursor greatly affects both the nanoparticle size and the structure of the resulting ZnO NPs. Moreover, the smallest particle size was associated with the sample derived from the ultrasonically prepared precursor. TEM analysis revealed that all samples have sphere-like morphologies. Structural analysis of the prepared ZnO samples was conducted and compared using Rietveld analysis of their PXRD patterns. Optical band gap calculations based on analysis of the UV–vis spectra of ZnO samples using Tauc's power law were achieved. The highest band gap of 3.63 eV was observed for ZnO sample obtained from the ultrasonically prepared precursor. Furthermore, the photocatalytic activity of ZnO NPs for the removal of Eosin Y color was monitored. The highest removal efficiency was recorded for ZnO originated from the ultrasonically synthesized precursor. Enhancement of removal efficiency that reached 98% was attained in only a period of 8 min. Its recycling test showed that it can be reused without structural changes over four cycling experiments. 相似文献
4.
Specimens of iron-doped indium oxide (In1-xFex)2O3 with x?=?0.015, 0.03, 0.045 and 0.06, amalgamated through a traditional solid-state reaction method followed by H2/air sintering, were characterised using an X-ray diffractometer (XRD), a vibrating sample magnetometer (VSM), and a scanning electron microscope (SEM) to investigate their structural, magnetic and morphological properties respectively. According to XRD plots, all the specimens exhibit cubic bixbyite structures along with ancillary phases. Magnetic assessment showed that In2O3 has a negative susceptibility, exhibiting diamagnetic behaviour at room temperature. The doping of Fe ions induces ferromagnetic (FM) ordering, which is enhanced with increasing doping content. The strength of the magnetisation increases when the specimens are exposed to H2 but is reduced on further air sintering. A bound magnetic polaron (BMP) model is successfully fitted to the observed FM data involving localised carriers and magnetic cations. A multivariate assessment viz. a hierarchical cluster analysis (HCA) was used to corroborate and strengthen the experimental determined magnetic properties. A homogeneous particle distribution was observed in all SEM micrographs and is validated through MATLAB-based simulation by applying a watershed segmentation algorithm. Surface plots also confirm the change in magnetic properties with increase in doping concentration. 相似文献
5.
An approach of dynamic mesh adaptation for simulating 3‐dimensional unsteady moving‐immersed‐boundary flows 下载免费PDF全文
In this paper, we present an approach of dynamic mesh adaptation for simulating complex 3‐dimensional incompressible moving‐boundary flows by immersed boundary methods. Tetrahedral meshes are adapted by a hierarchical refining/coarsening algorithm. Regular refinement is accomplished by dividing 1 tetrahedron into 8 subcells, and irregular refinement is only for eliminating the hanging points. Merging the 8 subcells obtained by regular refinement, the mesh is coarsened. With hierarchical refining/coarsening, mesh adaptivity can be achieved by adjusting the mesh only 1 time for each adaptation period. The level difference between 2 neighboring cells never exceeds 1, and the geometrical quality of mesh does not degrade as the level of adaptive mesh increases. A predictor‐corrector scheme is introduced to eliminate the phase lag between adapted mesh and unsteady solution. The error caused by each solution transferring from the old mesh to the new adapted one is small because most of the nodes on the 2 meshes are coincident. An immersed boundary method named local domain‐free discretization is employed to solve the flow equations. Several numerical experiments have been conducted for 3‐dimensional incompressible moving‐boundary flows. By using the present approach, the number of mesh nodes is reduced greatly while the accuracy of solution can be preserved. 相似文献
6.
Inside Cover: Selective Transformation of Syngas into Gasoline‐Range Hydrocarbons over Mesoporous H‐ZSM‐5‐Supported Cobalt Nanoparticles (Chem. Eur. J. 5/2015) 下载免费PDF全文
7.
José Elguero Ibon Alkorta Janet E. Del Bene 《Magnetic resonance in chemistry : MRC》2020,58(8):727-732
Equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) calculations have been performed to determine coupling constants 1J(X–Y) for 65 molecules HmX–YHn, with X,Y ═ 1H, 7Li, 9Be, 11B, 13C, 15N, 17O, 19F, 31P, 33S, and 35Cl. The computed 1J(X–Y) values are in good agreement with available experimental data. The reduced coupling constants 1K(X–Y) have been derived from 1J(X–Y) by removing the dependence on the magnetogyric ratios of X and Y. Patterns are found for the reduced coupling constants on a 1K(X–Y) surface that are related to the positions of X and Y in the periodic table. 相似文献
8.
Yichen Zhou Mingmin Jia Dr. Xiongfei Zhang Prof. Dr. Jianfeng Yao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(35):7918-7922
Zeolite ZIF-8 has been etched with acid to form microporous ZIF-8-E crystals. These were then introduced into a polyethersulfone (PES) membrane matrix to enhance its CO2/N2 separation performance. Open through pores of size about 100 nm formed in the ZIF-8 crystals allow the ingrowth of polyethersulfone chains, ensuring a reduction in the number of nonselective voids, thereby achieving better interaction between ZIF-8-E and PES. As a result, the CO2/N2 separation performance of the ZIF-8-E/PES membrane increased significantly, showing a CO2 permeability of 15.7 Barrer and a CO2/N2 ideal selectivity of 6.5. 相似文献
9.
Chenxia Kang Dr. Ju Fang Likang Fu Shuxian Li Prof. Qiming Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(69):16392-16401
A 3D hierarchical carbon cloth/nitrogen-doped carbon nanowires/Ni@MnO2 (CC/N-CNWs/Ni@MnO2) nanocomposite electrode was rationally designed and prepared by electrodeposition. The N-CNWs derived from polypyrrole (PPy) nanowires on the carbon cloth have an open framework structure, which greatly increases the contact area between the electrode and electrolyte and provides short diffusion paths. The incorporation of the Ni layer between the N-CNWs and MnO2 is beneficial for significantly enhancing the electrical conductivity and boosting fast charge transfer as well as improving the charge-collection capacity. Thus, the as-prepared 3D hierarchical CC/N-CNWs/Ni@MnO2 electrode exhibits a higher specific capacitance of 571.4 F g−1 compared with those of CC/N-CNWs@MnO2 (311 F g−1), CC/Ni@MnO2 (196.6 F g−1), and CC@MnO2 (186.1 F g−1) at 1 A g−1 and remarkable rate capability (367.5 F g−1 at 10 A g−1). Moreover, asymmetric supercapacitors constructed with CC/N-CNWs/Ni@MnO2 as cathode material and activated carbon as anode material deliver an impressive energy density of 36.4 W h kg−1 at a power density of 900 W kg−1 and a good cycling life (72.8 % capacitance retention after 3500 cycles). This study paves a low-cost and simple way to design a hierarchical nanocomposite electrode with large surface area and superior electrical conductivity, which has wide application prospects in high-performance supercapacitors. 相似文献
10.