Enhanced properties for visible-light-driven photocatalysis of Ag nanoparticle modified Bi2MoO6 nanoplates

The visible light driven Bi₂MoO₆ photocatalyst doped with different contents of Ag nanoparticles was successfully synthesized by a combination of hydrothermal and sonochemical methods. The as-synthesized samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning and transmission electron microscopy (SEM and TEM) and UV–visible spectroscopy to investigate crystalline structure, morphology, composition and photocatalytic properties. XRD patterns and TEM images of the samples revealed pure phase orthorhombic Bi₂MoO₆ nanoplates without any detection of Ag dopant due to its low concentration and very tiny particle size. TEM images showed that Ag nanoparticles with the size of 10–15 nm were dispersed randomly on the surface of Bi₂MoO₆. The XPS analysis of Ag/Bi₂MoO₆ nanocomposites revealed the presence of additional metallic Ag. Photocatalytic activities of the Ag/Bi₂MoO₆ nanocomposites were evaluated by determining the degradation of rhodamine B (RhB) under visible light radiation. In this research, the 10 wt% Ag/Bi₂MoO₆ nanocomposites showed the best photocatalytic activity. The results suggest that the dispersion of Ag nanoparticles on the surface of Bi₂MoO₆ significantly enhances its photocatalytic activity.     

Effect of Al content on the performance of Cu(In,Al)Se2 powders prepared by mechanochemical process

Cu(In,Al)Se₂ (CIAS) powders with varying Al/(In+Al) ratios x (x=0, 0.15, 0.23, 0.38, 0.57) were synthesized by mechanochemical process (MCP). Composition, morphology of CIAS powders was investigated by energy dispersive analysis and scanning electron microscopy, respectively. Influence of Al content on structural and optical properties of CIAS was detected by X-ray diffraction and UV–Vis spectroscopy, respectively. The results show molecularity and stoichiometry deviation of composition were small. Particle aggregation and inhomogeneous distribution of Cu, In, Al and Se element is observed at early milling stage. Field emission transmission electron microscopy image confirms that the particles can be milled to several hundred nanometers. Chalcopyrite characteristic peaks of CuInSe₂ are clearly observed. CIAS crystalline size decreases as Al₂O₃ increases in the products. CIAS (1 1 2) peaks shifts to high value and lattice constants for CIAS samples decrease with the Al additions. The band gap enlarged from 1.01 eV to 1.29 eV by adding Al. Al₂O₃ impurities impact CIAS powder grain size and the band gap seriously. All CIAS samples detected by hot probe method show the p-type conductivity.     

The surface morphology,structural properties and chemical composition of Cd1−xZnxTe polycrystalline thick films deposited by close spaced vacuum sublimation

Thick polycrystalline Cd_1−xZn_xTe films with x ranged from 0.37 to 0.80 were obtained by the close spaced vacuum sublimation method. In order to investigate properties of the films structural, PIXE and Raman studies were carried out. Determination of chemical composition of the films by EDS, PIXE and XRD has shown good correlation of results. Raman spectroscopy reveals the relation between zinc concentration and vibrational properties of the films. Studies of the spatial distribution of the chemical elements on the film surface by micro-PIXE and micro-Raman spectroscopy have shown that films are uniform and free of secondary phases such as CdTe, ZnTe and Te inclusions.     

T(x) phase diagram of the Cu2Se-Al2Se3 system

Twenty alloys of various compositions in the Cu₂Se-Al₂Se₃ system were prepared and investigated. The T(x) phase diagram of the Cu₂Se-Al₂Se₃ system was obtained from x-ray diffraction, differential thermal analysis, and microstructure investigation for the first time. The homogeneity region of the CuAlSe₂ semiconducting compound was established. Previous articles by this author were presented with the spelling of his name as B.V. Korzun.     

Structural,chemical bonding and optoelectronic properties of Mg doped zinc chalcogenides: A first principles study

A first-principal technique is employed to investigate the concentration dependence of the structural, electronic band structure, optical and chemical bonding properties of Zn_1−xMg_xS, Zn_1−xMg_xSe and Zn_1−xMg_xTe alloys. Structural parameters such as lattice constants and bulk moduli are found to vary non-linearly with changing concentration x and deviating from Vegard׳s law. Parent binaries as well as ternary alloys have a direct band gap (Γ–Γ) which increases non-linearly with increment in concentration. Chemical bonding nature changes from strong covalency to partial ionic character in increasing Mg-contents. The direct band gap and high optical activity in visible and ultraviolet range reveal the implication of these alloys in the optoelectronic devices applications.     

（英）组分过冲对InP基InAlAs递变缓冲层的影响

通过在InP基InxAl1-xAs 递变缓冲层上生长In0.78Ga0.22As/In0.78Al0.22As量子阱和In0.84Ga0.16As探测器结构,研究了缓冲层中组分过冲对材料特性的影响。原子力显微镜结果表明,在InAlAs缓冲层中采用组分过冲可以使量子阱及探测器样品表面粗糙度都得到降低。对于相对较薄的量子阱结构,X射线衍射倒易空间扫描图和光致发光谱的测量表明,使用组分过冲可以增加弛豫度、减小剩余应力并改善光学性质。而对于较厚的探测器结构,X射线衍射和光致发光谱测试发现使用组分过冲后的材料性质没有明显的变化。量子阱和探测器结构的这些不同特性需要在器件设计应用中加以考虑。     

The Shubnikov-de Haas effect and thermoelectric properties of Tl-doped Sb2Te3 and Bi2Se3

Semiconductors - The influence of doping with Tl on the Shubnikov-de Haas effect at T = 4.2 K in magnetic fields up to 38 T in p-Sb2−x Tl x Te3 (x = 0, 0.005, 0.015, and 0.05) and...     

Defect characterization of Tl4GaIn3Se2S6 layered single crystals by photoluminescence

Photoluminescence (PL) spectra of Tl₄GaIn₃Se₂S₆ layered crystals grown by the Bridgman method have been studied in the energy region of 2.02–2.35 eV and in the temperature range of 16–45 K. A broad PL band centered at 2.20 eV was observed at T=16 K. Variations of emission band has been studied as a function of excitation laser intensity in the 0.1 to 149.9 mW cm⁻² range. Radiative transitions from shallow donor level located at 10 meV below the bottom of conduction band to moderately deep acceptor level located at 180 meV above the top of the valence band were suggested to be responsible for the observed PL band. An energy level diagram showing transitions in the band gap of the crystal was plotted taking into account the results of present work and previously reported paper on thermally stimulated current measurements carried out below room temperature. Analysis of the transmission and reflection measurements performed in the wavelength range of 400–1030 nm at room temperature revealed the presence of indirect transitions with 2.22 eV band gap energy.     

Interrelation of vibrational spectra of Ag3Ga5Se9, Ag3Ga5Te9 and Ag3In5Te9 single crystals: A consequence of trivalent cation and anion substitutions

Silver gallium (indium) ternary selenides (tellurides) single crystals were studied through infrared reflection in the frequency range of 80–500 cm⁻¹. These spectra presented four infrared-active modes for studied crystals. Spectral dependencies of optical constants were computed from reflectivity spectra. The frequencies of transverse and longitudinal optical modes, damping constants and oscillator strengths were also evaluated. By replacing light selenium anions by heavier tellurium ones in Ag₃Ga₅Se₉ crystal and by substitution of light gallium cations by heavier indium ones in Ag₃Ga₅Te₉ crystal all the bands shift towards low frequencies. The bands observed in IR spectra of studied crystals were assigned to various vibration types (valence and valence-deformation). Crystal structure and atomic composition ratio of the constituent elements in Ag₃Ga₅Se₉, Ag₃Ga₅Te₉ and Ag₃In₅Te₉ crystals were revealed by structural characterization techniques of X-ray diffraction and energy dispersive spectroscopy.     

Electronic and optical properties of the doped TiO2 system

By the total energy pseudo-potential approach of plane wave, we study the electronic and optical properties of the anatase TiO2 systems with Sc-doped, oxygen vacancies included, and Sc and oxygen vacancies co-existing, respectively. The obtained results show that the contribution by the doped Sc lies mainly in the valence band, and the light absorption in the visible region is obvious. A Mott phase transformation takes place in the presence of oxygen vacancies, and the light absorption in the visible region is also obvious. In particular, the absorption in the visible region of the co-doped system is enhanced coherently due to the influences both from doped Sc and oxygen vacancies.     

A3BGa3Si2O14晶体的结构、光学性质的系统研究

用提拉法成功地生长了具有La3Ga5SiO14(LGS)结构的A3BGa3Si2O14(A=Ca，Sr；B=Nb，Ta)系列单晶；用X-射线粉末衍射证明了其单晶结构，并在200-3200nm间测其透过谱。     

Structure of 2-(iminocoumar-3-yl)-4-(coumar-3-yl)-thiazole,C2lHl4N2O3S

We have determined the structure of 2-(iminocouma-3-yl)-4-(coumar-3-yl)-thiazole, C₂₁H₁₄N₂O₃S, M_r=372.4, λ = 0.71073 Å, monoclinic, space group P2₁/n, a = 9.472(2) Å, b = 11.284(2) Å, c = 15.821(3) Å, β = 86.50(2)°, V = 1687.9(6) ų, Z = 4, D_x = 1.465 Mg m^?3, μ(Mo Kα) = 0.207 mm^?1, F(000) = 768, S = 1.91, R = 3.82%, wR = 3.26% for 1251 observed reflections (F > 6_σF). In the observed conformation of the molecule the imino group forms an intramolecular H…S bond of length 2.26 Å and the carbonyl oxygen makes a short contact with the hydrogen atom of the thiazolyl cycle. The molecule is planar. In the crystal structure a particular disorder of about 20% of molecules is observed with respect to the pseudo-mirror plane which is perpendicular to the molecular plane and passes through the thiazolyl N atom and the middle of the S? CH bond. The disagreement found between the observed conformation and that predicted by molecular mechanics calculations is explained by the tendency of the molecule to have the lowest value of dipole moment due to minimisation of the electrostatic contribution to the energy.     

Transition of nanocrystalline In(OH)3 as spherical Indium Oxide nanoparticles embedded platelets

Indium oxide nanoparticles were synthesized by a co-precipitation method using the basic raw materials like Indium (III) Chloride and the precipitating reagent as Ammonium hydroxide. The formation of Indium oxide is highly dependent on temperature. The morphology, structural, particle size, optical and electrical properties of In₂O₃ nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive microscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared radiation (FTIR), UV spectra, Photoluminescence spectroscopic (PL) and Electrical resistance measurements. The results exhibit a crystalline cubic structure in particles, spherical shape, size about 14 nm and optical band gap of 4.20 eV.     

Effects of Bi2Se3 Nanoparticle Inclusions on the Microstructure and Thermoelectric Properties of Bi2Te3-Based Nanocomposites

A series of thermoelectric nanocomposite samples were prepared by integrating Bi₂Se₃ nanoparticles into a bulk Bi₂Te₃ matrix. Primarily, spherical Bi₂Se₃ nanoparticles with diameter of ～30 nm were synthesized by combining bismuth acetate with elemental Te in oleic acid solution. Bi₂Te₃-based nanocomposite samples were prepared by consolidating the appropriate quantity of Bi₂Se₃ nanoparticles with the starting elements (Bi and Te) using typical solid-state synthetic reactions. The microstructure and composition of the Bi₂Te₃-based nanocomposites, as well as the effects of the Bi₂Se₃ nanoparticles on their thermoelectric properties, are investigated. Transmission electron microscopy observation of the Bi₂Te₃-based nanocomposites reveals two types of interface between the constituent materials, i.e., coherent and incoherent, depending on the Bi₂Se₃ concentration. The Bi₂Se₃ nanoparticles in the Bi₂Te₃ matrix act as scattering centers for a wider range of phonon frequencies, thereby reducing the thermal conductivity. As a result, the maximum ZT value of 0.75 is obtained for the Bi₂Te₃ nanocomposite with 10 wt.% Bi₂Se₃ nanoparticles at room temperature. It is clear that the reduction in the thermal conductivity plays a central role in the enhancement of the ZT value.     

Bi_2O_3含量对ZnO-BaO-Bi_2O_3-B_2O_3系玻璃性能的影响

用熔融冷却方法制备了ZnO-BaO-Bi2O3-B2O3系低熔点玻璃,研究了Bi2O3含量对所制玻璃热学性能和体积电阻率的影响。结果表明:随着Bi2O3含量的增大,所制玻璃密度和线膨胀系数增大,而膨胀转变温度(tg)、膨胀软化温度(tf)和体积电阻率(ρv)减小;当Bi2O3摩尔分数为0～12%时,随着Bi2O3含量增大,玻璃的tg、tf和ρv显著降低;而当Bi2O3摩尔分数为12%～25%时,这种变化趋势明显减弱。     

An oil-in-water self-assembly synthesis,characterization and photocatalytic properties of nano Ag@AgBr sensitized K2Ti4O9

Nano-sized plasmonic Ag@AgBr sensitized K₂Ti₄O₉ composite photocatalysts (hereafter designated as Ag@AgBr/K₂Ti₄O₉) was synthesized via a facile oil-in-water self-assembly method. The photocatalytic activity of the prepared materials for methylene blue (MB) degradation was examined under visible light irradiation. The results reveal that the size of Ag@AgBr, which evenly dispersed on the surface of K₂Ti₄O₉, distributes about 20 nm. The UV–vis diffuse reflectance spectra indicate that Ag@AgBr/K₂Ti₄O₉ samples have a significantly enhanced optical absorption in 420–800 nm. The photocatalytic activities of the Ag@AgBr/K₂Ti₄O₉ samples increase first and then decrease with increasing amount of loading Ag@AgBr and the Ag@AgBr(10 wt%)/K₂Ti₄O₉ sample exhibits the best photocatalytic activity and 95.75% MB was degraded after irradiation for 90 min. Additionally, studies performed using radical scavengers indicated that h⁺, ·OH and Br⁰ acted as the main reactive species.     

Mg2+和Mn2+掺杂对BaTiO3-金属复合系介电性能的影响

在钛酸钡基料中加入碱式碳酸镁、碳酸锰、金属氧化物及其它添加剂,经过球磨、预烧、造粒等工艺, 在Mg2 和Mn2 的综合作用下,系统得以在中温(低于1 150 ℃)下烧成.陶瓷的介电性能得到有效改善,εr达到2 587, tan δ小于1.2×10-2,在-55～ 170 ℃的宽广温区内,ΔC/C为± 15 %.     

Structural and optical properties of AlN/Si system

Aluminum nitride (AlN) is a wide band gap III–V semiconductor material which is often used for optical applications. Thin films of aluminum nitride were deposited by ion beam sputtering in an Ar–N₂ atmosphere on Si (1 0 0). For film preparation, the N₂ flow was kept at 5 sccm and the ratio of N₂ and Ar was 4:1. The films have been characterized by Grazing Incidence X-ray Diffraction (GIXRD), X-ray Reflectometry (XRR), Atomic Force Microscopy (AFM) and optical spectroscopy. GIXRD shows that the structure of the as-deposited sample of AlN is hexagonal. It is observed that neither the ion-beam-induced dissociation of the nitride film nor the enhanced nitrogen diffusion across the interface takes place after Au ion irradiation. XRR was used to determine the thickness of the films. The reflectance of the irradiated films increases in the range 200–280 nm. UV–vis spectra were taken in Kubelka Munk (KM) units for as-deposited and irradiated samples. The band gap was calculated for both types of samples, which shows that the band gap of irradiated films of aluminum nitride decreases due to the increase in metal content at the surface. AFM confirms that the roughness of aluminum nitride increases by irradiation.     

Electrical transport properties of cerium doped Bi2Te3 thin films grown by molecular beam epitaxy

Introducing magnetism into topological insulators (Tls) can tune the topological surface states and produce exotic physical effects.Rare earth elements are considered as important dopant candidates,due to their large magnetic moments from heavily shielded 4f electrons.As the first element with just one 4f electron,cerium (Ce) offers an ideal platform for explor-ing the doping effect of f-electron in Tls.Here in this work,we have grown cerium-doped topological insulator Bi2Te3 thin films on an Al2O3(0001) substrate by molecular beam epitaxy (MBE).Electronic transport measurements revealed the Kondo effect,weak anti-localization (WAL) effect and suppression of surface conducting channels by Ce doping.Our research shows the funda-mental doping effects of Ce in Bi2Te3 thin films,and demonstrates that such a system could be a good platform for further re-search.     

Bi2O3对TiO2系压敏陶瓷性能的影响

采用传统电子陶瓷工艺制作了TiO2系压敏陶瓷。通过测试其I-V特性、复阻抗特性、晶界电阻、晶粒电阻及势垒高度,研究了Bi2O3对TiO2-Bi2O3-Nb2O5-SrO系压敏陶瓷微结构及电性能的影响。结果表明,Bi2O3的适当掺杂范围在0.3%~0.5%(摩尔分数)。其掺杂量的变化,可显著改变TiO2-Bi2O3-Nb2O5-SrO系压敏陶瓷的晶界电阻及势垒高度,进而对压敏陶瓷的电学非线性特性产生影响。当x(Bi2O3)为0.4%时,压敏陶瓷的V1mA与α分别为40V/mm与6.2。