Synthesis of V5+‐doped Ag/AgCl photocatalysts with enhanced visible light photocatalytic activity

V⁵⁺‐doped Ag/AgCl photocatalysts were prepared via the ion exchange method. The catalysts were characterized using X‐ray diffractometry, transmission electron microscopy, and energy‐dispersive X‐ray, X‐ray photoelectron, Fourier transform infrared and ultraviolet–visible spectroscopies. The V⁵⁺‐doped Ag/AgCl photocatalysts show much higher photocatalytic activities than Ag/AgCl under visible light irradiation for methyl orange (MO) decomposition. Especially, the 2.0 wt% V⁵⁺‐doped Ag/AgCl photocatalyst shows the highest photocatalytic activity and also high stability after five cycles. The MO degradation rate during each cycle is almost maintained at 97%. Electron spin resonance spectroscopy and radical trapping experiments reveal that holes play an important role in the photocatalytic process.     

Quantitative Mikrobestimmung von Chlorid

Ohne Zusammenfassung

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Quantitative microdetermination of chloride

     

Ageing of AgCl/Cd nuclear track detectors monitored by luminescence spectroscopy

Abstract

Solid-state nuclear track detectors, made of Cd doped AgCl crystals, are commonly prepared by rolling into the form of thin foils. Subsequent long-term relaxation is however needed to obtain good quality tracks. The present communication shows for the first time that this detector “ageing” is reflected in lowtemperature (77 K) luminescence spectra. Maximum of the emission band shows a slow (lasting for ～ 100 hours) blue shift, the magnitude of which (as much as 25 nm) depends on the compression ratio caused by the rolling. The shift is believed to be due to the rearrangement of Cd⁺⁺ ions around freshly introduced dislocations. This finding opens the possibility of monitoring non-destructively the process of detector ageing and to determine the minimum time required for saturation.     

Electrochemically regenerative visible light-induced reactivity of α-Fe2O3 films with Ag(core)–AgCl(shell) microcrystal composites

Ag(core)–AgCl(shell) microcrystal composites (Ag@AgCl) have been formed on an α-Fe₂O₃ film-coated SnO₂ electrode by a 2 step method consisting of the electrochemical reduction of Ag⁺ ions and the subsequent electrochemical oxidation. The synergy of α-Fe₂O₃ and Ag@AgCl gave rise to a high visible light-induced reactivity (λ_ex > 420 nm) for the oxidation of 2-naphthol (2-NAP) used as a model water pollutant in the presence and absence of oxygen. These findings were attributable to the function of Ag@AgCl composites as an excellent charge-separation promoter and built-in acceptor.     

The second-order elastic constants of an AgBr-(56.6%) AgCl mixed crystal from 20°C to 400°C

Abstract

Initial measurements of the second-order elastic constants of an AgBr-(56.6%) AgCl mixed crystal have been made from 20—400°C. Over this temperature range, C'₁₁ decreased by 44%, C' by 71%, C₄₄ by 22%, C₁₁ by 53%, C₁₂ by 40%, and B _s by 46%. The decreases in the elastic constants are linear until approximately 280°C, whereupon all but C' begin to decrease more rapidly than linearly with variations from linearity of 4—20% at 400°C and C' remains linear at all temperatures. This anomalous behavior is similar to other silver halide physical properties and may be attributed to the unusually high defect concentration at high temperatures. Similar elastic constant changes are seen in superionic conductors near the superionic transition, indicating that the silver halides may be starting the transition to a superionic state when the halide sublattice melts and the transition is frustrated.     

Spin Hamiltonian parameters and local structures for tetragonal and orthorhombic Ir2+ centers in AgCl

The perturbation formulae of the spin Hamiltonian parameters (the anisotropic g factors, hyperfine structure constants and superhyperfine parameters) are established for a 5d⁷ ion in an orthorhombically elongated octahedron based on the cluster approach. These formulae are applied to the theoretical studies of the EPR spectra and the local structures for the tetragonal and orthorhombic Ir²⁺ centers in AgCl. For the tetragonal Ir²⁺ center, the uncompensated substitutional [IrCl₆]⁴ cluster is found to experience a relative elongation of about 0.08 Å along the C ₄ axis due to the Jahn–Teller effect. For the orthorhombic center, the ligand octahedron also suffers Jahn–Teller elongation (by about 0.08 Å) along the [001] (or Z) axis. Meanwhile, the ligand Cl intervening in the impurity Ir²⁺ and the next nearest neighbor silver vacancy V_Ag along the [100] (or X) axis may undergo an inward displacement of 0.004 Å towards the center of the octahedron due to electrostatic repulsion of the V_Ag. The calculated spin Hamiltonian parameters based on the above local structures show good agreement with experimental data for both centers.     

Photochemistry of a cyanine dye in reversed micelles

The effect of microenvironment on the existing state and spectral properties of a cyanine dye in different systems were investigated. Due to the space limitation and the polarity evolution of the water cell of reversed micelles, the optical behavior of the dye in reversed micelles was very different from in water and alcohol. The effect of surfactants with different charge on the interaction of a cyanine dye with AgCl nanoparticles in reversed micelles were also researched. The adsorption state of the dye on AgCl nanoparticles in reversed micelles was discussed.     

Ag/AgCl纳米粒子的制备及其共振散射光谱研究

以AgCl纳米粒子作晶种,在柠檬酸三钠存在条件下,AgCl纳米粒子表面结合的银离子被光化学还原而获得Ag/AgCl复合纳米粒子。研究了Ag/AgCl纳米粒子的光谱特性,在310和590nm处产生二个共振散射峰,在400nm处产生一个吸收峰。     

Nonequilibrium phase diagrams in the PbCl2−AgCl eutectic system

It is well-known that eutectics do not necessarily grow at the eutectic temperature, or with the eutectic composition. Thus, the eutectic point can be shifted due to nonequilibrium conditions in the system. This fact was observed in many experiments. We try to explain this behaviour on base of the study of phase transformation kinetics. We construct the kinetic phase diagrams of PbCl₂?AgCl within the framework as of the nucleation theory as of the theory of growth on the phase interface. Our models are based on the molecular model of the difference of chemical potential of components for the liquid and solid phases. The proposed model describes the position of the eutectic point very well and is practically applied for the study of nonequilibrium directional growth in the PbCl₂?AgCl system.     

钛/活细胞界面原位EIS研究

设计了原位电解池用于生物材料/活细胞界面电化学交流阻抗谱(EIS)的测量, 原位观测了钛/MG63细胞界面EIS行为及其随时间的变化. 原位电解池中引入Ag/AgCl作为参比电极, 解决了EIS测量过程中高频部分信号失真的问题. 钛/MG63细胞界面EIS研究初步结果表明: 活细胞在钛电极表面附着, 可改变界面双电层结构和电极的表面状态, 进而影响界面的电化学性质. 实验发现, 由于钛电极表面氧化层的阻抗信号处于中低频段, 而细胞膜层自身的电化学阻抗响应位于高频范围, 由此, 可分别分析不同的电极过程, 解析其相互关系, 研究活细胞在生物材料表面的作用机理.