AgBr/TiO2纳米纤维的制备及其光催化性能研究

以钛酸丁酯、聚乙烯吡咯烷酮(PVP)、无水乙醇为原料,利用静电纺丝技术制备出Ti(OC₄H₉)₄/PVP纳米纤维,经500~1 000 ℃高温煅烧制得TiO₂纳米纤维,再通过水热法将AgBr纳米颗粒负载到TiO₂纳米纤维表面。利用X射线衍射仪、场发射扫描电镜、差热-热重分析对AgBr/TiO₂纳米纤维进行表征分析。利用甲基橙(MO)为降解底物模拟染料废水,研究TiO₂、AgBr/TiO₂纳米纤维的光催化性能。分析结果表明,经800 ℃煅烧后的TiO₂纳米纤维,在添加量为100 mg时光催化效果较好;相同条件下,AgBr/TiO₂纳米纤维的光催化降解率高于TiO₂纳米纤维,AgBr/TiO₂纳米纤维对甲基橙的降解率为95.97%。     

F‐doped Ag/AgBr with enhanced visible‐light photocatalytic activity and mechanism

Novel F‐doped Ag/AgBr photocatalysts containing various amounts of F^? were synthesized by an ion exchange method. The photocatalysts were characterized using X‐ray diffraction (XRD), scanning and transmission electron microscopies, X‐ray photoelectron, ultraviolet–visible absorption and photoluminescence spectroscopies and electron spin resonance (ESR). Powder XRD revealed that F^? was inserted into the crystal lattices of AgBr and partially replaced Br^?, resulting in the contraction of the AgBr lattices. Methyl orange photodegradation experiments showed that the photocatalytic activity of F‐doped Ag/AgBr was significantly dependent on the amount of F^?. Ag/AgBr doped with 0.02 M F^? achieved the highest activity of 91% after 8 min. ESR showed the main active species in methyl orange degradation was ^?OH. The main enhancement mechanism is that F^? inhibits the recombination of electron–hole pairs.     

(AgBr)_核·(Ag)_壳纳米粒子的制备及其共振散射光谱研究

以 (AgBr) m 团簇作晶种 ,在柠檬酸钠存在条件下 ,(AgBr) m 团簇表面结合的Ag+被光化学还原而获得土红色的液相 (AgBr) 核·(Ag) 壳 纳米粒子 .研究了 (AgBr) 核·(Ag) 壳 纳米粒子的光谱特性 ,在 51 2nm处有最强共振散射峰 ,在41 0nm处产生一个吸收峰 .结果表明 ,(AgBr) 核·(Ag) 壳 纳米粒子的形成是导致51 2nm共振光散射的根本原因 .     

Thermodynamics and phase equilibrium studies of silver halide-cobalt(II) halide systems

Phase diagrams for the systems AgCl-CoCl₂ and AgBr-CoBr₂ were determined by differential scanning calorimetry. The systems are of the eutectic type. Eutectic points are at 271±2 K, 19.5 mol% CoCl₂ and 653±2 K, 17.0 mol% CoBr₂, respectively. The solid solubility does not exceed 2 and 4 mol% in the systems AgCl-CoCl₂ and AgBr-CoBr₂, respectively. Thermodynamic activities of components in molten mixtures and molar free enthalpies of mixing were determined for both systems on the basis of liquidus curves. Deviations from ideality were not found to be considerable.     

Study on time-resolved fluorescence dynamics of cyanine dye sensitizing AgBr

The fluorescence spectra of three different dyes adsorbed on the tabular and cubic AgBr microcrystals are obtained by the picosecond time-resolved streak camera technique. The dependence of the ultrafast electron transferring from dye-aggregates to the conduction band of AgBr and the efficiency of spectral sensitization on different kinds of dyes with different concentrations is analyzed. Further more, the microcosmic mechanism of the sensitization process is discussed. It is found that the fluorescence decay curves are fitted very well by the double exponential function, consisting of a slow component and a fast one with large amplitude. We consider this fast one mainly attributable to the electron transfer from dye J-aggregates to the conduction band of AgBr. Supported by the National Natural Science Foundation of China (Grant No. 60478033), the Doctoral Foundation of Hebei Province of China (Grant No. B2003119), and the Science and Technology Project of Hebei Province of China (Grant No. 05215102)