In order to understand the effect of surface chemical groups on the immobilized species, Au-containing imidazolium-based ionic liquid (IL) [Bmim][AuCl4] was intentionally immobilized on polystyrene (PS) submicrospheres (d～300 nm) with a very small surface area (4-10 m2/g), which possess carboxyl-moiety (COONa or COOH) on the surface. The behavior of immobilized [Bmim][AuCl4 ] on the two types of submicrospheres was investigated by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and powder X-ray diffraction (XRD). It was revealed that the melting points (Tm) of [Bmim][AuCl4 ] that had been immobilized on PS-COONa and PS-COOH submicrospheres were decreased by 2.7 and 4.1℃, respectively. The interaction mechanism between the IL and submicrosphere surface moieties was further analyzed by X-ray absorption fine structure (XAFS) analysis. The data indicated that the coordination environment of Au species changed markedly when [Bmim] [AuCl4] was immobilized on the surfaces of PS-COONa and PS-COOH submicrospheres, as illustrated by the decrease in white line peak intensity. The effect of surface COOH groups on Tm depression and the white line peak intensity of the XANES spectrum is more pronounced than that of COONa groups, most likely due to the possible hydrogen bond formation between the COOH group and [Bmim]+.
HE YaXingFU HaiYingLI ChengJI XiangGE XueWuZOU YangJIANG ZhengXU HongJieWU GuoZhong
Copper ion is the essential microelement to many organisms. In this paper, the local structure of Cu2+ in CuBr2 aqueous solutions with different concentrations are investigated by using X-ray absorption fine structure (XAFS) technique. XANES (X-ray Absorption Near Edge Structure) spectra indicate that charge transfer from Br- to Cu2+ decreases with the solution concentration, which lead to a shift of the absorption edge. The shoulder appearing at the rising edge proves to be characteristic of a tetragonal distortion. The Fourier transform magnitudes of EXAFS (Extended X-ray absorption fine structure) data of Cu species suggest that more Cu-Br bonds may exist in high concentrations. A fivefold coordination configuration like a pyramid is used as the fitting parameters. From the analysis of the coordination numbers, the proportion of Cu-O and Cu-Br is 4:1 in the saturated solution. The Br atom is on the equatorial plane of the model. The fitting results agree well with the experiment data.
DAI Binbin WANG Qian MA Jingyuan LI Jiong ZHANG Shuo HUANG Yuying HUANG Wei WU Guozhong ZOU Yang JIANG Zheng XU Hongjie
利用X射线近边吸收谱学(X-ray Absorption Near Edge Structure,XANES)方法研究了不同浓度的FeCl3水溶液中Fe3+离子的电子结构和近邻结构.在不同浓度的FeCl3水溶液的XANES谱中,XANES谱的形状随着FeCl3浓度的不同而发生改变.在XANES谱的边前结构中观测到边前锋的分裂,其分裂的能量差约为1.6eV,随着浓度的降低约有0.2eV的高能方向的位移,此边前结构由1s-3d轨道的电子跃迁引起,双峰分裂来源于配位体配位引起的3d轨道分裂.随着FeCl3浓度的改变,XANES谱的主峰也发生变化,此变化来源于溶液中Fe—Cl配位与Fe—O配位的比例变化.另外,利用量子化学计算的方法对于Fe3+与不同数目的H2O和Cl?配位体络合时的构型进行了计算,得到了Fe3+在水溶液中近邻结构的信息,从另一方面解释了FeCl3溶液中Fe3+离子3d轨道分裂能的变化.
本文介绍应用Labview软件、气体电离室、电流放大器及数据采集卡等仪器设备构成的同步辐射XAFS(X-ray absorption fine structure)光束线站(BL14W1)数据采集系统。该系统利用NI公司开发的新模块DSC module(Datalogging and Supervisory Control Module),实现了在Labview和EPICS(Experimental and Physics Industrial Control System)两个软件系统间数据的快速交换,使光束线控制的标准化和实验站用途的多样化有机结合。用Labview编写了数据采集软件,使该线站成功实现步进(step-by-step)模式和快扫(QXAFS)模式下的XAFS谱的采集。
