Leibniz-Institut für Analytische Wissenschaften - ISAS e.V. Bunsen-Kirchhoff-Str. 11, 44139 Dortmund, Germany.
Chemphyschem. 2010 Jul 12;11(10):2118-23. doi: 10.1002/cphc.201000166.
Measurements of ion distributions at a charged solid-liquid interface using X-ray standing waves (XSW) are presented. High energy synchrotron radiation (17.48 keV) is used to produce an XSW pattern inside a thin water film on a silicon wafer. The liquid phase is an aqueous solution containing Br and Rb ions. The surface charge is adjusted by titration. Measurements are performed over a pH range from 2.2-9, using the native Si oxide layer and functional (amine) groups as surface charge. The Debye length, indicating the extension of the diffuse layer, could be measured with values varying between 1-4 nm. For functionalized wafers, the pH dependent change from attraction to repulsion of an ion species could be detected, indicating the isoelectric point. In combination with the measurement of the streaming current, the surface charge of the sample could be quantified.
采用 X 射线驻波（XSW）测量了带电荷固-液界面处的离子分布。利用高能量同步辐射（17.48keV）在硅片上的薄水膜内产生 XSW 图案。该液相是含有 Br 和 Rb 离子的水溶液。通过滴定调节表面电荷。使用天然 Si 氧化物层和功能（胺）基团作为表面电荷，在 pH 值为 2.2-9 的范围内进行测量。德拜长度（Debye length），表示扩散层的延伸范围，其值在 1-4nm 之间变化。对于功能化的晶片，可以检测到离子物种从吸引到排斥的 pH 依赖性变化，这表明了等电点。与测量流动电流相结合，可以定量确定样品的表面电荷。
