Photoelectrokinetic Spectroscopy: A New Probe of Solid/Liquid Interfaces

在化学系化学测量和成像计划的支持下，加州大学伯克利分校的Richard Saykally教授和他的团队正在研究一种测量水界面光谱性质的新概念，长期目标是开发新的仪器和设备，以及加强对电解液界面基本性质的理解。具有适当光学窗口的选定材料(例如，玻璃、硅、具有各种涂层)的微型制造通道连接到液体色谱系统，该系统以精确控制的成分、压力和流经通道的液体输送。由此产生的电动电流/电压从喷嘴出口孔的上游和下游进行监测。这些观测值的大小明显取决于固/液界面的性质(Zeta电位、离子和电子的迁移率、电荷转移截面、电场)。当光入射到液/固界面时，观察到了动电电流和电势的变化。测量这些量作为光学波长和功率的函数的变化可以产生位于界面区域(吸附到固体或位于双层中)的发色团的光谱。这种新的方法可以帮助表征电解液界面的性质，为推进电池、燃料电池、太阳能燃料发电机和光伏等关键技术提供必要的信息。除了这一潜在的变革性科学影响外，这项工作还提供了开发新方法和仪器的培训。

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Prof. Richard Saykally and his group at the University of California - Berkeley are investigating a novel concept for measuring the spectroscopic properties of aqueous interfaces, with long-term aims of developing new instruments and devices, as well as an enhanced understanding of the basic nature of electrolyte interfaces. Microfabricated channels of selected materials (e.g. glass, silicon, with various coatings) with suitable optical windows are connected to a liquid chromatography system which delivers liquids with precisely controlled composition, pressure, and flow through the channel. The resulting electrokinetic current/voltage is monitored both upstream and downstream from a nozzle exit orifice. The magnitudes of these observables depend explicitly on the properties of the solid/liquid interface (zeta potential, ion and electron mobilities, charge transfer cross sections, electric field). When light impinges on the liquid/solid interface, changes induced in the electrokinetic current and potential are observed. Measuring the changes in these quantities as a function of the optical wavelength and power can produce a spectrum of the chromophores localized in the interfacial region (adsorbed to the solid or located in the double layer). This new approach can help characterize the nature of electrolyte interfaces, providing information essential for advancing the crucial technologies of batteries, fuel cells, solar fuel generators, and photovoltaics. In addition to this potentially transformative scientific impact, the work is providing training in the development of new methods and instrumentation.