该研究团队描述了一种基于光学显微镜的方法来探测一系列材料的表面电荷分布，包括与液体接触的无机氧化物、聚合物和聚电解质薄膜。该方法依赖于对扩散的带电探针分子和未知表面之间的电排斥的光学可视化。基于图像的快速测量使他们能够进一步确定材料的等电点以及其可电离化学基团的性质。
该研究团队进一步证明了以毫秒级的时间分辨率光学监测化学触发的表面电荷变化的能力。最后，研究人员提出了一种扫描表面探测技术，能够对化学成分和电荷的空间异质性进行衍射限制成像。这项技术将使固液界面的表征变得简单，与从生物到工程的各个应用领域都有广泛的联系。
研究人员表示，从分子和颗粒到浸泡在液体中的宏观表面，化学反应常常赋予界面以电荷，而电荷又支配着表面相互作用和界面现象。测量浸泡在任何溶剂中的材料的电学性质，以及监测其空间异质性和时间变化的能力，一直是一个长期的挑战。
附：英文原文
Title: Wide-field optical imaging of electrical charge and chemical reactions at the solid–liquid interface
Author: Mahanta, Sushanta, Vallejo-Ramirez, Pedro, Karedla, Narain, Puczkarski, Pawe, Krishnan, Madhavi
Issue&Volume: 2022-12-2
Abstract: From molecules and particles to macroscopic surfaces immersed in fluids, chemical reactions often endow interfaces with electrical charge which in turn governs surface interactions and interfacial phenomena. The ability to measure the electrical properties of a material immersed in any solvent, as well as to monitor the spatial heterogeneity and temporal variation thereof, has been a long-standing challenge. Here, we describe an optical microscopy-based approach to probe the surface charge distribution of a range of materials, including inorganic oxide, polymer, and polyelectrolyte films, in contact with a fluid. The method relies on optical visualization of the electrical repulsion between diffusing charged probe molecules and the unknown surface to be characterized. Rapid image-based measurements enable us to further determine isoelectric points of the material as well as properties of its ionizable chemical groups. We further demonstrate the ability to optically monitor chemically triggered surface charge changes with millisecond time resolution. Finally, we present a scanning-surface probe technique capable of diffraction-limited imaging of spatial heterogeneities in chemical composition and charge over large areas. This technique will enable facile characterization of the solid–liquid interface with wide-ranging relevance across application areas from biology to engineering.
DOI: 10.1073/pnas.2209955119
Source: https://www.pnas.org/doi/10.1073/pnas.2209955119