The interaction between a solid and water at their interface, especially proton transfer, impacts molecular-scale catalysis, macroscopic environmental science, and geoscience. Although being highly desired, directly probing proton transfer between a solid and water is a great challenge, given the subnanometer to nanometer scale of the interface. The fundamental challenge lies in the lack of a measurement tool to sensitively observe local proton concentration without introducing an exogenous electrode or nanoparticle with a minimum size of tens of nanometers. Here, we demonstrate an azo-enhanced Raman scattering strategy to design a 2 nm long small-molecule pH probe with a chelating group anchoring to the solid surface. Empowered by the intramolecular Raman enhancing sensitivity, the probe directly observes proton transfer between water and nanoscale zero-valent iron (nZVI), a famous environmental material for pollution control. This molecular-scale interfacial probing methodology offers a powerful tool to pave the way for advanced environmental and geochemical discernment and management.

中文翻译：

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偶氮增强拉曼散射探测水与纳米级零价铁之间的质子转移


固体和水在其界面处的相互作用，尤其是质子转移，会影响分子尺度催化、宏观环境科学和地球科学。尽管非常需要，但考虑到界面的亚纳米级，直接探测固体和水之间的质子转移是一个巨大的挑战。根本的挑战在于缺乏一种测量工具，可以在不引入最小尺寸为数十纳米的外源电极或纳米颗粒的情况下灵敏地观察局部质子浓度。在这里，我们展示了一种偶氮增强的拉曼散射策略，以设计一个 2 nm 长的小分子 pH 探针，其中螯合基团锚定在固体表面。在分子内拉曼增强灵敏度的支持下，该探针直接观察水和纳米级零价铁 （nZVI） 之间的质子转移，nZVI 是一种著名的污染控制环境材料。这种分子尺度的界面探测方法为先进的环境和地球化学鉴别和管理铺平了道路。