Nanoscale Chemical Reaction Imaging at the Solid-Liquid Interface via TERS

TL;DR

This paper demonstrates nanoscale chemical reaction imaging at the solid-liquid interface using tip-enhanced Raman scattering (TERS), enabling high-resolution, selective visualization of chemical transformations in aqueous environments for the first time.

Contribution

It introduces the first application of TERS for imaging chemical reactions at the solid-liquid interface with 10 nm resolution.

Findings

Successfully located plasmonic hotspots at the interface.

Monitored reactant-to-product transformation via Raman spectra.

Performed 2D correlation analysis to distinguish spectral components.

Abstract

Plasmon-enhanced chemical transformations at the solid-liquid interface can be imaged with high sensitivity, chemical selectivity, and nanoscale precision through tip-enhanced Raman scattering (TERS). We demonstrate the latter for the first time through measurements aimed at (i) locating plasmonic hotspots at the solid-liquid interface at which chemical transformations take place, (ii) monitoring the evolution from reactants to products through their distinct Raman spectra, and (iii) 2D correlation analysis of Raman time trajectories to unambiguously extract the spectral components that mark chemical transformation and to understand the correlations between the product and parent signatures. For our proof-of-principle study, we select a model plasmon-enhanced chemical process, namely, the dimerization of p-nitrothiophenol to dimercaptoazobenzene, but now, at the solid-liquid interface. Our plasmonic construct otherwise consists of chemically functionalized gold microplates in aqueous solution, which we image using a gold-coated TERS probe irradiated at 633-nm. Overall, we demonstrate chemical reaction imaging in aqueous solution via TERS for the first time, herein, at a pixel-limited lateral spatial resolution of 10 nm.