In-situ electrochemical-surface enhanced Raman scattering imaging for observing pH effects on the reduction of 4-Nitrobenzenethiol

Abstract

Herein, we present a strategy for visualizing spatially detailed changes in molecular structure and chemical composition during electrochemical reactions. This strategy is based on electrochemical-surface enhanced Raman scattering (EC-SERS) imaging with the use of 4-nitrobenzenethiol (4-NBT) as a redox-active and Raman-active probe. Cyclic voltammetry demonstrates that 4-NBT undergoes irreversible reduction to 4-aminobenzenethiol (4-ABT), with the reduction potential shifting between pH 3.0 and pH 10.0. The electrochemical reduction on the gold electrode surface was monitored in real-time through Raman imaging under applied voltages, confirming the pH-dependent spectral changes of 4-ABT on ultramicroelectrode (UME) and interdigitated array (IDA) electrodes. In particular, we achieved spatially resolved in-situ EC-SERS imaging, revealing that the b₂ modes of 4-ABT are strongly affected by the pH of electrolyte solution.