Systematic Assessment of Benzenethiol Self-Assembled Monolayers on Au(111) as a Standard Sample for Electrochemical Tip-Enhanced Raman Spectroscopy

A molecular-scale understanding of electrolyte/electrode interfaces has long been a challenging issue in electrochemistry. Spectroscopic tools with high spatial resolution are required for advancing beyond conventional electrochemical measurements such as cyclic voltammetry (CV). In this study, we developed tip-enhanced Raman spectroscopy (TERS), which is based on an electrochemical scanning tunneling microscope (EC-STM), and demonstrated electrochemical TERS (EC-TERS) measurements of benzenethiol self-assembled monolayers (SAMs) on Au(111). A specially designed cell enables us to carry out reproducible CV, EC-STM, and EC-TERS measurements, which indicates consistent results among these techniques for the oxidative desorption of the SAMs. We also present direct evidence that the measured EC-TERS signals originate from molecules adsorbed on Au(111) and not from those on the STM tip.