Electrochemically generated CuI and CuSCN nanocrystals on Cu surfaces as Raman enhancing substrates

Raman enhancing strategies, such as Surface-Enhance Raman scattering (SERS), are a key piece for the development of spectroscopic and analytical strategies based on Raman spectroscopy, due to the intrinsic low sensitivity of the Raman scattering. Some years ago, our group reported an unexpected Raman enhancement process observed during the electrochemical oxidation of metallic electrodes, named Electrochemical Oxidation Surface-Enhanced Raman scattering (EC-SOERS). This Raman enhancement phenomenon was recently explained as an interaction of the analyte and the SERS dielectric substrate promoted by a metal cation. The elucidation of the origin of this enhancement is now leading to the development of new Raman enhancing substrates, such as copper-based substrates. In this work, we present an overview of the use of copper electrodes as EC-SOERS substrates. The presented strategies allow the electrosynthesis of SERS-active CuI nanocrystals on a metallic copper surface, which provides Raman enhancement for a wide number of molecules. The influence of the electrochemical conditions and the structure of the studied molecules are discussed. The use of CuSCN nanocrystals is also explored as substrates to promote Raman enhancement.