Electrochemical Surface Oxidation Enhanced Raman Scattering on Cu

Abstract

One of the main characteristic of Analytical Chemistry is a constant searching for new methodologies to overcome analytical problems. Minimization of analysis time and sample volumes, replacement of extensive extraction protocols and improvement of selectivity are common tasks in analytical research all around the world. Spectroelectrochemistry is an instrumental technique that totally represents this spirit: The combination of electrochemical set-ups with spectroscopy techniques to study the surface processes has shown to be a powerful technique to resolve complex mixtures of molecules, where analytical signals can present severe interferences [1].Spectroelectrochemistry has been demonstrated to be a powerful analytical technique to study adsorption processes and molecular reactivity on electrode surfaces. More specifically, Raman spectroelectrochemistry (Raman-SEC) combined with plasmonic structures has been demonstrated to be an excellent tool to study molecules at low concentration thanks to Surface Enhanced Raman Scattering (SERS) phenomenon. [2].For almost half a century, Raman-SEC has broadly studied the properties of SERS substrates developed with nanoparticles of plasmonic metals, such as silver, gold and copper, focusing its efforts on the characterization of nanostructures morphology.In 2018, our group discovered a novel methodology to enhance the Raman signal during the electrochemical oxidation of silver electrodes in acidic media [3]. We denoted this phenomenon as Electrochemical Surface Oxidation Enhanced Raman Scattering (EC-SOERS), and represents a phenomenon similar to SERS, because of the enhancement of the Raman signal, but contrary to SERS, since it suggests the loss of plasmonic properties (and thus, Raman enhancement) of metallic structures during the electrochemical oxidation of the plasmonic nanostructures.In this communication, we demonstrate, for the first time, that EC-SOERS can be observed on copper electrodes. This metal, known for its SERS properties, can be also used to enhance selectively the Raman signal during its electrochemical oxidation, detecting different organic molecules with a wide variety of functional groups, opening new gates towards the development of new analytical tools based on EC-SOERS.