Plasmon induced decarboxylation of aromatic carboxylic acids on bipolar electrodeposited Au- and Ag-film monitored by SERS

This study delves into the intersection of plasmonics and catalysis, offering insights into tailoring nanoscale chemical reactions. Employing Surface Enhanced Raman Spectroscopy (SERS), we track the decarboxylation process of 4-mercaptobenzoic acid (4-MBA) and its isomers. Using a specially designed thin film platform of gold and silver, prepared via bipolar electrodeposition (BP-ED), we investigate the influence of laser-power, solution pH, and exposure duration. Decarboxylation predominantly occurs in alkaline pH environments, attributed to deprotonation. Notably, 2-MBA exhibits swift decarboxylation, even without alkaline conditions, likely due to its closer proximity to the nanostructured surface. The significance of the carboxylate anion (-COO-) is underscored, as experiments with ester forms of 2- and 3-MBA exhibit similar behavior. Additionally, experiments with linear chain thiocarboxylic acids highlight the necessity of a benzene ring for stable reaction intermediates. A key finding lies in the effectiveness of the bipolar electrodeposition technique for monitoring decarboxylation reactions across various compositions on a unified platform. This research sheds light on the potential of SERS in understanding chemical reactions near metal nanostructures, ultimately advancing our grasp of reaction pathways and the identification of new reactive species.