Is the Enhanced Adhesion of PEDOT Thin Films on Electrodes Due to Sulfur - Gold Interaction? - An XPS Study

Electrode materials obtained through electropolymerization of 3,4-ethylenedioxythiophene (EDOT) have sparked interest toward applications in neuroscience and neuroprosthetics due to their favorable electrochemical properties and their biocompatibility. However, insufficient mechanical stability had been an unresolved issue and hindered practical applications, until recent research by our group demonstrated proper adhesion of poly(3,4ethylenedioxythiophene) (PEDOT) to a gold surface. In the present study, X-ray photoelectron spectroscopy (XPS) was employed and in particular the chemical shift of the S2p band, which is indicative of binding between sulfur and gold, was used to assess the degree of interaction between 3,4-ethylenedioxythiophene (EDOT), thiophene, and 3thiophenecarboxylic acid (thiophene-COOH), with the gold surface. The results of the XPS investigations indicate a covalent bond between EDOT and gold, which should indeed contribute to improved adhesion.