| Abstract
| - The adsorption behavior of 2,5-dimercapto-1,3,4-thiadiazole (DMcT) and 2-mercapto-5-methyl-1,3,4-thiadiazole (McMT) on Au and Cu electrode surfaces was studied using a 5 MHz quartz crystal microbalance(QCM), cyclic voltammetry, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and phasemeasurement interferometric microscopy (PMIM). Different behaviors were observed for the adsorptionof DMcT and McMT on Au and Cu electrodes. Exposing the Au electrode to a McMT solution resulted inthe formation of a stable, self-assembled monolayer on the electrode surface. A sharp peak resulting fromthe reductive desorption (RD) of McMT was observed for McMT chemisorbed on the Au electrode. It wasalso found that dimer-DMcT (di-DMcT) should be used in order to construct a stable DMcT layer on anAu electrode. Detailed comparisons of charge consumption and mass change during reductive desorptionsuggest that chemisorbed di-DMcT is monomeric and desorbs completely from the Au electrode in the RDprocess. However, on a Cu electrode surface, a stable McMT layer could not be constructed. It was alsoconfirmed from PMIM experiments and Raman spectroscopy that DMcT etched copper electrodes, alongwith concurrent formation of a dimer form of DMcT (di-DMcT). The apparent reason for the differentadsorption behaviors between DMcT and McMT is that DMcT is a stronger proton donor and oxidant.
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