Thiols deposition onto the surface of glassy carbon electrodes mediated by electrical potential

Electrochemical oxidation of thiols in acetonitrile and application of this process for modification of glassy carbon electrodes were studied. Addition of strong deprotonating agent, tetrabutylammonium hydroxide, was found to facilitate oxidation of thiols as well as their deposition onto the carbon surface. Thus, in the presence of 1 mM tetrabutylammonium hydroxide, glassy carbon electrode can be grafted with 1 mM 3-(nitrobenzyl)mercaptan at as low as +200 mV (vs. SCE). The modified electrodes were characterized by electrochemical methods and XPS confirming the stable binding of thiols which were absent on the surface of unmodified and control treated electrodes. Surprisingly, surface modification occurs independent of RS radicals formation and is explained by nucleophilic addition of deprotonated thiols to the surface of carbon electrode. The electrode potential plays an important role in this process presumably modulating electrophilic properties of the carbon surface.