Chemisorption of aromatic thiols onto a glassy carbon surface

We report on the chemisorption of two aromatic thiols, 4-nitrothiophenol (4-NTP) and 4-aminothiophenol (4-ATP), onto a glassy carbon electrode. These modified electrodes were prepared by immersion of an oxidized glassy carbon substrate in a 4-NTP (or 4-ATP) ethanolic solution. The presence of aromatic thiols at the carbon surface was demonstrated by cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS). The electrochemical responses of the amino and nitro groups confirmed the adsorption of the aromatic thiols and revealed that their surface concentrations correspond to full monolayers. The presence of a doublet (S2p3/2, S2p1/2) centered at around 163.5 eV on the sulfur 2p core level XPS spectra for both modified electrodes was associated to the formation of a S–C bond with the glassy carbon surface. We suggest that the observed reactivity of aromatic thiols with the glassy carbon surface is related to their strong nucleophilicity.