Faradaic impedance titration and control of electron transfer of 1-(12-mercaptododecyl)imidazole monolayer on a gold electrode

In this work, we studied interfacial proton transfer of the self-assembled monolayer (SAM) of 1-(12-mercaptododecyl)imidazole on a gold electrode by faradaic impedance titration method with Fe(CN)(6) (3-) as an anionic redox probe molecule. The surface pK(1/2) was found to be 7.3, which was nearly the same as that of 1-alkylimidazole in solution. We also investigated the electrochemical properties of the SAM-modified electrode by cyclic voltammetry. Cyclic voltammetry was performed (1) in the solution containing Fe(CN)(6)(3-) with repeated alternation of pH values to investigate the electrostatic interaction of the protonated or deprotonated imidazole with Fe(CN)(6)(3-) and (2) in the acidic or basic electrolyte containing Ru(NH3)(6)(3+) as a cationic redox probe to verify the effect of the polarity of a redox probe. We observed the reversible adsorption/desorption of Fe(CN)(6)(3-) and concluded that the adsorbed Fe(CN)(6)(3-) catalyzed the electron transfer of both Fe(CN)(6)(3-) itself and 3, cationic Ru(NH3)(6)(3+). (c) 2007 Elsevier Ltd. All rights reserved.