Electron transfer kinetics across derivatized self-assembled monolayers on platinum: a cyclic voltammetry and electrochemical impedance spectroscopy study

Platinum surfaces derivatized with mercapto and amine compounds have been used to perform this study. The compounds used to derivatize the platinum surfaces were 3-mercaptopropionic acid (HSC2H4COOH, 3-MPA), 16-mercaptohexadecanoic acid (HSC15H30COOH, 16-MHDA), and 3-aminopropyltrimethoxysilane (H2NC3H6Si(OCH3)3, 3-APS). Previously, the derivatization process has been characterized by XPS and FT-IR [Electroanal. Chem. 540 (2003) 53]. In current work, the amide(3-MPA/Pt) and amide(16-MHDA/Pt) systems, formed by the derivatization of the 3-MPA/Pt and 16-MHDA/Pt surfaces with 3-APS, were characterized by cyclic voltammetry using 2.5 mM K3Fe(CN)6 in 0.1 M KCl or 2.5 mM Ru(NH3)6Cl3 in 0.1 M KCl solution. These redox systems were chosen to study the defect site induced by electrochemical desorption and its effect on the charge transfer processes. Electrochemical impedance spectroscopy was used as an additional electrochemical tool, to study these derivatized platinum surfaces. This technique was useful in the determination of the pinholes formed on the derivatized platinum surfaces, or different desorption potentials.