Self-assembled monolayers of l-cysteine on palladium electrodes

Abstract

l-cysteine modification of palladium (Pd) electrodes have been characterized using various electrochemical and surface analytical techniques such as cyclic voltammetry (CV), reductive/oxidative desorption, electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and specular reflectance Fourier transform infrared (FT-IR) spectroscopy. The electron transfer reaction of l-cysteine modified Pd electrode was probed by employing Fe ( CN ) 6 3 - / 4 - redox couple using cyclic voltammetry and electrochemical impedance. The CVs results revealed a quasi-reversible voltammograms for the Pd modified electrode, demonstrating that the electron transfer is not blocked due to surface modification. EIS results for the Pd modified electrode showed a decrease in the resistance in comparison with the bare Pd electrode. The surface coverage was 6.4 ± 0.4 × 10 −10 mol/cm 2. The XPS survey study for the l-cysteine modified Pd electrode exhibited the presence of sulfur on the surface. High energy resolution XPS and FT-IR indicated that the l-cysteine molecules are sulfur bonded to the Pd surface. These results suggest the modification of palladium surface by the l-cysteine amino acids.