Electron Transfer at L-Cysteine Monolayer on Palladium Surface: A pH Effect Study

Abstract

The electrochemical properties of L-cysteine self assembled monolayer on palladium surface has been investigated. The effect of immobilization time of L-cysteine monolayer on palladium was studied by cyclic voltammetry (CV). Further, the electron transfer of the Fe(CN)63-/4- redox couple at different pH values was used to evaluate the protonation and deprotonation of the functional groups (NH2, COOH) at the modified electrode surface by using CV and electrochemical impedance spectroscopy (EIS). When the pH of the solution is high (ca. 11), the monolayer posses negative charge, Fe(CN)63-/4- current is inhibited. On the contrary, a different behavior at low pH (ca. 2) has been found. From the data obtained by CV and EIS, the surface pKa was found to be 7.3 and 7.1, respectively. At pH 7, we have compared Fe(CN)63-/4- peak currents as a function of scan rate, at different supporting electrolytes.