Studies of electron transfer through self-assembled monolayers using impedance spectroscopy

An investigation of the kinetics of reduction of Ru(NH3)(6)(3+) has been carried out at single crystal electrodes modified by alkanethiols of varying chain lengths. Careful study of the impedance of the modified electrode system in the absence of the reaction has shown that there is a highly resistive path in parallel to the capacitance due to the self-assembled monolayer. Analysis of the kinetic data and extrapolation of the Tafel plots show that the standard rate constant for the Ru(NH3)(6)(3+/2+) system is 1.7 cm s(-1) at an unmodified Au surface with a transfer coefficient close to 0.5. These parameters are expected for a very fast simple heterogeneous electron transfer reaction. The present results are compared with whose reported previously in the literature. (C) 2000 Elsevier Science Ltd. All rights reserved.