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 ca rried out at single crystal electrodes modified by alkanethiols of varying chain lengths. Careful study of the impedance of the modified electrode sys tem in the absence of the reaction has shown that there is a highly resisti ve path in parallel to the capacitance due to the self-assembled monolayer. Analysis of the kinetic data and extrapolation of the Tafel plots show tha t 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. Th ese parameters are expected for a very fast simple heterogeneous electron t ransfer reaction. The present results are compared with whose reported prev iously in the literature. (C) 2000 Elsevier Science Ltd. All rights reserve d.