Kinetic Implications of the Presence of IntermolecularInteractions in the Response of Binary Self-Assembled ElectroactiveMonolayers

摘要

Quantitative analysis of the influence of intermolecular interactions on the response of electroactive binary monolayers, incorporating the presence of electroinactive coadsorbed species and Marcus–Hush kinetic formalism, has been deduced as an extension of previous models. An expression for the current–potential relationship in terms of two global phenomenological interaction parameters and the apparent charge-transfer rate constant and formal potential has been obtained and applied to multipotential chronoamperometry for the analysis of intermolecular interaction effects on the kinetics of the charge transfer. Experimental verification of the theoretical framework has been performed with binary ferrocenylundecanethiol/decanethiol monolayers on gold and platinum substrates for different coverage degrees of the redox probe. The increase of the ferrocene coverage gives rise to a slowing down of the charge-transfer process through a decrease of the apparent rate constant above a 90% for gold and platinum electrodes when the surface coverage increases from 1–2 to 15–30%. Significantdifferences in the magnitude of intermolecular interactions and thesymmetry degree of the charge-transfer process are observed betweengold and platinum electrodes. Moreover, for high surface coveragesof ferrocene, two different domains appear, from which it is possibleto carry out a kinetic discrimination of the two responses. Valuesof the interaction and kinetic parameters have been obtained for thedifferent monolayers under study, and the limit of applicability ofthis treatment is discussed.