Square Wave Voltcoulommetry Analysis of the Influence of the Electrostatic Environment on the Electrochemical Functionality of Redox Monolayers

The analysis of effects of intermolecular interactions on square wave voltcoulommetric (SWVC) responses of electroactive monolayers under Nernstian conditions is presented. Theoretical expressions are given for the Faradaic and non-Faradaic charge potential curves in terms of the potential perturbation variables and of the phenomenological interaction parameter G. Simple methods are proposed for determining the total excess of electroactive species, the apparent formal potential and the interaction parameter. The application of these methods to the analysis of the electrochemical behaviour of binary monolayers of ferrocenylundecanethiol/decanethiol at gold and platinum electrodes in two different non-aqueous solvents allows us to obtain reliable values of the above parameters that clearly improve those determined by using Cyclic Voltammetry. Electrostatic insights into the interaction parameters is provided on the basis of a previously reported model. The importance of the presence of ion pairing processes in the value of the parameter G is discussed. The results obtained with SWVC technique point out the fact that intermolecular interactions are not avoided at low surface excesses of the redox probe, indicating that the impact of electrostatics in the appearance of non-ideal electrochemical responses depends on the nature of the electrolytic media and on the structure of the monolayer in a complex way.