On the formation and dissolution kinetics of two-dimensional uracil ordered phases at the gold single crystal electrode-aqueous solution interface

Abstract

The adsorption of uracil on Au(111) from a 0.5 M NaF electrolyte solution is characterized by the formation of various films delimited by 2D phase transitions. The kinetics of the interfacial rearrangements were investigated by means of current and charge transients using the potential step technique. The transients associated with the formation of the condensed physisorbed layer from an adsorbate free initial state can be well described by a model involving a three-stage process. The first part of the relaxation curves corresponds to the concomitant charging of the initial double layer capacitance and the fast adsorption of the surfactant. The remaining peaked current curves are analyzed in terms of the growth of pre-existing nuclei which at long times becomes diffusion limited. When the initial film is composed of chemisorbed molecules similar transients are obtained and attributed to the dissolution of the film which proceeds from holes growing with a rate becoming time dependent. The analysis of the kinetic results obtained at different temperatures confirms the distinct nature of the interfacial rearrangement leading to the same type of transients.