The influence of electrolyte concentration on the adsorption of octadecanol on Au(111)

The influence of electrolyte concentration on the potential dependent adsor ption and desorption of octadecanol to/from a Au(111) electrode was investi gated utilizing electrochemical and elastically scattered light techniques. The electrolyte concentration was found to influence the potential driven changes of the adsorbed layer (adsorption and desorption). The capacitive c hanges in the adsorbed layer were found to occur at more negative potential s with lower electrolyte concentration. The changes in the optical measurem ent, used to measure the characteristics of the desorbed species, or aggreg ates, were also found to be affected similarly. The magnitude of the overal l change in the scattered light intensity was slightly dependent on electro lyte concentration. The re-adsorption of the aggregates was influenced by e lectrolyte concentration. The scattered light signal for an intermediate ad sorbed state (adsorbed aggregate) was more prevalent for higher electrolyte concentration, suggesting that these intermediates were somewhat different compared to lower electrolyte concentrations. The lower electrolyte concen tration displayed a larger potential region where this intermediate was sta ble, but the intensity of the scattered light was much lower. The electroly te concentration most strongly influenced the potentials of adsorption and desorption, as well as the potential region of stability for the adsorbed i ntermediates. The sweep rate also has an influence on the scattering charac teristics of the desorbed species, suggesting a possible method for measuri ng the kinetics of the adsorption-desorption process or for controlling the character of the desorbed species. These changes were explained in terms o f a mechanism for the wetting or de-wetting of a surface. The influence of electrolyte concentration provides another opportunity for investigating th e dynamics of this adsorption-desorption process. (C) 2001 Elsevier Science B.V. All rights reserved.