Studies of adsorption kinetics and defects of self-assembled thiol monolayers on gold by capacitance plane plot

The capacitive property of an electrode/electrolyte interface can be descri bed by complex capacitance. The capacitance plane plots (CPPs) of ideal pol arized and kinetic controlled electrodes are derived based on the concept o f complex capacitance. By using CPPs, the capacitance of electrode/electrol yte interface can be conveniently determined. In this work, CPPs obtained i n ac impedance experiments are employed for the first time in studying the kinetics of adsorption process of the thiol monolayer. The coverage of octa decanethiol (ODT) monolayer on gold is examined as a function of adsorption time. The adsorption process of ODT molecules on gold exhibits two distinc t phases: an initial rapid step followed by a slow one. The simple Langmuir model best explains our experimental data in the initial adsorption stage. CPPs and cyclic voltammetry (CV) indicate that, in the initial adsorption step, the ODT monolayer contains defects whose number decreases with the in creasing of adsorption time.