Voltammetric studies of colloidal particle monolayer on a gold rotating disk electrode

Adsorption of colloidal particles at a solid/liquid interface leads to a spontaneous formation of a porous structure, which may have a strong effect on the ion transport from the bulk solution to the adsorption surface. This effect can be investigated by employing the cyclic voltammetry and rotating disk electrode techniques. We used the cyclic voltammetry method to characterize monolayers of 1 μm sulfate polystyrene particles. We conducted measurements of the limiting diffusion current in a 1 mM solution of potassium hexacyanoferrate(III) at various rotational speeds of the disk. Before each experiment the gold rotating disk electrode was carefully prepared by mechanical polishing to obtain a smooth, clear, and reproducible gold surface. The state of the gold surface was then examined using optical microscopy, atomic force microscopy and cyclic voltammetry measurements. We used a diffusion cell for particle deposition under barrierless conditions. We demonstrated a good agreement between the experimental results and theoretically predicted limiting diffusion current at medium and high surface coverages of the rotating disk electrode. Our results suggest that the voltammetric method can be used for the characterization of monolayer thickness and porosity, as well as for the determination of surface concentration of deposited colloidal particles.