Effect of pH on Anodic Formation of Nanoporous Gold Films in Chloride Solutions: Optimization of Anodization for Ultrahigh Porous Structures

Nanoporous gold (NPG) structures have useful applications based on their unique physical and chemical properties; therefore, the development of NPG preparation methods is the subject of extensive research. Recently, the anodization of Au surfaces was suggested as an efficient method for preparing porous Au structures. In this work, the mechanistic aspects of the anodization of Au in Cl^–-containing solutions for the preparation of NPG layers were investigated. The effects of the experimental parameters of the anodization reaction on the porosity of the NPG layers in terms of the roughness factor (<i>R</i>_f) were examined. The anodic formation of NPG was more effective in buffered solutions than in unbuffered electrolytes. The <i>R</i>_f of the NPG layer was sensitive to the electrolyte pH; this was ascribed to the efficient formation of protecting layers of gold oxide on the newly formed NPG structures. In buffer solutions at pH 8, ultrahigh porous NPG layers with <i>R</i>_f values of 1300 were obtained within 15 min. The ultrahigh porous NPG layers were used for the electrochemical detection of glucose; a high sensitivity of 135 μA mM^–1 cm^–2 was achieved in the presence of 0.1 M Cl^–. This straightforward and time-saving preparation of NPG surfaces will provide new opportunities for applications of NPG structures