Effect of Temperature and Chloride Concentration on the Anodic Formation of Nanoporous Gold Films in Chloride Solutions

The preparation of nanoporous gold (NPG) has been the subject of extensive research, and the anodization of Au in chloride solutions has received recent attention as an efficient and time-saving method. In the present work, the effects of reaction temperature and Cl- concentration on the anodic formation of NPG structures were investigated. The anodization efficiency was evaluated in terms of the roughness factor (R-f) of NPG layers, which varied as a function of these two reaction parameters. The R-f of NPG gradually increased with temperature up to 40 degrees C and then leveled off at higher temperatures. In terms of Cl- concentration, 1.0 M yielded the maximum R-f of the NPG. The dependence of the anodization efficiency on the two reaction parameters was examined with regard to the electrochemical dissolution of Au as well as the formation of Au-Cl complexes and protective surface oxide layers. The mechanistic aspects of the anodic formation of NPG give insight into the efficient preparation of highly porous NPG structures.