Fabrication and surface functionalization of nanoporous gold by electrochemical alloying/dealloying of Au-Zn in an ionic liquid, and the self-assembly of L-cysteine monolayers

This paper describes a totally electrochemical process for the fabrication and functionalization of high-surface-area, nanoporous gold films. The fabrication process involves the electrodeposition of a binary gold-zinc alloy at gold wires, followed by subsequent electrochemical dealloying of the less noble component zinc from the surface. Both the deposition and dealloying steps are conducted in a single low-temperature bath of 40.0-60.0 mol-% zinc chloride-1-ethyl-3-methylimidazolium chloride ionic liquid at 120 °C without using any other corrosive acids or bases. The porous structure and morphology of the nanostructured gold film could be controlled by electrochemical variation of the composition of the Au-Zn surface alloy. It is demonstrated that the nanoporous gold surface can be successfully functionalized with self-assembled monolayers of L-cysteine. Such functionalization greatly improves the utility of the nanoporous gold, as is demonstrated in the sensitive and selective determination of Cu(II).