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).