We report a method for fabrication of free-standing porous gold material with high surface area, and well-defined, tunable pore morphology. Porous gold is formed via a simple procedure which involves an acidic treatment of a commercially available complex white-gold alloy. We used SEM and AFM techniques to characterize the surface morphology, size and shape of the meso-pores as well as the surface roughness of the prepared porous gold samples. Formation of self-assembled monolayers of a flavin sulfide on the gold surface was used to estimate the total surface area of porous gold material. The monolayers were found to be electrochemically active by cyclic and square-wave voltammetry. It was found that 24 hour HNO(3) treatment gave a 12,400 times surface enlargement and resulted in a surface area of 14.2 m(2)/g, whereas 72 hour HNO(3) treatment resulted in a 6900 times surface enlargement and a surface area of 8.7 m(2)/g. In addition, the enzyme acetylcholine esterase was immobilized on the different porous gold surfaces in order to demonstrate biocompatibility of the porous gold material. Kinetic parameters and the amount of the immobilized acetylcholine esterase were determined.

Nanoporous gold (NPG) is a material of emerging interest for immobilization of biomolecules and -especially enzymes. NPG materials provide a high gold surface area onto which biomolecules can either be directly physisorbed or covalently linked after first modifying the NPG with a self-assembled monolayer. The material can be used as a high surface area electrode and with immobilized enzymes can be used for amperometric detection schemes. NPG can be prepared in a variety of formats from alloys containing less than 50 atomic% gold by dealloying procedures. Related high surface area gold structures have been prepared using templating approaches. Covalent enzyme immobilization can be achieved by first forming a self-assembled monolayer on NPG bearing a terminal reactive functional group followed by conjugation to the enzyme through amide linkages to lysine residues.

Nanoporous gold (NPG) is a material of emerging interest for immobilization of biomolecules, especially enzymes. The material provides a high surface area form of gold that is suitable for physisorption or for covalent modification by self-assembled monolayers. The material can be used as a high surface area electrode and with immobilized enzymes can be used for amperometric detection schemes. NPG can be prepared in a variety of formats from alloys containing between 20 and 50 % atomic composition of gold and less noble element(s) by dealloying procedures. Materials resembling NPG can be prepared by hydrothermal and electrodeposition methods. Related high surface area gold structures have been prepared using templating approaches. Covalent enzyme immobilization can be achieved by first forming a self-assembled monolayer on NPG bearing a terminal reactive functional group followed by conjugation to the enzyme through amide linkages to lysine residues. Enzymes can also be entrapped by physisorption or immobilized by electrostatic interactions.