Electrochemical properties of colloidal Au-based surfaces:: Multilayer assemblies and seeded colloid films

The preparation, characterization, and electrochemical properties of two types of conductive Au films are described. Both films are made entirely by wet chemical procedures. In the first, successive treatment of a Au colloid monolayer/glass substrate with (i) 2-mercaptoethylamine and (ii) colloidal Au in solution leads to systematic buildup of a Au colloid multilayer. After seven to eight layers of Au nanoparticles have been deposited, the multilayers become conductive. Cyclic voltammograms of several different redox couples show that the peak-to-peak separation decreases as the number of layers increases. In the second type of film, a solution of hydroxylamine and Au3+ are used to selectively enlarge the size of a preimmobilized colloidal Au monolayer. Once the particles coalesce, the resulting film can be used to generate voltammograms with narrow peak separations. The ability to form conductive Au films using entirely wet-chemical steps may be valuable for fabrication of electrodes with complex shapes.