Preparation of Electrically Conductive Au Thin Films by Colloid Sedimentation.

A novel and facile wet-chemical method for the preparation of Au thin films is presented. These Au thin films were deposited on glass substrates by the gravitational sedimentation of Au colloids. The colloids were formed by chemical reduction in ethanol using HAuCl4 and NaBH4 with no added surfactants. Without stabilizing agents the colloids quickly aggregated, settled to the bottom and formed a thin film. The sedimentation of the colloids was monitored using UV-vis spectroscopy. Thin films with Au loads ranging between 0.25 and 4.0 g m-2 were prepared and characterized by means of UV-vis spectroscopy, electrical resistance measurements, optical microscopy, scanning electron microscopy, and cyclic voltammetry. The results showed that nanostructured Au films with a very high specific surface area were formed. The films were electrically conductive and partially transparent to visible light.