Surfactant Aggregates at a Metal Surface

Surfactant adsorption on metals has been used in the past to limit the activity of electrode surfaces and to stabilize colloidal clusters in solution, but the adsorption and aggregation morphology of these surfactants has not been known. We present direct images of ionic surfactant aggregates at a gold surface in aqueous solution using atomic force microscopy. These images are generally striped in appearance as viewed from the top, indicating linear aggregates (cylindrical or half-cylindrical) lying on the substrate plane. The orientation of these aggregates is controlled either by monatomic steps on the gold surface or by the gold lattice itself, depending on the surfactant counterion.