Physical Properties of Mercaptopyruvic-acid Layer Formed on Gold Surfaces

Abstract

E-mail: jwpark@seoultech.ac.krReceived June 7, 2011, Accepted June 24, 2011We studied the physical properties of the mercaptopyruvic-acid layer formed on gold surfaces, which has theinteractions with the titanium dioxide surface for design of gold- titanium dioxide distribution. Surface forcemeasurements were performed, using the atomic force microscope (AFM), between the surfaces as a functionof the salt concentration and pH value. The forces were analyzed with the DLVO (Derjaguin-Landau-Verwey-Overbeek) theory, to evaluate the potential and charge density of the surfaces quantitatively for each saltconcentration and each pH value. The difference in the properties reflected the effect of the isoelectric point onthe surface forces. The forces were interpreted for the evaluation with the law of mass action and the ionizablegroups on the surface. The salt concentration dependence of the surface properties, found from themeasurement at pH 8.0, was consistent with the prediction from the law. It was found that the mercaptopyruvic-acid layer had higher values for the surface charge densities and potentials than the titanium dioxide surfacesat pH 8, which may be attributed to the ionized-functional-groups of the mercaptopyruvic-acid layer.Key Words : Mercaptopyruvic-acid, Gold surface, TiO