Adsorption kinetics investigation for alkyltrimethylammonium bromides on ITO-aqueous interface

Abstract

The adsorption of dodecyltrimethylammonium bromide and cetyltrimethylammonium bromide onto indium-tin oxide (ITO) was studied by in-situ monitoring the capacitance and resistance of adsorbed layers for a series of concentrations of aqueous solutions. The experimental results suggested that the adsorption of both surfactants showed a three-region adsorption process and that the adsorption was driven by electrostatic attraction and hydrophobic interactions in two regions below critical micelle concentration (cmc). Above the cmc, the changes in electrical properties could be explained by the assumption that entire micelles were directly adsorbed onto the ITO surface and then underwent an adjustment process. The variations of water contact angle against surfactant concentration showed two distinct regions. The effect of high electrolyte concentration on the adsorbed layer structure was also discussed.