Electrochemical investigation on adsorption kinetics of long chain alkylsilanes and influence of solvents on their self-assembly and electron transfer behavior on indium tin oxide

Abstract

In situ adsorption kinetics of hexadecyltrimethoxy silane (HDTMS) and octadecyltrimethoxy silane (ODTMS) on indium tin oxide (ITO) surface at short time intervals were measured by electrochemical impedance (EIS) spectroscopy technique at constant frequency. The studies suggest that, self-assembly of silanes on ITO proceeds through two distinct adsorption steps, a fast first step followed by a slower second step. The inhibition of electron transfer by self-assembled silanes prepared in ethanol, toluene and hexane solvents were evaluated by cyclic voltammetry (CV) and EIS using [Fe(CN)6]3−/4− and [Ru(NH3)6]3+/2+ redox species. It is shown that, the quality of silane films are influenced by the polarity of solvent, chain length of silane and ITO substrate–solvent interactions. The effect of annealing on electron transfer barrier property of silane monolayers after their formation were studied. The pinhole characteristics of silane films on ITO prepared from various solvents under study were measured using EIS. This study demonstrates a strategy of producing an ultra-smooth and close-packed silane films on ITO surfaces which can have potential applications towards high performance organic electronics.