A NEXAFS orientation study of γ-aminopropyltriethoxysilane on zinc oxide surfaces

Bifunctional silanes, such as gamma-aminopropyltriethoxysilane (gamma-APS), are able to adsorb to a substrate via both functional groups creating a number of possible orientations for an adsorbed molecule within an organosilane film. The orientation of dip coated gamma-APS films on native zinc oxide surfaces as a function of solution pH has been studied using near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The NEXAFS results shed further light on the changes in the orientation that take place during the oscillatory adsorption of these molecules and reveal new insights into the molecular reorganisations that occur with changing solution pH. The results are discussed in terms of an electrokinetic model that has been developed. Copyright (C) 2006 John Wiley & Sons, Ltd.