Reactions on modified silica surfaces

Abstract

Molecular dynamic computer simulations have been used to model adsorbate interactions at silica surfaces. Deposition of alkali ions into vSiO 2 and SiO 2− x F x surfaces provided a means to study the effect of varying surface composition on the behavior of adsorbates. Silica surfaces with a range in the concentration of non-bridging oxygen and silica surfaces doped with varying concentrations of fluorine were exposed to the alkali adsorbates. The fluorinated surfaces were less reactive towards the alkali than were the vitreous silica surfaces. Reactivity was also reduced when the non-bridging oxygen concentration was decreased on the silica surfaces and the fluorine concentration was decreased on the fluorine doped surfaces. Non-bridging oxygen sites on the silica surfaces were energetically the most favorable for bonding, followed by fluorine sites on the fluorinated surfaces and bridging oxygen sites on both types of surfaces.