Adsorption of organophosphate nerve agent VX on the (101) surface of anatase titanium dioxide

We quantify the adsorption of the organophosphate venomous agent X (VX) on the clean and hydroxylated (101) surfaces of anatase titanium dioxide (TiO₂) with density functional theory (DFT) calculations. Our results show that adsorption on the clean anatase (101) surface occurs through the VX phosphoryl oxygen (O=P) site and involves the formation of a Ti···O=P dative bond. Steric effects inhibit adsorption through the VX nitrogen and sulfur sites by the formation of Ti···N and Ti···S dative bonds. On the hydroxylated (101) surface, adsorption similarly proceeds through the VX phosphoryl oxygen site but entails the formation of surface–adsorbate hydrogen bonds. Additionally, weak non-covalent interactions between the surface hydroxyl groups and the adsorbate’s nitrogen and sulfur atoms stabilize VX/(101) complexes formed by adsorption through these secondary sites.