Computational studies of catechol and water interactions with titanium oxide nanoparticles

The interaction of catechol and water with titanium oxide nanoparticles was investigated using ab initio molecular orbital theory and density functional theory. Hydrogen-terminated TiO2 clusters were used to model the surface of anatase nanoparticles. The calculations indicate that catechol reacts with a Ti=O defect site on the surface to form a bidentate structure that is favored over dissociative or molecular adsorption on the (101) anatase surface. The dissociative adsorption of catechol at the defect site leads to a much larger red shift in the TiO2 excitation energy than molecular adsorption on the (101) anatase surface on the basis of ZINDO/S calculations. This is consistent with recent experimental results on small (<2 mn) titania nanoparticles. The calculations on water adsorption indicate that it can also add to the Ti=O double bond site. However, molecular adsorption of water on the (101) anatase surface is more favorable.