Water Kinetics On The (101) TiO2 Anatase Surface
Fabrizio GALA
(Sapienza Università di Roma)
Abstract
Compatibility between biological molecules and metal oxides, is strongly dependent on the selectivity properties and the adhesion processes at the interface between the two systems. Among the many different aspects that affect the adsorption of biological materials onto inorganic surfaces (the charge state of the amino acids, the peptide 3D structure, the surface roughness for example), a major role is certainly played by the water solvent whose molecules mediate the interaction affecting the adsorption behavior of biological molecules. For the particular case of (101) anatase TiO2 surface that has great importance in the interaction of biocompatible nano-devices with biological environment: such as the adhesion of Arg and Lys that has been studied by density functional theory (DFT), where the interaction between amino acids and the surface is mediated by water. Moreover, It was experimentally shown that the water molecules are mobile at as low temperature values as 190 K, thus it is essential to understand the kinematical behavior of the hydration layers of the (101) anatase surface. In the present work DFTcalculations are used to investigate water diffusion on the (101) anatase TiO2 surface by sampling the potential energy surface of the H2O molecules of the first hydration layer thus calculating the water molecule migration energy along some relevant diffusion paths on the (101) surface, together with phonon frequencies for the obtained stable and saddle configurations. With these ingredients the hopping frequencies of water on TiO2 surface have been calculated in the framework of harmonic transition state theory; then the obtained transition frequencies have been employed as the starting parameters for kinetic Monte Carlo simulations of water diffusion on anatase TiO2,
in order to investigate possible local water clustering on the anatase surface.
