Ab initio molecular dynamics of solvation effects and reactivity at the interface between water and ascorbic acid...

In this work, we present a detailed study of the interaction between ascorbic acid (L-asc) and anatase TiO₂ (101) surface both in gas phase and in contact with water by using density functional theory and ab initio molecular dynamics simulations. In gas phase, L-asc strongly binds the TiO₂ (101) surface as a dianion (L-asc^2- ), adopting a bridging bidentate coordination mode (BB), with the two acid protons transferred to two surface 2-fold bridging oxygens (O2c). AIMD simulations show that the interaction between the organic ligand and the anatase surface is stable and comparable to the vacuum one despite the possible solvent effects and/or possible structural distortions of the ligand. In addition, during the AIMD simulations hydroxylation phenomena occur forming transient H₃ O⁺ ions at the solid-liquid interface. For the first time, our results provide insight into the role of the ascorbic acid on the electronic properties of the TiO₂ (101), the influence of the water environment on the ligand-surface interaction and the nature of the solid-liquid interface.