Cysteine on TiO₂(110): A Theoretical Study by Reactive Dynamics and Photoemission Spectra Simulation

Owing to the importance of bioinorganic interface properties for the biocompatibility of implants and for biosensing technology, it has become indispensable to gain understanding of their crucial structure–property relations at the atomistic level. Motivated by this fact, we use cysteine amino acid on perfect and defective TiO₂(110) surfaces as model systems and study adsorption by means of classical all-atom reactive molecular dynamics and ab initio O 1s, N 1s, and S 2p photoemission spectra (XPS) simulations of the most relevant adsorbate structures. By analysis of the dynamics results and a detailed comparison with spectra recently collected for this adsorbate, we obtain conclusions of both general and particular character. It is shown that the interaction of cysteine with the TiO₂(110) surface has multipoint character involving the carboxylic group as well as the amino and sulfur groups. The proton-transfer reactivity of cysteine is enhanced by the presence of the surface, and different forms of cysteines are confirmed to be present in the adsorbate. A general conclusion is that reactive force field dynamics combined with selected spectroscopy provides a viable path to understanding bioinorganic surfaces with ramifications for the design of such surfaces for future technological applications