Dopamine Adsorption on Anatase TiO2(101): A Photoemission and NEXAFS Spectroscopy Study

The adsorption of dopamine onto an anatase TiO2(101) single crystal has been studied using photoemission and NEXAFS techniques. Photoemission results suggest that the dopamine molecule adsorbs on the surface in a bidentate geometry, resulting in the removal of band gap states in the TiO2 valence band. Using the searchlight effect, carbon K-edge NEXAFS spectra indicate that the phenyl rings in the dopamine molecules are orientated normal to the surface. A combination of experimental and computational results indicates the appearance of new unoccupied states arising following adsorption. The possible role of these states in the charge-transfer mechanism of the dopamine-TiO2 system is discussed.