Binding of a Benzoate Dye-Molecule Analogue to Rutile Titanium Dioxide Surfaces

Scanning tunneling microscopy (STM) has been used to investigate the adsorption of benzoic acid on the rutile TiO 2 (110)(1 × 1) and the reconstructed TiO 2 (110)(1 × 2) surfaces. Benzoic acid binds to both surfaces dissociatively via a bridging geometry to two Ti 5c sites. At a slightly elevated sample temperature during deposition onto the (110) (1 × 1) surface, a well-ordered (2 × 1) overlayer was formed at saturated benzoate coverage. On the reconstructed (110) (1 × 2) surface, benzoate was observed to adsorb between the (1 × 2) strands leading to a (2 × 2) superstructure at higher coverage. Elongation along the [11̅0] direction in the STM images indicates a rotation of the benzene ring of 90° relative to the carboxylate group, which is reasonably explained by hydrogen bond interactions between terminating O-atoms on the surface and H-atoms of the ring.