Phosphonate molecular layers on TiO2 surfaces

We investigated the deposition of (HO)2-PO-S-(CH2)15-COOH on TiO2. The phosphonate group has been chosen to serve as the anchoring moiety while the carboxylic group can be exploited for further coupling with antibacterial peptides. Native oxide-covered polished Ti samples were used as substrates for the molecular deposition. Previous to deposition, the substrates were plasma-cleaned in order to enrich their surfaces of hydroxyl groups, suitable for phosphonate coupling. The combined analysis of atomic force microscopy, X-ray photoemission spectroscopy and differential spectroscopic ellipsometry measurements indicates the formation of a submonolayer film made of irregular islands, one molecule thick.