Abstract
Raman scattering (RS) was used as a powerful, efficient, and sensitive technique for studying intermolecular interactions between an organic ligand adsorbate and a metallic substrate. Functionalization of titanium (TiO2/Ti) surfaces was performed using lysine (Lys) as adsorbate and later developing a hydroxyapatite (HA) layer onto this functionalized surface. The functionalization process was performed at different pH values of the interacting chemical species. Chemisorption onto the TiO2Ti substrates through the Lys carboxylic group was demonstrated spectroscopically. Analysis of vibrational spectra showed that the CH side chain of Lys was relatively distant from the (TiO2/Ti) surface, preventing direct contact with the surface. Additionally, the signals corresponding to the unbound γ-NH2 group indicate that it is available for additional complexation. In vitro bioactivity of the Lys–TiO2/Ti surface was achieved by developing an HA layer onto already functionalized TiO2/Ti surfaces at various pH values. Spectroscopic data using the spectral markers of HA and Lys provided a decisive role in establishing the necessary baseline data for evidencing the intermolecular bonding. The functionalized TiO2/Ti surface reactivity is linked to the specific intermolecular interactions of –COO− (pH 7.0) with Ca2+ ions, as well as the –COOH (pH 2.0 and 12.0) groups of Lys, with the –OH groups of PO3−4 belonging to HA.
