The Shifts of Band Gap and Binding Energies of Titania/Hydroxyapatite Material

The titania/hydroxyapatite (TiO2/HAp) product was prepared by precipitating hydroxyapatite in the presence of TiO(OH)2 gel in the hydrothermal system. The characteristics of the material were determined by using the measurements such as X-ray photoemission spectroscopy (XPS), X-ray diffraction (XRD), diffuse reflectance spectra (DRS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX). The XPS analysis showed that the binding energy values of Ca (2p1/2, 2p3/2), P (2p1/2, 2p3/2), and O 1s levels related to hydroxyapatite phase whereas those of Ti (2p3/2, 2p1/2) levels corresponded with the characterization of titanium (IV) in TiO2. The XRD result revealed that TiO2/HAp sample had hydroxyapatite phase, but anatase or rutile phases were not found out. TEM image of TiO2/HAp product showed that the surface of the plate-shaped HAp particles had a lot of smaller particles which were considered as the compound of Ti. The experimental band gap of TiO2/HAp material calculated by the DRS measurement was 3.6 eV, while that of HAp pure was 5.3 eV and that of TiO2 pure was around 3.2 eV. The shift of the band gap energy of TiO2 in the range of 3.2–3.6 eV may be related to the shifts of Ti signals of XPS spectrum.