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

Abstract

The titania/hydroxyapatite (TiO 2 /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 TiO 2 . The XRD result revealed that TiO 2 /HAp sample had hydroxyapatite phase, but anatase or rutile phases were not found out. TEM image of TiO 2 /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 TiO 2 /HAp material calculated by the DRS measurement was 3.6 eV, while that of HAp pure was 5.3 eV and that of TiO 2 pure was around 3.2 eV. The shift of the band gap energy of TiO 2 in the range of 3.2–3.6 eV may be related to the shifts of Ti signals of XPS spectrum.