Research Article The Shifts of Band Gap and Binding Energies of Titania/Hydroxyapatite Material Nguyen Thi Truc Linh, 1 Phan Dinh Tuan, 2 and Nguyen Van Dzung 3 1 Ho Chi Minh City University of Pedagogy, Vietnam 2 Ho Chi Minh City University of Natural Resources and Environment, Vietnam 3 Institute of Applied Materials Science, VAST, Vietnam Correspondence should be addressed to Nguyen Ti Truc Linh; nttlinh2811@gmail.com Received 1 May 2014; Revised 22 June 2014; Accepted 23 June 2014; Published 10 July 2014 Academic Editor: Hui Shen Shen Copyright © 2014 Nguyen Ti Truc Linh et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te titania/hydroxyapatite (TiO 2 /HAp) product was prepared by precipitating hydroxyapatite in the presence of TiO(OH) 2 gel in the hydrothermal system. Te characteristics of the material were determined by using the measurements such as X-ray photoemission spectroscopy (XPS), X-ray difraction (XRD), difuse refectance spectra (DRS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX). Te 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 . Te 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. Te 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. Te shif of the band gap energy of TiO 2 in the range of 3.2–3.6 eV may be related to the shifs of Ti signals of XPS spectrum. 1. Introduction TiO 2 photocatalysis has gained much attention because of its low cost, nontoxicity, high stability, and easy prepara- tion. However, the slow rates of the photocatalytic chemical transformations, compared with other methods, the low quantum yields, the lack of visible-light utilization, and the low adsorption capacity of TiO 2 have hindered it from the practical application. To solve these problems, much efort has been made to enhance the photocatalytic efciency and visible-light utilization of TiO 2 by the additional components doping [1], improving its sensitization and metallization [2], or combining TiO 2 and absorbable inorganic materi- als [3]. Recently, the preparation of titania/hydroxyapatite (TiO 2 /HAp) materials was attracting considerable attention thanks to the photocatalytic property of TiO 2 and great adsorption ability of HAp. Among various features of the TiO 2 /HAp material which have been studied, the band gap evaluation was an important one because it decided the energy separation between the valence and conduction bands, the quantum efect, and the efect of visible-light utilization of that material [4]. Te band gap of HAp was reported in [5] to be 3.95 eV by photoluminescence measure- ment, meanwhile, in some papers, that of HAp was calculated to be around 4.51–5.4 eV [6, 7]. Te band gap of TiO 2 /HAp composites calculated by UV-Vis difuse refectance spectra was between 3.06 and 3.08eV while that of pure TiO 2 was broader (3.12 eV) [8]. However, the band gap of Ti- substituted hydroxyapatite evaluated by both experimental and theoretical methods was 3.65 eV [9]. Generally, the above researches mainly focused on explaining the efciency and photocatalytic mechanism of TiO 2 /HAp or Ti-substituted hydroxyapatite materials and have not mentioned the surface chemical bonding, particularly, the binding energy. In this study, the shifs of binding energy (  ) and band gap energy (  ) of TiO 2 /HAp material prepared by the hydrothermal process were investigated. Hindawi Publishing Corporation Journal of Composites Volume 2014, Article ID 283034, 5 pages http://dx.doi.org/10.1155/2014/283034