Synthesis and characterization of co-doped TiO 2 thin films on glass-ceramic Nasrin Ahmadi a,n , Ali Nemati b , Mehran Solati-Hashjin c a Young Researchers and Elite Club, Najafabad Branch, Islamic Azad University, Najafabad, Isfahan, Iran b Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box: 11365-9466, Tehran, Iran c Department of Biomedical Engineering, Amirkabir University of Technology, Tehran, Iran article info Keywords: N–Ce co-doped TiO 2 Sol–gel Thin films Photocatalytic activity Hydrophilicity abstract In this research, an attempt was made to improve TiO 2 photo-catalyst properties, thus pure, N–Ce co-doped TiO 2 thin films were prepared on glass-ceramic substrate using a sol–gel dip-coating technique. The samples were calcinated in air at 475 1C, 550 1C, and 650 1C for 2 h. The result of simultaneous thermal analysis (STA) and X-ray diffraction (XRD) showed that the presence of Ce in TiO 2 could inhibit the phase transformation from anatase to rutile and enhance the thermal stability, and anatase was the dominant phase in N–Ce co-doped TiO 2 samples. Also based on the results, the doping results in decreasing the size of TiO 2 crystallite. The results of ultra violet-visible light diffuse reflectance spectra (UV–vis DRS) presented that cerium doping results in a shift in the absorption spectra of N–Ce co-doped TiO 2 to the visible region. The photo-induced hydrophilicity and photo-catalytic activity of the films were evaluated by the water contact angle measure- ment and photo-catalytic degradation of aqueous methyl orange, respectively. It was found that N–Ce co-doped TiO 2 thin films showed a higher photo-catalytic activity, and better photo-induced hydrophilicity than the pure TiO 2 thin films. However, too much doping did not improve properties of N–Ce co-doped TiO 2 . The results of the experiments showed that doping with Ce content of Ce/Ti% equal to 3% and N content of urea/tetra n-butyl ortho titanate equal to 0.25 can improve N, Ce co-doped TiO 2 properties. & 2014 Elsevier Ltd. All rights reserved. 1. Introduction Titanium dioxide has received considerable attention as a photo-catalyst because of its strong oxidation activity and hydrophilicity under UV irradiation [1]. So, preparation of the titanium dioxide photo-catalysts coatings as thin films on different substrates could be useful in industrial applications, including self-cleaning glasses, ceramic tiles, glass-ceramics, etc. [2,3]. But, due to its wide-band gap (3.2 ev), TiO 2 is mainly active under UV irradiation. Thus, there are a lot of investigations planned to make TiO 2 photo-catalysts active under visible irradiation in the literature [4]. Recently, the doping of nonmetal atoms such as N, S and C into the TiO 2 lattice was reported, which can shift the absorption edge or band gap to lower energies and hence increases the visible absorption. In this regard, the substitution doping of N atoms was the most effective technique due to contribution of p orbitals into the band gap narrowing by mixing with oxygen 2p orbitals [5]. Furthermore, doping TiO 2 with lanthanides has also received consider- able attention due to their special 4f orbitals' electrons configuration. Among the mentioned elements, the cerium Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/mssp Materials Science in Semiconductor Processing http://dx.doi.org/10.1016/j.mssp.2014.04.006 1369-8001/& 2014 Elsevier Ltd. All rights reserved. n Corresponding author. E-mail address: ahmadi.nasrin@hotmail.com (N. Ahmadi). Materials Science in Semiconductor Processing 26 (2014) 41–48