Tin(II) doped anatase (TiO2) nanoparticles: A potential route to "greener" yellow pigments

Abstract

During our exploration of compounds in the SnII-Ti IV-O system, we discovered that hydrolysis of titanium alkoxide solution in the presence of Sn2 salts resulted in stable deep-yellow colored anatase nanoparticles. The samples were characterized by X-ray powder diffraction, electron micro-ACHTUNGTRENUNGprobe, thermal analysis, transmission electron microscopy, and 119Sn Mössbauer spectroscopy. Möcedil;ssbauer data of the yellow colored samples showed the presence of both SnII and SnIV in a distorted environment as expected in the anatase structure. It is suggested that the cationic charge imbalance is compensated by oxygen vacancies and/or hydroxyl groups as evidenced by Mçssbauer data which show two types of SnII environments. When heated in air to 300 °C the samples changed color to completely white and 119Sn Mçssbauer data of these samples showed only the presence of Sn4. These observations indicate that the origin of the yellow color in our Sn doped anatase nanoparticles arises from filled Sn 5s states just above the O 2p band, thus decreasing the band gap. The Sn2 doped anatase TiO2 nanoparticles reported here can potentially lead to environmentally benign yellow pigments. The simplistic nature of the synthetic procedure could easily be adapted to large-scale industrial manufacture. © 2009 Wiley-VCH Verlag GmbH&Co.