Synthesis and characterization of TiO 2 photocatalytic thin films prepared from refluxed PTA sols L. Ge * , M.X. Xu, M. Sun School of Materials Science and Engineering, Key Laboratory for advanced Ceramics and Machining Technology of Ministry of Education, Tianjin University 300072 PR China Received 20 June 2005; accepted 13 August 2005 Available online 6 September 2005 Abstract The peroxo titanic series refluxed sols (RS) were synthesized using titanyl sulfate (TiOSO 4 ), ammonia as raw materials and peroxide (H 2 O 2 ) as chelating agent by refluxing method from peroxo titanic acid sol. The transparent nano anatase TiO 2 thin films fixed on glass slide substrates were prepared from the RS precursors by dip-coating, then dried under infrared light and calcined at 500 -C for 30 min. Several characterization techniques, such as FT-IR, XRD, TEM, TG-DTA, SEM, were applied to characterize the RS sol and TiO 2 thin films. The results indicated that the RS sols were flavescent, semitransparent and alkalescent, the RS sols kept stable at room temperature, and contained needle-like TiO 2 anatase crystals which were 30¨80 nm in length, 15– 20 nm in diameter and well distributed in the sols. The TiO 2 films were uniform, compact and transparent. The degradation of 10 mg/L methyl orange results illustrated that the RS-6 TiO 2 thin films showed the best photocatalytic activities, the decoloration rate of the methyl orange solution with RS-6 TiO 2 thin films reached 99% after irradiated 160 min under UV light, which proved TiO 2 films prepared from RS sol showed high photocatalytic activities. D 2005 Elsevier B.V. All rights reserved. Keywords: Needle-like anatase crystals; Refluxed sol; Nano TiO 2 thin films; Photocatalysis 1. Introduction Thin films of TiO 2 formed of nanosized particles in the anatase phase show a very high efficiency photocatalytic activity due to their large internal surface and has gained extensive interest because of its important role in degradation of various toxic compounds [1]. Aqueous peroxotitanium acid gel derived from titanium metal [2] or metallorganic com- pounds [3] has been prepared and extensively studied. Ichinose et al. [4] have synthesized peroxo-modified anatase sol using peroxotitanium acid solution by mixing TiCl 4 with H 2 O 2 solution. Gao et al. [5] have reported the preparation of anatase TiO 2 thin films using the aqueous peroxotitanate solution obtained by dissolving metatitanic acid (H 2 TiO 3 ) in a mixture of H 2 O 2 and ammonia in water. Based on these studies, we have prepared PTA sol using titanyl sulfate (TiOSO 4 ), ammonia and peroxide (H 2 O 2 ) as starting materials [6], the AS sol contained needle-like anatase crystals has been synthesized by autoclaving the PTA sol at different conditions [7], the photocatalytic activities of TiO 2 thin films were discussed [8]. In this paper, in order to simplify the experimental process and avoid use of expensive equipment such as autoclave, a novel route was developed by refluxing method to prepare the refluxed sols (RS) with well-dispersed anatase crystals. TiO 2 thin films on glass slide substrates were prepared using the RS sols as precursors. This method is suitable for the deposition on various substrates at relative low temperatures. 2. Experimental 2.1. Preparation of RS sols The RS sols were prepared by using titanyl sulfate (TiOSO 4 InH 2 O), hydrogen peroxide (H 2 O 2 , 30%), ammonia (NH 3 IH 2 O, 3 mol/L) as staring materials. Titanyl sulfate (TiOSO 4 , 17.3 g) was first dissolved in distilled water, and then precipitated by adding ammonia solution (NH 4 OH, 3 mol/ L) resulting titanium hydroxide. The white precipitate was 0167-577X/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2005.08.036 * Corresponding author. E-mail address: gelei08@eyou.com (L. Ge). Materials Letters 60 (2006) 287 – 290 www.elsevier.com/locate/matlet