Materials Chemistry and Physics 85 (2004) 52–57 Preparation and photo-catalytic activity of Fe–TiO 2 thin films prepared by sol–gel dip coating R.S. Sonawane a,∗ , B.B. Kale a , M.K. Dongare b,∗ a Centre for Materials for Electronics Technology (C-MET), Panchwati, Pashan Road, Pune 411 008, India b Catalysis Division, National Chemical Laboratory, Pashan Road, Pune 411 008, India Received 9 September 2003; received in revised form 12 September 2003; accepted 2 December 2003 Abstract Thin films of iron (Fe) doped titanium dioxide (Fe–TiO 2 ) were prepared on a variety of substrates by using Ti-peroxy sol–gel dip coating method. The surface structure of the film was modified by adding different concentrations of polyethylene glycol (PEG) into the TiO 2 sol. Most of the metal ion doped entered TiO 2 lattice resulting the shift in optical absorption edge towards visible side. Addition of PEG alters the surface morphology and structure of the films. The increase in concentration of PEG increases the number and size of the pores on surface of the film by decomposition of PEG when the films are subjected to heat treatment. The adsorbed hydroxyl content of such porous films is found to increase with amount of PEG added. Photo-catalytic properties of the surface modified and Fe ion doped TiO 2 catalyst was investigated by degradation of methyl orange in sunlight. The photo-catalytic activity of the PEG added Fe–TiO 2 catalyst was enhanced by 2–2.5 times than undoped TiO 2 . © 2004 Elsevier B.V. All rights reserved. Keywords: Iron–titania; Thin films; Methyl orange; Photo-catalytic; Degradation; Sunlight 1. Introduction Photo-oxidation by using TiO 2 photo-catalyst is being widely studied as a relatively new technique of pollution abatement [1–3]. TiO 2 is a commonly used photo-catalyst because of its stability in UV light and water. However, the need of an ultraviolet (UV) excitation source, restricts its technological utility for limited applications. For widespread applications, TiO 2 photo-catalyst effective in solar light or light from visible region of the solar spectrum need to be developed as future generation photo-catalytic mate- rial. TiO 2 absorbs only 5% energy of the solar spectrum hence numerous studies have been performed to extend the photo-response and photo-catalytic activity by modifying its surface structure, surface properties and composition [4–6]. The surface modification by doping with metal ions and organic polymers has been proven to be an efficient route to improve the photo-catalytic activity of TiO 2 [7–10]. Many researchers have paid attention in developing mod- ified TiO 2 powder catalyst [11,12] but using the powder catalyst has the disadvantages like stirring during the reac- ∗ Corresponding authors. E-mail addresses: sonawaner@yahoo.com (R.S. Sonawane), dongare@cata.ncl.res.in (M.K. Dongare). tion and separation of catalyst after each run. The prepa- ration of thin film catalyst will overcome these problems and it will also extend the applications of catalyst towards antibacterial ceramic tiles as well as self-cleaning glasses [1]. Among the different thin film deposition techniques the sol–gel dip coating is the simplest, economical and has ad- vantages such as TiO 2 is easily anchored on the substrates bearing the complicated shapes and large area substrates. The deposition of TiO 2 by sol–gel method has been re- ported by few authors [1,13–15]. The present paper deals with the preparation of Fe–TiO 2 thin film photo-catalyst by sol–gel dip coating process and modification of the surface structure by addition of polyethylene glycol (PEG, average molecular weight: 4000). The effect of addition of PEG on the nature of the films and photo-catalytic activity has been investigated. 2. Experimental 2.1. Preparation of TiO 2 precursor sol The TiO 2 sol was prepared by using titanium tetraiso- propoxide (Ti(OC 3 H 7 ) 4 , 99.5%, Aldrich), hydrogen perox- ide (H 2 O 2 , 30%, Qualigen), Ferric nitrate (Fe(NO 3 ) 3 ·9H 2 O, 0254-0584/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.matchemphys.2003.12.007