Surface modified Nd doped TiO 2 nanoparticles as photocatalysts in UV and solar light irradiation Anuja Bokare a , Mrinal Pai b , Anjali A. Athawale a,⇑ a Department of Chemistry, University of Pune, Pune 411 007, India b Chemistry Division, Fuel Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India Received 17 January 2012; received in revised form 20 December 2012; accepted 2 February 2013 Available online 22 March 2013 Communicated by: Associate Editor Gion Calzaferri Abstract Nd doped TiO 2 nanoparticles were synthesized by sol–gel method exhibiting photocatalytic activity in solar light together with UV light irradiation. Photoactivities of the catalysts were investigated in terms of degradation of Methyl Orange dye. 1.0% Nd doping appears to be optimum, yielding highest degree of degradation. Ag coating on 1.0% Nd doped sample is seen to further improve the performance of the catalyst. Nd doping and Ag coating could be ensured through the EDAX analysis of the sample. The morphological investigations of the samples reveal the presence of nanoparticles with average size of 8 nm. The improvement in the optical properties of TiO 2 on Nd doping and Ag coating was confirmed by Diffuse Reflectance UV–Visible (DRUV) and Photoluminescence (PL) spec- troscopy. The decrease in the PL intensities together with increase in visible absorption peaks in DRUV spectra of the Nd doped and Ag coated sample implies improvement in the optical properties in comparison with undoped TiO 2 . Doped and coated samples exhibited high surface area than the undoped sample which was ensured by the BET surface area analysis. Ó 2013 Elsevier Ltd. All rights reserved. Keywords: TiO 2 nanoparticles; Nd doped; Ag coated; Methyl orange; Solar light activity; HPLC analysis 1. Introduction Efficient utilization of solar energy is a foremost objec- tive of the scientists and engineers of 21st century. In addi- tion to that, environmental pollution due to the release of toxic chemicals from industrial sectors is of major concern in recent years. Photocatalysts can effectively convert solar energy into chemical energy which can be used for decom- posing toxic organic and inorganic pollutants to purify water and air (Sharma et al., 2012). The most often used photocatalyst due to its optical and electronic properties, stability, low cost and non toxicity is TiO 2 (Burda et al., 2003; Diwald et al., 2004; Li et al., 2005; Shankar et al., 2008). However, its large band gap (3.2 eV) and high rate of electron–hole recombination limits its efficiency only up to UV light region (Wahi et al., 2005). Since the fraction of UV in the solar spectrum is less than 5%, TiO 2 cannot efficiently exploit the abundant natural resource, i.e. solar radiations, which dominantly consist of visible light. Hence, development of solar light active photocatalytic materials is a subject of extensive current research in this field. Doping TiO 2 with transition metals having ‘d’ electronic configuration (Kato and Kudo, 2002; Yu et al., 2002) or non-metals such as Nitrogen (Gole et al., 2004), Boron (Begum et al., 2008) and Sulphur (Rockafellow et al., 2009) is known to enhance their response in the visible light region. Few reports are also available accounting for the improvement in the efficiency of TiO 2 towards visible light when doped with lanthanide ions/oxides with 4f n electron configuration (Parida and Sahu, 2009). Amongst the few 0038-092X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.solener.2013.02.005 ⇑ Corresponding author. E-mail address: agbed@chem.unipune.ac.in (A.A. Athawale). www.elsevier.com/locate/solener Available online at www.sciencedirect.com Solar Energy 91 (2013) 111–119