International Journal of Advances in Science and Technology, Vol. 5, No.4, 2012 Synthesis, Characterization and Photocatalytic Activity of ZnO:Sn Nanocomposites G. Chaitanya Lakshmi* 1 , S. Ananda 1 , R. Somashekar 2 , C. Ranganathaiah 2 1 Department of Studies in Chemistry, University of Mysore, Mysore-560006, India chaitanyalakshmi.63@gmail.com, snananda@yahoo.com 2 Department of Studies in Physics, University of Mysore, Mysore-560006, India rs@physics.uni-mysore.ac.in, cr@physics.uni-mysore.ac.in Abstract Degradation of Rhodamine B dye (RhB) under solar light was carried out using ZnO:Sn nanocomposites synthesized by electrochemical method. The ZnO:Sn photocatalyst was characterized based on UV-Visible spectrometry, IR spectrometry, X-ray diffraction, Positron annihilation lifetime spectroscopy, Scanning electron microscopy data. The rate constant for the degradation of RhB was high at pH 7.5. The photodegradation efficiency for ZnO:Sn and ZnO were found to be 67% and 59% respectively. Keywords: ZnO:Sn nanocomposites, Rhodamine B dye, electrochemical method 1. INTRODUCTION Some of the important challenges of this decade include overall reduction of human exposure to the chemical pollutants and minimization of human impact in sensitive eco systems and biodiversity [1] . ZnO semiconductor is a potential photocatalyst used for the photodaegradation of dye pollutants. ZnO in some cases exhibits better photocatalytic efficiency than TiO 2 , due to its higher efficiency of generation, mobility and separation of photoinduced electrons and holes. One of the major drawbacks of ZnO is its photocorrosion which significantly decreases its photocatalytic activity. Several methods have been developed to improve its photostability, including surface organic coating of ZnO, surface hybridization of ZnO with carbon and fullerenes C 60 , surface complexation between phenolic compounds and ZnO, depositing metallic Ag on ZnO, doping transition metals on ZnO [2] . Doping is a very useful way to improve the charge separation in semiconductor systems, many dopants such as Sb, Er and Al have been used. Sn was considered as one of the most important doping elements for ameliorating the photocatalytic activity of ZnO [3] . The aim of this study is to synthesize Sn doped ZnO photocatalysts by electrochemical method. The synthesized photocatalyst were systematically characterized by Positron annihilation lifetime spectroscopy, XRD, SEM, FTIR, UV-Visible spectroscopy data. The photocatalytic activity of ZnO:Sn nanocomposites was evaluated by degradation of Rhodamine B (RhB) dye under sunlight irradiation. Electrochemical synthesis of ZnO:Sn nanocomposites The metal wires (Zn and Sn) are used as electrodes. The experiment was run for 3 hrs with continuous stirring (10mA, 6 V); the anodic dissolution of Zn and Sn to give Zn(II) and Sn(IV) ions which are electrochemically reacted with aqueous NaHCO 3 (0.5%) to form Zn(II) oxides/ hydroxides with Sn(IV). The solid obtained was washed with deionised water till complete removal of unreacted NaHCO 3 . The wet powder was then dried at a temperature 250ºC - 400ºC for dehydration and removal of hydroxides to get ZnO:Sn [4] . The rate of electrochemical reaction is not same for all the metals, as the redox potential of Zn and Sn is different. The rate of dissolution for Zn (- 0.7618 V) is faster than Sn (-0.13 V). So that higher proportion of Zn(II) or ZnO is formed than and Sn(IV) or SnO 2 in ZnO:Sn nanocomposites. The electrochemical reaction takes place according to the following mechanism: October Issue Page 54 of 71 ISSN 2229 5216