Indian J. Phys. 84 (9) 1211-1221 (2010) © 2010 IACS *Corresponding Author Optical properties of SnO 2 nanoparticles Smritimala Sarmah and A Kumar* Material Research Laboratory, Department of Physics, Tezpur University, Tezpur-784 028, Assam, India E-mail : ask@tezu.ernet.in Received 7 February 2010, accepted 26 April 2010 Abstract : In recent times, considerable research efforts have been focused on the exploration of novel optical properties of nanocrystalline SnO 2 particles such as photoluminescence (PL). In the present work, spherical SnO 2 nanoparticles are synthesized by solid state reaction at different temperatures using tin chloride dihydrate and sodium hydroxide flakes as precursors. Transmission electron micrograph shows uniform and spherical SnO 2 nanoparticles of diameter 30–40 nm. Micro-Raman spectra show an inverse relationship of line-width with SnO 2 particle size. The band gap of SnO 2 is calculated by plotting (ahn) 2 vs. hn and extrapolating the linear portion of it to a = 0 and found it to be 3.76–4.24 eV. Photoluminescence intensity increases with the increase of solid state reaction temperature up to 873 K. This is attributed to the generation of the oxygen ion vacancies in SnO 2 . Keywords : Tin oxide nanoparticles, solid state reaction, photoluminescence spectroscopy. PACS Nos. : 81.07.-b, 81.10.Jt, 81.40.Ef, 78.55.-m 1. Introduction Tin oxide is an n-type semiconducting metal oxide with a wide band gap (3.6 eV) [1]. It has multifaceted applications in the fields of gas sensing [2], solar energy conversion [3], catalysis, transparent conducting electrode preparation, antistatic coatings [4] etc. Multifunctionality of SnO 2 nanostructures arises due to their high surface to volume ratio, large band gap, high exciton binding energy of 130 meV at room temperature (300 K), remarkable resistivity variation in gaseous environment, mechanical, thermal and chemical stability etc. [5]. Optoelectronic properties of SnO 2 depend on the presence of impurities and its stoichiometry with respect to oxygen. Recently various SnO 2 based nanoscale devices have been fabricated from zero to three dimensional SnO 2 building blocks, e.g., nanosheets, nanowires, nanoribbons, nanoparticles, nanowhiskers, nanobelts, nanotubes etc. using different synthesis techniques like spray pyrolysis [6], decomposition [7], sol-gel method [8], laser