Pure and Er3+ doped SnO2 semiconductor nanoparticles have been synthesized by solgel technique. The X-ray diffraction patterns show peaks corresponding to tetragonal structure of SnO2. No Er related impurity peaks could be observed. From the TEM micrographs average crystallite size was estimated to be 12 nm. The UV-evisible absorption spectra of SnO2:Er showed blue shift in the absorption shoulder compared with the spectra of undoped SnO2 sample. Photoluminescence emission intensity of SnO2:Er nanoparticles was found to be quenched with increasing concentration of Er3+ ions. The electron spin resonance (ESR) analysis of Er doped SnO2 nanoparticles indicated Er in 3 + state with g = 2. (C) 2010 Elsevier B.V. All rights reserved.