Sol-gel based spin coated nanostructured films of tetragonal phase of antimony (10 at%) doped tin oxide (ATO) were prepared on silica glass. XRD and TEM images identify the crystallite size lying in the range, similar to 3.4-9.8 nm. Quantum confinement was observed in the nanoclusters. Evaluated band gaps at 3.62 eV correspond to the transition for bulk ATO and 4.51 eV, 5.26 eV for excitons and oxygen deficiency. Schemes have been proposed for absorption and photoluminescence excitation (PLE). Two excitonic transitions were observed at 275 nm and 310 nm for different nanocluster sizes. Evaluation of mean free path and Fermi energy correspond to ionized scattering and degeneracy of the ATO films. (C) 2013 Elsevier B. V. All rights reserved.