This paper presents the joint effect of strain-and doping-induced band gap change in Sn 1Àx Mn x O (0 # x # 0.05) nanoparticles. In addition, an effort was made to understand the effect of Mn doping on the structural and optical properties of SnO 2 . X-ray diffraction analysis showed a tetragonal structure and the unit cell volume decreased slightly with Mn 4+ content. The Mn:SnO 2 are spherical shaped particles with a size ranging from 7.7 to 13.8 nm as calculated by transmission electron microscopy, Scherrer's formula and Willamson-Hall plot. X-ray photoelectron spectroscopy showed clear evidence for tetragonal coordinated high-spin Mn 4+ ions occupying the lattice sites of Sn 4+ in the SnO 2 host. Electron energy loss spectroscopy further confirmed composition and oxidation states of Sn 4+ and Mn 4+ ions. Manganese doping increased the band gap of SnO 2 from 4 eV to 4.40 eV with Mn 4+ concentration. Variation in band gap energy was attributed to the increasing lattice strain with Mn content and the charge transfer transitions between Mn 4+ ions and conduction/valence bands of SnO 2 . Three photoluminescence emission bands observed at 320, 360 and 380 nm, when excited at 250 nm, proved Mn:SnO 2 to exhibit good optical emission and to have potential application in nanoscale optoelectronic devices.

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