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.
In this work, we have synthesized Mn-doped SnO2@ZnO nanocomposite for photo degradation of Methylene blue and Rhodamine B dyes upon visible light irradiation. The crystal structure, functional group, optical absorption, defect related emission, morphology, purity and binding energy state of synthesized samples were identified by using various analytical tools.The optical absorption shift and the reduction of band gap values are confirming the formation of hetero-junction of SnO2@ZnO composites. The Mn-SnO2@ZnO hetero-junction effectively induces the photo-generated charge carrier separation and enriches the charge transfer which helps in enhancing the photo-catalytic activities. The photocatalytic degradation results clearly indicate that the Mn-doped SnO2@ZnO nanocomposite has higher degradation efficiency of 98 % and 92 % for the Methylene blue and Rhodamine B dyes, respectively and is higher than the other synthesized samples. The present study reveals a low cost and highly efficient photocatalyst which works up on visible light irradiation for the purification of waste water from industries.
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