Structural, luminescent, and NO2 sensing properties of SnO2-core/V2O5-shell nanorods

SnO2-core/V2O5-shell nanorods were synthesized using a two-step process: thermal evaporation of Sn powders and sputter-deposition of V2O5. The core-shell nanorods were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and photoluminescence spectroscopy. The diameters of these core-shell nanorods ranged from 80 to 200 nm with a shell layer thickness in the range of 7-13 nm. The cores and shells of the annealed core-shell nanorods consisted of a single crystal tetragonal-structured SnO2 and a single crystal orthorhombic-structured V2O5, respectively. Photoluminescence measurements revealed the SnO2 nanorods to have a yellow emission band centered at approximately 590 nm, which was enhanced significantly by the V2O5 coating and further by thermal annealing. The sensitivity of the networked SnO2-core/V2O5-shell nanorod sensor to NO2 gas was slightly higher than that of the bare SnO2 nanorod sensor. The enhanced sensitivity of the SnO2 nanorods by the V2O5 coating was attributed to the modulation of electron transport by the SnO2-V2O5 heterojunction with an adjustable energy barrier height.