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 V₂O_5, 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.