Synthesis of burger/donut like V and W doped ZnO and study of their optical and gas sensing properties

Hierarchical undoped, vanadium and tungsten doped ZnO nanostructures have been synthesized via a surfactant assisted hydrothermal method. The as-synthesized products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDAX), UV–visible spectroscopy, photoluminescence (PL) and particle size distribution (PSD) analysis. A possible growth mechanism of the various hierarchical ZnO nanostructures is proposed. Gas response of sensors fabricated from the as-prepared as well as V- and W-doped ZnO were systematically investigated for acetone, ethanol, methanol, formaldehyde, dimethylsulfoxide (DMSO), triethylamine (TEA), ammonia and ethylenediammine (EDA). Undoped ZnO showed ~80% sensitivity towards acetone while on V-doping the sensitivity enhanced up to 92%. In the W-doped ZnO response towards acetone suppressed while the response towards TEA enhanced. The doping and morphology of ZnO are probably responsible for such a difference in the gas response. UV–visible absorption results reveal that doping ZnO with tungsten shows red-shift of the absorption edge. The photoluminescence (PL) studies reveal a slight red-shift in UV emission in pure ZnO upon V- and W-doping, which is assumed to be associated with the different compress stress in the architectures.