Nb-TiO2/ZnO nanostructures for chemoresistive alcohol sensing

Different nanostructures based on Nb doped TiO2 and ZnO combination prepared through chemical methods in a multistep synthesis process, were investigated for alcohols sensor. Sol-gel method combined with evaporation-induced self-assembly technique were used to deposit Nb-TiO2 mesoporous films. ZnO, consisting on nanowires, were obtained by chemical bath deposition method. Aspects of nanostructures preparation, important in sensing performance, such as the control of the ZnO wire diameter using Nb-TiO2 as a maks, or the control of titania porosity, are emphasized. Scanning electron microscopy (SEM), transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (TEM - EDS), and X-ray diffraction (XRD) were used to investigate the morphology and structure of the obtained nanostuctures. The sensing behavior of Nb:TiO2 /ZnO nanostructures towards 100 ppm methanol or ethanol was investigated between room temperature and 400 degrees C and the optimum operating temperatures for methanol and ethanol detection were found. The gas response of these complex nanostructures was superior compared with those of single oxide thin films reported in the literature. These enhanced gas-sensing characteristics were attributed to the formation of heterojunctions between these two n-type oxides. Also, the mechanism of ethanol and methanol sensing was discussed.