Alcohol-sensing characteristics of spray deposited ZnO nano-particle thin films

ZnO nano-particle thin films were deposited on cleaned glass substrates by spray pyrolysis technique using the precursor solution of zinc acetate dihydrate [Zn(CH3COO)(2)center dot 2H(2)O]. Structural analyses and surface morphology of the resulting films were carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analyses confirm that the films are polycrystalline zinc oxide, possessing hexagonal wurtzite structure with crystallite size similar to 25 nm. The SEM micrograph of the film shows a good uniformity and a dense surface having spherical-shaped grains. Alcohol sensing characteristics of the deposited films have been investigated for various concentrations of methanol, ethanol and propan-2-ol in air at different operating temperatures. At 150 ppm concentration, the film shows maximum response (85.2%) to propan-2-ol at the operating temperature of 250 inverted perpendicular C; whereas at the same concentration 150 ppm, the maximum responses to methanol and ethanol at 300 degrees C are observed to be 75.8% and 52.4%, respectively. Also, the film exhibits selective high response to propan-2-ol, followed by ethanol and methanol, respectively at each operating temperature up to 275 degrees C. This selectivity is more pronounced in the region of lower operating temperatures and concentrations. A possible reaction mechanism of alcohol sensing has been proposed. (C) 2011 Elsevier B.V. All rights reserved.