High response to sub-ppm level of NO2 with 50%RH of ZnO sensor obtained by an auto-combustion method

Pure zinc oxide was prepared by a simple auto-combustion method. The microstructure and morphological proprieties, of the prepared sample, were investigated by XRD, XPS, and SEM characterizations which indicated that the ZnO nanoparticles have a hexagonal wurtzite structure with space group P63mc. The average size estimated by Willams-Hall exhibits to be 61.45 nm which is in good agreement with that estimated by the SEM image (62 nm). The absorbance spectra indicated a high absorbance in the UV range and the gap energy, estimated by Tauc’s model, was 3.17 eV. The sensor was prepared by spraying the suspension of ZnO nanopowders on an alumina substrate with pre-deposited gold-interdigitated electrodes. The fabricated sensors exhibited a high response (ΔR/R = 208) and acceptable response/recovery times (5/2.5 min) to 1 ppm of NO₂ at low operational temperature (150 °C) in the dark and 50%RH.