Abstract
The sol-gel technique was utilized to synthesize alpha-Fe2O3 nanoparticles in supercritical conditions of ethanol. The morphology and microstructure were investigated by scanning and transmission electron microscopy (SEM and TEM) analysis and X-ray diffraction (XRD).The average crystallite size estimated by sherrer's equation was 60 nm. TEM images show that the obtained powder is composed of agglomeration of irregular shaped (between oval and spherical) grains. The prepared nanomaterial was used as sensing layer in gas sensing device. The sensor has been tested towards low concentrations in air of NO2 at different temperatures from 200 to 350 degrees C. We noticed that 225 degrees C was the best operating temperature. At this temperature, the obtained results indicated that the realized sensor has a high response towards 1 ppm of NO2 gas. The response and recovery times are 26 and 48 s, respectively. To show the selectivity of the sensor, we have tested it with different gases such as CO, CO2, and NH3. We found that hematite sensor exhibits high selectivity towards NO2 gas.