Hydrothermal synthesis of highly crystalline ZnO nanoparticles: A competitive sensor for LPG and EtOH

Highly crystalline zinc oxide (ZnO) nanoparticles have been synthesized by hydrothermal route at 120 °C over a range of different time periods. The synthesized nanoparticles are characterized for their phase and morphology by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermogravimetric-differential thermal analysis (TG-DTA) follows the thermal changes accompanying the heat treatment and ultra-violet diffuse reflectance spectroscopic studies (UV-DRS) give a measure of the optical properties. Electrical properties of the synthesized nanoparticles are studied by AC impedance and DC conductivity measurement. The gas sensing properties were studied towards reducing gases like liquefied petroleum gas (LPG), ammonia, hydrogen, ethanol (EtOH), etc., and it is observed that the nanoparticles show high sensitivity to LPG and ethanol at relatively low operating temperatures. Pd incorporation results in a decrease in operating temperature by more than 100 °C, and improves the sensing characteristics in terms of response and recovery times.