Biosynthesis of ZnO nanoparticles and effect of silver doping in gas sensing characteristics of volatile organic compounds

This experimental study describes the gas sensing characteristics of biosynthesized ZnO nanoparticles toward a group of volatile organic compounds (VOCs) like benzene, acetone, formaldehyde, methanol and ethanol. The effect of doping of different concentrations of silver nanoparticles in ZnO to improve the sensing response of the mentioned VOCs has also been studied. The structural analysis of the synthesized nanoparticles was carried out using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The morphological investigations were performed using high-resolution transmission electron microscopy (HRTEM). Elemental analysis of the synthesized thin film was carried out by energy-dispersive X-ray spectroscopy (EDX). The gas sensing properties for pure ZnO and Ag-doped ZnO thin films were carried out for different (VOCs). On the basis of experimental results, the optimized Ag-doped ZnO nanoparticles were used for the measurement of gas sensing properties of ethanol gas. The observed gas sensor response has been explained using a chemisorption-based sensing mechanism in metal oxide semiconductor devices. Different sensing parameters like sensitivity, sensor response and recovery time have been measured. The sensor response of both materials has been compared with different concentrations of targeted VOCs. It has been observed that Ag-ZnO exhibits improved sensitivity as compared to pure ZnO. The optimized Ag(15%)ZnO thin films were found to be more selective toward ethanol with ~81% sensor response at 250 °C.