Enhancement of ethanol gas sensing mechanism at high humidity levels and optical features using Sr-doped ZnO NPs

Abstract

In the present study, undoped and Sr-doped ZnO nanoparticles (NPs) were synthesized with the sol–gel method for enhancing selectivity and sensitivity of ethanol sensing at high humidity levels. The samples were identified through their microstructure, morphology, and surface chemistry. As can be seen from X-ray diffraction (XRD) analysis, the Sr doping significantly affected the crystalline quality of the NPs. The results of gas sensing were examined in terms of operating temperature, doping concentration, gas concentrations, gas type, and relative humidity (RH). The sensitivity was gradually increased by raising the variant humidity of 25–70%. Moreover, sensor response from 15 at 32% RH was increased to 57 at 70% RH for undoped and 6% Sr-doped ZnO NPs, respectively. When the RH rose to 70–90%, the sensitivity decreased gradually. The sensor showed a higher selectivity to ethanol compared to the other gases. Based on the obtained results, the sensors have high sensibility levels for 6% Sr-doped ZnO NPs that is ~ 52 at 240 °C and ~ 27 at room temperature, respectively. The achieved improvement in gas sensing behavior can be attributed to the increase in active site values for O adsorption after adding Sr concentrations.