NO2 gas sensing performance of Zinc Oxide Nanostructures synthesized by Surfactant Assisted Low Temperature Hydrothermal Technique

Abstract We report the results of NO2 gas sensing performance of zinc oxide nanostructures in two different morphologies, viz, nanoparticles and nanosheets, synthesized via cost effective surfactant assisted low temperature hydrothermal technique. The structural and morphology related characterizations of the samples were carried out using X-Ray diffraction, Field Emission Scanning Electron Microscopy, Raman spectroscopy, Photoluminescence spectroscopy and Transmission Electron Microscopy techniques. Photoluminescence and Raman spectral studies showed that the ZnO nanosheets (ZNS) possess more vacancies or lattice defects than ZnO nanoparticles (ZNP). The NO2 gas sensing studies revealed that the ZNS exhibited higher real sensing response of 21% /ppm compared to ZNP. The ZNS showed a quick response and recovery times of 4 s and 36 s respectively, good linearity, very low limit of detection and good stability. The NO2 gas sensing mechanism in ZNS has been understood to be due to the formation of chemisorbed and physisorbed layers. These layers enhance the depletion layer of ZNS leading to increase in electric resistance. A good real sensing response, short response and recovery times, low detection limit and stability exhibited by ZnO nanosheets make it a promising candidate in fabricating an efficient and reliable NO2 sensor.