Ultra-responsive and highly sensitive 1D ZnO nanotubes for detecting perilous low levels of NO2 gas

Abstract

1D ZnO nanotubes were synthesized using a combination of chemical bath deposition (CBD) and thermal methods. The resulting ZnO nanotubes maintained a hexagonal crystal structure with an average length of 500–700 nm. The 1D ZnO nanotube sensor developed in this study exhibited remarkable responses of 84% for 5 ppm and 20% for 1 ppm NO₂ at a relatively low operating temperature of 200 °C, significantly below the exposure limit of 20 ppm. Additionally, the 1D ZnO nanotube sensor demonstrated rapid response times of 1 second for 1 ppm NO₂ and 2.85 seconds for 5 ppm NO₂. The superior performance of the 1D ZnO nanotube sensor, when compared to those of nanoparticles and broken nanotubes, can be attributed to its higher surface area, enhanced charge transport, and improved sensitivity in gas sensing applications. Impedance spectroscopy was employed to investigate the mechanism responsible for the increase in resistance due to NO₂ gas molecule adsorption on ZnO nanotubes. Consequently, 1D ZnO nanotubes exhibit significant potential for the development of advanced gas sensing devices.