Defect controlled adsorption/desorption kinetics of ZnO nanorods for UV-activated NO2 gas sensing at room temperature

In this work, the adsorption/desorption kinetics of ZnO nanorods with two different levels of defects for UV-activated NO2 gas sensing at room temperature is investigated. It is found that the pristine ZnO has higher sensitivity than the thermally annealed ZnO and the consequence can be attributed to the presence of more oxygen vacancies that act as adsorption sites. Based on the Langmuir adsorption model, the adsorption and desorption constants are determined to be 2.7 x 10(-5) ppb(-1) s(-1) and 3.2 x 10(-3) s(-1), respectively, for the pristine ZnO; and 1.5 x 10(-5) ppb(-1) s(-1) and 2.1 x 10(-3) s(-1), respectively, for the annealed ZnO. Both kinetic constants for the pristine ZnO are higher, which manifests its higher sensitivity. The determination of kinetic constants could provide valuable information for better understanding of nanomaterials based gas sensors. (C) 2020 Elsevier B.V. All rights reserved.