UV-Activated NO2 Gas Sensing by Nanocrystalline ZnO: Mechanistic Insights from Mass Spectrometry Investigations

In this work, the photostimulated processes of O-2 and NO2 molecules with the surface of ZnO under UV radiation were studied by in situ mass spectrometry in the temperature range of 30-100 degrees C. Nanocrystalline needle-like ZnO was synthesized by decomposition of basic zinc carbonate at 300 degrees C, and the surface concentration of oxygen vacancies in it were controlled by reductive post-annealing in an inert gas at 170 degrees C. The synthesized materials were characterized by XRD, SEM, low-temperature nitrogen adsorption (BET), XPS, Raman spectroscopy, and PL spectroscopy. Irradiation of samples with UV light causes the photoabsorption of both O-2 and NO2. The photoadsorption properties of ZnO are compared with its defective structure and gas-sensitive properties to NO2. A model of the sensor response of ZnO to NO2 under UV photoactivation is proposed.