Light-induced oxygen sensing using ZnO/GO based gas sensor

We report gas sensing properties of a novel room temperature sensor based on ZnO nanowires and reduced graphene oxide (GO) sheet under UV and visible light exposure. The proposed sensor operates based on the photocurrent response of the ZnO/GO heterostructure and the photocatalytic reduction of GO. ZnO nanowires were deposited on interdigitated Au electrodes and the GO sheet was deposited on the ZnO nanowires by dip coating. Under UV light illumination, the fabricated device shows an enhanced sensitivity to different concentrations of oxygen gas. Oxygen adsorption/desorption on the surface of the ZnO nanowires and on the exposed surface of the GO sheet contribute to the decay and the growth of the photocurrent. We analyze the transient photocurrents using stretched exponential functions, showing that the specific times and the exponents of these fits are excellent candidates for distinguishing different ppm of oxygen gas in the medium. Because of oxygen vacancies and other defects in the ZnO nanowires, the sample is seen to show response to visible light. We study the case of visible light and show that once again the sample shows clear sensitivity to different concentrations of oxygen gas.