Room temperature CO sensor based on Au-decorated ZnO nanosheets

Abstract

As a flammable and explosive gas, CO poses substantial safety risk when it is detected by sensors operating at elevated temperatures. Consequently, the room temperature CO sensor based on Au-decorated ZnO nanosheets were successfully prepared by hydrothermal method and NaBH₄ reduction method, with an ultra-high response (139.75) towards 100 ppm CO, which is about 43 times higher than that of pristine ZnO. Moreover, the sensor exhibits a low detection limit (300 ppb) and a fast response/recovery speed (61/61 s to 100 ppm CO). According to in situ diffuse reflectance infrared Fourier transform spectroscopy (In-situ DRIFTS), the introduction of Au nanoparticles significantly enhances the adsorption kinetics of CO and fundamentally alters its oxidation mechanism, promoting a more direct pathway for CO oxidation, suggesting that Au nanoparticles play a crucial role in the adsorption and dissociation of gas molecules on ZnO surface. Furthermore, the formation of Schottky barriers modulates the carrier transport and the thickness of the space charge layer which are also contribute to the improve of room temperature gas-sensitive performance. Therefore, the Au-decorated ZnO sensor is promising for CO monitoring in various fields such as integration into personal protective equipment, part of an environmental monitoring network, early fire detection systems and safety monitoring in industrial environments.