Au@ZnO/rGO nanocomposite-based ultra-low detection limit highly sensitive and selective NO2 gas sensor

Nitrogen dioxide (NO2) is very toxic and harmful to humans and the environment; therefore, it is essential to develop a sensor for the detection of NO2 gas. In this paper, a NO2 sensing device was fabricated based on a Au-decorated ZnO/rGO heterostructure, which achieved a remarkable sensing response of 67.38 to 1 ppm NO2 and a notably low theoretical detection limit of 138 parts per trillion (ppt) at a low working temperature of 60 degrees C. Here, we demonstrate a synthesis approach involving Au decoration on the surface of the ZnO/rGO heterojunction. The chemical, morphological, structural, and electrical properties of the Au@ZnO/rGO heterostructure were studied through various characterization techniques. The Au@ZnO/rGO nanocomposite-based sensor exhibited good linearity and time constants of 248 s and 170 s during the adsorption and desorption of NO2 gas. Moreover, the Au@ZnO/rGO nanocomposite sensor demonstrated outstanding selectivity towards 1 ppm NO2, which is significantly higher than that of other interfering gases, indicating its potential for use in NO2 gas detection. The exceptional sensing response is attributed to the higher catalytic activity or synergistic effect between Au and the ZnO/rGO heterostructure. This study delivers an effective method for improving the sensing performance of metal oxide-based nanomaterials.