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

Abstract

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 °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.