Room-temperature NO2 sensing properties and mechanism of CuO nanorods with Au functionalization

In this work, a room-temperature NO2 gas sensor based on Au-functionalized CuO nanorods (Au-CNRs) via a facile one-pot hydrothermal route was fabricated. The material characterizations were studied by XRD, SEM, TEM, XPS, and FTIR, respectively. The diameter and length of the pristine CuO nanorods (CNRs) were 30–60 nm and 150–200 nm, respectively. The CNRs structure was not significantly affected by Au functionalization. Au nanoparticles with the diameters of less than 20 nm were uniformly distributed on the surface of 2 mol% Au-CNRs. The gas sensing test result showed that room-temperature NO2 sensing can be achieved by Au-functionalized CuO nanorods, especially the 2 mol% Au-CNRs, which exhibited the response of 3 towards 20 ppm NO2 with the response and recovery times of 8 s and 176 s at room temperature (25 °C). This sample also showed good selectivity and reproducibility to NO2. The related sensing mechanism of the CNRs based materials to NO2 was investigated by the changing of energy band gap and activation energy with Au functionalization, respectively.