CuO foam with <i>in-situ</i> grown polyaniline for high sensitivity room temperature NO ₂ gas sensors

The rapid and accurate detection of NO2 gas at ppm level is of great value in human health and environmental protection. However, the most widely used metal-oxide semiconductor (MOS)-based NO2 sensors usually require high operating temperatures (> 200 °C) to perform sensing functions. The preparation of these sensors possessing excellent sensing performance at room temperature (RT) remains a challenge. In this paper, copper oxide (CuO)-polyaniline (PANI) composites were prepared by heat treatment of copper foam and in situ growth of PANI. These composites exhibited a response value of 7.63 to 100 ppm NO2 at RT, which was 4.8 times higher than that of pure PANI. Moreover, the response time (3 s) was dramatically shortened compared with PANI (27 s). In addition, the prepared sensors demonstrated excellent stability and high NO2 selectivity. The excellent NO2 sensing properties of CuO-PANI were attributed to the p-p heterojunction between CuO and PANI and the large number of oxygen vacancies. This research contributes to a practical and cost-effective approach for the development of high-performance NO2 sensors operating at RT and offers potential applications for air quality testing.