N-/S- dual doped C@ZnO: An excellent material for highly selective and responsive NO2 sensing at ambient temperatures

Abstract

• The sensing properties of N/S dual doped C@ZnO is investigated for the first time. • Noble metal free sensing material with high sensitivity towards NO 2 at 25 °C. • The N/S dual doped C@ZnO composite exhibits excellent NO 2 selectivity. • N/S dual doped C significantly enhanced the sensing performance of ZnO. • Plausible gas sensing mechanism has been proposed. Nitrogen dioxide (NO 2 ) is an extremely toxic gas and harmful to human health and the environment. Inhalation of NO 2 reduces immunity to lung infections and causes respiratory problems such as wheezing, coughing, colds, flu, and bronchitis. To date, several sensors have been developed for the detection of NO 2 . Indeed, the development of highly sensitive and selective room temperature sensor with rapid response and recovery time could be called an “innovation” for metal oxide-based gas sensors for environmental remedy applications. Herein, we prepared ZnO nanospheres (ZNS), nitrogen-doped carbon-coated ZnO spheres (NC@ZNS), sulfur-doped carbon-coated ZnO spheres (SC@ZNS), and nitrogen-sulfur dual doped carbon-coated ZnO spheres (NSC@ZNS) for NO 2 sensing. Among them, the NSC@ZNS exhibits excellent NO 2 sensing characteristics with the sensor response (S R = R g /R a ) of 730.4 and 31.2 at 100 and 25 °C, respectively. The limit of detection (LOD) of the NSC@ZNS sensor is ~21 ppb at ambient temperature. The NSC@ZNS hybrid nanocomposite sensor exhibits ultrafast response and recovery times of ~88 s and 305 s to 500 ppb of NO 2 at 25 °C. Besides, the NSC@ZNS sensor shows excellent selectivity to NO 2 , which is ~31 times higher than other interfering gases. The enhanced sensing characteristics of the NSC@ZNS sensor is attributed to the synergy between the nitrogen-sulfur dual doped carbon and hierarchical mesoporous ZnO. The selective detection of NO 2 with significantly rapid response and recovery time at 25 °C makes for intriguing the promising practical applications of our proposed NSC@ZNS sensor.