High-performance NO2 gas sensor enabled by Fe, N co-doped GQDs modification and pulse-driven temperature modulation

Abstract

Nitrogen dioxide (NO₂) is a typical reactive nitrogen species harmful to health and the environment. However, NO₂ sensors still suffer from low sensitivity and poor response/recovery rates. Herein, 3D In₂O₃ assembled by stacked nanosheets were prepared and modified with N element-doped GQDs (N-GQDs) and Fe, N co-doped GQDs (Fe,N-GQDs), respectively. The results of NO₂-sensing performance indicated that the optimal sample (0.3 wt% Fe,N-GQDs/In₂O₃) showed a high response of 414.5 to 1 ppm NO₂ and could detect as low as 10 ppb at 50℃, which was 1.3 and 4.0 times higher than that of 0.3 wt% N-GQDs/In₂O₃ and In₂O₃, respectively. The gas-sensing kinetics were analyzed by establishing gas adsorption/desorption isotherms. The enhanced NO₂ sensing properties of 0.3 wt% Fe,N-GQDs/In₂O₃ were mainly due to the enhanced active site accessibility of stacked nanosheets with open layer spaces, the heterointerface between Fe,N-GQDs and In₂O₃, and electrical modulation of Fe,N-GQDs. Additionally, A pulse-driving circuit was designed for a pulse temperature modulation (PTM) strategy to further boost NO₂ detection. The sensor response is further enhanced by 1.7 times, and the response/recovery time is reduced by 42.5 %/60.1 %. The NO₂ concentration in vehicle exhaust was determined using PTM mode with good spike recoveries. It validated the reliability of the sensor for the quantitative detection of NO₂ in the real environment. This work provides insights into sensor design and has the potential to contribute to the development of novel sensing platforms for other gas pollutants.