Engineering an\nUltrafast Ambient NO<sub>2</sub> Gas\nSensor Using Cotton-Modified LaFeO<sub>3</sub>/MXene Composites

This work presents a room-temperature (RT) NO<sub>2</sub> gas sensor\nbased on cotton-modified LaFeO<sub>3</sub> (CLFO) combined with MXene.\nLaFeO<sub>3</sub> (LFO), CLFO, and CLFO/MXene composites were synthesized\nvia a hydrothermal method. The fabricated sensor, utilizing MXene/CLFO,\nexhibits a p-type behavior and fully recoverable sensing capabilities\nfor low concentrations of NO<sub>2</sub>, achieving a higher response\nof 14.2 times at 5 ppm. The sensor demonstrates excellent performance\nwith a response time of 2.7 s and a recovery time of 6.2 s, along\nwith notable stability. The sensor’s sensitivity is attributed\nto gas interactions on the material’s surface, adsorption energy,\nand charge-transfer mechanisms. Techniques such as in situ FTIR (Fourier\ntransform infrared) spectroscopy, GC–MS (gas chromatography–mass\nspectroscopy), and near-ambient pressure X-ray photoelectron spectroscopy\nwere employed to verify gas interactions and their byproducts. Additionally,\nfinite-difference time-domain simulations were used to model the electromagnetic\nfield distribution and provide insight into the interaction between\nNO<sub>2</sub> molecules and the sensor surface at the nanoscale.\nA prototype wireless IoT (Internet of Things)-based NO<sub>2</sub> gas leakage detection system was also developed, showcasing the\nsensor’s practical application. This study offers valuable\ninsight into the development of room-temperature NO<sub>2</sub> sensors\nwith a low detection limit.