Enhanced room-temperature detection of ultra-low level nitrogen dioxide: Improved sensitivity, selectivity and...

To address the increasing demand for wearable sensors, the development of gas sensors with high sensitivity and environmentally friendly power consumption for monitoring NO₂ at room temperature (RT) is particularly promising. In this paper, porous In₂O₃ microspheres are prepared via a hydrothermal method, followed by the incorporation of 2D MXene solution to synthesize In₂O₃@MXene composites. After characterizing the microstructures and morphology of the In₂O₃@MXene composites, the influence of MXene on the microstructures and NO₂ gas-sensing performance at RT is discussed in detail. The results indicate that a moderate amount of MXene greatly affects the energy band structure, chemisorbed and vacancy oxygen content, and the availability of reactive sites for oxygen and NO₂, thereby affecting the gas-sensing performance of the In₂O₃@MXene sensors. Notably, the In₂O₃@10MXene sensor exhibits the highest response value of 24.98 to 4 ppm NO₂ at RT, which is 5.90 times higher than that of In₂O₃ sensor (4.23). Furthermore, the In₂O₃@10MXene sensor still presents a response value of 2.83-500 ppb NO₂ under RT, confirming an ultra-low ppb level detection limit to NO₂ gas at RT. Additionally, the In₂O₃@10MXene sensor demonstrates favorable gas selectivity and long-term stability. The incorporation of an appropriate amount of MXene effectively enhances the gas-sensing performance of the In₂O₃@MXene sensors, attributed to the formation of a Schottky heterojunction, increased surface oxygen, and more reactive sites for oxygen and NO₂ from MXene.