Enhanced room-temperature detection of ultra-low level nitrogen dioxide: Improved sensitivity, selectivity and stability through MXene-modified InO microspheres.

To address the increasing demand for wearable sensors, the development of gas sensors with high sensitivity and environmentally friendly power consumption for monitoring NO at room temperature (RT) is particularly promising. In this paper, porous InO microspheres are prepared via a hydrothermal method, followed by the incorporation of 2D MXene solution to synthesize InO@MXene composites. After characterizing the microstructures and morphology of the InO@MXene composites, the influence of MXene on the microstructures and NO 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 NO, thereby affecting the gas-sensing performance of the InO@MXene sensors. Notably, the InO@10MXene sensor exhibits the highest response value of 24.98 to 4 ppm NO at RT, which is 5.90 times higher than that of InO sensor (4.23). Furthermore, the InO@10MXene sensor still presents a response value of 2.83-500 ppb NO under RT, confirming an ultra-low ppb level detection limit to NO gas at RT. Additionally, the InO@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 InO@MXene sensors, attributed to the formation of a Schottky heterojunction, increased surface oxygen, and more reactive sites for oxygen and NO from MXene.