Ultrasensitive and highly selective NO2 gas sensing of porous MXene nanoribbon assemblies

Nitrogen dioxide (NO2), a potential source for acid rain and photochemical smog, is known to harm human health, plant growth and crop yield, and the environment. Therefore, designing a room temperature operable NO2 gas sensor with exceptional sensitivity and selectivity is extremely important. Herein, we report that Ti3C2Tx MXene (Tx = -OH, -O, -F, etc.) nanoribbons containing inbuilt anatase TiO2 on their surfaces achieve highly sensitive detection of NO2 gas at room temperature with negligible cross-responses to other gas analytes. The MXene nanoribbons' ability to form porous gas sensor film facilitates the efficient diffusion of gas molecules and the sufficient utilization of surface-active sites, leading to a high response of -87.5 % to 50 ppm NO2 gas exposure with a response time of 9.2 s at room temperature. Signifying the low concentration NO2 detection abilities, MXene nanoribbons displayed a response of -4.4 % towards 500 ppb NO2 exposure. MXene nanoribbons' NO2 gas sensing ability is carrier gas dependent and declines monotonically as operating temperature increases. In addition, the performance comparison experiments conducted at 50 ppm NO2 gas exposure suggest that the MXene nanoribbons' response is 14.3, 1.6, and 45.3 times higher than the responses of multilayer MXene, MXene-TiO2 nanoplate, and MXene-TiO2 nanoparticle structures, respectively. The explicit selectivity and high sensitivity of MXene nanoribbons toward NO2 gas are expected to provide exciting opportunities for personal safety and environmental monitoring.