Ultrasensitive and Fully Reversible NO₂ Gas Sensing Based on p-Type MoTe₂ under Ultraviolet Illumination

The unique properties of two-dimensional (2D) materials make them promising candidates for chemical and biological sensing applications. However, most 2D material sensors suffer from extremely long recovery time due to the slow molecular desorption at room temperature. Here, we report an ultrasensitive p-type molybdenum ditelluride (MoTe₂) gas sensor for NO₂ detection with greatly enhanced sensitivity and recovery rate under ultraviolet (UV) illumination. Specifically, the sensitivity of the sensor to NO₂ is dramatically enhanced by 1 order of magnitude under 254 nm UV illumination as compared to that in the dark condition, leading to a remarkable low detection limit of 252 ppt. More importantly, the p-type MoTe₂ sensor can achieve full recovery after each sensing cycle well within 160 s at room temperature. Finally, the p-type MoTe₂ sensor also exhibits excellent sensing performance to NO₂ in ambient air and negligible response to H₂O, indicating its great potential in practical applications, such as breath analysis and ambient NO₂ detection. Such impressive features originate from the activated interface interaction between the gas molecules and p-type MoTe₂ surface under UV illumination. This work provides a promising and easily applicable strategy to improve the performance of the gas sensors based on 2D materials.