Two-dimensional MoSe₂ nanosheets via liquid-phase exfoliation for high-performance room temperature NO₂ gas sensors

Molybdenum selenide (MoSe₂) has drawn significant interest due to its typical semiconductor properties. MoSe₂ is a relatively novel material in the field of gas sensors especially at room temperature. Herein, we utilize a facile and efficient synthetic method of liquid-phase exfoliation to exfoliate bulk MoSe₂ into nanosheets. Anhydrous ethanol is used as dispersant, so the low boiling point makes it easy to be removed from MoSe₂ nanosheets, which does not affect the subsequent sensing performance. The exfoliated few-layered MoSe₂ nanosheets shows significantly enhanced NO₂ gas response (1500% to 10 ppm NO₂ which is 18 times greater than pristine bulk MoSe₂), a low detection concentration (50 ppb), an outstanding repeatability, a remarkable selectivity, and a reliable long-term device durability (more than 60 d) at room temperature (25 °C). The reason of the significant improvement in gas sensing performance can be attributed mainly to the higher surface-to-volume ratio of exfoliated MoSe₂ nanosheets. It promotes the adsorption of gas molecules on the surface of the material, thereby facilitating the charge transfer process. The superior performance of this gas sensor makes MoSe₂ nanosheets a potential candidate for room temperature NO₂ detection.