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.