Ultrasensitive room temperature NO2 sensors based on liquid phase exfoliated WSe2 nanosheets

Semiconducting two-dimensional (2D) transition metal dichalcogenides (TMDs) are promising gas-sensing materials due to their large surface-to-volume ratio, layered structures, susceptible surfaces, and excellent conductivities. Herein, a simple and effective method has been developed to exfoliate tungsten diselenide (WSe 2 ) into few-layered nanosheets with N- methyl-2-pyrrolidone (NMP) as a dispersant. The gas sensor based on the as-synthesized WSe 2 nanosheets shows an extremely high response (50 ppb, 5.06) under a low detection concentration of nitrogen dioxide (NO 2 ) at room temperature (25 °C), which is much higher than many other reports for 2D TMDs-based gas sensors. Additionally, our sensor also exhibits a response of 11.01 to 10 ppm NO 2 , an excellent selectivity, and a reliable long-term stability within 8 weeks. It is expected that the outstanding performances of the gas sensors based on WSe 2 nanosheets reported in the present work will make WSe 2 a promising candidate for ultrasensitive NO 2 sensing applications.