Synthesis and gas sensing properties of WS2 nanocrystallites assembled hierarchical WS2 fibers by electrospinning

Abstract

A gas sensor based on a hierarchical WS2 structure embedded with the vertically aligned WS2 nanocrystallites was demonstrated. The three-dimensional (3D) hierarchical structure provides many edge sites of nanocrystallites and an extremely large gas contact volume, resulting in a high gas response. The decreased contact resistance between the 3D hierarchical WS2 fibers and sensor electrode resulting in improved NO2 response. We fabricated a one-dimensional (1D) conductive WS2 fiber using a two-step annealing process under sulfur flow (sulfurization). It delivers a continuous and conductive carrier path and lowers the potential barrier at the interface of the WS2 nanocrystallites (top) and electrospun WS2 fiber (bottom), resulting in an improved gas response. We developed 3D hierarchical WS2 fibers embedded with vertically aligned WS2 nanocrystallites to increase the gas adsorption site in comparison with that of 1D WS2 fibers without WS2 flakes. Vertically aligned WS2 nanocrystallites were formed after a two-step annealing treatment. Sensors based on the 3D hierarchical WS2 fibers embedded with WS2 flakes, showed higher response to NO2 gas in comparison to that of pure WS2 fibers without WS2 flakes.