Liquid phase exfoliated WS2 nanosheet-based gas sensor for room temperature NO2 detection

Layered transition metal dichalcogenide (TMD) materials possess novel and unique semiconducting properties when exfoliated into thin sheets or individual layers. The exfoliation leads to effective sensing towards gas molecule due to the increase in surface-active sites and edge zone disorders. In this work, we present exfoliation of bulk WS2 sheets with liquid-based dispersion technique using facile bath sonication method for NO2 molecule sensing. The exfoliated WS2 nanosheets show reversible and selective response towards NO2 gas molecules operating at room temperature. The sensitive film shows p-type characteristics providing sensor response rate around 27% for 10 ppm NO2 with rapid response and recovery time around 45 s and 60 s, respectively. The sensitive response was further studied at high temperature of 150 °C showing a drastic increase in response rate as 45% with effective response and recovery time. This improvement in NO2 gas sensing was attributed to the facile exfoliation of WS2 nanosheets.