Novel insights into the unique intrinsic sensing behaviors of 2D nanomaterials for volatile organic compounds: from graphene to MoS2 and black phosphorous

Field-effect transistors (FETs) receive growing attention for gas detection owing to their superior sensing performance over traditional techniques. The sensitivity and selectivity of FET sensors can be enhanced by tuning the structure of channel materials via doping, surface functionalization, hybridization, etc. However, the intrinsic semiconductor characteristics of the channel material and its gas adsorption capacity largely determine the sensing performance. In this work, we compared the room-temperature sensing performance of FET sensors with few-layer graphene, black phosphorous (BP), and MoS2 with mixed polymorphic phases (metallic 1T phase and semiconducting 2H phase), and 2H-MoS2 as a channel material for formaldehyde. The sensing results indicate that 1T/2H-MoS2 exhibits the best sensitivity, response time as well as selectivity for formaldehyde detection. The theoretical calculation demonstrates that 1T/2H-MoS2 yields the optimum semiconducting properties and gas adsorption capability for formaldehyde over other 2D channels. Moreover, by investigating the sensing performance under humid conditions, it was discovered that high humidity enhances the sensing response. This study demonstrates that the regulation of the intrinsic electronic structures of the 2D semiconducting channel directly affects the gas detection performance.