Charge-transfer-based Gas Sensing Using Atomic-layer MoS2

TLDR

Two‑dimensional MoS₂ atomic layers hold great promise as electronic sensor components, yet synthesis difficulties and incomplete understanding of gas‑detection mechanisms have limited their practical use. The authors developed a high‑performance gas sensor by chemically vapor‑depositing atomic‑layer MoS₂ and characterizing its response with in‑situ photoluminescence to probe charge‑transfer processes. In‑situ PL monitoring of charged trion and neutral exciton peak shifts during gas adsorption elucidates the charge‑transfer mechanism between MoS₂ and the target molecules. The sensor exhibits high sensitivity and selectivity, with photoluminescence and DFT calculations confirming exothermic adsorption of NO₂ and NH₃, indicating these gases readily bind to the MoS₂ surface.

Abstract

Two-dimensional (2D) molybdenum disulphide (MoS2) atomic layers have a strong potential to be used as 2D electronic sensor components. However, intrinsic synthesis challenges have made this task difficult. In addition, the detection mechanisms for gas molecules are not fully understood. Here, we report a high-performance gas sensor constructed using atomic-layered MoS2 synthesised by chemical vapour deposition (CVD). A highly sensitive and selective gas sensor based on the CVD-synthesised MoS2 was developed. In situ photoluminescence characterisation revealed the charge transfer mechanism between the gas molecules and MoS2, which was validated by theoretical calculations. First-principles density functional theory calculations indicated that NO2 and NH3 molecules have negative adsorption energies (i.e., the adsorption processes are exothermic). Thus, NO2 and NH3 molecules are likely to adsorb onto the surface of the MoS2. The in situ PL characterisation of the changes in the peaks corresponding to charged trions and neutral excitons via gas adsorption processes was used to elucidate the mechanisms of charge transfer between the MoS2 and the gas molecules.