Functionalization of Molybdenum Disulfide via Plasma Treatment and 3-Mercaptopropionic Acid for Gas Sensors

Monolayer and multilayer molybdenum disulfide (MoS₂) materials are semiconductors with direct/indirect bandgaps of 1.2-1.8 eV and are attractive due to their changes in response to electrical, physicochemical, biological, and mechanical factors. Since the desired electrical properties of MoS₂ are known, research on its electrical properties has increased, with focus on the deposition and growth of large-area MoS₂ and its functionalization. While research on the large-scale production of MoS₂ is actively underway, there is a lack of studies on functionalization approaches, which are essential since functional groups can help to dissolve particles or provide adequate reactivity. Strategies for producing films of functionalized MoS₂ are rare, and what methods do exist are either complex or inefficient. This work introduces an efficient way to functionalize MoS₂. Functional groups are formed on the surface by exposing MoS₂ with surface sulfur vacancies generated by plasma treatment to 3-mercaptopropionic acid. This technique can create 1.8 times as many carboxyl groups on the MoS₂ surface compared with previously reported strategies. The MoS₂-based gas sensor fabricated using the proposed method shows a 2.6 times higher sensitivity and much lower detection limit than the untreated device.