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

Monolayer and multilayer molybdenum disulfide (MoS) 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 MoS are known, research on its electrical properties has increased, with focus on the deposition and growth of large-area MoS and its functionalization. While research on the large-scale production of MoS 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 MoS are rare, and what methods do exist are either complex or inefficient. This work introduces an efficient way to functionalize MoS. Functional groups are formed on the surface by exposing MoS 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 MoS surface compared with previously reported strategies. The MoS-based gas sensor fabricated using the proposed method shows a 2.6 times higher sensitivity and much lower detection limit than the untreated device.