Abstract
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.
Highlights
As a 2D material, graphene has been demonstrated to exhibit differing electrical and optical properties depending on factors such as electrical and magnetic fields [1], strain [2], stacking geometry [3], and edge chirality [4,5] many have realized the applicability limitations of graphene since it does not have a bandgap, which has raised interest in transition-metal dichalcogenide (TMD) materials
Sulfur vacancies were formed on the MoS2 film surface by a minimal plasma treatment (10 W and 2 s), and carboxyl groups were formed through coordinate bonds at the sulfur vacancies using an Mercaptopropionic acid (MPA) solution
The stable functionalization of MoS2 using this strategy was confirmed by the performance of an NH3 sensor
Summary
As a 2D material, graphene has been demonstrated to exhibit differing electrical and optical properties depending on factors such as electrical and magnetic fields [1], strain [2], stacking geometry [3], and edge chirality [4,5] many have realized the applicability limitations of graphene since it does not have a bandgap, which has raised interest in transition-metal dichalcogenide (TMD) materials. A field-effect transistor with monolayer MoS2 exhibited highly favorable electrical properties such as a mobility of 200 cm2/(V s), on/off ratio of 108, and sub-threshold swing of 70 mV/dec [11] Since these electrical properties of MoS2 were revealed, related studies have increased, and research toward extending its applicability has focused on large-area deposition and growth [18,19,20,21] and functionalization [22,23,24,25]. The method requires a transition-metal cation with a high sulfur affinity and octahedral coordination since the direct anchoring of organic ligands to the sulfur surface is impossible Their new method was simple, the application of transition-metal cations complicates the process. The direct synthesis of various organic functional groups on MoS2 thin films has been reported [25], but the method is less efficient than the proposed method and lacks optimization
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