Molybdenum disulfide nanoflakes through Li-AHA assisted exfoliation in an aqueous medium

Abstract

Two dimensional materials are promising candidates for sensing, catalysis, and energy storage applications because of their high surface area and excellent electronic properties. Layered materials such as graphite, transition metal dichalcogenides (TMDs) and transition metal oxides (TMOs) can be a major source of two dimensional systems. However, the development of two dimensional systems from layered materials has been hindered by the lack of a proper exfoliation technique. We report the exfoliation of bulk MoS₂ powder into few layered nanoflakes using lithium salt of 6-aminohexanoic acid (Li-AHA) in an aqueous dispersion. Li-AHA treated MoS₂ was ‘destacked’ to form few layered nanoflakes due to the electrostatic repulsion. XRD analysis showed that the Li-AHA treatment resulted in the formation of highly crystalline MoS₂ nanoflakes. Raman spectroscopic analysis indicated a shift in E¹_2g and A_1g peaks suggesting the reduction in interlayer interactions, which in turn indicates exfoliation. Electron microscopic observations strongly suggested the formation of a few layered structure. These nanoflakes can be further incorporated into various polymer matrices to prepare composites with superior mechanical and electrical properties as compared to its bulk counterpart. The reported exfoliation technique is simple, effective and can be extended to exfoliate various transition metal dichalcogenides.