Mechanism for Liquid Phase Exfoliation of MoS2

A highly efficient, reproducible, and scalable approach for exfoliation of MoS2 is critical for utilizing these emerging materials from coatings and composites to printable devices. Additive-free techniques, such as solvent-assisted exfoliation via sonication, are considered to be the most viable approach, where N-methyl-2-pyrrolidone (NMP) is the most effective solvent. However, understanding the mechanism of exfoliation and the key role NMP plays during the process have been elusive and challenges effective improvements in product yield and quality. Here, we report systematic experiments to understand the mechanism of solvent-assisted exfoliation by elucidating the sonolysis chemistries associated with NMP. It is confirmed that in the presence of O2(g) dissolved moisture in NMP plays a critical role during sonication. The higher the moisture content, the more efficient the exfoliation process is. Conversely, when exfoliations are carried out with dried solvents with an inert atmosphere, reaction yields ...