The National University of Singapore reports that a team of chemists has developed a novel method to chemically exfoliate molybdenum disulfide crystals into high quality monolayer flakes. The result of this new technique is higher yield and larger flake size than current methods. The flakes can be made into a printable solution, which can be used in printable photonics and electronics. The study’s results are published in the journal Nature Communications.

Current processes of producing printable single layer chalcogenides take a long time and the yield is poor. The flakes produced are of submicron sizes, which means that it is hard to isolate a single sheet for creating electronic devices. A majority of applications require clean, large-sized flakes.

Scientists from NUS studied the metal adducts of naphthalene. They prepared naphthalenide adducts of lithium, sodium and potassium, and compared the exfoliation efficiency and quality of molybdenum disulfide generated.

Using a two-step expansion and intercalation technique, they were able to produce high quality single-layer molybdenum disulfide sheets with big flake size. They also demonstrated that the exfoliated molybdenum disulfide flakes can be made into a printable solution, and wafer-size films can be printed.

“At present, there is a bottleneck in the development of solution-processed two dimensional chalcogenides,” noted first author Dr. Zheng Jian, a Research Fellow with the Department of Chemistry at NUS Faculty of Science, in a statement. “Our team has developed an alternative exfoliating agent using the organic salts of naphthalene and this new method is more efficient than previous solution-based methods. It can also be applied to other classes of two-dimensional chalcogenides.”