Researchers at the Tokyo Metropolitan University have developed a simple, groundbreaking method of rolling atomically thin sheets of atoms into nanoscrolls. Nanoscrolls have great possibilities for use in catalysis and photovoltaic devices.
The team – led by Associate Professor Yasumitsu Miyata – has been focusing on transition metal dichalcogenides (TMDC), which are a class of compounds with unique properties, such as flexibility, superconductivity, and exceptional optical absorbance. However, the symmetric atomic arrangement of a monolayer TMDC generally makes its tubular structure energetically unstable due to lattice strain in curved monolayers. Their goal was to create new, simple methods of creating stable TMDC nanoscrolls.
They used Janus nanosheets, named after the two-faced god from ancient mythology, as they have remarkable complementary surface properties and strongly favor adsorption to interfaces. They created asymmetry in the sheets by replacing atoms on one side of a monolayer molybdenum selenide (SE) nanosheet with sulfur through plasma treatment. The addition of a solvent then caused the sheets to spontaneously roll into nanoscrolls due to the inherent imbalance.
Scanning transmission electron microscopy observations demonstrated that the resulting nanoscrolls, which measured multiple microns in length, displayed a tight roll with a center diameter down to five nanometers. Atomic resolution elemental analysis confirmed that the Janus monolayers were rolled up with the Se-side surface on the outside.
This achievement surpasses previous attempts, creating nanoscrolls that interact strongly with polarized light and exhibit hydrogen-producing properties. This enhanced hydrogen-producing property could revolutionize the clean energy sector, providing a sustainable and efficient source of power.