Researchers at Tokyo Metropolitan University have proposed a new method of rolling atomic thin sheets into "nanoreels". Their unique method uses transition metal chalcogenide sheets with different compositions on both sides to achieve tight rolling, with a center diameter as small as 5 nanometers and a length as small as micrometers. The control of nanostructures in these vortices is expected to achieve new developments in catalysis and photovoltaic devices.
The research results are published on ACS Nano.
Nanotechnology provides us with new tools for controlling material structures at the nanoscale, and is expected to provide engineers with a complete set of nanotechnology tools to create the next generation of materials and devices. At the forefront of this movement, a team led by Associate Professor Yasumitsu Miyata at Tokyo Metropolitan University has been studying methods for controlling the structure of transition metal chalcogenides. TMDC is a class of compounds with a wide range of interesting properties, such as flexibility, superconductivity, and unique light absorption.
In their latest work, they have turned their attention to a new method of manufacturing nanoreels, where the nanosheets are rolled into a tightly coiled structure. This is an attractive method for creating multi wall structures: since each sheet has the same structure, the directions of the layers are aligned with each other. However, there are significant issues with the existing two methods of manufacturing nanoreels. On the one hand, removing sulfur atoms from the surface of nanosheets will cause deformation, leading to the rolling of the sheet material; But doing so will damage the crystal structure of the sheet. In another case, a solvent is introduced between the nanosheets and the substrate to release the thin sheets from the substrate and form defect free nanoreels. However, tubular structures like this often have larger diameters.
The team did not adopt this method, but came up with a new way to roll up the sheets. Starting from single-layer molybdenum selenide nanosheets, they treated the nanosheets with plasma and replaced one side of the selenium atom with sulfur; This structure is called Janus nanosheets, named after the ancient double-sided god. Then gently add solvent to release the sheet from the base, and due to the asymmetry between the two sides, the sheet will spontaneously roll into a roll.
These new nanovortex lengths are several micrometers, much longer than previously manufactured single-walled TMDC nanosheets. In addition, they have been found to roll more tightly than ever before, with a center diameter as low as five nanometers, in line with theoretical expectations. It was also found that these scrolls have strong interactions with polarized light and exhibit hydrogen production characteristics.
With unprecedented control over nanostructures, the team's new approach lays the foundation for studying the new applications of TMDC nanovortices in catalysis and photovoltaic devices.
Source: Laser Net