Researchers report technique to produce nanosheets in one minute

A research group led by Professor Minoru Osada (he, him) and postdoctoral researcher Yue Shi (she, her) at the Institute for Future Materials and Systems (IMaSS), Nagoya University in Japan, has developed a new technology to produce nanosheets, thin films of two-dimensional materials several nanometers thick in about one minute.

This technology enables the formation of high-quality, large nanosheet films in one click without the need for specialized knowledge or technology. Their findings are expected to contribute to the development of the industrial manufacturing process for various types of nanosheet devices. The study was published in ACS Applied Materials and Interfaces.

Nanosheets have a thickness that is measured in nanometers. The nanometers are so thin that the sheets cannot be seen from the side with the naked eye. They have potential applications in several different fields, including electronics, catalysis, energy storage, and biomedicine. Those made of graphene and inorganic nanosheets are being tested for use in a range of devices, from solar cells to sensors and batteries, because they have electrical, transparent and heat-resistant functions different from those of conventional bulk materials.

However, the current techniques used to produce these thin films, such as the Langmuir-Blodgett method, require skilled labor and complex conditions. “Using existing methods, it takes about an hour to produce one layer,” Osada said. “This creates a major bottleneck in the production of nanosheets.”

The group aimed to develop a new process that could produce high-quality, neatly arranged monolayer films of nanosheets easily and in a short time. They developed an automated film-forming process that produced nanosheets in about a minute with a simple drop of colloidal aqueous solution on a substrate heated on a hotplate using an automatic pipette. They then followed this up by aspiration of the solution and removal of the fluid. The result was a well-aligned monolayer film with no gaps between the nanosheets.

“Decreasing the surface tension of the colloidal aqueous solution and promoting convection of the nanosheets suppressed the overlap and gaps between the nanosheets and allowed us to control its alignment,” Osada said. “The layer-by-layer construction of multilayer films controlled by the unit thickness of the nanosheets was possible by repeating the operation of producing a monolayer film.”

“The newly developed method is expected to become an important technology as an industrial thin film fabrication method and a nanocoating method for nanosheets because it is simple, rapid, and requires only a small amount of solution to produce a high-quality, large-area film with neat alignment “, he said.

“The technology is based on simple drop and aspiration operations using an automatic pipette and does not require specialized knowledge or technology. This technology is applicable to nanosheets with different compositions and structures, such as oxides, graphene, and boron nitride, and can form films on substrates of different shapes, sizes, and materials, making it an extremely flexible film-forming technology,” Osada said.