Graphene is a carbon material derived from graphite, the same material found in pencils, but it is arranged in a one- atom-thin honeycomb lattice. Graphene’s two-dimensional arrangement gives it extraordinary properties, including extreme strength and high electron conductivity.
However, the tight lattice lacks a bandgap—the space between electron energy levels or bands—which is essential for controlling the flow of electrons in electronic devices. Scientists have been hunting for alternative materials that have a bandgap and a graphene-like structure. So far, they have made progress with mixtures of materials, but have not yet found a pure nanomaterial, which is considered ideal for ultra-thin, high-performance electronics, according to a review published in the journal Science and Technology of Advanced Materials.
Much focus has been on graphene quantum dots, which are small segments of graphene, 10 nm to 100 nm carbon hexagons across and less than 30 atomic sheets thick. To make the dots behave more like 2D graphene, research teams have added other molecules to change the structure and function of the material.
For example, one team attached molecular groups containing nitrogen to graphene quantum dots. They found that different molecular combinations altered the electronic structure of the quantum dot in unique ways. This shifted the colour of light produced by the material when exposed to electricity, which is useful for light emitting diodes (LEDs) and photodetectors, which convert light into electrical current. Several teams have built and tested photodetectors using graphene quantum dots with success. The material has also been shown to improve the performance of dye-sensitized solar cells.
Researchers are also investigating silicon and germanium analogues of graphene, called silicene and germanene, and their respective hydrogenated forms, silicane and germanane. They are testing how different preparation methods and structures, such as multiple layers and added molecules, affect performance for potential electronic or photonic devices.
While silicene and germanene have not yet been prepared without added molecules, the modified materials strongly resemble the predicted 2D materials. Understanding the properties of the modified materials is a “good starting point” for developing future nanomaterials, according to the paper’s authors.
Ultimately, the reviewers, led by Hideyuki Nakano of Toyota Central R&D Labs in Japan, are optimistic that electronic devices and energy storage materials could be developed using these materials in the near future.
For further information, contact:
Dr Hideyuki Nakano | E-mail: [email protected]
Toyota Central R&D Labs Japan
Mikiko Tanifuji | E-mail: [email protected]
Science and Technology of Advanced Materials
National Institute for Materials Science (NIMS)