Altered carbon: new 2D material discovered
Rearrangement of atoms creates metal-like carbon structure Metal Tech News – May 26, 2021
Last updated 7/10/2022 at 3:20pm
Roughly 200 times stronger than steel, highly conductive to electricity and heat, antibacterial, and only one atom thick, graphene is a wonder material that has captured the imagination of scientists. Now, researchers in Germany and Finland have created a new two-dimensional carbon material that offers new properties and possibilities.
In recent years, graphene has been used to make materials lighter and stronger, batteries charge faster and last longer, and even as a coating to prevent the spread of diseases such as COVID-19.
The wonderous properties of graphene are the product of the 2D structure of the carbon atoms it is made of, where each atom is linked to three neighbors, forming hexagons arranged in a honeycomb network.
Theoretical studies have indicated that carbon atoms should also be able to arrange in other 2D network patterns, while still binding to three neighbors, but none of these predicted networks had been realized until now.
This breakthrough came when researchers at the University of Marburg in Germany discovered a new carbon network that is one atom thick like graphene but made up of an ordered lattice of squares, hexagons, and octagons.
This new form of carbon, dubbed biphenylene, was confirmed by a research team led by Professor Peter Liljeroth from Aalto University in Finland. Using high-resolution scanning probe microscopy, this team created an image showing the square-hexagon-octagon arrangement of carbon atoms.
Another Aalto University research team led by Professor Peter Liljeroth found that, while made up of the same carbon atoms as graphene, this altered arrangement offers intriguing electronic properties that differ from its 2D carbon cousin.
In contrast to graphene and other forms of carbon, computer simulations show the new biphenylene network has metallic properties. Narrow stripes of the network, only 21 atoms wide, already behave like a metal, while graphene is a semiconductor at this size.
Theoretically, even smaller electronics could be made with graphene replacing the silicon semiconductor and biphenylene serving as the conductive wiring.
"These stripes could be used as conducting wires in future carbon-based electronic devices," said University of Marburg Professor Michael Gottfried, who leads the team that developed the idea.
The research team also sees potential for biphenylene going into smaller and more powerful rechargeable batteries.
"This novel carbon network may also serve as a superior anode material in lithium-ion batteries, with a larger lithium storage capacity compared to that of the current graphene-based materials," said Qitang Fan, a researcher from Marburg who was the lead author of the biphenylene study.
The researchers create biphenylene by assembling carbon-containing molecules on an extremely smooth gold surface. These molecules first form chains, which consist of linked hexagons, and a subsequent reaction connects these chains together to form the squares and octagons.
The scientist said an important feature of these carbon chains is that they are chiral, which means that they exist in two mirroring types, like left and right hands. Only chains of the same type aggregate on the gold surface, forming well-ordered assemblies, before they connect. This is critical for the formation of the altered carbon material because the reaction between two different types of chains leads only to graphene.
"The new idea is to use molecular precursors that are tweaked to yield biphenylene instead of graphene," explains Linghao Yan, who carried out the high-resolution microscopy experiments at Aalto University.
To fully understand the applications of biphenylene the research team will need to create larger sheets of this new 2D carbon material, which could lead to new breakthroughs.
"We are confident that this new synthesis method will lead to the discovery of other novel carbon networks," said Professor Liljeroth.