And that new arrangement is not graphene: researchers in Germany and Finland discover new type of atomically thin carbon material
From: Aalto University
May
20, 2021 -- Carbon exists in various forms. In addition to diamond and
graphite, there are recently discovered forms with astonishing properties. For
example graphene, with a thickness of just one atomic layer, is the thinnest
known material, and its unusual properties make it an extremely exciting
candidate for applications like future electronics and high-tech engineering.
In graphene, each carbon atom is linked to three neighbours, forming hexagons
arranged in a honeycomb network. Theoretical studies have shown that carbon
atoms can also arrange in other flat network patterns, while still binding to
three neighbours, but none of these predicted networks had been realized until
now.
Researchers
at the University of Marburg in Germany and Aalto University in Finland have
now discovered a new carbon network, which is atomically thin like graphene,
but is made up of squares, hexagons, and octagons forming an ordered lattice.
They confirmed the unique structure of the network using high-resolution
scanning probe microscopy and interestingly found that its electronic
properties are very different from those of graphene.
In
contrast to graphene and other forms of carbon, the new Biphenylene
network — as the new material is named —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. “These stripes could be used as
conducting wires in future carbon-based electronic devices.” said
professor Michael Gottfried, at University of Marburg, who leads
the team that developed the idea. The lead author of the study, Qitang
Fan from Marburg continues, “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.”
The
team at Aalto University helped image the material and decipher its properties.
The group of Professor Peter Liljeroth carried out the
high-resolution microscopy that showed the structure of the material, while
researchers led by Professor Adam Foster used computer
simulations and analysis to understand the exciting electrical properties of
the material.
The
new material is made 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. An important feature of the 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 new 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.
For
now, the teams work to produce larger sheets of the material, so that its
application potential can be further explored. However, “We are confident that
this new synthesis method will lead to the discovery of other novel carbon
networks.” said Professor Liljeroth.
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