It has metallic properties, with stripes of the network 21 atoms wide behaving like a metal while, according to Aalto University in Finland, 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 of the University of Marburg, which worked with Aalto. “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 material was grown on an extremely smooth gold surface using on-surface interpolymer de-hydrofluorination, also known as ‘HF-zipping’, and its conductive nature was revealed by scanning probe microscope.
Molecules first form as chains of linked hexagons, and a subsequent reaction connects these chains together to form the squares and octagons, according to Aalto. The chains are chiral (exist in two mirroring types) and only chains of the same type aggregate on the gold surface, forming well-ordered assemblies before they connect. Had both mirrored types aggregated, the reaction would have led to graphene.
“The new idea is to use molecular precursors that are tweaked to yield biphenylene instead of graphene”, said Linghao Yan of Aalto University.
The next steps are to produce larger sheets of biphenylene to better understand it properties, and to use the new synthesis method to create other novel carbon networks – graphenylene is another flat carbon network that is exciting anode researchers.
The work is described in the Science paper ‘Biphenylene network: A nonbenzenoid carbon allotrope‘ – abstract available without payment.
Bottom: scanning probe microscopy view of synthesised biphenylene
Top: artists impression of the structure