Confined linear carbon chains as a route to bulk carbine

Researchers present a direct first proof of stable ultra-long 1D carbon chains, thus paving the way for the bulk production of carbyne

Elemental carbon appears in many different modifications, including diamond, fullerenes and graphene. Their unique structural, electronic, mechanical, transport and optical properties have a broad range of applications in physics, chemistry and materials science, including composite materials, nanoscale light emitting devices and energy harvesting materials. Within the “carbon family”, only carbyne, the truly one-dimensional form of carbon, has not yet been synthesized despite having been studied for more than 50 years. Its extreme instability in ambient conditions rendered the final experimental proof of its existence elusive. An international collaboration of researchers now succeeded in developing a novel route for the bulk production of carbon chains composed of more than 6,400 carbon atoms by using thin double-walled carbon nanotubes as protective hosts for the chains. These findings are published in the journal Nature Materials and represent an elegant forerunner towards the final goal of carbyne’s bulk production. Besides the potential applications, these findings open the possibility to answer fundamental questions about electron correlations, electron-phonon interactions and quantum phase transitions in one-dimensional materials.

Figure 1. Carbon chains of increasing length have been successfully synthesized over the last 50 years.

Figure 2. Schematic representations of confined ultra-long linear acetylenic carbon chains inside different double-walled carbon nanotubes.

So far, the record has been a chain made of around 100 carbon atoms (2003). This record has now been broken by more than a factor 50 with the first-time demonstration of micrometer length-scale chains. Researchers from the University of Vienna led by Thomas Pichler have developed a novel and simple approach to stabilize carbon chains with a record length of more than 6,400 carbon atoms. They use the confined space inside a double-walled carbon nanotube as a nanoreactor to grow ultra-long carbon chains on a bulk scale. In collaboration with the groups of Kazu Suenagas at the AIST in Japan, Lukas Novotny at the ETH Zürich and the theory group of Angel Rubio at the Max Planck Institute for the Structure and Dynamics of Matter at CFEL in Hamburg and at the CFM (UPV/EHU-CSIC) in San Sebastián, the existence of the chains has been unambiguously confirmed by using a multitude of sophisticated, complementary methods.