A short section of carbon nanotube built from scratch forms a tiny Möbius strip – a one-sided surface that results from a band with a twist in it.
You would imagine you could just salami slice a carbon nanotube to get a band. But the tubes are difficult to manipulate because they are so small. They can’t be cut into cylindrical bands – which chemists call carbon nanobelts – as a tube of paper might be due to the powerful intramolecular forces at nanometre scales.
There is, however, one way to make a carbon nanobelt. In 2017, Yasutomo Segawa at the Institute for Molecular Science in Okazaki, Japan, and his colleagues showed they could be assembled piece-by-piece from a collection of smaller molecular units through a series of chemical reactions.
Now, Segawa and his team have gone one step further and created a Möbius strip-shaped carbon nanobelt. To build it, they modified the chemical process for building their carbon nanobelts – instead of using an even number of repeat units to form the belt, they used an odd number.
“The ultimate goal of organic chemistry is to create all possible molecular structures,” says Segawa. “Our achievement is one great step toward that purpose.”
After they had carried out the modified chemical reactions, Segawa and his team confirmed the resulting structure really was a Möbius strip using high-resolution spectroscopy.
While an immediate use for the carbon Möbius strip might not be apparent, the finesse required to create it could lend itself to other challenges in nanoengineering and chemistry, says Nicole Grobert at the University of Oxford.
“The precise application for this Möbius band may not be an obvious one, even for the researchers who have researched it, but if they can extend their magic chemistry to larger systems and achieve ultimate control of larger carbon systems, then you can start to think about upscaling and scaling to wet chemistry techniques,” says Grobert.