Molecular surgery traps hydrogen inside carbon cage

April 12, 2022 | Alexandra Goho

Molecular surgery traps hydrogen inside carbon cage

In a feat of precision chemistry, scientists have locked a single hydrogen molecule inside a soccer ball–shaped carbon molecule known as a buckyball, and they have used the technique to make large quantities of the tiny containers.

CAGEY STRATEGY. Depiction of a molecule of hydrogen (white) trapped inside a buckyball. Science

Encapsulating gases or metal atoms inside buckyballs or other types of carbon cages can endow the structures with unique electronic properties. Such structures could serve as transistors in molecular-scale electronic devices or as contrast agents for medical imaging, some researchers say. However, previous strategies for trapping tiny things inside carbon cages are inefficient and require extreme conditions.

To get the hydrogen inside the buckyball, Koichi Komatsu of Kyoto University in Japan and his colleagues synthesized buckyballs with each ball perforated by a hole with a sulfur atom in its rim. Once the two-atom hydrogen molecule entered the hole, the researchers sewed up the buckyball using a series of chemical reactions.

First, they oxidized the sulfur atom to create a sulfoxide group along the rim. Then, they exposed the buckyballs to light, which removed the sulfoxide group and caused the hole to shrink. Adding a titanium-containing compound tightened the hole even further. Finally, the researchers heated the buckyballs at 340°C for 2 hours to seal the gap.

The process fills all the buckyballs with hydrogen, whereas alternative processes have yields of only a few percent, the Kyoto researchers report in the Jan. 14 Science.