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How can helium be enclosed inside a C60 cage?
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fullerene
Two fullerene structures: an elongated carbon nanotube and a spherical buckminsterfullerene, or “buckyball.”
To enclose helium (He) inside a C60 cage, the fullerene is heated in helium vapour under high pressure. This process creates an endohedral complex, denoted as He@C60, in which the helium atom is physically trapped within the spheroidal carbon cage.1
While other endohedral species—such as those containing alkali metals or alkaline earth metals—are typically produced by vaporizing graphite rods impregnated with the desired metal, the method for trapping helium relies specifically on the application of heat and pressure to the pre-formed C60 molecule.1