Diffusion through a molecular ball check valve composed of a C₆₀ molecule and a nanotube cap

A nanostructure, consisting of C60 enclosed within a carbon nanotube near its cone shaped cap, is shown to behave like a ball check valve, a pressure-driven device for the storage of fluid. The van der Waals force acts like a spring that traps C60 near the cap section with a potential well around 1 eV. The restricted interstitial space around the valve produces a volume difference that forces C60 near the top center of the cap and therefore blocks the outward diffusion. It is estimated that such a mechanism can produce nanocapsules with internal pressure up to 40 GPa or above.