“The dynamics of atoms in a confined space are quite intriguing,” Kazu Suenaga of AIST told nanotechweb.org. “The atom trapped in a sub-nanometre space should not behave as atoms in a solid or in a vapour - it must show unusual behaviour. We wanted to demonstrate that.”
Suenaga and colleagues created their nanopeapods by positioning Gd2@C92 metallofullerenes inside single-walled carbon nanotubes. They made the Gd2@C92 molecules by d.c. arc-discharge and used a vapour-phase reaction to introduce them into the nanotubes. These are the largest metallofullerenes that the team has used to make nanopeapods.
HRTEM showed that the metallofullerenes were encapsulated inside the nanotubes, forming a one-dimensional array with an intermolecular distance of about 1.14 nm at room temperature. The gadolinium atoms were visible as regions of dark contrast on both sides of the metallofullerenes. Significantly, these contrast regions had an elongated profile, indicating that the gadolinium atoms were moving around their equilibrium positions with a large amplitude due to thermal activation.
Simulations indicated that the atoms were moving with an amplitude of about 0.2 nm. According to the researchers, this giant motion is “essentially different” from the ratcheting motion previously reported for other peapods.
The researchers reported their work in Nano Letters.