Low frequency excitations of C60 chains inserted inside single-walled carbon nanotubes

TL;DR

This study investigates the low frequency vibrational properties of C60 chains inside single-walled carbon nanotubes using inelastic neutron scattering and lattice dynamical models, revealing interactions and rotational motions of C60 molecules.

Contribution

It provides experimental and theoretical insights into the vibrational behavior and structural dynamics of C60 chains within nanotubes, highlighting the presence of interactions and mixed molecular structures.

Findings

Strong interactions between C60 cages around 10 meV

Evidence of rotational motion of C60 molecules

Presence of monomers and polymers in peapods

Abstract

The low frequency excitations of C60 chains inserted inside single-walled carbon nanotubes (SWNTs) have been studied by inelastic neutron scattering (INS) on a high quality sample of peapods. The comparison of the neutron-derived generalized phonon density of states (GDOS) of the peapods sample with that of a raw SWNTs allows the vibrational properties of the C60 chains encapsulated in the hollow core of the SWNTs to be probed. Lattice dynamical models are used to calculate the GDOS of chains of monomers, dimers and polymers inserted into SWNTs, which are compared to the experimental data. The presence of strong interactions between C60 cages inside the nanotube is clearly demonstrated by an excess of mode density in the frequency range around 10 meV. However, the presence of a quasi-elastic signal indicates that some of the C60\'s undergo rotational motion. This suggests that peapods are made from a mixture of C60 monomers and C60 n-mer (dimer, trimer ... polymer) structures.