Interaction between concentric Tubes in DWCNTs

TL;DR

This paper investigates the Raman response of inner tubes in double-wall carbon nanotubes, revealing an unexpectedly high number of RBMs due to splitting caused by interactions with various outer tubes and bundling effects.

Contribution

It provides new insights into the interaction effects between concentric tubes in DWCNTs and explains the increased number of observed RBMs.

Findings

Inner tube RBMs are more numerous than expected due to splitting.

Inner-outer tube interactions cause frequency shifts in RBMs.

Bundle interactions are stronger than inner-outer tube interactions.

Abstract

A detailed investigation of the Raman response of the inner tube radial breathing modes (RBMs) in double-wall carbon nanotubes is reported. It revealed that the number of observed RBMs is two to three times larger than the number of possible tubes in the studied frequency range. This unexpected increase in Raman lines is attributed to a splitting of the inner tube response. It is shown to originate from the possibility that one type of inner tube may form in different types of outer tubes and the fact that the inner tube RBM frequency depends on the diameter of the enclosing tube. Finally, a comparison of the inner tube RBMs and the RBMs of tubes in bundles gave clear evidence that the interaction in a bundle is stronger than the interaction between inner and outer tubes.