Effect of van der Waals Interactions on the Raman Modes in Single Walled Carbon Nanotubes

Abstract

We have measured the Raman spectrum of individual single walled carbon nanotubes in solution and compare it to that obtained from the same starting material where the tubes are present in ordered bundles or ropes. Interestingly, the radial mode frequencies for the tubes in solution are found to be approximately 10 cm (-1) higher than those observed for tubes in a rope, in apparent contradiction to lattice dynamics predictions. We suggest that there is no such contradiction, and propose that the upshift is due rather to a decreased energy spacing of the Van Hove singularities in isolated tubes over the spacings in a rope, thereby allowing the same laser excitation to excite different diameter tubes in these two samples.

Minimizing purification-induced defects in single-walled carbon nanotubes gives films with improved conductivity

“…From the peaks in the RBM region, we can confirm the samples are SWNTs and estimate their diameter. The frequency of the RBM mode is inversely proportional to the diameter of the SWNTs, and the relationship can be described by ω = 234/d + 10, where ω is the RBM frequency in cm 1 and d is the diameter of the SWNTs in nm, with consideration of the bundle effect [26]. The main peak at 198 cm 1 can therefore be attributed to carbon nanotubes with a diameter of 1.24 nm.…”

Directly observable G band splitting in Raman spectra from individual tubular graphite cones

“…In this kind of unique atomic configuration, it is possible that the TGCs have extraordinary electronic and phonon density of states compared with poly-chiral MWCNTs [30]. The van der Waals interaction between the constituent inner tubes in the TGCs is no longer akin to that in SWCNT bundles and general MWCNTs [31]. A strong resonant excitation may occur in these TGCs, similar to that observed in SWCNTs directly or MWCNTs with the magnification normally associated with electromagnetic and chemical enhancement effects [3,10].…”

Single‐wall carbon nanotube–polymer solar cells

“…The RBM is routinely used to calculate the diameter distribution. 19 Using two incident laser energies during analysis allows for the determination of SWNT type, i.e. semiconducting vs. metallic.…”