Infrared Spectroscopy of Single-Walled Carbon Nanotubes

Abstract

By using the spectral moments method, we calculate the infrared spectra of chiral and achiral single-walled carbon nanotubes (SWCNTs) of different diameters and lengths. We show that the number of the infrared modes, their frequencies, and intensities depend on the length and chirality of the nanotubes. Furthermore, the dependence of the infrared spectrum as a function of the size of the SWCNT bundle is analyzed. These predictions are useful to interpret the experimental infrared spectra of SWCNTs.

Infrared-active phonons in carbon nanotubes

“…The ir-active radial mode at 860 cm −1 does not show any significant sample dependence. Because the SWCNT samples under investigation mainly differ by the size of the bundles, we conclude, in agreement with recent calculations, 16 that the position of this infrared active mode does not significantly depend on the bundle size.…”

“…However, its intensity is expected to be weak with regards to the intensity of the main infrared modes in SWCNTs. 16 On the other hand, in the Raman spectrum of the same SWCNT samples, a D-band is observed. In Raman scattering, the D-band is activated by the presence of defects which lower the crystalline symmetry of the quasi-infinite lattice.…”

“…With regards to the large differencies between the structural parameters of the SWCNT samples investigated ͑bundles of different sizes͒, we conclude that the position of this band is not sensitive to the packing of the carbon nanotubes, in agreement with recent calculations. 16 With regards to the large width of this band and its nonsymmetric profile, a precise measurement of the position of this peak is not easy. In consequence, the wave number of this mode cannot be used as an efficient experimental tool to characterize the structure of SWCNT samples.…”

“…In summary, a large disagreement is found in the literature concerning the assignment of the ir-active modes of SWCNTs. On the other hand, the infrared-active phonon modes of SWCNTs have been calculated from different methods: zone folding model, [11][12][13] tight binding approach, 14 force constant model, [15][16][17][18] and ab initio calculations. 19 Concerning the diameter dependence of the ir active modes these predictions are sometimes opposite.…”

Size effects on water adsorbed on hydrophobic probes at the nanometric scale

“…Indeed, there is general agreement of the existence of a weak and a strong bands in the regions of 800-900 and 1500-1600 cm −1 , respectively. [55][56][57] This can be considered as a strong indication of the validity of the present force field to model correctly carbon interactions.…”