HiPCO SWCNT bundles

Carbon Nanotubes. An FT Raman band at 146 cm-1 was assigned as a radial breathing mode for bundles of SWCNT with a tube diameter of 1.53 nm.215 Oxidation of HipCO SWCNT (diameter 8-10 A) leads to irreversible disappearance of Raman breathing modes below 220 cm-1, in the temperature range 150 400 C.216 The Raman spectra of SWCNT produced by plasma-enhanced CVD gave evidence for the formation of single tubes at quite low temperatures (ca. 550°C).217... 

SWCNT bundles containing nanotubes with different diameters are easy to obtain experimentally, but such samples may lead to overlapping RBM modes and complex Raman spectra that are difficult to interpret. In contrast, SWCNTs synthesized via the HiPCO method are favored for spectroelectrochemical studies due to their small diameters, which lead to well-separated RBM peaks, thereby simplifying nanotube chirality assignments significantly [58, 72]. 

These two experimental observations point out that the purified CNTs are more bundled at the end of the exfoliation than the as-produced CNTs. This was confirmed by SEM images of the purified HiPCO SWCNTs of the high quality batch, which showed that these... 

Figure 3.15 UV-Vis spectra of SDS-HiPCO SWCNT aqueous dispersions before and after ultracentrifugation. Notice the broadening of the absorption features due to the presence of small CNT bundles in the non-centrifuged sample.

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