SWCNT surface damage and cutting

For this reason, SWCNT sample purity and wall perfection can be characterized by calculating this ratio, D/G, or the so-called quality factor, Q = 1 - D/G.  

Due to the high sensitivity of SWCNTs to their environment, shifts of some bands of their Raman spectrum (notably the G-band, located at 2,610 cm , which is characteristic of disordered carbon) can occur when, for instance, they are placed in air or immersed in different liquid media. It seems, however, that suspending SWCNTs in aqueous SDS solutions does not significantly affect the intensity of their Raman bands.  

Consequently, stopping the sonication when the maximum amount of exfoliable CNTs has been unbundled [e.g., at 100,000 J for HiPCO SWCNTs] should prevent further cutting of the SWCNTs, though SWCNT surface damage may not be particularly minimized. 

Hennrich et al. studied the ultrasonically induced cutting of SWCNTs as a function of the sonication time. Similar to results of studies on polymer scission, Hennrich observed that the length distribution of the CNTs exhibit a power law dependence as a function of the sonication time t, which scales as t As a result, there is a critical length, namely L, below which CNTs cannot be cut further, even after prolonged sonication. This critical length Ly can also be calculated by using the following formula  

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