Unzipping of CNTs

FIGURE 1.8 Different ways to unzip CNTs for production of graphene nanoribbons (GNRs) (a) Intercalation exfoliation (b) chemical oxidation (c) catalytic approach (d) the electrical method and (f) selective etching by Ar plasma. (From Nano Today, 5, Terrones, M. et al., 351, Copyright 2010, with permission from Elsevier.) 

FIGURE 1.9 (a) Pristine MWCNT, (b) MWCNT coated with a PMMA film, (c) the PMMA-MWCNT film was peeled from the substrate, turned over, and exposed to an Ar plasma etching, (d-g) possible products generated by controlling the etching time. (With permission from MacmUlan Publishers Ltd., Nature, Jiao, L. Y. et al., 458, 877, Copyright 2009.) 

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The preparation of GNRs from unzipping of CNTs has been investigated intensively by several groups and various routes have been developed (Figure 1.8). ° ... 

Fig. 9.4 Aberration-corrected transmission electron microscopy image of partially unzipped outer walls of CNTs forming graphene-CNT complex catalyst with a high degree of edge exposure (reprinted with permission from Macmillan Publishers Ltd [32], copyright 2012)...

Surfactants act as solubilizers to disperse CNTs via physical adsorption, and the procedures of solubilization are very simple. CNTs are placed in a solution containing solubilizer and then subjected to sonication treatment for a while. During sonication, the provided mechanical energy can overcome the van derWaals interactions between the CNT bundles and leads to the exfoliation of CNTs. At the same time, solubilizer molecules adsorb onto the surfaces of the CNT walls. Solubility of CNTs in a solvent depends on the type, the concentration of the solubilizer, and the purity of the CNTs. The mechanism for dispersion of CNTs by the solubilizer is believed to be an unzipping mechanism proposed by Strano and co-workers at Rice University in 2003. 

CNTs, on the other hand, come in various formats, including bundles, straight nanotubes, open nanotubes, or the so-called unzipped nanotubes, where the inner areas are more easily available than closed structures. As mentioned earlier, nanotubes are single sheets of graphite rolled up into cylinders, which can be opened along their axis and even flattened in flake forms. Handling tubes or such sheets will definitely have different structural effects with operational consequences (namely effective transport properties) and therefore, they need to be studied using computational reconstruction tools just as we did in the past sections. 

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