Growth of carbon nanotubes via twisted graphene nanoribbons

Abstract

Carbon nanotubes have long been described as rolled-up graphene sheets. It is only fairly recently observed that longitudinal cleavage of carbon nanotubes, using chemical, catalytical and electrical approaches, unzips them into thin graphene strips of various widths, the so-called graphene nanoribbons. In contrast, rolling up these flimsy ribbons into tubes in a real experiment has not been possible. Theoretical studies conducted by Kit et al. recently demonstrated the tube formation through twisting of graphene nanoribbon, an idea very different from the rolling-up postulation. Here we report the first experimental evidence of a thermally induced self-intertwining of graphene nanoribbons for the preferential synthesis of (7, 2) and (8, 1) tubes within parent-tube templates. Through the tailoring of ribbon’s width and edge, the present finding adds a radically new aspect to the understanding of carbon nanotube formation, shedding much light on not only the future chirality tuning, but also contemporary nanomaterials engineering.

Carbon Nanotubes as Electrically Active Nanoreactors for Multi-Step Inorganic Synthesis: Sequential Transformations of Molecules to Nanoclusters and Nanoclusters to Nanoribbons

“…This demonstrates a remarkable property of carbon nanotubes to act not only as nanoreactors constraining the space around the chemical reaction and templating the formation of nanoclusters or the growth of nanoribbons, but also as electrically active host-structures lending their electrons when they are required for a chemical reaction to occur inside SWNT, and retrieving electrons back when they are no longer required by the guest-species. In summary, carbon nanotubes are becoming an increasingly important class of nanoscale containers and reactors, where the pathways of chemical reactions can change significantly as a result of the restricted space of the reaction [5][6][7][8][9][10][11][12][13][14][15][16][17], or due to the interactions between the reactant molecules or catalyst particles with the host-nanotube [23,24]. Being highly conducting and having a symmetric distribution of filled and empty electronic states, SWNT possess remarkable electric properties and a unique ability to donate or accept electrons, which make nanotubes distinct among other nanocontainers and nanoreactors.…”

A Review of Double-Walled and Triple-Walled Carbon Nanotube Synthesis and Applications

“…Pea pod-derived DWNTs and TWNTs have specific advantages and disadvantages over the DWNTs and TWNTs grown by the arc-discharge method and the CVD method [104,120,130,131,[134][135][136][137][138][139][140][141][142]150]. One advantage is that the method of growing the multi-walled structures by thermally-treating pea pods makes it possible to obtain high-purity CNTs without contaminants, such as metallic impurities.…”

“…This happens because the electronic structure of the constituent inner tubes is predominantly determined by the outer tubes, as well as by the high temperature observed during the thermal treatment. It is very interesting to note that the interlayer spacing in pea pod-derived structures strongly depends on the high temperatures achieved during the thermal treatment [104,120,130,131,[134][135][136][137][138][139][140][141][142]150].…”

“…The chirality distribution of the encapsulated molecules-derived inner tube of the DWNT is dependent on the choice of the precursor molecules [137]. Even when fullerenes with a similar structure, such as C 60 and C 70 , are used as the precursor, these molecules produce inner tubes with a different chirality distribution.…”

“…(Figure 7a). When external stimuli, such as heat [132], an electron beam [133] and UV light [134], were applied to the pea pod (Figure 7b), the C 60 molecules inside the SWNTs partially coalesced with neighboring C 60 molecules to eventually be transformed thereby forming the inner tube of a DWNT (Figure 7c) Lim et al [137] found that there are two different intermediate states of the inner tube depending on the encapsulated molecular species. In the case of PTCDA, graphene nanoribbon-like intermediates were formed during annealing (Figure 7d), whereas fullerenes, picene and pentacene formed deformed fullerene-like intermediates prior to DWNT formation (Figure 7e).…”