Chirality Origination in Carbon Nanotubes by Carbon Structures
Carbon Nanotube Collaborators Workshop 2016, Yellow Springs, OH
The origin of single wall carbon nanotube chirality includes a fundamental understanding on the formation mechanism of tubular carbon topology. Elucidation of this mechanism is key for realizing the untapped potential of nanotubes, since nanotube chirality governs its physical properties. More than two decades of studies have revealed the essential contributions of a catalyst in chirality abundance of grown nanotubes. As a result, chirality preference origination by catalyst structure via an epitaxial relationship emerges as a dominant mechanism. Here we show that carbon structure itself can originate preference towards specific chiral angles in nanotubes depending on diameter: we decouple the influence of catalyst properties on the abundance of grown tube chiralities by exploitation of floating liquid Ga and solid Ru catalysts. We found that the tubes with chirality (11,1)/χ=4.31o grown on the isotropic surface of a liquid Ga catalyst can be up to eightfold preferable than tubes with larger helix angle (9,4)/χ=17.48o, despite having exactly the same diameter d=9.156Å. In contrast, for the pair of tubes with chiralities of (19,3)/χ=7.2o and (17,6)/χ=14.5o and the same diameter d=16.405Å, the larger helix angle tube is preferable. Abundances of the same pairs of tubes grown on solid polyhedral Ru catalysts show completely different trends. We discuss the relevance of carbon source on bias of chiral angles. This finding distinguishes between the chirality preferences originated by carbon structure and by catalyst and could lead to the comprehensive theory of chirality formation. In practice, our finding offers a new prospect for chirality-selective synthesis of carbon nanotubes by the exploitation of catalyst droplets.