2 research outputs found
Intrinsic Chirality Origination in Carbon Nanotubes
Elucidating
the origin of carbon nanotube chirality is key for
realizing their untapped potential. Currently, prevalent theories
suggest that catalyst structure originates chirality <i>via</i> an epitaxial relationship. Here we studied chirality abundances
of carbon nanotubes grown on floating liquid Ga droplets, which excludes
the influence of catalyst features, and compared them with abundances
grown on solid Ru nanoparticles. Results of growth on liquid droplets
bolsters the intrinsic preference of carbon nuclei toward certain
chiralities. Specifically, the abundance of the (11,1)/χ = 4.31°
tube can reach up to 95% relative to (9,4)/χ = 17.48°,
although they have exactly the same diameter, (9.156 Å). However,
the comparative abundances for the pair, (19,3)/χ = 7.2°
and (17,6)/χ = 14.5°, with bigger diameter, (16.405 Å),
fluctuate depending on synthesis temperature. The abundances of the
same pairs of tubes grown on floating solid polyhedral Ru nanoparticles
show completely different trends. Analysis of abundances in relation
to nucleation probability, represented by a product of the Zeldovich
factor and the deviation interval of a growing nuclei from equilibrium
critical size, explain the findings. We suggest that the chirality
in the nanotube in general is a result of interplay between intrinsic
preference of carbon cluster and induction by catalyst structure.
This finding can help to build the comprehensive theory of nanotube
growth and offers a prospect for chirality-preferential synthesis
of carbon nanotubes by the exploitation of liquid catalyst droplets
Super-stretchable Graphene Oxide Macroscopic Fibers with Outstanding Knotability Fabricated by Dry Film Scrolling
Graphene oxide (GO) has recently become an attractive building block for fabricating graphene-based functional materials. GO films and fibers have been prepared mainly by vacuum filtration and wet spinning. These materials exhibit relatively high Young’s moduli but low toughness and a high tendency to tear or break. Here, we report an alternative method, using bar coating and drying of water/GO dispersions, for preparing large-area GO thin films (<i>e.g.</i>, 800–1200 cm<sup>2</sup> or larger) with an outstanding mechanical behavior and excellent tear resistance. These dried films were subsequently scrolled to prepare GO fibers with extremely large elongation to fracture (up to 76%), high toughness (up to 17 J/m<sup>3</sup>), and attractive macroscopic properties, such as uniform circular cross section, smooth surface, and great knotability. This method is simple, and after thermal reduction of the GO material, it can render highly electrically conducting graphene-based fibers with values up to 416 S/cm at room temperature. In this context, GO fibers annealed at 2000 °C were also successfully used as electron field emitters operating at low turn on voltages of <i>ca.</i> 0.48 V/μm and high current densities (5.3 A/cm<sup>2</sup>). Robust GO fibers and large-area films with fascinating architectures and outstanding mechanical and electrical properties were prepared with bar coating followed by dry film scrolling