Crystalline Ropes of Metallic Carbon Nanotubes

Abstract

Fullerene single-wall nanotubes (SWNTs) were produced in yields of more than 70 percent by condensation of a laser-vaporized carbon-nickel-cobalt mixture at 1200degreesC. X-ray diffraction and electron microscopy showed that these SWNTs are nearly uniform in diameter and that they self-organize into "ropes," which consist of 100 to 500 SWNTs in a two-dimensional triangular lattice with a lattice constant of 17 angstroms. The x-ray form factor is consistent with that of uniformly charged cylinders 13.8 +/- 0.2 angstroms in diameter. The ropes were metallic, with a single-rope resistivity of <10(-4) ohm-centimeters at 300 kelvin. The uniformity of SWNT diameter is attributed to the efficient annealing of an initial fullerene tubelet kept open by a few metal atoms; the optimum diameter is determined by competition between the strain energy of curvature of the graphene sheet and the dangling-bond energy of the open edge, where growth occurs. These factors strongly favor the metallic (10,10) tube with C5v symmetry and an open edge stabilized by triple bonds.

Photophysics of Individual Single-Walled Carbon Nanotubes

“…9 In 1993, several small-scale methods were elucidated to produce carbon nanotubes with only one sidewall, 10,11 and the first method for the large-scale production of SWNTs was presented in 1996. 12 Since the appearance of SWNTs, the number of scientific publications involving nanotubes has grown exponentially and totals well over 19,000 papers, with research activity currently doubling every 2 to 3 years. 13 …”

“…2 Thus, it was not until 1996 that a scaled-up synthesis of SWNTs catalyzed vigorous fundamental research of nanotubes with only one sidewall. 12 In general, a high-quality SWNT synthesis is hallmarked by minimal amounts of MWNTs, fullerenes, carbon nanoparticles, and amorphous carbon. Because singlewalled carbon nanotubes are the centerpiece of this dissertation, the emphasis for carbon nanotube synthesis in this chapter is placed solely on the production of SWNTs.…”

“…14 In 1996, Smalley and co-workers developed laser ablation as a second technique to produce nanotubes (Figure 1-3b). 12 The process is carried out inside a quartz tube heated to 1200 ºC. To create gas phase carbon, two sequenced Nd:YAG laser pulses are focused onto a graphite target that is doped with Co and Ni catalyst particles.…”

Phase Transfer Catalysts Drive Diverse Organic Solvent Solubility of Single-Walled Carbon Nanotubes Helically Wrapped by Ionic, Semiconducting Polymers

“…Potential dispersion approaches are truncated severely by the fact that preservation of significant SWNT electrooptic properties require solubilization via agents that noncovalently interact with the nanotube surface. 24,25 It has thus been a long-standing goal to develop a universal SWNT solubilization strategy that (i) relies on noncovalent interactions for nanotube dispersion, (ii) provides a high yield of individualized tubes, (iii) enables dispersion in a wide range of dielectric media, and yet (iv) gives rise to suspended SWNT structures having a constant morphology, regardless of solvent.Ultrasonication 11,26 and high-speed vibrational milling techniques 27 are commonly utilized to drive exfoliation of nanotube ropes and bundles in the presence of surfactants, small molecules, and polymers. 28 The huge library of established noncovalent nanotube solubilizing agents is dominated by species that only exfoliate tubes in an aqueous medium; surfactants such as SDS, 11 SDBS,29,30 and sodium cholate, 31 and amphiphilic aromatic molecules, 32 typify these SWNT-solubilizing compositions.…”

“…2 Strong van der Waals interactions between SWNTs 24,25 are an anathema to SWNT solubilization. 13 Water-solubilized SWNTs dominate the literature; there exists no general method to disperse SWNTs in nonaqueous media.…”