Semiconducting and Metallic [5,5] Fullertube Nanowires: Characterization of Pristine D_5h(1)-C₉₀ and D_5d(1)-C₁₀₀

Although fullerenes were discovered nearly 35 years ago, scientists still struggle to isolate "single molecule" tubular fullerenes larger than C₉₀. In similar fashion, there is a paucity of reports for pristine single-walled carbon nanotubes (SWNTs). In spite of Herculean efforts, the isolation and properties of pristine members of these carbonaceous classes remain largely unfulfilled. For example, the low abundance of spherical and tubular higher fullerenes in electric-arc extracts (<0.01-0.5%) and multiplicity of structural isomers remain a major challenge. Recently, a new isolation protocol for highly tubular fullerenes, also called f ullertubes, was reported. Herein, we describe spectroscopic characterization including ¹³C NMR, XPS, and Raman results for purified [5,5] fullertube family members, D_5h-C₉₀ and D_5d-C₁₀₀. In addition, DFT computational HOMO-LUMO gaps, polarizability indices, and electron density maps were also obtained. The Raman and ¹³C NMR results are consistent with semiconducting and metallic properties for D_5h-C₉₀ and D_5d-C₁₀₀, respectively. Our report suggests that short [5,5] fullertubes with aspect ratios of only ∼1.5-2 are metallic and could exhibit unique electronic properties.