Schematic representation of the SWCNT bundles and CNF. (A) A hexagonal arrangement model of a bundle containing two layers of SWCNT. The labels dSWCNT and dbundle correspond to the diameters of SWCNT and a bundle of SWCNT, respectively. (B) A model of CNF showing five carbon layers. The labels dOD, and dHC correspond to the outer and hollow core diameters of CNF, respectively.