Carbon Nanotube Synthesis in Supercritical Toluene

Multiwall carbon nanotubes (MWNTs) were synthesized in supercritical toluene at 600 °C and ∼12.4 MPa using ferrocene, Fe, or FePt nanocrystals as growth catalysts. Toluene serves as both the carbon source for nanotube formation and the solvent. In contrast to vapor-phase synthetic routes, the supercritical solvent provides high precursor concentration and a homogeneous reaction environment with dispersed growth catalyst particles. Both carbon filaments and MWNTs are produced by this approach, and a growth mechanism is proposed to explain the factors that determine the nanotube versus filament morphology. The plasmon energies of the π and π + σ valence electrons were measured using electron energy-loss spectroscopy (EELS) of individual carbon fibers and MWNTs as a characterization tool to complement the imaging data obtained from electron microscopy.