DiameterControlled Synthesis of Carbon Nanotubes.pdf

J. Phys. Chem. B 2002, 106, 2429 Diameter-Controlled Synthesis of Carbon Nanotubes Chin Li Cheung, Andrea Kurtz, Hongkun Park,*,† and Charles M. Lieber*,‡ Department of Chemistry and Chemical Biology, Har ard Uniersity, 12 Oxford Street, Cambridge, Massachusetts 02138 Recei ed: Noember 15, 2001; In Final Form: January 18, 2002 Nearly monodisperse iron nanoclusters have been used to define the diameters of carbon nanotubes grown by chemical vapor deposition (CVD). Iron nanoparticles with average diameters of 3, 9, and 13 nm were used to grow carbon nanotubes with average diameters of 3, 7, and 12 nm, respectively. Transmission electron microscopy studies of the nanotubes show that the as-grown nanotubes are single-walled carbon nanotubes (SWNTs) or thin multiwalled carbon nanotubes (MWNTs) with 2 or 3 layers. Investigations of the growth conditions also demonstrate that the supply of carbon reactant is critical for enabling the growth of large diameter nanotubes from large iron nanoclusters, and that the growth temperature is especially important for achieving high-quality large diameter nanotubes. The implications of these results and possible applications of the nanotubes are discussed. Introduction Carbon nanotubes are currently the focus of intense research due to their unique properties and potential to impact broad areas of science and technology.1 The distinctive characteristics of carbon nanotubes arise from the atomic structure and size of these materials. For example, nanotubes can be either metals or se