Fullerenes growth mechanisms

The growth pathway of various fullerene- and graphene-type nano-objects may be related. They are synthesized in the vapor phase and often appear simultaneously on the same sample. A common growth mechanism with similar nucleation seeds may, therefore, lead to these different structures. 

To produce fullerenes and metallofullerenes, a temperature above 800 °C was found to be necessary, and below this critical temperature no fullerenes were produced (Haufler et al., 1991 Suzuki et al., 1997a Wakabayashi et al., 1997), suggesting that relatively slow thermal annealing processes are required to form fullerenes and metallofullerenes. The laser-furnace method is suited to the study of growth mechanism of fullerenes and metallofullerenes (Curl and Smalley, 1991 Haufler et al., 1991 ... 

Figure 6.23. Proposed mechanism for fullerene growth. Reprinted from Yamaguchi, Y Maruyama, S. Chem. Phys. Lett. 1998, 286, 343. Copyright 1998, with permission from Elsevier. 87985734.

Figure 6.29. Images of the calculated structures involved in the hole-repairing mechanism for endohedral fullerene growth. Shown from left to right are the Cyg open cage, top and side views of the CgY fragment, and the final Y Cg2 metallofullerene. Reproduced with permission from Gan, L.-H. Wang, C.-R. J. Phys. Chem. A 2005,109, 3980. Copyright 2005 American Chemical Society.

The observation of such an egg-shaped stmcture led us to an extension of the idea that such stmctures could be precursors of nanotubes. We therefore studied even larger silsesquioxanes with 72, 84, 96, 144, 192, and 240 silicon atoms in tube-like shapes.Figure 33.3 shows the three largest stmctures. We suggested a growth mechanism similar to the C2 insertion into fullerenes. 

Two main atomistic growth mechanisms have been proposed to account for the formation of individual carbon nanotubes. The first [4,5] states that carbon atoms (e.g. C, C2, C3 units) attach to the edges of a growing carbon cylinder, which closes when conditions are not suitable for growth. An alternative scheme [1] proposes that nanotubes are essentially elongated giant fullerenes which grow by direct insertion of carbon species, accreted from the vapour phase, into the closed network. 

Pyrolysis of hydrocarbons (e.g. benzene, acetylene, naphthalene, ethylene, etc.) in the presence of catalysts (e.g. Co, Ni and Fe deposited on substrates such as silicon, graphite or silica) provides an additional route to fullerenes and carbon nanotubes. Prior to the discovery of fullerenes in 1985, pyrolytically grown nanofibres/nanotubes had actually been observed and structurally identified by several authors [74, 89-91]. Even at that early stage, a growth mechanism was postulated involving metal (catalyst) particles, which were held to be responsible for the agglomeration of carbon and subsequent axial growth of the fibre. 

Mashino T, Okuda K, Hirota T, Hirobe M, Nagano T, Mochizuki M (1999) Inhibition of E. coli growth by fullerene derivatives and inhibition mechanism. Bioorg. Med. Chem. Lett. 9 2959-2962. 

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