THE synthesis of molecular carbon structures in the form of C60 and other fullerenes1 has stimulated intense interest in the structures accessible to graphitic carbon sheets. Here I report the preparation of a new type of finite carbon structure consisting of needle-like tubes. Produced using an arc-discharge evaporation method similar to that used for fullerene synthesis, the needles grow at the negative end of the electrode used for the arc discharge. Electron microscopy reveals that each needle comprises coaxial tubes of graphitic sheets, ranging in number from 2 up to about 50. On each tube the carbon-atom hexagons are arranged in a helical fashion about the needle axis. The helical pitch varies from needle to needle and from tube to tube within a single needle. It appears that this helical structure may aid the growth process. The formation of these needles, ranging from a few to a few tens of nanometres in diameter, suggests that engineering of carbon structures should be possible on scales considerably greater than those relevant to the fullerenes. On 7 November 1991, Sumio Iijima announced in Nature the preparation of nanometre-size, needle-like tubes of carbon — now familiar as 'nanotubes'. Used in microelectronic circuitry and microscopy, and as a tool to test quantum mechanics and model biological systems, nanotubes seem to have unlimited potential.

Helical microtubules of graphitic carbon

A new form of pure, solid carbon has been synthesized consisting of a somewhat disordered hexagonal close packing of soccer-ball-shaped C60 molecules. Infrared spectra and X-ray diffraction studies of the molecular packing confirm that the molecules have the anticipated 'fullerene' structure. Mass spectroscopy shows that the C70 molecule is present at levels of a few per cent. The solid-state and molecular properties of C60 and its possible role in interstellar space can now be studied in detail.

Solid C60: a new form of carbon

Raman spectroscopy of graphene and graphite: Disorder, electron phonon coupling, doping and nonadiabatic effects

The major part of this chapter has already appeared in [1], but because of the length restrictions (in Science), the discussion on why we think this form is given in only brief detail. This chapter goes into more depth to try to answer the questions of why the fullerenes form themselves. This is another example of the very special behavior of carbon. From a chemist’s standpoint, it is carbon’s ability to form multiple bonds that allows it to make these low dimensional forms rather than to produce tetrahedral forms. Carbon can readily accomplish this and it is in the mathematics and physics of the way this universe was put together, that carbon is given this property. One of the consequences of this property is that, if left to its own devices as carbon condenses from the vapor and if the temperature range is just right, above 1000°C, but lower than 1400°C, there is an efficient self-assembly process whose endpoint is C60.

https://science.sciencemag.org/content/sci/273/5274/483.full.pdf

Crystalline Ropes of Metallic Carbon Nanotubes

https://www.bc.edu/content/dam/files/schools/cas_sites/physics/pdf/Ren/p85.pdf

Advances in the science and technology of carbon nanotubes and their composites: a review

During experiments aimed at understanding the mechanisms by which long-chain carbon molecules are formed in interstellar space and circumstellar shells1, graphite has been vaporized by laser irradiation, producing a remarkably stable cluster consisting of 60 carbon atoms. Concerning the question of what kind of 60-carbon atom structure might give rise to a superstable species, we suggest a truncated icosahedron, a polygon with 60 vertices and 32 faces, 12 of which are pentagonal and 20 hexagonal. This object is commonly encountered as the football shown in Fig. 1. The C60 molecule which results when a carbon atom is placed at each vertex of this structure has all valences satisfied by two single bonds and one double bond, has many resonance structures, and appears to be aromatic. Before 1985, it was generally accepted that elemental carbon exists in two forms, or allotropes: diamond and graphite. Then, Kroto et al. identified the signature of a new, stable form of carbon that consisted of clusters of 60 atoms. They called this third allotrope of carbon 'buckminsterfullerene', and proposed that it consisted of polyhedral molecules in which the atoms were arrayed at the vertices of a truncated icosahedron. In 1990, the synthesis of large quantities of C60 [see Nature 347, 354–358 (1990)] confirmed this hypothesis.

C 60 : Buckminsterfullerene

Laser vaporization of graphite in a high-pressure supersonic nozzle produced a remarkable stable C60 molecule in high yield with striking and exciting new properties. Specifically it was found that the stability of the new species arises from its unique ability to close into a spheroidal, aromatic molecule in the form of a truncated icosahedron. This should be an exceptionally strong binding site for a wide range of atoms. Evidence is presented for clusters of carbon atoms which form very stable complexes with lanthanum atoms, particularly C60 La. Such aromatic egg-shell complexes of metal atoms may be stable enough to survive in normal condensed-phase chemical environments.

Lanthanum complexes of spheroidal carbon shells

Buckminsterfullerene, C{sub 60}, was prepared in gram quantities by contact-arc vaporization of a graphite rod in a 100-Torr atmosphere of helium, followed by extraction of the resultant graphite soot with toluene. The dominance of C{sub 60} in this extract was verified by mass, FTIR, and NMR spectroscopy. The molecule was successfully hydrogenated to C{sub 60}H{sub 36} via a Birch reduction and dehydrogenated back to bare C{sub 60} by treatment with DDQ reagent. Cyclic voltammetry of C{sub 60} in methylene chloride revealed highly reversible formation of at least two stable anionic forms of C{sub 60} in solution. A broad new class of these fulleride and fulleronium ions is anticipated, both with the internal cavity empty and with any one of a large number of elements inside, thus providing a means of fine-tuning the chemical, optical, and redox properties.

Efficient production of C60 (buckminsterfullerene), C60H36, and the solvated buckide ion

The reactivity of bare carbon clusters produced by laser vaporization has been studied by a fast-flow gas-phase reactor followed by F/sub 2/ excimer laser ionization and time-of-flight mass analysis. Although most small carbon clusters (C/sub n/, with n < 40) were found to be highly reactive with such small molecules as NO, SO/sub 2/, and CO, the larger even n clusters (40 < n < 80) were found to be relatively inert. This lack of reactivity was most pronounced for C/sub 60/ (Buckminsterfullerene). Inertness of the large even C/sub n/ clusters is evidence that they have closed into edgeless, spheroidal shells composed of 12 pentagonal rings and n/2 - 10 hexagonal rings. The possible role of similar shell structures in the formation and morphology of soot is considered. 16 references, 4 figures.

Reactivity of large carbon clusters: spheroidal carbon shells and their possible relevance to the formation and morphology of soot

The laser-induced fragmentation behavior of positive carbon cluster ions has been investigated by tandem time-of-flight techniques for the jet-cooled clusters up to 80 atoms in size. Two distinct photophysical regimes were found. The first applies to clusters with 34 atoms or more, all of which dissociate to produce even numbered fragments. Large even clusters fragment by the loss of the high energy species C2, odd ones lose a C atom. The second regime applies to clusters composed of 31 or less atoms, all of which fragment by the loss of C3. These two regimes are sharply separated by C + 32 which fragments to produce small cluster ions in the 10–19 atom size range. Fragmentation of the large clusters occurs on a microsecond or faster time scale only at very high levels of excitation (>12.8 eV). These photophysical results are interpreted as consequences of the large even clusters having edgeless, spheroidal cage structures while the small ones have linear chain or ring structures.

/pdf/photophysics-of-buckminsterfullerene-and-other-carbon-l9t4ltxnpx.pdf

Sean C. O'Brien

Papers

C 60 : Buckminsterfullerene

Lanthanum complexes of spheroidal carbon shells

Efficient production of C60 (buckminsterfullerene), C60H36, and the solvated buckide ion

Reactivity of large carbon clusters: spheroidal carbon shells and their possible relevance to the formation and morphology of soot

Photophysics of buckminsterfullerene and other carbon cluster ions