“Fullerenes are the molecular form of the element carbon.  They are distinguished by their multi-faceted, closed structure, where the carbon-carbon bonds form a framework of hexagons and pentagons that resembles the familiar hexagon/pentagon surface of a soccer ball.  The number and positioning of the hexagons and pentagons can vary, within both constraints that exactly 12 pentagons and that an even number of carbon atoms be present.  It happens that the essentially spherical molecule formed by sixty carbon atoms (C60) comprises a particularly stable combination of hexagons and pentagons and is the most widely studied fullerene to date.  In general, more than one arrangement of the hexagons and pentagons is possible, leading to a great variety of possible isomers for any particular number of carbon atoms in a fullerene. To help specify a particular fullerene isomer, the symmetry group name to which that isomer belongs is affixed to the molecular formula, but even this is imperfect as it is common for many isomers belonging to the same point group to be present for any particular number of carbon atoms.”

“There are two widely practiced methods for making fullerenes.  The first involves evaporating carbon atoms from graphite and cooling them in such a way that some of them assemble into fullerene molecules.  The second involves burning a hydrocarbon in a fuel-rich flame, and adjusting the conditions such that some of the unburnt carbon atoms condense into fullerenes.  For both methods, even under optimal conditions, not all of the evaporated carbon atoms end up in fullerene molecules.  The remainder condenses into carbon structures that are not molecular in nature, which we will refer to as soot. While C60—Ih forms a significant fraction of the total fullerene production, the fullerene molecules that are produced can have more than three hundred carbon atoms.”

“There are three established methods for the extraction of fullerenes from the surrounding carbon matrix: sublimation, solvent extraction, and, for small-bandgap fullerenes, altering the charge of the fullerene to render it soluble. Other methods for separating fullerenes from the carbon matrix involving the formation of covalent bonds between an extracting reagent and the fullerenes have been proposed, but incur the additional and usually difficult step of subsequently undoing the bond formation in order to achieve pure fullerenes. These methods are generally not practiced, except when the fullerenes are created solely for the purpose of preparing a specific fullerene derivative.”

(Diener et al of TDA Research, US Patent 7,794,682, 9/14/2010)

(Wikipedia, Fullerenes, 11/17/2010)

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