Difference between revisions of "Fullerene" - New World Encyclopedia

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[[Image:Fullerene c540.png|thumb|right|250px|Fullerene C<sub>540</sub>]]
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:''"C60" and "C-60" redirect here.''
  
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The '''fullerenes''' are recently-discovered [[allotropes of carbon|allotropes of carbon]].  They are [[molecule|molecules]] composed entirely of [[carbon]], which take the form of a hollow [[sphere]], [[ellipsoid]], or [[cylinder (geometry)|tube]]. Spherical fullerenes are sometimes called '''buckyballs''', while cylindrical fullerenes are called '''buckytubes''' or '''[[Carbon nanotube|nanotubes]]'''.
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'''Fullerenes''' are a family of [[carbon]] [[Allotropy|allotropes]] (other allotropes of carbon are graphite and diamond) consisting of [[molecule]]s composed entirely of carbon atoms arranged in the form of hollow [[sphere]]s, [[ellipsoid]]s, or [[cylinder (geometry)|tubes]]. Each molecule generally has both pentagonal and hexagonal faces.
  
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==Naming==
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The most common fullerene is ''Buckminsterfullerene,'' in which each molecule is composed of 60 carbon atoms that together take the shape of a [[soccer]] ball. It was named after [[Richard Buckminster Fuller]], because its shape resembles Fuller's design of a [[geodesic dome]]. By extension, spherical fullerenes are often called '''buckyballs,''' and cylindrical ones are called '''buckytubes,''' or, more accurately, '''[[carbon nanotube]]s.''' Fullerenes are similar in structure to [[graphite]], which is composed of stacked sheets of linked hexagonal rings. In the case of a fullerene, however, the presence of pentagonal (or sometimes heptagonal) rings prevents its sheets from being planar.
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Buckminsterfullerene (C60) was named for [[Richard Buckminster Fuller]], a noted architect who popularized the [[geodesic dome]]. Since buckminsterfullerenes have a similar shape to that sort of dome, the name was thought to be appropriate.
 
  
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Fullerenes are similar in structure to [[graphite]], which is composed of a sheet of linked hexagonal rings, but they contain pentagonal (or sometimes heptagonal) rings that prevent the sheet from being planar.
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Chemists can now produce various derivatives of fullerenes. For example, hydrogen atoms, halogen atoms, or organic [[functional group]]s can be attached to fullerene molecules. Also, [[metal]] ions, [[noble gas]] atoms, or small molecules can be trapped in the cage-like structures of fullerene molecules, producing complexes that are known as '''endohedral fullerenes.''' If one or more carbon atoms in a fullerene molecule is replaced by metal atoms, the resultant compound is called a '''fulleride.''' Some doped fullerenes (doped with [[potassium]] or [[rubidium]] atoms, for example) are [[superconductor]]s at relatively high temperatures.
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{{Toc}}
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==Buckminsterfullerene==
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Potential applications of fullerenes include the preparation of [[pharmaceutical]]s, [[lubricant]]s, [[catalyst]]s, and superconductors.
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[[Image:Buckfull.jpg|thumb|right|250px|Buckminsterfullerene (C<sub>60</sub>)]]
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[[Image:Fullerene c540.png|thumb|right|250px|A model of the [[icosahedron|icosahedral]] fullerene C<sub>540</sub>.]]
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The smallest fullerene in which no two pentagons share an edge (which is destabilizing &#8212; see [[pentalene]]) is C<sub>60</sub> ('''buckminsterfullerene'''), and this is also the most common.
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[[Image:c60 isosurface.png|thumb|right|200px|A model of Buckminsterfullerene, C<sub>60</sub>, showing ground state electron density.]]
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==Coining the name==
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The structure of C<sub>60</sub> is that of a [[truncated icosahedron]], which resembles a round [[football (ball)|soccer ball]] of the type made of hexagons and pentagons, with a carbon atom at the corners of each hexagon and a bond along each edge. A [[polymer]]ized single-walled nanotubule ([[P-SWNT]]) is a substance composed of polymerized fullerenes in which carbon atoms from one buckytube bond with carbons in other buckytubes.
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Buckminsterfullerene (C<sub>60</sub>) was named after [[Richard Buckminster Fuller]], a noted architectural modeler who popularized the [[geodesic dome]]. Since buckminsterfullerenes have a similar shape to that sort of dome, the name was thought to be appropriate. As the discovery of the fullerene family came ''after'' buckminsterfullerene, the shortened name "fullerene" was used to refer to the family of fullerenes.
  
 
==Prediction and discovery==
 
==Prediction and discovery==
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In molecular beam experiments, discrete peaks were observed corresponding to molecules with the exact mass of 60, 70, or greater numbers of carbon atoms.  [[Harold Kroto]], from the [[University of Sussex]], James Heath, Sean O'Brien, [[Robert Curl]] and [[Richard Smalley]], from [[Rice University]], discovered C<sub>60</sub> and the fullerenes in 1985.  Kroto, Curl, and Smalley were awarded the 1996 [[Nobel Prize in Chemistry]] for their roles in the discovery of this class of compounds.  C<sub>60</sub> and other fullerenes were later noticed occurring outside of a laboratory environment (e.g. in normal [[candle]] soot).  By [[1991]], it was relatively easy to produce grams of fullerene powder using the techniques of [[Donald Huffman]] and [[Wolfgang Krätschmer]]. [[Fullerene purification]] remains a challenge to chemists and determines fullerene prices to a large extent. So called [[endohedral fullerenes]] have ions or small molecules incorporated inside the cage atoms. Fullerene is an unusual reactant in many [[organic reaction]]s such as the [[Bingel reaction]] discovered in 1993.
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In 1970, Eiji Osawa of [[Toyohashi University of Technology]] predicted the existence of C<sub>60</sub> molecules. He noticed that the structure of a [[corannulene]] molecule was a subset of a soccer-ball shape, and he made the hypothesis that a full ball shape could also exist. His idea was reported in Japanese magazines, but did not reach Europe or America.
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==Properties==
 
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As of the early twenty-first century, the chemical and physical properties of fullerenes are still under heavy study, in both pure and applied research labs. In [[April 2003]], fullerenes were under study for potential medicinal use &#8212; binding specific antibiotics to the structure to target resistant [[bacterium|bacteria]] and even target certain cancer cells such as [[melanoma]].  In the October 2005 issue of Chemistry and Biology, an article [http://linkinghub.elsevier.com/retrieve/pii/S1074-5521(05)00270-X] describing the use of fullerenes as light-activated antimicrobial agents was published.
 
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Fullerenes are not very reactive due to the stability of the graphite-like bonds, and are also sparingly soluble in many [[solvent]]s. Common solvents for the fullerenes include toluene and carbon disulfide.  Solutions of pure Buckminsterfullerene have a deep purple color.  Fullerenes are the only known allotrope of carbon that can be dissolved.  Researchers have been able to increase the reactivity by attaching active groups to the surfaces of fullerenes. Buckminsterfullerene does not exhibit "superaromaticity". That is, the electrons in the hexagonal rings do not delocalize over the whole molecule.
 
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Other atoms can be trapped inside fullerenes, and indeed recent evidence for a meteor impact at the end of the [[Permian]] period was found by analysing [[noble gas]]es so preserved.
 
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In the field of [[nanotechnology]], heat resistance and [[superconductivity]] are some of the more heavily studied properties.
 
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A common method used to produce fullerenes is to send a large current between two nearby graphite electrodes in an inert atmosphere. The resulting carbon plasma arc between the electrodes cools into sooty residue from which many fullerenes can be isolated.
 
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== Possible dangers ==
 
  
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Although buckyballs have been thought in theory to be relatively inert, a presentation given to the [[American Chemical Society]] in [[March]] [[2004]] and described in an article in  [[New Scientist]] on [[April 3]] [[2004]], suggests the molecule is injurious to organisms. An experiment by Eva Oberdörster at [[Southern Methodist University]], which introduced fullerenes into water at concentrations of 0.5 parts per million, found that [[largemouth bass]] suffered a 17-fold increase in cellular damage in the brain tissue after 48 hours. The damage was of the type [[lipid peroxidation]], which is known to impair the functioning of [[cell membrane]]s. There were also inflammatory changes in the liver and activation of genes related to the making of repair enzymes. At the time of presentation, the SMU work had not been [[peer review]]ed.
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In [[Mass spectroscopy|molecular beam experiments]], discrete peaks were observed corresponding to molecules with the exact masses of 60, 70, or more carbon atoms. In 1985, [[Harold Kroto]] (then at the [[University of Sussex]]), [[James R. Heath]], [[Sean O'Brien (scientist)|Sean O'Brien]], [[Robert Curl]], and [[Richard Smalley]], of [[Rice University]], discovered C<sub>60</sub>, and shortly thereafter discovered other fullerenes.<ref>H.W. Kroto, J.R. Heath, S.C. O'Brien, R.F. Curl, and R.E. Smalley, C<sup>60</sup>: Buckminsterfullerene, ''Nature'' 318: 162–163.</ref> The first nanotubes were obtained in 1991.<ref>Machine Design, [http://machinedesign.com/ContentItem/60618/Anewbuckyballbouncesintotown.aspx A new buckyball bounces into town.] Retrieved October 21, 2008.</ref>
  
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Because of their notable properties, buckyballs may be part of many products in the near future. With this knowledge in mind, many researchers are investigating ways to reduce the toxicity of the buckyballs [http://www.newscientist.com/article.ns?id=dn6458]. They have discovered that they can reduce the toxicity by adding hydroxyls, among other chemical groups. With each chemical group added to the buckyball, the scientists could reduce its toxicity level by an order of magnitude.
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Kroto, Curl, and Smalley were awarded the 1996 [[Nobel Prize in Chemistry]] for their roles in the discovery of this class of compounds.
  
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It is believed that buckyballs acquire their toxicity by producing [[Radical (chemistry)|free radicals]] in water that damage the lipids on the cellular membranes of animals, destroying the cells.
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== Natural occurrence and artificial production ==
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Minute quantities of the fullerenes—in the form of C<sub>60</sub>, C<sub>70</sub>, C<sub>76</sub>, and C<sub>84</sub> molecules—have been found in [[soot]] and in the residue of [[carbon arc]] lamps. These molecules are also produced by lightning discharges in the atmosphere.<ref>ASU, [http://invsee.asu.edu/nmodules/Carbonmod/everywhere.html World of Carbon,] The Allotropes of Carbon. Retrieved October 21, 2008.</ref> Some analyses indicate that they are present in meteorites and interstellar dust. Recently, Buckminsterfullerenes were found in a family of minerals known as [[Shungites]] in [[Karelia]], Russia.
  
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Pristine C60 can be suspended in water at low concentrations as large clusters often termed nC60.  These clusters are spherical clumps of C60 between 250-350 nm in diameter.  Thus, nC60 represents a different chemical entity than solutions of C60 in which the fullerenes exist as individual molecules.  Recently, results presented at the ACS meeting in Anaheim, CA suggest that nC60 is moderately toxic to water fleas and juvenile largemouth bass at concentrations in water of around 800 ppb.   The first study of its kind on marine life, these preliminary results quickly spread across the scientific community.  However, the overwhelming evidence of the essential non-toxicity of C60 (not nC60) in previously peer-reviewed articles of C60 and many of its derivatives indicates that our compounds are likely to have little (if any) toxicity, especially at the very low concentration at which it is used (~1-10 µM).
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A common method used to produce fullerenes is to send a large current between two nearby [[graphite]] electrodes in an [[inert]] atmosphere. The resultant [[carbon]] [[Plasma (physics)|plasma]] arc between the electrodes cools into sooty residue from which many fullerenes can be isolated.
  
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==Fullerene extract mixture (C<sub>60</sub>/C<sub>70</sub>) solubility==
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By 1991, it became relatively easy to produce gram-sized samples of fullerene powder using the techniques of [[Donald Huffman]] and [[Wolfgang Krätschmer]]. However, purification of fullerenes remains a challenge.
  
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Solvents that dissolve fullerenes are listed below in order from highest solubility. The value in parentheses is the approximate saturated concentration.
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== Structural variations ==
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Since the discovery of fullerenes in 1985, a number of structural variations of fullerenes have been found. Examples include:<ref>Gary L. Miessler and Donald A. Tarr, ''Inorganic Chemistry'' (Upper Saddle River, NJ: Pearson Education International, 2004, ISBN 0131201980).</ref>
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*'''buckyball clusters:''' Smallest member is {{chem | C | 20}} (unsaturated version of [[dodecahedrane]]) and the most common is {{chem | C | 60}}
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*'''Nanotubes:''' Hollow tubes of very small dimensions, having single or multiple walls; potential applications in electronics industry
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*'''Megatubes:''' Larger in diameter than nanotubes and prepared with walls of different thickness; potentially used for the transport of a variety of molecules of different sizes<ref>D.R. Mitchel, et al., The Synthesis of Megatubes: New Dimensions in Carbon Materials, ''Inorg. Chem.'' 40: 2751.</ref>
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*'''Polymers:''' Chain, two-dimensional and three-dimensional polymers are formed under high pressure high temperature conditions
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*'''Nano onions:''' Spherical particles based on multiple carbon layers surrounding a buckyball core; proposed for lubricant<ref>N. Sano, Synthesis of carbon "onions" in water, ''Nature (London)'' 414: 506.</ref>
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*'''Linked "ball-and-chain" dimers:''' Two buckyballs linked by a carbon chain<ref>A.A. Shvartsburg, Observation of “Stick” and “Handle” Intermediates along the Fullerene Road, ''J. Phys. Chem.'' 103: 5275.</ref>
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*'''Fullerene rings'''<ref>Y. Li, et al., Structures and stabilities of C60-rings, ''Chem. Phys. Lett.'' 335: 524.</ref>
  
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# 1,2,4-trichlorobenzene (20mg/ml)
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==Buckyballs==
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# [[carbon disulfide]] (12mg/ml)
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[[Image:C60a.png|thumb|left|160px|Buckminsterfullerene C<sub>60</sub>]]
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# [[toluene]] (3.2mg/ml)
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[[Image:Fussball.jpg|thumb|right|160px|A [[soccer ball]] is a model of the Buckminsterfullerene C<sub>60</sub>]]
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# [[benzene]] (1.8mg/ml)
 
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# [[chloroform]] (0.5mg/ml)
 
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# [[carbon tetrachloride]] (0.4mg/ml)
 
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# [[cyclohexane]] (0.054mg/ml)
 
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# n-hexane (0.046mg/ml)
 
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# [[THF]] (0.037mg/ml)
 
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# [[acetonitrile]] (0.02mg/ml)
 
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# [[methanol]] (0.0009mg/ml)
 
  
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== Diffraction of fullerene ==
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===Buckminsterfullerene===
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'''Buckminsterfullerene''' ([[IUPAC]] name '''(C<sub>60</sub>-I<sub>h</sub>)[5,6]fullerene''') is the smallest fullerene molecule in which no two pentagons share an edge (which can be destabilizing). It is also the most common in terms of natural occurrence, as it can often be found in [[soot]].
  
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In [[1999]], researchers from the [[University]] of [[Vienna]] {{an|Arndt}} demonstrated that the [[wave-particle duality]] applied to macro-molecules such as fullerene.
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The structure of C<sub>60</sub> is a [[Truncated icosahedron|truncated (T = 3) icosahedron]], which resembles a [[football (ball)#Association football|soccer ball]] of the type made of twenty hexagons and twelve pentagons, with a carbon atom at the vertices of each polygon and a bond along each polygon edge.
  
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==Notes==
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The [[van der Waals diameter]] of a C<sub>60</sub> molecule is about 1 [[nanometer]] (nm). The nucleus to nucleus diameter of a C<sub>60</sub> molecule is about 0.7 nm.
  
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# {{anb|Arndt}} ''Wave-particle duality of C60'', M. Arndt , O. Nairz, J. Voss-Andreae, C. Keller, G. van der Zouw, [[Anton Zeilinger|A. Zeilinger]], ''Nature'' 401, 680-682, [[14 October]] [[1999]]
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The C<sub>60</sub> molecule has two bond lengths. The 6:6 ring bonds (between two hexagons) can be considered "[[double bond]]s" and are shorter than the 6:5 bonds (between a hexagon and a pentagon).
  
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==Mathematics of fullerenes==  
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===Boron buckyball===
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In [[mathematics|mathematical]] terms, the structure of a '''fullerene''' is a trivalent
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A new type of buckyball utilizing [[boron]] atoms instead of the usual carbon has been predicted and described by researchers at Rice University. The B-80 structure is predicted to be more stable than the C-60 buckyball.<ref>Jade Boyd, [http://www.eurekalert.org/pub_releases/2007-04/ru-bbt042307.php Bucky's brother—The boron buckyball makes its début,] eurekalert.org. Retrieved October 21, 2008.</ref> One reason for this given by the researchers is that the B-80 is actually more like the original geodesic dome structure popularized by Buckminster Fuller which utilizes triangles rather than hexagons.
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convex polyhedron with pentagonal and hexagonal faces.
 
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Using Euler formula F - E + V = 2, (plus the fact that every vertex in a fullerene structure belongs to exactly 3 faces) one can easily prove that there are
 
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exactly 12 pentagons in a fullerene. The smallest fullerene is C<sub>20</sub>, the [[dodecahedron]]. There are
 
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no fullerenes with 22 vertices. The number of fullerenes
 
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C<sub>2n</sub> grows rapidly with increasing n = 12,13, ... For instance, there are 1812 non-isomorphic
 
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fullerenes C<sub>60</sub> but only one of them, the buckminsterfullerene alias [[truncated icosahedron]], has no pair of adjacent pentagons.
 
  
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==Carbon nanotube==
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===Variations of buckyballs===  
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[[Image:Louie nanotube.jpg|thumb||330px|An electronic device known as a [[diode]] can be formed by joining two nanoscale carbon tubes with different electronic properties.]]
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Besides C<sub>60</sub>, a fairly common buckyball is C<sub>70</sub>,<ref>bristol.ac.uk, [http://www.bristol.ac.uk/Depts/Chemistry/MOTM/buckyball/c60a.htm Buckminsterfullerene: Molecule of the Month.] Retrieved October 21, 2008.</ref> but fullerenes with 72, 76, 84, and even up to 100 carbon atoms are commonly obtained.
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'''Carbon nanotubes''' are cylindrical [[carbon]] [[molecules]] with novel properties that make them potentially useful in a wide variety of applications (e.g., nano-electronics, [[optics]], [[materials]] applications, etc.). They exhibit extraordinary strength and unique [[electricity|electrical]] properties, and are efficient conductors of [[heat]]. [[Inorganic nanotubes]] have also been synthesized.
 
  
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A nanotube (also known as a buckytube) is a member of the [[fullerene]] structural family, which also includes [[Buckyball#Buckminsterfullerene|buckyballs]]. Whereas buckyballs are [[spherical]] in shape, a nanotube is [[cylinder (geometry)|cylindrical]], with at least one end typically capped with a hemisphere of the buckyball structure. Their name is derived from their size, since the diameter of a nanotube is on the order of a few [[nanometer]]s (approximately 50,000 times smaller than the width of a human hair), while they can be up to several centimeters in length. There are two main types of nanotubes: [[single-walled nanotubes]] (SWNTs) and [[multi-walled nanotubes]] (MWNTs).
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In [[mathematics|mathematical]] terms, the structure of a '''fullerene''' is a [[Valence (chemistry)|trivalent]] convex [[polyhedron]] with pentagonal and hexagonal faces. In [[graph theory]], the term '''fullerene''' refers to any 3-[[Regular graph|regular]], [[planar graph]] with all faces of size 5 or 6 (including the external face). It follows from [[Euler characteristic|Euler's polyhedron formula]], |V|-|E|+|F| = 2, (where |V|, |E|, |F| indicate the number of vertices, edges, and faces), that there are exactly 12 pentagons in a fullerene and |V|/2-10 hexagons.
  
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Nanotubes are composed entirely of [[sp² bond]]s, similar to [[graphite]]. Stronger than the sp³ bonds found in [[diamond]], this bonding structure provides them with their unique strength. Nanotubes naturally align themselves into "ropes" held together by [[Van der Waals force]]s. Under high pressure, nanotubes can merge together, trading some sp² bonds for sp³ bonds, giving great possibility for producing strong, unlimited-length wires through high-pressure nanotube linking. [http://www.ncnr.nist.gov/staff/taner/nanotube/interlink.pdf]
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{|align="center" style="border: 1px solid #aaaaaa; background: #f8f8f8; padding: 2px; font-size: 88%; margin: 0 0px 0 0px;"
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| [[Image:Graph of 20-fullerene w-nodes.svg|200px]]  
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| [[Image:Graph of 26-fullerene 5-base w-nodes.svg|200px]]  
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| [[Image:Graph of 60-fullerene w-nodes.svg|200px]]
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| [[Image:Graph of 70-fullerene w-nodes.svg|200px]]
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|-
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| align=center | 20-fullerene<br/>(dodecahedral graph)
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| align=center | 26-fullerene graph
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| align=center | 60-fullerene<br/>(truncated icosahedral graph)
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| align=center | 70-fullerene graph
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|}
  
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While it has long been known that [[carbon fiber]]s can be produced with a carbon arc, and patents were issued for the process, it was not until 1991 that [[Sumio Iijima]], a researcher with the [[NEC Corporation|NEC]] Laboratory in Tsukuba, Japan, observed that these fibers were hollow. This feature of nanotubes is of great interest to [[physics|physicists]] because it permits experiments in one-dimensional [[quantum physics]].  
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The smallest fullerene is the [[dodecahedron]]—the unique C<sub>20</sub>. There are no fullerenes with 22 vertices. The number of fullerenes C<sub>2n</sub> grows with increasing n = 12,13,14…, roughly in proportion to n<sup>9</sup>. For instance, there are 1812 non-isomorphic fullerenes C<sub>60</sub>. Note that only one form of C<sub>60</sub>, the buckminsterfullerene alias [[truncated icosahedron]], has no pair of adjacent pentagons (the smallest such fullerene). To further illustrate the growth, there are 214,127,713 non-isomorphic fullerenes C<sub>200</sub>, 15,655,672 of which have no adjacent pentagons.
  
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==Single-walled nanotubes==
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[[Trimetasphere]] carbon nanomaterials were discovered by researchers at [[Virginia Tech]] and licensed exclusively to [[Luna Innovations]]. This class of novel molecules comprises 80 carbon atoms (C80) forming a sphere which encloses a complex of three metal atoms and one nitrogen atom. These fullerenes encapsulate metals which puts them in the subset referred to as [[metallofullerenes]]. Trimetaspheres have the potential for use in diagnostics (as safe imaging agents), therapeutics and in organic solar cells.
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[[Image:CNTnames.png|thumb|300px|The (''n'',''m'') nanotube naming scheme can be thought of as a vector ('''C'''<sub>h</sub>) in an infinite graphene sheet that describes how to 'roll up' to graphene sheet to make the nanotube. '''T''' denotes the tube axis, and '''a'''<sub>1</sub> and '''a'''<sub>2</sub> are the unit vectors of graphene in real space.]]
 
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[[Image:Kohlenstoffnanoroehre Animation.gif|thumb|right|200px|Animation of a carbon nanotube]]
 
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Most SWNTs have a diameter of close to 1nm, with a tube length that can be many thousands of times larger. The structure of a SWNT can be conceptualized by wrapping a one-atom-thick layer of [[graphite]] (called [[graphene]]) into a seamless cylinder. The way the graphene sheet is wrapped is represented by a pair of indices (''n'',''m'') called the chiral vector. The integers ''n'' and ''m'' denote the number of unit [[vector (spatial)|vector]]s along two directions in the honeycomb [[lattice]] of graphene. If ''m''=0, the nanotubes are called "zigzag". If ''n''=''m'', the nanotubes are called "armchair".  Otherwise, they are called "chiral".
 
  
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==Carbon nanotubes==
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[[Image:Kohlenstoffnanoroehre Animation.gif|frame|This animation of a rotating Carbon nanotube shows its 3D structure.]]
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{{Main|Carbon nanotube}}
  
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SWNTs are a very important variety of carbon nanotube because they exhibit important electric properties that are not shared by the multi-walled carbon nanotube (MWNT) variants. SWNTs are the most likely candidate for miniaturizing electronics past the microelectromechanical scale that is currently the basis of modern electronics. The most basic building block of these systems is the electric wire, and SWNTs can be excellent conductors. (Dekker, et al., 1999) One useful application of SWNTs is in the development of the first intramolecular field effect transistors (FETs). The production of the first intramolecular logic gate useing SWNT FETs has recently become possible as well (Derycke, et al., 2001). To create a logic gate you must have both a p-FET and an n-FET. Because SWNTs are p-FETs when exposed to air and n-FETs when unexposed to oxygen, they were able to protect half of a SWNT from oxygen exposure, while exposing the other half to oxygen. The result was a single SWNT that acted as a NOT logic gate with both p and n-type FETs within the same molecule.
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Nanotubes are cylindrical fullerenes. These tubes of carbon are usually only a few nanometers wide, but they can range from less than a micrometer to several millimeters in length. They often have closed ends, but can be open-ended as well. There are also cases in which the tube reduces in diameter before closing off. Their unique molecular structure results in extraordinary macroscopic properties, including high tensile strength, high electrical conductivity, high ductility, high resistance to heat, and relative chemical inactivity (as it is cylindrical and "planar"—that is, it has no "exposed" atoms that can be easily displaced). One proposed use of carbon nanotubes is in [[paper battery|paper batteries]], developed in 2007 by researchers at [[Rensselaer Polytechnic Institute]].<ref>V.L. Pushparaj, M.M. Shaijumon, A. Kumar, S. Murugesan, L. Ci, R. Vajtai, R.J. Linhardt, O. Nalamasu, and P.M. Ajayan, Flexible energy storage devices based on nanocomposite paper, ''Proceedings of the National Academy of Sciences'' 104(34): 13574.</ref> Another proposed use in the field of space technologies and science fiction is to produce high-tensile carbon cables required by a [[space elevator]].  
  
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SWNTs are still very expensive to produce, and the development of more affordable synthesis techniques is vital to the future of carbon nanotechnology. If cheaper means of synthesis cannot be discovered, it would make it financially impossible to apply this technology to commercial-scale applications.
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===Carbon nanobuds===
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{{main|Carbon nanobud}}
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'''Nanobuds''' have been obtained by adding Buckminsterfullerenes to carbon nanotubes.
  
 
==Properties==
 
==Properties==
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The covalent bonding undergone in CNTs means they have very high [[tensile strength]]s. In 2000, a SWNT was tested to have a tensile strength of 63 [[Pascal|GPa]]. In comparison, high-carbon steel has a tensile strength of approximately 1.2 GPa. CNTs also have very high [[elastic modulus]], in the order of 1 TPa [http://ipn2.epfl.ch/CHBU/papers/ourpapers/Forro_NT99.pdf].  
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For the past decade, the chemical and physical properties of fullerenes have been a hot topic in the field of research and development, and are likely to continue to be for a long time. [[Popular Science]] has published articles about the possible uses of fullerenes in [[armor]]. In April 2003, fullerenes were under study for [[Nanomedicine|potential medicinal use]]: Binding specific [[antibiotic]]s to the structure to target resistant [[bacterium|bacteria]] and even target certain [[cancer]] cells such as [[melanoma]]. The October 2005 issue of [[Chemistry and Biology]] contains an article describing the use of fullerenes as light-activated [[antimicrobial]] agents.<ref>G. Tegos and T. Demidova, D. Arcila-Lopez, H. Lee, T. Wharton, H. Gali, and M. Hamblin, 2005, [http://linkinghub.elsevier.com/retrieve/pii/S1074-5521(05)00270-X Cationic Fullerenes Are Effective and Selective Antimicrobial Photosensitizers,] ''Chemistry & Biology'' 12(10): 1127–1135. Retrieved October 21, 2008.</ref>
  
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Under excessive tensile strain, the tubes will undergo plastic deformation, which means the deformation is permanent. This deformation begins at strains of approximately 5% [Qian et al, 2002] and can increase the maximum strain the tube undergoes before fracture by releasing strain energy.  
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In the field of [[nanotechnology]], [[thermal conductivity|heat resistance]], and [[superconductivity]] are some of the more heavily studied properties.
  
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CNTs are not nearly as strong under compression. Due to their hollow structure, they tend to undergo buckling, when placed under compressive, torsional or bending stress.  
+
There are many calculations that have been done using ''ab initio'' Quantum Methods applied to fullerenes. By [[density functional theory]] (DFT) and [[Time-dependent density functional theory]] (TD-DFT) methods, one can obtain [[Infra-red spectroscopy|IR]], [[Raman spectroscopy|Raman]] and [[Ultraviolet-visible spectroscopy|UV]] spectra. Results of such calculations can be compared with experimental results.
  
−
Due to the symmetry and unique electronic structure of graphene, the structure of a nanotube strongly affects its electrical properties. For a given (''n'',''m'') nanotube, if  2''n'' + ''m''=3''q'' (where ''q'' is an integer), then the nanotube is [[metallic]], otherwise the nanotube is a [[semiconductor]]. Thus all armchair (''n''=''m'') nanotubes are metallic, and nanotubes (5,0), (6,4), (9,1), etc. are semiconducting. An alternative (equivalent) representation of this condition is if (''n'' -  ''m'') /3=integer, then the SWNT is metallic. In theory, metallic nanotubes can have an electrical current density more than 1,000 times stronger than metals such as [[silver]] and [[copper]].  
+
===Aromaticity===
 +
Researchers have been able to increase the reactivity of fullerenes by attaching active groups to their surfaces. Buckminsterfullerene does not exhibit "[[Aromaticity|superaromaticity]]:" That is, the electrons in the hexagonal rings do not [[Delocalized electron|delocalize]] over the whole molecule.
  
−
All nanotubes are expected to be very good thermal conductors along the tube, exhibiting a property known as "ballistic conduction," but good insulators laterally to the tube axis.
+
A spherical fullerene of ''n'' carbon atoms has ''n'' [[pi-bond]]ing electrons. These should try to delocalize over the whole molecule. The quantum mechanics of such an arrangement should be like one shell only of the well-known quantum mechanical structure of a single atom, with a stable filled shell for ''n'' = 2, 8, 18, 32, 50, 72, 98, 128, and so on; that is, twice a [[perfect square]]; but this series does not include 60. As a result, C<sub>60</sub> in water tends to pick up two more electrons and become an [[anion]]. The nC<sub>60</sub> described below may be the result of C<sub>60</sub>'s trying to form a loose [[metallic bonding]].
  
−
As with any material, the existence of defects affect the material properties. Defects can occur in the form of atomic vacancies. High levels of such defects can lower the tensile strength by up to 85% [http://lib.tkk.fi/Diss/2004/isbn9512273799/article5.pdf]. Due to the almost one-dimensional structure of CNTs, the tensile strength of the tube is dependent on the weakest segment of it in a similar manner to a chain, where a defect in a single link will greatly diminish the strength of the entire chain.  
+
===Chemistry===
 +
{{Main|Fullerene chemistry}}
 +
Fullerenes are stable, but not totally unreactive. They are unusual reactants in many [[organic reaction]]s such as the [[Bingel reaction]] discovered in 1993.
  
−
In terms of the tube's electrical properties, they too are affected by the presence of defects. A common result is the lowered conductivity through the defected region of the tube. Some defect formation in armchair type tubes (which are metallic) can cause the region surrounding that defect to become semiconducting.
+
Planar graphite is made up of carbon atoms that are at their energy minimum, with outer [[atomic orbital|orbital]]s that are said to be "sp<sup>2</sup>-hybridized." These orbitals must be bent to form the closed sphere or tube of a buckyball or buckytube, producing [[angle strain]]. The characteristic reaction of fullerenes is [[electrophilic addition]] at 6,6-double bonds, which reduces angle strain by changing sp<sup>2</sup>-hybridized carbons into sp<sup>3</sup>-hybridized ones. The change in hybridized orbitals causes the bond angles to decrease from about 120 degrees in the sp<sup>2</sup> orbitals to about 109.5 degrees in the sp<sup>3</sup> orbitals. This decrease in bond angles allows for the bonds to bend less when closing the sphere or tube, and thus, the molecule becomes more stable.
  
−
==Synthesis==
+
Other atoms can be trapped inside fullerenes to form [[inclusion compound]]s known as [[endohedral fullerenes]]. An unusual example is the egg shaped fullerene Tb<sub>3</sub>N@C<sub>84</sub>, which violates the isolated pentagon rule.<ref>C.M. Beavers, T. Zuo, J.C. Duchamp, K. Harich, H.C. Dorn, M.M. Olmstead, and A.L. Balch, Tb3N@C84: An improbable, egg-shaped endohedral fullerene that violates the isolated pentagon rule, ''Journal of the American Chemical Society'' 128(35): 11352–3.</ref> Recent evidence for a meteor impact at the end of the [[Permian]] period was found by analyzing [[noble gas]]es so preserved.<ref>Luann Becker and Robert J. Poreda, Andrew G. Hunt, Theodore E. Bunch, and Michael Rampino, 2007, Impact Event at the Permian-Triassic Boundary: Evidence from Extraterrestrial Noble Gases in Fullerenes, ''Science'' 291(5508): 1530–3.</ref>
−
Techniques have been developed to produce nanotubes in sizeable quantities, but their cost still prohibits any large scale use of them.
 
−
Fullerenes and carbon nanotubes are not necessarily products of high-tech laboratories, they are commonly formed in such mundane places as candle flames. However, these naturally occurring varieties are highly irregular in size and quality, and the high degree of uniformity necessary to meet the needs of research and industry is impossible in such an uncontrolled environment. There are several methods employed to make nanotubes, such as [[arc discharge]], [[laser ablation]], high pressure carbon monoxide ([[HiPco]]), and [[chemical vapor deposition]] (CVD). In general, the CVD method has shown the most promise in being able to produce larger quantities of nanotube (compared to the other methods) at lower cost. This is usually done by reacting a carbon-containing gas (such as [[acetylene]], [[ethylene]], [[ethanol]], etc.) with a metal catalyst particle (usually [[cobalt]], [[nickel]], [[iron]] or a combination of these as cobalt/iron or cobalt/molybdenium) at temperatures above 600°C.
 
  
−
==Applications==
+
===Solubility===
 +
Fullerenes are sparingly soluble in many [[solvent]]s. Common solvents for the fullerenes include aromatics, such as [[toluene]], and others like [[carbon disulfide]]. Solutions of pure Buckminsterfullerene have a deep purple color. Solutions of C<sub>70</sub> are a reddish brown. The higher fullerenes C<sub>76</sub> to C<sub>84</sub> have a variety of colors. C<sub>76</sub> has two optical forms, while other higher fullerenes have several structural isomers. Fullerenes are the only known [[allotrope]] of carbon that can be dissolved in common solvents at room temperature.
  
−
The strength and flexibility of carbon nanotubes makes them of potential use in controlling other nanoscale structures, which suggests they will have an important role in [[nanotechnology]] engineering. The highest [[tensile strength]] an individual SWNT has been tested to be is 63 [[Pascal|GPa]] [http://www.google.com/search?hl=en&ie=ISO-8859-1&q=nanotubes+%22tensile+strength%22+%2263+GPa%22&btnG=Google+Search]. In Earth's upper atmosphere, atomic [[oxygen]] erodes the carbon nanotubes, but other applications of carbon nanotubes rarely need the surface to be protected. Though it is debatable if nanotube materials can ever be made with a tensile strength approaching that of individual tubes, composites may still yield incredible strengths potentially sufficient to allow the building of such things as [[space elevator]]s, artificial muscles, ultrahigh-speed flywheels, and more. MIT is working on combat jackets utilizing carbon nanotubes for ultrastrong fibers and for monitoring its wearer's condition.
+
Some fullerene structures are not soluble because they have a small [[band gap]] between the ground and [[excited state]]s. These include the small fullerenes C<sub>28</sub>,<ref>Ting Guo, Richard E. Smalley, and Gustavo E. Scuseria, [http://adsabs.harvard.edu/abs/1993JChPh..99..352G Ab initio theoretical predictions of C28, C28H4, C28F4, (Ti at C28)H4, and M at C28 (M = Mg, Al, Si, S, Ca, Sc, Ti, Ge, Zr, and Sn),] Harvard. Retrieved October 21, 2008.</ref> C<sub>36</sub> and C<sub>50</sub>. The C<sub>72</sub> structure is also in this class, but the endohedral version with a trapped [[lanthanide]]-group atom is soluble due to the interaction of the metal atom and the electronic states of the fullerene. Researchers had originally been puzzled by C<sub>72</sub> being absent in fullerene plasma-generated soot extract, but found in endohedral samples. Small band gap fullerenes are highly reactive and bind to other fullerenes or to soot particles.
  
−
Carbon nanotubes have already been used as composite fibers in [[polymers]] and [[concrete]] to improve the mechanical, thermal and electrical properties of the bulk product. Researchers have also found that adding them to [[polyethylene]] increases the polymer's [[elastic modulus]] by 30%. In concrete, they increase the tensile strength, and halt crack propagation.
+
Solvents that are able to dissolve buckminsterfullerene (C<sub>60</sub>) are listed below in order from highest solubility. The value in parentheses is the approximate saturated concentration.<ref>V.N. Bezmel'nitsyn, A.V. Eletskiĭ, and M.V. Okun', Uspekhi Fizicheskikh Nauk. (Fullerenes in Solutions). ''Russian Academy of Sciences'' 41.</ref>
 +
# [[1-chloronaphthalene]] (51 mg/mL)
 +
# [[1-methylnaphthalene]] (33 mg/mL)
 +
# [[1,2-dichlorobenzene]] (24 mg/mL)
 +
# [[1,2,4-trimethylbenzene]] (18 mg/mL)
 +
# [[tetrahydronaphthalene]] (16 mg/mL)
 +
# [[carbon disulfide]] (8 mg/mL)
 +
# [[1,2,3-tribromopropane]] (8 mg/mL)
 +
# [[bromoform]] (5 mg/mL)
 +
# [[toluene]] (3 mg/ml)
 +
# [[benzene]] (1.5 mg/ml)
 +
# [[cyclohexane]] (1.2 mg/ml)
 +
# [[carbon tetrachloride]] (0.4 mg/ml)
 +
# [[chloroform]] (0.25 mg/ml)
 +
# n-[[hexane]] (0.046 mg/ml)
 +
# [[tetrahydrofuran]] (0.006 mg/ml)
 +
# [[acetonitrile]] (0.004 mg/ml)
 +
# [[methanol]] (0.00004 mg/ml)
 +
# [[water]] (1.3x10<sup>-11</sup> mg/mL)
  
−
Conductive carbon nanotubes have been used for several years in brushes for commercial electric motors. They replace traditional [[carbon black]], which is mostly impure spherical carbon fullerenes. The nanotubes improve electrical and thermal conductivity because they stretch through the plastic matrix of the brush. This permits the carbon filler to be reduced from 30% down to 3.6%, so that more matrix is present in the brush. Nanotube composite motor brushes are better-lubricated (from the matrix), cooler-running (both from better lubrication and superior thermal conductivity), less brittle (more matrix, and fiber reinforcement), stronger and more accurately moldable (more matrix). Since brushes are a critical failure point in electric motors, and also don't need much material, they became economical before almost any other application.
+
Solubility of C<sub>60</sub> in some solvents shows unusual behavior due to existence of solvate phases (analogues of crystallohydrates). For example, solubility of C<sub>60</sub> in [[benzene]] solution shows maximum at about 313 K. Crystallization from benzene solution at temperatures below maximum results in formation of triclinic solid solvate with four benzene molecules C<sub>60</sub>•4C<sub>6</sub>H<sub>6</sub> which is rather unstable in air. Out of solution, this structure decomposes into usual fcc C<sub>60</sub> in few minutes' time. At temperatures above solubility maximum the solvate is not stable even when immersed in saturated solution and melts with formation of fcc C<sub>60</sub>. Crystallization at temperatures above the solubility maximum results in formation of pure fcc C<sub>60</sub>. Large millimeter size crystals of C<sub>60</sub> and C<sub>70</sub> can be grown from solution both for solvates and for pure fullerenes.<ref>A.V. Talyzin, Phase transition C60-C60*4C6H6 in liquid benzene, ''J. of Phys. Chem.'' 101(47).</ref><ref>A.V. Talyzin, I. Engstrцm, C70 in a Benzene, Hexane and Toluene solutions, ''J. of Phys. Chem.'' 102(34): 6477–6481.</ref>
  
−
A recent 2005 Science paper notes that drawing transparent high strength swathes of SWNT is a functional production technique. These conductive elastic materials are among the many applications listed here of photovoltaic active structures as well as load structures.
+
== Safety and toxicity ==
 +
When considering toxicological data, care must be taken to distinguish as necessary between what are normally referred to as fullerenes: (C<sub>60</sub>, C<sub>70</sub>,…); fullerene derivatives: C<sub>60</sub> or other fullerenes with covalently bonded chemical groups; fullerene complexes (for example, C<sub>60</sub>-PVP, host-guest complexes), where the fullerene is physically bound to another molecule; C<sub>60</sub> nanoparticles, which are extended solid-phase aggregates of C<sub>60</sub> crystallites; and nanotubes, which are generally much larger (in terms of molecular weight and size) compounds, and are different in shape to the spheroidal fullerenes C<sub>60</sub> and C<sub>70</sub>, as well as having different chemical and physical properties.  
  
−
Carbon nanotubes additionally can also be used to produce nanowires of other chemicals, such as gold or zinc oxide. These nanowires in turn can be used to cast nanotubes of other chemicals, such as gallium nitride. These can have very different properties from CNTs - for example, gallium nitride nanotubes are hydrophilic, while CNTs are hydrophobic, giving them possible uses in organic chemistry that CNTs could not be used for.
+
The above different compounds span the range from insoluble materials in either hydrophilic or lipophilic media, to hydrophilic, lipophilic, or even amphiphilic compounds, and with other varying physical and chemical properties. Therefore any broad generalization extrapolating for example results from C<sub>60</sub> to nanotubes or vice versa is not possible, though technically all are fullerenes, as the term is defined as a close-caged all-carbon molecule. Any extrapolation of results from one compound to other compounds must take into account considerations based on a Quantitative Structural Analysis Relationship Study (QSARS), which mostly depends on how close the compounds under consideration are in physical and chemical properties.  
  
−
One use for nanotubes that has already been developed is as extremely fine electron guns, which could be used as miniature [[cathode ray tube]]s in thin high-brightness low-energy low-weight displays. This type of display would consist of a group of many tiny CRTs, each providing the [[electron]]s to hit the [[phosphor]] of one [[pixel]], instead of having one giant CRT whose electrons are aimed using electric and [[magnetic field]]s. These displays are known as [[field emission display]]s (FEDs). A nanotube formed by joining nanotubes of two different diameters end to end can act as a [[diode]], suggesting the possibility of constructing electronic computer circuits entirely out of nanotubes. Nanotubes have been shown to be [[superconductivity|superconducting]] at low temperatures.
+
In 1996<ref>F. Moussa, et al., In vivo studies of fullerene-based materials using endohedral metallofullerene radiotracers, ''Fullerene Sci. Technol.'' 4: 21–29.</ref> and 1997, Moussa ''et al.'' studied the ''in vivo'' toxicity of C<sub>60</sub> after intra-peritoneal administration of large doses. No evidence of toxicity was found and the mice tolerated a dose of 5&nbsp;000 mg/kg of body weight (BW). Mori ''et al.'' (2006)<ref>T. Mori, et al., Preclinical studies on safety of fullerene upon acute oral administration and evaluation for no mutagenesis, ''Toxicology'' 225: 48–54.</ref> could not find toxicity in rodents for C<sub>60</sub> and C<sub>70</sub> mixtures after oral administration of a dose of 2&nbsp;000 mg/kg BW and did not observed evidence of genotoxic or mutagenic potential ''in vitro''.
 +
Other studies could not establish the toxicity of fullerenes: On the contrary, the work of Gharbi ''et al.'' (2005)<ref>Najla Gharbi, M. Pressac, M. Hadchouel, H. Szwarc, S.R. Wilson, and F. Moussa, 2005, [60]fullerene is a powerful antioxidant in vivo with no acute or subacute toxicity, ''Nano Letters'' 5(12):2578–2585.</ref> suggested that aqueous C<sub>60</sub> suspensions failing to produce acute or subacute toxicity in rodents could also protect their livers in a dose-dependent manner against free-radical damage.  
  
−
Nanotubes can be opened and filled with materials such as [[biological molecule|biological molecules]], raising the possibility of applications in [[biotechnology]]. They can be used to dissipate heat from tiny computer chips.
+
A comprehensive and recent review on fullerene toxicity is given by Kolosnjaj ''et al.'' (2007a,b, c).<ref>J. Kolosnjaj, et al., "13. Toxicity studies of fullerenes and derivatives," in W.C. Chan, ''Bioapplications of nanoparticles'' (Toronto, CA: Landes Biosciences, 2006), 168-180.</ref><ref>J. Kolosnjaj, H. Szwarc, and F. Moussa, Toxicity studies of carbon nanotubes, ''Adv. Exp. Med. Biol.'' 620: 181–204.</ref> These authors review the works on fullerene toxicity beginning in the early 1990s to present, and conclude that very little evidence gathered since the discovery of fullerenes indicate that C<sub>60</sub> is toxic.  
  
−
==Carbon nanotube fiber & film==
+
With reference to nanotubes, a recent study of Poland ''et al.'' (2008)<ref>C.A. Poland, R. Duffin, I. Kinloch, A. Maynard, W.A.H. Wallace, and A. Seaton et al. 2008, Carbon nanotubes introduced into the abdominal cavity of mice show asbestos-like pathogenicity in a pilot study, ''Nature Nanotechnology'' 3: 423.</ref> on carbon nanotubes introduced into the abdominal cavity of mice led the authors to suggest comparisons to "asbestos-like pathogenicity." It should be noted that this was not an inhalation study, though there have been several performed in the past, therefore it is premature to conclude that nanotubes should be considered to have a toxicological profile similar to asbestos. Conversely, and perhaps illustrative of how the various classes of compounds which fall under the general term fullerene cover a wide range of properties, Sayes, et al., found that ''in vivo'' inhalation of C60(OH)<sub>24</sub> and nano-C60 in rats gave no effect, whereas in comparison quartz particles produced an inflammatory response under the same conditions (Nano Letters, 2007, Vol. 7, No. 8, 2399-2406). As stated above, nanotubes are quite different in chemical and physical properties to C<sub>60</sub>, i.e., molecular weight, shape, size, physical properties (such as solubility) all are very different, so from a toxicological standpoint, different results for C<sub>60</sub> and nanotubes are not suggestive of any discrepancy in the findings.
−
One application for nanotubes that is currently being researched is high [[tensile strength]] [[fiber]]s. Two methods are currently being tested for the manufacture of such fibers. A French team has developed a liquid spun system that involves pulling a fiber of nanotubes from a bath which yields a product that is approximately 60% nanotubes. The other method, which is simpler but produces weaker fibers uses traditional melt-drawn [[polymer]] fiber techniques with nanotubes mixed in the [[polymer]]. After drawing, the fibers can have the polymer burned out of them to make them purely nanotube or they can be left as they are.  
 
  
−
Ray Baughman's group from the [[NanoTech Institute]] at [[University of Texas at Dallas]] produced the current toughest material known in mid-2003 by spinning fibers of single wall carbon nanotubes with [[polyvinyl alcohol]]. Beating the previous contender, [[spider silk]], by a factor of four, the fibers require 600 [[Joule|J]]/[[gram|g]] to break. In comparison, the bullet-resistant fiber [[Kevlar]] is 27-33J/g. In mid-2005 Baughman and co-workers from [[Australia]]'s [[Commonwealth Scientific and Industrial Research Organization]] developed a method for producing transparent carbon nanotube sheets 1/1000th the thickness of a human hair capable of supporting 50,000 times their own mass.
+
== Quantum mechanics ==
−
In August 2005, Ray Baughman's team managed to develop a fast method to manufacture up to seven meters per minute of nanotube tape [http://www.worldchanging.com/archives/003330.html]. Once washed with [[ethanol]], the ribbon is only 50 [[nanometer]]s thick; a square kilometer of the material would only weigh 30 kilograms.
+
In 1999, researchers from the University of Vienna demonstrated the [[wave-particle duality]] applied to molecules such as fullerene.<ref>M. Arndt, O. Nairz, J. Voss-Andreae, C. Keller, G. van der Zouw, and A. Zeilinger, Wave-particle duality of C60, ''Nature'' 401: 680–682.</ref> One of the co-authors of this research, [[Julian Voss-Andreae]], became an artist and has since created several sculptures [[fullerenes in popular culture|symbolizing wave-particle duality in Buckminsterfullerenes]].
  
−
In 2004 Alan Windle's group of scientists at the [[Cambridge-MIT Institute]] developed a way to make carbon nanotube fiber continuously at the speed of several centimetres per second just as nanotubes are produced. One thread of carbon nanotubes was more than 100 metres long. The resulting fibers are electrically conductive and as strong as ordinary textile threads. [http://news.bbc.co.uk/2/hi/science/nature/3872931.stm]
+
Science writer Marcus Chown stated on the CBC radio show, ''[[Quirks And Quarks]],'' in May 2006, that scientists are trying to make buckyballs exhibit the quantum behavior of existing in two places at once ([[quantum superposition]]).<ref>CBC, [http://www.cbc.ca/quirks/archives/05-06/jun17.html Quirks & Quarks.] Retrieved October 21, 2008.</ref>
−
[http://www.newscientist.com/news/news.jsp?id=ns99994769]
 
  
−
==Current progress==
+
==Fullerite (solid state)==
−
*In April of 2001, [[International Business Machines|IBM]] announced it had developed a technique for automatically developing pure [[semiconductor]] surfaces from nanotubes.
+
[[Image:C60-Fulleren-kristallin.JPG|thumb|right|250px|The ''C''<sub>60</sub> [[fullerene]] in crystalline form]]
−
*On [[September 19]], [[2003]], [[NEC Corporation]], [[Japan]], [http://www.nec.co.jp/press/en/0309/1901.html announced] stable fabrication technology of carbon nanotube transistors.
+
'''Fullerites''' are the solid-state manifestation of [[fullerene]]s and related compounds and materials.  
−
*High purity (80%) nanotubes were reported in June 2003 with metallic properties can be extracted with [[electrophoresis|electrophoretic]] techniques. [http://physicsweb.org/article/news/7/6/19/1]
 
−
*As of 2003, nanotubes cost from 20 euro per gram to 1000 euro per gram, depending on purity, composition (single-wall, double-wall, multi-wall) and other characteristics.
 
−
*In June 2004 scientists from China's [[Tsinghua University]] and [[Louisiana State University]] demonstrated the use of nanotubes in [[incandescent lamp]]s, replacing a [[tungsten]] [[filament]] in a [[lightbulb]] with a carbon nanotube one.
 
−
*In 2004, Nature published [http://healthspace.ca/Websites/Staff/AJP/DanglingParticiple.nsf/d6plinks/APRE-6B5UMS a photo] of an individual 4 cm long single-wall nanotube (SWNT).
 
−
*In August 2005, [[General Electric|GE]] announced the development of an ideal carbon nanotube [[diode]] that operates at the "theoretical limit," or best possible performance. The company also observed a [[photovoltaic effect]] in the nanotube diode device that could lead to breakthroughs in [[solar cell]]s that make them more efficient and a more viable alternative in the mainstream energy market.[http://www.research.ge.com/04_media/news/20050819_cnd.shtml]
 
−
*In September of 2005 Texas-based Applied Nanotech, in conjunction with six Japanese electronics firms, have created a prototype of a 25-inch TV using carbon nanotubes. The prototype TV does not suffer from "ghosting," as some types of digital TVs.
 
−
* In September 2005 researchers at [[Lawrence Livermore National Laboratory]] demonstrated that [[ignition]] by a conventional [[flashbulb]] takes place when a layer of 29% [[iron]] enriched SWNT is placed on top of a layer of [[explosive]] material such as [[PETN]]. With ordinary explosives optical ignition is only possible with high powered [[laser]]s [http://pubs3.acs.org/acs/journals/doilookup?in_doi=10.1021/ja0547127].
 
−
* In September 2005 researchers demonstrated a new way to coat MWNT's with [[magnetite]] which after orientation in a [[magnetic field]] were able to attract each other over a distance of at least 10 [[micrometre]]s.  [http://www.rsc.org/Publishing/Journals/CC/article.asp?doi=b506758h]. The nanotubes were functionalized with negatively charged [[carboxylic acid]] groups in a [[AIBN]] type [[free radical addition]]. Magnetite nanoparticles prepared by the [[magnetite|Massart method]] were given a positive charge by washing with [[nitric acid]] which made them stick to the nanotubes by [[electrostatic force]]s.
 
−
* In September 2005, Korean scientists lead by [[Pohang University of Science and Technology]] Professor Kim Kwang-Soo developed the longest carbon-nanotubes; they succceeded in pulling out the nested tubes from the multiwalled nanotubes (MWNTs). They extracted 1 millimeter, 1,000 times longer than the previous achievement of 1 micrometer.
 
  
−
==Carbon nanotubes in electrical circuits==
+
[[Polymerized]] [[Carbon nanotube|single-walled nanotubes]] (P-SWNT) are a class of fullerites and are comparable to [[diamond]] in terms of [[hardness]]. However, due to the way that [[nanotube]]s intertwine, P-SWNTs do not have the corresponding [[crystal lattice]] that makes it possible to cut diamonds neatly. This same structure results in a less brittle material, as any impact that the structure sustains is spread out throughout the material. Because nanotubes are still very expensive to produce in useful quantities, uses for a material lighter and stronger than [[steel]] will have to wait until nanotube production becomes more [[Economics|economically viable]].
  
−
Carbon nanotubes have many properties—from their unique dimensions to an unusual current [[electrical conduction|conduction]] mechanism—that make them ideal components of electrical circuits.  Currently, there is no reliable way to arrange carbon nanotubes into a circuit.
+
===Ultrahard fullerite, Buckyball===
 +
Ultrahard fullerite (C<sub>60</sub>) is a form of [[carbon]] synthesized under high pressure high temperature conditions. It is believed that fullerene molecules are three-dimensionally polymerized in this material.<ref>Lucy Sherriff, [http://www.theregister.com/2005/08/30/diamonds_hard_material Diamonds lose "world's hardest" title,] The Register. Retrieved October 21, 2008.</ref>
  
−
The major hurdles that must be jumped for carbon nanotubes to find prominent places in circuits relate to fabrication difficulties. The carbon nanotube production processes are very different from the traditional [[Fabrication (semiconductor)|IC fabrication process]]. The IC fabrication process is somewhat like [[sculpture]]—films are deposited onto a wafer and pattern-etched away. Carbon nanotubes are fundamentally different from films; they are like atomic-level spaghetti (and every bit as sticky).
+
== See also ==
−
 
+
* [[Allotrope]]
−
Researchers sometimes resort to manipulating nanotubes one-by-one with the tip of an [[atomic force microscope]] in a painstaking, time-consuming process. Perhaps the best hope is that carbon nanotubes can be grown through a [[chemical vapor deposition]] process from patterned [[catalyst]] material on a wafer, which serve as growth sites and allow designers to position one end of the nanotube. During the deposition process, an [[electric field]] can be applied to direct the growth of the nanotubes, which tend to grow along the field lines from negative to positive polarity. Another way for the self assembly of the carbon nanotube transistors consist in using chemical or biological techniques to place the nanotubes from solution to determinate place on a substrate.
+
* [[Buckypaper]]
−
 
+
* [[Carbon]]
−
Even if nanotubes could be precisely positioned, there remains the problem that, to this date, engineers have been unable to control the types of nanotubes—metallic, semiconducting, single-walled, multi-walled—produced. A [[chemical engineering|chemical engineers]] solution is needed if nanotubes are to become feasible for commercial circuits.
+
* [[Carbon nanotube]]
 +
* [[Diamond]]
 +
* [[Graphene]]
 +
* [[Graphite]]
  
−
==External links and sources==
+
== Notes ==
−
{{Commons|Carbon nanotube}}
+
<references/>
−
* [http://www.pa.msu.edu/cmp/csc/NTSite/nanopage.html The Nanotube site] - This site last update:  2005.08.05 (Friday) 10:08:05 EDT by David Tomanek.
 
−
* [http://deaddog.duch.udel.edu/~frey/research/tubegenonline.html "TubeGen Online: Web-Accessible Nanotube Structure Generator"]
 
−
* [http://www.xnri.com/English/rd/cnri/index.html Industrial source for MWNT] CNT manufacturer in Japan
 
−
* [http://www.future-carbon.de Multi-Wall-Nanotubes, Nanofibers, metallised Nanotubes] manufacturer in Germany
 
−
* [http://www.ntp.com.cn Commercial source of carbon nanotubes] NTP-nanotube manufacturer in China
 
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* [http://www.ahwahneetech.com Ahwahnee Technology] Silicon Valley carbon nanotube developer
 
−
* [http://students.chem.tue.nl/ifp03/Wondrous%20World%20of%20Carbon%20Nanotubes_Final.pdf The wonderous World of Carbon Nanotubes] (Good introduction to nanotubes)
 
−
* [http://www.newscientist.com/hottopics/tech/article.jsp?id=23864900&sub=Nanotechnology Jamieson V. "Open secret"  ''New Scientist'']
 
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* [http://www.nantero.com/mission.html Nantero] (developers of nanotube based non-volatile memory)
 
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* [http://www.cheng.cam.ac.uk/research/groups/biosci/hg_research.html University of Cambridge, UK, Research group website] (Affordable methods for making carbon nanotubes and using them for gene delivery)
 
−
* [http://www.utdallas.edu/dept/chemistry/nanotech University of Texas at Dallas NanoTech Institute]
 
−
* [http://nanoDiamond.info/ NanoDiamond] (nanotubes arranged in a diamond formation yielding a very high strength-to-weight ratio material)
 
−
* [http://www.vincentherr.com/cf/ Carbon Nanotube & Fullerene Models - Vincent Herr, Houston, TX]
 
−
* [http://www.sciencenews.org/articles/20030614/fob3.asp Science News - Nanotube Super Fibers] - From Science News, Vol. 163, No. 24, June 14, 2003, p. 372. No Updates.
 
−
* [http://nanotech-now.com Nanotube production surveys]  Last Update September 18, 2005
 
−
* [http://www.nanosprint.com/nanotubes/newsletter/ Carbon Nanotubes Monthly Newsletter] - focuses on various applications of carbon nanotubes and surveys research papers and issued patents
 
−
* [http://smalley.rice.edu/ Columbia University Nanoscale Science and Engineering Center presents "Our Energy Challege" September 23, 2003]
 
−
* [http://www.house.gov/science/hearings/energy03/dec04/smalley.htm Review of Non-Oil and Gas Research Activities in the Houston-Galveston-Gulf Coast Area]
 
−
* [http://www.helixmaterial.com/product.html commercial sources]
 
−
* [http://www.carbondesignsinc.com/ Carbon Designs, Inc.] Only home page. No technical data as of Sept 25, 2005.
 
−
* [http://trnmag.com/Stories/2004/120104/For_pure_nanotubes_add_water_120104.html "For pure nanotubes add water" article by  Eric Smalley 2004-12] "stands of single-wall carbon nanotubes as tall as 2.5 millimeters and 99.98 percent pure. Individual nanotubes range from one to three nanometers in diameter."
 
−
* [http://msnbc.msn.com/id/8976160/ Nanotubes show their strength in numbers (MSNBC, August 18, 2005)] Super-strong sheets could be used in future screens and surfaces
 
−
*[http://www.patagon.8m.com/equations/cnt.html Nanotube composites, current applications and challenges, electrical conductivity records in 2005]
 
−
*[http://nanotechweb.org nanotechweb.org: news on nanotubes and other fields of nanotechnology]
 
−
*[http://arxiv.org/abs/cond-mat/0310067 Bose-Einstein Condensation of Helium and Hydrogen inside Bundles of Carbon Nanotubes]
 
−
*[http://carbonnantotu.be Image of a carbon nanotube]
 
  
 
==References==
 
==References==
 +
* Aldersey-Williams, Hugh. ''The Most Beautiful Molecule: The Discovery of the Buckyball.'' Hoboken, NJ: John Wiley & Sons, 1995. ISBN 0471193333.
 +
* Fowler, P.W. and D.E. Manolopoulos. ''An Atlas of Fullerenes.'' Mineola, NY: Dover Publications, 2007. ISBN 0486453626.
 +
* Miessler, Gary L., and Donald A. Tarr. ''Inorganic Chemistry.'' Upper Saddle River, NJ: Pearson Education International, 2004. ISBN 978-0130354716
  
−
* [http://www.personal.rdg.ac.uk/~scsharip/bookpage.htm Carbon Nanotubes and Related Structures -  New Materials for the Twenty-First Century, P.J.F. Harris (Cambridge University Press, 1999)] Introductory textbook
+
==External links==
 +
All links retrieved May 15, 2017.
  
−
{{Journal reference | Author=Deepak Srivastava and Chenyu Wei| Title=Nanomechanics of Carbon Nanotubes and Composite | Journal=Applied Mechanics Review | Volume=56 | Issue=2 | Year=2003 | Pages=215–230}}
+
* [http://www.sesres.com/PhysicalProperties.asp Properties of C60 fullerene].
 +
* [http://cben.rice.edu/ Center for Biological and Environmental Nanotechnology].
 +
* [http://www.nobel.se/chemistry/laureates/1996/smalley-autobio.html Dr. Smalley's autobiography].
 +
* [http://www.kroto.info/ Sir Harry Kroto's webpage].
 +
* [http://www.ch.ic.ac.uk/rzepa/mim/century/html/c60.htm Buckminster Fullerene C60].
 +
* [http://www.classzone.com/books/earth_science/terc/content/visualizations/es0504/es0504page01.cfm Simple model of Fullerene.]
 +
* [http://www.news.ucdavis.edu/search/news_detail.lasso?id=7891 Story on "Buckyeggs" (UC Davis website)].
 +
* [http://www.chemistry.wustl.edu/~edudev/Fullerene/solidstate.html Introduction to fullerites].
  
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{{Journal reference | Author=Dong Qian et al. | Title=Mechanics of Carbon Nanotubes | Journal=Applied Mechanical Review | Volume=55 | Issue=6 | Year=2002 | Pages=495–533}}
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{{Allotropes of carbon}}
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Dekker, C., Carbon Nanotubes as Molecular Quantum Wires, Phys. Today, 1999, May, 22-28.
 
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* [http://www.mindspring.com/~kimall/Fuller/index.html Kim Allen]
 
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* [http://cnst.rice.edu/ Center for Nanoscale Science and Technology]
 
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* [http://www.nobel.se/chemistry/laureates/1996/smalley-autobio.html Dr. Smalley's brief autobiography]
 
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* [http://www.chem.rice.edu/CHEM_faculty_dtl.cfm?FDSID=437 Dr. Smalley's webpage]
 
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* [http://www.sciencedaily.com//releases/2003/04/030418081522.htm Potential use of fullerenes in medicine]
 
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* [http://www.vincentherr.com/cf/ Carbon Fullerene & Nanotube Models ] Vincent Herr, Houston, TX
 
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* [http://3dscience.com/nanotechnology_buckyball_fullerene.asp Fullerene Images for Web and Presentation]
 
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* [http://www.physorg.com/news1667.html Discovery of graphene]
 
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* [http://www.quantum.univie.ac.at/research/matterwave/c60/index.html Diffraction and Interference with Fullerenes: Wave-particle duality of C60], University of Vienna
 
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* Fullerene-based architectures for quantum computing in [http://www.physik.fu-berlin.de/~ag-harneit Germany] and in [http://www.nanotech.org Great Britain] at the [http://www.qipirc.org QIP IRC]
 
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* [http://www.bluerhinos.co.uk/molview/indv.php?id=3 Molview from bluerhinos.co.uk] See Buckminsterfullerene (C<sub>60</sub>) in 3D
 
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* [http://www.sciencetechnologies.com/molviz/molviz.swf Interactive 3D molecular visualization of fullerene] (requires [[Macromedia Flash]])
 
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* [http://www.compchemwiki.org/index.php?title=Buckminsterfullerene Computational Chemistry Wiki]
 
  
 
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Revision as of 08:05, 18 October 2022

Part of a series of articles on
Nanomaterials

Fullerenes
Carbon nanotubes
Fullerene chemistry
Applications
In popular culture
Timeline
Carbon allotropes

Nanoparticles
Quantum dots
Nanostructures
Colloidal gold
Colloidal silver
Iron nanoparticles
Platinum nanoparticles

See also
Nanotechnology

"C60" and "C-60" redirect here.

Fullerenes are a family of carbon allotropes (other allotropes of carbon are graphite and diamond) consisting of molecules composed entirely of carbon atoms arranged in the form of hollow spheres, ellipsoids, or tubes. Each molecule generally has both pentagonal and hexagonal faces.

The most common fullerene is Buckminsterfullerene, in which each molecule is composed of 60 carbon atoms that together take the shape of a soccer ball. It was named after Richard Buckminster Fuller, because its shape resembles Fuller's design of a geodesic dome. By extension, spherical fullerenes are often called buckyballs, and cylindrical ones are called buckytubes, or, more accurately, carbon nanotubes. Fullerenes are similar in structure to graphite, which is composed of stacked sheets of linked hexagonal rings. In the case of a fullerene, however, the presence of pentagonal (or sometimes heptagonal) rings prevents its sheets from being planar.

Chemists can now produce various derivatives of fullerenes. For example, hydrogen atoms, halogen atoms, or organic functional groups can be attached to fullerene molecules. Also, metal ions, noble gas atoms, or small molecules can be trapped in the cage-like structures of fullerene molecules, producing complexes that are known as endohedral fullerenes. If one or more carbon atoms in a fullerene molecule is replaced by metal atoms, the resultant compound is called a fulleride. Some doped fullerenes (doped with potassium or rubidium atoms, for example) are superconductors at relatively high temperatures.

Potential applications of fullerenes include the preparation of pharmaceuticals, lubricants, catalysts, and superconductors.

A model of the icosahedral fullerene C540.
A model of Buckminsterfullerene, C60, showing ground state electron density.

Coining the name

Buckminsterfullerene (C60) was named after Richard Buckminster Fuller, a noted architectural modeler who popularized the geodesic dome. Since buckminsterfullerenes have a similar shape to that sort of dome, the name was thought to be appropriate. As the discovery of the fullerene family came after buckminsterfullerene, the shortened name "fullerene" was used to refer to the family of fullerenes.

Prediction and discovery

In 1970, Eiji Osawa of Toyohashi University of Technology predicted the existence of C60 molecules. He noticed that the structure of a corannulene molecule was a subset of a soccer-ball shape, and he made the hypothesis that a full ball shape could also exist. His idea was reported in Japanese magazines, but did not reach Europe or America.

In molecular beam experiments, discrete peaks were observed corresponding to molecules with the exact masses of 60, 70, or more carbon atoms. In 1985, Harold Kroto (then at the University of Sussex), James R. Heath, Sean O'Brien, Robert Curl, and Richard Smalley, of Rice University, discovered C60, and shortly thereafter discovered other fullerenes.[1] The first nanotubes were obtained in 1991.[2]

Kroto, Curl, and Smalley were awarded the 1996 Nobel Prize in Chemistry for their roles in the discovery of this class of compounds.

Natural occurrence and artificial production

Minute quantities of the fullerenes—in the form of C60, C70, C76, and C84 molecules—have been found in soot and in the residue of carbon arc lamps. These molecules are also produced by lightning discharges in the atmosphere.[3] Some analyses indicate that they are present in meteorites and interstellar dust. Recently, Buckminsterfullerenes were found in a family of minerals known as Shungites in Karelia, Russia.

A common method used to produce fullerenes is to send a large current between two nearby graphite electrodes in an inert atmosphere. The resultant carbon plasma arc between the electrodes cools into sooty residue from which many fullerenes can be isolated.

By 1991, it became relatively easy to produce gram-sized samples of fullerene powder using the techniques of Donald Huffman and Wolfgang Krätschmer. However, purification of fullerenes remains a challenge.

Structural variations

Since the discovery of fullerenes in 1985, a number of structural variations of fullerenes have been found. Examples include:[4]

  • buckyball clusters: Smallest member is C 20 (unsaturated version of dodecahedrane) and the most common is C 60
  • Nanotubes: Hollow tubes of very small dimensions, having single or multiple walls; potential applications in electronics industry
  • Megatubes: Larger in diameter than nanotubes and prepared with walls of different thickness; potentially used for the transport of a variety of molecules of different sizes[5]
  • Polymers: Chain, two-dimensional and three-dimensional polymers are formed under high pressure high temperature conditions
  • Nano onions: Spherical particles based on multiple carbon layers surrounding a buckyball core; proposed for lubricant[6]
  • Linked "ball-and-chain" dimers: Two buckyballs linked by a carbon chain[7]
  • Fullerene rings[8]

Buckyballs

Buckminsterfullerene C60
A soccer ball is a model of the Buckminsterfullerene C60

Buckminsterfullerene

Buckminsterfullerene (IUPAC name (C60-Ih)[5,6]fullerene) is the smallest fullerene molecule in which no two pentagons share an edge (which can be destabilizing). It is also the most common in terms of natural occurrence, as it can often be found in soot.

The structure of C60 is a truncated (T = 3) icosahedron, which resembles a soccer ball of the type made of twenty hexagons and twelve pentagons, with a carbon atom at the vertices of each polygon and a bond along each polygon edge.

The van der Waals diameter of a C60 molecule is about 1 nanometer (nm). The nucleus to nucleus diameter of a C60 molecule is about 0.7 nm.

The C60 molecule has two bond lengths. The 6:6 ring bonds (between two hexagons) can be considered "double bonds" and are shorter than the 6:5 bonds (between a hexagon and a pentagon).

Boron buckyball

A new type of buckyball utilizing boron atoms instead of the usual carbon has been predicted and described by researchers at Rice University. The B-80 structure is predicted to be more stable than the C-60 buckyball.[9] One reason for this given by the researchers is that the B-80 is actually more like the original geodesic dome structure popularized by Buckminster Fuller which utilizes triangles rather than hexagons.

Variations of buckyballs

Besides C60, a fairly common buckyball is C70,[10] but fullerenes with 72, 76, 84, and even up to 100 carbon atoms are commonly obtained.

In mathematical terms, the structure of a fullerene is a trivalent convex polyhedron with pentagonal and hexagonal faces. In graph theory, the term fullerene refers to any 3-regular, planar graph with all faces of size 5 or 6 (including the external face). It follows from Euler's polyhedron formula, |V|-|E|+|F| = 2, (where |V|, |E|, |F| indicate the number of vertices, edges, and faces), that there are exactly 12 pentagons in a fullerene and |V|/2-10 hexagons.

Graph of 20-fullerene w-nodes.svg File:Graph of 26-fullerene 5-base w-nodes.svg Graph of 60-fullerene w-nodes.svg File:Graph of 70-fullerene w-nodes.svg
20-fullerene
(dodecahedral graph) 		26-fullerene graph 60-fullerene
(truncated icosahedral graph) 		70-fullerene graph

The smallest fullerene is the dodecahedron—the unique C20. There are no fullerenes with 22 vertices. The number of fullerenes C2n grows with increasing n = 12,13,14…, roughly in proportion to n9. For instance, there are 1812 non-isomorphic fullerenes C60. Note that only one form of C60, the buckminsterfullerene alias truncated icosahedron, has no pair of adjacent pentagons (the smallest such fullerene). To further illustrate the growth, there are 214,127,713 non-isomorphic fullerenes C200, 15,655,672 of which have no adjacent pentagons.

Trimetasphere carbon nanomaterials were discovered by researchers at Virginia Tech and licensed exclusively to Luna Innovations. This class of novel molecules comprises 80 carbon atoms (C80) forming a sphere which encloses a complex of three metal atoms and one nitrogen atom. These fullerenes encapsulate metals which puts them in the subset referred to as metallofullerenes. Trimetaspheres have the potential for use in diagnostics (as safe imaging agents), therapeutics and in organic solar cells.

Carbon nanotubes

This animation of a rotating Carbon nanotube shows its 3D structure.
Main article: Carbon nanotube

Nanotubes are cylindrical fullerenes. These tubes of carbon are usually only a few nanometers wide, but they can range from less than a micrometer to several millimeters in length. They often have closed ends, but can be open-ended as well. There are also cases in which the tube reduces in diameter before closing off. Their unique molecular structure results in extraordinary macroscopic properties, including high tensile strength, high electrical conductivity, high ductility, high resistance to heat, and relative chemical inactivity (as it is cylindrical and "planar"—that is, it has no "exposed" atoms that can be easily displaced). One proposed use of carbon nanotubes is in paper batteries, developed in 2007 by researchers at Rensselaer Polytechnic Institute.[11] Another proposed use in the field of space technologies and science fiction is to produce high-tensile carbon cables required by a space elevator.

Carbon nanobuds

Nanobuds have been obtained by adding Buckminsterfullerenes to carbon nanotubes.

Properties

For the past decade, the chemical and physical properties of fullerenes have been a hot topic in the field of research and development, and are likely to continue to be for a long time. Popular Science has published articles about the possible uses of fullerenes in armor. In April 2003, fullerenes were under study for potential medicinal use: Binding specific antibiotics to the structure to target resistant bacteria and even target certain cancer cells such as melanoma. The October 2005 issue of Chemistry and Biology contains an article describing the use of fullerenes as light-activated antimicrobial agents.[12]

In the field of nanotechnology, heat resistance, and superconductivity are some of the more heavily studied properties.

There are many calculations that have been done using ab initio Quantum Methods applied to fullerenes. By density functional theory (DFT) and Time-dependent density functional theory (TD-DFT) methods, one can obtain IR, Raman and UV spectra. Results of such calculations can be compared with experimental results.

Aromaticity

Researchers have been able to increase the reactivity of fullerenes by attaching active groups to their surfaces. Buckminsterfullerene does not exhibit "superaromaticity:" That is, the electrons in the hexagonal rings do not delocalize over the whole molecule.

A spherical fullerene of n carbon atoms has n pi-bonding electrons. These should try to delocalize over the whole molecule. The quantum mechanics of such an arrangement should be like one shell only of the well-known quantum mechanical structure of a single atom, with a stable filled shell for n = 2, 8, 18, 32, 50, 72, 98, 128, and so on; that is, twice a perfect square; but this series does not include 60. As a result, C60 in water tends to pick up two more electrons and become an anion. The nC60 described below may be the result of C60's trying to form a loose metallic bonding.

Chemistry

Fullerenes are stable, but not totally unreactive. They are unusual reactants in many organic reactions such as the Bingel reaction discovered in 1993.

Planar graphite is made up of carbon atoms that are at their energy minimum, with outer orbitals that are said to be "sp2-hybridized." These orbitals must be bent to form the closed sphere or tube of a buckyball or buckytube, producing angle strain. The characteristic reaction of fullerenes is electrophilic addition at 6,6-double bonds, which reduces angle strain by changing sp2-hybridized carbons into sp3-hybridized ones. The change in hybridized orbitals causes the bond angles to decrease from about 120 degrees in the sp2 orbitals to about 109.5 degrees in the sp3 orbitals. This decrease in bond angles allows for the bonds to bend less when closing the sphere or tube, and thus, the molecule becomes more stable.

Other atoms can be trapped inside fullerenes to form inclusion compounds known as endohedral fullerenes. An unusual example is the egg shaped fullerene Tb3N@C84, which violates the isolated pentagon rule.[13] Recent evidence for a meteor impact at the end of the Permian period was found by analyzing noble gases so preserved.[14]

Solubility

Fullerenes are sparingly soluble in many solvents. Common solvents for the fullerenes include aromatics, such as toluene, and others like carbon disulfide. Solutions of pure Buckminsterfullerene have a deep purple color. Solutions of C70 are a reddish brown. The higher fullerenes C76 to C84 have a variety of colors. C76 has two optical forms, while other higher fullerenes have several structural isomers. Fullerenes are the only known allotrope of carbon that can be dissolved in common solvents at room temperature.

Some fullerene structures are not soluble because they have a small band gap between the ground and excited states. These include the small fullerenes C28,[15] C36 and C50. The C72 structure is also in this class, but the endohedral version with a trapped lanthanide-group atom is soluble due to the interaction of the metal atom and the electronic states of the fullerene. Researchers had originally been puzzled by C72 being absent in fullerene plasma-generated soot extract, but found in endohedral samples. Small band gap fullerenes are highly reactive and bind to other fullerenes or to soot particles.

Solvents that are able to dissolve buckminsterfullerene (C60) are listed below in order from highest solubility. The value in parentheses is the approximate saturated concentration.[16]

  1. 1-chloronaphthalene (51 mg/mL)
  2. 1-methylnaphthalene (33 mg/mL)
  3. 1,2-dichlorobenzene (24 mg/mL)
  4. 1,2,4-trimethylbenzene (18 mg/mL)
  5. tetrahydronaphthalene (16 mg/mL)
  6. carbon disulfide (8 mg/mL)
  7. 1,2,3-tribromopropane (8 mg/mL)
  8. bromoform (5 mg/mL)
  9. toluene (3 mg/ml)
  10. benzene (1.5 mg/ml)
  11. cyclohexane (1.2 mg/ml)
  12. carbon tetrachloride (0.4 mg/ml)
  13. chloroform (0.25 mg/ml)
  14. n-hexane (0.046 mg/ml)
  15. tetrahydrofuran (0.006 mg/ml)
  16. acetonitrile (0.004 mg/ml)
  17. methanol (0.00004 mg/ml)
  18. water (1.3x10-11 mg/mL)

Solubility of C60 in some solvents shows unusual behavior due to existence of solvate phases (analogues of crystallohydrates). For example, solubility of C60 in benzene solution shows maximum at about 313 K. Crystallization from benzene solution at temperatures below maximum results in formation of triclinic solid solvate with four benzene molecules C60•4C6H6 which is rather unstable in air. Out of solution, this structure decomposes into usual fcc C60 in few minutes' time. At temperatures above solubility maximum the solvate is not stable even when immersed in saturated solution and melts with formation of fcc C60. Crystallization at temperatures above the solubility maximum results in formation of pure fcc C60. Large millimeter size crystals of C60 and C70 can be grown from solution both for solvates and for pure fullerenes.[17][18]

Safety and toxicity

When considering toxicological data, care must be taken to distinguish as necessary between what are normally referred to as fullerenes: (C60, C70,…); fullerene derivatives: C60 or other fullerenes with covalently bonded chemical groups; fullerene complexes (for example, C60-PVP, host-guest complexes), where the fullerene is physically bound to another molecule; C60 nanoparticles, which are extended solid-phase aggregates of C60 crystallites; and nanotubes, which are generally much larger (in terms of molecular weight and size) compounds, and are different in shape to the spheroidal fullerenes C60 and C70, as well as having different chemical and physical properties.

The above different compounds span the range from insoluble materials in either hydrophilic or lipophilic media, to hydrophilic, lipophilic, or even amphiphilic compounds, and with other varying physical and chemical properties. Therefore any broad generalization extrapolating for example results from C60 to nanotubes or vice versa is not possible, though technically all are fullerenes, as the term is defined as a close-caged all-carbon molecule. Any extrapolation of results from one compound to other compounds must take into account considerations based on a Quantitative Structural Analysis Relationship Study (QSARS), which mostly depends on how close the compounds under consideration are in physical and chemical properties.

In 1996[19] and 1997, Moussa et al. studied the in vivo toxicity of C60 after intra-peritoneal administration of large doses. No evidence of toxicity was found and the mice tolerated a dose of 5 000 mg/kg of body weight (BW). Mori et al. (2006)[20] could not find toxicity in rodents for C60 and C70 mixtures after oral administration of a dose of 2 000 mg/kg BW and did not observed evidence of genotoxic or mutagenic potential in vitro. Other studies could not establish the toxicity of fullerenes: On the contrary, the work of Gharbi et al. (2005)[21] suggested that aqueous C60 suspensions failing to produce acute or subacute toxicity in rodents could also protect their livers in a dose-dependent manner against free-radical damage.

A comprehensive and recent review on fullerene toxicity is given by Kolosnjaj et al. (2007a,b, c).[22][23] These authors review the works on fullerene toxicity beginning in the early 1990s to present, and conclude that very little evidence gathered since the discovery of fullerenes indicate that C60 is toxic.

With reference to nanotubes, a recent study of Poland et al. (2008)[24] on carbon nanotubes introduced into the abdominal cavity of mice led the authors to suggest comparisons to "asbestos-like pathogenicity." It should be noted that this was not an inhalation study, though there have been several performed in the past, therefore it is premature to conclude that nanotubes should be considered to have a toxicological profile similar to asbestos. Conversely, and perhaps illustrative of how the various classes of compounds which fall under the general term fullerene cover a wide range of properties, Sayes, et al., found that in vivo inhalation of C60(OH)24 and nano-C60 in rats gave no effect, whereas in comparison quartz particles produced an inflammatory response under the same conditions (Nano Letters, 2007, Vol. 7, No. 8, 2399-2406). As stated above, nanotubes are quite different in chemical and physical properties to C60, i.e., molecular weight, shape, size, physical properties (such as solubility) all are very different, so from a toxicological standpoint, different results for C60 and nanotubes are not suggestive of any discrepancy in the findings.

Quantum mechanics

In 1999, researchers from the University of Vienna demonstrated the wave-particle duality applied to molecules such as fullerene.[25] One of the co-authors of this research, Julian Voss-Andreae, became an artist and has since created several sculptures symbolizing wave-particle duality in Buckminsterfullerenes.

Science writer Marcus Chown stated on the CBC radio show, Quirks And Quarks, in May 2006, that scientists are trying to make buckyballs exhibit the quantum behavior of existing in two places at once (quantum superposition).[26]

Fullerite (solid state)

The C60 fullerene in crystalline form

Fullerites are the solid-state manifestation of fullerenes and related compounds and materials.

Polymerized single-walled nanotubes (P-SWNT) are a class of fullerites and are comparable to diamond in terms of hardness. However, due to the way that nanotubes intertwine, P-SWNTs do not have the corresponding crystal lattice that makes it possible to cut diamonds neatly. This same structure results in a less brittle material, as any impact that the structure sustains is spread out throughout the material. Because nanotubes are still very expensive to produce in useful quantities, uses for a material lighter and stronger than steel will have to wait until nanotube production becomes more economically viable.

Ultrahard fullerite, Buckyball

Ultrahard fullerite (C60) is a form of carbon synthesized under high pressure high temperature conditions. It is believed that fullerene molecules are three-dimensionally polymerized in this material.[27]

See also

Notes

  1. ↑ H.W. Kroto, J.R. Heath, S.C. O'Brien, R.F. Curl, and R.E. Smalley, C60: Buckminsterfullerene, Nature 318: 162–163.
  2. ↑ Machine Design, A new buckyball bounces into town. Retrieved October 21, 2008.
  3. ↑ ASU, World of Carbon, The Allotropes of Carbon. Retrieved October 21, 2008.
  4. ↑ Gary L. Miessler and Donald A. Tarr, Inorganic Chemistry (Upper Saddle River, NJ: Pearson Education International, 2004, ISBN 0131201980).
  5. ↑ D.R. Mitchel, et al., The Synthesis of Megatubes: New Dimensions in Carbon Materials, Inorg. Chem. 40: 2751.
  6. ↑ N. Sano, Synthesis of carbon "onions" in water, Nature (London) 414: 506.
  7. ↑ A.A. Shvartsburg, Observation of “Stick” and “Handle” Intermediates along the Fullerene Road, J. Phys. Chem. 103: 5275.
  8. ↑ Y. Li, et al., Structures and stabilities of C60-rings, Chem. Phys. Lett. 335: 524.
  9. ↑ Jade Boyd, Bucky's brother—The boron buckyball makes its début, eurekalert.org. Retrieved October 21, 2008.
  10. ↑ bristol.ac.uk, Buckminsterfullerene: Molecule of the Month. Retrieved October 21, 2008.
  11. ↑ V.L. Pushparaj, M.M. Shaijumon, A. Kumar, S. Murugesan, L. Ci, R. Vajtai, R.J. Linhardt, O. Nalamasu, and P.M. Ajayan, Flexible energy storage devices based on nanocomposite paper, Proceedings of the National Academy of Sciences 104(34): 13574.
  12. ↑ G. Tegos and T. Demidova, D. Arcila-Lopez, H. Lee, T. Wharton, H. Gali, and M. Hamblin, 2005, Cationic Fullerenes Are Effective and Selective Antimicrobial Photosensitizers, Chemistry & Biology 12(10): 1127–1135. Retrieved October 21, 2008.
  13. ↑ C.M. Beavers, T. Zuo, J.C. Duchamp, K. Harich, H.C. Dorn, M.M. Olmstead, and A.L. Balch, Tb3N@C84: An improbable, egg-shaped endohedral fullerene that violates the isolated pentagon rule, Journal of the American Chemical Society 128(35): 11352–3.
  14. ↑ Luann Becker and Robert J. Poreda, Andrew G. Hunt, Theodore E. Bunch, and Michael Rampino, 2007, Impact Event at the Permian-Triassic Boundary: Evidence from Extraterrestrial Noble Gases in Fullerenes, Science 291(5508): 1530–3.
  15. ↑ Ting Guo, Richard E. Smalley, and Gustavo E. Scuseria, Ab initio theoretical predictions of C28, C28H4, C28F4, (Ti at C28)H4, and M at C28 (M = Mg, Al, Si, S, Ca, Sc, Ti, Ge, Zr, and Sn), Harvard. Retrieved October 21, 2008.
  16. ↑ V.N. Bezmel'nitsyn, A.V. Eletskiĭ, and M.V. Okun', Uspekhi Fizicheskikh Nauk. (Fullerenes in Solutions). Russian Academy of Sciences 41.
  17. ↑ A.V. Talyzin, Phase transition C60-C60*4C6H6 in liquid benzene, J. of Phys. Chem. 101(47).
  18. ↑ A.V. Talyzin, I. Engstrцm, C70 in a Benzene, Hexane and Toluene solutions, J. of Phys. Chem. 102(34): 6477–6481.
  19. ↑ F. Moussa, et al., In vivo studies of fullerene-based materials using endohedral metallofullerene radiotracers, Fullerene Sci. Technol. 4: 21–29.
  20. ↑ T. Mori, et al., Preclinical studies on safety of fullerene upon acute oral administration and evaluation for no mutagenesis, Toxicology 225: 48–54.
  21. ↑ Najla Gharbi, M. Pressac, M. Hadchouel, H. Szwarc, S.R. Wilson, and F. Moussa, 2005, [60]fullerene is a powerful antioxidant in vivo with no acute or subacute toxicity, Nano Letters 5(12):2578–2585.
  22. ↑ J. Kolosnjaj, et al., "13. Toxicity studies of fullerenes and derivatives," in W.C. Chan, Bioapplications of nanoparticles (Toronto, CA: Landes Biosciences, 2006), 168-180.
  23. ↑ J. Kolosnjaj, H. Szwarc, and F. Moussa, Toxicity studies of carbon nanotubes, Adv. Exp. Med. Biol. 620: 181–204.
  24. ↑ C.A. Poland, R. Duffin, I. Kinloch, A. Maynard, W.A.H. Wallace, and A. Seaton et al. 2008, Carbon nanotubes introduced into the abdominal cavity of mice show asbestos-like pathogenicity in a pilot study, Nature Nanotechnology 3: 423.
  25. ↑ M. Arndt, O. Nairz, J. Voss-Andreae, C. Keller, G. van der Zouw, and A. Zeilinger, Wave-particle duality of C60, Nature 401: 680–682.
  26. ↑ CBC, Quirks & Quarks. Retrieved October 21, 2008.
  27. ↑ Lucy Sherriff, Diamonds lose "world's hardest" title, The Register. Retrieved October 21, 2008.

References
ISBN links support NWE through referral fees

  • Aldersey-Williams, Hugh. The Most Beautiful Molecule: The Discovery of the Buckyball. Hoboken, NJ: John Wiley & Sons, 1995. ISBN 0471193333.
  • Fowler, P.W. and D.E. Manolopoulos. An Atlas of Fullerenes. Mineola, NY: Dover Publications, 2007. ISBN 0486453626.
  • Miessler, Gary L., and Donald A. Tarr. Inorganic Chemistry. Upper Saddle River, NJ: Pearson Education International, 2004. ISBN 978-0130354716

External links

All links retrieved May 15, 2017.

Allotropes of carbon
Common forms: Amorphous carbon - Graphite - Diamond
Exotic : Fullerenes: Buckminsterfullerene · Carbon nanotube · Carbon nanobud - Aggregated diamond nanorods - Glassy carbon - Carbon nanofoam - Lonsdaleite
Other : Chaoite - Prismane C8 - Tricarbon - Atomic carbon

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