Editing Fullerene (section)

==Types==
There are two major families of fullerenes, with fairly distinct properties and applications: the closed buckyballs and the open-ended cylindrical carbon nanotubes.<ref name="miess2004">{{Cite book |last1=Miessler |first1=G.L. |url=https://archive.org/details/inorganicchemist03edmies |title=Inorganic Chemistry |last2=Tarr |first2=D.A. |publisher=[[Pearson Education]] |year=2004 |isbn=978-0-13-120198-9 |edition=3rd |url-access=registration}}</ref> However, hybrid structures exist between those two classes, such as [[carbon nanobuds]] — nanotubes capped by [[wikt:hemisphere|hemispherical]] meshes or larger "buckybuds".

===Buckyballs===
[[Image:c60 isosurface.png|thumb|right|{{chem|C|60}} with isosurface of ground state electron density as calculated with [[Density functional theory|DFT]]]]
[[Image:C60 Buckyball.gif|thumb|right|Rotating view of {{chem|C|60}}, one kind of fullerene]]

====Buckminsterfullerene====
{{main|Buckminsterfullerene}}
Buckminsterfullerene is the smallest fullerene molecule containing pentagonal and hexagonal rings in which no two pentagons share an edge (which can be destabilizing, as in [[pentalene]]). It is also most common in terms of natural occurrence, as it can often be found in [[soot]].

The empirical formula of buckminsterfullerene is {{chem|C|60}} and its structure is a [[truncated icosahedron]], which resembles an [[Association football (ball)|association football 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 buckminsterfullerene molecule is about 1.1 [[nanometer]]s (nm).<ref>{{Cite journal |last1=Qiao |first1=Rui |last2=Roberts |first2=Aaron P. |last3=Mount |first3=Andrew S. |last4=Klaine |first4=Stephen J. |last5=Ke |first5=Pu Chun |display-authors=3 |year=2007 |title=Translocation of {{chem|C|60}} and Its Derivatives Across a Lipid Bilayer |journal=Nano Letters |volume=7 |issue=3 |pages=614–9 |bibcode=2007NanoL...7..614Q |citeseerx=10.1.1.725.7141 |doi=10.1021/nl062515f |pmid=17316055}}</ref> The nucleus to nucleus diameter of a buckminsterfullerene molecule is about 0.71&nbsp;nm.

The buckminsterfullerene molecule has two bond lengths. The 6:6 ring bonds (between two hexagons) can be considered "[[double bond]]s" and are shorter  (1.401 Å) than the 6:5 bonds (1.458 Å, between a hexagon and a pentagon). The weighted average bond length is 1.44 Å.<ref>{{Cite journal |last1=Hedberg |first1=Kenneth |last2=Hedberg |first2=Lise |last3=Bethune |first3=Donald S. |last4=Brown |first4=C. A. |last5=Dorn |first5=H. C. |last6=Johnson |first6=Robert D. |last7=De Vries |first7=M. |date=1991-10-18 |title=Bond Lengths in Free Molecules of Buckminsterfullerene, C 60, from Gas-Phase Electron Diffraction |url=https://www.science.org/doi/10.1126/science.254.5030.410 |journal=Science |language=en |volume=254 |issue=5030 |pages=410–412 |doi=10.1126/science.254.5030.410 |pmid=17742230 |issn=0036-8075}}</ref>

====Other fullerenes====
[[File:Fullerene_C70.png|thumb|{{chem|C|70}} has 10 additional atoms (shown in red) added to {{chem|C|60}} and a hemisphere rotated to fit]]
Another fairly common fullerene has empirical formula {{chem|C|70}},<ref>{{Cite web |last=Locke |first=W. |date=13 October 1996 |title=Buckminsterfullerene: Molecule of the Month |url=http://www.bristol.ac.uk/Depts/Chemistry/MOTM/buckyball/c60a.htm |access-date=4 July 2010 |publisher=[[Imperial College]]}}</ref> but fullerenes with 72, 76, 84 and even up to 100 carbon atoms are commonly obtained.

The smallest possible fullerene is the [[Dodecahedron|dodecahedral]] {{chem|C|20}}. There are no fullerenes with 22 vertices.<ref>{{Cite journal |last=Meija |first=Juris |year=2006 |title=Goldberg Variations Challenge |url=https://www.springer.com/cda/content/document/cda_downloaddocument.pdf?SGWID=0-0-45-275900-0 |journal=[[Analytical and Bioanalytical Chemistry]] |volume=385 |issue=1 |pages=6–7 |doi=10.1007/s00216-006-0358-9 |pmid=16598460 |s2cid=95413107}}</ref> The number of different fullerenes C<sub>2n</sub> grows with increasing ''n''&nbsp;=&nbsp;12,&nbsp;13,&nbsp;14,&nbsp;..., roughly in proportion to ''n''<sup>9</sup> {{OEIS|id=A007894}}. For instance, there are 1812 non-isomorphic fullerenes {{chem|C|60}}. Note that only one form of {{chem|C|60}}, buckminsterfullerene, has no pair of adjacent pentagons (the smallest such fullerene). To further illustrate the growth, there are 214,127,713 non-isomorphic fullerenes {{chem|C|200}}, 15,655,672 of which have no adjacent pentagons. Optimized structures of many fullerene isomers are published and listed on the web.<ref>Fowler, P. W. and Manolopoulos, D. E. [https://web.archive.org/web/20150109011908/http://www.nanotube.msu.edu/fullerene/fullerene-isomers.html {{chem|C|''n''}} Fullerenes]. nanotube.msu.edu</ref>

[[Heterofullerene]]s have heteroatoms substituting carbons in cage or tube-shaped structures. They were discovered in 1993<ref>Harris, D.J. "Discovery of Nitroballs: Research in Fullerene Chemistry" http://www.usc.edu/CSSF/History/1993/CatWin_S05.html {{Webarchive|url=https://web.archive.org/web/20151129202804/http://www.usc.edu/CSSF/History/1993/CatWin_S05.html |date=29 November 2015 }}</ref> and greatly expand the overall fullerene class of compounds and can have dangling bonds on their surfaces. Notable examples include boron, nitrogen ([[azafullerene]]), oxygen, and phosphorus derivatives.

===Carbon nanotubes===
[[Image:Kohlenstoffnanoroehre Animation.gif|frame|This rotating model of a [[carbon nanotube]] shows its 3D structure.]]
[[Carbon nanotubes]] are cylindrical fullerenes. These tubes of carbon are usually only a few nanometres 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 [[Ultimate tensile strength|tensile strength]], high [[electrical conductivity]], high [[ductility]], high [[Thermal conductivity|heat conductivity]], and relative [[Chemically inert|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>{{Cite journal |last1=Pushparaj |first1=V.L. |last2=Shaijumon, Manikoth M. |last3=Kumar |first3=A. |last4=Murugesan |first4=S. |last5=Ci |first5=L. |last6=Vajtai |first6=R. |last7=Linhardt |first7=R. J. |last8=Nalamasu |first8=O. |last9=Ajayan |first9=P. M. |display-authors=3 |year=2007 |title=Flexible energy storage devices based on nanocomposite paper |journal=[[Proceedings of the National Academy of Sciences]] |volume=104 |issue=34 |pages=13574–7 |bibcode=2007PNAS..10413574P |doi=10.1073/pnas.0706508104 |pmc=1959422 |pmid=17699622 |doi-access=free}}</ref> Another highly speculative proposed use in the field of space technologies is to produce high-tensile carbon cables required by a [[space elevator]].