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Spherical fullerenes, also referred to as Buckminsterfullerenes or buckyballs, resemble the balls used in association football. Cylindrical fullerenes are also called carbon nanotubes buckytubes. Fullerenes are similar in structure to graphite , which is composed of stacked graphene sheets of linked hexagonal rings. Unless they are cylindrical, they must also contain pentagonal or sometimes heptagonal rings.
The name was an homage to Buckminster Fuller , whose geodesic domes it resembles. The structure was also identified some five years earlier by Sumio Iijima , from an electron microscope image, where it formed the core of a "bucky onion".
The discovery of fullerenes greatly expanded the number of known carbon allotropes , which had previously been limited to graphite , graphene , diamond , and amorphous carbon such as soot and charcoal. Buckyballs and buckytubes have been the subject of intense research, both for their chemistry and for their technological applications, especially in materials science , electronics , and nanotechnology.
The icosahedral C 60 H 60 cage was mentioned in as a possible topological structure. Japanese scientific journals reported his idea, but neither it nor any translations of it reached Europe or the Americas.
Also in , R. Henson then of the Atomic Energy Research Establishment proposed the structure and made a model of C Unfortunately, the evidence for this new form of carbon was very weak and was not accepted, even by his colleagues. The results were never published but were acknowledged in Carbon in In , independently from Henson, a group of scientists from the USSR made a quantum-chemical analysis of the stability of C 60 and calculated its electronic structure.
As in the previous cases, the scientific community did not accept the theoretical prediction. In mass spectrometry discrete peaks appeared corresponding to molecules with the exact mass of sixty or seventy or more carbon atoms. C 60 and other fullerenes were later noticed occurring outside the laboratory for example, in normal candle - soot.
By it was relatively easy to produce gram-sized samples of fullerene powder using the techniques of Donald Huffman , Wolfgang Krätschmer , Lowell D. Lamb , and Konstantinos Fostiropoulos. Fullerene purification remains a challenge to chemists and to a large extent determines fullerene prices.
So-called endohedral fullerenes have ions or small molecules incorporated inside the cage atoms. Fullerene is an unusual reactant in many organic reactions such as the Bingel reaction discovered in Carbon nanotubes were first discovered and synthesized in Minute quantities of the fullerenes, in the form of C 60 , C 70 , C 76 , C 82 and C 84 molecules, are produced in nature, hidden in soot and formed by lightning discharges in the atmosphere.
In , fullerenes C 60 have been discovered in a cloud of cosmic dust surrounding a distant star light years away. Using NASA's Spitzer infrared telescope the scientists spotted the molecules' unmistakable infrared signature. Sir Harry Kroto, who shared the Nobel Prize in Chemistry for the discovery of buckyballs commented: The discoverers of the Buckminsterfullerene C 60 allotrope of carbon named it after Richard Buckminster Fuller , a noted architectural modeler who popularized the geodesic dome.
Since buckminsterfullerenes have a similar shape to those of such domes, they thought the name appropriate. The suffix "-ene" indicates that each C atom is covalently bonded to three others instead of the maximum of four , a situation that classically would correspond to the existence of bonds involving two pairs of electrons " double bonds ".
Since the discovery of fullerenes in , structural variations on fullerenes have evolved well beyond the individual clusters themselves. 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 structure of C 60 is a truncated icosahedron , which resembles an 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 C 60 molecule is about 1. The C 60 molecule has two bond lengths. Its average bond length is 1.
A type of buckyball which uses boron atoms, instead of the usual carbon, was predicted and described in The B 80 structure, with each atom forming 5 or 6 bonds, is predicted to be more stable than the C 60 buckyball.
However, this work has been subject to much criticism by quantum chemists   as it was concluded that the predicted I h symmetric structure was vibrationally unstable and the resulting cage undergoes a spontaneous symmetry break, yielding a puckered cage with rare T h symmetry symmetry of a volleyball. There is an additional atom in the center of each six-member ring, bonded to each atom surrounding it. By employing a systematic global search algorithm, later it was found that the previously proposed B80 fullerene is not global minimum for 80 atom boron clusters and hence can not be found in nature.
Another fairly common fullerene is C 70 ,  but fullerenes with 72, 76, 84 and even up to 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. The smallest fullerene is the dodecahedral C There are no fullerenes with 22 vertices. For instance, there are non-isomorphic fullerenes C Note that only one form of C 60 , the buckminsterfullerene alias truncated icosahedron , has no pair of adjacent pentagons the smallest such fullerene.
To further illustrate the growth, there are ,, non-isomorphic fullerenes C , 15,, of which have no adjacent pentagons. Optimized structures of many fullerene isomers are published and listed on the web. Heterofullerenes have heteroatoms substituting carbons in cage or tube-shaped structures. They were discovered in  and greatly expand the overall fullerene class of compounds.
Notable examples include boron, nitrogen azafullerene , oxygen, and phosphorus derivatives. 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 C 80 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.
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 tensile strength , high electrical conductivity , high ductility , high heat conductivity , 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 by researchers at Rensselaer Polytechnic Institute.
Fullerites are the solid-state manifestation of fullerenes and related compounds and materials. Such treatment converts fullerite into a nanocrystalline form of diamond which has been reported to exhibit remarkable mechanical properties. In the early s, the chemical and physical properties of fullerenes were a hot topic in the field of research and development. Popular Science discussed possible uses of fullerenes graphene in armor. In the field of nanotechnology , heat resistance and superconductivity are some of the more heavily studied properties.
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.
There are many calculations that have been done using ab-initio quantum methods applied to fullerenes. Results of such calculations can be compared with experimental results. Researchers have been able to increase the reactivity of fullerenes by attaching active groups to their surfaces.
Buckminsterfullerene does not exhibit " superaromaticity ": A spherical fullerene of n carbon atoms has n pi-bonding electrons, free to delocalize. These should try to delocalize over the whole molecule. This has been shown to be the case using quantum chemical modelling, which showed the existence of strong diamagnetic sphere currents in the cation. As a result, C 60 in water tends to pick up two more electrons and become an anion. The n C 60 described below may be the result of C 60 trying to form a loose metallic bond.
Fullerenes are stable, but not totally unreactive. The sp 2 -hybridized carbon atoms, which are at their energy minimum in planar graphite , must be bent to form the closed sphere or tube, which produces angle strain. The characteristic reaction of fullerenes is electrophilic addition at 6,6-double bonds, which reduces angle strain by changing sp 2 -hybridized carbons into sp 3 -hybridized ones.
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 Tb 3 N C 84 , which violates the isolated pentagon rule.
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 C 70 are a reddish brown. The higher fullerenes C 76 to C 84 have a variety of colors. C 76 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 C 28 ,  C 36 and C The C 72 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 72 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 C 60 and C 70 are listed at left in order from highest solubility. The solubility value given is the approximate saturated concentration.
Solubility of C 60 in some solvents shows unusual behaviour due to existence of solvate phases analogues of crystallohydrates. For example, solubility of C 60 in benzene solution shows maximum at about K. Out of solution, this structure decomposes into usual face-centered cubic fcc C 60 in few minutes' time. Common Elements Let's work with the alphabet idea again.
If you read a book, you will find words on each page. Letters make up those words. In English, we only have twenty-six letters, but we can make thousands of words.
In chemistry , you are working with almost elements. When you combine them, you can make millions of different molecules. Molecules are groups of atoms in the same way that words are groups of letters. An "A" will always be an "A" no matter what word it is in. A sodium Na atom will always be a sodium atom no matter what molecule it is in.
While atoms from different elements have different masses and structures, they are all built with the same parts. Electrons , protons, and neutrons are the basic subunits for all atoms across the Universe.
From Simple to Complex If you want to do a little more thinking, imagine the smallest particles of matter. Super-tiny subatomic particles are used to create the parts of atoms. Protons, neutrons, and electrons can then organize to form atoms. Atoms are then used to create the molecules around us. As we just learned, there are almost elements that can be found in the molecules we know. Smaller molecules can work together and build macromolecules. It just goes on. Everything you see or imagine is built from something else.
You could start really small And finish really big. All of that is possible because of atoms.