Реферат: Fullerenes Essay Research Paper Overall View of
Fullerenes Essay, Research Paper
Overall View of Fullerenes
Natural Carbons can usually exist in several forms. The most common are Graphite and diamond, but most people don t know that there is a third type fullerenes. Many have mistaken these fullerenes for a new type of carbon. Fullerenes have been discovered in interstellar dust as well as in geological formations on Earth, but they are very new to us. As with many important scientific discoveries, Fullerenes were discovered by accident. The C60 molecule was discovered by Harold Kroto, James Heath, Sean O’Brien, Robert Curl, and Richard Smalley in 1985. The group actually tried to understand the absorption spectra of interstellar dust, which they suspected to be related to some kind of long-chained carbon molecules. Unfortunately they could not solve that problem. But their work was not completely unsuccessful, since in the course of their experiments they discovered the Buckyball, which gathered so much excitement among scientists and won Curl, Kroto, and Smalley the 1996 Nobel Prize in chemistry.
This new family of non-planar carbon compounds has gathered enormous interest within the scientific community in such a short period of time, with thousands of papers published about fullerenes and fullerene-based materials to date.
Buckminster fullerene molecules consist of 60 carbon atoms linked together, arranged as 12 pentagons and 20 hexagons, to form an almost spherical ball with the chemical formula C60. The bonds between atoms form a pattern of joined hexagons and pentagons that is similar to the panels on a soccer ball. The most striking property of the C60 molecule is its high symmetry. There are 120 symmetry operations, like rotations around an axis or reflections in a plane, which map the molecule on to itself. This makes C60 the molecule with the largest number of symmetry operations, the most symmetric molecule. It should come as no surprise that a shape as symmetric and striking as that of the C60 molecule, has occupied many artists and mathematicians over the centuries. Probably it was already known to Archimedes, although no drawings seem to have survived. The oldest known picture of the this shape seems to be a drawing found in the Vatican Library. It is from a book of the painter and mathematician Piero della Francesca and dates from the 1480s.
Fullerenes are large carbon-cage molecules. By far the most common one is C 60. C 60 is also known as a Buckyball. These fullerenes known as Buckyballs were named after American Architect Buckminster Fuller because the structure of this molecule greatly resembles the elaborate geometrical structures that Fuller once designed. A few other common fullerenes are C70, C76, and C80. Fullerene cages are around 7-15 angstroms in diameter (which is about a billionth of a meter, or 6-10 times the diameter of a typical atom. In atomic terms, fullerenes are enormous.
Chemically, Fullerenes are actually very stable. To break these molecules you d have to have temperatures of over 1000 degrees. At much lower temperatures fullerenes will do what is known as sublime. This means that vapor will form directly from the solid. These molecules do not break they just separate from the solid intact.
The thing that is most interesting about these new carbons is that they have a number of uses. As one example shows, Fullerenes have been used as lubricants because the tiny balls can roll between surfaces. Studies later found that pure fullerenes are not good for this; they must be changed chemically first by having other atoms bonded around the ball. Another use is that fullerenes turn out to have strong optical effects. This means that they can change their properties with the aid of irradiation with light. Something like this could be extremely useful in photolithography. Overall fullerenes are found interesting because they are not like any other molecules scientists have worked with so far. Although we’ve known about carbon as long as we’ve known about fire, we are still discovering new aspects of this element every decade.