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HISTORY OF TECHNOLOGY, TECHNOLOGY, OBJECTS AROUND US
Fullerenes. History of invention and production
Directory / The history of technology, technology, objects around us Fullerene, buckyball or buckyball is a molecular compound belonging to the class of allotropic forms of carbon and representing convex closed polyhedra composed of an even number of three-coordinated carbon atoms. Fullerenes owe their name to the engineer and architect Richard Buckminster Fuller, whose geodesic structures are built on this principle. Initially, this class of joints was limited to structures containing only pentagonal and hexagonal faces.
The hardest substance in nature is diamond. This carbon compound has a crystal lattice in the form of a tetrahedron - a pyramid with four equal triangular faces. Its tops are formed by four carbon atoms. A triangle is a very rigid figure; it can be broken, but it cannot be deformed or crushed. That is why the strength of diamond is so high. In nature, crystals are known with a lattice consisting not of atoms, but of molecules. If the molecules are large enough and the bonds between them are strong, then the crystal lattice is extremely strong. Fullerenes fully meet these conditions: having a diameter greater than 0,5 nm, they combine into a crystal with cells smaller than 1,5 nm. As is often the case, the discovery of fullerenes was not the result of a targeted search. The main direction of work in the laboratory of R. Smalley at Rice University (Texas), where a discovery was made in the 1980s related to the study of the structure of metal clusters. The technique of such studies is based on measuring the mass spectra of particles that are formed as a result of the intense action of laser radiation on the surface of the material under study.
“In August 1985, the famous astrophysicist G. Kroto came to Smalley’s laboratory,” writes Alexander Valentinovich Yeletsky in the Soros Educational Journal, “who worked on the problem of identifying the spectra of infrared radiation emitted by some interstellar clusters. One of the possible solutions to this problem is enough long standing in astrophysics, could be associated with carbon clusters, which, as you know, form the basis of interstellar clusters.The purpose of Kroto's visit to Texas was an attempt, using the equipment of Smalley's laboratory, to obtain a conclusion about their possible structure from the mass spectrum of carbon clusters. The results of the experiments led to a shock state of its participants. While for most of the previously studied clusters, the typical values of magic numbers are 13, 19, 55, etc., depending on the mutual arrangement of atoms, clearly pronounced peaks with the number of atoms of 60 and 70 were observed in the mass spectrum of carbon clusters. The only consistent This feature of carbon clusters was explained by the hypothesis that carbon atoms form stable closed spherical and spheroidal structures, later called fullerenes. This hypothesis, later confirmed by more detailed studies, essentially formed the basis for the discovery of fullerenes. The publication of the first observations of fullerenes was sent to the journal "Nature" 20 days after Kroto's arrival in Texas. In this article, in addition to the assumption of the spheroidal shape of fullerenes, there were ideas about the possibility of the existence of endohedral fullerene molecules, that is, molecules that contain one or more atoms of another element. Further research confirmed this assumption. The distance between molecules in such crystals is less than the distance between atoms in the diamond lattice. In addition, in both types of cells there is a "special" fullerene that interacts with the rest through 12-16 very short and strong intermolecular bonds. All this determines the extraordinary hardness of crystalline fullerite: it is two to three times higher than the hardness of diamond. For the discovery of fullerenes G. Kroto, R. Smalley and R. Curl were awarded the Nobel Prize in Chemistry. The real boom in fullerene research began in 1990. This happened after the German astrophysicist W. Kretschmer and the American researcher D. Huffman developed a technology for obtaining fullerenes in sufficient quantities. The technology is based on thermal atomization of an electric arc with graphite electrodes and the subsequent extraction of fullerenes from the atomization products using organic solvents, such as benzene, toluene. The new technology has allowed numerous scientific laboratories to investigate fullerenes not only in molecular form, but also in the crystalline state. As a result, new discoveries were made. So, in 1991, American scientists discovered the superconductivity of fullerene crystals doped with alkali metal atoms, with a critical temperature of 18 to 40 degrees Kelvin, depending on the type of alkali metal. And to this day, research and development in the field of fullerenes is one of the priority areas of world science and technology. Such popularity is associated with the amazing physicochemical properties of fullerenes, which open up the possibility of their practical use. Fullerene molecules have a high electronegativity. They are able to attach up to six free electrons to themselves. This makes fullerenes strong oxidizers. They are able to form many new chemical compounds with new interesting properties. The chemical compounds of fullerenes include six-membered carbon rings with single and double bonds. Therefore, they can be considered as a three-dimensional analogue of aromatic compounds. Fullerene crystals are semiconductors with a band gap of 1-2 eV. They exhibit photoconductivity when irradiated with visible light. “The range of possible technological applications of fullerenes is wide,” Ezersky writes. “For example, the use of fullerenes as an additive to lubricating oil significantly (up to 10 times) reduces the friction coefficient of metal surfaces and, accordingly, increases the wear resistance of parts and assemblies. Other possibilities for mass applications of fullerenes are also being actively developed. associated, in particular, with the creation of a new type of rechargeable batteries, which, unlike traditionally used lithium-based batteries, are not subject to destruction of electrodes. The problem of the use of fullerenes in medicine and pharmacology deserves special attention. One of the main difficulties standing in the way of a successful solution of this problem is associated with the creation of water-soluble non-toxic fullerene compounds that could be introduced into the human body and delivered with blood to the organ subject to therapeutic action. The idea of creating anticancer medicines based on water-soluble endohedral fullerene compounds (fullerene molecules containing one or more atoms of an element) with radioactive isotopes embedded inside the fullerene structure is widely discussed in the literature. The introduction of such a drug into the tissue will make it possible to selectively affect the cells affected by the tumor, preventing their further reproduction." Author: Musskiy S.A.
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