Share this article with friends
This somewhat puzzling term stands for a special crystalline form of carbon. This chemical element-the basic component of all organic life on our planet- seems to have been investigated down to the finest details in two of its best- known forms-diamond and graphite-which differ by their physical and chemical properties. In the former atoms are "packed" in the form of spatial tetrahedrons, and in the latter-in hexagonal and rhombohedral laminated structures.
Over the past few decades, however, scientists came to question the finality of these two forms of carbon; some suggested the existence of other spatial chemically stable structures of carbon atoms. Speaking in metric terms, one such structure could be an icosahedron whose geometry was originally described by Archimedes. This structure is a hollow spatial configuration which can be compared to a football with a multitude of pentahedral and hexahedral sides, or facets. Its molecule should have the chemical formula of C 6 O. And after a long search astrophysicists finally traced in the mass spectra of carbon vapor a characteristic peak which suggested the existence of a matching molecule.
These, however, were but purely theoretical assumptions which could not be confirmed by any practical findings here on Earth. And it was only in 1985 that a team of American researchers, investigating carbon by what is called the atomic cluster method using laser evaporation, identified for the first time ever as C 6 O molecule with the help of timed-flight mass-spectrometer. What is more, in subsequent experiments not only C 6 O, but also C 7 O could be identified.
More detailed studies of the new substance suggested the existence of a carbon molecule in the form of a closed hexagonal cell, or cage. The latter reminded the investigators of a geodesic dome with 60 apexes-a structure brainstormed by the US inventor and architect Richard Buckminster Fuller which was translated into building construction reality at the EXPO-67 in Montreal. This similarity suggested the name for the new molecule which was called - buckminsterfullerene - a mouthfull which was later reduced to just fullerene. However, the unit which helped trace C 6 O molecules for the first time could be used for analytical studies only, and not for any quantitative isolation of the substance in question.
This problem was finally solved in 1990 by the German scientist W. Kretschmer who not only developed an appropriate unit, but also designed a technology for obtaining sample amounts of fullerene. He demonstrated for the first time that using arc discharges with graphite electrodes and helium (as buffer gas), one can obtain carbon condensate containing C 6 O molecules. That marked the start of what we call fullerene technologies.
Within a short span of time researchers were able to discover what were called lower, or base fullerenes (up to 22 atoms) and higher ones (up to 270 atoms), all of them possessing a range of specific properties. Because of all that they were regarded not just a new and challenging object of basic research, but also as the basis for a range of promising applied innovations.
Studies of this amazing phenomenon led the researchers to the conclusion that it can be used in some very different areas of science and technology, above all in electronics and optoelectronics, organic chemistry and metallurgy and in the manufacture of tyres and jewellery, to name but a few. And the range of the newly discovered and unique properties of fullerenes continues to grow just as does the scale of their applications.
With all that, there is but one snag in using this material on a really broad scale, and this is the cost. In 1994, for example, the price of pure C 6 O fullerene on the world market was 550 US dollars for one gram, and it was 1,600 dollars for C 7 O.
Studies of fullerenes at the Physics Institute (named after L. Kirensky) of the Siberian Branch of the Russian Academy of Sciences (Krasnoyarsk) were initiated in 1992. Dr. G. Churilov, a specialist in plasmotrons, or plasma generators * , offered to his
* Plasmotron (plasma generator) - gas discharge unit for generating low-temperature plasma (T= 10 4 K ). - Ed.
colleagues-physicists his own experimental unit for the production of this material. It took them two years to make the necessary adjustments before they were finally able to isolate the material from a carbonic jet in the plasma generator. All of these efforts finally led to the development of a very simple and productive, while likewise unique, technology of synthesis of this variety of carbon.
The new area of research focused on fullerenes found a most fitting "niche" in the Federal Program of INTEGRATION adopted in this country in 1995. Within the framework of this program a Physico-Technological Research Institute was set up with a special chair of plasmochemical technologies. And this form of carbon has since caught the attention of scientists in various fields of research. Chemists, for example, focused on ways of obtaining fullerene solutions and their purification, while physicists have been trying to identify this unique substance with the help of electron spectroscopy in the visible, ultraviolet and infrared bands, while medical experts try using them as biological solutions and biophysicists take special interest in their water- soluble complexes.
The latter studies provided an incentive for research in a promising area linked with practical uses of the new material in biology and medicine. The point is that fullerenes, having a definite number of non-saturated bonds, are unique objects capable of gaining electrons, and are also ideal components for reactions with free radicals. This makes it possible to use them as "traps" (antioxidants) in the hyperproduction of active forms of oxygen-the predominant mechanism of body ageing and pathologies. Specialists are now studying the effect of various water-soluble complexes, containing both higher and lower fullerenes, upon oxygen metabolism in the blood of patients with different pathologies. It has been demonstrated that higher fullerenes are hyperactive and have a strong effect on redox processes in organic compounds. This is very important, for it thus becomes possible to develop new anti-cancer and anti-viral medicines.
The results obtained point to a very promising nature of the current studies of fullerenes. For example, a method developed by Dr. G. Churilov, using an HF plasma jet in the range of up to 0.75 m, makes it possible to design various fullerene complexes at the molecular level. These complexes (obtained by introducing various fractions of other substances or combinations thereof into a CeO molecule) may reveal some very unexpected and useful properties. If, let us say, an excited hydrogen atom is implanted into a fullerene structure and fixed therein, the resulting substance can become what we call an absolute absorbent of electromagnetic emissions, so that any object coated with a paint of this kind will become absolutely invisible to radars. Apart from the above, a "sustained" source of plasmochemical synthesis should make it possible to boost the production of fullerenes and cut back their cost.
The problem of synthesis of such minute particles is drawing considerable attention and interest on the part of specialists, including theoreticians, experimenters and practical, or applied researchers. This area of research is in the list of what we call critical national technologies, which proves how important and promising it is. At Krasnoyarsk this line of research began with studies of ultra-dispersed diamond powders and has since branched out into many fields, including studies of nanostructures of various materials and some theoretical and practical problems of nuclear engineering.
Nauka v Sibiri (Science in Siberia), 2000
Permanent link to this publication:
LRussia LWorld Y G