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Making scads of molecular soccer balls.

Making scads of molecular soccer balls

Give a technician a day and he or she now can make about 90 million trillion soccer-ball-shaped molecules, each tiny enough for virus-sized athletes, and collectively weighing about one-tenth of a gram. That should yield enough of the spherical structures to prove their physical properties and even to change the minds of skeptics -- scientists who had likened most previous evidence for the wee carbon soccer balls to sightings of unicorns and UFOs.

In 1985, researchers in England and Houston suggested that vaporized carbon atoms from laser-blasted graphite might rearrange into exceptionally stable cage structures -- most notably a 20-sided truncated icosahedron composed of exactly 60 carbon atoms (SN: 1/28/89, p.56). Researchers now refer to these and related hypothetical molecules as "fullerenes" for their resemblane to the geodesic structures popularized by the engineer and designer R. Buckminster Fuller. Many scientists have since published theories and some experimental data indicating that these carbon balls emerge in sooty combustion processes and even the clouds around stars.

However, because no one had corralled enough of the molecules to convincingly establish their structure with X-ray diffraction studies, skeptics argued that claims of the sooty sphere's existence relied more on theoretical and aesthetic pillars than on hard evidence.

Now Donald R. Huffman of the University of Arizona in Tucson and his co-workers at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany, have developed a simple method for making and harvesting cyrstals and films made almost entirely of the 60-carbon balls. "A new form of pure, solid carbon has been synthesized," the researchers assert in the Sept. 27 NATURE. To make this material, christened "fullerite," they vaporize a bar of graphite within a helium-filled chamber maintained at about one-eighth atmospheric pressure. About 10 percent of the resulting, largely insoluble, soot consists of fullerenes -- mostly the 60-carbon version with a touch of its 70-carbon cousin. These molecules dissolve in benzene, allowing the researchers to remove this insoluble soot particles that settle out. As the benzene evaporates from drops of the solution placed on microscope slides, fullerene crystals form. A battery of tests including X-ray diffraction studies indicate that the molecules in these crystals contain the chemical bonds and physical features expected from a 60-carbon fullerene.

Preparing large quantities of these fullerenes "opens the way to the examination of more propeties and many technical possibilities," says crystallographer Alan L. Mackay of Birkbeck College in London. Writing in the same issue of NATURE, he speculates that fullerite might one day serve as new solid lubricants or as tiny bubbles to encapsulate smaller molecules.
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Title Annotation:20-sided truncated icosahedron composed of exactly 60 carbon atoms
Publication:Science News
Date:Oct 13, 1990
Words:433
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