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Tiniest Carbon Sphere Sparks Big Reaction

24 June 1998 7:00 pm
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Buckyball's little brother. C36 (yellow) is the first fullerene to have fewer carbons than the original (blue).

Researchers have isolated a pint-sized spherical carbon molecule, or fullerene, that could turn out to be far more useful than its bigger cousins. Experts say the new fullerene, described in tomorrow's issue of Nature, may be easier to fashion into everything from high-temperature superconductors to high-strength materials.

In 1985 researchers discovered soccer ball-like molecules, made of 60 carbon atoms, that are formally called buckminsterfullerenes. Since then they've turned up a variety of larger all-carbon spheres. Now researchers have isolated a fullerene with just 36 carbons atoms, making it the first member of the family to have fewer than 60 carbons. To do so, University of California, Berkeley, physicists Charles Piskoti and Alex Zettl, along with chemist Jeff Yarger, vaporized carbon in a vacuum chamber containing a whiff of helium. When they boosted the helium concentration, Zettl and his colleagues got scads of C36, which they were able to purify.

Because the carbon atoms in a C36 fullerene must strain to form a sphere, the bonds between atoms are brittle; thus, the molecule is very reactive and quickly decomposes in air. But that could turn out to be a blessing: Linking C36 to other atoms could yield compounds that are more stable than C36 alone, as well as impart useful optical and electronic properties. By contrast, tacking add-ons to C60 typically creates molecules that are far less stable than the original.

The Berkeley group's success is "really heroic," says James Heath, a chemist at the University of California, Los Angeles, who helped discover fullerenes: "Every chemistry department in the world has been making fullerenes. Yet, before this not a single bit of evidence ever came forth that you could make something smaller than C60 and stabilize it."

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