Great Balls of Carbon

By J. Madeleine Nash/Chicago

Carbon is a kind of natural backbone: the all-important element that anchors the molecules of everything from crude oil to DNA. For the past six years, groups of scientists have been chasing down an exotic form of carbon believed to have a particularly elegant configuration: 60 atoms of carbon arranged like a miniature soccer ball. The improbably spherical molecules were dubbed buckminsterfulleren es, or simply buckyballs, because they resemble the geodesic domes designed by inventor Buckminster Fuller. Researchers knew that some sort of 60-atom carbon molecule existed, but they had trouble producing enough of the stuff to study its properties or confirm its structure.

Now scientists have finally managed to snare the elusive molecule, and the first "snapshot" of a buckyball, taken with the aid of X rays, has been published by Science magazine. The computer-generated drawing matches the perfect soccer-ball shape that had been predicted. "This molecule is just as marvelous as we thought," exclaims Joel Hawkins, who headed the team of University of California, Berkeley, chemists that took the picture.

For scientists, the discovery of buckyballs has been like stumbling across % an unexpected cache of buried treasure. Only two other distinctive forms of pure carbon have ever been found: ordinary graphite and precious diamonds. The atom clusters in graphite are flattened into hexagons, like tiles on a bathroom floor, while the atoms in diamonds form tiny pyramids. The molecular structure of buckyballs is so radically different that researchers hope this third form of carbon will lead to a whole new class of materials with a multitude of uses.

The first known encounter with a buckyball was recorded in 1985 by Richard Smalley, a chemical physicist at Rice University, and Harold Kroto, a British chemist from the University of Sussex who was visiting Smalley's lab. The two scientists were studying what would happen if they heated carbon vapor to about 8,000 degreesC (14,500 degrees F). Unexpectedly, they detected a mysterious new form of carbon. Chemical tests proved two things: 1) the molecules had 60 carbon atoms, and 2) they had no "edges," as chemists call the unpaired electrons that cause atoms to form chemical bonds with one another. Smalley and Kroto theorized that the molecule with no edges must have the shape of a soccer ball, but they were unable to confirm the idea.

It was not until last fall that a team of scientists produced visible aggregations of buckyballs. At first, University of Arizona physicist Donald Huffman and his German colleague, Wolfgang Kratschmer, thought they had come up with nothing more extraordinary than a thimbleful of grimy soot. Then their microscope revealed a swarm of translucent specks that sparkled like stars in a moonless sky. "As soon as we saw these beautiful little crystals," Huffman recalls, "we knew we were looking at something no one had ever seen before."

But these crystals were disorganized piles of buckyballs; the scientists had no way of viewing the individual molecules. One difficulty is that when buckyballs are on their own, they spin like tiny planets, completing more than a billion rotations in a second. They do not normally stay still long enough to have their picture taken.

The Berkeley team got around that problem by "grabbing" the whirling buckyballs with atomic "handles" containing the element osmium. The handles enabled the scientists to manipulate billions of buckyballs and align them in an orderly, crystalline fashion. By bombarding the carbon samples with a thin beam of X rays, the Berkeley scientists got an accurate computer representation of the soccer ball-like arrangement of the atoms.

Now the rush is on to study the properties of buckyballs and explore their possible uses. Scientists have already concluded that the molecule is remarkably durable. Chemist Robert Whetten of UCLA has fired buckyballs at speeds of 27,000 km/h (17,000 m.p.h.) into miniature walls of graphite and silicon. The sturdy spheres bounced back unharmed.

Their shape may turn out to be a structural achievement that on the molecular level is as noteworthy as the keystone arch. "This molecule," says IBM physicist Donald Bethune, "looks like something some genius engineer sat down and designed." In essence, a buckyball forms a cage that begs to be filled. By placing different atoms inside the cage, scientists should be able to engineer materials with unique electronic, catalytic and even biomedical properties. One intriguing possibility: if they prove nontoxic, buckyballs might encapsulate radioactive atoms used in cancer therapy, serving as shields that protect normal tissue from damage.

Buckyballs, which have been found to come in larger sizes, have already been altered by adding atoms to their exteriors. Researchers at AT&T Bell Laboratories and elsewhere have created thin films of buckyballs and studded them with impurities that help the molecules carry electric current. Their report indicates such film could lead to a new class of useful superconductors. Other items on the buckyball wish list include tiny ball bearings, featherweight batteries and wires perhaps only one molecule thick.

For the present, such developments are just dreams. "Buckyballs," stresses Berkeley's Hawkins, "are still so new and special that we can only hope they will be new and special in useful ways." But most researchers are betting that the sooty spheres with the playful name are diamonds in the rough.