TIME: Almanac 1993/TIME Almanac 1993.iso/time/050691/0506300.000

Text File | 1992-08-28 | 5.8 KB | 122 lines

                                                                                SCIENCE, Page 66

Great Balls of Carbon


It looks as though you could play soccer with it, but a newly
discovered sphere may lead to novel materials, even medicines

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 buckminsterfullerenes, 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 bucky ball 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.