prove the growth of diamond films. And they have interestin
properties and potential as superconductors.
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Fullerenes: Surprise Surprise
Charles Sheffield
It’s not what we don’t know that causes the trouble; it’s the things we know that ain’t so.
Textbooks on inorganic chemistry for the past couple of centuries have stated, without a hint of doubt, that carbon occurs in two and only two elementar forms: diamond and graphite. In diamond, the carbon atoms form tetrahedra, triangular pyramids with one carbon atom at each vertex and one in the center. This is a strong and stable configuration, so diamond is famously hard. In graphite, the carbon atoms form hexagons with an atom at each vertex, an the hexagons line up as layers of flat sheets. Since the sheets are not strongly coupled with each other, graphite is famously slippery and a well-known lubricant
The discovery in 1985 of a third elementary form of carbon was a shock i two different ways. First, the existence of the third form could have been predicted, or at least conjectured, since the middle of the eighteenth century. In fact, its existence was suggested in 1966, as a piece of near-whimsical speculation, by a columnist in the New Scientist magazine. No one took any notice. Second, and almost a disgrace to a self-respecting chemist the third form is not at all hard to make. In fact, it had been around, waitin to be discovered, in every layer of soot produced by a hot carbon fire. Every time you light a candle, at least some of the soot will be this new and previously unknown form of carbon.
I said, a new form of carbon, but actually there is a family of them. The simplest form, C60, is sixty carbon atoms arranged in a roun hollow shape involving 12 pentagons and 20 hexagons. Technically, this form is called a truncated icosahedron, but the name is neither suggestive no catchy. However, the structure looks exactly like a tiny soccer ball.
Leonhard Euler, the great Swiss mathematician, studied the possible geometry of closed spheroidal structures more than two hundred years ago, and proved that while they must have exactly 12 pentagons, the number of hexagons ma vary. And vary they do. Continuing the sporting motif, the next simplest form, C70, is an oblong spheroid of 12 pentagons and 25 hexagon that closely resembles a rugby ball. And after that there are carbon molecules with 76, 84, 90, and 94 atoms, and still bigger versions that form hollo closed tubes. All of these are known by the generic name of "fullerenes," or if they are round, "buckyballs."
The form with 60 atoms, C60, is the simplest, most stable, and most abundant form, with C70 in second place. Not surprisingly, C60 was the first form to be discovered.
So how was it discovered? Not, as one might think, by direct observation. The C60 molecule is less than a millionth of a millimeter across (about 7x10-10 meters), but it is big enough to be seen using a scanning tunneling microscope. It wasn’t, though. It was found by a very curious and apparently improbable route. A British chemist, Harold Kroto, was studying how carbon-rich stars might lead to the production of long chains of carbon molecules in open space. In the United States, at the Houston campus of Rice University, American chemists Robert Curl and Richard Smalley had suitable lab equipment to simulate the carbon-rich star environment and see what might be happening.
The team did indeed find evidence of a variety of carbon clusters, but as the carbon vapor was allowed to condense, everything else seemed to fade away except for a 60-atom cluster, and, much less abundant, a 70-atom cluster. It seemed that there must be a very stable form of carbon with just 60 atoms, and another, rather less stable structure, with 70 atoms.
At this point, the team faced a problem. Carbon is highly reactive. If the cluster had the form of a flat sheet, like graphite, it ought to have free edges, which would latch on to other carbon atoms, and so grow rapidly in size. The only way around that would be if the structure could somehow clos in on itself and tie up all the loose ends.
The first fullerenes were produced in minute quantities. Research on them was therefore difficult. Then in 1990, a German team discovered a shockingly simple production method. Burning a graphite rod electrically resulted in soot containing a substantial percentage of C60. Combining this with the suitable use of a benzene solvent formed an almost-pure mixture of fullerenes. Now anyone who wants fullerenes for research can easily buy them. And they are doing so, in ever-increasing numbers. The buckyball wa named "Molecule of the Year" by Science magazine in 1991, and today the most frequently cited chemistry papers all seem to be on the subjec of fullerenes. The 1996 Nobel Prize in chemistry went to Robert Curl, Richard Smalley, and Harold (now Sir Harold) Kroto.
good for, apart from winning
Nobel Prizes? Potentially, many things. Because they are hollow,
buckyballs can be used to trap other atoms inside
them and to provide miniature "chemical test sites." They are phenomenally
robust and stable, and could be the basis for materials stronger than anything
we have today. They have been proposed as nanotechnology building blocks
They are already being used to
improve the growth of diamond films. And they have interestin
properties and potential as superconductors.
The best answer to the question, though, is that it is too soon to say. Lik lasers in 1965, fullerenes seem to be a solution waiting for a problem. And like lasers, fullerenes will almost certainly become enormously valuable technological tools in the next thirty years.
What does all this have to do with Bucconeer? Well, we could argu that since space may be sprinkled with fullerenes spewed out by carbon-rich stars, that is one connection to science fiction. And since there will almost certainly be numerous applications in the future, that is another SF connection.
The truth, though, is that because fullerenes are known as buckyballs, the tenuous link of a similarity in sound to "buccaneer" was quite enough for us
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