Clever it may be, but what does it do?: Hugh Aldersey-Williams reports on the discovery of a dramatic new form of carbon

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The Independent Online
The galleried shelves of London's Science Reference Library encourage respectful behaviour. Everything is in its place as researchers go about their errands with hushed decorum.

Well, not quite everything. For one topic has so excited a visitor that a key paper has been quietly excised from among the rows of learned journals.

The missing paper, sliced neatly from a 1990 issue of the Royal Society of Chemistry's Chemical Communications, describes how Professor Harold Kroto and his colleagues at the University of Sussex raced to prepare two new molecules composed entirely of carbon atoms, dramatically different from any other known form of carbon. In the event, they were pipped at the post by a team led by Dr Wolfgang Kratschmer from the Max Planck Institute for Nuclear Physics at Heidelberg in Germany and Dr Donald Huffman of the University of Arizona at Tucson.

In the synthesis, both groups followed an extremely simple procedure by the standards of modern science. They heated graphite rods by passing an electric current through them in an inert atmosphere. They then scraped the resulting soot from their apparatus and set about separating and purifying its constituents. The principal ingredient had 60 carbon atoms in equivalent positions across the surface of a tiny sphere joined by chemical bonds that formed a mesh of pentagons and hexagons. It was the most highly symmetrical molecule ever created by man. Professor Kroto had christened it buckminsterfullerene for its resemblance to the geodesic domes of the maverick American architect, Buckminster Fuller. The soot was found also to contain a similar molecule with a girdle of 10 more carbon atoms, giving it an elongated rugby-ball shape.

Since its initial detection in 1985 and manufacture in 1990, buckminsterfullerene (whose chemical formula is C60) has been hailed as a third stable form of carbon, after graphite and diamond. Scientists were stunned that such a stable and beautiful new molecule should have eluded detection for so long. As Professor Kroto says: 'Anyone who's switched on a Bunsen burner's yellow flame has made it.'

C60 has recently been joined not only by C70, but by a whole family of fullerenes and related molecules. The volume of papers in this new branch of chemistry has mushroomed. Perhaps 200 were published in the five years between the key 1985 and 1990 experiments; in 1992 alone, it is estimated that there could be 800 papers published. Buckminsterfullerene has been the subject of questions in the House of Lords and this week will be the focus of a meeting at the Royal Society.

Exxon, IBM, AT & T and other companies have been quick to explore the commercial potential of buckminsterfullerene and its relations. The pure scientists who have had to fight hard for funding merely to confirm its existence now look on in some bemusement as these Croesus corporations scramble to exploit it.

Professor Kroto adopts an ironic tone as he talks about his discovery. His lecture has become something of a roadshow, with giant stick models of various fullerenes, precious samples that are passed around for audience inspection, and even a football whose leather panels are stitched together in the same array of pentagons and hexagons that form the buckminsterfullerene carbon bonds. He ranges over astronomy, chemistry, architecture, geometry and mathematics and yet still finds time to include a sardonic repetition of some banter in the House of Lords - Hansard records one lord indignantly demanding of the discovery: 'My lords, what does it do?'

Despite the frenzied efforts of corporate and academic laboratories alike, Professor Kroto can answer: 'We really don't know. The jury is out.' Experiments have, in fact, shown that a number of what seemed at first to be promising uses were unrealistic. It was thought buckminsterfullerene might prove an ideal superlubricant if fluorine atoms could be added to each carbon atom to form a tiny ball-bearing analogue of the carbon-fluorine non-stick polymer, Teflon. In another simple experiment, a team from Sussex and Leicester universities duly passed fluorine gas over C60. The resulting white solid was the compound they wanted, but it was found, unlike Teflon, to be too reactive for practical purposes.

Early potential seen for buckminsterfullerene as a superconductor has also suffered a setback. Scientists at AT & T reported that fullerenes in combination with a suitable metal become superconductive at a significantly higher temperature than is usual for most materials. Unfortunately, the 'doped' fullerenes are also spontaneously inflammable if exposed to air.

Other applications are still on the cards. Fullerene surfaces can act as catalysts. Solutions of C60 and C70 have been found to transmit low-intensity light but to block brighter light. They may be useful as switches in optical circuits in which light takes the place of electric currents.

The pure scientists have meanwhile found plenty to distract them, cataloguing a growing menagerie of strange new molecules constructed from this most familiar of elements. Dr Roger Taylor of the Sussex group describes the recent discoveries as 'tales of the unexpected'. There are fullerenes with as few as 28 carbon atoms, giant fullerenes with 240 or more atoms; fullerenes with atoms trapped inside or on their surfaces; fullerenes with holes. Each modified species could have radically different properties.

Japanese researchers have discovered a related group of carbon compounds called nanotubes in which graphite-like carbon mesh sheets are rolled like brandy snaps. According to Dr Thomas Ebbesen of NEC in Tsukuba, a concentric double nanotube may act as a tiny electrical wire with the inner tube conducting and the outer one insulating. In principle, a length of nanotube could be capped with hemispherical fullerene ends to create molecules for which Professor Kroto has suggested the name zeppelenes.

Professor Alan Mackay, a crystallographer, reasons that if convex fullerene balls are stable, then so should concave carbon mesh surfaces be. A small sample of such a surface looks like a scaffolding joint. Joining these fragments, the negative curvature would lead not to discrete molecules but to an endless sponge-like structure.

Taken together, these carbon- species balls and tubes, caps and joints can be seen as a kit of parts. Could they be assembled to form tiny structures? The politicians would immediately want to know what they could do. But for the scientists finding these new molecules, the excitement of discovering such a well-stocked molecular- scale toyshop is enough in itself.

The author is writing a book about buckminsterfullerene to be published by Aurum Press.

(Photograph omitted)

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