Until the mid–1980s, the only known allotropes of carbon were graphite, diamond, lonsdaleite and amorphous carbon such as soot and charcoal. But that all changed with the discovery of the fullerenes.
Fullerenes are a class of 'hollow' carbon allotropes, whose molecules consist of carbon atoms connected by single and double bonds so as to form a closed or partially closed mesh, with fused rings of five to seven atoms. The molecule may be a hollow sphere, ellipsoid, tube, or many other shapes and sizes. Graphene can be seen as an extreme member of the family; it consists of a single layer of atoms arranged in a two–dimensional (i.e. flat) honeycomb lattice. The first fullerene to be discovered – still the best–known example, and the one that gave its name to the class – was buckminsterfullerene (a.k.a. buckyballs).
Hollow carbon molecules were first predicted in 1966 by the British chemist David Edward Hugh Jones, writing in New Scientist magazine under the pen name Daedalus. In 1970, the Japanese chemist Eiji Osawa predicted a C60 molecule (consisting of 60 carbon atoms joined together in the shape of a football); but his work gained little attention outside Japan.
In 1984, a team working at Exxon's laboratory in Annandale, New Jersey, managed to form carbon clusters by using lasers to vaporise graphite. The following year, the British chemist Harold Walter (Harry) Kroto persuaded Robert Curl and Richard Smalley to allow him to use their equipment at Walter Marsh Rice University in Houston, Texas, for his work on forming chains of carbon molecules. Together they detected a prevalence of molecules with the exact mass of sixty or seventy or more carbon atoms (C60 and C70) in the sooty residue created by vaporising carbon in a helium atmosphere. This was the crucial clue that the Exxon team had missed.
Kroto, Curl and Smalley identified the structure of these molecules as the now–familiar 'buckyballs'. They named the molecule after Richard Buckminster Fuller, an American architect who (writing as R. Buckminster Fuller) had coined the word 'geodesic' and popularised the concept of the geodesic dome. (In architecture, the point of the geodesic dome is that it can withstand very heavy loads for its size because of the way it distributes stress throughout its structure.)
It soon became clear that buckminsterfullerene was only one member of a whole new class of carbon allotropes. As well as being generated synthetically, fullerenes have been discovered in sooty flames, in lightning discharges in the atmosphere, and in outer space. It has even been suggested that "buckyballs from outer space [may have] provided seeds for life on Earth."
Fullerenes have long been the subject of intense research, both for their chemistry and for their technological applications, especially in materials science, electronics, and nanotechnology. Kroto, Curl and Smalley were jointly awarded the Nobel Prize in Chemistry in 1996, eleven years after their ground–breaking discovery.
Two Manchester University scientists, Andre Geim and Konstantin Novoselov (both born in Russia) won the Nobel Prize in Physics in 2010 for their work on graphene.
© Haydn Thompson 2017–22