Dieter M. Gruen, Materials Science Division, Argonne National Laboratory
Fullerenes, nanotubes and ultrananocrystalline diamond:
There's a bit less room at the bottom*

Where did they come from? Where are they going? These three nanostructured forms of carbon were discovered between 1985 and 1994 opening new vistas for cross cutting work in several disciplines including physics, chemistry, biology and materials science. The discovery of these substances, which had eluded detection despite the enormous amount of work that had been done on carbon by generations of scientists, helped both to spark and to emphasize the importance of nanoscience which was just beginning to emerge as a discipline in its own right during that period.

It has turned out that the three nanocarbons are exemplars par excellence of the profound changes in properties that occur when materials reach single digit nanometer dimensions. And size matters in a most profound way in the case of carbon because uniquely the sp2 and sp3 configurations differ by only 0.02ev in this element. Consequently, relatively small, size dependent complex changes in bond hybridization, influenced as well by curvature, steric and other factors are responsible for carbon nanostructures with vastly different physical and chemical properties. Furthermore, because of the close energetic relationships, kinetic factors strongly influence the product channels that determine the outcome of experiments designed to synthesize one or another of the three forms. One can arrange matters such that the simultaneous synthesis of more than one of these forms is possible resulting surprisingly in a �self composite� material.

In this colloquium, I will attempt to convey some of the excitement many of us working in this field feel because of the abundance of new science that continues to be produced. I will illustrate the basis for this feeling with examples to try to convince you that fullerenes, nanotubes, and ultrananocrystalline diamond in film and disperse forms occupy significant positions in the spacious �room at the bottom�.

*Work performed under the auspices of the U.S. Department of Energy, BES-Materials Sciences,under Contract W-31-109-ENG-38