Inorganic Fullerenes, Onions, and Tubes

Abstract

Since the exciting and unexpected discovery of the soccerball-shaped Buckminsterfullerene (C60) molecule almost two decades ago, great advances in fullerene research have been made. This includes the discovery of inorganic, noncarbon cage and nanotube structures. Of particular interest are the molybdenum and tungsten sulfides and selenides that, when viewed under an electron microscope, are remarkably similar in appearance to the more famous carbon cages and nanotubes. Among other materials capable of forming fullerene structures, nickel chloride is of importance owing to its potential nanoscale magnetic properties, while the synthesis of pure boron nitride fullerenes, with their fascinating structures, was a particular challenge. All of these materials are able to form closed cages as a result of their sheetlike structure, which can, under the right conditions, curl around and either join with an opposite edge to form a tube or roll up into a scroll. Capping of the structures is possible owing to bends in the sheets caused by the inclusion of defects: pentagons for carbon, squares and octagons for boron nitride, and triangular defects for the sulfides. Proposed applications for the inorganic fullerenes include electronic devices and storage media, probes and electron microscope tips, and nano-ball bearings and high temperature lubricants.