aza-fullerene
Image: COURTESY OF LARS HULTMAN/University of Linkping

The difficulty in finding practical applications for buckyballs, those cagey spheres of pure carbon, has frustrated scientists ever since the new form of crystalline carbon was first discovered more than a decade ago. Part of the problem is that the bonds that form between individual buckyballs are very weak. Consequently, the solids they form, called fullerides, degrade easily. Now new research, published in the November 26 issue of Physical Review Letters, describes a fullerenelike material that is at once both strong and elastic.

Lars Hultman of the University of Linkping in Sweden and colleagues added nitrogen into the conventional carbon mix to produce a so-called aza-fullerene (see image). In the compound, nitrogen atoms replace 12 of the buckminsterfullerene's carbon atoms. The researchers dubbed their product a carbon nitride nano-onion because concentric layers of pure carbon formed, one atom at a time, around the new C48N12 material. The onions, which measure up to seven nanometers across and consist of seven to 10 shells, formed strong bonds with each other. (The presence of nitrogen lowers the energy barriers associated with bonding.)

The researchers next examined the new fulleride with a sharp diamond-tipped probe to test its properties. The tests, the authors write, "show evidence of a highly elastic material combined with an appreciable hardness." Such qualities, they conclude, indicate the material might hold promise for wear-protective applications.