Search for arc-produced heterofullerenes

Abstract

Replacing one or more of the carbon atoms in a fullerene cage with one or more non-carbon atoms is expected to result in a structure (heterofullerene) with significantly altered and potentially useful properties. While (C59N)- and (C69N)-based compounds can be synthesized via solution-phase modification of C-60 and C-70, respectively, a general, high-yield method for producing heterofullerenes has not been identified. We report the results of a search for heterofullerenes using atmospheric pressure photo-ionization mass spectrometry on samples of fullerene soot produced in nitrogen and carbon monoxide via the Kratschmer-Huffman arc technique. Contrary to earlier reports, we found no evidence of the presence of heterofullerenes in any of the samples we examined. X-ray photoelectron spectroscopy of fullerene soot produced in nitrogen indicates that while nitrogen is incorporated into the carbon matrix, the observed nitrogen-carbon bonding configurations do not permit the formation of fullerenes. We also report the discovery of production conditions under which argon can be used as a buffer gas and the yield of soluble fullerenes is comparable to the best yield achievable using helium. These findings may shed light on the general problem of the fullerene formation process.