Generation of higher fullerenes in flames

The presence of fullerenes up to C-116 was observed in condensable material from a benzene/oxygen flame. The flame material was Soxhlet-extracted with toluene for 363 h, fractionationed by means of a silica-based semipreparative HPLC column, and analyzed by HPLC coupled to a mass spectrometer via a heated nebulizer interface using a 2-(1-pyrenyl)ethylsilica stationary phase. UV-vis spectra were measured for C-60, C60O, C-60. CH4, C-70, C70O, C-76, C-78, C-80, C-84, a C-84 adduct, C-86, C-88, C-90, C-92, C-94, C-96, C-98, C-1OO, C-102, and C-108. Isomers could be discerned for C-78, C-90, and C-94. A calibration using external standards was performed for C-60, C-70, C-76, C-78, and C-84. For all other species the relative abundances were estimated based on HPLC peak integration results. Electric are soot was extracted under similar conditions and the quantification of fullerenes compared to the data obtained with flame-generated condensable material. Except for C-60 and C-76, the abundances were significantly higher in the case of flame-generated condensable material. Also, striking differences between the two fullerene production methods are seen in the relative abundances of C-78 isomers. Considering the present results and the ease with which the experimental setup could be scaled up, flame-generated condensable material represents an excellent starting material for the preparative isolation of higher fullerenes.