Evidence for the Presence of Fullerene in Diesel Soot Using Laser Desorption/Ionization Mass Spectrometry

Intact soot exhausted from diesel engines from a large cargo ship and from a farm tractor, which work with heavy and light oil respectively, has been analyzed using laser desorption/ionization (LDI) mass spectrometry. Caged carbon clusters (or fullerene family) were detected as molecular ions M+· with relatively intense peaks at m/z 600, 720, and 840 corresponding to C50, C60, and C70, respectively. There were also other even number carbon clusters C2n (n=20-142 or higher). Small carbon clusters Cn (n=7-29) with the magic number n=7, 11, 15, 19, 23, and 27 were also observed in the LDI mass spectra. The LDI mass spectra of a fullerene C60 (99%) and intact soot showed definite metastable ion peaks originating from successive C2 loss from molecular ions. It was confirmed that under the same LDI conditions the laser vaporization of graphite never gives any products of the fullerene family or even number carbon clusters.