Chemical characterization of nanometer-sized elemental carbon particles emitted from diesel vehicles

In order to obtain the exact chemical structure and further discuss the global warming effect of elemental carbon (EC) particles, the morphology and the chemical structure of EC particles emitted from diesel vehicles were first investigated in detail using scan electron microscopy equipped with an energy dispersive X-ray spectrometer (SEM-EDX), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), Fourier Transformation Infrared (FT-IR) spectrum and ¹³C Nuclear Magnetic Resonance (NMR) spectrum in this study. The SEM-EDX results showed that EC particles emitted from diesel bus are 50 nm spherical particles with smooth surface and an O/C ratio (mass ratio) of 0.07±0.01. The 50 nm EC particles were further deduced to be an aggregate of new fullerene C₃₆(OH)₂ according to the results of MALDI-TOF-MS, FT-IR and ¹³C NMR. Fullerenes smaller than ⁶⁰C were considered to be unstable since they cannot fulfill the so-called isolated pentagon rule. So far, most of our knowledge regarding small fullerenes comes from gas-phase experiments and theoretical investigations, the production and separation of small fullerene solids in the macroscopic quantity has been reported. The present report is the first discovery of C₃₆(OH)₂-based solid.