Formation of Fullerenes from Humic Substances: An Investigation by Laser Ablation Fourier Transform Ion Cyclotron Resonance Mass Spectroscopy

摘要

New carbon clusters called fullerenes, the most common of which is sometimes known as "soccerball carbon" and has the molecular formula C_(60), can be produced by laser ablation or plasma arcing. Laser ablation Fourier transform ion cyclotron resonance mass spectroscopy has recently demonstrated fullerene formation from polycyclic hydrocarbons and geochemically related materials, such as coals of various ranks, kerogen and its pyrolysis products, and algal residues. McKinnon has reported that the ease of formation of fullerenes under identical conditions could be related to the atomic hydrogen to carbon ratios of the reactive substrate. However, the issue is more complex than this. For coals, it has been shown that the ease of formation of fullerenes is largely dependent on the aromatic array size. Thus Greenwood et al [7,8] reported that coal rank affects the ease with which fullerenes are formed. The formation of even numbered positive ion high mass carbon clusters decreases with increasing rank whereas the aromatic array size increases with increasing rank. Coals of highest rank (anthracites) with average aromatic ring clusters of 350 or larger do not produce carbon clusters at relatively low laser irradiances (i.e. 3 to 30 MW cm~(-2) for the 8 ns pulse and 10 to 100 kW.cm~(-2) for the 230μs pulse) and neither does graphite. Of course, at higher powers and irradiance times anthracites and graphite will form fullerenes.