The Observation of Large Concentric Shell Fullerenes and Fullerene-like Nanoparticles in Laser Pyrolysis Carbon Blacks

It has been shown that carbon blacks produced by iron carbonyl-catalyzed CO 2 -laser pyrolysis of benzene (laser pyrolysis carbon blacks) are characterized by a two-level nanostructure, i.e., they consist of amorphous carbon nanoparticles 30−40 nm in size and fullerene molecules where the fullerenes are predominantly represented by C 60 . Heat treatment of the blacks at 3000 °C causes restructurization with the appearance of fullerene-like multishell nanoparticles of ∼20 nm in size, higher fullerenes, and multishell fullerenes. Unlike classical fullerenes, which have a cage structure and are known to have been synthesized in a variety of sizes (C 60, C 70, C 84, C 102, etc.), multishell fullerenes have a cage-inside-cage structure. Direct transmission electron microscopy observation of the cage-inside-cage clusters shows the occurrence of at least three varieties: two-shell 14-Å-sized C 60 @C 240, two-shell 20-Å-sized (C 240 @C 560 ), and also three-shell 20-Å-sized (C 80 @C 240 @C 560 ).