Beam-induced graphitic carbon cage transformation from sumanene aggregates

Abstract

We found that electron-beam irradiation of sumanene aggregates strongly enhanced their transformation into a graphitic carbon cage, having a diameter of about 20 nm. The threshold electron dose was about 32 mC/cm2 at 200 keV, but the transformation is still induced at 20 keV. The transformation sequence suggested that the cage was constructed accompanied by the dynamical movement of the transiently linked sumanene molecules in order to pile up inside the shell. Thus, bond excitation in the sumanene molecules rather than a knock-on of carbon atoms seems to be the main cause of the cage transformation.

Graphitic cage transformation by electron-beam-induced catalysis with alkali-halide nanocrystals

“…Electron-beam-induced cage transformation has been extensively investigated using in situ transmission electron microscopy techniques. [13][14][15][16][17][18][19][20][21][22] Static Joule heating under extensive electron dose with the assistance of the "knockon" process [23][24][25] seems to induce dynamic edge deformations, such as the curling up of the graphene edge and zipping up of the nearest stack of graphene, resulting in the formation of fullerene molecules. Mild activation, such as periodic pulse current injection into the graphite edge, 7) is crucial for promoting the transformation of larger graphitic carbon cages.…”