By using a double-aberration-corrected (scanning) transmission electron microscope at an acceleration voltage of only 80kV, it was demonstrated that, due to the low solubility of Cu in carbon and its affinity with oxygen, single-crystal Cu catalysts dissociated into small cuprous oxide nanoparticles after the growth of carbon nanofibers, and Cu2O nanoparticles ultimately localize on the fiber surfaces. This new finding was a step toward a better understanding of the interactions between Cu catalysts and carbon nanomaterials and could suggest a simple and effective method for eliminating Cu impurities from the fibers.

Direct Imaging of Copper Catalyst Migration Inside Helical Carbon Nanofibers. L.Dong, L.Yu, Z.Cui, H.Dong, P.Ercius, C.Song, T.Duden: Nanotechnology, 2012, 23[3], 035702