Direct evidence for covalent functionalization of carbon nanohorns by high-resolution electron microscopy imaging of C60 conjugated onto their skeleton

Carbon nanohorns (CNHs) functionalized with aryl units, possessing ethylene glycol chains terminated to amine groups, were condensed with modified C60 carrying a free carboxylic acid group. Direct evidence for the covalent functionalization of CNHs was given by high-resolution transmission electron microscopy (HR-TEM) imaging of C60 present in that CNH hybrid material. In addition, it was found that C60 remained unaffected even after prolonged exposure to the electron beam. Finally, monitoring the wave motion of the connecting ethylene glycol chains, through sequential HR-TEM images, further proved the stability of the covalent bond that links the two carbon nanostructures.