Effect of functional group polarity on the encapsulation of C60 derivatives in the inner space of carbon nanohorns.

Abstract: Encapsulation of C60, its hydroxides (C60(OH) n , n =10, 36, 44), and its hydride (C60H36) into inner space of carbon nanohorns (CNHs) from solutions or dispersions in various solvents by the nano-condensation method was attempted. The effect of the functional groups on the encapsulation was evaluated by transmission electron microscopy. C60, C60(OH)10, and C60H36 can be efficiently encapsulated inside CNHs using toluene, THF, and DMSO as solvents, whereas C60(OH)36 and C60(OH)44 are hardly encapsulated from any solution. Because the molecular size of C60(OH)10 is similar to that of C60(OH)36 and C60(OH)44, the difference in encapsulation is not caused by molecular size. The efficient encapsulation of C60H36 in CNHs suggests that molecules can be encapsulated in carbon nanomaterials even when the π–π interaction with the sp 2-hybridized carbon walls is weak. These results suggest the polarity of the functional group of the C60 derivatives as the main factor in determining whether they can be encapsulated in CNHs. C60(OH)36 and C60(OH)44 contain many hydroxyl groups, thus these molecules self-aggregate and do not pass the holes of CNHs, resulting in poor encapsulation. [Copyright &y& Elsevier]