Photoinduced electron transfer in a carbon nanohorn-C60 conjugate

A nanohybrid combining two allotropic forms of carbon, namely carbon nanohorns (CNH) and C-60, has been obtained from a C-60 derivative bearing a benzocrown ether subunit (crown-C60) and a CNH functionalized with NH3+ groups (CNH-sp-NH3+F-) through ammonium-crown ether interactions. The resulting CNH-C-60 nanohybrid has been characterized by Raman and XPS spectroscopies, thermogravimetric analysis (TGA) and high-resolution transmission electron microscopy (HR-TEM). The photophysical properties of the CNH-C60 conjugate have been investigated in benzonitrile. Femtosecond laser flash photolysis measurements revealed the occurrence of an efficient electron transfer from the singlet excited state of the C-60 moiety to the CNH with a rate constant of 6.5 x 10(10) s(-1) to produce a radical ion pair, which decayed by charge recombination with a lifetime of 1.0 ns to afford the triplet excited state of CNH-sp-NH3+F-and crown-C-60. The two carbon nanoforms play therefore complementary roles in the CNH-C-60 conjugate, the CNH acting as an electron donor and C-60 as an electron acceptor.