Photoinduced electron transfer in a carbon nanohorn-C_(60) conjugate

摘要

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-C_(60)) 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-C_(60) 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 × 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.