| Abstract
| - Tetracationic water-soluble porphyrin (H2P4+) has been immobilized by π−π stacking interactions onto theskeleton of carbon nanohorns (CNH), without disrupting their π-electronic network. The stable aqueous solutionof the CNH−H2P4+ nanoensemble was examined by both electron microscopy and spectroscopic techniques.The efficient fluorescence quenching of the H2P4+ moiety in the CNH−H2P4+ nanoensemble was probed bysteady-state as well as time-resolved fluorescence emission spectroscopy, suggesting charge separation fromthe photoexcited H2P4+ to CNH. In the presence of methyl viologen dication (MV2+) and a hole trap,accumulation of the reduced species of methyl viologen was observed by the photoillumination of CNH−H2P4+, suggesting that the electron migration from the initially formed charge-separated state takes place.Transient absorption spectroscopy gave further insights on the transient species such as the charge-separatedstate (CNH•-)−(H2P4+)•+, which was consumed in the presence of MV2+ and hole shifter, leaving the reducedmethyl viologen.
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