Photoinduced electron transfer of nanohybrids of carbon nanohorns with amino groups and tetrabenzoic acid porphyrin in aqueous media

Amino carbon nanohorns (CNH–NH₂) are covalently and non-covalently functionalized with tetrabenzoic acid porphyrin (H₂P(CO₂H)₄) forming dispersible nanohybrids in aqueous solution; the nanohybrids are characterized by spectroscopy and electron microscopy. Photoinduced electron-transfer processes of the nanohybrids of carbon nanohorns in aqueous solution are revealed with time-resolved absorption and fluorescence measurements. From the observed fluorescence quenching of the H₂P(CO₂H)₄ moieties by CNH–NH₂, charge separation via the excited singlet state of the H₂P moieties, generating radical cations localized in the H₂P moieties and electrons trapped in CNH, is suggested. In the presence of methylviologen dication (MV²⁺) and a hole-shifting reagent, electron pooling is observed by the light-illumination of the H₂P(CO₂H)₄ moieties in CNH–NH₂ nanohybrids, suggesting that the electron generated by the charge-separation migrates to MV²⁺ in aqueous solution.