Singlet oxygen phosphorescence photosensitized in nano-aggregates of C60 buckminsterfullerene is insensitive to solvent and quenchers and strongly red-shifted indicating highly polarizable interior.

We investigated the strongly red-shifted singlet oxygen (1O2) phosphorescence spectra in an aqueous preparation of C60 buckminsterfullerene. The ~10 nm red shift was associated with H2O dispersions of C60 nanoaggregates (C60)n that can photosensitize 1O2 in their polarizable cores. In contrast to 1O2 produced by the water-soluble C60-(γ-cyclodextrin)2 complex, 1O2 trapped inside (C60)n was short-lived (~2-3 μs), insensitive to solvent and 1O2 quenchers, and did not induce photocytotoxicity. To our knowledge, 1O2 spectrum from (C60)n is the most red-shifted 1O2 spectrum recorded to date and it may be used to probe the inner polarizability of carbon (nano)aggregates.