Enhanced Oxygen Singlet Production by Hybrid System of Porphyrin and Enriched (6,5) Single-Walled Carbon Nanotubes for Photodynamic Therapy

We demonstrate that hybrid systems of porphyrins and chirality enriched (6,5) single-walled carbon nanotubes (E-SWCNTs) are better candidates for photodynamic therapy (PDT) than their components alone. Surprisingly, the E-SWCNTs act as optical absorption enhancers to the porphyrins increasing the oxygen singlet production when illuminated by a light source with energy higher than the E-SWCNT gap plus the equivalent in energy of an E-SWCNT phonon. The phenomenon is explained based on energy transfer from the E-SWCNT to the porphyrin which finally transfers it to the oxygen molecule. The large optical absorption cross section of E-SWCNT and the resonance of the porphyrin to the oxygen singlet–triplet transition are responsible for the synergistic effect.