Comparison of Singlet Oxygen Production Efficiency of C60 with Other Photosensitizers, Based on 1268nm Emission

Singlet oxygen generation from laser-excited C60 was measured directly by using a sensitive near-infrared emission spectrometer to monitor the O2(1Δg)→O2(3Σg-) transition at 1268nm. The emission intensity was proportional to both the laser power and the concentration of C60. When nitrogen gas was bubbled into the C60 solution, the spectrum disappeared. Dose-dependent quenching of singlet oxygen by β-carotene was observed by monitoring the 1268nm emission. Based on the quenching, the rate constant of the reaction of singlet oxygen with β-carotene was determined to be 1.5-2.3×1010M-1s-1, which is consistent with the reported value (1.5-2.5×1010M-1s-1). A comparison of the singlet oxygen-producing ability of C60 as a photosensitizer with those of rose bengal. eosin and methylene blue, revealed C60 to have considerably higher efficiency.