Observation of the luminescence of singlet oxygen at λ = 1270 nm under LED irradiation of CCl4

The efficiency of singlet-oxygen generation under optical pumping of oxygen dissolved in CCl4 has been analyzed using light-emitting diode arrays at three wavelengths (465, 525, and 625 nm), with direct recording of singlet-oxygen luminescence from the volume of irradiated solvent. The results obtained are compared with the efficiency of singlet-oxygen generation using C60 dissolved in CCl4 as a photosensitizer; it is shown that the efficiencies of singlet-oxygen generation differ by four orders of magnitude (on average) for only the radiation at the input of the solvent volume under study. The quantum yield of singlet oxygen upon direct optical excitation is about unity with respect to the optical-pump radiation absorbed in the solvent volume.