Spectroscopic Determination of Very Low Quantum Yield of Singlet Oxygen Formation Photosensitized by Dyes and Pigments

We have measured the quantum yield QΔ of 1Δg molecular oxygen (singlet oxygen, 1O2) formation photosensitized by some dyes for industrial uses, because the photofading processes of dyes are usually triggered by 1O2. QΔ for industrial dyes, however, is generally very low, and it has been difficult to determine accurately QΔ for them. We have made a highly sensitive spectrometer for 1.27-μm 1O2 phosphorescence detection, and determined QΔ for an azo dye as low as (2.2 ± 1.5) × 10−5. This is the first demonstration of QΔ lower than 10−4 as far as we know. Relationship between QΔ and the lightfastness of practical dyes is also discussed in this study.