A clean, well-defined solid system for photosensitized 1O2 production measurements

Abstract

Generation of singlet molecular oxygen (¹O₂) by photosensitization with methylene blue (MB) supported in Nafion®–Na films has been quantified by integration of the ¹O₂ emission decay at 1270 nm. The quantum yield of ¹O₂ production (Φ_Δ) in the air-equilibrated solid phase is 0.24 ± 0.03. Information on the ¹O₂ generation environment has been gained from complementary techniques such as UV-Vis absorption and emission spectroscopy, as well as MB fluorescence and triplet–triplet absorption decay. Results are compared with the ¹O₂ generation by MB in methanol solution (Φ_Δ = 0.51) and in methanol-swollen Nafion® films (Φ_Δ = 0.49 ± 0.06). Differences and similarities are discussed in terms of the factors that influence Φ_Δ in solution and in the solid media. The optical and mechanical features of Nafion®, ease of dye loading, compatibility with most solvents, homogeneity, reproducibility and stability of the photosensitizing material makes it a convenient reference for ¹O₂ generation quantum yield measurements in transparent (micro)heterogeneous and homogeneous media.