A clean, well-defined solid system for photosensitized 1O 2 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 (ΦΔ) 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 (ΦΔ = 0.51) and in methanol-swollen Nafion® films (ΦΔ = 0.49 ± 0.06). Differences and similarities are discussed in terms of the factors that influence ΦΔ 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.