Zusammenfassung
We report on a new method for sensing trace oxygen in the gas phase. It is based on the extreme efficiency of the quenching of the thermally activated delayed fluorescence of isotopically enriched carbon-13 fullerene C-70 (C-13(70)). This fullerene was dissolved in polymer matrixes of varying oxygen permeability, viz., polystyrene (PS), ethyl cellulose (EC) and an organically modified silica gel ...
Zusammenfassung
We report on a new method for sensing trace oxygen in the gas phase. It is based on the extreme efficiency of the quenching of the thermally activated delayed fluorescence of isotopically enriched carbon-13 fullerene C-70 (C-13(70)). This fullerene was dissolved in polymer matrixes of varying oxygen permeability, viz., polystyrene (PS), ethyl cellulose (EC) and an organically modified silica gel ("ormosil"; OS). The sensor films (5-10 mu m thick), on photoexcitation at 470 nm, display a strong delayed photoluminescence with peaks between 670 and 700 nm. Its quenching by molecular oxygen was studied at 25 and 60 degrees C and at concentrations from zero up to 150 ppmv of oxygen in nitrogen. The rapid lifetime determination (RLD) method was applied to determine oxygen-dependent lifetimes and for fluorescence lifetime imaging of oxygen. The lower limits of detection (at 1% quenching) vary with the polymer used (EC similar to 250 ppbv, OS similar to 320 ppbv, PS similar to 530 ppbv at 25 degrees C) and with temperature. The oxygen sensors reported here are the most sensitive ones described so far.
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