Temperature dependence of tryptophan and tyrosine luminescence in poly(vinyl alcohol) films

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Abstract
The temperature dependence of the fluorescence and phosphorescence from tyrosine and tryptophan in poly(vinyl alcohol) films has been studied over the temperature range 90-295 K. A kinetic scheme is proposed which allows the calculation of activation energies for excited singlet and triplet state deactivation processes. A single temperature-dependent radiationless process from the singlet state is observed for tyrosine and tryptophan, with activation energies of 5.2�0.4 and 7.1�0.6 kJ mol-1 respectively. However, two distinct temperature transitions have been detected for triplet-state relaxation at 180 and 255 K. The role of polymer phase transitions in determining excited state relaxation pathways of embedded luminescent probes is discussed.

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