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

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.