Excited state behaviour of acridinedione dyes in PMMA matrix: inhomogeneous broadening and enhancement of triplet

Photophysics and photochemistry of acridinedione (ADD) dyes doped in PMMA matrix have been studied using fluorescence and flash photolysis technique. The absorption and emission spectra of acridinedione dyes in PMMA matrix are broad. A pronounced influence of λexc on the red shift of ADD fluorescence spectra was found which is independent of the various substituents in the ADD dyes. This observed shift was explained by the inhomogeneity in the PMMA matrix site results in the migration of the electronic excitation energy from the blue centres to red ones. The inhomogeneous distribution of ADD dyes in PMMA matrix causes the non-exponential fluorescence decay. The triplet lifetimes of these dyes in polymer matrix is found to be in millisecond time domain, whereas in solution the triplet lifetime is in microseconds. Laser flash photolysis shows that the photoionisation of ADD dyes in PMMA matrix results in the formation of an electron and a cation radical. Steady state photolysis of ADD dyes in PMMA matrix was carried out. ADD dyes have higher photostability in PMMA matrix than in solution.