Photophysics of dimethylamino-substituted polymethine dye in polymeric media

Autor: A.D. Kachkovski, Jacques Gallay, Alexander P. Demchenko, Yuri Slominsky, Michel Vincent, Mikhail V. Bondar, Olga V. Przhonska
Rok vydání: 1999
Předmět:
Zdroj: Journal of Photochemistry and Photobiology B: Biology. 52:19-29
ISSN: 1011-1344
DOI: 10.1016/s1011-1344(99)00096-2
Popis: The photophysical mechanism responsible for the large Stokes shift in dimethylamino-substituted polymethine dye (DMA-PD) has been studied by steady-state and time-resolved fluorescence spectroscopy. Experiments in low-temperature ethanol glass and in polymer polyurethane acrylate (PUA) in glassy and elastic states allow us to conclude that the emission occurs mainly from two excited states with Lifetimes of 2-3 and 6-7 ns, respectively. The excited-state dynamics includes fast subnanosecond rotation of the DMA group around the carbon-dimethylamino bond of the dye molecule and stabilization of this form due to environmental rearrangement. The large Stokes shift remains for this dye in solid media. This process is dynamic even in polymeric media, where it occurs in the subnanosecond-nanosecond time scale. The major spectral shift can be described as an intramolecular excited-state reaction affecting either or both emissive species. We suggest a model in which the twisting of the small dimethylamino group modulates the effective length of the polymethine chromophore, producing the spectral shift. In addition, time-resolved fluorescence anisotropy decays show a slow rotational motion (about 40 ns) of the dye inside the polymer microcavities. These interesting features of the spectral behavior of the PUA matrix doped by DMA-PD may find various applications. (C) 1999 Elsevier Science S.A. All rights reserved.
Databáze: OpenAIRE
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