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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 18: Light-Induced Phenomena

CPP 18.3: Vortrag

Mittwoch, 28. März 2007, 15:00–15:15, H40

Reversible and Irreversible Photobleaching of Organic Dyes in Polymers — •Jörg Schuster, Jörg Brabandt, and Christian von Borczyskowski — Center for nanostructured materials and analytics, TU Chemnitz, 09107 Chemnitz

The photoinduced decay of fluorescence of organic dyes (photobleaching) is usually discussed in terms of irreversible photochemical modifications of the dye molecules (often photooxidation). We can show now, that the fluorecence decay from a number of dyes is mostly reversible in the initial part. The reversible decay is due to fluorescence intermittency with power law distributed on- and off- intervals (blinking) [1,2].

By measuring the recovery of the initially bleached lumincescence after a given waiting time as a function of the bleaching time we are able to discriminate the reversible and irreversible fraction of the luminescence decay. The finding, that an intermittency induced photophysical bleaching process dominates the initial stages of photobleaching may shine new light on the puzzling variety of data on nonexponential photobleaching kinetics which has been published in the literature on photobleaching during the past decades. Once deconvoluted, the irreversible photochemical bleaching kinetics follows a simple single exponential decay. The photophysical bleaching is assigned to the photoejection of charges into the polymer. This reversible photoionisation process takes place on time scales from milliseconds to minutes.

[1] Schuster et al., Appl. Phys. Lett. 87 (2005), 051915

[2] Schuster et al., J. Luminescence, in press