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CPP: Chemische Physik und Polymerphysik

CPP 9: Single Molecule Spectroscopy

CPP 9.1: Vortrag

Montag, 8. März 2004, 14:00–14:15, H 38

Controlled Fluorescence Bursts from Single Conjugated Polymers induced by Triplet Quenching — •Florian Schindler¹, John M. Lupton¹, Ullrich Scherf², and Jochen Feldmann¹ — ¹Photonics and Optoelectronics Group, Sektion Physik, LMU Munich — ²FB Chemie, University Wuppertal

Single molecule spectroscopy provides fundamental insight into the nature of emission from conjugated polymers. Triplet excitons are particularly important in these materials. We demonstrate here that triplet quenching by molecular oxygen can lead to dramatic fluorescence bursts from conjugated polymers before photo-oxidation sets in. The fluorescence burst is imaged in single molecules of a comparatively photostable ladder-type poly(para-phenylene). Triplet shelving is identified as an important mechanism limiting the fluorescence yield of conjugated polymers due to both a reduction in photon cycling rates and singlet-triplet quenching in the multichromophoric system. The fact that triplet quenching clearly enhances the fluorescence intensity from polymers suggests that intramolecular energy transfer of singlet excitons to long-lived triplet states generated simultaneously on a single polymer chain can also form a quenching pathway for singlet excitons. Besides enabling a direct monitoring of oxygen diffusion through thin polymer films, the sudden fluorescence burst provides a novel tool to study the properties of triplet excitons in conjugated polymers at room temperature down to the single molecule level.