Hannover 2010 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 17: Biomolecules

MO 17.2: Vortrag

Mittwoch, 10. März 2010, 16:45–17:00, F 142

Long-lived fluorescence of 1,6-Diphenyl-1,3,5-hexatriene — •Katharina Hunger and Karl Kleinermanns — Heinrich-Heine-Universität, Düsseldorf, Deutschland

Carotines are an important molecule class for photosynthesis. They are part of the light-harvesting complex, with the task to absorb visible light and transfer the energy to the reaction center of the photosystem. All-trans-α,ω-diphenylpolyenes (also referred to as minicarotines) are well established model compounds for the bigger carotenoids such as β-carotene or lutein. Because of its favourable emission behaviour 1,6-diphenyl-1,3,5-hexatriene (DPH) is also used as fluorescence probe in biological membrane systems. The kinetic behaviour of the fluorescence of 1,6-diphenyl-1,3,5-hexatriene solution after excitation with a 355 nm laser pulse was observed in dependence of concentration and excitation pulse energy. Two mechanisms which cause fluorescence with different lifetimes compete. Below concentrations of 2.5 μM and excitation energies of 1 mJ only ordinary, short-lived fluorescence with a lifetime <20 ns is observed. Above this concentration and excitation energy, very intense and long-lived fluorescence is dominating. The lifetime of the emission can reach up to 70 ns and is decreased dramatically in presence of oxygen. We assume, that reverse intersystem crossing from the triplet state ladder repopulates the fluorescing S2 state after absorption of further photons in the triplet manifold.