Abstract
The fluorescence kinetics of 1,6-diphenyl-1,3,5-hexatriene (DPH) dissolved in cyclohexane was investigated as a function of temperature, concentration and 355 nm excitation pulse energy. At concentrations above 2.5 μM and excitation energies above 1 mJ a long-lived, very intense emission, which appears within less than 5 ns and lasts up to 70 ns, is observed. During the first 50 ns the decay does not follow an exponential but rather a linear behaviour. In oxygen saturated solutions the long-lived emission is suppressed and solely short-lived fluorescence with τ 1-state and competes with the formation of DPH-O2 contact charge-transfer complexes and intersystem crossing which both quench the fluorescence. Our investigations show that even the small amount of oxygen dissolved in nitrogen saturated solutions has a distinct influence on the fluorescence kinetics of DPH.
Highlights
Carotenes constitute an important molecular class for photosynthesis
In this work we studied the temporal fluorescence behavior under different conditions like various DPH and O2 concentrations and different temperatures and excitation laser pulse energies to identify the various competing processes like formation of DPH-O2 contact charge-transfer (CCT) complexes, whose interplay leads to the linear decay of the longlived emission
The fluorescence kinetics can be investigated in our setup
Summary
Carotenes constitute an important molecular class for photosynthesis They are part of the light-harvesting complex, where they absorb visible light and transfer the energy to the reaction center of the photosystem. Alltrans-α,ω-diphenylpolyenes ( referred to as minicarotenes) are well established as model compounds for the bigger carotenoids such as β-carotene or lutein [1,2,3,4,5,6] The latter absorb light and transfer the energy to the chlorophyll unit of the pigment [7]. In this work we studied the temporal fluorescence behavior under different conditions like various DPH and O2 concentrations and different temperatures and excitation laser pulse energies to identify the various competing processes like formation of DPH-O2 contact charge-transfer (CCT) complexes, whose interplay leads to the linear decay of the longlived emission
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