Polarisation single molecule spectroscopy of conjugated polymers

This project is related to the following Fields, Subjects and Techniques:

Fig.1. Examples of fitting polarisation SMS model to experimental 2D plots.

Fig.2. Statistics on absorption and luminescence polarisation depths for samples cast from chloroform and toluene.

Fig.3. Comparison of statistics on the fraction of excitations undergoing energy transfer, derived from the fitting model for samples cast from chloroform and toluene.

Fluctuations of fluorescence polarization degree and polarization direction of as large as 30^o were observed in single molecules of a polythiophene PDOPT. Such fluctuations of polarization of multi-chromophore emission unambiguously show that contribution of each emitting chromophore of different transition dipole moment orientation is changing over time. This "energy redistribution" over the polymer molecule was attributed to conformational fluctuations of the chain and influence of long-living local exciton quenchers presumably triplet states. It is obvious that "standard" model of energy funnelling to a single fluorescence trap is not applicable for this polymer.

M.Forster, D. Thomsson, P.R.Hania, I.G.Scheblykin, "Redistribution of emitting state population in conjugated polymers probed by single-molecule fluorescence polarization spectroscopy", PCCP, 2007, 9, 761