Enhanced Förster resonance energy transfer in electrostatically self-assembled multilayer films made from new fluorescently labeled polycations
The synthesis of two new complementary fluorescently labeled polycations, which are derived from 4-(vinylbenzyl chloride) and coumarin, and their use for layer-by-layer multilayers films applying electrostatic self-assembly (ESA) are reported. The alternating polyelectrolyte deposition cycles were followed by UV-vis spectroscopy, ellipsometry, and X-ray reflectivity. Regular growth was observed. Fluorescence and UV-vis measurements showed the formation of fluorescent dye aggregates for one coumarin derivative in the ESA multilayers. The resulting shift in the spectra enhances the spectral overlap between the two fluorescently labeled polycations when used in mixed thin films, improving the efficiency of the Förster resonance energy transfer between the chromophores. The nonradiative nature of the energy transfer was confirmed by fluorescence decay time measurements.