| Abstract
| - We report on the fluorescence properties and the combined effects of energy diffusion and energy transfer inpolyfluorene nanoparticles doped with a variety of fluorescent dyes. As the doping host, polyfluorene possessesextraordinary “light harvesting” ability, resulting in higher per-particle brightness as compared to dye-loadedsilica nanoparticles of similar dimensions. Both the steady-state fluorescence spectra and time-resolvedfluorescence measurements indicate highly efficient energy transfer from the host polymer to the acceptordye molecules. A model that takes into account the combined effects of energy diffusion, Förster transfer,and particle size was developed. Comparisons of experimental data to the model results elucidate the importanceof particle size and energy diffusion within the polymer in determining the optical properties of the dopedconjugated polymer nanoparticles. Fluorescence quantum yields of ∼40% and peak extinction coefficients of1.5 × 109 M-1cm-1 were determined for aqueous suspensions of ∼30 nm diameter polymer nanoparticlesdoped with perylene or coumarin 6 (2 wt %). Photobleaching experiments indicate that energy transferphenomena strongly influence the photostability of these dye-doped nanoparticles. Significant features ofthese nanoparticles include the high brightness, highly red-shifted emission spectrum, and excellentphotostability, which are promising for biological labeling and sensing applications. In addition, thenanoparticles are a useful model system for studying energy transfer in dense, nanostructured, multichromophoric systems.
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