Energy Transfer in a Nanoscale Multichromophoric System:  Fluorescent Dye-Doped Conjugated Polymer Nanoparticles

Abstract

We report on the fluorescence properties and the combined effects of energy diffusion and energy transfer in polyfluorene nanoparticles doped with a variety of fluorescent dyes. As the doping host, polyfluorene possesses extraordinary "light harvesting" ability, resulting in higher per-particle brightness as compared to dye-loaded silica nanoparticles of similar dimensions. Both the steady-state fluorescence spectra and time-resolved fluorescence measurements indicate highly efficient energy transfer from the host polymer to the acceptor dye 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 importance of particle size and energy diffusion within the polymer in determining the optical properties of the doped conjugated polymer nanoparticles. Fluorescence quantum yields of ~40% and peak extinction coefficients of 1.5 × 10(9) M(-1)cm(-1) were determined for aqueous suspensions of ~30 nm diameter polymer nanoparticles doped with perylene or coumarin 6 (2 wt %). Photobleaching experiments indicate that energy transfer phenomena strongly influence the photostability of these dye-doped nanoparticles. Significant features of these nanoparticles include the high brightness, highly red-shifted emission spectrum, and excellent photostability, which are promising for biological labeling and sensing applications. In addition, the nanoparticles are a useful model system for studying energy transfer in dense, nanostructured, multichromophoric systems.

Nanomaterials in fluorescence-based biosensing

“…Materials other than silica, such as polystyrene and liposomes, can also be used, but the relatively large size of the latex microspheres and the chemical instability of liposomes limit their applications in modern biosensing. Recently, fluorescent dye-doped conjugated polymer nanoparticles with an average size of 30 nm have been synthesized which offer several features, including high fluorescence intensity, a highly redshifted emission spectrum, and outstanding photostability [87]. The conjugated polyfluorene is one of this type, which possesses excellent harvesting ability for encapsulated fluorophores of perylene or coumarin 6 [87].…”

“…Recently, fluorescent dye-doped conjugated polymer nanoparticles with an average size of 30 nm have been synthesized which offer several features, including high fluorescence intensity, a highly redshifted emission spectrum, and outstanding photostability [87]. The conjugated polyfluorene is one of this type, which possesses excellent harvesting ability for encapsulated fluorophores of perylene or coumarin 6 [87]. The polymer acted as a highly efficient energy donor to the dye molecule and the high efficiency of the energy transfer was attributed to the combined effects of energy diffusion, Föster transfer, and particle size [87].…”

“…The conjugated polyfluorene is one of this type, which possesses excellent harvesting ability for encapsulated fluorophores of perylene or coumarin 6 [87]. The polymer acted as a highly efficient energy donor to the dye molecule and the high efficiency of the energy transfer was attributed to the combined effects of energy diffusion, Föster transfer, and particle size [87]. The authors demonstrated that such particles had an approximately 200-fold higher fluorescence than QDs and were [82] ∼40 times brighter than silica nanoparticles of a comparable size that had been doped with the same dye molecules [87].…”

In‐ and Out‐of‐Cavity Interactions by Modulating the Size of Ruthenium Metallarectangles

“…Perylene has been intensively used as fluorescent probe, and its basic fluorescence is well documented [19]. The fluorescence quenching of perylene via exciplex formation [20] or energy transfer [21] in solution has been also studied in detail, and we propose here to see whether or not such quenching by encapsulation of perylene inside the cavity of a metallarectangle 10 occurred. The emission spectra of a CH 2 Cl 2 solution of perylene (10 À7 m, 350 nm as excitation wavelength) upon gradual addition of metallarectangle 10 (0.0 -10 equiv.)…”

Non-radiative resonance energy transfer in bi-polymer nanoparticles of fluorescent conjugated polymers

“…Also, recently blends of polymers and dyes have been described by McNeill and associates. This group reported the fluorescence properties and effects of energy diffusion and energy transfer in polyfluorene based nanoparticles, which are doped with various fluorescent dyes [20]. Another study conducted by Scherf and associates involves the excitation energy transfer from polymer nanoparticles prepared via the miniemulsion method to surface-bound Rhodamine 6G [21].…”