Amphiphilic Fluorescence Resonance Energy-Transfer Dyes: Synthesis, Fluorescence, and Aggregation Behavior in Water.

Amphiphilic pyrene/perylene bis-chromophore dyes were synthesized from unsymmetrically substituted perylene bisimide dyes, which were obtained through three synthetic methods. The optical and aggregation behaviors of these functional dyes were studied by means of UV/Vis absorption and fluorescence spectroscopy, dynamic light scattering, and TEM. These dyes are highly fluorescent and cover the whole visible-light region. A donor/acceptor dye displays intramolecular fluorescence resonance energy transfer (FRET), with a high efficiency of up to 96.4 % from pyrene to perylene bisimide chromophores, which leads to a high fluorescence color sensitivity to environmental polarity. Under a λ=365 nm UV lamp, the light-emitting colors of the donor/acceptor dye change from green to yellow with increasing solvent polarity, which demonstrates application potential as a new class of FERT probes. The donor/acceptor dye in water was assembled into hollow vesicles with a narrow size distribution. The bilayer structure of the vesicular wall was directly observed by means of TEM. These vesicular aggregates in water are fluorescent at λ=650-850 nm within the near-infrared region.