Efficient light harvesting in self-assembled organic luminescent nanotubes.

Luminescent organic nanotubes derived from the co-assembly of cyanostilbene (CS) based cationic supramolecular polymers and bio-polyanion heparin, a known anticoagulant, have been utilized as highly efficient FRET (fluorescence resonance energy transfer) donors in aqueous media resulting in amplified acceptor emission in the orange-red and near-infrared (NIR). Energy transfer efficiencies higher than 80% and an ultra-high antenna effect of 150 were achieved even at high donor/acceptor ratios (500 : 1-100 : 1) translating to emission quenching of several hundred donors by one acceptor. Utilizing the temperature responsiveness of the FRET process, these systems were employed as ratiometric emission thermometers in the temperature range 20-90 °C. Moreover, the energy transfer was very effective in solid and polymer films. This allowed us to generate multi-color emissions ranging from blue to red including white light in solution as well as in solid and polymer films.