• Aggregation of hydrophobic chelate complexes and organic dyes in aqueous environment by reprecipitation from water-miscible solvents leads to formation of fluorescent nanoparticles. It was found that chelate nanoparticles uptake cationic, neutral, and anionic dyes in its structure.
• The phenomenon of FRET was observed in the dye-doped chelate nanoparticles. Dye molecules act as energy acceptors and quench fluorescence of chelates; simultaneously the rise of sensitized dyes fluorescence is observed.
• The change of doping dye opens way to convert ultraviolet radiation absorbed by chelates into visible light of different spectral regions.
• The strong influence of nanoparticles composition on the efficiency of energy transfer between chelates and dyes was observed. It was found that complexes of Al3+ and Sc3+ have 10-times higher fluorescence quantum yields than complexes of Ln3+ ions as the intersystem crossing rates drop in the complexes of lighter metal ions. The increase of singlet state lifetimes stimulates energy migration on chelate complexes and provides better efficiency of energy transfer from chelates to dyes. Ln3+ ions with suitable energy levels can accept energy absorbed by ligand molecules. The process of cascade energy transfer involving Ln3+ energy states as intermediate states in energy transfer from chelate ligands to dyes was observed. This process significantly enhances sensitized dyes fluorescence.
(a) Photography of nanoparticles samples doped by different dyes under ultraviolet irradiation. (b) Fluorescent spectra of nanoparticles. 1 – undoped nanoparticles, 2 – Coumarin 30 doped nanoparticles, 3 – Rhodamine B doped nanoparticles, 4 - Oxazine 170 doped nanoparticles
• Fluorescent labels for bioimaging application. Fluorescence of dye-doped nanoparticles is significantly brighter than that of organic molecules.
• Highly sensitive immunofluorescence assays.