Micelles as Fluorescence Protector for an Europium Complex in Microcapsules

Microcapsules with excellent fluorescence enhancement arc assembled by using cetyltrimethylammonium bromide (CTAB) micelles to enrich Eu(DBM)(3)Phen (DBM and Phen are dibenzoylmethane and 1,10-phenanthroline, respectively) on CaCO3 particles by the LbL technique. Compared to microcapsules without micelles, the fluorescence intensity of microcapsules with micelles increases 9 times, larger than the 6 times increase of absorbance. This unexpected fluorescence enhancement is attributed to the fluorescence protector effect of CTAB micelles in microcapsules. Energy loss from nonradiative deactivation through energy transfer to high-energy O-H vibrations from the emissive D-5(0) state of Eu(III) is greatly prohibited. The new strategy using micelles in this work not only enriches europium complexes during assembly in aqueous solution hut also yields a fluorescence enhancement ratio larger than the enrichment ratio.