Eu(III)-modified properties of thermosensitive core–shell microspheres

We successfully prepared PNIPAM-g-P(NIPAM-co-St) (PNNS) core–shell microsphere by an emulsifier-free emulsion polymerization method. When PNNS with a core–shell structure is interacted with Eu(III), Eu(III) mainly bonds to oxygen of the carbonyl groups of PNNS, forming the novel PNNS-Eu(III) complex. It was found that the complex showed thermosensitive and fluorescent properties at one time. Especially, the maximum emission intensity of Eu(III) in the complex at 614 nm is significantly enhanced in comparison with that of pure Eu(III), demonstrating that there exists an efficient intermolecular energy transfer from the polymer ligand to Eu(III) and then the excited Eu(III) generates the enhanced fluorescence. When the weight ratio of Eu(III) and the PNNS is 8 wt%, the enhancement of the emission fluorescence intensity at 614 nm is highest.