Preparation and Sensing Properties of Covalent-linked Europium Complex Monodisperse Polystyrene Microspheres

Covalent-linked Eu-complex monodisperse polystyrene microspheres were prepared by a simple environment-friendly one-step soap-free emulsion polymerization. Styrene (St) , Eu-complex monomer Eu (AA) (3) Phen] and methacrylic acid (MAA) were separately selected as matric monomer , fluorescent monomer, and water-soluble monomer. Meanwhile, Eu-complex monomer was also acted as cross-linked monomer. The chemical composition and morphology of the copolymer microspheres were characterized by( 13)C CP/MAS NMR , Fourier transform infrared spectrophotometer (FTIR) , X-ray photoelectron spectroscopy (XPS) , scanning electron microscope (SEM) , transmission electron microscope (TEM) , particle size analysis and zeta potential analysis. With the increase of Eu-complex content, the stability of the emulsion decreased, and the particle size and its distribution of the polystyrene microspheres increased; meanwhile , the thermal stability of the polystyrene microspheres was also decreased. Through regulating Eu-complex monomer content (0. 25%-2. 5% , mass fraction) , the polystyrene microspheres feature a stable spherical morphology with a narrow size distribution. Excited by ultraviolet light, the polystyrene microspheres can emit the characteristic red light of europium ion. The luminescence of the polystyrene microspheres originates mainly from the sensitization of ligands to europium ions , that is , the energy transfer from ligands to europium ions. Due to the strong binding ability of Fe3+ to N and O atoms , the coordination structure of Eu-complex has changed after adding iron ions. As a result , the luminescence of the polystyrene microspheres can be quenched by Fe3+, and the common anions and other metal ions have little interference. The quenching efficiency are linearly related to the concentration of Fe3+ ranged from 0 to 300 mu mol/L. With the increase of the content of the europium complex monomer, the fluorescence intensity of the polystyrene microspheres is enhanced, and the fluorescence detection K(SV )of Fe(3+ )is increased , while limit of determent (LOD) is decreased. Regulating the content of the europium complex, the monodisperse copolymer fluorescent microspheres exhibit excellent thermal stability, strong red light emission, and high selectivity for Fe3+ fluorescence detection, which have high application value in biological detection and environmental protection.