Surface Plasmon Resonance Enhanced Luminescence of Europium Complexes with Ag@SiO2 Core-Shell Structure

Three types of Ag@SiO2 nanoparticles with silica shell thicknesses of around 10, 25, and 80 nm were prepared. Europium complexes with benzoate (BA) in different proportions, 1,10-phenanthroline (phen) and 2,2'-bipyridine (bpy), were synthesized and characterized. The results suggest that the complexes have the formulas Eu(BA)(n)Cl3-n center dot 2H(2)O (n=1, 2, 3), Eu(phen) Cl-3 center dot 2H(2)O, and Eu(bpy) Cl-3 center dot 2H(2)O. The luminescence spectra of the complexes showed that adding Ag@SiO2 nanoparticles increased the fluorescence intensity. The fluorescence enhancement sequence of the different silica shell thickness Ag@SiO2 nanoparticles was 25 nm>80 nm>10 nm, which showed that the local surface plasmon resonance was strongest at the silica shell thickness of about 25 nm. Furthermore, the enhancement effect for the Eu(phen) Cl-3 center dot 2H(2)O complex was the strongest and that for the benzoic complex Eu(BA)(n)Cl3-n center dot 2H(2)O was the weakest in these complexes. For the three benzoic complexes, the enhancement effect of Eu(BA)(3)center dot 2H(2)O was the lowest. The nitrogenous complexes (Eu(phen) Cl-3 and Eu(bpy) Cl-3) could combine withAg@SiO2 nanoparticles very well, while the interaction of Eu(BA)(3)center dot 2H(2)O with Ag@SiO2 nanoparticles was weaker. Ag@SiO2 nanoparticles are expected to enhance luminescence of rare earth materials.