Origin of luminescence enhancement and quenching of europium complex in solution phase containing Ag nanoparticles

Luminescence enhancement and quenching of Eu(TTA)(3)center dot 2H(2)O complex in DMF (N,N-dimethylformamide) solution containing silver nanoparticles were observed, which depended on the concentrations of both europium complex and silver nanoparticles. Their origins were discussed based on absorption spectra, excitation and emission spectra, and luminescent decay dynamics. The results indicated that when the concentration of Eu complex was high enough, strong interaction among complex molecules occurred. The presence of Ag nanoparticles definitely decreased the interaction among complex molecules. In the solution containing Ag nanoparticles the electronic-dipole transition rate of D-5(0)-F-7(2) increased due to enhanced local field surrounding Eu3+ ions, while the nonradiative transition rate from D-5(0) decreased owing to decreased resonant energy transfer among europium complex molecules. These two factors lead to the luminescence enhancement of europium complex. As to the luminescent quenching, was attributed to absorption competition between Ag nanoparticles and europium complex at excited wavelength.