A series of Sm (x) Tb1-x (TTA)(3)Phen (x = 1.0, 0.9, 0.7, 0.5, 0.3, 0.1, 0) complexes was synthesized by wet chemical method and characterized using Fourier transform infrared spectroscopy and fluorescence spectroscopy. The IR absorption spectra indicate that alpha-thenoyltrifluoroacetone was coordinated to the rare earth ions and that chemical bonds were formed between rare earth ions and the nitrogen atoms in 1,10-Phenanthroline (Phen). The fluorescence spectra of the complexes indicate that the emission intensity of Sm3+ was enhanced by the addition of substitutive Tb3+. These data show that not only the ligands (TTA and Phen) but also Tb3+ could absorb and transmit energy to Sm3+ in the complexes. Formation of dual-core complexes appears to be responsible for co-fluorescence, which can greatly promote the illuminant ability of Sm (TTA)(3)Phen complex. After further encapsulation by SiO2, the Sm (x) Tb1-x (TTA)(3)Phen@SiO2 core-shell structure was very stable to UV light.