Preparation and luminescence characteristics of the europium and terbium complexes incorporated into a silica matrix using a sol-gel method

A series of silica-based composite materials incorporating lanthanide bipyridyl (bpy) and phenanthroline (phen) complexes, SiO2:Ln(bpy)(2)(3+) and SiO2:Ln(phen)(2)(3+) (Ln = Eu, Tb), was prepared by the sol-gel method with luminescence properties studied before and after heat treatment up to 873 K. For the SiO2:Ln(bpy)(2)(3+) and SiO2:Ln(phen)(2)(3+) composites heated at appropriate temperatures, the energy transfer from the bpy or phen ligands to Ln(3+) ions took place smoothly, as for the original complexes, and consequently strong red or green emissions based on Eu3+ and Tb3+ ions were observed. Emission outputs from the lanthanide complexes incorporated into silica gel matrices were intensified by optimizing the concentration of complexes and heat treating at individual temperatures, and the maximum relative emission intensities (vs. Y(P,V)O-4:Eu and LaPO4:Ce,Tb phosphors, as practically used) were ca. 15% and 45% for SiO2:Eu(phen)(2)(3+) and SiO2:Tb(bpy)(2)(3+) composite materials. Furthermore, thermal stability of Ln(bpy)(2)(3+) complexes was effectively improved compared with the original lanthanide complexes by incorporation into an SiO2 matrix.