Synthesis and Fluorescence Properties of Eu2+-Complex-Doped SiO2 Gels

Eu2+-complex-doped SiO2 gels were prepared and their fluorescence properties were studied. SiO2 gels were obtained by the reactions of silicon tetrachloride, tert-butyl alcohol, and methyl alcohol under nitrogen. Both to protect Eu2+ against oxidation and to enhance the emission intensity of Eu2+, Eu2+ was complexed with 15-crown-5 or its derivative. Samples showed blue emission. Fluorescence lifetimes of samples varied from 690 to 955 ns depending on the Eu2+ concentration at 290 K. After drying of samples, 50-70% of Eu2+ remained in the divalent state without oxidation in the samples. It was found that Eu2+ complexes inside gels were stable against oxidation in air.