Blue emission and energy transfer characteristics of Eu-doped sol–gel glasses without post-processing

We have fabricated SiO 2 -Al 2 O 3 sol-gel glasses which show a distinct blue emission from Eu 2+ ions without any deoxidizing heat-treatment nor post-doping by soaking in Eu-solution. Homogeneity and versatility of the sol-gel process itself, considering combinations with various organic molecules, are thus maintained. The fabrication process required only the hydrolysis of starting materials Si(OC 2 H 5 ) 4 . Al(OC 4 H 9 ) 3 , and Eu(NO 3 ) 3+ . Detailed study of photoluminescence (PL) revealed that the incorporation of Al in correct proportion to the concentration of Eu changes Eu 3+ into Eu 2+ effectively through the sol--gel process. In the blue-emission band of Eu 2+ , centered at 410 nm, a distinct dip due to the dominant absorption line of Eu 3+ was observed at 395 nm, which indicates clearly the energy transfer from Eu 2+ to Eu 3+ .