Temperature-dependent luminescence and energy transfer in europium and rare earth codoped nanostructured xerogel and sol–gel silica glasses

Luminescence and decay times of Eu3‘ ions codoped with other rare-earth ions (Nd3‘ ,S m 3 ‘ ,D y 3 ‘ ,E r 3 ‘and Yb3‘) were measured at temperatures between 10 and 300 K in order to investigate the excitation energy transfer processes in the nanostructured xerogel and annealed sol}gel silica glasses. Decay-time pro"les were analyzed as the sum of two exponents by applying two models for the electric dipole}dipole type of resonant energy transfer. The critical distances (R 0 ) of energy transfer in Dexter model are con"ned to be in the range of 0.88$0.07 nm (at 300 K), 0.92$0.08 nm (at 10 K) for annealed glasses and 0.93$0.11 nm at 300 K for xerogels. The energy transfer processes are considered to re#ect optical properties of con"ned nanostructured networks in the sol}gel SiO 2 glasses. ( 1999 Elsevier Science B.V. All rights reserved.