The fluorescence properties of Er3+ in densified sol-gel silica and alkyl-modified silicates are presented. In sol-gel silica, strong infrared (4I13/2→4I15/2) emission was observed over a wide range of Er3+ concentrations. The effect of metal ion co-dopants, which are known to inhibit clustering of Eu3+ in sol-gel silica, on Er3+ fluorescence are also considered. The co-dopants La3+, Y3+, Yb3+, and Al3+ are increasingly more effective at inhibiting Er3+ clustering and promoting a more uniform spatial distribution of Er3+ ions. Lifetime studies were also conducted to assess the extent of hydroxyl quenching.
Organic/inorganic hybrid silica gels are expected to contain a lower amount of water than simple sol-gel silica gels and should be better hosts for rare earth ions. Er3+-doped hybrid organic/inorganic gels were prepared using Si(OC2H5)4 and CH3Si(OC2H5)3, (CH3)2Si(OC2H5)2 or C2H5Si(OC 2H5)3. Er3+ fluorescence spectra and lifetime studies of these gels are presented and compared to simple Er3+-doped sol-gel silica. The effect of organic modification on Er3+ clustering and hydroxyl retention are discussed. Er3+ upconversion properties are also discussed.