Contribution of Eu ions on the precipitation of silver nanoparticles in Ag-Eu co-doped borate glasses

Ag+ doped sodium borate glasses with different Eu ions concentration were prepared by the melt-quenching method. The absorption at about 410 nm which was caused by the surface plasmon resonance (SPR) of Ag nanoparticles (NPs) is promoted with increasing of Eu ions concentration. Meanwhile, the luminescent spectra showed that the emission intensity of Ag+ decreased while that of the Ag aggregates increased simultaneously. The results indicated that the Ag ions intend to form the high-polymeric state such as Ag aggregates and nanoparticles with increasing of europium ions. Owing to the self-reduction of Eu3+ to Eu2+ in our glass system, it revealed that Ag+ has been reduced by the neighboring Eu2+ which leads to the formation of Ag aggregates and the precipitation of Ag NPs in the matrix. In addition, energy transfer (ET) process from Ag+/Ag aggregates to the Eu3+ was investigated for the enhancement of Eu3+ luminescence.