Enhancement of the Eu3+ luminescence in Li2B4O7 glasses co-doped with Eu and Ag

The luminescence properties of the Eu-doped and Eu-Ag co-doped glasses with Li2B4O7 (Li2O-2B2O3) basic composition are investigated and analysed. The Li2B4O7 glasses of high chemical purity and optical quality, doped with Eu and/or Ag were obtained in the air atmosphere using standard glass technology. Spectroscopic properties of the obtained Li2B4O7:Eu and Li2B4O7:Eu,Ag glasses were studied using optical absorption, photoluminescence (excitation, emission, decay kinetics), and quantum yield measurements. Photoluminescence spectra of the Li2B4O7:Eu glass reveal emission bands, which correspond to the 5D0 → 7FJ (J = 0 - 6) transitions of Eu3+ ions. The enhancement of Eu3+ luminescence in the Li2B4O7:Eu,Ag glass have been observed. The external quantum yield (QY) of luminescence was measured via an absolute method. The QY of Eu3+ luminescence increases from 11.7% to 26.1% in the Li2B4O7:Eu,Ag glass in comparison with Li2B4O7:Eu glass. Such enhancement is attributed to the energy transfer from Ag+ ions and very small molecule-like non-plasmonic silver aggregates to the Eu3+ ions as the major factor, and local field effects induced by surface plasmon resonance of the silver nanoparticles. The obtained high external quantum yield shows that the Li2B4O7:Eu,Ag glasses belong to perspective luminescent materials.