Effect of silver co-doping on enhancement of the Sm3+ luminescence in lithium tetraborate glass

Luminescent properties of the Sm3+-doped and Sm3+-Ag co-doped glasses with Li2B4O7 (or Li2O-2B(2)O(3)) basic composition are investigated and analysed. Spectroscopic properties of the obtained Li2B4O7:Sm and Li2B4O7:Sm, Ag glasses were studied using measurements of optical absorption, electron paramagnetic resonance (EPR), photoluminescence (excitation, emission, decay kinetics), and quantum yield (QY) via an absolute method. Optical absorption spectra exhibit absorption bands related with transitions from the ground H-6(5/2) state of Sm3+ ions to several excited states. Photoluminescence spectra of the Sm3+-doped glasses reveal emission bands, which correspond to the (4)G(5/2) -> H-6(J) (J = 5/2-13/2) transitions of Sm(3+)ions. Luminescence excitation spectra and decay curves of the Sm3+ luminescence also have been analysed. The EPR study confirms presence of Ag species in the Sm3+-Ag co-doped samples. Photoluminescence emission and excitation spectra and luminescence decay kinetics of the Ag+ ions and small non-plasmonic molecule-like silver (ML-Ag) nanoclusters are observed and discussed. Enhancement of Sm3+ luminescence in the Li2B4O7:Sm, Ag glass has been observed. Measurements confirm the increasing of external QY of the Sm3+ luminescence in 1.43 times in the Ag co-doped glass. Such enhancement of the luminescence is attributed to the excitation energy transfer from Ag+ ions and ML-Ag nanoclusters to the Sm3+ ions. The obtained high QY of the Sm3+ luminescence shows that Li2B4O7:Sm, Ag glasses belong to promising luminescent materials.