Impact of silver nanoparticles growth on Europium photoluminescence properties in tellurite-based glass

In this work, a europium and silver-co-doped tellurite glass system was developed employing melt-quenching techniques. The glassy samples have been subjected to thermal treatments for various durations at temperatures above T_g. XRD analysis has shown the formation of metallic nanostructures within the synthesized glasses. Using Judd–Ofelt theory and Raman analysis, it was proven that the presence of such nanoparticles, after annealing processes, causes considerable changes in the crystal field environments surrounding Eu³⁺, along with a notable enhancement in the Raman signal. Furthermore, luminescence measurements revealed that increasing annealing times resulted in increased photoluminescence intensities of europium ions and significant improvements in certain spectroscopic parameters associated with the ⁵D₀ → ⁷F₂ transition. Notably, we obtained a high transition probability of around 970 s⁻¹ and a branching ratio exceeding 60%, an average lifetime approximately equal to 0.79 ms, and a high fluorescence quantum efficiency (76.7%) for samples subjected to prolonged heat treatments. Accordingly, we suggested that one of the main reasons which could explain these improvements is the increase in excitation rates of europium ions as a result of both the energy transfers from nanometallic particles and effects of the local electric field. These results may be of great significance in the development of glass materials with high-efficiency luminescent properties, suitable for designing some optoelectronic devices, like luminescent solar concentrators, optical sensors, lasers, and LEDs.