Impact of thermal annealing time on luminescence properties of Eu3+ ions in silver nanoparticles embedded lanthanum sodium borate glasses

Abstract

Eu3+ ions doped Ag NPs embedded glasses have been prepared in a glass composition (80-x-y)B2O3-15Na2O-5La2O3-xEu2O3-yAgCl (where × = 0.0, 0.5 mol% and y = 0.1 mol%) by a well-known conventional melt quenching method. Tuning of the surface plasmon resonance band and the nucleation of silver nanoparticles (Ag NPs) was controlled by a thermal annealing schedule. Annealed samples displayed a broad surface plasmon resonance band positioned at 426 nm and its intensity gradually increases with increasing annealing time. HR-TEM micrographs reveal the formation of spherical Ag NPs inside the glass system with an average particle size around 6 nm (for annealed samples). The structural characterizations FESEM and EDX measurements has been also carried out. Photoluminescence (PL) excitation and emission spectra were recorded for studied glasses. The optimum PL enhancement of the Ag NPs embedded glass system was obtained at 10 h of heat treatment and subsequently PL intensity decreased beyond 10 h annealing time (PL quenching was observed). Photoluminescence results reveal that the improvement in the PL intensity of Eu3+ ions is predominantly due to the local field effect attributed by the silver NPs and the PL intensity quenching of Eu3+ ions attributed to the resonance energy transfer from Eu3+ ions to silver nanoparticles. Judd-Ofelt theory has been used to calculate the radiative parameters like intensity parameters, radiation transition probabilities, branching ratios and radiative lifetimes of Eu3+ ions. The calculated radiative parameters and luminescence studies suggested that the investigated 10 h annealed glass system was practically appropriate material for the development of LEDs and solid state lasers.