Influence of surface plasmon resonance of Ag nanoparticles on photoluminescence of Ho3+ ions in magnesium-zinc-sulfophosphate glass system

Abstract

Two series of magnesium-zinc-sulfophosphate glasses with the high (Series 1) and low (Series 2) doping levels of Ho3+ under varying Ag nanoparticles (Ag NPs) contents were prepared using the melt-quenching method and characterized. The XRD pattern of the as-quenched samples verified their glassy nature. The TEM image revealed the existence of Ag nanocrystallites of diameter ≈4.93 nm with (422) lattice plane orientation inside the glass matrix. The LSPR absorption band of Ag NPs was probed at 408 nm. Absorption spectra of glasses consisted of twelve significant bands wherein 5I8 → 5G6 transition in Ho3+ disclosed the highest intensity. The optical band gap energies of glasses were increased with the rise in Ag NPs contents. The nephelauxetic ratio of both glass series displayed the ionic character of Ho3+ bond with surrounding ligands. The oscillator strength and intensity parameters (Ω2, Ω4, Ω6) were determined using Judd-Ofelt theory. The photoluminescence emission intensity was appreciably influenced by the Ag NPs concentration changes. Series 2 glass showed the highest emission enhancement factor of 2.04 and 2.15 for the 5F4→ 5I8 (green) and 5F5→ 5I8 (red) transition, respectively. The branching ratio and stimulated emission cross-section of the glasses were estimated from the emission spectra. Intense green and red emission obtained from the proposed glasses may be useful for the development of the efficient solid state laser medium.