Enhanced spectroscopic properties of holmium doped phosphate glass: Role of Ag/TiO2 nanoparticles embedment

Abstract

Metal nanoparticles sensitized rare earth ions–doped inorganic oxide glasses with improved optical characteristics and optimum compositions became demanding for practical applications. However, the basic understanding of the interaction mechanism between various rare earth ions and metallic nanoparticles remains deficient. Based on this fact, some holmium ions (Ho3+)–doped magnesium zinc sulfophosphate glasses with Ag/TiO2 nanoparticles (NPs) co–activation were prepared using the melt–quenching process and characterized. Effects of Ag/TiO2 NPs co–activation at various contents on the physical, optical and structural properties of the glasses were determined. XRD analyses of the as–quenched samples confirmed their amorphous nature. FTIR and Raman spectra of the glasses showed structural modifications due to NPs incorporation. HRTEM image verified the existence of spherical Ag and non–spherical TiO2 NPs (mean size of 13.01 nm) in the glass matrix. The absorption spectra of the glasses displayed eleven significant peaks and photoluminescence spectra revealed prominent green (5F4 → 5I8) and red (5F5 → 5I8) emission peaks corresponding to various transitions in Ho3+. The oscillator strengths, Judd–Ofelt intensity and radiative parameters of the glasses were calculated to support the experimental results. The optical properties of the glasses were shown to improve via the Ag/TiO2 NPs co–activation. Among the prepared samples, glass containing 0.3 mol% of TiO2 NPs showed high stimulated emission cross–section (3.24 × 10−20 cm2) for the green emission, maximum quantum efficiency and radiative lifetime. The explanation of PL intensity enhancement and quenching mechanisms of Ho3+ may provide better understanding on the co−activation of metal/semiconductor NPs in the studied glasses.