Structural and optical correlation of europium and dysprosium co-doped boro-telluro-dolomite glasses incorporated with silver nanoparticles

Abstract

Rare earth ions doped glasses with tailored lasing and light emitting potency are active area of materials science research. In this view, a series of Eu3+ and of Dy3+ co-doped (at various concentrations) boro-telluro-dolomite (BTD) glasses included with silver nanoparticles (Ag NPs) were prepared by melt-quenching method and characterized for the first time. The role of co-dopants and Ag NPs contents on the optical and structural performance of the studied glasses was evaluated. X-Ray diffraction (XRD) patterns of the as-quenched samples affirmed their amorphous nature, and the energy dispersive X-ray (EDX) spectra showed the presence of actual chemical compositions of the glasses. The existence of Ag NPs with an average diameter of 25.50 nm in the glass matrix was verified using the high-resolution transmission electron microscopy (HRTEM) analyses. Ultrasonic and Vicker‘s micro-hardness analyses displayed high mechanical stability of these glasses. Fourier transformed infrared (FTIR) and Raman spectra of the glasses revealed various chemical functional units in their network structure. Ultraviolet-visible-near-infrared (UV-Vis-NIR) spectral data was used to estimate the optical band gap energies and refractive indices of the glasses using three different models. BTD1.0AgCl sample exhibited a distinct broad surface plasmon resonance (SPR) band at 479 nm. The photoluminescence spectra of the Eu3+-doped glasses (under 464 nm excitation) displayed five significant emission bands at 577, 591, 611, 652 and 702 nm matching with 5D0 7FJ transitions (with J 0, 1, 2, 3, and 4) wherein the band intensities were quenched beyond 1 mol% of Eu3+ doping. The symmetry of the ligands in the vicinity of Eu3+ and Dy3+ in addition to their bonding nature of the glasses were evaluated from the Judd-Ofelt intensity parameters Ω2, Ω4, and Ω6. The observed emission spectral overlap and change in the fluorescence lifetime indicated a substantial bi-directional energy transfer between Eu3+ and Dy3+ in the glass matrix, confirming the Forster-Dexter energy transfer process via the electric dipole–dipole interactions. Besides, the inclusion of Dy3+ altered the emission color of Eu3+ from red region with CIE coordinates of (0.638, 0.361, for BTD1.0Eu glass) to white light zone with CIE coordinates of (0.395, 0.317). The achieved hue was very close to the ideal red color phosphor value of (0.67, 0.33) and pure white light value of (0.33, 0.33). The calculated lasing parameters such as the transition probability, stimulated emission cross-section, luminescence branching ratio, optical gain, gain bandwidth, and radiative lifetime showed enhancement due to the incorporation of Dy3+ and Ag NPs. The produced glasses exhibited high color purity (ranged from 24 – 97.04%) and better quantum efficiency (ranged from 54.88 – 97.81%), wherein such improvements were mainly attributed to the efficient energy transfer between Eu3+ and Dy3+ as well as the Ag NPs SPR-induced local field effects. Overall, a correlation between the structural and optical features of the BTD glasses was determined. Based on the obtained results it can be concluded that the proposed glasses have great potential for the solid-state red laser and white light emitting devices applications.