The effect of silver and gold nanoparticles on optical properties of europium-doped magnesium-zinc-sulfophosphate glass system

Abstract

Three series of europium doped magnesium zinc sulfophosphate glasses co-embedded with silver and gold nanoparticles of composition 65P2O5-20MgO-15ZnSO4–(x)Eu2O3with 0 ≤ x ≤ 2.0 mol%, 63.5P2O5-20MgO-15ZnSO4–1.5Eu2O3–(y)AgCl with 0.1 ≤ y ≤ 1.1 grams and 63.5P2O5-20MgO-15ZnSO4–1.5Eu2O3–0.9gAg–(z)Au with 0.05 ≤ z ≤ 0.30 grams in excess were prepared using melt quenching technique. Pink samples were obtained. The existence of broad hump in X-ray diffraction (XRD) pattern verifies the amorphous nature of glasses. The presence of silver nanoparticles with an average diameter of 27.65 nanometer in the glass matrix is confirmed by transmission electron microscope (TEM) image but when co-embedded with gold and silver nanoparticles, Au-Ag core-shell structure was formed. The glass density (ρ) and molar volume (Vm) are in the range of (2.5481 - 4.3304 g/cm3) and (30.8883 - 62.8024 cm3.mol-1), respectively. The Fourier transform infrared (FTIR) and Raman spectra reveal no modification in the network structures. Two surface plasmon resonance (SPR) peaks are detected at 457 nm for AgNPs and 510 nm for AuNPs from ultraviolet-visible (UV-Vis) absorption spectra. The optical energy band gap and Urbach energy are found in the range of (3.2665 - 3.8988 eV) and (0.1659 - 0.4024 eV), respectively. Refractive index has been computed and found in the range of (1.7439 - 1.7592). The absorption measurement is complemented with the determination of bonding characteristics of Eu3+ and ligand via calculations of nephelauxetic ratio and Racah parameters. Racah parameters B and C are found in the range of (60.1111 - 111.7894 cm-1) and (7648.0342 - 8308.2407 cm-1), respectively. Crystal field ranged between (21.8049 - 42.2446 cm-1). Mechanical properties such as hardness were found to increase linearly from (217 - 386 Hv). The glass samples are excited under 396 nm excitation wavelength and the emission at 613 nm. Intensity parameters (Ω2 and Ω4) and radiative properties were evaluated using Judd-Ofelt (J-O) theory. The synthesized glasses revealed a trend of Ω2 > Ω4 which signify high symmetry environment around Eu3+. The prepared glass shows excellent values of optical gain and branching ratio (5.10×10-25 - 15.87×10-25 cm2s-1) and (8.27% - 61.6%), respectively. Optimum values of critical laser parameters for 5D0→7F2 transition in PEAAu0.25 glass was 15.7×10-25 cm2s-1 for optical gain and 9.55×10-22 cm2 for gain bandwidth. The photoluminescence intensity enhancement of such transition rises twice in comparison to glass without Ag NPs and Au NPs which is attributed to the local field effect via surface plasmon resonance and energy transfer from Ag0 to Eu3+. The decay half-life is determined in the range of (2.045 - 2.001 μs). The properties of glasses are largely dependent on europium, Ag NPs and Au NPs concentrations. The achieved colour purity by Commission Internationale de I’éclairage (CIE) diagram and the achieved high quantum efficiency (=97.9%) of the synthesized glasses with usual standard chromaticity coordinates of red colour region suggest that the proposed glass composition may contribute towards the development of light emitting diodes (LEDs). The optical properties of each glass were improved due to the embedment of Ag and Au NPs into the glass matrix.