Physical and spectroscopic characterisation of samarium doped magnesium tellurite glass embedded silver nanoparticles

Abstract

Three series of samarium doped magnesium tellurite glasses embedded with silver nanoparticles (Ag NPs) of composition (89-x)TeO2-10MgO-1Sm2O3-xAgCl with 0 ≤ x ≤ 1.0 mol%, (89.6-x)TeO2-10MgO-(x)Sm2O3-0.4AgCl with 0.2 ≤ x ≤ 1.2 mol% and 88.6TeO2-10MgO-(x)Sm2O3-(1.4-x)AgCl with 0.2 ≤ x ≤ 1.0 mol% were prepared using melt quenching technique. It is found that the glass samples are yellowish in colour depending on their compositions. The existence of broad hump in X-ray diffraction (XRD) pattern verifies the amorphous nature of glasses and the presence of silver nanoparticles with average diameter of 16.94 nm in the glass matrix is confirmed by transmission electron microscope (TEM) image. The glass density (ρ), molar volume (Vm) and ionic packing density (Vt) are in the range of (4.91-5.51) g cm-3 , (27.13-30.46) cm3 mol-1 and (0.444-0.498), respectively. The samples exhibit glass stability up to 102oC which indicates the enhancement in ability of glass formation. The fourier transform infrared (FTIR) and Raman spectra reveal modification in network structures which is evident from the shifted vibrational wave-number of TeO4 and TeO3 structural units located around 600 cm-1 and 700 cm-1, respectively. Two surface plasmon resonance (SPR) peaks are detected at 550 nm for transverse oscillation and 578 nm for longitudinal oscillation from ultraviolet-visible (UV-Vis) absorption spectra. The optical energy band gap and Urbach energy are found in the range of (2.81-3.13) eV and (0.18-0.26) eV, respectively. Refractive index and electronic polarisability have also been calculated and found in the range of (2.35-2.45) and (6.68-7.51) Å3, respectively. The absorption measurement is complemented with determination of bonding characteristic of Sm3+ and ligand via calculations of nephelauxetic ratio and Racah parameters. It is found that the addition of Sm3+ and Ag0 alters the electron distribution which leads to the increase of the covalent bond between Sm and ligand. The glass samples are excited under 554 nm excitation wavelength and the emission spectra are found to consist of a single emission band corresponding to 4G5/2→6H11/2 transition. The intensity enhancement of such transition rises up to 3 times compare to glass without Ag NPs which is attributed to the local field effect and energy transfer from Ag0 to Sm3+. The quality factor, Q is also obtained in the range of 19.20-24.25 which is due to the phonon loss during the non-radiative emission. Meanwhile, decay half-life is determined in the range of (1.4405-1.4459) μs depending on composition. The properties of this glass are very much dependent on the concentration of Sm3+ and Ag NPs. This type of glass has a wide potential to be used as red laser medium and in various photonic applications.