Spectroscopic studies of erbium doped zinc tellurite glass embedded with gold nanoparticles

Abstract

Series of glasses based on (70-x)TeO2 – 30ZnO – 0.5Er2O3 – xAu, where 0.0≤ x ≤ 0.5 mol % were prepared using melt-quenching technique. The nature of the glass was confirmed using X-ray diffraction and the size of Au NPs (GNPs) was estimated by using transmission electron microscope image. It was found that the glass was amorphous in nature with an average diameter size of GNPs of about 2.6 ± 1.6 nm. The thermal stability of the glass was determined by means of differential thermal analysis (DTA). From the DTA curve, the glass transition temperature (Tg), crystallization temperature (Tc) and melting temperature (Tm) was identified and thermal stability was calculated. The structural characteristic was investigated using Fourier transform infra red spectroscopy in the range of 400 cm-1 to 3500 cm-1. The spectra of the glass shows two absorption peaks around 646 cm-1 and 748 cm-1 corresponding to the TeO4 and TeO3 structural units, respectively. The absorption properties of these samples were obtained by using UV-Visible spectrometer which showed six absorption peaks. The values of optical band gap (Eopt) and Urbach energy (Eu) were calculated from the absorption peak and were found to be in the range of 2.57 - 2.64 eV and increased as the concentration of GNPs was increased, while (Eu) was found in the range 0.39 - 0.41 eV. The emission characteristic of this glass was characterized using photoluminescence spectroscopy. It was observed that there were two distinctive emissions centered at 650 nm and 845 nm which are assigned to 4F9/2 - 4I15/2 and 4I13/2 - 4I15/2 transition, respectively under 488 nm excitation wavelength. It was observed that sample of 0.3 mol % GNPs exhibits the highest enhancement due to energy transfer from GNPs to Er3+ ion.