Gold nanoparticles assisted structural and optical modifications of samarium doped sodium-lithium tellurite glass

Abstract

Modifying the physical and the optical properties of rare earth doped tellurite glasses by embedding metallic nanoparticles (NPs) with controlled size and optimized concentration is ever-demanding in solid state lasing materials. Thus, the influences of gold (Au) NPs concentration on the structural and the optical enhancements were examined. Two series of samarium (Sm3+) doped sodium tellurite glasses, with and without Au NPs, which had compositions of (80-x)TeO2 + 10Li2O + 10Na2O + xSm2O3 (where 0.0 ≤ x ≤ 3.0 mol%) and 79TeO2 + 10Li2O + 10Na2O + 1Sm2O3 + yAuCl3 (where 0.03 ≤ y ≤ 0.15 mol% in excess), respectively, were prepared using melt-quenching technique. Subsequent annealing at 300°C for 3 hours was performed to control the growth of NPs. Structural and optical characterizations were determined using XRD, TEM, UV-Vis-NIR, FTIR, and PL measurements. XRD pattern confirmed the amorphous nature of the prepared glasses, whereas the TEM image manifested the growth of spherical NPs with mean size ~18 nm. Meanwhile, FTIR spectra displayed four broad absorption bands, which were assigned to TeO4 and TeO3 tetragonal pyramids, stretching vibration of hydroxyl group, and stretching vibration of strong metal bonding. In addition, the UV-Vis spectra exhibited six peaks that were centered at 471, 948, 1085, 1246, 1395 and 1494 nm, corresponding to the transition from ground state to different excited states of Sm3+ ion. Besides, significant enhancement in the absorption was observed for 0.09 mol% of Au NPs, while the Urbach energy showed an increase from 0.2374 to 0.2588 eV with the increase of NPs concentration. On top of that, the PL spectra displayed four enhanced peaks that were centered at 573, 613, 658 and 718 nm, which had been associated with the transition from the excited states to the ground state of Sm3+ ion. The enhancement was attributed to the surface plasmon resonance (SPR) effect and the strong local field of NPs positioned in the proximity of Sm3+ ion. Modifications in the physical, structural, and optical properties that originated from the alteration of glass network structure in the presence of Au NPs were analyzed and discussed. Furthermore, the mechanism of enhancement was comprehended and compared. The excellent features of the retrieved results suggest that these glasses may be nominated as potential candidates for solid state lasers, displays, and amplifiers.