Optical properties of gold nanoparticle embedded Er3+ doped lead–tellurite glasses

Abstract

Enhanced optical properties of rare earth doped glasses for sundry applications are current challenges in materials science and technology. Series of gold nanoparticles (GNPs) embedded Er3+ doped TeO2–PbO–PbO2 glasses are synthesized and the influences of GNPs on the optical behaviors are examined. XRD spectra confirm the amorphous nature of all the glass samples. TEM images display the existence of a broad distribution of spherical crystalline GNPs with average diameter ∼6.09nm. UV–Vis–NIR spectra reveal seven absorption bands centered at 490, 526, 551, 652, 800, 982 and 1520nm due to the absorptions from the ground state to different excited states. Two surface plasmon resonance bands of gold (Au0) are evidenced at 556 and 585nm. The sizable decrease in the optical band gap (2.82–1.09eV) with the increase of GNPs concentration from 0.025 to 0.1mol% is attributed to the generation of higher NPs nucleation sites. The intensity parameters related to the radiative transitions within 4fn configuration of Er3+ ion are determined and analyzed using Judd–Ofelt (J–O) theory. The room temperature up-conversion emission spectra under 779nm excitations shows three peaks centered at 520, 550 and 660nm corresponding to the transitions from 2H11/2, 4S3/2 and 4F9/2 excited states to 4I15/2 ground state. Significant enhancement in the luminescence intensity is primarily ascribed to surface plasmon resonance mediated strong local field effect of GNPs in the proximity Er3+ ion and radiative energy transfer. The maximum enhancement are evident for green and red bands at 0.05mol% of Au. The stimulated emission cross-section exhibits maximum value ∼40.2×10−19 and the branching ratio as much as 90% for 4S3/2→4I15/2 transition is accomplished. The excellent features of achieved results suggest that our findings may provide useful information toward the development of functional glasses.