Gold nanoparticles assisted surface enhanced Raman scattering and luminescence of Er3+ doped zinc-sodium tellurite glass

Abstract

Significant enhancements in Er3+ luminescence and Raman intensity mediated via surface plasmon resonance (SPR) of gold (Au) nanoparticles (NPs) embedded zinc-sodium tellurite glass are reported. The observed modifications in the physical and spectroscopic properties are ascribed to the alterations in the glass network. XRD pattern confirms the amorphous nature of prepared glass sample. UV-vis-NIR spectra reveal seven absorption bands. Surface plasmon band is evidenced around 626-630 nm. TEM images manifest the growth of non-spherical Au NPs with average diameter between ~7.2 nm and 8.6 nm. The visible up-conversion (UC) emission for all samples under 779 nm excitation exhibits three bands centered at 503 nm (green), 546 (green) and 637 nm (red) ascribed to 2H11/2?4I15/2, 4S3/2?4I15/2 and 4F9/2?4I15/2 transitions. Glass sample with 0.4 mol% Au displaying the highest luminescence intensity with enhancement factor of 3.85 and 3.56 for green bands, and 7.61 for the red band is ascribed to the NPs local field enhancement and energy transfer between rare earth (RE) ions and NPs. FTIR spectra show the vibration of ZnO4 bonds, TeO bond in TeO3 (tp) and TeO4 (tbp) units and the hydroxyl groups. Raman spectra demonstrate the presence of ErO and ZnO bond, anti-symmetric vibrations of TeOTe bonds and stretching modes of non-bonded oxygen exists in TeO3 and TeO3+1 unit. The amplifications in Raman signals by a factor of 1.62, 1.58, 1.64, 1.68 and 1.69 corresponding to the peak centered at 262 cm-1, 382 cm-1, 521 cm-1, 670 cm-1 and 725 cm-1 are attributed to the contribution of a surface plasmon generating a strong, localized and secondary field. We assert that our glass compositions offer favorable potential to develop solid state lasers and other versatile nanophotonic device