Surface enhanced Raman scattering and up-conversion emission by silver nanoparticles in erbium-zinc-tellurite glass

Enhancing the up-conversion luminescence and Raman intensity in rare-earth doped glasses is an important issue for nanophotonics. Erbium-doped zinc tellurite glass with and without silver nanoparticles (NPs) were prepared using melt quenching method. The effect of NPs concentration and annealing time on the Raman and photoluminescence (PL) response were investigated. The presence of silver NPs with Gaussian size distribution having average size ∼12 nm were confirmed by transmission electron microscopy. The Raman spectra consist of six peaks that show red shift. The up-conversion emission exhibits three major visible lines corresponding to the transitions from 2H11/2, 4S3/2 and 4F9/2 excited states to 4I15/2 ground state of Er3+ ion. An eight times enhancement in the Raman and five times in photoluminescence (PL) intensities were attributed to the large electric field originated from the face-centered cubic silver NPs. Quenching of PL emission in the visible range for longer annealing time interval was observed and attributed to dissolution of the growth of NPs in the host glass. The prominent absorption plasmon bands of silver were also evidenced that confirms the non-spherical shape of nanoparticles.