Optik 136 (2017) 553–557 Contents lists available at ScienceDirect Optik j ourna l ho me pa ge: www.elsevier.de/ijleo Enhanced luminescence properties of Nd 3+ doped boro-tellurite glasses via silver additive M. Reza Dousti a,b,∗ a Instituto de Física, Universidade Federal de Alagoas, Maceió-AL, Brazil b Department of Physics, Islamic Azad University, Tehran-North Branch, Tehran, Iran a r t i c l e i n f o Article history: Received 1 December 2016 Accepted 21 February 2017 Keywords: Nd 3+ ions Silver nanoparticles Tellurite glass Enhanced luminescence a b s t r a c t The improvement in the luminescence intensity of the rare earth doped glasses is a chal- lenging issue. In this work, the effect of the silver nanoparticles on luminescence spectrum of Nd 3+ doped boro-tellurite glasses is studied. The glasses are prepared by conventional melt-quenching technique and thermal processing to reduce the silver ions and nucleate metallic particles. The transmission electron microscopy is used to probe the formation and growth of the silver nanoparticles with an average size of about 18 nm after 12 h of contin- uous heat-treatments. The visible upconversion emissions are enhanced up to 3 times after 4 h of heat-treatment, applying an excitation wavelength at 800 nm. A 2.3-fold enhance- ment is also observed in near-infrared emission (centered at 1.06 m). The mechanisms and interactions between metal species and rare earth ions are discussed. © 2017 Elsevier GmbH. All rights reserved. 1. Introduction Rare earth (RE) doped glasses have recently attracted a large attention due to their specific spectroscopic properties, structural characterizations and mechanical strength. In general, glasses are good hosts for RE ions due to their excellent thermal stability, optical transparency, RE solubility, ease of large-scale preparation and low-cost fabrication. Among the transparent heavy metal oxide glasses, tellurite glasses are nominated as promising candidates for various applications thanks to their high linear and non-linear refractive indices, wide transparency window, low phonon energy, low melting temperature, thermal stability, high chemical durability and again high RE solubility [1–4]. The latter properties is of utmost importance for RE-doped glasses when it comes to application point of view, where population inversion plays the key role to achieve lasers or upconversion emissions. Although tellurite glasses possess higher RE solubility than silicate glasses increasing the concentration of dopants may decrease the luminescence quantum efficiency of RE ions, due to the fast energy transfer among the ions. Such phenomenon is called “concentration quenching” and several proposals have been suggested to overcome such drawbacks in the glasses. Among the given approaches [5], incorporation of metallic nanoparticles (NPs) has recently attracted an especial attention, though it opened a controversial window to the topic [6,7]. The work of Malta [8] is the first report on the enhancement of emissions of RE ions (in his case, Eu 3+ ions) doped glasses by introduction of small silver particles. They observe 5.6 times enhancement in the 5 D 0 → 7 F 2 transition of Eu 3+ ions doped calcium borofluoride glasses, and this magnification was discussed in terms of short-distance and long-distance electromag- netic interactions between Eu 3+ ions and silver nanocrystals (NCs). Recently, Jimenez and Sendova [9] also reported on the enhancement in the intensity of emissions of RE ions doped glasses due to presence of NCs (non-plasmonic clusters), while ∗ Corresponding author at: Instituto de Física, Universidade Federal de Alagoas, Maceió-AL, Brazil. E-mail addresses: mrezadousti@mail.com, mrdphysics@gmail.com http://dx.doi.org/10.1016/j.ijleo.2017.02.073 0030-4026/© 2017 Elsevier GmbH. All rights reserved.