This paper reports citrate-stabilized silver nanoparticles (AgNPs) synthesized by nitrate ion chemical reduction with sodium borohydride, at different pHs (2–9). The AgNPs synthesized by this method exhibited size distribution from 5 to 249 nm, depending on pH, as determined by dynamic light scattering, and morphology spherical, as determined by transmission electron microscopy. In pH range 3–7 occurred aggregation of the nanoparticles. The size distribution depending on pH was determined by dynamic light scattering. The zeta potential was determined, and the colloidal stability was correlated with nanoparticles aggregation at different pHs. The size-dependent antimicrobial activity was evaluated for two solutions, wherein both samples exhibited antimicrobial activity, although the smallest AgNPs without agglomeration have enhanced antimicrobial properties.

Glasses with base composition (in mol%) 70TeO₂–15GeO₂–5K₂O–10Bi₂O₃ were prepared by the melt-quenching method. Er³⁺/Yb³⁺-doped and non-doped glass compositions were used as core and cladding, respectively, in the preparation of optical fibers through the sucking method. Infrared emission at 1550 nm and up-conversion emission in the visible range under 980 nm pumping are reported for glasses and optical fibers. A relatively large (Δλ = 91 nm) bandwidth was observed for the Er³⁺ 1550 nm emission. Up-conversion luminescence was observed and evaluated as a function of pump power at 980 nm. The efficient emission in the visible and infrared ranges makes this optical fiber potentially useful for amplifier and laser applications in photonics.