Formation of Au@Ag Bimetallic Nanoparticles via Ion Implantation and Its Effects on Boosting the Near-Infrared Emission of Er³⁺ Ions in Germanate Glass for Applications in Optical Amplifiers

In this work, germanate glasses of composition 59GeO2-41PbO in mol% doped with Er3+ ions were synthesized using the melt-quenching route. Au and Ag nanoparticles and Au@Ag bimetallic nanoparticles were formed on the surface of the germanate glasses by ion implantation followed by thermal treatments. X-ray diffraction patterns confirmed the amorphous structure of the implanted glasses. Molecular dynamics was used to simulate the GeO2–PbO glass structure. Surface plasmon resonance bands centered at 486, 537, and 574 nm, obtained through ultraviolet–visible absorption spectra, supported the formation of Ag, Au, and Au@Ag nanoparticles, respectively. Transmission electron microscopy (TEM) revealed the presence of spherical Au and Ag nanoparticles as well as the presence of nonspherical Au@Ag bimetallic nanoalloys. Refractive index n and extinction coefficient k were measured by ellipsometry. Judd–Ofelt theory was applied to evaluate the phenomenological intensity parameters Ωλ(λ = 2,4,6) , radiative parameters, and stimulated emission cross-sections for glasses doped with Er3+ and implanted with Au @Ag bimetallic nanoalloys. Efficient boosting of the near-infrared emission for the 4I13/2 → 4I15/2 transition was observed in the glass doped with Er3+ ions due to the presence of Au@Ag bimetallic nanoalloys. The possible cause of this improvement in luminescent intensity was attributed to the strong local field effect due to the efficient synergy between Au@Ag bimetallic nanoalloys and the Er3+ ions. The results obtained in this work indicate that the vitreous system GeO2–PbO glass doped with Er3+ ions and with the incorporation of Au@Ag bimetallic nanoalloys via ionic implantation exhibit excellent spectroscopic properties compared to other vitreous host glasses doped with the Er3+, indicating its potential applications in optical amplifiers.