Near-IR Photoluminescence of Pr/Cu/Sn Tridoped Phosphate Glass: Nonplasmonic Material System Versus Plasmonic Nanocomposite

An optical spectroscopy study of Pr₂O₃, CuO, and SnO tridoped barium phosphate glass prepared by the melt-quenching technique has been carried out, emphasizing near-infrared (IR) emission properties. The material is studied in its nonplasmonic state (as synthesized) and plasmonic form (heat-treated), aiming to elucidate the effects of Cu nanoparticles. The data indicate that Cu⁺ ions and Sn centers are stabilized in the melt-quenched glass. Broad ultraviolet excitations of both species can lead to near-IR emission of Pr³⁺ ions via energy transfer. The plasmonic nanocomposite is produced upon heat treatment as Sn²⁺ reduces Cu⁺ to Cu⁰ atoms, ultimately precipitating as Cu nanoparticles sustaining the surface plasmon resonance. Consequently, depletion of primarily Cu⁺ modified the ultraviolet excitation properties for the sensitized near-IR Pr³⁺ emission. Further, suppression of the Pr³⁺ emission from near-IR emitting states ¹D₂ and ¹G₄ was observed in the Cu nanocomposite in accord with a “plasmonic diluent” role of the nanoparticles.