Spectroscopic investigation of neodymium and copper co-doped phosphate glass incorporating plasmonic nanoparticles

Seeking improvements in the emission from Nd3+ ions in dielectric hosts is currently a topic of interest for applications in laser materials and solar spectral conversion. In this work, the spectroscopic properties of neodymium and copper co-doped phosphate glass were examined focusing on the impact of plasmonic Cu nanoparticles (NPs). Material preparation was achieved by melting and heat treatment processes wherein Nd2O3 (2 mol%) alongside CuO/SnO as redox couple (10 mol%) were added to BaO:P2O5 glass. Characterizations were then performed by dilatometry, UV–Vis-NIR spectrophotometry, X-ray diffraction (XRD), Raman scattering, and photoluminescence (PL) spectroscopy. From dilatometry, the coefficient of thermal expansion and glass transition & softening temperatures of the melt-quenched glass were estimated. Absorption spectroscopy revealed the surface plasmon resonance band of Cu NPs around 573 nm in heat-treated glass, while XRD allowed to estimate mean NP size around 30.0 nm. The Raman spectroscopy appraisal indicated a depolymerization effect of the glass induced by dopants, however, supporting no significant structural alterations upon Cu NP inclusion. The Nd3+ PL assessment which encompassed up-conversion and near-infrared emission demonstrated consistent PL quenching in the plasmonic glass, while the lifetimes for the Nd3+ 4F3/2 emitting state were akin to the melt-quenched precursor. The most favorable conditions for using the Nd3+ emission for applications were then achieved in the melt-quenched glass rather than the nanocomposite. It is suggested that energy transfer processes from Nd3+ ions to Cu NPs primarily induce the PL quenching which supersedes any plasmonic local field enhancement effects. Graphical Abstract Luminescent down-shifting (LDS) and up-conversion (UC) processes relevant for solar spectral conversion were evaluated in Cu/Nd co-doped phosphate glass and plasmonic nanocomposite (glass spectra-solid traces; AM1.5G solar spectrum-dash dot green curve; c-Si cell response-dash dot dot blue curve)