Ultraviolet-C Upconversion Luminescence of Pr³⁺-Doped Fluorophosphate Glass

Abstract

High Resolution Image Download MS PowerPoint Slide The increasing demand for ultraviolet (UV) sterilization requires the development of new luminescent materials in the UVC region (100–280 nm). In this study, to obtain blue-to-UVC upconversion (UC) luminescence, fluorophosphate glasses doped with various Pr 3+ concentrations were prepared by using the melt-quenching method, and their optical properties were evaluated. Absorption bands attributed to the 4f 1 5d 1 → 4f 2 and 4f 2 → 4f 2 transitions of Pr 3+ were observed at shorter than 230 nm and in the 430–490 nm range, respectively. The relatively high phonon energies promote strong 1 D 2 emission, which is highly sensitive to concentration quenching, leading to a decrease of the Pr 3+ luminescence quantum yield at doping levels above 0.1%. Due to the small centroid shift and small crystal field splitting of the Pr 3+ 4f 1 5d 1 states caused by F – coordination in glass matrices, the Pr 3+ -doped fluorophosphate glass samples exhibited broad luminescence bands attributed to the 4f 1 5d 1 → 4f 2 transition in the UVC region under 180 nm excitation. UC luminescence, peaking at 276 nm, was observed under excitation with a 455 nm blue laser diode. When the Pr 3+ concentration exceeded 0.1% in the fluorophosphate glass, UC luminescence was scarcely observed due to cross-relaxation between neighboring Pr 3+ ions. The results of this study demonstrate that Pr 3+ -doped fluorophosphate glasses possess higher 4f 1 5d 1 energy levels than Pr 3+ -doped oxide ceramics and glasses and exhibit luminescence in the UVC region, suggesting that they are promising blue-to-UVC upconverters for UV disinfection applications through compositional tuning.

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