Investigation of Monovalent Ion-Induced Luminescence Enhancement in La₂Zr₂O₇:Eu³⁺ for WLEDs and Latent Fingerprint...

Luminescent rare-earth oxide phosphors are of considerable interest for advanced lighting, anticounterfeiting, security applications, dosimetry, etc. because of their unique performance of sharp and distinct emission peaks, spectral tunability, long luminescence decay times, exceptional thermal stability, etc. In this work, the Eu³⁺-activated La₂Zr₂O₇ (LZO) nanophosphors having a defect fluorite structure were synthesized by the nitrate-citrate gel combustion method, and the influence of monovalent alkali-ion co-doping (Li⁺/Na⁺/K⁺) on their defect chemistry and luminescence behavior was systematically studied. Among them, Li⁺ co-doped nanophosphor (La_1.72Eu_0.22Li_0.06Zr₂O₇) showed a 1.5-fold increase in the PL emission intensity with better CIE chromaticity coordinates (0.6394, 0.3598), a higher correlated color temperature value (1973 K), and excellent color purity (89%), overcoming the shortcomings in the red component of LEDs. X-ray photoelectron spectroscopy analysis indicated oxygen vacancy-related defect centers in Li⁺ ion co-doped phosphor materials. Judd-Ofelt (J-O) analysis studied the increased asymmetric environment around the activator ion, Eu³⁺, upon co-doping. Furthermore, La_1.72Eu_0.22Li_0.06Zr₂O₇ nanophosphor demonstrated latent fingerprint detection as well as dosimetry applications via gamma radiation. Hence, this Li⁺ co-doped Eu³⁺: LZO nanophosphor can be a plausible option for the red component in lasers, display devices, and solid-state lighting, latent fingerprint analysis, and dosimetry studies.