Study on the Luminescence Performance and Anti-Counterfeiting Application of Eu, Nd Co-Doped SrAlO Phosphor.

This manuscript describes the synthesis of green long afterglow nanophosphors SrAlO:Eu, Nd using the combustion process. The study encompassed the photoluminescence behavior, elemental composition, chemical valence, morphology, and phase purity of SrAlO:Eu, Nd nanoparticles. The results demonstrate that after introducing Eu into the matrix lattice, it exhibits an emission band centered at 508 nm when excited by 365 nm ultraviolet light, which is induced by the 4f5d→4f transition of Eu ions. The optimal doping concentrations of Eu and Nd were determined to be 2% and 1%, respectively. Based on X-ray diffraction (XRD) analysis, we have found that the physical phase was not altered by the doping of Eu and Nd. Then, we analyzed and compared the quantum yield, fluorescence lifetime, and afterglow decay time of the samples; the co-doped ion Nd itself does not emit light, but it can serve as an electron trap center to collect a portion of the electrons produced by the excitation of Eu, which gradually returns to the ground state after the excitation stops, generating an afterglow luminescence of about 15 s. The quantum yields of SrAlO:Eu and SrAlO:Eu, Nd phosphors were 41.59% and 10.10% and the fluorescence lifetimes were 404 ns and 76 ns, respectively. In addition, the E value of 4.98 eV was determined based on the diffuse reflectance spectra of the material, which closely matches the calculated bandgap value of SrAlO. The material can be combined with polyacrylic acid to create optical anti-counterfeiting ink, and the butterfly and ladybug patterns were effectively printed through screen printing; this demonstrates the potential use of phosphor in the realm of anti-counterfeiting printing.