Strong Red Luminescence in Europium Complexes Solution for Anti-Counterfeiting Applications

Eu³⁺-activated phosphors with distinct photoluminescence properties are well-suited for diverse applications, including lighting, sensing, and imaging. Despite their potential, the large-scale and energy-efficient production of Eu³⁺-doped phosphors remains a significant challenge for industrial applications. This research delves into the luminescent performance of Eu³⁺ ions in nitrate solutions at room temperature by employing detailed spectroscopic characterization. Results reveal vibrant red luminescence at 594 nm and 616 nm in europium nitrate solutions, irrespective of concentration or solvent. We proposed a luminescent mechanism based on the formation of coordination complexes in nitrate solution. Furthermore, the investigation highlights the superior performance of NH₂- over CH₂-ligands in mitigating the deactivation of Eu³⁺ emissive state induced by OH^- oscillators in H₂O solvent, leading to enhanced photoluminescence. Particularly, europium nitrate solutions without lengthy preparation exhibit ligand-dependent luminescent feature, showcasing potential applications in anti-counterfeiting and coordination group structure detection. This study here not only enhances our understanding of rare earth luminescence mechanisms, but also broadens the range of rare earth luminescent materials.