Core-shell dual-excitation sodium yttrium fluoride nanoparticles doped with Ce3+ ions for secure anti-counterfeiting applications

Rare earth doped nanomaterials have attracted considerable attention in photonics and information security due to their tunable multicolor luminescence and rapid response properties. However, achieving dual-mode luminescence with tunable emission colors in a single material remains a significant challenge. Herein, NaYF 4 :Yb/Ho/Ce@NaYF 4 :Ce/Tb core-shell nanocrystals were synthesized, which exhibit dual-excitation response under both 254 nm ultraviolet and 980 nm near-infrared light sources. This innovative design facilitates tunable upconversion luminescence through the cross-relaxation process between Ce 3+ and Ho 3+ ions in the inner cores. Moreover, the system exhibits synergistic downshifting luminescence attributed to the energy transfer from Ce 3+ to Tb 3+ ions in the shells. By combining upconversion and downshifting luminescence, this dual-functional platform delivers a versatile and highly efficient solution for advanced security-related applications.