Synthesis of Samarium-incorporated X-ray-sensitive nanoparticles and hydrogels: Diverse applications in radiation...

With the advancement of X-ray-activated persistent luminescent phosphors, the exploration of smart materials with tunable luminescence and afterglow properties is a promising topic. In this study, the red-emission X-ray scintillators, Samarium(Sm³⁺)-doped NaLuF₄, with regular micromorphology and well-controlled afterglow property were synthesized under mild conditions. Both of Sm³⁺-doped α-NaLuF₄ and β-NaLuF₄, abbreviated as α-NaLuF₄:xSm³⁺ and β-NaLuF₄:ySm³⁺ (x, y = 1, 3%, 5%, 10%, and 15%), respectively, emit the maximum emission peak at 598 nm (4G_5/2 → 6H_7/2) under X-rays, while only Sm³⁺-doped β-NaLuF₄ exhibits remarkable afterglow ability. The optimal luminescent property can be obtained when the doping rate is fixed at 3%. Then β-NaLuF₄:3%Sm³⁺ was surface modified and incorporated into the chemically crosslinked hydrogels to endow X-ray-activated luminescence or afterglow abilities in the obtained hybrid hydrogel. With the self-healing ability, the β-NaLuF₄:3%Sm³⁺-incorporated hydrogel can be further programmed with other types of hydrogels to enable tunable emission behaviors and time-dependent color changes. By taking advantage of these features, the hydrogels were programmed as a display panel that can be used for extra safety information encryption.