Bifunctional hybrid persistent luminescent materials with optical and magnetic response

Persistent luminescent materials have attracted significant interest due to their unique afterglow emission and duration. These properties have been studied for decades but the potential applications of such materials are limited. In this work we introduce the concept of bi-functional hybrid materials combining optical and magnetic properties. Persistent phosphor crystals CaAl2O4: Eu2+, Nd3+ (CAO) were combined with various loadings of polyethyleneimine (PEI) functionalized Fe3O4 magnetic nanoparticles using Tylose (ty) as a binder, leading to hybrid materials CAO@ty@[PEI@Fe3O4] (1-4) with optical/magnetic bifunctionality. Persistent phosphor crystals CaAl2O4: Eu2+, Nd3+ (CAO) were combined with various loadings of polyethyleneimine (PEI) functionalized Fe3O4 magnetic nanoparticles using Tylose (ty) as a binder, leading to four (i.e., 1-4) hybrid materials CAO@ty@[PEI@Fe3O4] (1-4) with optical/magnetic bifunctionality, differing in their content of PEI-functionalized Fe3O4 nanoparticles. Study of the structural, optical and magnetic properties confirmed that the addition of Fe3O4 nanoparticles does not affect the structure and hence the luminescence details of the CAO crystal, however the luminescence intensity decreases systematically with increasing the Fe3O4 mass loading. In addition, photoluminescence studies revealed a distinct afterglow emission peak centered at similar to 440 nm, attributed to Eu2+. Magnetic studies demonstrated superparamagnetic behavior, with reduced magnetization due to Fe3O4@PEI mass loading. The bifunctional hybrid persistent phosphors 1-4 exhibited synergistic luminescent and magnetic properties, paving the way for applications in bioimaging, sensors, and multifunctional materials.