Multicolor Fluorescent Hydrogels Based on CaZnOS Phosphors for Anticounterfeiting Applications

As an inorganic phosphor, CaZnOS with highly efficient and stable emission exhibits strong potential in the fields of lighting display and information encryption. Although it has only a single luminescent region after sintering, it is anticipated that the unique differences in excitation and emission wavelengths of luminescent ions can be exploited to achieve information encryption by doping various luminescent ions. The hydrophilicity and water resistance of CaZnOS make it a suitable candidate for incorporation into hydrogel systems. In this study, we present a strategy for combining inorganic phosphors with hydrogel materials to prepare fluorescent hydrogels, utilizing poly(vinyl alcohol) (PVA) as a matrix to stabilize CaZnOS. The luminescence color range of the hydrogels (orange, red, dark red, and blue) can be conveniently adjusted by regulating the doping concentrations of Mn²⁺ and Bi³⁺ in the CaZnOS hosts. The prepared fluorescent hydrogels can be customized into various shapes and arranged to form arrays of encrypted information, which are essential for high-performance anticounterfeiting applications. We anticipate that this strategy will facilitate the development of diverse types of fluorescent hydrogels and enhance the security of anticounterfeiting applications.