Fluorescence-structural color photonic crystal security card based on ultraviolet-responsive core-interlayer-shell colloidal particles

In this study, we report a kind of fluorescence-structural color photonic crystals (FSC-PCs) based on ultraviolet (UV)-responsive core-interlayer-shell (CIS) colloidal particles. The preparation process includes the synthesis of UV-responsive CIS colloidal particles and quick fabrication of FSC-PCs patterns. Here, fluorescent precursor spiropyran was added to the semi-continuous emulsion polymerization system and grafted onto polymer chains to form the colloidal particles, which were quickly assembled by spray coating method into FSC-PCs within a few minutes. The FSC-PCs have long-range disorder arrangement and angle-independent structural colors, which show structural colors in visible light and red fluorescent color in 365 nm UV light. Therefore, we designed and fabricated a two-side security card, both sides of which show different information under different light conditions. During the light switching progress, completely different information can be demonstrated reversibly, allowing data encryption and reading. The FSC-PCs with a simple quick assembly process and unique optical properties have profound potential in anti-counterfeiting and data display. Graphical abstract