Vapor Absorption and Liquefication Triggered Dynamic Color Changes and Pattern Conversions on Photonic Crystal Films for Anticounterfeiting

The widespread use of counterfeit goods caused significant damage to economy, personal data security, and public health. There is an urgent need to develop innovative anticounterfeiting materials to enhance their performance. Anticounterfeiting labels based on responsive photonic crystals have been widely researched for the inherent difficulty in replicating the delicate structures and structure colors. By integrating various distinct nanoparticles (NPs), it is expected to produce photonic crystal patterns that offer more intricate color effects and improved anticounterfeiting capabilities. In this work, we reported a photonic crystal anticounterfeiting label with dynamic color variations in solvent vapors and pattern conversions upon vapor liquefication by utilizing three different nanoparticles including d-SiO₂, h-SiO₂, and m-SiO₂ NPs as building blocks. This anticounterfeiting label exhibits a wealth of dynamic color changes associated with the absorption time, absorption rate, absorption medium, and microstructure of the nanoparticles, offering diverse visual effects and showcasing interesting anticounterfeiting performances. The dynamic color change or pattern conversion effect of this photonic crystal (PC) pattern is realized through refractive index changes induced by vapor absorption or solvent filling, which involves no volume changes and shows exceptional durability for repeated applications. This label shows promising broad applications in anticounterfeiting areas.