Butterfly-Inspired Tri-State Photonic Crystal Composite Film for Multilevel Information Encryption and Anti-Counterfeiting.

Counterfeiting is a worldwide issue and has long troubled legitimate businesses, while the nowadays anti-counterfeiting materials and technology are still insufficient to combat the escalating counterfeit behaviors. Inspired by the hindwing structure of Troides magellanus, we prepared a new kind of anti-counterfeiting material taking advantage of both physical and chemical structures to display multiple optical states. The chemical units (luminescent lanthanide) were blended with physical units (monodispersed colloidal particles) and mediating molecule, which were then assembled into periodic photonic crystal structure at room temperature in less than 10 seconds through a new and scalable assembly technique called molecule-mediated shear-induced assembly technique (MSAT). The as-prepared photonic crystal films feature three unique optical states, each displaying structural, fluorescent and phosphorescent color under different lighting conditions, which integrates colors from both physical and chemical origins. Furthermore, through incorporating different luminescent materials into different parts of the photonic crystal pattern, a high-level information encryption system was designed to be capable of carrying three distinct types of information. Thanks to this powerful and universal tool of MSAT, it is now possible to assemble different-sized, even irregular non-spherical units with monodispersed spherical units into large-sized and high-quality photonic crystal films, which provides an easy access to incorporating new features into the photonic crystal system. This article is protected by copyright. All rights reserved.