Thermo-Responsive Tri-State Photonic Crystals

Counterfeiting remains a pervasive global challenge, persistently undermining legitimate enterprises. Despite advancements, current anti-counterfeiting materials and technologies fall short in addressing the escalating sophistication of counterfeit activities. A significant hurdle in this domain is the difficulty in achieving multi-mode dynamic anti-counterfeiting materials. Herein, thermo-responsive tri-state photonic crystals is presented that enable thermochromism of structural color, fluorescence (FL), and organic afterglow. The fabrication of this system integrates the incorporation of organic phosphors into polymeric colloids via solid-phase extraction and embeds thermochromic microcapsules into colloidal crystals to regulate incoherent scattering and far-field light absorption. In typical triplet-to-singlet Förster resonance energy transfer (TS-FRET) for afterglow color tuning, higher energy transfer efficiency reduces the afterglow lifetime. In contrast, the far-field light absorption-based energy transfer in this photonic crystal system avoids this trade-off, thereby preserving the long-lived triplet emission. The resultant photonic crystals exhibit three thermochromic optical states including FL, phosphorescent, and structural coloration. This general strategy, leveraging tunable thermochromic temperatures and diverse organic phosphors, enables the creation of multi-responsive anti-counterfeiting patterns. It paves the way for dynamic, high-capacity, and multimodal information storage.