Regulation of the Secondary Structure of Silk Fibroin to Fabricate Room-Temperature Phosphorescent Materials with Adjustable and Responsive Performance

While bulk luminescence in polymeric and doped systems has been widely studied, protein-based bulk phosphorescence remains largely unexplored. Existing research has predominantly focused on the aggregation-induced emission of proteins in solution, with limited understanding of the role of protein secondary structure. Herein, we demonstrate a design strategy for silk fibroin (SF)-based room-temperature phosphorescent (RTP) materials by leveraging the synergy between SF secondary structure and metal ion interactions. Specifically, we find that reducing β-sheet content, when combined with calcium ion incorporation, cooperatively amplifies phosphorescence emission. Furthermore, covalent conjugation of bulky chromophores to SF suppresses β-sheet formation, endowing the resulting materials with ultralong afterglow, full-color tunability, and controllable coloration. The as-prepared materials exhibit excitation-dependent emission, dual responsiveness to thermal and moisture stimuli, and exceptional solvent stability—maintaining RTP even after immersion in organic solvents for multiple days. With good processability and programmable RTP printing, these materials show promise for anticounterfeiting and information encryption.