Cellulose-based room temperature phosphorescent gels with ultra-strong hydrogen-bonded networks driven by phase separation for advanced anti-counterfeiting.

Room temperature phosphorescent (RTP) hydrogels have garnered extensive attraction owing to their distinctive optical properties, low toxicity and cost-effectiveness. However, achieving efficient and long-lived afterglow emission in hydrogel systems remains a formidable challenge due to the severe quenching of triplet excitons by water molecules. Herein, taking inspiration from stimuli-responsive luminescent behavior of jellyfish, we propose a solvent exchange strategy to construct a cellulose-based RTP gel with polyethylene glycol (PEG)-induced phosphorescent behavior. Specifically, a cellulose/polyvinyl alcohol (PVA) double-network hydrogel system was constructed to confine carbon dots (CDs) within a rigid matrix, which preliminarily enabled phosphorescence emission. Driven by phase separation induced by PEG, the resulting gel with ultra-strong hydrogen-bonded networks exhibits green RTP emission with an extended lifetime of 255.55 ms and a tensile strength of 3.79 MPa, representing 370-fold and 17-fold enhancements, respectively, compared to the gel prepared using water as the solvent. Furthermore, the phosphorescent properties of the gel can be tuned by adjusting the molecular weight of PEG. Taking advantage of these properties, the cellulose-based RTP gels were further fabricated into various luminescent materials, which exhibited promising potential for information encryption and advanced anti-counterfeiting applications.