Fire resistance, antibacterial and UV to blue light blocking highly transparent cellulose films enabled by gardenia yellow/phosphorylated chitosan synergistic networks

A simple and scalable method is used to prepare multifunctional bio-based films. • Natural gardenia yellow was first used as a UV and blue light absorber. • The films exhibit high transparency and excellent protection against harmful light. • Integrated fire safety and antibacterial properties were achieved. • The films exhibit excellent mechanical strength and biodegradability. The integration of multiple functionalities into a single material system, while simultaneously ensuring sustainable processing and high transparency, remains a critical challenge in materials design. Herein, a multifunctional cellulose film is developed through a supramolecular engineering strategy that orchestrates the synergistic interplay of carboxymethylated cellulose, gardenia yellow (GY), and phosphorylated chitosan (PCS). The process involves alkali/urea assisted regeneration of cellulose into hydrogel matrix, followed by incorporation of a pre-assembled GY-PCS complex. The resulting films exhibit exceptional optical management capabilities, achieving light shielding efficiencies of 52.5–69.9% for UV-A, 55.6–68.3% for UV-B, and 72.5–91.1% for high-energy blue light (HEBL). The films demonstrate superior blue light filtering performance compared to commercial counterparts. Encouragingly, the films exhibit high transmittance of 90–90.8% and low haze of 1.8–2.0% at 600 nm. In practical applications, the films effectively block blue light radiated by illumination system, computer screen and smartphone screen. Notably, the incorporation of PCS imparts ideal flame-retardant properties, increasing the limiting oxygen index (LOI) from 19.2% to 32.1%. Moreover, the films exhibit excellent antimicrobial activity. Benefiting from the synergistic hydrogen-bonding network, the tensile strength of the films achieves a substantial increase ranging from 11.1% to 18.7%. This simple strategy would direct cellulose films toward diversified applications.