Multifunctional chitosan films reinforced by cellulose nanocrystals and nitrogen-phosphorus co-doped carbon dots for fruit preservation.

Fruit preservation poses a significant challenge, as conventional materials often fail to simultaneously mitigate microbial contamination, physicochemical degradation, and sustainability concerns. To address these limitations, this study developed a multifunctional chitosan (CS)-based film co-reinforced with cellulose nanocrystals (CNC) and nitrogen-phosphorus co-doped carbon dots (NPCDs) for fruit preservation. A two-step fabrication strategy was employed, wherein NPCDs were first homogenized with CNC and then blended into the CS matrix. The optimized CNC/NPCDs@CS film exhibited superior properties, including a tensile strength of 26.50 MPa (a 382.6% increase compared to pure CS film), a reduction in oxygen permeability of over 99% under tested conditions, efficient UV shielding (reducing UV-A and UV-B transmittance to 30.5% and 8.4%, respectively), and potent antibacterial activity (with inhibition rates against E. coli and S. aureus increased by 76.8% and 107.7%, respectively, compared to the pure CS film). Preservation trials demonstrated the film's efficacy in extending shelf-life, which was attributed to these enhanced material properties. Furthermore, microbial community analysis revealed suppressed microbial richness, optimized dominance, and stabilized microbiota, indicating a synergistic preservation mechanism involving physical barrier effects and antibacterial action. This film represents a sustainable, high-performance material for active food packaging, integrating material innovation with food safety and sustainability objectives.