Incorporation of broccoli leaf-derived CDs and Ag/AgCl nanoparticles into PVA/chitosan as multifunctional food...

The incorporation of hybrid nanofillers with complementary functionalities into packaging materials has emerged as an effective strategy for achieving multifunctionality. In this study, multifunctional PVA/chitosan-based films were fabricated by simultaneously incorporating broccoli leaf-derived N,S-doped carbon dots (CDs) and in situ synthesized Ag/AgCl nanoparticles (0-0.70% Ag relative to polymer mass). CDs served as reducing agents for the formation of ∼27.4 nm Ag/AgCl nanoparticles within the polymer matrix. The resulting films exhibited tunable mechanical and functional properties depending on the Ag content. At 0.45% Ag loading, the composite film displayed enhanced mechanical properties (tensile strength of 61.1 MPa and elongation at break of 190%) and excellent UV-shielding (∼93% UVA and nearly 100% UVB/UVC blocking). The films also showed strong antioxidant activity (∼93% 2,2-diphenyl-1-picrylhydrazyl scavenging), mainly attributed to CDs. Furthermore, the films demonstrated significant antibacterial activity against Escherichia coli and Staphylococcus aureus, primarily attributed to Ag/AgCl nanoparticles, with inhibition zones of 13.4 and 12.9 mm, respectively. Practical tests confirmed that the composite film significantly extended the shelf life of guavas and strawberries, outperforming commercial polyethylene films. These results highlight its strong potential for multifunctional food packaging applications.