Carboxymethylcellulose/Agar-Based Multifunctional Films Incorporated with Zn-Doped SnO₂ Nanoparticles for Active Food Packaging Application

SnO₂ and Zn-SnO₂ nanoparticles were prepared by chemical precipitation, and the rutile phase of SnO₂ was confirmed through X-ray diffraction studies. X-ray photoelectron spectroscopy (XPS) confirmed the doping of SnO₂ with Zn and elucidated the surface chemistry before and after doping. The average sizes of SnO₂ and Zn-SnO₂ nanoparticles determined using TEM were 3.96 ± 0.85 and 3.72 ± 0.9 nm, respectively. UV–visible and photoluminescence spectrophotometry were used to evaluate the optical properties of SnO₂ and Zn-SnO₂ nanoparticles, and their energy gaps (E_g) were 3.8 and 3.9 eV, respectively. The antibacterial activity of these nanoparticles against Salmonella enterica and Staphylococcus aureus was evaluated under dark and light conditions. Antibacterial activity was higher in light, showing the highest activity (99.5%) against S. enterica. Carboxymethylcellulose (CMC)/agar-based functional composite films were prepared by adding different amounts of SnO₂ and Zn-SnO₂ nanoparticles (1 and 3 wt % of polymers). The composite film showed significantly increased UV barrier properties while maintaining the mechanical properties, water vapor barrier, and transparency compared to the neat CMC/agar film. These composite films showed significant antibacterial activity; however, the Zn-SnO₂-added film showed stronger antibacterial activity (99.2%) than the SnO₂-added film (15%).