Structural and Physical Properties of Chitosan Films Containing UV-Driven In Situ Growth of Silver Nanoparticles

Chitosan (CS), a naturally abundant biopolymer mainly sourced from marine crustacean waste, has emerged as a sustainable alternative to conventional, nonbiodegradable synthetic polymers in food packaging due to its intrinsic biocompatibility, nontoxicity, higher sustainability, biodegradability, and excellent film-forming ability. Furthermore, CS exhibits a remarkable dual role as both a reducing and capping agent in the green synthesis of silver nanoparticles (AgNPs). In the present work, CS-based nanocomposite films embedded with green AgNPs were produced via a straightforward one-step UV photoreduction method. CS simultaneously acted as a reducing and capping agent for AgNPs obtained in situ and as a rigid matrix for their confinement. By varying the UV exposure times (15, 45, and 90 min), the morphology and size of the NPs were characterized using transmission electron microscopy (TEM), revealing a predominantly spherical shape with an average diameter of ∼60 nm. In parallel, each resulting film was thoroughly analyzed using different techniques to evaluate the impact of UV radiation and in situ AgNP formation on the polymers' physical and structural properties, including wettability, moisture content, swelling degree, water solubility, surface morphology, roughness, and mechanical behavior. In addition, antibacterial efficacy was assessed against both Escherichia coli and Staphylococcus aureus, demonstrating inhibition of both Gram-positive and Gram-negative strains. Moreover, the silver ion release in aqueous media (pH 7) was quantified via ICP-OES. The simplicity, scalability, and effectiveness of the proposed method underscore the potential of the AgNPs@CS film as a sustainable antibacterial material for next-generation food packaging solutions.