Preparations and characterization of alginate/silver composite films: Effect of types of silver particles

• Alginate/AgNPs composite films were prepared by solvent casting method.
• The alginate/AgNPs composite films exhibited a UV screening effect.
• The film properties were greatly influenced by the types of silver used.
• The composite films showed strong antibacterial activity against E. coli and L. monocytogenes.

Alginate-based films reinforced with different types of silver particles such as metallic silver (AgM), silver zeolite (AgZ), citrate reduced silver nanoparticles (AgNPC), laser ablated silver nanoparticles (AgNPLA), and silver nitrate (AgNO3) were prepared using a solvent casting method and the effect of silver particles on the optical, mechanical, water vapor barrier, and antimicrobial properties the composite films was evaluated. Size and shape of the silver particles were varied depending on the types of silver source and the preparation method. The alginate films incorporated with AgNPC, AgNPLA, and AgNO3 showed a characteristic surface plasmon resonance absorption peaks of AgNPs around 420 nm. Film properties such as mechanical, optical, and water vapor barrier properties were greatly influenced by the types of AgNPs used. Alginate/AgNPs composite films except AgM and AgNPLA incorporated ones exhibited strong antimicrobial activity against two food-borne pathogenic bacteria, Escherichia coli and Listeria monocytogenes. The developed films have a high potential for the application as antimicrobial food packaging films.