Porous carbon nitride-chitosan/zein bilayer functional films with efficient photocatalytic antibacterial activity and tunable water barrier performance for food packaging

The development of functional films with both antibacterial and preservative properties is crucial to ensure food safety. Herein, porous carbon nitride-chitosan/zein (PCN-CS/ZN) bilayer active films were developed via layer-by-layer deposition method. The incorporation of PCN into the inner CS layer imparted the bilayer films with efficient photocatalytic antibacterial activity. The bilayer structure featuring a moisture absorption inner layer (PCN-CS) and a moisture barrier outer layer (ZN), allowed tuning of the water barrier performance. The addition of the ZN layer increased the tensile strength (TS) and elongation at break (EAB) and decreased the water vapor permeability (WVP, CS side), moisture content (MC), water solubility (WS) and swelling degree (SD) of the CS film. Addition an appropriate amount of PCN was able to further increase the TS and decrease the WVP (CS side), MC, WS, and SD of the bilayer films. Antibacterial experiments confirmed that the addition of PCN photocatalyst significantly increased the antibacterial activity of the bilayer films against Escherichia coli(E. coli) and Staphylococcus aureus(S. aureus). The banana fruits covered with 10% PCN-CS/ZN bilayer films had a long shelf life, with no obvious deterioration observed over 10 days under visible light at room temperature (about 32 °C). Therefore, PCN-CS/ZN bilayer films represent a promising low-cost food packaging material with good functional properties.