Carboxymethyl Cellulose-Stabilized Copper Sulfide Nanoparticles-Based Photothermal Composite Films: Integrating Hydrophobicity, Biodegradability, and Antibacterial Activity for Long-Term Food Preservation

Conventional fruit and vegetable packaging films are often not only environmentally unsustainable but also lack effective antibacterial activity. To address this, we developed a multifunctional composite film (C@CuSAP) by incorporating carboxymethyl cellulose (CMC)-stabilized copper sulfide nanoparticles (CMC-CuS NPs) into a poly(vinyl alcohol) (PVA) and dialdehyde cellulose (DAC) matrix. The resulting C@CuSAP film exhibited proper hydrophobicity with a contact angle of 93.2°, enhanced mechanical properties with a tensile strength of 7599 N/m, and burst strength of 470.3 kPa. Under near-infrared (NIR) light irradiation, the film rapidly reached 190.7 °C within 33 s, indicating outstanding photothermal conversion efficiency. Antibacterial evaluations revealed a 99% inhibition rate against both Escherichia coli and Staphylococcus aureus, and it extended the shelf life of cherries by 6 days. This study proposes an eco-friendly approach for designing biodegradable packaging materials that integrate photothermal antimicrobial functionality with hydrophobic characteristics, demonstrating significant potential for application in food preservation.