Carboxymethyl cellulose-based functional film integrated with chitosan-based carbon quantum dots for active food packaging applications

A chitosan-based carbon quantum dots (CQDs) with multifunctional properties were synthesized using a hydrothermal process. The CQDs were spherical with an average size of 7.8 ± 2.4 nm. The CQD showed strong antioxidant activity, potent antibacterial activity against E. coli and L. monocytogenes, and antifungal activity against A. niger and P. chrysogenum. In addition, the prepared CQD showed negligible cytotoxicity against L929 cells even at a concentration of 500 μg/mL. Carboxymethyl cellulose (CMC)-based functional films were fabricated by adding various amounts of CQD. The CQDs were evenly dispersed in the polymer matrix to form a highly transparent UV-blocking film. The addition of CQD increased the tensile strength (TS) (by up to 27.6%) and elastic modulus (EM) (by up to 61.5%) of the CMC film. The CQD-added CMC films showed excellent antioxidant and strong antimicrobial activity. Lemon fruits were coated with the film solutions to test the efficacy of the CQD-added CMC film. The lemon coated with CMC/CQD film showed an excellent appearance without mold growth even after 21 days of storage. The CMC/CQD coating film with superior functional properties has great potential in active food packaging applications.