<i>In Situ</i> Fabrication of the ZnO-Embedded Carboxymethyl Cellulose Nanocomposite Film for Food Packaging Materials: A Sustainable Approach

The present study reports the fabrication and characterization of carboxymethyl cellulose (CMC) biofilms incorporated with in situ synthesized zinc oxide (ZnO) nanoparticles as a sustainable alternative to conventional plastic packaging. ZnO was generated within the CMC matrix (1−5 wt %) via solution casting, and structural analyses (XRD and FTIR) confirmed ZnO formation and coordination between Zn2+ and CMC carboxylate groups. The incorporation of ZnO increased the film thickness, exceeding the predicted additive volume trend, indicating nanoparticle-induced microstructural rearrangements within the polymer network. At low loading (1%), ZnO created a more tortuous diffusion pathway, yielding the lowest water vapor permeability (∼9.3×10−12 g m−1 Pa−1 s−1). Mechanical testing showed an optimal balance of tensile strength (∼5.5MPa) and elongation (∼64%) at 1% ZnO, whereas higher loadings led to agglomeration, reducing flexibility. Optical evaluation revealed increased opacity and strong UV shielding due to wide band-gap absorption of ZnO. ABTS•+ scavenging activity rose from 6.6% (neat CMC) to 21.2% at 5% ZnO, likely due to ZnO-induced electron transfer. Storage studies using tomatoes demonstrated extended shelf life, with 5% ZnO-CMC films limiting weight loss to 7.7% after 7 days. These findings highlight ZnO-CMC films as multifunctional, biodegradable materials for effective food preservation.