Development and characterization of HPMC/NaAlg-CuO bio-nanocomposites: Enhanced optical, electrical, and antibacterial properties for sustainable packaging applications.

Copper oxide nanoparticles (CuO NP) were incorporated into a hydroxypropyl cellulose (HPMC) and sodium alginate (NaAlg) matrix through a casting method to create bio-nanocomposite films. XRD analysis confirmed the semi-crystalline nature of the HPMC/NaAlg matrix, with a broad peak at 2θ = 21.22°, which decreased in intensity as CuO concentration increased, indicating a shift towards an amorphous structure. FT-IR analysis demonstrated changes in band intensity, which can be attributed to the reduced volume fraction of the polymer blend in the presence of the CuO nanofiller. SEM images showed homogeneity at low CuO NP concentrations, but at 0.9 wt% CuO, nanoparticle aggregation became evident. The UV-visible spectra indicated a redshift from 212 nm to 246 nm and a decrease in optical energy gap from 4.78 eV for the pure blend to 2.99 eV at 0.9 wt% CuO, associated with increased localized defect states. AC electrical conductivity and dielectric properties improved with CuO dispersion, enhancing the bio-nanocomposite's suitability for electrochemical and optoelectronic applications. The bio-nanocomposites demonstrated significant antibacterial activity, with films containing 0.4 and 0.7 wt% CuO achieving the largest inhibition zones against B. subtilis, S. aureus, P. aeruginosa, and E. coli. Overall, these findings suggest that HPMC/NaAlg-CuO bio-nanocomposites are promising candidates for use in antibacterial packaging and optoelectronics.