Maqam Ali, Muhammad Kaleem Khosa, Awal Noor, Sadaf Qayyum
Composite films of gelatin/polyethylene glycol/chitosan (GPC) doped with varying amounts (0.5-2.5% w/w) of zinc oxide nanoparticles (ZnO-NPs) were prepared by a solution casting/ultrasonic method. The ZnO-NPs with average crystallite sizes of 10.20 nm were successfully synthesized by the co-precipitation method, and the formation of the GPC/ZnO-nanocomposite films was confirmed by Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). UV-vis diffuse reflectance analysis showed a modest decrease in the optical band gap from approximately 3.24 eV for bare ZnO to 3.18 eV for GPC-ZnO containing 2.5% ZnO. FT-IR spectroscopy revealed a bathochromic shift of the amide I, amide II and O-H/N-H stretching bands, which confirmed the strong hydrogen bonding and coordination interactions between the ZnO-NPs and the functional groups of the polymers. The XRD studies showed that the hexagonal wurtzite structure of the ZnO NPs was retained in the amorphous biopolymer matrix with up to 2% loading. SEM studies confirmed the homogeneous dispersion of the NPs in the biopolymer without any agglomeration. Mechanical properties and water barrier (water vapor permeability, moisture absorption and water solubility), antibacterial (Escherichia coli, Staphylococcus aureus, and Bacillus subtilis) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant activities were found to be the maximum at 2% ZnO loading. The photocatalytic test results revealed that the GPC-ZnO nanocomposite can degrade Direct Green 6 dye by up to ∼95% at the optimized catalyst dose (0.5 g/100 mL) as compared with ∼68% for bare ZnO-NPs. The efficiency of degradation was favored at pH 5-7 and with increasing temperatures from 30 °C to 50 °C. Based on the biological results and photocatalytic degradation of dyes, the ZnO-NP-doped GPC nanocomposite films reported herein are promising as multifunctional materials for applications such as wound dressing or antimicrobial barrier films and for the photocatalytic treatment of dye-containing water.