Plant-mediated synthesis of thermally stable metal-polystyrene nanocomposites for antioxidant and antibacterial food packaging

Abstract

Annually, millions of individuals are hospitalized worldwide because of illnesses attributed to foodborne pathogens. With the surge in foodborne diseases, the importance of reliable and optimized food packaging has become more crucial than ever. Okra (Abelmoschus esculentus) seed extract was utilized as a mediator for synthesizing thermally stable nanoparticles (NPs) of Fe0, Zn0, Ag0, Fe2O3, ZnO, and Ag2O. These NPs were subsequently incorporated into polystyrene (PS) sheets to fabricate NPs-PS composites. Nanoparticle synthesis with a uniform morphology and size range of 20–60 nm was confirmed through various characterization techniques, including surface plasmon resonance, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray (EDX) techniques. The antioxidant potential, as determined by the 2,2-diphenylpicrylhydrazyl (DPPH) free radical scavenging and Phosphomolybdenum assay, followed the order of Silver > Iron > Zinc. Conversely, the antimicrobial potential, evaluated through the agar well diffusion method, was in the order of Silver ≈ Zinc > Iron. Zero-valent metal NPs and NPs-PS Composites exhibited superior results compared to metal oxide NPs and NPs-PS Composites. Lemon and Apple slices wrapped in NPs-PS composite sheets exhibited significantly improved shelf life compared to pure PS, demonstrating the high effectiveness of metal NPs modified composites for food packaging by protecting it from oxidative decay and microorganisms.