The effect of ZnO nanoparticles morphology on the barrier and antibacterial properties of hybrid ZnO/graphene oxide/montmorillonite coatings for flexible packaging

The need for eco-friendly packaging solutions is continuously increasing, with several materials being investigated to develop functional coatings able to contrast food degradation due to oxidation and bacterial growth. In this work, ZnO nanoparticles (NPs) with various morphology and size from spherical to hexagonal, dots-like and platelets-like shape, were synthesized. Hybrid coatings constituted by ZnO NPs, graphene oxide (GO) and montmorillonite (MMT) were applied onto flexible polyethylene (PE) in order to exploit the 2D nanomaterials self-assembly ability and gas barrier properties and to synergistically combine these functionalities with the antibacterial activity of ZnO. The effect of ZnO NPs morphology and the ZnO/GO/MMT relative content was explored to obtain nanostructured coatings with optimized functionality. Results evidence a correlation between oxygen permeability and microbial proliferation, allowing to reach 88 % of reduction of PE oxygen permeability and about 60 % inhibition towards Gram-positive (i.e. Weizmannia coagulans) and Gram-negative (i.e. Escherichia coli) microorganisms.