Atmospheric pressure plasma jet-assisted fabrication of antibacterial PET/ZnO NP composite

Abstract

In this research, PET/ZnO composites with different ZnO concentrations were synthesized with a method assisted by an atmospheric pressure plasma jet (APPJ). The method is based on the pre-treatment of PET using an APPJ, followed by drop coating with a ZnO colloidal solution synthesized via pulsed laser ablation in water, ensuring clean nanoparticles (NPs). Subsequently, the PET/ZnO composite undergoes an additional APPJ treatment to firmly embed the NPs into the ripples created on the PET surface during the plasma treatment. To determine the suitability of composites for direct food contact and to confirm the tight incorporation of NPs, the PET/ZnO composites were subjected to a leaching test. The OES was employed for the identification of elements and compounds present in the produced argon APPJ. Furthermore, ZnO NPs were characterized using UV–Vis spectroscopy, while PET/ZnO composites were analyzed using water contact angle measurements, FTIR, SEM, AFM, XPS, SIMS, and ICP-MS techniques. Additionally, embedding ZnO NPs into PET improves its UV protection, with the highest concentration leading to a 29 % increase in the UPF value. However, APPJ treatment reduces the modulus of elasticity, but incorporating ZnO NPs at 200 and 500 µL helps reinforce PET’s elasticity. Given the potential application of the PET/ZnO composite in food packaging, antimicrobial activity tests were conducted against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria. For the highest ZnO NP concentration, specifically 245.75 mg of Zn per kg of PET, nearly 100 % antibacterial efficiency was achieved for both bacterial strains.