Influence of thickness and coatings morphology in the antimicrobial performance of zinc oxide coatings

• Published in: Applied surface science 2014-07, Vol.307, p.548-557
• Main Authors: Carvalho, P., Sampaio, P., Azevedo, S., Vaz, C., Espinós, J.P., Teixeira, V., Carneiro, J.O.
• Format: Article
• Language: English
• Subjects: Antiinfectives and antibacterials; Antimicrobial activity; Bacteria; Coatings; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Deposition; Escherichia coli; Exact sciences and technology; Food packaging; Magnetron sputtering; Morphology; Physics; Silver; Thin films; Zinc oxide; ZnO thin films
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2014.04.072

SEM cross-section micrograph of the silver doped ZnO thin films. The sample having the highest Ag/Zn atomic ratio of 0.04 presents a complete growth inhibition. •50–100nm thin films present an increase of generation time by a factor of 1.26 and 1.4, respectively.•Thin films with 200–600nm induced an increase of the generation time by a factor from 2 to 3.3.•Antibacterial activity increases with the amount of silver content in the zinc oxide based coatings. In this research work, the production of undoped and silver (Ag) doped zinc oxide (ZnO) thin films for food-packaging applications were developed. The main goal was to determine the influence of coatings morphology and thickness on the antimicrobial performance of the produced samples. The ZnO based thin films were deposited on PET (Polyethylene terephthalate) substrates by means of DC reactive magnetron sputtering. The thin films were characterized by optical spectroscopy, X-Ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Scanning Electron Microscopy (SEM). The antimicrobial performance of the undoped and Ag-doped ZnO thin films was also evaluated. The results attained have shown that all the deposited zinc oxide and Ag-doped ZnO coatings present columnar morphology with V-shaped columns. The increase of ZnO coatings thickness until 200nm increases the active surface area of the columns. The thinner samples (50 and 100nm) present a less pronounced antibacterial activity than the thickest ones (200–600nm). Regarding Ag-doped ZnO thin films, it was verified that increasing the silver content decreases the growth rate of Escherichia coli and decreases the amount of bacteria cells present at the end of the experiment