Antimicrobial properties dependence on the composition and architecture of copper-alumina coatings prepared by plasma electrolytic oxidation (PEO)

Abstract

This study presents environmentally friendly and low-cost synthetic routes to produce antimicrobial coatings over 5052 Al alloy based on plasma electrolytic oxidation (PEO) technology. Two methodologies were explored: the decoration with copper and anodic doping with copper ions. The porous oxide layers produced in silicate media presented two porous layers consisting of γ-Al₂O₃ crystalline phase and amorphous phases of aluminosilicate, silica, and Al(OH)₃. Small amounts of copper (<0.3 at.%) were detected in the PEO films. In the Cu-decorated film, copper clusters composed of Cu⁰ and Cu²⁺ species were observed visually as small black dots on the surface. In the Cu-doped film, the Cu²⁺ and Cu⁺ species were homogeneously distributed on the surface. The copper content affected the corrosion performance in aggressive corrosive media. The PEO coatings showed a remarkable antimicrobial activity after 24 h in standard tests. The antimicrobial effectiveness of the Cu-decorated sample was higher against S. aureus, while the Cu-doped sample was more effective against E. coli. The results demonstrated that differences in the PEO coating architecture can affect the material composition and, consequently, the bacterial inactivation mechanism. These findings can serve as a guide to tailor aluminum alloys for specific antimicrobial surfaces.