Zn and Ag Co-doped Anti-microbial TiO2 Coatings on Ti by Micro-arc Oxidation

Abstract

Micro-porous TiO 2 coatings co-doped with Zn 2+ and Ag nanoparticles were fabricated on Ti by micro-arc oxidation (MAO) for 0.5, 1.5, 2 and 4 min, respectively. The evolutions of morphology and phase component of the coating as a function of processing time were investigated. The microstructure of the 2 min treated coating was further observed by transmission electron microscopy to explore the coating formation mechanism. The amounts of Ag and Zn released from the 2 min treated coating were measured and the antibacterial properties of the coatings against Staphylococcus aureus ( S. aureus ) were also investigated. The obtained results showed that with prolonged MAO time, the contents of Ag and Zn on the coating surfaces increased. All the coatings were micro-porous with pore diameters of 1–4 µm; however, some pores were blocked by deposits on the 4 min treated coating. The 2 min treated coating was composed of amorphous TiO 2 , anatase, rutile, ZnO, Zn 2 TiO 4 and homogenously distributed Ag nanoparticles. After immersion, Zn 2+ , Ag + , Ti 2+ and Ca 2+ were released from the coating and with the immersion time prolonged, the accumulated concentrations of these ions increased. After immersion for 36 weeks, the accumulated Zn 2+ and Ag + concentrations were 6.88 and 0.684 ppm, respectively, which are higher than the minimal inhibitory concentration but much lower than the cytotoxic concentration. Compared with polished Ti control, the coatings co-doped with Zn 2+ and Ag nanoparticles significantly inhibited the adhesions of S. aureus and reduced the amounts of planktonic bacteria in culture medium, indicating that the Zn and Ag co-doped TiO 2 could be a bio-adaptable coating for long-lasting anti-microbial performance.