Bilayer microstructure of antibacterial TiO2 coating on Ti6Al4V fabricated via micro-arc oxidation in W-containing electrolytes

In our previous report, W-incorporated TiO2 coating was fabricated on Ti6Al4V by micro-arc oxidization (MAO), and exhibited excellent antibacterial performance. However, the antibacterial mechanism of W-incorporated TiO2 coating has not yet been clarified. Toward this end, the antibacterial mechanism of W-containing TiO2 coating was thoroughly disclosed through analyzing the physicochemical properties of MAO coatings in this work. The microstructure of W-incorporated TiO2 coating was analyzed in comparison with W-free TiO2 coating. The characterization confirms that the MAO coating is a bilayer microstructure with an amorphous outer layer and poly-crystalline inner layer, and the W-containing new electrolyte system is beneficial to the formation of the amorphous layer with great electron storage capability. The excellent antibacterial activity of W-incorporated TiO2 coating is related to its strong electron storage capability, which can induce sufficient valence-band holes (h(+)) to accumulate in the amorphous outer layer by trapping electrons from bacterial cell extrusion and microgalvanic corrosion, arousing oxidation damage to bacterial cells. This finding provides a novel and controlled strategy to design antibacterial coatings.