Fabrication of a Ag2O/SiO2/Ta2O5 nanocomposite coating for orthopaedic applications: Anticorrosion, photocatalytical and antimicrobial activities
School of Engineering
National Natural Science Foundation of China
With the considerable growth of the world's elderly population, there is an urgent need to develop bone implants with multifunctional surfaces, including high wear/corrosion resistance, favorable biocompatibility and excellent self-sterilization characteristics. Here, a Ag2O/SiO2/Ta2O5 nanocomposite coating was deposited on a Ti–6Al–4V substrate by double-cathode glow discharge technology. The mechanical characteristics, microstructure, biological corrosion resistance, biocompatibility, visible light catalytic activity and antibacterial properties of the nanocomposite coating were comprehensively evaluated. The Ag2O/SiO2/Ta2O5 coating was composed of crystalline Ta2O5 and Ag2O particles embedded in amorphous SiO2, and showed significantly improved surface hardness relative to the substrate. Further, this coating significantly reduced the corrosion damage from Ringer's solution to the substrate and was conducive to the spreading, adhesion and proliferation of MC3T3-E1 cells. Through investigation of the coating's photocatalytic activity, it was found that the nanocomposite coating solved the limitation that commercial Ta2O5 could not be induced by visible light. Further DFT calculations revealed the orbital occupation of the density of states of the Ag2O/SiO2/Ta2O5 heterojunction and the transfer path of the photogenerated electron-hole pairs. This finding was validated by investigation of antibacterial behaviour under the conditions of dark and visible light. It was shown that the antibacterial rate for the Ag2O/SiO2/Ta2O5 nanocomposite coating against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) under visible-light is close to 100%, which is higher than the single antibacterial rate for Ag+ ions under dark conditions. Thus, the multifunctional Ag2O/SiO2/Ta2O5 nanocomposite coating is expected to become an attractive alternative for the surface modification of the next generation of bone implants.