Silver influence on the antibacterial activity of multi-functional Zr-Cu based thin film metallic glasses

Influence of the silver content of magnetron-sputtered Zr-Cu-based thin film metallic glasses (TFMGs) on their antibacterial activity is investigated to enlarge their multifunctional character. These TFMGs are also characterized from microstructural, mechanical and electrochemical points of view. Ternary Zr-Cu-Ag thin films are amorphous (DRX) for silver contents higher than 11 at.%. TEM analysis shows the formation of nanoparticles embedded in amorphous matrix for 25 Ag at.%. These thin films appear uniformly thick and smooth. Mechanical properties were determined by nanoindentation and an effect of silver on Young's modulus and hardness was observed for ternary Zr-Cu-Ag. The silver content favors the corrosion protectiveness of Zr-based TFMG in moderately aggressive medium. The presence of nanoparticles however induces pitting corrosion for Ag-rich thin film in chloride medium. Finally, the antibacterial activity of these TFMGs against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) is evaluated and correlated to the electrochemical behavior. Besides, a beneficial influence of silver addition on the antibacterial activity of Zr-Cu-based TFMGs is clearly established and a critical silver content of 11 at.% leading to a biocide effect is determined.