Contribution to the understanding of antibacterial properties of CuTiZn thin film: From crystalline alloy to metallic glass

Abstract

In this work, thin films of CuZn and CuTiZn alloys were synthesized by magnetron sputter deposition. Their antibacterial activity on the proliferation of Escherichia coli was investigated after incubation during 24 h at 37.0 °C by measuring the bacteria solution absorbance at 600 nm. Among tests usually employed in laboratories to evaluate the antibacterial properties of coatings, this one specially characterizes the action of chemical elements dissolved in the solution, i.e. the so-called release killing mechanism. The obtained results are discussed depending on the film chemical composition (in depth and at the surface), microstructure and crystallinity. A good antibacterial activity was found for pure Zn and CuZn films, whereas a rapid degradation was observed as soon as Ti is added, which coincides with the formation of a dense amorphous phase. At close chemical compositions, formation of this stable metallic glass phase seems to be detrimental to the ion release mechanism. This work highlighted that the microstructural and crystalline properties (more or less porous polycrystalline film/dense, defect free metallic glass) significantly influence the antibacterial properties of such alloy thin films.