Preparation,characterizations, and antibacterial properties of Cu/SnO2 nanocomposite bilayer coatings

A nano-bilayer structure consisting of copper and SnO₂ nanocomposites was prepared by a magnetron sputtering method. A nano-SnO₂ thin layer with a thickness of 52 nm was achieved on quartz glass. A nano-copper layer was then deposited on top of the SnO₂ thin layer by the sputtering method. The thickness of the nano-copper layer was approximately 7 nm, such that the SnO₂ layer was not only completely covered by the copper layer but it also resulted in transparent bilayer films. Post-annealing was carried out at 400°C in air for 1 h to obtain a crystalline SnO₂ phase and simultaneously the copper layer was oxidized to CuO. Sputtered nanocomposites of CuO/SnO₂ bilayer films showed a synergistic effect toward E. coli inactivation under indoor light exposure. A possible mechanism for the synergistic effect with respect to the antibacterial properties of CuO/SnO₂ bilayer nanocomposites has been proposed. Incorporating CuO onto the SnO₂ layer achieves photocatalyst works under indoor light and provides an antimicrobial function even under a dark environment by the antimicrobial property of CuO itself. Reported CuO/SnO₂ sputter coating can be useful to apply, for instance, to electric devices such as touch panel displays in a hospital in order to reduce hospital-acquired infections (HAIs).