Antibacterial Ag–ZrN surfaces promoted by subnanometric ZrN-clusters deposited by reactive pulsed magnetron sputtering

Ag–ZrN films were deposited on polyester by direct current pulsed magnetron sputtering (from now on DCMSP) in Ar + N2 atmosphere. ZrN on the polyester surface interacts with Ag leading to Ag–ZrN films. These composite films were more active in Escherichia coli inactivation compared to the Ag-films by themselves. The E. coli inactivation kinetics on Ag–ZrN polyester surfaces was accelerated >4 times compared to samples sputtering only Ag. Sputtering Zr in N2 atmosphere presented no antibacterial activity by itself when applied for short times (< one min). The Ag–ZrN polyester sample sputtered for 20 s at 300 mA led to the fastest antibacterial E. coli inactivation kinetics within 11/2 h. This sample consisted of Ag-particles with sizes of 15–40 nm, within a layer thickness of 30–45 nm covering ∼60–70% of the polyester fiber in the direction of the Ago/Ag-ion-flux from the Ag-target. An Ag sputtering time of 20 s lead to the optimal ratio of Ag-loading/Ag cluster size with the highest amount of Ag-sites held in exposed positions on the polyester surface. The Ag-nanoparticles sputtered for times >20 s agglomerated to bigger units leading to longer bacterial inactivation times. The Ag-atoms are shown to be immiscible with the ZrN-layer. The increase in thickness of the Ag–ZrN at longer sputtering times lead to a concomitant increase in rugosity and hydrophobic character of the Ag–ZrN sputtered layers. Several up-to date techniques have been used to characterize the catalytic Ag–ZrN film providing a full description of its structure. The Ag–ZrN films showed a uniform metal distribution and a semi-transparent gray-brown color.

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► Ag–ZrN films were deposited on polyester by direct current pulsed magnetron sputtering (from now on DCMSP) in Ar + N2 atmosphere. ZrN on the polyester surface interacts with Ag leading to Ag–ZrN films.
► The E. coli inactivation kinetics on Ag–ZrN polyester surfaces was accelerated >4 times compared to samples sputtering only Ag.
► Evidence is presented for the lack of miscibility of the Ag-atoms and the fcc-ZrN subnanometric crystallites.
► This study presents the first experimental evidence relating the thickness of the Ag–ZrN layer to the hydrophobic and roughness properties of the Ag–ZrN film. These properties are shown to be controlling parameters affecting the observed E. coli inactivation kinetics.