Ag-surfaces sputtered by DC and pulsed DC-magnetron sputtering effective in bacterial inactivation: Testing and characterization

This study addresses the deposition of active, uniform nanoparticulate Ag-thin films on polyester textiles by DC-magnetron sputtering (DC) and pulsed DC-magnetron sputtering (DCP). The deposition of Ag on the polyester fiber was observed to be the function of the type of sputtering used and this has direct implications on the E. coli inactivation kinetics. The shortest E. coli inactivation was observed within two hours when sputtering with DCP Ag-layers 160 nm thick ~ at 300 mA within 2.7 min. This is equivalent to a growing coating rate of 74 nm/min. By electron microscopy (TEM) Ag-polyester fibers it was found that Ag sputtered by DCP penetrated more deeply into the polyester full fiber compared to DC-sputtering leading to a more favorable E. coli inactivation kinetics. The E. coli inactivation times were found to be a function of the applied DC and DCP energies and higher sputtering energies reduced the E. coli inactivation times. X-ray photoelectron spectroscopy (XPS) was used to determine the surface atomic concentration of O, Ag, C and N for the DC- and DCP samples as a function of the bacterial inactivation time. The change hydrophobic/hydrophilic balance of the Ag-polyester was determined by contact angle measurements and the implications of these changes discussed.