Preparation, Characterization and Evaluation of the Antibacterial Activity of Ag Nanoparticles Embedded in Transparent Oxide Matrices

Daily exposure to contaminated environments and surfaces leads to serious health issues, increasing healthcare costs. Active materials that act against pathogens can effectively prevent their proliferation and contribute to increased protection against infections. In this contribution, nanostructured thin films containing silver are investigated, using SiO2 and TiO2 as transparent matrices to embed the Ag atoms. The thin transparent films were obtained via magnetron sputtering, using HiPIMS for Ag deposition and RF sputtering for oxides, in either an Ar or Ar/O2 environment. Atomic Force Microscopy provided information on coating topography and the thin films’ preferential growth on the textured polymer foil, X-Ray Diffraction highlighted the structural difference between different versions, Ultraviolet–Visible–Near-Infrared spectroscopy proved the thin films’ optical quality and their transparency and Energy-Dispersive X-ray Spectroscopy revealed the composition changes for different processes. The effect of O2 addition is analyzed and compared in terms of changes induced on the properties of the thin films. Following 24 h of incubation in a media containing 104 CFU/mL Escherichia coli, the TiO2+Ag sample with O2 addition showed the highest antibacterial effectiveness, as indicated by the largest inhibition zone. Experiments on selective media showed a hierarchy of efficiency, namely, TiO2+Ag+O2 > TiO2+Ag > SiO2+Ag.