a b s t r a c tThis study reports the details Escherichia coli inactivation kinetics on TiON and TiON-Ag films sputtered on polyester by direct current reactive magnetron sputtering (DC) and pulsed magnetron sputtering (DCP) in an Ar/N 2 /O 2 atmosphere. The use of TiON leads to bacterial inactivation avoiding leaching of Ag. The surface of TiON and TiON-Ag was characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), electron microscopy (EM), X-ray fluorescence (XRF) and contact angle (CA) measurements. Evidence for the photocatalyst self-cleaning after the bacterial inactivation was shown by XPS, contact angle (CA) and the Zetasizer zeta-potential of the proteins. The photo-induced charge transfer from Ag 2 O and TiO 2 is discussed considering the relative positions of the electronic bands of the two oxides. An interfacial charge transfer mechanism (IFCT) for the photo-induced electron injection is suggested. The most suitable TiON coating sputtered on polyester was 70 nm thick and inactivated E. coli within 120 min under low intensity visible/actinic light (400-700 nm, 4 mW/cm 2 ). TiON-Ag sputtered catalysts shortened E. coli inactivation to ∼55 min, since Ag accelerated bacterial inactivation due to its disinfecting properties. Evidence is presented for the repetitive performance within short times of the TiON and TiON-Ag polyester under low intensity visible light.
a b s t r a c tThis study presents the design, preparation, testing and characterization of TiN and TiN-Ag nanoparticulate films leading to photocatalytic and catalytic inactivation of Escherichia coli. When Ti was sputtered in N 2 atmosphere, the TiN films unexpectedly revealed semiconductor properties when irradiated under visible light due to the formation of TiO 2 showing absorption in the visible spectral region. In TiN-Ag films, Ag enhances the photocatalytic activity of TiN leading to faster bacterial inactivation. Evidence for the presence of TiO 2 and TiN in the films is presented by XPS. The TiN layers 50 nm thick sputtered by DC for 3 min led to complete inactivation of E. coli within 120 min. But TiN layers with a thickness >50 nm hinder the surface diffusion of charges reducing bacterial inactivation. The rate of TiN deposition was ∼1.4 × 10 15 atoms TiN/cm 2 s. For the TiN-polyester samples under visible light a 3 log 10 bacterial reduction (99.9%) was observed within 30 min while for TiN-Ag samples the same bacterial reduction was attained within ∼15 min. The absorption of the TiN-Ag samples in Kubelka-Munk (KM) units was directly proportional to the E. coli inactivation kinetics. TiN-Ag plasmon nanostructures are concurrently formed under low intensity visible light and accelerated bacterial inactivation. This study shows that TiN films have the potential to replace Ag-based disinfection materials leaching Ag into the environment.
This study reports HIPIMS-sputtered samples of Cu-particulate films with currents at 6 and 60 amps leading to E. coli inactivation. The Cu coverage and nanoparticle structure of the fibers is reported by TEM. Evidence is presented of redox processes in the Cu taking place during E. coli inactivation and the buildup of intermediate species resulting from the bacterial oxidation. Cu is deposited on the polyester in the form of Cu 2 O and CuO as observed by XPS. During the bacterial oxidation, the CuO on the polyester after 30 min decreases from 84 to 70%. After longer bacterial inactivation times, the CuO oxidizes again increases its presence to 94% when the bacterial inactivation has been completed within 90 min. The broadening of the OÀCdO signal during E. coli inactivation suggests direct interaction of Cu with carboxylic groups. The surface atomic concentration of O, Cu, and C was determined within the E. coli inactivation time. The E. coli inactivation occurred within 90 min on Cu-nanoparticulate films sputtered for 61 s at 60 amps being 28 nm thick. This Cu-layer thickness is equivalent to 140 layers with a content of 1.4 Â 10 17 atoms Cu/cm 2 , and the sputtering proceeded with deposition rate of 2.3 Â 10 15 atoms/cm 2 s. The values found for the rugosity indicate that the texture of the Cu-nanoparticulate film is smooth. R q values and the R a were similar before and after the E. coli inactivation, providing further evidence of the stability of the Cu-nanoparticulate films during the bacterial inactivation process. The Cu-loading percentage required in the Cu-nanoparticulate films sputtered by HIPIMS to inactivate E. coli completely was about three times lower compared with DCMS-sputtered Cu-nanoparticulate films. This indicates a substantial Cumetal savings within the preparation of antibacterial films.
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