Accelerated bacterial inactivation obtained by HIPIMS sputtering on low cost surfaces with concomitant reduction in the metal/semiconductor content

Novel ultrathin TiO2-Cu nanoparticulate films sputtered by highly ionized pulsed plasma magnetron sputtering (HIPIMS) lead to faster bacterial inactivation compared to more traditional sputtering approaches with an appreciable metal saving. HIPIMS sputtering induces a strong interaction of the TiO2-Cu-ions (M+) with the polyester surface due to the high fraction and density of M+-ions interacting with the biased substrate

Modification of titania nanoparticles for photocatalytic antibacterial activity via a colloidal route with glycine and subsequent annealing

Changes in the colloid-chemical and photocatalytic properties of titania nanoparticles by attrition milling in the presence of glycine (Gly) and subsequent heat treatment were examined. By milling at 1500 rpm for 6 h, the average particle size was decreased from 123 to 85 nm, with simultaneous decrease in the specific surface area from 35.1 to 23.5 m2/g. Interfacial reactions between titania and Gly were confirmed by Fourier transform infrared spectroscopy, from the blue shift of the COO− related vibrational bands by 25 cm−1, relative to the same band from the pristine Gly. The bimodal N1s x-ray photoelectron spectroscopy peak similar to that from the reported titania—amino acid complex is another indication of the complex formation with the participation of nitrogen. When the dispersion was dried and calcined at 500 °C in air, the powder exhibited pale yellow color. Diffuse reflectance spectroscopy showed significant visible light absorption, suggesting nitrogen incorporation into titania. The fired product showed high photocatalytic antibacterial activity by irradiation of blue light centered at around 440 nm, using Escherichia coli as a specimen of bacterial species. Thus, the present Gly-modified titania nanoparticles could be used for eliminating indoor bacteria under soft blue illumination. The series of interfacial chemical processes involved are also discusse

Growth of TiO2/Cu films by HiPIMS for accelerated bacterial loss of viability

This study shows the first complete report on ultrathin TiO2/Cu nano-particulate films sputtered by highly ionized pulsed plasma magnetron sputtering (HIPIMS) leading to fast bacterial loss of viability. The Cu- and the TiO2/Cu sputtered films induced complete Escherichia coil inactivation in the dark, which was not observed in the case of TiO2. When Cu was present, the bacterial inactivation was accelerated under low intensity solar simulated light and this has implications for a potential for a practical technology. The design, preparation, testing and surface characterization of these innovative films are described in this study. The HIPIMS sputtered composite films present an appreciable savings in metals compared to films obtained by conventional sputtering methods. HIPIMS sputtering induces a strong interaction with the rugous polyester 3-D structure due to the higher fraction of the Cu-ions (M+) attained in the magnetron chamber. The Cu-leaching during the bacterial inactivation was monitored by ion-coupled plasma mass spectrometry (ICP-MS) and found to be in the ppb range. The amounts found were below the cytotoxicity level allowed by the standards related to human health. The immiscibility of Cu and TiO2 in the TiO2/Cu films is shown by High Angular Dark Field (HAADF) microscopy. A mechanism for the photo-induced interfacial charge transfer (IFCT) between TiO2 and Cu is suggested. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved

TiON and TiON-Ag sputtered surfaces leading to bacterial inactivation under indoor actinic light

This 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/N2 /O2 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 Ag2 O and TiO2 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/cm2 ). 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

Photocatalysis/catalysis by innovative TiN and TiN-Ag surfaces inactivate bacteria under visible light

This 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 N2 atmosphere, the TiN films unexpectedly revealed semiconductor properties when irradiated under visible light due to the formation of TiO2 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 TiO2 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 ×1015 atoms TiN/cm2s. For the TiN-polyester samples under visible light a 3 log10 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

Sputtered Cu-polyethylene films inducing bacteria inactivation in the dark and under low intensity sunlight

This study addresses the preparation of uniform, adhesive and robust thin Cu-polyethylene films (PE-CuOx) by direct current magnetron sputtering (DCMS). Cu-coatings of 25 nm sputtered with 60W deposited 0.16% weight Cu/weight PE leading to the fastest bacterial inactivation under low intensity simulated sunlight irradiation equivalent to 20% AM1. These films were able to induce complete bacterial inactivation in the dark within 90 min and at a faster rate within 15 min under low intensity sunlight. Repetitive photo-induced bacterial inactivation was observed on the CuOx-PE. The Cu-released during the catalyst recycling in the ppb-range was determined by inductively coupled plasma mass spectrometry (ICP-MS) and showed the electrostatic interaction between bacteria and the CuOx-PE film. An increase in the applied light intensity accelerated the bacterial inactivation kinetics providing evidence for the semiconductor behavior of the CuOx film. By X-ray photoelectron spectroscopy (XPS), the binding energy (BE) of the Cu-species, were seen to shift after bacterial inactivation concomitantly with the variation in the atomic surface concentration percentage of Cu, O, C, N and S. Insight is provided for the reasons leading to the variation in the surface composition during the bacterial inactivation period. (C) 2016 Elsevier B.V. All rights reserved

Comparison of HIPIMS sputtered Ag- and Cu-surfaces leading to accelerated bacterial inactivation in the dark

Recently, compact uniform and adhesive films of Ag and Cu have been prepared by DC-magnetron sputtering (DC), pulsed DC magnetron sputtering (DCP) and high power impulse magnetron sputtering (HIPIMS). This study reports the HIPIMS deposition for Ag and Cu on textile fabrics, the bacterial inactivation kinetics and the nature of the species in the plasma produced during HIPIMS sputtering. The deposition rates of Ag and Cu atoms and the bacterial inactivation times are reported in the dark and under light as a function of the applied peak currents during the sputtering by HIPIMS. By X-ray photoelectron spectroscopy (XPS), the surface percentage atomic concentration and the oxidation state changes are reported during bacterial inactivation. The Ar and metal-ions produced in the magnetron chamber were determined by mass spectroscopy (QMS). A mechanism for the bacterial inactivation is suggested for Ag and Cu HIPIMS sputtered surfaces