Indoor Light Enhanced Photocatalytic Ultra-Thin Films on Flexible Non-Heat Resistant Substrates Reducing Bacterial Infection Risks

Photocatalytic antibacterial sol-gel coated substrates have been reported to kill bacteria under light or in the dark. These coatings showed non-uniform distribution, poor adhesion to the substrate and short effective lifetime as antibacterial surfaces. These serious limitations to the performance/stability retard the potential application of antibacterial films on a wide range of surfaces in hospital facilities and public places. Here, the preparation, testing and performance of flexible ultra-thin films prepared by direct current magnetron sputtering (DCMS) at different energies are reviewed. This review reports the recent advancements in the preparation of highly adhesive photocatalytic coatings prepared by up to date sputtering technology: High Power Impulse Magnetron Sputtering (HIPIMS). These latter films demonstrated an accelerated antibacterial capability compared to thicker films prepared by DCMS leading to materials saving. Nanoparticulates of Ti and Cu have been shown during the last decades to possess high oxidative redox potentials leading to bacterial inactivation kinetics in the minute range. In the case of TiO2-CuOx films, the kinetics of abatement of Escherichia coli (E. coli) and methicillin resistant Staphylococcus aureus (MRSA) were enhanced under indoor visible light and were perceived to occur within few minutes. Oligodynamic effect was seen to be responsible for bacterial inactivation by the small amount of released material in the dark and/or under light as detected by inductively-coupled plasma mass spectrometry (ICP-MS). The spectral absorbance (detected by Diffuse Reflectance Spectroscopy (DRS)) was also seen to slightly shift to the visible region based on the preparation method

Thin films for Healthcare Acquired Infections (HAIs) prevention:materials preparation, testing and characterization

This thesis addresses the preparation of antibacterial surfaces for hospital facilities taking biomedical thin polymer films, textiles and catheter as probes. Magnetron sputtering is used to apply the coatings leading to fast bacterial inactivation in the dark and under low intensity light on the selected substrates. These coating are designed and prepared to achieve fast bacterial inactivation to avoid biofilm formation on textiles and polymer films and later on the catheter surface. The infection due to catheters is one of the major problem leading to catheter associated infections (CAIs). The design, preparation, testing and the characterization of the surface properties of uniform and adhesive TiO2,TiO2/Cu, Ag, Cu-films presenting fast bacterial inactivation kinetics on textiles and catheters by up to date HIPIMS and DCMS/DCPMS has been addressed very sparsely until now mainly on 3D objects. No evidence for Ag-Cu coating applied by sputtering covering uniformly the entire catheter surface has been reported up to this date. A modification of the sputtering unit was carried out to coat 3D objects and is one of the main novelties reported in this thesis. The antimicrobial activity was tested on antibiotic resistant bacteria Methycillin resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli) alone or jointly representing an important focus of infection by themselves or in the form of pathogenic biofilms in hospital facilities. The bacterial inactivation kinetics was investigated in details under low intensity light and in the dark. The active part of the catheter remains under the patient skin (in the dark). Ag/Cu-has been selected since fast bacterial inactivation proceeds in with a quasi-instantaneous kinetics inducing a cytotoxicity below the limit authorized by the sanitary regulations for mammalian cells. These coatings are also well tolerated by osteoblasts. The sputtered films leading to fast bacterial inactivation and showing low cytotoxicity consisted mainly of TiO2, Cu-TiO2, and Ag/Cu films on 2D surfaces and on catheters with 3D-geometry. This is the first report for materials of this kind, their evaluation and surface properties

Recent Developments in Accelerated Antibacterial Inactivation on 2D Cu-Titania Surfaces under Indoor Visible Light

This review focuses on Cu/TiO2 sequentially sputtered and Cu-TiO2 co-sputtered catalytic/photocatalytic surfaces that lead to bacterial inactivation, discussing their stability, synthesis, adhesion, and antibacterial kinetics. The intervention of TiO2, Cu, and the synergic effect of Cu and TiO2 on films prepared by a colloidal sol-gel method leading to bacterial inactivation is reviewed. Processes in aerobic and anaerobic media leading to bacterial loss of viability in multidrug resistant (MDR) pathogens, Gram-negative, and Gram-positive bacteria are described. Insight is provided for the interfacial charge transfer mechanism under solar irradiation occurring between TiO2 and Cu. Surface properties of 2D TiO2/Cu and TiO2-Cu films are correlated with the bacterial inactivation kinetics in dark and under light conditions. The intervention of these antibacterial sputtered surfaces in health-care facilities, leading to Methicillin-resistant Staphylococcus Aureus (MRSA)-isolates inactivation, is described in dark and under actinic light conditions. The synergic intervention of the Cu and TiO2 films leading to bacterial inactivation prepared by direct current magnetron sputtering (DCMS), pulsed direct current magnetron sputtering (DCMSP), and high power impulse magnetron sputtering (HIPIMS) is reported in a detailed manner

New evidence for Cu-decorated binary-oxides mediating bacterial inactivation/mineralization in aerobic media

Binary oxide semiconductors TiO2-ZrO2 and Cu-decorated TiO2-ZrO2 (TiO2-ZrO2-Cu) uniform films were sputtered on polyester (PES). These films were irradiated under low intensity solar simulated light and led to bacterial inactivation in aerobic and anaerobic media as evaluated by CFU-plate counting. But bacterial mineralization was only induced by TiO2-ZrO2-Cu in aerobic media. The highly oxidative radicals generated on the films surface under light were identified by the use of appropriate scavengers. The hole generated on the TiO2-ZrO2 films is shown to be the main specie leading to bacterial inactivation. TiO2-ZrO2 and Cu-decorated TiO2-ZrO2 films release Zr and Ti< 1ppb and Cu 4.6 ppb/cm2 as determined by inductively coupled plasma mass spectrometry (ICP-MS) This level is far below the citotoxicity permitted level allowed for mammalian cells suggesting that bacterial disinfection proceeds through an oligodynamic effect. By Fourier transform attenuated infrared spectroscopy (ATR-FTIR) the systematic shift of the predominating vs(CH2) vibrational-rotational peak making up most of the bacterial cell-wall content in C was monitored. Based on this evidence a mechanism suggested leading to C-H bond stretching followed by cell lysis and cell death. Bacterial inactivation cycling was observed on TiO2-ZrO2-Cu showing the stability of these films leading to bacterial inactivation

Evidence for TiON sputtered surfaces showing accelerated antibacterial activity under simulated solar irradiation

New evidence is reported for TiON sputtered polyester surfaces activated by sunlight irradiation leading to the accelerated bacterial inactivation in the minute range. The absorption in Kubelka-Munk units of the TiON film was observed to be directly proportional to the time of Escherichia coil inactivation as detected by diffuse reflection spectroscopy (DRS). TiON layers were characterized by electron microscopy and by high angle angular dark field (HAADF) showing the continuous coverage of the polyester fibers by the TiON film. Ti4+/Ti3+ redox catalysis was detected on the TiON surface by the XPS shifts during the bacteria inactivation process. Production of HO radicals on TiON polyester as a function of sunlight irradiation was determined following the fluorescence of 2-hydroxyterephthalic acid. Release of Na and K-ions was determined by ICP-MS and provides the evidence that cell wall damage is a preceding step leading the bacterial inactivation. A stable performance of the TiON films was observed during repetitive bacterial inactivation. (C) 2013 Elsevier Ltd. All rights reserved

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

Novel FeOx–polyethylene transparent films: synthesis and mechanism of surface regeneration

The first evidence for the synthesis of a uniform, adhesive polyethylene–FeOx (PE–FeOx) surface leading efficiently to bacterial inactivation is addressed in this study. PE was loaded with 0.04–0.08% Fe wt/wt PE after RF-plasma pretreatment was required to increase the active sites/polarity and roughness to adhere FeOx on PE. The repetitive bacterial inactivation proceeded in a stable way for several cycles. The oxidative radicals leading to bacterial inactivation under aerobic/anaerobic conditions were investigated by the use of appropriate scavengers. By X-ray photoelectron spectroscopy (XPS) and diffuse reflection spectroscopy (DRS) the changes on the PE–FeOx oxidation states and spectroscopic features during bacterial inactivation were monitored. The regeneration of the initial Fe-oxidation state and consequently of the initial Fe-oxidation state in the PE–FeOx was possible and followed by DRS. Inductive plasma coupled mass spectrometry (ICP-MS) indicated that only sub-ppb levels of Fe were released from the PE–FeOx surface within the reaction time

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

Magnetron Sputtering of Transition Metal Nitride Thin Films for Environmental Remediation

The current economic and ecological situation encourages the use of steel to push the technological limits and offer more cost-effective products. The enhancement of steel properties like wear, corrosion, and oxidation resistance is achieved by the addition of small amounts of chemical elements such as Cr, Ni, Si, N, etc. The steel surface can be protected by different treatments such as heating and coating, among others. For many decades, coatings have been an effective solution to protect materials using thin hard films. Several technologies for thin film deposition have been developed. However, some of them are restricted to certain fields because of their complex operating conditions. In addition, some deposition techniques cannot be applied to a large substrate surface type. The magnetron sputtering deposition process is a good option to overcome these challenges and can be used with different substrates of varying sizes with specific growth modes and for a wide range of applications. In this review article, we present the sputtering mechanism and film growth modes and focus on the mechanical and tribological behavior of nitride thin films deposited by the magnetron sputtering technique as a function of process conditions, particularly bias voltage and nitrogen percentage. The biomedical properties of transition metal nitride coatings are also presented

Supported TiO2 films deposited at different energies: Implications of the surface compactness on the catalytic kinetics

Insight is provided in this study for the effect of the TiO2film densification/compactness on polyethy-lene (PE-TiO2) by sputtering TiO2at two very different energy levels. Uniform, adhesive low energy filmswere prepared by direct current magnetron sputtering (DCMS) and compared with films sputtered athigh energy levels by high power impulse magnetron sputtering (HIPIMS). Nano-particulate TiO2filmssputtered by HPIMS presented sizes of ∼10.2 nm compared to films sputtered by DCMS with TiO2sizesof ∼16.5 nm as determined by X-ray diffraction (XRD). The E. coli inactivation kinetics was three timesfaster for the samples sputtered by HIPIMS compared to their DCMS counterparts. This is an unexpectedfinding since the DCMS presenting larger TiO2sized nanoparticles released a higher amount of Ti-ionscompared to the HIPIMS samples as monitored by inductively coupled plasma mass-spectrometry (ICP-MS). The Ti-ions released do not seem to react through an oligodynamic effect but diffuse through theless compact TiO2sputtered by DCMS. The faster bacterial inactivation kinetics observed by the HIPIMSsputtered samples can be understood in terms of the complete of Ti4+/Ti3+redox conversion during bacte-rial inactivation detected by X-ray photo-electron spectroscopy (XPS) compared to the smaller Ti4+/Ti3+effect observed in the DCMS-samples. A higher optical density was detected for the HIPIMS sputteredsamples by diffuse reflectance spectroscopy (DRS). Evidence is presented for the shift in surface potentialand local pH during bacterial inactivation under aerobic and anaerobic conditions. A reaction mechanismis suggested based on the findings described in this study. The sputtered films present the potential tohinder biofilm formation on flexible thin polymers/textiles widely used in hospitals and health facilities