FeOx magnetization enhancing E-coli inactivation by orders of magnitude on Ag-TiO2 nanotubes under sunlight

Stefanos Giannakis, Juan Kiwi, Arnaud Magrez, Marco Mangayayam, César Pulgarin, Sami Rtimi, Ivica Zivkovic
Elsevier, 2017
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Résumé

Drastic bacterial enhancement was observed when the Ag(3%)-TiO2 nanotubes were modified with FeOx (3%) magnetic oxide. On bare TiO2- nanotubes a reduction of 0.21og(10)CFU was observed within one hour under simulated low intensity solar light. Under similar conditions, a bacterial reduction of 2.5log(10)CFU was observed, on Ag(3%)TiO2 increasing to 6.0log(10)CFU on Ag(3%)-TiO2-FeOx(3%) magnetic nanotubes. The bacterial inactivation kinetics is strongly influenced by the addition of FeOx. The fast inactivation induced by the composite catalyst seems to involve an increase in the interfacial charge transfer (IFCT) compared to a 2-oxide composite photocatalyst. Stable recycling of the photocatalyst was observed leading to bacterial oxidation. The unambiguous identification of the radical intermediates: OH-radicals, O-singlet and the valence holes vb(h +) on the Ag-TiO2-FeOx interface showed that the valence band holes vb(h +) were the main oxidative intermediates leading to bacterial inactivation. Nanotubes size, crystallinity and bulk composition of magnetite 1% (0 = 51.0 degrees), anatase 5% (0 = 8.9 degrees), goethite 37.3% (0 = 9.0 degrees), silver 1% (0=2.7 degrees) was obtained by the Rietveld refinement for the Ag(3%)-TiO2-FeOx(3%) nanotubes. The redox chemistry during bacterial inactivation was determined by X-ray photoelectron spectroscopy (XPS). (C) 2016 Elsevier B.V. All rights reserved.

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Stefanos Giannakis, Juan Kiwi, Arnaud Magrez, Marco Mangayayam, César Pulgarin, Sami Rtimi, Ivica Zivkovic
Elsevier, 2017
Article

Résumé

Official source

https://infoscience.epfl.ch/record/224861?ln=fr

À propos de ce résultat

Concepts associés (17)

Concepts associés

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Publications associées (25)

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This study presents new evidence for the events leading to Escherichia coil reduction in the absence of light irradiation on TiO2-polyester (from now on TiO2-PES. By transmission electron microscopy (TEM) the diffusion of TiO2 NP's aggregates with the E. coil outer lipo-polyssacharide (LPS) layer is shown to be a prerequisite for the loss of bacterial cultivability. Within 30 min in the dark the TiO2 aggregates interact with E. coil cell wall leading within 120 min to the complete loss of bacterial cultivability on a TiO2-PES 5% TiO2 sample. The bacterial reduction was observed to increase with a higher TiO2 loading on the PES up to 5%. Bacterial disinfection on TiO2-PES in the dark was slower compared to the runs under low intensity simulated sunlight light irradiation. The interaction between the TiO2 aggregates and the E. coil cell wall is discussed in terms of the competition between the TiO2 units collapsing to form TiO2-aggregates at a physiologic pH-value followed by the electrostatic interaction with the bacteria surface. TiO2-PES samples were able to carry repetitive bacterial inactivation. This presents a potential for practical applications. X-ray photoelectron spectroscopy (XPS) evidence was found for the reduction of Ti4+ to Ti3+ contributing to redox interactions between TiO2-PES and the bacterial cell wall. Insight is provided into the mechanism of interaction between the E. coil cell wall and TiO2 NP's. The properties of the TiO2-PES surface like percentage atomic concentration, TiO2-loading, optical absorption, surface charge and crystallographic phases are reported in this study. (C) 2014 Elsevier B.V. All rights reserved.

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The wafers used by the photovoltaic industry are mostly produced by multi-wire slurry sawing. One of the key factors determining the wafer quality (presence of saw marks and chips, increased roughness, wafer thickness variations and wafer strength) is the abrasive slurry. For cost reduction, the slurry is regularly exchanged and the debris it contains is removed in a recycling operation. To optimise the slurry usage, it is of utmost importance to understand the effects of the silicon debris concentration in the slurry. This was studied by sawing several bricks one after the other with the same slurry. It was found that when the amount of debris is too high (more than 4% of the slurry volume), saw marks appear on the wafers and they become more fragile. Finally, a first qualitative model explaining the apparition of the saw marks and the reduction of wafer strength is proposed. (C) 2011 Elsevier B.V. All rights reserved.

Elsevier2011

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Duality in the Escherichia coli and methicillin resistant Staphylococcus aureus reduction mechanism under actinic light on innovative co-sputtered surfaces

Myriam Koumba Sarah Ballo, Juan Kiwi, Danièle Laub, César Pulgarin, Sami Rtimi, Rosendo Sanjines

The kinetics of bacterial reduction of Staphylococcus aureus (MRSA) on co-sputtered TiO2/Cu-polyester (TiO2/Cu-PES) was found to be little dependent on the applied light dose. But in the case of Escherichia coil, the bacterial reduction kinetics was observed to be strongly dependent on the applied light dose. The reasons for the different effect of the applied light dose on the bacterial reduction are discussed. Mechanistic considerations are suggested to account for this observation.TiO2/Cu-PES obtained by direct current magnetron co-sputtering and the bacterial reduction features compared to PES sputtered individually by TiO2 and Cu. This study presents the first evidence for the stabilizing effect of TiO2 on the amounts of the Cu released during bacterial inactivation by co-sputtered surfaces compared to sequential sputtering of Ti and/or Cu on PES. The release of Cu-monitored in the ppb range by inductively coupled plasma-mass spectrometry (ICP-MS) is indicative of an oligodynamic effect leading to bacterial reduction. The bacterial reduction of MRSA ATCC 43300 on co-sputtered TiO2/Cu led to a 5 log(10) (99.999%) reduction within 120 min in the dark and 60 min under low intensity actinic light. Diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM) and X-ray fluorescence (XRF) describe the TiO2/Cu surfaces investigated in this study. (C) 2015 Elsevier B.V. All rights reserved.

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