Rosendo Sanjines - Academia.edu (original) (raw)
Papers by Rosendo Sanjines
Applied Catalysis B: Environmental, 2018
ZnO-films although the conduction band potential energy position of the two semiconductors were i... more ZnO-films although the conduction band potential energy position of the two semiconductors were iso-energetic. By X-ray photoelectron spectroscopy (XPS), Cu2O was identified as the predominant Cu-oxidation state in the sputtered film. A mechanism for the NFX degradation is suggested in which the holes generated by Cu2O transfer to ZnO in the ZnO(n)/CuO(p) in the hetero-junction. This transfer is favored by the electrostatic interaction between both semiconductors. The catalyst optical properties and surface potential were monitored during NFX degradation. Stable repetitive NFX degradation kinetics was observed under visible light on the sputtered ZnO/CuxO films. The use of appropriate scavengers allowed the identification of the intermediate radical species (ROS). XPS analysis provided the proof for redox catalysis taking place within the time of NFX abatement. The application of ZnO/CuxO films in a photo-reactor for the degradation of emerging pollutants seems feasible due to the low cost of Zn and Cu and the fast kinetics found for NFX degradation.
Thin Solid Films, 2019
The present paper reports on an experimental investigation of the structural, electrical and opti... more The present paper reports on an experimental investigation of the structural, electrical and optical properties of Ru rich Ru 1-x Ti x O 2 thin films. Rutile single-phase Ru 1-x Ti x O 2 thin films have been deposited by reactive hybrid High-power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) at a substrate temperature of 250°C. The HiPIMS source was applied to the Ru target while the DCMS source was connected to the Ti target in order to vary the Ti content in the films. The films are well crystallized and compact with randomly orientated nanocrystallites. The optical properties have been investigated by ellipsometric measurements in the optical energy range from 1.3 eV to 3.3 eV, while the electrical resistivity has been measured in the Van der Paw configuration at room temperature. The electrical resistivity increases gradually from 70 μΩcm for pure RuO 2 to about 243 μΩcm for Ru 1-x Ti x O 2 films with x = 0.13. The optical properties are correlated with the Ti doping. The refractive index n changes from a strong dispersion relationship to a moderate one with increasing Ti content. The Ru 1-x Ti x O 2 thin films have been deposited by reactive hybrid
ACS applied materials & interfaces, Jan 11, 2018
This study presents innovative TiNb N-Ag films obtained by a suitable combination of low-energy a... more This study presents innovative TiNb N-Ag films obtained by a suitable combination of low-energy and high-energy sputtering leading to bacterial inactivation. The bacterial inactivation kinetics by the TiNbN layers was drastically enhanced by the addition of 6-7% Ag and proceeded to completion within 3 h after the film autoclaving. By X-ray photoelectron spectroscopy (XPS), the samples after autoclaving presented in their upper layers TiO, NbO and AgO with a surface composition of TiNbNAg. Surface potential/pH changes in the TiNb N-Ag films were monitored during bacterial inactivation. Surface redox processes during the bacterial inactivation were detected by XPS. The diffusion of Ag in the TiNb N-Ag films was followed at 50 and 70 °C pointing. The beneficial thermal treatment points out to the bifunctional bacterial inactivation properties of these films and their potential application in healthcare facilities. Interfacial charge transfer (IFCT) under light irradiation between AgO, ...
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, 2002
With the development of sub-0.25 μm technologies, interconnect integration is more sensitive to t... more With the development of sub-0.25 μm technologies, interconnect integration is more sensitive to the surface quality and to the roughness of tungsten-polished layers. Consequently, alumina-based slurries are progressively replaced by silica-based slurries (fumed or colloidal), characterized by much smaller and softer particles. In contrast to the many investigators of alumina-based slurries, only a few investigations have been carried out on the effect of the particle size on the physical vapor deposition (PVD) tungsten, PVD titanium, and thermal oxide removal rates and on the surface roughness after polishing. In this article, we evaluate four different colloidal silica-based slurries having different particle sizes. We find that the most promising slurry is the one with the smallest particle size. We also show that the tungsten removal rate mechanism is probably neither a scratching/indentation nor a surface contact type mechanism, but most likely a mechanism controlled by the grow...
Applied Catalysis A: General, 2016
This study reports an innovative preparation polyethylene-FeOx (PE-FeOx films) leading to the deg... more This study reports an innovative preparation polyethylene-FeOx (PE-FeOx films) leading to the degradation of the methylene blue (MB) dye under low intensity sunlight/visible light (>400 nm). The intermediate highly oxidative radicals generated by PE-FeOx leading to MB discoloration/degradation in the presence of H 2 O 2 were identified. The relative contribution to the MB discoloration by the Feions leached from the PE-FeOx films into solution was determined quantitatively. This allows estimating the contribution of the heterogeneous and of the homogeneous leading to MB-degradation. The shift in the peak binding energy (BE) for Fe was detected by photoelectron spectroscopy (XPS) after the MBdegradation providing the evidence for redox catalysis occurring during MB-degradation at the PE-FeOx surface. The particle size and roughness of the PE-FeOx surfaces were determined by atomic force spectroscopy (AFM). The spectral properties of PE-FeOx films are reported and insight is provided for the mechanism of MB-degradation.
Solar Energy, 2014
Overheating is a common problem both with the use of active and passive solar energy in thermal s... more Overheating is a common problem both with the use of active and passive solar energy in thermal solar energy systems and in highly glazed buildings, even in central European latitudes. In solar thermal collectors, the elevated temperatures occurring during stagnation result in reduced lifetime of the collector materials. They lead to water evaporation, glycol degradation and stresses in the collector with increasing vapor pressure. Special precautions are necessary to release this pressure; only mechanical solutions exist nowadays. The temperature of degradation of glycols is above 160-170°C. However, it would be preferable to limit the temperature of the collector to approximately 100°C, avoiding likewise the evaporation of the used water-glycol mixture. Additionally, the elevated temperatures lead to degradation of the materials that compose the collector, such as sealing, thermal insulation and the selective absorber coating. A new way of protecting solar thermal systems without any mechanical device (e.g. for shading or for pressure release) is proposed. A durable inorganic thermochromic material, which exhibits a change in optical properties at a transition temperature T t , is vanadium dioxide (VO 2). At 68°C, VO 2 undergoes a reversible crystal structural phase transition accompanied by a strong variation in optical properties. Therefore, a dynamical switching of the thermal emittance th can be achieved by VO 2. By doping the material with tungsten, it is possible to lower the transition temperature making it suitable as a glazing coating. The possibility of using the switch in emittance of the absorber coating in order to trigger the transition of a thermochromic coating on the glazing of the solar collector has been studied. An analytical approach yielded the required transition temperature of such a switching glazing. The fascinating optical properties of these switchable films elucidate the way towards novel intelligent thermal solar collector materials.
Journal of Advanced Oxidation Technologies, 2017
This study reports new findings on the sputtered Cu-polyester (Cu-PES) bacterial inactivation und... more This study reports new findings on the sputtered Cu-polyester (Cu-PES) bacterial inactivation under low intensity visible light (λ >400 nm). Cu-PES samples sputtered for 160 s led to the complete inactivation of
Journal of Environmental Chemical Engineering, 2017
The methylene blue (MB) discoloration on innovative photocatalysts made up of Raschig-rings coate... more The methylene blue (MB) discoloration on innovative photocatalysts made up of Raschig-rings coated by pre-formed TiO 2 nanoparticles decorated with CuOx (RR@TiO 2-Cu) is presented. The MB-discoloration was drastically accelerated by the subsequent addition of 0.004% Cu. This Cu-content being 3000timesbelowtheTiO2presentintheRR@TiO2samplesledtoMB−discolorationinshortertimes.TheCu−ionsreleasedfromtheRR@TiO2−Cu0.0043000 times below the TiO 2 present in the RR@TiO 2 samples led to MB-discoloration in shorter times. The Cu-ions released from the RR@TiO 2-Cu 0.004% were determined 1ppb by inductively coupled plasma massspectrometry (ICP-MS). Cu-percentages >0.018% decreased the MB-discoloration kinetics due to the Cu acting as recombination sites for the photogenerated charges. The total organic carbon (TOC) reduction concomitant with the MB-discoloration is reported as well as the effect of the initial MB-concentration and pH on the discoloration kinetics. The Cu-addition shifted significantly the TiO 2 absorption into the visible region even when added in sub-microgram quantities (0.004%) to RR@TiO 2 as detected by diffuse reflectance spectroscopy (DRS). The Cu level added to RR@TiO 2 was too low to be detected by X-ray diffraction (XRD). The roughness of the RR@TiO 2-Cu (0.018%-0.081% Cu) presented Rg-values between 11.8 nm and 23.9 nm. The RR@TiO 2 Cu presented agglomerate sizes of 3000timesbelowtheTiO2presentintheRR@TiO2samplesledtoMB−discolorationinshortertimes.TheCu−ionsreleasedfromtheRR@TiO2−Cu0.004200 nm for TiO 2 and for the Cu aggregates sizes of $20 nm. The MB discoloration kinetics and reuse of the RR@TiO 2-Cu suggest the potential as a supported catalyst in environmental cleaning process. A reaction mechanism is suggested taking into consideration the role of the Cu 1+/2+ intra-gap states involving redox catalysis as detected by X-ray photoelectron-spectroscopy (XPS).
Surface and Coatings Technology, 2016
Reference EPFL-ARTICLE-219560doi:10.1016/j.surfcoat.2016.04.065View record in Web of Science Reco... more Reference EPFL-ARTICLE-219560doi:10.1016/j.surfcoat.2016.04.065View record in Web of Science Record created on 2016-07-19, modified on 2017-05-12
Applied Catalysis B: Environmental, 2016
Insight is provided in this study for the effect of the TiO 2 film densification/compactness on p... more Insight is provided in this study for the effect of the TiO 2 film densification/compactness on polyethylene (PE-TiO 2) by sputtering TiO 2 at two very different energy levels. Uniform, adhesive low energy films were prepared by direct current magnetron sputtering (DCMS) and compared with films sputtered at high energy levels by high power impulse magnetron sputtering (HIPIMS). Nano-particulate TiO 2 films sputtered by HPIMS presented sizes of ∼10.2 nm compared to films sputtered by DCMS with TiO 2 sizes of ∼16.5 nm as determined by X-ray diffraction (XRD). The E. coli inactivation kinetics was three times faster for the samples sputtered by HIPIMS compared to their DCMS counterparts. This is an unexpected finding since the DCMS presenting larger TiO 2 sized nanoparticles released a higher amount of Ti-ions compared 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 the less compact TiO 2 sputtered by DCMS. The faster bacterial inactivation kinetics observed by the HIPIMS sputtered samples can be understood in terms of the complete of Ti 4+ /Ti 3+ redox conversion during bacterial inactivation detected by X-ray photo-electron spectroscopy (XPS) compared to the smaller Ti 4+ /Ti 3+ effect observed in the DCMS-samples. A higher optical density was detected for the HIPIMS sputtered samples by diffuse reflectance spectroscopy (DRS). Evidence is presented for the shift in surface potential and local pH during bacterial inactivation under aerobic and anaerobic conditions. A reaction mechanism is suggested based on the findings described in this study. The sputtered films present the potential to hinder biofilm formation on flexible thin polymers/textiles widely used in hospitals and health facilities.
RSC Advances, 2015
This study reports the photosensitizing effect/mechanism of FeOx under visible light irradiation ... more This study reports the photosensitizing effect/mechanism of FeOx under visible light irradiation and charge transfer to TiO2 on FeOx–TiO2 cosputtered film.
Applied Catalysis B: Environmental, 2016
Co-sputtered TiO 2-Cu polyester (TiO 2-Cu-PES) under actinic light induced bacterial reduction of... more Co-sputtered TiO 2-Cu polyester (TiO 2-Cu-PES) under actinic light induced bacterial reduction of Escherichia coli in the presence of O 2 (air) and under anaerobic conditions. The bacterial inactivation/oxidation proceeds in the absence of O 2 (air) probably due to the highly oxidative TiO 2 vb(h +) species and the toxic Cu present. By the choice of suitable scavengers, the presence of highly oxidative radicals was confirmed in aerobic media. The E. coli inactivation in aerobic media proceeds on TiO 2-Cu-PES within ∼30 min and with a slower kinetics of ∼90 min in anaerobic media. Malondialdehyde generation a product of bacterial inactivation, was observed on the TiO 2-Cu-PES in air and in lesser amounts under anaerobic conditions. Repetitive bacterial inactivation cycles show a Cu-release of ∼2 ppb/cm 2 by the TiO 2-Cu-PES surface as determined by inductively coupled plasma mass spectrometry (IPC-MS). The Cu released is far below the values reported for the Cu released by TiO 2-Cu-PES samples by sputtering Ti and Cu in sequential order from two targets. By X-ray photoelectron spectroscopy (XPS), redox catalysis by the Cu and TiO 2-species was observed under anaerobic conditions providing further evidence for processes leading to bacterial inactivation in anaerobic media. A mechanism for the TiO 2-Cu-PES bacterial inactivation is suggested consistent with the results reported in this study.
Applied Catalysis B: Environmental, 2015
Polyethylene-TiO2 (from now on PE-TiO2) transparent, non-scattering sputtered films have been fou... more Polyethylene-TiO2 (from now on PE-TiO2) transparent, non-scattering sputtered films have been found effective in the discoloration of methylene blue (MB) under low intensity solar simulated light. By Fourier transform attenuated infrared spectroscopy (ATR-FTIR), the systematic shift and decrease in the nu(s)(CH2) and nu(s)(C=C) vibration-rotational bands was observed preceding MB discoloration. RF-pretreatment allowed a significant increase in the TiO2 loading on PE compared to non-pretreated PE as shown by X-ray fluorescence (XRF). The PE-TiO2 photo-switching from a hydrophobic to a hydrophilic surface was observed within 60 min under light while the reverse process was complete within 24h in the dark. The position of the MB* and MB*/MB+ levels allowing electron injecting into the TiO(2)cb is discussed. The probability for the MBT deactivation and of MB* reacting with O-2 leading to the short lived MB+ cation is estimated. A mechanism for MB discoloration on PE-TiO2 is suggested. (C) 2014 Elsevier B.V. All rights reserved.
ACS applied materials & interfaces, Jan 23, 2015
The first evidence for Cu-Ag (50%/50%) nanoparticulate hybrid coatings is presented leading to a ... more The first evidence for Cu-Ag (50%/50%) nanoparticulate hybrid coatings is presented leading to a complete and almost instantaneous bacterial inactivation in the dark (≤5 min). Dark bacterial inactivation times on Cu-Ag (50%/50%) were observed to coincide with the times required by actinic light irradiation. This provides the evidence that the bimetal Cu-Ag driven inactivation predominates over a CuO/Cu2O and Ag2O oxides inducing a semiconductor driven behavior. Cu- or Ag-coated polyurethane (PU) catheters led to bacterial inactivation needing about ∼30 min. The accelerated bacterial inactivation by Cu-Ag coated on 3D catheters sputtered was investigated in a detailed way. The release of Cu/Ag ions during bacterial inactivation was followed by inductively coupled plasma mass-spectrometry (ICP-MS) and the amount of Cu and Ag-ions released were below the cytotoxicity levels permitted by the sanitary regulations. By stereomicroscopy the amount of live/dead cells were followed during the...
ACS applied materials & interfaces, Jan 23, 2015
The preparation, characterization, and antibacterial testing of Cu-Ag sputtered polyurethane (PU)... more The preparation, characterization, and antibacterial testing of Cu-Ag sputtered polyurethane (PU) catheters are addressed in this study. PU catheters with different atomic ratios Cu:Ag have been sputtered and led to different optical properties as followed by diffuse reflectance spectroscopy (DRS) and the surface redox properties were also different for different Cu-Ag ratios as observed by X-ray photoelectron spectroscopy (XPS). The surface atomic percentage concentration of the oxidized/reduced C-species originating from bacterial cultures before and after bacterial inactivation were determined on the Cu-Ag PU catheters. The crystallographic properties were determined by X-ray diffraction (XRD). The XRD-diffractogram showed the presence of Cu2O (111), Cu (200), CuO (020), and Ag (111) indicating that Cu nanoparticles present a more crystalline character compared to Ag nanoparticles. Increasing the percentage of Ag in the Cu-Ag films, bigger Ag-particle agglomerates were detected b...
Studies in surface science and catalysis
ABSTRACT
Surface and Coatings Technology, 2016
Nb1 - xTixNy thin films (with 0 <= x <= 1 and 0.85 <= y <= 1.15) were deposited from ... more Nb1 - xTixNy thin films (with 0 <= x <= 1 and 0.85 <= y <= 1.15) were deposited from Nb and Ti metallic targets using a hybrid process combining high-power impulse magnetron sputtering (HiPIMS) and DC magnetron sputtering (DCMS) techniques. Two series of Nb1-xTixNy films were deposited in which the HiPIMS mode was applied either to the Nb or to the Ti target while the second target (Ti or Nb) was operated in DCMS mode. The HiPIMS generator was operated at a fixed time-average power of 100 W (5 W cm(-2)) with a pulse-width of 50 mu s and a repetition frequency of 1000 Hz whereas the DC power applied to the second target was varied from 0 to 90 W to adjust the relative contents of Ti or Nb in the films. Depositions were performed in an Ar + N-2 atmosphere at a total pressure of 0.5 Pa. The substrate temperature was fixed at 250 degrees C and the sample holder was biased at -50 V. The films were characterized by XRD, SEM, EDS, nanoindentation, optical and electrical measurements. All the ternary films crystallize in the fcc NaCl-type of the structure. The films exhibit a dense columnar structure and their hardness values increase from 26 for TiN to 35 GPa for NbN. The optical properties of the Nb1 - xTixNy films progressively evolve from those of the fcc-NbN to those of the fcc-TiN as the Ti content x increases from 0 to 1. The room temperature resistivity value decreases from about 300 mu Omega cm (for NbN0.99) down to 25 mu Omega cm (for TiN0.98) as x increases from 0 to 1. In contrast to that, Nb1 - xTixNy films deposited under similar deposition conditions using DCMS exhibit open columnar structure, low hardness values (15 to 22 GPa), high electrical resistivity in the range of 200-360 mu Omega cm, and optical properties without clear correlation with the chemical composition of the films. The peculiar physical properties of these films, compared with those obtained by the hybrid process, are mainly attributed to their open columnar morphology. (C) 2015 Elsevier B.V. All rights reserved.
Applied Catalysis B: Environmental, 2018
ZnO-films although the conduction band potential energy position of the two semiconductors were i... more ZnO-films although the conduction band potential energy position of the two semiconductors were iso-energetic. By X-ray photoelectron spectroscopy (XPS), Cu2O was identified as the predominant Cu-oxidation state in the sputtered film. A mechanism for the NFX degradation is suggested in which the holes generated by Cu2O transfer to ZnO in the ZnO(n)/CuO(p) in the hetero-junction. This transfer is favored by the electrostatic interaction between both semiconductors. The catalyst optical properties and surface potential were monitored during NFX degradation. Stable repetitive NFX degradation kinetics was observed under visible light on the sputtered ZnO/CuxO films. The use of appropriate scavengers allowed the identification of the intermediate radical species (ROS). XPS analysis provided the proof for redox catalysis taking place within the time of NFX abatement. The application of ZnO/CuxO films in a photo-reactor for the degradation of emerging pollutants seems feasible due to the low cost of Zn and Cu and the fast kinetics found for NFX degradation.
Thin Solid Films, 2019
The present paper reports on an experimental investigation of the structural, electrical and opti... more The present paper reports on an experimental investigation of the structural, electrical and optical properties of Ru rich Ru 1-x Ti x O 2 thin films. Rutile single-phase Ru 1-x Ti x O 2 thin films have been deposited by reactive hybrid High-power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) at a substrate temperature of 250°C. The HiPIMS source was applied to the Ru target while the DCMS source was connected to the Ti target in order to vary the Ti content in the films. The films are well crystallized and compact with randomly orientated nanocrystallites. The optical properties have been investigated by ellipsometric measurements in the optical energy range from 1.3 eV to 3.3 eV, while the electrical resistivity has been measured in the Van der Paw configuration at room temperature. The electrical resistivity increases gradually from 70 μΩcm for pure RuO 2 to about 243 μΩcm for Ru 1-x Ti x O 2 films with x = 0.13. The optical properties are correlated with the Ti doping. The refractive index n changes from a strong dispersion relationship to a moderate one with increasing Ti content. The Ru 1-x Ti x O 2 thin films have been deposited by reactive hybrid
ACS applied materials & interfaces, Jan 11, 2018
This study presents innovative TiNb N-Ag films obtained by a suitable combination of low-energy a... more This study presents innovative TiNb N-Ag films obtained by a suitable combination of low-energy and high-energy sputtering leading to bacterial inactivation. The bacterial inactivation kinetics by the TiNbN layers was drastically enhanced by the addition of 6-7% Ag and proceeded to completion within 3 h after the film autoclaving. By X-ray photoelectron spectroscopy (XPS), the samples after autoclaving presented in their upper layers TiO, NbO and AgO with a surface composition of TiNbNAg. Surface potential/pH changes in the TiNb N-Ag films were monitored during bacterial inactivation. Surface redox processes during the bacterial inactivation were detected by XPS. The diffusion of Ag in the TiNb N-Ag films was followed at 50 and 70 °C pointing. The beneficial thermal treatment points out to the bifunctional bacterial inactivation properties of these films and their potential application in healthcare facilities. Interfacial charge transfer (IFCT) under light irradiation between AgO, ...
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, 2002
With the development of sub-0.25 μm technologies, interconnect integration is more sensitive to t... more With the development of sub-0.25 μm technologies, interconnect integration is more sensitive to the surface quality and to the roughness of tungsten-polished layers. Consequently, alumina-based slurries are progressively replaced by silica-based slurries (fumed or colloidal), characterized by much smaller and softer particles. In contrast to the many investigators of alumina-based slurries, only a few investigations have been carried out on the effect of the particle size on the physical vapor deposition (PVD) tungsten, PVD titanium, and thermal oxide removal rates and on the surface roughness after polishing. In this article, we evaluate four different colloidal silica-based slurries having different particle sizes. We find that the most promising slurry is the one with the smallest particle size. We also show that the tungsten removal rate mechanism is probably neither a scratching/indentation nor a surface contact type mechanism, but most likely a mechanism controlled by the grow...
Applied Catalysis A: General, 2016
This study reports an innovative preparation polyethylene-FeOx (PE-FeOx films) leading to the deg... more This study reports an innovative preparation polyethylene-FeOx (PE-FeOx films) leading to the degradation of the methylene blue (MB) dye under low intensity sunlight/visible light (>400 nm). The intermediate highly oxidative radicals generated by PE-FeOx leading to MB discoloration/degradation in the presence of H 2 O 2 were identified. The relative contribution to the MB discoloration by the Feions leached from the PE-FeOx films into solution was determined quantitatively. This allows estimating the contribution of the heterogeneous and of the homogeneous leading to MB-degradation. The shift in the peak binding energy (BE) for Fe was detected by photoelectron spectroscopy (XPS) after the MBdegradation providing the evidence for redox catalysis occurring during MB-degradation at the PE-FeOx surface. The particle size and roughness of the PE-FeOx surfaces were determined by atomic force spectroscopy (AFM). The spectral properties of PE-FeOx films are reported and insight is provided for the mechanism of MB-degradation.
Solar Energy, 2014
Overheating is a common problem both with the use of active and passive solar energy in thermal s... more Overheating is a common problem both with the use of active and passive solar energy in thermal solar energy systems and in highly glazed buildings, even in central European latitudes. In solar thermal collectors, the elevated temperatures occurring during stagnation result in reduced lifetime of the collector materials. They lead to water evaporation, glycol degradation and stresses in the collector with increasing vapor pressure. Special precautions are necessary to release this pressure; only mechanical solutions exist nowadays. The temperature of degradation of glycols is above 160-170°C. However, it would be preferable to limit the temperature of the collector to approximately 100°C, avoiding likewise the evaporation of the used water-glycol mixture. Additionally, the elevated temperatures lead to degradation of the materials that compose the collector, such as sealing, thermal insulation and the selective absorber coating. A new way of protecting solar thermal systems without any mechanical device (e.g. for shading or for pressure release) is proposed. A durable inorganic thermochromic material, which exhibits a change in optical properties at a transition temperature T t , is vanadium dioxide (VO 2). At 68°C, VO 2 undergoes a reversible crystal structural phase transition accompanied by a strong variation in optical properties. Therefore, a dynamical switching of the thermal emittance th can be achieved by VO 2. By doping the material with tungsten, it is possible to lower the transition temperature making it suitable as a glazing coating. The possibility of using the switch in emittance of the absorber coating in order to trigger the transition of a thermochromic coating on the glazing of the solar collector has been studied. An analytical approach yielded the required transition temperature of such a switching glazing. The fascinating optical properties of these switchable films elucidate the way towards novel intelligent thermal solar collector materials.
Journal of Advanced Oxidation Technologies, 2017
This study reports new findings on the sputtered Cu-polyester (Cu-PES) bacterial inactivation und... more This study reports new findings on the sputtered Cu-polyester (Cu-PES) bacterial inactivation under low intensity visible light (λ >400 nm). Cu-PES samples sputtered for 160 s led to the complete inactivation of
Journal of Environmental Chemical Engineering, 2017
The methylene blue (MB) discoloration on innovative photocatalysts made up of Raschig-rings coate... more The methylene blue (MB) discoloration on innovative photocatalysts made up of Raschig-rings coated by pre-formed TiO 2 nanoparticles decorated with CuOx (RR@TiO 2-Cu) is presented. The MB-discoloration was drastically accelerated by the subsequent addition of 0.004% Cu. This Cu-content being 3000timesbelowtheTiO2presentintheRR@TiO2samplesledtoMB−discolorationinshortertimes.TheCu−ionsreleasedfromtheRR@TiO2−Cu0.0043000 times below the TiO 2 present in the RR@TiO 2 samples led to MB-discoloration in shorter times. The Cu-ions released from the RR@TiO 2-Cu 0.004% were determined 1ppb by inductively coupled plasma massspectrometry (ICP-MS). Cu-percentages >0.018% decreased the MB-discoloration kinetics due to the Cu acting as recombination sites for the photogenerated charges. The total organic carbon (TOC) reduction concomitant with the MB-discoloration is reported as well as the effect of the initial MB-concentration and pH on the discoloration kinetics. The Cu-addition shifted significantly the TiO 2 absorption into the visible region even when added in sub-microgram quantities (0.004%) to RR@TiO 2 as detected by diffuse reflectance spectroscopy (DRS). The Cu level added to RR@TiO 2 was too low to be detected by X-ray diffraction (XRD). The roughness of the RR@TiO 2-Cu (0.018%-0.081% Cu) presented Rg-values between 11.8 nm and 23.9 nm. The RR@TiO 2 Cu presented agglomerate sizes of 3000timesbelowtheTiO2presentintheRR@TiO2samplesledtoMB−discolorationinshortertimes.TheCu−ionsreleasedfromtheRR@TiO2−Cu0.004200 nm for TiO 2 and for the Cu aggregates sizes of $20 nm. The MB discoloration kinetics and reuse of the RR@TiO 2-Cu suggest the potential as a supported catalyst in environmental cleaning process. A reaction mechanism is suggested taking into consideration the role of the Cu 1+/2+ intra-gap states involving redox catalysis as detected by X-ray photoelectron-spectroscopy (XPS).
Surface and Coatings Technology, 2016
Reference EPFL-ARTICLE-219560doi:10.1016/j.surfcoat.2016.04.065View record in Web of Science Reco... more Reference EPFL-ARTICLE-219560doi:10.1016/j.surfcoat.2016.04.065View record in Web of Science Record created on 2016-07-19, modified on 2017-05-12
Applied Catalysis B: Environmental, 2016
Insight is provided in this study for the effect of the TiO 2 film densification/compactness on p... more Insight is provided in this study for the effect of the TiO 2 film densification/compactness on polyethylene (PE-TiO 2) by sputtering TiO 2 at two very different energy levels. Uniform, adhesive low energy films were prepared by direct current magnetron sputtering (DCMS) and compared with films sputtered at high energy levels by high power impulse magnetron sputtering (HIPIMS). Nano-particulate TiO 2 films sputtered by HPIMS presented sizes of ∼10.2 nm compared to films sputtered by DCMS with TiO 2 sizes of ∼16.5 nm as determined by X-ray diffraction (XRD). The E. coli inactivation kinetics was three times faster for the samples sputtered by HIPIMS compared to their DCMS counterparts. This is an unexpected finding since the DCMS presenting larger TiO 2 sized nanoparticles released a higher amount of Ti-ions compared 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 the less compact TiO 2 sputtered by DCMS. The faster bacterial inactivation kinetics observed by the HIPIMS sputtered samples can be understood in terms of the complete of Ti 4+ /Ti 3+ redox conversion during bacterial inactivation detected by X-ray photo-electron spectroscopy (XPS) compared to the smaller Ti 4+ /Ti 3+ effect observed in the DCMS-samples. A higher optical density was detected for the HIPIMS sputtered samples by diffuse reflectance spectroscopy (DRS). Evidence is presented for the shift in surface potential and local pH during bacterial inactivation under aerobic and anaerobic conditions. A reaction mechanism is suggested based on the findings described in this study. The sputtered films present the potential to hinder biofilm formation on flexible thin polymers/textiles widely used in hospitals and health facilities.
RSC Advances, 2015
This study reports the photosensitizing effect/mechanism of FeOx under visible light irradiation ... more This study reports the photosensitizing effect/mechanism of FeOx under visible light irradiation and charge transfer to TiO2 on FeOx–TiO2 cosputtered film.
Applied Catalysis B: Environmental, 2016
Co-sputtered TiO 2-Cu polyester (TiO 2-Cu-PES) under actinic light induced bacterial reduction of... more Co-sputtered TiO 2-Cu polyester (TiO 2-Cu-PES) under actinic light induced bacterial reduction of Escherichia coli in the presence of O 2 (air) and under anaerobic conditions. The bacterial inactivation/oxidation proceeds in the absence of O 2 (air) probably due to the highly oxidative TiO 2 vb(h +) species and the toxic Cu present. By the choice of suitable scavengers, the presence of highly oxidative radicals was confirmed in aerobic media. The E. coli inactivation in aerobic media proceeds on TiO 2-Cu-PES within ∼30 min and with a slower kinetics of ∼90 min in anaerobic media. Malondialdehyde generation a product of bacterial inactivation, was observed on the TiO 2-Cu-PES in air and in lesser amounts under anaerobic conditions. Repetitive bacterial inactivation cycles show a Cu-release of ∼2 ppb/cm 2 by the TiO 2-Cu-PES surface as determined by inductively coupled plasma mass spectrometry (IPC-MS). The Cu released is far below the values reported for the Cu released by TiO 2-Cu-PES samples by sputtering Ti and Cu in sequential order from two targets. By X-ray photoelectron spectroscopy (XPS), redox catalysis by the Cu and TiO 2-species was observed under anaerobic conditions providing further evidence for processes leading to bacterial inactivation in anaerobic media. A mechanism for the TiO 2-Cu-PES bacterial inactivation is suggested consistent with the results reported in this study.
Applied Catalysis B: Environmental, 2015
Polyethylene-TiO2 (from now on PE-TiO2) transparent, non-scattering sputtered films have been fou... more Polyethylene-TiO2 (from now on PE-TiO2) transparent, non-scattering sputtered films have been found effective in the discoloration of methylene blue (MB) under low intensity solar simulated light. By Fourier transform attenuated infrared spectroscopy (ATR-FTIR), the systematic shift and decrease in the nu(s)(CH2) and nu(s)(C=C) vibration-rotational bands was observed preceding MB discoloration. RF-pretreatment allowed a significant increase in the TiO2 loading on PE compared to non-pretreated PE as shown by X-ray fluorescence (XRF). The PE-TiO2 photo-switching from a hydrophobic to a hydrophilic surface was observed within 60 min under light while the reverse process was complete within 24h in the dark. The position of the MB* and MB*/MB+ levels allowing electron injecting into the TiO(2)cb is discussed. The probability for the MBT deactivation and of MB* reacting with O-2 leading to the short lived MB+ cation is estimated. A mechanism for MB discoloration on PE-TiO2 is suggested. (C) 2014 Elsevier B.V. All rights reserved.
ACS applied materials & interfaces, Jan 23, 2015
The first evidence for Cu-Ag (50%/50%) nanoparticulate hybrid coatings is presented leading to a ... more The first evidence for Cu-Ag (50%/50%) nanoparticulate hybrid coatings is presented leading to a complete and almost instantaneous bacterial inactivation in the dark (≤5 min). Dark bacterial inactivation times on Cu-Ag (50%/50%) were observed to coincide with the times required by actinic light irradiation. This provides the evidence that the bimetal Cu-Ag driven inactivation predominates over a CuO/Cu2O and Ag2O oxides inducing a semiconductor driven behavior. Cu- or Ag-coated polyurethane (PU) catheters led to bacterial inactivation needing about ∼30 min. The accelerated bacterial inactivation by Cu-Ag coated on 3D catheters sputtered was investigated in a detailed way. The release of Cu/Ag ions during bacterial inactivation was followed by inductively coupled plasma mass-spectrometry (ICP-MS) and the amount of Cu and Ag-ions released were below the cytotoxicity levels permitted by the sanitary regulations. By stereomicroscopy the amount of live/dead cells were followed during the...
ACS applied materials & interfaces, Jan 23, 2015
The preparation, characterization, and antibacterial testing of Cu-Ag sputtered polyurethane (PU)... more The preparation, characterization, and antibacterial testing of Cu-Ag sputtered polyurethane (PU) catheters are addressed in this study. PU catheters with different atomic ratios Cu:Ag have been sputtered and led to different optical properties as followed by diffuse reflectance spectroscopy (DRS) and the surface redox properties were also different for different Cu-Ag ratios as observed by X-ray photoelectron spectroscopy (XPS). The surface atomic percentage concentration of the oxidized/reduced C-species originating from bacterial cultures before and after bacterial inactivation were determined on the Cu-Ag PU catheters. The crystallographic properties were determined by X-ray diffraction (XRD). The XRD-diffractogram showed the presence of Cu2O (111), Cu (200), CuO (020), and Ag (111) indicating that Cu nanoparticles present a more crystalline character compared to Ag nanoparticles. Increasing the percentage of Ag in the Cu-Ag films, bigger Ag-particle agglomerates were detected b...
Studies in surface science and catalysis
ABSTRACT
Surface and Coatings Technology, 2016
Nb1 - xTixNy thin films (with 0 <= x <= 1 and 0.85 <= y <= 1.15) were deposited from ... more Nb1 - xTixNy thin films (with 0 <= x <= 1 and 0.85 <= y <= 1.15) were deposited from Nb and Ti metallic targets using a hybrid process combining high-power impulse magnetron sputtering (HiPIMS) and DC magnetron sputtering (DCMS) techniques. Two series of Nb1-xTixNy films were deposited in which the HiPIMS mode was applied either to the Nb or to the Ti target while the second target (Ti or Nb) was operated in DCMS mode. The HiPIMS generator was operated at a fixed time-average power of 100 W (5 W cm(-2)) with a pulse-width of 50 mu s and a repetition frequency of 1000 Hz whereas the DC power applied to the second target was varied from 0 to 90 W to adjust the relative contents of Ti or Nb in the films. Depositions were performed in an Ar + N-2 atmosphere at a total pressure of 0.5 Pa. The substrate temperature was fixed at 250 degrees C and the sample holder was biased at -50 V. The films were characterized by XRD, SEM, EDS, nanoindentation, optical and electrical measurements. All the ternary films crystallize in the fcc NaCl-type of the structure. The films exhibit a dense columnar structure and their hardness values increase from 26 for TiN to 35 GPa for NbN. The optical properties of the Nb1 - xTixNy films progressively evolve from those of the fcc-NbN to those of the fcc-TiN as the Ti content x increases from 0 to 1. The room temperature resistivity value decreases from about 300 mu Omega cm (for NbN0.99) down to 25 mu Omega cm (for TiN0.98) as x increases from 0 to 1. In contrast to that, Nb1 - xTixNy films deposited under similar deposition conditions using DCMS exhibit open columnar structure, low hardness values (15 to 22 GPa), high electrical resistivity in the range of 200-360 mu Omega cm, and optical properties without clear correlation with the chemical composition of the films. The peculiar physical properties of these films, compared with those obtained by the hybrid process, are mainly attributed to their open columnar morphology. (C) 2015 Elsevier B.V. All rights reserved.