HiPIMS plasma diagnostic to study the repeatability of low temperature deposition of crystalline titania

In the last few decades, Titanium dioxide (also called Titania or TiO2) has experienced significant scientific interest due to its range of properties and possibility for further developments in a range of applications, including photocatalysis. Initially, the material was widely used in this application in powder form for water decontamination applications. It was later developed as a thin film coating onto glasses and metals (industrial, construction scale) for its self-cleaning properties. Indeed, the scientific community realised that TiO2 coatings could present both antimicrobial properties (via degradation of cell walls) and a strong hydrophilic behaviour. Recently, thin films technologies, and more particularly magnetron sputtering processes, have undergone a new expansion: the HiPIMS (High Power Impulse Magnetron Sputtering) process. The HiPIMS process is 15 years old and its principal aim is to provide a more ionized deposition flux (by an order of magnitude), easing the control of the deposited film properties (density, structure, composition, targeted areas on the substrate, etc…). It has also been shown to facilitate low substrate temperatures during operation. The combination of both characteristics should lead to the possible deposition of crystalline films at low temperature. The first aim in this work is to provide the reader with a deep understanding of the HiPIMS discharge and how it can influence the deposition process. To do so, plasma diagnostics have been carried out on different coating systems (rigs) and using different power supplies to show how both of these aspects can drastically change the processes occurring within the discharge. For the rig used for deposition of the films, thermal and deposition rates measurements have also been carried out. This leads to the establishment of a process envelope, suitable for the deposition of crystalline titanium dioxide films. Subsequently, TiO2 coatings have been deposited by HiPIMS onto various substrates and the influences of the deposition parameters studied to better understand the plasma behaviour and its consequences on the thin film properties, in order to optimize the latter’s crystallography. The final aim of this project is to deposit a crystalline photo-active (i.e. photocatalytic, hydrophilic) film onto a polymeric substrate at low temperature. This project implies the use of a large range of characterisation techniques. The structural, mechanical, chemical and crystallographic properties have been studied by using a large array of techniques including X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Raman spectroscopy, etc… The photocatalytic activity was assessed using dye degradation tests under UV light, and the hydrophilicity by contact angle measurements. In this project, it has been shown that a modification of the deposition rig can bring drastic changes to the plasma. These changes are even more important when it comes to the reactive plasma. Each rig has its own process envelope and transferring from a laboratory scaled rig to an industrial rig is not a simple task. Parameters influences on the plasma can also vary from one configuration to another and optimized deposition conditions are not necessarily repeatable from one rig to another. Mainly, it seems that the oxidation process is greatly modified by the rig configuration. This thesis presents plasma diagnostic conducted using only an oscilloscope, to show that this is a simple and cheap way for industrials to deposit in reactive atmosphere. Here, the author has optimized deposition conditions on a given apparatus, where crystalline Anatase (TiO2) has been deposited at low temperature, typically, below 60 °C. These films have also been deposited onto polymeric substrates with no destruction of the latter. The oxygen content during deposition appears to be the more important point to control during deposition. For the rig used here, films have been deposited in the poisoned mode, at low pressure, high frequency and short pulse width as it seemed to provide the more ionized discharge, facilitating the films crystallization

Novel and versatile tio2 thin films on pet for photocatalytic removal of contaminants of emerging concern from water

The current work presents new and versatile photocatalytic surfaces designed to remove contaminants of emerging concerns (CECs) from water. Photocatalytic thin films of titanium dioxide (TiO2) were deposited on a polyethylene terephthalate (PET) surface (PET-TiO2) and photosensitized by a natural and non-hazardous curcumin (turmeric). The TiO2 thin film was deposited in a single stage and solvent-free process, without thermal post treatment, using the high power impulse magnetron sputtering (HiPIMS) technique. The photocatalytic film was characterized by different techniques (SEM/EDS, STEM, AFM, UV–Vis spectroscopy, and wettability via water droplet contact angle). The photocatalytic activity was assessed by the degradation of two model CECs: the fungicide carbendazim (CBZ), used in different crops around the world (coffee, rice, fruits, etc.), and the anthropogenic pollution tracer caffeine (CAF). Removal of these model CECs of up to 39% were achieved under combined UV and visible irradiation under 7 h photocatalytic treatments. The degradation process was further studied by dissolved organic carbon analysis, with up to 80% removal, and acute ecotoxicity tests with Aliivibrio fischeri, indicating reduction of toxicity or non-change. The PET-TiO2 surfaces remained stable for 5 consecutive cycles of use, with similar kinetic rates. Finally, the species involved in photocatalytic reactions were investigated by the use of h+, HO and O2− trapping agents, both in the presence and absence of turmeric. The results indicated that the addition of the turmeric led to an increase in photogenerated O2− radicals due to a synergistic effect between the photocatalyst and photosensitizer. The results demonstrate the potential of the PET-TiO2 surfaces as a straightforward solution for the removal of CECs from waters, using a flexible, scalable, reusable and environmental friendly photocatalytic material

The effect of pre-exercise alkalosis on lactate/pH regulation and mitochondrial respiration following sprint-interval exercise in humans

Purpose: The purpose of this study was to evaluate the effect of pre-exercise alkalosis, induced via ingestion of sodium bicarbonate, on changes to lactate/pH regulatory proteins and mitochondrial function induced by a sprint-interval exercise session in humans.Methods: On two occasions separated by 1 week, eight active men performed a 3 × 30-s all-out cycling test, interspersed with 20 min of recovery, following either placebo (PLA) or sodium bicarbonate (BIC) ingestion.Results: Blood bicarbonate and pH were elevated at all time points after ingestion in BIC vs PLA (p < 0.05). The protein content of monocarboxylate transporter 1 (MCT1) and basigin (CD147), at 6 h and 24 h post-exercise, and sodium/hydrogen exchanger 1 (NHE1) 24 h post-exercise, were significantly greater in BIC compared to PLA (p < 0.05), whereas monocarboxylate transporter 4 (MCT4), sodium/bicarbonate cotransporter (NBC), and carbonic anhydrase isoform II (CAII) content was unchanged. These increases in protein content in BIC vs. PLA after acute sprint-interval exercise may be associated with altered physiological responses to exercise, such as the higher blood pH and bicarbonate concentration values, and lower exercise-induced oxidative stress observed during recovery (p < 0.05). Additionally, mitochondrial respiration decreased after 24 h of recovery in the BIC condition only, with no changes in oxidative protein content in either condition.Conclusion: These data demonstrate that metabolic alkalosis induces post-exercise increases in several lactate/pH regulatory proteins, and reveal an unexpected role for acidosis in mitigating the loss of mitochondrial respiration caused by exercise in the short term

The effect of pre-exercise alkalosis on lactate/pH regulation and mitochondrial respiration following sprint-interval exercise in humans

Purpose: The purpose of this study was to evaluate the effect of pre-exercise alkalosis, induced via ingestion of sodium bicarbonate, on changes to lactate/pH regulatory proteins and mitochondrial function induced by a sprint-interval exercise session in humans. Methods: On two occasions separated by 1 week, eight active men performed a 3 × 30-s all-out cycling test, interspersed with 20 min of recovery, following either placebo (PLA) or sodium bicarbonate (BIC) ingestion. Results: Blood bicarbonate and pH were elevated at all time points after ingestion in BIC vs PLA (p < 0.05). The protein content of monocarboxylate transporter 1 (MCT1) and basigin (CD147), at 6 h and 24 h post-exercise, and sodium/hydrogen exchanger 1 (NHE1) 24 h post-exercise, were significantly greater in BIC compared to PLA (p < 0.05), whereas monocarboxylate transporter 4 (MCT4), sodium/bicarbonate cotransporter (NBC), and carbonic anhydrase isoform II (CAII) content was unchanged. These increases in protein content in BIC vs. PLA after acute sprint-interval exercise may be associated with altered physiological responses to exercise, such as the higher blood pH and bicarbonate concentration values, and lower exercise-induced oxidative stress observed during recovery (p < 0.05). Additionally, mitochondrial respiration decreased after 24 h of recovery in the BIC condition only, with no changes in oxidative protein content in either condition. Conclusion: These data demonstrate that metabolic alkalosis induces post-exercise increases in several lactate/pH regulatory proteins, and reveal an unexpected role for acidosis in mitigating the loss of mitochondrial respiration caused by exercise in the short term

Effets de l'acidose métabolique mis en exergue par une alcalose induite sur la performance et les réponses physiologiques, cellulaires et moléculaires du muscle strié squelettique au cours d'exercices de haute-intensité

This thesis falls within the general framework of the energetic physiology, and includes three studies, ranging from global exploration of the humans in motion (field tests with athletes of the French Cycling Team, laboratory exploration during exercise on trained cyclists) to studies of muscle metabolism by techniques of cellular and molecular investigations in active subjects. This work has focused on high-intensity exercise generating high levels of muscle fatigue and the resulting adaptive cardiorespiratory and muscular responses. Supplementation of sodium bicarbonate against placebo was used to study the precise role of the accumulation of protons during sprint cycling sessions. Through this work, we have shown that, if an induced alkalosis did not systematically improve sprint cycling performances, a significant disruption of the pH led to changes in oxygen transport during exercise, in mitochondrial function after 24h of recovery, but also in the expression of some proteins involved in pH regulation (i. E. , lactate/proton co-transporter (MCT1) its chaperone protein CD147, and the sodium/proton exchanger (NHE1)). These changes were related to a reduction of the oxidative stress induced by alkalosis, suggesting a harmful role of the carbonylation in these protein expressions. These results provide a new perspective on the role played by acidosis in the regulatory mechanisms at physiological, cellular and molecular levels in humans.Ce travail de thèse s’inscrit dans le cadre général de la physiologie énergétique, et comprend trois études, qui vont de l’exploration globale de l’Homme en mouvement (tests de terrain chez des athlètes de l’Equipe de France de Cyclisme, explorations à l’effort en laboratoire chez des cyclistes entrainés) jusqu’à des études du métabolisme musculaire par des techniques d’investigations cellulaires et moléculaires chez des sujets actifs. Ce travail a porté sur l’exercice de haute intensité générant de hauts niveaux de fatigue musculaire et sur les réponses adaptatives qui en résultent au niveau cardio-respiratoire et musculaire. La prise de bicarbonate de sodium contre placebo a permis d’étudier précisément le rôle de l’accumulation de protons au cours de séances de sprints en cyclisme. Grâce à ces travaux, nous avons pu montrer que si une alcalose induite n’améliorait pas systématiquement les performances de sprint en cyclisme, une perturbation importante du pH conduisait à des modifications du transport de l’oxygène pendant l’exercice, du fonctionnement des mitochondries après 24h de récupération, mais également de l’expression de certaines protéines impliquées dans la régulation du pH, à savoir le cotransporteur lactate/proton (MCT1) et sa protéine chaperonne CD147, ainsi que l’échangeur sodium/proton (NHE1). Ces modifications étaient en lien avec une réduction du stress oxydatif par l’alcalose induite, suggérant un rôle délétère de la carbonylation des protéines sur l’expression de ces protéines. Ces résultats permettent d’avoir un nouveau regard sur le rôle de l’acidose dans les mécanismes de régulation au niveau physiologique, cellulaire et moléculaire chez l’Homme

Acidose et performance, quelles sont les nouvelles avancées ? : Retour sur les exercices de haute intensité

Le lactate a longtemps été suspecté d’être à l’origine de l’acidose, phénomène impliqué dans l’altération de fonctions physiologiques conduisant à la chute de la performance en fin d’exercice. Or, il est acquis que l’acidose est liée à l’augmentation de la présence de l’ion hydrogène, donc à la diminution du pH, et non au lactate. Retour sur les avancées scientifiques portant sur l’acidose et la performance lors d’exercices de haute intensité