Academic literature on the topic 'Redox de l’Oxygène'
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Dissertations / Theses on the topic "Redox de l’Oxygène":
Prévoteau, Antonin. "Électrodes enzymatiques à base d’hydrogels rédox en vue de l’oxydation du glucose : effet de la déglycosylation de la glucose oxydase et mise en évidence d’une réduction parasite de l’oxygène sur le médiateur rédox." Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14102/document.
The possibility of converting the catalytic activity of oxidoreductase enzymes into electric current has led to the development of a high diversity of enzyme electrodes. Anodes catalysing glucose oxidation have been amongst the most studied, especially for their application in monitoring blood glucose or glucose/O2 biofuel cells. Although one of the numerous strategies available, the use of osmium-based hydrogels as redox mediators, has given excellent results, some limitations still remain such as rather low current densities, stability or selectivity Initially, the study focused on the deglycosylation of glucose oxidase (GOx). When most of the oligosaccharides around this glycoenzyme were removed, the ensuing increase in the electrode catalytic current seemed a priori to support the hypothesis of a decrease in the electron hopping distance between the enzyme redox centres and the redox mediator. However, a systematic study of electrode response for different compositions leads us to conclude that deglycosylation does not improve the intrinsic electron transfer but the whole hydrogel structure. This seems due to the smaller size and higher surface charge of the deglycosylated GOx inducing smaller hydrogel volumes than in the native-based GOx. The study then proceeded to examine the oxygen side reduction of commonly used osmium-based redox polymers. The interference of O2 on glucose oxidation current has generally been attributed to O2 reactivity with GOx. The present study shows that O2 reduction also occurs on osmium-based polymers if their formal potential E°’ is below + 0.07 V vs. Ag/AgCl. The kinetics of this reaction appears to increase exponentially when E°’ decreases. As well as reducing the oxidation current and, consequently, lowering anode performances, the generation of hydrogen peroxide could also modify electrode stability. These results suggest that the choice of redox mediator for a given E°'must also take into account the extent of O2 reduction
Tonda-Mikiela, Pradel. "Étude des interfaces des nanocatalyseurs / glucose et enzymes / O2 pour une application biopile." Thesis, Poitiers, 2012. http://www.theses.fr/2012POIT2308/document.
The work developed in this thesis concerns the study of the behavior of redox reactions at the interfaces "nanocatalyst/glucose" and "enzyme/O2" for a hybrid Biofuel Cell. In this framework, a novel synthesis method of based gold and platinum nanoparticles has been achieved. These synthesized nanomaterials were characterized by different physicochemical techniques to determine their size, morphology and their dispersion in Vulcan XC72R used as substrate. The active surface area of each electrode material was determined by cyclic voltammetry and CO stripping. It has been shown that in the bimetallic catalyst gold promotes platinum activity towards the glucose oxidation. The bimetallic composition Au70Pt30 exhibits the better efficiency. The study by spectroelectrochemistry determined that the B-gluconolactone is the primary product of the glucose oxidation which proceeds at low potential by the dehydrogenation of anomeric carbon on platinum. The reduction reaction of O2 was catalyzed by an enzyme, bilirubin oxidase (BOD). Mediated electronic transfer was performed with two redox mediators, ABTS and an Osmium complex (Os). They have been encapsulated with the enzyme in a Nafion® matrix to construct the interfaces: BOD/ABTS/O2 and BOD/Os/O2. The voltammetric study of the mediators in phosphate buffer revealed two quasi-reversible systems with an apparent potential close to the theoretical potential of the T1 BOD center. Although hardly comparable in terms of current density with the Pt nanocatalyst the O2 reduction is a four electron reaction at the cathodes BOD/ABTS and BOD/Os which deliver an electrode potential close to the Nernst one
Deville, Quentin. "Nouvelles phases désordonnées de type Rocksalt comme matériaux d'électrode positive à haute densité d'énergie pour batteries lithium-ion." Electronic Thesis or Diss., Bordeaux, 2023. http://www.theses.fr/2023BORD0469.
In commercial Li-ion batteries, positive electrodes are primarily composed of layered nickel or cobalt oxide-based materials. Replacing these two cations has become a necessity due to ethical, ecological, and economic reasons, as well as concerns about their scarcity. To increase capacity, structural stability, and use transition metals that are less critical, such as manganese, disordered materials with a NaCl-type structure have emerged as one of the solutions among many explored possibilities. With a stable three-dimensional structure, over-lithiated disordered rocksalt materials have demonstrated reversible specific capacities exceeding 200 mAh.g-1. One commonly employed synthesis method is high-energy mechanosynthesis, which yields highly disordered materials. However, these materials, like their layered counterparts, suffer from irreversible oxygen oxidation at high voltage. It has been discovered that fluorination is an interesting approach to suppress this oxidation while preserving high capacities. In this study, the first goal was to understand how to choose between different precursor sets to obtain Li2MnO2F, a disordered material with a disordered rocksalt type structure. Subsequently, the impact of fluorination on the structural, morphological, and electrochemical properties of Li1.25Mn0.5+y/2Nb0.25-y/2O2-yFy (0 ≤ y ≤ 0.5) was studied at different scales. Nuclear Magnetic Resonance (NMR) studies of 7Li and 19F nuclei under magic angle spinning, coupled with X-ray Diffraction (XRD) and Pair Distribution Function (PDF) analysis, allowed detailed examination of the materials' structures at various scales. Ex-situ and in-situ experiments conducted via X-ray Absorption Spectroscopy (XAS) at the synchrotron enabled the study of redox mechanisms involved during cycling. In the first part, it was demonstrated that the progress of mechanosynthesis could be tracked by XRD and at a local scale by NMR. These analyses highlighted the necessity for an extended reaction period. Subsequently, it was observed that the nature of the precursors, with minimal variations (replacing Mn2O3 and Li2O with LiMnO2), had a negligible impact on the structural and electrochemical properties of Li2MnO2F. The second part of the study showed through TEM-EDX that it was possible to uniformly introduce fluorine fractions greater than 0.2 into Li1.25Mn0.5+y/2Nb0.25-y/2O2-yFy via mechanosynthesis. While at the particle scale fluorination seemed uniform, introducing significant fractions of fluorine appeared to deviate the surrounding cations repartition from the statistical distribution around lithium (6% more lithium). This increased fluorination also led to a decrease in the lattice parameter observed by XRD and PDF, tending to create lithium and niobium-rich environments around fluorine, as noted with NMR by studying diamagnetic-to-paramagnetic environment ratios. Morphology did not change with fluorination and consisted of agglomerated nanometric primary particles in clusters of several hundred nanometres. Electrochemically, it was shown that two redox mechanisms occurred: first, the oxidation of manganese from +III to +IV, followed by oxygen oxidation starting from 4.5 V vs Li+/Li. The irreversible contribution of this second irreversible contribution to the capacity could be mitigated for materials Li1.25Mn0.55Nb0.2O1.9F0.1, Li1.25Mn0.6Nb0.15O1.8F0.2, Li1.25Mn0.65Nb0.1O1.7F0.3 and eliminated for higher fluorination rates. Thus, it was demonstrated that an optimal composition could be achieved for fluorination amount between 0.2 and 0.4 in Li1.25Mn0.5+y/2Nb0.25-y/2O2-yFy. Within this range, these materials exhibited the lowest polarisation and good capacity retention while preserving a high capacity exceeding 200 mAh.g-1 after 20 discharge cycles
Haeussler, Anita. "Solar fuels production by CO2 and H2O splitting via thermochemical processes." Thesis, Perpignan, 2021. https://theses-public.univ-perp.fr/2021PERP0003.pdf.
This study is focused on the development of thermochemical H2O and CO2 splitting processes using non-stoichiometric metal oxides and concentrated solar energy to produce solar fuels. The redox process is composed of two distinct reactions: first, a thermal reduction at high temperature of the metal oxide with creation of oxygen vacancies in the crystallographic structure, resulting in released oxygen; second, the re-oxidation of the metal oxide by H2O and/or CO2, leading to H2 and/or CO production. Ceria and perovskite materials have been investigated as reactive oxides for thermochemical cycles. To increase the thermochemical process efficiency, different aspects were investigated, such as chemical composition and morphology of the metal oxide, operating parameters, and solar reactor configuration. The redox activities, kinetics and thermodynamics of different perovskite materials were first experimentally investigated for two-step thermochemical cycles. Then, the thermochemical performances of various reactive materials shaped as porous structures or particulate media were investigated in solar reactors (monolithic or packed-bed configurations) able to perform two-step thermochemical cycles. A detailed parametric study was performed to determine fuel production rates and yields. The highest CO production rate (9.9 mL/min/g) was achieved with ceria reticulated foams. Finally, a solar membrane reactor was developed for isothermal and continuous production of CO (or H2) by CO2 (or H2O) splitting with a reactive and oxygen-permeable membrane. The highest CO production rate reached 0.133 µmol/cm2/s at 1550 °C using a perovskite-coated ceria membrane
He, Tiantian. "Studying the Role of Peroxiredoxin 1 in ROS Modulation and Drug Resistance." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112139.
Peroxiredoxins have multiple cellular functions as major antioxidants, signaling regulators, molecular chaperones and tumor suppressors. Peroxiredoxin 1 (Prx1) is the most abundant among the six isoforms of human peroxiredoxins. It is frequently over-expressed in various cancer cells, which is known associated with carcinogenesis, metastasis and resistance to radiotherapy or chemotherapy. Prx1 could thus be an interesting anticancer target. In this study, we first evaluated the impact of Prx1 knockdown (Prx1–) on cellular sensitivity to dozens of anticancer drugs including vinblastine, taxol, doxorubicin, daunorubicin, actinomycin D, and 5-fluorouracil, and of reactive oxygen species (ROS)-generating agents, including hydrogen peroxide, 2-phenylethyl isothiocyanate, β-lapachone (β-lap) and menadione. We observed that Prx1 knockdown significantly enhanced cancer cell sensitivity to β-lap and menadione, two naphthoquinones with anti-cancer activity.We first investigated the underlying mechanisms responsible for the specifically enhanced cytotoxicity to β-lap in a Prx1 knockdown context. Prx1 knockdown markedly potentiated β-lap-induced cytotoxicity through ROS accumulation. This effect was largely NAD(P)H:quinone oxidoreductase 1 (NQO1)-dependent and associated with the phosphorylation of c-Jun N-terminal kinases (JNK), protein 38 (p38) and extracellular signal-regulated kinases (Erk) proteins in mitogen-activated protein kinase (MAPK) pathways, and a decrease in thioredoxin 1 protein levels. Based on the fact that Prx1 is a major ROS scavenger and a partner of apoptosis signaling kinase 1 (ASK1) and JNK, two key components of MAPK pathways, we propose that Prx1 knockdown-induced sensitization to β-lap is achieved through the combined action of ROS accumulation and MAPK pathway activation, leading to cell apoptosis.We then investigated the underlying mechanisms responsible for the specifically enhanced cytotoxicity to menadione in Prx1– cells. Enhanced sensitivity to menadione was associated with a rapid and significant intracellular ROS accumulation and necroptotic-like cell death. Menadione-induced ROS accumulation occurred immediately in the cytosol, the nucleus, and even more noticeably in the mitochondrial matrix, correlated with significant oxidation of both mitochondria-localized thioredoxin 2 and peroxiredoxin 3. Prx1 knockdown significantly up-regulated mRNA and protein levels of NRH: quinone oxidoreductase 2 (NQO2). Increased activity of NQO2 was largely responsible for menadione-induced ROS accumulation and consequent cell death. Our data indicate that massive ROS accumulation results from the combined effect of increased ROS generation by higher NQO2 activity during menadione metabolism, and diminished Prx1 scavenging activity. Finally and noteworthy, the metabolic pathways that lead to ROS accumulation, downstream signaling pathways and cell death mechanisms appear to be distinct for β-lap and menadione