Towards metathesis growth of intrinsically conducting polymers from metal surfaces

Cette thèse présentera l'étude d'un catalyseur de carbure de molybdène modifié par des alkylidenes dans le but de faire de la polymérisation par réaction de métathèse induite par la surface, le tout dans des conditions de ultra-haut vide (UHV). Ce système catalytique a été caractérisé par différentes techniques d'analyse utilisées en science des surfaces : la spectroscopic infrarouge par reflexion-adsorption (RAIRS), la spectroscopie des photoélectrons par rayons X (XPS) et la spectrométrie de masse par thermodésorption (TDS). La première partie de la thèse décrira le système expérimental à la manière d'un guide pour les nouveaux utilisateurs de ce type de système multi-analytique. La caractérisation et l'étude de l'activité catalytique du carbure de molybdène modifié par des alkylidenes sera présentée en deux parties. La première partie sera dédiée à la préparation et à la caractérisation de nouvelles espèces métal-alkylidène sur la surface du β-Mo₂C. Deux nouvelles espèces ont été étudiées, soient le diméthyle alkylidene ((CH₃)₂C=Mo) et le vinyl alkylidene (CH₂CHCH=Mo). Des données spectroscopiques sur la chimisorption de cétones aliphatiques telles que l'acétone, l'acétone-dô et l'acroléine indiquent que le β-Mo₂C induit un bris du lien carbonyle à température ambiante dans des conditions d'ultra-haut vide pour former les espèces métal-alkylidène et métal-oxo. Cette réaction produit aussi une couche superficielle de carbone de nature indéfinie qui diminue la réactivité de la surface de β-Mo₂C face à la décomposition moléculaire conférant ainsi une très haute stabilité thermique aux espèces formées. Le principal sujet de cette thèse concerne l'étude de ces alkylidenes comme des espèces initiatrices pour la polymérisation de surface en vue de former le polyacétylène. Deux méthodes de polymérisation ont été testées. Premièrement, la polymérisation par métathèse par ouverture de cycle du 1,3,5,7-cyclooctatétraène (COT) a été effectuée sur des sites actifs de cyclopentylidene et de vinyl alkylidene. Deuxièmement, la polymérisation par métathèse avec l'acétylène a été effectuée sur des sites de cyclopentylidene. Les résultats de ces deux méthodes sont comparables malgré des différences mineures dans la conformation des polymères, lesquelles sont suggérées par les données des spectres vibrationnels. Le comportement des monomères adsorbés sur β-Mo₂C est aussi analysé à la fin de chaque chapitre. La spectroscopic vibrationnelle suggère que le cyclooctatétraène adopte une configuration plate qui pourrait favoriser sa réactivité en augmentant la tension moléculaire ainsi que le temps de résidence de la molécule sur la surface. Ces effets pourront être responsables du faite que le cyclooctatétraène réagisse à une plus basse température face à la polymérisation par ouverture de cycle que le norbornène et le cyclopentène. Pour ce qui concerne l'acétylène, il réagit avec lui-même à température plus basse que la température de polymérisation pour donner du benzène et du butadiene sur la surface du carbure de molybdène. Cette réaction est, alors, en compétition avec la formation du polyacétylène sur la surface modifiée avec des espèces alkylidene

Toward Reversible and Moisture-Tolerant Aprotic Lithium-Air Batteries

The development of moisture-tolerant, LiOH-based non-aqueous Li-O2 batteries is a promising route to bypass the inherent limitations caused by the instability of their typical discharge products, LiO2 and Li2O2. The use of the I−/I3− redox couple to mediate the LiOH-based oxygen reduction and oxidation reactions has proven challenging due to the multiple reaction paths induced by the oxidation of I− on cell charging. In this work, we introduce an ionic liquid to a glyme-based electrolyte containing LiI and water and demonstrate a reversible LiOH-based Li-O2 battery cycling that operates via a 4 e−/O2 process with a low charging overpotential (below 3.5 V versus Li/Li+). The addition of the ionic liquid increases the oxidizing power of I3−, shifting the charging mechanism from IO−/IO3− formation to O2 evolution

Binder-free CNT cathodes for Li-O2_2 batteries with more than one life

Li-O$_2$ batteries (LOB) performance degradation ultimately occurs through the accumulation of discharge products and irreversible clogging of the porous electrode during the cycling. Electrode binder degradation in the presence of reduced oxygen species can result in additional coating of the conductive surface, exacerbating capacity fading. Herein, we establish a facile method to fabricate free-standing, binder-free electrodes for LOBs in which multi-wall carbon nanotubes (MWCNT) form cross-linked networks exhibiting high porosity, conductivity, and flexibility. These electrodes demonstrate high reproducibility upon cycling in LOBs. After cell death, efficient and inexpensive methods to wash away the accumulated discharge products are demonstrated, as reconditioning method. The second life usage of these electrodes is validated, without noticeable loss of performance. These findings aim to assist in the development of greener high energy density batteries while reducing manufacturing and recycling costs.Comment: 24 pages, 6 figures, 10 figures in S

Onset Potential for Electrolyte Oxidation and Ni-Rich Cathode Degradation in Lithium-Ion Batteries

High-capacity Ni-rich layered metal oxide cathodes are highly desirable to increase the energy density of lithium-ion batteries. However, these materials suffer from poor cycling performance, which is exacerbated by increased cell voltage. We demonstrate here the detrimental effect of ethylene carbonate (EC), a core component in conventional electrolytes, when NMC811 (LiNi0.8Mn0.1Co0.1O2) is charged above 4.4 V vs Li/Li+-the onset potential for lattice oxygen release. Oxygen loss is enhanced by EC-containing electrolytes-compared to EC-free-and correlates with more electrolyte oxidation/breakdown and cathode surface degradation, which increase concurrently above 4.4 V. In contrast, NMC111 (LiNi0.33Mn0.33Co0.33O2), which does not release oxygen up to 4.6 V, shows a similar extent of degradation irrespective of the electrolyte. This work highlights the incompatibility between conventional EC-based electrolytes and Ni-rich cathodes (more generally, cathodes that release lattice oxygen such as Li-/Mn-rich and disordered rocksalt cathodes) and motivates further work on wider classes of electrolytes and additives

Synergistic Degradation Mechanism in Single Crystal Ni-Rich NMC//Graphite Cells

Acknowledgments We acknowledge Diamond Light Source for time on beamline I09 under Proposals SI30201-1 and SI30201-2. This work is supported by the Faraday Institution under Grants FIRG044, FIRG024, and FIRG060.Peer reviewedPublisher PD

A Multitrait Genetic Study of Hemostatic Factors and Hemorrhagic Transformation after Stroke Treatment

BACKGROUND: Thrombolytic recombinant tissue plasminogen activator (r-tPA) treatment is the only pharmacologic intervention available in the ischemic stroke acute phase. This treatment is associated with an increased risk of intracerebral hemorrhages, known as hemorrhagic transformations (HTs), which worsen the patient\u27s prognosis. OBJECTIVES: to investigate the association between genetically determined natural hemostatic factors\u27 levels and increased risk of HT after r-tPA treatment. METHODS: Using data from genome-wide association studies on the risk of HT after r-tPA treatment and data on 7 hemostatic factors (factor [F]VII, FVIII, von Willebrand factor [VWF], FXI, fibrinogen, plasminogen activator inhibitor-1, and tissue plasminogen activator), we performed local and global genetic correlation estimation multitrait analyses and colocalization and 2-sample Mendelian randomization analyses between hemostatic factors and HT. RESULTS: Local correlations identified a genomic region on chromosome 16 with shared covariance: fibrinogen-HT, P = 2.45 × 10 CONCLUSION: We identified 4 shared loci between hemostatic factors and HT after r-tPA treatment, suggesting common regulatory mechanisms between fibrinogen and VWF levels and HT. Further research to determine a possible mediating effect of fibrinogen on HT risk is needed

A multitrait genetic study of hemostatic factors and hemorrhagic transformation after stroke treatment

[Background] Thrombolytic recombinant tissue plasminogen activator (r-tPA) treatment is the only pharmacologic intervention available in the ischemic stroke acute phase. This treatment is associated with an increased risk of intracerebral hemorrhages, known as hemorrhagic transformations (HTs), which worsen the patient’s prognosis.[Objectives] To investigate the association between genetically determined natural hemostatic factors’ levels and increased risk of HT after r-tPA treatment.[Methods] Using data from genome-wide association studies on the risk of HT after r-tPA treatment and data on 7 hemostatic factors (factor [F]VII, FVIII, von Willebrand factor [VWF], FXI, fibrinogen, plasminogen activator inhibitor-1, and tissue plasminogen activator), we performed local and global genetic correlation estimation multitrait analyses and colocalization and 2-sample Mendelian randomization analyses between hemostatic factors and HT.[Results] Local correlations identified a genomic region on chromosome 16 with shared covariance: fibrinogen-HT, P = 2.45 × 10−11. Multitrait analysis between fibrinogen-HT revealed 3 loci that simultaneously regulate circulating levels of fibrinogen and risk of HT: rs56026866 (PLXND1), P = 8.80 × 10−10; rs1421067 (CHD9), P = 1.81 × 10−14; and rs34780449, near ROBO1 gene, P = 1.64 × 10−8. Multitrait analysis between VWF-HT showed a novel common association regulating VWF and risk of HT after r-tPA at rs10942300 (ZNF366), P = 1.81 × 10−14. Mendelian randomization analysis did not find significant causal associations, although a nominal association was observed for FXI-HT (inverse-variance weighted estimate [SE], 0.07 [−0.29 to 0.00]; odds ratio, 0.87; 95% CI, 0.75-1.00; raw P = .05).[Conclusion] We identified 4 shared loci between hemostatic factors and HT after r-tPA treatment, suggesting common regulatory mechanisms between fibrinogen and VWF levels and HT. Further research to determine a possible mediating effect of fibrinogen on HT risk is needed.This study is supported in part by the National Heart, Lung, and Blood Institute grants HL134894, HL139553, and HL141291. G.T.-S. is supported by the Pla Estratègic de Recerca i Innovació en Salut grant from the Catalan Department of Health for junior research personnel (SLT017/20/000100). M.S.-L. is supported by a Miguel Servet contract from the Instituto de Salud Carlos III (ISCIII) Spanish Health Institute (CPII22/00007) and cofinanced by the European Social Fund. E.M. is supported by a Río Hortega Contract (CM18/00198) from the ISCIII. J.C.-M. is supported by an Agència de Gestió d’Ajuts Universitaris i de Recerca Contract (FI_DGR 2020, grant number 2020FI_B1 00157) cofinanced by the European Social Fund. C.G.-F. is supported by a Sara Borrell Contract (CD20/00043) from ISCIII and Fondo Europeo de Desarrollo Regional (ISCIII- FEDER). M.L. is supported by a Contratos Predoctorales de Formación en Investigación en Salud Contract from the ISCIII (FI19/00309).Peer reviewe

Treatment with tocilizumab or corticosteroids for COVID-19 patients with hyperinflammatory state: a multicentre cohort study (SAM-COVID-19)

Objectives: The objective of this study was to estimate the association between tocilizumab or corticosteroids and the risk of intubation or death in patients with coronavirus disease 19 (COVID-19) with a hyperinflammatory state according to clinical and laboratory parameters. Methods: A cohort study was performed in 60 Spanish hospitals including 778 patients with COVID-19 and clinical and laboratory data indicative of a hyperinflammatory state. Treatment was mainly with tocilizumab, an intermediate-high dose of corticosteroids (IHDC), a pulse dose of corticosteroids (PDC), combination therapy, or no treatment. Primary outcome was intubation or death; follow-up was 21 days. Propensity score-adjusted estimations using Cox regression (logistic regression if needed) were calculated. Propensity scores were used as confounders, matching variables and for the inverse probability of treatment weights (IPTWs). Results: In all, 88, 117, 78 and 151 patients treated with tocilizumab, IHDC, PDC, and combination therapy, respectively, were compared with 344 untreated patients. The primary endpoint occurred in 10 (11.4%), 27 (23.1%), 12 (15.4%), 40 (25.6%) and 69 (21.1%), respectively. The IPTW-based hazard ratios (odds ratio for combination therapy) for the primary endpoint were 0.32 (95%CI 0.22-0.47; p < 0.001) for tocilizumab, 0.82 (0.71-1.30; p 0.82) for IHDC, 0.61 (0.43-0.86; p 0.006) for PDC, and 1.17 (0.86-1.58; p 0.30) for combination therapy. Other applications of the propensity score provided similar results, but were not significant for PDC. Tocilizumab was also associated with lower hazard of death alone in IPTW analysis (0.07; 0.02-0.17; p < 0.001). Conclusions: Tocilizumab might be useful in COVID-19 patients with a hyperinflammatory state and should be prioritized for randomized trials in this situatio

Partial Reduction of NO to N2O on Cu{311}: Role of Intermediate N2O2

We investigate the adsorption and reaction of NO on Cu{311} via a combination of Reflection Absorption Infrared Spectroscopy (RAIRS) and first-principles Density Functional Theory (DFT), providing a mechanistic understanding of the reaction as it progresses. Our results support an interpretation that N2O is formed via an associative mechanism involving N2O2 as the crucial intermediate species. Consistent with previous work, we find that such an intermediate readily converts between its initial nitrogen-down configuration and an inverted oxygen-down configuration, prior to decomposition by cleavage of a single N-O bond. As the reaction proceeds, the surface is progressively poisoned by the accumulation of O adatoms resulting from N-O bond scission, and we probe this aspect of the reaction in detail as a function both of temperature and of the surface’s pre-exposure to oxygen. Our results indicate that sustained conversion of NO to N2O on Cu would be contingent upon identifying some co-reactant capable of continuously removing O from the surface as the reaction proceed