Liquides ioniques électroactifs dans la composition d’électrolytes avancés pour des applications en énergie

Cette thèse contribue au développement de nouveaux électrolytes pour améliorer la sécurité des batteries à ion lithium par le biais d’une étude et du développement d'électrolytes avancés à base de nouveaux liquides ioniques. En utilisant des approches synthétiques nouvellement développées, plusieurs liquides ioniques électroactifs, qui sont obtenus en modifiant le cation ou l'anion du liquide ionique, sont étudiés pour comprendre comment la structure des constituants ioniques du sel affecte ses propriétés physico-chimiques et électrochimiques. La méthodologie générale qui a guidé le travail tout au long de la thèse doit établir des comparaisons entre des liquides ioniques similaires qui présentent le groupe redox sur le cation et sur l'anion. Les progrès réalisés dans la compréhension des liquides ioniques redox dans cette thèse ont permis leur application dans plusieurs types de dispositifs de stockage d'énergie. La thèse décrira comment les électrolytes avancés basés sur ces liquides ioniques ont été appliqués pour éviter la surcharge des électrodes positives dans les batteries à ion lithium, pour améliorer la sécurité en réduisant l'inflammabilité, pour augmenter la concentration des additifs utilisant leur grande solubilité, pour augmenter la densité énergétique des supercapaciteurs et afin d'obtenir des espèces électrochromes stables avec l'air et avec l'humidité dans les dispositifs électrochromiques autoblanchiments. Cette thèse contribue au domaine du stockage d'énergie en améliorant les électrolytes et au domaine du liquide ionique en fournissant de nouvelles méthodes de synthèse, de nouvelles structures ioniques et une meilleure compréhension du fondamental des liquides ioniques électroactifs.This thesis contribute to the development of new electrolytes to improve the safety of lithium-ion batteries through the study and development of advanced electrolytes based on novel ionic liquids. Using newly developed synthetic approaches, several electroactive ionic liquids, which are obtained by modifying either the cation or the anion of the ionic liquid, are studied to understand how the structure of the salt’s ionic constituents affect its physico-chemical and electrochemical properties. The general methodology that guided the work throughout the whole thesis has to establish comparisons between similar ionic liquids that present the redox group on the cation and on the anion. The progress that has been made in understanding redox ionic liquids in this thesis allowed their application in several types of energy storage devices. The thesis will describe how advanced electrolytes based on these ionic liquids have been applied to prevent overcharging positive electrode materials in lithium-ion batteries, to improve safety by decreasing flammability, to increase the concentration of additives over their solubility, to increase energy density of supercapacitors and to achieve air- and moisture-stable electrochromic species for self-bleaching electrochromic devices. This thesis contributes to the field of energy storage by improving electrolytes and to the domain of ionic liquid by providing new synthesis methods, novel ion structures, and a better understanding of the fundamental of electroactive ionic liquids

Resonant energy transfer of triplet excitons from pentacene to PbSe nanocrystals.

The efficient transfer of energy between organic and inorganic semiconductors is a widely sought after property, but has so far been limited to the transfer of spin-singlet excitons. Here we report efficient resonant-energy transfer of molecular spin-triplet excitons from organic semiconductors to inorganic semiconductors. We use ultrafast optical absorption spectroscopy to track the dynamics of triplets, generated in pentacene through singlet exciton fission, at the interface with lead selenide (PbSe) nanocrystals. We show that triplets transfer to PbSe rapidly (<1 ps) and efficiently, with 1.9 triplets transferred for every photon absorbed in pentacene, but only when the bandgap of the nanocrystals is close to resonance (±0.2 eV) with the triplet energy. Following triplet transfer, the excitation can undergo either charge separation, allowing photovoltaic operation, or radiative recombination in the nanocrystal, enabling luminescent harvesting of triplet exciton energy in light-emitting structures.This is the author's accepted manuscript and will be under embargo until the 5th of April 2015. The final version is published by NPG in Nature Materials here: http://www.nature.com/nmat/journal/v13/n11/full/nmat4093.html

Evaluation of novel HIV vaccine candidates using recombinant vesicular stomatitis virus vector produced in serum-free Vero cell cultures.

Acquired Immune Deficiency Syndrome (AIDS) in humans is a result of the destruction of the immune system caused by Human Immunodeficiency Virus (HIV) infection. This serious epidemic is still progressing world-wide. Despite advances in treatment, a safe and effective preventive HIV vaccine is desired to combat this disease, and to save millions of lives. However, such a vaccine is not available yet although extensive amounts of resources in research and development have been invested over three decades. In light of the recently approved Ebola virus disease vaccine based on a recombinant vesicular stomatitis virus (rVSV-ZEBOV), we present the results of our work on three novel VSV-vectored HIV vaccine candidates. We describe the design, rescue, production and purification method and evaluate their immunogenicity in mice prior to preclinical studies that will be performed in non-human primates. The production of each of the three candidate vaccines (rVSV-B6-NL4.3Env/SIVtm, rVSV-B6-NL4.3Env/Ebtm and rVSV-B6-A74Env(PN6)/SIVtm) was evaluated in small scale in Vero cells and it was found that production kinetics on Vero cells vary depending on the HIV gp surface protein used. Purified virus preparations complied with the WHO restrictions for the residual DNA and host cell protein contents. Finally, when administered to mice, all three rVSV-HIV vaccine candidates induced an HIV gp140-specific antibody response

Electrochemistry and transport properties of electrolytes modified with ferrocene redox-active ionic liquid additives

Used in their pure, undiluted form, ionic liquids usually result in Li-ion battery electrolytes with inadequate performance due low Li+ transport numbers (tLi+). Alternatively, they can be used as additives dissolved in carbonates to maintain a high tLi+ while providing the electrolyte with additional properties such as resistance to combustion, current collector passivation, and decreased Li dendritic growth. Additional properties can be imparted to the ionic liquid via the modification of their structure. Ionic liquids modified with electroactive moieties such as ferrocene (Fc-IL) can be used as an additive in Li-ion battery (LiB) electrolytes to prevent cathode over-oxidation via the redox shuttle mechanism. The aim of the present work is to evaluate the properties of LiB electrolytes modified with such Fc-IL at different concentrations. At low concentrations (0.3–0.5 mol/L), the redox-active ionic liquid behaves as expected for a redox shuttle. We show that at 1 mol/L, however, the redox ionic liquid yields a different discharge behavior after the overcharging step, providing an increase in discharge capacity. This behavior is linked to the deposition of the ferrocenium-IL at the positive electrode. Such electrolyte is non-flammable and is highly efficient to achieve shuttling of excess charge. Based on this principle, it is expected that novel ionic liquids can be designed for development of other types of additives and contribute to developing safer battery electrolytes. As a part of this commemorative issue, this contribution highlights the type of collaborative research currently being done on energy storage devices at the Department of Chemistry at the Université de Montréal.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Enhancing thermoelectrochemical properties by tethering ferrocene to the anion or cation of ionic liquids:Altered thermodynamics and solubility

The thermoelectrochemistry of ferrocene tethered to anions and cations expands current theory to entropy changes involving zwitterions and adjacent charges.</p

Remodeling of lipid landscape in high fat fed very-long chain acyl-CoA dehydrogenase null mice favors pro-arrhythmic polyunsaturated fatty acids and their downstream metabolites

International audienceVery-long chain acyl-CoA dehydrogenase (VLCAD) catalyzes the initial step of mitochondrial long chain (LC) fatty acid β-oxidation (FAO). Inherited VLCAD deficiency (VLCADD) predisposes to neonatal arrhythmias whose pathophysiology is still not understood. We hypothesized that VLCADD results in global disruption of cardiac complex lipid homeostasis, which may set conditions predisposing to arrhythmia. To test this, we assessed the cardiac lipidome and related molecular markers in seven-month-old VLCAD-/- mice, which mimic to some extent the human cardiac phenotype. Mice were sacrificed in the fed or fasted state after receiving for two weeks a chow or a high-fat diet (HFD), the latter condition being known to worsen symptoms in human VLCADD. Compared to their littermate counterparts, HFD/fasted VLCAD-/- mouse hearts displayed the following lipid alterations: (1) Lower LC, but higher VLC-acylcarnitines accumulation, (2) higher levels of arachidonic acid (AA) and lower docosahexaenoic acid (DHA) contents in glycerophospholipids (GPLs), as well as (3) corresponding changes in pro-arrhythmogenic AA-derived isoprostanes and thromboxane B2 (higher), and anti-arrythmogenic DHA-derived neuroprostanes (lower). These changes were associated with remodeling in the expression of gene or protein markers of (1) GPLs remodeling: higher calcium-dependent phospholipase A2 and lysophosphatidylcholine-acyltransferase 2, (2) calcium handling perturbations, and (3) endoplasmic reticulum stress. Altogether, these results highlight global lipid dyshomeostasis beyond FAO in VLCAD-/- mouse hearts, which may set conditions predisposing the hearts to calcium mishandling and endoplasmic reticulum stress and thereby may contribute to the pathogenesis of arrhythmias in VLCADD in mice as well as in humans