Nanoparticules d'orthovanadate d'yttrium : fonctionnalisation et application comme sondes luminescentes pour la biologie.

This thesis has been conducted in the laboratory of Condensed Matter Physics, in Within the group of Solid State Chemistry. One of the themes for this team the development of luminescent nanomaterials used in many applications such as lighting systems or display transparencies. A recent application of certain luminescent nanomaterials has been in the biology, both for the development of biochips, contrast agents, the revealing fabrics. Among them, use as biological fluorescent probe appears as most promising. A biological probe is an object attached to the target biomolecule that can easily be detected. It is divided into two parts, the part carrying the "function" Biological and Part detectable. Detection can be achieved through different physical properties, and in this case, we chose to develop fluorescent probes.Ce travail de thèse a été réalisé au laboratoire de Physique de la Matière Condensée, au sein du groupe de Chimie du Solide. L'une des thématiques de cette équipe concerne l'élaboration de nanomatériaux luminescents, utilisés dans de nombreuses applications comme les systèmes d'éclairage ou de visualisation transparents. L'une des récentes applications de certains nanomatériaux luminescents a été dans le domaine de la biologie, tant pour le développement de biopuces, d'agents de contraste, de révélateurs de tissus. Parmi elles, l'utilisation comme sonde biologique fluorescente apparaît comme des plus prometteuses. Une sonde biologique est un objet attaché à la biomolécule ciblée qui peut facilement être détecté. Elle se divise en deux parties, la partie portant la « fonction » biologique, et la partie détectable. La détection peut se faire grâce à différentes propriétés physiques, et dans le cas présent, nous avons choisi de développer des sondes fluorescentes

Oxydes lamellaires nanométriques pour condensateurs électrochimiques

L objectif de ce travail a été de proposer des oxydes lamellaires nanométriques de cobalt et de vanadium pour des applications en tant qu électrodes positives de systèmes électrochimiques à haute puissance en technologie lithium ou sodium, aqueuse ou organique. Une étude de formulation d électrodes composites à base de polymère, d oxydes et de carbone conducteur a montré que la percolation du carbone ainsi que la pression appliquée jouaient un rôle prépondérant dans l exploitation maximale des propriétés intrinsèques des oxydes. Une formulation d électrode en milieu aqueux et une autre en milieu organique ont été étudiées afin d en optimiser les propriétés à fort régime de charge - décharge. Des méthodes de synthèse originale de nanoparticules d oxyde de cobalt au sodium ont été développées. Ces particules présentent de fortes capacités à haut régime grâce à des mécanismes pseudo-capacitifs de stockage des charges. Des nano-rubans de pentoxyde de vanadium hydratés ont été obtenus par voie sol-gel. Deux méthodes de modification ont été testées : l intercalation par simple échange ionique ou l insertion d alcalins (bronzes) par réduction. Les bronzes présentent des capacités deux fois supérieures aux composés intercalés et conservent ces très bonnes propriétés électrochimiques même à fort vitesse de charge - décharge.This thesis focuses on cobalt and vanadium lamellar nanometric oxides used as positive electrode materials for electrochemical capacitors in either sodium or lithium electrolytes. First, a study on composite electrodes formulation was made to fully understand the key parameters necessary to maximize the electrochemical performances. It appears that carbon percolation and applied pressure drastically increase the electrode conductivity. One electrode formulation in aqueous electrolyte and another one in organic electrolyte have been proposed to investigate the kinetics properties at high charge/discharge rates. An original synthesis of nanometric cobalt oxide by direct precipitation in alkaline and oxidizing medium has been done. These particles have been structurally and electrochemically characterized at high charge/discharge rate. The hydrated sodium phase exhibits very nice electrochemical properties at high rate in sodium aqueous electrolyte but this phase is metastable. Nevertheless the dried phases show a pseudo-capacitive behavior in either lithium or sodium aqueous electrolyte. Last, nano-ribbons of vanadium oxide were made thanks to a well known sol-gel synthesis. These particles were modified by substitution with alkaline ions thanks to a simple ionic exchange or through reduction. The vanadium bronzes showed the best electrochemical performances at high charge/discharge rates in either lithium or sodium organic electrolyte.PARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF

Prediction of isoelectric point of manganese and cobalt lamellar oxides : application to controlled synthesis of mixed oxides

To design novel layered materials, bottom-up strategy is very promising. It consists of (1) synthesizing various layered oxides, (2) exfoliating them, then (3) restacking them in a controlled way. The last step is based on electrostatic interactions between different layered oxides and is difficult to control. The aim of this study is to facilitate this step by predicting the isoelectric point (IEP) of exfoliated materials. The Multisite Complexation model (MUSIC) was used for this objective and was shown to be able to predict IEP from the mean oxidation state of the metal in the (hydr)oxides, as the main parameter. Moreover, the effect of exfoliation on IEP has also been calculated. Starting from platelets with a high basal surface area over total surface area, we show that the exfoliation process has no impact on calculated IEP value, as verified with experiments. Moreover, the restacked materials containing different monometallic (hydr)oxide layers also have an IEP consistent with values calculated with the model. This study proves that MUSIC model is a useful tool to predict IEP of various complex metal oxides and hydroxides

Cross-Section Auger Analysis to Study the Bulk Organization/Structure of Mn-Co Nano-Composites for Hybrid Supercapacitors

Developing new methods to prepare pseudocapacitive materials with high pseudocapacitance/electronic conductivity is of great interest for hybrid supercapacitors. Recently, the exfoliation/restacking of manganese and cobalt layered transition metal oxides was proposed. Despite improved electrochemical performance of such Mn-Co composites, their bulk organization (i.e. the scale at which the stacking occurs) and structure (i.e. porosity…) remains to be elucidated so far. To tackle this issue, here, SEM and Auger analysis with a nanoscale resolution, coupled to cross-section preparation is proposed. A good correlation between the restacking method, the nanoscale organization/structure of composites and resulting electrochemical performance is obtained. Importantly, the combination of cross-section with Auger analysis allows revealing the nanoscale stacking of the Mn and Co phases. Also, the porosity of the nano-composites, revealed by the cross-section preparation, is correlated to the speed of the restacking process. A fast flocculation step forms aggregates with a porous bulk structure while a slow flocculation step leads to a dense and closed bulk structure of the aggregates. These results highlight that a better control/understanding of the organization/structure of such nanocomposites can lead to further improvement. Overall, the innovative cross-section Auger approach proposed in this study should also benefit to the understanding of other nano-composites.Laboratory of excellency for electrochemical energy storag

FeNC catalysts for CO 2 electroreduction to CO: effect of nanostructured carbon supports

International audienceCO2 electroreduction to CO is an attractive strategy for using CO2 as a feedstock for the production of organic chemicals. However, there is still a need to develop catalysts based on non-noble metals since the best catalytic systems for that specific reaction are based on silver and gold, in particular when high current densities are required. Iron- and nitrogen-doped carbon materials (FeNC) have recently emerged as cheap, stable and active alternatives, however with still limited current densities. Here we report that both the current density and the selectivity of FeNC-based cathodes can be significantly improved by mixing FeNC with carbon materials such as carbon nanotubes (CNT) or carbon nanofibers (CNF). More specifically, we show that a cathode based on a FeNC–CNF composite material shows ca. a twice higher jCO/jH2 ratio and up to twice higher jCO value over a broad potential range. The FeNC–CNF electrode compares well with Ag and Au electrodes with a very high selectivity for CO production (FY for CO of almost 90%) and current densities above 10 mA cm−2 at −0.7 V vs. RHE

Synergy of Mn and Co in slab-based nanocomposites for hybrid supercapacitors: impact of restacking process on electrochemical properties

To develop materials with enhanced electrochemical properties, an original synthesis strategy based on the exfoliation and restacking of manganese and cobalt layered transition metal oxides has been explored. Successful exfoliation yielded “building nanoblocks”, which were further reassembled in mixed nanocomposites, by modifications of electrostatic interactions in solution. Three methods were tested, differing by the acidification procedure and time of mixing. The restacking conditions play a key role on the microstructural homogeneity of the nanocomposites. Such a nanocomposite approach marrying a good electronic conductor (cobalt oxyhydroxide) with a pseudocapacitive material (manganese oxide) should thus be very beneficial for development of highly efficient pseudocapacitors.Laboratory of excellency for electrochemical energy storag

A Dissolution/Precipitation Equilibrium on the Surface of Iridium-Based Perovskites Controls Their Activity as Oxygen Evolution Reaction Catalysts in Acidic Media

anie201814075-sup-0001-misc_information.pdfInternational audienceRecently, IrV‐based perovskite‐like materials were proposed as oxygen evolution reaction (OER) catalysts in acidic media with promising performance. However, iridium dissolution and surface reconstruction were observed, questioning the real active sites on the surface of these catalysts. In this work, Sr2MIr(V)O6 (M=Fe, Co) and Sr2Fe0.5Ir0.5(V)O4 were explored as OER catalysts in acidic media. Their activities were observed to be roughly equal to those previously reported for La2LiIrO6 or Ba2PrIrO6. Coupling electrochemical measurements with iridium dissolution studies under chemical or electrochemical conditions, we show that the deposition of an IrOx layer on the surface of these perovskites is responsible for their OER activity. Furthermore, we experimentally reconstruct the iridium Pourbaix diagram, which will help guide future research in controlling the dissolution/precipitation equilibrium of iridium species for the design of better Ir‐based OER catalysts

Organic functionalization of luminescent oxide nanoparticles towards their application as biological probes

International audienceLuminescent inorganic nanoparticles are now widely studied for their applications as biological probes for in vitro or in vivo experiments. The functionalization of the particles is a key step toward these applications, since it determines the control of the coupling between the particles and the biological species of interest. This paper is devoted to the case of rare earth doped oxide nanoparticles and their functionalization through their surface encapsulation with a functional polysiloxane shell. The first step of the process is the adsorption of silicate ions that will act as a primary layer for the further surface polymerization of the silane, either aminopropyltriethoxysilane (APTES) or glycidoxypropyltrimethoxysilane (GPTMS). The amino- or epoxy- functions born by the silane allow the versatile coupling of the particles with bio-organic species following the chemistry that is commonly used in biochips. Special attention is paid to the careful characterization of each step of the functionalization process, especially concerning the average number of organic functions that are available for the final coupling of the particles with proteins. The surface density of amino or epoxy functions was found to be 0.4 and 1.9 functions per square nanometer for GPTMS and APTES silanized particles, respectively. An example of application of the amino-functionalized particles is given for the coupling with α-bungarotoxins. The average number (up to 8) and the distribution of the number of proteins per particle are given, showing the potentialities of the functionalization process for the labeling of biological species

Synergy of Mn and Co in slab-based nanocomposites for hybrid supercapacitors: impact of restacking process on electrochemical properties

To develop materials with enhanced electrochemical properties, an original synthesis strategy based on the exfoliation and restacking of manganese and cobalt layered transition metal oxides has been explored. Successful exfoliation yielded “building nanoblocks”, which were further reassembled in mixed nanocomposites, by modifications of electrostatic interactions in solution. Three methods were tested, differing by the acidification procedure and time of mixing. The restacking conditions play a key role on the microstructural homogeneity of the nanocomposites. Such a nanocomposite approach marrying a good electronic conductor (cobalt oxyhydroxide) with a pseudocapacitive material (manganese oxide) should thus be very beneficial for development of highly efficient pseudocapacitors.Laboratory of excellency for electrochemical energy storag