Water-mediated structuring of bone apatite

International audienceIt is well known that organic molecules from the vertebrate extracellular matrix of calcifying tissues are essential in structuring the apatite mineral. Here, we show that water also plays a structuring role. By using solid-state nuclear magnetic resonance, wide-angle X-ray scattering and cryogenic transmission electron microscopy to characterize the structure and organization of crystalline and biomimetic apatite nanoparticles as well as intact bone samples, we demonstrate that water orients apatite crystals through an amorphous calcium phosphate-like layer that coats the crystalline core of bone apatite. This disordered layer is reminiscent of those found around the crystalline core of calcified biominerals in various natural composite materials in vivo. This work provides an extended local model of bone biomineralization

Synthèse et caractérisation de nanoparticules d'oxydes sous-stoechiométriques (vers des applications dans le domaine de l'énergie)

L objectif de ce travail a été de proposer de nouveaux matériaux à base d oxydes réduits de vanadium, molybdène et tungstène, à l échelle nanométrique, pour des propriétés liées au stockage de l énergie. Dans cette optique, 6 systèmes différents ont été élaborés : un système de nanoparticules de MoO2 de taille variant entre 2 et 100 nm ; des assemblages hiérarchiques cœur-coquille constitués de billes carbonées enrobées de nanoparticules de MoO2; des nanoparticules de haggite et de duttonite (deux oxyhydroxydes de vanadium réduits) et enfin des nanoparticules de deux bronzes différents de tungstène basés sur deux structures hexagonales différentes, l une découverte au cours de la thèse. Dans tous les cas, l innovation provient de la réduction des tailles de nanoparticules (jusqu à un ordre de grandeur inférieur aux tailles répertoriées), de la texturation d assemblages multi-échelle originaux, ou encore de la structure cristalline, la morphologie et la nature des faces exposées par les particules. Les propriétés physico-chimiques de tous ces systèmes ont été caractérisées (structure cristalline, morphologie, surface spécifique, propriétés optiques, électriques et électrochimiques). Les mécanismes de formation ont également été étudiés. Les propriétés électrochimiques mesurées ont enfin été discutées au regard des caractéristiques comparées des matériaux : taille des particules, texturation de la matière active (cas des C@MoO2), ouverture des sites d insertion sur l extérieur des particules (cas des bronzes). Ces travaux ont permis d évaluer le potentiel des matériaux en batteries au lithium ou au sodium et a ouvert des perspectives intéressantes sur des applications telles que la catalyse (MoO2 de 9 nm) ou encore les électrochromes (W-346).The aim of this work was to propose new nanomaterials based on reduced vanadium, molybdenum or tungsten oxides, with interesting properties for energy storage. In that purpose, 6 different systems were elaborated: MoO2 nanoparticles with diameters ranging from 2 to 100 nm; hierarchical core-shell assemblies based on carbonaceous cores decorated with MoO2 nanoparticles; haggite and duttonite (two vanadium oxyhydroxides) nanoparticles; and finally nanoparticles of two different tungsten bronzes based on two hexagonal structures of WO3, one having been discovered during this work. Each time, the innovation comes from the particles size reduction (up to 10 times smaller), from the texturation of original multi-scale assemblies, or even from the crystal structure, morphology and nature of the exposed faces. The physical and chemical properties of these systems were characterized (cristal structure, morphology, specific surface, optical, electrical and electrochemical properties). Synthesis mechanisms were also investigated. Finally, the differences of electrochemical properties were discussed considering materials characteristics: size of the particles, texturation of active materials, and accessibility of the insertion sites. This work enabled us to evaluate the materials potentialities towards lithium or sodium batteries, and opened new prospects for applications such as catalysis or electrochromic devices.PARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF

Impact of the F– for O2– substitution in Na3V2(PO4)2F3–yOy on their transport properties and electrochemical performance

International audienceThe series of polyanionic compounds Na3V 3+ 2-yV 4+ y(PO4)2F3-yOy (0 ≤ y ≤ 2) attracts much attention as positive electrode material for Na-ion batteries, because of its high operating potential and stable cycling performance. A series of nanospherical Na3V 3+ 2-yV 4+ y(PO4)2F3-yOy (NVPFOy) materials with y = 0.8, 1.35, 1.6 and 2 was synthesized using a solvothermal reaction and changes in the vanadium average oxidation state were fully characterized combining analyses by Raman and infrared spectroscopies and X-ray diffraction. Raman spectroscopy, beyond checking for the absence of a carbon coating, was in fact used for its sensitivity to the vanadium environment and turn out to be an efficient characterization technique to estimate the oxygen content within the Na3V 3+ 2-yV 4+ y(PO4)2F3-yOy family. The impact of the oxygen content on the transport properties was evaluated by electrochemical impedance spectroscopy. The material with y = 1.35 demonstrates the smallest electrical resistivity in the series, as well as the best rate capability and cyclability upon long-term cycling, despite no carbon coating and a high mass loading positive electrode

Basic concepts of the crystallization from aqueous solutions: The example of aluminum oxy(hydroxi)des and aluminosilicates

International audienceThis overview features the chemical background on condensation phenomena of the aluminum cation in aqueous solution. The formation of polycationic molecular clusters and nanosized solid phases of aluminum oxy(hydroxi)des is interpreted with illustrative mechanisms, building a bridge between solution chemistry and solid-state chemistry. The formation of the main structural types of aluminosilicates (zeolites, clays, imogolite) is also illustrated through the aqueous chemistry of aluminum and silicates

Facile synthetic route towards nanostructured Fe–TiO2(B), used as negative electrode for Li-ion batteries

International audienceWe present here a novel simple method for the synthesis of highly pure TiO2(B). The fast microwave-assisted synthetic route allows facile scale-up of the process. Aiming at an application of the titania polymorph as negative electrode for Li-ion batteries, we have prepared a Fe-containing TiO2(B) and tested the electrochemical performances of both pure and Fe-containing materials. Fe insertion in TiO2(B) allows enhancing capacity and rate capability

Optical Properties of Nanostructured Silica Structures From Marine Organisms

International audienceLight is important for the growth, behavior, and development of both phototrophic and autotrophic organisms. A large diversity of organisms used silica-based materials as internal and external structures. Nano-scaled well-organized silica biomaterials are characterized by a low refractive index and an extremely low absorption coefficient in the visible range, which make them interesting for optical studies. Recent studies on silica materials from glass sponges and diatoms, have pointed out very interesting optical properties, such as light waveguiding, diffraction, focusing, and photoluminescence. Light guiding and focusing have been shown to be coupled properties found in spicule of glass sponge or shells of diatoms. Moreover, most of these interesting studies have used purified biomaterials and the properties have addressed in non-aquatic environments, first in order to enhance the index contrast in the structure and second to enhance the spectral distribution. Although there is many evidences that silica biomaterials can present interesting optical properties that might be used for industrial purposes, it is important to emphases that the results were obtained from a few numbers of species. Due to the key roles of light for a large number of marine organisms, the development of experiments with living organisms along with field studies are require to better improve our understanding of the physiological and structural roles played by silica structures