53 research outputs found
1D Organization of ZnO and TiO2 nanoparticles toward advanced photonic and photocatalytic materials
No full textNowadays Chemist are request to construct more and more complex architectures bearing multifunctionalities enable to respond to external stimuli. The construction of such complex architectures will be addressed through strong interplay in chemical science, as proposed recently with the concept of integrative Chemistry.[1] We synthesized PVA/ZnO-nanorods composite fibers using co-axial flux extrusion.[2] These fibers exhibit higher anisotropic photonic properties, both in absorption and emission, as a result of the collective alignment of the ZnO nanorods along the main axis of the PVA fiber. This photonic anisotropy is triggered by a synergistic interaction between the PVA matrix, stretched above Tg, and cooled down under strain. Compared with non-elongated fibers that present an isotropic emission, composite fibers previously submitted to a tensile stress absorb selectively UV emission when the polarized laser beam is parallel to the main axis of the fiber. In addition, their photolumincescence is also anisotropic, with a waveguide behavior along the main axis of the fiber. Mechanical properties of these composite fibers are also drastically improved, compared with pure PVA fibers: the longitudinal Young modulus of these fibers is increased from 2 to 6 GPa upon ZnO addition, a value similar to those already observed for composite fibers, prepared either with carbon nanotubes, or Vanadium Oxide macroscopic fibers.
[1] N. Brun, S. Ungureanu, H. Deleuze and R. Backov. Chem. Soc. Rev., 2011, 40, 771
[2] Kinadjian, N., Achard, M.-F., Julián-López, B., Maugey, M., Poulin, P., Prouzet, E. and Backov, R. (2012). Adv. Funct. Mater.. doi: 10.1002/adfm.20120036
Chimie intégrative : un outil pour la synthèse rationnelle de matériaux avancés
No full textDossier Techniques de l'Ingénieur RE 173Les sciences chimiques, en perpétuelle évolution, sont associées à des synthèses de plus en plus complexes et transdisciplinaires. Dans ce contexte, nous montrons comment la chimie intégrative parvient à compartimentaliser les réacteurs chimiques au travers de réactions déclenchées aux interfaces huile/eau d'émulsions diluées (réacteurs chimiques dispersés) et concentrées (réacteurs chimiques en contact). Pour illustrations, quelques exemples non exhaustifs de morphosynthèses de matériaux fonctionnels avancés sont donnés dans les domaines de la biocatalyse hétérogène, de la conversion d'énergie et du relargage thermostimulé de substances d'intérêt encapsulées
Chimie intégrative : un outil pour la synthèse rationnelle de matériaux avancés
No full text11 pagesDossier Techniques de l'Ingénieur RE 173Les sciences chimiques, en perpétuelle évolution, sont associées à des synthèses de plus en plus complexes et transdisciplinaires. Dans ce contexte, nous montrons comment la chimie intégrative parvient à compartimentaliser les réacteurs chimiques au travers de réactions déclenchées aux interfaces huile/eau d'émulsions diluées (réacteurs chimiques dispersés) et concentrées (réacteurs chimiques en contact). Pour illustrations, quelques exemples non exhaustifs de morphosynthèses de matériaux fonctionnels avancés sont donnés dans les domaines de la biocatalyse hétérogène, de la conversion d'énergie et du relargage thermostimulé de substances d'intérêt encapsulées
LiBH4@Carbon Micro-Macrocellular Foams: Tuning Hydrogen Release through Varying Microporosity
No full textMicroporous-macroporous carbononaceous monolith-type materials, prepared through a hard template method using silica as exo-templating matrices, have been impregnated by an etheric solution of LiBH4 to prepare LiBH4@Carbon samples. It has been shown that the amorphous character of LiBH4 is largely favoured when developing the carbon microporosity (pores smaller than 2 nm) and that LiBH4 dehydrogenation is strongly enhanced at low temperatures. The onset temperature of dehydrogenation can be decreased to 200°C and hydrogen capacity reaching 4.0 wt.% is obtained at 300°C with the carbon having the largest microporous volume, whereas the hydrogen release for bulk LiBH4 is negligible at the same temperature. In addition to some irreversible reactions with carbon surface groups the explanation for such modification could lie in the LiBH4 destabilization through confinement to the nanoscale range and associated amorphization
A novel three-dimensional macrocellular carbonaceous biofuel cell
No full textHere we report the first membrane-free biofuel cell obtained using three-dimensional carbonaceous foam electrodes. We first developed a new synthetic pathway to produce a new carbonaceous foam electrode material bearing porosity both on the meso and macroporous scales. We proved that by increasing the porosity of our three-dimensional foams we could increase the current density of our modified electrodes. Then, by choosing the right combination of enzyme and mediator, and the right loading of active components, we achieved high current densities for an anodic system. Finally, we combined the improved cathode and anode to build a new membrane-free hybrid enzymatic biofuel cell consisting of a mediated anode and a mediator-free cathode
Gold nanoparticles spontaneously generated in onion-type multilamellar vesicles. Bilayers-particle coupling imaged by Cryo-TEM
No full textWe report the spontaneous, in-situ synthesis of gold nanoparticles within onion-type multilamellar vesicles (MLV) using a simple and mild strategy. Monoolein, one of the MLV components, was used as reductant, without any additional chemical. Two different preparative pathways were employed that resulted in gold particle formation as asserted by UV-vis spectroscopy and transmission electron microscopy (TEM). When onions were prepared from a lamellar phase containing gold ions, nanoparticles with a rice grain shape and narrow size distribution (6 × 10 nm*nm) were formed, suggesting synthesis within the vesicles. When preformed onions were dispersed in a KAuCl4 solution, TEM and cryogenic temperature-transmission electron microscopy (cryo-TEM) analysis reveal that both extra- and intravesicular syntheses took place. Cryo-TEM imaging evidences the insertion of gold nanoparticles between MLV leaflets and the close coupling between particle morphology and the lamellar phase. A simple mechanism of particle growth within a lamellar phase is proposed that could explain the differences in nanoparticle size and shape observed between both preparative pathways
Controlled production of hierarchically large particles and emulsions using integration on line of tubular millifluidic devices
No full textControlled production of hierarchically large particles and emulsions using integration on line of tubular millifluidic devices
No full textMacrocellular Silica Monoliths Hierarchically Textured: Mesostructured Si-HIPE Materials
No full textABSTRACTInterface between sol-gel process and soft matter appears recently as a very nice tool to generate new materials with complex textures or/and structures extended at various length scales. In this general context, hierarchical inorganic porous monoliths have been prepared using a double templates procedure, namely concentrated emulsion as a macroscopic pattern and mesoscopic micellar templates. The texture of those monoliths can vary dramatically playing either with the oil volume fraction, synthetic pH conditions or the emulsification process. These materials show interconnected macroporosity associated to vermicular-type mesostructuration with an average mesoporosity of 800 m2/g associated to bulk density as low as 0.08 g cm-3 which is comparable to values obtained for silica aerogel.</jats:p
: Advanced functional cellular materials bearing multiscale porosity
No full textWith this mini review we show through the sol-gel and emulsion-based Integrative Chemistry how it is possible to trigger materials dimensionality and beyond their functionalities when reaching enhanced applications. In here we focus on 3D macrocellular monolithic foams bearing hierarchical porosities and applications thereof. We first depict the general background of emulsions focusing on concentrated ones, acting as soft templates for the design of PolyHIPE foams, HIPE being the acronym of High Internal Phase Emulsions while encompassing both sol-gel and polymer chemistry. Secondly we extend this approach toward the design of hybrid organic-inorganic foams, labeled Organo-Si(HIPE), where photonics and heterogeneous catalysis applications are addressed. In a third section we show how inorganic Si(HIPE) matrices can be employed as sacrificial hard templates for the generation carbonaceous foams, labeled Carbon(HIPE). These foams being conductive we show applications when employed as electrodes for Li-S battery and as hosts for Li(BH4)-based hydrogen storage
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