CNRS Paul Pascal Research Center

Bordeaux, France

CNRS Paul Pascal Research Center

Bordeaux, France
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Divoux T.,CNRS Paul Pascal Research Center | Fardin M.A.,University Paris Diderot | Manneville S.,CNRS Physics Laboratory | Lerouge S.,University Paris Diderot
Annual Review of Fluid Mechanics | Year: 2016

Even in simple geometries, many complex fluids display nontrivial flow fields, with regions where shear is concentrated. The possibility for such shear banding has been known for several decades, but in recent years, we have seen an upsurge in studies offering an ever-more precise understanding of the phenomenon. The development of new techniques to probe the flow on multiple scales with increasing spatial and temporal resolution has opened the possibility for a synthesis of the many phenomena that could only have been thought of separately before. In this review, we bring together recent research on shear banding in polymeric and soft glassy materials and highlight their similarities and disparities. © Copyright 2016 by Annual Reviews. All rights reserved.

Lips F.,University of Marburg | Clerac R.,CNRS Paul Pascal Research Center | Dehnen S.,University of Marburg
Angewandte Chemie - International Edition | Year: 2011

La cage aux folles: The [Eu@Sn6Bi8]4- anion (see picture: Sn/Bi blue/orange, Eu black) is the first example of an intermetalloid cluster anion that embeds a lanthanide ion in the solid state. Magnetic measurements and calculations both point to an S=7/2 ground state and indicate ionic interactions of the EuII ion with the main-group-metal cage. ESI mass spectrometry suggest that the cage forms from two seven-atom hemispheres. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Drummond C.,CNRS Paul Pascal Research Center
Physical Review Letters | Year: 2012

Friction is always present when surfaces in contact are set in motion. In this work I describe how a precise, active control of the global friction is possible by adjusting the local molecular conformation of a polyelectrolyte coating via the application of an alternating electric field. The intensity of the applied field determines the degree of interpenetration between polymer brushes in contact, regulating chain stretching while sliding, which is the process at the origin of the global friction. The dynamics of the problem is controlled by the relaxation times of the polyelectrolyte. © 2012 American Physical Society.

Schmitt V.,CNRS Paul Pascal Research Center | Ravaine V.,CNRS Institute of Molecular Sciences
Current Opinion in Colloid and Interface Science | Year: 2013

Colloidal gel particles called microgels have shown their ability to adsorb at an oil-water interface and stabilise emulsion named Pickering emulsions. Such particles are soft, deformable, and porous, and they can swell or contract under the action of an external stimulus. These specificities make them emulsifiers of special interest as they offer a large versatility to emulsions and materials elaborated thereof. This modularity is in counterpart at the origin of an abundant and often contradictory literature. The aim of this paper is to review recent advances in the emulsion stabilisation mechanism, particularly focusing on the microgel conformation at the interface in relation with the mechanical interface behaviour and the emulsion macroscopic stability. A sum up of the unambiguous knowledge is also proposed as well as few central questions that remain to be answered to in the domain. © 2013 Elsevier Ltd.

Mano N.,CNRS Paul Pascal Research Center | Edembe L.,CNRS Paul Pascal Research Center
Biosensors and Bioelectronics | Year: 2013

Bilirubin oxidases, a sub class of the Multicopper oxidases family, were discovered in 1981 by Tanaka and Murao (Murao and Tanaka, 1981) and first used for the detection of bilirubin. Since 2001 and the pioneering work of Tsujimura, these BODs have attracted a lot of attention for the reduction of O2. Unlike laccases, these BODs are stable in physiological conditions (20mM phosphate buffer, pH 7.4, 0.14M NaCl, 37°C) and more than 120 papers have been published in the last 7 years. Here, we will first briefly describe some general features of BODs and then review the use of BODs for bilirubin biosensors and the recent achievements and progress toward the elaboration of efficient O2 reducing cathodes. © 2013 Elsevier B.V.

Pedersen K.S.,CNRS Paul Pascal Research Center | Pedersen K.S.,Copenhagen University | Bendix J.,Copenhagen University | Clerac R.,CNRS Paul Pascal Research Center
Chemical Communications | Year: 2014

Tailoring the specific magnetic properties of any material relies on the topological control of the constituent metal ion building blocks. Although this general approach does not seem to be easily applied to traditional inorganic bulk magnets, coordination chemistry offers a unique tool to delicately tune, for instance, the properties of molecules that behave as "magnets", the so-called single-molecule magnets (SMMs). Although many interesting SMMs have been prepared by a more or less serendipitous approach, the assembly of predesigned, isolatable molecular entities into higher nuclearity complexes constitutes an elegant and fascinating strategy. This Feature article focuses on the use of building blocks or modules (both terms being used indiscriminately) to direct the structure, and therefore also the magnetic properties, of metal ion complexes exhibiting SMM behaviour. This journal is © the Partner Organisations 2014.

Grelet E.,CNRS Paul Pascal Research Center
Physical Review X | Year: 2014

We report on the phase behavior of a model system of colloidal rodlike particles, namely, the filamentous fd viruses, in the dense liquid crystalline states. After determining the phase boundaries as a function of the added salt, we propose a renormalization of the phase diagram accounting for the screened electrostatic repulsions between the particles through an effective hard-rod diameter. Including explicitly counterion condensation, we show that our heuristic model captures the main feature of the nematic-to-smectic phase transition of long hard rods, i.e., its universal packing fraction. The importance of rod flexibility on the relative stability of the different concentrated mesophases is also demonstrated, evidencing, in particular, the existence of a smectic-B phase in between the smectic-A and the columnar phases.

Mano N.,CNRS Paul Pascal Research Center
Applied Microbiology and Biotechnology | Year: 2012

Discovered in 1981 by Tanaka and Murao (Agric Biol Chem 45:2383-2384, 1981), bilirubin oxidase (BOD) is a sub-group of multicopper oxidases (MCOs) also utilizing four Cu+/2+ ions. It catalyzes the oxidation of bilirubin to biliverdin, hence the classification of bilirubin oxidase, and has been primarily used in the determination of bilirubin in serum and thereby in the diagnostic of jaundice. Unlike laccases, the most studied MCOs, BODs display a high activity and stability at neutral pH, a high tolerance towards chloride anions and other chelators, and for some species, a high thermal tolerance. Therefore, BODs could potentially be an alternative to laccase which are so far mainly restricted to applications in acid media. Because of growing interest in BODs for numerous applications under mild pH conditions, based on the number of patents and publications published in the last 5 years, here I will summarize the available data on the biochemical properties of BODs, their occurrence, and their possible biotechnological use in (1) the field of Healthcare for the elaboration of biofuel cells or bilirubin sensors or (2) the field of environmentally desirable applications such as depollution, decolorization of dyes, and pulp bleaching. © Springer-Verlag 2012.

Gao F.,CNRS Paul Pascal Research Center
Nature communications | Year: 2010

Poor electron transfer and slow mass transport of substrates are significant rate-limiting steps in electrochemical systems. It is especially true in biological media, in which the concentrations and diffusion coefficients of substrates are low, hindering the development of power systems for miniaturized biomedical devices. In this study, we show that the newly engineered porous microwires comprised of assembled and oriented carbon nanotubes (CNTs) overcome the limitations of small dimensions and large specific surface area. Their improved performances are shown by comparing the electroreduction of oxygen to water in saline buffer on carbon and CNT fibres. Under air, and after several hours of operation, we show that CNT microwires exhibit more than tenfold higher performances than conventional carbon fibres. Consequently, under physiological conditions, the maximum power density of a miniature membraneless glucose/oxygen CNT biofuel cell exceeds by far the power density obtained for the current state of art carbon fibre biofuel cells.

Penicaud A.,CNRS Paul Pascal Research Center | Drummond C.,CNRS Paul Pascal Research Center
Accounts of Chemical Research | Year: 2013

Growing interest in graphene over past few years has prompted researchers to find new routes for producing this material other than mechanical exfoliation or growth from silicon carbide. Chemical vapor deposition on metallic substrates now allows researchers to produce continuous graphene films over large areas. In parallel, researchers will need liquid, large scale, formulations of graphene to produce functional graphene materials that take advantage of graphene's mechanical, electrical, and barrier properties. In this Account, we describe methods for creating graphene solutions from graphite. Graphite provides a cheap source of carbon, but graphite is insoluble. With extensive sonication, it can be dispersed in organic solvents or water with adequate additives. Nevertheless, this process usually creates cracks and defects in the graphite. On the other hand, graphite intercalation compounds (GICs) provide a means to dissolve rather than disperse graphite. GICS can be obtained through the reaction of alkali metals with graphite. These compounds are a source of graphenide salts and also serve as an excellent electronic model of graphene due to the decoupling between graphene layers. The graphenide macroions, negatively charged graphene sheets, form supple two-dimensional polyelectrolytes that spontaneously dissolve in some organic solvents. The entropic gain from the dissolution of counterions and the increased degrees of freedom of graphene in solution drives this process. Notably, we can obtain graphenide solutions in easily processable solvents with low boiling points such as tetrahydrofuran or cyclopentylmethylether. We performed a statistical analysis of high resolution transmission electronic micrographs of graphene sheets deposited on grids from GICs solution to show that the dissolved material has been fully exfoliated. The thickness distribution peaks with single layers and includes a few double- or triple-layer objects. Light scattering analysis of the solutions shows the presence of two-dimensional objects. The typical size of the dissolved flakes can be determined by either static or dynamic light scattering (DLS) using models available in the literature for disk-shape objects. A mean lateral size of ca. 1 μm is typically observed. We also used DLS to monitor the reaggregation that occurs as these sensitive solutions are exposed to air.The graphenide solutions reported in this Account can be used to deposit random arrays of graphene flakes and large single flakes of a lateral size of tens of micrometers onto different substrates. Using the graphenide solutions described in this Account, we foresee the large-scale production of graphene-based printings, coatings, and composites. © 2012 American Chemical Society.

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