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International audience; Dispersion of tubules made of diacetylenic phospholipids (DC 8,9 PC), in aqueous colloidal dispersions of magnetic nanoparticles is studied as a function of the sign of particles surface charges. In every case the tubule-vesicle transition temperature is decreased by the presence of the magnetic nanoparticles. Electrophoresis experiments on the tubules in pure water permits to conclude on a negative apparent surface charge. We study the magnetic response of the system to a static or stationary rotating field and to a magnetic field gradient. These experiments reveal an excess or a lack of magnetic permeability between tubules and the surrounding medium. Electron microscopy confirms these results showing an electrostatic interaction between the phospholipidic bilayer and the magnetic particles.

International audience; Magnetic nanoparticles exhibit a high potential to selectively treat cancer by hyperthermia provided that high heating capacity can be reached. In this work, we report an efficient synthesis of novel structures of magnetic iron oxide. The particles, obtained by applying a modified “polyol” protocol, present a particular shape: they look constituted of smaller grains of approximately 11 nm, assembled in a flower-shaped structure. These nanoflowers, dispersed in water at physiological pH, present particularly interesting magnetic properties and a great capacity of heating. The value of the specific loss power (SLP) of these nanoflowers is 1 order of magnitude higher than the SLP reported for conventional 11 nm single-domain maghemite nanoparticles in the same condition of field exposure.

Nous presentons la synthese par chimie verte de nanocomposites magnetiques qui pourraient etre utilises dans le traitement de l’eau. Ils sont constitues par une matrice de silice encapsulant des nanoparticules d’oxyde de fer. Outre les avantages lies a leur faible impact sur l’environnement, les methodes de synthese decrites ici ont conduit a des particules structurees sur plusieurs echelles de taille. Deux types de synthese ont ete etudies. Des billes millimetriques parfaitement monodisperses ont ete obtenues par voie sol-gel en utilisant comme agent structurant des biopolymeres non-toxiques et biodegradables. Des microspheres ou des nanospheres magnetiques ont ete preparees a l’aide de reactions sol-gel dans des emulsions a base d’huile vegetale. Nous avons teste ces solides comme adsorbants magnetiques dans des procedes de depollution des eaux utilisant la separation magnetique. Nous montrons ici les premiers resultats quant a l’application de ces materiaux comme adsorbants de colorants et de metaux lourds apres une eventuelle modification chimique de leur surface.

Magnetic fluid based on cobalt ferrite nanoparticles was obtained using a hydrothermal treatment added to the Massart procedure. This treatment increases the average size of the nanoparticles from 11.9 to 18.7 nm and also improves the dispersity and crystallinity of the cobalt ferrite particles. The nanoparticles obtained after the hydrothermal treatment were dispersed in aqueous solvent by the classical procedure for ionic magnetic fluids. The ferrofluid thus obtained is stable at pH 7 and may be useful for hyperthermia applications.

International audience; Among drug delivery systems, catanionic vesicles now appear as powerful candidates for pharmaceutical applications because they are relatively cheap and easy to use, thus well corresponding to industrial requirements. Using labelled vesicles made of a tricatenar catanionic surfactant, the work reported here aims at exploring the mechanisms by which internalisation into a cell occurs. The study was performed on various cell types such as phagocytic as well as non-phagocytic cells using confocal laser scanning microscopy and flow cytometry. Using various inhibitors, endocytosis and also a passive process, as probably fusion, were highlighted as interaction phenomena between catanionic vesicles and cell membranes. Finally, the interaction modelled with giant liposomes as membrane models confirmed the hypothesis of the occurrence of a fusion phenomenon between the nanovectors and cell membranes. This process highlights the potential of catanionic vesicles for a future pharmaceutical application as a universal drug delivery system.

The present study deals with the morphological modifications of giant dioleoyl phosphatidylcholine vesicles (DOPC GUVs) induced by the nonionic surfactant n-octyl β,D-glucopyranoside at sublytic levels, i.e., in the first steps of the vesicle-to-micelle transition process, when surfactant inserts into the vesicle bilayer without disruption. Experimental conditions were perfected to exactly control the surfactant bilayer composition of the vesicles, in line with former work focused on the mechanical properties of the membrane of magnetic-fluid-loaded DOPC GUVs submitted to a magnetic field. The purpose here was to systematically examine, in the absence of any external mechanical constraint, the dynamics of giant vesicle shape and membrane deformations as a function of surfactant partitioning between the aqueous phase and the lipid membrane, beforehand established by turbidity measurements from small unilamellar vesicles.

In this study, a series of batch experiments is conducted to investigate the ability of magnetic alginate beads containing Cyanex 272® to remove Co(II) ions from aqueous solutions. Equilibrium sorption experiments show a Co(II) uptake capacity of 0.4 mmol g−1. The data are successfully modelled with a Langmuir equation. A series of kinetics experiments is then carried out and a pseudo-second order equation is used to fit the experimental data. The effect of pH on the sorption of Co(II) ions is also investigated. Desorption experiments by elution of the loaded beads with nitric acid at pH 1 show that the magnetic alginate beads could be reused without significant losses of their initial properties even after 3 adsorption–desorption cycles.

Interactions between vesicles made of a sugar-derived tricatenar catanionic surfactant (TriCat), used as drug delivery vectors, and giant unilamellar vesicles (GUVs) encapsulating magnetic nanoparticles are investigated in order to understand the drug internalisation process. It appears that the addition of the catanionic vesicles to the GUV induces important shape modifications and membrane instabilities that cannot be explained by the insertion of monomeric TriCat into the membrane. This indicates a specific interaction between the TriCat vesicles and the lipidic membrane.

We describe the phase behavior of an aqueous mixture of discotic nanoparticles of laponite and spherical magnetic nanoparticles of maghemite. To obtain stable mixtures from a chemical point of view, the maghemite nanoparticles are first coated by a thin layer of silica in order to adapt their surface chemistry to that of laponite nanoparticles: this enables one to raise volume fractions of maghemite Phi mag in the laponite suspensions up to several percent. Although the system is out of equilibrium, a "fluid-solid" state diagram was established showing that the mixtures undergo a fluid-solid transition, similar to that of pure suspensions of laponite, over a given volume fraction of laponite Phi lap and over a given Phi mag. An increase in Phi mag shifts Phi lap toward the lower values. When a solid sample is just above Phi lap, the application of an external magnetic field gradient induces a solid-to-liquid transition if the sample is located not too far from Phi lap on the state diagram. The structure of the mixtures, determined either at small scale by small-angle neutron scattering (SANS) or at intermediate scales by optical microscopy, shows that the solid samples are phase separated at a local scale: they are made of densely connected domains of laponite nanoparticles surrounding liquid pockets of maghemite nanoparticles. The size of the pockets grows with time. The magnetic liquid pockets are responsible for the rupture of the solid samples when an external magnetic field gradient is applied since their deformation induces local mechanical stress, internally damaging the network formed by the solid domains of laponite. The microscopic phase separation is the result of two opposite effects: (i) entropic effects that tend to phase separate the system macroscopically when the packing entropy overcomes the orientational entropy and (ii) long-range electrostatic repulsions that freeze the system.

An organophosphorous ligand terminated by an amine group has been used here for the first time to functionalize γ-Fe 2 O 3 nanoparticles and to immobilize an enzyme onto their surface in a covalent way. The immobilization of β-glucosidase onto the maghemite nanoparticles was carried in this work out via a reductive amination reaction pathway which involves the terminal amine group on the ligand. The enzymatic activity of the bound enzyme was evaluated in terms of the classical Michaelis–Menten kinetics. Indeed, the affinity of the bound enzyme for the substrate is preserved and is not affected by the high amount of enzymes onto the surface of the nanoparticles. Moreover, the related enzymatic activity slightly decreases compared to that of the free enzyme. Such functionalized nanoparticles could help to improve the delivery and the recovery of biomolecules in biomedical applications by using a magnetic field. They could also provide a magnetic support which could be involved as a contrast agent, a biological label and a mediator for magnetic hyperthermia.

In this paper, we demonstrate the production of highly magnetic and fluorescent giant vesicles by encapsulating gamma-Fe2O3-rhodamine B nanoparticles. The liposomes containing the nanoparticles were made of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). We found that the ionic strength of the initial magnetic fluid is a crucial parameter in controlling the physicochemical properties of the bilayer. At high ionic strength, we obtained very important deformations of liposomes with high magnetic susceptibilities induced by an applied magnetic field. The encapsulation rate was studied using magnetophoresis and photobleaching tests, and the membrane properties were studied using confocal microscopy and elastic measurements.

International audience

This paper describes the synthesis of a magnetic and conducting liquid consisting of cobalt nanoparticles dispersed in mercury. The magnetic nanoparticles are obtained in one step by the electroreduction of a cobalt(II) solution on mercury. These particles are then extracted using an organic solution of surfactant in order to obtain a ferrofluid based on cobalt nanoparticles.

The synthesis and characterization of original ferrite multishell magnetic nanoparticles made of a soft core (manganese ferrite) covered with two successive shells, a hard one (cobalt ferrite) and then a soft one (nickel ferrite), are described. The results demonstrate the modulation of the coercivity when new magnetic shells are added.

International audience; Maghemite (γ-Fe2O3) nanocrystals stable at neutral pH and in isotonic aqueous media were synthesized and encapsulated within large unilamellar vesicles of egg phosphatidylcholine (EPC) and distearoyl-SN-glycero-3-phosphoethanolamine-N-[methoxy(poly(ethylene glycol))-2000] (DSPE-PEG2000, 5 mol %), formed by film hydration coupled with sequential extrusion. The nonentrapped particles were removed by flash gel exclusion chromatography. The magnetic-fluid-loaded liposomes (MFLs) were homogeneous in size (195 ± 33 hydrodynamic diameters from quasi-elastic light scattering). Iron loading was varied from 35 up to 167 Fe(III)/lipid mol %. Physical and superparamagnetic characteristics of the iron oxide particles were preserved after liposome encapsulation as shown by cryogenic transmission electron microscopy and magnetization curve recording. In biological media, MFLs were highly stable and avoided ferrofluid flocculation while being nontoxic toward the J774 macrophage cell line. Moreover, steric stabilization ensured by PEG-surface-grafting significantly reduced liposome association with the macrophages. The ratios of the transversal (r2) and longitudinal (r1) magnetic resonance (MR) relaxivities of water protons in MFL dispersions (6 < r2/r1 < 18) ranked them among the best T2 contrast agents, the higher iron loading the better the T2 contrast enhancement. Magnetophoresis demonstrated the possible guidance of MFLs by applying a magnetic field gradient. Mouse MR imaging assessed MFLs efficiency as contrast agents in vivo: MR angiography performed 24 h after intravenous injection of the contrast agent provided the first direct evidence of the stealthiness of PEG-ylated magnetic-fluid-loaded liposomes.

International audience; Hydrophilic magnetic microgels were synthesized by a free-radical polymerization in inverse emulsion. Two sizes of magnetic microgels were obtained depending on the initial droplet size of the emulsion. As the polymer matrix is a hydrogel, the novelty of this paper is that the magnetic particles are incorporated from an aqueous magnetic fluid instead of an organic one. In this paper, we underline the physicochemical aspects necessary to control the proper dispersion of the magnetic particles in the polymer matrix. The size, the magnetic content and the swelling degree of micron-sized and sub-micron sized magnetic microgels are characterized.

In this paper, we report on how to take advantage of good knowledge of both the chemistry and the stability of an aqueous magnetic colloidal suspension to realize different magnetic composites. The osmotic pressure of the magnetic nanoparticles is set prior to the realization of the composite to a given value specially designed for the purpose for each hybrid material: magnetic particles in polymer networks, particles as probes for studying the structure of clay suspensions and shape modification of giant liposomes. First, we show that the introduction of magnetic particles in polyacrylamide gels enhances their Young modulus and reduces the swelling caused by water. The particles cause both a mechanical and an osmotic effect. The latter is strongly dependent on the ionic strength and is attributed to an attraction between particles and the polymeric matrix. In the second part, we determine the microscopic structure of suspensions of laponite as a function of concentration, by combining SANS and magneto-optical experiments with the probes. This study requires conditions suitable for including the magnetic particles as probes without disturbing the clay suspensions. The third part presents giant magnetoliposomes, which encapsulate magnetic nanoparticles. Shape transitions are obtained with either a magnetic field or an osmotic stress.

A new way to probe the microscopic structure of suspensions of discotic particles of Laponite is reported. Magnetic spherical colloidal particles of maghemite are incorporated into the Laponite suspensions to study their spatial repartition and their microrheological behavior. Chemicals conditions are found for the synthesis of stable mixtures. The determination of the equation of state of the obtained mixtures by osmotic measurements shows that the inclusion of the probes does not modify the structure of Laponite suspensions which exhibit a fluid−solid transition at a given volume fraction. The transition is related to the appearance of a pseudoplateau in the equation of state of the system. SANS and microrheological measurements show that the probes are homogeneously dispersed in the mixture out ofthe pseudoplateau and that there is a microscopic phase separation between Laponite particles and maghemite probes in the region of the pseudoplateau of the equation of state. This microscopic phase separation...

This article describes hybrid materials and systems in which the core integrity of inorganic nanobuilding blocks (NBBs) is preserved and reviews the main synthetic procedures presented in the literature. The relation between the NBB and the resulting hybrid networks is discussed for several striking examples: silicon and tin oxo clusters, polyoxometalates, and transition metal−oxo-based clusters. This approach is extended to nanoparticule-based hybrids. The chemical strategies offered by the coupling of soft chemistry processes and this approach based on functional NBBs allows, through an intelligent and tuned coding, to develop a new vectorial chemistry that is able to direct the assembly of a large variety of structurally well-defined clusters or nanoparticles into complex architectures.

We report on the study of the critical point of gas–liquid transitions in an electrostatically stabilized colloidal suspension. Suspensions are constituted of spherical magnetic nanoparticles dispersed in water and stabilized by electrostatic repulsions. The coexistence line is constructed on the Π-V diagram (Π: osmotic pressure, Φ: volume fraction) by the determination of transitions’ threshold by optical microscopy on a large range of volume fractions. This coexistence line presents a maximum that corresponds to a “critical area” where density fluctuations are seen at the microscopic scale. The measurement of these density fluctuations when reaching transitions by small angle neutron scattering (SANS) shows that the transition is of the second order in the critical area and of the first order out of the critical area. SANS measurements also allow to conclude that the interparticle potential is attractive at long range near the coexistence lines of the phase diagram. Long-range attractions are due to dip...

We present an optical study of silica gel matrix doped with maghemite /spl gamma/-Fe/sub 2/O/sub 3/ nanoparticles originating from a ferrofluid. This work is a preliminary study for building adjusted birefringent components suitable for ellipsometry. Silica gel matrix is obtained as sol-gel synthesis. Results show that pure and doped samples solidified out of a magnetic field are quasi-isotropic, whereas samples solidified in the presence of a magnetic field exhibit a very large permanent linear birefringence comparable to that produced by the ferrofluid under the same magnetic field.

International audience; We explore how a magnetic field breaks the symmetry of an initially spherical giant liposome filled with a magnetic colloid. The condition of rotational symmetry along the field axis leads either to a prolate or to an oblate ellipsoid. We demonstrate that an electrostatic interaction between the nanoparticles and the membrane triggers the shape transition. PACS numbers: 75.

We study here the phase behavior of colloidal dispersions, which are constituted of almost monodisperse γ-Fe2O3 magnetic nanoparticles dispersed in water at pH 7. Those electrostatically stabilized dispersions present, if the interparticle repulsion is decreased, gas−liquid transitions, a phase behavior scarcely reported for such charged nanoparticles. Small-angle neutron scattering experiments prove that there is no chaining of the particles and that, from the point of view of interparticle interactions, increasing ionic strength (through addition of NaCl) is equivalent to decreasing temperature. A phenomenological expression of the osmotic pressure π is determined and shown to be in agreement with direct π measurements. The scattering experiments associated to optical microscopy determinations of phase diagrams lead to a general π−Φ diagram. Gas−solid transitions may exist even if their observation is disturbed by metastability phenomena. The results are in qualitative agreement with theoretical predict...

This work describes the detailed structural investigation of mesophase-templated mesoporous silica films by 1D and 2D X-ray scattering techniques and transmission electron microscopy. The films are prepared by sol−gel dip coating with 2D hexagonal templating mesophases, yielding 2D mesoporous structures consisting of cylindrical pores whose axes are aligned parallel to the surface. It is shown that drying and thermal treatments induce an unidirectional shrinkage of the layers in the direction of the normal of the film. The true rectangular symmetry is only evidenced by 2D X-ray scattering in two different scattering geometries. 1D diffraction gives only an apparent hexagonal symmetry. It is furthermore shown that although the cylinder axes are randomly orientated within the plane parallel to the surface, there are large domains with well aligned 2D planar unit cells perpendicular to the surface. It is demonstrated that this preferential ordering is destroyed by nanoparticle seeding with amorphous silica o...

The results of the study of the potassium laurate-1-decanol-water lyotropic composition are pre- sented. The procedure of preparation of micellar solutions provides the good reproducibility of the phase dia- grams. The configurations of the domains of the liquid crystal order are constructed on the concentration plane at the constant temperature as well as the temperature sections ( T , C 1-decanol ) (at the constant ratio of potassium laurate to water) and ( T , C water ) (at the constant ratio of potassium laurate to 1-decanol). The liquid-crystal phases observed are described. © 2000 MAIK "Nauka/Interperiodica".

The copolymerization of acrylamide with the tetrafunctionalized polyanion [gamma-SiW(10)O(36)(RSiO)(4)](4-) (R=C(3)H(6)OC(O)C(Me)=CH(2)), which acts as a cross-linker, is performed in an aqueous dispersion of maghemite (gamma-Fe(2)O(3)) nanoparticles. It results in a magnetic hybrid hydrogel with superabsorption properties (see scheme). The magnetic properties of the nanoparticles enables their mobility inside the network to be estimated and their release during the swelling of the hydrogel to be observed.

Die Copolymerisation von Acrylamid und dem tetrafunktionalisierten Polyanion [γ-SiW10O36(RSiO)4]4− (R=C3H6OC(O)C(Me)=CH2), das als Vernetzungsmittel dient, in einer wasrigen Dispersion von Maghemit(γ-Fe2O3)-Nanopartikeln fuhrt zu einem magnetischen Hybridhydrogel (siehe Schema) mit superabsorbierenden Eigenschaften. Die magnetischen Eigenschaften der Nanopartikel ermoglichen es, die Partikelbeweglichkeit im Innern des Netzes zu bestimmen und die Freisetzung der Partikel wahrend des Quellens des Hydrogels zu verfolgen.

Osmotic pressure measurements are performed, either using a membrane-osmometer, or by the method of osmotic stress, in order to determine the equation of state of acidic and pH 7 magnetic liquids. Both systems are stabilized by electrostatic repulsions and the magnitude of interactions is estimated through the value of the second-virial coefficient. The effect of the ionic strength and of particle size is investigated. It appears that, even for high ionic strength, repulsions dominate the sum of interactions.

New aqueous magnetic fluids constituted of nickel-zinc ferrite particles are synthesized using a soft chemical approach. Ferrofluids and solid particles are characterized using several techniques : chemical analysis, X-ray diffraction, transmission electron microscopy, infrared spectroscopy, and magnetization measurements. The stability of the aqueous magnetic fluids is studied as a function of pH and their magnetization is measured as a function of the degree of zinc substitution in the mixed ferrite particles.

Nanometric maghemite and cobalt ferrite particles are chemically synthesized. The process produces particles polydisperse in size. The positive charges of their surface allow one to disperse them in aqueous acidic solutions and to obtain dispersions stabilized through electrostatic repulsions. Increasing acid concentration (in the range 0.1 to 0.5 mol.L−1), interparticles repulsions are screened and phase transitions are induced. Using this phenomenon, we describe a two-step size sorting process, in order to get significant amounts of nanometric monosized particles (with diameters monitored between typically 6 and 13 nm). As the surface of the latter is not modified by the size sorting process, usual procedures are used to disperse them in several aqueous or oily media.

Synthesis of lyotropic mixtures of potassium laurate, 1-decanol, and water is presented, and the phase diagram of this ternary system is investigated in the vicinity of the nematic region. Several phases are identified and the corresponding concentration and temperature-induced phase transitions are studied. To prepare ferronematic liquid-crystalline samples, positively charged magnetic nanoparticles are introduced into the lyotropic matrix. Modifications of the phase behavior of the system induced by the particle incorporation are described.

Monolayers of hydrophobic magnetic nanoparticles are deposited on a water subphase in a Langmuir trough. The shape of the surface isotherms and the electron-micrograph pictures appear to be strongly dependent on the particle size. Small particles are organized in more compact aggregates than larger ones. We interpret this behavior as a size-dependent balance between van der Waals and magnetic interparticle interactions.

We report the synthesis of lyotropic ferronematics with a content of magnetic nanoparticles (~6 nm) up to 1 vol.%. In the ferrodiscotic phase we observe a magnetic Frederiks transition with critical fields about two orders of magnitude lower than that for an undoped lyotropic system. A model accounting for the magnetic polarization behavior of the studied ferronematics is presented.

In this article we review the flow chemistry methodologies for the controlled synthesis of different kind of nano and microparticles for biomedical applications. Injection mechanism has emerged as new alternative for the synthesis of nanoparticles due to this strategy allows achieving superior levels of control of self-assemblies, leading to higher-ordered structures and rapid chemical reactions. Self-assembly events are strongly dependent on factors such as the local concentration of reagents, the mixing rates, and the shear forces, which can be finely tuned, as an example, in a microfluidic device. Injection methods have also proved to be optimal to elaborate microsystems comprising polymer solutions. Concretely, extrusion based methods can provide controlled fluid transport, rapid chemical reactions, and cost-saving advantages over conventional reactors. We provide an update of synthesis of nano and microparticles such as core/shell, Janus, nanocrystals, liposomes, and biopolymeric microgels through flow chemistry, its potential bioapplications and future challenges in this field are discussed.

The synthesis of gold nanoparticles (Au NPs) from HAuCl4 by using EDTA as a reducing agent is investigated for the first time using UV−vis spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). We show that the size of resulting Au NPs is dictated by the reactivity of ionic Au(III) species and the charge density of EDTA molecules with pH. Moreover by varying the pH of the reaction media, the size of Au NPs can be tuned from 25 to 100 nm. Investigation of the nucleation and growth of Au NPs by time-resolved UV−vis and TEM revealed the presence of nanowires that progressively increase in size at the same time the connected network is fragmented into small segments before the final spherical particles are formed. The identification of reaction intermediates and final products resulting from the reduction of Au(III) by EDTA was possible by recording several 1D- and 2D-nuclear magnetic resonance (NMR) spectra. Our results show that Au(III) reduction to Au(0) NPs by EDTA is accompanied by decarbonylation of EDTA and the formation of formaldehyde which, depending on pH, interferes with the reduction process and contributes to the synthesis. Besides the immense flexibility that can be provided by EDTA for further conjugation with functional molecules to diversify the surface functionality and in turn broaden the application, many synthetic routes concerned with the elaboration of nanoshells and core−shell metal nanoparticles use a large excess of the toxic formaldehyde as a reducing agent. Given the interest in biomedical applications of such nanomaterials and the important role of formaldehyde as a reducing agent in the synthesis process, using EDTA as a reducing agent can be a good starting point for minimizing or replacing formaldehyde use in the synthesis. Refereed/Peer-reviewed

In this study, magnetic beads were prepared by encapsulation of magnetic nanoparticles in epichlorohydrin cross-linked chitosan beads. Their adsorption characteristics were assessed by using methyl orange (MO) as an adsorbate. MO adsorption onto chitosan beads was found to be optimal in the pH range of 3-5. The adsorption isotherm was well described by the Langmuir model and showed high MO adsorption capacity (2.38 mmol/g, i.e. 779 mg/g). MO adsorption kinetics followed a pseudo-second-order kinetic model, indicating that adsorption was the rate-limiting step. At 0.305 mmol/L, only 19 min was required to reach 90% adsorption and 50% of the MO was adsorbed in 2 min. Desorption studies of MO using NaOH showed the reusability of the magsorbent. No release of iron species was observed at pH>2.4.

International audience; Liquid sodium is used as coolant in sodium-cooled fast nuclear reactors. Among many parameters to monitor to ensure the safe operation of the reactor, the coolant chemical purity is a relevant indicator of several undesirable situations, like corrosion of structural materials or sodium contamination, which may release different elements in the coolant. Several techniques have already been implemented to measure the sodium purity, but their response time is long and not suited for continuous monitoring. Therefore, as a complement to them, Laser-Induced Breakdown Spectroscopy (LIBS) is considered as a promising technique for real-time analysis of the coolant purity. In this paper we report on the first LIBS quantitative measurements performed in liquid sodium at 150℃. Calibration curves were traced for lead and indium using the standard addition method. Important intensity drifts and fluctuations were observed, mostly due to pressure variations in the sodium oven. Background subtraction and/or normalization was used to compensate for those intensity fluctuations. To describe the effect of these corrections on the analytical signal noise, a simple model was proposed and its results were found to satisfactorily fit the experimental data. Using this approach, the best detection limits were obtained for the background-subtracted and normalized data, and were found to be 6 ppm for lead and 5 ppm for indium.

International audience

Magneto-plasmonic microcapsules were prepared by the assembly of gold and γ-Fe(2)O(3) magnetic nanoparticles at the oil-water interface of microdroplets generated in a microfluidic device.

A ‘size sorting’ method performed on ionic magnetic fluids, constituted by polydisperse anionic particles dispersed in water at pH 7 allows ‘monodisperse’ samples to be obtained. Here results on phase transitions observed in these samples with decreasing temperature, application of a magnetic field or increasing ionic strength are presented.

The synthesis of magnetic vesicles is described. The vesicles are constituted by didodecyldimethylammonium bromide and have a diameter of about 1 μm. An aqueous magnetic fluid, constituted by charged magnetic nanoparticles dispersed in water without surfactant, is encapsulated in the vesicle with a volume fraction in particles that may range up to 10%. The first step of the encapsulation is the synthesis of a multiple emulsion the intermediate oily phase being evaporated to obtain the DDAB bilayer. The magnetic vesicles thus synthesized align and change shape when a magnetic field is applied.

International audience

Ferrofluids are colloidal solutions of subdomain magnetic grains dispersed in a fluid carrier. Chemically synthesized ionic ferrofluids are stabilized in aqueous media through electrostatic charges at the surface of the particles. Like binary mixtures of polymeric solutions, ferrofluids may undergo a phase separation in two coexisting liquids. We explore here the monophasic area of the phase diagram using small-angle neutron scattering from solutions of γ-Fe2O3 particles of typical size 80 A in the scattering vector q range from 7 × 10−3 to 1.3 × 10−1 A −1. In zero magnetic field the isolated particle behaviour is separated from the interparticle structure factor, which varies with the volume fraction up to 8% of magnetic particles.

SANS measurements are performed for the first time on monophasic ionic ferrofluids. Intraparticle form factors and interparticle structure factors are both extracted from the scattering intensity in a zero magnetic field. The deduced radius of gyration of particles g =83 A and their molar mass Mw=4.2×106g/mol are in full agreement with magnetization measurements. The second virial of the osmotic pressure which is determined to be A2=4.7×10-7cm3molg-2 is positive, indicating that the experiment is performed in a ‘good solvent’ situation.

International audience; In this article, we present new samples of lamellar magnetic nanocomposites based on the self-assembly of a polystyrene-b-poly(n-butyl methacrylate) diblock copolymer synthesized by atom transfer radical polymerization. The polymer films were loaded with magnetic iron oxide nanoparticles covered with polystyrene chains grown by surface initiated-ATRP. The nanostructuration of the pure and magnetically loaded copolymer films on silicon was studied by atomic force microscopy, ellipsometry, neutron reflectivity and contact angle measurement. The present study highlights the strong influence of the copolymer extremity - driven itself by the choice of the ATRP chemical route - on the order of the repetition sequences of the blocks in the multi-lamellar films. In addition, a narrower distribution of the nanoparticles' sizes was examined as a control parameter of the SI-ATRP reaction.

International audience; The application of microfluidics in chemistry has gained significant importance in the recent years. Miniaturized chemistry platforms provide controlled fluid transport, rapid chemical reactions and costsaving advantages over conventional reactors. The advantages of microfluidics have been clearly established in the field of analytical and bioanalytical sciences and in the field of organic synthesis. It is less true in the field of inorganic chemistry and materials science. Yet, inorganic chemistry is mostly concerned by the development of microreactors for the separation and selective extraction of metallic ions. Concerning materials science, microfluidic has been mainly used for the improvement of nanoparticle synthesis, namely metals, metal oxides and semiconductor nanoparticles. Microfluidic devices can also be used for the formulation of more advanced and sophisticated inorganic materials or hybrids.