Covalent Grafting of Ruthenium Complexes on Iron Oxide Nanoparticles: Hybrid Materials for Photocatalytic Water Oxidation.

The present environmental crisis prompts the search for renewable energy sources such as solar-driven production of hydrogen from water. Herein, we report an efficient hybrid photocatalyst for water oxidation, consisting of a ruthenium polypyridyl complex covalently grafted on core/shell nanoparticles a phosphonic acid group. The photoelectrochemical measurements were performed under 1 sun illumination in 1 M KOH.

Correlation between surface chemistry and magnetism in iron nanoparticles.

To shed light on the factors governing the stability and surface properties of iron nanoparticles, a series of iron nanoparticles has been produced by hydrogenation of two different iron amido complexes: the bis[bis(trimethylsilyl)amido] Fe(ii), [Fe(N(SiMe))], and the bis(diphenylamido) Fe(ii), [Fe(NPh)]. Nanostructured materials of bcc structure, or nanoparticles displaying average sizes below 3 nm and a polytetrahedral structure, have been obtained. Depending on the synthesis conditions, the magnetization of the nanoparticles was either significantly lower than that of bulk iron, or much higher as for clusters elaborated under high vacuum conditions.

Silica Coated Iron/Iron Oxide Nanoparticles as a Nano-Platform for T Weighted Magnetic Resonance Imaging.

The growing concern over the toxicity of Gd-based contrast agents used in magnetic resonance imaging (MRI) motivates the search for less toxic and more effective alternatives. Among these alternatives, iron-iron oxide (Fe@FeOx) core-shell architectures have been long recognized as promising MRI contrast agents while limited information on their engineering is available. Here we report the synthesis of 10 nm large Fe@FeOx nanoparticles, their coating with a 11 nm thick layer of dense silica and functionalization by 5 kDa PEG chains to improve their biocompatibility.

On-chip and freestanding elastic carbon films for micro-supercapacitors.

Integration of electrochemical capacitors with silicon-based electronics is a major challenge, limiting energy storage on a chip. We describe a wafer-scale process for manufacturing strongly adhering carbide-derived carbon films and interdigitated micro-supercapacitors with embedded titanium carbide current collectors, fully compatible with current microfabrication and silicon-based device technology. Capacitance of those films reaches 410 farads per cubic centimeter/200 millifarads per square centimeter in aqueous electrolyte and 170 farads per cubic centimeter/85 millifarads per square centimeter in organic electrolyte.

Isoprene Polymerization on Iron Nanoparticles Confined in Carbon Nanotubes.

The confinement of air-protected metallic magnetic nanoparticles in the inner cavity of carbon nanotubes (CNTs) should offer an interesting perspective for biomedical applications or for controlling CNT alignment in composites. Because the direct confinement of polymer-precoated nanoparticles in CNTs could be restricted by diffusion limitations, we developed a process based on: 1) the confinement of iron nanoparticles surface-modified with an iron polymerization catalyst in the cavity of CNTs and 2) the polymerization of isoprene on the confined nanoparticles. The resulting material consists in CNT-confined iron nanoparticles coated with a polyisoprene air barrier.

Oriented Metallic Nano-Objects on Crystalline Surfaces by Solution Epitaxial Growth.

Chemical methods offer the possibility to synthesize a large panel of nanostructures of various materials with promising properties. One of the main limitations to a mass market development of nanostructure based devices is the integration at a moderate cost of nano-objects into smart architectures. Here we develop a general approach by adapting the seed-mediated solution phase synthesis of nanocrystals in order to directly grow them on crystalline thin films.

Room-Temperature, Strain-Tunable Orientation of Magnetization in a Hybrid Ferromagnetic Co Nanorod-Liquid Crystalline Elastomer Nanocomposite.

Hybrid nanocomposites based on magnetic nanoparticles dispersed in liquid crystalline elastomers are fascinating emerging materials. Their expected strong magneto-elastic coupling may open new applications as actuators, magnetic switches, and for reversible storage of magnetic information. We report here the synthesis of a novel hybrid ferromagnetic liquid crystalline elastomer.

An air-cooled Litz wire coil for measuring the high frequency hysteresis loops of magnetic samples--a useful setup for magnetic hyperthermia applications.

A setup for measuring the high-frequency hysteresis loops of magnetic samples is described. An alternating magnetic field in the range 6-100 kHz with amplitude up to 80 mT is produced by a Litz wire coil. The latter is air-cooled using a forced-air approach so no water flow is required to run the setup.

Design of FeBi nanoparticles for imaging applications.

A variety of imaging technologies are now routinely used in the medical field, their use being continuously enlarged through the development of contrast agents. Recently nanoparticles (NPs) proved efficient to improve imaging in vivo by increasing contrast and targeting capabilities. The current trend is now focused on the development of dual contrast agents combining two or more functionalities on the same NP.

Tuning deposition of magnetic metallic nanoparticles from periodic pattern to thin film entrainment by dip coating method.

In this work, we report on the self-assembly of bimetallic CoFe carbide magnetic nanoparticles (MNPs) stabilized by a mixture of long chain surfactants. A dedicated setup, coupling dip coating and sputtering chamber, enables control of the self-assembly of MNPs from regular stripe to continuous thin films under inert atmosphere. The effects of experimental parameters, MNP concentration, withdrawal speed, amount, and nature of surfactants, as well as the surface state of the substrates are discussed.

Solution epitaxial growth of cobalt nanowires on crystalline substrates for data storage densities beyond 1 Tbit/in2.

The implementation of nano-objects in numerous emerging applications often demands their integration in macroscopic devices. Here we present the bottom-up epitaxial solution growth of high-density arrays of vertical 5 nm diameter single-crystalline metallic cobalt nanowires on wafer-scale crystalline metal surfaces. The nanowires form regular hexagonal arrays on unpatterned metallic films.

Liquid crystalline polymer-Co nanorod hybrids: structural analysis and response to a magnetic field.

This work deals with the structural analysis of side-chain liquid crystalline polysiloxanes, doped with magnetic cobalt nanorods, and their orientational properties under a magnetic field. These new materials exhibit the original combination of orientational behavior and ferromagnetic properties at room temperature. Here we show that, within the liquid crystal polymer matrix, the cobalt nanorods self-assemble in bundles made of nanorod rows packed in a 2-dimensional hexagonal lattice.

Large scale production of biocompatible magnetite nanocrystals with high saturation magnetization values through green aqueous synthesis.

In this work, a straightforward aqueous synthesis for mass production (up to 20 g) of uniform and crystalline magnetite nanoparticles with core sizes between 20 and 30 nm, which are the optimum nanoparticle core sizes for hyperthermia applications, is proposed. Magnetic and heating properties have been analyzed showing very high saturation magnetization and magnetic heating values. To stabilize the naked magnetite nanocrystals at physiological pH and increase their circulation time in blood, they have been covalently coated with carboxymethyl dextran, a biocompatible polymer.

Nano-electromanipulation of spin crossover nanorods: towards switchable nanoelectronic devices.

The nanoscale manipulation and charge transport properties of the [Fe(Htrz)2(trz)](BF4) spin-crossover compound is demonstrated. Such 1D spin-crossover nanostructures are attractive building blocks for nanoelectronic switching and memory devices.

Ultrasensitive magnetometers based on carbon-nanotube mechanical resonators.

We describe herein how a nanoelectromechanical system based on a carbon nanotube used as a force sensor can enable one to assess the magnetic properties of a single and very small nano-object grafted onto the nanotube. Numerical simulations performed within the framework of the Euler-Bernoulli theory of beams predict that the magnetic field dependence of the nanotube mechanical resonance frequency is a direct probe for the nano-object magnetic properties and that a sensitivity around a few (few hundreds) Bohr magnetic moments at low temperature (room temperature) can be expected.

Ultrafine metallic Fe nanoparticles: synthesis, structure and magnetism.

The results of the investigation of the structural and magnetic (static and dynamic) properties of an assembly of metallic Fe nanoparticles synthesized by an organometallic chemical method are described. These nanoparticles are embedded in a polymer, monodisperse, with a diameter below 2 nm, which corresponds to a number of around 200 atoms. The X-ray absorption near-edge structure and Mössbauer spectrum are characteristic of metallic Fe.

Magnetic configurations of 30 nm iron nanocubes studied by electron holography.

Ferromagnetic nanomaterials exhibit unique magnetic properties common to materials with dimensions approaching the atomic scale and have potential applications in magnetic data storage. Technological applications, however, require that the detailed magnetic behaviors and configurations of individual and interacting magnetic nano-objects be clarified. We determined the magnetic remnant configurations in single crystalline 30 nm Fe nanocubes and groups of nanocubes using off-axis electron holography in a transmission electron microscope.