Fabien Grasset

Magnetic nanoparticle design for medical diagnosis and therapy

Magnetic nanoparticles have attracted attention because of their current and potential usefulness as contrast agents for magnetic resonance imaging (MRI) or colloidal mediators for cancer magnetic hyperthermia. This review examines these in vivo applications through an understanding of the involved problems and the current and future possibilities for resolving them. A special emphasis is made on magnetic nanoparticle requirements from a physical viewpoint (e.g. relaxivity for MRI and specific absorption rate for hyperthermia), the factors affecting their biodistribution (e.g. size, surface hydrophobic/hydrophilic balance, etc.) and the solutions envisaged for enhancing their half-life in the blood compartment and targeting tumour cells.

Surface modification of zinc oxide nanoparticles by aminopropyltriethoxysilane

Commercial zinc oxide nanoparticles (20–30 nm) were coated by aminopropyltriethoxysilane (APTES) under varying environments. Three different processes, acidic, basic and toluene were used. The effects of coating conditions (acidic, basic and toluene) on the grafting, structural and optical properties of these nanoparticles were studied. In the three cases, it was possible to control the coating and according to X-ray diffraction, BET, TEM and SEM results, it is clear that the APTES coating plays a role of growth inhibitor even at 800 °C...

Functional silica nanoparticles synthesized by water-in-oil microemulsion processes.

Water-in-oil (W/O) microemulsion is a well-suitable confined reacting medium for the synthesis of structured functional nanoparticles of controlled size and shape. During the last decade, it allowed the synthesis of multi-functional silica nanoparticles with morphologies as various as core-shell, homogenous dispersion or both together. The morphology and properties of the different intermediates and final materials obtained through this route are discussed in the light of UV-Vis-NIR spectroscopy, dynamic light scattering (DLS) and X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and magnetometer SQUID analysis.

DNA-magnetite nanocomposite materials

It is shown here that magnetite nanoparticles can be associated with double-stranded DNA. In a first step, a complex of DNA with Fe 2q and Fe 3q ions is formed. qThen, in a second step, magnetite nanoparticles are formed by increasing the pH. As shown by electrophoresis, the nanoparticles are strongly attached to the nucleic acid. From TEM imaging and Mossbauer measurement, a tentative model for the textural organization of DNA and magnetite is proposed. q 2000 Elsevier ¨

One-pot synthesis and characterizations of bi-functional phosphor–magnetic @SiO2nanoparticles: controlled and structured association of Mo6 cluster units and γ-Fe2O3nanocrystals

Nanostructured silica coated bifunctional nanoparticles based on [Mo(6)Br(14)](2-) units as phosphorescent dye and magnetic gamma-Fe(2)O(3) nanocrystals were synthesized and characterized.

Synthesis, crystal structure and magnetic properties of A3A′RuO6 (A = Ca, Sr; A′ = Li, Na)

The compounds A{sub 3}A{prime}RuO{sub 6} (A = Ca, Sr; A{prime} = Li, Na) have been synthesized by solid state reactions and studied by x-ray powder diffraction and magnetometry. They all adopt the K{sub 4}CdCl{sub 6} (Sr{sub 4}PtO{sub 6}) structure with the cations A{prime} and Ru occupying the trigonal prismatic and octahedral sites respectively. Infinite chains of octahedra and trigonal prisms sharing faces run parallel to the c axis, the chains being separated by the cations A (Ca, Sr). The validity of this description of the structure is discussed in the light of magnetic susceptibility data which suggest that these phases all transform to a magnetically ordered state in the temperature range 70 < T/K < 120. Preliminary results of powder neutron diffraction experiments confirm the presence of long-range magnetic order in the low temperature phase.

Chalcogenide coatings of Ge15Sb20S65 and Te20As30Se50

Chalcogenide coatings are investigated to obtain either optical components for spectral applications or optochemical sensors in the mid-infrared. The deposition of Ge(15)Sb(20)S(65) and Te(20)As(30)Se(50) chalcogenide glasses is performed by two physical techniques: electron-beam and pulsed-laser deposition. The quality of the film is analyzed by scanning electron microscopy, atomic force microscopy, and energy dispersive spectroscopy to characterize the morphology, topography, and chemical composition. The optical properties and optical constants are also determined. A CF(4) dry etching is performed on these films to obtain a channeled optical waveguide. For a passband filter made by electron-beam deposition, cryolite as a low-refractive-index material and chalcogenide glasses as high-refractive-index materials are used to favor a large refractive-index contrast. A shift of a centered wavelength of a photosensitive passband filter is controlled by illumination time.

Selective oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran over intercalated vanadium phosphate oxides

The selective oxidation of 5-hydroxymethylfurfural (5-HMF) to 2,5-diformylfuran (DFF) was studied over vanadium phosphate oxide (VPO)-based heterogeneous catalysts in the liquid phase. The selectivity to DFF was highly increased when using intercalated vanadium phosphate oxides under mild conditions (1 atm of oxygen, 110 °C) in an aromatic solvent. We found that the length of the intercalated ammonium alkyl chain had no clear influence on the catalytic performances, and a maximum yield of 83% could be achieved over C14VOPO4 and C14VOHPO4 after 6 h of reaction. Recycling of the catalyst was successfully performed, and we further obtained some insights in the reaction pathway: while the desired oxidation reaction indeed proceeded over the catalyst, the formation of by-products was linked to the presence of free radicals in solution.

Root uptake and phytotoxicity of nanosized molybdenum octahedral clusters

Here are examined the root uptake and phytotoxicity of octahedral hexamolybdenum clusters on rapeseed plants using the solid state compound Cs(2)Mo(6)Br(14) as cluster precursor. [Mo(6)Br(14)](2-) cluster units are nanosized entities offering a strong and stable emission in the near-infrared region with numerous applications in biotechnology. To investigate cluster toxicity on rapeseed plants, two different culture systems have been set up, using either a water-sorbing suspension of cluster aggregates or an ethanol-sorbing solution of dispersed nanosized clusters. Size, shape, surface area and state of clusters in both medium were analyzed by FE-SEM, BET and XPS. The potential contribution of cluster dissolution to phytotoxicity was evaluated by ICP-OES and toxicity analysis of Mo, Br and Cs. We showed that the clusters did not affect seed germination but greatly inhibited plant growth. This inhibition was much more important when plants were treated with nanosized entities than with microsized cluster aggregates. In addition, nanosized clusters affected the root morphology in a different manner than microsized cluster aggregates, as shown by FE-SEM observations. The root penetration of the clusters was followed by secondary ion mass spectroscopy with high spatial resolution (NanoSIMS) and was also found to be much more important for treatments with nanosized clusters.

Crystal structures and magnetic properties of Ba4Ru3O10 and Ba5Ru3O12

Abstract The study of the solid state reactions in air or oxygen of the ternary system Ba-Ru-O shows the existence of the new compounds Ba4Ru3O10 and Ba5Ru3O12. The crystal symmetry of Ba4Ru3O10 is monoclinic (P21/a) with the unit cell constants a = 5.776(1) A , b = 13.076(1) A , c = 7.234(2) A and β = 113.53(3)°. Ba4Ru3O10 is isostructural with Ba4Ir3O10 and the structure consists of trinuclear groups [Ru3O12] of face-sharing octahedra two-dimensionally connected via terminal corners to form [Ru3O10] zig-zag layers. The magnetic properties confirm the oxidation state (Ru4+) of ruthenium. Ba5Ru3O12 is isostructural with Ba5(Ir1.5Ru1.5)O12 with the cell parameters a = 10.862(1) A , b = 5.893(1) A and c = 19.790(2) A (Pnma). The crystal structure was refined on the basis of a single crystal in which part of the ruthenium was replaced by platinum. The structure consists of isolated [Ru3O12] trimeric groups separated by barium atoms. Valence bond calculation confirms that the electronic charges are localized, and the magnetic behaviour is interpreted in terms of antiferromagnetic isolated trimeric units.