Direct synthesis of mesoporous silica containing cobalt: A new strategy using a cobalt soap as a co-template

A novel approach to incorporate transition metals into porous structures is presented, which makes use of a cobalt soap in combination with the templating agent C16TMABr. An ordered mesoporous silica MCM-41 type material doped with Co is obtained after removal of the organic part by calcination. The a unit cell parameter of the cobalt containing mesoporous matrices is larger than that of pure MCM-41 and increases with the amount of cobalt present in the sample as well as the diameter of the pores. This is not observed when e.g. cobalt acetate is employed instead of the metal soap. The procedure presented establishes a new route for the incorporation of a transition metal into MCM-41 together with a tuning of the porous structure

Tunable synthesis of Prussian Blue in exponentially growing polyelectrolyte multilayer films.

Polyelectrolyte multilayer (PEM) films have become very popular for surface functionalization and the design of functional architectures such as hollow polyelectrolyte capsules. It is known that properties such as permeability to small ionic solutes are strongly dependent on the buildup regime of the PEM films. This permeability can be modified by tuning the ionization degree of the polycations or polyanions, provided the film is made from weak polyelectrolytes. In most previous investigations, this was achieved by playing on the solution pH either during the film buildup or by a postbuildup pH modification. Herein we investigate the functionalization of poly(allylamine hydrochloride)/poly(glutamic acid) (PAH/PGA) multilayers by ferrocyanide and Prussian Blue (PB). We demonstrate that dynamic exchange processes between the film and polyelectrolyte solutions containing one of the component polyelectrolyte allow one to modify its Donnan potential and, as a consequence, the amount of ferrocyanide anions able to be retained in the PAH/PGA film. This ability of the film to be a tunable reservoir of ferrocyanide anions is then used to produce a composite film containing PB particles obtained by a single precipitation reaction with a solution containing Fe(3+) cations in contact with the film. The presence of PB in the PEM films then provides magnetic as well as electrochemical properties to the whole architecture.journal article2009 Dec 15importe

Lamellar nickel hydroxy-halides: anionic exchange synthesis, structural characterization and magnetic behavior:

Nickel-layered hydroxy-halides LHS-Ni-X (X = Cl, Br, and I) have been prepared by exchange reactions conducted in an aqueous medium under an inert atmosphere starting from the parent nickel-layered hydroxyacetate. The latter was prepared by a hydrolysis reaction conducted in a polyol medium. IR and X-ray diffraction (XRD) studies show total exchange. These compounds exhibit a brucite-like structure with a turbostratic nature. Their interlamellar distance varies linearly with the radius of the halide anion in the range 7.9-8.7 angstrom while the hydroxyacetate interlamellar distance is 10.53 angstrom. In comparison with the acetate ion which replaces hydroxyl groups in the brucite-like layer, EXAFS and XRD investigations show that halide ions are intercalated into the interlayer space along with water molecules without any covalent bonding to the nickel ion. All compounds have similar structural features and can be considered as alpha-type nickel hydroxides, alpha-Ni(OH)(2). These compounds exhibit a ferromagnetic character. The latter is discussed on the basis of the Drillon-Panissod model of ferromagnetic layers interacting via dipole interactions and taking into account the structural features established by XANES and XRD studies along with the intrinsic properties of the halide anions

Magnetic and luminescent coordination networks based on imidazolium salts and lanthanides for sensitive ratiometric thermometry

The synthesis and characterization of six new lanthanide networks [Ln(L)(ox)(H2O)] with Ln = Eu3+, Gd3+, Tb3+ , Dy3+ , Ho3+ and Yb3+ is reported. They were synthesized by solvo-ionothermal reaction of lanthanide nitrate Ln(NO3)(3)center dot xH(2)O with the 1,3-bis(carboxymethyl)imidazolium [HE] ligand and oxalic acid (H(2)ox) in a water/ethanol solution. The crystal structure of these compounds has been solved on single crystals and the magnetic and luminescent properties have been investigated relying on intrinsic properties of the lanthanide ions. The synthetic strategy has been extended to mixed lanthanide networks leading to four isostructural networks of formula [Tb1-xEux(L)(ox)(H2O)] with x = 0.01, 0.03, 0.05 and 0.10. These materials were assessed as luminescent ratiometric thermometers based on the emission intensities of ligand, Tb3+ and Eu3+ . The best sensitivities were obtained using the ratio between the emission intensities of Eu3+ (D-5(0) -> F-7(2) transition) and of the ligand as the thermometric parameter. [Tb0.97Eu0.03 (L)(ox)(H2O)] was found to be one of the best thermometers among lanthanide-bearing coordination polymers and metal-organic frameworks, operative in the physiological range with a maximum sensitivity of 1.38%.K-1 at 340 K

Etude cristallochimique des composes a structure composite incommensurable (LnS)_nNbS_2 (Ln: Yttrium, elements terre-rare)

SIGLEINIST T 73549 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Nanomatériaux, nanotechnologies: quel nanomonde pour le futur?

Chapitre de livreCe chapitre traite de nanomatériaux et de nanostructures, essentiellement artificiels, élaborés et manipulés avec des moyens beaucoup plus compliqués et beaucoup plus lourds que ce que fait la nature

Matériaux hybrides multifonctionnels (Elaboration et propriétés d'hydroxydes lamellaires de métaux de transition magnétiques et luminescents)

STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

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Synthèse, études structurales et magnétiques d'a-hydroxy carboxylates de métaux de transition

Ce travail de thèse porte sur la synthèse solvothermale, la caractérisation structurale et l étude magnétique de familles de composés de coordination de métaux de transition et de ligands chiraux de type -hydroxy carboxylate. Avec l acide mandélique, nous avons obtenu une série iso-structurale de 5 composés de coordination avec les ions MnII, FeII, CoII, NiII, CuII. Ils possèdent une structure lamellaire. Les produits à base de MnII, FeII, CoII, CuII ont montré un comportement antiferromagnétique en revanche, le produit au nickel présente un comportement ferromagnétique. Avec l acide méthoxy-mandélique, trois nouveaux produits ont été obtenus. Les structures des produits au cobalt et au cuivre correspondent à des chaînes isolées formant des plans, alors que le produit au nickel a été obtenu sous forme de poudre. Un comportement antiferromagnétique est observé pour le produit au cobalt, alors que le méthoxy mandélate de cuivre présente un comportement ferromagnétique. Le produit au nickel a un comportement analogue à celui d'ions NiII isolés. Avec l acide malique, nous avons obtenu 13 produits et nous avons mis en évidence une nouvelle famille de malates de métaux de transition chiraux. Plusieurs types de structures ont été obtenus avec des taux d'hydratation variables. Ces structures présentent diverses dimensionnalités magnétique (1D à 3D). Des produits magnétiques et chiraux ont pu être obtenus dont les spectres de dichroïsme à l état solide indiquent un transfert de chiralité du ligand au centre magnétique. Les propriétés magnétiques de tous les composés ont été analysées en détail et interprétées sur la base de leurs structures cristallines. Le dernier ligand utilisé est l acide citramalique. Nous avons pu synthétiser 3 nouveaux composés à base de MnII, CoII, NiII. Ses produits présentent des comportements magnétiques très différents. Des mesures de dichroïsme effectuées sur le composé au cobalt.This thesis concerns the solvothermal synthesis, the structural and magnetic characterization of families of coordination polymers based on transition metals and -hydroxy carboxylate type chiral ligands. With the mandelic acid, we obtained a series of 5 iso-structural compounds with the ions MnII, FeII, CoII, NiII, CuII. Their crystal structure consists in layers of 6-coordinated metal(II) ions, thus forming planar arrays of octahedra interconnected through carboxylato bridges. From the magnetic point of view, antiferromagnetic interactions between neighboring M(II) ions is observed for the series of transition metal mandelates except the nickel derivative for which a ferromagnetic behavior is observed. Methoxy-mandelic acid, three new products were obtained. The structures of the cobalt and copper products correspond to isolated chains forming planes. The nickel product was obtained as a powders. An antiferromagnetic behavior is observed for the cobalt product, whereas the copper methoxy mandelate presents a ferromagnetic behavior. The nickel compound has a behavior similar to that of isolated NiII ions. With the malic acid we obtained 13 compounds, and we highlighted a new family of chiral transition metal malates. Several types of structures were obtained with variable rates of hydration. These structures present various magnetic dimensionnalities (1D to 3D). No racemization was observed and magnetic chiral compounds could be obtained. The dichroic spectra in the solid state indicate a transfer of chirality from the ligand to the magnetic center. The magnetic properties of all the compounds were analyzed in detail and were interpreted on the basis of their crystal structure. The last ligand used was citramalic acid. We could synthesize 3 new MnII, CoII, NiII compounds. In spite of very close structures, these products show very different magnetic behaviors. Dichroism measurements on the cobalt compound showed a chirality transfer from the ligand to the magnetic center.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF