Insertion study of alkali metal cations into layered vanadium oxide foam

The reaction of inorg. ions (Li+, Na+, and K+) with the lamellar material of compn. (V2O5)​(C16H33NH2)​1.3 under reflux conditions in alc.-​water mixed medium results in the rapid and quant. displacement of the surfactant to form inorg. ions intercalated vanadium oxides. The products were characterized by employing powder X-​ray diffraction (PXRD)​, Fourier transform IR (FTIR)​, thermogravimetric​/DTA (TG​/DTA)​, and SEM (SEM)​. FTIR and thermal studies showed the displacement of surfactants by inorg. ions during ion-​exchange process. The XRD peaks obsd. at lower and wider 2θ angles reflect the interlayer sepn. and crystallinity of the host vanadium oxide framework

Morphological Evolution of (NH4)0.5V2O5·mH2O Fibers into Belts, Triangles, and Rings

In this contribution, single-crystalline (NH4)0.5V2O5·mH2O xerogels made of belts, rings, triangles, and ovals have been synthesized using a surfactant-free hydrothermal method. The analytical techniques of scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR), high-resolution TEM (HRTEM), and selected area electron diffraction (SAED) have been used to characterize the morphology, composition, and structure of the as-prepared products. On the basis of SEM and TEM observations, we suggested that the as-prepared (NH4)0.5V2O5·mH2O rings, triangles, and ovals have been formed by connecting two ends of the vanadium oxide sheet made of edge and corner sharing VO5 square pyramids. The as-prepared (NH4)0.5V2O5·mH2O nanobelts are up to several hundreds of micrometers long, 402–551 nm wide, and 235–305 nm thick. The thickness and width of the rings are respectively 454 nm and 1 μm. Triangles with three unequal sides having a thickness of 143 nm and a width of 1 μm were also formed. The crystalline orthorhombic phase of shcherbianite V2O5 was obtained on calcination of (NH4)0.5V2O5·mH2O at 350 °C for 2 h. The SEM image of this V2O5 product retains the parent morphology of the preheated compound. A possible reaction mechanism and the growth process involved in the formation of belts/rings/triangles and ovallike microstructures are discussed

Synthesis and structural characterization of a new macrocyclic polysiloxane-immobilized ligand system

A new porous solid macrocyclic 1,4,7,11,14-pentaazapentadecane-3,15-dione polysiloxane ligand system of the general formula P–(CH2)3–C11H22O2N5 (where P represents [Si–O] n siloxane network) has been prepared by the reaction of polysiloxane-immobilized iminobis(N-(2-aminoethyl)acetamide) with 1,3-dibromopropane. The FTIR and XPS results confirm the introduction of the macrocyclic functional ligand group into the polysiloxane network. The new macrocyclic polysiloxane ligand system exhibits high potential for the uptake of metal ions (Fe3+, Co2+, Ni2+, Cu2+ and Zn2+)

Crystallographic and structural transformations of sedimentary chalcedony in flint upon heat treatment

International audienceThe early occurrence of intentional heat treatment of silica rocks has recently become a key element in the discussion about the cultural modernity of prehistoric populations. Lithic vestiges are the only sources that remain of this process and the understanding of the material's properties and transformations are essential for reconstructing the conditions and parameters applied during heat treatment. Several models of the structural transformations upon heating have been proposed in the current literature. These models are often contradictory and do not account for the most recent structural and mineralogical data on chalcedony. In order to propose a new model, we elaborated an experimental procedure and applied different techniques involving infrared spectroscopy, solid state NMR, X-ray diffraction and electron microscopy. The results show that the major transformation to happen is the loss of silanole (SiOH) and the creation of new Si-O-Si bonds according to the reaction: Si-OH HO-Si -> Si -O-Si + H2O. This reaction starts between 200 degrees C and 300 degrees C and causes an increase in the hardness of the rocks. The maximal annealing temperature and the ramp rate are the functions of the ability of the structure to evacuate newly created H2O and depend on the size of the specimen and the volume of its porosity. These results also show that the annealing duration at maximum temperature can be relatively short (<50 min) for a sufficiently large amount of transformation to be accomplished

Editorial: Biogeochemistry and Genomics of Silicification and Silicifiers

International audienc

In vitro studies and preliminary in vivo evaluation of silicified concentrated collagen hydrogels

Hybrid and nanocomposite silicacollagen materials derived from concentrated collagen hydrogels were evaluated in vitro and in vivo to establish their potentialities for biological dressings. Silicification significantly improved the mechanical and thermal stability of the collagen network within the hybrid systems. Nanocomposites were found to favor the metabolic activity of immobilized human dermal fibroblastswhile decreasing the hydrogel contraction. Cell adhesion experiments suggested that in vitro cell behavior was dictated by mechanical properties and surface structure of the scaffold. First-to-date in vivo implantation of bulk hydrogels in subcutaneous sites of rats was performed over the vascular inflammatory period. These materials were colonized and vascularized without inducing strong inflammatory response. These data raise reasonable hope for the future application of silicacollagen biomaterials as biological dressings.Fil: Desimone, Martín Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Hélary, Christophe. Université Pierre et Marie Curie; FranciaFil: Quignard, Sandrine. Université Pierre et Marie Curie; FranciaFil: Rietveld, Ivo B. Universite de Paris; FranciaFil: Bataille, Clement. Université de Versailles Saint-quentin-en-yvelines.; FranciaFil: Copello, Guillermo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Mosser, Gervaise. Université Pierre et Marie Curie; FranciaFil: Giraud Guille, Marie-Madeleine. Université Pierre et Marie Curie; FranciaFil: Livage, Jacques. Université Pierre et Marie Curie; FranciaFil: Meddahi Pellé, Anne. Université de Versailles Saint-quentin-en-yvelines.; FranciaFil: Coradin, Thibaud. Université Pierre et Marie Curie; Franci