Zeolite-Polymer Composite Materials as Water Scavenger.

The influence of the charge compensating cation nature (Na, Mg) on the water adsorption properties of LTA-type zeolites used as filler in composite materials (zeolite/polymers) was investigated. Large scale cation exchanges were performed on zeolite powder at 80 °C for 2 h using 1 M magnesium chloride (MgCl) aqueous solutions. XRF, ICP, and EDX analyses indicate a successful cationic exchange process without the modification of the zeolite structure as shown by XRD and solid-state NMR analyses.

Grafting Diels-Alder moieties on cellulose nanocrystals through carbamation.

The Diels-Alder reaction is a promising click chemistry for the design of advanced materials from cellulose nanocrystals (CNCs). Transferring such chemistry to cellulose nanocrystals requires the precise grafting of reactive Diels-Alder moeities under heterogeneous conditions without compromising the nanocrystals morphology. In this study toluene diisocyanate is used as a spacer to graft Diels-Alder moieties viz the furyl and protected maleimido moieties onto cellulose nanocrystals.

Amorphous mesostructured zirconia with high (hydro)thermal stability.

Here, combining the evaporation-induced self-assembly (EISA) method and the liquid crystal templating pathway, mesostructured amorphous zirconium oxides have been prepared by a soft templating method without addition of any heteroelement to stabilize the mesopore framework. The recovered materials have been characterized by SAXS measurements, nitrogen adsorption-desorption analysis and X-ray diffraction (XRD). The obtained mesostructured zirconia exhibits a high thermal stability.

Influence of the Compensating Cation Nature on the Water Adsorption Properties of Zeolites.

The influence of the compensating cation (Na, Li, Mg) nature on the water adsorption properties of LTA and FAU-type zeolites was investigated. Cation exchanges were performed at 80 °C for 2 h using 1 M aqueous solutions of lithium chloride (LiCl) or magnesium chloride (MgCl). XRF and ICP-OES analyses indicate that the cation exchange yields reach values between 59 to 89% depending on the number of exchange cycles and the nature of the zeolite and cation, while both zeolites structures are preserved during the process, as shown by XRD and solid state NMR analyses.

Influence of framework Si/Al ratio and topology on electron transfers in zeolites.

H-ZSM-5 and H-*BEA zeolites were hydrothermally synthesized with different Si/Al ratios (∼12 to ∼40). The physico-chemical properties of the resulting materials were fully characterized by several techniques (NMR, BET, PXRD, and pyridine thermal desorption followed by infrared spectroscopy). To assess the effect of the zeolite type and Si/Al ratio on sample reactivity, the charge separation processes between the zeolite framework and the adsorbed trans-stilbene (t-St) molecule were investigated by UV-visible diffuse reflectance and FT-Raman spectroscopy.

Influence of hierarchization on electron transfers in structured MFI-type zeolites.

H-ZSM-5 zeolite (Si/Al = 19.3) was hydrothermally synthesized. Alkaline and/or acid post-synthesis treatments were carried out to give rise to an interconnected mesoporous volume.

Assessment of the energetic performances of various ZIFs with SOD or RHO topology using high pressure water intrusion-extrusion experiments.

The energetic performances of seven SOD or RHO-topology ZIFs, with zinc or cobalt metal cation (ZIF-8, ZIF-90, Zn(dcim)2-SALE, ZIF-67, ZIF-7, ZIF-71, ZIF-11) were evaluated using water intrusion-extrusion under high pressure. The relationship between the structural parameters (in particular the pore system SOD or RHO, the type of linker, the metal cation nature) and the intrusion pressure was studied to better understand the mechanism of water intrusion and the energetic behaviour for a given ZIF crystal type. "ZIF-8-water", "ZIF-67-water" and "ZIF-71-water" systems display a shock-absorber behaviour.

Enhanced interlayer trapping of a tetracycline antibiotic within montmorillonite layers in the presence of Ca and Mg.

The formation of a ternary antibiotic-metal-clay complex is hypothesized as the primary adsorption mechanism responsible for the increased adsorption of tetracycline antibiotics on smectites in the presence of divalent metal cations under circumneutral and higher pH conditions. To evaluate this hypothesis, we conducted a spectroscopic investigation of oxytetracycline (OTC) interacting with Na-montmorillonite in the presence and absence of Ca or Mg salts at pH 6 and pH 8. Despite a two-fold increase in OTC adsorbed in the presence of Ca or Mg, both solid-state nuclear magnetic resonance and infrared signatures of the OTC functional groups involved in metal complexation implied that the formation of an inner-sphere ternary complexation was not significant in stabilizing the adsorbate structures.

Origin of anomalous slip in tungsten.

Low-temperature deformation of body-centered cubic metals shows a significant amount of plastic slip on planes with low shear stresses, a phenomenon called anomalous slip. Despite progress in atomistic modeling of the consequences of complex stress states on dislocation mobility, the phenomenon of anomalous slip remained elusive. Using in situ Laue microdiffraction and discrete dislocation dynamics in micrometer sized tungsten single crystals, we demonstrate the occurrence of significant anomalous slip.

{110} Slip with {112} slip traces in bcc Tungsten.

While propagation of dislocations in body centered cubic metals at low temperature is understood in terms of elementary steps on {110} planes, slip traces correspond often with other crystallographic or non-crystallographic planes. In the past, characterization of slip was limited to post-mortem electron microscopy and slip trace analysis on the sample surface. Here with in-situ Laue diffraction experiments during micro-compression we demonstrate that when two {110} planes containing the same slip direction experience the same resolved shear stress, sharp slip traces are observed on a {112} plane.

Energetic performances of the metal-organic framework ZIF-8 obtained using high pressure water intrusion-extrusion experiments.

The "ZIF-8-water" system displays reproducible shock-absorber behaviour over several cycles with a stored energy of 13.3 J g(-1) and an energy yield close to 85%. The combination of the main features evidenced for ZIF-8, i.

A Novel Fluoride Route for the Synthesis of Aluminosilicate Nanotubes.

In this work we present a novel method for synthesis of aluminosilicate nanotubes: the fluoride route. F-containing imogolite (F-IMO) exhibits an improved crystallization rate and improved yield. The structure of F-IMO was investigated and compared with F-free imogolite (IMO) by means of X-ray diffraction (XRD) and Fourier transformed infrared spectroscopy (FTIR) confirming imogolite structure.

Interactions of oxytetracycline with a smectite clay: a spectroscopic study with molecular simulations.

Binding of antibiotics to clay minerals can decrease both their physical and biological availability in soils. To elucidate the binding mechanisms of tetracycline antibiotics on smectite clays as a function of pH, we probed the interactions of oxytetracycline (OTC) with Na-montmorillonite (MONT) using X-ray diffraction (XRD), infrared (IR), and solid-state nuclear magnetic resonance (NMR) spectroscopies, and Monte Carlo molecular simulations. The XRD patterns demonstrate the presence of OTC in the MONT interlayer space at acidic pH whereas complexation of OTC by external basal and edge sites seems to prevail at pH 8.

Multiarm cyclam-grafted mesoporous silica: a strategy to improve the chemical stability of silica materials functionalized with amine ligands.

We have explored in this work the stability and the reactivity of multiarm cyclam-grafted mesoporous silica samples in aqueous solution. A series of hybrid materials have been prepared by grafting silylated cyclam molecules bearing one, two, or four silyl groups onto both amorphous silica gel (K60) and ordered mesoporous silica (SBA15). Under these conditions, cyclam moieties are attached to the silica walls via one, two, or four arms.

Intrinsic porosity of calcium phosphate cements and its significance for drug delivery and tissue engineering applications.

One key point in the field of tissue engineering and drug delivery is to provide materials with an adequate porosity. Many events, including nutrient and waste exchange in scaffolds for tissue engineering, as well as the drug-loading capacity and control of the release rate in drug delivery systems, are controlled by the size, shape and distribution of the pores in the material. Calcium phosphate cements (CPCs) possess an intrinsic porosity that is highly suited for these applications, and this porosity can be controlled by modifying some processing parameters.

Efficient synthesis of dimethyl ether over HZSM-5 supported on medium-surface-area beta-SiC foam.

In this study, we aimed to produce a highly selective and stable catalyst for the production of dimethyl ether by methanol dehydration. The activities were compared of different active phases of the employed system, zeolite HZSM-5 or gamma-alumina, supported on silicon carbide as foam, and it was found that the supported zeolite catalysts are more active than and as selective as the alumina-based catalysts. The as-prepared zeolite/SiC composites reveal good stability in long-term tests in the presence or absence of steam.

Pure silica chabazite molecular spring: a structural study on water intrusion-extrusion processes.

Water intrusion-extrusion isotherms performed at room temperature on hydrophobic pure silica chabazite show that the water-Si-CHA system displays real spring behavior. However, differences in pressure-volume diagrams are observed between the first and the other intrusion-extrusion cycles, indicating that some water molecules interact with the inorganic framework after the first intrusion. (29)Si and especially (1)H solid-state NMR showed the creation of new defect sites upon the intrusion-extrusion of water and the existence of two kinds of water molecules trapped in the supercage of Si-CHA: a first layer of water strongly hydrogen bonded with the silanols of the framework and a subsequent layer of liquidlike physisorbed water molecules undergoing interaction with the first layer.

Tripling of the unit cell volume of the non-centrosymmetric AlPO4-SOD after dehydration: a structural study of a reversible process.

The structure of AlPO4-SOD, a microporous aluminophosphate synthesized in a quasi-nonaqueous system using dimethylformamide as template and solvent, was previously reported. Then, various solid state nuclear magnetic resonance techniques applied on the dehydrated compound at 200 degrees C were performed and suggested a rearrangement of one-third of the template molecules inside the sodalite cages and a tripling of the unit cell parameter c. We present here the structure determined from molecular modeling and Rietveld analysis on synchrotron data of AlPO4-SOD dehydrated under vacuum at 100 degrees C together with some solid state NMR experiments of the rehydrated product.

One-step synthesis and solvent-induced exfoliation of hybrid organic-inorganic phyllosilicate-like materials.

A room-temperature sol-gel-based process was used to produce by direct synthesis talc-like organosilicates having hexadecyl or aminopropyl groups pending in the interlayer space. Thermal analyses, Fourier transform infrared and 13C/29Si solid-state nuclear magnetic resonance spectroscopies confirmed the presence of organic moieties bonded to the inorganic network. Exfoliation of these organoclays in polar solvents such as water for the positively charged magnesium phyllo(aminopropyl)silicate, and in low polar solvents such as toluene and chloroform for hydrophobic magnesium phyllo(hexadecyl)silicate, was investigated by TEM.

Fluorescence probing investigation of the mechanism of formation of MSU-type mesoporous silica prepared in fluoride medium.

The mechanism of formation of a MSU-type siliceous material from tetraethyl orthosilicate (TEOS) in the presence of the nonionic surfactant tergitol T-15-S-12, sulfuric acid, and sodium fluoride has been investigated using mainly fluorescence probing techniques and, to a lesser extent, dynamic light scattering (DLS) and 29Si NMR spectroscopy. The tergitol micelles present in the systems obtained by progressively generating the reaction mixture giving rise to the mesostructured material by adding to an appropriate tergitol solution sulfuric acid, TEOS, and NaF were characterized by fluorescence probing (micelle aggregation number, micropolarity, and microviscosity) and also by dynamic light scattering (apparent micelle diameter). 29Si NMR experiments were also performed on selected systems after hydrolysis of the TEOS.

X-[1H, 19F] triple resonance with a X-[1H] CP MAS probe and characterisation of a 29Si-19F spin pair.

An economic approach for implementing X-[1H,19F] double-decoupling MAS NMR experiments with a conventional X-[1H] dual-channel CP MAS probe is demonstrated. The parameters characterising the isolated 29Si-19F spin pair in an organosilicon compound R(3)SiF (R = 9-anthryl) are determined. In addition, we discuss the optimum choice of experimental parameters for determining all 29Si-19F spin-pair parameters from straightforward 29Si MAS NMR spectra with only 1H decoupling applied during acquisition.

Double-quantum filtered MAS NMR in the presence of chemical shielding anisotropies and direct dipolar and J couplings.

Double-quantum filtered MAS NMR spectra of an isolated homonuclear spin-1/2 pair are considered, at and away from rotational resonance conditions. The pulse sequence used is the solid-state NMR equivalent of double-quantum filtered COSY, known from solution-state NMR. The 119Sn spin pair in [(chex3Sn)2S] is characterized by a difference in isotropic chemical shielding smaller than the two chemical shielding anisotropies and by direct dipolar and isotropic J-coupling constants of similar magnitudes.

Gene expression in an intact ex-vivo skin tissue model following percutaneous delivery of cationic liposome-plasmid DNA complexes.

The skin represents an attractive site for the localised gene therapy of dermatological pathologies and as a potential antigen bioreactor following transdermal delivery. Potential also exists for the gene therapy of skin as a cosmetic intervention. The most exploited non-viral gene delivery system involves the complexation of cationic liposomes with plasmid DNA (pDNA) to form lipid:pDNA vectors that protect the DNA from nuclease-mediated degradation and improve transgene-cell interactions.

51V magic-angle-spinning NMR and electric field gradient calculations in V2O5 and gamma-LiV2O5 crystals.

51V Magic-angle-spinning (MAS) NMR has been applied to V2O5 at two different magnetic field strengths (4.7 and 7.1 T).