Gas Permeation Characteristics of TiO2-ZrO2-Aromatic Organic Chelating Ligand (aOCL) Composite Membranes

Methyl gallate (MG) and ethyl ferulate (EF) with a benzene ring were separately used as aromatic organic chelating ligands (aOCLs) to prepare two versions of TiO2-ZrO2-aOCL composite sols via hydrolysis and polycondensation reactions with titanium(IV) isopropoxide (Ti(OC3H7)4) and zirconium(IV) butoxide (Zr(OC4H9)4). Thermogravimetric and FT-IR analysis of dry gels revealed that aromatic rings were present in the residual organic matter when the gel was fired under nitrogen at 300 °C. In X-ray diffraction (XRD) measurements, the TiO2-ZrO2 composite material prepared using these two aOCLs showed an amorphous structure with no crystalline peaks for TiO2 and ZrO2. In N2 adsorption/desorption measurements at 77 K, the TiO2-ZrO2 samples using the aOCLs as a template appeared porous with a larger specific surface area than TiO2-ZrO2 without aOCL. TiO2-ZrO2-aOCL composite membranes were prepared by coating and firing TiO2-ZrO2-aOCL sol onto a SiO2 intermediate layer using an α-alumina porous tube as a substrate. Compared with the TiO2-ZrO2 membrane, the TiO2-ZrO2-aOCL membranes had higher gas permselectivity. The TiO2-ZrO2-EF membrane showed a He permeance of 2.69 × 10−6 mol m−2 s−1 Pa−1 with permeance ratios of He/N2 = 10.6 and He/CF4 = 163, while the TiO2-ZrO2-MG membrane revealed a bit less He permeance at 8.56 × 10−7 mol m−2 s−1 Pa−1 with greater permeance ratios of He/N2 = 61.7 and He/CF4 = 209 at 200 °C. A microporous TiO2-ZrO2 amorphous structure was obtained by introducing aOCL. The differences in the side chains of each aOCL could possibly account for the differences in the microporous structures of the resultant TiO2-ZrO2-aOCL membranes.

Catalysis and specificity of the polycondensation of aminopropyltrimethoxysilane on nucleic acids

The polycondensation of a silane derivative such as aminopropyltrimethoxysilane (ATMS) in the presence of nucleic acids has never been investigated. Our group has previously demonstrated that in chloroform ATMS hydrolysis and polycondensation were faster when the reaction were carried out in the presence of double stranded DNA (146 bp). The results showed that the kinetics of ATMS hydrolysis was affected by the base type used, a fast hydrolysis reaction rate being observed with nucleotide molecules containing adenosine group, and that in the absence of water the amino group of deoxyadenosine units, and not the hydroxylic group of the sucrose residue, can react with ATMS methoxy groups. The present work was initiated aiming at providing a better understanding of this effect. It was observed that the polymerization degree of oligodeoxyadenylate has a clear impact on the kinetic of reaction this effect being as much important as the polymerization degree of the oligodeoxyadenylate was high. Structural investigation by molecular modeling showed that this enhanced reactivity can be explained by conformational effects. Altogether, these results are accounted for assuming that DNA can act as a specific template for ATMS polycondensation, in organic medium such as chloroform, opening the way to possible DNA encapsulation, and a new way for DNA chemical modification in organic solvent.

Hierarchically porous monoliths based on low-valence transition metal (Cu, Co, Mn) oxides: gelation and phase separation

Hierarchically porous monoliths based on copper (Cu), cobalt (Co) and manganese (Mn) oxides with three-dimensionally (3D) interconnected macropores and open nanopores were prepared using metal bromides as precursors via a sol–gel process accompanied by phase separation. The difficulty of gelation for low-valence metal cation was overcome by introducing a highly electronegative Br atom near to the metal atom to control the rates of hydrolysis and polycondensation. The 3D interconnected macropores were obtained using appropriate polymers to induce phase separation. The domain sizes of macropores and skeletons can be controlled by reaction parameters such as concentration and/or average molecular weight of polymers, and the amount of hydrochloric acid. The crystalline metal oxide monoliths with their 3D interconnected macroporous structure preserved were obtained after heat treatment in air.

The Mechanisms of Nickel-Iron Spinel Phase Nucleation in Aquous Solutions: Crystal Quasichemical Approach

The phenomenological model of nikel-iron spinel nucleation with spinel structure based on the partial charge theory and analysis of hydrolysis and polycondensation processes at the interaction of Fe3+-, Fe2+- and Ni2+- hydroxocomplexes at different pH values of reaction medium was proposed. UV-vis optical spectroscopy was used for verification of the obtained results about the regularities of hydroxocomplexes formation. Crystal quasichemistry approach was applied for nucleation of nikel-iron spinel under the conditions of predomination of different defect types in NixFe3-xO4-δ (δ is oxygen non-stoichiometry) spinel lattice. The analysis of changes in electrical conductivity and lattice parameter of defect nickel-iron spinel as a function of Ni2+ atomic concentration was done for different values of d parameter.

New Layered Polythiophene-Silica Composite Through the Self-Assembly and Polymerization of Thiophene-Based Silylated Molecular Precursors

A new layered hybrid polythiophene-silica material was obtained directly by hydrolysis and polycondensation (sol-gel) of a silylated-thiophene bifunctional precursor, and its subsequent oxidative polymerization by FeCl3. This precursor was judiciously designed to guarantee its self-assembly and the formation of a lamellar polymer-silica structure, exploiting the cooperative effect between the hydrogen bonding interactions, originating from the ureido groups and the π-stacking interactions between the thiophene units. The lamellar structure of the polythiophene-silica composite was confirmed by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) analyses. The solid-state nuclear magnetic resonance (NMR), UV-Vis, and photoluminescence spectra unambiguously indicate the incorporation of polythiophene into the silica matrix. Our work demonstrates that using a polymerizable silylated-thiophene precursor is an efficient approach towards the formation of nanostructured conjugated polymer-based hybrid materials.

Monodispersed strontium containing bioactive glass nanoparticles and MC3T3-E1 cellular response

Non-porous monodispersed strontium containing bioactive glass (Si2O-CaO-SrO) nanoparticles (Sr- BGNPs), were synthesised using a modified Stöber process. Silica nanoparticles (Si-NPs) with diameters 90 ± 10 nm were produced through hydrolysis and polycondensation reactions of the silicon alkoxide precursor, tetraethyl orthosilicate (TEOS), prior to the incorporation of cations; calcium (Ca) and strontium (Sr), into the silica networks through heat treatment (calcination). Sr was substituted for Ca on a mole basis from non- (0SrBGNPs) to fullsubstitution (100SrBGNPs) in order to increase the amount of network modifiers in the Si-NPs. The different ratios of Si: Ca; 1:1.3 and 1:8.0, presented various elemental compositions (i.e. 77–92 mol% of SiO

Facile preparation of stable palygorskite/cationic red X-GRL@SiO2“Maya Red” pigments

We report the fabrication of stable “Maya Red” pigments with a purple-red hue by adsorption of cationic red X-GRL (CR-XGRL) onto palygorskite, which is followed by hydrolysis and polycondensation of tetraethoxysilaneviaa modified Stöber method to form a layer of SiO2.