Composition Effect on the Formation of Oxide Phases by Thermal Decomposition of CuNiM(III) Layered Double Hydroxides with M(III) = Al, Fe.

The thermal decomposition processes of coprecipitated Cu-Ni-Al and Cu-Ni-Fe hydroxides and the formation of the mixed oxide phases were followed by thermogravimetry and derivative thermogravimetry analysis (TG - DTG) and in situ X-ray diffraction (XRD) in a temperature range from 25 to 800 °C. The as-prepared samples exhibited layered double hydroxide (LDH) with a rhombohedral structure for the Ni-richer Al- and Fe-bearing LDHs and a monoclinic structure for the CuAl LDH. Direct precipitation of CuO was also observed for the Cu-richest Fe-bearing samples. After the collapse of the LDHs, dehydration, dehydroxylation, and decarbonation occurred with an overlapping of these events to an extent, depending on the structure and composition, being more pronounced for the Fe-bearing rhombohedral LDHs and the monoclinic LDH. The Fe-bearing amorphous phases showed higher reactivity than the Al-bearing ones toward the crystallization of the mixed oxide phases. This reactivity was improved as the amount of embedded divalent cations increased. Moreover, the influence of copper was effective at a lower content than that of nickel.

Tunable vegetable oil/silica hybrid microparticles for poorly water-soluble drug delivery.

To encapsulate and deliver poorly water-soluble drugs, castor oil/silica hybrid microparticles (HMP)s were synthesized. Green chemistries were used to silylate the oil and further cross-link it into solid microparticles by sol-gel reaction. Silylated castor oils (ICO)s at various silylation ratios were prepared and allowed the solubilization of ibuprofen at several concentrations up to 16 wt%. The HMPs were formulated by ThermoStabilized Emulsion (TSE) process which permits to "freeze" the oil-in-water emulsion while the sol-gel reaction occurs. The hybrid mineral/organic composition and the morphology (spherical shape and micrometric size) of these HMPs were determined by complementary technics (SEM, TGA, EDX, 29Si NMR and FTIR spectroscopies). The HMPs reached a good ibuprofen loading efficiency regardless to the formulation used while the release kinetics in simulated oral administration exhibited a tunable release during 3 h according to the silylation ratio. The ibuprofen rate also influenced its own amorphous or crystalline character within the HMPs. For subcutaneous conditions, ibuprofen release took place over 15 days. Finally, biodegradability assays in simulated digestion medium suggested a surface-limited hydrolysis of the particles and cytocompatibility studies on NIH-3T3 and Caco-2 cells demonstrated an excellent cellular viability.

pH-mediated control over the mesostructure of ordered mesoporous materials templated by polyion complex micelles.

Ordered mesoporous silica materials were prepared under different pH conditions by using a silicon alkoxide as a silica source and polyion complex (PIC) micelles as the structure-directing agents. PIC micelles were formed by complexation between a weak polyacid-containing double-hydrophilic block copolymer, poly(ethylene oxide)-b-poly(acrylic acid) (PEO-b-PAA), and a weak polybase, oligochitosan-type polyamine. As both the micellization process and the rate of silica condensation are highly dependent on pH, the properties of silica mesostructures can be modulated by changing the pH of the reaction medium. Varying the materials synthesis pH from 4.5 to 7.9 led to 2D-hexagonal, wormlike or lamellar mesostructures, with a varying degree of order. The chemical composition of the as-synthesized hybrid organic/inorganic materials was also found to vary with pH. The structure variations were discussed based on the extent of electrostatic complexing bonds between acrylate and amino functions and on the silica condensation rate as a function of pH.

Supramolecular Chemistry-Driven Preparation of Nanostructured, Transformable, and Biologically Active Chitosan-Clustered Single, Binary, and Ternary Metal Oxide Bioplastics.

Aside from their economical cost and resource depletion, petroleum-based plastics generate annually a substantial amount of waste with a negative and extremely alarming impact on the environment and public health. Consequently, rising interest was devoted to search for biobased materials to find sustainable alternatives. Herein, we report a new and straightforward method to incorporate endogenous nano-objects (exemplified herein by metal oxide clusters) within polysaccharide-based films. Supramolecular chemistry based on polysaccharide self-assembly associated with the sol-gel polymerization allowed converting soluble chitosan and metal alkoxide precursors to nanostructured chitosan-clustered metal oxide films. A broad range of discrete single, binary, and ternary mixed metal oxides was successfully incorporated in the resulting bioplastics. The multifaceted use of these films was demonstrated by transforming them under gentle thermal treatment to partially oxidized chitosan-metal oxide materials or by disintegrating them in aqueous conditions to yield stable, water-dispersed chitosan-coated-metal oxide nanoparticles. The utility of these functional films was demonstrated through their use as antimicrobial agents, where significant improvement for inhibiting growth of positive and negative bacteria was observed compared to native, nonmodified chitosan films.

Revelation on the Complex Nature of Mesoporous Hierarchical FAU-Y Zeolites.

The texture of mesoporous FAU-Y (FAUmes) prepared by surfactant-templating in basic media is a subject of debate. It is proposed that mesoporous FAU-Y consists of: (1) ordered mesoporous zeolite networks formed by a surfactant-assisted zeolite rearrangement process involving local dissolution and reconstruction of the crystalline framework, and (2) ordered mesoporous amorphous phases as Al-MCM-41, which coexist with zeolite nanodomains obtained by a dissolution-reassembly process. By the present systematic study, performed with FAU-Y (Si/Al = 15) in the presence of octadecyltrimethylammonium bromide and 0 < NaOH/Si ratio < 0.25 at 115 °C for 20 h, we demonstrate that mesoporous FAU zeolites consist, in fact, of a complex family of materials with textural features strongly impacted by the experimental conditions. Two main families have been disclosed: (1) for 0.0625 < NaOH/Si < 0.10, FAUmes are ordered mesoporous materials with zeolite walls, which coexist with zeolite nanodomains (100-200 nm) and (2) for 0.125 < NaOH/Si < 0.25, FAUmes are ordered mesoporous materials with amorphous walls as Al-MCM-41, which coexist with zeolite nanodomains (5-100 nm). The zeolite nanodomains decrease in size with the increase of NaOH/Si ratio. Increasing NaOH/Si ratio leads to an increase of mesopore volume, while the total surface area remains constant, and to a decrease of strong acidity in line with the decrease of micropore volume. The ordered mesoporous materials with zeolite walls feature the highest acidity strength. The ordered mesoporous materials with amorphous walls present additional large pores (50-200 nm), which increase in size and amount with the increase of NaOH/Si ratio. This alkaline treatment of FAU-Y represents a way to obtain ordered mesoporous materials with zeolite walls with high mesopore volume for NaOH/Si = 0.10 and a new way to synthesize mesoporous Al-MCM-41 materials containing extralarge pores (50-200 nm) ideal for optimal diffusion (NaOH/Si = 0.25).

Sodium and acidic alginate foams with hierarchical porosity: Preparation, characterization and efficiency as a dye adsorbent.

A novel approach for the preparation of sodium alginate foams by ice-templating, followed by freeze-drying was described. Important effects of the preparation parameters on the macroporous structure of the final materials could be evidenced. A functionalization procedure for the preparation of acidified macro/meso-porous foams with high surface area was optimized and the efficiency of one alginic acid foam was demonstrated for the adsorption of a basic dye (methylene blue) from aqueous solution. The comparison of the maximum monolayer adsorption capacity of this adsorbent with the values already reported for other biosorbents clearly identified alginic acid foams as competitive sorbents for the removal of methylene blue from aqueous solutions.

Spray-dried solid dispersions of nifedipine and vinylcaprolactam/vinylacetate/PEG6000 for compacted oral formulations.

The aim of this work was to investigate an alternative processing technology for a new polymeric solubilizer used mainly in hot melt extrusion. Poorly soluble nifedipine was co-processed through spray-drying with poly(vinyl caprolactam-co-vinyl acetate-co-ethylene glycol) (PVCVAEG) in different ratios. The resulting spray-dried powders were formulated and compacted into tablets forms. Spray drying produced reduced smooth spherical particles with PVCVAEG and more rough surfaces without PVCVAEG. Crystallinity of the co-processed nifedipine with the polymeric solubilizer was reduced. Plasticization of the polymeric solubilizer was observed with increasing drug content. Diffraction patterns in the small angle region as well as transmission electron microscopy showed results supporting phase separation throughout the spray dried particles of high drug content. Compaction with PVCVAEG improved cohesiveness of spray-dried compacts. Heckel modeling showed that deformation of PVCVAEG containing powders was more plastic compared than brittle nifedipine powders. Dissolution kinetics of all spray-dried samples was improved compared to original nifedipine crystals. Co-processed nifedipine with PVCVAEG did not show improved dissolution rate when compared to spray drying nifedipine alone. All though PVCVAEG is more commonly co-processed with drugs by hot melt extrusion to produce solid dispersions, the results show that it also can be processed by spray drying to produce solid dispersions. PVCVAEG improved compactibility of formulated spray dried powders.

Pseudomorphic synthesis of mesoporous zeolite Y crystals.

A simple method for the conception of mesoporous zeolite Y crystals with a narrow intracrystalline mesopore size distribution is reported. It involves the pseudomorphic transformation of parent zeolite crystals by recrystallisation in the presence of surfactants, and leads to two interconnected pore systems in the zeolite crystals.

One step synthesis of highly crystalline and high coercive cobalt-ferrite nanocrystals.

Highly crystalline and almost monodisperse spinel cobalt-ferrite nanocrystals are synthesized in a one step process, which has very high coercivity at 10 K and exhibits superparamagnetic behaviour at 300 K.