New Class Of Hybrid Materials Research Articles

Metal–organic frameworks as potential drug carriers

Nanoparticle-based therapeutics have received increasing attention, as these systems can alleviate many drawbacks of conventional therapy. Metal-organic frameworks (MOFs), a new class of hybrid materials composed of metal ions and organic bridging ligands, have emerged as a promising platform for drug delivery, owing to their high drug loadings, biodegradability, and versatile functionality. The bulk MOF materials can absorb and release large amounts of therapeutics including ibuprofen, procainamide, and nitric oxide. Scale-down of MOFs to the nanoregime yields nanoscale metal-organic frameworks (NMOFs) that are more applicable as delivery vehicles, such as selective delivery of cisplatin prodrugs. Although progress has been made in utilizing NMOFs for drug delivery, many improvements must occur before they can become viable nanotherapeutics.

Solvent-Free Production of Singlet Oxygen at the Gas−Solid Interface: Visible Light Activated Organic−Inorganic Hybrid Microreactors Including New Cyanoaromatic Photosensitizers

We synthesized new cyanoaromatics, benzo[b]triphenylene-9,14-dicarbonitrile (DBTP) 1a and a graftable derivative, 9,14-dicyanobenzo[b]triphenylene-3-carboxylic acid (DBTP-COOH) 1b, easily prepared from commercial reagents. Their photosensitizing properties were investigated. Hybrid porous silica monoliths loaded with encapsulated 1a or grafted 1b were prepared, and their adsorption, spectroscopic and photosensitizing properties, as well as stability, were compared. Solvent-free, efficient oxidation of dimethylsulfide (DMS) was observed at the gas-solid interface under visible light irradiation. Quantum yields of formation of 1O2 inside the porous monoliths are comparable to those of phenalenone. Singlet oxygen lifetimes (approximately 25 micros) were found to be longer in silica monoliths than in usual polar solvents such as methanol or ethanol. This new class of hybrid materials work as porous, transparent, and highly efficient microreactors for oxidation reactions under visible light.

Evaluation of Composite Electronic Materials Based upon Single-Wall Carbon Nanotubes and Highly Charged Poly(aryleneethynylene)s for Supercapacitor Applications

Although substantial improvement in capacitance, energy densities, and discharge times has been achieved for redox supercapacitors over the last several years, important challenges remain. These include high series resistance which limits the ability to quickly discharge these devices, excessive heat generation, and the coupled thermoelastic strain field which tends to deform the device materials. High stability composites based upon conjugated polymers that wrap single-wall carbon nanotubes (SWNTs) provide a platform to develop materials that can broadly impact these issues. This work compares the performance of a new class of hybrid materials, polymer-wrapped SWNTs to established electroactive polymer-based anode and cathode material benchmarks of poly(3,4-propylenedioxythiophene) for the construction of supercapacitors. These polymer-wrapped SWNT composites exploit rigid, polyanionic poly(aryleneethynylene)s which provide unusual solubility and dispersion characteristics for carbon nanotubes in several solvents.

Layered Single-Metal Hydroxide/Ethylene Glycol as a New Class of Hybrid Material

Neutral ethylene glycol (EG) molecules have been intercalated into zinc hydroxide layers to produce a new hybrid material in which only one kind of metal ion is included. Initially, layered basic zinc acetate (LBZA, Zn(5)(OH)(8)(CH(3)COO)(2).2H(2)O) was prepared from a methanolic zinc acetate dihydrate solution. The immersion of LBZA in EG resulted in its intercalation, which was accompanied by an interlayer expansion of 7.12 A, as revealed by X-ray diffractometry. A Fourier transform infrared spectroscopic study indicated that the new compound contained both the acetate groups and the EG molecules. Together with thermogravimetry-differential thermal analysis, a composition of the new compound was estimated to be Zn(5)(OH)(8)(CH(3)COO)(2)(HOC(2)H(4)OH)(2).2H(2)O. The EG intercalation was found to increase the dehydration temperature of the zinc hydroxide layers from 130 to 180 degrees C. So the thermally stable material is then promising as a new class of precursors in creating organic-inorganic nanocomposites.

An hybrid organic–inorganic approach to erbium-functionalized nanodots for emission in the telecom window

A new class of hybrid materials for efficient laser emission and amplification in the 1.55 μm eye-safe telecommunication window has been designed, elaborated and characterized, based on lanthanide-doped yttrium oxide nanoparticle guests embedded in a polymer host matrix. The average size of these nanocrystals can be finely tuned by controlling the relative quantities of an organic fuel (glycine) with respect to the yttrium- and lanthanide-containing reactants involved in the combustion reaction leading to nanoparticle synthesis. Two complementary sensitizers have been added to Er/Y 2O 3 nanocrystals in order to improve the Erbium luminescence efficiency: cerium to increase population inversion between the emitting and the ground state by accelerating the de-excitation process from the 4I 11/2 initially uppermost excited state at 980 nm down to 4I 13/2 state emitting around 1.55 μm, and ytterbium to improve the pumping efficiency of the material owing to its strong absorption cross section at 980 nm and subsequent efficient energy transfer towards the 4I 11/2 state of erbium ion. Y 2O 3 nanoparticles with an optimized erbium–ytterbium composition have been incorporated in a PMMA polymer matrix, resulting in a hybrid amorphous material displaying high gain coefficient values (up to 30 cm −1 as from Amplified Spontaneous Emission experiments) upon moderate 980 nm pumping intensities. These materials open attractive perspectives in the domain of polymer-based telecom amplifiers, with the additional asset of multifunctional properties whereby gain originating from the inorganic Y 2O 3 nanocrystals can be associated to nonlinear responses attached to an adequately functionalized polymer host matrix.

Spectroscopic Studies of Poly(ε-Caprolactone)/Sodium Montmorillonite Nanocomposites

Polymer-layered silicate nanocomposites belong to a new class of hybrid materials consisting of organic-synthetic polymer matrix and inorganic filler-layered structure clay minerals. The paper presents the results of FTIR, NMR, and SAXS studies of poly(e-caprolactone)/sodium montmorillonite nanocomposites. We observed a correlation between the concentration of poly(e-caprolactone) in nanocomposite samples and structural changes both of the clay mineral and the intercalated polymer. Stiffening of the clay structure appears as a result of poly(e-caprolactone) intercalation into a clay structure. Al NMR studies indicated in nanocomposites two non-equivalent sites of aluminium ions, i.e. in octahedral and tetrahedral coordination, whereas in the montmorillonite clay structure the aluminium ions are located in the interlayer space too. We found also that the temperatures of structural changes and softening process of poly(e-caprolactone) chains in the nanocomposites depend on the concentration of poly(e-caprolactone).

Establishment of de facto standard catalysts in the polypropylene industry.

Polypropylene (PP) has become an indispensable material in our daily lives. Annual worldwide production of PP is now more than 30000000 tons and is predicted to grow at an annual rate of about 6% during the first decade of the 21st century. Commercial production of PP began in 1957 with the use of TiCl(3) catalysts established by Ziegler and Natta. However, the low activities and low stereospecificities of the catalysts resulted in large amounts of catalyst residue and atactic PP in the product, necessitating steps for their removal in commercial production. As a means of finding appropriate catalysts, we developed MgCl(2)-supported TiCl(4) catalysts, which basic concept was introduction of organic compounds onto the inorganic crystal catalyst surface. This addition led to remarkable enhancements in stereospecificity with extremely high activity. Use of the new catalysts enlarged and simplified the PP production process by eliminating the steps previously required for removal of catalyst residue and atactic PP. In addition, it greatly improved the properties of the PP, enabling a much wider range of PP applications by replacing metal and engineering plastics with the highly stereoregular PP. Therefore, these catalysts helped the rapid establishment of the current PP industry and now play a major role in production. The latest MgCl(2)-supported TiCl(4) catalyst is providing precise control of the isotactic PP structure. Future expectations for this type of catalyst are to acquire a single-site nature and to contribute to the creation of a new class of hybrid materials.

A New Class of Hybrid Materials via Salt Inclusion: Novel Copper(II) Arsenates Na5ACu4(AsO4)4Cl2 (A: Rb, Cs) Composed of Alternating Covalent and Ionic Lattices.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Gold-Containing dendrimers: A new class of macromolecules

The synthesis of dendrimers possessing gold atoms on the surface or inside the internal layers is reported. They have been shown to be precursors to mixed gold-transition metal cluster-containing dendrimers, which represent a new class of hybrid materials. The latter species are rather soluble in common solvents and can be characterized by spectroscopic methods. Moreover, gold-containing dendrimers are useful for making gold nanoparticles, which have very interesting electronic, optical, and catalytic properties.

Soluble Stoichiometric Complexes from Poly(N-ethyl-4-vinylpyridinium) Cations and Poly(ethylene oxide)-block-polymethacrylate Anions

Block ionomer complexes formed between the block copolymers containing poly(sodium methacrylate) (PMANa) and poly(ethylene oxide) (PEO) segments and poly(N-ethyl-4-vinylpyridinium bromide) (PEVP) were investigated. The data obtained suggest that (i) these systems form water-soluble stoichiometric complexes; (ii) these complexes are stable in a much broader pH range compared to the polyelectrolyte complexes prepared from homopolymers; (iii) they self-assemble to form the core of a micelle comprised of neutralized polyions, surrounded by the PEO corona; (iv) they are salt sensitive since they fall apart as the salt concentration increases beyond a critical value; and (v) they can participate in the cooperative polyion substitution reactions. Therefore, these complexes represent a new class of hybrid materials which combine properties of polyelectrolyte complexes and block copolymer micelles.