Lanthanide-based luminescent hybrid materials.

Sterically encumbered Lewis acid and Lewis base combinations do not undergo the ubiquitous neutralization reaction to form "classical" Lewis acid/Lewis base adducts. Rather, both the unquenched Lewis acidity and basicity of such sterically "frustrated Lewis pairs (FLPs)" is available to carry out unusual reactions. Typical examples of frustrated Lewis pairs are inter- or intramolecular combinations of bulky phosphines or amines with strongly electrophilic RB(C(6)F(5))(2) components. Many examples of such frustrated Lewis pairs are able to cleave dihydrogen heterolytically. The resulting H(+)/H(-) pairs (stabilized for example, in the form of the respective phosphonium cation/hydridoborate anion salts) serve as active metal-free catalysts for the hydrogenation of, for example, bulky imines, enamines, or enol ethers. Frustrated Lewis pairs also react with alkenes, aldehydes, and a variety of other small molecules, including carbon dioxide, in cooperative three-component reactions, offering new strategies for synthetic chemistry.

Frustrated Lewis pairs: metal-free hydrogen activation and more.

Data Reduction And Error Analysis For The Physical Sciences

Heavy metal remediation of aqueous streams is of special concern due to recalcitrant and persistency of heavy metals in environment. Conventional treatment technologies for the removal of these toxic heavy metals are not economical and further generate huge quantity of toxic chemical sludge. Biosorption is emerging as a potential alternative to the existing conventional technologies for the removal and/or recovery of metal ions from aqueous solutions. The major advantages of biosorption over conventional treatment methods include: low cost, high efficiency, minimization of chemical or biological sludge, regeneration of biosorbents and possibility of metal recovery. Cellulosic agricultural waste materials are an abundant source for significant metal biosorption. The functional groups present in agricultural waste biomass viz. acetamido, alcoholic, carbonyl, phenolic, amido, amino, sulphydryl groups etc. have affinity for heavy metal ions to form metal complexes or chelates. The mechanism of biosorption process includes chemisorption, complexation, adsorption on surface, diffusion through pores and ion exchange etc. The purpose of this review article is to provide the scattered available information on various aspects of utilization of the agricultural waste materials for heavy metal removal. Agricultural waste material being highly efficient, low cost and renewable source of biomass can be exploited for heavy metal remediation. Further these biosorbents can be modified for better efficiency and multiple reuses to enhance their applicability at industrial scale.

Agricultural waste material as potential adsorbent for sequestering heavy metal ions from aqueous solutions

White light‐emitting electroluminescent devices were fabricated using poly(N‐vinylcarbazole) (PVK) as a hole‐transporting emitter layer and a double layer of 1,2,4‐triazole derivative (TAZ) and tris(8‐quinolinolato)aluminum(III) complex (Alq) as an electron transport layer. The PVK layer was doped with fluorescent dyes such as blue‐emitting 1,1,4,4‐tetraphenyl‐1,3‐butadiene, green‐emitting coumarin 6, and orange‐emitting DCM 1. A cell structure of glass substrate/indium‐tin‐oxide/doped PVK/TAZ/Alq/Mg:Ag was employed. White emission covering a wide range of the visible region and a high luminance of 3400 cd/m2 were obtained at a drive voltage of 14 V.

White light‐emitting organic electroluminescent devices using the poly(N‐vinylcarbazole) emitter layer doped with three fluorescent dyes

The role of fluoropolymer physicochemical properties in the dynamic evolution of nanostructure and ionic conductivity in perfluorinated sulfonic acid ionomer thin films was investigated by in situ ...

Dynamic Emergence of Nanostructure and Transport Properties in Perfluorinated Sulfonic Acid Ionomers

Three novel partially fluorinated monomers, bis(2,2-difluorovinyl)formal (I), bis(2,2-difluorovinyl)difluoroformal (II), and bis(1-deuterio-2,2-difluorovinyl)difluoroformal (III), were prepared. These monomers were polymerized in bulk via free radical mechanism. Monomer I produced a cross-linked polymer, but monomers II and III yielded amorphous polymers (II-P and III-P) having five- and six-membered rings along the backbone. Polymers II-P and III-P were soluble not only in fluorinated solvents but also in nonfluorinated solvents such as THF, 1, 4-dioxane, DMF, and DMSO. They have good thermal stability (onset of decomposition >400 °C), high glass transition temperatures (105 °C), and low dielectric constant (1.98−1.82 at frequency ranging from 0.1 to 3 × 106 Hz). Furthermore, these polymers are completely amorphous and possess outstanding optical clarity extending from visible to near-IR regions. The refractive indices of both polymers were measured at various wavelengths to evaluate material dispersion....

Synthesis and properties of partially fluorinated amorphous ring containing polymers: Poly[bis(2,2-difluorovinyl)formal], poly[bis(2,2-difluorovinyl)difluoroformal], and poly[bis(1-deuterio-2,2-difluorovinyl)difluoroformal]

Since the discovery of polytetrafluoroethylene (PTFE) in 1938, fluorinated polymers have drawn attention in the chemical and pharmaceutical field, as well as in optical and microelectronics applications. The reasons for this attention are their high thermal and oxidative stability, excellent chemical resistance, superior electrical insulating ability, and optical transmission properties. Despite their unprecedented combination of desirable attributes, PTFE and copolymers of tetrafluoroethylene (TFE) with hexafluoropropylene and perfluoropropylvinylether are crystalline and exhibit poor solubility in solvents, which makes their processability very challenging. Since the 1980s, several classes of solvent-soluble amorphous perfluorinated polymers showing even better optical and gas transport properties were developed and commercialized. Amorphous perfluoropolymers exhibit, however, moderate selectivity in gas and liquid separations. Recently, we have synthesized various new perfluorodioxolane polymers which are amorphous, soluble, chemically and thermally stable, while exhibiting much enhanced selectivity. In this article, we review state-of-the-art and recent progress in these perfluorodioxolane polymers for gas separation membrane applications.

https://www.mdpi.com/2077-0375/10/12/394/pdf

Perfluorodioxolane Polymers for Gas Separation Membrane Applications.

The low and the high molecular weight poly(perfluoro-2-methylene-1,3-dioxolane)s were prepared using perfluorobenzoyl peroxide as a free radical initiator. Both polymers obtained were semicrystalline and insoluble in organic solvents. The glass transition temperatures (Tg) of polymers obtained were 94–106°C, and their melting points were 224–229°C. Wide-angle X-ray diffraction measurements showed that polymers as prepared are semi-crystalline (21% crystalline fraction) and the crystallinity increased to 47% after annealing at 170°C. However, the films prepared by heating (at 230–250°C) and pressing of the high molecular weight polymers are transparent and flexible. The refractive index of the film is 1.3320 and 1.3245 at 533 and 1546 nm, respectively. The transparent polymer films did not recrystallize while annealing below Tg, and they are chemically and thermally stable. This polymer may have potential applications in optoelectronic fields. Copyright © 2011 John Wiley & Sons, Ltd.

Characterization and properties of semicrystalline and amorphous perfluoropolymer: Poly(perfluoro-2-methylene-1,3-dioxolane)

STUDIES of the solid state properties of metallic azides are at present restricted by the lack of availability of single crystal specimens because of preparative difficulties. According to reports, lead azide, for example, may explode spontaneously during solution growth, particularly when faster growth rates are used1–3. Crystal growth in gels at near ambient temperatures seems to be an attractive technique for growing single crystals of such metal azides4–7. In gels, the diffusion controlled growth rates are lower than in solution and convection currents, which may be a causative disturbance for explosions are virtually eliminated.

/pdf/preparation-and-growth-of-single-crystals-of-metallic-azides-3nkhwd0zc4.pdf

Yoshiyuki Okamoto

Papers

Dynamic Emergence of Nanostructure and Transport Properties in Perfluorinated Sulfonic Acid Ionomers

Synthesis and properties of partially fluorinated amorphous ring containing polymers: Poly[bis(2,2-difluorovinyl)formal], poly[bis(2,2-difluorovinyl)difluoroformal], and poly[bis(1-deuterio-2,2-difluorovinyl)difluoroformal]

Perfluorodioxolane Polymers for Gas Separation Membrane Applications.

Characterization and properties of semicrystalline and amorphous perfluoropolymer: Poly(perfluoro-2-methylene-1,3-dioxolane)

Preparation and Growth of Single Crystals of Metallic Azides by Controlled Diffusion in Silica Gel System