Shape evolution of CdSe nanocrystals in vegetable oils: A synergistic effect of selenium precursor

In this contribution, common vegetable oils are used as coordination solvents for synthesis of high quality CdSe nanocrystals. Various shaped nanocrystals (quantum dots, quantum rods, multipods, arc structure, etc.) can be produced free of alkylphosphonic acids. Shape evolution can be induced by three types of selenium precursors: ODE-Se, VO-Se and TOP-Se (ODE, 1-octadecene; VO, vegetable oil; TOP, trio-n-octylphosphine). The quantum yields of NCs are 15-40%. The full width at half-maximum (fwhm) of the photoluminescence spectra are 27 +/- 1 nm for quantum clots and 23 +/- 1 nm for quantum rods/multipods.

Synthesis of Tributylphosphate Capped Luminescent Rare Earth Phosphate Nanocrystals in an Ionic Liquid Microemulsion

Uniform rare earth phosphate (REPO4, RE = La-Tb) nanocrystals were successfully synthesized in a properly designed TBP/[Omim]Cl/H2O (tributylphosphate/1-octyl-3-methyl-imidazolium chloride/water) microemulsion system. The phosphoryl groups anchored the TBP molecules oil the surfaces of the nanocrystals, and this made the nanocrystals easily dispersed in some imidazolium-based ILs. LaPO4:Eu3+ and CePO4:Tb3+ nanocrystals capped with TBP showed bright red and green emission under UV excitation, with enhanced emission intensity and lifetimes compared with the uncapped ones.

Novel Route to 2-Trifluoromethylated Benzofurans

A novel route for the synthesis of a variety of 2-trifluoromethylbenzofurans is reported. By selection of solvents, the key intermediates, 2-chloro-3,3,3-trifluoropropenyl phenyl acetates, were cyclized either to give 2-trifluoromethyl-substituted benzofurans or to yield trifluoromethyl modified o-alkynylphenols. The latter intermediates could also be cyclized to give 3-iodo-2-trifluoromethyl-substituted benzofurans.

Controlled synthesis of monodisperse nanocrystals by a two-phase approach without the separation of nucleation and growth processes

The synthesis of monodisperse nanocrystals is an important topic in the field of nanomaterials not only for practical applications, but also for scientific interest in fundamental research. In this feature article, we mainly focus on synthesis of monodisperse nanocrystals by a two-phase approach without the separation of nucleation and growth processes, and report some progress made recently in the observation and understanding of nucleation and growth of semiconductor nanocrystals. Firstly, a novel two-phase approach to monodisperse nanocrystals, which is different from the well-established synthesis models, is discussed. We demonstrate that the two-phase approach has a quite lengthy nucleation process, and can be applied to the synthesis of many kinds of binary monodisperse nanocrystals.

Microphase Separation of Mixed Polymer Brushes: Dependence of the Morphology on Grafting Density, Composition, Chain-Length Asymmetry, Solvent Quality, and Selectivity

Microphase separation of binary mixed A/B polymer brushes exposed to different solvents is studied using Single-Chain-in-Mean-Field simulations. Effects of solvent quality and selectivity, grafting density, composition, and chain-length asymmetry are systematically investigated, and diagrams of morphologies in various solvents are constructed as a function of grafting density and composition or chain-length asymmetry. The structure of the microphase segregated morphologies lacks long-range periodic order, and it is analyzed quantitatively Using Minkowski measures.

An Engineering-Purpose Preparation Strategy for Ammonium-Type Ionic Liquid with High Purity

A new strategy for preparing ammonium-type ionic liquid (IL) by acid/base neutralization reaction was proposed. The method contributed to preparing hydroxide-based ammonium IL and resulting task specific ionic liquid (TSIL) with high purity using a low-costly and environment-friendly synthetic. route. Halide contamination in the prepared ILs could be markedly decreased than those prepared by well-established anion metathesis method. Moreover, some novel TSILs composed of cations and anions with big steric hindrances could be prepared by this method. Physicochemical properties of the bifunctional TSILs, i.e., density, water content, decomposition temperature, and munal solubility, were also studied in this article.

Facile EG/ionic liquid interfacial synthesis of uniform RE3+ doped NaYF4 nanocubes

Uniform multicolor upconversion luminescent RE3+ doped NaYF4 nanocubes are fabricated through a facile ethylene glycol (EG)/ionic liquid interfacial synthesis route at 80 degrees C, with the ionic liquids acting as both reagents and templates.

Synthesis of Soluble Poly(arylene ether sulfone) Ionomers with Pendant Quaternary Ammonium Groups for Anion Exchange Membranes

A new bisphenol monomer, 2,2'-dimethylaminemetllylene-4,4'-biphenol (DABP), was easily prepared by Mannich reaction of dimethylamine and formaldehyde with 4,4'-biphenol. Novel partially fluorinated poly(arylene ether sulfone)s with pendant quaternary ammonium groups were prepared by copolymerization of DABP, 4,4'-biphenol, and 3,3',4,4'- tetrafluorodiphenylsulfone, followed by reaction with iodomethane. The resulting copolymers PSQNI-x (where x represents the molar fraction of DABP in the feed) with high molecular weight exhibited outstanding solubility in polar aprotic solvents; thus, the flexible and tough membranes of PSQNI-x with varying ionic content could be prepared by casting from the DMAc solution. Novel anion exchange membranes, PSQNOH-x, were obtained by an anion exchange of PSQNI-x with 1 N NaOH.

Synthesis and properties of soluble poly[bis(benzimidazobenzisoquinolinones)] based on novel aromatic tetraamine monomers

Four aromatic tetraamine monomers possessing flexible ether linkages were successfully synthesized by nucleophilic aromatic substitution of hydroquinone, 4,4'-dihydroxybiphenyl, 2,2'-bis(4-hydroxyphenyl)propane, and 2,7-dihydroxynaphthalene with 5-chloro-2-nitroaniline, followed by reduction, respectively. With these monomers, a new class of soluble poly[ bis(benzimidazobenzisoquinolinones)] was prepared by a one-step, high-temperature solution polycondensation. The resulting polymers were completely soluble in phenolic solvents and had high inherent viscosities ranging from 1.2 to 1.5 g dL(-1). These polymers had glass transition temperatures in the range of 427-449 degrees C. Thermogravimetric analysis showed that all polymers were thermally stable, with 5% weight loss recorded above 510 degrees C in nitrogen.

Novel proton exchange membranes based on water resistant sulfonated poly[bis(benzimidazobenzisoquinolinones)]

Novel water resistant sulfonated poly[bis(benzimidazobenzisoquinolinones)] (SPBIBIs) were synthesized from 6,6'-disulfonic-4,4'-binaphthy]-1,1',8,8'-tetracarboxylic dianhydride (SBTDA) and various aromatic ether tetraamines. The resulting polymers with IEC in the range of 2.17-2.87 mequiv g(-1) have a combination of desired properties such as high solubility in common organic solvents, film-forming ability, and excellent thermal and mechanical properties. Flexible and tough membranes, obtained by casting from m-cresol solution, had tensile strength, elongation at break, and tensile modulus values in the range of 87.6-98.4 MPa, 35.8-52.8%, and 0.94-1.07 GPa. SPBIBI membranes with a high degree of sulfonation displayed high proton conductivity and a good resistance to water swelling as well. SPBIBI-b with IEC of 2.80 mequiv g(-1) displayed the conductivity of 1.74 x 10(-1) S cm(-1) at 100 degrees C, which was comparable to that of Nafion (R) 117 (1.78 x 10(-1) S cm(-1), at 100 degrees C).

Synthesis and properties of ferrocene-functionalised polythiophene derivatives

The ferrocene-functionalised thiophene derivatives (TFn) with different length of oxyethylene chains were synthesized and polymerized chemically with iron (III) chloride as an oxidant. The resulting ferrocene-functionalised polythiophenes (PTFn) show good solubility in most solvents, such as chloroform (CHCl3) tetrahydrofuran (THF), acetone, etc. The structure and properties of the PTFn polymers were confirmed by IR, H-1 NMR, AFM and photoluminescence (PL). The polymers PTFn show good redox activity with no attenuation of the electroactivity after multiple potential cycling. (C) 2009 Elsevier B.V. All rights reserved.

Insulin nanoparticle preparation and encapsulation into poly(lactic-co-glycolic acid) microspheres by using an anhydrous system

Insulin has been encapsulated in poly(lactic-co-glycolic acid) (PLGA) microspheres by solid-in-oil-in-oil (S/O/O) emulsion technique using DMF/corn oil as new solvent pairs. To get better encapsulation efficiency, insulin nanoparticles were prepared by the modified isoelectric point precipitation method so that it had good dispersion in the inner oil phase. The resulting microspheres had drug loading of 10% (w/w), while the encapsulation efficiency could be up to 90-100%. And the insulin release from the microspheres could last for 60 days. Microspheres encapsulated original insulin with the same method had lower encapsulation efficiency, and shorter release period. Laser scanning confocal microscopy indicated the insulin nanoparticle and original insulin had different distribution in microspheres. The results suggested that using insulin nanoparticle was better than original insulin for microsphere preparation by S/O/O method.

Preparation of Polyacrylamide Aqueous Dispersions Using Poly(sodium acrylic acid) as Stabilizer

High-solids, low-viscosity, stable polyacrylamide (PAM) aqueous dispersions were prepared by dispersion polymerization of acrylamide in aqueous solution of ammonium sulfate (AS) using Poly (sodium acrylic acid) (PAANa) as the stabilizer, ammonium persulfate (APS) or 2,2'-Azobis (N,N'-dimethyleneisobutyramidine) dihydrochloride (VA-044) as the initiator. The molecular weight of the formed PAM, ranged from 710, 000 g/mol to 4,330,000 g/mol, was controlled by the addition of sodium formate as a conventional chain-transfer agent. The progress of a typical AM dispersion polymerization was monitored with aqueous size exclusion chromatography. The influences, of the AS concentration, the poly(sodium acrylic acid) concentration, the initiator type and concentration, the chain-transfer agent concentration and temperature Oil the monomer conversion, the dispersion viscosity, the PAM molecular weight and distribution, the particle size and morphology were systematically investigated.

Solvent Vapor-Induced Self Assembly and its Influence on Optoelectronic Conversion of Poly(3-hexylthiophene): Methanofullerene Bulk Heterojunction Photovoltaic Cells

Nanoscale-phase separation of electron donor/acceptor blends is crucial for efficient charge generation and collection in Polymer bulk heterojunction photovoltaic cells. We investigated solvent vapor annealing effect of poly(3-hexylthiophene) (P3HT)/methanofullerene (PCBM) blend oil its morphology and optoelectronic properties. The organic solvents of choice for the treatment have a major effect oil the morphology of P3HT/PCBM blend and the device performance. Ultraviolet-visible absorption spectro,;copy shows that specific solvent vapor annealing can induce P3HT self-assembling to form well-ordered structure; and hence, file absorption in the red region and the hole transport are enhanced. The solvent that has a poor Solubility to PCBM Would cause large PCBM Clusters and result in a rough blend film. By combining an appropriate solvent vapor treatment and post-thermal annealing of the devices, the power conversion efficiency is enhanced.

Performance Enhancement of Polymer Light-Emitting Diodes by Using Ultrathin Fluorinated Polyimide Modifying the Surface of Poly(3,4-ethylene dioxythiophene):Poly(styrenesulfonate)

Herein, an insulating fluorinated polyimide (F-PI) is utilized as an ultrathin buffer layer of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) in polymer light-emitting diodes to enhance the device performance. The selective solubility of F-PI in common solvents avoids typical intermixing interfacial problems during the sequential multilayer spin-coating process. Compared to the control device, the F-PI modification causes the luminous and power efficiencies of the devices to be increased by a factor of 1.1 and 4.7, respectively, along with almost 3-fold device lifetime enhancement. Photovoltaic measurement, single-hole devices, and X-ray photoelectron spectroscopy, are utilized to investigate the underlying, mechanisms, and it is found that the hole injection barrier is lowered owing to the interactions between the PEDOT:PSS and F-PI. The F-PI modified PEDOT:PSS layer demonstrates step-up ionization potential profiles from the intrinsic bulk PEDOT:PSS side toward the F-PI-modified PEDOT:PSS surface, which facilitate the hole injection.