Home About us Contact
|
Home About us Contact | ||
|
|
||
High Crystallinity (high + crystallinity)
Selected AbstractsHierarchical ZnS-In2S3 -CuS Nanospheres with Nanoporous Structure: Facile Synthesis, Growth Mechanism, and Excellent Photocatalytic ActivityADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Yingxuan Li Abstract Without using any templates or surfactants, hierarchical ZnS-In2S3 -CuS nanospheres with nanoporous structure are successfully synthesized via a simple and convenient process. The nanospheres are aggregations of densely packed nanoparticles and nanorods. Different to the oriented attachment (OA) mechanism reported in the literature, the formation of these nanorods is believed to follow a lateral OA mechanism (nanoparticles attach along the direction perpendicular to the crystallographic axes with lateral planes as the juncture) based on the experimental data. This process could be a general phenomenon and would provide a new insight into the OA mechanism. A detailed time-resolved TEM kinetic study of the formation of the complex structure is shown. The dipole mechanism and electric field-induced growth are found to be responsible for the final architecture. Photocatalytic activities for water splitting are investigated under visible-light irradiation (, > 400 nm) and an especially high photocatalytic activity (apparent yield of 22.6% at 420 nm) is achieved by unloaded ZnIn0.25Cu0.02S1.395 prepared at 180 °C for 18 h because of their high crystallinity, large pore volume, and the presence of nanorods with special microstructures. [source] Lateral Inhomogeneity in the Electronic Structure of a Conjugated Poly(3-hexylthiophene) Thin FilmADVANCED FUNCTIONAL MATERIALS, Issue 13 2010Kaname Kanai Abstract How annealing influences the morphology of a highly regioregular poly(3-hexylthiophene) (RR-P3HT) film at the substrate interface as well as the lateral inhomogeneity in the electronic structure of the film are elucidated. Whereas previous studies have reported that high-molecular-weight (MW) RR-P3HT films tend to show low crystallinity even after annealing, it is found that high-MW RR-P3HT does show high crystallinity after annealing at high temperature for a long time. Photoemission electron microscopy (PEEM), X-ray photoemission spectroscopy, and ultraviolet photoemission spectroscopy results clearly resolve a considerable lateral inhomogeneity in the morphology of RR-P3HT film, which results in a variation of the electronic structure depending on the local crystallinity. The PEEM results show how annealing facilitates crystal growth in a high-MW RR-P3HT film. [source] Kinetically Controlled Synthesis of Hexagonally Close-Packed Cobalt Nanorods with High Magnetic CoercivityADVANCED FUNCTIONAL MATERIALS, Issue 12 2009Yaghoub Soumare Abstract High-quality monodisperse metallic cobalt nanorods are obtained by the reduction of carboxylate salts of CoII in 1,2-butanediol using a rapid, simple, and solid-template-free procedure. In this polyol process, particle shape can be controlled via the growth rate, which depends on three parameters: i) the nature of the cobalt carboxylate, ii) the temperature ramp, and iii) the basicity of the medium. Cobalt in the hexagonally close-packed phase favored the growth of anisotropic particles. Magnetic measurements of the cobalt nanorods indicate they are ferromagnetic at room temperature. They have a very high coercivity of 9.0 kOe at 140,K, much higher than that observed for wires prepared with solid templates. This can be attributed to their small mean diameter and high crystallinity. [source] Field Emission and Cathodoluminescence of ZnS Hexagonal Pyramids of Zinc Blende Structured Single CrystalsADVANCED FUNCTIONAL MATERIALS, Issue 3 2009Zhi-Gang Chen Abstract Single-crystal hexagonal pyramids of zinc blende ZnS are fabricated by facile thermal evaporation in an ammonia atmosphere at 1150,°C. It is found that ZnS pyramids grow along the [111] crystal axis and possess a sharp tip with a diameter of ,10,nm and a micrometer-sized base. The structural model and growth mechanism are proposed based on crystallographic characteristics. This unique ZnS pyramid structure exhibits a low turn-on field (2.81,V µm,1), a high field-enhancement factor (over 3000), a large field-emission current density (20,mA cm,2), and good stability with very small fluctuation (0.9%). These superior field-emission properties are clearly attributed to the pyramid morphology, with micrometer-sized bases and nanotips, and high crystallinity. Moreover, a stable UV emission of 337,nm at room temperature is observed and can be ascribed to the band emission of the zinc blende phase. These results suggest that the ZnS hexagonal pyramids can be expected to find promising applications as field emitters and optoelectronic devices. [source] A Facile Route to Polymer Solar Cells with Optimum Morphology Readily Applicable to a Roll-to-Roll Process without Sacrificing High Device PerformancesADVANCED MATERIALS, Issue 35 2010Hui Joon Park A new fabrication method for polymer solar cells that can produce optimized vertical distribution of components is reported. The favorable donor,acceptor morphology showing a well-organized photo-induced charge transporting pathway with fine nanodomains and high crystallinity is achieved. This process is also readily scalable to a large-area and high-speed roll-to-roll process without sacrificing high device performances, even without a PEDOT:PSS layer. [source] Inorganic Nanoparticles for MRI Contrast AgentsADVANCED MATERIALS, Issue 21 2009Hyon Bin Na Abstract Various inorganic nanoparticles have been used as magnetic resonance imaging (MRI) contrast agents due to their unique properties, such as large surface area and efficient contrasting effect. Since the first use of superparamagnetic iron oxide (SPIO) as a liver contrast agent, nanoparticulate MRI contrast agents have attracted a lot of attention. Magnetic iron oxide nanoparticles have been extensively used as MRI contrast agents due to their ability to shorten T2* relaxation times in the liver, spleen, and bone marrow. More recently, uniform ferrite nanoparticles with high crystallinity have been successfully employed as new T2 MRI contrast agents with improved relaxation properties. Iron oxide nanoparticles functionalized with targeting agents have been used for targeted imaging via the site-specific accumulation of nanoparticles at the targets of interest. Recently, extensive research has been conducted to develop nanoparticle-based T1 contrast agents to overcome the drawbacks of iron oxide nanoparticle-based negative T2 contrast agents. In this report, we summarize the recent progress in inorganic nanoparticle-based MRI contrast agents. [source] High Electron Mobility and Ambient Stability in Solution-Processed Perylene-Based Organic Field-Effect TransistorsADVANCED MATERIALS, Issue 16 2009Claudia Piliego Bottom-contact n-channel OFETs based on spin-coated films of N,N, -1H,1H -perfluorobutyl dicyanoperylenediimide (PDI-FCN2) exhibit a saturation-regime mobility of 0.15,cm2 V,1 s,1 in vacuum and good air stability. These performances are attributed to the high crystallinity and to the edge-on orientation promoted by the thermal treatment, as showed by confocal laser microscopy. [source] Micrometer- and Nanometer-Sized, Single-Crystalline Ribbons of a Cyclic Triphenylamine Dimer and Their Application in Organic TransistorsADVANCED MATERIALS, Issue 16 2009Rongjin Li A cyclic triphenylamine dimer with high crystallinity is demonstrated. Micrometer- and nanometer-sized single-crystalline ribbons are easily produced by a physical vapor transport technique. Field-effect transistors of the ribbons exhibit mobilities up to 0.05,cm2 V,1 s,1. The mobility of the devices depends greatly on the size of the ribbons: the smaller the ribbons, the higher the mobility. [source] Utilizing Highly Crystalline Pyroelectric Material as Functional Gate Dielectric in Organic Thin-Film TransistorsADVANCED MATERIALS, Issue 8 2009Nguyen Thanh Tien Highly crystalline P(VDF-TrFE) materials have a large remnant polarization that causes the ID,VD curves to have no current saturation in the region where they normally would. This high crystallinity also results in a positive pyroelectricity, which is different from the conventional low response and nonlinear negative pyroelectricity. [source] Rapid Synthesis of Non-Aggregated Fine Chloroapatite Blue Phosphor Powders with High Quantum Efficiency,ADVANCED MATERIALS, Issue 18 2008Wei-Ning Wang Sub-micrometer-sized chloroapatite blue phosphors are successfully synthesized from aqueous precursors using a spray pyrolysis method with a very short processing time and without any post-heat treatments. The as-prepared phosphors reveal high quantum efficiency in the long-UV range (around 80% under excitation at 400,nm), spherical morphology, high crystallinity, and high color purity, showing great promise for white LED applications. [source] Synthesis and characterization of polypyrrole rod doped with p -toluenesulfonic acid via micelle formationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Duk Ki Kim Abstract Rod-type polypyrrole (PPY) doped with p -toluenesulfonic acid (TSA) was synthesized by chemical oxidative polymerization via a self-assembly process. The shape of the PPY particles is mainly determined by the ratio of TSA/pyrrole (PY) and feed rate of the oxidant. Particle of different shapes (rod, grain, and partially rod) exhibit differences in morphology, electrical properties, dispersity, and thermal properties. Wide-angle X-ray diffraction patterning analysis was used to investigate the mechanism of rod formation. The effect of the TSA concentration on the PPY structure was investigated using Fourier transform infrared spectroscopy. The PPY rods doped with TSA exhibited better electrical conductivity than granular PPY doped with TSA, and their dispersity and thermal stability were also higher. Self-orientation of PPY in the micelles of TSA and high crystallinity of the rod particles led to improved thermal stability. Hence, the decomposition temperature of the polymer chain was considerably increased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source] Yttria,polystyrene,polypropylene composite for fine dyeable fibersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Chengbing Yu Abstract Fine polypropylene fiber has many excellent properties, but it is difficult to dye because of the absence of dye sites in the molecular chain and high crystallinity. Fine polypropylene/hybrid polystyrene (yttria) fiber melt-spun from blends of polypropylene and a small amount of nanohybrid polystyrene with modified yttria incorporated was prepared to improve the dyeing properties. The dyeability, orientation, degree of crystallinity, phase morphology, and mechanical properties of pure polypropylene and the blend fibers were investigated. It was found that the crystallinity and morphology of these phases in the blend systems were different. With the existence of nanohybrid polystyrene, the fine modified polypropylene filaments had practical mechanical properties, the amorphous region of the polypropylene/hybrid polystyrene (yttria) fiber increased, and the modified polypropylene fiber dyed easily and had good fastness to soaping because of the complexation of the disperse dye and yttrium in the blend system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Synthesis of well-defined rod-coil block copolymers containing trifluoromethylated poly(phenylene oxide)s by chain-growth condensation polymerization and atom transfer radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2010Yun Jun Kim Abstract Well-defined trifluoromethylated poly(phenylene oxide)s were synthesized via nucleophilic aromatic substitution (SNAr) reaction by a chain-growth polymerization manner. Polymerization of potassium 4-fluoro-3-(trifluoromethyl)phenolate in the presence of an appropriate initiator yielded polymers with molecular weights of ,4000 and polydispersity indices of <1.2, which were characterized by 1H nuclear magnetic resonance spectroscopy and gel permeation chromatography. Initiating sites for atom transfer radical polymerization (ATRP) were introduced at the either side of chain ends of the poly(phenylene oxide), and used for ATRP of styrene and methyl methacrylate, yielding well-defined rod-coil block copolymers. Differential scanning calorimetry study indicated that the well-defined trifluoromethylated poly(phenylene oxide)s showed high crystallinity and were immiscible with polystyrene. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1049,1057, 2010 [source] Synthesis and characterization of postsulfonated poly(arylene ether sulfone) diblock copolymers for proton exchange membranesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2009Shogo Takamuku Abstract Sulfonated poly(arylene ether sulfone) diblock copolymers were studied through the postsulfonation process. Two kinds of hydrophobic oligomers with a molecular weight of 20 kDa were prepared in advance as block sequences and then coupled together to obtain diblock copolymers. One oligomer was synthesized from bis(4-hydroxyphenyl) sulfone (BHPS) and 4,4,-difluorodiphenyl sulfone (DFDPS), which was thought to be incapable of postsulfonation. The other oligomer was synthesized from hydroquinone (HQ) and 4,4,-dichlorodiphenyl sulfone (DCDPS), which successfully proceeded to a hydrophilic sequence as a result of sulfonation onto the HQ moiety after the coupling reaction. Consequently, a diblock copolymer with high molecular weight was obtained; although its intrinsic viscosity was too low to form a tough membrane because of its high rigidity and high crystallinity. Therefore, the use of decafluorobiphenyl (10F) as a termination reagent was investigated with the aim of achieving higher coupling reactivity and a kinky property. As a result, a sulfonated diblock copolymer was successfully obtained with sufficient molecular weight and intrinsic viscosity to form the membrane, as well as with adequate thermal properties. It was observed that proton conductivity, water uptake, and the water diffusion coefficient increased with higher ion exchange capacity. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 700,712, 2009 [source] Synthesis of a [60] fullerene,Functionalized isotactic polypropylene derivativeJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2008Gerardo Martínez Abstract The covalent attachment of [60] fullerene (C60) to isotactic polypropylene (i-PP) is achieved by direct reaction in 1,2,4-trichlorobenzene (TCB) solution in the presence of dicumyl peroxide (DCP). The chemically modified pendant C60/i-PP polymers are soluble in chlorinated solvents and have been characterized by ultraviolet,visible and fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, cyclic voltametry, and thermogravimetric analysis. From the results it can be concluded that the modification of i-PP by grafting via a free-radical reaction competes with the possibility of chain scission of i-PP due to the presence of DCP. The functionalized polymers crystallize in the monoclinic crystal modification, and have high crystallinity. The incorporation of C60 significantly enhances the thermal stability of the i-PP. Electrochemical measurements demonstrate good electron acceptor properties of the fullerenated i-PP samples. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6722,6733, 2008 [source] Preparation of single-walled carbon nanotubes-induced poly(p -oxybenzoyl) crystalsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2008Kazufumi Kobashi Abstract Crystallization of oligomers was applied for the preparation of single-walled carbon nanotubes (SWNTs)/poly(p -oxybenzoyl) (POB) crystals using SWNTs as a nucleating agent. Polymerization conditions were investigated to induce the crystallization of POB oligomers through SWNTs. SWNTs/POB plate-like or lozenge-shaped crystals were successfully prepared by direct polymerization of p -hydroxybenzoic acid (HBA) in a mixed solvent of DMF/Py with TsCl in the presence of functionalized SWNTs. The size of the plate-like crystals were ,200 nm to 3 ,m. The crystals consisted of some layers, ,3 nm thick plates. Model reactions showed that esterification reactions proceed between functionalized SWNTs and HBA monomers in the polymerization system. The obtained crystals exhibited unique morphology and high crystallinity, producing a novel SWNT/POB hybrid. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1265,1277, 2008 [source] Well-Defined Crystalline TiO2 Nanoparticles Generated and Immobilized on a Colloidal NanoreactorMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 5 2009Yan Lu Abstract We synthesized well-defined, crystalline TiO2 nanoparticles at room temperature by using spherical polyelectrolyte brush particles as a template. The template particles consist of a polystyrene core from which long chains of poly(styrene sodium sulfonate) are grafted. Tetraethylorthotitanate is hydrolyzed in the presence of brush particles leading to the formation of well-dispersed TiO2 nanoparticles (d,=,4,12 nm). Wide-angle X-ray scattering demonstrates that anatase nanoparticles with high crystallinity have been generated at room temperature. The as-prepared TiO2 nanocomposites present high photocatalytic activity for the degradation of Rhodamine B under UV irradiation. Finally, mesoporous TiO2 structures with defined pore size are formed after calcination. [source] Heterometal Alkoxides as Precursors for the Preparation of Porous Fe, and Mn,TiO2 Photocatalysts with High EfficienciesCHEMISTRY - A EUROPEAN JOURNAL, Issue 35 2008Xiao-Xin Zou Abstract Transition-metal-doped titanium glycolates (M,TG, with M=Fe, Mn), which are the first non-stoichiometric heterometal alkoxides, have been synthesised through a solvothermal doping approach. X-ray diffraction, UV/Vis diffuse reflectance and ESR spectroscopy revealed that the dopant ion (Fe3+ or Mn2+) is substituted for Ti4+ in the TG lattice. Fe3+ prolongs the crystallisation time of Fe,TG, whereas Mn2+ has a smaller effect on the crystallisation time in comparison with Fe3+. The as-synthesised M,TG materials were used directly as single-source precursors for the preparation of metal-doped titania (M,TiO2) through a simple thermal treatment process. The as-prepared M,TiO2 materials maintain the rod-like morphology of the precursors and possess a mesoporous structure with high crystallinity. It has been proved that the dopant ions are incorporated into the TiO2 lattice at the Ti4+ positions. The photocatalytic activities of the M,TiO2 materials obtained were evaluated by testing the degradation of phenol under UV irradiation. From the photocatalytic results, it was concluded that high crystallinity, a large surface area and appropriate transition-metal-doping are all beneficial to the enhancement of the photocatalytic performance of the doped TiO2 material. In addition, it was noted that in comparison with Mn,TiO2, Fe,TiO2 shows higher photocatalytic activity due to the better inhibition effect of Fe3+ on recombination of photogenerated electron,hole pairs. In contrast to the conventional nanosized TiO2 photocatalyst, the micrometre-sized M,TiO2 particles we obtained can be easily separated and recovered after the photocatalytic reactions. [source] | ||||||||||||||||||||||