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Morphology Control (morphology + control)
Selected AbstractsMorphology Control in Solution-Processed Bulk-Heterojunction Solar Cell MixturesADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Adam J. Moulé Abstract The efficiency of bulk-heterojunction solar cells is very sensitive to the nanoscale structure of the active layer. In the past, the final morphology in solution-processed devices has been controlled by varying the casting solvent and by curing the layer using heat tempering or solvent soaking. A recipe for making the "best-performing" morphology can be achieved using these steps. This article presents a review of several new techniques that have been developed to control the morphology in polymer/fullerene heterojunction mixtures. The techniques fall into two broad categories. First, the morphology can be controlled by preparing nanoparticle suspensions of one component. The size and shape of the nanoparticles in solution determine the size and shape of the domain in a mixed layer. Second, the morphology can be controlled by adding a secondary solvent or an additive that more strongly affects one component of the mixture during drying. In both cases, the as-cast efficiency of the solar cell is improved with respect to the single-solvent case, which strongly argues that morphology control is an issue that will receive increasing attention in future research. [source] Dramatic Morphology Control in the Fabrication of Porous Polymer Films,ADVANCED FUNCTIONAL MATERIALS, Issue 22 2008Luke A. Connal Abstract Highly ordered, porous honeycomb films are prepared by the breath-figure (BF) technique using dendron-functionalized star polymers as precursors. By changing the nature of the dendritic end groups, dramatically different porous morphologies can be produced. Three series of star polymers are prepared with both the size of the 2,2-bis(methoxy)propionic acid (bis-MPA)-based dendron end group and the dendron functionality being varied. Star polymers end-functionalized with acetonide-protected dendrons (generations 1 to 4) are initially prepared and the acetonide groups subsequently deprotected to yield hydroxyl-functionalized star polymers. Modification of these hydroxyl groups with pentadecafluorooctanoyl chloride yields a third series of functionalized star polymers. The resulting star polymers have surface groups with very different polarity and by utilizing these star polymers to form honeycomb films by the BF technique, the morphology produced is dramatically different. The star polymers with amphiphilic character afford interconnected porous morphologies with multiple layers of pores. The star polymers with pentadecafluorooctanoyl end groups show highly ordered monolayers of pores with extremely thin walls and represent a new porous morphology that has previously not been reported. The ability to prepare libraries of different dendronized star polymers has given further insights into the BF technique and allows the final porous morphology to be controllably tuned utilizing the functional chain ends and generation number of the dendronized star polymers. [source] Nonspherical Noble Metal Nanoparticles: Colloid-Chemical Synthesis and Morphology ControlADVANCED MATERIALS, Issue 16 2010Tapan K. Sau Abstract Metal nanoparticles have been the subject of widespread research over the past two decades. In recent years, noble metals have been the focus of numerous studies involving synthesis, characterization, and applications. Synthesis of an impressive range of noble metal nanoparticles with varied morphologies has been reported. Researchers have made a great progress in learning how to engineer materials on a nanometer length scale that has led to the understanding of the fundamental size- and shape-dependent properties of matter and to devising of new applications. In this article, we review the recent progress in the colloid-chemical synthesis of nonspherical nanoparticles of a few important noble metals (mainly Ag, Au, Pd, and Pt), highlighting the factors that influence the particle morphology and discussing the mechanisms behind the nonspherical shape evolution. The article attempts to present a thorough discussion of the basic principles as well as state-of-the-art morphology control in noble metal nanoparticles. [source] Nanotube Arrays: Morphology Control of Nanotube Arrays (Adv. Mater.ADVANCED MATERIALS, Issue 29 200929/2009) On p. 2983 Michael J. Brett and co-workers demonstrate a template-directed technique to produce arrays of silicon nanotubes (SiNTs) with highly engineerable morphology. Fabrication steps include glancing angle deposition (GLAD) of the templates, low-pressure CVD of a shell-Si coating, ion milling to expose the templates, and wet-chemical etching for removal of the templates. The technique may be generally adapted to a wide variety of morphologies and NT materials. [source] Morphology Control of Nanotube ArraysADVANCED MATERIALS, Issue 29 2009Zhifeng Huang Arrays of silicon nanotubes (SiNTs) with controllable architectures, wall thicknesses and crystallinity are fabricated by a new template-assisted technique. The method includes a sequence of glancing angle deposition of the templates, low-pressure CVD shell-Si coating, ion-milling to expose the templates, and wet-chemical etching for template removal. The technique may be generally adapted to a wide variety of morphologies and NT materials. [source] Self-Assembled Nanostructures of Tailored Multi-Metal Complexes and Morphology Control by Counter-Anion ExchangeCHEMISTRY - A EUROPEAN JOURNAL, Issue 35 2010Dr. Masaki Yamamura Improved solubility: Trisaloph complexes bearing PEGylated adamantane units were designed (see figure) and synthesized to improve their solubility in aqueous media. The complexes afforded a self-assembled nanostructure in aqueous media. Spherical and fibril aggregates were successfully formed based on the structural change caused by the coordinated anions. [source] Morphology Control over the Organic Nanoparticles of 1, 3-Diphenyl-5-(9-anthryl)-2-pyrazolineCHINESE JOURNAL OF CHEMISTRY, Issue 12 2003Lu Xi Abstract The organic nanoparticles of a blue-light-emitting molecule, 1, 3-diphenyl-5-(9-anthryl)-2-pyrazoline, were prepared by reprecipitation method using acetonitrile as the solvent for the molecular precursor. Three morphologies, spherical, doughnut-shaped and cubic, could be observed on the silicon substrate for the nanoparticles by the volume-controlled addition of acetonitrile. The evolution of particle morphology as a function of acetonitrile addition was attributed to the variation of the growth habits of the particles in the different environment. The nanoparticles exhibit the novel photoluminescence spectra as compared to those of monomer and the bulk crystals. [source] Porous Polymer Coatings: a Versatile Approach to Superhydrophobic SurfacesADVANCED FUNCTIONAL MATERIALS, Issue 12 2009Pavel A. Levkin Abstract Here, a facile and inexpensive approach to superhydrophobic polymer coatings is presented. The method involves the in situ polymerization of common monomers in the presence of a porogenic solvent to afford superhydrophobic surfaces with the desired combination of micro- and nanoscale roughness. The method is applicable to a variety of substrates and is not limited to small areas or flat surfaces. The polymerized material can be ground into a superhydrophobic powder, which, once applied to a surface, renders it superhydrophobic. The morphology of the porous polymer structure can be efficiently controlled by composition of the polymerization mixture, while surface chemistry can be adjusted by photografting. Morphology control is used to reduce the globule size of the porous architecture from micro down to nanoscale thereby affording a transparent material. The influence of both surface chemistry as well as the length scale of surface roughness on the superhydrophobicity is discussed. [source] Morphology control of GaN nanowires by vapor-liquid-solid growthPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008Y. Inoue Abstract We synthesized GaN nanowires on sapphire substrate by metal organic chemical vapour deposition. The GaN nanowires were grown via vapor-liquid-solid (VLS) growth catalyzed with Ni thin film. Shape of nanowires depended on the substrate temperature and the growth pressure. The wire-like structure with high aspect ratio changed into the tapered structure with increasing substrate temperature, and with increasing the growth pressure. This dependency was attributed to the change of the surface diffusion length of source atoms. The VLS growth of GaN nanowire was revealed that the source species, absorbed at the eutectic droplet, came along the side wall of the nanowire as well as other semiconductor nanowires. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Morphology control of polyoxy-methylene/thermoplastic polyurethane blends by adjusting their viscosity ratioPOLYMER INTERNATIONAL, Issue 9 2006Zhengang Cheng Abstract Polyoxymethylene (POM) is an important plastic with very good properties. However, its poor impact strength limits its applications. Theoretical and experimental studies have confirmed that thermoplastic polyurethane (TPU) can effectively enhance the notched impact strength of POM. This paper reports that the notched impact strength of POM/TPU blends can be further improved when these blends are endowed with a fine morphology by changing the viscosity ratio of TPU to POM (P = ,TPU/,POM) during processing. The experimental results show that the viscosity of TPU is more sensitive to temperature than that of POM, and that the viscosity ratio P decreases with increasing temperature; also for quite a wide range of shear rate, P is close to 1 when the processing temperature (Tp) is around 190 °C. Accordingly, the phase structure of POM/TPU blends changes with P. The dispersed phase of TPU shows ellipsoidal morphology when P > 1 at Tp < 190 °C, filamental morphology when P , 1 at Tp , 190 °C and spheroidal morphology when P < 1 at Tp > 190 °C. The results suggest that the filamental morphology endows POM/TPU (90/10) blends with the highest notched impact strength (,14 kJ m,2). Copyright © 2006 Society of Chemical Industry [source] Morphology Control in Solution-Processed Bulk-Heterojunction Solar Cell MixturesADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Adam J. Moulé Abstract The efficiency of bulk-heterojunction solar cells is very sensitive to the nanoscale structure of the active layer. In the past, the final morphology in solution-processed devices has been controlled by varying the casting solvent and by curing the layer using heat tempering or solvent soaking. A recipe for making the "best-performing" morphology can be achieved using these steps. This article presents a review of several new techniques that have been developed to control the morphology in polymer/fullerene heterojunction mixtures. The techniques fall into two broad categories. First, the morphology can be controlled by preparing nanoparticle suspensions of one component. The size and shape of the nanoparticles in solution determine the size and shape of the domain in a mixed layer. Second, the morphology can be controlled by adding a secondary solvent or an additive that more strongly affects one component of the mixture during drying. In both cases, the as-cast efficiency of the solar cell is improved with respect to the single-solvent case, which strongly argues that morphology control is an issue that will receive increasing attention in future research. [source] Nonspherical Noble Metal Nanoparticles: Colloid-Chemical Synthesis and Morphology ControlADVANCED MATERIALS, Issue 16 2010Tapan K. Sau Abstract Metal nanoparticles have been the subject of widespread research over the past two decades. In recent years, noble metals have been the focus of numerous studies involving synthesis, characterization, and applications. Synthesis of an impressive range of noble metal nanoparticles with varied morphologies has been reported. Researchers have made a great progress in learning how to engineer materials on a nanometer length scale that has led to the understanding of the fundamental size- and shape-dependent properties of matter and to devising of new applications. In this article, we review the recent progress in the colloid-chemical synthesis of nonspherical nanoparticles of a few important noble metals (mainly Ag, Au, Pd, and Pt), highlighting the factors that influence the particle morphology and discussing the mechanisms behind the nonspherical shape evolution. The article attempts to present a thorough discussion of the basic principles as well as state-of-the-art morphology control in noble metal nanoparticles. [source] Bioinspired Mineralization of Inorganics from Aqueous Media Controlled by Synthetic PolymersMACROMOLECULAR BIOSCIENCE, Issue 2 2007Katarzyna Gorna Abstract The formation of inorganic structures in nature is commonly controlled by biogenic macromolecules. The understanding of mineralization phenomena and the nucleation and growth mechanisms involved is still a challenge in science but also of great industrial interest. This article focuses on the formation and mineralization of two archetypical inorganic materials: zinc oxide and amorphous calcium carbonate (ACC). Zinc oxide is selected as a model compound to investigate the role that polymers play in mineralization. Most of the effort has been devoted to the investigation of the effects of double-hydrophilic block and graft copolymers. Recent work has demonstrated that latex particles synthesized by miniemulsion polymerization, properly functionalized by various chemical groups, have similar effects to conventional block copolymers and are excellently suited for morphology control of ZnO crystals. Latex particles might serve as analogues of natural proteins in biomineralization. The second example presented, ACC, addresses the issue of whether this amorphous phase is an intermediate in the biomineralization of calcite, vaterite, or aragonite. Conditions under which amorphous calcium carbonate can be obtained as nanometer-sized spheres as a consequence of a liquid,liquid phase segregation are presented. Addition of specific block copolymers allows control of the particle size from the micrometer to the submicrometer length scale. The physical properties of novel materials synthesized from concentrated solution and their potential applications as a filler of polymers are also discussed. [source] Ammonium oxotrifluorotitanate: morphology control and conversion to anatase TiO2PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2008Lei Zhou Abstract Uniform ammonium oxotrifluorotitanate (NH4TiOF3) mesocrystals were synthesized from an aqueous solution containing (NH4)2TiF6 and H3BO3 in presence of nonionic surfactant. Effects of various reaction conditions on the morphology of the NH4TiOF3 mesocrystals were examined by electron microscopy techniques. Results indicate that static solution, high surfactant concentration and low reaction temperature enhance the formation of uniform NH4TiOF3 mesocrystals with regular shapes. By sintering in atmosphere, the NH4TiOF3 mesocrystals were converted to anatase TiO2, which retain the original shapes of the NH4TiOF3 precursor due to similarities on their atom structures. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fabrication of porous ZnO nanostructures and morphology controlPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2007Sang Hyun Lee Abstract Porous ZnO nanostructures were easily fabricated by annealing and etching of as-grown ZnO nanorods using an aqueous solution method at low temperature. The density of ZnO nanorods was changed by repetition of coating and drying of zinc acetate hydrate in ethanol. The annealing process is a very critical step to make porous ZnO nanorods because nano-sized pore are formed at this step. Without annealing, pores could not be observed at the surface of ZnO nanorods. Furthermore, pore the size gets larger in etching steps following the annealing. The structural and optical properties for porous ZnO nanostructures were investigated using TEM and PL. Porous ZnO nanostructures were grown along the c-axis and pores were distributed in the whole body. PL intensity was increased by annealing and etching. This is ascribed to the improved crystallinity and large surface area. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Novel aromatic polyimide fiber with biphenyl side-groups: Dope synthesis and filament internal morphology controlPOLYMER ENGINEERING & SCIENCE, Issue 2 2006Xiangyang Liu A new organic-soluble aromatic polyimide with biphenyl side-groups has been synthesized from 4,4,-oxydiphthalic anhydride and 3,5-diamino-benzonic-4,-biphenyl ester (DABBE) via a one-step polymerization in m -cresol. A higher molecular weight polyimide has been obtained by the addition of chlorotrimethylsilane (TMSCl) in the solution of DABBE to form, in situ, silylated diamine. The optimum mole amount of TMSCl relative to the number of amino groups is 100%. This polyimide is soluble in m -cresol, allowing fibers to be spun from isotropic solution using a dry-jet wet spinning method. Based on a ternary phase diagram of m -cresol, ethanol, and water, controlling of the internal morphology of as-spun fibers has been achieved by varying the rate of polyimide coagulation through adjustment of nonsolvent/solvent miscibility in the coagulation bath. Scanning electron microscopic pictures show that filament internal morphologies ranged from porous-like to fully solid. The solid as-spun fibers can be drawn at high temperatures (>330°C) under tension to high drawn ratios (up to 6×), which produces a remarkable increase in tensile strength to about 1.0 GPa and an initial modulus higher than 60 GPa. POLYM. ENG. SCI. 46:123,128, 2006. © 2005 Society of Plastics Engineers [source] Morphology in Immiscible Polymer Blends During Solidification of an Amorphous Dispersed Phase under ShearingTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2002Yves Deyrail Abstract Solidification under shear of dispersed polycarbonate (PC) fibers in copolymer polyethylene-methyl acrylate matrix (EMA) was investigated using a hot optical shear device. First, the deformation of PC droplets and its modeling under isothermal conditions were studied for comprehension purposes. Overall agreement with literature models was found and the main influence of the viscosity ratio has been stressed. Second, the morphology control through dynamic quenching was experimented. It consists of solidifying the amorphous PC dispersed phase under shear flow. Break-up times of PC fibers were taken into account. Shear rate and quenching-time balance was demonstrated. Thus, during dynamic solidification, a fibrillar morphology could be obtained through rapid quenching. Long quenching times allow nodular morphology, whose size depends on the shear rate used. PC rods can be obtained by adjusting the shear rate during dynamic quenching. La solidification sous cisaillement du polycarbonate (PC) dispersé dans une matrice copolymère éthylène-acétate de vinyle (EMA) a été suivie à l'aide d'un microscope et d'une platine de cisaillement chauffante. Dans un premier temps la déformation isotherme de billes de PC pour différentes températures a été étudiée, ainsi que sa modélisation. Une bonne corrélation avec les modèles issus de la littérature a été obtenue. L'importance du rapport des viscosités a été ainsi soulignée. Dans un second temps le contrôle de la morphologie par le procédé de « refroidissement dynamique » a été expérimenté. Celui-ci consiste à solidifier le PC sous cisaillement pendant le refroidissement. Les temps de rupture des fibres de PC ont été considérés et l'importance du couple gradient de cisaillement-temps de refroidissement sur le contrôle de la morphologie a été mis en évidence. Pendant la solidification, un refroidissement rapide permet d'obtenir une morphologie fibrillaire. [source] Organic,inorganic hybrid mesoporous silicas: functionalization, pore size, and morphology controlTHE CHEMICAL RECORD, Issue 1 2006Sung Soo Park Abstract Topological design of mesoporous silica materials, pore architecture, pore size, and morphology are currently major issues in areas such as catalytic conversion of bulky molecules, adsorption, host,guest chemistry, etc. In this sense, we discuss the pore size-controlled mesostructure, framework functionalization, and morphology control of organic,inorganic hybrid mesoporous silicas by which we can improve the applicability of mesoporous materials. First, we explain that the sizes of hexagonal- and cubic-type pores in organic,inorganic hybrid mesoporous silicas are well controlled from 24.3 to 98.0,Å by the direct micelle-control method using an organosilica precursor and surfactants with different alkyl chain lengths or triblock copolymers as templates and swelling agents incorporated in the formed micelles. Second, we describe that organic,inorganic hybrid mesoporous materials with various functional groups form various external morphologies such as rod, cauliflower, film, rope, spheroid, monolith, and fiber shapes. Third, we discuss that transition metals (Ti and Ru) and rare-earth ions (Eu3+ and Tb3+) are used to modify organic,inorganic hybrid mesoporous silica materials. Such hybrid mesoporous silica materials are expected to be applied as excellent catalysts for organic reactions, photocatalysis, optical devices, etc. © 2006 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 6: 32,42; 2006: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20070 [source] Tetraethylenepentamine-Directed Controllable Synthesis of Wurtzite ZnSe Nanostructures with Tunable MorphologyCHEMISTRY - A EUROPEAN JOURNAL, Issue 31 2008Baojuan Xi Dr. Abstract A novel tetraethylenepentamine (TEPA)-directed method has been successfully developed for the controlled synthesis of ZnSe particles with distinctive morphologies, including nanobelts, nanowires, and hierarchically solid/hollow spheres. These structures, self-assembled from nanobelts and nanorods, have been synthesized by adjusting the reaction parameters, such as the solvent composition, reaction temperature, and the aging time. Results reveal that the volume ratio of H2O and TEPA plays a crucial role in the final morphology of ZnSe products. The mechanisms of phase formation and morphology control of ZnSe particles are proposed and discussed in detail. The products have been characterized by means of X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy (TEM), selected area electron diffraction, high-resolution TEM, Raman spectra and luminescence spectroscopy. The as-prepared ZnSe nanoparticles display shape- and size-dependent photoluminescent optical properties. This is the first time to report preparation of complex hollow structures of ZnSe crystals with hierarchy through a simple solution-based route. This synthetic route is designed to exploit a new H2O/TEPA/N2H4,H2O system possibly for the preparation of other semiconductor nanomaterials. [source] | ||||||||||||||||||||||||||||