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Experimental realization of crossover in shape and director field of nematic tactoids

Physical Review E 2015年第4期91卷 042507-042507页

作者： Vida Jamali Natnael Behabtu Bohdan Senyuk J. Alex Lee Ivan I. Smalyukh Paul van der Schoot Matteo Pasquali Department of Chemical and Biomolecular Engineering Rice University Houston Texas 77005 USA Department of Physics University of Colorado at Boulder Boulder Colorado 80309 USA Department of Electrical Computer and Energy Engineering and Materials Science and Engineering Program and Liquid Crystals Materials Research Center University of Colorado at Boulder Colorado 80309 USA Renewable and Sustainable Energy Institute National Renewable Energy Laboratory and University of Colorado Boulder Colorado 80309 USA Polymer Physics Group for Theory of Polymers and Soft Matter Group Department of Applied Physics Eindhoven University of Technology P.O. Box 513 5600 MB Eindhoven The Netherlands Institute for Theoretical Physics Utrecht University Leuvenlaan 4 3584 CE Utrecht The Netherlands Department of Chemistry Department of Materials Science and NanoEngineering The Smalley Institute for Nanoscale Science and Technology Rice University Houston Texas 77005 USA

Spindle-shaped nematic droplets (tactoids) form in solutions of rod-like molecules at the onset of the liquid crystalline phase. Their unique shape and internal structure result from the interplay of the elastic deformation of the nematic and anisotropic surface forces. The balance of these forces dictates that tactoids must display a continuous variation in aspect ratio and director-field configuration. Yet, such continuous transition has eluded observation for decades: tactoids have displayed either a bipolar configuration with particles aligned parallel to the droplet interface or a homogeneous configuration with particles aligned parallel to the long axis of the tactoid. Here, we report the first observation of the continuous transition in shape and director-field configuration of tactoids in true solutions of carbon nanotubes in chlorosulfonic acid. This observation is possible because the exceptional length of carbon nanotubes shifts the transition to a size range that can be visualized by optical microscopy. Polarization micrographs yield the interfacial and elastic properties of the system. Absorbance anisotropy measurements provide the highest nematic order parameter (S=0.79) measured to date for a nematic phase of carbon nanotubes at coexistence with its isotropic phase.

关键词： NEMATIC liquid crystals RESEARCH CARBON nanotubes ABSORBANCE (Light) CHLOROSULFONIC acid OPTICAL microscopes ELASTICITY

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Field testing to estimate ozone emission rates of in-duct air cleaners in occupied homes 13

Field testing to estimate ozone emission rates of in-duct ai...

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13th International Conference on Indoor Air Quality and Climate, Indoor Air 2014

作者： Shaughnessy, Richard Reisdorph, David Morrison, Glenn Indoor Air Program Department of Chemical Engineering University of Tulsa OK United States Civil Architectural and Environmental Engineering Department Missouri University of Science and Technology RollaMO United States

Considerable concern, research, and regulation have been linked to the use of portable air cleaners that intentionally (or unintentionally) produce ozone in the indoor environment. This research focuses on the potential for electrically connected in-duct air cleaners to increase indoor concentrations of ozone in field sites. The objective of the research was to measure the incremental increase in the ozone concentration and estimate the in-use ozone emission rate when a commercially available in-duct air cleaning device is operating. Devices tested included UV lamps, photocatalytic oxidation systems and electrostatic precipitators. A field method was implemented in 6 houses and 1 commercial space. In-duct air cleaners produced ozone to varying degrees, increasing the indoor home concentration by as much as 134 ppb while operating normally in residences. Emission rates as high as 436 mg h-1 were observed., Explicit ozone generators were the highest emitters, raising indoor concentrations above 50 ppb in most tests. Most other devices did not raise ozone concentrations above 50 ppb and ozone emission rates for these devices were below 50 mg h-1.

关键词： Ozone

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Development of hydroxyapatite-mediated synthesis of collagen-based copolymers for application as bio scaffolds in bone regeneration

Development of hydroxyapatite-mediated synthesis of collagen...

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2013 MRS Fall Meeting

作者： Bhuiyan, Didarul Middleton, John Tannenbaum, Rina Department of Biomedical Engineering University of Alabama at Birmingham Birmingham AL 35924 United States Department of Materials Science and Engineering Program in Chemical and Molecular Engineering Stony Brook University Stony Brook NY 11794 United States

Hydroxyapatite (HAP) is a biocompatible bio-ceramic whose structure and composition is similar to bone. However, its lack of strength and toughness have seriously hampered its applications as a bone graft substitute material. Attempts have been made to overcome these mechanical properties deficiencies by combining HAP bioceramic material with absorbable polymers in order to improve its mechanical properties. However, poor interfacial bonding between the HAP and the polymers has limited the benefits of such biocomposite structures. At the other end of the biomaterials spectrum is collagen, which constitutes the most abundant proteins in the body and exhibits properties such as biodegradability, bioadsorbability with low antigenicity, high affinity to water, and the ability to interact with cells through integrin recognition. These favorable properties renders collagen as a natural candidate for the modification and compatibilization of the polymer-HAP biocomposite. In this study, we developed a novel approach to the synthesis of a potential bone graft material, where the HAP moiety acts not only as a bioceramic filler, but also constitutes the initiator surface that promotes the in-situ polymerization of the adsorbable polymer of choice. The synthesis of poly(D,L-lactide-co-glycolide) (PLGA) polymer was catalyzed by nano-hydroxyapatite (nHAP) particles and upon reaction completion, the biocomposite material was tethered with collagen. The synthesis was monitored by 1H NMR and FTIR spectroscopies and the products after each step were characterized by thermal analysis to probe both thermal stability, morphological integrity and mechanical properties. Copyright © Materials Research Society 2014.

关键词： Hydroxyapatite

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Barrier coatings for packaging papers 13

Barrier coatings for packaging papers

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13th TAPPI Advanced Coating Fundamentals Symposium 2014

作者： Richmond, Finley Bousfield, Doug Spender, Jonathan Bilodeau, Mike Paper Surface Science Program United States Process Development Center University of Maine Department of Chemical and Biological Engineering United States

ISBN: (纸本)9781510801295

• Blade coating works well and gives better values than rod coating at low coat weights. (no wire marks to link to defects). • 50 % zein and 50% soy protein provided good barrier properties. • The addition of pigment helps enhance barrier properties, if not at too high a level. PVC must be less than 40 • Films that are brittle likely generate fine cracks that result in poor performance. • Diffusion mechanisms are likely to be less important than capillary flow phenomena related to barrier properties. • Removing all pores, even pores less than 0.1 microns in diameter, is critical. • Barrier pigments are good at low PVC.

关键词： Coatings

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Nanocrystalline gold-based hydrogen sulfide (H2S) sensor from M13 bacteriophage template

Nanocrystalline gold-based hydrogen sulfide (H2S) sensor fro...

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Nanotechnology 2014: MEMS, Fluidics, Bio Systems, Medical, Computational and Photonics - 2014 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2014

作者： Moon, Chung Hee Zhang, Miluo Myung, Nosang V. Haberer, Elaine D. Materials Science and Engineering Program University of California Riverside CA United States Department of Chemical and Environmental Engineering University of California Riverside CA United States Department of Electrical Engineering University of California Riverside CA United States

ISBN: (纸本)9781482258271

Bio-templated assembly enables facile bottom-up assembly of complex and unique nanostructures for chemiresistive gas sensors. Viral-templated gold nanowires have been synthesized for use in highly sensitive H2S sensors that operate at room temperature. The biological template served as a physical template for gold nanoparticle alignment and as a functional component to enhance sensor sensitivity. Viral-templated gold nanowire H2S sensors displayed high performance with sensitivity near 850%/ppm, lowest detection limit of 1 ppb, and 70% recovery after 6 min for 0.025 ppm. In comparison, a H2S sensor in which the viral template was removed showed a 170 times lower sensitivity of 5%/ppm and no recovery. High sensitivity, room temperature operational viral-templated gold nanowire based H2S sensors have been fabricated and characterized, showing promise of biological-templated nanostructures for enhanced gas sensing.

关键词： Hydrogen sulfide

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Chemiresistive hydrogen (H2) gas sensor based on viral-templated Pd nanowires

Chemiresistive hydrogen (H2) gas sensor based on viral-templ...

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Nanotechnology 2014: MEMS, Fluidics, Bio Systems, Medical, Computational and Photonics - 2014 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2014

作者： Moon, Chung Hee Yan, Yiran Zhang, Miluo Myung, Nosang V. Haberer, Elaine D. Materials Science and Engineering Program University of California Riverside CA United States Department of Chemical and Environmental Engineering University of California Riverside CA United States Department of Electrical Engineering University of California Riverside CA United States

ISBN: (纸本)9781482258271

A simple, novel technique for chemiresistive H2 gas sensor fabrication has been developed using an M13 bacteriophage template. The biological template was used to assemble chains of gold (Au) nanoparticles which were covered with palladium (Pd) using electroless deposition, thus producing Au@Pd core-shell nanowires. Sensors were composed of a randomly dispersed, nanowire network and had measured resistances between 1 and 1000 kΩ. Room temperature sensing analysis was completed for H2 gas concentrations from 100 ppm to 2000 ppm. Device resistance increased with H2 gas exposure. For these viral-templated Pd nanowire sensors, a maximum response of 160% was found at 2000 ppm and a lowest limit of detection of 6 ppm was determined.

关键词： Hydrogen

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Fine control of carbon-polyelectrolyte thin film sensors sensitivity for human motion monitoring

Fine control of carbon-polyelectrolyte thin film sensors sen...

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Fifth Asia International Symposium on Mechatronics (AISM 2015)

作者： S. Seo J. J. Park Y. T. Park Myongji University Seodaemun-gu Seoul KR Department of Chemical and Biomolecular Engineering (BK21+Graduate Program) Korea Advanced Institute of Science and Technology (KAIST) 291 Daehak-ro Yuseong-gu Daejeon 305-701 Republic of Korea Department of Mechanical Engineering Myongji University 116 Myongji-ro Cheoin-gu Youngin Gyeonggi-do 449-728 Republic of Korea

Carbon nanomaterials have emerged as highly promising nanomaterials for recent thirty years. There have been numerous researches regarding potential applications of carbon nanomaterials due to their outstanding properties which originate from the network of sp2-hybridized carbon atoms. In this regard, it is also reported that a variety of functional composites or hybrid materials with carbon nanomaterials result in novel applications as well as synergistic enhancements in target properties. In this study, multi-functional polymer/graphene nanoplatelet multilayer composite films were fabricated by layer-by-layer assembly. Graphene nanoplatelets (GNPs), two-dimensional carbon nanomaterials provide not only excellent electrical conductivity but barrier property for gas molecules. Layer-by-layer assembly is a simple, inexpensive bottom-up techniques for multilayer film deposition with easy control of inner structures. In this study, transparent conductor for next generation flexible electronics was considered as a potential application of layer-by-layer assembled polymer/GNP multilayer composites films. GNP coating on thin polymer substrates was expected to be applicable to flexible display applications, while metal oxides such as indium tin oxide have a limitation due to its mechanical fragility. Thus, electrically conductive layer-by-layer assembled GNP films which shows gas barrier property as well as mechanical flexibility could be fabricated with low material and processing cost. Though thermal annealing and acid treatment on GNP films effectively lowered the sheet resistance of the films, their transmittance and sheet resistance still need to improve further to be used as transparent conductors for flexible display applications. Meanwhile, further efforts must be focused on the possibility of other applications.

关键词： Carbon nanotube Conductive electrode Graphene Layer-by-layer (LbL) self-assembly Strain sensor Surface resistance fine control graphene Carbon Nanotubes BARRIER PROPERTIES economic indicators flexible displays Carbon Nanomaterials strain sensors thin film sensors functional composite material assemblies multilayers Composite films

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On the origin of anisotropic lithiation in crystalline silicon over germanium: A first principles study

On the origin of anisotropic lithiation in crystalline silic...

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作者： Chou, Chia-Yun Hwang, Gyeong S. Materials Science and Engineering Program University of Texas at Austin AustinTX78712 United States Department of Chemical Engineering University of Texas at Austin AustinTX78712 United States

Silicon (Si) and germanium (Ge) are both recognized as a promising anode material for high-energy lithium-ion batteries. Si is abundant and best known for its superior gravimetric energy storage capacity, while Ge exhibits faster charge/discharge rates and better capacity retention. Recently, it was discovered that Si lithiation exhibits strong orientation dependence while Ge lithiation proceeds isotropically, although they have the same crystalline structure. To better understand the underlying reasons behind these distinctive differences, we examine and compare the lithiation behaviors at the Li4Si/c-Si(1 1 0) and Li4Ge/c-Ge(1 1 0) model systems using ab initio molecular dynamics simulations. In comparison to lithiated c-Si, where a sharp amorphous-crystalline interface remains and advances rather slowly, lithiated c-Ge tends to loose its crystallinity rapidly, resulting in a graded lithiation front of fast propagation speed. Analysis of the elastic responses and dynamics of the host Si and Ge lattices clearly demonstrate that from the beginning of the lithiation process, Ge lattice responds with more significant weakening as compared to the rigid Si lattice. Moreover, the more flexible Ge lattice is found to undergo facile atomic rearrangements during lithiation, overshadowing the original crystallographic characteristic. These unique properties of Ge thereby contribute synergistically to the rapid and isotropic lithiation. © 2014 Elsevier B.V. All rights reserved.

关键词： Density functional theory

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The effects of biolatex binders on the dynamic water retention properties of paper coating formulations

O Papel

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O Papel 2014年第3期75卷 55-65页

作者： Bloembergen, Steven Santos, Marcelo Pampolha Greenall, Phil DeJong, Ralph Shin, Jae Y. Jones, Nathan Fleming, Paul D. Joyce, Margaret K. Lee, Ik Executive VP Technology EcoSynthetix Inc. Lansing MI United States Latin America São Paulo Brazil EcoSynthetix Europe Germany Customer Solutions Burlington ON Canada Dep. of Chemical and Paper Engineering Western Michigan University Kalamazoo MI United States Macromolecular Science and Engineering University of Michigan Ann Arbor MI United States Department of Chemical and Paper Engineering Western Michigan University Kalamazoo MI United States EcoSynthetix Inc. Midland MI United States

The following paper is a continuation of findings presented by the authors at PaperCon 2012 demonstrating the interesting rheological properties of biolatex binder dispersions and their coating colors relative to conventional coating starches and SB latex binders. The previous work indicated that the rheological performance of biolatex binder is significantly different from that of conventional cooked coating starches and all-synthetic latex containing formulations. This study investigates the dynamic water retention and wall slip properties of the same materials in order improve the understanding on coater runnability performance. Ensuring the correct rheology and water retention of coating colors is important as coater speeds increase and in order to achieve good runnability, productivity and final product quality it is critical to have a comprehensive understanding. It is common that quality and runnability problems originate from the interaction between base paper and the water phase of the coating color. Failure to control this interaction can lead to excessive migration of coating color to the base paper. This results in poor machine runnability, unstable systems and a non-uniform coating layer. In these evaluations an ultra-high shear ACA Viscometer (ACAV) was used to provide further insight into the wall slip properties of coating colors at shear rates that are relevant to industrial-scale paper coating processes. Results from these studies in combination with the results from previously presented rheological studies help explain some of the fundamental differences of these binder systems.

关键词： Binders

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A xylose-fermenting yeast hybridized by intergeneric fusion between Saccharomyces cerevisiae and Candida intermedia mutants for ethanol production

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Sustainable chemical Processes 2014年第1期2卷 1-12页

作者： Prihardi Kahar Shuzo Tanaka Department of Chemical Science and Engineering Faculty of Engineering Kobe University Kobe Japan Program in Environment and Ecology Department of Interdisciplinary Science and Engineering Faculty of Science and Engineering Meisei University Tokyo Japan

Bioethanol production from lignocellulosic biomass, in particular xylose, is currently of great concern, given the abundance of this sugar in the world, because Saccharomyces cerevisiae, which is widely used for bioethanol production, is unable to naturally ferment xylose. The aim of this study was to obtain a novel yeast capable of stably producing ethanol from biomass containing xylose by protoplast fusion between S. cerevisiae and xylose-utilizing yeast. We describe a novel xylose-fermenting yeast strain, FSC1, developed for ethanol production by intergeneric hybridization between S. cerevisiae and Candida intermedia mutants by using a protoplast fusion technique. The characteristics of the FSC1 strain are reported with respect to xylose fermentation, morphology, gene, and protein expression. Mutation of the parental strains prior to protoplast fusion endowed the FSC1 strain with the ability to convert xylose to ethanol. Microscopic analysis confirmed that the parental and FSC1 strains produced spores in the potassium acetate medium. The FSC1 strain is uninucleate diploid, has a stable metabolism, and expresses proteins at a higher level than the parental strains. We found that FSC1 strain could stably achieve an ethanol yield of 0.38 g/g-substrate in fermentation of a mixture of glucose and xylose. In addition, the fermentation ability of FSC1was improved by successive chemical mutation, resulting in a higher ethanol yield of 0.42 g/g-substrate, corresponding to 82% theoretical yield. The mutation-fusion technique we have described here is very useful for the development of intergeneric hybrids capable of xylose fermentation, and the FSC strains generated using this technique have the potential for industrial use in ethanol production from lignocellulosic biomass.

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