Science.gov

Sample records for rod-like pyreneperylene bisimide

  1. Rod-like nano-light harvester.

    PubMed

    Ling, Jun; Zheng, Zhicheng; Köhler, Anna; Müller, Axel H E

    2014-01-01

    Imitating the natural "energy cascade" architecture, we present a single-molecular rod-like nano-light harvester (NLH) based on a cylindrical polymer brush. Block copolymer side chains carrying (9,9-diethylfluoren-2-yl)methyl methacrylate units as light absorbing antennae (energy donors) are tethered to a linear polymer backbone containing 9-anthracenemethyl methacrylate units as emitting groups (energy acceptors). These NLHs exhibit very efficient energy absorption and transfer. Moreover, we manipulate the energy transfer by tuning the donor-acceptor distance.

  2. Phosphorus-containing bisimide resins

    NASA Technical Reports Server (NTRS)

    Varma, I. K.; Fohlen, G. M.; Parker, J. A. (Inventor)

    1981-01-01

    The production of fire-resistant resins particularly useful for making laminates with inorganic fibers such as graphite fibers is discussed. The resins are by (1) condensation of an ethylenically unsaturated cyclic anhydride with a bis(diaminophenyl) phosphine oxide, and (2) by addition polymerization of the bisimide so obtained. Up to about 50%, on a molar basis, of benzophenonetetracarboxylic acid anhydride can be substituted for some of the cyclic anhydride to alter the properties of the products. Graphite cloth laminates made with these resins show 800 C char yields greater than 70% by weight in nitrogen. Limiting oxygen indexes of more than 100% are determined for these resins.

  3. Percolation thresholds for rod-like particles: polydispersity effects

    NASA Astrophysics Data System (ADS)

    Chatterjee, Avik P.

    2008-06-01

    A model based upon excluded volume considerations is presented for the connectedness percolation thresholds in polydisperse systems of cylindrical rod-like nanoparticles. The dependence of the percolation threshold upon polydispersity index and number-averaged aspect ratio is examined for two different distribution functions for the rod radii and lengths. The importance of accounting for polydispersity is explored in the context of measurements of the elastic moduli and electrical conductance in fibre-filled nanocomposites.

  4. New phosphorus-containing bisimide resins

    NASA Technical Reports Server (NTRS)

    Varma, I. K.; Fohlen, G. M.; Hsu, M.-T.; Parker, J. A.

    1984-01-01

    Phosphorus-based flame retardants have been effectively used in a wide variety of polymeric materials. Such additives, however, may either influence the decomposition reaction in polymers or lack durability due to a tendency to be leached out by solvents. Attention is given to the synthesis, characterization, thermal stability and degradation mechanisms of bisimide resins, and an evaluation is conducted of the flammability and mechanical properties of graphite cloth-reinforced laminates fabricated from one of the six phosphorus-containing bisimide resins considered.

  5. Rod-like polyelectrolyte brushes with mono- and multivalent counterions

    NASA Astrophysics Data System (ADS)

    Fazli, H.; Golestanian, R.; Hansen, P. L.; Kolahchi, M. R.

    2006-02-01

    A model of rod-like polyelectrolyte brushes in the presence of monovalent and multivalent counterions but with no added salt is studied using Monte Carlo simulation. The average height of the brush, the histogram of rod conformations, and the counterion density profile are obtained for different values of the grafting density of the charge-neutral wall. For a domain of grafting densities, the brush height is found to be relatively insensitive to the density due to a competition between counterion condensation and inter-rod repulsion. In this regime, multivalent counterions collapse the brush in the form of linked clusters. Nematic order emerges at high grafting densities, resulting in an abrupt increase of the brush height.

  6. 2-Hydroxypropyltrimethylammonium xylan adsorption onto rod-like cellulose nanocrystal.

    PubMed

    Sim, Jae Hyun; Dong, Shuping; Röemhild, Katrin; Kaya, Abdulaziz; Sohn, Daewon; Tanaka, Keiji; Roman, Maren; Heinze, Thomas; Esker, Alan R

    2015-02-15

    Chemical incompatibility and relatively weak interaction between lignocellulosic fibers and synthetic polymers have made studies of wood fiber-thermoplastic composite more challenging. In this study, adsorption of 2-hydroxypropyltrimethylammonium xylans onto rod-like cellulose nanocrystals are investigated by zeta-potential measurements, and polarized and depolarized dynamic light scattering as a factor for better understanding of lignocellulosic fibers and cellulose nanocrystals. Zeta-potential measurements show xylan derivative adsorption onto cellulose nanocrystals. Decay time distributions of the ternary system and binary system from dynamic light scattering show that aggregates exist in the binary system and they disappear in the ternary system. At low 2-hydroxypropyltrimethylammonium xylan concentrations relative to that of cellulose nanocrystal, xylan derivatives adsorbed onto some of the cellulose nanocrystal. Hence, more xylan derivatives adsorbed onto cellulose nanocrystal increased with increasing xylan derivative concentration. Also, the concentration dependence of the ratio of the rotational diffusion coefficient to the translational diffusion coefficient revealed a strong adsorptive interaction between xylan derivatives and the cellulose nanocrystals.

  7. Size Dependent Cellular Uptake of Rod-like Bionanoparticles with Different Aspect Ratios

    PubMed Central

    Liu, Xiangxiang; Wu, Fengchi; Tian, Ye; Wu, Man; Zhou, Quan; Jiang, Shidong; Niu, Zhongwei

    2016-01-01

    Understanding the cellular internalization mechanism of nanoparticles is essential to study their biological fate. Especially, due to the anisotropic properties, rod-like nanoparticles have attracted growing interest for the enhanced internalization efficiency with respect to spherical nanoparticles. Here, to elucidate the effect of aspect ratio of rod-like nanoparticles on cellular uptake, tobacco mosaic virus (TMV), a typical rod-like bionanoparticle, is developed as a model. Nanorods with different aspect ratios can be obtained by ultrasound treatment and sucrose density gradient centrifugation. By incubating with epithelial and endothelial cells, we found that the rod-like bionanoparticles with various aspect ratios had different internalization pathways in different cell lines: microtubules transport in HeLa and clathrin-mediated uptake in HUVEC for TMV4 and TMV8; caveolae-mediated pathway and microtubules transport in HeLa and HUVEC for TMV17. Differently from most nanoparticles, for all the three TMV nano-rods with different aspect ratios, macropinocytosis takes no effect on the internalization in both cell types. This work provides a fundamental understanding of the influence of aspect ratio on cellular uptake decoupled from charge and material composition. PMID:27080246

  8. Theory and simulations of toroidal and rod-like structures in single-molecule DNA condensation.

    PubMed

    Cortini, Ruggero; Caré, Bertrand R; Victor, Jean-Marc; Barbi, Maria

    2015-03-14

    DNA condensation by multivalent cations plays a crucial role in genome packaging in viruses and sperm heads, and has been extensively studied using single-molecule experimental methods. In those experiments, the values of the critical condensation forces have been used to estimate the amplitude of the attractive DNA-DNA interactions. Here, to describe these experiments, we developed an analytical model and a rigid body Langevin dynamics assay to investigate the behavior of a polymer with self-interactions, in the presence of a traction force applied at its extremities. We model self-interactions using a pairwise attractive potential, thereby treating the counterions implicitly. The analytical model allows to accurately predict the equilibrium structures of toroidal and rod-like condensed structures, and the dependence of the critical condensation force on the DNA length. We find that the critical condensation force depends strongly on the length of the DNA, and finite-size effects are important for molecules of length up to 10(5)μm. Our Langevin dynamics simulations show that the force-extension behavior of the rod-like structures is very different from the toroidal ones, so that their presence in experiments should be easily detectable. In double-stranded DNA condensation experiments, the signature of the presence of rod-like structures was not unambiguously detected, suggesting that the polyamines used to condense DNA may protect it from bending sharply as needed in the rod-like structures.

  9. Theory and simulations of toroidal and rod-like structures in single-molecule DNA condensation

    NASA Astrophysics Data System (ADS)

    Cortini, Ruggero; Caré, Bertrand R.; Victor, Jean-Marc; Barbi, Maria

    2015-03-01

    DNA condensation by multivalent cations plays a crucial role in genome packaging in viruses and sperm heads, and has been extensively studied using single-molecule experimental methods. In those experiments, the values of the critical condensation forces have been used to estimate the amplitude of the attractive DNA-DNA interactions. Here, to describe these experiments, we developed an analytical model and a rigid body Langevin dynamics assay to investigate the behavior of a polymer with self-interactions, in the presence of a traction force applied at its extremities. We model self-interactions using a pairwise attractive potential, thereby treating the counterions implicitly. The analytical model allows to accurately predict the equilibrium structures of toroidal and rod-like condensed structures, and the dependence of the critical condensation force on the DNA length. We find that the critical condensation force depends strongly on the length of the DNA, and finite-size effects are important for molecules of length up to 105μm. Our Langevin dynamics simulations show that the force-extension behavior of the rod-like structures is very different from the toroidal ones, so that their presence in experiments should be easily detectable. In double-stranded DNA condensation experiments, the signature of the presence of rod-like structures was not unambiguously detected, suggesting that the polyamines used to condense DNA may protect it from bending sharply as needed in the rod-like structures.

  10. Effect of the ortho alkylation of perylene bisimides on the alignment and self-assembly properties.

    PubMed

    Dasgupta, Debarshi; Kendhale, Amol M; Debije, Michael G; Ter Schiphorst, Jeroen; Shishmanova, Ivelina K; Portale, Giuseppe; Schenning, Albertus P H J

    2014-08-01

    The effect of the ortho alkylation of perylene bisimides on the alignment and self-assembly properties has been studied. It was found that the dichroic properties of perylene bisimides in a liquid crystal host can be reversed with a single synthetic step by ortho alkylation. Furthermore, a solvent-induced growth of ultralong organic n-type semiconducting fibrils from non-ortho-alkylated perylene bisimide was observed. Ortho substitution of the perylene bisimide core alters the mode of fibrillar growth, leading to isotropic crystallization.

  11. Effect of the Ortho Alkylation of Perylene Bisimides on the Alignment and Self-Assembly Properties

    PubMed Central

    Dasgupta, Debarshi; Kendhale, Amol M; Debije, Michael G; ter Schiphorst, Jeroen; Shishmanova, Ivelina K; Portale, Giuseppe; Schenning, Albertus P H J

    2014-01-01

    The effect of the ortho alkylation of perylene bisimides on the alignment and self-assembly properties has been studied. It was found that the dichroic properties of perylene bisimides in a liquid crystal host can be reversed with a single synthetic step by ortho alkylation. Furthermore, a solvent-induced growth of ultralong organic n-type semiconducting fibrils from non-ortho-alkylated perylene bisimide was observed. Ortho substitution of the perylene bisimide core alters the mode of fibrillar growth, leading to isotropic crystallization. PMID:25478308

  12. Novel self-growth photocatalytic rod-like heterojunction for hydrogen production under visible light

    NASA Astrophysics Data System (ADS)

    Liu, Xiaobin; Que, Wenxiu; Xing, Yonglei; Yin, Xingtian; He, Yucheng; Javed, H. M. Asif

    2015-06-01

    Novel H3ONb3O8-CuNb3O8 (HN-CN) semiconductors with a configuration of rod-like heterojunction were formed through analogous self-growth process, including ion-exchange and crystal structure transition processes. A p-type CuNb3O8 nano-semiconductor was grown on a layer structured rod-like KNb3O8 crystal and the as-prepared HN-CN sample showed a broad absorption range (~800 nm). Especially, the HN-CN sample exhibited an improved photocatalytic activity for hydrogen production, and a model was proposed to explain the improvement in photocatalytic activity. Current study may provide a new way for the preparation of the p-n heterojunction with high performance under visible light.

  13. Preparation of hydroxyapatite rod-like crystals by protein precursor method

    SciTech Connect

    Han Yingchao; Li Shipu . E-mail: zlhyc@yahoo.com.cn; Wang Xinyu; Jia Li; He Jianhua

    2007-06-05

    Hydroxyapatite (HAP) rod-like crystals were successfully prepared by thermolysis of bovine serum albumin (BSA)/calcium-phosphate (CaP) colloidal precursors. The precursors were obtained by precipitation method from Ca(H{sub 2}PO{sub 4}){sub 2} and Ca(OH){sub 2}, in which BSA was added as regulation additive and ultrasound irradiation was utilized as assistant technology. The properties of the precursors, such as size distribution, morphology, thermodynamic changes, were determined by DLS, SPM and TGA-DTA. The characterization results from DLS, SPM, TG-DTA, XRD and SEM indicated that BSA interacted with CaP particles and formed about 7-130 nm BSA/CaP hybrid colloidal particles between 2 and 4 g/L of BSA concentration. With the increasing of sintering temperature, BSA disintegrated and burned out, and rod-like HAP crystals formed at about 600 deg. C. With the increasing of BSA concentration, the phase composition of products did not change and the HAP crystals became more uniform and smaller. The ratio of length to width ranged from 7.6 to 12 at 4 g/L BSA concentration. This method provides for a controllable bottom-up fabrication of HAP rod-like crystals.

  14. Rod-like bacterial shape is maintained by feedback between cell curvature and cytoskeletal localization

    PubMed Central

    Ursell, Tristan S.; Nguyen, Jeffrey; Monds, Russell D.; Colavin, Alexandre; Billings, Gabriel; Ouzounov, Nikolay; Gitai, Zemer; Shaevitz, Joshua W.; Huang, Kerwyn Casey

    2014-01-01

    Cells typically maintain characteristic shapes, but the mechanisms of self-organization for robust morphological maintenance remain unclear in most systems. Precise regulation of rod-like shape in Escherichia coli cells requires the MreB actin-like cytoskeleton, but the mechanism by which MreB maintains rod-like shape is unknown. Here, we use time-lapse and 3D imaging coupled with computational analysis to map the growth, geometry, and cytoskeletal organization of single bacterial cells at subcellular resolution. Our results demonstrate that feedback between cell geometry and MreB localization maintains rod-like cell shape by targeting cell wall growth to regions of negative cell wall curvature. Pulse-chase labeling indicates that growth is heterogeneous and correlates spatially and temporally with MreB localization, whereas MreB inhibition results in more homogeneous growth, including growth in polar regions previously thought to be inert. Biophysical simulations establish that curvature feedback on the localization of cell wall growth is an effective mechanism for cell straightening and suggest that surface deformations caused by cell wall insertion could direct circumferential motion of MreB. Our work shows that MreB orchestrates persistent, heterogeneous growth at the subcellular scale, enabling robust, uniform growth at the cellular scale without requiring global organization. PMID:24550515

  15. High performance mixed bisimide resins and composites based thereon

    NASA Technical Reports Server (NTRS)

    Parker, J. A.; ations.

    1986-01-01

    Mixtures of bismaleimide/biscitraconirnide resins produces materials which have better handling, processing or mechanical and thermal properties, particularly in graphite composites, than materials made with the individual resins. The mechanical strength of cured graphite composites prepared from a 1:1 copolymer of such bisimide resins is excellent at both ambient and elevated temperatures. The copolymer mixture provides improved composites which are lighter than metals and replace metals in many aerospace applications.

  16. Biotemplating rod-like viruses for the synthesis of copper nanorods and nanowires

    PubMed Central

    2012-01-01

    Background In the past decade spherical and rod-like viruses have been used for the design and synthesis of new kind of nanomaterials with unique chemical positioning, shape, and dimensions in the nanosize regime. Wild type and genetic engineered viruses have served as excellent templates and scaffolds for the synthesis of hybrid materials with unique properties imparted by the incorporation of biological and organic moieties and inorganic nanoparticles. Although great advances have been accomplished, still there is a broad interest in developing reaction conditions suitable for biological templates while not limiting the material property of the product. Results We demonstrate the controlled synthesis of copper nanorods and nanowires by electroless deposition of Cu on three types of Pd-activated rod-like viruses. Our aqueous solution-based method is scalable and versatile for biotemplating, resulting in Cu-nanorods 24–46 nm in diameter as measured by transmission electron microscopy. Cu2+ was chemically reduced onto Pd activated tobacco mosaic virus, fd and M13 bacteriophages to produce a complete and uniform Cu coverage. The Cu coating was a combination of Cu0 and Cu2O as determined by X- ray photoelectron spectroscopy analysis. A capping agent, synthesized in house, was used to disperse Cu-nanorods in aqueous and organic solvents. Likewise, reactions were developed to produce Cu-nanowires by metallization of polyaniline-coated tobacco mosaic virus. Conclusions Synthesis conditions described in the current work are scalable and amenable for biological templates. The synthesized structures preserve the dimensions and shape of the rod-like viruses utilized during the study. The current work opens the possibility of generating a variety of nanorods and nanowires of different lengths ranging from 300 nm to micron sizes. Such biological-based materials may find ample use in nanoelectronics, sensing, and cancer therapy. PMID:22548773

  17. Spatial configurations of charged rod-like particles in external electric field

    NASA Astrophysics Data System (ADS)

    Lisina, I.; Lisin, E.; Vaulina, O.

    2016-03-01

    Formation of different spatial configurations for system of charged rod-like particles is considered theoretically and numerically, including formation of layered structures in the external electric field. Analytical model for a determination of the angle between the axis of a rod and the symmetry axis of electric trap is presented. New algorithm is proposed here for a dynamical simulation of many interacting non-spherical particles. Conditions for a correct replacement of the interaction between uniformly charged rods by the interaction of "bipoles" (i.e., by two similar point charges) are obtained. Study was performed in a wide range of parameters that are similar to conditions of laboratory experiments in a dusty plasma.

  18. Thin film growth of aromatic rod-like molecules on graphene

    NASA Astrophysics Data System (ADS)

    Kratzer, M.; Teichert, C.

    2016-07-01

    Research on graphene (Gr) is a vastly expanding field due to its potential for technological applications. Its close structural and chemical relationship to conjugated organic molecules makes it a superior candidate as a transparent electrode material in organic electronics and optoelectronics. The growth of organic thin films—intensively investigated in the past few decades—has demonstrated the complexity in growth and nucleation processes arising from the anisotropy and spatial extension of the molecular building blocks. Choosing the small, conjugated rod-like molecules para-hexaphenyl and pentacene as model representatives for small organic molecules, we review recent findings in organic thin film growth on a variety of Gr substrates. Special attention is paid to the differences in the resulting growth arising from the various methods of Gr fabrication and support that affect both the Gr–molecule interfacing and the involved molecular diffusion processes.

  19. Transport of spherical colloids in layered phases of binary mixtures with rod-like particles.

    PubMed

    Piedrahita, Mauricio; Cuetos, Alejandro; Martínez-Haya, Bruno

    2015-05-01

    The transport properties of colloids in anisotropic media constitute a general problem of fundamental interest in experimental sciences, with a broad range of technological applications. This work investigates the transport of soft spherical colloids in binary mixtures with rod-like particles by means of Monte Carlo and Brownian Dynamics simulations. Layered phases are considered, that range from smectic phases to lamellar phases, depending on the molar fraction of the spherical particles. The investigation serves to characterize the distinct features of transport within layers versus those of transport across neighboring layers, both of which are neatly differentiated. The insertion of particles into layers and the diffusion across them occur at a smaller rate than the intralayer diffusion modulated by the formation of transitory cages in its initial stages. Collective events, in which two or more colloids diffuse across layers in a concerted way, are described as a non-negligible process in these fluids.

  20. Template- and micelle-free synthesis of rod-like gold nanoparticles with UVA irradiation

    NASA Astrophysics Data System (ADS)

    Li, Xue-Zheng; Lu, Qi-Fei; Zeng, Xian-Shun; Wang, Da-Jian

    2010-01-01

    Rod-like gold nanoparticles can be formed from HAuCl4 aqueous solution with ultraviolet (UV) irradiation in the absence of templates, avoiding possible poisonous surfactant embedded into the surface of functional gold nanoparticles applied in biomedicine. The aspect ratio of nanorods ranges from 1.1 to 4.4 with the concentration of HAuCl4 0.2 mM, which can be verified by HRTEM images and the absorption spectrum. It is found that the nanocluster with several atoms occurs prior to the formation of nanorods, highly corresponding to its typical absorption spectrum. Tracing the evolution in absorption spectra of HAuCl4 aqueous solution, it can be concluded that the formation mechanism of gold nanoparticles in this process is different from that in the conventional inductive growth model, possibly in a growth pattern with imperfect oriented attachment (IOA) relevant to the colliding-and-growing.

  1. Synthesis of flower- and rod-like nickel sulfide nanostructures by an organic-free hydrothermal process

    SciTech Connect

    Pan Qingtao; Huang Kai; Ni Shibing; Yang Feng; He Deyan

    2008-06-03

    Well-crystalline flower- and rod-like NiS nanostructures have been synthesized by an organic-free hydrothermal process at a low temperature of 200 deg. C. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were employed to characterize the as-synthesized NiS nanostructures. The effects of temperature and reaction time on the morphology have been also investigated. The two-step flake-cracking mechanism for the formation of flower- and rod-like NiS nanostructures was discussed. The products were also investigated by photoluminescence (PL) spectroscopy.

  2. Mucin aggregation from a rod-like meso-scale model

    NASA Astrophysics Data System (ADS)

    Moreno, Nicolas; Perilla, Jairo E.; Colina, Coray M.; Lísal, Martin

    2015-05-01

    Dissipative particle dynamics, a meso-scale particle-based model, was used to study the aggregation of mucins in aqueous solutions. Concentration, strength of the mucin-water interactions, as well as the effects of size, shape, and composition of the model molecules were studied. Model proteins were represented as rod-like objects formed by coarse-grained beads. In the first model, only one type of beads formed the mucin. It was found that all the surfaces were available to form aggregates and the conformation of the aggregates was a function of the strength of the mucin-water interaction. With this model, the number of aggregates was unaffected by the initial position of the mucins in the simulation box, except for the lowest mucin concentration. In a more refined mucin model, two kinds of beads were used in the molecule in order to represent the existence of cysteine-like terminal groups in the actual molecule. With this new scheme, aggregation took place by the interaction of the terminal groups between model molecules. The kinetic analysis of the evolution of the number of aggregates with time was also studied for both mucin models.

  3. Synthesis, Characterization and Luminescence Properties of Rod-Like LaPO4:Eu3+ Nanostructures.

    PubMed

    Peng, Li; Yun, Liu; Xiaolei, Shi; Yaxin, Guo; Gangqiang, Zhu

    2016-04-01

    Large-scale, rod-like nanostructures of LaPO4:Eu3+ phosphors were synthesized using a simple hydrothermal method. The phase composition, structure and morphology of the final products were characterized by XRD, FE-SEM and TEM. Highly crystalline material was obtained as confirmed by X-ray powder diffraction measurements. The FE-SEM and TEM observations indicate that the obtained LaPO4:Eu3+ nanorods have a diameter of about 10-20 nm, and a length of about 100-600 nm. Meanwhile, the excitation and emission spectra of the products at room temperature were measured using a fluorescence spectrometer. The effects of pH and Eu3+-doping on the morphology and luminescence properties of the as-prepared powders were investigated. The photoluminescence (PL) spectra show that the emission intensity of the LaPO4:Eu3+ phosphors improved with increases in concentrations of Eu3+ from 3 mol% to 14 mol%, and then decreased for higher concentrations. PMID:27451758

  4. Molecular dynamics in rod-like liquid crystals probed by muon spin resonance spectroscopy.

    PubMed

    McKenzie, Iain; Scheuermann, Robert; Sedlak, Kamil; Stoykov, Alexey

    2011-08-01

    Muoniated spin probes were produced by the addition of muonium (Mu) to two rod-like liquid crystals: N-(4-methoxybenzylidene)-4'-n-butylaniline (MBBA) and cholesteryl nonanoate (CN). Avoided level crossing muon spin resonance spectroscopy was used to characterize the muoniated spin probes and to probe dynamics at the molecular level. In MBBA Mu adds predominantly to the carbon of the bridging imine group and the muon and methylene proton hyperfine coupling constants (hfccs) of the resulting radical shift in the nematic phase due to the dipolar hyperfine coupling, the ordering of the molecules along the applied magnetic field and fluctuations about the local director. The amplitude of these fluctuations in in the nematic phase of MBBA is determined from the temperature dependence of the methylene proton hfcc. Mu adds to the double bond of the steroidal ring system of CN and the temperature dependence of the Δ(1) line width provides information about the amplitude of the fluctuations about the local director in the chiral nematic phase and the slow isotropic reorientation in the isotropic phase.

  5. Stiffness parameter of brush-like polymers with rod-like side chains.

    PubMed

    Nakamura, Yo

    2016-07-01

    The stiffness parameter λ(-1) of brush-like polymers having rod-like side chains with the hard core potential was calculated. Side chains are, first, assumed to be connected with a free joint to the main chain. The free energy per molecule F was calculated invoking the single contact approximation in which only the interaction between two side chains is considered and the higher interactions are ignored. In the calculation, the contact is assumed to occur when the two side chains are in a plain and the condition for the angles between the side chain and the main chain to make a triangle by two side chains and the main chain was exactly taken into account. The change of F after bending the main chain with a certain curvature from the straight state was calculated to obtain λ(-1). The resulting λ(-1) came close to the experimental value for brush-like polymers with a poly(methacrylate) main chain and poly(hexylisocyanate) (PHIC) side chains if we add a constant as the intrinsic stiffness of the main chain, λ0 (-1), to it. By considering the potential function having a minimum when the angle between the side and main chains equals π/2, the data for brush-like polymers with a poly(styrene) main chain and PHIC side chains were also closely fitted by the theoretical values with an appropriate value of λ0 (-1) and the force constant of the angle.

  6. Transformation of amorphous calcium carbonate to rod-like single crystal calcite via "copying" collagen template.

    PubMed

    Xue, Zhonghui; Hu, Binbin; Dai, Shuxi; Du, Zuliang

    2015-10-01

    Collagen Langmuir films were prepared by spreading the solution of collagen over deionized water, CaCl2 solution and Ca(HCO3)2 solution. Resultant collagen Langmuir monolayers were then compressed to a lateral pressure of 10 mN/m and held there for different duration, allowing the crystallization of CaCO3. The effect of crystallization time on the phase composition and microstructure of CaCO3 was investigated. It was found that amorphous calcium carbonate (ACC) was obtained at a crystallization time of 6 h. The amorphous CaCO3 was transformed to rod-like single crystal calcite crystals at an extended crystallization time of 12 h and 24 h, via "copying" the symmetry and dimensionalities of collagen fibers. Resultant calcite crystallites were well oriented along the longitudinal axis of collagen fibers. The ordered surface structure of collagen fibers and electrostatic interactions played key roles in tuning the oriented nucleation and growth of the calcite crystallites. The mineralized collagen possessing both desired mechanical properties of collagen fiber and good biocompatibility of calcium carbonate may be assembled into an ideal biomaterial for bone implants.

  7. Multistep photochemical charge separation in rod-like molecules based on aromatic insides and diimides

    SciTech Connect

    Greenfield, S.R.; Svec, W.A.; Gosztola, D.; Wasielewski, M.R. |

    1996-07-17

    A series of intramolecular triads with linear, rod-like structures has been developed that undergo very efficient two-step electron transfer following direct excitation of a chromophore possessing a charge transfer (CT) excited state. The CT state of 4-aminonaphthalene-1,8-imide (ANI), produced by direct excitation of the chromophore, has about 70% of a negative charge transferred from the amine to the imide. Attachment of aniline (AN) and p-methoxyaniline (MeOAn) donors to ANI by means of a piperazine bridge results in linear dyads. An-ANI and MeOAn-ANI, that undergo rapid electron transfer in about 10{sup -11} s to give a >99% yield of the ion pairs, An{sup +}-ANI{sup -} and MeOAn{sup +}-ANI{sup -}, in which the charges are separated by 7.7 A. Further attachment of a 1,8:4,5-naphthalene-dimide (NI) electron acceptor to the imide group of ANI using a 2,5-dimethyphenyl spacer results in triads An-ANI-NI and MeOAn-ANI-NI. Excitation of the CT state of ANI within these triads results in the same high yield charge separation step observed in the corresponding dyads followed by a subnanosecond charge shift reaction to yield the giant dipole states An{sup +}-ANI-NI{sup -} and MeOAn{sup +}-ANI-NI{sup -} in 72% and 92% yield, respectively, in toluene. The lifetime of MeOAn{sup +}-ANI-NI{sup -} is 310 ns. These triad molecules make explicit use of a CT excited state to initiate a multistep electron transfer process. 67 refs., 10 figs., 4 tabs.

  8. Competing mechanisms in the wear resistance behavior of biomineralized rod-like microstructures

    NASA Astrophysics Data System (ADS)

    Escobar de Obaldia, Enrique; Herrera, Steven; Grunenfelder, Lessa Kay; Kisailus, David; Zavattieri, Pablo

    2016-11-01

    guidelines for abrasion resistance rod-like microstructures in composites with high volume fraction of brittle minerals or ceramics with tailored performance for specific applications.

  9. Syntheses and Chemosensory of Anthracene and Phenanthrene Bisimide Derivatives

    NASA Technical Reports Server (NTRS)

    Bogusz, Zachary A.

    2004-01-01

    As the present technology of biochemical weapons advances, it is essential for science to attempt to prepare our nation for such an occurrence. Various areas of current research are devoted to precautionary measures and potential antidotes for national security. A practical application of these precautions would be the development of a chemical capable of detecting harmful gas. The benefits of being capable to synthesis a chemical compound that would warn and identify potentially deadly gases would ensure a higher level of safety. The chemicals in question can be generalized as bisimide anthracene derivatives. The idea behind these compounds is that in the presence of certain nerve gases, the compound will actually fluoresce, giving an indication that there is a strong likelihood of the presence of a nerve gas and ensure the proper precautionary measures are taken. The fluorescence is due to the quenching of an electric proton transfer within the structure of the molecule. The system proves to be very unique on account of the fact that the fluorescence can be "turned off" by reducing the system. By utilizing the synthesis designed by Dr. Faysal Ilhan, four distinct compounds can be synthesized through photochemical reactions involving para- and ortho- diketones. The photochemistry involved is very modem and much research is being devoted to fully understanding the possibilities and alternative applications of such materials. and meta-nitro anthracene bisimide (ABI-NO2), the amine of each (ABI-NH2), a para- and meta-nitro phenanthrene bisimjde (PBI-NO2), and the amine of each (PBI-NH2). Upon synthesizing these distinct compounds, I must then purify and analyze them in order to obtain any relevant trends, behaviors, and characteristics. The chemical composition analyses that will be conducted are the procedures taken by Dr. Daniel Tyson on previous experiments. The results generated from the data will point further research in the correct direction and hopefully

  10. Perylene bisimide macrocycles and their self-assembly on HOPG surfaces.

    PubMed

    Schlosser, Felix; Stepanenko, Vladimir; Würthner, Frank

    2010-11-28

    Acetylene-linked macrocycles incorporating multiple perylene tetracarboxylic acid bisimide (PBI) chromophores have been synthesised and separated by recycling GPC. The very first example of such macrocycles, i.e., cyclic trimer 5, containing three PBI dyes self-assembles into highly ordered donut-shaped unique hexagonal nanopatterns on HOPG surfaces as revealed by atomic force microscopy (AFM).

  11. Photoinduced processes in self-assembled porphyrin/perylene bisimide metallosupramolecular boxes.

    PubMed

    Indelli, M Teresa; Chiorboli, Claudio; Scandola, Franco; Iengo, Elisabetta; Osswald, Peter; Würthner, Frank

    2010-11-18

    Two new supramolecular boxes, (ZnMC)(2)(rPBI)(2) and (ZnMC)(2)(gPBI)(2), have been obtained by axial coordination of N,N'-dipyridyl-functionalized perylene bisimide (PBI) dyes to the zinc ion centers of two 2+2 porphyrin metallacycles (ZnMC = [trans,cis,cis-RuCl(2)(CO)(2)(Zn·4'-cis-DPyP)](2)). The two molecular boxes involve PBI pillars with different substituents at the bay area: the "red" PBI (rPBI = N,N'-di(4-pyridyl)-1,6,7,12-tetra(4-tert-butylphenoxy)perylene-3,4:9,10-tetracarboxylic acid bisimide) containing tert-butylphenoxy substituents and the "green" PBI (gPBI = N,N'-di(4-pyridyl)-1,7-bis(pyrrolidin-1-yl)perylene-3,4:9,10-tetracarboxylic acid bisimide) bearing pyrrolidinyl substituents. Due to the rigidity of the modules and the simultaneous formation of four pyridine-zinc bonds, these discrete adducts self-assemble quantitatively and are remarkably stable in dichloromethane solution. The photophysical behavior of the new supramolecular boxes has been studied in dichloromethane by emission spectroscopy and ultrafast absorption techniques. A different photophysical behavior is observed for the two systems. In (ZnMC)(2)(rPBI)(2), efficient electron transfer quenching of both perylene bisimide and zinc porphyrin chromophores is observed, leading to a charge separated state, PBI(-)-Zn(+), in which a perylene bisimide unit is reduced and zinc porphyrin is oxidized. In the deactivation of the perylene bisimide localized excited state, an intermediate zwitterionic charge transfer state of type PBI(-)-PBI(+) seems to play a relevant role. In (ZnMC)(2)(gPBI)(2), singlet energy transfer from the Zn porphyrin chromophores to the perylene bisimide units occurs with an efficiency of 0.7. This lower than unity value is due to a competing electron transfer quenching, leading to the charge separated state PBI(-)-Zn(+). The distinct photophysical behavior of these two supramolecular boxes is interpreted in terms of energy changes occurring upon replacement of the "red" r

  12. Highly active ZnO rod-like nanomaterials: Synthesis, characterization and photocatalytic activity for dye removal

    NASA Astrophysics Data System (ADS)

    Hafez, Hoda S.

    2012-04-01

    Highly active ZnO rod-like nanostructures with pointed-shape ends have been synthesized via a simple hydrothermal method using acetic acid as an organic capping agent. The X-ray diffraction (XRD) pattern of the prepared sample reveals that the ZnO rod-like nanostructures are of pure hexagonal wurtzite structure. Morphology of the nanorods has been investigated by transmission electron microscope (TEM), which showed the formation of pointed nanorods of 30-50 nm in diameter and 400-650 nm in length. Optical properties have been investigated by UV-vis diffuse reflectance and photoluminescence spectroscopy. UV-vis absorption spectrum indicated that the ZnO nanorods have higher visible light harvesting as compared to the other morphologies in the literature. Intense room temperature green-red photoluminescence peaks at 486 nm and 564 nm has been observed for the prepared ZnO. This gives a good evidence of the presence of ionized oxygen vacancies which are favorable for photocatalytic reactions. The BET surface area and the average (BJH) adsorption pore size were 269.86 m2/g and 2.86 nm, respectively. The photocatalytic activity of the prepared sample was tested on the degradability of an industrial textile dye, Reactive Yellow 15 (Yellow GR), under sunlight irradiation. A 85.7% dye removal was achieved by applications of these rod-like nanostructures as a photocatalyst. The reusability of the synthesized ZnO nanomaterial has been investigated under the same experimental conditions for three time to evaluate the photoactivity of the photocatalyst.

  13. TiO{sub 2} supported on rod-like mesoporous silica SBA-15: Preparation, characterization and photocatalytic behaviour

    SciTech Connect

    Li, Yanjuan; Li, Nan; Tu, Jinchun; Li, Xiaotian; Wang, Beibei; Chi, Yue; Liu, Darui; Yang, Dianfan

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer Rod-like SBA-15 and normal SBA-15 were used to prepare TiO{sub 2}/SBA-15 composites. Black-Right-Pointing-Pointer TiO{sub 2}/SBA-15 composites were studied as catalysts for methyl orange photodegradation. Black-Right-Pointing-Pointer TiO{sub 2}/Rod-SBA-15 exhibited higher photocatalytic activity than TiO{sub 2}/Nor-SBA-15. Black-Right-Pointing-Pointer The higher catalytic activity was a result of the controlled morphology of SBA-15. -- Abstract: TiO{sub 2} nanoparticles have been successfully incorporated in the pores of mesoporous silica SBA-15 with different morphologies by a wet impregnation method. The composites were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma (ICP) emission spectroscopy, transmission electron microscopy (TEM), N{sub 2}-sorption and UV-Vis diffuse reflectance spectroscopy. The photodegradation of methyl orange (MO) was used to study their photocatalytic property. It is indicated that the morphology of SBA-15 had a great influence on the photocatalytic activity of the composites. When TiO{sub 2}/SBA-15 composite was prepared by loading TiO{sub 2} nanoparticles on uniform rod-like SBA-15 of 1 {mu}m length, it showed higher photocatalytic degradation rate than that on less regular but much larger SBA-15 support. This difference was rationalized in terms of the homogeneously distributed and shorter channels of rod-like SBA-15, which favored mass transport and improved the efficient utilization of the pore surface.

  14. Determination of the positions and orientations of concentrated rod-like colloids from 3D microscopy data.

    PubMed

    Besseling, T H; Hermes, M; Kuijk, A; de Nijs, B; Deng, T-S; Dijkstra, M; Imhof, A; van Blaaderen, A

    2015-05-20

    Confocal microscopy in combination with real-space particle tracking has proven to be a powerful tool in scientific fields such as soft matter physics, materials science and cell biology. However, 3D tracking of anisotropic particles in concentrated phases remains not as optimized compared to algorithms for spherical particles. To address this problem, we developed a new particle-fitting algorithm that can extract the positions and orientations of fluorescent rod-like particles from three dimensional confocal microscopy data stacks. The algorithm is tailored to work even when the fluorescent signals of the particles overlap considerably and a threshold method and subsequent clusters analysis alone do not suffice. We demonstrate that our algorithm correctly identifies all five coordinates of uniaxial particles in both a concentrated disordered phase and a liquid-crystalline smectic-B phase. Apart from confocal microscopy images, we also demonstrate that the algorithm can be used to identify nanorods in 3D electron tomography reconstructions. Lastly, we determined the accuracy of the algorithm using both simulated and experimental confocal microscopy data-stacks of diffusing silica rods in a dilute suspension. This novel particle-fitting algorithm allows for the study of structure and dynamics in both dilute and dense liquid-crystalline phases (such as nematic, smectic and crystalline phases) as well as the study of the glass transition of rod-like particles in three dimensions on the single particle level. PMID:25922931

  15. Simulation of the electron diffraction patterns from needle/rod-like precipitates in Al-Mg-Si alloys

    SciTech Connect

    Li Kai; Song Min; Du Yong; Zhang Hong

    2011-09-15

    The origin of the selected area electron diffraction (SAED) patterns from needle/rod-like metastable precipitates embedded in {alpha}-Al matrix in Al-Mg-Si alloys have been studied via an example of {beta}'' phase. In addition, the SAED pattern from {beta}'' phase has been simulated with significant improvement in comparison with the previous simulations. Three important factors, i.e. the 12 crystallographically equivalent variants of {beta}'' phase in the {alpha}-Al matrix due to the highly symmetric f.c.c. structure of {alpha}-Al, the coherence between {beta}'' phase and the {alpha}-Al matrix, and the double diffractions from the {alpha}-Al matrix and {beta}'' phase, are proved to contribute to the special square-shaped features in the SAED patterns from {beta}'' phase and thus fully taken into account in the simulation. An improved but simplified method for simulating the SAED patterns from needle/rod-like metastable precipitates has been developed. This method is further verified by simulating the SAED pattern from Q phase. The simulated SAED patterns from both {beta}'' and Q phases fit the experimentally determined patterns very well. - Highlights: {yields}An improved method has been developed to simulate the SADPs of Al alloys. {yields}The formation mechanism of SADPs of Al alloys has been systemically studied. {yields}Double diffraction contributes to the formation of the SADPs of Al alloys.

  16. Penetration of spherical and rod-like gold nanoparticles into intact and barrier-disrupted human skin

    NASA Astrophysics Data System (ADS)

    Graf, Christina; Nordmeyer, Daniel; Ahlberg, Sebastian; Raabe, Jörg; Vogt, Annika; Lademann, Jürgen; Rancan, Fiorenza; Rühl, Eckart

    2015-03-01

    The penetration of spherical and rod-like gold nanoparticles into human skin is reported. Several skin preparation techniques are applied, including cryo techniques, such as plunge freezing and freeze drying, and the use of wet cells. Their advantages and drawbacks for observing nanoparticle uptake are discussed. Independent of the particle shape no uptake into intact skin is observed by a combination of imaging approaches, including scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and scanning X-ray microscopy (STXM). These results are discussed along with suitable skin preparation approaches. Experiments on barrier-disrupted skin, i.e. mechanical lesions made by pricking, indicate, however, that gold particles can be identified deep in the dermis, as follows from STXM studies on wet skin samples.

  17. Directional Freezing of Nanocellulose Dispersions Aligns the Rod-Like Particles and Produces Low-Density and Robust Particle Networks.

    PubMed

    Munier, Pierre; Gordeyeva, Korneliya; Bergström, Lennart; Fall, Andreas B

    2016-05-01

    We show that unidirectional freezing of nanocellulose dispersions produces cellular foams with high alignment of the rod-like nanoparticles in the freezing direction. Quantification of the alignment in the long direction of the tubular pores with X-ray diffraction shows high orientation of cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC) at particle concentrations above 0.2 wt % (CNC) and 0.08 wt % (CNF). Aggregation of CNF by pH decrease or addition of salt significantly reduces the particle orientation; in contrast, exceeding the concentration where particles gel by mobility constraints had a relatively small effect on the orientation. The dense nanocellulose network formed by directional freezing was sufficiently strong to resist melting. The formed hydrogels were birefringent and displayed anisotropic laser diffraction patterns, suggesting preserved nanocellulose alignment and cellular structure. Nondirectional freezing of the hydrogels followed by sublimation generates foams with a pore structure and nanocellulose alignment resembling the structure of the initial directional freezing.

  18. Binary mixtures of rod-like colloids under shear: microscopically-based equilibrium theory and order-parameter dynamics.

    PubMed

    Lugo-Frías, Rodrigo; Klapp, Sabine H L

    2016-06-22

    This paper is concerned with the dynamics of a binary mixture of rod-like, repulsive colloidal particles driven out of equilibrium by means of a steady shear flow (Couette geometry). To this end we first derive, starting from a microscopic density functional in Parsons-Lee approximation, a mesoscopic free energy functional whose main variables are the orientational order parameter tensors. Based on this mesoscopic functional we then explore the stability of isotropic and nematic equilibrium phases in terms of composition and rod lengths. Second, by combining the equilibrium theory with the Doi-Hess approach for the order parameter dynamics under shear, we investigate the orientational dynamics of binary mixtures for a range of shear rates and coupling parameters. We find a variety of dynamical states, including synchronized oscillatory states of the two components, but also symmetry breaking behavior where the components display different in-plane oscillatory states.

  19. Binary mixtures of rod-like colloids under shear: microscopically-based equilibrium theory and order-parameter dynamics.

    PubMed

    Lugo-Frías, Rodrigo; Klapp, Sabine H L

    2016-06-22

    This paper is concerned with the dynamics of a binary mixture of rod-like, repulsive colloidal particles driven out of equilibrium by means of a steady shear flow (Couette geometry). To this end we first derive, starting from a microscopic density functional in Parsons-Lee approximation, a mesoscopic free energy functional whose main variables are the orientational order parameter tensors. Based on this mesoscopic functional we then explore the stability of isotropic and nematic equilibrium phases in terms of composition and rod lengths. Second, by combining the equilibrium theory with the Doi-Hess approach for the order parameter dynamics under shear, we investigate the orientational dynamics of binary mixtures for a range of shear rates and coupling parameters. We find a variety of dynamical states, including synchronized oscillatory states of the two components, but also symmetry breaking behavior where the components display different in-plane oscillatory states. PMID:27115342

  20. Complete separation of macroscopic rod-like bimetallic nanoassembly perpendicular and parallel on substrate for simultaneous sensing of microorganisms.

    PubMed

    Jia, HaoWei; Wang, Jin; Qiu, Li; Ge, HongGua

    2015-10-01

    Although two kinds of macroscopic ordered tridimensional nanoassemblies, i.e., alignment of nanorods, can be yielded by controllable droplet evaporation methods, complete separation of the nanoassembly perpendicular or parallel to substrate is quite challenging. It can, however, be realized by the aid of facet blocking combined with the tuning of ionic strength and colloidal concentration. The as-fabricated rod-like bimetallic nanoassembly has proved to be an excellent SERS active substrate compared to random aggregates. It should be mentioned that macroscopic ordered tridimensional nanoassembly perpendicular to the substrate can be used as a highly active SERS substrate with good uniformity and can be successfully applied for finely discriminating two microorganisms: Escherichia coli bacteria and Saccharomycetes.

  1. Directional Freezing of Nanocellulose Dispersions Aligns the Rod-Like Particles and Produces Low-Density and Robust Particle Networks.

    PubMed

    Munier, Pierre; Gordeyeva, Korneliya; Bergström, Lennart; Fall, Andreas B

    2016-05-01

    We show that unidirectional freezing of nanocellulose dispersions produces cellular foams with high alignment of the rod-like nanoparticles in the freezing direction. Quantification of the alignment in the long direction of the tubular pores with X-ray diffraction shows high orientation of cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC) at particle concentrations above 0.2 wt % (CNC) and 0.08 wt % (CNF). Aggregation of CNF by pH decrease or addition of salt significantly reduces the particle orientation; in contrast, exceeding the concentration where particles gel by mobility constraints had a relatively small effect on the orientation. The dense nanocellulose network formed by directional freezing was sufficiently strong to resist melting. The formed hydrogels were birefringent and displayed anisotropic laser diffraction patterns, suggesting preserved nanocellulose alignment and cellular structure. Nondirectional freezing of the hydrogels followed by sublimation generates foams with a pore structure and nanocellulose alignment resembling the structure of the initial directional freezing. PMID:27071304

  2. Binary mixtures of rod-like colloids under shear: microscopically-based equilibrium theory and order-parameter dynamics

    NASA Astrophysics Data System (ADS)

    Lugo-Frías, Rodrigo; Klapp, Sabine H. L.

    2016-06-01

    This paper is concerned with the dynamics of a binary mixture of rod-like, repulsive colloidal particles driven out of equilibrium by means of a steady shear flow (Couette geometry). To this end we first derive, starting from a microscopic density functional in Parsons-Lee approximation, a mesoscopic free energy functional whose main variables are the orientational order parameter tensors. Based on this mesoscopic functional we then explore the stability of isotropic and nematic equilibrium phases in terms of composition and rod lengths. Second, by combining the equilibrium theory with the Doi-Hess approach for the order parameter dynamics under shear, we investigate the orientational dynamics of binary mixtures for a range of shear rates and coupling parameters. We find a variety of dynamical states, including synchronized oscillatory states of the two components, but also symmetry breaking behavior where the components display different in-plane oscillatory states.

  3. Rod-like particles matching algorithm based on SOM neural network in dispersed two-phase flow measurements

    NASA Astrophysics Data System (ADS)

    Abbasi Hoseini, Afshin; Zavareh, Zahra; Lundell, Fredrik; Anderson, Helge I.

    2014-04-01

    A matching algorithm based on self-organizing map (SOM) neural network is proposed for tracking rod-like particles in 2D optical measurements of dispersed two-phase flows. It is verified by both synthetic images of elongated particles mimicking 2D suspension flows and direct numerical simulations-based results of prolate particles dispersed in a turbulent channel flow. Furthermore, the potential benefit of this algorithm is evaluated by applying it to the experimental data of rod-like fibers tracking in wall turbulence. The study of the behavior of elongated particles suspended in turbulent flows has a practical importance and covers a wide range of applications in engineering and science. In experimental approach, particle tracking velocimetry of the dispersed phase has a key role together with particle image velocimetry of the carrier phase to obtain the velocities of both phases. The essential parts of particle tracking are to identify and match corresponding particles correctly in consecutive images. The present study is focused on the development of an algorithm for pairing non-spherical particles that have one major symmetry axis. The novel idea in the algorithm is to take the orientation of the particles into account for matching in addition to their positions. The method used is based on the SOM neural network that finds the most likely matching link in images on the basis of feature extraction and clustering. The fundamental concept is finding corresponding particles in the images with the nearest characteristics: position and orientation. The most effective aspect of this two-frame matching algorithm is that it does not require any preliminary knowledge of neither the flow field nor the particle behavior. Furthermore, using one additional characteristic of the non-spherical particles, namely their orientation, in addition to its coordinate vector, the pairing is improved both for more reliable matching at higher concentrations of dispersed particles and

  4. Synthesis of arylated perylene bisimides through C-H bond cleavage under ruthenium catalysis.

    PubMed

    Nakazono, Satomi; Easwaramoorthi, Shanmugam; Kim, Dongho; Shinokubo, Hiroshi; Osuka, Atsuhiro

    2009-12-01

    Treatment of perylene bisimide (PBI) with various arylboronates in the presence of a ruthenium catalyst provides tetraarylated PBIs at 2,5,8,11-positions in good yields with perfect regioselectivity. The electronic nature of the introduced aryl substituents has a significant impact on their optical and electronic properties. This protocol has been applied to the synthesis of a water-soluble emissive PBI derivative.

  5. High excimer-state emission of perylene bisimides and recognition of latent fingerprints.

    PubMed

    Wang, Ke-Rang; Yang, Zi-Bo; Li, Xiao-Liu

    2015-04-01

    High excimer-state emission in the H-type aggregate of a novel asymmetric perylene bisimide derivative, 6, with triethyleneglycol chains and lactose functionalization was achieved in water. Furthermore, its application for enhancing the visualization of transfer latent fingerprints from glass slides to the poly(vinylidene fluoride) (PVDF) membrane was explored, which showed clear images of the latent fingerprint in daylight and under 365 nm ultraviolet illumination.

  6. Review of crystalline structures of some selected homologous series of rod-like molecules capable of forming liquid crystalline phases.

    PubMed

    Zugenmaier, Peter

    2011-01-01

    The crystal structures of four homologous series of rod-like molecules are reviewed, two of which form hydrogen bonds and two with a symmetric chemical constitution. Many of the compounds investigated turn into liquid crystalline phases upon temperature increase. It is of valuable interest to know possible conformations and possible packing arrangements as prerequisites to model liquid crystalline structures. The hydrogen bonds of homologous series of pure 4-(ω-hydroxyalkyloxy)-4'-hydroxybiphenyl (HnHBP, n the alkyloxy tail length) are realized through head to tail arrangements of the hydroxyl groups and crystallize except one compound in chiral space groups without the molecules containing any asymmetric carbon. The hydrogen bonds of the homologous series of 4-substituted benzoic acids with various lengths of the tail provide dimers through strong polar bonding of adjacent carboxyl groups and thus provide the stiff part of a mesogenic unit prerequisite for liquid crystalline phases. The homologous series of dialkanoyloxybiphenyls (BP-n, n = 1, 19), of which nine compounds could be crystallized, show liquid crystalline behavior for longer alkane chain lengths, despite the high mobility of the alkane chain ends already detectable in the crystal phase. A single molecule, half a molecule or two half molecules form the asymmetric unit in a centrosymmetric space group. The homologous series of 1,4-terephthalidene-bis-N-(4'-n-alkylaniline) (TBAA-n) exhibit a large variety of packing arrangements in the crystalline state, with or without relying on the symmetry center within the molecules. PMID:22174604

  7. Numerical simulations on active rod like particles as a model for the collective behavior of Myxococcus xanthus

    NASA Astrophysics Data System (ADS)

    Wigbers, Manon; Thutupalli, Shashi; Shaevitz, Joshua

    2015-03-01

    We study collective behavior of Myxococcus xanthus using numerical simulations. Under starvation conditions, these social bacteria organize into multi-cellular structures, called ``fruiting bodies,'' within which cells sporulate. During the process of fruiting body formation, cells show various collective motion patterns. One of the most striking of these patterns is the so called rippling motility, characterized by standing density waves of reversing bacteria. Similar rippling behaviour is also observed during predatory feeding of the bacteria. Until now, the principles underlying this rippling behavior are not fully elucidated. Analogous to the well studied liquid crystalline phases in condensed matter physics, the ordering of the baceria within these rippling waves resembles a smectic like layered structure. In contrast to active nematic liquid crystalline phases widely studied in recent times, this represents the first known empirical example of an active smectic phase. Inspired by single-cell resolution experimental data of the bacteria, we develop a modelof active rod like particles and use numerical simulations to study the organizing principles that drive the transitions between the various active liquid crystalline phases in the myxobacterial collective behavior.

  8. Electrodeposition of Pluronic F127 assisted rod-like EMD/carbon arrays for efficient energy storage.

    PubMed

    Biswal, Avijit; Tripathy, Bankim Ch; Li, Dan; Minakshi, Manickam

    2015-10-01

    In the traditional Duracell battery, the results obtained to date remain marginal in terms of cyclability. The development of the existing Zn-MnO2 with superior electrochemical performance for use in alkaline rechargeable batteries is reported. Electrolytic manganese dioxide (EMD) was synthesized from a conventional manganese sulphate bath but having a unique non-ionic surfactant (Pluronic F127), and activated carbon, in an electrolytic cell. The surface areas and morphologies of the as-prepared EMDs were influenced by the presence of these novel additives in the solution while the X-ray data revealed that there was no noticeable change in the crystal orientations thus all the EMDs were structurally similar. The synergistic effect of the optimal ratio of surfactant to carbon powder produced rod-like arrays exhibiting a larger surface area, which facilitates ion transport for better energy storage. It is interesting to note that EMD deposited in the presence of F127 showed better cyclability whereas in the presence of carbon, although it showed better storage capability, it was endowed with poor efficiency when compared with the surfactant added sample, nevertheless the results are better than the existing Zn-MnO2 technology (additive free EMD). Therefore, both the surfactant (50 mg dm(-3)) and the activated carbon (5 g dm(-3)) have been added together in the bath and the resultant EMD exhibits a high specific capacity and an excellent cycling stability. Moreover, the presence of surfactant and activated carbon improved the discharge capacity and its retention thus making this alkaline technology feasible for storing renewable energy for future use. The synergistic effect and the mechanism involved have been discussed. PMID:26314493

  9. Tetrahydrophthalic Anhydrides as Addition Curing Polyimide End Caps: Thermal Isomerization of Methylendianiline 3,6-Diphenyltetrahydrophthalic Bisimides

    NASA Technical Reports Server (NTRS)

    Frimer, Aryeh A.; Gilinsky-Sharon, Pessia; Gottlieb, Hugo E.; Meador, Mary Ann B.; Johnston, J. Christopher

    2005-01-01

    In depth NMR studies confirm that heating a 1:2 mixture of cis, cis, cis 3,6-diphenyltetrahydrophthalic anhydride (end cap 9c) with methylenedianiline at 316 C initially yields the corresponding highly congested cis, cis, cis 3,6-diphenyltetrahydrophthalic bisimide 11, which is converted at this temperature to the observed product, the less hindered trans, cis, trans isomer 12.

  10. Domain-like ultra-thin layers deposited electrochemically from carbazole-functionalized perylene bisimides for electron collection in inverted photovoltaic cells.

    PubMed

    Feng, Tao; Xiao, Biao; Lv, Ying; Xie, Zengqi; Wu, Hongbin; Ma, Yuguang

    2013-07-18

    Domain-like ultra-thin layers deposited electrochemically on an ITO electrode from perylene bisimide derivatives are found to improve the electron collection effectively in inverted photovoltaic cells.

  11. Intramolecular Charge-Transfer Interaction of Donor-Acceptor-Donor Arrays Based on Anthracene Bisimide.

    PubMed

    Iwanaga, Tetsuo; Ogawa, Marina; Yamauchi, Tomokazu; Toyota, Shinji

    2016-05-20

    We designed anthracene bisimide (ABI) derivatives having two triphenylamine (TPA) groups as donor units at the 9,10-positions to form a novel π-conjugated donor-acceptor system. These compounds and their analogues with ethynylene linkers were synthesized by Suzuki-Miyaura and Sonogashira coupling reactions, respectively. In UV-vis spectra, the linker-free derivatives showed broad absorption bands arising from intramolecular charge-transfer interactions. Introducing ethynylene linkers resulted in a considerable red shift of the absorption bands. In fluorescence spectra, the ethynylene derivatives showed intense emission bands at 600-650 nm. Their photophysical and electrochemical properties were compared with those of the corresponding mono TPA derivatives on the basis of theoretical calculations and cyclic voltammetry to evaluate the intramolecular electronic interactions between the donor and acceptor units.

  12. Rod-like CuMnOx transformed from mixed oxide particles by alkaline hydrothermal treatment as a novel catalyst for catalytic combustion of toluene.

    PubMed

    Li, W B; Liu, Z X; Liu, R F; Chen, J L; Xu, B Q

    2016-08-17

    Rod-like copper manganese mixed oxides (CuMnx-NR) have been synthesized from copper manganese mixed oxide particles by sodium hydroxide hydrothermal treatment, and a higher BET surface area of 221 m(2) g(-1) is obtained on the nanorod-like sample, which exhibits superior catalytic activity toward toluene combustion at 210 °C due to the increase in its oxygen mobility of the chemisorbed oxygen species as well as the increase in surface concentrations of higher valance cations, Cu(2+), Mn(3+) and Mn(4+), in the samples. PMID:27498822

  13. Poly(acrylic acid)-regulated Synthesis of Rod-Like Calcium Carbonate Nanoparticles for Inducing the Osteogenic Differentiation of MC3T3-E1 Cells

    PubMed Central

    Yang, Wei; Yao, Chenxue; Cui, Zhengyang; Luo, Dandan; Lee, In-Seop; Yao, Juming; Chen, Cen; Kong, Xiangdong

    2016-01-01

    Calcium carbonate, especially with nanostructure, has been considered as a good candidate material for bone regeneration due to its excellent biodegradability and osteoconductivity. In this study, rod-like calcium carbonate nanoparticles (Rod-CC NPs) with desired water dispersibility were achieved with the regulation of poly (acrylic acid). Characterization results revealed that the Rod-CC NPs had an average length of 240 nm, a width of 90 nm with an average aspect ratio of 2.60 and a negative ζ-potential of −22.25 ± 0.35 mV. The degradation study illustrated the nanoparticles degraded 23% at pH 7.4 and 45% at pH 5.6 in phosphate-buffered saline (PBS) solution within three months. When cultured with MC3T3-E1 cells, the Rod-CC NPs exhibited a positive effect on the proliferation of osteoblast cells. Alkaline phosphatase (ALP) activity assays together with the osteocalcin (OCN) and bone sialoprotein (BSP) expression observations demonstrated the nanoparticles could induce the differentiation of MC3T3-E1 cells. Our study developed well-dispersed rod-like calcium carbonate nanoparticles which have great potential to be used in bone regeneration. PMID:27164090

  14. Poly(acrylic acid)-regulated Synthesis of Rod-Like Calcium Carbonate Nanoparticles for Inducing the Osteogenic Differentiation of MC3T3-E1 Cells.

    PubMed

    Yang, Wei; Yao, Chenxue; Cui, Zhengyang; Luo, Dandan; Lee, In-Seop; Yao, Juming; Chen, Cen; Kong, Xiangdong

    2016-01-01

    Calcium carbonate, especially with nanostructure, has been considered as a good candidate material for bone regeneration due to its excellent biodegradability and osteoconductivity. In this study, rod-like calcium carbonate nanoparticles (Rod-CC NPs) with desired water dispersibility were achieved with the regulation of poly (acrylic acid). Characterization results revealed that the Rod-CC NPs had an average length of 240 nm, a width of 90 nm with an average aspect ratio of 2.60 and a negative ζ-potential of -22.25 ± 0.35 mV. The degradation study illustrated the nanoparticles degraded 23% at pH 7.4 and 45% at pH 5.6 in phosphate-buffered saline (PBS) solution within three months. When cultured with MC3T3-E1 cells, the Rod-CC NPs exhibited a positive effect on the proliferation of osteoblast cells. Alkaline phosphatase (ALP) activity assays together with the osteocalcin (OCN) and bone sialoprotein (BSP) expression observations demonstrated the nanoparticles could induce the differentiation of MC3T3-E1 cells. Our study developed well-dispersed rod-like calcium carbonate nanoparticles which have great potential to be used in bone regeneration. PMID:27164090

  15. Poly(acrylic acid)-regulated Synthesis of Rod-Like Calcium Carbonate Nanoparticles for Inducing the Osteogenic Differentiation of MC3T3-E1 Cells.

    PubMed

    Yang, Wei; Yao, Chenxue; Cui, Zhengyang; Luo, Dandan; Lee, In-Seop; Yao, Juming; Chen, Cen; Kong, Xiangdong

    2016-05-06

    Calcium carbonate, especially with nanostructure, has been considered as a good candidate material for bone regeneration due to its excellent biodegradability and osteoconductivity. In this study, rod-like calcium carbonate nanoparticles (Rod-CC NPs) with desired water dispersibility were achieved with the regulation of poly (acrylic acid). Characterization results revealed that the Rod-CC NPs had an average length of 240 nm, a width of 90 nm with an average aspect ratio of 2.60 and a negative ζ-potential of -22.25 ± 0.35 mV. The degradation study illustrated the nanoparticles degraded 23% at pH 7.4 and 45% at pH 5.6 in phosphate-buffered saline (PBS) solution within three months. When cultured with MC3T3-E1 cells, the Rod-CC NPs exhibited a positive effect on the proliferation of osteoblast cells. Alkaline phosphatase (ALP) activity assays together with the osteocalcin (OCN) and bone sialoprotein (BSP) expression observations demonstrated the nanoparticles could induce the differentiation of MC3T3-E1 cells. Our study developed well-dispersed rod-like calcium carbonate nanoparticles which have great potential to be used in bone regeneration.

  16. Effect of N-substituents on redox, optical, and electronic properties of naphthalene bisimides used for field-effect transistors fabrication.

    PubMed

    Gawrys, Pawel; Djurado, David; Rimarcík, Ján; Kornet, Aleksandra; Boudinet, Damien; Verilhac, Jean-Marie; Lukes, Vladimír; Wielgus, Ireneusz; Zagorska, Malgorzata; Pron, Adam

    2010-02-11

    Three groups of naphthalene bisimides were synthesized and comparatively studied, namely, alkyl bisimides, alkylaryl ones, and novel bisimides containing the alkylthienyl moiety in the N-substituent. The experimental absorption spectra measured in CHCl(3) exhibit one intensive absorption band that is uniformly detected in the spectral range of 340 to 400 nm for all studied molecules. This band consists of three or four vibronic peaks. The introduction of an alkylthienyl group results in the appearance of an additional band (in the spectral range from 282 to 326 nm, depending on the position of the substituent) that can be ascribed to the pi-pi* transition in the thienyl chromophore. The minimal substituent effect on the lowest electronic transitions was explained using the quantum chemical calculations based on the time-dependent density functional theory. The investigation of the shapes of frontier orbitals have also shown that the oxidation of bisimides containing thiophene moiety is primary connected with the electron abstraction from the thienyl ring. To the contrary, the addition of an electron in the reduction process leads to an increase in the electron density in the central bisimide core. As shown by the electrochemical measurements, the onset of the first reduction potential (so-called "electrochemically determined LUMO level") is sensitive toward the type of the substituent being shifted from about -3.72 eV for bisimides with alkyl substituents to about -3.83 eV for alkylaryl ones and to about -3.94 eV for bisimides with thienyl groups. The presence of the thienyl ring also lowers the energy difference between the HOMO and LUMO orbitals. These experimental data can be well correlated with the DFT calculations in terms of HOMO/LUMO shapes and energies. Taking into account the low position of their LUMO level and their highly ordered supramolecular organization, the new bisimides are good candidates for the use in n-channel field effect transistors

  17. Synthesis of a non-aggregating bay-unsubstituted perylene bisimide dye with latent bromo groups for C-C cross coupling.

    PubMed

    Frischmann, Peter D; Würthner, Frank

    2013-09-20

    To address the absence of synthetic routes to access easily functionalizable, non-aggregating, and soluble bay-unsubstituted perylene bisimide dyes, an efficient, three-step, multigram-scale synthesis of the divergent building block N,N'-bis(4-bromo-2,6-diisopropylphenyl)perylene-3,4:9,10-tetracarboxylic bisimide is reported. Suzuki coupling yields new dyes that maintain excellent solubility and exhibit unity quantum yields in CHCl3, THF, toluene, and CH3CN. The methodology reported here enables access to dyes with sensitive functional groups such as aldehydes that are not accessible by traditional imidization routes. PMID:24015879

  18. Polymerization of rod-like macromolecular monomers studied by stopped-flow, multiangle light scattering: set-up, data processing, and application to fibrin formation.

    PubMed Central

    Bernocco, S; Ferri, F; Profumo, A; Cuniberti, C; Rocco, M

    2000-01-01

    Many biological supramolecular structures are formed by polymerization of macromolecular monomers. Light scattering techniques can provide structural information from such systems, if suitable procedures are used to collect the data and then to extract the relevant parameters. We present an experimental set-up in which a commercial multiangle laser light scattering photometer is linked to a stopped-flow mixer, allowing, in principle, the time-resolved extrapolation of the weight-average molecular weight M(w) and of the z-average square radius of gyration (z) of the polymers from Zimm-like plots. However, if elongated structures are formed as the polymerization proceeds, curved plots rapidly arise, from which M(w) and (z) cannot be recovered by linear fitting. To verify the correctness of a polynomial fitting procedure, polydisperse collections of rod-like or worm-like particles of different lengths, generated at various stages during bifunctional polycondensations of rod-like macromolecular monomers, were considered. Then, the angular dependence of their time-averaged scattered intensity was calculated in the Rayleigh-Gans-Debye approximation, with random and systematic noise also added to the data. For relatively narrow size distributions, a third-degree polynomial fitting gave satisfactory results across a broad range of conversion degrees, yielding M(w) and (z) values within 2% and no greater than 10-20%, respectively, of the calculated values. When more broad size distributions were analyzed, the procedure still performed well for semiflexible polymers, but started to seriously underestimate both M(w) and (z) when rigid rod-like particles were analyzed, even at relatively low conversion degrees. The data were also analyzed in the framework of the Casassa approximation, from which the mass per unit length of the polymers can be derived. These procedures were applied to a set of data taken on the early stages of the thrombin

  19. Effects of molecular chirality on self-assembly and switching in liquid crystals at the cross-over between rod-like and bent shapes.

    PubMed

    Ocak, Hale; Poppe, Marco; Bilgin-Eran, Belkız; Karanlık, Gürkan; Prehm, Marko; Tschierske, Carsten

    2016-09-21

    A bent-core compound derived from a 4-cyanoresorcinol core unit with two terephthalate based rod-like wings and carrying chiral 3,7-dimethyloctyloxy side chains has been synthesized in racemic and enantiomerically pure form and characterized by polarizing microscopy, differential scanning calorimetry, X-ray diffraction and electro-optical investigations to study the influence of molecular chirality on the superstructural chirality and polar order in lamellar liquid crystalline phases. Herein we demonstrate that the coupling of molecular chirality with superstructural layer chirality in SmCsPF domain phases (forming energetically distinct diastereomeric pairs) can fix the tilt direction and thus stabilize synpolar order, leading to bistable ferroelectric switching in the SmC* phases of the (S)-enantiomer, whereas tristable modes determine the switching of the racemate. Moreover, the mechanism of electric field induced molecular reorganization changes from a rotation around the molecular long axis in the racemate to a rotation on the tilt-cone for the (S)-enantiomer. At high temperature the enantiomer behaves like a rod-like molecule with a chirality induced ferroelectric SmC* phase and an electroclinic effect in the SmA'* phase. At reduced temperature sterically induced polarization, due to the bent molecular shape, becomes dominating, leading to much higher polarization values, thus providing access to high polarization ferroelectric materials with weakly bent compounds having only "weakly chiral" stereogenic units. Moreover, the field induced alignment of the SmCsPF(()*()) domains gives rise to a special kind of electroclinic effect appearing even in the absence of molecular chirality. Comparison with related compounds indicates that the strongest effects of chirality appear for weakly bent molecules with a relatively short coherence length of polar order, whereas for smectic phases with long range polar order the effects of the interlayer interfaces can override

  20. Complex columnar hexagonal polymorphism in supramolecular assemblies of a semifluorinated electron-accepting naphthalene bisimide.

    PubMed

    Wu, Yu-Chun; Leowanawat, Pawaret; Sun, Hao-Jan; Partridge, Benjamin E; Peterca, Mihai; Graf, Robert; Spiess, Hans W; Zeng, Xiangbing; Ungar, Goran; Hsu, Chain-Shu; Heiney, Paul A; Percec, Virgil

    2015-01-21

    Simple synthetic methods for a strongly electron-accepting naphthalene bisimide (NBI) derivative functionalized with a new environmentally friendly chiral racemic semifluorinated alkyl group and with AB3 minidendrons containing the same semifluorinated group are reported. The semifluorinated dendron was attached to the imide groups of the NBI via one, two, and three (m = 1, 2, 3) methylenic units. The NBI-containing semifluorinated groups and the dendronized NBI with m = 1 and 2 self-organize into lamellar crystals. The dendronized NBI with m = 3 self-assembles into an unprecedentedly complex and ordered column that self-organizes in a columnar hexagonal periodic array. This array undergoes a continuous transition to a columnar hexagonal superlattice that does not display a first-order phase transition during analysis by differential scanning calorimetry at heating and cooling rates of 10 and 1 °C/min. These complex columnar hexagonal periodic arrays with intramolecular order could be elucidated only by a combination of powder and fiber X-ray diffraction studies and solid-state NMR experiments. The lamellar crystals self-organized from m = 1 and the two highly ordered columnar hexagonal periodic arrays of m = 3 are assembled via thermodynamically controlled processes. Since strongly electron-accepting derivatives are of great interest to replace fullerene acceptors in organic photovoltaics and for other supramolecular electronic materials, the multitechnique structural analysis methodology elaborated here must be taken into consideration in all related studies.

  1. Photoluminescence and conductivity of self-assembled pi-pi stacks of perylene bisimide dyes.

    PubMed

    Chen, Zhijian; Stepanenko, Vladimir; Dehm, Volker; Prins, Paulette; Siebbeles, Laurens D A; Seibt, Joachim; Marquetand, Philipp; Engel, Volker; Würthner, Frank

    2007-01-01

    The self-assembly of a new, highly fluorescent perylene bisimide dye 2 into pi stacks, both in solution and condensed phase, has been studied in detail by NMR spectroscopy, vapor pressure osmometry (VPO), UV/Vis and fluorescence spectroscopy, differential scanning calorimetry (DSC), optical polarizing microscopy (OPM) and X-ray diffraction. The NMR and VPO measurements revealed the formation of extended pi-pi stacks of the dye molecules in solution. The aggregate size determined from VPO and DOSY NMR measurements agree well with that obtained from the concentration and temperature-dependent UV/Vis spectral data by employing the isodesmic model (equal K model). In the condensed state, dye 2 possesses a hexagonal columnar liquid crystalline (LC) phase as confirmed by X-ray diffraction analysis. The columnar stacking of this dye has been further explored by atomic force microscopy (AFM). Well-resolved columnar nanostructures of the compound are observed on graphite surface. A color-tunable luminescence from green to red has been observed upon aggregation which is accompanied by an increase of the fluorescence lifetime and depolarization. The observed absorption properties can be explained in terms of molecular exciton theory. The charge transport properties of dye 2 have been investigated by pulse radiolysis-time resolved microwave conductivity measurements and a 1D charge carrier mobility up to 0.42 cm(2) V(-1) s(-1) is obtained. Considering the promising self-assembly, semiconducting, and luminescence properties of this dye, it might serve as a useful functional material for nano(opto)electronics.

  2. Controlled synthesis of CeO2 microstructures from 1D rod-like to 3D lotus-like and their morphology-dependent properties

    NASA Astrophysics Data System (ADS)

    Gong, Jinfeng; Meng, Fanming; Fan, Zhenghua; Li, Huijie

    2016-10-01

    Monodisperse 3D lotus-like CeO2 microstructures have been successfully synthesized via controlling the morphology of CeCO3OH precursors under hydrothermal condition as well as subsequent calcination. The reaction time was systematically investigated. XRD, FT-IR, SEM, TEM, XPS, Raman scattering and Photoluminescence (PL) spectra were employed to characterize the samples. The lotus-like CeO2 hierarchical structures with an average of 4-6 μm are composed of many nanoplates of 100-200 nm in thickness as the petals stacking together to form open flowers and have a fluorite cubic structure. Based on the time-dependent morphology evolution evidences, a nucleation-dissolution-recrystallization mechanism has been proposed to explain the transformation from rod-like structures to lotus-like CeO2 hierarchical structures with the increase of reaction time. It is found that there are Ce3+ ions and oxygen vacancies in surface of samples. The magnetic and photoluminescence measurements indicated that all CeO2 samples exhibit excellent ferromagnetism and optical properties at room temperature, and while increasing the reaction time, the ferromagnetism and optical properties increase more, which can be reasonably explained for the influences of the different morphology of the particles and the concentration of oxygen vacancies and Ce3+ ions. [Figure not available: see fulltext.

  3. Bifunctional DNA architectonics: three-way junctions with sticky perylene bisimide caps and a central metal lock.

    PubMed

    Stubinitzky, Claudia; Bijeljanin, Andrea; Antusch, Linda; Ebeling, Daniel; Hölscher, Hendrik; Wagenknecht, Hans-Achim

    2014-09-15

    A new type of a bifunctional DNA architecture based on a three way junction is developed that combines the structural motif of sticky perylene bisimide caps with a tris-bipyridyl metal ion lock in the center part. A clear stabilizing effect was observed in the presence of Fe(3+), Ni(2+) and Zn(2+) by the formation of corresponding bipyridyl complexes in the branching part of the DNA three way junctions. The dimerization of the 5'-terminally attached perylene diimides (PDI) chromophores by hydrophobic interactions can be followed by significant changes in the UV/Vis absorption and steady-state fluorescence. The PDI-mediated DNA assembly occurs at temperatures below the melting temperature and is not influenced by the metal-ion bipyridyl locks in the central part. The corresponding AFM images revealed the formation of higher-ordered structures as the result of DNA assemblies mediated by the PDI interactions.

  4. Fabrication and humidity sensing performance studies of a fluorescent film based on a cholesteryl derivative of perylene bisimide.

    PubMed

    Zhang, Shujuan; Zhou, Feng; Peng, Haonan; Liu, Taihong; Ding, Liping; Fang, Yu

    2016-08-01

    A fluorescent film based on a cholesteryl derivative of perylene bisimide (PTCDI-co-CholDEA) was fabricated via utilization of an electrostatic spinning technique on a glass plate surface. SEM studies revealed that the film was characterized by fibrous network structure. It is the structure and the chemical composition that make the fluorescence emission of the film sensitive to the variation of local environmental humidity. The sensitivity of the sensing is 0.1497 (×10(4)a.u. of the intensity)/1% RH, of which RH is the abbreviation of relative humidity. The maximum quenching efficiency of the film is 55.4% when humidity reaches 97% RH. Furthermore, the sensing process is fully reversible, and presence of other commonly found liquids shows little effect to the monitoring process.

  5. Folding-induced modulation of excited-state dynamics in an oligophenylene-ethynylene-tethered spiral perylene bisimide aggregate.

    PubMed

    Son, Minjung; Fimmel, Benjamin; Dehm, Volker; Würthner, Frank; Kim, Dongho

    2015-06-01

    The excited-state photophysical behavior of a spiral perylene bisimide (PBI) folda-octamer (F8) tethered to an oligophenylene-ethynylene scaffold is comprehensively investigated. Solvent-dependent UV/Vis and fluorescence studies reveal that the degree of folding in this foldamer is extremely sensitive to the solvent, thus giving rise to an extended conformation in CHCl(3) and a folded helical aggregate in methylcyclohexane (MCH). The exciton-deactivation dynamics are largely governed by the supramolecular structure of F8. Femtosecond transient absorption (TA) in the near-infrared region indicates a photoinduced electron-transfer process from the backbone to the PBI core in the extended conformation, whereas excitation power- and polarization-dependent TA measurements combined with computational modeling showed that excitation energy transfer between the unit PBI chromophores is the major deactivation pathway in the folded counterpart. PMID:25827823

  6. Fabrication and humidity sensing performance studies of a fluorescent film based on a cholesteryl derivative of perylene bisimide

    NASA Astrophysics Data System (ADS)

    Zhang, Shujuan; Zhou, Feng; Peng, Haonan; Liu, Taihong; Ding, Liping; Fang, Yu

    2016-08-01

    A fluorescent film based on a cholesteryl derivative of perylene bisimide (PTCDI-co-CholDEA) was fabricated via utilization of an electrostatic spinning technique on a glass plate surface. SEM studies revealed that the film was characterized by fibrous network structure. It is the structure and the chemical composition that make the fluorescence emission of the film sensitive to the variation of local environmental humidity. The sensitivity of the sensing is 0.1497 (× 104 a.u. of the intensity)/1% RH, of which RH is the abbreviation of relative humidity. The maximum quenching efficiency of the film is 55.4% when humidity reaches 97% RH. Furthermore, the sensing process is fully reversible, and presence of other commonly found liquids shows little effect to the monitoring process.

  7. Supramolecular block copolymers by kinetically controlled co-self-assembly of planar and core-twisted perylene bisimides

    NASA Astrophysics Data System (ADS)

    Görl, Daniel; Zhang, Xin; Stepanenko, Vladimir; Würthner, Frank

    2015-05-01

    New synthetic methodologies for the formation of block copolymers have revolutionized polymer science within the last two decades. However, the formation of supramolecular block copolymers composed of alternating sequences of larger block segments has not been realized yet. Here we show by transmission electron microscopy (TEM), 2D NMR and optical spectroscopy that two different perylene bisimide dyes bearing either a flat (A) or a twisted (B) core self-assemble in water into supramolecular block copolymers with an alternating sequence of (AmBB)n. The highly defined ultralong nanowire structure of these supramolecular copolymers is entirely different from those formed upon self-assembly of the individual counterparts, that is, stiff nanorods (A) and irregular nanoworms (B), respectively. Our studies further reveal that the as-formed supramolecular block copolymer constitutes a kinetic self-assembly product that transforms into thermodynamically more stable self-sorted homopolymers upon heating.

  8. Supramolecular block copolymers by kinetically controlled co-self-assembly of planar and core-twisted perylene bisimides

    PubMed Central

    Görl, Daniel; Zhang, Xin; Stepanenko, Vladimir; Würthner, Frank

    2015-01-01

    New synthetic methodologies for the formation of block copolymers have revolutionized polymer science within the last two decades. However, the formation of supramolecular block copolymers composed of alternating sequences of larger block segments has not been realized yet. Here we show by transmission electron microscopy (TEM), 2D NMR and optical spectroscopy that two different perylene bisimide dyes bearing either a flat (A) or a twisted (B) core self-assemble in water into supramolecular block copolymers with an alternating sequence of (AmBB)n. The highly defined ultralong nanowire structure of these supramolecular copolymers is entirely different from those formed upon self-assembly of the individual counterparts, that is, stiff nanorods (A) and irregular nanoworms (B), respectively. Our studies further reveal that the as-formed supramolecular block copolymer constitutes a kinetic self-assembly product that transforms into thermodynamically more stable self-sorted homopolymers upon heating. PMID:25959777

  9. Subcomponent self-assembly of a 4 nm M4 L6 tetrahedron with Zn(II) vertices and perylene bisimide dye edges.

    PubMed

    Frischmann, Peter D; Kunz, Valentin; Stepanenko, Vladimir; Würthner, Frank

    2015-02-01

    Formation of a tetrahedron with >4 nm perylene bisimide (PBI) dye edges and Zn(II) vertices in a one-pot 22 component self-assembly reaction is reported. The luminescent polyhedron equilibrates to a Zn2 L3 helicate and disassembles upon dilution. Insights into the subcomponent self-assembly of extended PBI ligands help to refine design rules for constructing large photofunctional metallosupramolecular hosts.

  10. Two-fold odd-even effect in self-assembled nanowires from oligopeptide-polymer-substituted perylene bisimides.

    PubMed

    Marty, Roman; Nigon, Robin; Leite, Deborah; Frauenrath, Holger

    2014-03-12

    Organic nanowires are important building blocks for nanoscopic organic electronic devices. In order to ensure efficient charge transport through such nanowires, it is important to understand in detail the molecular parameters that guide self-assembly of π-conjugated molecules into one-dimensional stacks with optimal constructive π-π overlap. Here, we investigated the subtle relationship between molecular structure and supramolecular arrangement of the chromophores in self-assembled nanowires prepared from perylene bisimides with oligopeptide-polymer side chains. We observed a "two-fold" odd-even effect in circular dichroism spectra of these derivatives, depending on both the number of l-alanine units in the oligopeptide segments and length of the alkylene spacer between chromophore and oligopeptide substituents. Our results indicate that there is a complex interplay between the translation of molecular chirality into supramolecular helicity and the molecules' inherent propensity for well-defined one-dimensional aggregation into β-sheet-like superstructures in the presence of a central chromophore. Strong excitonic coupling as expressed by the appearance of hypsochromically and bathochromically shifted UV-vis absorptions and strong CD signals was systematically observed for molecules with an odd number of l-alanines in the side chains. The latter derivatives gave rise to nanowires with a significantly higher electron mobility. Our results, hence, provide an important design rule for self-assembled organic nanowires.

  11. Direct observation of ultrafast coherent exciton dynamics in helical π-stacks of self-assembled perylene bisimides

    PubMed Central

    Sung, Jooyoung; Kim, Pyosang; Fimmel, Benjamin; Würthner, Frank; Kim, Dongho

    2015-01-01

    Ever since the discovery of dye self-assemblies in nature, there have been tremendous efforts to exploit biomimetic supramolecular assemblies for tailored artificial photon processing materials. This feature necessarily has resulted in an increasing demand for understanding exciton dynamics in the dye self-assemblies. In a sharp contrast with J-type aggregates, however, the detailed observation of exciton dynamics in H-type aggregates has remained challenging. In this study, as we succeed in measuring transient fluorescence from Frenkel state of π-stacked perylene tetracarboxylic acid bisimide dimer and oligomer aggregates, we present an experimental demonstration on Frenkel exciton dynamics of archetypal columnar π–π stacks of dyes. The analysis of the vibronic peak ratio of the transient fluorescence spectra reveals that unlike the simple π-stacked dimer, the photoexcitation energy in the columnar π-stacked oligomer aggregates is initially delocalized over at least three molecular units and moves coherently along the chain in tens of femtoseconds, preceding excimer formation process. PMID:26492820

  12. Sensing of Double-Stranded DNA/RNA Secondary Structures by Water Soluble Homochiral Perylene Bisimide Dyes.

    PubMed

    Gershberg, Jana; Radić Stojković, Marijana; Škugor, Marko; Tomić, Sanja; Rehm, Thomas H; Rehm, Stefanie; Saha-Möller, Chantu R; Piantanida, Ivo; Würthner, Frank

    2015-05-18

    A broad series of homochiral perylene bisimide (PBI) dyes were synthesized that are appended with amino acids and cationic side chains at the imide positions. Self-assembly behavior of these ionic PBIs has been studied in aqueous media by UV/Vis spectroscopy, revealing formation of excitonically coupled H-type aggregates. The interactions of these ionic PBIs with different ds-DNA and ds-RNA have been explored by thermal denaturation, fluorimetric titration and circular dichroism (CD) experiments. These PBIs strongly stabilized ds-DNA/RNA against thermal denaturation as revealed by high melting temperatures of the formed PBI/polynucleotide complexes. Fluorimetric titrations showed that these PBIs bind to ds-DNA/RNA with high binding constants depending on the number of the positive charges in the side chains. Thus, spermine-containing PBIs with six positive charges each showed higher binding constants (logKs =9.2-9.8) than their dioxa analogues (logKs =6.5-7.9) having two positive charges each. Induced circular dichroism (ICD) of PBI assemblies created within DNA/RNA grooves was observed. These ICD profiles are strongly dependent on the steric demand of the chiral substituents of the amino acid units and the secondary structure of the DNA or RNA. The observed ICD effects can be explained by non-covalent binding of excitonically coupled PBI dimer aggregates into the minor groove of DNA and major groove of RNA which is further supported by molecular modeling studies. PMID:25900531

  13. Perylene Bisimide as a Promising Zinc Oxide Surface Modifier: Enhanced Interfacial Combination for Highly Efficient Inverted Polymer Solar Cells.

    PubMed

    Nian, Li; Zhang, Wenqiang; Wu, Siping; Qin, Leiqiang; Liu, Linlin; Xie, Zengqi; Wu, Hongbin; Ma, Yuguang

    2015-11-25

    We report the application of a perylene bisimide (PBI-H) as zinc oxide (ZnO) surface modifier to afford an organic-inorganic co-interlayer for highly efficient inverted organic photovoltaics (i-OPV). By thermal annealing, a N-Zn chemical bond formed between PBI-H and ZnO, inducing close organic-inorganic combination. In addition, this co-interlayer shows decreased work function and increased electron transportation and conductivity, which are benefits for the cathode to enhance charge extraction efficiency and decrease recombination losses. As a result a highly efficient i-OPV was achieved with a power conversion efficiency (PCE) of 9.43% based on this co-interlayer with PTB7:PC71BM as the active layer, which shows over 35% enhancement compared to that of the device without the PBI-H layer. Moreover, this co-interlayer was widely applicable for i-OPVs based on various material systems, such as P3HT:PC61BM and PTB7-Th:PC71BM, resulting in PCE as high as 4.78% and 10.31%, respectively.

  14. High-Performance Solution-Processed Non-Fullerene Organic Solar Cells Based on Selenophene-Containing Perylene Bisimide Acceptor.

    PubMed

    Meng, Dong; Sun, Dan; Zhong, Chengmei; Liu, Tao; Fan, Bingbing; Huo, Lijun; Li, Yan; Jiang, Wei; Choi, Hyosung; Kim, Taehyo; Kim, Jin Young; Sun, Yanming; Wang, Zhaohui; Heeger, Alan J

    2016-01-13

    Non-fullerene acceptors have recently attracted tremendous interest because of their potential as alternatives to fullerene derivatives in bulk heterojunction organic solar cells. However, the power conversion efficiencies (PCEs) have lagged far behind those of the polymer/fullerene system, mainly because of the low fill factor (FF) and photocurrent. Here we report a novel perylene bisimide (PBI) acceptor, SdiPBI-Se, in which selenium atoms were introduced into the perylene core. With a well-established wide-band-gap polymer (PDBT-T1) as the donor, a high efficiency of 8.4% with an unprecedented high FF of 70.2% is achieved for solution-processed non-fullerene organic solar cells. Efficient photon absorption, high and balanced charge carrier mobility, and ultrafast charge generation processes in PDBT-T1:SdiPBI-Se films account for the high photovoltaic performance. Our results suggest that non-fullerene acceptors have enormous potential to rival or even surpass the performance of their fullerene counterparts. PMID:26652276

  15. Sensing of Double-Stranded DNA/RNA Secondary Structures by Water Soluble Homochiral Perylene Bisimide Dyes.

    PubMed

    Gershberg, Jana; Radić Stojković, Marijana; Škugor, Marko; Tomić, Sanja; Rehm, Thomas H; Rehm, Stefanie; Saha-Möller, Chantu R; Piantanida, Ivo; Würthner, Frank

    2015-05-18

    A broad series of homochiral perylene bisimide (PBI) dyes were synthesized that are appended with amino acids and cationic side chains at the imide positions. Self-assembly behavior of these ionic PBIs has been studied in aqueous media by UV/Vis spectroscopy, revealing formation of excitonically coupled H-type aggregates. The interactions of these ionic PBIs with different ds-DNA and ds-RNA have been explored by thermal denaturation, fluorimetric titration and circular dichroism (CD) experiments. These PBIs strongly stabilized ds-DNA/RNA against thermal denaturation as revealed by high melting temperatures of the formed PBI/polynucleotide complexes. Fluorimetric titrations showed that these PBIs bind to ds-DNA/RNA with high binding constants depending on the number of the positive charges in the side chains. Thus, spermine-containing PBIs with six positive charges each showed higher binding constants (logKs =9.2-9.8) than their dioxa analogues (logKs =6.5-7.9) having two positive charges each. Induced circular dichroism (ICD) of PBI assemblies created within DNA/RNA grooves was observed. These ICD profiles are strongly dependent on the steric demand of the chiral substituents of the amino acid units and the secondary structure of the DNA or RNA. The observed ICD effects can be explained by non-covalent binding of excitonically coupled PBI dimer aggregates into the minor groove of DNA and major groove of RNA which is further supported by molecular modeling studies.

  16. Understanding ground- and excited-state properties of perylene tetracarboxylic acid bisimide crystals by means of quantum chemical computations.

    PubMed

    Zhao, Hong-Mei; Pfister, Johannes; Settels, Volker; Renz, Manuel; Kaupp, Martin; Dehm, Volker C; Würthner, Frank; Fink, Reinhold F; Engels, Bernd

    2009-11-01

    Quantum chemical protocols explaining the crystal structures and the visible light absorption properties of 3,4:9,10-perylene tetracarboxylic acid bisimide (PBI) derivates are proposed. Dispersion-corrected density functional theory has provided an intermolecular potential energy of PBI dimers showing several energetically low-lying minima, which corresponds well with the packing of different PBI dyes in the solid state. While the dispersion interaction is found to be crucial for the binding strength, the minimum structures of the PESs are best explained by electrostatic interactions. Furthermore, a method is introduced, which reproduces the photon energies at the absorption maxima of PBI pigments within 0.1 eV. It is based on time-dependent Hartree-Fock (TD-HF) excitation energies calculated for PBI dimers with the next-neighbor arrangement in the pigment and incorporates crystal packing effects. This success provides clear evidence that the electronically excited states, which determine the color of these pigments, have no significant charge-transfer character. The developed protocols can be applied in a routine manner to understand and to predict the properties of such pigments, which are important materials for organic solar cells and (opto-)electronic devices.

  17. Hydrothermal synthesis of mesoporous rod-like nanocrystalline vanadium oxide hydrate V{sub 3}O{sub 7}·H{sub 2}O from hydroquinone and V{sub 2}O{sub 5}

    SciTech Connect

    Mjejri, I.; Etteyeb, N.; Sediri, F.

    2013-09-01

    Graphical abstract: - Highlights: • Rod-like nanocrystalline V{sub 3}O{sub 7}·H{sub 2}O has heen synthesized hydrothermally. • Molar ratio is key factor for structure and morphology. • Electrochemical properties were also studied. • CV has revealed reversible redox behavior with charge–discharge cycling. - Abstract: Rod-like nanocrystalline V{sub 3}O{sub 7}·H{sub 2}O has been synthesized hydrothermally via a simple and elegant route. Techniques X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermal analysis (TG-DTA), X-ray photoelectron spectroscopy (XPS), UV–vis spectroscopy and nitrogen adsorption/desorption isotherms have been used to characterize the structure, morphology and composition of the materials. The as-prepared V{sub 3}O{sub 7}·H{sub 2}O nanorods are up to several of micrometers in length, about 130 nm in width and about 70 nm in thickness in average, respectively. Cyclic voltammetric characterization of thin films of V{sub 3}O{sub 7}·H{sub 2}O nanorods has revealed reversible redox behavior with charge–discharge cycling corresponding to the reversible lithium intercalation/deintercalation.

  18. Ce (III) - Porphyrin Sandwich Complex Ce2(TPP)3: A Rod-Like Nanoparticle as a Fluorescence Turn-Off Probe for Detection of Hg (II) and Cu (II).

    PubMed

    Boroujerdi, Ramin

    2016-05-01

    In this study the researcher reports a novel, one step synthesized rod-like nanoparticles of cerium (III)-tetraphenylporphyrin sandwich complex as a spectrofluorometric sensor to measure trace amount of Hg (II) and Cu (II) metal ions. Moreover, the synthesized fluorescent probe was able to detect higher amounts (>10(-4) M) of Hg (II) in aqueous media by changing the color which can also be used as a selective mercury naked-eye sensor. The selectivity and sensitivity of the sensor based on its fluorescence quenching in the presence of Hg (II) and Cu (II) were studied according to the Stern-Volmer equation. The detection limit of the sensor was 16 nM for Hg (II) and about 2.34 μM for Cu (II) ions. Graphical Abstract Ce2(TPP)3 sandwich complex application as a fluorescent probe for measuring trace amounts of mercury and copper in real samples. PMID:26856340

  19. Vanadium bisimide bonding investigated by X-ray crystallography, 51V and 13C nuclear magnetic resonance spectroscopy, and V L(3,2)-edge X-ray absorption near-edge structure spectroscopy.

    PubMed

    La Pierre, Henry S; Minasian, Stefan G; Abubekerov, Mark; Kozimor, Stosh A; Shuh, David K; Tyliszczak, Tolek; Arnold, John; Bergman, Robert G; Toste, F Dean

    2013-10-01

    Syntheses of neutral halide and aryl vanadium bisimides are described. Treatment of VCl2(NtBu)[NTMS(N(t)Bu)], 2, with PMe3, PEt3, PMe2Ph, or pyridine gave vanadium bisimides via TMSCl elimination in good yield: VCl(PMe3)2(N(t)Bu)2 3, VCl(PEt3)2(N(t)Bu)2 4, VCl(PMe2Ph)2(N(t)Bu)2 5, and VCl(Py)2(N(t)Bu)2 6. The halide series (Cl-I) was synthesized by use of TMSBr and TMSI to give VBr(PMe3)2(N(t)Bu)2 7 and VI(PMe3)2(N(t)Bu)2 8. The phenyl derivative was obtained by reaction of 3 with MgPh2 to give VPh(PMe3)2(N(t)Bu)2 9. These neutral complexes are compared to the previously reported cationic bisimides [V(PMe3)3(N(t)Bu)2][Al(PFTB)4] 10, [V(PEt3)2(N(t)Bu)2][Al(PFTB)4] 11, and [V(DMAP)(PEt3)2(N(t)Bu)2][Al(PFTB)4] 12 (DMAP = dimethylaminopyridine, PFTB = perfluoro-tert-butoxide). Characterization of the complexes by X-ray diffraction, (13)C NMR, (51)V NMR, and V L(3,2)-edge X-ray absorption near-edge structure (XANES) spectroscopy provides a description of the electronic structure in comparison to group 6 bisimides and the bent metallocene analogues. The electronic structure is dominated by π bonding to the imides, and localization of electron density at the nitrogen atoms of the imides is dictated by the cone angle and donating ability of the axial neutral supporting ligands. This phenomenon is clearly seen in the sensitivity of (51)V NMR shift, (13)C NMR Δδ(αβ), and L3-edge energy to the nature of the supporting phosphine ligand, which defines the parameters for designing cationic group 5 bisimides that would be capable of breaking stronger σ bonds. Conversely, all three methods show little dependence on the variable equatorial halide ligand. Furthermore, this analysis allows for quantification of the electronic differences between vanadium bisimides and the structurally analogous mixed Cp/imide system CpV(N(t)Bu)X2 (Cp = C5H5(1-)). PMID:24024833

  20. Bisimide amine cured epoxy /IME/ resins and composites. II - Ten-degree off-axis tensile and shear properties of Celion 6000/IME composites

    NASA Technical Reports Server (NTRS)

    Scola, D. A.

    1982-01-01

    Bisimide amines (BIAs), which are presently used as curing agents in a state-of-the-art epoxy resin, are oligomeric and polymeric mixtures. A series of composites consisting of the novel BIA-cured epoxy resin reinforced with Celion 6000 graphite fibers were fabricated and evaluated, and the ten-degree, off-axis uniaxial tensile and shear properties of these composites were determined. The use of the intralaminar shear strain-to-failure was used in the calculation of resin shear strain-to-failure. Study results indicate that several of these novel composite systems exhibit shear strain properties that are superior to those of the control composite system of the present experiments, which employed a sulfone curing agent.

  1. Identification of Different Donor-Acceptor Structures via Förster Resonance Energy Transfer (FRET) in Quantum-Dot-Perylene Bisimide Assemblies

    PubMed Central

    Kowerko, Danny; Krause, Stefan; Amecke, Nicole; Abdel-Mottaleb, Mohamed; Schuster, Jörg; von Borczyskowski, Christian

    2009-01-01

    Nanoassemblies are formed via self-assembly of ZnS capped CdSe quantum dots (QD) and perylene bisimide (PBI) dyes. Upon assembly formation the QD photoluminescence is quenched, as can be detected both via single particle detection and ensemble experiments in solution. Quenching has been assigned to FRET and NON-FRET processes. Analysis of FRET allows for a distinction between different geometries of the QD dye assemblies. Time-resolved single molecule spectroscopy reveals intrinsic fluctuations of the PBI fluorescence lifetime and spectrum, caused by rearrangement of the phenoxy side groups. The distribution of such molecular conformations and their changed dynamics upon assembly formation are discussed in the scope of FRET efficiency and surface ligand density. PMID:20054469

  2. A novel water-soluble fluorescent polymer based on perylene bisimides dyes: one-pot preparation and its bio-imaging.

    PubMed

    Tan, Haijian; Liu, Hongmei; Liu, Yaojun; Duan, Wenfeng; Yi, Xuegang; Wu, Yonggang; Zhao, Hongchi; Bai, Libin

    2016-01-01

    Perylene bisimides dye-based water-soluble fluorescent polymer P3, N,N'-bis(3-amyl)-1-bromo-7-{4'-[3''-(S-poly(N-acryloyl ethylene diamine hydrochloride)-2'''-methyl propionic acid)propionyloxy hexyloxy]phenyl} perylene-3,4:9,10-tetracarboxylic bisimides, was synthesized with polyelectrolyte modification via one-pot reaction (the reduction reaction of trithioester and click reaction between the thiol group and carbon-carbon double bond were simultaneously conducted in one pot with high conversion). One-pot method can overcome the limitation that usual click reaction between thiol and other groups has low conversion because thiol group is subject to rapid oxidation during purification and storage. Chemical, structural, and optical properties of P3 and intermediate products were fully characterized by nuclear magnetic resonance spectroscopy, Fourier transform infrared, gel permeation chromatograph, UV-vis spectra, and fluorescence spectra, respectively. The results revealed that P3 displayed excellent water solubility and not only exhibited red strong fluorescence emission band in water but also had the similar photoluminescent spectra to those of intermediate products (M4 and P2) in chloroform. Allowing for the potential application in biological detection field, cell viability and live cell imaging with the presence of P3 were further investigated with Hela cells. The results showed that P3 had low cytotoxicity with strong intracellular fluorescence entry. Meanwhile, with the augment of concentration of P3 (0-0.500 mg mL(-1)), the cell uptake and accumulation of P3 increased and thereby result in enhancement of the intracellular fluorescence. These experiment results suggested that P3 had enormous potential as a fluorescence probe to be an important component in biological detection field.

  3. Photoinduced electron transfer (PET) versus excimer formation in supramolecular p/n-heterojunctions of perylene bisimide dyes and implications for organic photovoltaics.

    PubMed

    Nowak-Król, Agnieszka; Fimmel, Benjamin; Son, Minjung; Kim, Dongho; Würthner, Frank

    2015-01-01

    Foldamer systems comprised of two perylene bisimide (PBI) dyes attached to the conjugated backbones of 1,2-bis(phenylethynyl)benzene and phenylethynyl-bis(phenylene)indane, respectively, were synthesized and investigated with regard to their solvent-dependent properties. UV/Vis absorption and steady-state fluorescence spectra show that both foldamers exist predominantly in a folded H-aggregated state consisting of π-π-stacked PBIs in THF and in more random conformations with weaker excitonic coupling between the PBIs in chloroform. Time-resolved fluorescence spectroscopy and transient absorption spectroscopy reveal entirely different relaxation pathways for the photoexcited molecules in the given solvents, i.e. photoinduced electron transfer leading to charge separated states for the open conformations (in chloroform) and relaxation into excimer states with red-shifted emission for the stacked conformations (in THF). Supported by redox data from cyclic voltammetry and Rehm-Weller analysis we could relate the processes occurring in these solution-phase model systems to the elementary processes in organic solar cells. Accordingly, only if relaxation pathways such as excimer formation are strictly avoided in molecular semiconductor materials, excitons may diffuse over larger distances to the heterojunction interface and produce photocurrent via the formation of electron/hole pairs by photoinduced electron transfer.

  4. Increasing 3D Supramolecular Order by Decreasing Molecular Order. A Comparative Study of Helical Assemblies of Dendronized Nonchlorinated and Tetrachlorinated Perylene Bisimides.

    PubMed

    Partridge, Benjamin E; Leowanawat, Pawaret; Aqad, Emad; Imam, Mohammad R; Sun, Hao-Jan; Peterca, Mihai; Heiney, Paul A; Graf, Robert; Spiess, Hans W; Zeng, Xiangbing; Ungar, Goran; Percec, Virgil

    2015-04-22

    A nonplanar, twisted, and flexible tetrachlorinated perylene bisimide (Cl4PBI) was functionalized with two AB3 minidendrons containing hydrogenated or semifluorinated dodecyl groups. The hydrogenated dendron was attached to the imide groups of Cl4PBI via m = 0, 1, and 2 methylenic units, whereas the dendron containing semifluorinated groups was attached via m = 3 or a di(ethylene oxide) linker (m = 2EO). The supramolecular structures of these compounds, determined by a combination of differential scanning calorimetry, X-ray diffraction, and solid-state NMR, were compared with those of nonchlorinated planar and rigid PBI reported previously, which demonstrated the thermodynamically controlled formation of 2D periodic arrays at high temperatures and 3D arrays at low temperatures. The molecularly less ordered Cl4PBI containing hydrogenated dendrons self-organize into exclusively 3D crystalline periodic arrays under thermodynamic control for m = 0 and 2, while the more highly molecularly ordered PBI produced less stable and ordered 3D crystals and also 2D assemblies. This induction of a higher degree of 3D order in supramolecular assemblies of the less well-ordered molecular building blocks was unanticipated. The semifluorinated dendronized Cl4PBI with m = 3 formed a 2D columnar hexagonal array under kinetic control, whereas the compound with m = 2EO formed an unusual 2D honeycomb-like hexagonal phase under thermodynamic control. These Cl4PBI compounds provide a new route to stable crystalline assemblies via thermodynamic control at lower temperatures than previously obtained with PBI, thus generating 3D order in an accessible range of temperature of interest for structural analysis and for technological applications. PMID:25830346

  5. Naphthalene bisimides asymmetrically and symmetrically N-substituted with triarylamine--comparison of spectroscopic, electrochemical, electronic and self-assembly properties.

    PubMed

    Rybakiewicz, Renata; Zapala, Joanna; Djurado, David; Nowakowski, Robert; Toman, Petr; Pfleger, Jiri; Verilhac, Jean-Marie; Zagorska, Malgorzata; Pron, Adam

    2013-02-01

    Two semiconducting naphthalene bisimides were comparatively studied: NBI-(TAA)(2), symmetrically N-substituted with triaryl amine and asymmetric NBI-TAA-Oc with triaryl amine and octyl N-substituents. Both compounds show very similar spectroscopic and redox properties but differ in their supramolecular organization. As evidenced by STM, in monolayers on HOPG they form ordered 2D structures, however of different packing patterns. NBI-(TAA)(2) does not form ordered 3D structures, yielding amorphous thin films whereas films of NBI-TAA-Oc are highly crystalline. DFT calculations predict the ionization potential (IP) of 5.22 eV and 5.18 eV for NBI-TAA-Oc and NBI-(TAA)(2), respectively, as well as the electron affinity values (EA) of -3.25 eV and -3.22 eV. These results are consistent with the cyclic voltammetry data which yield similar values of IP (5.20 eV and 5.19 eV) and somehow different values of EA (-3.80 eV and -3.83 eV). As judged from these data, both semiconductors should exhibit ambipolar behavior. Indeed, NBI-TAA-Oc is ambipolar, showing hole and electron mobilities of 4.5 × 10(-5) cm(2)/(V s) and of 2.6 × 10(-4) cm(2)/(V s), respectively, in the field effect transistor configuration. NBI-(TAA)(2) is not ambipolar and yields field effect only in the p-channel configuration. This different behavior is rationalized on the basis of structural factors.

  6. Bright Fluorescence and Host-Guest Sensing with a Nanoscale M₄L₆ Tetrahedron Accessed by Self-Assembly of Zinc-Imine Chelate Vertices and Perylene Bisimide Edges.

    PubMed

    Frischmann, Peter D; Kunz, Valentin; Würthner, Frank

    2015-06-15

    A highly luminescent Zn4L6 tetrahedron is reported with 3.8 nm perylene bisimide edges and hexadentate Zn(II)-imine chelate vertices. Replacing Fe(II) and monoamines commonly utilized in subcomponent self-assembly with Zn(II) and tris(2-aminoethyl)amine provides access to a metallosupramolecular host with the rare combination of structural integrity at concentrations <10(-7) mol L(-1) and an exceptionally high fluorescence quantum yield of Φ(em) =0.67. Encapsulation of multiple perylene or coronene guest molecules is accompanied by strong luminescence quenching. We anticipate this self-assembly strategy may be generalized to improve access to brightly fluorescent coordination cages tailored for host-guest light-harvesting, photocatalysis, and sensing.

  7. Fis-protein induces rod-like DNA bending

    NASA Astrophysics Data System (ADS)

    Fu, Chi-Cheng; Lin, Ching-Fong; Gao, Quan-Ze; Yang, Wei-Zen; Lim, Tsong-Shin; Yang, Li-Ling; Yen, Chi-Fu; Chang, Wei-Hau; Yuan, Hanna S.; Sheu, Sheh-Yi; Yang, Dah-Yen; Fann, Wunshain

    2010-11-01

    Fis protein can bend DNA chain with length much shorter than its persistence length. We applied single-molecule fluorescence resonance energy transfer method to probe these conformational changes. A broad distribution of end-to-end distances correlates well with the molecular dynamics simulation. The flexibility of DNA upon Fis binding is attributed to the breakages of hydrogen bonds between base pairs. DNA kinks at specific sites, instead of continuous bending. The loosening of DNA structures might have biological implications for the functions of Fis-proteins as transcription cofactors.

  8. Triggering activity of catalytic rod-like supramolecular polymers.

    PubMed

    Huerta, Elisa; van Genabeek, Bas; Lamers, Brigitte A G; Koenigs, Marcel M E; Meijer, E W; Palmans, Anja R A

    2015-02-23

    Supramolecular polymers based on benzene-1,3,5-tricarboxamides (BTAs) functionalized with an L- or D-proline moiety display high catalytic activity towards aldol reactions in water. High turnover frequencies (TOF) of up to 27×10(-4) s(-1) and excellent stereoselectivities (up to 96% de, up to 99% ee) were observed. In addition, the catalyst could be reused and remained active at catalyst loadings and substrate concentrations as low as 0.1 mol % and 50 mM, respectively. A temperature-induced conformational change in the supramolecular polymer triggers the high activity of the catalyst. The supramolecular polymer's helical sense in combination with the configuration of the proline (L- or D-) is responsible for the observed selectivity. PMID:25614098

  9. Thermotropic rod-like mesogens as stabilizers for polyolefins and polyvinyl chloride

    NASA Astrophysics Data System (ADS)

    Burmistrov, V. A.; Kuvshinova, S. A.; Koifman, O. I.

    2016-02-01

    The main approaches to stabilization of polymers and requirements to anti-ageing agents are discussed. Considerable attention is paid to the progress in the studies of the stabilizing activity of various substances in polyolefin- and polyvinyl chloride-based compositions. Particular demand for environmentally benign organic heat stabilizers and antioxidants is noted. The so-called mesogenic structures serving as effective light and heat stabilizers for polymer composites are presented. The effects of mesogens on the supramolecular structure of polyethylene, deformation and relaxation properties and thermal parameters as well as melt flow index, tribological properties and other properties of polymer materials are discussed. The bibliography includes 112 references.

  10. Curvature-driven capillary migration and assembly of rod-like particles.

    PubMed

    Cavallaro, Marcello; Botto, Lorenzo; Lewandowski, Eric P; Wang, Marisa; Stebe, Kathleen J

    2011-12-27

    Capillarity can be used to direct anisotropic colloidal particles to precise locations and to orient them by using interface curvature as an applied field. We show this in experiments in which the shape of the interface is molded by pinning to vertical pillars of different cross-sections. These interfaces present well-defined curvature fields that orient and steer particles along complex trajectories. Trajectories and orientations are predicted by a theoretical model in which capillary forces and torques are related to Gaussian curvature gradients and angular deviations from principal directions of curvature. Interface curvature diverges near sharp boundaries, similar to an electric field near a pointed conductor. We exploit this feature to induce migration and assembly at preferred locations, and to create complex structures. We also report a repulsive interaction, in which microparticles move away from planar bounding walls along curvature gradient contours. These phenomena should be widely useful in the directed assembly of micro- and nanoparticles with potential application in the fabrication of materials with tunable mechanical or electronic properties, in emulsion production, and in encapsulation.

  11. Nanomechanical characterization of rod-like superlattice assembled from tobacco mosaic viruses

    NASA Astrophysics Data System (ADS)

    Wang, Haoran; Wang, Xinnan; Li, Tao; Lee, Byeongdu

    2013-01-01

    Tobacco mosaic virus (TMV) and TMV-derived materials have demonstrated their great potential in biomedical applications, where the mechanical properties are determining factors for their proper functionalities and structural integrity. Recently, it has been found that a superlattice structure can be formed by two-dimensional hexagonal packing TMV self-assembly in Barium ions solution. In parallel to the exploration of possible applications of TMV superlattice, the mechanical properties were characterized by the atomic force microscopy based nanoindentation. The elastic modulus of 2.14 GPa was obtained by application of the extended Johnson-Kendall-Roberts (JKR) model with the force vs sample deformation data. The adhesion force was taken into consideration, and an easy-to-implement approach of using the extended JKR model was proposed by processing both the theoretical model and the experimental data. Finite element analysis was conducted to evaluate the reinforcing effect of the like-charge forces between the TMVs and the mechanical properties of the TMV superlattice. Using the Halpin-Tsai model, the transverse elastic modulus of the superlattice sample varied within 2.00-4.38 GPa, depending on the indentation locations. Attraction-repulsion equilibrium was found to maintain the packing of TMVs. This provides useful information to address the sources of the attraction and repulsion forces to control the TMV assembly.

  12. On the nucleation and initial film growth of rod-like organic molecules

    NASA Astrophysics Data System (ADS)

    Winkler, Adolf

    2016-10-01

    In this article, some fundamental topics related to the initial steps of organic film growth are reviewed. General conclusions will be drawn based on experimental results obtained for the film formation of oligophenylene and pentacene molecules on gold and mica substrates. Thin films were prepared via physical vapor deposition under ultrahigh-vacuum conditions and characterized in-situ mainly by thermal desorption spectroscopy, and ex-situ by X-ray diffraction and atomic force microscopy. In this short review article the following topics will be discussed: What are the necessary conditions to form island-like films which are either composed of flat-lying or of standing molecules? Does a wetting layer exist below and in between the islands? What is the reason behind the occasionally observed bimodal island size distribution? Can one describe the nucleation process with the diffusion-limited aggregation model? Do the impinging molecules directly adsorb on the surface or rather via a hot-precursor state? Finally, it will be described how the critical island size can be determined by an independent measurement of the deposition rate dependence of the island density and the capture-zone distribution via a universal relationship.

  13. Combustion synthesized rod-like nanostructure hematite with enhanced lithium storage properties

    SciTech Connect

    Xiong, Q.Q.; Shi, S.J.; Tang, H.; Wang, X.L.; Gu, C.D.; Tu, J.P.

    2015-01-15

    Graphical abstract: Fe{sub 2}O{sub 3} nanorods are synthesized by combustion method using alcohol as both solvent and fuel. As an anode material for lithium-ion batteries, the Fe{sub 2}O{sub 3} nanorod electrode delivers good electrochemical performance. - Highlights: • We prepared Fe{sub 2}O{sub 3} nanorod by a facile and powerful combustion method. • The Fe{sub 2}O{sub 3} nanorod shows high capacity, good cycle stability, and rate performance. • Combustion saves time and energy to meet the demand of green and sustainable industry. - Abstract: Fe{sub 2}O{sub 3} nanorods are synthesized by combustion method using alcohol as both solvent and fuel, which is a facile and effective strategy for the large-scale and inexpensive fabrication. The Fe{sub 2}O{sub 3} nanorods are with the well distributed diameters of 20–30 nm and length ranging from 80 to 100 nm. As an anode material for lithium-ion batteries, the Fe{sub 2}O{sub 3} nanorod electrode delivers a high discharge capacity of 761.7 mA h g{sup −1} after 60 cycles at 500 mA g{sup −1}, and 727.2 mA h g{sup −1} at a high current density of 2000 mA g{sup −1}. The good electrochemical performance is attributed to the sufficient contact of active material and electrolyte, large surface area, and short diffusion length of Li{sup +}.

  14. Detection of Target Biomolecules by Magnetic Reporting Using Rod-Like Nanosensors

    NASA Astrophysics Data System (ADS)

    Guertin, R. P.; Goldberg, E.; Harrah, T. P.; Sonkusale, S.; Park, K.; Sun, S.; Oh, J. I.; Naughton, M.

    2008-03-01

    We describe the ongoing development of a device to assay a variety of cellular, viral and molecular targets by measuring the increase of the Brownian relaxation time, τ, in solution of magnetically-tagged nanoscale detectors. The shift shows as a frequency reduction of the peak of the complex magnetic susceptibility, χ(φ)''. Measurements of χ(φ)'' with 12 nm monodisperse nanoparticles of CoFe2O4 coated with polyethelyne glycol reveal spectra with the narrowest lines yet reported. Thin avidin coating of these particles reveals small shifts in χ(φ)''. Bacteriophage T4 tail fibers, engineered to specific lengths (30-150 nm), were employed as the platform for magnetic nanoparticle attachment and at the other end for an inserted target peptide epitope. Attachment of the nanoparticles to bacteriophage T4 tail fibers was successful, though no detectable shifts in χ(φ)'' were detected due to weak attachment. The advantages associated with non-spherical geometry detectors will be discussed, as will preliminary measurements with rare earth oxide magnetic nanoparticles. Progress on miniaturization and low power requirements of the electronic detection system will be reported. Supported by NERCE/BEID (NIAID).

  15. Synthesis and ESR studies of 2'-deoxyuridines tethered with alkynyl, rod-like linkages#

    PubMed Central

    Sniady, Adam; Sevilla, Michael D.; Meneni, Srinivasarao; Lis, Tadeusz; Szafert, Slawomir; Khanduri, Deepthi; Finke, John M.; Dembinski, Roman

    2015-01-01

    Sonogashira coupling of diacetyl 5-ethynyl-2'-deoxyuridine with diacetyl 5-iodo-2'-deoxyuridine gave the acylated ethynediyl-linked 2'-deoxyuridine dimer (3b) (63%) that was deprotected with ammonia/methanol to ethynediyl-linked 2'-deoxyuridines (3a) (79%). Reaction of 5-ethynyl-2'-deoxyuridine (1a) with 5-iodo-2'-deoxyuridine gave the furopyrimidine linked to 2'-deoxyuridine (78%). Catalytic oxidative coupling of 1a (O2, CuI, Pd/C, DMF) gave the butadiynediyl-linked 2'-deoxyuridines (4) (84%). Double Sonogashira coupling of 5-iodo-2'-deoxyuridine with 1,4-bis(ethynyl)benzene gave 1,4-phenylenediethyne-bridged 5-ethynyl-2'-deoxyuridines (5, 83%). Cu-catalyzed cycloisomerization of dimers 4 and 5 gave their furopyrimidine derivatives. One electron addition to 1a, 3a and 4 gave the anion radical whose ESR spectra showed the unpaired electron largely localized at C6 of one uracil ring (17 G doublet) at 77 K. For the ethynediyl- and butadiynyl-linked uridines 3a and 4 the ESR spectra of their one electron oxidized species at 77 K showed that the unpaired electron is delocalized over both rings. Thus structures 3a and 4 provide an efficient electronic link for hole conduction between the uracil rings. However, for the excess electron, an activation barrier prevents coupling to both rings. These dimeric structures could provide a gate that could separate hole transfer from electron transport between strands in DNA systems. In the crystal structure of acylated dimer 3b the bases were found in the anti position to each other across the ethynyl link. Similar anti conformation was preserved in the derived furopyrimidine–deoxyuridine dinucleoside. PMID:19609983

  16. Optical gating of perylene bisimide fluorescence using dithienylcyclopentene photochromic switches

    SciTech Connect

    Pärs, Martti; Köhler, Jürgen; Gräf, Katja; Bauer, Peter; Thelakkat, Mukundan

    2013-11-25

    The emission of millions of fluorescence photons from a chromophore is controlled by the absorption of a few tens of photons in a photochromic molecule. The parameters that determine the efficiency of this process are investigated, providing insights for the development of an all-optical gate.

  17. RGD-conjugated rod-like viral nanoparticles on 2D scaffold improved bone differentiation of mesenchymal stem cells

    NASA Astrophysics Data System (ADS)

    Wang, Qian; Pongkwan, Sitasuwan; Lee, L.; Li, Kai; Nguyen, Huong

    2014-05-01

    Viral nanoparticles have uniform and well-defined nano-structures and can be produced in large quantities. Several plant viral nanoparticles have been tested in biomedical applications due to the lack of mammalian cell infectivity. We are particularly interested in using Tobacco mosaic virus (TMV), which has been demonstrated to enhance bone tissue regeneration, as a tuneable nanoscale building block for biomaterials development. Unmodified TMV particles have been shown to accelerate osteogenic differentiation of adult stem cells by synergistically upregulating BMP2 and IBSP expression with dexamethasone. However, the lack of affinity to mammalian cell surface resulted in low initial cell adhesion. In this study, to increase cell binding capacity of TMV based material the chemical functionalization of TMV with arginine-glycine-aspartic acid (RGD) peptide was explored. An azide-derivatized RGD peptide was “clicked” to tyrosine residues on TMV outer surface via an efficient copper(I) catalysed azide-alkyne cycloaddition reaction. The ligand spacing is calculated to be 2-4 nm, which could offer a polyvalent ligand clustering effect for enhanced cell receptor signalling, further promoting the proliferation and osteogenic differentiation of bone marrow derived mesenchymal stem cells.

  18. Rod-like plasmonic nanoparticles as optical building blocks: how differences in particle shape and structural geometry influence optical signal

    SciTech Connect

    Stender, Anthony

    2013-01-01

    Gold nanoparticles, particularly those with an anisotropic shape, have become a popular optical probe for experiments involving work on the nanoscale. However, to carry out such delicate and intricate experiments, it is first necessary to understand the detailed behavior of individual nanoparticles. In this series of experiments, optical and electron microscopy were utilized for the characterization of individual nanoparticles and small assemblies of nanoparticles. In the first experiment, gold nanorods were investigated. Single, isolated nanorods exhibit two maxima of localized surface plasmon resonance (LSPR), which are associated with the two nanorod axes. Upon the physical rotation of a nanorod at one of its LSPR wavelengths under polarized illumination, the optical behavior varies in a sinusoidal fashion. A dimer of nanorods exhibits optical behavior quite similar to a nanorod, except the LSPR maxima are shifted and broader. Under differential interference contrast (DIC) microscopy, a pair of nanorods separated by a distance below the diffraction limit can be distinguished from a single nanorod due to its optical behavior upon rotation. Dark field microscopy is unable to distinguish the two geometries. For the second set of experiments, the optical behavior of single gold nanorods at non-plasmonic wavelengths was investigated. The same nanorod was rotated with respect to a polarized light source under DIC, dark field, and polarized light microscopy. DIC microscopy was found to produce diffraction pattern peaks at non-plasmonic wavelengths, which could be altered by adjusting the setting of the polarizer. In the third set of experiments, the optical behavior of a single gold dumbbell and several simple dumbbell geometries were investigated with microscopy and simulations. The single dumbbell displayed behavior quite similar to that of a nanorod, but dumbbells exhibit a shift in both LSPR wavebands. Moreover, the shape of dumbbell particles allows them to interlock with one another quite easily. The dimers that form as a result display optical behavior that differs from what has been previously reported about nanorod dimers. Simulated surface charge density patterns reveal that hybridization of LSPR modes occurs readily along the lobes of individual dumbbells in some situations. A pentamer of dumbbells also displays hybridization of modes, and “hot spots” are observed at junctions between pairings of dumbbells. In the final set of experiments, the assembly behavior of nanoparticles in solution was observed in real time. In general, large assemblies of nanoparticles display backbone-like rigidity, but an interesting variety of movements is permitted within the larger structures.

  19. Structure and Stability of Long Rod-like Dodecyltrimethylammonium Chloride Micelles in Solutions of Hydroxybenzoates: A Molecular Dynamics Simulation Study.

    PubMed

    Gujt, Jure; Bešter-Rogač, Marija; Spohr, Eckhard

    2016-08-16

    The relative position of the hydroxylic and carboxylic groups in the isomeric hydroxybenzoate (HB) anions is experimentally known to have a large impact on the thermodynamics of micellization of cationic surfactants, such as dodecyltrimethylammonium chloride (DTAC), and on the structure of the resulting micelles. To understand the effect of the different isomers on the molecular level, we employed atomistic molecular dynamics simulations to study systems containing infinitely long cylindrical DTAC micelles in aqueous solutions of the sodium salts of all three isomers of HB at a temperature and a pressure of 298.15 K and 1 atm. In all studied systems, the number of DTAC unimers is identical to the number of HB anions. At this concentration, the initially cylindrical micelles remain stable, irrespective of the nature of the isomer, whereas micelles rapidly disintegrated in the absence of HB anions. The HB isomers decrease the line density of unimers along the micellar axis and its concomitant thickness in the order o-HB > m-HB > p-HB. It is further observed that o-HB anions penetrate more deeply into the micellar core, induce a more ordered internal structure of the micelle, and are oriented more strongly than the other two isomers. In addition, the ortho isomer shows two different preferential orientations with respect to the radial direction of the cylindrical micelle; it can either be incorporated almost completely into the micelle or it can be attached through hydrogen bonding to one of those o-HB anions that are already incorporated into the micelle, and thus stick out of the micellar surface. PMID:27442259

  20. Fabrication of the C-N co-doped rod-like TiO{sub 2} photocatalyst with visible-light responsive photocatalytic activity

    SciTech Connect

    Li, Liang-Hai; Lu, Juan; Wang, Zuo-Shan; Yang, Lu; Zhou, Xiu-Feng; Han, Lu

    2012-06-15

    Highlights: ► Novel synthesis of C-N co-doped TiO{sub 2}. ► Self-assembly of C-N co-doped TiO{sub 2} nanorods by nanoparticles. ► Excellent photocatalytic efficiency. -- Abstract: The C-N co-doped TiO{sub 2} nanorods were synthesized by the vapor transport method of water molecules, and urea was used as the carbon and nitrogen source. The samples were characterized by X-ray diffraction and photoelectron spectroscopy analysis. The scanning electron microscope images showed that as-prepared TiO{sub 2} powders were nanorods, which were formed by the stacking of nanoparticles with a uniform size around 40 nm. The degradation of methylene blue with the prepared nanorods demonstrated the photocatalytic activities of TiO{sub 2} under visible light are improved by doping with C and N elements. The main reasons were discussed: doping with C and N elements could enhance the corresponding visible-light absorption of TiO{sub 2}. On the other hand, doping C and N could create more oxygen vacancies in the TiO{sub 2} crystals, which could capture the photogenerated electrons more effectively. Thus, more photogenerated holes could be left to improve the photocatalytic activity of TiO{sub 2}.

  1. Mechanoresponsive change in photoluminescent color of rod-like liquid-crystalline compounds and control of molecular orientation on photoaligned layer

    NASA Astrophysics Data System (ADS)

    Kondo, Mizuho; Miura, Seiya; Okumoto, Kentaro; Hashimoto, Mayuko; Fukae, Ryohei; Kawatsuki, Nobuhiro

    2014-10-01

    In this paper, we reported novel liquid-crystalline luminophore that switches its photoluminescent color by mechanically grinding. Mechanochromic luminescence (MCL) is expected for mechanical sensor, cellular imaging, detection of microenvironmental changes, and optical memory. In this work, we focused on liquid-crystalline MCL compounds on alignment layer. Controlling the molecular alignment of MCL compounds with photoalignment layer have potential to succeed in functional MCL film such as polarized micropatterned MCL and directional detection of mechanical stimuli. Herein, we prepared asymmetric rodlike MCL compounds containing cyano- and pyridyl molecular terminal and explored their photoluminescence behavior under mechanical stimulus. The cyano terminated compound showed a nematic phase and tuned its photoluminescent color from green to yellow upon grinding, while the pyridyl-terminated compounds that show no mesophase changed its photoluminescent color from blue to green and reverted to its initial color by heating above its melting point. The cyano-terminated MCL was aligned along the orientation direction of photoalignment layer and pyridyl-terminated MCL exhibited uniaxial alignment when it coated on photoaligned film containing carboxylic acid.

  2. Synthesis and luminescent properties of Sr3Al2O5Cl2: Eu2+, Dy3+ rod-like nanocrystals

    NASA Astrophysics Data System (ADS)

    Wang, Zhengliang; Zhang, Qiuhan; Rong, Meizhu; Tan, Huiying; Wang, Qin; Zhou, Qiang; Chen, Guo

    2016-08-01

    White long afterglow phosphor with nano-rods, Sr3Al2O5Cl2: Eu2+, Dy3+, has been successfully synthesized by the solid state reaction. Their structure, morphology, scanning electron microscopy, luminescent properties and long afterglow properties were investigated by X-ray diffraction, transmission electron microscopy luminescence spectra and the luminescence decay curve. The obtained phosphor Sr3Al2O5Cl2: Eu2+, Dy3+ exhibits two broad emission bands, which are located at ∼445 nm and ∼590 nm, respectively. White light can be observed from this phosphor with appropriate CIE values (x = 0.357, y = 0.332). The white afterglow duration of this phosphor is about 0.5 h (>0.35 mcd/m2).

  3. Modification of the Electro-optical Properties of the B1 Liquid Crystal Phase using a Rod-like Liquid Crystal Dopant

    SciTech Connect

    J Kirchhoff; L Hirst

    2011-12-31

    It has recently been observed that on application of an alternating electric field, the B1 liquid-crystalline phase may be induced to form a switchable phase. This induced phase has been shown to have an almost thresholdless dielectric response. In this paper we examine this E-field-induced transition as a function of temperature both with and without a ferroelectric liquid-crystal dopant. Although the aim of this experiment was to enhance and stabilize the field-induced phase on addition of dopant, we find that the opposite is the case. The ferroelectric dopant actually increases the threshold E-fields required for transformation to the switching phase and at just 5 wt?% dopant a smectic-A phase is formed. Addition of the dopant also acts against the low-field switching and significantly speeds relaxation back to the B1 phase on field removal. In addition we find that the field-induced phase experiences a slower crystallization. We use polarized optical microscopy, differential scanning calorimetry, and x-ray scattering experiments to characterize the physical properties of the mixtures.

  4. Fluorescent labelling of DNA on superparamagnetic nanoparticles by a perylene bisimide derivative for cell imaging.

    PubMed

    Maltas, Esra; Malkondu, Sait; Uyar, Pembegul; Ozmen, Mustafa

    2015-03-01

    N,N'-Bis[tris-(2-aminoethyl) amine]-3,4,9,10-perylenetetracarboxylic diimide (PBI-TRIS), nonfluorescent dye was used to fluorescent labelling of DNA. For this aim, (3-aminopropyl) triethoxysilane (APTS) modified superparamagnetic iron oxide nanoparticles (SPIONs) were synthesized to provide a suitable surface for binding of DNA. Amine functionalized nanoparticles showed a high immobilization capacity (82.70%) at 25mg of nanoparticle concentration for Calf thymus DNA. Binding capacity of PBI-TRIS to DNA-SPION was also found as 1.93μM on 25mg of nanoparticles by using UV-vis spectroscopy. Binding of PBI-TRIS to DNA onto nanoparticles was also characterized by scanning electron microscopy and infrared spectroscopy. The confocal images of PBI-TRIS labelled DNA-SPION and breast cells were taken at 488 and 561.7nm of excitation wavelengths. Cell image was also compared with a commercial dye, DAPI at 403.7nm of excitation wavelength. Results showed that PBI-TRIS can be used for cell staining.

  5. Optical gating with organic building blocks. A quantitative model for the fluorescence modulation of photochromic perylene bisimide dithienylcyclopentene triads

    PubMed Central

    Pärs, Martti; Gradmann, Michael; Gräf, Katja; Bauer, Peter; Thelakkat, Mukundan; Köhler, Jürgen

    2014-01-01

    We investigated the capability of molecular triads, consisting of two strong fluorophores that were covalently linked to a photochromic molecule, for optical gating. Therefore we monitored the fluorescence intensity of the fluorophores as a function of the isomeric state of the photoswitch. From the analysis of our data we develop a kinetic model that allows us to predict quantitatively the degree of the fluorescence modulation as a function of the mutual intensities of the lasers that are used to induce the fluorescence and the switching of the photochromic unit. We find that the achievable contrast for the modulation of the fluorescence depends mainly on the intensity ratio of the two light beams and appears to be very robust against absolute changes of these intensities. The latter result provides valuable information for the development of all-optical circuits which would require to handle different signal strengths for the input and output levels. PMID:24614963

  6. Synthesis and Luminescent Chemosensory Behavior of N,N'-bis(p-aminophenyl)-1,5-bis(p-(tetraethyleneglycoloxy)phenyl)anthracene-2,3,6,7-tetracarboxyl bisimide

    NASA Technical Reports Server (NTRS)

    Ilhan, Faysal; Tyson, Daniel S.; Meador, Michael A.

    2004-01-01

    We have utilized the photoenolization reaction of a dibenzoyl-p-xylene derivative to synthesize two new, highly substituted anthracene-based molecules. ABI-NO2 and ABI-NH2 maintained photostability with longer wavelength absorption and emission spectra as compared to unsubstituted anthracene. Conversion of the periphery nitro groups to amines created an internal photoinduced electron transfer scenario that quenched the luminescence of ABI-NH2. Reversible or irreversible reaction of the attached amines resulted in fluorescence recovery. Sensitivity, of ABI-NH2 and other potential derivatives, to toxic chemicals may prove useful for early detection systems.

  7. Fluorescence quenching in an organic donor-acceptor dyad: a first principles study.

    PubMed

    Körzdörfer, T; Tretiak, S; Kümmel, S

    2009-07-21

    Perylene bisimide and triphenyl diamine are prototypical organic dyes frequently used in organic solar cells and light emitting devices. Recent Forster-resonant-energy-transfer experiments on a bridged organic dyad consisting of triphenyl diamine as an energy-donor and perylene bisimide as an energy-acceptor revealed a strong fluorescence quenching on the perylene bisimide. This quenching is absent in a solution of free donors and acceptors and thus attributed to the presence of the saturated CH(2)O(CH(2))(12)-bridge. We investigate the cause of the fluorescence quenching as well as the special role of the covalently bound bridge by means of time dependent density functional theory and molecular dynamics. The conformational dynamics of the bridged system leads to a charge transfer process between donor and acceptor that causes the acceptor fluorescence quenching. PMID:19624200

  8. A unique perylene-based DNA intercalator: localization in cell nuclei and inhibition of cancer cells and tumors.

    PubMed

    Xu, Zejun; Guo, Kunru; Yu, Jieshi; Sun, Haili; Tang, Jun; Shen, Jie; Müllen, Klaus; Yang, Wantai; Yin, Meizhen

    2014-10-29

    To date, perylene derivatives have not been explored as DNA intercalator to inhibit cancer cells by intercalating into the base pairs of DNA. Herein, a water-soluble perylene bisimide (PBDI) that efficiently intercalates into the base pairs of DNA is synthesized. Excitingly, PBDI is superior to the commercial DNA intercalator, amonafide, for specific nuclear accumulation and effective suppression of cancer cells and tumors.

  9. A hyperbranched supramolecular polymer constructed by orthogonal triple hydrogen bonding and host-guest interactions.

    PubMed

    Gu, Ruirui; Yao, Jian; Fu, Xin; Zhou, Wei; Qu, Da-Hui

    2015-03-28

    A hyperbranched supramolecular polymer has been constructed through orthogonal self-crosslinking by two classical binding interactions: triple hydrogen bonding interaction between a three-arm melamine derivative and DB24C8-containing bisimide and host-guest interaction between DB24C8 crown ether and ditopic dibenzyl ammonium moieties. PMID:25421931

  10. Alignment and alignment transition of bent core nematics

    NASA Astrophysics Data System (ADS)

    Elamain, Omaima; Hegde, Gurumurthy; Komitov, Lachezar

    2013-07-01

    We report on the alignment of nematics consisting of bimesogen bent core molecules of chlorine substituent of benzene derivative and their binary mixture with rod like nematics. It was found that the alignment layer made from polyimide material, which is usually used for promoting vertical (homeotropic) alignment of rod like nematics, promotes instead a planar alignment of the bent core nematic and its nematic mixtures. At higher concentration of the rod like nematic component in these mixtures, a temperature driven transition from vertical to planar alignment was found near the transition to isotropic phase.

  11. Synthesis and properties of a covalently linked angular perylene imide dimer.

    PubMed

    Thorley, Karl J; Würthner, Frank

    2012-12-21

    Utilizing the unexplored chemistry of a monocarbon analog to perylene bisimide, a covalently linked angular perylene dimer was synthesized. On the basis of measured optical properties and molecular modeling, the spectral changes relative to a monomeric reference perylene can be explained by an angle-dependent oblique exciton coupling model. With a roughly trigonal interchromophore arrangement, the dimer building block is promising for larger, cyclic assemblies to mimic naturally occurring light harvesting complexes.

  12. Trapping on demand: External regulation of excitation energy transfer in a photoswitchable smart matrix

    NASA Astrophysics Data System (ADS)

    Schmidt, R.; Pärs, M.; Weller, T.; Thelakkat, M.; Köhler, J.

    2014-01-01

    A thin film of polystyrene has been doped with small amounts of dithienylcyclopentene (DCP) based molecular switches and perylene bisimide (PBI) chromophores to obtain a photoswitchable smart matrix. The photochromic DCP can be converted by light between two bistable conformations and thereby changes the energetic position of its lowest excited singlet state. We exploit this feature to regulate the transfer of excitation energy between PBI and DCP as a function of the externally controllable illumination conditions in such a blend.

  13. Imide modified epoxy matrix resins

    NASA Technical Reports Server (NTRS)

    Scola, D. A.

    1984-01-01

    The results of a program designed to develop tough imide modified epoxy resins cured by bisimide amine (BIA) hardeners are described. State-of-the-art epoxides MY720 and DER383 were used, and four bismide amines were evaluated. These were the BIA's derived from the 6F anhydride (4,4'-(hexafluoroisopropylidene) bis(phthalic anhydride) and the diamines 3,3'-diaminodiphynyl sulfone, 4,4'-oxygianiline, 4,4'-methylene dianiline, and 1,12-dodecane diamine. A key intermediate, designated 6F anhydride, is required for the synthesis of the bisimide amines. Reaction parameters to synthesize a precursor to the 6F anhydride (6FHC) in high yields were investigated. The catalyst trifluoromethane sulfonic acid was studied. Although small scale runs yielded the 6FHC in 50 percent yield, efforts to ranslate these results to a larger scale synthesis gave the 6FHC in only 9 percent yield. Results show that the concept of using bisimide amine as curing agents to improve the toughness properties of epoxies is valid.

  14. A supramolecular helix that disregards chirality.

    PubMed

    Roche, Cécile; Sun, Hao-Jan; Leowanawat, Pawaret; Araoka, Fumito; Partridge, Benjamin E; Peterca, Mihai; Wilson, Daniela A; Prendergast, Margaret E; Heiney, Paul A; Graf, Robert; Spiess, Hans W; Zeng, Xiangbing; Ungar, Goran; Percec, Virgil

    2016-01-01

    The functions of complex crystalline systems derived from supramolecular biological and non-biological assemblies typically emerge from homochiral programmed primary structures via first principles involving secondary, tertiary and quaternary structures. In contrast, heterochiral and racemic compounds yield disordered crystals, amorphous solids or liquids. Here, we report the self-assembly of perylene bisimide derivatives in a supramolecular helix that in turn self-organizes in columnar hexagonal crystalline domains regardless of the enantiomeric purity of the perylene bisimide. We show that both homochiral and racemic perylene bisimide compounds, including a mixture of 21 diastereomers that cannot be deracemized at the molecular level, self-organize to form single-handed helical assemblies with identical single-crystal-like order. We propose that this high crystalline order is generated via a cogwheel mechanism that disregards the chirality of the self-assembling building blocks. We anticipate that this mechanism will facilitate access to previously inaccessible complex crystalline systems from racemic and homochiral building blocks. PMID:26673268

  15. Imide modified epoxy matrix resins

    NASA Technical Reports Server (NTRS)

    Scola, D. A.; Pater, R. H.

    1981-01-01

    High char yield epoxy using novel bisimide amines (BIA's) as curing agents with a state of the art epoxy resin was developed. Stoichiometric quantities of the epoxy resin and the BIA's were studied to determine the cure cycle required for preparation of resin specimens. The bisimide cured epoxies were designated IME's (imide modified epoxy). The physical, thermal and mechanical properties of these novel resins were determined. The levels of moisture absorption exhibited by the bisimide amine cured expoxies (IME's) were considerably lower than the state of the art epoxies. The strain-to-failure of the control resin system was improved 25% by replacement of DDS with 6F-DDS. Each BIA containing resin exhibited twice the char yield of the control resin MY 720/DDS. Graphite fiber reinforced control (C) and IME resins were fabricated and characterized. Two of the composite systems showed superior properties compared to the other Celion 6000/IME composite systems and state of the art graphite epoxy systems. The two systems exhibited excellent wet shear and flexural strengths and moduli at 300 and 350 F.

  16. Faraday polarization fluctuations of satellite beacon signals

    NASA Technical Reports Server (NTRS)

    Lee, M. C.; Klobuchar, J. A.

    1988-01-01

    The anisotropic effects of random density irregularities in causing Faraday polarization fluctuations of VHF radio signals are examined, taking both rod-like and sheet-like irregularities into consideration. It is found that the variance of Faraday polarization fluctuations depends on the ratio of perpendicular to parallel correlation lengths. The anisotropic effect of rod-like ionospheric irregularities are shown to be most appreciable for longitudinal propagation. The anisotropic effect of sheet-like ionospheric irregularities, however, is not strongly dependent on the radio propagation angle. During transionospheric propagation at large angles with respect to the geomagnetic field, sheet-like irregularities may cause greater Faraday polarization fluctuations than rod-like irregularities.

  17. On the rigidity of polynorbornenes with dipolar pendant groups.

    PubMed

    Lin, Wei-Yu; Murugesh, Modachur G; Sudhakar, Sundarraj; Yang, Hsiao-Ching; Tai, Hwan-Ching; Chang, Chia-Seng; Liu, Yi-Hung; Wang, Yu; Chen, I-Wen Peter; Chen, Chun-Hsien; Luh, Tien-Yau

    2005-12-16

    A range of polynorbornenes (PNBs) with fused dipolar pendant groups at C-5,6 positions was synthesized by ring-opening metathesis polymerization catalyzed by a ruthenium carbene complex (Grubbs I). Photophysical studies, EFISH measurements, and atomic force microscopy images have been used to investigate the structures and morphology of these polymers. These results suggest that the polymers may adopt rigid rod-like structures. The presence of the double bonds in PNBs appeared to be indispensable for the rigidity of the polymers. Interaction between unsaturated pendant groups may result in coherent alignment leading to a rod-like structure.

  18. Unsaturated syn- and anti-1,2-amino alcohols by cyclization of allylic bis-trichloroacetimidates. stereoselectivity dependence on substrate configuration.

    PubMed

    Grigorjeva, Liene; Kinens, Artis; Jirgensons, Aigars

    2015-01-16

    Disubstituted allylic bis-imidates undergo Lewis acid catalyzed or spontaneous cyclization to oxazolines, which are precursors of unsaturated amino alcohols. Stereoselectivity of the cyclization is mainly determined by the substrate configuration. Highly selective cis-oxazoline formation is achieved starting from anti-E-bis-imidates while trans-oxazoline predominantly forms from anti-Z-bis-imidates. On the basis of DFT calculations, the stereoselectivity trends can be explained by the formation of the energetically most stable carbenium ion conformation, followed by the cyclization via most favorable bond rotations. PMID:25484278

  19. Reduction of aryl halides by consecutive visible light-induced electron transfer processes.

    PubMed

    Ghosh, Indrajit; Ghosh, Tamal; Bardagi, Javier I; König, Burkhard

    2014-11-01

    Biological photosynthesis uses the energy of several visible light photons for the challenging oxidation of water, whereas chemical photocatalysis typically involves only single-photon excitation. Perylene bisimide is reduced by visible light photoinduced electron transfer (PET) to its stable and colored radical anion. We report here that subsequent excitation of the radical anion accumulates sufficient energy for the reduction of stable aryl chlorides giving aryl radicals, which were trapped by hydrogen atom donors or used in carbon-carbon bond formation. This consecutive PET (conPET) overcomes the current energetic limitation of visible light photoredox catalysis and allows the photocatalytic conversion of less reactive chemical bonds in organic synthesis.

  20. Preparation and characterization of homogeneous chitosan-polylactic acid/hydroxyapatite nanocomposite for bone tissue engineering and evaluation of its mechanical properties.

    PubMed

    Cai, Xuan; Tong, Hua; Shen, Xinyu; Chen, Weixuan; Yan, Juan; Hu, Jiming

    2009-09-01

    Homogeneous nanocomposites composed of hydroxyapatite and chitosan in the presence of polylactic acid were synthesized by a novel in situ precipitation method. The morphological and compositional properties of composites were investigated. Hydroxyapatite nanoparticles in a special rod-like shape with a diameter of about 50nm and a length of about 300nm were distributed homogeneously within the chitosan-polylactic acid matrix. The interaction between the organic matrix and the inorganic crystallite and the formation mechanism of the rod-like nanoparticles were also studied. The results suggested that the formation of the special rod-like nanoparticles could be controlled by a multiple-order template effect. High-resolution images showed that the rod-like inorganic particles were composed of randomly orientated subparticles about 10nm in diameter. The mechanical properties of the composites were evaluated by measuring their compressive strength and elastic modulus. The data indicated that the addition of polylactic acid can make homogeneous composites scaffold resist significantly higher stress. The elastic modulus of the composites was also improved by the addition of polylactic acid, which can make them more beneficial for surgical applications.

  1. Method for preparing spherical thermoplastic particles of uniform size

    DOEpatents

    Day, J.R.

    1975-11-17

    Spherical particles of thermoplastic material of virtually uniform roundness and diameter are prepared by cutting monofilaments of a selected diameter into rod-like segments of a selected uniform length which are then heated in a viscous liquid to effect the formation of the spherical particles.

  2. Morphological influence of cellulose nanoparticles (CNs) from cottonseed hulls on rheological properties of polyvinyl alcohol/CN suspensions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This work aims to extract and characterize fibrous, rod-like and spherical cellulose nanoparticles (CNs) from cottonseed hull and to investigate the structure-morphology-rheology relationships. The rheological behavior of poly(vinyl alcohol) (PVA)/CNs suspensions was also examined to guide the solve...

  3. Study and Characterization of Tobacco Mosaic Virus Head-to-tail Assembly Assisted by Aniline Polymerization

    SciTech Connect

    Niu,Z.; Bruckman, M.; Kotakadi, V.; He, J.; Emrick, T.; Russell, T.; Yang, L.; Wang, Q.

    2006-01-01

    One-dimensional composite nanofibres with narrow dispersity, high aspect ratio and high processibility have been fabricated by head-to-tail self-assembly of rod-like tobacco mosaic virus assisted by aniline polymerization, which can promote many potential applications including electronics, optics, sensing and biomedical engineering.

  4. Recent biophysical studies in high magnetic fields

    NASA Astrophysics Data System (ADS)

    Maret, Georg

    1990-06-01

    A brief overview of biophysical effects of steady magnetic fields is given. The need of high field strength is illustrated by several recent diamagnetic orientation experiments. They include rod-like viruses, purple membranes and chromosomes. Results of various studies on bees, quails, rats and pigeons exposed to fields above 7 T are also resumed.

  5. Flagella as a novel alignment medium for the measurement of residual dipolar couplings in proteins.

    PubMed

    Singh, Himanshu; Shukla, Manish; Rao, Basuthkar J; Chary, Kandala V R

    2013-12-18

    The two flexible rod-like flagella (∼500 nm in diameter and 5-15 μm long) of Chlamydomonas reinhardtii, a unicellular green alga, can weakly align molecules in an external magnetic field, thereby enabling the measurement of various residual dipolar couplings in solution NMR spectroscopy. PMID:24165953

  6. [SEM investigations on the human sclerosed dentinal tubules].

    PubMed

    Yagi, T; Suga, S

    1990-08-01

    Sclerotic changes of dentinal tubules appeared in the dentin beneath the carious, attrition and abrasion lesions and in the transparent root dentin were investigated using the scanning electron microscopy. 1) Shape of crystal-like substances appeared in the dentinal tubules could not be closely related to kinds of dentin destruction. 2) In the dentinal tubules beneath the carious lesions, cuboidal or rhomboid-shaped, short rod-like, long rod-like, plate-like and droplet-like crystals were mainly observed. Combination of cuboidal or rhomboid-shaped and short rod-like crystals or that of long rod-like and plate-like crystals were most frequently observed. 3) In the dentinal tubules beneath attrition and abrasion lesions, cuboidal or rhomboid-shaped, short rod-like and droplet-like crystals were mainly observed, however, the size of cuboidal or rhomboid-shaped crystal was usually smaller than that observed beneath carious lesion and they deposited compactly within the tubules. 4) In the sclerosed dentinal tubules in the transparent root dentin, compact deposition of rhomboid-shaped and irregular sand-like crystals were usually observed. Size of rhomboid-shaped crystal is smaller than that observed beneath carious lesion. The deposit of sand-like crystal in the tubules was easily discriminated from the matrix of peritubular dentin. 5) In any case, the kinds of crystals and pattern of deposition were not necessarily same between the neighboring tubules. However, in a tubule, they were almost same in shape and mode of deposition throughout the entire length of tubule from the outer side to the pulpal side. These facts seem to indicate that mineral deposition within the tubule due to sclerosis is performed under individual condition. 6) Finding showing biological control of mineral deposition within the dentinal tubules by the odontoblasts could not be observed.

  7. Energy transfer within self-assembled cyclic multichromophoric arrays based on orthogonally arranged donor-acceptor building blocks.

    PubMed

    Karakostas, Nikolaos; Kaloudi-Chantzea, Antonia; Martinou, Elisabeth; Seintis, Kostas; Pitterl, Florian; Oberacher, Herbert; Fakis, Mihalis; Kallitsis, Joannis K; Pistolis, George

    2015-01-01

    We herein present the coordination-driven supramolecular synthesis and photophysics of a [4+4] and a [2+2] assembly, built up by alternately collocated donor-acceptor chromophoric building blocks based, respectively, on the boron dipyrromethane (Bodipy) and perylene bisimide dye (PBI). In these multichromophoric scaffolds, the intensely absorbing/emitting dipoles of the Bodipy subunit are, by construction, cyclically arranged at the corners and aligned perpendicular to the plane formed by the closed polygonal chain comprising the PBI units. Steady-state and fs time-resolved spectroscopy reveal the presence of efficient energy transfer from the vertices (Bodipys) to the edges (PBIs) of the polygons. Fast excitation energy hopping - leading to a rapid excited state equilibrium among the low energy perylene-bisimide chromophores - is revealed by fluorescence anisotropy decays. The dynamics of electronic excitation energy hopping between the PBI subunits was approximated on the basis of a theoretical model within the framework of Förster energy transfer theory. All energy-transfer processes are quantitatively describable with Förster theory. The influence of structural deformations and orientational fluctuations of the dipoles in certain kinetic schemes is discussed. PMID:26396034

  8. Solubility and crystallizability: facile access to functionalized π-conjugated compounds with chlorendylimide protecting groups.

    PubMed

    Gebers, Jan; Rolland, Damien; Marty, Roman; Suàrez, Stéphane; Cervini, Luca; Scopelliti, Rosario; Brauer, Jan Cornelius; Frauenrath, Holger

    2015-01-19

    Functional π-conjugated molecules are relevant for the preparation of new organic electronic materials with improved performance. However, their synthesis is often rendered difficult by their inherently low solubility, and the permanent attachment of solubilizing groups may change the properties of the material. Here, we introduced the chlorendylimidyl moiety as a new temporary protecting group for the straightforward large-scale synthesis of protected quarter-, sexi-, octathiophene, and perylene bisimide diamine and dicarboxylic acid derivatives. The obtained chlorendylimides and chlorendylimidyl active esters were highly soluble in organic solvents, and optical spectroscopy confirmed the low tendency of the compounds to aggregate in solution. At the same time, they could be conveniently purified by recrystallization or precipitation. Single-crystal X-ray structures obtained for most compounds showed supramolecular motifs highlighting the role of the rigid, polychlorinated chlorendyl moieties in their crystallization. The obtained protected diamine and dicarboxylic acid derivatives were easily deprotected and converted into various amide-substituted oligothiophenes and perylene bisimides that are of interest as new functional materials for organic electronic thin film or nanowire devices. PMID:25427947

  9. Cationic Porphyrin-Anionic Surfactant Mixtures for the Promotion of Self-Organized 1:4 Ion Pairs in Water with Strong Aggregation Properties.

    PubMed

    Pradines, Vincent; Bijani, Christian; Stigliani, Jean-Luc; Blanzat, Muriel; Rico-Lattes, Isabelle; Pratviel, Geneviève

    2015-12-21

    We performed a systematic study on the spectroscopic and aggregation properties of stoichiometric mixtures (1:4) of the tetracationic meso-tetrakis(4-N-methylpyridinium)porphyrin (H2 TMPyP) and three sodium alkylsulfate surfactants (tetradecyl, hexadecyl, and octadecylsulfate) in an aqueous solution. The objective was to build a supramolecular aggregate, which would favor the internalization of tetracationic porphyrins in cells without chemical modification of the structure of the porphyrin. We show that stoichiometric H2 TMPyP/alkylsulfate (1:4) mixtures lead to the formation of large hollow spherical aggregates (60-160 nm). The TEM images show that the membrane of these aggregates are composed of smaller aggregates, which are probably rod-like micelles. These rod-like micelles have a hydrophobic core composed of the alkyl chains of the alkylsulfate surfactant, whereas the charged surface corresponds to the tetracationic porphyrins.

  10. Controllable growth of dendrite-like CuO nanostructures by ethylene glycol assisted hydrothermal process

    SciTech Connect

    Zhang Hui; Li Shenzhong; Ma Xiangyang; Yang Deren

    2008-05-06

    The dendrite-like CuO nanostructures, consisting of a rod-like main stem and some rod-like sub-branches, have been synthesized by a simple ethylene glycol (EG) assisted hydrothermal method. The X-ray diffraction (XRD) and the selected area electron diffraction (SAED) patterns indicate that the dendrite-like CuO nanostructures are of monoclinic phase and the individual branch of CuO is single crystalline in nature. The effects of the growth conditions such as temperature and pH value on the morphology and structures of CuO have also been investigated. It is indicated that different temperature and pH value result in the morphology and structure evolution of CuO. Moreover, a possible mechanism for the morphology and structures evolution of CuO has been primarily presented.

  11. A green chemical approach for synthesis of shape anisotropic gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Kalyan Kamal, S. S.; Vimala, J.; Sahoo, P. K.; Ghosal, P.; Ram, S.; Durai, L.

    2014-06-01

    A complete green chemical reaction between aurochloric acid and tea polyphenols resulted in the reduction of Au3+ → Au0. The reaction was carried out in a Teflon-coated bomb digestion vessel at 200 °C. It was observed that with increasing the reaction time from 1 to 5 h, the shape of the nanoparticles changed from spherical- to rod-like structures. The reaction was followed with the help of UV-vis spectrometer, which showed a single absorption peak at 548 nm for 1-h reaction product and two peaks for a 5-h reaction product at 533 and 745 nm corresponding to the transverse and longitudinal surface plasmon resonance bands. Microstructures obtained from transmission electron microscope revealed that the samples obtained after 1-h reaction are predominantly spherical in shape with an average size of 15 nm. Whereas samples obtained after 5 h of reaction exhibited rod-like structures with an average size of 45 nm.

  12. Incorporating headgroup structure into the Poisson-Boltzmann model of charged lipid membranes

    NASA Astrophysics Data System (ADS)

    Wang, Muyang; Chen, Er-Qiang; Yang, Shuang; May, Sylvio

    2013-07-01

    Charged lipids often possess a complex headgroup structure with several spatially separated charges and internal conformational degrees of freedom. We propose a headgroup model consisting of two rod-like segments of the same length that form a flexible joint, with three charges of arbitrary sign and valence located at the joint and the two terminal positions. One terminal charge is firmly anchored at the polar-apolar interface of the lipid layer whereas the other two benefit from the orientational degrees of freedom of the two headgroup segments. This headgroup model is incorporated into the mean-field continuum Poisson-Boltzmann formalism of the electric double layer. For sufficiently small lengths of the two rod-like segments a closed-form expression of the charging free energy is calculated. For three specific examples—a zwitterionic headgroup with conformational freedom and two headgroups that carry an excess charge—we analyze and discuss conformational properties and electrostatic free energies.

  13. Effects of four types of hydroxyapatite nanoparticles with different nanocrystal morphologies and sizes on apoptosis in rat osteoblasts.

    PubMed

    Xu, Zhengli; Liu, Changsheng; Wei, Jie; Sun, Jiao

    2012-06-01

    Hydroxyapatite nanoparticles (nano-HAP) have been reported to cause inflammatory reactions. Here, we aimed to compare the effects of four types of nano-HAP with different nanocrystal morphologies (short rod-like, long rod-like, spherical or needle-shaped crystals) and sizes (10-20, 10-30 or 20-40 nm) on growth inhibition and apoptosis in primary cultured rat osteoblasts. The osteoblasts was treated with the four types of nano-HAP at various concentrations (20, 40, 60, 80 or 100 mg l⁻¹). The nano-HAP specific surface area was detected using the Brunauer, Emmet and Teller method. The cell growth rate was detected using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay; apoptotic alterations and the level of reactive oxygen species in osteoblasts were measured using flow cytometry; and the amounts of apoptotic p53 and cytochrome c proteins were measured using western blotting. We observed that all four types of nano-HAP inhibited the growth of osteoblasts in a dose-dependent manner. These nano-HAP significantly induced apoptosis in osteoblasts. Nano-HAP with smaller specific surface areas induced lower apoptosis rates. The needle-shaped and the short rod-like particles induced greater cellular injury than the spherical and long rod-like particles, respectively. The increased apoptosis rates were accompanied by increased p53 and cytochrome c expression. These findings indicate that nano-HAP inhibit the activity of osteoblasts and also induce the apoptosis of osteoblasts in vitro. These findings also suggest that the nano-HAP-induced apoptotic pathway is mediated by a mitochondrial-dependent pathway. Moreover, the sizes, morphologies and concentrations of nano-HAP have significant effects on the apoptotic level.

  14. Process for forming shaped group II-VI semiconductor nanocrystals, and product formed using process

    DOEpatents

    Alivisatos, A. Paul; Peng, Xiaogang; Manna, Liberato

    2001-01-01

    A process for the formation of shaped Group II-VI semiconductor nanocrystals comprises contacting the semiconductor nanocrystal precursors with a liquid media comprising a binary mixture of phosphorus-containing organic surfactants capable of promoting the growth of either spherical semiconductor nanocrystals or rod-like semiconductor nanocrystals, whereby the shape of the semiconductor nanocrystals formed in said binary mixture of surfactants is controlled by adjusting the ratio of the surfactants in the binary mixture.

  15. Process for forming shaped group III-V semiconductor nanocrystals, and product formed using process

    DOEpatents

    Alivisatos, A. Paul; Peng, Xiaogang; Manna, Liberato

    2001-01-01

    A process for the formation of shaped Group III-V semiconductor nanocrystals comprises contacting the semiconductor nanocrystal precursors with a liquid media comprising a binary mixture of phosphorus-containing organic surfactants capable of promoting the growth of either spherical semiconductor nanocrystals or rod-like semiconductor nanocrystals, whereby the shape of the semiconductor nanocrystals formed in said binary mixture of surfactants is controlled by adjusting the ratio of the surfactants in the binary mixture.

  16. In situ synthesis carbonated hydroxyapatite layers on enamel slices with acidic amino acids by a novel two-step method.

    PubMed

    Wu, Xiaoguang; Zhao, Xu; Li, Yi; Yang, Tao; Yan, Xiujuan; Wang, Ke

    2015-09-01

    In situ fabrication of carbonated hydroxyapatite (CHA) remineralization layer on an enamel slice was completed in a novel, biomimetic two-step method. First, a CaCO3 layer was synthesized on the surface of demineralized enamel using an acidic amino acid (aspartic acid or glutamate acid) as a soft template. Second, at the same concentration of the acidic amino acid, rod-like carbonated hydroxyapatite was produced with the CaCO3 layer as a sacrificial template and a reactant. The morphology, crystallinity and other physicochemical properties of the crystals were characterized using field emission scanning electron microscopy (FESEM), Fourier transform infrared spectrometry (FTIR), X-ray diffraction (XRD) and energy-dispersive X-ray analysis (EDAX), respectively. Acidic amino acid could promote the uniform deposition of hydroxyapatite with rod-like crystals via absorption of phosphate and carbonate ions from the reaction solution. Moreover, compared with hydroxyapatite crystals coated on the enamel when synthesized by a one-step method, the CaCO3 coating that was synthesized in the first step acted as an active bridge layer and sacrificial template. It played a vital role in orienting the artificial coating layer through the template effect. The results show that the rod-like carbonated hydroxyapatite crystals grow into bundles, which are similar in size and appearance to prisms in human enamel, when using the two-step method with either aspartic acid or acidic glutamate (20.00 mmol/L).

  17. De novo morphogenesis in L-forms via geometric control of cell growth

    PubMed Central

    Billings, Gabriel; Ouzounov, Nikolay; Ursell, Tristan; Desmarais, Samantha M.; Shaevitz, Joshua; Gitai, Zemer; Huang, Kerwyn Casey

    2015-01-01

    Summary In virtually all bacteria, the cell wall is crucial for mechanical integrity and for determining cell shape. Escherichia coli’s rod-like shape is maintained via the spatiotemporal patterning of cell-wall synthesis by the actin homologue MreB. Here, we transiently inhibited cell-wall synthesis in E. coli to generate cell-wall-deficient, spherical L-forms, and found that they robustly reverted to a rod-like shape within several generations after inhibition cessation. The chemical composition of the cell wall remained essentially unchanged during this process, as indicated by liquid chromatography. Throughout reversion, MreB localized to inwardly curved regions of the cell, and fluorescent cell wall labelling revealed that MreB targets synthesistothose regions. When exposed to the MreB inhibitor A22, reverting cells regrew a cell wall but failed to recover a rod-like shape. Our results suggest that MreB provides the geometric measure that allows E. coli to actively establish and regulate its morphology. PMID:24995493

  18. Manipulation and stretching of bacteria and liposomes by Microfluidics

    NASA Astrophysics Data System (ADS)

    Zussman, Eyal; Salalha, Wael

    2006-03-01

    Microfluidic technology can be useful in lab-on-a-chip applications of biological assays, environmental monitoring, detection of toxic materials, as well as for assembly of nano- and micro-scale objects into more complex systems. In this work we focused on the orientation of rod-shaped bacteria (Bacillus) by employing shear flow and a high rate elongation flow, and stretching of giant liposomes with diameter size of tens of microns, which can be used as a simplified model for cell behavior. This was achieved by flows of dilute rod-like bacteria and liposome suspensions within a micro-channel by means of a capillary-driven motion. Fluidic alignment situations were tested, firstly by Venturi-like flow which produces a sufficiently converging and diverging flow, and secondly by sink-like flow in a converging microchannel. In the first method we found that the converging part of the flow aligns rod-like bacteria, whereas the diverging part disaligns them, while in the second method the rod-like bacteria can perfectly align along the streamlines. In addition we used the same technology to test liposome deformation while they are flowing through a Venturi-like microchannel. The microfluidics devices were fabricated from poly(dimethylsiloxane) (PDMS) by soft lithographic techniques.

  19. Simulation study of proton transport in ionomers

    NASA Astrophysics Data System (ADS)

    Taylor, Philip; Allahyarov, Elshad

    2008-03-01

    Coarse-grained molecular-dynamics simulations were used to study the morphological changes induced in a Nafion-like ionomer by the imposition of a strong electric field. We observe that proton transport through this polymer electrolyte membrane is accompanied by morphological changes that include the formation of structures aligned along the direction of the applied field. The polar head groups of the ionomer side chains assemble into clusters, which then form rod-like formations, and these cylindrical structures then assemble into a hexagonally ordered array aligned with the direction of current flow. For dry ionomers, at current densities in excess of 1 A/cm^2 these rod-like clusters undergo an inner micro-phase separation, in which distinct wire-like lines of sulfonate head groups are accompanied by similar wire-like alignments of bound protons. The clusters appear to be of two types. If there are two, four, or five lines of sulfonates then there is an equal number of lines of protons, but if there are three lines of sulfonates then they are accompanied by four lines of protons. Occasionally these lines of sulfonates and protons form a helical structure. Upon removal of the electric field, the hexagonal array of rod-like structures remains, but the microphase separation disappears below the threshold current of 1 A/cm^2.

  20. Morphology and crystal phase evolution of GeO 2 in liquid phase deposition process

    NASA Astrophysics Data System (ADS)

    Jing, Chengbin; Sun, Wei; Wang, Wei; Li, Yi; Chu, Junhao

    2012-01-01

    Morphology and crystal phase evolution of GeO 2 in liquid phase deposition (LPD) process is investigated. Rod-like solid phases precipitate out of solution ahead of truncated cube-like phases. SEM, XRD and TEM analyses reveal that the two sorts of solid phases are tetragonal GeO 2 and hexagonal GeO 2, respectively. The tetragonal GeO 2 phases start to experience a re-dissolving process as soon as the hexagonal phases come into being. The prior precipitation of the rod-like phase arises from a relatively low solute saturation of tetragonal GeO 2. Fast growth of a tetragonal GeO 2 phase along [111] direction leads to development of a rod-like shape. The re-dissolving phenomenon does not agree with the classic growth kinetics of crystals but is strongly favored by our calculations based on thermodynamics. The GeO 2 solutes are released in a fluctuant way by germanate ions, which promotes the occurrence of the re-dissolution phenomenon. The current researches open a door for room-temperature LPD growth of not only the hexagonal GeO 2 particles and film but also the one-dimensional tetragonal GeO 2 product.

  1. Morphological Effect of Non-targeted Biomolecule-Modified MNPs on Reticuloendothelial System

    NASA Astrophysics Data System (ADS)

    Li, Xiao; Hu, Yan; Xiao, Jie; Cheng, Dengfeng; Xiu, Yan; Shi, Hongcheng

    2015-09-01

    Magnetic nanoparticles (MNPs) with special morphology were commonly used as biomaterials, while morphological effects of non-targeted biomolecule-modified MNPs on biological behaviors were still unclear. In this research, spherical and rod-like Fe3O4 in a comparable size were synthesized and then surface-modified by bovine serum albumin (BSA) as a model of non-targeted biomolecule-modified MNPs. Morphological effects were featured by TEM and quantification of in vitro phagocytic uptake, as well as the in vivo quantification of particles in reticuloendothelial system (RES)-related organs of normal Kunming mice. For these non-targeted BSA-modified MNPs, intracellular distributions were the same, but the rod-like MNPs were more likely to be uptake by macrophages; furthermore, the BSA-modified MNPs gathered in RES-related organs soon after intravenous injection, but the rod-like ones were expelled from the lung more quickly and expelled from the spleen more slowly. These preliminary results may be referable if MNPs or other similar biomolecule-modified nanoparticles were used.

  2. Entropically Driven Self-Assembly of Bolaamphiphilic Perylene Dyes in Water.

    PubMed

    Görl, Daniel; Würthner, Frank

    2016-09-19

    The specific hydrophobic effect involved in the self-assembly of a bolaamphiphilic perylene bisimide (PBI) dye bearing oligoethylene glycol (OEG) chains has been identified. In pure water, the self-assembly is entropically driven and enthalpically disfavored, as explored by optical spectroscopy and isothermal titration calorimetry studies. Besides strong π-π interactions between the PBI units that are primarily of enthalpic nature, the major contribution to the self-assembly is the gain of entropy by release of confined water molecules from the hydration shell of the hydrophilic OEG moieties. Both contributions favor self-assembly, but their countervailing thermodynamic parameters are reflected in an uncommon temperature dependence, which can be inverted upon gradual addition of an organic cosolvent that makes the π-π interaction increasingly dominant. PMID:27558471

  3. Adsorption and desorption behavior of asphaltene on polymer-brush-immobilized surfaces.

    PubMed

    Higaki, Yuji; Hatae, Kaoru; Ishikawa, Tatsuya; Takanohashi, Toshimasa; Hayashi, Jun-ichiro; Takahara, Atsushi

    2014-11-26

    The adsorption behavior of a model compound for surface-active component of asphaltenes, N-(1-hexylheptyl)-N'-(12-carboxylicdodecyl) perylene-3,4,9,10-tetracarboxylic bisimide (C5Pe), and detachment behavior of asphaltene deposit films for high-density polymer brushes were investigated. Zwitterionic poly(3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate (PMAPS) brushes and hydrophobic poly(n-hexyl methacrylate) (PHMA) brushes exhibit less C5Pe adsorption than poly(methyl methacrylate) (PMMA). The asphaltene deposit films on the PHMA brush detached in a model oil (toluene/n-heptane=1/4 (v/v)), and the asphaltene films on the PMAPS brush detached in water. The antifouling character was explained by the interface free energy for the polymer-brush/asphaltenes (γSA) and polymer-brush/toluene (γSO). PMID:25370500

  4. Sensitivity and specificity of PS/AA-modified nanoparticles used in malaria detection.

    PubMed

    Thiramanas, Raweewan; Jangpatarapongsa, Kulachart; Asawapirom, Udom; Tangboriboonrat, Pramuan; Polpanich, Duangporn

    2013-07-01

    Polystyrene (PS) nanoparticle (NP) copolymerized with acrylic acid (AA) and coloured monomer, i.e. 2,3,6,7-tetra(2,2'-bithiophene)-1,4,5,8-naphthalenetetracarboxylic-N,N'-di(2-methylallyl)-bisimide (ALN8T), was synthesized via the miniemulsion polymerization. Before applying for malaria antigen detection, the blue NP was conjugated with human polyclonal malaria IgG antibody (Ab) specific to Plasmodium falciparum. For the conjugation, three methods, i.e. physical adsorption, covalent coupling and affinity binding via streptavidin (SA) and biotin interaction, were employed. The optimum ratio of Ab to NPs used in each immobilization procedure and the latex agglutination test based on the reaction between Ab conjugated NPs and malaria patient plasma were investigated. All Ab-latex conjugates provided the high sensitivity for the detection of P. falciparum malaria plasma. The highest specificity to P. falciparum was obtained from using Ab-NPs conjugated via the SA-biotin interaction.

  5. A new efficient method for calculation of Frenkel exciton parameters in molecular aggregates

    NASA Astrophysics Data System (ADS)

    Plötz, Per-Arno; Niehaus, Thomas; Kühn, Oliver

    2014-05-01

    The Frenkel exciton Hamiltonian is at the heart of many simulations of excitation energy transfer in molecular aggregates. It separates the aggregate into Coulomb-coupled monomers. Here it is shown that the respective parameters, i.e., monomeric excitation energies and Coulomb couplings between transition densities can be efficiently calculated using time-dependent tight-binding-based density functional theory (TD-DFTB). Specifically, Coulomb couplings are expressed in terms of self-consistently determined Mulliken transition charges. The approach is applied to two dimer systems. First, formaldehyde oxime for which a detailed comparison with standard DFT using the B3LYP and the PBE functionals as well as with SCS-CC2 is provided. Second, the Coulomb coupling is explored in dependence on the intermolecular coordinates for a perylene bisimide dimer. This provides structural evidence for the previously observed biphasic aggregation behavior of this dye.

  6. Adsorption and desorption behavior of asphaltene on polymer-brush-immobilized surfaces.

    PubMed

    Higaki, Yuji; Hatae, Kaoru; Ishikawa, Tatsuya; Takanohashi, Toshimasa; Hayashi, Jun-ichiro; Takahara, Atsushi

    2014-11-26

    The adsorption behavior of a model compound for surface-active component of asphaltenes, N-(1-hexylheptyl)-N'-(12-carboxylicdodecyl) perylene-3,4,9,10-tetracarboxylic bisimide (C5Pe), and detachment behavior of asphaltene deposit films for high-density polymer brushes were investigated. Zwitterionic poly(3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate (PMAPS) brushes and hydrophobic poly(n-hexyl methacrylate) (PHMA) brushes exhibit less C5Pe adsorption than poly(methyl methacrylate) (PMMA). The asphaltene deposit films on the PHMA brush detached in a model oil (toluene/n-heptane=1/4 (v/v)), and the asphaltene films on the PMAPS brush detached in water. The antifouling character was explained by the interface free energy for the polymer-brush/asphaltenes (γSA) and polymer-brush/toluene (γSO).

  7. Fire and heat resistant laminating resins based on maleimido and citraconimido substituted 1-(diorgano oxyphosphonyl) methyl -2,4- and -2,6- diaminobenzenes

    NASA Technical Reports Server (NTRS)

    Mikroyannidis, John A. (Inventor); Kourtides, Demetrius A. (Inventor)

    1987-01-01

    A class of fire and heat resistant bisimide resins prepared by thermal polymerization of maleimido or citraconimido substituted 1-((dialkoxyphosphonyl) methyl)-2-4 and -2,6-diaminobenzenes are described. The polymer precursors are prepared by reacting 1-((diorganooxyphosphonyl) methyl)-2-4 and -2,6-diaminobenzenes with maleic anhydride or citraconic anhydride in a mole ratio 1:2. Chain extension of the monomers is achieved by reacting the mono-N-maleimido derivatives of 1-((diorganooxyphosphonyl) methyl)-2,4 and -2,6-diaminobenzenes with aryl tetracarboxylic dianhydrides, such as benzophenone tetracarbocylic dianhydride, or aryl diisocyanates, such as methylenebis (4-phenylisocyanate), in a mole ratio 2:1. The polymerization of the monomers is studied by differential scanning calorimetry (DSC) and the thermal stability of the polymers is ascertained by thermogravimetric analysis (TGA).

  8. Entropically Driven Self-Assembly of Bolaamphiphilic Perylene Dyes in Water.

    PubMed

    Görl, Daniel; Würthner, Frank

    2016-09-19

    The specific hydrophobic effect involved in the self-assembly of a bolaamphiphilic perylene bisimide (PBI) dye bearing oligoethylene glycol (OEG) chains has been identified. In pure water, the self-assembly is entropically driven and enthalpically disfavored, as explored by optical spectroscopy and isothermal titration calorimetry studies. Besides strong π-π interactions between the PBI units that are primarily of enthalpic nature, the major contribution to the self-assembly is the gain of entropy by release of confined water molecules from the hydration shell of the hydrophilic OEG moieties. Both contributions favor self-assembly, but their countervailing thermodynamic parameters are reflected in an uncommon temperature dependence, which can be inverted upon gradual addition of an organic cosolvent that makes the π-π interaction increasingly dominant.

  9. Delayed cure bismaleimide resins

    DOEpatents

    Adams, Johnnie E.; Jamieson, Donald R.

    1984-08-07

    Polybismaleimides prepared by delayed curing of bis-imides having the formula ##STR1## wherein R.sub.1 and R.sub.2 each independently is H, C.sub.1-4 -alkyl, C.sub.1-4 -alkoxy, Cl or Br, or R.sub.1 and R.sub.2 together form a fused 6-membered hydrocarbon aromatic ring, with the proviso that R.sub.1 and R.sub.2 are not t-butyl or t-butoxy; X is O, S or Se; n is 1-3; and the --(CH.sub.2).sub.n -- group, optionally, is substituted by 1-3 methyl groups or by fluorine.

  10. Glyconanosomes: disk-shaped nanomaterials for the water solubilization and delivery of hydrophobic molecules.

    PubMed

    Assali, Mohyeddin; Cid, Juan-José; Pernía-Leal, Manuel; Muñoz-Bravo, Miguel; Fernández, Inmaculada; Wellinger, Ralf E; Khiar, Noureddine

    2013-03-26

    Herein, we describe the first report on a new class of disk-shaped and quite monodisperse water-soluble nanomaterials that we named glyconanosomes (GNS). GNSs were obtained by sliding out the cylindrical structures formed upon self-organization and photopolymerization of glycolipid 1 on single-walled carbon nanotube (SWCNT) sidewalls. GNSs present a sheltered hydrophobic inner cavity formed by the carbonated tails, surrounded by PEG and lactose moieties. The amphiphilic character of GNSs allows the water solubility of insoluble hydrophobic cargos such as a perylene-bisimide derivative, [60]fullerene, or the anti-carcinogenic drug camptothecin (CPT). GNS/C60 inclusion complexes are able to establish specific interactions between peanut agglutinin (PNA) lectin and the lactose moiety surrounding the complexes, while CPT solubilized by GNS shows higher cytotoxicity toward MCF7-type breast cancer cells than CPT alone. Thus, GNS represents an attractive extension of nanoparticle-based drug delivery systems.

  11. Synthesis, Photophysical, and Biological Evaluation of Sulfated Polyglycerol Dendronized Perylenebisimides (PBIs)--A Promising Platform for Anti-Inflammatory Theranostic Agents?

    PubMed

    Heek, T; Kühne, C; Depner, H; Achazi, K; Dernedde, J; Haag, R

    2016-03-16

    A set of four water-soluble perylene bisimides (PBI) based on sulfated polyglycerol (PGS) dendrons were developed, their photophysical properties determined via UV/vis and fluorescence spectroscopy, and their performance as possible anti-inflammatory agents evaluated via biological in vitro studies. It could be shown that in contrast to charge neutral PG-PBIs the introduction of the additional electrostatic repulsion forces leads to a decrease in the dendron generation necessary for aggregation suppression, allowing the preparation of PBIs with fluorescence quantum yields of >95% with a considerable decreased synthetic effort. Furthermore, the values determined for L-selectin binding down to the nanomolar range, their limited impact on blood coagulation, and their minor activation of the complement system renders these systems ideal for anti-inflammatory purposes. PMID:26890394

  12. Bismaleimides and related maleimido polymers as matrix resins

    NASA Technical Reports Server (NTRS)

    Parker, J. A.; Kourtides, D. A.; Fohlen, G. M.

    1985-01-01

    Significant processing and property improvements can be achieved by copolymerization of state-of-the-art bisimides with various vinyl stilbazole derivatives to give both fire resistance and high-temperature properties from hot-melt compositions. Significant improvement in mechanical properties is achieved through these modifications, which may make these new matrix resins ideal candidates for fireworthy secondary graphite composite structures. Phosphorous modifications of maleimido polymers through phosphonate structure and tricyclophosphazene derivatives provide families of new matrix resins for short-time applications in severe thermo-oxidative environments. With further research these may provide matrix resins for long-term thermo-oxidative stability of advanced composites at temperatures up to 400 to 500 C.

  13. Kinetics-controlled growth of bimetallic RhAg on Au nanorods and their catalytic properties

    NASA Astrophysics Data System (ADS)

    Ye, Wei; Guo, Xia; Xie, Fang; Zhu, Rui; Zhao, Qing; Yang, Jian

    2014-03-01

    Controlled growth of hybrid metallic nanocomposites for a desirable structure in a combination of selected components is highly important for their applications. Herein, the controllable growth of RhAg on the gold nanorods is achieved from the dumbbell-like RhAg-tipped nanorods to the brushy RhAg-coated nanorods, or the rod-like Au@Ag-Rh nanorattles. These different growth modes of RhAg on the gold nanorods are correlated with the reducing kinetics of RhCl3 and AgNO3. In view of the promising catalytic properties of Rh, the gold nanorods modified by RhAg in different structures are examined as catalysts for the oxidation of o-phenylenediamine. It is found that brushy RhAg-coated nanorods present a higher catalytic efficiency than dumbbell-like RhAg-tipped nanorods and rod-like Au@Ag-Rh nanorattles. These results would benefit the overgrowth control on the one-dimensional metallic nanorods and the rational design of new generation heterogeneous catalysts and optical devices.Controlled growth of hybrid metallic nanocomposites for a desirable structure in a combination of selected components is highly important for their applications. Herein, the controllable growth of RhAg on the gold nanorods is achieved from the dumbbell-like RhAg-tipped nanorods to the brushy RhAg-coated nanorods, or the rod-like Au@Ag-Rh nanorattles. These different growth modes of RhAg on the gold nanorods are correlated with the reducing kinetics of RhCl3 and AgNO3. In view of the promising catalytic properties of Rh, the gold nanorods modified by RhAg in different structures are examined as catalysts for the oxidation of o-phenylenediamine. It is found that brushy RhAg-coated nanorods present a higher catalytic efficiency than dumbbell-like RhAg-tipped nanorods and rod-like Au@Ag-Rh nanorattles. These results would benefit the overgrowth control on the one-dimensional metallic nanorods and the rational design of new generation heterogeneous catalysts and optical devices. Electronic

  14. Effect of metal ions (Sn and Zn) on the thermal property of akaganeite nanorods

    SciTech Connect

    Wang, Wei-Wei; Yao, Jia-Liang

    2012-07-15

    Graphical abstract: Compared with β-FeOOH and Zn doped β-FeOOH, the thermal stability of tin doped β-FeOOH increases both in solution and air. Zn and Sn ions doping favor the formation of rod like shape β-FeOOH. Highlights: ► The addition of tin ions increases the thermal stability of β-FeOOH nanorods both in solution and air. ► Tin ions doped β-FeOOH nanorods show higher decomposition temperature (ΔT = 200 °C). ► The presence of tin and zinc ions is favor of the formation of rod like shape. -- Abstract: The electrical, optical, and adsorption properties of akaganeite (β-FeOOH) can be modified by doping or combining with variety of elements. We prepared metal ions (Sn, Zn) doped β-FeOOH using β-FeOOH nanorods as the precursor by the hydrothermal method and investigated the effect of metal ions (Sn, Zn) on the thermal property of β-FeOOH nanorods. The doping of metal ions (Sn, Zn) was confirmed by X-ray powder diffraction, energy dispersive spectroscopy, and atomic emission spectrometer analysis. Thermogravimetric analysis and differential thermal analysis showed that they have different thermal decomposition temperatures. β-FeOOH nanorods and Zn doped β-FeOOH nanorods were transformed into α-Fe{sub 2}O{sub 3} particles at 400 °C. While Sn doped β-FeOOH nanorods should be heated to higher temperature (600 °C). Sn doped β-FeOOH nanorods showed higher thermal stability due to the Sn ions binding with the framework of β-FeOOH. Both Sn and Zn ions doped β-FeOOH remained the rod like shape.

  15. Anisotropy of low dielectric constant materials and reliability of copper/low-k interconnects

    NASA Astrophysics Data System (ADS)

    Cho, Taiheui

    2000-10-01

    Cu/low-k material interconnects are a solution to overcome problems that occur in deep submicron Al/SiO2 based interconnects. Several challenges have to be resolved before successfully integrating copper and low-k dielectric materials into interconnects. In this work, Cu and several low-k polymers were used for interconnect applications and their effects on interconnect performance were investigated. Dielectric anisotropy is one of the factors that affect interconnect performance. Two fluorinated polymers, a rigid rod-like polyimide (Dupont FPI-136M) and a flexible poly(aryl ether) (Allied Signal FLARE 1.51) were used to investigate the relationship between dielectric anisotropy and molecular orientation. The dielectric anisotropy of the rigid rod-like polyimide was reduced relative to that in blanket films when it was confined in submicron trenches. Such a reduction was not observed in the flexible polymer. Polarized FTIR experiments showed that when rigid rod-like polymer was confined in submicron trenches polymer chains preferentially oriented parallel to metal lines. The preferential orientation reduced the in-plane dielectric constant of the polymer. A barrier layer has to be used to prevent Cu diffusion into an interlayer dielectric material. Ta, TaN, and TaSiN were used to investigate the relationship between barrier capability and microstructures using a bias temperature stress. TaSiN performed best because TaSiN was amorphous, followed by TaN then Ta because TaN had impurities segregated in grain boundaries. When Cu/BCB interconnects were fabricated and their reliability was investigated with the bias temperature stress, some of the interconnect structures performed properly and their life times were comparable to those of Cu/SiO2 interconnects, while other interconnect structures rapidly failed because the Cu readily diffused through defects in the barrier. The defects were introduced during chemical-mechanical polishing and plasma etching processes.

  16. Study of gelatin-agar intermolecular aggregates in the supernatant of its coacervate.

    PubMed

    Singh, S Santinath; Bohidar, H B; Bandyopadhyay, S

    2007-05-15

    Intermolecular interaction leading to formation of aggregates between gelatin, a polyampholyte, and agar, a polysaccharide was studied in the supernatant of the complex coacervate formed by these biopolymers. Electrophoresis, laser light scattering and viscometry data were used to determine the interaction and the physical structure of these intermolecular soluble complexes by modeling these to be prolate ellipsoids of revolution (rod-like structures with well defined axial ratio and Perrin's factor). Solution ionic strength was found to reduce the axial ratio of these complexes implying the presence of screened polarization-induced electrostatic interaction between the two biopolymers.

  17. Complexation between dodecyl sulfate surfactant and zein protein in solution.

    PubMed

    Ruso, Juan M; Deo, Namita; Somasundaran, P

    2004-10-12

    Interactions between sodium dodecyl sulfate and zein protein, a model system for the understanding of the effect of surfactants on skin, were investigated using a range of techniques involving UV-vis spectroscopy, TOC (total organic carbon analysis), electrophoresis, and static and dynamic light scattering. Zein protein was solubilized by SDS. The adsorption of SDS onto insoluble protein fraction caused the zeta potential of the complex to become more negative. From these values, we calculated the Gibbs energy of absorption, which decreases when the SDS concentration is raised. Finally the structure of the complex, based on the analysis by static and dynamic light scattering, is proposed to be rod like.

  18. An indolocarbazole dimer as a new stereodynamic probe for chiral 1,2-diamines.

    PubMed

    Jeon, Hae-Geun; Kim, Min Jun; Jeong, Kyu-Sung

    2014-08-01

    An indolocarbazole dimer that contains aldehyde groups at both ends was prepared by connecting two monomeric units through a rod-like 1,4-butadiynyl spacer. Upon mixing with chiral 1,2-diamines at room temperature, the dimer was in situ converted to the corresponding cyclic diimines in the presence of tetrabutylammonium acetate as a template. The resulting diimines fold to helical conformations of right-handed (P) or left-handed (M) orientations, depending on the absolute stereochemistries of chiral 1,2-diamines. The patterns and intensities of the CD spectra can be used to determine the absolute configurations and enantiomeric excesses of chiral 1,2-diamines.

  19. Torque-generating malaria-infected red blood cells in an optical trap

    NASA Astrophysics Data System (ADS)

    Dharmadhikari, J. A.; Roy, S.; Dharmadhikari, A. K.; Sharma, S.; Mathur, Deepak

    2004-03-01

    We have used optical tweezers to trap normal and Plasmodiuminfected red blood cells (iRBCs). Two different facets of the behavior of RBCs in infrared light fields emerge from our experiments. Firstly, while the optical field modifies both types of RBCs in the same fashion, by folding the original biconcave disk into a rod-like shape, iRBCs rotate with linearly polarized light whereas normal RBCs do not. Secondly, and in the context of known molecular motors, our measurements indicate that the torque of rotating iRBCs is up to three orders of magnitude larger.

  20. Spherical and rodlike inorganic nanoparticle regulated the orientation of carbon nanotubes in polymer nanofibers

    NASA Astrophysics Data System (ADS)

    Jiang, Linbin; Tu, Hu; Lu, Yuan; Wu, Yang; Tian, Jing; Shi, Xiaowen; Wang, Qun; Zhan, Yingfei; Huang, Zuqiang; Deng, Hongbing

    2016-04-01

    PVA nanofibers containing carboxylic-modified MWCNTs were fabricated via electrospinning of PVA/MWCNTs mixed solution. The alignment of MWCNTs in PVA nanofibers was studied using transmission electron microscope and scanning electron microscope. In addition, the orientation of MWCNTs in PVA nanofibers was further investigated in the presence of rod-like nanoparticle rectorite (REC) and of spherical nanoparticle titanium dioxide (TiO2). The images demonstrated the embedment of MWCNTs in the nanofibers and the alignment of MWCNTs along the fiber axis. Moreover, the addition of REC and TiO2 improved the alignment of MWCNTs in PVA nanofibers.

  1. Spatial organization of plastic deformation in single crystals with different structure of slip dislocation

    SciTech Connect

    Kunitsyna, T. S.; Teplyakova, L. A. Koneva, N. A.; Poltaranin, M. A.

    2015-10-27

    It is established that different structure of slip dislocation at the end of the linear hardening stage results in different distribution of dislocation charges in the volume of a single crystal. In the alloy with a near atomic order the slip of single dislocations leads to formation of planar structures—layers with the excess density of dislocations. In the alloy with long-range atomic order the slip of superdislocations brings the formation of the system of parallel rod-like charged dislocation linking.

  2. Simulation study of poled low-water ionomers with different architectures

    NASA Astrophysics Data System (ADS)

    Allahyarov, Elshad; Taylor, Philip L.; Löwen, Hartmut

    2011-11-01

    The role of the ionomer architecture in the formation of ordered structures in poled membranes is investigated by molecular dynamics computer simulations. It is shown that the length of the sidechain Ls controls both the areal density of cylindrical aggregates Nc and the diameter of these cylinders in the poled membrane. The backbone segment length Lb tunes the average diameter Ds of cylindrical clusters and the average number of sulfonates Ns in each cluster. A simple empirical formula is noted for the dependence of the number density of induced rod-like aggregates on the sidechain length Ls within the parameter range considered in this study.

  3. The barbel-like specialization of the pelvic fins in Ophidion rochei (Ophidiidae).

    PubMed

    Codina, Elisabet; Loïc, Kéver; Compère, Philippe; Dragičević, Branko; Dulčić, Jakov; Parmentier, Eric

    2012-12-01

    Pelvic fins in Ophidion rochei are reduced to four rod-like structures situated at the ventral jaws. While the fish is swimming, they make continuous sweeping movements on the bottom. This paper examines and describes the anatomy of the pelvic fins to determine the possible functions of these appendages in relation to the mode of life of this fish species. The pelvic fins of O. rochei show strong similarities with barbels because they have identical sensory cell types, (taste buds, solitary chemosensory cells, and goblet cells), innervations and sensory function. Having nocturnal habits, specialization of pelvic fins in O. rochei corresponds to a supporting role to the life in dark environment.

  4. New method for fabrication of superconducting pipes in the Bi-Sr-Ca-Cu-O system

    NASA Astrophysics Data System (ADS)

    Abe, Yoshihiro; Hosono, Hideo; Lee, Won-Hyuk; Hosoe, Masahiro; Nakamura, Koichi; Inukai, Eikichi

    1993-01-01

    Pipes or hollow cylinders in the Bi-Sr-Ca-Cu-O system were found to be fabricated easily by inspiring or sucking the low viscosity melt into a cold silica glass tube. The outer part of the cast rod-like melt solidified, and the inner hot low-viscosity part of the rod melt was expired. The precursor pipes were reheated at 800 C for 50 h in air, resulting in the formation of superconducting (Tc = 87 K) pipes which were of smooth surface without machining and high bending strength (100-150 MPa).

  5. Polystyrene-ZnO core-shell microspheres and hollow ZnO structures synthesized with the sulfonated polystyrene templates

    SciTech Connect

    Yang Yang; Chu Ying . E-mail: chuying@nenu.edu.cn; Zhang Yanping; Yang Fuyong; Liu Jinglin

    2006-02-15

    Mono-sized sulfonated polystyrene (PS) microspheres were used as templates to prepare PS-zinc oxide (ZnO) core-shell microspheres. Two different hollow ZnO structures were obtained after removing the PS cores by solvent extraction or calcinations. However, we obtained rod-like ZnO by either using unsulfonated PS microspheres as templates or without any templates. Transmission electron microscope (TEM) and scanning electron microscope (SEM) images were used to characterize the structures and morphologies of all the samples. X-ray diffraction (XRD), electron diffraction (ED) and infrared (IR) spectra were, respectively, used to study the crystal structure and composition of samples, respectively.

  6. Shape effects on dynamics of inertia-free spheroids in wall turbulence

    SciTech Connect

    Challabotla, Niranjan Reddy; Zhao, Lihao; Andersson, Helge I.

    2015-06-15

    The rotational motion of inertia-free spheroids has been studied in a numerically simulated turbulent channel flow. Although inertia-free spheroids were translated as tracers with the flow, neither the disk-like nor the rod-like particles adapted to the fluid rotation. The flattest disks preferentially aligned their symmetry axes normal to the wall, whereas the longest rods were parallel with the wall. The shape-dependence of the particle orientations carried over to the particle rotation such that the mean spin was reduced with increasing departure from sphericity. The streamwise spin fluctuations were enhanced due to asphericity, but substantially more for prolate than for oblate spheroids.

  7. Lattice model for biaxial and uniaxial nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Sauerwein, Ricardo A.; de Oliveira, Mário J.

    2016-05-01

    We use a lattice gas model to describe the phase transitions in nematic liquid crystals. The phase diagram displays, in addition to the isotropic phase, the two uniaxial nematics, the rod-like and discotic nematics, and the biaxial nematic. Each site of the lattice has a constituent unit that takes only six orientations and is understood as being a parallelepiped brick with the three axes distinct. The possible orientations of a brick are those in which its axes are parallel to the axes of a Cartesian reference frame. The analysis of the model is performed by the use of a mean-field approximation and a Landau expansion of the free energy.

  8. Nanocrystalline cellulose from aspen kraft pulp and its application in deinked pulp.

    PubMed

    Xu, Qinghua; Gao, Yang; Qin, Menghua; Wu, Kaili; Fu, Yingjuan; Zhao, Jian

    2013-09-01

    Nanocrystalline cellulose (NCC) isolated from bleached aspen kraft pulp was characterized, and its application as pulp strengthening additive and retention aid was investigated. Results showed that NCC with high crystallinity of more than 80% can be obtained using 64 wt% sulfuric acid. The structure of nanocrystalline cellulose is parallelepiped rod-like, and their cross-sectional dimension is in the nanometer range with a high aspect ratio. The formation of microparticle retention systems during the application of NCC together with cationic polyacrylamide and cationic starch in deinked pulp was able to further improve pulp retention and strength properties without negative influence on the drainage.

  9. Photoluminescence of Eu{sup 3+}-doped LaPO{sub 4} nanocrystals synthesized by combustion method

    SciTech Connect

    Xiu Zhiliang; Liu Suwen; Lue Mengkai . E-mail: mklu@icm.sdu.edu.cn; Zhang Haiping; Zhou Guangjun

    2006-03-09

    Eu{sup 3+}-doped LaPO{sub 4} nanocrystals were synthesized for the first time by a combustion method with urea as a fuel calcined at 700 deg. C. The diffraction profile of the obtained sample was indexed as a monoclinic monazite-structure by X-ray diffraction (XRD) data. The obtained nanocrystals appeared to be short rod-like with diameters of 5-10 nm and lengths of 20-70 nm. The luminescence intensities of Eu{sup 3+}-doped LaPO{sub 4} nanocrystals were found to be strongly dependent on the quantities of urea added and the concentration of Eu{sup 3+}.

  10. Production of SnO 2 nanorods by redox reaction

    NASA Astrophysics Data System (ADS)

    Liu, Yingkai; Zheng, Chenglin; Wang, Wenzhong; Zhan, Yongjie; Wang, Guanghou

    2001-11-01

    SnO 2 nanorods were prepared by annealing precursor powders produced by mixing three kinds of inverse microemulsions (IμE). The microstructures of the resultant nanorods were studied by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAD). It has been found that the as-prepared materials have a rod-like shape with lengths of tens of micrometers and diameters of 30-200 nm under different conditions. We discussed the influences of temperature and surfactant on the formation of SnO 2 nanorods and the mechanism of the formation of SnO 2 nanorods.

  11. Microwave absorption by nanoresonator vibrations tuned with surface modification

    NASA Astrophysics Data System (ADS)

    Krivosudský, Ondrej; Cifra, Michal

    2016-08-01

    Elucidating the physical and chemical parameters that govern viscous damping of nanoresonator vibrations and their coupling to electromagnetic radiation is important for understanding the behavior of matter at the nanoscale. Here we develop an analytical model of microwave absorption of a longitudinally oscillating and electrically polar rod-like nanoresonator embedded in a viscoelastic fluid. We show that the slip length, which can be tuned via surface modifications, controls the quality factor and coupling of nanoresonator vibration modes to microwave radiation. We demonstrate that the larger slip length brings the sharper frequency response of the nanoresonator vibration and electromagnetic absorption. Our findings contribute to design guidelines of fluid embedded nanoresonator devices.

  12. Spectroscopic characterization of nanohydroxyapatite synthesized by molten salt method.

    PubMed

    Gopi, D; Indira, J; Kavitha, L; Kannan, S; Ferreira, J M F

    2010-10-01

    Hydroxyapatite (HAP) nanopowders were synthesized by molten salt method at 260 degrees C. The as-prepared powders were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM) and thermo gravimetric analysis (TGA). With the aid of the obtained results the effect of calcining time on the crystallinity, size and morphology of HAP nanopowders is presented. The HAP nanopowders synthesized by molten salt method consist of pure phase of HAP without any impurities and showed the rod-like morphology without detectable decomposition up to 1100 degrees C.

  13. ELECTROMAGNETIC APPARATUS FOR MOVING A ROD

    DOEpatents

    Young, J.N.

    1958-04-22

    An electromagnetic apparatus for moving a rod-like member in small steps in either direction is described. The invention has particular application in the reactor field where the reactor control rods must be moved only a small distance and where the use of mechanical couplings is impractical due to the high- pressure seals required. A neutron-absorbing rod is mounted in a housing with gripping uaits that engage the rod, and coils for magnetizing the gripping units to make them grip, shift, and release the rod are located outside the housing.

  14. Negligible effect of grain boundaries on the thermal conductivity of rocks

    SciTech Connect

    Vandersande, J.W.; Pohl, R.O.

    1982-08-01

    The thermal conductivity of marble, gabbro, quartz-monzonite, basalt and of labradorite was measured between 0.3 and 80 K. In all cases, the phonon mean free paths l-bar were found to increase with decreasing temperature, but even at the lowest temperatures, l-bar was far smaller than the average grain sizes. This demonstrates that phonon scattering by grain boundaries has very little influence on the heat transport in these rocks. Evidence is presented that lamellae due to twinning or exsolution, rod-like large inclusions, and density fluctuations inside the grains mask the effect of grain boundaries.

  15. Mean and turbulence structures of Couette-Poiseuille flows at different mean shear rates in a square duct

    NASA Astrophysics Data System (ADS)

    Lo, Wei; Lin, Chao-An

    2006-06-01

    Turbulent Couette-Poiseuille flows inside a square duct at bulk Reynolds number 9700 are investigated using the large eddy simulation technique. Suppression of turbulence intensities and a tendency towards rod-like axisymmetric turbulence state at the wall bisector near the moving wall are identified. The turbulence generated secondary flow is modified by the presence of the top moving wall, where the symmetric vortex pattern vanishes. The angle between the two top vortices is found to correlate with the ratio of moving wall velocity to duct bulk velocity.

  16. Optical and surface morphological studies on CuPcOC8 thin films prepared by physical vapour deposition

    NASA Astrophysics Data System (ADS)

    Vadakel, Vinu. T.; Menon, C. S.

    2013-08-01

    2,3,9,10,16,17,23,24-copper octakis (octyloxy) phthalocyanine (CuPcOC8) thin films deposited at room temperature have exhibited a change in their surface morphology with the post deposition annealing temperature under normal atmosphere.These films have been characterised by optical absorption also. SEM images have shown densely packed nano particles and nano-rod like structures on the substrates annealed at different temperatures. The optical transition was found to be direct allowed and the direct energy gap changed with the annealing temperature. The results of optical and surface morphological studies on CuPcOC8 have been discussed.

  17. Morphology evolution of ZrB{sub 2} nanoparticles synthesized by sol-gel method

    SciTech Connect

    Zhang Yun; Li Ruixing; Jiang Yanshan; Zhao Bin; Duan Huiping; Li Junping; Feng Zhihai

    2011-08-15

    Zirconium diboride (ZrB{sub 2}) nanoparticles were synthesized by sol-gel method using zirconium n-propoxide (Zr(OPr){sub 4}), boric acid (H{sub 3}BO{sub 3}), sucrose (C{sub 12}H{sub 22}O{sub 11}), and acetic acid (AcOH). Clearly, it was a non-aqueous solution system at the very beginning of the reactions. Here, AcOH was used as both chemical modifier and solvent to control Zr(OPr){sub 4} hydrolysis. Actually, AcOH could dominate the hydrolysis by self-produced water of the chemical propulsion, rather than the help of outer water. C{sub 12}H{sub 22}O{sub 11} was selected, since it can be completely decomposed to carbon. Thus, carbon might be accounted precisely for the carbothermal reduction reaction. Furthermore, we investigated the influence of the gelation temperature on the morphology of ZrB{sub 2} particles. Increasing the gelation temperature, the particle shapes changed from sphere-like particles at 65 deg. C to a particle chain at 75 deg. C, and then form rod-like particles at 85 deg. C. An in-depth HRTEM observation revealed that the nanoparticles of ZrB{sub 2} were gradually fused together to evolve into a particle chain, finally into a rod-like shape. These crystalline nature of ZrB{sub 2} related to the gelation temperature obeyed the 'oriented attachment mechanism' of crystallography. - Graphical Abstract: Increasing the gelation temperature, the particle shapes changed from sphere-like particles at 65 deg. C to a particle chain at 75 deg. C, and then form rod-like particles at 85 deg. C. Highlights: > ZrB{sub 2} nanoparticles were synthesized by sol-gel method in an non-aqueous solution system. > AcOH was used as both chemical modifier and solvent to control Zr(OPr){sub 4} hydrolysis. > C{sub 12}H{sub 22}O{sub 11} was selected since it can be completely decomposed to carbon. > Increasing the gelation temperature, the particles changed from sphere-like to rod-like ones. > Crystalline nature of ZrB{sub 2} obeyed the 'oriented attachment mechanism' of

  18. Draft genome sequence of Rhodococcus rhodochrous strain ATCC 17895

    PubMed Central

    Chen, Bi-Shuang; Otten, Linda G.; Resch, Verena; Muyzer, Gerard; Hanefeld, Ulf

    2013-01-01

    Rhodococcus rhodochrous ATCC 17895 possesses an array of mono- and dioxygenases, as well as hydratases, which makes it an interesting organism for biocatalysis. R. rhodochrous is a Gram-positive aerobic bacterium with a rod-like morphology. Here we describe the features of this organism, together with the complete genome sequence and annotation. The 6,869,887 bp long genome contains 6,609 protein-coding genes and 53 RNA genes. Based on small subunit rRNA analysis, the strain is more likely to be a strain of Rhodococcus erythropolis rather than Rhodococcus rhodochrous. PMID:24501654

  19. Preparation and characterization of hydroxyapatite/liposome core shell nanocomposites

    NASA Astrophysics Data System (ADS)

    Chu, Maoquan; Liu, Guojie

    2005-08-01

    Hydroxyapatite (HAP)/liposome core-shell nanocomposites have been prepared at room temperature. The liposome shells and the precipitate cores ranged in diameter mainly from 80 to 140 nm and from 40 to 120 nm, respectively. Rod-like whiskers ranging in length mainly from 10 to 30 nm were obtained after separating the precipitates from the liposomes. In contrast, the whiskers synthesized without liposomes ranged in length mainly from 70 to 140 nm. The precipitates synthesized both with and without liposomes were poorly crystalline, and had a similar chemical composition to the natural HAP.

  20. Electronic transduction in model enzyme sensors assisted by a photoisomerizable azo-polymer.

    PubMed

    Voinova, M V; Jonson, M

    2004-12-15

    We develop a stochastic model of electronic transduction by means of a rod-like azo-polymer (single peptide molecule doped with a given amount of azo-benzene structural units) in polymer-redox enzyme biosensor. We propose a configuration where the azo-polymer is anchored next to the enzyme reaction center and functions as a light-driven micromechanical actuator shuttling electrons toward the electrode. We show that the output catalytic current is exponentially sensitive to variations in geometrical size of the polymer (a 'switch off' effect) and suggest a scheme where the switching effect is triggered by polymer photoisomerization, resulting in its overall length change.

  1. Proteomics computational analyses suggest that hepatitis C virus E1 and pestivirus E2 envelope glycoproteins are truncated class II fusion proteins.

    PubMed

    Garry, Robert F; Dash, Srikanta

    2003-03-15

    Class II fusion proteins encoded by tick-borne encephalitis virus (TBEV), dengue virus, and Semliki Forest virus have a fusion peptide located at the end of a rod-like molecule comprised of three antiparallel beta sheet domains. Proteomics computational analyses suggest that hepatitis C virus (HCV) envelope glycoprotein E1 and pestivirus envelope glycoprotein E2 are truncated class II fusion proteins. Similarities were also detected between the receptor-binding portion of TBEV E and HCV E2, and between TBEV small membrane protein precursor prM and pestivirus E1. The proposed models of Flaviviridae envelope proteins can facilitate drug and vaccine development.

  2. Electronic properties of binary and mixed [RMNH]{sub n} (R=H,CH{sub 3}, M=Al,Ga,In) oligomers

    SciTech Connect

    Oranskaya, A. A. Pomogaeva, A. V. Timoshkin, A. Y.

    2015-03-30

    Theoretical investigation of structural and electronic properties is presented for the rod-like oligomers R{sub 3}-[MRNH]{sub 3n}-H{sub 3} and [RMNH]{sub n+1} (M=Ga,Al,In R=H,CH{sub 3}) of different lengths. Electronic structures of the oligomers with and without substitutions of Ga atoms with Al or In were studied at DFT level of theory. Clusters up to 8 nm of length were considered. A type of terminal groups of the oligomers is found to have a dominant influence on their electronic properties.

  3. A Tightly Stretched Ultralong Supramolecular Multiporphyrin Array Propagated by Double-Strand Formation.

    PubMed

    Morisue, Mitsuhiko; Hoshino, Yuki; Shimizu, Masaki; Uemura, Shinobu; Sakurai, Shinichi

    2016-09-01

    A shape-programmed linearity through supramolecular polymerization is demonstrated by a step-growth double-strand formation of a telechelic oligomeric porphyrin array in which two alternating pyridyl-porphyrin sequenced units are held together by self-complementary ligand-to-metal coordination. The stiff rod-like structure and sufficiently large binding constant of the double-strand unit considerably extended a supramolecular array in the one dimension, which produced a tightly stretched string with a length that exceeded several micrometers. PMID:27490938

  4. Renal Light Chain Deposition Associated with the Formation of Intracellular Crystalline Inclusion Bodies in Podocytes: A Rare Case Report.

    PubMed

    Wang, Yuan-da; Dong, Zhe-yi; Zhang, Xue-guang; Zhang, Wei; Yin, Zhong; Qiu, Qiang; Chen, Xiang-mei

    2016-01-01

    We herein report the case of an elderly woman with bone pain and proteinuria as the main clinical manifestations. The patient was diagnosed with the IgG κ type of multiple myeloma. Her renal pathology consisted of widespread κ light chain protein deposition associated with the formation of large quantities of rod-like crystals in podocytes. This phenomenon is very rare. We explored the significance of this crystal formation via a detailed and descriptive analysis and also performed a literature review, thus providing data to increase the available information about this type of disease.

  5. Dielectric Properties of 4-methoxy-4'-cyanobiphenyl (1 OCB) in the Supercooled Isotropic and Nematic Phases

    NASA Astrophysics Data System (ADS)

    Urban, Stanisław; Gestblom, Bo; Pawlus, Sebastian

    2003-06-01

    Dielectric studies of 4-methoxy-4'-cyanobiphenyl (1 OCB) in the supercooled isotropic and nematic phases were performed with the aid of three set-ups covering the frequency range 10 kHz - 5 GHz. In the static measurements the nematic phase could be supercooled down to 25 K below the clearing point, whereas in the dynamic studies a 12 K range was covered in a single run. The relaxation times and activation enthalpies characterising the molecular rotations around the principal inertia moment axes were determined. The predictions of theories based on the assumption of the rod-like molecules are well applicable to the dielectric data obtained.

  6. Intranuclear bundles of microfilaments and microtubules in chromaffin cells of the auricle of the heart of a lungfish, Protopterus aethiopicus.

    PubMed

    Scheuermann, D W; Adriaensen, D; De Groodt-Lasseel, M H

    1988-01-01

    Intranuclear microtubular-microfilamentous rod-like inclusions were investigated in chromaffin cells of the auricle of the heart of lungfishes. In conventional electron microscopy, these inclusions reveal a wide variety in appearance, depending on their orientation to the plane of sectioning. Whereas originally they were merely interpreted as a bundle of microfilaments, application of a goniometer stage showed the rod- or spindle-shaped intranuclear inclusions to have a basic substructure of parallel arranged microtubules among microfilaments, which are clearly connected to chromatin granules, occasionally penetrating dense areas of chromatin. The chemical nature and biological significance of these structures, which so far remain enigmatic, are discussed. PMID:3227775

  7. Imide modified epoxy matrix resins

    NASA Technical Reports Server (NTRS)

    Scola, D. A.

    1982-01-01

    Results of a program designed to develop tough imide modified epoxy (IME) resins cured by bisimide amine (BIA) hardeners are presented. State of the art epoxy resin, MY720, was used. Three aromatic bisimide amines and one aromatic aliphatic BIA were evaluated. BIA's derived from 6F anhydride (3,3 prime 4,4 prime-(hexafluoro isopropyl idene) bis (phthalic anhydride) and diamines, 3,3 prime-diam nodiphenyl sulfone (3,3 prime-DDS), 4,4 prime-diamino diphenyl sulfone (4,4 prime-DDS), 1.12-dodecane diamine (1,12-DDA) were used. BIA's were abbreviated 6F-3,3 prime-DDS, 6F-4,4 prime-DDS, 6F-3,3 prime-DDS-4,4 prime DDS, and 6F-3,3 prime-DDS-1,12-DDA corresponding to 6F anhydride and diamines mentioned. Epoxy resin and BIA's (MY720/6F-3,3 prime-DDS, MY720/6F-3,3 prime-DDS-4,4 prime-DDS, MY720/6F-3,3 prime-DDS-1,12-DDA and a 50:50 mixture of a BIA and parent diamine, MY720/6F-3,3 prime-DDS/3,3 prime-DDS, MY720/6F-3,3 prime-DDS-4,4 prime-DDS/3,3 prime-DDS, MY720/6F-3,3 prime-DDS-1,12-DDA/3,3 prime-DDS were studied to determine effect of structure and composition. Effect of the addition of two commercial epoxies, glyamine 200 and glyamine 100 on the properties of several formulations was evaluated. Bisimide amine cured epoxies were designated IME's (imide modified epoxy). Physical, thermal and mechanical properties of these resins were determined. Moisture absorption in boiling water exhibited by several of the IME's was considerably lower than the state of the art epoxies (from 3.2% for the control and state of the art to 2.0 wt% moisture absorption). Char yields are increased from 20% for control and state of the art epoxies to 40% for IME resins. Relative toughness characteristics of IME resins were measured by 10 deg off axis tensile tests of Celion 6000/IME composites. Results show that IME's containing 6F-3,3 prime-DDS or 6F-3,3 prime-DDS-1,12-DDA improved the "toughness" characteristics of composites by about 35% (tensile strength), about 35% (intralaminar shear

  8. Sedimentation Field-Flow Fractionation of Nonspherical Particles

    PubMed

    Blau; Zollars

    1996-11-10

    Sedimentation field-flow fractionation (SdFFF) has proved to be a very powerful technique for the particle size analysis of submicrometer hydrosols. Recently reports have been published on the analysis of coagulated latex samples via SdFFF. In these investigations the coagulated particles do not behave as predicted by SdFFF theory but elute from the SdFFF channel more rapidly than expected. This behavior has been ascribed to the effect of particle shape on retention. In this investigation samples of monodisperse polystyrene latices were coagulated under shear to yield particles which were all alike in shape (rod-like). Analyzing these samples via SdFFF indicated that retention is determined by the maximum dimension of the particle rather than by any average size. For highly retained particles there was an additional effect acting to shorten the expected retention time due to the tumbling motion of the rod-like particles in the shear flow through the SdFFF channel.

  9. Systematic study on the influence of the morphology of α-MoO3 in the selective oxidation of propylene

    NASA Astrophysics Data System (ADS)

    Schuh, Kirsten; Kleist, Wolfgang; Høj, Martin; Jensen, Anker Degn; Beato, Pablo; Patzke, Greta R.; Grunwaldt, Jan-Dierk

    2015-08-01

    A variety of morphologically different α-MoO3 samples were prepared by hydrothermal synthesis and applied in the selective oxidation of propylene. Their catalytic performance was compared to α-MoO3 prepared by flame spray pyrolysis (FSP) and a classical synthesis route. Hydrothermal synthesis from ammonium heptamolybdate (AHM) and nitric acid at pH 1-2 led to ammonium containing molybdenum oxide phases that were completely transformed into α-MoO3 after calcination at 550 °C. A one-step synthesis of α-MoO3 rods was possible starting from MoO3·2H2O with acetic acid or nitric acid and from AHM with nitric acid at 180 °C. Particularly, if nitric acid was used during synthesis, the rod-like morphology of the samples could be stabilized during calcination at 550 °C and the following catalytic activity tests, which was beneficial for the catalytic performance in propylene oxidation. Characterization studies using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy showed that those samples, which retained their rod-like morphology during the activity tests, yielded the highest propylene conversion.

  10. Strong, Tough Ceramics Containing Microscopic Reinforcements: Tailoring In-Situ Reinforced Silicon Nitride Ceramics

    SciTech Connect

    Becher, P.F.

    1999-06-27

    Ceramics with their hardness, chemical stability, and refractoriness could be used to design more efficient energy generation and conversion systems as well as numerous other applications. However, we have needed to develop a fundamental understanding of how to tailor ceramics to improve their performance, especially to overcome their brittle nature. One of the advances in this respect was the incorporation of very strong microscopic rod-like reinforcements in the form of whiskers that serve to hold the ceramic together making it tougher and resistant to fracture. This microscopic reinforcement approach has a number of features that are similar to continuous fiber-reinforced ceramics; however, some of the details are modified. For instance, the strengths of the microscopic reinforcements must be higher as they typically have much stronger interfaces. For instance, single crystal silicon carbide whiskers can have tensile strengths in excess of {ge}7 GPa or >2 times that of continuous fibers. Furthermore, reinforcement pullout is limited to lengths of a few microns in the case of microscopic reinforcement due as much to the higher interfacial shear resistance as to the limit of the reinforcement lengths. On the other hand, the microscopic reinforcement approach can be generated in-situ during the processing of ceramics. A remarkable example of this is found in silicon nitride ceramics where elongated rod-like shape grains can be formed when the ceramic is fired at elevated temperatures to form a dense component.

  11. Nanoscale X-ray microscopic imaging of mammalian mineralized tissue.

    PubMed

    Andrews, Joy C; Almeida, Eduardo; van der Meulen, Marjolein C H; Alwood, Joshua S; Lee, Chialing; Liu, Yijin; Chen, Jie; Meirer, Florian; Feser, Michael; Gelb, Jeff; Rudati, Juana; Tkachuk, Andrei; Yun, Wenbing; Pianetta, Piero

    2010-06-01

    A novel hard transmission X-ray microscope (TXM) at the Stanford Synchrotron Radiation Lightsource operating from 5 to 15 keV X-ray energy with 14 to 30 microm2 field of view has been used for high-resolution (30-40 nm) imaging and density quantification of mineralized tissue. TXM is uniquely suited for imaging of internal cellular structures and networks in mammalian mineralized tissues using relatively thick (50 microm), untreated samples that preserve tissue micro- and nanostructure. To test this method we performed Zernike phase contrast and absorption contrast imaging of mouse cancellous bone prepared under different conditions of in vivo loading, fixation, and contrast agents. In addition, the three-dimensional structure was examined using tomography. Individual osteocytic lacunae were observed embedded within trabeculae in cancellous bone. Extensive canalicular networks were evident and included processes with diameters near the 30-40 nm instrument resolution that have not been reported previously. Trabecular density was quantified relative to rod-like crystalline apatite, and rod-like trabecular struts were found to have 51-54% of pure crystal density and plate-like areas had 44-53% of crystal density. The nanometer resolution of TXM enables future studies for visualization and quantification of ultrastructural changes in bone tissue resulting from osteoporosis, dental disease, and other pathologies. PMID:20374681

  12. RodZ links MreB to cell wall synthesis to mediate MreB rotation and robust morphogenesis.

    PubMed

    Morgenstein, Randy M; Bratton, Benjamin P; Nguyen, Jeffrey P; Ouzounov, Nikolay; Shaevitz, Joshua W; Gitai, Zemer

    2015-10-01

    The rod shape of most bacteria requires the actin homolog, MreB. Whereas MreB was initially thought to statically define rod shape, recent studies found that MreB dynamically rotates around the cell circumference dependent on cell wall synthesis. However, the mechanism by which cytoplasmic MreB is linked to extracytoplasmic cell wall synthesis and the function of this linkage for morphogenesis has remained unclear. Here we demonstrate that the transmembrane protein RodZ mediates MreB rotation by directly or indirectly coupling MreB to cell wall synthesis enzymes. Furthermore, we map the RodZ domains that link MreB to cell wall synthesis and identify mreB mutants that suppress the shape defect of ΔrodZ without restoring rotation, uncoupling rotation from rod-like growth. Surprisingly, MreB rotation is dispensable for rod-like shape determination under standard laboratory conditions but is required for the robustness of rod shape and growth under conditions of cell wall stress.

  13. Twisted and tubular silica structures by anionic surfactant fibers encapsulation.

    PubMed

    Chekini, Mahshid; Guénée, Laure; Marchionni, Valentina; Sharma, Manish; Bürgi, Thomas

    2016-09-01

    Organic molecules imprinting can be used for introducing specific properties and functionalities such as chirality to mesoporous materials. Particularly organic self-assemblies can work as a scaffold for templating inorganic materials such as silica. During recent years chiral imprinting of anionic surfactant for fabrication of twisted rod-like silica structures assisted by co-structuring directing agent were thoroughly investigated. The organic self-assemblies of anionic surfactants can also be used for introducing other shapes in rod-like silica structures. Here we report the formation of amphiphilic N-miristoyl-l-alanine self-assemblies in aqueous solution upon stirring and at presence of l-arginine. These anionic surfactant self-assemblies form fibers that grow by increasing the stirring duration. The fibers were studied using transmission electron microscopy, infra-red spectroscopy and vibrational circular dichroism. Addition of silica precursor 1,2-bis(triethoxysilyl)ethylene and co-structuring directing agent N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride at different stages of fibers' growth leads to formation of different silica structures. By controlling stirring duration, we obtained twisted tubular silica structures as a result of fibers encapsulation. We decorated these structures with gold nanoparticles by different methods and measured their optical activity.

  14. A Deep Look Into Erionite Fibres: an Electron Microscopy Investigation of their Self-Assembly.

    PubMed

    Matassa, Roberto; Familiari, Giuseppe; Relucenti, Michela; Battaglione, Ezio; Downing, Clive; Pacella, Alessandro; Cametti, Georgia; Ballirano, Paolo

    2015-01-01

    The exposure of humans to erionite fibres of appropriate morphology and dimension has been unambiguously linked to the occurrence of Malignant Mesothelioma. For this reason, a detailed morpho-structural investigation through Electron Microscopy techniques has been performed on erionite samples collected at two different localities, Durkee (ED) and Rome (ER), Oregon, USA. The sample from Rome has been also investigated after a prolonged leaching with Gamble's solution (ER4G) in order to evaluate the possible occurrence of morpho-structural modifications induced by this Simulated-Lung-Fluid (SLF). Here we report how the micrometric erionite fibres evolve in irregular ribbon- or rod-like bundles as a function of different nano-structural features. The reasons for the observed morphological variability have been explained by considering the structural defects located at ED surface fibrils (bi-dimensional ribbons) and the presence of nontronite, an iron-bearing clay mineral embedding the ER fibrils (mono-dimensional rods). ER4G shows a decrease in width of the rod-like fibres due to their partial digestion by SLF leaching, which synchronously dissolves nontronite. The reported results represent a valuable background toward the full comprehension of the morphological mechanisms responsible for potentially damage of lung tissue through the potential relocation of fibers to extrapulmonary sites, increasing the carcinogenic risk to humans. PMID:26567530

  15. Photoluminescence study of self-interstitial clusters and extended defects in ion-implanted silicon

    NASA Astrophysics Data System (ADS)

    Giri, P. K.

    2003-12-01

    We report on the photoluminescence (PL) studies of self-interstitial (I) clustering in ion-implanted Si at various stages of post-implantation annealing. Low-temperature PL measurements on as-implanted and low-temperature annealed (up to 450°C) samples show sharp X and W bands at 1200 and 1218 nm which are attributed to I4 and I3 clusters, respectively. Annealing at 600°C shows a drastic change in the PL spectra. In case of high-energy self-ion-implanted samples, 600°C annealing produces several peaks in the range 1250-1400 nm. For longer duration annealing, two broad bands form at 1322 and 1392 nm irrespective of the ion fluence. These PL signatures are attributed to I8 clusters and/or (1 0 0) I-chains, and they are believed to be the precursor of {3 1 1} rod-like defects. For annealing above 600°C and for fluence ⩾1×1013 cm-2, a sharp PL band is observed at 1376 nm and it is attributed to {3 1 1} rod-like defects. At higher fluences, an additional broad band appears in the PL spectrum at ∼1576 nm which is related to residual ion-damage or extended defect formation. These results illustrate the potential of silicon I-clusters as a possible source of light emission from Si.

  16. Viroids: from genotype to phenotype just relying on RNA sequence and structural motifs.

    PubMed

    Flores, Ricardo; Serra, Pedro; Minoia, Sofía; Di Serio, Francesco; Navarro, Beatriz

    2012-01-01

    As a consequence of two unique physical properties, small size and circularity, viroid RNAs do not code for proteins and thus depend on RNA sequence/structural motifs for interacting with host proteins that mediate their invasion, replication, spread, and circumvention of defensive barriers. Viroid genomes fold up on themselves adopting collapsed secondary structures wherein stretches of nucleotides stabilized by Watson-Crick pairs are flanked by apparently unstructured loops. However, compelling data show that they are instead stabilized by alternative non-canonical pairs and that specific loops in the rod-like secondary structure, characteristic of Potato spindle tuber viroid and most other members of the family Pospiviroidae, are critical for replication and systemic trafficking. In contrast, rather than folding into a rod-like secondary structure, most members of the family Avsunviroidae adopt multibranched conformations occasionally stabilized by kissing-loop interactions critical for viroid viability in vivo. Besides these most stable secondary structures, viroid RNAs alternatively adopt during replication transient metastable conformations containing elements of local higher-order structure, prominent among which are the hammerhead ribozymes catalyzing a key replicative step in the family Avsunviroidae, and certain conserved hairpins that also mediate replication steps in the family Pospiviroidae. Therefore, different RNA structures - either global or local - determine different functions, thus highlighting the need for in-depth structural studies on viroid RNAs.

  17. CTAB-assisted synthesis of mesoporous F-N-codoped TiO{sub 2} powders with high visible-light-driven catalytic activity and adsorption capacity

    SciTech Connect

    Xie Yi Zhao Xiujian Li Yuanzhi; Zhao Qingnan; Zhou Xuedong; Yuan Qihua

    2008-08-15

    This article describes the preparation of mesoporous rod-like F-N-codoped TiO{sub 2} powder photocatalysts with anatase phase via a sol-gel route at the temperature of 373 K, using cetyltrimethyl ammonium bromide (CTAB) as surfactant. The as-prepared photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance spectra (UV-vis DRS). The results showed that the photocatalysts possessed a homogeneous pore diameter and a high surface area of 106.3-160.7 m{sup 3} g{sup -1}. The increasing CTAB reactive concentration extended the visible-light absorption up to 600 nm. The F-N-codoped TiO{sub 2} powders exhibited significant higher adsorption capacity for methyl orange (MO) than that of Degussa P25 and showed more than 6 times higher visible-light-induced catalytic degradation for MO than that of P25. - Graphical abstract: The introduction of surfactant CTAB not only extended the visible light absorption of mesoporous F-N-codoped TiO{sub 2} up to 600 nm but also significantly enhanced the adsorption capacity and visible-light-induced degradation for methyl orange. Mesoporous rod-like F-N-codoped TiO{sub 2} powder photocatalysts were synthesized via a sol-gel route at low temperature of 373 K.

  18. Computer simulations of nematic drops: Coupling between drop shape and nematic order

    NASA Astrophysics Data System (ADS)

    Rull, L. F.; Romero-Enrique, J. M.; Fernandez-Nieves, A.

    2012-07-01

    We perform Monte Carlo computer simulations of nematic drops in equilibrium with their vapor using a Gay-Berne interaction between the rod-like molecules. To generate the drops, we initially perform NPT simulations close to the nematic-vapor coexistence region, allow the system to equilibrate and subsequently induce a sudden volume expansion, followed with NVT simulations. The resultant drops coexist with their vapor and are generally not spherical but elongated, have the rod-like particles tangentially aligned at the surface and an overall nematic orientation along the main axis of the drop. We find that the drop eccentricity increases with increasing molecular elongation, κ. For small κ the nematic texture in the drop is bipolar with two surface defects, or boojums, maximizing their distance along this same axis. For sufficiently high κ, the shape of the drop becomes singular in the vicinity of the defects, and there is a crossover to an almost homogeneous texture; this reflects a transition from a spheroidal to a spindle-like drop.

  19. Nanometer to Millimeter Scale Peptide-Porphyrin Materials

    SciTech Connect

    D Zaytsev; F Xie; M Mukherjee; A Bludin; B Demeler; R Breece; D Tierney; M Ogawa

    2011-12-31

    AQ-Pal14 is a 30-residue polypeptide that was designed to form an {alpha}-helical coiled coil that contains a metal-binding 4-pyridylalanine residue on its solvent-exposed surface. However, characterization of this peptide shows that it exists as a three-stranded coiled coil, not a two-stranded one as predicted from its design. Reaction with cobalt(III) protoporphyrin IX (Co-PPIX) produces a six-coordinate Co-PPIX(AQ-Pal14){sub 2} species that creates two coiled-coil oligomerization domains coordinated to opposite faces of the porphyrin ring. It is found that this species undergoes a buffer-dependent self-assembly process: nanometer-scale globular materials were formed when these components were reacted in unbuffered H{sub 2}O, while millimeter-scale, rod-like materials were prepared when the reaction was performed in phosphate buffer (20 mM, pH 7). It is suggested that assembly of the globular material is dictated by the conformational properties of the coiled-coil forming AQ-Pal14 peptide, whereas that of the rod-like material involves interactions between Co-PPIX and phosphate ion.

  20. Preparation of molybdenum carbides with multiple morphologies using surfactants as carbon sources

    SciTech Connect

    Wang, Hongfen; Wang, Zhiqi; Chen, Shougang

    2012-10-15

    Molybdenum carbides with surfactants as carbon sources were prepared using the carbothermal reduction of the appropriate precursors (molybdenum oxides deposited on surfactant micelles) at 1023 K under hydrogen gas. The carburized products were characterized using scanning electron microscopy (SEM), X-ray diffraction and BET surface area measurements. From the SEM images, hollow microspherical and rod-like molybdenum carbides were observed. X-ray diffraction patterns showed that the annealing time of carburization had a large effect on the conversion of molybdenum oxides to molybdenum carbides. And BET surface area measurements indicated that the difference of carbon sources brought a big difference in specific surface areas of molybdenum carbides. - Graphical abstract: Molybdenum carbides having hollow microspherical and hollow rod-like morphologies that are different from the conventional monodipersed platelet-like morphologies. Highlights: Black-Right-Pointing-Pointer Molybdenum carbides were prepared using surfactants as carbon sources. Black-Right-Pointing-Pointer The kinds of surfactants affected the morphologies of molybdenum carbides. Black-Right-Pointing-Pointer The time of heat preservation at 1023 K affected the carburization process. Black-Right-Pointing-Pointer Molybdenum carbides with hollow structures had larger specific surface areas.

  1. A Deep Look Into Erionite Fibres: an Electron Microscopy Investigation of their Self-Assembly

    PubMed Central

    Matassa, Roberto; Familiari, Giuseppe; Relucenti, Michela; Battaglione, Ezio; Downing, Clive; Pacella, Alessandro; Cametti, Georgia; Ballirano, Paolo

    2015-01-01

    The exposure of humans to erionite fibres of appropriate morphology and dimension has been unambiguously linked to the occurrence of Malignant Mesothelioma. For this reason, a detailed morpho-structural investigation through Electron Microscopy techniques has been performed on erionite samples collected at two different localities, Durkee (ED) and Rome (ER), Oregon, USA. The sample from Rome has been also investigated after a prolonged leaching with Gamble’s solution (ER4G) in order to evaluate the possible occurrence of morpho-structural modifications induced by this Simulated-Lung-Fluid (SLF). Here we report how the micrometric erionite fibres evolve in irregular ribbon- or rod-like bundles as a function of different nano-structural features. The reasons for the observed morphological variability have been explained by considering the structural defects located at ED surface fibrils (bi-dimensional ribbons) and the presence of nontronite, an iron-bearing clay mineral embedding the ER fibrils (mono-dimensional rods). ER4G shows a decrease in width of the rod-like fibres due to their partial digestion by SLF leaching, which synchronously dissolves nontronite. The reported results represent a valuable background toward the full comprehension of the morphological mechanisms responsible for potentially damage of lung tissue through the potential relocation of fibers to extrapulmonary sites, increasing the carcinogenic risk to humans. PMID:26567530

  2. Improving the stability of coal slurries: Final report. [Polygalacturonic acid and gum tragacanth

    SciTech Connect

    Fogler, H.S.

    1988-12-01

    Polysaccharides were found to stabilize colloidal dispersions (such as coal particles and polystyrene latex particles) even at high ionic strengths. The stability studies with various kinds of polysaccharides showed that rod-like molecules (such as poly (galacturonic acid) and gum tragacanth) are much more effective stabilizers than highly-branched molecules such as arabinogalactan. This effective stabilization with the rod-like molecules was found to result from the adsorption of polysaccharides on the particles, i.e., the steric stabilization mechanism. The stability depends significantly on the solution pH, the molecular weight and the surface charge of particles. Adsorption isotherms, the zeta potential and the conformation of adsorbed molecules (the steric layer thicknesses) were measured as a function of the solution pH, the molecular weight and the surface charge. Photon correlation spectroscopy studies showed that the conformation of adsorbed molecules is strongly dependent on the solution pH, the molecular weight and the surface charge, suggesting that the dependence of stability on these parameters is due to the change of the conformation of the molecules adsorbed on the surface. In addition, the solution pH has a significant effect on the flocculation behavior of particles and can be modulated to bring about peptization of particles. This type of stabilization is referred to as electrosteric stabilization whereby steric stabilization is induced by changing the electrical properties of the system (the solution pH in this case). 41 refs., 43 figs., 10 tabs.

  3. Hydrothermal synthesis of brookite-type titanium dioxide with snowflake-like nanostructures using a water-soluble citratoperoxotitanate complex

    NASA Astrophysics Data System (ADS)

    Kobayashi, Makoto; Petrykin, Valery; Tomita, Koji; Kakihana, Masato

    2011-12-01

    Hydrothermal synthesis of brookite-type titanium dioxide was performed with excellent reproducibility using an aqueous NH 3 solution of a water-soluble citratoperoxotitanate (CPT) complex. X-ray diffraction confirmed that the brookite phase was formed by hydrothermal treatment of the CPT complex in NH 3 solution with a concentration of more than 6.5 wt%, whereas single phase anatase was obtained when distilled water without any additives was applied as the solvent. The aspect ratios of the obtained rod-like brookite particles increased from 5 up to 20 with an increase of the NH 3 concentration. Transmission electron microscopy and selected area electron diffraction measurements provided evidence that the growth of the brookite particles is along the c-axis. Hydrothermal treatment of the CPT complex at high NH 3 concentrations resulted in the formation of agglomerated brookite particles with unusual shapes, where many rod-like particles were branched around a somewhat longer central particle, and the side view of the agglomerated particles revealed two-dimensional crystal growth within a given restricted plane. The multi-needle agglomerate of particles was snowflake shaped. The reason for the formation of brookite with this unique morphology may be attributed to an intrinsic character of the CPT complex itself, although the mechanism is yet to be clarified.

  4. Hydrogel containing silica shell cross-linked micelles for ocular drug delivery.

    PubMed

    Lu, Changhai; Yoganathan, Roshan B; Kociolek, Michael; Allen, Christine

    2013-02-01

    Poly(2-hydroxyethyl methacrylate-methacrylic acid-ethylene glycol dimethacrylate) hydrogels loaded with silica shell cross-linked methoxy(polyethylene glycol)-block-polycaprolactone (MePEG-b-PCL) micelles with rod-like morphology were prepared as a potential soft contact lens material for the sustained release of ocular drugs. The silica shell cross-linked methoxy micelles (SSCMs) comprising a polycaprolactone core surrounded by a silica shell were synthesized and their size, morphology, stability, and drug release kinetics were evaluated. The relationships between the composition of the SSCM-loaded poly(2-hydroxyethyl methacrylate) (pHEMA)-based hydrogels and their transparency, surface wettability, and equilibrium water content were determined. Scanning electron microscopy (SEM) images of SSCM-hydrogel systems showed the presence of intact SSCMs within the hydrogel matrix. Dexamethasone acetate (DMSA), a hydrophobic ophthalmic drug, was loaded into the SSCMs prior to their incorporation into the hydrogels. In vitro release of DMSA from the SSCM-hydrogels, with varying drug loading levels, was observed for up to 30 days. Overall, the incorporation of rod-like SSCMs within pHEMA-based hydrogels provided sustained release over prolonged periods while maintaining optical transparency. This delivery system may be suitable for use as a therapeutic soft contact lens material. PMID:23203974

  5. Networking and rheology of concentrated clay suspensions "matured" in mineral medicinal water.

    PubMed

    Aguzzi, Carola; Sánchez-Espejo, Rita; Cerezo, Pilar; Machado, José; Bonferoni, Cristina; Rossi, Silvia; Salcedo, Inmaculada; Viseras, César

    2013-09-10

    This work studied the influence of "maturation" conditions (time and agitation) on aggregation states, gel structure and rheological behaviour of a special kind of pharmaceutical semisolid products made of concentrated clay suspensions in mineral medicinal water. Maturation of the samples was carried out in distilled and sulphated mineral medicinal water, both in static conditions (without agitation) and with manual stirring once a week, during a maximum period of three months. At the measured pH interval (7.5-8.0), three-dimensional band-type networks resulting from face/face contacts were predominant in the laminar (disc-like) clay suspensions, whereas the fibrous (rod-like) particles formed micro-aggregates by van der Waals attractions. The high concentration of solids in the studied systems greatly determined their behaviour. Rod-like sepiolite particles tend to align the major axis in aggregates promoted by low shearing maturation, whereas aggregates of disc-like smectite particles did not have a preferential orientation and their complete swelling required long maturation time, being independent of stirring. Maturation of both kinds of suspensions resulted in improved rheological properties. Laminar clay suspensions became more structured with time, independently from static or dynamic maturation conditions, whereas for fibrous clay periodic agitation was also required. Rheological properties of the studied systems have been related to aggregation states and networking mechanisms, depending on the type of clay minerals constituents. Physical stability of the suspensions was not impaired by the specific composition of the Graena medicinal water.

  6. Preparation and electrochemical properties of lamellar MnO{sub 2} for supercapacitors

    SciTech Connect

    Yan, Jun; Wei, Tong; Cheng, Jie; Fan, Zhuangjun; Zhang, Milin

    2010-02-15

    Lamellar birnessite-type MnO{sub 2} materials were prepared by changing the pH of the initial reaction system via hydrothermal synthesis. The interlayer spacing of MnO{sub 2} with a layered structure increased gradually when the initial pH value varied from 12.43 to 2.81, while the MnO{sub 2}, composed of {alpha}-MnO{sub 2} and {gamma}-MnO{sub 2}, had a rod-like structure at pH 0.63. Electrochemical studies indicated that the specific capacitance of birnessite-type MnO{sub 2} was much higher than that of rod-like MnO{sub 2} at high discharge current densities due to the lamellar structure with fast intercalation/deintercalation of protons and high utilization of MnO{sub 2}. The initial specific capacitance of MnO{sub 2} prepared at pH 2.81 was 242.1 F g{sup -1} at 2 mA cm{sup -2} in 2 mol L{sup -1} (NH{sub 4}){sub 2}SO{sub 4} aqueous electrolyte. The capacitance increased by about 8.1% of initial capacitance after 200 cycles at a current density of 100 mA cm{sup -2}.

  7. The Impact of Grain Alignment of the Electron Transporting Layer on the Performance of Inverted Bulk Heterojunction Solar Cells.

    PubMed

    Murali, Banavoth; Labban, Abdulrahman El; Eid, Jessica; Alarousu, Erkki; Shi, Dong; Zhang, Qiang; Zhang, Xixiang; Bakr, Osman M; Mohammed, Omar F

    2015-10-21

    This report presents a new strategy for improving solar cell power conversion efficiencies (PCEs) through grain alignment and morphology control of the ZnO electron transport layer (ETL) prepared by radio frequency (RF) magnetron sputtering. The systematic control over the ETL's grain alignment and thickness is shown, by varying the deposition pressure and operating substrate temperature during the deposition. Notably, a high PCE of 6.9%, short circuit current density (J(sc)) of 12.8 mA cm(-2), open circuit voltage (V(oc)) of 910 mV, and fill factor of 59% are demonstrated using the poly(benzo[1,2-b:4,5-b']dithiophene-thieno[3,4-c]pyrrole-4,6-dione):[6,6]-phenyl-C(71) -butyric acid methyl ester polymer blend with ETLs prepared at room temperature exhibiting oriented and aligned rod-like ZnO grains. Increasing the deposition temperature during the ZnO sputtering induces morphological cleavage of the rod-like ZnO grains and therefore reduced conductivity from 7.2 × 10(-13) to ≈1.7 × 10(-14) S m(-1) and PCE from 6.9% to 4.28%. An investigation of the charge carrier dynamics by femtosecond (fs) transient absorption spectroscopy with broadband capability reveals clear evidence of faster carrier recombination for a ZnO layer deposited at higher temperature, which is consistent with the conductivity and device performance.

  8. Seed-Mediated Growth of Gold Nanocrystals: Changes to the Crystallinity or Morphology as Induced by the Treatment of Seeds with a Sulfur Species

    SciTech Connect

    Zheng, Yiqun; Luo, Ming; Tao, Jing; Peng, Hsin-Chieh; Wan, Dehui; Zhu, Yimei; Xia, Younan

    2014-12-11

    We report our observation of changes to the crystallinity or morphology during seed-mediated growth of Au nanocrystals. When single-crystal Au seeds with a spherical or rod-like shape were treated with a chemical species such as S₂O₃²⁻ ions, twin defects were developed during the growth process to generate multiply twinned nanostructures. X-ray photoelectron spectroscopy analysis indicated that the S₂O₃²⁻ ions were chemisorbed on the surfaces of the seeds during the treatment. The chemisorbed S₂O₃²⁻ ions somehow influenced the crystallization of Au atoms added onto the surface during a growth process, leading to the formation of twin defects. In contrast to the spherical and rod-like Au seeds, the single-crystal structure was retained to generate a concave morphology when single-crystal Au seeds with a cubic or octahedral shape were used for a similar treatment and then seed-mediated growth. The different outcomes are likely related to the difference in spatial distribution of S₂O₃²⁻ ions chemisorbed on the surface of a seed. This approach based on surface modification is potentially extendable to other noble metals for engineering the crystallinity and morphology of nanocrystals formed via seed-mediated growth.

  9. Self-assembly of DNA origami particles in suspension of non-absorbing depleting polymers

    NASA Astrophysics Data System (ADS)

    Siavashpouri, Mahsa; Zakhary, Mark; Wachauf, Christian; Dietz, Hendrik; Dogic, Zvonimir

    2015-03-01

    The connection between the macroscopic properties of a liquid crystalline material and the microscopic features of the constituent molecules is the essential theme that permeates the field of liquid crystals. Previous studies have shown that monodisperse rod-like colloids such as filamentous bacteriophage self-assemble into 1D twisted ribbons in presence of attractive interactions mediated by non-absorbing polymers. The microscopic properties of the colloidal particles play an important role in determining the physical properties of these mesoscopic assemblages. Using structural DNA nanotechnology, we present the design and structure of DNA origami six-helix bundles with tunable microscopic properties, which can be used as a new building block for the self-assembly of rod-like colloidal particles. We demonstrate that formation of higher order structures from the assembly of colloidal rods is universal. By tuning the chirality, aspect ratio and flexibility of the DNA origami particles we can control the physical properties of the entire self-assembled structures.

  10. Nuclear Pasta at Finite Temperature with the Time-Dependent Hartree-Fock Approach

    NASA Astrophysics Data System (ADS)

    Schuetrumpf, B.; Klatt, M. A.; Iida, K.; Maruhn, J. A.; Mecke, K.; Reinhard, P.-G.

    2016-01-01

    We present simulations of neutron-rich matter at sub-nuclear densities, like supernova matter. With the time-dependent Hartree-Fock approximation we can study the evolution of the system at temperatures of several MeV employing a full Skyrme interaction in a periodic three-dimensional grid [1]. The initial state consists of α particles randomly distributed in space that have a Maxwell-Boltzmann distribution in momentum space. Adding a neutron background initialized with Fermi distributed plane waves the calculations reflect a reasonable approximation of astrophysical matter. The matter evolves into spherical, rod-like, connected rod-like and slab-like shapes. Further we observe gyroid-like structures, discussed e.g. in [2], which are formed spontaneously choosing a certain value of the simulation box length. The ρ-T-map of pasta shapes is basically consistent with the phase diagrams obtained from QMD calculations [3]. By an improved topological analysis based on Minkowski functionals [4], all observed pasta shapes can be uniquely identified by only two valuations, namely the Euler characteristic and the integral mean curvature. In addition we propose the variance in the cell-density distribution as a measure to distinguish pasta matter from uniform matter.

  11. A bizarre Jurassic maniraptoran theropod with preserved evidence of membranous wings.

    PubMed

    Xu, Xing; Zheng, Xiaoting; Sullivan, Corwin; Wang, Xiaoli; Xing, Lida; Wang, Yan; Zhang, Xiaomei; O'Connor, Jingmai K; Zhang, Fucheng; Pan, Yanhong

    2015-05-01

    The wings of birds and their closest theropod relatives share a uniform fundamental architecture, with pinnate flight feathers as the key component. Here we report a new scansoriopterygid theropod, Yi qi gen. et sp. nov., based on a new specimen from the Middle-Upper Jurassic period Tiaojishan Formation of Hebei Province, China. Yi is nested phylogenetically among winged theropods but has large stiff filamentous feathers of an unusual type on both the forelimb and hindlimb. However, the filamentous feathers of Yi resemble pinnate feathers in bearing morphologically diverse melanosomes. Most surprisingly, Yi has a long rod-like bone extending from each wrist, and patches of membranous tissue preserved between the rod-like bones and the manual digits. Analogous features are unknown in any dinosaur but occur in various flying and gliding tetrapods, suggesting the intriguing possibility that Yi had membranous aerodynamic surfaces totally different from the archetypal feathered wings of birds and their closest relatives. Documentation of the unique forelimbs of Yi greatly increases the morphological disparity known to exist among dinosaurs, and highlights the extraordinary breadth and richness of the evolutionary experimentation that took place close to the origin of birds. PMID:25924069

  12. Electron microscopy and computational studies of Ebh, a giant cell-wall-associated protein from Staphylococcus aureus

    SciTech Connect

    Sakamoto, Sou; Tanaka, Yoshikazu; Tanaka, Isao; Takei, Toshiaki; Yu, Jian; Kuroda, Makoto; Yao Min; Ohta, Toshiko; Tsumoto, Kouhei

    2008-11-14

    Ebh, a giant protein found in staphylococci, contains several domains, including a large central region with 52 imperfect repeats of a domain composed of 126 amino acids. We used electron microscopy to observe the rod-like structure of a partial Ebh protein containing 10 repeating units. This is the first report of the direct observation of an Ebh structure containing a large number of repeating units, although structures containing one, two, or four repeating units have been reported. The observed structure of the partial Ebh protein was distorted and had a length of ca. 520 A and a width of ca. 21 A. The observed structures were consistent with those deduced from crystal structure analysis, suggesting that the Ebh domains are connected to form a rod-like structure. The crystal structure data revealed distorted, string-like features in the simulated structure of the whole-length Ebh protein. Superposition of fragments of the simulated whole-length structure of the Ebh protein onto each electron micrograph showed a high level of correlation between the observed and calculated structures. These results suggest that Ebh is composed of highly flexible filate molecules. The highly repetitive structure and the associated unique structural flexibility of Ebh support the proposed function of this protein, i.e. binding to sugars in the cell wall. This binding might result in intra-cell-wall cross-linking that contributes to the rigidity of bacterial cells.

  13. Formation of metastable RNA structures by sequential folding during transcription: time-resolved structural analysis of potato spindle tuber viroid (-)-stranded RNA by temperature-gradient gel electrophoresis.

    PubMed Central

    Repsilber, D; Wiese, S; Rachen, M; Schröder, A W; Riesner, D; Steger, G

    1999-01-01

    A model of functional elements critical for replication and infectivity of the potato spindle tuber viroid (PSTVd) was proposed earlier: a thermodynamically metastable structure containing a specific hairpin (HP II) in the (-)-strand replication intermediate is essential for template activity during (+)-strand synthesis. We present here a detailed kinetic analysis on how PSTVd (-)-strands fold during synthesis by sequential folding into a variety of metastable structures that rearrange only slowly into the structure distribution of the thermodynamic equilibrium. Synthesis of PSTVd (-)-strands was performed by T7-RNA-polymerase; the rate of synthesis was varied by altering the concentration of nucleoside triphosphates to mimic the in vivo synthesis rate of DNA-dependent RNA polymerase II. With dependence on rate and duration of the synthesis, the structure distributions were analyzed by temperature-gradient gel electrophoresis (TGGE). Metastable structures are generated preferentially at low transcription rates--similar to in vivo rates--or at short transcription times at higher rates. Higher transcription rates or longer transcription times lead to metastable structures in low or undetectable amounts. Instead different structures do gradually appear having a more rod-like shape and higher thermodynamic stability, and the thermodynamically optimal rod-like structure dominates finally. It is concluded that viroids are able to use metastable as well as stable structures for their biological functions. PMID:10199573

  14. Morphological control of CuPc and its application in organic solar cells

    NASA Astrophysics Data System (ADS)

    Hsiao, Yu-Sheng; Whang, Wha-Tzong; Suen, Shich-Chang; Shiu, Jau-Ye; Chen, Chih-Ping

    2008-10-01

    We have prepared organic photovoltaic (OPV) cells possessing an ideal bulk heterojunction (BHJ) structure using the self-assembly of copper phthalocyanine (CuPc) as the donor material and fullerene (C60) as the acceptor. The variable self-assembly behavior of CuPc on a diverse range of substrates (surface energies) allowed us to control the morphology of the interface and the degree of carrier transportation within the active layer. We observed rod-like CuPc structures on indium-tin oxide (ITO), poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulfonate) (PEDOT:PSS) and Au substrates. Accordingly, the interfaces and continuing transport path between CuPc and fullerene domains could be greatly improved due to the ideal BHJ structure. In this paper, we discuss the mechanisms of producing CuPc rod-like films on ITO, PEDOT:PSS and Au. The OPV cell performance was greatly enhanced when a mixture of horizontal and vertical CuPc rods was present on the PEDOT:PSS surfaces, i.e. the power conversion efficiency was 50 times greater than that of the corresponding device featuring a planar CuPc structure.

  15. Morphological control of CuPc and its application in organic solar cells.

    PubMed

    Hsiao, Yu-Sheng; Whang, Wha-Tzong; Suen, Shich-Chang; Shiu, Jau-Ye; Chen, Chih-Ping

    2008-10-15

    We have prepared organic photovoltaic (OPV) cells possessing an ideal bulk heterojunction (BHJ) structure using the self-assembly of copper phthalocyanine (CuPc) as the donor material and fullerene (C(60)) as the acceptor. The variable self-assembly behavior of CuPc on a diverse range of substrates (surface energies) allowed us to control the morphology of the interface and the degree of carrier transportation within the active layer. We observed rod-like CuPc structures on indium-tin oxide (ITO), poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulfonate) (PEDOT:PSS) and Au substrates. Accordingly, the interfaces and continuing transport path between CuPc and fullerene domains could be greatly improved due to the ideal BHJ structure. In this paper, we discuss the mechanisms of producing CuPc rod-like films on ITO, PEDOT:PSS and Au. The OPV cell performance was greatly enhanced when a mixture of horizontal and vertical CuPc rods was present on the PEDOT:PSS surfaces, i.e. the power conversion efficiency was 50 times greater than that of the corresponding device featuring a planar CuPc structure. PMID:21832648

  16. The filler-rubber interface in styrene butadiene nanocomposites with anisotropic silica particles: morphology and dynamic properties.

    PubMed

    Tadiello, L; D'Arienzo, M; Di Credico, B; Hanel, T; Matejka, L; Mauri, M; Morazzoni, F; Simonutti, R; Spirkova, M; Scotti, R

    2015-05-28

    Silica-styrene butadiene rubber (SBR) nanocomposites were prepared by using shape-controlled spherical and rod-like silica nanoparticles (NPs) with different aspect ratios (AR = 1-5), obtained by a sol-gel route assisted by a structure directing agent. The nanocomposites were used as models to study the influence of the particle shape on the formation of nanoscale immobilized rubber at the silica-rubber interface and its effect on the dynamic-mechanical behavior. TEM and AFM tapping mode analyses of nanocomposites demonstrated that the silica particles are surrounded by a rubber layer immobilized at the particle surface. The spherical filler showed small contact zones between neighboring particles in contact with thin rubber layers, while anisotropic particles (AR > 2) formed domains of rods preferentially aligned along the main axis. A detailed analysis of the polymer chain mobility by different time domain nuclear magnetic resonance (TD-NMR) techniques evidenced a population of rigid rubber chains surrounding particles, whose amount increases with the particle anisotropy, even in the absence of significant differences in terms of chemical crosslinking. Dynamic measurements demonstrate that rod-like particles induce stronger reinforcement of rubber, increasing with the AR. This was related to the self-alignment of the anisotropic silica particles in domains able to immobilize rubber. PMID:25899456

  17. A bizarre Jurassic maniraptoran theropod with preserved evidence of membranous wings.

    PubMed

    Xu, Xing; Zheng, Xiaoting; Sullivan, Corwin; Wang, Xiaoli; Xing, Lida; Wang, Yan; Zhang, Xiaomei; O'Connor, Jingmai K; Zhang, Fucheng; Pan, Yanhong

    2015-05-01

    The wings of birds and their closest theropod relatives share a uniform fundamental architecture, with pinnate flight feathers as the key component. Here we report a new scansoriopterygid theropod, Yi qi gen. et sp. nov., based on a new specimen from the Middle-Upper Jurassic period Tiaojishan Formation of Hebei Province, China. Yi is nested phylogenetically among winged theropods but has large stiff filamentous feathers of an unusual type on both the forelimb and hindlimb. However, the filamentous feathers of Yi resemble pinnate feathers in bearing morphologically diverse melanosomes. Most surprisingly, Yi has a long rod-like bone extending from each wrist, and patches of membranous tissue preserved between the rod-like bones and the manual digits. Analogous features are unknown in any dinosaur but occur in various flying and gliding tetrapods, suggesting the intriguing possibility that Yi had membranous aerodynamic surfaces totally different from the archetypal feathered wings of birds and their closest relatives. Documentation of the unique forelimbs of Yi greatly increases the morphological disparity known to exist among dinosaurs, and highlights the extraordinary breadth and richness of the evolutionary experimentation that took place close to the origin of birds.

  18. Seed-Mediated Growth of Gold Nanocrystals: Changes to the Crystallinity or Morphology as Induced by the Treatment of Seeds with a Sulfur Species

    DOE PAGES

    Zheng, Yiqun; Luo, Ming; Tao, Jing; Peng, Hsin-Chieh; Wan, Dehui; Zhu, Yimei; Xia, Younan

    2014-12-11

    We report our observation of changes to the crystallinity or morphology during seed-mediated growth of Au nanocrystals. When single-crystal Au seeds with a spherical or rod-like shape were treated with a chemical species such as S₂O₃²⁻ ions, twin defects were developed during the growth process to generate multiply twinned nanostructures. X-ray photoelectron spectroscopy analysis indicated that the S₂O₃²⁻ ions were chemisorbed on the surfaces of the seeds during the treatment. The chemisorbed S₂O₃²⁻ ions somehow influenced the crystallization of Au atoms added onto the surface during a growth process, leading to the formation of twin defects. In contrast to themore » spherical and rod-like Au seeds, the single-crystal structure was retained to generate a concave morphology when single-crystal Au seeds with a cubic or octahedral shape were used for a similar treatment and then seed-mediated growth. The different outcomes are likely related to the difference in spatial distribution of S₂O₃²⁻ ions chemisorbed on the surface of a seed. This approach based on surface modification is potentially extendable to other noble metals for engineering the crystallinity and morphology of nanocrystals formed via seed-mediated growth.« less

  19. Hierarchical self-assembly of spider silk-like block copolymers

    NASA Astrophysics Data System (ADS)

    Krishnaji, Sreevidhya; Huang, Wenwen; Cebe, Peggy; Kaplan, David

    2011-03-01

    Block copolymers provide an attractive venue to study well-defined nano-structures that self-assemble to generate functionalized nano- and mesoporous materials. In the present study, a novel family of spider silk-like block copolymers was designed, bioengineered and characterized to study the impact of sequence chemistry, secondary structure and block length on assembled morphology. Genetic variants of native spider dragline silk (major ampullate spidroin I, Nephila clavipes) were used as polymer building blocks. Characterization by FTIR revealed increased ?-sheet content with increasing hydrophobic A blocks; SEM revealed spheres, rod-like structures, bowl-shaped and giant compound micelles. Langmuir Blodgett monolayers were prepared at the air-water interface at different surface pressures and monolayer films analyzed by AFM revealed oblate to prolate structures. Circular micelles, rod-like, densely packed circular structures were observed for HBA6 at increasing surface pressure. Exploiting hierarchical assembly provide a promising approach to rationale designs of protein block copolymer systems, allowing comparison to traditional synthetic systems.

  20. Helical polyurethane-attapulgite nanocomposite: Preparation, characterization and study of optical activity

    SciTech Connect

    Wang Zhiqiang; Zhou Yuming; Sun Yanqing; Fan Kai; Guo Xingxing; Jiang Xiaolei

    2009-08-15

    Helical polyurethane-attapulgite (BM-ATT) based on R-1,1'-binaphthyl-2',2-diol (R-BINOL) composite was prepared after the surface modification of attapulgite (ATT). BM-ATT was characterized by Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HTEM) and vibrational circular dichroism (VCD) spectroscopy. FT-IR and XRD analyses indicate that the helical polyurethane has been successfully grafted onto the surfaces of the modified ATT without destroying the original crystalline structure of ATT. BM-ATT exhibits the rod-like structure by SEM, TEM, and HTEM photographs. BM-ATT displays obvious Cotton effect for some absorbance in VCD spectrum, and its optical activity results from the singlehanded conformation of helical polyurethane. - Graphical Abstract: Helical polyurethane-attapulgite (BM-ATT) based on R-1,1'-binaphthyl-2',2-diol (R-BINOL) nanocomposite was prepared after surface modification of attapulgite (ATT). This rod-like composite is coated by the optically active polyurethane shell on the surfaces.

  1. Controllable Synthesis of Formaldehyde Modified Manganese Oxide Based on Gas-Liquid Interfacial Reaction and Its Application of Electrochemical Sensing.

    PubMed

    Bai, Wushuang; Sheng, Qinglin; Nie, Fei; Zheng, Jianbin

    2015-12-30

    Controllable synthesis of manganese oxides was performed via a simple one-step synthetic method. Then obtained manganese oxides which exhibit flower-like, cloud-like, hexagon-like, and rod-like morphologies were modified by formaldehyde based on a simple self-made gas-liquid reaction device respectively and the modified manganese oxides with coral-like, scallop-like and rod-like morphology were synthesized accordingly. The obtained materials were characterized and the formation mechanism was also researched. Then the modified manganese oxides were used to fabricate electrochemical sensors to detect H2O2. Comparison of electrochemical properties between three kinds of modified manganese oxides was investigated and the best one has been successfully employed as H2O2 sensor which shows a low detection limit of 0.01 μM, high sensitivity of 162.69 μA mM(-1) cm(-2), and wide linear range of 0.05 μM-12.78 mM. The study provides a new method for controllable synthesis of metal oxides, and electrochemical application of formaldehyde modified manganese oxides will provides a new strategy for electrochemical sensing with high performance, low cost, and simple fabrication. PMID:26647786

  2. Boundary-induced segregation in nanoscale thin films of athermal polymer blends.

    PubMed

    Teng, Chih-Yu; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2016-05-18

    The surface segregation of binary athermal polymer blends confined in a nanoscale thin film was investigated by dissipative particle dynamics. The polymer blend included linear/linear, star/linear, bottlebrush/linear, and rod-like/linear polymer systems. The segregation was driven by purely entropic effects and two different mechanisms were found. For the linear/linear and star/linear polymer blends, the smaller sized polymers were preferentially segregated to the boundary because their excluded volumes were smaller than those of the matrix polymers. For the bottlebrush/linear and rod-like/linear polymer blends, the polymers with a larger persistent length were preferentially segregated to the boundary because they favored staying in the depletion zone by alignment with the wall. Our simulation outcome was consistent with experimental results and also agreed with theoretical predictions - that is, a surface excess dictated by the chain ends for the branch/linear system. These consequences are of great importance in controlling the homogeneity and surface properties of polymer blend thin films. PMID:27108653

  3. Pretransitional Clusters in Multicolor Liquid Crystalline Honeycombs

    NASA Astrophysics Data System (ADS)

    Ungar, Goran; Zeng, Xiangbing; Liu, Feng; Kieffer, Robert; Nürnberger, Constance; Tschierske, Carsten; Gehring, Gillian

    2012-02-01

    X-shaped tetraphilic molecules consisting of a rod-like core with two hydrogen-bonding terminal groups and two mutually incompatible side-chains A and B form a range of honeycomb-like structures in which the rods act as bricks in the walls of polygonal cylinder cells containing the fluid side-chains. Some of these systems exhibit a 2nd-order transition from the high-temperature mixed (``1-color'') phase to a low-temperature phase in which the side-chains are separated in A and B cells (``2-color''). This is the situation with triangular, rectangular and square honeycombs. Strong pre-transitional 2-color domains formation is observed above the transition temperature. Particularly interesting is the case of the hexagonal honeycomb, where no fully phase-separated ground state can exist. Here the 2-color ``ordered'' phase consists of [A] cells and [A(1/4)B(3/4)] cells. The situation is similar to frustrated ferro- and antiferromagnets on a kagome lattice. Instead of the spins flipping, it is the molecules that undergo 180 degree rotations about the axis of their rod-like cores [Science 331, 1302 (2011)].

  4. Morphology-controlled synthesis of α-FeOOH and its derivatives

    NASA Astrophysics Data System (ADS)

    Sun, Zhengzong; Feng, Xiaomiao; Hou, Wenhua

    2007-11-01

    α-FeOOH nanocrystals were synthesized in high yield via a facile and template-free hydrothermal method at low temperature. The morphology and composition of the samples were controlled by slowly releasing the SO42- ions from ammonium persulfate. The rod-like, bundle-like, and urchin-like α-FeOOH nanocrystals could be acquired respectively through a direct hydrothermal route with different quantities of SO42- ions. The rod-like α-FeOOH nanocrystals obtained have a diameter of 5-25 nm and a length of 100-200 nm. When the molar ratio of iron to SO42- was 1:1, the product was pure α-FeOOH phase. However, as the molar ratio was decreased from 1:1 to 1:4, pure FeSO4OH·2H2O phase was obtained. When the molar ratio was between 1:4 and 1:1, the prepared product was composed of two phases (α-FeOOH and FeSO4OH·2H2O). After hydrothermally aging the as-synthesized α-FeOOH nanorods at 180 °C for 1 d, α-Fe2O3 nanorods were obtained. However, the edge of the α-Fe2O3 nanorods was sword-like and different from the blunt edge of α-FeOOH nanorods due to a recrystallization mechanism.

  5. Behavior of osteoblast-like cells on calcium-deficient hydroxyapatite ceramics composed of particles with different shapes and sizes.

    PubMed

    Kamitakahara, Masanobu; Uno, Yuika; Ioku, Koji

    2014-01-01

    In designing the biomaterials, it is important to control their surface morphologies, because they affect the interactions between the materials and cells. We previously reported that porous calcium-deficient hydroxyapatite (HA) ceramics composed of rod-like particles had advantages over sintered porous HA ceramics; however, the effects of the surface morphology of calcium-deficient HA ceramics on cell behavior have remained unclear. Using a hydrothermal process, we successfully prepared porous calcium-deficient HA ceramics with different surface morphologies, composed of plate-like particles of 200-300, 500-800 nm, or 2-3 μm in width and rod-like particles of 1 or 3-5 μm in width, respectively. The effects of these surface morphologies on the behavior of osteoblast-like cells were examined. Although the numbers of cells adhered to the ceramic specimens did not differ significantly among the specimens, the proliferation rates of cells on the ceramics decreased with decreasing particle size. Our results reveal that controlling the surface morphology that is governed by particle shape and size is important for designing porous calcium-deficient HA ceramics.

  6. Controllable Synthesis of Formaldehyde Modified Manganese Oxide Based on Gas-Liquid Interfacial Reaction and Its Application of Electrochemical Sensing.

    PubMed

    Bai, Wushuang; Sheng, Qinglin; Nie, Fei; Zheng, Jianbin

    2015-12-30

    Controllable synthesis of manganese oxides was performed via a simple one-step synthetic method. Then obtained manganese oxides which exhibit flower-like, cloud-like, hexagon-like, and rod-like morphologies were modified by formaldehyde based on a simple self-made gas-liquid reaction device respectively and the modified manganese oxides with coral-like, scallop-like and rod-like morphology were synthesized accordingly. The obtained materials were characterized and the formation mechanism was also researched. Then the modified manganese oxides were used to fabricate electrochemical sensors to detect H2O2. Comparison of electrochemical properties between three kinds of modified manganese oxides was investigated and the best one has been successfully employed as H2O2 sensor which shows a low detection limit of 0.01 μM, high sensitivity of 162.69 μA mM(-1) cm(-2), and wide linear range of 0.05 μM-12.78 mM. The study provides a new method for controllable synthesis of metal oxides, and electrochemical application of formaldehyde modified manganese oxides will provides a new strategy for electrochemical sensing with high performance, low cost, and simple fabrication.

  7. Controlled morphology synthesis of {beta}-FeOOH and the phase transition to Fe{sub 2}O{sub 3}

    SciTech Connect

    Shao Huafeng; Qian Xuefeng . E-mail: xfqian@sjtu.edu.cn; Yin Jie; Zhu Zikang

    2005-10-15

    The hexagram and arrayed {beta}-FeOOH nanorods were first synthesized free of surfactants through the solvent-thermal method. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectrum (EDAX) and thermal gravimetric analysis (TGA) were used to characterize the as-prepared products. The TEM and FESEM images showed that hexagram {beta}-FeOOH and arrayed rod-like {beta}-FeOOH with an average diameter of 10-15 nm and an average length of 100 nm (aspect ratio is about 10) were prepared. Electrochemical tests show that these nanorods deliver a large discharge capacity of 277 mA h g{sup -1} versus Li metal at 0.1 mA cm{sup -2} (voltage at 1.5-4.2 V). Treated the as-synthesized rod-like {beta}-FeOOH by annealing, rhombus hematite was obtained. - Graphical abstract: The TEM images of the as-synthesized sample II.

  8. Microstructural characterization of the cycling behavior of electrodeposited manganese oxide supercapacitors using 3D electron tomography

    NASA Astrophysics Data System (ADS)

    Dalili, N.; Clark, M. P.; Davari, E.; Ivey, D. G.

    2016-10-01

    Manganese oxide has been investigated extensively as an electrochemical capacitor or supercapacitor electrode material. Manganese oxide is inexpensive to fabricate and exhibits relatively high capacitance values, i.e., in excess of 200 F g-1 in many cases; the actual value depends very much on the fabrication method and test conditions. The cycling behavior of Mn oxide, fabricated using anodic electrodeposition, is investigated using slice and view techniques, via a dual scanning electron microscope (SEM) and focused ion beam (FIB) instrument to generate three-dimensional (3D) images, coupled with electrochemical characterization. The initial as-fabricated electrode has a rod-like appearance, with a fine-scale, sheet-like morphology within the rods. The rod-like structure remains after cycling, but there are significant morphological changes. These include partial dissolution of Mn oxide followed by redeposition of Mn oxide in regions close to the substrate. The redeposited material has a finer morphology than the original as-fabricated Mn oxide. The Mn oxide coverage is also better near the substrate. These effects result in an increase in the specific capacitance.

  9. Hydration characteristics and environmental friendly performance of a cementitious material composed of calcium silicate slag.

    PubMed

    Zhang, Na; Li, Hongxu; Zhao, Yazhao; Liu, Xiaoming

    2016-04-01

    Calcium silicate slag is an alkali leaching waste generated during the process of extracting Al2O3 from high-alumina fly ash. In this research, a cementitious material composed of calcium silicate slag was developed, and its mechanical and physical properties, hydration characteristics and environmental friendly performance were investigated. The results show that an optimal design for the cementitious material composed of calcium silicate slag was determined by the specimen CFSC7 containing 30% calcium silicate slag, 5% high-alumina fly ash, 24% blast furnace slag, 35% clinker and 6% FGD gypsum. This blended system yields excellent physical and mechanical properties, confirming the usefulness of CFSC7. The hydration products of CFSC7 are mostly amorphous C-A-S-H gel, rod-like ettringite and hexagonal-sheet Ca(OH)2 with small amount of zeolite-like minerals such as CaAl2Si2O8·4H2O and Na2Al2Si2O8·H2O. As the predominant hydration products, rod-like ettringite and amorphous C-A-S-H gel play a positive role in promoting densification of the paste structure, resulting in strength development of CFSC7 in the early hydration process. The leaching toxicity and radioactivity tests results indicate that the developed cementitious material composed of calcium silicate slag is environmentally acceptable. This study points out a promising direction for the proper utilization of calcium silicate slag in large quantities.

  10. Cyclization and Catenation Directed by Molecular Self-Assembly

    SciTech Connect

    Wang, Wei; Wang, Li Q; Palmer, Bruce J; Exarhos, Gregory J; Li, Alexander D

    2006-08-30

    We report here that molecular self-assembly can effectively direct and enhance specific reaction pathways. Using perylene π-π stacking weak attractive forces, we succeeded in synthesizing perylene bisimide macrocyclic dimer and a concatenated dimer-dimer ring from dynamic self-assembly of monomeric bis-N, N’-(2-(2-(2-(2-thioacetyl ethoxy) ethoxy) ethoxy) ethyl) perylene tetracarboxylic diimide. The monocyclic ring closure and the dimer-dimer ring concatenation were accomplished through formation of disulfide bonds, which was readily triggered by air oxidization under basic deacetylation conditions. The perylene cyclic dimer and its concatenated tetramer were characterized using both structural methods (NMR, mass spectroscopy) and photophysical measurements (UV-vis spectroscopy). Kinetic analyses offer informative insights about reaction pathways and possible mechanisms, which lead to the formation of fascinating concatenated rings. Molecular dynamic behaviors of both the monocyclic dimer and the concatenated dimer-dimer ring were modeled with the NWChem molecular dynamics software module, which shows distinct stacking activities for the monocyclic dimer and the concatenated tetramer.

  11. A switchable bis-branched [1]rotaxane featuring dual-mode molecular motions and tunable molecular aggregation.

    PubMed

    Li, Hong; Li, Xin; Cao, Zhan-Qi; Qu, Da-Hui; Ågren, Hans; Tian, He

    2014-01-01

    A multifunctional bis-branched [1]rotaxane containing a perylene bisimide (PBI) core and two identical bistable[1]rotaxane arms terminated with ferrocene units was prepared and characterized by (1)H NMR, (13)C NMR, and 2D ROESY NMR spectroscopies and by HR-ESI spectrometry. The system is shown to possess several key features: (1) In acetone solution, external acid-base stimuli can result in relative mechanical movements of its ring and thread, which can induce extension and contraction movements of the whole system accompanied by a rotational movement of the ferrocene units, thus realizing dual-mode molecular motions, and the optimized conformations at different states are obtained through molecular dynamics simulations employing the general Amber force field. (2) The introduction of PBI enables the system fluorescence encoding through distance-dependent photoinduced electron transfer process from the ferrocene units to the PBI fluorophore. (3) The addition of Zn(2+) can increase the degree of aggregation of the system, while adding base hinders aggregation because of the movement of the macrocycle. The tunable aggregated nanostructural morphologies of [1]rotaxane were examined by scanning electron microscopy. These results can pave the way to achieve precise control of integrated and coupling nanomechanical motions at a single-molecule level and provide more insight into controlling the aggregate behavior of switchable mechanically interlocked molecules. PMID:25302680

  12. Phosphorus-containing imide resins - Modification by elastomers

    NASA Technical Reports Server (NTRS)

    Varma, I. K.; Fohlen, G. M.; Parker, J. A.; Varma, D. S.

    1984-01-01

    The syntheses and general features of addition-type maleimide resins based on bis(m-aminophenyl)phosphine oxide and tris(m-aminophenyl)phosphine oxide have been reported previously. These resins have been used to fabricate graphite cloth laminates having excellent flame resistance. These composites did not burn even in pure oxygen. However, these resins were somewhat brittle. This paper reports the modification of these phosphorus-containing resins by an amine-terminated butadiene-acrylonitrile copolymer (ATBN) and a perfluoroalkylene diaromatic amine elastomer (3F). An approximately two-fold increase in short beam shear strength and flexural strength was observed at 7 percent ATBN concentration. The tensile, flexural, and shear strengths were reduced when 18 percent ATBN was used. Anaerobic char yields of the resins at 800 C and the limiting oxygen indexes of the laminates decreased with increasing ATBN concentration. The perfluorodiamine (3F) was used with both imide resins at 6.4 percent concentration. The shear strength was doubled in the case of the bisimide with no loss of flammability characteristics. The modified trisimide laminate also had improved properties over the unmodified one. The dynamic mechanical analysis of a four-ply laminate indicated a glass transition temperature above 300 C. Scanning electron micrographs of the ATBN modified imide resins were also recorded.

  13. Photorefractive polymer device with improved sensitizing property

    NASA Astrophysics Data System (ADS)

    Nguyen, Tam V.; Giang, Ha N.; Kinashi, K.; Sakai, W.; Tsutsumi, N.

    2015-09-01

    photorefractive (PR) application because of a fast hole mobility. In most of the previous studies, phenyl-C61-butyric acid methyl ester (PCBM) was used as a sensitizer. In this study, a high-performance charge generator perylene bisimide (PBI) is synthesized and added into the composite. PBI derivatives owning a large core of π-conjugated rings provide a high electron affinity and high charge carrier mobility. These features are promising to improve PR properties. To the best of our knowledge, it is the first time for using a combine of PCBM and PBI to improve the PR performance of PDAA-based composites. 2-(4-(azepan-1-yl)benzylidene)malononitrile (7-DCST) is used as a nonlinear optical chromophore. (4-diphenylamino)phenyl)methanol (TPAOH) is used as a plasticizer. Consequently, a diffraction efficiency of 76 % and a response time of 8 ms were obtained with 532 nm green laser under the electric field of 55 V μm-1. As a conclusion, the introduction of PBI is a promising approach for the photorefractive composite owning the video rate response.

  14. The preparation of nylon-tube-supported hexokinase and glucose 6-phosphate dehydrogenase and the use of the co-immobilized enzymes in the automated determination of glucose.

    PubMed Central

    Morris, D L; Campbell, J; Hornby, W E

    1975-01-01

    Triethyloxonium tetrafluoroborate was used to O-alkylate nylon-tube thus producing the imidate salt of the nylon which was further made to react with 1,6-diaminohexane. 2. Hexokinase (EC 2.7.1.1) and glucose 6-phosphate dehydrogenase (EC 1.1.1.49) were immobilized on the amino-substituted nylon tube through glutaraldeyde and bisimidates. 3. The effect of varying the conditions of O-alkylation and the amount of enzyme immobilized on the activity of nylon tube-hexokinase derivatives was determined. 4. The effect of varying the amount of enzyme immobilized on the activity of nylon-tube-glucose 6-phosphate dehydrogenase derivatives was determined. 5. The thermal stability of nylon-tube-hexokinase and nylon-tube-glucose 6-phosphate dehydrogenase derivatives was studied. 6. Different ratios of hexokinase and glucose 6-phosphate dehydrogenase were co-immobilized on nylon tube, and the rate of conversion of glucose into 6-phosphogluconolactone was compared with the individual activities of the immobilized enzymes. 7. Hexokinase and glucose 6-phosphate dehydrogenase co-immobilized on nylon tube were used in the automated analysis of glucose. PMID:1167161

  15. P3HT:DiPBI bulk heterojunction solar cells: morphology and electronic structure probed by multiscale simulation and UV/vis spectroscopy.

    PubMed

    Winands, Thorsten; Böckmann, Marcus; Schemme, Thomas; Ly, Phong-Minh Timmy; de Jong, Djurre H; Wang, Zhaohui; Denz, Cornelia; Heuer, Andreas; Doltsinis, Nikos L

    2016-02-17

    Coarse grained molecular dynamics simulations are performed for a mixture of poly(3-hexylthiophene) (P3HT) and diperylene bisimide (DiPBI). The effect of different annealing and cooling protocols on the morphology is investigated and the resulting domain structures are analyzed. In particular, π-stacked clusters of DiPBI molecules are observed whose size decreases with increasing temperature. Domain structure and diffusivity data suggest that the DiPBI subsystem undergoes an order → disorder phase transition between 700 and 900 K. Electronic structure calculations based on density functional theory are carried out after backmapping the coarse grained model onto an atomistic force field representation built upon first principles. UV/vis absorption spectra of the P3HT:DiPBI mixture are computed using time-dependent density functional linear response theory and recorded experimentally for a spin-coated thin film. It is demonstrated that the absorption spectrum depends sensitively on the details of the amorphous structure, thus providing valuable insight into the morphology. In particular, the results show that the tempering procedure has a significant influence on the material's electronic properties. This knowledge may help to develop effective processing routines to enhance the performance of bulk heterojunction solar cells. PMID:26853376

  16. Impact of Alkyl Spacer Length on Aggregation Pathways in Kinetically Controlled Supramolecular Polymerization.

    PubMed

    Ogi, Soichiro; Stepanenko, Vladimir; Thein, Johannes; Würthner, Frank

    2016-01-20

    We have investigated the kinetic and thermodynamic supramolecular polymerizations of a series of amide-functionalized perylene bisimide (PBI) organogelator molecules bearing alkyl spacers of varied lengths (ethylene to pentylene chains, PBI-1-C2 to PBI-1-C5) between the amide and PBI imide groups. These amide-functionalized PBIs form one-dimensional fibrous nanostructures as the thermodynamically favored states in solvents of low polarity. Our in-depth studies revealed, however, that the kinetic behavior of their supramolecular polymerization is dependent on the spacer length. Propylene- and pentylene-tethered PBIs follow a similar polymerization process as previously observed for the ethylene-tethered PBI. Thus, the monomers of these PBIs are kinetically trapped in conformationally restricted states through intramolecular hydrogen bonding between the amide and imide groups. In contrast, the intramolecularly hydrogen-bonded monomers of butylene-tethered PBI spontaneously self-assemble into nanoparticles, which constitute an off-pathway aggregate state with regard to the thermodynamically stable fibrous supramolecular polymers obtained. Thus, for this class of π-conjugated system, an unprecedented off-pathway aggregate with high kinetic stability could be realized for the first time by introducing an alkyl linker of optimum length (C4 chain) between the amide and imide groups. Our current system with an energy landscape of two competing nucleated aggregation pathways is applicable to the kinetic control over the supramolecular polymerization by the seeding approach. PMID:26699283

  17. Dipole-moment-driven cooperative supramolecular polymerization.

    PubMed

    Kulkarni, Chidambar; Bejagam, Karteek K; Senanayak, Satyaprasad P; Narayan, K S; Balasubramanian, S; George, Subi J

    2015-03-25

    While the mechanism of self-assembly of π-conjugated molecules has been well studied to gain control over the structure and functionality of supramolecular polymers, the intermolecular interactions underpinning it are poorly understood. Here, we study the mechanism of self-assembly of perylene bisimide derivatives possessing dipolar carbonate groups as linkers. It was observed that the combination of carbonate linkers and cholesterol/dihydrocholesterol self-assembling moieties led to a cooperative mechanism of self-assembly. Atomistic molecular dynamics simulations of an assembly in explicit solvent strongly suggest that the dipole-dipole interaction between the carbonate groups imparts a macro-dipolar character to the assembly. This is confirmed experimentally through the observation of a significant polarization in the bulk phase for molecules following a cooperative mechanism. The cooperativity is attributed to the presence of dipole-dipole interaction in the assembly. Thus, anisotropic long-range intermolecular interactions such as dipole-dipole interaction can serve as a way to obtain cooperative self-assembly and aid in rationalizing and predicting the mechanisms in various synthetic supramolecular polymers. PMID:25756951

  18. Interfacial Layer Properties of a Polyaromatic Compound and its Role in Stabilizing Water-in-Oil Emulsions.

    PubMed

    Bi, Jiebin; Yang, Fan; Harbottle, David; Pensini, Erica; Tchoukov, Plamen; Simon, Sébastien; Sjöblom, Johan; Dabros, Tadek; Czarnecki, Jan; Liu, Qingxia; Xu, Zhenghe

    2015-09-29

    Physical properties of interfacial layers formed at the xylene-water interface by the adsorption of a polyaromatic organic compound, N-(1-hexylheptyl)-N'-(5-carbonylicpentyl) perylene-3,4,9,10-tetracarboxylic bisimide (in brief, C5Pe), were studied systematically. The deprotonation of the carboxylic group of C5Pe at alkaline pH made it highly interfacially active, significantly reducing the xylene-water interfacial tension. Thin liquid film experiments showed a continuous buildup of heterogeneous C5Pe interfacial layers at the xylene-water interfaces, which contributed to the formation of stable W/O emulsions. Continual accumulation and rearrangement of C5Pe aggregates at the xylene-water interface to form a thick layer was confirmed by in situ Brewster angle microscopy (BAM) and atomic force microscopy (AFM). The rheology measurement of the interfacial layer by double-wall ring interfacial rheometry under oscillatory shear showed that the interfacial layers formed from C5Pe solutions of high concentrations were substantially more elastic and rigid. The presence of elastically dominant interfacial layers of C5Pe led to the formation of stable water-in-xylene emulsions.

  19. Avoiding bias effects in NMR experiments for heteronuclear dipole-dipole coupling determinations: principles and application to organic semiconductor materials.

    PubMed

    Kurz, Ricardo; Cobo, Marcio Fernando; de Azevedo, Eduardo Ribeiro; Sommer, Michael; Wicklein, André; Thelakkat, Mukundan; Hempel, Günter; Saalwächter, Kay

    2013-09-16

    Carbon-proton dipole-dipole couplings between bonded atoms represent a popular probe of molecular dynamics in soft materials or biomolecules. Their site-resolved determination, for example, by using the popular DIPSHIFT experiment, can be challenged by spectral overlap with nonbonded carbon atoms. The problem can be solved by using very short cross-polarization (CP) contact times, however, the measured modulation curves then deviate strongly from the theoretically predicted shape, which is caused by the dependence of the CP efficiency on the orientation of the CH vector, leading to an anisotropic magnetization distribution even for isotropic samples. Herein, we present a detailed demonstration and explanation of this problem, as well as providing a solution. We combine DIPSHIFT experiments with the rotor-directed exchange of orientations (RODEO) method, and modifications of it, to redistribute the magnetization and obtain undistorted modulation curves. Our strategy is general in that it can also be applied to other types of experiments for heteronuclear dipole-dipole coupling determinations that rely on dipolar polarization transfer. It is demonstrated with perylene-bisimide-based organic semiconductor materials, as an example, in which measurements of dynamic order parameters reveal correlations of the molecular dynamics with the phase structure and functional properties.

  20. Synthesis and Microstructural Characterization of Manganese Oxide Electrodes for Application as Electrochemical Supercapacitors

    NASA Astrophysics Data System (ADS)

    Babakhani, Banafsheh

    The aim of this thesis work was to synthesize Mn-based oxide electrodes with high surface area structures by anodic electrodeposition for application as electrochemical capacitors. Rod-like structures provide large surface areas leading to high specific capacitances. Since templated electrosynthesis of rods is not easy to use in practical applications, it is more desirable to form rod-like structures without using any templates. In this work, Mn oxide electrodes with rod-like structures (˜1.5 µm in diameter) were synthesized from a solution of 0.01 M Mn acetate under galvanostatic control without any templates, on Au coated Si substrates. The electrochemical properties of the synthesized nanocrystalline electrodes were investigated to determine the effect of morphology, chemistry and crystal structure on the corresponding electrochemical behavior of Mn oxide electrodes. Mn oxides prepared at different current densities showed a defective antifluoritetype crystal structure. The rod-like Mn oxide electrodes synthesized at low current densities (5 mAcm.2) exhibited a high specific capacitance due to their large surface areas. Also, specific capacity retention after 250 cycles in an aqueous solution of 0.5 M Na2SO4 at 100 mVs -1 was about 78% of the initial capacity (203 Fg-1 ). To improve the electrochemical capacitive behavior of Mn oxide electrodes, a sequential approach and a one-step method were adopted to synthesize Mn oxide/PEDOT electrodes through anodic deposition on Au coated Si substrates from aqueous solutions. In the former case, free standing Mn oxide rods (about 10 µm long and less than 1.5 µm in diameter) were first synthesized, then coated by electro-polymerization of a conducting polymer (PEDOT) giving coaxial rods. The one-step, co-electrodeposition method produced agglomerated Mn oxide/PEDOT particles. The electrochemical behavior of the deposits depended on the morphology and crystal structure of the fabricated electrodes, which were affected

  1. Facile synthesis, spectral properties and formation mechanism of sulfur nanorods in PEG-200

    SciTech Connect

    Xie, Xin-yuan; Li, Li-yun; Zheng, Pu-sheng; Zheng, Wen-jie; Bai, Yan; Cheng, Tian-feng; Liu, Jie

    2012-11-15

    Graphical abstract: Homogeneous rod-like structure of sulfur with a typical diameter of about 80 nm and an average aspect ratio of about 6–8 was obtained. The sulfur nanoparticles could self-assemble from spherical particles to nanorods in PEG-200. During the self-assembling process, the absorption band showed a red shift which was due to the production of nanorods. Highlights: ► A novel, facile and greener method to synthesize sulfur nanorods by the solubilizing and templating effect of PEG-200 was reported. ► S{sup 0} nanoparticles could self assemble in PEG-200 and finally form monodisperse and homogeneous rod-like structure with an average diameter of about 80 nm, the length ca. 600 nm. ► The absorption band showed a red shift and the RRS intensity enhanced continuously during the self-assembling process. ► PEG-200 induced the oriented attachment of sulfur nanoparticles by the terminal hydroxyl groups. -- Abstract: The synthesis of nano-sulfur sol by dissolving sublimed sulfur in a green solvent-PEG-200 was studied. Homogeneous rod-like structure of sulfur with a typical diameter of about 80 nm and an average aspect ratio of 6–8 was obtained. The structure, morphology, size, and stability of the products were investigated by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and dynamic light scattering (DLS) measurements. The spectral properties of the products were investigated by ultraviolet-visible (UV–vis) absorption and resonance Rayleigh scattering spectroscopy (RRS). The results showed that the spherical sulfur nanoparticles could self-assemble into nanorods in PEG-200. During the self-assembling process, the absorption band showed a red shift and the RRS intensity enhanced continuously. There was physical cross-linking between PEG and sulfur nanoparticles. PEG-200 induced the oriented attachment of sulfur nanoparticles by

  2. Role of nanomaterial physicochemical properties on fate and toxicity in bacteria and plants

    NASA Astrophysics Data System (ADS)

    Slomberg, Danielle

    Nanomaterials, defined as those having at least one dimension <100 nm, are ubiquitous in nature. However, engineered nanomaterials have gained increasing attention for use in drug-delivery applications and consumer goods. Examination of nanomaterial toxicity, both beneficial (e.g., drug delivery to bacterial pathogens) and detrimental (e.g., death of terrestrial plants), thus warranted. Herein, I present the evaluation of nitric oxide-releasing nanomaterial toxicity to bacteria and silica particle toxicity to plants as a function of nanomaterial physicochemical properties. Nanomaterial toxicity toward planktonic (i.e., free-floating) Pseudomonas aeruginosa and Staphylococcus aureus bacteria was evaluated as a function of scaffold size, shape, and exterior functionality using nitric oxide-releasing (NO) silica particles, dendrimers, and chitosan oligosaccharides. Improved bactericidal efficacy was observed for silica particles with decreased size and increased aspect ratio (i.e., rod-like) due to improved particle-cell interactions. Likewise, better nanomaterial-bacteria association and biocidal action was noted for more hydrophobic NO-releasing dendrimers and chitosan oligosaccharides. Planktonic bacterial killing was not dependent on chitosan molecular weight due to rapid association between the cationic scaffolds and negatively-charged bacterial cell membranes. Given the importance of nanomaterial physicochemical properties in planktonic bacterial killing, the NO-releasing scaffolds were also evaluated against clinically-relevant bacterial biofilms. Similar to planktonic studies, smaller particle sizes proved more efficient in delivering NO throughout the biofilm. Particles with rod-like shape also eradicated biofilms more effectively. The role of NO-releasing dendrimer and chitosan oligosaccharide hydrophobicity was prominent in scaffold diffusion through the biofilm and subsequent NO delivery, with hydrophobic functionalities generally exhibiting better

  3. Increased calcium content and inhomogeneity of mineralization render bone toughness in osteoporosis: mineralization, morphology and biomechanics of human single trabeculae.

    PubMed

    Busse, Björn; Hahn, Michael; Soltau, Markus; Zustin, Jozef; Püschel, Klaus; Duda, Georg N; Amling, Michael

    2009-12-01

    The differentiation and degree of the effects of mineral content and/or morphology on bone quality remain, to a large extent, unanswered due to several microarchitectural particularities in spatial measuring fields (e.g., force transfer, trajectories, microcalli). Therefore, as the smallest basic component of cancellous bone, we focused on single trabeculae to investigate the effects of mineralization and structure, both independently and in superposition. Transiliac Bordier bone cores and T12 vertebrae were obtained from 20 females at autopsy for specimen preparation, enabling radiographical analyses, histomorphometry, Bone Mineral Density Distribution (BMDD) analyses, and trabecular singularization to be performed. Evaluated contact X-rays and histomorphometric limits from cases with osteoporotic vertebral fractures generated two subdivisions, osteoporotic (n=12, Ø 78 years) and non-osteoporotic (n=8, Ø 49 years) cases, based on fracture appearance and bone volume (BV/TV). Measurements of trabecular number (Tb.N.), trabecular separation (Tb.Sp.), trabecular thickness (Tb.Th.), trabecular bone pattern factor (TBPf) and eroded surface (ES/BS) were carried out to provide detailed structural properties of the investigated groups. The mechanical properties of 400 rod-like single vertebral trabeculae, assessed by three-point bending, were matched with mineral properties as quantified by BMDD analyses of cross-sectioned rod-like and plate-like trabeculae, both in superposition and independently. Non-osteoporotic iliac crests and vertebrae displayed linear dependency on structure parameters, whereas osteoporotic compartments proved to be non-correlated with bone structure. Independent of trabecular thickness, osteoporotic rod-like trabeculae showed decreases in Young's modulus, fracture load, yield strength, ultimate stress, work to failure and bending stiffness, along with significantly increased mean calcium content and calcium width. Non-osteoporotic trabeculae

  4. Fabrication of shape controlled Fe{sub 3}O{sub 4} nanostructure

    SciTech Connect

    Zheng, Y.Y.; Wang, X.B.; Shang, L.; Li, C.R.; Cui, C.; Dong, W.J.; Tang, W.H.; Chen, B.Y.

    2010-04-15

    Shape-controlled Fe{sub 3}O{sub 4} nanostructure has been successfully prepared using polyethylene glycol as template in a water system at room temperature. Different morphologies of Fe{sub 3}O{sub 4} nanostructures, including spherical, cubic, rod-like, and dendritic nanostructure, were obtained by carefully controlling the concentration of the Fe{sup 3+}, Fe{sup 2+}, and the molecular weight of the polyethylene glycol. Transmission Electron Microscope images, X-ray powder diffraction patterns and magnetic properties were used to characterize the final product. This easy procedure for Fe{sub 3}O{sub 4} nanostructure fabrication offers the possibility of a generalized approach to the production of single and complex nanocrystalline oxide with tunable morphology.

  5. Micrometer size rod formed by secondary self assembly of omeprazole with α- and β-cyclodextrins

    NASA Astrophysics Data System (ADS)

    Rajendiran, N.; Venkatesh, G.

    2015-02-01

    Self assembly of α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD) micro rods induced by omeprazole (OMP) were observed by SEM and TEM. OMP/CD inclusion complexes have formed the secondary self assembly micro meter size rod like structure. This structure was driven by the intermolecular hydrogen bonding as well as van der Waals forces. Both forces induced the ordered assembly and arrangement of OMP/CD inclusion complexes, whereas CD molecules acted as molecular bricks. The OMP/CD inclusion complexes primary assembled form individual nanorods and then secondary self aggregate nanorods were form a micro meter rod structure. The results indicate that inter-nanotubular hydrogen bonding plays a crucial role in the formation of the self assembled micro rods. The inclusion complexes were also characterized using FT-IR, DSC, powder XRD, 1H NMR, absorption, fluorescence, life time measurements and molecular modeling methods.

  6. Micrometer size rod formed by secondary self assembly of omeprazole with α- and β-cyclodextrins.

    PubMed

    Rajendiran, N; Venkatesh, G

    2015-02-25

    Self assembly of α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD) micro rods induced by omeprazole (OMP) were observed by SEM and TEM. OMP/CD inclusion complexes have formed the secondary self assembly micro meter size rod like structure. This structure was driven by the intermolecular hydrogen bonding as well as van der Waals forces. Both forces induced the ordered assembly and arrangement of OMP/CD inclusion complexes, whereas CD molecules acted as molecular bricks. The OMP/CD inclusion complexes primary assembled form individual nanorods and then secondary self aggregate nanorods were form a micro meter rod structure. The results indicate that inter-nanotubular hydrogen bonding plays a crucial role in the formation of the self assembled micro rods. The inclusion complexes were also characterized using FT-IR, DSC, powder XRD, (1)H NMR, absorption, fluorescence, life time measurements and molecular modeling methods.

  7. Statistical foundations of liquid-crystal theory

    PubMed Central

    Seguin, Brian; Fried, Eliot

    2013-01-01

    We develop a mechanical theory for systems of rod-like particles. Central to our approach is the assumption that the external power expenditure for any subsystem of rods is independent of the underlying frame of reference. This assumption is used to derive the basic balance laws for forces and torques. By considering inertial forces on par with other forces, these laws hold relative to any frame of reference, inertial or noninertial. Finally, we introduce a simple set of constitutive relations to govern the interactions between rods and find restrictions necessary and sufficient for these laws to be consistent with thermodynamics. Our framework provides a foundation for a statistical mechanical derivation of the macroscopic balance laws governing liquid crystals. PMID:23772091

  8. The Landau-de Gennes free energy expansion of a melt of V-shaped polymer molecules.

    PubMed

    Aliev, M A; Ugolkova, E A; Kuzminyh, N Yu

    2016-08-28

    The phase behavior of a monodisperse melt of polymer molecules consisting of two rod-like segments joined at an angle α has been inspected within the Landau theory of phase transitions. The interactions between monomer units were assumed to be of the Maier-Saupe form. The Landau-de Gennes expansion of the free energy of the melt has been obtained up to the sixth order in powers of the nematic order parameter, the coefficients of this expansion have been calculated from the microscopic model of polymer molecule. The phase diagram contains the regions of stability of isotropic, prolate uniaxial, oblate uniaxial, and biaxial nematic phases. The isotropic-uniaxial nematic and uniaxial-biaxial nematic transitions are of the first and second order, respectively. We found two Landau points in the phase diagram at which continuous transition from biaxial nematic state to isotropic phase occurs.

  9. M23C6 carbides and Cr2N nitrides in aged duplex stainless steel: A SEM, TEM and FIB tomography investigation.

    PubMed

    Maetz, J-Y; Douillard, T; Cazottes, S; Verdu, C; Kléber, X

    2016-05-01

    The precipitation evolution during ageing of a 2101 lean duplex stainless steel was investigated, revealing that the precipitate type and morphology depends on the nature of the grain boundary. Triangular M23C6 carbides precipitate only at γ/δ interfaces and rod-like Cr2N nitrides precipitate at both γ/δ and δ/δ interfaces. After 15min of ageing, the M23C6 size no longer evolves, whereas that of the Cr2N continues to evolve. For Cr2N, the morphology is maintained at γ/δ interfaces, whereas percolation occurs to form a continuous layer at δ/δ interfaces. By combining 2D and 3D characterisation at the nanoscale using transmission electron microscopy (TEM) and focused ion beam (FIB) tomography, a complete description of the precipitation evolution was obtained, including the composition, crystallographic structure, orientation relationship with the matrix phases, location, morphology, size and volume fraction. PMID:26925831

  10. The Landau-de Gennes free energy expansion of a melt of V-shaped polymer molecules.

    PubMed

    Aliev, M A; Ugolkova, E A; Kuzminyh, N Yu

    2016-08-28

    The phase behavior of a monodisperse melt of polymer molecules consisting of two rod-like segments joined at an angle α has been inspected within the Landau theory of phase transitions. The interactions between monomer units were assumed to be of the Maier-Saupe form. The Landau-de Gennes expansion of the free energy of the melt has been obtained up to the sixth order in powers of the nematic order parameter, the coefficients of this expansion have been calculated from the microscopic model of polymer molecule. The phase diagram contains the regions of stability of isotropic, prolate uniaxial, oblate uniaxial, and biaxial nematic phases. The isotropic-uniaxial nematic and uniaxial-biaxial nematic transitions are of the first and second order, respectively. We found two Landau points in the phase diagram at which continuous transition from biaxial nematic state to isotropic phase occurs. PMID:27586947

  11. Effect of Minor Zn Additions on the Mechanical and Corrosion Properties of Solution-Treated AM60-2%RE Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Liu, Z. L.; Liu, Y.; Liu, X. Q.; Wang, M. M.

    2016-07-01

    The microstructure, mechanical properties, and corrosion behaviors of solution-treated AM60-2%RE magnesium alloy containing 0.2-0.8% wt.% Zn were investigated. With the increase of Zn, the volume fraction of dispersed rod-like Al4RE and granular-like Al11RE3 phases of solution-treated AM60-2%RE + x%Zn increased, which improved the mechanical properties by dispersion strengthening. With increasing Zn content, the corrosion current density decreased, and the corrosion potential and electrochemical impedance of the alloys increased, and the corrosion resistance of solution-treated AM60-2%RE + x%Zn was improved. With the increase of Zn content, the leaf-like corrosion products of the alloy became smaller and more compact, and the content of Zn, Al, Ce, and La in corrosion products increased, which was beneficial to inhibit the corrosion progress.

  12. A new species of Strongylacron (Copepoda, Harpacticoida, Cletodidae) from intertidal mudflats in the Korean peninsula

    PubMed Central

    Kim, Jong Guk; Jung, Tae Won; Yoon, Seong Myeong

    2016-01-01

    Abstract A new species, Strongylacron glabrum sp. n. is described from intertidal mudflats in the Korean peninsula. The new species is assigned to the monospecific genus Strongylacron Gee & Huys, 1996 in accordance with the generic morphological features of the rostrum, antennary exopod, and thoracic legs. However, Strongylacron glabrum sp. n. is clearly distinguished from the type species, Strongylacron buchholtzi (Boeck, 1873), by the naked anterior margin of rostrum, the elongate exopod and endopodal lobe of female P5 approximately 3.5 and 2.7 times as long as width, respectively, and the presence of 8–10 rod-like projections on prosomites. The genus Strongylacron is first recorded from Korean waters by the present study.

  13. Effects of electric field on structures and dynamics in a two-dimensional dust dipole particle system

    NASA Astrophysics Data System (ADS)

    Hou, X. N.; Liu, Y. H.; Huang, F.; Jiang, S. Z.; Chen, Z. Y.; Zhang, R. Y.

    2016-09-01

    Effects of radial electric field on the structures and dynamics of dust dipoles are studied by molecular dynamics simulations. The dipoles' configuration and mean distance to the system center are used to illustrate the structures of the whole system. It is shown that the dipole particles can arrange themselves into ring-like structures in the absence of external electric field, which can gradually transform to vortex, and then to radial arrangement with the increase of the strength of electric field. The trajectories, mean square displacement, and the mean speed in radial and tangential directions of dipoles are investigated to depict the effects of the radial electric filed on the collective motion of dust dipolar particles, which are closely associated with the growth of dust particle, especially for the formation of rod-like and some other complex fractal dust particles.

  14. Simulation study of poled low-water ionomers with different architectures.

    PubMed

    Allahyarov, Elshad; Taylor, Philip L; Löwen, Hartmut

    2011-11-16

    The role of the ionomer architecture in the formation of ordered structures in poled membranes is investigated by molecular dynamics computer simulations. It is shown that the length of the sidechain L(s) controls both the areal density of cylindrical aggregates N(c) and the diameter of these cylinders in the poled membrane. The backbone segment length L(b) tunes the average diameter D(s) of cylindrical clusters and the average number of sulfonates N(s) in each cluster. A simple empirical formula is noted for the dependence of the number density of induced rod-like aggregates on the sidechain length L(s) within the parameter range considered in this study.

  15. A new species of Strongylacron (Copepoda, Harpacticoida, Cletodidae) from intertidal mudflats in the Korean peninsula.

    PubMed

    Kim, Jong Guk; Jung, Tae Won; Yoon, Seong Myeong

    2016-01-01

    A new species, Strongylacron glabrum sp. n. is described from intertidal mudflats in the Korean peninsula. The new species is assigned to the monospecific genus Strongylacron Gee & Huys, 1996 in accordance with the generic morphological features of the rostrum, antennary exopod, and thoracic legs. However, Strongylacron glabrum sp. n. is clearly distinguished from the type species, Strongylacron buchholtzi (Boeck, 1873), by the naked anterior margin of rostrum, the elongate exopod and endopodal lobe of female P5 approximately 3.5 and 2.7 times as long as width, respectively, and the presence of 8-10 rod-like projections on prosomites. The genus Strongylacron is first recorded from Korean waters by the present study. PMID:27667951

  16. Bismuth oxide thin films prepared by chemical bath deposition (CBD) method: annealing effect

    NASA Astrophysics Data System (ADS)

    Gujar, T. P.; Shinde, V. R.; Lokhande, C. D.; Mane, R. S.; Han, Sung-Hwan

    2005-08-01

    Bismuth oxide thin films have been deposited by room temperature chemical bath deposition (CBD) method and annealed at 623 K in air. They were characterized for structural, surface morphological, optical and electrical properties. From the X-ray diffraction patterns, it was found that after annealing a non-stoichiometric phase, Bi 2O 2.33, was removed and phase pure monoclinic Bi 2O 3 was obtained. Surface morphology of Bi 2O 3 film at lower magnification SEM showed rod-like structure, however, higher magnification showed a rectangular slice-like structure perpendicular to substrate, giving rise to microrods on the surface. The optical studies showed the decrease in band gap by 0.3 eV after annealing. The electrical resistivity variation showed semiconductor behavior and from thermoemf measurements, the electrical conductivity was found to be of n-type.

  17. Length-dependence of intramolecular electron transfer in σ-bonded rigid molecular rods: an ab initio molecular orbital study

    NASA Astrophysics Data System (ADS)

    Pati, Ranjit; Karna, Shashi P.

    2002-01-01

    The dependence of electron transfer (ET) coupling element, VAB, on the length of rigid-rod-like systems consisting of bicyclo[1.1.1]pentane (BCP), cubane (CUB), and bicyclo[2.2.2]octane (BCO) monomers, has been investigated with the use of ab initio Hartree-Fock (HF) method employing Marcus-Hush two-state (TS) model. The value of VAB decreases exponentially with increase in the number of the cage units of the σ-bonded molecules. The calculated decay constant, β, shows good agreement with previously reported data. For molecular length⩾15 Å, the value of VAB becomes negligibly small, suggesting complete suppression of the through bond direct tunneling contribution to ET process.

  18. Facile synthesis of SrCO3 nanostructures in methanol/water solution without additives

    PubMed Central

    2012-01-01

    Highly dispersive strontium carbonate (SrCO3) nanostructures with uniform dumbbell, ellipsoid, and rod-like morphologies were synthesized in methanol solution without any additives. These SrCO3 were characterized by X-ray diffraction, field emission scanning electron microscopy, and N2 adsorption-desorption. The results showed that the reaction temperature and the methanol/water ratio had important effects on the morphologies of SrCO3 particles. The dumbbell-like SrCO3 exhibited a Broader-Emmett-Teller surface area of 14.9 m2 g−1 and an average pore size of about 32 nm with narrow pore size distribution. The formation mechanism of the SrCO3 crystal was preliminary presented. PMID:22704526

  19. A magnetic protein biocompass

    NASA Astrophysics Data System (ADS)

    Qin, Siying; Yin, Hang; Yang, Celi; Dou, Yunfeng; Liu, Zhongmin; Zhang, Peng; Yu, He; Huang, Yulong; Feng, Jing; Hao, Junfeng; Hao, Jia; Deng, Lizong; Yan, Xiyun; Dong, Xiaoli; Zhao, Zhongxian; Jiang, Taijiao; Wang, Hong-Wei; Luo, Shu-Jin; Xie, Can

    2016-02-01

    The notion that animals can detect the Earth’s magnetic field was once ridiculed, but is now well established. Yet the biological nature of such magnetosensing phenomenon remains unknown. Here, we report a putative magnetic receptor (Drosophila CG8198, here named MagR) and a multimeric magnetosensing rod-like protein complex, identified by theoretical postulation and genome-wide screening, and validated with cellular, biochemical, structural and biophysical methods. The magnetosensing complex consists of the identified putative magnetoreceptor and known magnetoreception-related photoreceptor cryptochromes (Cry), has the attributes of both Cry- and iron-based systems, and exhibits spontaneous alignment in magnetic fields, including that of the Earth. Such a protein complex may form the basis of magnetoreception in animals, and may lead to applications across multiple fields.

  20. Observation of Precipitation Evolution in Fe-Ni-Mn-Ti-Al Maraging Steel by Atom Probe Tomography

    NASA Astrophysics Data System (ADS)

    Pereloma, E. V.; Stohr, R. A.; Miller, M. K.; Ringer, S. P.

    2009-12-01

    We describe the full decomposition sequence in an Fe-Ni-Mn-Ti-Al maraging steel during isothermal annealing at 550 °C. Following significant pre-precipitation clustering reactions within the supersaturated martensitic solid solution, (Ni,Fe)3Ti and (Ni,Fe)3(Al,Mn) precipitates eventually form after isothermal aging for ~60 seconds. The morphology of the (Ni,Fe)3Ti particles changes gradually during aging from predominantly plate-like to rod-like, and, importantly, Mn and Al were observed to segregate to these precipitate/matrix interfaces. The (Ni,Fe)3(Al,Mn) precipitates occurred at two main locations: uniformly within the matrix and at the periphery of the (Ni,Fe)3Ti particles. We relate this latter mode of precipitation to the Mn-Al segregation.

  1. Growth of well-defined ZnO microparticles with additives from aqueous solution

    SciTech Connect

    Li Ping; Wei Yu . E-mail: weiyu@mail.hebtu.edu.cn; Liu Hui; Wang Xinkui

    2005-03-15

    By heating Zn(OH){sub 2} precursor in aqueous solution to reflux temperature (101 deg. C), ZnO microparticles with a diversity of well-defined morphologies, including rod-like, nut-like, and rice-like samples, have been successfully synthesized. The shape of the crystallite depends critically on the additive added in the reaction solution. To further understand the effect of the additive on the formation process of ZnO crystallite, scanning electron microscopy analyses of the solid product and concentration measurements of zinc ion remaining in the solution have been made at regular intervals throughout the reaction with and without the addition of sodium dodecyl sulfate (SDS) and triethanolamine (TEA). Results show that SDS and TEA added in the solution remarkably lower the formation rate of ZnO crystallite.

  2. Growth of well-defined ZnO microparticles with additives from aqueous solution

    NASA Astrophysics Data System (ADS)

    Li, Ping; Wei, Yu; Liu, Hui; Wang, Xin-kui

    2005-03-01

    By heating Zn(OH) 2 precursor in aqueous solution to reflux temperature (101 °C), ZnO microparticles with a diversity of well-defined morphologies, including rod-like, nut-like, and rice-like samples, have been successfully synthesized. The shape of the crystallite depends critically on the additive added in the reaction solution. To further understand the effect of the additive on the formation process of ZnO crystallite, scanning electron microscopy analyses of the solid product and concentration measurements of zinc ion remaining in the solution have been made at regular intervals throughout the reaction with and without the addition of sodium dodecyl sulfate (SDS) and triethanolamine (TEA). Results show that SDS and TEA added in the solution remarkably lower the formation rate of ZnO crystallite.

  3. Dynamics of rod eutectic growth patterns in confined geometry

    NASA Astrophysics Data System (ADS)

    Şerefoǧlu, Melis; Bottin-Rousseau, S.; Akamatsu, S.; Faivre, G.

    2012-01-01

    The dynamics of rod-like eutectics are examined using a directional solidification setup, which allows real-time observation of the whole solidification front in specimens of transparent eutectic alloys -here, succinonitrile-(D)camphor. In steady-state, rod eutectic growth patterns consist of triangular arrays, more or less disturbed by topological defects. In the absence of strong convection and of crystallographic anisotropy, the long-time evolution of the pattern is dominated by "imperfections" of the system, such as misalignment of the temperature gradient, and finite-size. In this study, we present experimental results on the finite-size effects on rod eutectics and show that a rod to lamella transition takes place as a result of finite-size effect only, at a given alloy concentration.

  4. Switchable focus using a polymeric lenticular microlens array and a polarization rotator.

    PubMed

    Ren, Hongwen; Xu, Su; Liu, Yifan; Wu, Shin-Tson

    2013-04-01

    We demonstrate a flat polymeric lenticular microlens array using a mixture of rod-like diacrylate monomer and positive dielectric anisotropy nematic liquid crystal (LC). To create gradient refractive index profile in one microlens, we generate fringing fields from a planar top electrode and two striped bottom electrodes. After UV stabilization, the film is optically anisotropic and can stand alone. We then laminate this film on a 90° twisted-nematic LC cell, which works as a dynamic polarization rotator. The static polymeric lenticular lens exhibits focusing effect only to the extraordinary ray, but no optical effect to the ordinary ray. Such an integrated lens system offers several advantages, such as low voltage, fast response time, and temperature insensitivity, and can be used for switchable 2D/3D displays.

  5. Surfactant-assisted Nanocasting Route for Synthesis of Highly Ordered Mesoporous Graphitic Carbon and Its Application in CO2 Adsorption

    PubMed Central

    Wang, Yangang; Bai, Xia; Wang, Fei; Qin, Hengfei; Yin, Chaochuang; Kang, Shifei; Li, Xi; Zuo, Yuanhui; Cui, Lifeng

    2016-01-01

    Highly ordered mesoporous graphitic carbon was synthesized from a simple surfactant-assisted nanocasting route, in which ordered mesoporous silica SBA-15 maintaining its triblock copolymer surfactant was used as a hard template and natural soybean oil (SBO) as a carbon precursor. The hydrophobic domain of the surfactant assisted SBO in infiltration into the template’s mesoporous channels. After the silica template was carbonized and removed, a higher yield of highly-ordered graphitic mesoporous carbon with rod-like morphology was obtained. Because of the improved structural ordering, the mesoporous carbon after amine modification could adsorb more CO2 compared with the amine-functionalized carbon prepared without the assistance of surfactant. PMID:27220563

  6. High lift function of the pteroid bone and forewing of pterosaurs

    PubMed Central

    Wilkinson, Matthew T; Unwin, David M; Ellington, Charles P

    2005-01-01

    The pteroid bone is a rod-like element found only in pterosaurs, the flying reptiles of the Mesozoic. It articulated at the wrist, and supported a membranous forewing in front of the inner part of the wing spar. The function of this bone, particularly its orientation, has been much debated. It is widely believed that it pointed towards the body, and that the forewing was relatively narrow. An alternative hypothesis states that it was directed forwards during flight, resulting in a much broader forewing that acted as a leading edge flap. We tested scale models in a wind tunnel to determine the aerodynamic consequences of these conflicting hypotheses, and found that performance is greatly improved if the pteroid is directed forwards: the lift : drag ratios are superior and the maximum lift is exceptionally high in comparison with conventional aerofoils. This high lift capability may have enabled even the largest pterosaurs to take off and land without difficulty. PMID:16519243

  7. Structural health monitoring using time reversal and cracked rod spectral element

    NASA Astrophysics Data System (ADS)

    Lucena, R. L.; Dos Santos, J. M. C.

    2016-10-01

    Structural health monitoring (SHM) has received substantial attention in the last decades. Damage detection methods based on dynamic analysis seem to be appropriate to detect large damages, but fail for small ones. Alternative methods use elastic wave propagation allowing a quick and long range test. In this paper, a new approach based on the combination of Time Reversal Method (TRM) and Spectral Element Method (SEM) is proposed to perform structural damage detection. The main novelty is to combine wave-based spectral element model together with time reversal signal processing. Although the methodology is evaluated by numerical simulation, this combination of numerical modeling and time reversal signal processing can be applied as an experimental approach to provide a useful tool for damage detection. Simulated examples of the damage detection method using rod-like structures are illustrated and the results discussed and compared with those from literature.

  8. Characterization of a trimeric MPER containing HIV-1 gp41 antigen

    SciTech Connect

    Hinz, Andreas; Schoehn, Guy; Quendler, Heribert; Hulsik, David Lutje; Stiegler, Gabi; Katinger, Hermann; Seaman, Michael S.; Montefiori, David; Weissenhorn, Winfried

    2009-08-01

    The membrane-proximal external region (MPER) of gp41 is considered as a prime target for the induction of neutralizing antibodies, since it contains the epitopes for three broadly neutralizing antibodies (2F5, 4E10 and Z13). Here we present a novel gp41 construct (HA-gp41) comprising gp41 HR2 and MPER fused to two triple-stranded coiled-coil domains at both ends. HA-gp41 is trimeric, has a high helical content in solution and forms rod-like structures as revealed by negative staining electron microscopy. Immunization of rabbits with HA-gp41 induced antibodies directed against MPER, which failed to exert significant neutralization capacity against envelopes from primary isolates. Thus trimerisation of MPER regions does not suffice to induce a potent neutralizing antibody response specific for conserved regions within gp41.

  9. Connection between the conformation and emission properties of poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] single molecules during thermal annealing

    NASA Astrophysics Data System (ADS)

    Ou, Jiemei; Yang, Yuzhao; Lin, Wensheng; Yuan, Zhongke; Gan, Lin; Lin, Xiaofeng; Chen, Xudong; Chen, Yujie

    2015-03-01

    We investigated the transitions of conformations and their effects on emission properties of poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) single molecules in PMMA matrix during thermal annealing process. Total internal reflection fluorescence microscopy measurements reveal the transformation from collapsed conformations to extended, highly ordered rod-like structures of MEH-PPV single molecules during thermal annealing. The blue shifts in the ensemble single molecule PL spectra support our hypnosis. The transition occurs as the annealing temperature exceeds 100 °C, implying that an annealing temperature near the glass transition temperature Tg of matrix is ideal for the control and optimization of blend polymer films.

  10. Thermodynamic processes of si-interstitial clusters

    SciTech Connect

    Kim, J.; Birner, S.; Richie, D. A.; Voter, A. F.

    2001-01-01

    Structural and dynamical properties of silicon interstitial defects are extracted from extensive atomistic simulations using ab initio total energy calculations. With increasing number of interstitials, the stable defect shape evolves from compact to chain-like to rod-like. The rodlike {l_brace}311{r_brace} defect, formed from (011) interstitial chains, is stabilized as it grows, elongating in the chain direction. We utilize new accelerated dynamics algorithms based on the parallel-replica method and reliable empirical potentials to efficiently explore large configurational space involving many degrees of freedom. We evaluate the empirical potentials that have been widely used for bulk silicon in light of the energetic and structural properties of interstitial defects.

  11. Attachment limited versus diffusion limited nucleation of organic molecules: Hexaphenyl on sputter-modified mica.

    PubMed

    Tumbek, L; Winkler, A

    2012-08-01

    The nucleation and growth of organic molecules is usually discussed in the framework of diffusion limited aggregation (DLA). In this letter we demonstrate for the rod-like organic molecules hexaphenyl (6P) on sputter-modified mica, that under specific experimental conditions the nucleation has to be described by attachment limited aggregation (ALA). The crucial parameter for the growth mode is the roughness of the substrate surface, as induced by ion sputtering. With decreasing surface roughness the diffusion probability of the molecules increases and the growth mode changes from DLA to ALA. This was derived from the deposition rate dependence of the island density. A critical size of i = 7 molecules was determined for the nucleation of 6P on a moderately sputtered mica surface. PMID:23470898

  12. Attachment limited versus diffusion limited nucleation of organic molecules: Hexaphenyl on sputter-modified mica

    NASA Astrophysics Data System (ADS)

    Tumbek, L.; Winkler, A.

    2012-08-01

    The nucleation and growth of organic molecules is usually discussed in the framework of diffusion limited aggregation (DLA). In this letter we demonstrate for the rod-like organic molecules hexaphenyl (6P) on sputter-modified mica, that under specific experimental conditions the nucleation has to be described by attachment limited aggregation (ALA). The crucial parameter for the growth mode is the roughness of the substrate surface, as induced by ion sputtering. With decreasing surface roughness the diffusion probability of the molecules increases and the growth mode changes from DLA to ALA. This was derived from the deposition rate dependence of the island density. A critical size of i = 7 molecules was determined for the nucleation of 6P on a moderately sputtered mica surface.

  13. Nematic twist-bend phase with nanoscale modulation of molecular orientation

    PubMed Central

    Borshch, V.; Kim, Y.-K.; Xiang, J.; Gao, M; Jákli, A; Panov, V. P.; Vij, J. K.; Imrie, C. T.; Tamba, M. G.; Mehl, G. H.; Lavrentovich, O. D.

    2013-01-01

    A state of matter in which molecules show a long-range orientational order and no positional order is called a nematic liquid crystal. The best known and most widely used (for example, in modern displays) is the uniaxial nematic, with the rod-like molecules aligned along a single axis, called the director. When the molecules are chiral, the director twists in space, drawing a right-angle helicoid and remaining perpendicular to the helix axis; the structure is called a chiral nematic. Here using transmission electron and optical microscopy, we experimentally demonstrate a new nematic order, formed by achiral molecules, in which the director follows an oblique helicoid, maintaining a constant oblique angle with the helix axis and experiencing twist and bend. The oblique helicoids have a nanoscale pitch. The new twist-bend nematic represents a structural link between the uniaxial nematic (no tilt) and a chiral nematic (helicoids with right-angle tilt). PMID:24189583

  14. Morphological Control and Characterization of Monodispersed Ceria Particles

    SciTech Connect

    Minamidate, Y.; Yin, S.; Devaraju, M. K.; Sato, T.

    2010-11-24

    The morphological control of cerium oxide particles was carried out by a homogeneous precipitation followed by calcination in air at 400 deg. C. The effects of pre-aging temperature, aging time and precipitation reagents on the morphologies of final products were investigated. When urea was used as a precipitation reagent, monodispersed spherical and flake-like cerium carbonate hydroxide precursor was precipitated in the solution at 90 deg. C for 2 h after pre-aging at 25 deg. C - 50 deg. C for 24-72 h. On the other hand, monodispersed nanosize rod-like cerium hydroxide particles were obtained using triethanolamine as precipitation reagent. Ceria particles with the same morphologies and slightly smaller particle size than those of as-prepared cerium precursor could be obtained after calcination in air at 400 deg. C. Physical-chemical characteristics of the monodispersed cerium oxide particles were evaluated.

  15. Orientational fluctuations of amorphous nematogenic solids

    NASA Astrophysics Data System (ADS)

    Ye, Fangfu; Lu, Bing; Goldbart, Paul

    2012-02-01

    Amorphous nematogenic solids (ANS) are media comprising rod-like nematogens that have been randomly linked to form elastically deformable macroscopic networks. Classes of ANS include chemical nematogen gels (i.e., networks of small molecules) and liquid crystalline elastomers (built from crosslinked nematogen-containing macromolecules), as well as biophysical networks such as those composed of actin filaments. We use a method inspired by the cavity approach to construct a replica free energy for these random systems, and investigate the correlations of the thermal fluctuations of the orientational alignment of the nematogens at spatially separated points. We identify two qualitatively distinct regimes: (a) a weakly localized regime, in which the correlations decay exponentially with separation; and (b) a strongly localized regime, characterized by correlations that also decay but oscillate as they do.

  16. Method for preparing metallated filament-wound structures

    DOEpatents

    Peterson, George R.

    1979-01-01

    Metallated graphite filament-wound structures are prepared by coating a continuous multi-filament carbon yarn with a metal carbide, impregnating the carbide coated yarn with a polymerizable carbon precursor, winding the resulting filament about a mandrel, partially curing the impregnation in air, subjecting the wound composite to heat and pressure to cure the carbon precursor, and thereafter heating the composite in a sizing die at a pressure loading of at least 1000 psi for graphitizing the carbonaceous material in the composite. The carbide in the composite coalesces into rod-like shapes which are disposed in an end-to-end relationship parallel with the filaments to provide resistance to erosion in abrasive laden atmospheres.

  17. Bismuth sulfide nanoflakes and nanorods as high performance photodetectors and photoelectrochemical cells

    NASA Astrophysics Data System (ADS)

    Chao, Junfeng; Xing, Shumin; Zhao, Yanchun; Gao, Suling; Song, Qinghua; Guo, Lixia; Wang, Di; Zhang, Tingliang

    2016-11-01

    Flake-like and rod-like bismuth sulfide nanostructures were synthesized via a facile polyol refluxing process. The rigid photodetectors based on both nanomaterials have the features of linear photocurrent characteristics and good sensitivity. Especially, the rigid bismuth sulfide nanoflakes photodetector has fast response time of 0.5 s and recovery time of 0.7 s. The flexible photodetectors were then fabricated on PET substrate, and this caused both the response time and the recovery time to increase by a factor of ∼2.5. Moreover, the photoelectrochemical (PEC) devices exhibited photosensitivity with the features of rapid response and recovery time, high on/off ratio and stable switching cycle performance. Our results imply that the two types of bismuth sulfide nanomaterials are prospective candidates for next generation photodetectors and optoelectronic switches.

  18. The avian intervertebral disc arises from rostral sclerotome and lacks a nucleus pulposus: Implications for evolution of the vertebrate disc

    PubMed Central

    Bruggeman, Bradley J.; Maier, Jennifer A.; Mohiuddin, Yasmin S.; Powers, Rae; Lo, YinTing; Guimarães-Camboa, Nuno; Evans, Sylvia M.; Harfe, Brian D.

    2012-01-01

    Deterioration of the intervertebral discs is an unfortunate consequence of aging. The intervertebral disc in mammals is composed of three parts: a jelly-like center called the nucleus pulposus, the cartilaginous annulus fibrosus and anterior and posterior endplates that attach the discs to vertebrae. In order to understand the origin of the disc, we have investigated the intervertebral region of chickens. Surprisingly, our comparison of mouse and chicken discs revealed that chicken discs lack nuclei pulposi. In addition, the notochord, which in mice forms nuclei pulposi, was found to persist as a rod-like structure and express Shh throughout chicken embryogenesis. Our fate mapping data indicates that cells originating from the rostral half of each somite are responsible for forming the avian disc while cells in the caudal region of each somite form vertebrae. A histological analysis of mammalian and non-mammalian organisms suggests that nuclei pulposi are only present in mammals. PMID:22354863

  19. A new species of Strongylacron (Copepoda, Harpacticoida, Cletodidae) from intertidal mudflats in the Korean peninsula

    PubMed Central

    Kim, Jong Guk; Jung, Tae Won; Yoon, Seong Myeong

    2016-01-01

    Abstract A new species, Strongylacron glabrum sp. n. is described from intertidal mudflats in the Korean peninsula. The new species is assigned to the monospecific genus Strongylacron Gee & Huys, 1996 in accordance with the generic morphological features of the rostrum, antennary exopod, and thoracic legs. However, Strongylacron glabrum sp. n. is clearly distinguished from the type species, Strongylacron buchholtzi (Boeck, 1873), by the naked anterior margin of rostrum, the elongate exopod and endopodal lobe of female P5 approximately 3.5 and 2.7 times as long as width, respectively, and the presence of 8–10 rod-like projections on prosomites. The genus Strongylacron is first recorded from Korean waters by the present study. PMID:27667951

  20. Low-workfunction photocathodes based on acetylide compounds

    DOEpatents

    Terdik, Joseph Z; Spentzouris, Linda; Terry, Jr., Jeffrey H; Harkay, Katherine C; Nemeth, Karoly; Srajer, George

    2014-05-20

    A low-workfunction photocathode includes a photoemissive material employed as a coating on the photocathode. The photoemissive material includes A.sub.nMC.sub.2, where A is a first metal element, the first element is an alkali metal, an alkali-earth element or the element Al; n is an integer that is 0, 1, 2, 3 or 4; M is a second metal element, the second metal element is a transition metal or a metal stand-in; and C.sub.2 is the acetylide ion C.sub.2.sup.2-. The photoemissive material includes a crystalline structure or non-crystalline structure of rod-like or curvy 1-dimensional polymeric substructures with MC.sub.2 repeating units embedded in a matrix of A.

  1. Collective motion of microswimmers in viscoelastic fluids

    NASA Astrophysics Data System (ADS)

    Li, Gaojin; Ardekani, Arezoo

    2015-11-01

    The dynamics of suspension of self-propelled microorganisms show fascinating hydrodynamic phenomena, such as, large scale swarming motion, locally correlated motion, enhanced particle diffusion, and enhanced fluid mixing. Even though many studies have been conducted in a Newtonian fluid, the collective motion of microorganisms in non-Newtonian fluids is less understood. The non-Newtonian fluid rheological properties, such as viscoelasticity and shear-dependent viscosity in saliva, mucus and biofilm, significantly affect the swimming properties and hydrodynamic interaction of microorganisms. In this work, we use direct numerical simulation to investigate the collective motion of rod-like swimmers in viscoelastic fluids. Two swimming types, pusher and puller, are investigated. The background viscoelastic fluid is modeled using an Oldroyd-B constitutive equation. This work is supported by NSF CBET-1445955 and Indiana CTSI TR001108.

  2. Mineralized deposits in pulps of incompletely developed permanent monkey incisors after pulpotomy with tungsten carbide fissure burs.

    PubMed

    Heide, S; Koppang, H S

    1994-06-01

    The exposed pulp of incompletely developed permanent incisors of nine monkeys were treated with partial pulpotomy with tungsten carbide fissure burs on an air turbine equipment. The pulps were capped with calcium hydroxide (Dycal) followed by insertion of conventional amalgam. The results were studied by conventional light microscopy after 1 and 6 months. Rod-like mineralized pulpal deposits were seen in five of the nine animals, in 9 out of 67 teeth, evenly distributed at the two observation times. Also the lengths of the deposits appeared similar, while the thickness had increased markedly after 6 months. After 1 month the presence of a central vessel lumen was observed in the deposits. The results seemed to indicate that the mechanism of formation was an initial pathologic mineralization of the vessel wall, and a growth of the deposits by the elaboration of fibrous, atubular dentin on to the outside of this wall.

  3. Bionanowhiskers from jute: preparation and characterization.

    PubMed

    Kasyapi, Nibedita; Chaudhary, Vidhi; Bhowmick, Anil K

    2013-02-15

    Bionanowhiskers were extracted from jute by acid hydrolysis. At first cellulose microfibrils were formed by alkali treatment. Addition of an acid to the microfibrils triggered the formation of cellulose nanowhiskers. These were characterized by using different techniques viz. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry (TGA), scanning electron microscopy (SEM) and atomic force microscopy (AFM). In the FTIR study, absence of peak at 1738 cm(-1) indicated removal of hemicellulose. The rod like morphology of the nanowhiskers (length - 550±100 nm, width - 77±30 nm) was observed after 1h of acid hydrolysis, whereas further increase in time resulted in triangular shape morphology. Acid hydrolysis increased crystallinity, but decreased the temperature corresponding to major degradation (T(max)) and onset of degradation (T(i)). These bionanowhiskers might be useful as reinforcing element in nanocomposites.

  4. Synthesis and conformation of 3,6-connected cyclohexadiene chains.

    PubMed

    Golling, Florian E; Koch, Amelie H R; Fytas, George; Müllen, Klaus

    2015-05-01

    3,6-Connected cyclohexadienes as precursors for polyphenylenes are synthesized and characterized by mass spectrometry and NMR spectroscopy. Pure fractions of trimers, hexamers, and nonamers are collected after separation of the product mixture by recycling GPC. The anticipated formation of rigid linear structures, due to the trans-configuration of the monomeric units, is supported by density functional theory and experimentally confirmed by dynamic light scattering from dilute solution at low scattering angles. The obtained translational diffusion coefficients are represented by rigid rod-like or prolate ellipsoid-like molecular shapes. The measurements of diffusion coefficients reveal a length-dependent ratio of 1:2:3 between the three oligomers, which directly correlates to the expected length extension from trimer to nonamer.

  5. Green self-assembly of zein-conjugated ZnO/Cd(OH)Cl hierarchical nanocomposites with high cytotoxicity and immune organs targeting.

    PubMed

    Wang, Hua-Jie; Cao, Ying; Wang, Cai-Feng; Cui, Shi-Zhong; Mi, Li-Wei; Miyazawa, Teruo

    2016-01-01

    Inorganic nanomedicines in the fight against cancer have progressed rapidly during recent years, with the synergistic advantages of multifunctional nanosystems compared to single component. Herein, a drug-combination opinion was introduced into "nanomedicine" based on the understanding of Trojan horse-anti-tumor mechanism of inorganic nano-medicines. Moreover, we reported the green and facile synthesis route of mono-dispersed and rod-like zein-conjugated ZnO/Cd(OH)Cl hierarchical nanocomposites. We found that the nanocomposites exhibited high-efficiency killing ability to tumor cells through lipid peroxidation mediated-membrane disintegration route. The safety studies in BALB/c mice didn't detect injection anaphylaxis, hemolysis and cytotoxicity. More interestingly, the nano-composites could specially accumulate in liver and kidney, which will be helpful for targeting cure to these regional cancers. PMID:27075504

  6. A facile hydrothermal approach to the synthesis of nanoscale rare earth hydroxides

    NASA Astrophysics Data System (ADS)

    Li, Chengyin; Liu, Hui; Yang, Jun

    2015-03-01

    Nanosized rare earth (RE) hydroxides including La(OH)3, Nd(OH)3, Pr(OH)3, Sm(OH)3, Gd(OH)3, and Er(OH)3 with rod-like morphology are fabricated via a convenient hydrothermal approach. This strategy calls for the first preparation of metal complexes between RE precursors and dodecylamine (DDA) in water/ethanol mixture at room temperature and subsequent thermal decomposition at elevated temperature. The influence of reaction time and water/ethanol volume ratios on the morphology and size of as-prepared RE hydroxides are investigated. CeO2 nanoparticles with spherical shape could be directly obtained by hydrothermal treatment of complexes formed between Ce precursors and DDA. In addition, by further calcinating the RE hydroxides at high temperature in air, RE oxide nanorods could be readily produced.

  7. Bound water in Kevlar 49 fibers

    SciTech Connect

    Garza, R.G.; Pruneda, C.O.; Morgan, R.J.

    1981-04-01

    From elemental analyses, thermogravimetric-mass spectroscopy studies and re-evaluation of previous water diffusion studies in Kevlar 49 fibers it is concluded that these fibers can contain two types of sorbed moisture. The fibers can absorb up to approx. 6 wt % loosely bound water with an activation energy for outgassing by desorption of 6 kcal/mole. This loosely bound water is a direct result of the presence of Na/sub 2/SO/sub 4/ impurities and the perturbations they induce on the packing of the rod-like poly (p-phenylene terephthalamide) macromolecules. Kevlar 49 fibers also inherently contain up to 30 wt % additional water which is tightly bound within the crystal lattice. This water exhibits an activation energy for outgassing by diffusion of approx. 40 kcal/mole and is only evolved from the fiber in significant quantities at t > 350/sup 0/C over a period of hours.

  8. Self-contained instrument for measuring subterranean tunnel wall deflection

    DOEpatents

    Rasmussen, Donald Edgar; Hof, Jr., Peter John

    1978-01-01

    The deflection of a subterranean tunnel is measured with a rod-like, self-contained instrument that is adapted to be inserted into a radially extending bore of the tunnel adjacent an end of the tunnel where the tunnel is being dug. One end of the instrument is anchored at the end of the bore remote from the tunnel wall, while the other end of the intrument is anchored adjacent the end of the wall in proximity to the tunnel wall. The two ends of the instrument are linearly displaceable relative to each other; the displacement is measured by a transducer means mounted on the instrument. Included in the instrument is a data storage means including a paper tape recorder periodically responsive to a parallel binary signal indicative of the measured displacement.

  9. Fluorescence probe studies of the effect of concentration on the state of aggregation of surfactants in aqueous solution

    SciTech Connect

    Lianos, P.; Zana, R.

    1981-11-01

    The results obtained in this study indicate that the aggregation numbers of a zwitterionic surfactant where the charges are well separated, and of various ionic surfactants, are independent of the surfactant concentration from the critical micelle concentration to ca. 0.3 M. In the absence of added salts these n values are consistent with the quasi-spherical oil drop model for micelles. The n values obtained for a zwitterionic surfactant where the 2 charges nearly neutralize each other and for a nonionic surfactant are large, and probably indicative of rod-like micelles. In addition the aggregation number for the nonionic surfactant has been found to increase with concentration, in the concentration range investigated. The values of the 14/13 ratio confirm that pyrene is solubilized preferentially in the micelle palisade layer rather than in the hydrophobic core. 41 references.

  10. Thermal behavior of nano cellulose doped polymer dispersed liquid crystal (PDLC)

    NASA Astrophysics Data System (ADS)

    Kashyap, Swati; Saxena, S. K.; Gupta, S. J.; Mahajan, Jyoti

    2016-05-01

    Nano cellulose or cellulose nanofibers (CNF) material is composed of Nano sized cellulose fibrils with a high aspect ratio and typical lateral dimensions are 20-50 nm. Its pseudo-plastic characteristics exhibit the property of certain gels or fluids (viscous) and over a period of time, becomes, Thixotropic. The ability of CNFs to go into a PDLC ultrasonically with a helical arrangement results in dried CNF films. The films thus acquire attractive thermal properties, creating possibilities for their use in various applications. In this presentation, we discuss the thermal behavior of Nano cellulose doped in PDLC that governs the formation of the desired helical structure. By comparison with the corresponding self-assembly processes of other rod-like nanoparticles, for example, carbon nanotubes particles, we outline in the present paper the variation in the number of mesogen phases in varying compositions of Nano Cellulose doped PDLCs.

  11. Double-twist cylinders in liquid crystalline cholesteric blue phases observed by transmission electron microscopy

    PubMed Central

    Tanaka, Shu; Yoshida, Hiroyuki; Kawata, Yuto; Kuwahara, Ryusuke; Nishi, Ryuji; Ozaki, Masanori

    2015-01-01

    Cholesteric blue phases are liquid crystalline phases in which the constituent rod-like molecules spontaneously form three-dimensional, helical structures. Despite theoretical predictions that they are composed of cylindrical substructures within which the liquid crystal molecules are doubly twisted, real space observation of the arrangement of such structures had not been performed. Through transmission electron microscopy of photopolymerized blue phases with controlled lattice plane orientations, we report real space observation and comparison of the lattice structures of blue phases I and II. The two systems show distinctly different contrasts, reflecting the theoretically predicted, body centred and simple cubic arrangement of the double-twist cylinders. Transmission electron microscopy also reveals different tendencies of the two blue phases to align on unidirectionally rubbed surfaces. We thus show that TEM observation of alignment-controlled, photopolymerized liquid crystals can be a powerful tool to investigate complex liquid crystalline order. PMID:26530779

  12. Double-twist cylinders in liquid crystalline cholesteric blue phases observed by transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Tanaka, Shu; Yoshida, Hiroyuki; Kawata, Yuto; Kuwahara, Ryusuke; Nishi, Ryuji; Ozaki, Masanori

    2015-11-01

    Cholesteric blue phases are liquid crystalline phases in which the constituent rod-like molecules spontaneously form three-dimensional, helical structures. Despite theoretical predictions that they are composed of cylindrical substructures within which the liquid crystal molecules are doubly twisted, real space observation of the arrangement of such structures had not been performed. Through transmission electron microscopy of photopolymerized blue phases with controlled lattice plane orientations, we report real space observation and comparison of the lattice structures of blue phases I and II. The two systems show distinctly different contrasts, reflecting the theoretically predicted, body centred and simple cubic arrangement of the double-twist cylinders. Transmission electron microscopy also reveals different tendencies of the two blue phases to align on unidirectionally rubbed surfaces. We thus show that TEM observation of alignment-controlled, photopolymerized liquid crystals can be a powerful tool to investigate complex liquid crystalline order.

  13. Active tensor magnetic gradiometer system final report for Project MM–1514

    USGS Publications Warehouse

    Smith, David V.; Phillips, Jeffrey D.; Hutton, S. Raymond

    2014-01-01

    An interactive computer simulation program, based on physical models of system sensors, platform geometry, Earth environment, and spheroidal magnetically-permeable targets, was developed to generate synthetic magnetic field data from a conceptual tensor magnetic gradiometer system equipped with an active primary field generator. The system sensors emulate the prototype tensor magnetic gradiometer system (TMGS) developed under a separate contract for unexploded ordnance (UXO) detection and classification. Time-series data from different simulation scenarios were analyzed to recover physical dimensions of the target source. Helbig-Euler simulations were run with rectangular and rod-like source bodies to determine whether such a system could separate the induced component of the magnetization from the remanent component for each target. This report concludes with an engineering assessment of a practical system design.

  14. Synthesis of pyrite FeS2 nanorods by simple hydrothermal method and its photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Morales-Gallardo, M. V.; Ayala, A. M.; Pal, Mou; Cortes Jacome, M. A.; Toledo Antonio, J. A.; Mathews, N. R.

    2016-09-01

    In this work, FeS2 nanorods were synthetized by hydrothermal method. The advantages of our process were the high yield, simplicity and reproducibility. The material was studied in detail using different experimental tools such as XRD, SEM, HRTEM, EDXS, XPS, Raman, and UV-vis reflectance. XRD pattern and Raman data revealed good crystalline quality for the as synthesized pyrite FeS2. SEM analysis displayed the rod-like morphologies of FeS2 which seemed to grow radially from a center giving a flower-like appearance. From TEM images the approximate length and diameter of nano-rods were determined as 275 and 15 nm respectively. The material showed excellent photocatalytic activity which was assessed from the degradation of the methlyene blue.

  15. Undulatory Swimming in Fluids with Polymer Networks

    NASA Astrophysics Data System (ADS)

    Gagnon, David; Shen, Xiaoning; Arratia, Paulo

    2013-11-01

    In this talk, we systematically investigate the motility behavior of the nematode Caenorhabditis elegans in polymeric solutions of varying concentration using tracking and velocimetry methods. As the polymer concentration is increased, the solution undergoes a transition from the semi-dilute to the concentrated regime, where these rod-like polymers entangle, align, and form networks. Remarkably, we find an enhancement in the nematode's swimming speed of approximately 65 percent in concentrated solutions compared to semi-dilute solutions. Using velocimetry methods, we show that the undulatory swimming motion of the nematode induces an anisotropic mechanical response in the fluid. This anisotropy, which arises from the fluid micro-structure, is responsible for the observed increase in swimming speed. This work was supported by NSF CAREER (CBET) 0954084.

  16. Undulatory swimming in fluids with polymer networks

    NASA Astrophysics Data System (ADS)

    Gagnon, D. A.; Shen, X. N.; Arratia, P. E.

    2013-10-01

    The motility behavior of the nematode Caenorhabditis elegans in polymeric solutions of varying concentrations is systematically investigated in experiments using tracking and velocimetry methods. As the polymer concentration is increased, the solution undergoes a transition from the semi-dilute to the concentrated regime, where these rod-like polymers entangle, align, and form networks. Remarkably, we find an enhancement in the nematode's swimming speed of approximately 65% in concentrated solutions compared to semi-dilute solutions. Using velocimetry methods, we show that the undulatory swimming motion of the nematode induces an anisotropic mechanical response in the fluid. This anisotropy, which arises from the fluid micro-structure, is responsible for the observed increase in swimming speed.

  17. Flexibility and rigidity of cross-linked Straight Fibrils under axial motion constraints.

    PubMed

    Nagy Kem, Gyula

    2016-09-01

    The Straight Fibrils are stiff rod-like filaments and play a significant role in cellular processes as structural stability and intracellular transport. Introducing a 3D mechanical model for the motion of braced cylindrical fibrils under axial motion constraint; we provide some mechanism and a graph theoretical model for fibril structures and give the characterization of the flexibility and the rigidity of this bar-and-joint spatial framework. The connectedness and the circuit of the bracing graph characterize the flexibility of these structures. In this paper, we focus on the kinematical properties of hierarchical levels of fibrils and evaluate the number of the bracing elements for the rigidity and its computational complexity. The presented model is a good characterization of the frameworks of bio-fibrils such as microtubules, cellulose, which inspired this work. PMID:27289214

  18. Green self-assembly of zein-conjugated ZnO/Cd(OH)Cl hierarchical nanocomposites with high cytotoxicity and immune organs targeting

    PubMed Central

    Wang, Hua-Jie; Cao, Ying; Wang, Cai-Feng; Cui, Shi-Zhong; Mi, Li-Wei; Miyazawa, Teruo

    2016-01-01

    Inorganic nanomedicines in the fight against cancer have progressed rapidly during recent years, with the synergistic advantages of multifunctional nanosystems compared to single component. Herein, a drug-combination opinion was introduced into “nanomedicine” based on the understanding of Trojan horse-anti-tumor mechanism of inorganic nano-medicines. Moreover, we reported the green and facile synthesis route of mono-dispersed and rod-like zein-conjugated ZnO/Cd(OH)Cl hierarchical nanocomposites. We found that the nanocomposites exhibited high-efficiency killing ability to tumor cells through lipid peroxidation mediated-membrane disintegration route. The safety studies in BALB/c mice didn’t detect injection anaphylaxis, hemolysis and cytotoxicity. More interestingly, the nano-composites could specially accumulate in liver and kidney, which will be helpful for targeting cure to these regional cancers. PMID:27075504

  19. Measuring the equation of state for a 2D colloidal membrane: A microfluidic approach to buffer exchange

    NASA Astrophysics Data System (ADS)

    Balchunas, Andrew; Cabanas, Rafael; Fraden, Seth; Dogic, Zvonimir

    Previous work has shown that monodisperse rod-like colloidal particles, such as a filamentous bacteriophage, self assemble into a 2D monolayer smectic in the presence of a non-adsorbing depleting polymer. These structures have the same functional form of bending rigidity and lateral compressibility as conventional lipid bi-layers, so we name the monolayer smectic a colloidal membrane. We have developed a microfluidic device such that the osmotic pressure acting on a colloidal membrane may be controlled via a full in situ buffer exchange. Rod density within individual colloidal membranes was measured as a function of osmotic pressure and a first order phase transition, from 2D fluid to 2D solid, was observed. kon and koff rates of rod to membrane binding were measured by lowering the osmotic pressure until membrane evaporation occurred.

  20. Revisiting Taylor Dispersion: Differential enhancement of rotational and translational diffusion under oscillatory shear

    NASA Astrophysics Data System (ADS)

    Leahy, Brian; Ong, Desmond; Cheng, Xiang; Cohen, Itai

    2013-03-01

    The idea of Taylor dispersion - enhancement of translational diffusion under shear - has found applications in fields from pharmacology to chemical engineering. Here, in a combination of experiment and simulations, we study the translational and rotational diffusion of colloidal dimers under triangle-wave oscillatory shear. We find that the rotational diffusion is enhanced, in addition to the enhanced translational diffusion. This ``rotational Taylor dispersion'' depends strongly on the strain rate (Peclet number), aspect ratio, and the shear strain, in contradistinction to translational Taylor dispersion in a shear flow, which depends only weakly on strain rate and aspect ratio. This separate tunability of translations and orientations promises important applications in mixing and self-assembly of solutions of anisometric colloids. We discuss the corresponding effect on the structure and rheology of denser suspensions of rod-like particles. B. L. acknowledges supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program.

  1. Influence of Flexibility and Dimensions of Nanocelluloses on the Flow Properties of Their Aqueous Dispersions.

    PubMed

    Tanaka, Reina; Saito, Tsuguyuki; Hondo, Hiromasa; Isogai, Akira

    2015-07-13

    We report that the intrinsic viscosity [η] of nanocellulose dispersions can be solely expressed as a function of the aspect ratio p of the nanocellulose. Both short rod-like nanocrystalline and long spaghetti-like nanofibrillated celluloses were prepared as dispersions in water. The influence of the flexibility and dimensions of the nanocelluloses on the flow properties of their dispersions was investigated by experimental and theoretical approaches using seven nanocellulose samples with different widths (2.6-14.4 nm) and aspect ratios (23-376). As the aspect ratio of a nanocellulose increases, it becomes more flexible, and its dispersion has higher viscosity. Irrespective of the flexibility and dimensions of these nanocelluloses, the relationship between [η] and p was ρ[η] = 0.15 × p(1.9), where ρ is the density of the nanocellulose.

  2. Controlling electrical percolation in multicomponent carbon nanotube dispersions

    NASA Astrophysics Data System (ADS)

    Kyrylyuk, Andriy V.; Hermant, Marie Claire; Schilling, Tanja; Klumperman, Bert; Koning, Cor E.; van der Schoot, Paul

    2011-06-01

    Carbon nanotube reinforced polymeric composites can have favourable electrical properties, which make them useful for applications such as flat-panel displays and photovoltaic devices. However, using aqueous dispersions to fabricate composites with specific physical properties requires that the processing of the nanotube dispersion be understood and controlled while in the liquid phase. Here, using a combination of experiment and theory, we study the electrical percolation of carbon nanotubes introduced into a polymer matrix, and show that the percolation threshold can be substantially lowered by adding small quantities of a conductive polymer latex. Mixing colloidal particles of different sizes and shapes (in this case, spherical latex particles and rod-like nanotubes) introduces competing length scales that can strongly influence the formation of the system-spanning networks that are needed to produce electrically conductive composites. Interplay between the different species in the dispersions leads to synergetic or antagonistic percolation, depending on the ease of charge transport between the various conductive components.

  3. Initial stages of organic film growth characterized by thermal desorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Winkler, Adolf

    2016-01-01

    In the wake of the increasing importance of organic electronics, a more in-depth understanding of the early stages of organic film growth is indispensable. In this review a survey of several rod-like and plate-like organic molecules (p-quaterphenyl, p-sexiphenyl, hexaazatriphenylene-hexacarbonitrile (HATCN), rubicene, indigo) deposited on various application relevant substrates (gold, silver, mica, silicon dioxide) is given. The focus is particularly put on the application of thermal desorption spectroscopy to shed light on the kinetics and energetics of the molecule-substrate interaction. While each adsorption system reveals a manifold of features that are specific for the individual system, one can draw some general statements on the early stages of organic film formation from the available datasets. Among the important issues in this context is the formation of wetting layers and the dewetting as a function of the substrate surface conditions, organic film thickness and temperature.

  4. The effect of surface charge and KNO 3 additive on the crystallization of potassium chloride

    NASA Astrophysics Data System (ADS)

    Abdullah Ceyhan, Ayhan; Nusret Bulutcu, A.

    2011-07-01

    In this study, crystal growth and dissolution rates of potassium chloride crystals in pure solution and in the presence of potassium nitrate were investigated in a stagnant type single crystal cell using an image analyzer system. Closely sized seed crystals were separated with respect to their surface potentials using an electrostatic separator and then growth and dissolution behavior of potassium chloride crystals having different surface charges were systematically measured in pure solution and at 10, 100 and 1000 ppm additive concentrations at around 20 °C. In high supersaturation levels, very thin but very long rod-like growth, growing perpendicular to the surface, were observed. This is considered to result from surface nucleation. A dead zone was detected and its width was a function of surface potential of seed crystals. It was determined that, potassium nitrate additive, which has a common ion with KCl leads to increase the surface potential but not to affect the growth behavior, significantly.

  5. Optical anisotropy of uniaxially drawn and silver-dispersed polyimide films

    NASA Astrophysics Data System (ADS)

    Sawada, Takashi; Ando, Shinji; Sasaki, Shigekuni

    1999-02-01

    Distinct anisotropy in optical transmittance in the visible and near-infrared region for uniaxially drawn and silver-dispersed polyimide films was observed. The films were prepared in a one-step operation that involves thermal curing and simultaneous uniaxial drawing of poly(amic acid) (PAA) films, which were made by dissolving silver nitrate in the PAA solution at a 1:4 mol ratio. The polyimide molecular chains with a rod-like structure were oriented along the drawing direction during curing, and this orientation accompanied the generation of silver nanoparticles with elongated shapes. An anisotropy in the optical transmittance of 5:1 was obtained for a 22-μm-thick film at 850 nm with transmittance of 68% perpendicular to the drawing direction. The optical and mechanical properties of this film were retained after annealing at 300 °C for 1 h.

  6. Microfluidic techniques for the study of self-assembly of soft materials

    NASA Astrophysics Data System (ADS)

    Aguade Cabanas, Rafael

    This research is an approach to the study of soft condensed matter where the use of new microfluidic technology plays a central role. Often, in the study of soft matter, the sample volumes are very small, of the order of nanoliters. Therefore to quantitatively measure the equilibrium or non-equilibrium phase behavior requires microfluidics. Presented here are (1) a new way of producing aqueous drops of order 1 nl volume, in oil, (2) a new fabrication protocol to make microfluidic devices out of epoxy glue, and (3) a new microfluidic flow cell to study colloidal self-assembly. Also presented here is a new kind of colloidal particle, consisting of single strands of DNA linked to the surface of fd virus. This new particle may serve as a liquid crystalline colloid with a temperature dependent tunable potential. The fabrication process is the first step in the study of the self-assembly of rod-like particles with a temperature dependent potential.

  7. Pseudo-Casimir forces in nematics with disorders in the bulk.

    PubMed

    Karimi Pour Haddadan, Fahimeh

    2016-10-12

    A nematic liquid-crystalline slab is considered in which some rod-like particles are randomly distributed. The particles are locally elongated either homeotropic or planar with respect to the confining substrates of the cell. We consider thermal fluctuations of a nematic director which is aligned perpendicular to the confining substrates due to strong homeotropic anchoring at the substrates. The resulting fluctuation-induced force across the cell is analyzed for an annealed disorder in the anchoring of the nematic director at the dispersed mesoscopic particles. Within the saddle-point approximation to free energy of the system, the effect of the disorder is renormalization of the strength of the mean anchoring which is assumed to be homeotropic. By increasing the variance of the disorder, the modes become less massive and deviations from the mean behavior become larger, so that the disorder-free universal long-range attraction, due to the soft modes, is approached. PMID:27537426

  8. Role for primary cilia as flow detectors in the cardiovascular system.

    PubMed

    Van der Heiden, Kim; Egorova, Anastasia D; Poelmann, Robert E; Wentzel, Jolanda J; Hierck, Beerend P

    2011-01-01

    The cardiovascular system is exposed to biochemical and biomechanical signals. Various sensors for these signals have been described and they contribute to cardiovascular development, maintenance of vessel integrity during adult life, and to pathogenesis. In the past 10years, primary cilia, membrane-covered, rod-like cellular protrusions, were discovered on multiple cell types of the cardiovascular system. Primary cilia are sensory organelles involved in several key (developmental) signaling pathways and in chemo- and mechanosensing on a myriad of cell types. In the embryonic and adult cardiovascular system, they have been demonstrated to function as shear stress sensors on endothelial cells and could act as strain sensors on smooth muscle cells and cardiomyocytes and as chemosensors on fibroblasts. This review will cover their occurrence and elaborate on established and possible functions of primary cilia in the cardiovascular system.

  9. Preparation and characterization of CuI nanorods using Cu(dmg) 2 as precursor via water-in-oil (w/o) microemulsions

    NASA Astrophysics Data System (ADS)

    Li, Xue-Liang; Zhu, Xiao-Yun; Duan, Ti-Lan; Qian, Yi-Tai

    2006-06-01

    CuI nanorods have been firstly prepared by water-in-oil microemulsions using Cu(dmg) 2 as precursor at low temperature as low as 70 °C. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements show that the CuI nanorods are pure γ-phase crystals with diameters ranging from 50 to 80 nm and lengths up to 500 nm. UV-vis spectrum reveals that the nanorods exhibit a blue shift and possess of wider band gap energy. Electrochemical impedance spectroscopy (EIS) reveals the nanorods own larger grain boundary resistance. Results of comparative experiments indicate that the rod-like structure of Cu(dmg) 2 crystals leads the CuI crystals growing in one direction especially and the reverse microemulsion system plays a crucial role in making products symmetrical and uniform.

  10. Efficient thermolysis route to monodisperse Cu₂ZnSnS₄ nanocrystals with controlled shape and structure.

    PubMed

    Zhang, Xiaoyan; Guo, Guobiao; Ji, Cheng; Huang, Kai; Zha, Chenyang; Wang, Yifeng; Shen, Liming; Gupta, Arunava; Bao, Ningzhong

    2014-01-01

    Monodisperse Cu2ZnSnS4 (CZTS) nanocrystals with tunable shape, crystalline phase, and composition are synthesized by efficient thermolysis of a single source precursor of mixed metal-oleate complexes in hot organic solvents with dissolved sulfur sources. Suitable tuning of the synthetic conditions and the Cu/(Zn + Sn) ratio of the precursor has enabled precise control of the crystalline phase in the form of kesterite, or a newly observed wurtzite structure. Nanocrystals with morphology in the form of spherical, rice-like, or rod-like shapes are obtained over a wide range of compositions (0.5 ≤ Cu/(Zn + Sn) ≤ 1.2). Both the final products and intermediates for each shape exhibit consistent composition and structure, indicating homogenous nucleation and growth of single-phase nanocrystals. Thin films prepared from colloidal nanocrystal suspensions display interesting shape-dependent photoresponse behavior under white light illumination from a solar simulator. PMID:24866987

  11. Phase Transformation Behavior at Low Temperature in Hydrothermal Treatment of Stable and Unstable Titania Sol

    PubMed

    So; Park; Kim; Moon

    1997-07-15

    Nanosize titania sol was prepared from titanium tetraisopropoxide (TTIP) and conditions for the formation of stable sol were identified. As the H+/TTIP mole ratio decreased and H2O/TTIP mole ratio increased, stable sol was likely to be formed. The size and crystallinity remained unchanged after hydrothermal treatment of the stable sol at between 160 and 240°C. However, hydrothermal treatment of unstable sol produced rod-like particles and crystallinity of particles was changed from anatase to rutile. This difference in phase transformation at low hydrothermal treatment temperature was likely to be caused by the fact that stable sol remained to be stable even after hydrothermal treatment, while unstable sol had a tendency to be aggregated. PMID:9268523

  12. DNA-Grafted Supramolecular Polymers: Helical Ribbon Structures Formed by Self-Assembly of Pyrene-DNA Chimeric Oligomers.

    PubMed

    Vyborna, Yuliia; Vybornyi, Mykhailo; Rudnev, Alexander V; Häner, Robert

    2015-06-26

    The controlled arraying of DNA strands on adaptive polymeric platforms remains a challenge. Here, the noncovalent synthesis of DNA-grafted supramolecular polymers from short chimeric oligomers is presented. The oligomers are composed of an oligopyrenotide strand attached to the 5'-end of an oligodeoxynucleotide. The supramolecular polymerization of these oligomers in an aqueous medium leads to the formation of one-dimensional (1D) helical ribbon structures. Atomic force and transmission electron microscopy show rod-like polymers of several hundred nanometers in length. DNA-grafted polymers of the type described herein will serve as models for the development of structurally and functionally diverse supramolecular platforms with applications in materials science and diagnostics.

  13. One-pot size and interior-cavity controlled synthesis of ZnO hollow micro-/nano-structured spheres.

    PubMed

    Yu, Yifei; Wang, Xi; Zhong, Yeteng; Zhang, Meng; Cao, Xinqiang; Zeng, Yi; Zheng, Jianyao; Ma, Ying; Yao, Jiannian

    2012-05-01

    In this work, ZnO hollow micro-/nano-structured microspheres were prepared via a one-pot solution route. The size and interior-cavity of these microspheres could be easily controlled by varying the precursor concentration. The hollow spherical assemblies were composed of short rod-like building units at low precursor concentration. When the precursor concentration increased, one-dimensional (1D) "pearl-chain-like" building units formed firstly and then self organized into hollow microspheres. The organization process and ripening of "pearl-chain-like" building units could be modulated by simply altering the reaction time. When tested in photocatalytic experiments, the hollow microspheres composed of loosely packed 1D "pearl-chain-like" building units showed higher activity than the densely packed ones. This method is very simple, mild, and may provide a new strategy to synthesize hierarchical self-assembled hollow structures.

  14. Structural constraints on the evolution of the collagen fibril: convergence on a 1014-residue COL domain.

    PubMed

    Slatter, David Anthony; Farndale, Richard William

    2015-05-01

    Type I collagen is the fundamental component of the extracellular matrix. Its α1 gene is the direct descendant of ancestral fibrillar collagen and contains 57 exons encoding the rod-like triple-helical COL domain. We trace the evolution of the COL domain from a primordial collagen 18 residues in length to its present 1014 residues, the limit of its possible length. In order to maintain and improve the essential structural features of collagen during evolution, exons can be added or extended only in permitted, non-random increments that preserve the position of spatially sensitive cross-linkage sites. Such sites cannot be maintained unless the twist of the triple helix is close to 30 amino acids per turn. Inspection of the gene structure of other long structural proteins, fibronectin and titin, suggests that their evolution might have been subject to similar constraints.

  15. Improved stoichiometry and photoanode efficiency of thermally evaporated CdS film with quantum dots as precursor.

    PubMed

    Fan, Libo; Wang, Peng; Guo, Qiuquan; Lei, Yan; Li, Ming; Han, Hongpei; Zhao, Haifeng; Yang, Dongluo; Zheng, Zhi; Yang, Jun

    2015-08-21

    Good stoichiometry of cadmium sulfide (CdS) film facilitates its application in photovoltaic devices; however, traditional thermal evaporation usually results in a Cd-deficient CdS film at a low-substrate temperature. In this study, Cd-rich CdS quantum dots (QDs) were synthesized by a facile co-precipitation method and used as the precursor to thermally evaporate CdS film on indium tin oxide-coated glass (ITO/glass). As a consequence, the stoichiometry of CdS film was greatly improved with atomic ratio of Cd to S restored to unity. More importantly, the newly developed CdS film, with its rod-like surface microstructure, acted as an efficient photoanode in a photoelectrochemical (PEC) cell. Its properties, including surface morphology and roughness, crystal structure, chemical composition, film thickness, energy-level structure and photosensitivity, are studied in detail. PMID:26221785

  16. Improved stoichiometry and photoanode efficiency of thermally evaporated CdS film with quantum dots as precursor

    NASA Astrophysics Data System (ADS)

    Fan, Libo; Wang, Peng; Guo, Qiuquan; Lei, Yan; Li, Ming; Han, Hongpei; Zhao, Haifeng; Yang, Dongluo; Zheng, Zhi; Yang, Jun

    2015-08-01

    Good stoichiometry of cadmium sulfide (CdS) film facilitates its application in photovoltaic devices; however, traditional thermal evaporation usually results in a Cd-deficient CdS film at a low-substrate temperature. In this study, Cd-rich CdS quantum dots (QDs) were synthesized by a facile co-precipitation method and used as the precursor to thermally evaporate CdS film on indium tin oxide-coated glass (ITO/glass). As a consequence, the stoichiometry of CdS film was greatly improved with atomic ratio of Cd to S restored to unity. More importantly, the newly developed CdS film, with its rod-like surface microstructure, acted as an efficient photoanode in a photoelectrochemical (PEC) cell. Its properties, including surface morphology and roughness, crystal structure, chemical composition, film thickness, energy-level structure and photosensitivity, are studied in detail.

  17. Morphological influence of cellulose nanoparticles (CNs) from cottonseed hulls on rheological properties of polyvinyl alcohol/CN suspensions.

    PubMed

    Zhou, Ling; He, Hui; Li, Mei-Chun; Song, Kunlin; Cheng, H N; Wu, Qinglin

    2016-11-20

    The present work describes the isolation of cellulose nanoparticles (CNs) with different morphologies and their influence on rheological properties of CN and CN-poly (vinyl alcohol) (PVA) suspensions. Cottonseed hulls were used for the first time to extract three types of CNs, including fibrous cellulose nanofibers, rod-like cellulose nanocrystals and spherical cellulose nanoparticles through mechanical and chemical methods. Rheology results showed that the rheological behavior of the CN suspensions was strongly dependent on CN concentration and particle morphology. For PVA/CN systems, concentration of PVA/CN suspension, morphology of CNs, and weight ratio of CN to PVA were three main factors that influenced their rheology behaviors. This research reveals the importance of CN morphology and composition concentration on the rheological properties of PVA/CN, providing new insight in preparing high performance hydrogels, fibers and films base on PVA/CN suspension systems. PMID:27561516

  18. Luminescent LaF3:Ce-doped organically modified nanoporous silica xerogels

    NASA Astrophysics Data System (ADS)

    Yao, Mingzhen; Hall, Ryan; Chen, Wei; Mohite, Dhairyashil P.; Leventis, Nicholas; Lu, Ning; Wang, Jinguo; Kim, Moon J.; Luo, Huiyang; Lu, Hongbing

    2013-01-01

    Organically modified silica compounds (ORMOSILs) were synthesized by a sol-gel method from amine-functionalized 3-aminopropyl triethoxylsilane and tetramethylorthosilicate and were doped in situ with LaF3:Ce nanoparticles, which in turn were prepared either in water or in ethanol. Doped ORMOSILs display strong photoluminescence either by UV or X-ray excitation and maintain good transparency up to a loading level of 15.66% w/w. The TEM observations demonstrate that ORMOSILs remain nanoporous with pore diameters in the 5-10 nm range. LaF3:Ce nanoparticles doped into the ORMOSILs are rod-like, 5 nm in diameter and 10-15 nm in length. Compression testing indicates that the nanocomposites have very good strength, without significant lateral dilatation and buckling under quasi-static compression. LaF3:Ce nanoparticle-doped ORMOSILs have potential for applications in radiation detection and solid state lighting.

  19. Bionanowhiskers from jute: preparation and characterization.

    PubMed

    Kasyapi, Nibedita; Chaudhary, Vidhi; Bhowmick, Anil K

    2013-02-15

    Bionanowhiskers were extracted from jute by acid hydrolysis. At first cellulose microfibrils were formed by alkali treatment. Addition of an acid to the microfibrils triggered the formation of cellulose nanowhiskers. These were characterized by using different techniques viz. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry (TGA), scanning electron microscopy (SEM) and atomic force microscopy (AFM). In the FTIR study, absence of peak at 1738 cm(-1) indicated removal of hemicellulose. The rod like morphology of the nanowhiskers (length - 550±100 nm, width - 77±30 nm) was observed after 1h of acid hydrolysis, whereas further increase in time resulted in triangular shape morphology. Acid hydrolysis increased crystallinity, but decreased the temperature corresponding to major degradation (T(max)) and onset of degradation (T(i)). These bionanowhiskers might be useful as reinforcing element in nanocomposites. PMID:23399136

  20. Filamentous Phages As a Model System in Soft Matter Physics.

    PubMed

    Dogic, Zvonimir

    2016-01-01

    Filamentous phages have unique physical properties, such as uniform particle lengths, that are not found in other model systems of rod-like colloidal particles. Consequently, suspensions of such phages provided powerful model systems that have advanced our understanding of soft matter physics in general and liquid crystals in particular. We described some of these advances. In particular we briefly summarize how suspensions of filamentous phages have provided valuable insight into the field of colloidal liquid crystals. We also describe recent experiments on filamentous phages that have elucidated a robust pathway for assembly of 2D membrane-like materials. Finally, we outline unique structural properties of filamentous phages that have so far remained largely unexplored yet have the potential to further advance soft matter physics and material science. PMID:27446051

  1. Recessive RYR1 mutations in a patient with severe congenital nemaline myopathy with ophthalomoplegia identified through massively parallel sequencing.

    PubMed

    Kondo, Eri; Nishimura, Takafumi; Kosho, Tomoki; Inaba, Yuji; Mitsuhashi, Satomi; Ishida, Takefumi; Baba, Atsushi; Koike, Kenichi; Nishino, Ichizo; Nonaka, Ikuya; Furukawa, Toru; Saito, Kayoko

    2012-04-01

    Nemaline myopathy (NM) is a group of congenital myopathies, characterized by the presence of distinct rod-like inclusions "nemaline bodies" in the sarcoplasm of skeletal muscle fibers. To date, ACTA1, NEB, TPM3, TPM2, TNNT1, and CFL2 have been found to cause NM. We have identified recessive RYR1 mutations in a patient with severe congenital NM, through high-throughput screening of congenital myopathy/muscular dystrophy-related genes using massively parallel sequencing with target gene capture. The patient manifested fetal akinesia, neonatal severe hypotonia with muscle weakness, respiratory insufficiency, swallowing disturbance, and ophthalomoplegia. Skeletal muscle histology demonstrated nemaline bodies and small type 1 fibers, but without central cores or minicores. Congenital myopathies, a molecularly, histopathologically, and clinically heterogeneous group of disorders are considered to be a good candidate for massively parallel sequencing. PMID:22407809

  2. Helical polyurethane@attapulgite nanocomposite: Preparation, characterization and study of optical activity

    NASA Astrophysics Data System (ADS)

    Wang, Zhiqiang; Zhou, Yuming; Sun, Yanqing; Fan, Kai; Guo, Xingxing; Jiang, Xiaolei

    2009-08-01

    Helical polyurethane@attapulgite (BM-ATT) based on R-1,1'-binaphthyl-2',2-diol (R-BINOL) composite was prepared after the surface modification of attapulgite (ATT). BM-ATT was characterized by Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HTEM) and vibrational circular dichroism (VCD) spectroscopy. FT-IR and XRD analyses indicate that the helical polyurethane has been successfully grafted onto the surfaces of the modified ATT without destroying the original crystalline structure of ATT. BM-ATT exhibits the rod-like structure by SEM, TEM, and HTEM photographs. BM-ATT displays obvious Cotton effect for some absorbance in VCD spectrum, and its optical activity results from the singlehanded conformation of helical polyurethane.

  3. Layer-stacked tin disulfide nanorods in silica nanoreactors with improved lithium storage capabilities.

    PubMed

    Wu, Ping; Du, Ning; Zhang, Hui; Liu, Jie; Chang, Lantao; Wang, Lei; Yang, Deren; Jiang, Jian-Zhong

    2012-07-01

    A new structure of layered materials, layer-stacked nanorod, has been fabricated through an entirely new template-engaged structural transformation methodology. The formation of layer-stacked hexagonal tin disulfide (SnS(2)) nanorods has been demonstrated as an example by using tetragonal tin (Sn) nanorods as sacrificing templates and silica (SiO(2)) as nanoreactors. In addition, the structural transformation process probably involves the formation of orthorhombic tin sulfide (SnS) nanorods as an intermediate product. The rod-like morphology and single-crystal feature of the Sn templates are well preserved in both SnS(2) and SnS products due to the nanoscale confinement in silica. Owing to its unique structural characteristics, the SnS(2)-SiO(2) nanorod anode exhibits excellent capacity retention and improved rate capability, facilitating its application in lithium ion batteries with long cycle life and high power density.

  4. Highly ordered Pb(Zr₀.₅₂ Ti₀.₄₈)O₃ piezoelectric nanorod arrays.

    PubMed

    Yang, Su Chul; Sanghadasa, Mohan; Priya, Shashank

    2013-06-01

    One-dimensional (1D) piezoelectric nanostructures have attracted significant attention for a broad range of applications including optoelectronics, thermoelectrics, electrochemical and electromechanical converters. We demonstrate the synthesis of 1D nanostructures based upon Pb(Zr0.52Ti0.48)O3 (PZT) on conductive substrates via sol-gel template synthesis. The vertically aligned PZT nanostructures with heights around one micron were synthesized by vacuum infiltration of sol-gel precursors into highly ordered cylindrical pores of anodized aluminum oxide templates. The 1D nanostructures were developed on large scale platinized silicon wafers and exhibited dense rod-like structure with a uniform diameter of 90 nm and an aspect ratio of 10. Scanning probe microscopy conducted on individual nanorods demonstrated good electromechanical properties with a high piezoelectric magnitude of 41 pm V(-1). We believe that this study opens the possibility of developing high performance nanoscale piezoelectric sensors and transducers. PMID:23637024

  5. Identification and molecular properties of a 306 nucleotide viroid associated with apple dimple fruit disease.

    PubMed

    Di Serio, F; Aparicio, F; Alioto, D; Ragozzino, A; Flores, R

    1996-11-01

    A new viroid associated with an apple fruit disorder similar to, but more severe than, the dapple apple disease induced in some varieties by apple scar skin viroid (ASSVd) has been found. The new viroid, tentatively termed apple dimple fruit viroid (ADFVd), is a circular RNA of 306 nucleotides which adopts a quasi-rod-like conformation of minimum free energy. It contains the core nucleotides of the central conserved region (CCR) of the ASSVd group as well as the terminal conserved region (TCR) present in all members of the ASSVd and potato spindle tuber viroid (PSTVd) monophyletic groups. ADFVd has the highest sequence similarity with ASSVd and the 294 nucleotide citrus viroid CVd-IIIb sharing with the latter an almost identical left terminal domain. The right- and left-hand termini of ADFVd are formed by almost perfect duplications of sequences found in the CCR upper and lower strands, respectively, of PSTVd and closely related viroids.

  6. DNA-Grafted Supramolecular Polymers: Helical Ribbon Structures Formed by Self-Assembly of Pyrene-DNA Chimeric Oligomers.

    PubMed

    Vyborna, Yuliia; Vybornyi, Mykhailo; Rudnev, Alexander V; Häner, Robert

    2015-06-26

    The controlled arraying of DNA strands on adaptive polymeric platforms remains a challenge. Here, the noncovalent synthesis of DNA-grafted supramolecular polymers from short chimeric oligomers is presented. The oligomers are composed of an oligopyrenotide strand attached to the 5'-end of an oligodeoxynucleotide. The supramolecular polymerization of these oligomers in an aqueous medium leads to the formation of one-dimensional (1D) helical ribbon structures. Atomic force and transmission electron microscopy show rod-like polymers of several hundred nanometers in length. DNA-grafted polymers of the type described herein will serve as models for the development of structurally and functionally diverse supramolecular platforms with applications in materials science and diagnostics. PMID:25960306

  7. Anisotropic magnetic porous assemblies of oxide nanoparticles interconnected via silica bridges for catalytic application.

    PubMed

    Wacker, Josias B; Parashar, Virendra K; Gijs, Martin A M

    2011-04-19

    We report the microfluidic chip-based assembly of colloidal silanol-functionalized silica nanoparticles using monodisperse water-in-oil droplets as templates. The nanoparticles are linked via silica bridges, thereby forming superstructures that range from doublets to porous spherical or rod-like micro-objects. Adding magnetite nanoparticles to the colloid generates micro-objects that can be magnetically manipulated. We functionalized such magnetic porous assemblies with horseradish peroxidase and demonstrate the catalytic binding of fluorescent dye-labeled tyramide over the complete effective surface of the superstructure. Such nanoparticle assemblies permit easy manipulation and recovery after a heterogeneous catalytic process while providing a large surface similar to that of the individual nanoparticles. PMID:21417232

  8. The Landau-de Gennes free energy expansion of a melt of V-shaped polymer molecules

    NASA Astrophysics Data System (ADS)

    Aliev, M. A.; Ugolkova, E. A.; Kuzminyh, N. Yu.

    2016-08-01

    The phase behavior of a monodisperse melt of polymer molecules consisting of two rod-like segments joined at an angle α has been inspected within the Landau theory of phase transitions. The interactions between monomer units were assumed to be of the Maier-Saupe form. The Landau-de Gennes expansion of the free energy of the melt has been obtained up to the sixth order in powers of the nematic order parameter, the coefficients of this expansion have been calculated from the microscopic model of polymer molecule. The phase diagram contains the regions of stability of isotropic, prolate uniaxial, oblate uniaxial, and biaxial nematic phases. The isotropic-uniaxial nematic and uniaxial-biaxial nematic transitions are of the first and second order, respectively. We found two Landau points in the phase diagram at which continuous transition from biaxial nematic state to isotropic phase occurs.

  9. Synthesis of MoS(2) nanorods and their catalytic test in the HDS of dibenzothiophene.

    PubMed

    Albiter, M A; Huirache-Acuña, R; Paraguay-Delgado, F; Rico, J L; Alonso-Nuñez, G

    2006-07-28

    Partially sulfided nanostructures were synthesized by direct sulfurization of alpha-MoO(3) nanorods using a mixture of H(2)S/H(2), 15 vol%, at several temperatures (400, 500, 600, 700, and 800 degrees C). These materials were tested as catalysts in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and characterized by specific surface areas using the expression developed by Brunauer, Emmett, and Teller (BET equation), x-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The TEM images show a gradual evolution from a smooth surface to a rough material, presenting some type of holes all over the particles, but keeping their rod-like structure throughout sulfidation. The results of evaluating the catalysts in the HDS of DBT showed that the best temperature for sulfidation is 500 degrees C. In all samples, a higher selectivity for hydrogenation over sulfur removal was observed.

  10. The human RNA polymerase II interacts with the terminal stem-loop regions of the hepatitis delta virus RNA genome

    SciTech Connect

    Greco-Stewart, Valerie S.; Miron, Paul; Abrahem, Abrahem; Pelchat, Martin . E-mail: mpelchat@uottawa.ca

    2007-01-05

    The hepatitis delta virus (HDV) is an RNA virus that depends on DNA-dependent RNA polymerase (RNAP) for its transcription and replication. While it is generally accepted that RNAP II is involved in HDV replication, its interaction with HDV RNA requires confirmation. A monoclonal antibody specific to the carboxy terminal domain of the largest subunit of RNAP II was used to establish the association of RNAP II with both polarities of HDV RNA in HeLa cells. Co-immunoprecipitations using HeLa nuclear extract revealed that RNAP II interacts with HDV-derived RNAs at sites located within the terminal stem-loop domains of both polarities of HDV RNA. Analysis of these regions revealed a strong selection to maintain a rod-like conformation and demonstrated several conserved features. These results provide the first direct evidence of an association between human RNAP II and HDV RNA and suggest two transcription start sites on both polarities of HDV RNA.

  11. Primary breast amyloidosis presenting as microcalcifications only.

    PubMed

    Shim, Youngsub; Kim, Min Jung; Ryu, Han Suk; Park, Sung Hee

    2013-01-01

    Amyloidosis is a rare disease characterized by the formation of pathological protein deposits in organs or tissues. It is typically a systemic disease which can occur in a localized form. Amyloidosis of the breast is uncommon. Common mammographic findings of breast amyloidosis are multiple nodules with or without calcifications. We report a case of primary localized breast amyloidosis presenting suspicious microcalcifications on mammography without associated masses. Mammography in a 72-year-old woman displayed multiple, linearly distributed, irregular and rod-like calcifications in the subareolar area of the left breast. The patient underwent surgical excision under mammo-guided needle localization and the pathology was confirmed to be breast amyloidosis. PMID:24043964

  12. Primary Breast Amyloidosis Presenting as Microcalcifications Only

    PubMed Central

    Shim, Youngsub; Kim, Min Jung; Ryu, Han Suk

    2013-01-01

    Amyloidosis is a rare disease characterized by the formation of pathological protein deposits in organs or tissues. It is typically a systemic disease which can occur in a localized form. Amyloidosis of the breast is uncommon. Common mammographic findings of breast amyloidosis are multiple nodules with or without calcifications. We report a case of primary localized breast amyloidosis presenting suspicious microcalcifications on mammography without associated masses. Mammography in a 72-year-old woman displayed multiple, linearly distributed, irregular and rod-like calcifications in the subareolar area of the left breast. The patient underwent surgical excision under mammo-guided needle localization and the pathology was confirmed to be breast amyloidosis. PMID:24043964

  13. Highly ordered Pb(Zr₀.₅₂ Ti₀.₄₈)O₃ piezoelectric nanorod arrays.

    PubMed

    Yang, Su Chul; Sanghadasa, Mohan; Priya, Shashank

    2013-06-01

    One-dimensional (1D) piezoelectric nanostructures have attracted significant attention for a broad range of applications including optoelectronics, thermoelectrics, electrochemical and electromechanical converters. We demonstrate the synthesis of 1D nanostructures based upon Pb(Zr0.52Ti0.48)O3 (PZT) on conductive substrates via sol-gel template synthesis. The vertically aligned PZT nanostructures with heights around one micron were synthesized by vacuum infiltration of sol-gel precursors into highly ordered cylindrical pores of anodized aluminum oxide templates. The 1D nanostructures were developed on large scale platinized silicon wafers and exhibited dense rod-like structure with a uniform diameter of 90 nm and an aspect ratio of 10. Scanning probe microscopy conducted on individual nanorods demonstrated good electromechanical properties with a high piezoelectric magnitude of 41 pm V(-1). We believe that this study opens the possibility of developing high performance nanoscale piezoelectric sensors and transducers.

  14. Controlled synthesis of crystalline calcium carbonate aggregates with unusual morphologies involving the phase transformation from amorphous calcium carbonate

    SciTech Connect

    Tang Hua; Yu Jiaguo Zhao Xiufeng

    2009-04-02

    Peanut-shaped CaCO{sub 3} aggregates, featured of two dandelion-like heads built up from rod-like subunits, have been synthesized via a facile precipitation reaction between Na{sub 2}CO{sub 3} and CaCl{sub 2} at ambient temperature in the presence of magnesium ions and ethanol solvent. The as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and inductively coupled plasma atomic emission spectrometry (ICP-AES). The results show that a high magnesium concentration and ethanol solvent are necessary for the formation of the unusual peanut-like aggregates. In addition, a multistep phase transformation process from amorphous calcium carbonate (ACC) to a mixture of ACC and calcite and ultimately to calcite and aragonite was observed in the formation process of the unusual structures. A possible mechanism for the formation of the unusual peanut-shape aggregates has been proposed and discussed.

  15. Chitin nanocrystals for Pickering high internal phase emulsions.

    PubMed

    Perrin, Emilie; Bizot, Hervé; Cathala, Bernard; Capron, Isabelle

    2014-10-13

    Chitin is a natural polymer of glucosamine bearing N-acetyl groups. Chitin nanocrystals (ChiNCs), resulting from the acid hydrolysis of amorphous regions of chitin, are crystalline positively charged rod-like particles. ChiNCs show some interfacial properties and very efficiently stabilize oil/water interfaces, leading to the so-called Pickering emulsions. In accordance with the irreversible adsorption of particles, these Pickering emulsions proved stable over time, with constant emulsion volume for several months, even though natural creaming may occur. The emulsions produced are not clearly susceptible to ionic strength or pH in terms of average droplet diameter. However, when mixed with a large amount of oil, high internal phase emulsions (HIPE) containing up to 96% of internal phase are formed as a gel with a texture that can be modulated from soft to solid gel by adjusting concentration, pH, and ionic strength.

  16. Growth of gold nanoclusters and nanocrystals induced by lysozyme protein in thin film conformation

    NASA Astrophysics Data System (ADS)

    Bhowal, Ashim Chandra; Kundu, Sarathi

    2016-08-01

    Structures and growth behavior of gold nanoclusters and nanocrystals have been explored on thin films of globular protein lysozyme by using UV-vis and photoluminescence spectroscopy, X-ray diffraction (XRD) and atomic force microscopy (AFM). A simple and one-step environment friendly method has been used to grow nanocrystals on protein surface from HAuCl4 solution. It has been found that if different interaction times are provided between lysozyme films and HAuCl4 solution, then initially formed tiny gold nanoclusters on protein surface transform into nanocrystals with the passage of time. XRD analysis shows the formation of faced-centered cubic lattice along (1 1 1) crystalline direction and AFM images confirm the presence of circular, rod-like, triangular and hexagonal crystal structures. Langmuir-like growth behavior has been identified for both the gold nanoclusters and nanocrystals formation induced by the lysozyme films, however, nanocrystal growth is relatively slower than nanocluster.

  17. Tetracene confinement in L-methionine gratings on the Ag(111) surface

    NASA Astrophysics Data System (ADS)

    Urgel, José I.; Vijayaraghavan, S.; Ecija, D.; Auwärter, W.; Barth, J. V.

    2016-01-01

    We present a direct study on the positioning and mobility of tetracene molecules in self-assembled methionine nanogratings on the Ag(111) surface. Our scanning tunneling microscopy observations reveal the preferential arrangement of isolated tetracene units within substrate stripes framed by one-dimensional methionine supramolecular rows, under the influence of long-range indirect interactions. However, the orientational order of the rod-like tetracene species is induced by the epitaxial fit to the underlying surface atomic lattice; and preferential alignment with the tetracene axes along the direction of the methionine grating could not be achieved. In scanning tunneling microscopy measurements under perturbative conditions, we find a one-dimensional diffusion of the confined tetracene along the direction of the molecular axis and restricted by the methionine gratings for non-parallel orientations.

  18. Determination of collagen fibril structure and orientation in connective tissues by X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Wilkinson, S. J.; Hukins, D. W. L.

    1999-08-01

    Elastic scattering of X-rays can provide the following information on the fibrous protein collagen: its molecular structure, the axial arrangement of rod-like collagen molecules in a fibril, the lateral arrangement of molecules within a fibril, and the orientation of fibrils within a biological tissue. The first part of the paper reviews the principles involved in deducing this information. The second part describes a new computer program for measuring the equatorial intensity distribution, that provides information on the lateral arrangement of molecules within a fibril, and the angular distribution of the equatorial peaks that provides information on the orientation of fibrils. Orientation of fibrils within a tissue is quantified by the orientation distribution function, g( φ), which represents the probability of finding a fibril oriented between φ and φ+ δφ. The application of the program is illustrated by measurement of g( φ) for the collagen fibrils in demineralised cortical bone from cow tibia.

  19. Viscosity of Sheared Helical filament Suspensions

    NASA Astrophysics Data System (ADS)

    Sartucci, Matthew; Urbach, Jeff; Blair, Dan; Schwenger, Walter

    The viscosity of suspensions can be dramatically affected by high aspect ratio particles. Understanding these systems provides insight into key biological functions and can be manipulated for many technological applications. In this talk, the viscosity as a function of shear rate of suspensions of helical filaments is compared to that of suspensions of straight rod-like filaments. Our goal is to determine the impact of filament geometry on low volume fraction colloidal suspensions in order to identify strategies for altering viscosity with minimal volume fraction. In this research, the detached flagella of the bacteria Salmonella Typhimurium are used as a model system of helical filaments and compared to mutated straight flagella of the Salmonella. We compare rheological measurements of the suspension viscosity in response to shear flow and use a combination of the rheology and fluorescence microscopy to identify the microstructural changes responsible for the observed rheological response.

  20. A Nanoscale Multiresponsive Luminescent Sensor Based on a Terbium(III) Metal-Organic Framework.

    PubMed

    Dang, Song; Wang, Ting; Yi, Feiyan; Liu, Qinghui; Yang, Weiting; Sun, Zhong-Ming

    2015-08-01

    A nanoscale terbium-containing metal-organic framework (nTbL), with a layer-like structure and [H2 NMe2 ](+) cations located in the framework channels, was synthesized under hydrothermal conditions. The structure of the as-prepared sample was systematically confirmed by powder XRD and elemental analysis; the morphology was characterized by field-emission SEM and TEM. The photoluminescence studies revealed that rod-like nTbL exhibited bright-green emission, corresponding to (5)D4 →(7)FJ (J=6-3) transitions of the Tb(3+) ion under excitation. Further sensing measurements revealed that as-prepared nTbL could be utilized as a multiresponsive luminescent sensor, which showed significant and exclusive detection ability for Fe(3+) ions and phenylmethanol. These results highlight the practical applications of lanthanide-containing metal-organic frameworks as fluorescent probes.

  1. Binary Mixtures of Calamitic and Discotic Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Martin, Joshua S.; Garg, Shila

    2002-03-01

    It has been suggested that the elusive biaxial nematic phase could be achieved by a suitable mixture of discotic and calamitic liquid crystals [1]. We propose to investigate the miscibility and phase diagram of such a mixture. For this study, the rod-like molecule is chosen to be the commercially purchased p-hexyloxy benzoic acid. The disk-like molecule is triarylamino-1,3,5-triazine [2] and is synthesized by us. Physical characteristics of this mixture will be studied with the primary objective being the phase properties. Measurements of elastic properties of p-hexyloxy benzoic acid will also be presented. [1] G.R. Luckhurst, Thin Solid Films, 393, 40 (2001). [2] D. Goldmann, D. Janietz. R. Festag, C. Schmidt and J. Wendorff, Liquid Crystals, 21, 619 (1996). This research was supported by the Copeland Fund as administered by The College of Wooster.

  2. Preparation and photoluminescence study of mesoporous indium hydroxide nanorods

    SciTech Connect

    Li, Changyu; Lian, Suoyuan; Liu, Yang; Liu, Shouxin; Kang, Zhenhui

    2010-02-15

    Mesoporous indium hydroxide nanorods were successfully synthesized by a mild one-step one-pot method. The obtained samples were characterized by X-ray diffraction, transmission electron microscopy with selected area electron diffraction, N{sub 2} adsorption, ultraviolet-visible absorption and photoluminescence, respectively. Transmission electron microscopy showed that there were some pores in the samples, which were mainly composed of rod-like shapes with length of 300 nm and diameter of 90 nm. N{sub 2} adsorption/desorption measurements confirmed that the prepared powder was mesoporous with average pore diameter of 3.1 nm. The ultraviolet-visible absorption spectroscopy analysis indicated that the band gap energy of the samples was 5.15 eV. Photoluminescence spectrum showed that there were two strong emissions under ultraviolet light irradiation. The growth mechanism of indium hydroxide nanorods and the role of cetyltrimethyl ammonium bromide were also discussed.

  3. Optimization of experimental parameters based on the Taguchi robust design for the formation of zinc oxide nanocrystals by solvothermal method

    SciTech Connect

    Yiamsawas, Doungporn; Boonpavanitchakul, Kanittha; Kangwansupamonkon, Wiyong

    2011-05-15

    Research highlights: {yields} Taguchi robust design can be applied to study ZnO nanocrystal growth. {yields} Spherical-like and rod-like shaped of ZnO nanocrystals can be obtained from solvothermal method. {yields} [NaOH]/[Zn{sup 2+}] ratio plays the most important factor on the aspect ratio of prepared ZnO. -- Abstract: Zinc oxide (ZnO) nanoparticles and nanorods were successfully synthesized by a solvothermal process. Taguchi robust design was applied to study the factors which result in stronger ZnO nanocrystal growth. The factors which have been studied are molar concentration ratio of sodium hydroxide and zinc acetate, amount of polymer templates and molecular weight of polymer templates. Transmission electron microscopy and X-ray diffraction technique were used to analyze the experiment results. The results show that the concentration ratio of sodium hydroxide and zinc acetate ratio has the greatest effect on ZnO nanocrystal growth.

  4. Genetically Engineered Plant Viral Nanoparticles Direct Neural Cells Differentiation and Orientation.

    PubMed

    Feng, Sheng; Lu, Lin; Zan, Xingjie; Wu, Yehong; Lin, Yuan; Wang, Qian

    2015-09-01

    An important aim of tissue engineering is to design biomimetic materials with specific cell binding motifs and precisely controlled structural organization, thereby providing biochemical and physical cues for desired cellular behaviors. Previously, our group generated genetically modified tobacco mosaic virus (TMV) displaying integrin binding motifs, RGD1, RGD7, PSHRN3, P15, and DGEA. The resulting rod-like virus particles displaying integrin binding motifs were biocompatible with Neuro 2A (N2a), a mouse neural crest-derived cell line, and could promote the neurite outgrowth of N2a. The genetically modified viruses could be assembled with aligned orientation in the capillary by applying a shear force. The resulting aligned substrates were able to dictate directional neurite outgrowth of N2a cells. Therefore, this method could be potentially applied for neural tissue engineering, as a neural conduit for repairing peripheral nerve injuries. PMID:26247572

  5. Fundamental measure theory for smectic phases: scaling behavior and higher order terms.

    PubMed

    Wittmann, René; Marechal, Matthieu; Mecke, Klaus

    2014-08-14

    The recent extension of Rosenfeld's fundamental measure theory to anisotropic hard particles predicts nematic order of rod-like particles. Our analytic study of different aligned shapes provides new insights into the structure of this density functional, which is basically founded on experience with hard spheres. We combine scaling arguments with dimensional crossover and motivate a modified expression, which enables an appropriate description of smectic layering. We calculate the nematic-smectic-A transition of monodisperse hard spherocylinders with and without orientational degrees of freedom and present the equation of state and phase diagram including these two liquid crystalline phases in good agreement with simulations. We also find improved results related to the isotropic-nematic interface. We discuss the quality of empirical corrections and the convergence towards an exact second virial coefficient, including higher order terms.

  6. Efficient Thermolysis Route to Monodisperse Cu2ZnSnS4 Nanocrystals with Controlled Shape and Structure

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoyan; Guo, Guobiao; Ji, Cheng; Huang, Kai; Zha, Chenyang; Wang, Yifeng; Shen, Liming; Gupta, Arunava; Bao, Ningzhong

    2014-05-01

    Monodisperse Cu2ZnSnS4 (CZTS) nanocrystals with tunable shape, crystalline phase, and composition are synthesized by efficient thermolysis of a single source precursor of mixed metal-oleate complexes in hot organic solvents with dissolved sulfur sources. Suitable tuning of the synthetic conditions and the Cu/(Zn + Sn) ratio of the precursor has enabled precise control of the crystalline phase in the form of kesterite, or a newly observed wurtzite structure. Nanocrystals with morphology in the form of spherical, rice-like, or rod-like shapes are obtained over a wide range of compositions (0.5 <= Cu/(Zn + Sn) <= 1.2). Both the final products and intermediates for each shape exhibit consistent composition and structure, indicating homogenous nucleation and growth of single-phase nanocrystals. Thin films prepared from colloidal nanocrystal suspensions display interesting shape-dependent photoresponse behavior under white light illumination from a solar simulator.

  7. Adsorption of N-(1-(2-bromophenyl)-2-(2-nitrophenyl)ethyl)-4-methylbenzenesulfonamide on silver nanoparticles: SERS investigation.

    PubMed

    Anuratha, M; Jawahar, A; Umadevi, M; Sathe, V G; Vanelle, P; Terme, T; Khoumeri, O; Meenakumari, V; Milton Franklin Benial, A

    2015-03-01

    SERS provides essential data regarding the interaction of molecules in drugs with DNA. In the present study silver nanoparticles were synthesized using a solution combustion method with urea as fuel. The prepared silver nanoparticles are rod like structure. Surface-enhanced Raman scattering (SERS) of N-(1-2-bromophenyl)-2-(2-nitrophenyl)ethyl)-4-methylbenzenesulfonamide (BrS) adsorbed on the silver nanoparticle was studied. The nRs and Raman spectral analysis reveal that the BrS adsorbed tilted orientation on the silver surface. Vibrational modes of nRs along with HF calculations are also performed to study the HOMO and LUMO behavior and vibrational features of BrS. PMID:25498819

  8. Elastocapillary interactions on nematic films

    PubMed Central

    Liu, Iris B.; Gharbi, Mohamed A.; Ngo, Victor L.; Kamien, Randall D.; Yang, Shu; Stebe, Kathleen J.

    2015-01-01

    Rod-like colloids distort fluid interfaces and interact by capillarity. We explore this interaction at the free surface of aligned nematic liquid crystal films. Naive comparison of capillary and elastic energies suggests that particle assembly would be determined solely by surface tension. Here, we demonstrate that, under certain circumstances, the capillary and elastic effects are complementary and each plays an important role. Particles assemble end-to-end, as dictated by capillarity, and align along the easy axis of the director field, as dictated by elasticity. On curved fluid interfaces, however, curvature capillary energies can overcome the elastic orientations and drive particle migration along curvature gradients. Domains of dominant interaction and their transition are investigated. PMID:25941380

  9. Improved Atomistic Monte Carlo Simulations Demonstrate that Poly-L-Proline Adopts Heterogeneous Ensembles of Conformations of Semi-Rigid Segments Interrupted by Kinks

    PubMed Central

    Radhakrishnan, Aditya; Vitalis, Andreas; Mao, Albert H.; Steffen, Adam T.; Pappu, Rohit V.

    2012-01-01

    Poly-L-proline (PLP) polymers are useful mimics of biologically relevant proline-rich sequences. Biophysical and computational studies of PLP polymers in aqueous solutions are challenging because of the diversity of length scales and the slow time scales for conformational conversions. We describe an atomistic simulation approach that combines an improved ABSINTH implicit solvation model, with conformational sampling based on standard and novel Metropolis Monte Carlo moves. Refinements to forcefield parameters were guided by published experimental data for proline-rich systems. We assessed the validity of our simulation results through quantitative comparisons to experimental data that were not used in refining the forcefield parameters. Our analysis shows that PLP polymers form heterogeneous ensembles of conformations characterized by semi-rigid, rod-like segments interrupted by kinks, which result from a combination of internal cis peptide bonds, flexible backbone ψ-angles, and the coupling between ring puckering and backbone degrees of freedom. PMID:22329658

  10. Filamentous Phages As a Model System in Soft Matter Physics.

    PubMed

    Dogic, Zvonimir

    2016-01-01

    Filamentous phages have unique physical properties, such as uniform particle lengths, that are not found in other model systems of rod-like colloidal particles. Consequently, suspensions of such phages provided powerful model systems that have advanced our understanding of soft matter physics in general and liquid crystals in particular. We described some of these advances. In particular we briefly summarize how suspensions of filamentous phages have provided valuable insight into the field of colloidal liquid crystals. We also describe recent experiments on filamentous phages that have elucidated a robust pathway for assembly of 2D membrane-like materials. Finally, we outline unique structural properties of filamentous phages that have so far remained largely unexplored yet have the potential to further advance soft matter physics and material science.

  11. Synthesis of a microhydrogel composite from cellulose nanowhiskers and starch for drug delivery.

    PubMed

    Mauricio, Marcos R; da Costa, Pablo G; Haraguchi, Shirani K; Guilherme, Marcos R; Muniz, Edvani C; Rubira, Adley F

    2015-01-22

    This work describes the preparation of a microhydrogel composite from cellulose nanowhiskers (CNW) and starch in an ultrasound assisted-emulsion. CNW, which showed rod-like morphology, was obtained by acid hydrolysis of cane-based cellulose. The introduction of vinyl bonds to both CNW and starch enabled us to create the microhydrogel composite in which CNW played a role as a covalent cross-linker. Furthermore, CNW may act as an emulsifying agent for emulsion, improving both sphericity and homogeneity of the microparticles. The drug release was regulated in response to changes in the CNW amounts. The modeling of the release kinetics indicated that the drug release is driven by an anomalous mechanism and that the addition of CNW to starch microparticles led to differences in that mechanism. The release rate became ca. 2.9 times slower when CNW is added. When combined with starch, CNW played a role as a retardant factor for drug release.

  12. A superhydrophobic chip based on SU-8 photoresist pillars suspended on a silicon nitride membrane.

    PubMed

    Marinaro, Giovanni; Accardo, Angelo; De Angelis, Francesco; Dane, Thomas; Weinhausen, Britta; Burghammer, Manfred; Riekel, Christian

    2014-10-01

    We developed a new generation of superhydrophobic chips optimized for probing ultrasmall sample quantities by X-ray scattering and fluorescence techniques. The chips are based on thin Si3N4 membranes with a tailored pattern of SU-8 photoresist pillars. Indeed, aqueous solution droplets can be evaporated and concentrated at predefined positions using a non-periodic pillar pattern. We demonstrated quantitatively the deposition and aggregation of gold glyconanoparticles from the evaporation of a nanomolar droplet in a small spot by raster X-ray nanofluorescence. Further, raster nanocrystallography of biological objects such as rod-like tobacco mosaic virus nanoparticles reveals crystalline macro-domain formation composed of highly oriented nanorods.

  13. Carrier concentration and mobility in two-phase eutectic A/sup III/B/sup V/-Ge(Si) alloys

    SciTech Connect

    Leonov, V.V.

    1988-06-01

    The authors proposes a technique of determining the carrier concentration and mobility in the separate phases of two-phase alloys in which oriented rod-like inclusions have carrier concentrations similar to the host material. The calculations are then used to determine the carrier concentration and mobility in each alloy phase, and to discuss the doping processes and mechanisms of impurity incorporation in two-phase semiconductors. He studied the Hall constant R in two-phase, oriented eutectic alloys of InSb-Ge, InAs-Ge, GaAs-Ge, and GaAs-Si. He established that R depends on the relative orientations of the current flow, magnetic field, and elongated inclusions. Furthermore, the particular impurity concentration in the alloy also has an effect on R.

  14. ZnO nanorods prepared via ablation of Zn with millisecond laser in liquid media.

    PubMed

    Honda, Mitsuhiro; Goto, Taku; Owashi, Tatsuki; Rozhin, Alex G; Yamaguchi, Shigeru; Ito, Tsuyohito; Kulinich, Sergei A

    2016-09-14

    ZnO nanomaterials with controlled size, shape and surface chemistry are required for applications in diverse areas, such as optoelectronics, photocatalysis, biomedicine and so on. Here, we report on ZnO nanostructures with rod-like and spherical shapes prepared via laser ablation in liquid using a laser with millisecond-long pulses. By changing laser parameters (such as pulse width and peak power), the size or aspect ratio of such nanostructures could be tuned. The surface chemistry and defects of the products were also strongly affected by applied laser conditions. The preparation of different structures is explained by the intense heating of liquid media caused by millisecond-long pulses and secondary irradiation of already-formed nanostructures. PMID:27507010

  15. Tuning of Supramolecular Architectures of l-Valine-Containing Dicyanoplatinum(II) 2,2'-Bipyridine Complexes by Metal-Metal, π-π Stacking, and Hydrogen-Bonding Interactions.

    PubMed

    Fu, Heidi Li-Ki; Po, Charlotte; He, Hexiang; Leung, Sammual Yu-Lut; Wong, Kam Sing; Yam, Vivian Wing-Wah

    2016-08-01

    A series of newly synthesized dicyanoplatinum(II) 2,2'-bipyridine complexes exhibits self-assembly properties in solution after the incorporation of the l-valine amino units appended with various hydrophobic motifs. These l-valine-derived substituents were found to have critical control over the aggregation behaviors of the complexes in the solution state. On one hand, one of the complexes was found to exhibit interesting circularly polarized luminescence (CPL) signals at low temperature due to the formation of chiral spherical aggregates in the temperature-dependent studies. On the other hand, systematic transformation from less uniform aggregates to well-defined fibrous and rod-like structures via Pt⋅⋅⋅Pt and π-π stacking interactions has also been observed in the mixed-solvent studies. These changes were monitored by UV/Vis absorption, emission, circular dichroism (CD), and CPL spectroscopies, and morphologies were studied by electron microscopy.

  16. A route for producing nano-CaRuO3 perovskite by combusting precursors prepared using reverse micelle synthesis

    NASA Astrophysics Data System (ADS)

    Jiao, Shuqiang; Tripuraneni Kilby, Kamal; Zhang, Lijuan; Fray, Derek J.

    2009-02-01

    Nanoparticles of Ca-Ru-O precursors have been prepared using a reverse micelle. Transmission electron microscopy and x-ray diffraction techniques showed that the precursors had an amorphous structure. The average diameter of the amorphous Ca-Ru-O particles was shown to be approximately 10 nm (within a range of ± 2 nm). An interesting result was that a rod-like nano-CaRuO3 perovskite was observed when the precursor was sintered at a temperature of 950 °C. Furthermore, the conversion of the powders to crystalline CaRuO3 perovskite occurred upon heat treatment at 450 °C in air. This is much lower than that for a standard solid-state reaction for CaCO3 and RuO2.

  17. Pseudo-Casimir forces in nematics with disorders in the bulk

    NASA Astrophysics Data System (ADS)

    Karimi Pour Haddadan, Fahimeh

    2016-10-01

    A nematic liquid-crystalline slab is considered in which some rod-like particles are randomly distributed. The particles are locally elongated either homeotropic or planar with respect to the confining substrates of the cell. We consider thermal fluctuations of a nematic director which is aligned perpendicular to the confining substrates due to strong homeotropic anchoring at the substrates. The resulting fluctuation-induced force across the cell is analyzed for an annealed disorder in the anchoring of the nematic director at the dispersed mesoscopic particles. Within the saddle-point approximation to free energy of the system, the effect of the disorder is renormalization of the strength of the mean anchoring which is assumed to be homeotropic. By increasing the variance of the disorder, the modes become less massive and deviations from the mean behavior become larger, so that the disorder-free universal long-range attraction, due to the soft modes, is approached.

  18. Effect of filler alignment on percolation in polymer nanocomposites using tunneling-percolation model

    NASA Astrophysics Data System (ADS)

    Kale, Sohan; Sabet, Fereshteh A.; Jasiuk, Iwona; Ostoja-Starzewski, Martin

    2016-07-01

    In this study, we examine the effect of filler alignment on percolation behavior of polymer nanocomposites using Monte Carlo simulations of monodisperse prolate and oblate hard-core soft-shell ellipsoids representing carbon nanotubes and graphene nanoplatelets, respectively. The percolation threshold is observed to increase with increasing extent of alignment as expected. For a highly aligned system of rod-like fillers, the simulation results are shown to be in good agreement with the second virial approximation based predictions. However, for a highly aligned system of disk-like fillers, the second virial approximation based results are observed to significantly deviate from the simulations, even for higher aspect ratios. The effect of filler alignment on anisotropy in percolation behavior is also studied by predicting the percolation threshold along different directions. The anisotropy in percolation threshold is found to vanish even for highly aligned systems of fillers with increasing system size.

  19. A new human gene (DXS1357E) with ubiquitous expression, located in Xq28 adjacent to the adrenoleukodystrophy gene

    SciTech Connect

    Mosser, J.; Sarde, C.O.; Vicaire, S.

    1994-07-15

    The authors have isolated a new human gene (DXS1357E; laboratory name: CDM) localized in Xq28. This gene is transcribed from the same CpG island as the adrenoleukodystrophy gene (ALD) and is oriented in the opposite direction. It encodes a 1.5-kb transcript that exhibits ubiquitous expression and contains a single open reading frame. The 246 deduced amino acid sequence suggests the presence of membrane-associated segments and a weak similarity with the rod-like tail portion of heavy chain myosins from different species. The DXS1357E gene may be a candidate for one of the many diseases mapping to this region. A preliminary analysis did not show rearrangements of the gene in 19 independent patients with Emery-Dreifuss muscular dystrophy. 21 refs., 2 figs.

  20. M23C6 carbides and Cr2N nitrides in aged duplex stainless steel: A SEM, TEM and FIB tomography investigation.

    PubMed

    Maetz, J-Y; Douillard, T; Cazottes, S; Verdu, C; Kléber, X

    2016-05-01

    The precipitation evolution during ageing of a 2101 lean duplex stainless steel was investigated, revealing that the precipitate type and morphology depends on the nature of the grain boundary. Triangular M23C6 carbides precipitate only at γ/δ interfaces and rod-like Cr2N nitrides precipitate at both γ/δ and δ/δ interfaces. After 15min of ageing, the M23C6 size no longer evolves, whereas that of the Cr2N continues to evolve. For Cr2N, the morphology is maintained at γ/δ interfaces, whereas percolation occurs to form a continuous layer at δ/δ interfaces. By combining 2D and 3D characterisation at the nanoscale using transmission electron microscopy (TEM) and focused ion beam (FIB) tomography, a complete description of the precipitation evolution was obtained, including the composition, crystallographic structure, orientation relationship with the matrix phases, location, morphology, size and volume fraction.

  1. Understanding nanocellulose chirality and structure–properties relationship at the single fibril level

    PubMed Central

    Usov, Ivan; Nyström, Gustav; Adamcik, Jozef; Handschin, Stephan; Schütz, Christina; Fall, Andreas; Bergström, Lennart; Mezzenga, Raffaele

    2015-01-01

    Nanocellulose fibrils are ubiquitous in nature and nanotechnologies but their mesoscopic structural assembly is not yet fully understood. Here we study the structural features of rod-like cellulose nanoparticles on a single particle level, by applying statistical polymer physics concepts on electron and atomic force microscopy images, and we assess their physical properties via quantitative nanomechanical mapping. We show evidence of right-handed chirality, observed on both bundles and on single fibrils. Statistical analysis of contours from microscopy images shows a non-Gaussian kink angle distribution. This is inconsistent with a structure consisting of alternating amorphous and crystalline domains along the contour and supports process-induced kink formation. The intrinsic mechanical properties of nanocellulose are extracted from nanoindentation and persistence length method for transversal and longitudinal directions, respectively. The structural analysis is pushed to the level of single cellulose polymer chains, and their smallest associated unit with a proposed 2 × 2 chain-packing arrangement. PMID:26108282

  2. The dopant dependent photocatalytic activity of polyaniline towards the degradation of Rose Bengal dye

    NASA Astrophysics Data System (ADS)

    Chatterjee, Mukulika Jana; Banerjee, Dipali; Ghosh, Amrita; Mondal, Anup

    2016-05-01

    Polyaniline (PANI) with two different dopants, hydrochloric acid (HCl) and bismuth nitrate (Bi (NO3)3), were synthesized to investigate the effect of dopant on photocatalytic degradation of Rose Bengal, an organic dye, in presence of sunlight. PANI, synthesized by in situ polymerization was characterized by FESEM images, FTIR and UV-Vis spectra. FESEM images show rod like structures obtained for both the dopants. FTIR spectra confirms the formation of conducting PANI with the presence of C=N, C=C stretching modes in quinoid and benzenoid units. Band gap of PANI has been obtained from UV-Vis spectrum. Doped polyaniline exhibited a fast degradation of dye by 98.62 % & 98.12 % within 5 min & 8 min under visible light illumination for the dopant HCl & Bi (NO3)3 respectively.

  3. Green self-assembly of zein-conjugated ZnO/Cd(OH)Cl hierarchical nanocomposites with high cytotoxicity and immune organs targeting

    NASA Astrophysics Data System (ADS)

    Wang, Hua-Jie; Cao, Ying; Wang, Cai-Feng; Cui, Shi-Zhong; Mi, Li-Wei; Miyazawa, Teruo

    2016-04-01

    Inorganic nanomedicines in the fight against cancer have progressed rapidly during recent years, with the synergistic advantages of multifunctional nanosystems compared to single component. Herein, a drug-combination opinion was introduced into “nanomedicine” based on the understanding of Trojan horse-anti-tumor mechanism of inorganic nano-medicines. Moreover, we reported the green and facile synthesis route of mono-dispersed and rod-like zein-conjugated ZnO/Cd(OH)Cl hierarchical nanocomposites. We found that the nanocomposites exhibited high-efficiency killing ability to tumor cells through lipid peroxidation mediated-membrane disintegration route. The safety studies in BALB/c mice didn’t detect injection anaphylaxis, hemolysis and cytotoxicity. More interestingly, the nano-composites could specially accumulate in liver and kidney, which will be helpful for targeting cure to these regional cancers.

  4. Dissecting Biological Dark Matter: Single Cell Genetic Analysis of TM7, a Rare and Uncultivated Microbe from the Human Mouth

    SciTech Connect

    Fenner, Marsha W; Marcy, Yann; Ouverney, Cleber; Bik, Elisabeth M.; Losekann, Tina; Ivanova, Natalia; Martin, H. Garcia; Szeto, E.; Platt, Darren; Hugenholtz, Philip; Relman, David A.; Quake, Stephen R.

    2007-07-01

    We have developed a microfluidic device that allows the isolation and genome amplification of individual microbial cells, thereby enabling organism-level genomic analysis of complex microbial ecosystems without the need for culture. This device was used to perform a directed survey of the human subgingival crevice and to isolate bacteria having rod-like morphology. Several isolated microbes had a 16S rRNA sequence that placed them in candidate phylum TM7, which has no cultivated or sequenced members. Genome amplification from individual TM7 cells allowed us to sequence and assemble >1,000 genes, providing insight into the physiology of members of this phylum. This approach enables single-cell genetic analysis of any uncultivated minority member of a microbial community.

  5. Variable Emission Changes in Bi3+/Ln3+ (Ln = Eu, Sm, Dy) Co-doped Lutetium Vanadates (LuVO4)

    NASA Astrophysics Data System (ADS)

    Zheng, Yuhui; Hu, Jing; Deng, Surong; Gao, Jinwei; Wang, Qianming

    2016-06-01

    High-purity LuVO4: Ln3+/Bi3+ (Ln = Eu, Sm, Dy) phosphors with tetragonal zircon structures were successfully synthesized. The reactions have been carried out by multiple irradiations with very high efficiency. Transmission electron microscope images showed that the phosphors had rod-like structures with average lengths of about 200 nm. The host absorption edge of LuVO4: Ln3+/Bi3+ (Ln = Eu, Sm) shifted to the longer wavelength side. Furthermore, the red emission of Eu3+ ion and the orange emission of Sm3+ ion are remarkably enhanced by encapsulating Bi3+ in LuVO4 system, whereas in the case of LuVO4: Dy3+/Bi3+, the host absorption and the yellow emission from dysprosium have been suppressed in the presence of Bi3+. These novel findings will facilitate their use in the display field.

  6. Initial stages of organic film growth characterized by thermal desorption spectroscopy

    PubMed Central

    Winkler, Adolf

    2015-01-01

    In the wake of the increasing importance of organic electronics, a more in-depth understanding of the early stages of organic film growth is indispensable. In this review a survey of several rod-like and plate-like organic molecules (p-quaterphenyl, p-sexiphenyl, hexaazatriphenylene-hexacarbonitrile (HATCN), rubicene, indigo) deposited on various application relevant substrates (gold, silver, mica, silicon dioxide) is given. The focus is particularly put on the application of thermal desorption spectroscopy to shed light on the kinetics and energetics of the molecule-substrate interaction. While each adsorption system reveals a manifold of features that are specific for the individual system, one can draw some general statements on the early stages of organic film formation from the available datasets. Among the important issues in this context is the formation of wetting layers and the dewetting as a function of the substrate surface conditions, organic film thickness and temperature. PMID:26778860

  7. Electron Transfer Rate Maxima at Large Donor-Acceptor Distances.

    PubMed

    Kuss-Petermann, Martin; Wenger, Oliver S

    2016-02-01

    Because of their low mass, electrons can transfer rapidly over long (>15 Å) distances, but usually reaction rates decrease with increasing donor-acceptor distance. We report here on electron transfer rate maxima at donor-acceptor separations of 30.6 Å, observed for thermal electron transfer between an anthraquinone radical anion and a triarylamine radical cation in three homologous series of rigid-rod-like donor-photosensitizer-acceptor triads with p-xylene bridges. Our experimental observations can be explained by a weak distance dependence of electronic donor-acceptor coupling combined with a strong increase of the (outer-sphere) reorganization energy with increasing distance, as predicted by electron transfer theory more than 30 years ago. The observed effect has important consequences for light-to-chemical energy conversion. PMID:26800279

  8. Filamentous Phages As a Model System in Soft Matter Physics

    PubMed Central

    Dogic, Zvonimir

    2016-01-01

    Filamentous phages have unique physical properties, such as uniform particle lengths, that are not found in other model systems of rod-like colloidal particles. Consequently, suspensions of such phages provided powerful model systems that have advanced our understanding of soft matter physics in general and liquid crystals in particular. We described some of these advances. In particular we briefly summarize how suspensions of filamentous phages have provided valuable insight into the field of colloidal liquid crystals. We also describe recent experiments on filamentous phages that have elucidated a robust pathway for assembly of 2D membrane-like materials. Finally, we outline unique structural properties of filamentous phages that have so far remained largely unexplored yet have the potential to further advance soft matter physics and material science. PMID:27446051

  9. Ligand-assisted soft-chemical synthesis of self-assembled different shaped mesoporous Co3O4: efficient visible light photocatalysts.

    PubMed

    Roy, Mouni; Ghosh, Sourav; Naskar, Milan Kanti

    2015-04-21

    Mesoporous self-assembled cobalt oxide (Co3O4) of different shapes was synthesized by a facile soft-chemical process using cobalt nitrate, oxalic acid and phosphoric acid in the presence of cationic templates, cetyltrimethylammonium bromide, 1-butyl-3-methylimidazolium bromide, and pyridinium bromide at 75 °C/2 h followed by calcination at 300 °C. The effect of cationic templates of the samples on the physico-chemical properties, and the photocatalytic efficiency for the degradation of Chicago Sky Blue 6B was studied. Pyridinium bromide and 1-butyl-3-methylimidazolium bromide facilitated formation of particles with different shaped morphology compared to cetyltrimethylammonium bromide. The rod-like particles having higher surface area exhibited higher photocatalytic performance. PMID:25792483

  10. Microstructure Evolution and Mechanical Properties of Long Period Stacking Ordered Mg96Gd3Ni1 Alloy with Al and Sr Additions

    NASA Astrophysics Data System (ADS)

    Wang, Dandan; Zhang, Jinshan; Zhang, Wenbo; Nie, Kaibo; Niu, Xiaofeng; You, Zhiyong; Xu, Chunxiang; Wang, Hongxia

    2015-06-01

    The effects of 0.3 at. pct Al and x at. pct Sr ( x = 0.0, 0.1, 0.2, 0.3) on the microstructure and mechanical properties of as-cast Mg96Gd3Ni1 alloy were investigated. With addition of 0.3 at. pct Al, new quaternary Mg-Gd-Ni-Al phases with peculiar rod-like and petal-like morphologies are uniformly distributed in the alloy. The angles between petals of the petal-like phase are all about 60 deg. The microstructure of the alloy is refined, leading to fine grain strengthening. The volume fraction of the long-period stacking ordered phase which is excellent reinforcement phase of Mg alloys increases significantly. Moreover, combined addition of 0.3 at. pct Al and 0.1 at. pct Sr refines the microstructure further and enhances the mechanical properties of the alloy simultaneously.

  11. Empty liquid phase of colloidal ellipsoids: the role of shape and interaction anisotropy.

    PubMed

    Varga, Szabolcs; Meneses-Júarez, Efrain; Odriozola, Gerardo

    2014-04-01

    We study the effect of anisotropic excluded volume and attractive interactions on the vapor-liquid phase transition of colloidal ellipsoids. In our model, the hard ellipsoid is embedded into an ellipsoidal well, where both the shape of the hard ellipsoid and that of the added enclosing ellipsoidal well can be varied independently. The bulk properties of these particles are examined by means of a van der Waals type perturbation theory and validated with replica exchange Monte Carlo simulations. It is shown that both the critical volume fraction (ηc) and the critical temperature (Tc) of the vapor-liquid phase transition vanish with increasing shape anisotropy for oblate shapes, while ηc → 0 and Tc ≠ 0 are obtained for very elongated prolate shapes. These results suggest that the chance to stabilize empty liquids (a liquid phase with vanishing density) is higher in suspensions of rod-like colloidal ellipsoids than in those of plate-like ones.

  12. Shape-Selectivity with Liquid Crystal and Side-Chain Liquid Crystalline Polymer SAW Sensor Interfaces

    SciTech Connect

    FRYE-MASON,GREGORY CHARLES; OBORNY,MICHAEL C.; PUGH,COLEEN; RICCO,ANTONIO; THOMAS,ROSS C.; ZELLERS,EDWARD T.; ZHANG,GUO-ZHENG

    1999-09-23

    A liquid crystal (LC) and a side-chain liquid crystalline polymer (SCLCP) were tested as surface acoustic wave (SAW) vapor sensor coatings for discriminating between pairs of isomeric organic vapors. Both exhibit room temperature smectic mesophases. Temperature, electric-field, and pretreatment with self-assembled monolayers comprising either a methyl-terminated or carboxylic acid-terminated alkane thiol anchored to a gold layer in the delay path of the sensor were explored as means of affecting the alignment and selectivity of the LC and SCLCP films. Results for the LC were mixed, while those for the SCLCP showed a consistent preference for the more rod-like isomer of each isomer pair examined.

  13. Switching plastic crystals of colloidal rods with electric fields

    PubMed Central

    Liu, Bing; Besseling, Thijs H.; Hermes, Michiel; Demirörs, Ahmet F.; Imhof, Arnout; van Blaaderen, Alfons

    2014-01-01

    When a crystal melts into a liquid both long-ranged positional and orientational order are lost, and long-time translational and rotational self-diffusion appear. Sometimes, these properties do not change at once, but in stages, allowing states of matter such as liquid crystals or plastic crystals with unique combinations of properties. Plastic crystals/glasses are characterized by long-ranged positional order/frozen-in-disorder but short-ranged orientational order, which is dynamic. Here we show by quantitative three-dimensional studies that charged rod-like colloidal particles form three-dimensional plastic crystals and glasses if their repulsions extend significantly beyond their length. These plastic phases can be reversibly switched to full crystals by an electric field. These new phases provide insight into the role of rotations in phase behaviour and could be useful for photonic applications. PMID:24446033

  14. Self-assembly of 2D membranes from mixtures of hard rods and depleting polymers().

    PubMed

    Yang, Yasheng; Barry, Edward; Dogic, Zvonimir; Hagan, Michael F

    2012-01-01

    We combine simulations and experiments to elucidate the molecular forces leading to the assembly of two dimensional membrane-like structures composed of a one rod-length thick monolayer of aligned rods from an immiscible suspension of hard rods and depleting polymers. Computer simulations predict that monolayer membranes are thermodynamically stable above a critical rod aspect ratio and below a critical depletion interaction length scale. Outside of these conditions alternative structures such as stacked smectic columns or nematic droplets are thermodynamically stable. These predictions are confirmed by subsequent experiments using a model system of virus rod-like molecules and non-adsorbing polymer. Our work demonstrates that collective molecular protrusion fluctuations alone are sufficient to stabilize membranes composed of homogenous rods with simple excluded volume interactions.

  15. Effect of Ca addition on the microstructure and mechanical properties of as-cast Mg-Sm alloys.

    PubMed

    Luo, Xiaoping; Fang, Daqing; Chai, Yuesheng; Yang, Bin

    2016-08-01

    This study investigated the effect of Ca addition on the microstructure and mechanical properties of as-cast Mg-4Sm alloys. The addition of 1.0 wt% Ca led to a significant grain refinement of Mg-4.0Sm alloys owing to the formation of rod-like Mg2Ca phases that acted as active nucleates for the Mg matrix. The as-cast Mg-4.0Sm-1.0Ca alloy showed the smallest grain size at 45 μm. Furthermore, the Mg-4.0Sm-1.0Ca alloy exhibited greater hardness, higher tensile strength, and higher yield tensile strength and elongation than the other two alloys with different Ca contents. These results were attributed to the grain refinement and precipitation strengthening of the Mg2Ca and Mg41Sm5 phases. Microsc. Res. Tech. 79:707-711, 2016. © 2016 Wiley Periodicals, Inc.

  16. Surfactant-assisted Nanocasting Route for Synthesis of Highly Ordered Mesoporous Graphitic Carbon and Its Application in CO2 Adsorption

    NASA Astrophysics Data System (ADS)

    Wang, Yangang; Bai, Xia; Wang, Fei; Qin, Hengfei; Yin, Chaochuang; Kang, Shifei; Li, Xi; Zuo, Yuanhui; Cui, Lifeng

    2016-05-01

    Highly ordered mesoporous graphitic carbon was synthesized from a simple surfactant-assisted nanocasting route, in which ordered mesoporous silica SBA-15 maintaining its triblock copolymer surfactant was used as a hard template and natural soybean oil (SBO) as a carbon precursor. The hydrophobic domain of the surfactant assisted SBO in infiltration into the template’s mesoporous channels. After the silica template was carbonized and removed, a higher yield of highly-ordered graphitic mesoporous carbon with rod-like morphology was obtained. Because of the improved structural ordering, the mesoporous carbon after amine modification could adsorb more CO2 compared with the amine-functionalized carbon prepared without the assistance of surfactant.

  17. Synthesis and characterization of an electro-deposited polyaniline-bismuth telluride nanocomposite - A novel thermoelectric material

    SciTech Connect

    Chatterjee, Krishanu; Suresh, Asaithambi; Ganguly, Saibal; Kargupta, Kajari; Banerjee, Dipali

    2009-12-15

    The present work consists of synthesis and characterization of a novel thermoelectric material polyaniline (PANI)-bismuth telluride (Bi{sub 2}Te{sub 3}) nanocomposite using simultaneous electrochemical reactions and deposition method. The inorganic bismuth nitrate has been used as a dopant for polyaniline to achieve high electrical conductivity. A semi-batch mode of operation has been employed to control the rate of deposition of an individual component and thus the molecular architecture of the composite. The electro-deposited composite film on ITO coated glass substrate has been characterized by X-ray diffraction analysis (XRD), FTIR analysis, scanning electron microscope (SEM), and transmission electron microscope (TEM). The microscopic analysis reveals the formation of rod-like nanostructures of diameter less than 100 nm. It has been found that smaller molecules of Bi{sub 2}Te{sub 3} are dispersed in the macromolecules of PANI. The nanocomposite has been characterized by thermoelectric power.

  18. Distinct Roles for the N- and C-terminal Regions of M-Sec in Plasma Membrane Deformation during Tunneling Nanotube Formation.

    PubMed

    Kimura, Shunsuke; Yamashita, Masami; Yamakami-Kimura, Megumi; Sato, Yusuke; Yamagata, Atsushi; Kobashigawa, Yoshihiro; Inagaki, Fuyuhiko; Amada, Takako; Hase, Koji; Iwanaga, Toshihiko; Ohno, Hiroshi; Fukai, Shuya

    2016-01-01

    The tunneling nanotube (TNT) is a structure used for intercellular communication, and is a thin membrane protrusion mediating transport of various signaling molecules and cellular components. M-Sec has potent membrane deformation ability and induces TNT formation in cooperation with the Ral/exocyst complex. Here, we show that the N-terminal polybasic region of M-Sec directly binds phosphatidylinositol (4,5)-bisphosphate for its localization to the plasma membrane during the initial stage of TNT formation. We further report a crystal structure of M-Sec, which consists of helix bundles arranged in a straight rod-like shape, similar to the membrane tethering complex subunits. A positively charged surface in the C-terminal domains is required for M-Sec interaction with active RalA to extend the plasma membrane protrusions. Our results suggest that the membrane-associated M-Sec recruits active RalA, which directs the exocyst complex to form TNTs.

  19. Understanding nanocellulose chirality and structure-properties relationship at the single fibril level

    NASA Astrophysics Data System (ADS)

    Usov, Ivan; Nyström, Gustav; Adamcik, Jozef; Handschin, Stephan; Schütz, Christina; Fall, Andreas; Bergström, Lennart; Mezzenga, Raffaele

    2015-06-01

    Nanocellulose fibrils are ubiquitous in nature and nanotechnologies but their mesoscopic structural assembly is not yet fully understood. Here we study the structural features of rod-like cellulose nanoparticles on a single particle level, by applying statistical polymer physics concepts on electron and atomic force microscopy images, and we assess their physical properties via quantitative nanomechanical mapping. We show evidence of right-handed chirality, observed on both bundles and on single fibrils. Statistical analysis of contours from microscopy images shows a non-Gaussian kink angle distribution. This is inconsistent with a structure consisting of alternating amorphous and crystalline domains along the contour and supports process-induced kink formation. The intrinsic mechanical properties of nanocellulose are extracted from nanoindentation and persistence length method for transversal and longitudinal directions, respectively. The structural analysis is pushed to the level of single cellulose polymer chains, and their smallest associated unit with a proposed 2 × 2 chain-packing arrangement.

  20. [Electrochemical synthesis and spectroscopic characterization of gold nanoparticles].

    PubMed

    Shen, Li-Ming; Yao, Jian-Lin; Gu, Ren-Ao

    2005-12-01

    Two electrochemical methods were used to synthesize Au nanoparticles (AuNPs) with different shapes depending on the applied current. The dumbbell, spheroid and rod-like AuNPs were synthesized by increasing the current with a certain increment, while spheroid and dumbbell AuNPs were obtained by applying constant current. The AuNPs were characterized by TEM, UV-Vis spectrum and surface enhanced Raman spectra (SERS). One absorption band located at near-IR region was observed on the AuNPs, indicating the existence of gold nanorods with the aspect ratio of about 6. The SERS effect from the AuNPs surface was studied by using crystal violet as probe molecules, which adsorbed on AuNPs surface with flat orientation. Meanwhile, the forming mechanism of AuNPs involving crystallization and growth was deduced based on the TEM results. PMID:16544491

  1. Depletion interactions effected by different variants of fd virus.

    PubMed

    July, Christoph; Lang, Peter R

    2010-12-21

    The depletion interaction between a probe sphere and a flat wall induced by fd virus is investigated by means of total internal reflection microscopy (TIRM). The viruses serve as a model system for monodisperse, rod-like colloids. We find that the experimental potentials are well described by the first-order density approximation up to an fd content of several overlap concentrations. This is in accordance with higher order density theory as confirmed by numerical calculations. Since the first-order analytical description still holds for all measurements, this exemplifies that higher order terms of the theory are unimportant for our system. Comparing the potentials induced by wild-type fd to those induced by a more rigid fd variant, it can be shown that the influence of the virus stiffness is beyond our experimental resolution and plays only a negligible role for the measured depletion potentials.

  2. Biaxial ferromagnetic liquid crystal colloids.

    PubMed

    Liu, Qingkun; Ackerman, Paul J; Lubensky, Tom C; Smalyukh, Ivan I

    2016-09-20

    The design and practical realization of composite materials that combine fluidity and different forms of ordering at the mesoscopic scale are among the grand fundamental science challenges. These composites also hold a great potential for technological applications, ranging from information displays to metamaterials. Here we introduce a fluid with coexisting polar and biaxial ordering of organic molecular and magnetic colloidal building blocks exhibiting the lowest symmetry orientational order. Guided by interactions at different length scales, rod-like organic molecules of this fluid spontaneously orient along a direction dubbed "director," whereas magnetic colloidal nanoplates order with their dipole moments parallel to each other but pointing at an angle to the director, yielding macroscopic magnetization at no external fields. Facile magnetic switching of such fluids is consistent with predictions of a model based on competing actions of elastic and magnetic torques, enabling previously inaccessible control of light. PMID:27601668

  3. Flexibility of the Cytoplasmic Domain of the Phototaxis Transducer II from Natronomonas pharaonis

    PubMed Central

    Budyak, Ivan L.; Mironova, Olga S.; Yanamala, Naveena; Manoharan, Vijayalaxmi; Büldt, Georg; Schlesinger, Ramona; Klein-Seetharaman, Judith

    2008-01-01

    Chemo- and phototaxis systems in bacteria and archaea serve as models for more complex signal transduction mechanisms in higher eukaryotes. Previous studies of the cytoplasmic fragment of the phototaxis transducer (pHtrII-cyt) from the halophilic archaeon Natronomonas pharaonis showed that it takes the shape of a monomeric or dimeric rod under low or high salt conditions, respectively. CD spectra revealed only approximately 24% helical structure, even in 4 M KCl, leaving it an open question how the rod-like shape is achieved. Here, we conducted CD, FTIR, and NMR spectroscopic studies under different conditions to address this question. We provide evidence that pHtrII-cyt is highly dynamic with strong helical propensity, which allows it to change from monomeric to dimeric helical coiled-coil states without undergoing dramatic shape changes. A statistical analysis of predicted disorder for homologous sequences suggests that structural flexibility is evolutionarily conserved within the methyl-accepting chemotaxis protein family. PMID:20107574

  4. From liquid crystal models to the guiding-center theory of magnetized plasmas

    NASA Astrophysics Data System (ADS)

    Tronci, Cesare

    2016-08-01

    Upon combining Northrop's picture of charged particle motion with modern liquid crystal theories, this paper provides a new description of guiding center dynamics (to lowest order). This new perspective is based on a rotation gauge field (gyrogauge) that encodes rotations around the magnetic field. In liquid crystal theory, an analogue rotation field is used to encode the rotational state of rod-like molecules. Instead of resorting to sophisticated tools (e.g. Hamiltonian perturbation theory and Lie series expansions) that still remain essential in higher-order gyrokinetics, the present approach combines the WKB method with a simple kinematical ansatz, which is then replaced into the charged particle Lagrangian. The latter is eventually averaged over the gyrophase to produce the guiding-center equations. A crucial role is played by the vector potential for the gyrogauge field. A similar vector potential is related to liquid crystal defects and is known as wryness tensor in Eringen's micropolar theory.

  5. Giant negative mobility of Janus particles in a corrugated channel

    NASA Astrophysics Data System (ADS)

    Ghosh, Pulak K.; Hänggi, Peter; Marchesoni, Fabio; Nori, Franco

    2014-06-01

    We numerically simulate the transport of elliptic Janus particles along narrow two-dimensional channels with reflecting walls. The self-propulsion velocity of the particle is oriented along either its major (prolate) or minor axis (oblate). In smooth channels, we observe long diffusion transients: ballistic for prolate particles and zero diffusion for oblate particles. Placed in a rough channel, prolate particles tend to drift against an applied drive by tumbling over the wall protrusions; for appropriate aspect ratios, the modulus of their negative mobility grows exceedingly large (giant negative mobility). This suggests that a small external drive suffices to efficiently direct self-propulsion of rod-like Janus particles in rough channels.

  6. Nanomechanical Characterization of Bacillus anthracis Spores by Atomic Force Microscopy

    PubMed Central

    Burggraf, Larry W.; Xing, Yun

    2016-01-01

    ABSTRACT The study of structures and properties of bacterial spores is important to understanding spore formation and biological responses to environmental stresses. While significant progress has been made over the years in elucidating the multilayer architecture of spores, the mechanical properties of the spore interior are not known. Here, we present a thermal atomic force microscopy (AFM) study of the nanomechanical properties of internal structures of Bacillus anthracis spores. We developed a nanosurgical sectioning method in which a stiff diamond AFM tip was used to cut an individual spore, exposing its internal structure, and a soft AFM tip was used to image and characterize the spore interior on the nanometer scale. We observed that the elastic modulus and adhesion force, including their thermal responses at elevated temperatures, varied significantly in different regions of the spore section. Our AFM images indicated that the peptidoglycan (PG) cortex of Bacillus anthracis spores consisted of rod-like nanometer-sized structures that are oriented in the direction perpendicular to the spore surface. Our findings may shed light on the spore architecture and properties. IMPORTANCE A nanosurgical AFM method was developed that can be used to probe the structure and properties of the spore interior. The previously unknown ultrastructure of the PG cortex of Bacillus anthracis spores was observed to consist of nanometer-sized rod-like structures that are oriented in the direction perpendicular to the spore surface. The variations in the nanomechanical properties of the spore section were largely correlated with its chemical composition. Different components of the spore materials showed different thermal responses at elevated temperatures. PMID:26969703

  7. Facile room temperature synthesis of SrSO{sub 4}:RE (RE = Sm{sup 3+}, Tb{sup 3+}, Ce{sup 3+}) microrods via a precipitation method and its luminescence properties

    SciTech Connect

    Sun, Jiayue Sun, Guangchao; Du, Haiyan

    2013-10-15

    Graphical abstract: PL emission spectra of SrSO{sub 4}:xSm{sup 3+} powder phosphors under 401 nm excitation. The inset shows Sm{sup 3+} concentration of relative luminescence intensity. - Highlights: • Three SrSO{sub 4} phosphors were synthesized by a facile precipitation reaction. • Rod-like SrSO{sub 4} obtained microcrystals are about 14 μm length and 6 μm width. • In the PL spectrum of SrSO{sub 4}:Ce{sup 3+}, two overlapping bands are observed. • Narrow bands are observed in spectra of SrSO{sub 4}:RE (RE = Sm{sup 3+} and Tb{sup 3+}). • The critical quenching concentrations are 0.8, 2 and 0.8 mol%, respectively. - Abstract: Three SrSO{sub 4}:RE phosphors activated with rare-earth ions (RE = Sm{sup 3+}, Tb{sup 3+} and Ce{sup 3+}) were synthesized by a facile precipitation reaction without using any surfactants or templates. Especially, rod-like SrSO{sub 4} microcrystals with size of about 14 μm length and 6 μm width can be obtained under ambient condition at room temperature. The phase structure, microstructure and luminescence properties were characterized. In the photoluminescence property investigation of SrSO{sub 4}:Ce{sup 3+}, two overlapping bands with peaks at 301 and 320 nm due to Ce{sup 3+} were observed. Narrow bands observed in emission spectra and excitation spectra of SrSO{sub 4}:RE (RE = Sm{sup 3+} and Tb{sup 3+}) phosphors were well identified with the electronic transitions within the 4f{sup n} (n = 5 and 8) configurations of RE{sup 3+}.

  8. Cell responses to two kinds of nanohydroxyapatite with different sizes and crystallinities

    PubMed Central

    Liu, Xiaochen; Zhao, Minzhi; Lu, Jingxiong; Ma, Jian; Wei, Jie; Wei, Shicheng

    2012-01-01

    Introduction Hydroxyapatite (HA) is the principal inorganic constituent of human bone. Due to its good biocompatibility and osteoconductivity, all kinds of HA particles were prepared by different methods. Numerous reports demonstrated that the properties of HA affected its biological effects. Methods Two kinds of nanohydroxyapatite with different sizes and crystallinities were obtained via a hydrothermal treatment method under different temperatures. It was found that at a temperature of 140°C, a rod-like crystal (n-HA1) with a diameter of 23 ± 5 nm, a length of 47 ± 14 nm, and crystallinity of 85% ± 5% was produced, while at a temperature of 80°C, a rod-like crystal (n-HA2) with a diameter of 16 ± 3 nm, a length of 40 ± 10 nm, and crystallinity of 65% ± 3% was produced. The influence of nanohydroxyapatite size and crystallinity on osteoblast viability was studied by MTT, scanning electron microscopy, and flow cytometry. Results n-HA1 gave a better biological response than n-HA2 in promoting cell growth and inhibiting cell apoptosis, and also exhibited much more active cell morphology. Alkaline phosphatase activity for both n-HA2 and n-HA1 was obviously higher than for the control, and no significant difference was found between n-HA1 and n-HA2. The same trend was observed on Western blotting for expression of type I collagen and osteopontin. In addition, it was found by transmission electron microscopy that large quantities of n-HA2 entered into the cell and damaged the cellular morphology. Release of tumor necrosis factor alpha from n-HA2 was markedly higher than from n-HA1, indicating that n-HA2 might trigger a severe inflammatory response. Conclusion This work indicates that not all nanohydroxyapatite should be considered a good biomaterial in future clinical applications. PMID:22419871

  9. Self-assembly mechanisms of nanofibers from peptide amphiphiles in solution and on substrate surfaces

    NASA Astrophysics Data System (ADS)

    Liao, Hsien-Shun; Lin, Jing; Liu, Yang; Huang, Peng; Jin, Albert; Chen, Xiaoyuan

    2016-08-01

    We report the investigation of the self-assembly mechanism of nanofibers, using a small peptide amphiphile (NapFFKYp) as a model. Combining experimental and simulation methods, we identify the self-assembly pathways in the solution and on the substrates, respectively. In the solution, peptide amphiphiles undergo the nucleation process to grow into nanofibers. The nanofibers can further twist into high-ordered nanofibers with aging. On the substrates, peptide amphiphiles form nanofibers and nanosheet structures simultaneously. This surface-induced nanosheet consists of rod-like structures, and its thickness is substrate-dependent. Most intriguingly, water can transform the nanosheet into the nanofiber. Molecular dynamic simulation suggests that hydrophobic and ion-ion interactions are dominant forces during the self-assembly process.We report the investigation of the self-assembly mechanism of nanofibers, using a small peptide amphiphile (NapFFKYp) as a model. Combining experimental and simulation methods, we identify the self-assembly pathways in the solution and on the substrates, respectively. In the solution, peptide amphiphiles undergo the nucleation process to grow into nanofibers. The nanofibers can further twist into high-ordered nanofibers with aging. On the substrates, peptide amphiphiles form nanofibers and nanosheet structures simultaneously. This surface-induced nanosheet consists of rod-like structures, and its thickness is substrate-dependent. Most intriguingly, water can transform the nanosheet into the nanofiber. Molecular dynamic simulation suggests that hydrophobic and ion-ion interactions are dominant forces during the self-assembly process. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr04672j

  10. Analysis of the mechanical response of biomimetic materials with highly oriented microstructures through 3D printing, mechanical testing and modeling.

    PubMed

    de Obaldia, Enrique Escobar; Jeong, Chanhue; Grunenfelder, Lessa Kay; Kisailus, David; Zavattieri, Pablo

    2015-08-01

    Many biomineralized organisms have evolved highly oriented nanostructures to perform specific functions. One key example is the abrasion-resistant rod-like microstructure found in the radular teeth of Chitons (Cryptochiton stelleri), a large mollusk. The teeth consist of a soft core and a hard shell that is abrasion resistant under extreme mechanical loads with which they are subjected during the scraping process. Such remarkable mechanical properties are achieved through a hierarchical arrangement of nanostructured magnetite rods surrounded with α-chitin. We present a combined biomimetic approach in which designs were analyzed with additive manufacturing, experiments, analytical and computational models to gain insights into the abrasion resistance and toughness of rod-like microstructures. Staggered configurations of hard hexagonal rods surrounded by thin weak interfacial material were printed, and mechanically characterized with a cube-corner indenter. Experimental results demonstrate a higher contact resistance and stiffness for the staggered alignments compared to randomly distributed fibrous materials. Moreover, we reveal an optimal rod aspect ratio that lead to an increase in the site-specific properties measured by indentation. Anisotropy has a significant effect (up to 50%) on the Young's modulus in directions parallel and perpendicular to the longitudinal axis of the rods, and 30% on hardness and fracture toughness. Optical microscopy suggests that energy is dissipated in the form of median cracks when the load is parallel to the rods and lateral cracks when the load is perpendicular to the rods. Computational models suggest that inelastic deformation of the rods at early stages of indentation can vary the resistance to penetration. As such, we found that the mechanical behavior of the system is influenced by interfacial shear strain which influences the lateral load transfer and therefore the spread of damage. This new methodology can help to elucidate

  11. Mesomorphic properties of chiral three-arm liquid crystals containing 1,2,4-butanetriol as core

    NASA Astrophysics Data System (ADS)

    Tian, Mei; Wu, Shuang-jie; Tian, Xiao-Wei; Yao, Dan-Shu; Li, Chong-Liang; Hu, Jian-She; Zhang, Bao-Yan

    2016-03-01

    A series of symmetric and asymmetric three-arm liquid crystals (TALCs) of which the molecular structure with a central core of 1, 2, 4-butanetriol attached by three rod-like mesogenic moieties have successfully been synthesized. The rod-like mesogenic side arms are 4‧-(4-(trifluoromethyl) benzoyloxy) biphenyl-4-carboxylic acid (TFBA) and 4‧-(4-(allyloxy) benzoyloxy) biphenyl-4-carboxylic acid (AOBA), respectively. BTA0 and BTA3 are symmetric TALCs with three TFBA or three AOBA as LC side arms, respectively. BTA1 is an asymmetric TALC with one AOBA and two TFBA as side arms. BTA2 is an asymmetric TALC with two AOBA and one TFBA as side arms. The chemical structures and LC properties of the LC side arms and TALCs were characterised by FTIR, 1H NMR, elemental analysis, DSC, TG, POM and X-ray diffractometer. TFBA displayed smectic B (SmB) phase, AOBA exhibited nematic (N) phase. The TALCs all displayed chiral mesophase properties. BTA0 displayed chiral smectic C (SmC∗) mesophase. BTA1, BTA2 and BTA3 exhibited cholesteric (ch) mesophase. In addition, a chiral smectic A (SmA∗) mesophase was observed for BTA1. The results indicated that the 1, 2, 4-butanetriol is vital in inducing chiral mesophase of the TALCs. The side arms also played an important role in the mesophase type and mesogenic region. The TALCs displayed cholesteric mesophase when nematic LC side arm AOBA was introduced into the chiral core. The mesogenic region of the TALCs increased with the content of the wide-mesophase-region LC side arm AOBA introduced into the TALCs increasing. The melting temperature and the clear temperature of the TALCs were lower than those of the LC side arms (TFBA and AOBA). The mesophase regions of the TALCs were wider than those of the LC side arms.

  12. Solution structure of copper ion-induced molecular aggregates of tyrosine melanin.

    PubMed

    Gallas, J M; Littrell, K C; Seifert, S; Zajac, G W; Thiyagarajan, P

    1999-08-01

    Melanin, the ubiquitous biological pigment, provides photoprotection by efficient filtration of light and also by its antioxidant behavior. In solutions of synthetic melanin, both optical and antioxidant behavior are affected by the aggregation states of melanin. We have utilized small-angle x-ray and neutron scattering to determine the molecular dimensions of synthetic tyrosine melanin in its unaggregated state in D(2)O and H(2)O to study the structure of melanin aggregates formed in the presence of copper ions at various copper-to-melanin molar ratios. In the absence of copper ions, or at low copper ion concentrations, tyrosine melanin is present in solution as a sheet-like particle with a mean thickness of 12.5 A and a lateral extent of approximately 54 A. At a copper-to-melanin molar ratio of 0.6, melanin aggregates to form long, rod-like structures with a radius of 32 A. At a higher copper ion concentration, with a copper-to-melanin ratio of 1.0, these rod-like structures further aggregate, forming sheet-like structures with a mean thickness of 51 A. A change in the charge of the ionizable groups induced by the addition of copper ions is proposed to account for part of the aggregation. The data also support a model for the copper-induced aggregation of melanin driven by pi stacking assisted by peripheral Cu(2+) complexation. The relationship between our results and a previous hypothesis for reduced cellular damage from bound-to-melanin redox metal ions is also discussed.

  13. Aqueous dispersions of magnetite nanoparticles with NH3+ surfaces for magnetic manipulations of biomolecules and MRI contrast agents.

    PubMed

    Shieh, Dar-Bin; Cheng, Fong-Yu; Su, Chia-Hao; Yeh, Chen-Sheng; Wu, Ming-Ting; Wu, Ya-Na; Tsai, Chiau-Yuang; Wu, Chao-Liang; Chen, Dong-Hwang; Chou, Chen-Hsi

    2005-12-01

    In the current study, amine surface modified iron-oxide nanoparticles of 6 nm diameter without polymer coating were fabricated in an aqueous solution by organic acid modification as an adherent following chemical coprecipitation. Structure and the superparamagnetic property of magnetite nanoparticles were characterized by selected area electron diffraction (SAED) and superconducting quantum interference measurement device (SQUID). X-ray photoelectron spectrometer (XPS) and zeta potential measurements revealed cationic surface mostly decorated with terminal -NH(3)(+). This feature enables them to function as a magnetic carrier for nucleotides via electrostatic interaction. In addition, Fe(3)O(4)/trypsin conjugates with well-preserved functional activity was demonstrated. The nanoparticles displayed excellent in vitro biocompatibility. The NMR and the in vitro MRI measurements showed significantly reduced water proton relaxation times of both T(1) and T(2). Significantly reduced T(2) and T(2)*-weighted signal intensity were observed in a 1.5 T clinical MR imager. In vivo imaging contrast effect showed a fast and prolonged inverse contrast effect in the liver that lasted for more than 1 week. In addition, it was found that the spherical Fe(3)O(4) assembled as rod-like configuration through an aging process in aqueous solution at room temperature. Interestingly, TEM observation of the liver tissue revealed the rod-like shape but not the spherical-type nanoparticles being taken up by the Kupffer cells 120 h after tail vein infusion. Combining these results, we have demonstrated the potential applications of the newly synthesized magnetite nanoparticles in a broad spectrum of biomedical applications.

  14. Effects of Nano-CeO2 with Different Nanocrystal Morphologies on Cytotoxicity in HepG2 Cells

    PubMed Central

    Wang, Lili; Ai, Wenchao; Zhai, Yanwu; Li, Haishan; Zhou, Kebin; Chen, Huiming

    2015-01-01

    Cerium oxide nanoparticles (nano-CeO2) have been reported to cause damage and apoptosis in human primary hepatocytes. Here, we compared the toxicity of three types of nano-CeO2 with different nanocrystal morphologies (cube-, octahedron-, and rod-like crystals) in human hepatocellular carcinoma cells (HepG2). The cells were treated with the nano-CeO2 at various concentrations (6.25, 12.5, 25, 50, 100 μg/mL). The crystal structure, size and morphology of nano-CeO2 were investigated by X-ray diffractometry and transmission electron microscopy. The specific surface area was detected using the Brunauer, Emmet and Teller method. The cellular morphological and internal structure were observed by microscopy; apoptotic alterations were measured using flow cytometry; nuclear DNA, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) and glutathione (GSH) in HepG2 cells were measured using high content screening technology. The scavenging ability of hydroxyl free radicals and the redox properties of the nano-CeO2 were measured by square-wave voltammetry and temperature-programmed-reduction methods. All three types of nano-CeO2 entered the HepG2 cells, localized in the lysosome and cytoplasm, altered cellular shape, and caused cytotoxicity. The nano-CeO2 with smaller specific surface areas induced more apoptosis, caused an increase in MMP, ROS and GSH, and lowered the cell’s ability to scavenge hydroxyl free radicals and antioxidants. In this work, our data demonstrated that compared with cube-like and octahedron-like nano-CeO2, the rod-like nano-CeO2 has lowest toxicity to HepG2 cells owing to its larger specific surface areas. PMID:26404340

  15. Microwave heating synthesis and formation mechanism of chalcopyrite structured CuInS{sub 2} nanorods in deep eutectic solvent

    SciTech Connect

    Zhang, Jianjun Chen, Jun; Li, Qiang

    2015-03-15

    Graphical abstract: Chalcopyrite structured CuInS{sub 2} nanorods were synthesized by an environmentally friendly microwave heating method in deep eutectic solvent. Results show that microwave heating time plays an important role in the formation of CuInS{sub 2} nanostructure phase. The SEM results indicated that the obtained CuInS{sub 2} nanostructures display rod-like morphology with diameters of about 40 nm and lengths of about 400 nm. The UV–vis spectrum results indicated that the CuInS{sub 2} nanorods exhibit strong absorption from the entire visible light region to the near-infrared region beyond 1100 nm. The possible growth mechanism of CuInS{sub 2} nanorods was discussed. - Abstract: Chalcopyrite structured CuInS{sub 2} nanorods were synthesized by an environmentally friendly microwave heating method in deep eutectic solvent. The as-synthesized CuInS{sub 2} nanorods were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), respectively. The results indicated that the obtained CuInS{sub 2} nanostructures display rod-like morphology with diameters of about 40 nm and lengths of about 400 nm. The influences of microwave heating time on the formation of CuInS{sub 2} phase were discussed. Ultraviolet–visible (UV–vis) and photoluminescence (PL) spectra were utilized to investigate the optical properties of CuInS{sub 2} nanorods. The results showed that the as-synthesized CuInS{sub 2} nanorods exhibit strong absorption from the entire visible light region to the near-infrared region beyond 1100 nm. PL spectrum of the as-synthesized CuInS{sub 2} nanorods displays an emission peak centered at 580 nm under excitation wavelength of 366 nm at room temperature. The possible growth mechanism of CuInS{sub 2} nanorods was discussed.

  16. Viewing angle compensation of various LCD modes by using a liquid crystalline polymer film

    NASA Astrophysics Data System (ADS)

    Matsumoto, Takuya; Nishimura, Suzushi

    2013-09-01

    The authors have developed liquid crystalline retardation films to improve certain aspects of LCD image quality such as viewing angle performance and coloration. We have successfully created several types of optical retardation films using a rod-like liquid crystalline polymer. The resulting liquid crystalline polymer films have several advantages over conventional uni- or biaxially stretched retardation films. Precisely controlled structures such as twisted nematic, homogeneous nematic, hybrid nematic and homeotropic structures can provide ideal compensation of various LCD types, such as STN, TN, ECB, VA and IPS-LCDs. Twisted nematic film effectively prevents coloration of STN-LCDs, which is a critical flaw affecting color representation. Short pitch cholesteric film, which utilizes said rod-like liquid crystalline polymer and is the optical equivalent of a negative C-plate, can expand the viewing angle of VA-LCDs. Hybrid nematic film is quite unique in that the film functions not only as a wave plate but also as a viewing angle compensator for TN and ECB-LCDs. Homeotropic film, which acts as a positive-C plate, greatly improves the viewing angle performance of IPS and CPVA-LCDs. Our homeotropically aligned liquid crystalline film, called "NV film", is the world's thinnest retardation film. The thickness of the liquid crystalline layer is a mere 1 micrometer. Homeotropic film can be used to expand the viewing angle not only of LCDs but also OLED displays. And NV film, when used in in combination with a quarter wavelength plate, can expand the viewing angles of the circular polarizers used to prevent reflection in OLED displays.

  17. Complex tiling patterns in liquid crystals

    PubMed Central

    Tschierske, C.; Nürnberger, C.; Ebert, H.; Glettner, B.; Prehm, M.; Liu, F.; Zeng, X.-B.; Ungar, G.

    2012-01-01

    In this account recent progress in enhancing the complexity of liquid crystal self-assembly is highlighted. The discussed superstructures are formed mainly by polyphilic T-shaped and X-shaped molecules composed of a rod-like core, tethered with glycerol units at both ends and flexible non-polar chain(s) in lateral position, but also related inverted molecular structures are considered. A series of honeycomb phases composed of polygonal cylinders ranging from triangular to hexagonal, followed by giant cylinder honeycombs is observed for ternary T-shaped polyphiles on increasing the size of the lateral chain(s). Increasing the chain size further leads to new modes of lamellar organization followed by three-dimensional and two-dimensional structures incorporating branched and non-branched axial rod-bundles. Grafting incompatible chains to opposite sides of the rod-like core leads to quaternary X-shaped polyphiles. These form liquid crystalline honeycombs where different cells are filled with different material. Projected on an Euclidian plane, all honeycomb phases can be described either by uniformly coloured Archimedean and Laves tiling patterns (T-shaped polyphiles) or as multi-colour tiling patterns (X-shaped polyphiles). It is shown that geometric frustration, combined with the tendency to segregate incompatible chains into different compartments and the need to find a periodic tiling pattern, leads to a significant increase in the complexity of soft self-assembly. Mixing of different chains greatly enhances the number of possible ‘colours’ and in this way, periodic structures comprising up to seven distinct compartments can be generated. Relations to biological self-assembly are discussed shortly. PMID:24098852

  18. EBSD analysis of magnesium addition on inclusion formation in SS400 structural steel

    SciTech Connect

    Luo, Sin-Jie; Su, Yen-Hao Frank; Lu, Muh-Jung; Kuo, Jui-Chao

    2013-08-15

    In this study, the effect of magnesium addition on the inclusion formation in SS400 steel was investigated. The experimental specimens with and without Mg addition treatment were compared. The microstructure was observed using optical microscopy after etching with 3% nital. The morphology and chemical composition of the inclusions were analyzed via scanning electron microscopy and energy dispersive spectrometry. The lattice structure and orientation of the inclusions were identified by electron backscattering diffraction. The average size of inclusions in SS400 was between 0.67 and 0.75 μm, and between 0.65 and 0.68 μm in SS400 + Mg. The 2 ppm Mg addition resulted in the oxide formation change from Al{sub 2}O{sub 3} to MgO·Al{sub 2}O{sub 3} and in the inclusion formation change from Al{sub 2}O{sub 3}–MnS to MgO·Al{sub 2}O{sub 3}–MnS. Moreover, a simple-phase MnS with an average grain size of 1 μm to 2 μm was observed in rod-like, globular, and polyhedron forms. - Highlights: • The effect of magnesium addition was investigated for SS400 steel. • 2 ppm Mg addition changes the inclusion formation from Al2O3-MnS to MgO·Al2O3-MnS. • MnS observed in inclusions exhibits rod-like, globular, and polyhedron forms.

  19. Thermodynamic stability of a smectic phase in a system of hard rods

    NASA Astrophysics Data System (ADS)

    Frenkel, D.; Lekkerkerker, H. N. W.; Stroobants, A.

    1988-04-01

    One of the most remarkable phenomena exhibited by colloidal suspensions of monodisperse rod-like particles is the spontaneous formation of smectic liquid crystals1 5. In these smectic phases, the particles order in periodic layers; on average, the axes of the rods are perpendicular to the layers. Smectics are distinct from crystals in that there is no long-range positional order within the layers. Because the spacing of the smectic layers is of the order of optical wavelengths, white light is separated into colours when scattered, giving rise to beautiful iridescence as in the colour photographs of ref. 2. As early as 1949, Onsager6 showed that nematic ordering may arise from hard-core repulsions between anisometric particles. However, it appears to have been generally accepted in the literature that smectic liquid crystalline ordering demands that attractive forces also operate7. There is nevertheless experimental evidence that smectic ordering does occur in colloidal systems where the particles interact predominantly through repulsive electrostatic interactions. This observation raises the fundamental question of whether smectic ordering can occur in a system of particles with purely repulsive interactions. Inspired by the seminal work of Alder and Wainwright8 on the freezing of a system of hard spheres, we have explored the possibility that smectic ordering occurs in a fluid of hard rod-like particles. Earlier computer simulations on hard parallel spherocylinders9,10 (cylinders with length L and diameter D, capped at each end with hemispheres of the same diameter) indicated that, in this somewhat artificial system, smectic order was indeed possible. Here we present numerical evidence that hard spherocylinders with both translational and orientational freedom can form a thermodynamically stable smectic phase.

  20. Ca2+-stabilized adhesin helps an Antarctic bacterium reach out and bind ice

    PubMed Central

    Vance, Tyler D. R.; Olijve, Luuk L. C.; Campbell, Robert L.; Voets, Ilja K.; Davies, Peter L.; Guo, Shuaiqi

    2014-01-01

    The large size of a 1.5-MDa ice-binding adhesin [MpAFP (Marinomonas primoryensis antifreeze protein)] from an Antarctic Gram-negative bacterium, M. primoryensis, is mainly due to its highly repetitive RII (Region II). MpAFP_RII contains roughly 120 tandem copies of an identical 104-residue repeat. We have previously determined that a single RII repeat folds as a Ca2+-dependent immunoglobulin-like domain. Here, we solved the crystal structure of RII tetra-tandemer (four tandem RII repeats) to a resolution of 1.8 Å. The RII tetra-tandemer reveals an extended (~190-Å × ~25-Å), rod-like structure with four RII-repeats aligned in series with each other. The inter-repeat regions of the RII tetra-tandemer are strengthened by Ca2+ bound to acidic residues. SAXS (small-angle X-ray scattering) profiles indicate the RII tetra-tandemer is significantly rigidified upon Ca2+ binding, and that the protein's solution structure is in excellent agreement with its crystal structure. We hypothesize that >600 Ca2+ help rigidify the chain of ~120 104-residue repeats to form a ~0.6 μm rod-like structure in order to project the ice-binding domain of MpAFP away from the bacterial cell surface. The proposed extender role of RII can help the strictly aerobic, motile bacterium bind ice in the upper reaches of the Antarctic lake where oxygen and nutrients are most abundant. Ca2+-induced rigidity of tandem Ig-like repeats in large adhesins might be a general mechanism used by bacteria to bind to their substrates and help colonize specific niches. PMID:24892750

  1. Analysis of the mechanical response of biomimetic materials with highly oriented microstructures through 3D printing, mechanical testing and modeling.

    PubMed

    de Obaldia, Enrique Escobar; Jeong, Chanhue; Grunenfelder, Lessa Kay; Kisailus, David; Zavattieri, Pablo

    2015-08-01

    Many biomineralized organisms have evolved highly oriented nanostructures to perform specific functions. One key example is the abrasion-resistant rod-like microstructure found in the radular teeth of Chitons (Cryptochiton stelleri), a large mollusk. The teeth consist of a soft core and a hard shell that is abrasion resistant under extreme mechanical loads with which they are subjected during the scraping process. Such remarkable mechanical properties are achieved through a hierarchical arrangement of nanostructured magnetite rods surrounded with α-chitin. We present a combined biomimetic approach in which designs were analyzed with additive manufacturing, experiments, analytical and computational models to gain insights into the abrasion resistance and toughness of rod-like microstructures. Staggered configurations of hard hexagonal rods surrounded by thin weak interfacial material were printed, and mechanically characterized with a cube-corner indenter. Experimental results demonstrate a higher contact resistance and stiffness for the staggered alignments compared to randomly distributed fibrous materials. Moreover, we reveal an optimal rod aspect ratio that lead to an increase in the site-specific properties measured by indentation. Anisotropy has a significant effect (up to 50%) on the Young's modulus in directions parallel and perpendicular to the longitudinal axis of the rods, and 30% on hardness and fracture toughness. Optical microscopy suggests that energy is dissipated in the form of median cracks when the load is parallel to the rods and lateral cracks when the load is perpendicular to the rods. Computational models suggest that inelastic deformation of the rods at early stages of indentation can vary the resistance to penetration. As such, we found that the mechanical behavior of the system is influenced by interfacial shear strain which influences the lateral load transfer and therefore the spread of damage. This new methodology can help to elucidate

  2. Effects of Nano-CeO₂ with Different Nanocrystal Morphologies on Cytotoxicity in HepG2 Cells.

    PubMed

    Wang, Lili; Ai, Wenchao; Zhai, Yanwu; Li, Haishan; Zhou, Kebin; Chen, Huiming

    2015-09-02

    Cerium oxide nanoparticles (nano-CeO₂) have been reported to cause damage and apoptosis in human primary hepatocytes. Here, we compared the toxicity of three types of nano-CeO₂ with different nanocrystal morphologies (cube-, octahedron-, and rod-like crystals) in human hepatocellular carcinoma cells (HepG2). The cells were treated with the nano-CeO₂ at various concentrations (6.25, 12.5, 25, 50, 100 μg/mL). The crystal structure, size and morphology of nano-CeO₂ were investigated by X-ray diffractometry and transmission electron microscopy. The specific surface area was detected using the Brunauer, Emmet and Teller method. The cellular morphological and internal structure were observed by microscopy; apoptotic alterations were measured using flow cytometry; nuclear DNA, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) and glutathione (GSH) in HepG2 cells were measured using high content screening technology. The scavenging ability of hydroxyl free radicals and the redox properties of the nano-CeO₂ were measured by square-wave voltammetry and temperature-programmed-reduction methods. All three types of nano-CeO₂ entered the HepG2 cells, localized in the lysosome and cytoplasm, altered cellular shape, and caused cytotoxicity. The nano-CeO₂ with smaller specific surface areas induced more apoptosis, caused an increase in MMP, ROS and GSH, and lowered the cell's ability to scavenge hydroxyl free radicals and antioxidants. In this work, our data demonstrated that compared with cube-like and octahedron-like nano-CeO₂, the rod-like nano-CeO₂ has lowest toxicity to HepG2 cells owing to its larger specific surface areas.

  3. Ceria-containing uncoated and coated hydroxyapatite-based galantamine nanocomposites for formidable treatment of Alzheimer's disease in ovariectomized albino-rat model.

    PubMed

    Wahba, Sanaa M R; Darwish, Atef S; Kamal, Sara M

    2016-08-01

    This paper upraises delivery and therapeutic actions of galantamine drug (GAL) against Alzheimer's disease (AD) in rat brain through attaching GAL to ceria-containing hydroxyapatite (GAL@Ce-HAp) as well ceria-containing carboxymethyl chitosan-coated hydroxyapatite (GAL@Ce-HAp/CMC) nanocomposites. Physicochemical features of such nanocomposites were analyzed by XRD, FT-IR, Raman spectroscopy, UV-vis spectrophotometer, N2-BET, DLS, zeta-potential measurements, SEM, and HR-TEM. Limited interactions were observed in GAL@Ce-HAp with prevailed existence of dispersed negatively charged rod-like particles conjugated with ceria nanodots. On contrary, GAL@Ce-HAp/CMC was well-structured developing aggregates of uncharged tetragonal-shaped particles laden with accession of ceria quantum dots. Such nanocomposites were i.p. injected into ovariectomized AD albino-rats at galantamine dose of 2.5mg/kg/day for one month, then brain tissues were collected for biochemical and histological tests. GAL@Ce-HAp adopted as a promising candidate for AD curativeness, whereas oxidative stress markers were successfully upregulated, degenerated neurons in hippocampal and cerebral tissues were wholly recovered and Aβ-plaques were vanished. Also, optimizable in-vitro release for GAL and nanoceria were displayed from GAL@Ce-HAp, while delayed in-vitro release for those species were developed from GAL@Ce-HAp/CMC. This proof of concept work allow futuristic omnipotency of rod-like hydroxyapatite particles for selective delivery of GAL and nanoceria to AD affected brain areas. PMID:27157738

  4. Modulation of cardiac myocyte phenotype in vitro by the composition and orientation of the extracellular matrix.

    PubMed

    Simpson, D G; Terracio, L; Terracio, M; Price, R L; Turner, D C; Borg, T K

    1994-10-01

    Cellular phenotype is the result of a dynamic interaction between a cell's intrinsic genetic program and the morphogenetic signals that serve to modulate the extent to which that program is expressed. In the present study we have examined how morphogenetic information might be stored in the extracellular matrix (ECM) and communicated to the neonatal heart cell (NHC) by the cardiac alpha 1 beta 1 integrin molecule. A thin film of type I collagen (T1C) was prepared with a defined orientation. This was achieved by applying T1C to the peripheral edge of a 100 mm culture dish. The T1C was then drawn across the surface of the dish in a continuous stroke with a sterile cell scraper and allowed to polymerize. When NHCs were cultured on this substrate, they spread, as a population, along a common axis in parallel with the gel lattice and expressed an in vivo-like phenotype. Individual NHCs displayed an elongated, rod-like shape and disclosed parallel arrays of myofibrils. These phenotypic characteristics were maintained for at least 4 weeks in primary culture. The evolution of this tissue-like organizational pattern was dependent upon specific interactions between the NHCs and the collagen-based matrix that were mediated by the cardiac alpha 1 beta 1 integrin complex. This conclusion was supported by a variety of experimental results. Altering the tertiary structure of the matrix or blocking the extracellular domains of either the cardiac alpha 1 or beta 1 integrin chain inhibited the expression of the tissue-like pattern of organization. Neither cell-to-cell contact or contractile function were necessary to induce the formation of the rod-like cell shape. However, beating activity was necessary for the assembly of a well-differentiated myofibrillar apparatus. These data suggest that the cardiac alpha 1 beta 1 integrin complex serves to detect and transduce phenotypic information stored within the tertiary structure of the surrounding matrix.

  5. Phase behavior of mixtures of colloidal rods and spheres

    NASA Astrophysics Data System (ADS)

    Adams, Marie Elizabeth

    In this thesis we study entropy driven order in mixtures of rods and spheres. Systems of rod-like particles, as pure systems, exhibit rich liquid crystalline phase behavior. We chose to work with aqueous suspensions of either TMV or fd virus particles, both rod-like lyotropic systems. We complicate the phase behavior by adding a second component, colloidal spheres (PEG/PEO, BSA, polystyrene latex, or Dextran). Our first paper explores the phase behavior of TMV mixed with BSA or PEO, mapping out a phase diagram based on optical microscopy observations. We found our qualitative observations of TMV mixtures to be consistent with theoretical models of the depletion force. The second paper extends our study of phase behavior to mixtures of fd virus and polystyrene latex spheres. We qualitatively observe bulk demixing for very small diameter added spheres and for very large diameter added spheres. In addition, we observed microphase separation morphologies, such as lamellar and columnar structures, which formed for fd mixed with polystyrene latex spheres 0.1 microns in diameter. All of these microphase samples were viewed with differential interference microscopy (a few samples were further investigated using electron microscopy). Both our data and theoretical calculations illustrated that 0.1 micron diameter spheres have a stabilizing effect on the smectic phase. Our final work focused on fd virus mixed with Dextran. The purpose of these experiments was to examine the effect of added polymer on the isotropic-cholesteric co-existence region. I-Ch samples were prepared and fd and Dextran concentrations were measured using a spectrophotometer. Several conditions were explored, including two different molecular weights of Dextran and a range of ionic strengths. In agreement with theoretical predictions, the I-Ch coexistence region widens with added Dextran with the polymer preferentially partioned into the isotropic phase.

  6. Solution structures of {beta}-amyloid{sub 10-35} and {beta}-amyloid{sub 10-35} PEG3000 aggregates.

    SciTech Connect

    Benzinger, T. L. S.; Burkoth, T. S.; Gordon, D.; Lynn, D. G.; Meredith, S. C.; Morgan, D. M.; Seifert, S.; Thiyagarajan, P.; Urban, V.

    1999-07-02

    Small angle neutron and x-ray scattering (SANS/SAXS) studies were conducted on the structure of the aggregates formed from both the truncated model peptide {beta}-Amyloid(10-35) (A{beta}{sub 10-35}) and a block copolymer {beta}-Amyloid (10-35)-PEG3000 (A{beta}{sub 10-35}-PEG) in D{sub 2}O at pHs from 3.0 to 7.0. These studies indicate that A{beta}{sub 10-35} aggregates into rod-like particles (fibril) and their radii are strongly dependent on the Pm of the solution. The fibril-fibril association in A{beta}{sub 10-35} solutions is less of pH < 5.6, but becomes larger at higher pH. A{beta}{sub 10-35}-PEG also assembles into rod-like particles whose radius is larger by about 30 {angstrom} than that for A{beta}{sub 10-35} fibril at pH 4.2, while it is about 23 {angstrom} larger at higher pH. Contrast matching SAXS/SANS experiments that eliminate the coherent scattering from PEG reveal that PEG moiety is located at the periphery of the fibril. Also, the mass per unit length of the peptide portion is similar for both A{beta}{sub 10-35} and A{beta}{sub 10-35}-PEG fibrils at pH 5.6. The mass per unit length of the rods from SANS provides key information on the packing of A{beta}{sub 10-35} peptides in the fibril.

  7. A mechanistic study on the synthesis of β-Sialon whiskers from coal fly ash

    SciTech Connect

    Zhao, H.; Wang, P.Y.; Yu, J.L.; Zhang, J.

    2015-05-15

    Graphical abstract: The appearance of bead-like whiskers indicated that the growth mechanism of the β-Sialon whiskers was different from the conventional one, in which a chain of droplets were formed and then consumed to participate in the formation of the whiskers. - Highlights: • β-Sialon whiskers were synthesized using waste fly ash by carbothemal reduction reaction under nitrogen atmosphere. • Rod-like β-Sialon whiskers with a diameter of 100–500 nm were formed. • Bead-like whiskers as intermediate morphology of the growing β-Sialon whiskers were found with increasing sintering time. • The growth mechanism of β-Sialon whiskers was different from the conventional VLS mechanism. • A chain of droplets were formed and participated in the formation of the whiskers. - Abstract: β-Sialon whiskers were produced at 1420 °C through carbothemal reduction reaction under nitrogen atmosphere using fly ash from coal-fired power plants. The effects of sintering time on the phase formation and morphology of the products were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) techniques. Rod-like β-Sialon whiskers with the diameter of 100–500 nm were successfully formed. With increasing sintering time, bead-like morphology during the growth process of the whiskers was found, and growth mechanism of β-Sialon whiskers was also discussed in detail. The growth mechanism proposed in this study was different from the conventional vapor–liquid–solid (VLS) mechanism.

  8. Interference between Coulombic and CT-mediated couplings in molecular aggregates: H- to J-aggregate transformation in perylene-based π-stacks

    SciTech Connect

    Hestand, Nicholas J.; Spano, Frank C.

    2015-12-28

    The spectroscopic differences between J and H-aggregates are traditionally attributed to the spatial dependence of the Coulombic coupling, as originally proposed by Kasha. However, in tightly packed molecular aggregates wave functions on neighboring molecules overlap, leading to an additional charge transfer (CT) mediated exciton coupling with a vastly different spatial dependence. The latter is governed by the nodal patterns of the molecular LUMOs and HOMOs from which the electron (t{sub e}) and hole (t{sub h}) transfer integrals derive. The sign of the CT-mediated coupling depends on the sign of the product t{sub e}t{sub h} and is therefore highly sensitive to small (sub-Angstrom) transverse displacements or slips. Given that Coulombic and CT-mediated couplings exist simultaneously in tightly packed molecular systems, the interference between the two must be considered when defining J and H-aggregates. Generally, such π-stacked aggregates do not abide by the traditional classification scheme of Kasha: for example, even when the Coulomb coupling is strong the presence of a similarly strong but destructively interfering CT-mediated coupling results in “null-aggregates” which spectroscopically resemble uncoupled molecules. Based on a Frenkel/CT Holstein Hamiltonian that takes into account both sources of electronic coupling as well as intramolecular vibrations, vibronic spectral signatures are developed for integrated Frenkel/CT systems in both the perturbative and resonance regimes. In the perturbative regime, the sign of the lowest exciton band curvature, which rigorously defines J and H-aggregation, is directly tracked by the ratio of the first two vibronic peak intensities. Even in the resonance regime, the vibronic ratio remains a useful tool to evaluate the J or H nature of the system. The theory developed is applied to the reversible H to J-aggregate transformations recently observed in several perylene bisimide systems.

  9. Formation of An Ionic PTCA-β-CDNH2 Complex and Its Application for Phenol Sensing in Aqueous Phase.

    PubMed

    Liu, Lingling; Chen, Xiangli; Liu, Kaiqiang; He, Meixia; Wang, Gang; Chang, Xingmao; Fang, Yu

    2015-09-30

    On the basis of proton transfer in aqueous phase, we prepared a water-soluble and highly fluorescent ionic complex of 3,4,9,10-perylene tetracarboxylic acid (PTCA) and 6-deoxy-6-amino-β-CD (β-CDNH2) and studied its fluorescence behavior. It was found that the fluorescence emission of the complex is sensitive and selective to the presence of trace amount of toxic phenolic compounds, in particular phenol, which is crucial for water quality control. The detection limit (DL) of the method to the analyte is ~0.03 μM, a lowest value reported in literatures for similar techniques. Interestingly, the detection at an unprecedented subnanogram (DL, ~0.12 ng/cm(2)) level can also be conducted in a visualized manner, which may provide a simple and low-cost protocol for on-site and real-time detection of the analyte. Moreover, the complex is humidity sensitive in dry state, and its color changes from bright yellow to bright green when exposed to wet vapor. Unlike other PTCA bisimide derivatives, preparation of the ionic complex of PTCA/β-CDNH2 is simple and avoids complicated synthetic burden. Furthermore, introduction of methanol into the aqueous solution of the complex resulted in aggregation as indicated by solution color change and proved by transmission electron microscopy and dynamic light scattering studies, which explains why the compound in dry state is sensitive to the presence of water and water vapor. X-ray diffraction, UV-vis, and fluorescence studies uncovered the H-packing nature of the structure of the aggregate. PMID:26348064

  10. Interference between Coulombic and CT-mediated couplings in molecular aggregates: H- to J-aggregate transformation in perylene-based π-stacks.

    PubMed

    Hestand, Nicholas J; Spano, Frank C

    2015-12-28

    The spectroscopic differences between J and H-aggregates are traditionally attributed to the spatial dependence of the Coulombic coupling, as originally proposed by Kasha. However, in tightly packed molecular aggregates wave functions on neighboring molecules overlap, leading to an additional charge transfer (CT) mediated exciton coupling with a vastly different spatial dependence. The latter is governed by the nodal patterns of the molecular LUMOs and HOMOs from which the electron (te) and hole (th) transfer integrals derive. The sign of the CT-mediated coupling depends on the sign of the product teth and is therefore highly sensitive to small (sub-Angstrom) transverse displacements or slips. Given that Coulombic and CT-mediated couplings exist simultaneously in tightly packed molecular systems, the interference between the two must be considered when defining J and H-aggregates. Generally, such π-stacked aggregates do not abide by the traditional classification scheme of Kasha: for example, even when the Coulomb coupling is strong the presence of a similarly strong but destructively interfering CT-mediated coupling results in "null-aggregates" which spectroscopically resemble uncoupled molecules. Based on a Frenkel/CT Holstein Hamiltonian that takes into account both sources of electronic coupling as well as intramolecular vibrations, vibronic spectral signatures are developed for integrated Frenkel/CT systems in both the perturbative and resonance regimes. In the perturbative regime, the sign of the lowest exciton band curvature, which rigorously defines J and H-aggregation, is directly tracked by the ratio of the first two vibronic peak intensities. Even in the resonance regime, the vibronic ratio remains a useful tool to evaluate the J or H nature of the system. The theory developed is applied to the reversible H to J-aggregate transformations recently observed in several perylene bisimide systems.

  11. (Photo)physical Properties of New Molecular Glasses End-Capped with Thiophene Rings Composed of Diimide and Imine Units

    PubMed Central

    2014-01-01

    New symmetrical arylene bisimide derivatives formed by using electron-donating–electron-accepting systems were synthesized. They consist of a phthalic diimide or naphthalenediimide core and imine linkages and are end-capped with thiophene, bithiophene, and (ethylenedioxy)thiophene units. Moreover, polymers were obtained from a new diamine, N,N′-bis(5-aminonaphthalenyl)naphthalene-1,4,5,8-dicarboximide and 2,5-thiophenedicarboxaldehyde or 2,2′-bithiophene-5,5′-dicarboxaldehyde. The prepared azomethine diimides exhibited glass-forming properties. The obtained compounds emitted blue light with the emission maximum at 470 nm. The value of the absorption coefficient was determined as a function of the photon energy using spectroscopic ellipsometry. All compounds are electrochemically active and undergo reversible electrochemical reduction and irreversible oxidation processes as was found in cyclic voltammetry and differential pulse voltammetry (DPV) studies. They exhibited a low electrochemically (DPV) calculated energy band gap (Eg) from 1.14 to 1.70 eV. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels and Eg were additionally calculated theoretically by density functional theory at the B3LYP/6-31G(d,p) level. The photovoltaic properties of two model compounds as the active layer in organic solar cells in the configuration indium tin oxide/poly(3,4-(ethylenedioxy)thiophene):poly(styrenesulfonate)/active layer/Al under an illumination of 1.3 mW/cm2 were studied. The device comprising poly(3-hexylthiophene) with the compound end-capped with bithiophene rings showed the highest value of Voc (above 1 V). The conversion efficiency of the fabricated solar cell was in the range of 0.69–0.90%. PMID:24966893

  12. (Photo)physical Properties of New Molecular Glasses End-Capped with Thiophene Rings Composed of Diimide and Imine Units.

    PubMed

    Grucela-Zajac, Marzena; Bijak, Katarzyna; Kula, Slawomir; Filapek, Michal; Wiacek, Malgorzata; Janeczek, Henryk; Skorka, Lukasz; Gasiorowski, Jacek; Hingerl, Kurt; Sariciftci, Niyazi Serdar; Nosidlak, Natalia; Lewinska, Gabriela; Sanetra, Jerzy; Schab-Balcerzak, Ewa

    2014-06-19

    New symmetrical arylene bisimide derivatives formed by using electron-donating-electron-accepting systems were synthesized. They consist of a phthalic diimide or naphthalenediimide core and imine linkages and are end-capped with thiophene, bithiophene, and (ethylenedioxy)thiophene units. Moreover, polymers were obtained from a new diamine, N,N'-bis(5-aminonaphthalenyl)naphthalene-1,4,5,8-dicarboximide and 2,5-thiophenedicarboxaldehyde or 2,2'-bithiophene-5,5'-dicarboxaldehyde. The prepared azomethine diimides exhibited glass-forming properties. The obtained compounds emitted blue light with the emission maximum at 470 nm. The value of the absorption coefficient was determined as a function of the photon energy using spectroscopic ellipsometry. All compounds are electrochemically active and undergo reversible electrochemical reduction and irreversible oxidation processes as was found in cyclic voltammetry and differential pulse voltammetry (DPV) studies. They exhibited a low electrochemically (DPV) calculated energy band gap (E g) from 1.14 to 1.70 eV. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels and E g were additionally calculated theoretically by density functional theory at the B3LYP/6-31G(d,p) level. The photovoltaic properties of two model compounds as the active layer in organic solar cells in the configuration indium tin oxide/poly(3,4-(ethylenedioxy)thiophene):poly(styrenesulfonate)/active layer/Al under an illumination of 1.3 mW/cm(2) were studied. The device comprising poly(3-hexylthiophene) with the compound end-capped with bithiophene rings showed the highest value of V oc (above 1 V). The conversion efficiency of the fabricated solar cell was in the range of 0.69-0.90%. PMID:24966893

  13. Long distance energy transfer in a polymer matrix doped with a perylene dye.

    PubMed

    Fennel, Franziska; Lochbrunner, Stefan

    2011-02-28

    Exciton migration over long distances is a key issue for various applications in organic electronics. We investigate a disordered material system which has the potential for long exciton diffusion lengths in combination with a high versatility. The perylene bisimide dye Perylene Red is incorporated in a polymer matrix with a high concentration. The dye molecules represent active sites with a narrow energy distribution for the electronically excited states. Excitons can be efficiently exchanged between them by Förster resonance energy transfer (FRET). The narrow energy distribution reduces drastically the trapping probability of the excitons compared to polymers and allows for long transfer distances. To characterize the mobility of the excitons and their diffusion length the dye Oxazine 1 is added as an acceptor in low concentration and the transfer probability to the acceptor is determined by measuring the reduction of Perylene Red fluorescence. The quenched quantum yield is measured for dye concentrations varying from 0.05 M to 0.15 M for Perylene Red and from 0.3 mM to 3 mM for Oxazine 1. The experimental results are compared to a model which assumes that excitons can diffuse through the material by FRET between Perylene Red sites and are trapped at an acceptor with a final hetero FRET step. We find a quite good match between theory and experiment though the observed diffusion constant is about two times smaller than the calculated one. The exciton diffusion length extracted from the data is 30 nm for a Perylene Red concentration of 0.1 M and demonstrates that long distance energy transfer is possible in this disordered material system.

  14. Investigations into complex liquid crystal mixtures

    NASA Astrophysics Data System (ADS)

    Kirchhoff, Jennifer

    Liquid crystal phases exhibit physical characteristics that lie between those of liquid and crystal phases. The many liquid crystal sub-phases are defined based on the degree of positional and orientational ordering the molecules have and the materials that make up these liquid crystal phases. This thesis presents a study of the molecular packing and physical properties of complex liquid crystal phases using dopants to better examine the stability and packing mechanisms of these phases. It also looks at the dispersion of quantum dots in liquid crystal materials, examining the electro-optical properties of the mixtures. The main goal of this thesis is to examine the effects of dopants on the properties of liquid crystal phases using optical microscopy, differential scanning calorimetry, electro-optical measurements, and X-ray scattering. For those mixtures with quantum dots fluorescence microscopy and photoluminescence measurements were also conducted. Rod-like liquid crystals are commonly used in display applications when the material is in a nematic liquid crystal phase, which is the least ordered phase exhibiting no positional ordering. The more complicated chiral smectic liquid crystal phases, which have a one dimensional layer structure, show potential for faster and tri-stable switching. A chiral rod-like liquid crystal material is doped with both chiral and achiral rod-like liquid crystals to examine the stability of one of the chiral smectic sub-phase, the SmC* FI1 phase. This phase consists of tilted molecules rotating about the cone defined by the tilt angle with a periodicity of three layers and an overall helical structure. The SmC*FI1 phase is stabilized by the competition between antiferroelectric and ferroelectric interactions, and small amounts of the achiral dopant broadens the range of this phase by almost 5°C. Higher dopant concentrations of the achiral material result in the destabilization of not just the SmC*FI1 phase but all tilted sub

  15. Investigations into complex liquid crystal mixtures

    NASA Astrophysics Data System (ADS)

    Kirchhoff, Jennifer

    Liquid crystal phases exhibit physical characteristics that lie between those of liquid and crystal phases. The many liquid crystal sub-phases are defined based on the degree of positional and orientational ordering the molecules have and the materials that make up these liquid crystal phases. This thesis presents a study of the molecular packing and physical properties of complex liquid crystal phases using dopants to better examine the stability and packing mechanisms of these phases. It also looks at the dispersion of quantum dots in liquid crystal materials, examining the electro-optical properties of the mixtures. The main goal of this thesis is to examine the effects of dopants on the properties of liquid crystal phases using optical microscopy, differential scanning calorimetry, electro-optical measurements, and X-ray scattering. For those mixtures with quantum dots fluorescence microscopy and photoluminescence measurements were also conducted. Rod-like liquid crystals are commonly used in display applications when the material is in a nematic liquid crystal phase, which is the least ordered phase exhibiting no positional ordering. The more complicated chiral smectic liquid crystal phases, which have a one dimensional layer structure, show potential for faster and tri-stable switching. A chiral rod-like liquid crystal material is doped with both chiral and achiral rod-like liquid crystals to examine the stability of one of the chiral smectic sub-phase, the SmC* FI1 phase. This phase consists of tilted molecules rotating about the cone defined by the tilt angle with a periodicity of three layers and an overall helical structure. The SmC*FI1 phase is stabilized by the competition between antiferroelectric and ferroelectric interactions, and small amounts of the achiral dopant broadens the range of this phase by almost 5°C. Higher dopant concentrations of the achiral material result in the destabilization of not just the SmC*FI1 phase but all tilted sub

  16. Synthesis and characterization of F-doped Cs{sub 0.33}WO{sub 3−x}F{sub x} particles with improved near infrared shielding ability

    SciTech Connect

    Liu, Jingxiao; Luo, Jiayu; Shi, Fei Liu, Suhua; Fan, Chuanyan; Xu, Qiang; Shao, Guolin

    2015-01-15

    F-doped Cs{sub 0.33}WO{sub 3−x}F{sub x} particles were successfully synthesized by the hydrothermal method with hydrofluoric acid as fluorine source, and a new kind of heat insulating films were prepared from dispersion of Cs{sub 0.33}WO{sub 3−x}F{sub x} nanoparticles in polyvinyl alcohol (PVA) aqueous solution. The effects of F doping on the crystal structure and morphology of Cs{sub 0.33}WO{sub 3−x}F{sub x} particles as well as the near-infrared (NIR) shielding ability and heat insulation properties of Cs{sub 0.33}WO{sub 3−x}F{sub x} films were investigated. The results indicated that HF acid addition could promote the formation of rod-like Cs{sub 0.33}WO{sub 3−x}F{sub x} particles during hydrothermal synthesis and increase the yield of Cs{sub 0.33}WO{sub 3−x}F{sub x} powders. Moreover, the as-prepared films from dispersion solution of Cs{sub 0.33}WO{sub 3−x}F{sub x} particles exhibited higher near-infrared (NIR) shielding ability and heat insulating properties than that of the undoped Cs{sub 0.33}WO{sub 3} film. Particularly, the as-prepared Cs{sub 0.33}WO{sub 3−x}F{sub x} sample with F/W (molar ratio)=0.45 showed best NIR shielding ability and transparent heat insulating performance. The formation mechanism of nanorod-like particles and the effects of F doping on the properties of Cs{sub 0.33}WO{sub 3−x}F{sub x} products were discussed. - Graphical abstract: F-doped Cs{sub 0.33}WO{sub 3−x}F{sub x} particles were successfully synthesized by the hydrothermal method with hydrofluoric acid as fluorine source. HF acid addition in the precursor solution could increase the yield of Cs{sub 0.33}WO{sub 3−x}F{sub x} powders and promote the formation of rod-like Cs{sub 0.33}WO{sub 3−x}F{sub x} particles. Moreover, the as-prepared Cs{sub 0.33}WO{sub 3−x}F{sub x} films from dispersion solution of Cs{sub 0.33}WO{sub 3−x}F{sub x} particles exhibited higher near-infrared (NIR) shielding ability and heat insulating properties than that of the undoped

  17. Iron oxide nanorods as high-performance magnetic resonance imaging contrast agents

    NASA Astrophysics Data System (ADS)

    Mohapatra, Jeotikanta; Mitra, Arijit; Tyagi, Himanshu; Bahadur, D.; Aslam, M.

    2015-05-01

    An efficient magnetic resonance imaging (MRI) contrast agent with a high R2 relaxivity value is achieved by controlling the shape of iron oxide to rod like morphology with a length of 30-70 nm and diameter of 4-12 nm. Fe3O4 nanorods of 70 nm length, encapsulated with polyethyleneimine show a very high R2 relaxivity value of 608 mM-1 s-1. The enhanced MRI contrast of nanorods is attributed to their higher surface area and anisotropic morphology. The higher surface area induces a stronger magnetic field perturbation over a larger volume more effectively for the outer sphere protons. The shape anisotropy contribution is understood by calculating the local magnetic field of nanorods and spherical nanoparticles under an applied magnetic field (3 Tesla). As compared to spherical geometry, the induced magnetic field of a rod is stronger and hence the stronger magnetic field over a large volume leads to a higher R2 relaxivity of nanorods.An efficient magnetic resonance imaging (MRI) contrast agent with a high R2 relaxivity value is achieved by controlling the shape of iron oxide to rod like morphology with a length of 30-70 nm and diameter of 4-12 nm. Fe3O4 nanorods of 70 nm length, encapsulated with polyethyleneimine show a very high R2 relaxivity value of 608 mM-1 s-1. The enhanced MRI contrast of nanorods is attributed to their higher surface area and anisotropic morphology. The higher surface area induces a stronger magnetic field perturbation over a larger volume more effectively for the outer sphere protons. The shape anisotropy contribution is understood by calculating the local magnetic field of nanorods and spherical nanoparticles under an applied magnetic field (3 Tesla). As compared to spherical geometry, the induced magnetic field of a rod is stronger and hence the stronger magnetic field over a large volume leads to a higher R2 relaxivity of nanorods. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00055f

  18. Light scattering characterization of carbon nanotube dispersions and reinforcement of polymer composites

    NASA Astrophysics Data System (ADS)

    Zhao, Jian

    Dispersion and morphology of carbon nanotubes as well as enhancement for rubber reinforcement are studied. Several approaches including surfactant aids, functionalization and plasma treatment are used to assist dispersion. Several characterization methods are used to assess both the degree of dispersion and the level of reinforcement. Small angle light scattering is carried out as a primary tool to assess structure and dispersion of nanotubes treated through these approaches Stress-strain measurement and dynamic mechanical analysis are performed on elastomeric composites to study polymer reinforcement. These results are divided into five sections. The first section focuses on dispersion of untreated and acid-treated multi-walled carbon nanofibers (MWNF) suspended in water. Light scattering data provide the first insights into the mechanism by which surface treatment promotes dispersion. Both acid-treated and untreated nanofibers exhibit hierarchical morphology consisting of small-scale aggregates (bundles) that agglomerate to form fractal clusters that eventually precipitate. Although the morphology of the aggregates and agglomerates is nearly independent of surface treatment, their time evolution is quite different. Acid oxidation has little effect on bundle morphology. Rather acid treatment inhibits agglomeration of the bundles. The second section focuses on dispersion of the solubilized nanofibers. Light scattering data indicate that PEG-functionalized sample is dispersed at small rod-like bundle (side-by-side aggregate) level. Solubilization is achieved not by disrupting small-scale size-by-side bundles, but mainly by completely inhibiting large-scale agglomeration. The third section focuses on dispersion of plasma-treated carbon nanofibers. Comparison of untreated and plasma-treated nanofibers indicates that plasma treatment facilitates dispersion of nanofibers. The fourth section focuses on dispersion and structure of single-walled carbon nanotubes (SWNTs

  19. Effect of Carbide Ceramic Zone on Wear Resistance of the (Fe,Cr)7C3/Fe Surface Gradient Composite

    NASA Astrophysics Data System (ADS)

    Ye, Fangxia; Xu, Yunhua; Hojamberdiev, Mirabbos; Lai, Yujun; Wang, Chong; Wang, Xin

    2015-08-01

    In this work, we report on the influence of microstructure and mechanical properties of the (Fe,Cr)7C3 ceramic zone on wear resistance of the (Fe,Cr)7C3/Fe surface gradient composite fabricated by in situ synthesis method followed by a post-heat treatment at 1100 °C for 20 h in argon atmosphere. The phase composition, microstructure, nanoindentation hardness, elastic modulus, fracture toughness, and relative wear resistance of the (Fe,Cr)7C3/Fe surface gradient composite were investigated by means of x-ray diffraction, scanning electron microscopy, nanoindentation tester, and wear resistance testing instrument, respectively. The XRD results showed that (Fe,Cr)7C3 is the predominant crystalline phases in the fabricated composite. The volume fraction of the (Fe,Cr)7C3 particulates formed has a gradient distribution from the surface to the iron matrix, and the microstructure also changes significantly. The (Fe,Cr)7C3 bulk ceramic zone with the volume fraction of about 100% and the (Fe,Cr)7C3 dense ceramic zone with the volume fraction of about 90% were synthesized on the upper surface of the (Fe,Cr)7C3/Fe surface gradient composite, respectively. The average nanoindentation hardness and elastic modulus of the (Fe,Cr)7C3 bulk ceramic zone of the composite were determined to be 12.711 and 256.054 GPa, respectively. The fracture toughness of the (Fe,Cr)7C3 bulk ceramic zone is in the range of 2.06-4.19 MPa m1/2, and its relative wear resistance is about 56 times higher than that of the iron matrix. The (Fe,Cr)7C3 dense ceramic zone with rod-like, secondary (Fe,Cr)7C3 particulates was formed at the bottom of the (Fe,Cr)7C3 bulk ceramic zone. Rod-like, secondary (Fe,Cr)7C3 particulates are dense and grew in the direction of the iron substrate, providing higher wear resistance to the composite. The wear mechanisms of the (Fe,Cr)7C3 bulk and dense ceramic zones are considered to be microcutting, microcracking, and spalling pit.

  20. Anisotropy in CdSe quantum rods

    SciTech Connect

    Li, Liang-shi

    2003-09-01

    The size-dependent optical and electronic properties of semiconductor nanocrystals have drawn much attention in the past decade, and have been very well understood for spherical ones. The advent of the synthetic methods to make rod-like CdSe nanocrystals with wurtzite structure has offered us a new opportunity to study their properties as functions of their shape. This dissertation includes three main parts: synthesis of CdSe nanorods with tightly controlled widths and lengths, their optical and dielectric properties, and their large-scale assembly, all of which are either directly or indirectly caused by the uniaxial crystallographic structure of wurtzite CdSe. The hexagonal wurtzite structure is believed to be the primary reason for the growth of CdSe nanorods. It represents itself in the kinetic stabilization of the rod-like particles over the spherical ones in the presence of phosphonic acids. By varying the composition of the surfactant mixture used for synthesis we have achieved tight control of the widths and lengths of the nanorods. The synthesis of monodisperse CdSe nanorods enables us to systematically study their size-dependent properties. For example, room temperature single particle fluorescence spectroscopy has shown that nanorods emit linearly polarized photoluminescence. Theoretical calculations have shown that it is due to the crossing between the two highest occupied electronic levels with increasing aspect ratio. We also measured the permanent electric dipole moment of the nanorods with transient electric birefringence technique. Experimental results on nanorods with different sizes show that the dipole moment is linear to the particle volume, indicating that it originates from the non-centrosymmetric hexagonal lattice. The elongation of the nanocrystals also results in the anisotropic inter-particle interaction. One of the consequences is the formation of liquid crystalline phases when the nanorods are dispersed in solvent to a high enough

  1. Effects of Solute and Surfactant Addition on the Crystallization and Morphology of Hydroxyapatite Powders Synthesized by Hydrolysis of Calcium Hydrogen Phosphate Dehydrate (DCPD)

    NASA Astrophysics Data System (ADS)

    Chen, Hui-Ting; Chang, Hsin-Fang; Ko, Horng-Huey; Hung, I.-Ming; Yen, Feng-Lin; Huang, Hong-Hsin; Hon, Min-Husing; Wang, Moo-Chin; Shih, Wei-Jen

    2013-02-01

    The effects of the addition of alcohol and cetyltrimethylammonium bromide (CTAB) on the crystallization and the morphology of hydroxyapatite (HA) powders synthesized by hydrolysis of calcium hydrogen phosphate dehydrate (DCPD) in the 2.5 M NaOH solutions at 348 K (75 °C) for 1 hour have been studied. The values of zeta potential have large differences between the sums of DCPD with CTAB ( Z DCPD+CTAB) minus the sum of DCPD and CTAB ( Z DCPD + Z CTAB), and of HA with CTAB ( Z HA+CTAB) minus the sum of HA and CTAB ( Z HA + Z CTAB), respectively. When the hydrolysis of DCPD occurred in the 2.5 M NaOH solutions at 348 K (75 °C) for 1 hour both with and without alcohol and CTAB, XRD results show the only one phase of HA in the as-dried powders. When the NaOH solution does not contain CTAB, the crystallite size of HA powders decreased from 23 ± 1 to 16 ± 1 nm as the alcohol content was more than 50 pct. The crystallite size of HA powders obtained from DCPD synthesized in the 2.5 M NaOH solution with 1.0 × 10-3 M CTAB decreased when the alcohol content was increased to 70 pct, whereas the crystallite size increased when the alcohol concentration was greater than that of 70 pct. SEM images show that the HA powders have a rod-like shape when DCPD was synthesized in the 2.5 M NaOH solution without CTAB or alcohol. When the NaOH solution had 1.0 × 10-3 M CTAB and various alcohol concentrations, the morphology of HA powder still maintained a rod-like or needle-like shape. The HA powder had a maximum specific surface area of 180.25 m2/g when the hydrolysis of DCPD occurred in a 2.5 M NaOH solution containing 1.0 × 10-3 M CTAB and 70 pct alcohol at 348 K (75 °C) for 1 hour.

  2. Investigating the orientational order in smectic liquid crystals

    NASA Astrophysics Data System (ADS)

    Wang, Shun

    This thesis is composed of two projects. The first one is the investigation of a reversed phase sequence, which subsequently leads to the discovery of a novel Smectic-C liquid crystal phase. The 10OHFBBB1M7 (10OHF) compound shows a reversed phase sequence with the SmC*d4 phase occurring at a higher temperature than the SmC* phase. This phase sequence is stabilized by moderate doping of 9OTBBB1M7 (C9) or 11OTBBB1M7 (C11). To further study this unique phase sequence, the mixtures of 10OHFBBB1M7 and its homologs have been characterized by optical techniques. In order to perform the resonant X-ray diffraction experiment, we have added C9 and C11 compounds to the binary mixtures and pure 10OHF. In two of the studied mixtures, a new smectic-C* liquid crystal phase with six-layer periodicity has been discovered. Upon cooling, the new phase appears between the SmC*a phase having a helical structure and the SmC*d4 phase with four-layer periodicity. The SmC*d6 phase shows a distorted clock structure. Three theoretical models have predicted the existence of a six-layer phase. However, our experimental findings are not consistent with the theories. The second project involves the mixtures of liquid crystals with different shapes. The role of different interactions in stabilizing the antiferroelectric smectic liquid crystal phases have been a long-standing questions in the community. By mixing the antiferroelectric smectic liquid crystal with achiral liquid crystal molecules with rod and hockey-stick shapes, distinct different behaviors are obtained. In the case of the mixtures of chiral smectic liquid crystals with rod-like molecules, all the smectic-C* variant phases vanish with a small amount of doping. However, the hockey-stick molecule is much less destructive compared to the rod-like molecule. This suggests that the antiferroelectric smectic liquid crystal molecules may have a shape closer to a hockey-stick rather than a rod.

  3. Synthesis of Co-based bimetallic nanocrystals with one-dimensional structure for selective control on syngas conversion

    NASA Astrophysics Data System (ADS)

    Ba, Rongbin; Zhao, Yonghui; Yu, Lujing; Song, Jianjun; Huang, Shuangshuang; Zhong, Liangshu; Sun, Yuhan; Zhu, Yan

    2015-07-01

    Co-based bimetallic nanocrystals with one-dimensional (1D) branches were synthesized by the heterogeneous nucleation of Co atoms onto prenucleated seeds, such as Pd or Cu, through a facile wet-chemical route. The peripheral branches (rod-like) of the Co-Pd and Co-Cu nanocrystals were outspread along the (001) direction and were enclosed by (101) facets. By switching the prenucleated metals to form robust Co-Pd or Co-Cu bimetallic nanocatalysts, the selectivity of CO hydrogenation could be adjusted purposely towards heavy paraffins, light olefins or oxygenates. The Anderson-Schulz-Flory chain-lengthening probabilities for products were up to 0.9 over Co-Pd nanocrystals, showing that long-chain hydrocarbons can be formed with high selectivity using the targeted design of Co-Pd nanocrystal catalysts. These Co-based bimetallic nanocrystals with a 1D structure exhibited superior catalytic activities over the corresponding Co-based nanoparticles for synthesis gas conversion.Co-based bimetallic nanocrystals with one-dimensional (1D) branches were synthesized by the heterogeneous nucleation of Co atoms onto prenucleated seeds, such as Pd or Cu, through a facile wet-chemical route. The peripheral branches (rod-like) of the Co-Pd and Co-Cu nanocrystals were outspread along the (001) direction and were enclosed by (101) facets. By switching the prenucleated metals to form robust Co-Pd or Co-Cu bimetallic nanocatalysts, the selectivity of CO hydrogenation could be adjusted purposely towards heavy paraffins, light olefins or oxygenates. The Anderson-Schulz-Flory chain-lengthening probabilities for products were up to 0.9 over Co-Pd nanocrystals, showing that long-chain hydrocarbons can be formed with high selectivity using the targeted design of Co-Pd nanocrystal catalysts. These Co-based bimetallic nanocrystals with a 1D structure exhibited superior catalytic activities over the corresponding Co-based nanoparticles for synthesis gas conversion. Electronic supplementary

  4. Brevipalpus-transmitted plant virus and virus-like diseases: cytopathology and some recent cases.

    PubMed

    Kitajima, E W; Chagas, C M; Rodrigues, J C V

    2003-01-01

    An increasing number of diseases transmitted by Brevipalpus mite species (Acari: Tenuipalpidae) is being identified that affect economically important plants such as citrus, coffee, passion fruit, orchids, and several ornamentals. All of these diseases are characterized by localized lesions (chlorotic, green spots, or ringspots) on leaves, stems, and fruits. Virus or virus-like agents are considered to be the causal agents, possibly transmitted in a circulative-propagative manner by Brevipalpus mites. The virus or virus-like particles are short, rod-like, or bacilliform, that induce two characteristic types of cell alteration: (1) 'Nuclear type'--nuclei of parenchyma and epidermal cells in the lesions often contain a large electron lucent inclusion. Short, naked, rod-like (40-50 nm x 100-110 nm) particles may be seen in the viroplasm or nucleoplasm and in the cytoplasm. These particles are commonly arranged perpendicularly on the membranes of the nuclear envelope or endoplasmic reticulum (ER). In a very few instances, they were found to be membrane-bound, within the ER cavities. (2) 'Cytoplasmic type'--short bacilliform particles (60-70 nm x 110-120 nm) are present within the cisternae of the ER and often have electron dense viroplasm of varied shapes present in the cytoplasm. Bacilliform particles may be seen budding into the ER lumen near the viroplasm. These particles resemble those of members of the Rhabdoviridae, but are shorter. The only sequenced virus of this group, orchid fleck virus (OFV), has a negative sense (bipartite) type ssRNA genome, but its organization is similar to known rhabdoviruses, which are monopartite. Both types of cytopathological effects have been found associated with citrus leprosis. In orchids, OFV has a 'nuclear type' of cytopathology, but in some species the 'cytoplasmic type' has been found associated with ringspot symptoms. In Hibiscus and Clerodendron, green spot symptoms have been associated with the cytoplasmic type of cell

  5. Layer-stacked tin disulfide nanorods in silica nanoreactors with improved lithium storage capabilities

    NASA Astrophysics Data System (ADS)

    Wu, Ping; Du, Ning; Zhang, Hui; Liu, Jie; Chang, Lantao; Wang, Lei; Yang, Deren; Jiang, Jian-Zhong

    2012-06-01

    A new structure of layered materials, layer-stacked nanorod, has been fabricated through an entirely new template-engaged structural transformation methodology. The formation of layer-stacked hexagonal tin disulfide (SnS2) nanorods has been demonstrated as an example by using tetragonal tin (Sn) nanorods as sacrificing templates and silica (SiO2) as nanoreactors. In addition, the structural transformation process probably involves the formation of orthorhombic tin sulfide (SnS) nanorods as an intermediate product. The rod-like morphology and single-crystal feature of the Sn templates are well preserved in both SnS2 and SnS products due to the nanoscale confinement in silica. Owing to its unique structural characteristics, the SnS2-SiO2 nanorod anode exhibits excellent capacity retention and improved rate capability, facilitating its application in lithium ion batteries with long cycle life and high power density.A new structure of layered materials, layer-stacked nanorod, has been fabricated through an entirely new template-engaged structural transformation methodology. The formation of layer-stacked hexagonal tin disulfide (SnS2) nanorods has been demonstrated as an example by using tetragonal tin (Sn) nanorods as sacrificing templates and silica (SiO2) as nanoreactors. In addition, the structural transformation process probably involves the formation of orthorhombic tin sulfide (SnS) nanorods as an intermediate product. The rod-like morphology and single-crystal feature of the Sn templates are well preserved in both SnS2 and SnS products due to the nanoscale confinement in silica. Owing to its unique structural characteristics, the SnS2-SiO2 nanorod anode exhibits excellent capacity retention and improved rate capability, facilitating its application in lithium ion batteries with long cycle life and high power density. Electronic supplementary information (ESI) available: Detailed experimental procedures, EDX elemental mapping, XPS, IFFT, XRD and SEM images. See

  6. Stopped-flow kinetic studies of sphere-to-rod transitions of sodium alkyl sulfate micelles induced by hydrotropic salt.

    PubMed

    Zhang, Jingyan; Ge, Zhishen; Jiang, Xiaoze; Hassan, P A; Liu, Shiyong

    2007-12-15

    The kinetics and mechanism of sphere-to-rod transitions of sodium alkyl sulfate micelles induced by hydrotropic salt, p-toluidine hydrochloride (PTHC), were investigated by stopped-flow with light scattering detection. Spherical sodium dodecyl sulfate (SDS) micelles transform into short ellipsoidal shapes at low salt concentrations ([PTHC]/[SDS], chi(PTHC)=0.3 and 0.4). Upon stopped-flow mixing aqueous solutions of spherical SDS micelles with PTHC, the scattered light intensity gradually increases with time. Single exponential fitting of the dynamic traces leads to characteristic relaxation time, tau(g), for the growth process from spherical to ellipsoidal micelles, and it increases with increasing SDS concentrations. This suggests that ellipsoidal micelles might be produced by successive insertion of unimers into spherical micelles, similar to the case of formation of spherical micelles as suggested by Aniansson-Wall (A-W) theory. At chi(PTHC) > or = 0.5, rod-like micelles with much higher axial ratio form. The scattered light intensity exhibits an initially abrupt increase and then levels off. The dynamic curves can be well fitted with single exponential functions, and the obtained tau(g) decreases with increasing SDS concentration. Thus, the growth from spherical to rod-like micelles might proceed via fusion of spherical micelles, in agreement with mechanism proposed by Ikeda et al. At chi(PTHC)=0.3 and 0.6, the apparent activation energies obtained from temperature dependent kinetic studies for the micellar growth are 40.4 and 3.6 kJ/mol, respectively. The large differences between activation energies for the growth from spherical to ellipsoidal micelles at low chi(PTHC) and the sphere-to-rod transition at high chi(PTHC) further indicate that they should follow different mechanisms. Moreover, the sphere-to-rod transition kinetics of sodium alkyl sulfate with varying hydrophobic chain lengths (n=10, 12, 14, and 16) are also studied. The longer the carbon chain

  7. Stopped-flow kinetic studies of sphere-to-rod transitions of sodium alkyl sulfate micelles induced by hydrotropic salt.

    PubMed

    Zhang, Jingyan; Ge, Zhishen; Jiang, Xiaoze; Hassan, P A; Liu, Shiyong

    2007-12-15

    The kinetics and mechanism of sphere-to-rod transitions of sodium alkyl sulfate micelles induced by hydrotropic salt, p-toluidine hydrochloride (PTHC), were investigated by stopped-flow with light scattering detection. Spherical sodium dodecyl sulfate (SDS) micelles transform into short ellipsoidal shapes at low salt concentrations ([PTHC]/[SDS], chi(PTHC)=0.3 and 0.4). Upon stopped-flow mixing aqueous solutions of spherical SDS micelles with PTHC, the scattered light intensity gradually increases with time. Single exponential fitting of the dynamic traces leads to characteristic relaxation time, tau(g), for the growth process from spherical to ellipsoidal micelles, and it increases with increasing SDS concentrations. This suggests that ellipsoidal micelles might be produced by successive insertion of unimers into spherical micelles, similar to the case of formation of spherical micelles as suggested by Aniansson-Wall (A-W) theory. At chi(PTHC) > or = 0.5, rod-like micelles with much higher axial ratio form. The scattered light intensity exhibits an initially abrupt increase and then levels off. The dynamic curves can be well fitted with single exponential functions, and the obtained tau(g) decreases with increasing SDS concentration. Thus, the growth from spherical to rod-like micelles might proceed via fusion of spherical micelles, in agreement with mechanism proposed by Ikeda et al. At chi(PTHC)=0.3 and 0.6, the apparent activation energies obtained from temperature dependent kinetic studies for the micellar growth are 40.4 and 3.6 kJ/mol, respectively. The large differences between activation energies for the growth from spherical to ellipsoidal micelles at low chi(PTHC) and the sphere-to-rod transition at high chi(PTHC) further indicate that they should follow different mechanisms. Moreover, the sphere-to-rod transition kinetics of sodium alkyl sulfate with varying hydrophobic chain lengths (n=10, 12, 14, and 16) are also studied. The longer the carbon chain

  8. Voltage-gated inward currents of morphologically identified cells of the frog taste disc.

    PubMed

    Suwabe, Takeshi; Kitada, Yasuyuki

    2004-01-01

    We used the patch clamp technique to record from taste cells in vertical slices of the bullfrog (Rana catesbeiana) taste disc. Cell types were identified by staining with Lucifer yellow in a pipette after recording their electrophysiological properties. Cells could be divided into the following three groups: type Ib (wing) cells with sheet-like apical processes, type II (rod) cells with single thick rod-like apical processes and type III (rod) cells with thin rod-like apical processes. No dye-coupling was seen either between cells of the same type or between cells of different types. We focused on the voltage-gated inward currents of the three types of cells. Type Ib and type II cells exhibited tetrodotoxin (TTX)-sensitive voltage-gated Na+ currents. Surprisingly, type III cells showed TTX-resistant voltage-gated Na+ currents and exhibited a lack of TTX-sensitive Na+ currents. TTX-resistant voltage-gated Na+ currents in taste cells are reported for the first time here. The time constant for the inactivating portion of the voltage-gated inward Na+ currents of type III cells was much larger than that of type Ib and type II cells. Therefore, slow inactivation of inward Na+ currents characterizes type III cells. Amplitudes of the maximum peak inward currents of type III cells were smaller than those of type Ib and type II cells. However, the density (pA/pF) of the maximum peak inward currents of type III cells was much higher than that of type Ib cells and close to that of type II cells. No evidence of the presence of voltage-gated Ca2+ channels in frog taste cells has been presented up to now. In this study, voltage-gated Ba2+ currents were observed in type III cells but not in type Ib and type II cells when the bath solution was a standard Ba2+ solution containing 25 mM Ba2+. Voltage-gated Ba2+ currents were blocked by addition of 2 mM CoCl2 to the standard Ba2+ solution, suggesting that type III cells possess the voltage-gated Ca2+ channels and they do classical

  9. Surface and related bulk properties of titania nanoparticles recovered from aramid–titania hybrid films: A novel attempt

    SciTech Connect

    Al-Omani, Sara J.; Bumajdad, Ali; Al Sagheer, Fakhreia A.; Zaki, Mohamed I.

    2012-11-15

    Highlights: ► Aramid–titania hybrid films (5 and 10 wt%-TiO{sub 2}) were prepared via sol–gel processing. ► 450 °C calcination of the films yield anatase-TiO{sub 2} nanoparticles of rod-like morphology. ► The titania nanoparticle, crystal structure, high surface area are stable up to 800 °C. ► The novel approach has the advantage of nearly 100% recovery of titania. ► Increasing calcination temperature up to 1100 °C triggers anatase → rutile transition. -- Abstract: 5 and 10 wt%-TiO{sub 2}-containing aramid–titania hybrid films were prepared using sol–gel processing improved by the inclusion of 3-isocyanato-propyltriethoxysilane (ICTOS) to strengthen bonding of the titania species to the polymer backbone and, hence, lessen its agglomeration. The films were thermally degraded by heating at 450 °C in a dynamic atmosphere of air. The solid residues were found by thermogravimetry, X-ray diffractometry and electron microscopy to consist dominantly of uniformly agglomerated rod-like anatase-TiO{sub 2} nanoparticles, irrespective of the titania content of the film. The recovered titania particle morphology and surface microstructure were examined by field emission scanning and high-resolution transmission electron microscopy, respectively. Whereas, the particle surface chemistry and texture were assessed, respectively, by means of X-ray photoelectron spectroscopy and N{sub 2} sorptiometry. The recovered titanias were found, irrespective of the film content of titania, to enjoy not only a high temperature (up to 800 °C) stable nanoscopic anatase bulk structure, but also a high-temperature stable surface chemical composition (lattice Ti{sup 4+} and O{sup 2−}, and adsorbed OH/CH{sub x} species), (101)-faceted microstructure and highly accessible (145–112 m{sup 2}/g), uniform mesoporous texture with average pore diameter in the narrow range of 3.9–6.3 nm. Increasing the calcination temperature up to 1100 °C enhances an anatase → rutile

  10. Photoreceptor proteins and melatonin rhythm generating AANAT in the carp pineal: Temporal organization and correlation with natural photo-thermal cues.

    PubMed

    Seth, Mohua; Maitra, Saumen Kumar

    2010-04-01

    We studied temporal organization of both the photoreceptor (rod-like opsin, alpha subunit of the G protein transducin or alpha-TD) and melatonin generating (AANAT) proteins in the same pineal of a tropical surface dwelling free-living carp Catla catla, and analyzed possible correlation between them as well as with natural photo-thermal variables in an annual cycle. The pineal from individual fish was collected at four different time points (06.00 h, 12.00 h, 18.00 h, and 24.00 h) in a 24.00 h cycle and the same was repeated in four distinct seasons in an annual reproductive cycle to study each protein following Western blot and densitometric analyses of respective immunoblots. The rod-like opsin was represented by four distinct bands, a closely spaced doublet of 39 kDa and bands of 78 and 115 kDa. Two separate bands, one at 43 kDa and another at 65 kDa, were detected for alpha-TD, and a single band at 23 kDa for AANAT. Both the pineal photoreceptor proteins exhibited an identical pattern of diurnal variations with a peak at midday (12.00 h) and fall at midnight (24.00 h), while maximum band intensity of AANAT was noted in midnight (24.00 h) and minimum at midday (12.00 h) depicting a significant negative correlation (p<0.001) between them. Likewise, in an annual cycle, a significant (p<0.01) negative correlation was found between the expression of each pineal photoreceptor protein (being highest during the spawning phase) and AANAT (maximum during the post-spawning phase). Seasonal fluctuations of both the photoperiod and water temperature exhibited a significant (p<0.01) positive correlation with the expression of pineal photoreceptor proteins and a significant (p<0.05) negative correlation with the pineal AANAT. Collectively, the present phenological study is the first report on temporal organization of pineal photoreceptor proteins and their correlation with the melatonin rhythm-generating enzyme AANAT as well as environmental photo-thermal cues depicting their

  11. Systematic study on the influence of the morphology of α-MoO{sub 3} in the selective oxidation of propylene

    SciTech Connect

    Schuh, Kirsten; Kleist, Wolfgang; Høj, Martin; Jensen, Anker Degn; Beato, Pablo; Grunwaldt, Jan-Dierk

    2015-08-15

    A variety of morphologically different α-MoO{sub 3} samples were prepared by hydrothermal synthesis and applied in the selective oxidation of propylene. Their catalytic performance was compared to α-MoO{sub 3} prepared by flame spray pyrolysis (FSP) and a classical synthesis route. Hydrothermal synthesis from ammonium heptamolybdate (AHM) and nitric acid at pH 1–2 led to ammonium containing molybdenum oxide phases that were completely transformed into α-MoO{sub 3} after calcination at 550 °C. A one-step synthesis of α-MoO{sub 3} rods was possible starting from MoO{sub 3}·2H{sub 2}O with acetic acid or nitric acid and from AHM with nitric acid at 180 °C. Particularly, if nitric acid was used during synthesis, the rod-like morphology of the samples could be stabilized during calcination at 550 °C and the following catalytic activity tests, which was beneficial for the catalytic performance in propylene oxidation. Characterization studies using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy showed that those samples, which retained their rod-like morphology during the activity tests, yielded the highest propylene conversion. - Graphical abstract: Hydrothermal synthesis from MoO{sub 3}·2H{sub 2}O in the presence of HNO{sub 3} led to rod-shaped particles which mainly expose (1 0 0) facets which are the most active surfaces. - Highlights: • Hydrothermal synthesis of MoO3 resulted in either rod or slab shaped particles depending on pH. • At pH<0 rods stable towards calcination and catalytic activity testing were formed. • Rod shaped particles had significantly higher activity than slab shaped ones. • The rod shaped particles mainly expose the (1 0 0) facets which are the most active surfaces. • Total surface area is not main determining factor for catalytic activity.

  12. Ascorbic-acid-assisted growth of high quality M@ZnO: a growth mechanism and kinetics study.

    PubMed

    Yang, Yun; Han, Shuhua; Zhou, Guangju; Zhang, Lijie; Li, Xingliang; Zou, Chao; Huang, Shaoming

    2013-12-01

    We present a general route for synthesizing M@ZnO nanoparticles (NPs) by using ascorbic acid (AA) to induce deposition of ZnO on various shaped and structured cationic-surfactant-capped NP surfaces (noble, magnetic, semiconductor, rod-like, spherical, cubic, dendrite, alloy, core@shell). The results show that the complexing (AA and Zn(2+)) and cooperative effects (AA and CTAB) play important roles in the formation of polycrystalline ZnO shells. Besides, the growth kinetics of M@ZnO was systematically studied. It was found that the slow growth rate favors the successful formation of uniform core@ZnO NPs with relatively loose shells. An appropriate growth rate allows achieving high quality M@ZnO NPs with dense shells. However, very fast growth causes significant additional nucleation and the formation of pure ZnO NPs. This general method is suitable for preparing M@ZnO using seed NPs prepared in both water and organic phases. It might be an alternative route for functionalizing NPs for bioapplications (ZnO is biocompatible), modulating material properties as designed, or synthesizing template materials for building other nanostructures. PMID:24122007

  13. Shape-dependent dispersion and alignment of nonaggregating plasmonic gold nanoparticles in lyotropic and thermotropic liquid crystals.

    PubMed

    Liu, Qingkun; Tang, Jianwei; Zhang, Yuan; Martinez, Angel; Wang, Shaowei; He, Sailing; White, Timothy J; Smalyukh, Ivan I

    2014-05-01

    We use both lyotropic liquid crystals composed of prolate micelles and thermotropic liquid crystals made of rod-like molecules to uniformly disperse and unidirectionally align relatively large gold nanorods and other complex-shaped nanoparticles at high concentrations. We show that some of these ensuing self-assembled orientationally ordered soft matter systems exhibit polarization-dependent plasmonic properties with strongly pronounced molar extinction exceeding that previously achieved in self-assembled composites. The long-range unidirectional alignment of gold nanorods is mediated mainly by anisotropic surface anchoring interactions at the surfaces of gold nanoparticles. Polarization-sensitive absorption, scattering, and extinction are used to characterize orientations of nanorods and other nanoparticles. The experimentally measured unique optical properties of these composites, which stem from the collective plasmonic effect of the gold nanorods with long-range order in a liquid crystal matrix, are reproduced in computer simulations. A simple phenomenological model based on anisotropic surface interaction explains the alignment of gold nanorods dispersed in liquid crystals and the physical underpinnings behind our observations.

  14. Linked topological colloids in a nematic host.

    PubMed

    Martinez, Angel; Hermosillo, Leonardo; Tasinkevych, Mykola; Smalyukh, Ivan I

    2015-04-14

    Geometric shape and topology of constituent particles can alter many colloidal properties such as Brownian motion, self-assembly, and phase behavior. Thus far, only single-component building blocks of colloids with connected surfaces have been studied, although topological colloids, with constituent particles shaped as freestanding knots and handlebodies of different genus, have been recently introduced. Here we develop a topological class of colloids shaped as multicomponent links. Using two-photon photopolymerization, we fabricate colloidal microparticle analogs of the classic examples of links studied in the field of topology, the Hopf and Solomon links, which we disperse in nematic fluids that possess orientational ordering of anisotropic rod-like molecules. The surfaces of these particles are treated to impose tangential or perpendicular boundary conditions for the alignment of liquid crystal molecules, so that they generate a host of topologically nontrivial field and defect structures in the dispersing nematic medium, resulting in an elastic coupling between the linked constituents. The interplay between the topologies of surfaces of linked colloids and the molecular alignment field of the nematic host reveals that linking of particle rings with perpendicular boundary conditions is commonly accompanied by linking of closed singular defect loops, laying the foundations for fabricating complex composite materials with interlinking-based structural organization.

  15. Dynamics of Small Inertia-Free Spheroidal Particles in a Turbulent Channel Flow

    NASA Astrophysics Data System (ADS)

    Challabotla, Niranjan Reddy; Zhao, Lihao; Andersson, Helge I.; Department of Energy; Process Engineering Team

    2015-11-01

    The study of small non-spherical particles suspended in turbulent fluid flows is of interest in view of the potential applications in industry and the environment. In the present work, we investigated the dynamics of inertia-free spheroidal particles suspended in fully-developed turbulent channel flow at Re τ = 180 by using the direct numerical simulations (DNS) for the Eulerian fluid phase coupled with the Lagrangian point-particle tracking. We considered inertia-free spheroidal particles with a wide range of aspect ratios from 0.01 to 50, i.e. from flat disks to long rods. Although the spheroids passively translate along with the fluid, the particle orientation and rotation strongly depend on the particle shape. The flattest disks were preferentially aligned with their symmetry axis normal to the wall, whereas the longest rods aligned parallel to the wall. Strong mean rotational spin was observed for spherical particles and this has been damped with increasing asphericity both for rod-like and disk-like spheroids. The anisotropic mean and fluctuating fluid vorticity resulted in particle spin anisotropies which exhibited a complex dependence on the particle asphericty. The Research Council of Norway, Notur and COST Action FP1005 are gratefully acknowledged.

  16. Quantifying the ion atmosphere of unfolded, single-stranded nucleic acids using equilibrium dialysis and single-molecule methods

    PubMed Central

    Jacobson, David R.; Saleh, Omar A.

    2016-01-01

    To form secondary structure, nucleic acids (NAs) must overcome electrostatic strand–strand repulsion, which is moderated by the surrounding atmosphere of screening ions. The free energy of NA folding therefore depends on the interactions of this ion atmosphere with both the folded and unfolded states. We quantify such interactions using the preferential ion interaction coefficient or ion excess: the number of ions present near the NA in excess of the bulk concentration. The ion excess of the folded, double-helical state has been extensively studied; however, much less is known about the salt-dependent ion excess of the unfolded, single-stranded state. We measure this quantity using three complementary approaches: a direct approach of Donnan equilibrium dialysis read out by atomic emission spectroscopy and two indirect approaches involving either single-molecule force spectroscopy or existing thermal denaturation data. The results of these three approaches, each involving an independent experimental technique, are in good agreement. Even though the single-stranded NAs are flexible polymers that are expected to adopt random-coil configurations, we find that their ion atmosphere is quantitatively described by rod-like models that neglect large-scale conformational freedom, an effect that we explain in terms of the competition between the relevant structural and electrostatic length scales. PMID:27036864

  17. Investigation of microemulsion microstructure and its impact on skin delivery of flufenamic acid.

    PubMed

    Mahrhauser, Denise-Silvia; Kählig, Hanspeter; Partyka-Jankowska, Ewa; Peterlik, Herwig; Binder, Lisa; Kwizda, Kristina; Valenta, Claudia

    2015-07-25

    Microemulsions are well known penetration enhancing delivery systems. Several properties are described that influence the transdermal delivery of active components. Therefore, this study aimed to characterize fluorosurfactant-based microemulsions and to assess the impact of formulation variables on the transdermal delivery of incorporated flufenamic acid. The microemulsion systems prepared in this study consisted of bistilled water, oleic acid, isopropanol as co-solvent, flufenamic acid as active ingredient and either Hexafor(TM)670 (Hex) or Chemguard S-550-100 (Sin) as fluorosurfactant. Characterization was performed by a combination of techniques including electrical conductivity measurements, small-angle X-ray scattering (SAXS) and nuclear magnetic resonance (NMR) self-diffusion experiments. In vitro skin permeation experiments were performed with each prepared microemulsion using Franz type diffusion cells to correlate their present microstructure with their drug delivery to skin. Electrical conductivity increased with added water content. Consequently, the absence of a conductivity maximum as well as the NMR and SAXS data rather suggest O/W type microemulsions with spherical or rod-like microstructures. Skin permeation data revealed enhanced diffusion for Hex- and Sin-microemulsions if the shape of the structures was rather elongated than spherical implying that the shape of droplets had an essential impact on the skin permeation of flufenamic acid. PMID:26022888

  18. Collagen-like antimicrobial peptides.

    PubMed

    Masuda, Ryo; Kudo, Masakazu; Dazai, Yui; Mima, Takehiko; Koide, Takaki

    2016-11-01

    Combinatorial library composed of rigid rod-like peptides with a triple-helical scaffold was constructed. The component peptides were designed to have various combinations of basic and neutral (or hydrophobic) amino acid residues based on collagen-like (Gly-Pro-Yaa)-repeating sequences, inspired from the basic and amphiphilic nature of naturally occurring antimicrobial peptides. Screening of the peptide pools resulted in identification of antimicrobial peptides. A structure-activity relationship study revealed that the position of Arg-cluster at N-terminus and cystine knots at C-terminus in the triple helix significantly contributed to the antimicrobial activity. The most potent peptide RO-A showed activity against Gram-negative Escherichia coli and Gram-positive Bacillus subtilis. In addition, Escherichia coli exposed to RO-A resulted in abnormal elongation of the cells. RO-A was also shown to have remarkable stability in human serum and low cytotoxicity to mammalian cells. © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 453-459, 2016. PMID:27271210

  19. Controlling the growth and shape of chiral supramolecular polymers in water

    PubMed Central

    Besenius, Pol; Portale, Giuseppe; Bomans, Paul H. H.; Janssen, Henk M.; Palmans, Anja R. A.; Meijer, E. W.

    2010-01-01

    A challenging target in the noncovalent synthesis of nanostructured functional materials is the formation of uniform features that exhibit well-defined properties, e.g., precise control over the aggregate shape, size, and stability. In particular, for aqueous-based one-dimensional supramolecular polymers, this is a daunting task. Here we disclose a strategy based on self-assembling discotic amphiphiles that leads to the control over stack length and shape of ordered, chiral columnar aggregates. By balancing out attractive noncovalent forces within the hydrophobic core of the polymerizing building blocks with electrostatic repulsive interactions on the hydrophilic rim we managed to switch from elongated, rod-like assemblies to small and discrete objects. Intriguingly this rod-to-sphere transition is expressed in a loss of cooperativity in the temperature-dependent self-assembly mechanism. The aggregates were characterized using circular dichroism, UV and 1H-NMR spectroscopy, small angle X-ray scattering, and cryotransmission electron microscopy. In analogy to many systems found in biology, mechanistic details of the self-assembly pathways emphasize the importance of cooperativity as a key feature that dictates the physical properties of the produced supramolecular polymers. PMID:20921365

  20. Growth of Hydrothermally Derived CdS-Based Nanostructures with Various Crystal Features and Photoactivated Properties

    NASA Astrophysics Data System (ADS)

    Liang, Yuan-Chang; Lung, Tsai-Wen

    2016-05-01

    CdS crystallites with rod- and flower-like architectures were synthesized using a facile hydrothermal growth method. The hexagonal crystal structure of CdS dominated the growth mechanisms of the rod- and flower-like crystallites under specific growth conditions, as indicated by structural analyses. The flower-like CdS crystallites had a higher crystal defect density and lower optical band gap value compared with the rod-like CdS crystallites. The substantial differences in microstructures and optical properties between the rod- and flower-like CdS crystallites revealed that the flower-like CdS crystallites exhibited superior photoactivity, and this performance could be further enhanced through appropriate thermal annealing in ambient air. A postannealing procedure conducted in ambient air oxidized the surfaces of the flower-like CdS crystallites and formed a CdO phase. The formation of heterointerfaces between the CdS and CdO phases mainly contributed to the improved photoactivity of the synthesized flower-like CdS crystallites.

  1. Preparation and in vitro-in vivo evaluation of teniposide nanosuspensions.

    PubMed

    He, Suna; Yang, Hui; Zhang, Ruizhi; Li, Yan; Duan, Lengxin

    2015-01-15

    Teniposide (TEN) is a potent, broad spectrum antitumor agent, especially for cerebroma. But the application in clinic was limited because of its poor solubility. In this paper, teniposide nanosuspensions drug delivery system (TEN-NSDDS) for intravenous administration was developed for the first time. Specifically, TEN nanosuspensions were prepared by an anti-solvent sonication-precipitation method and evaluated in comparison with teniposide injection (VUMON) in vitro and in vivo. TEN nanosuspensions prepared showed rod-like morphology and the size was 151 ± 11 nm with a narrow poly dispersion index 0.138 determined by dynamic light scattering. The obtained TEN nanosuspensions were physically stable at least 10 days at 4°C. And the freeze-drying preparations were stable during 3 months. The cytotoxicity of TEN nanosuspensions were considerable to that of VUMON against U87MG and C6 cells in vitro. When tested in rats bearing C6 tumors, the TEN concentration in the tumors treated by the nanosuspensions was more than 20 times than that by the TEN solution at 2h. The TEN nanosuspensions exhibited significant tumor growth inhibition. Overall, the results suggested that nanosuspensions was an alternative formulation for teniposide to be administered intravenously, and it would be a promising formulation in clinic.

  2. A Luminescent Nitrogen-Containing Polycyclic Aromatic Hydrocarbon Synthesized by Photocyclodehydrogenation with Unprecedented Regioselectivity.

    PubMed

    Gu, Xinggui; Wang, Hong; Roose, Jesse; He, Zikai; Zhou, Yue; Yan, Yongli; Cai, Yuanjing; Shi, Heping; Zhang, Yilin; Sung, Herman H Y; Lam, Jacky W Y; Miao, Qian; Zhao, Yongsheng; Wong, Kam Sing; Williams, Ian D; Tang, Ben Zhong

    2015-12-01

    We present a nitrogen-containing polycyclic aromatic hydrocarbon (N-PAH), namely 12-methoxy-9-(4-methoxyphenyl)-5,8-diphenyl-4-(pyridin-4-yl)pyreno[1,10,9-h,i,j]isoquinoline (c-TPE-ON), which exhibits high quantum-yield emission both in solution (blue) and in the solid state (yellow). This molecule was unexpectedly obtained by a three-fold, highly regioselective photocyclodehydrogenation of a tetraphenylethylene-derived AIEgen. Based on manifold approaches involving UV/Vis, photoluminescence, and NMR spectroscopy as well as HRMS, we propose a reasonable mechanism for the formation of the disk-like N-PAH that is supported by density functional theory calculations. In contrast to most PAHs that are commonly used, our system does not suffer from entire fluorescence quenching in the solid state due to the peripheral aromatic rings preventing π-π stacking interactions, as evidenced by single-crystal X-ray analysis. Moreover, its rod-like microcrystals exhibit excellent optical waveguide properties. Hence, c-TPE-ON comprises a N-PAH with unprecedented luminescent properties and as such is a promising candidate for fabricating organic optoelectronic devices. Our design and synthetic strategy might lead to a more general approach to the preparation of solution- and solid-state luminescent PAHs. PMID:26490877

  3. Continuous microwave flow synthesis of mesoporous hydroxyapatite.

    PubMed

    Akram, Muhammad; Alshemary, Ammar Z; Goh, Yi-Fan; Wan Ibrahim, Wan Aini; Lintang, Hendrik O; Hussain, Rafaqat

    2015-11-01

    We have successfully used continuous microwave flow synthesis (CMFS) technique for the template free synthesis of mesoporous hydroxyapatite. The continuous microwave flow reactor consisted of a modified 2.45GHz household microwave, peristaltic pumps and a Teflon coil. This cost effective and efficient system was exploited to produce semi-crystalline phase pure nano-sized hydroxyapatite. Effect of microwave power, retention time and the concentration of reactants on the phase purity, degree of crystallinity and surface area of the final product was studied in detail. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to study the phase purity and composition of the product, while transmission electron microscopy (TEM) was used to study the effect of process parameters on the morphology of hydroxyapatite. The TEM analysis confirmed the formation of spherical particles at low microwave power; however the morphology of the particles changed to mesoporous needle and rod-like structure upon exposing the reaction mixture to higher microwave power and longer retention time inside the microwave. The in-vitro ion dissolution behavior of the as synthesized hydroxyapatite was studied by determining the amount of Ca(2+) ion released in SBF solution.

  4. Thiol ligand-induced transformation of Au38(SC2H4Ph)24 to Au36(SPh-t-Bu)24.

    PubMed

    Zeng, Chenjie; Liu, Chunyan; Pei, Yong; Jin, Rongchao

    2013-07-23

    We report a disproportionation mechanism identified in the transformation of rod-like biicosahedral Au38(SCH2CH2Ph)24 to tetrahedral Au36(TBBT)24 nanoclusters. Time-dependent mass spectrometry and optical spectroscopy analyses unambiguously map out the detailed size-conversion pathway. The ligand exchange of Au38(SCH2CH2Ph)24 with bulkier 4-tert-butylbenzenethiol (TBBT) until a certain extent starts to trigger structural distortion of the initial biicosahedral Au38(SCH2CH2Ph)24 structure, leading to the release of two Au atoms and eventually the Au36(TBBT)24 nanocluster with a tetrahedral structure, in which process the number of ligands is interestingly preserved. The other product of the disproportionation process, i.e., Au40(TBBT)m+2(SCH2CH2Ph)24-m, was concurrently observed as an intermediate, which was the result of addition of two Au atoms and two TBBT ligands to Au38(TBBT)m(SCH2CH2Ph)24-m. The reaction kinetics on the Au38(SCH2CH2Ph)24 to Au36(TBBT)24 conversion process was also performed, and the activation energies of the structural distortion and disproportionation steps were estimated to be 76 and 94 kJ/mol, respectively. The optical absorption features of Au36(TBBT)24 are interpreted on the basis of density functional theory simulations.

  5. Conformational Differences Among Solution Structures of the Type I[alpha], II[alpha], and II[beta] Protein Kinase A Regulatory Subunit Homodimers: Role of the Linker Regions

    SciTech Connect

    Vigil, D.; Blumenthal, D.K.; Heller, W.T.; Brown, S.; Canaves, J.M.; Taylor, S.S.; Trewhella, J.

    2010-11-16

    The regulatory (R) subunits of the cAMP-dependent protein kinase (protein kinase A or PKA) are multi-domain proteins responsible for conferring cAMP-dependence and localizing PKA to specific subcellular locations. There are four isoforms of the R subunit in mammals that are similar in molecular mass and domain organization, but clearly serve different biological functions. Although high-resolution structures are available for the cAMP-binding domains and dimerization/docking domains of two isoforms, there are no high-resolution structures of any of the intact R subunit homodimer isoforms. The results of small-angle X-ray scattering studies presented here indicate that the RI{alpha}, RII{alpha}, and RII{beta} homodimers differ markedly in overall shape, despite extensive sequence homology and similar molecular masses. The RII{alpha} and RII{beta} homodimers have very extended, rod-like shapes, whereas the RI{alpha} homodimer likely has a compact Y-shape. Based on a comparison of the R subunit sequences, we predict that the linker regions are the likely cause of these large differences in shape among the isoforms. In addition, we show that cAMP binding does not cause large conformational changes in type I{alpha} or II{alpha} R subunit homodimers, suggesting that the activation of PKA by cAMP involves only local conformational changes in the R subunits.

  6. Preparation and electrochemical characterization of manganese dioxide-zirconia nanorods

    NASA Astrophysics Data System (ADS)

    Muthuchudarkodi, R. R.; Vedhi, C.

    2015-04-01

    MnO2-ZrO2 nanorods were prepared by wet chemical method by mixing the solutions of MnSO4 and ZrOCl2 varying in the range (0.05-0.45 M) in aqueous NaOH at an elevated temperature. The morphologies of the synthesized products are characterized by scanning electron microscopy and transmission electron microscopy (TEM). X-ray diffraction (XRD) and energy-dispersive spectroscopic measurements were also employed for the characterization of the nanostructures. The synthesized nanoparticles were also characterized by ultraviolet visible spectroscopy, Fourier transform infrared spectroscopy, electrochemical impedance and cyclic voltammetric studies. The morphological studies of the nanoparticles revealed particle distribution with uniform rod-like structure. Energy-dispersive analysis indicated the presence of Mn, Zr and O. The nanostructures of the product were characterized by TEM studies and the mixed rod and granular structure that was found clearly indicated the presence of MnO2-ZrO2 mixed oxide. The size of the synthesized nanorod was found to be 20 nm. From XRD studies the size of the nanorods was found to be in the range 39-56 nm calculated by Debye-Scherrer's formula. Thermal stability of the nanorods was characterized by thermogravimetric and differential scanning colorimetric analysis. Cyclic voltammetric studies exhibit good adherent behavior on electrode surface and good electroactivity at a pH value of 1.0.

  7. Simultaneous specific heat and thermal conductivity measurement of individual nanostructures

    NASA Astrophysics Data System (ADS)

    Zheng, Jianlin; Wingert, Matthew C.; Moon, Jaeyun; Chen, Renkun

    2016-08-01

    Fundamental phonon transport properties in semiconductor nanostructures are important for their applications in energy conversion and storage, such as thermoelectrics and photovoltaics. Thermal conductivity measurements of semiconductor nanostructures have been extensively pursued and have enhanced our understanding of phonon transport physics. Specific heat of individual nanostructures, despite being an important thermophysical parameter that reflects the thermodynamics of solids, has remained difficult to characterize. Prior measurements were limited to ensembles of nanostructures in which coupling and sample inhomogeneity could play a role. Herein we report the first simultaneous specific heat and thermal conductivity measurements of individual rod-like nanostructures such as nanowires and nanofibers. This technique is demonstrated by measuring the specific heat and thermal conductivity of single ˜600-700 nm diameter Nylon-11 nanofibers (NFs). The results show that the thermal conductivity of the NF is increased by 50% over the bulk value, while the specific heat of the NFs exhibits bulk-like behavior. We find that the thermal diffusivity obtained from the measurement, which is related to the phonon mean free path (MFP), decreases with temperature, indicating that the intrinsic phonon Umklapp scattering plays a role in the NFs. This platform can also be applied to one- and two- dimensional semiconductor nanostructures to probe size effects on the phonon spectra and other transport physics.

  8. Phase transformation and deformation behavior of NiTi-Nb eutectic joined NiTi wires.

    PubMed

    Wang, Liqiang; Wang, Cong; Zhang, Lai-Chang; Chen, Liangyu; Lu, Weijie; Zhang, Di

    2016-01-01

    NiTi wires were brazed together via eutectic reaction between NiTi and Nb powder deposited at the wire contact region. Phase transformation and deformation behavior of the NiTi-Nb eutectic microstructure were investigated using transmission electron microscopy (TEM) and cyclic loading-unloading tests. Results show that R phase and B19' martensite transformation are induced by plastic deformation. R phase transformation, which significantly contributes to superelasticity, preferentially occurs at the interfaces between NiTi and eutectic region. Round-shaped Nb-rich phase with rod-like and lamellar-type eutectics are observed in eutectic regions. These phases appear to affect the deformation behavior of the brazed NiTi-Nb region via five distinct stages in stress-strain curves: (I) R phase reorientation, (II) R phase transformation from parent phase, (III) elastic deformation of reoriented martensite accompanied by the plastic deformation of Nb-rich phase and lamellar NiTi-Nb eutectic, (IV) B19' martensitic transformation, and (V) plastic deformation of the specimen. PMID:27049025

  9. Spectroscopy investigation on chemo-catalytic, free radical scavenging and bactericidal properties of biogenic silver nanoparticles synthesized using Salicornia brachiata aqueous extract

    NASA Astrophysics Data System (ADS)

    Seralathan, Janani; Stevenson, Priscilla; Subramaniam, Shankar; Raghavan, Rachana; Pemaiah, Brindha; Sivasubramanian, Aravind; Veerappan, Anbazhagan

    2014-01-01

    Nanosized silver have been widely used in many applications, such as catalysis, photonics, sensors, medicine etc. Thus, there is an increasing need to develop high-yield, low cost, non-toxic and eco-friendly procedures for the synthesis of nanoparticles. Herein, we report an efficient, green synthesis of silver nanoparticles utilizing the aqueous extract of Salicornia brachiata, a tropical plant of the Chenopodiaceae family. Silver nanoparticles have been characterized by ultraviolet-visible spectroscopy, scanning electron microscopy and transmission electron microscopy. The morphology of the particles formed consists of highly diversified shapes like spherical, rod-like, prism, triangular, pentagonal and hexagonal pattern. However, addition of sodium hydroxide to the extract produces mostly spherical particles. The stable nanoparticles obtained using this green method show remarkable catalytic activity in the reduction of 4-nitro phenol to 4-amino phenol. The reduction catalyzed by silver nanoparticles followed the first-order kinetics, with a rate constant of, 0.6 × 10-2 s-1. The bactericidal activity of the synthesized silver nanoparticles against the pathogenic bacteria, Staphylococcus aureus, Staphylococcus aureus E, Bacillus subtilis and Escherichia coli, was also explored using REMA. The obtained results showed that the minimum inhibitory concentration required to induce bactericidal effect is lower than the control antibiotic, ciprofloxacin. In addition to these, the biogenic synthesized nanoparticles also exhibited excellent free radical scavenging activity.

  10. Solvothermal synthesis of α-PbO from lead dioxide and its electrochemical performance as a positive electrode material

    NASA Astrophysics Data System (ADS)

    Gao, Pengran; Liu, Yi; Bu, Xianfu; Hu, Meng; Dai, Yuan; Gao, Xiaorui; Lei, Lixu

    2013-11-01

    Lead acid batteries have been widely used and have dominated the global secondary battery market. It is very important to recycle the spent batteries efficiently to eliminate possible pollution and to ensure sustainable production. In this paper, we report our investigation on the solvothermal treatment of PbO2, which is one of the model compounds for the positive active mixture, in methanol and the subsequent calcination of its product. The results show that the solvothermal treatment of PbO2 in pure methanol at 140 °C can produce a mixture of PbO and lead oxide carbonate, which can be calcined at a temperature below 500 °C to produce α-PbO. The as-prepared PbO powders are rod-like particles of about 0.5 micrometer in diameter and several micrometers in length, which can achieve a high discharge capacity of 165 mAh g-1 at the discharge current density of 5 mA g-1, and more than 90 mAh g-1 at 200 mA g-1 with excellent cycle stability. This study demonstrates a new way for the reuse of lead dioxide in spent lead acid batteries to produce highly active PbO.

  11. 1D-TlInSe2: Band Structure, Dielectric Function and Nanorods

    NASA Astrophysics Data System (ADS)

    Mamedov, Nazim; Wakita, Kazuki; Akita, Seiji; Nakayama, Yoshikazu

    2005-01-01

    Linear combination of atomic orbitals (LCAO) analysis of the electronic band states has been completed for one-dimensional (1D) TlInSe2 having rod-like ground state shape of bulky crystal. The total scenario of the occurrence of the band states from the atomic states has been established. According to this scenario, in dipole approximation the optical transitions at band gap (point T of Brillouin zone) are either entirely forbidden or allowed for T2-T10 transitions in e\\perpc configuration provided that either initial or terminate state has T2 symmetry and both are Se-like. As a whole, the obtained results on the electronic spectrum, including dielectric function, are applicable to all obtained 1D-TlInSe2 nanorods which were as thin as 30--50 nm in cross-section, and apparently preserved tetragonal crystal structure of bulky material. The thermal instabilities developing already in bulky samples of 1D-TlInSe2 are considered to be an ultimate source of the nanoparticles emerging in plenty during nanorods preparation. The nanoplates of a chemically similar but 2D material, TlInS2, are demonstrated for comparison to show the absence of nanoparticles in that case. A possibility of nanoparticle preparation using laser excited coherent phonon trains in the nanorods of 1D-TlInSe2 is figured out.

  12. Citrus viroid V: molecular characterization and synergistic interactions with other members of the genus Apscaviroid.

    PubMed

    Serra, P; Barbosa, C J; Daròs, J A; Flores, R; Duran-Vila, N

    2008-01-01

    Studies on Atalantia citroides, a citrus relative, revealed the existence of a viroid not described previously. The new viroid has a GC-rich genome of 293-294 nucleotides and contains the central conserved region characteristic of members of the genus Apscaviroid, and the terminal conserved region present in this and other genera of the family Pospiviroidae. The secondary structure of minimum free energy predicted for the new viroid is a rod-like conformation with 68.7% paired nucleotides and showing sequence identities with other viroids always lower than 90%, the conventional limit that separates different species within a given genus. Infectivity assays showed that the new viroid induces mild but characteristic symptoms on the indicator Etrog citron. Co-inoculation of CVd-V with either Citrus bent leaf viroid or Citrus viroid III, two other members of the genus Apscaviroid infecting citrus, disclosed synergistic interactions manifested in enhanced leaf symptoms and very pronounced dwarfing. Viroid titers, however, remained unaltered in co-infected plants. Possible mechanisms underlying the observed synergistic effects are discussed. According to its molecular and biological properties and its unusual ability to replicate in A. citroides, the new viroid, tentatively named Citrus viroid V (CVd-V), should be considered a new species of the genus Apscaviroid.

  13. An artificial chimeric derivative of Citrus viroid V involves the terminal left domain in pathogenicity.

    PubMed

    Serra, Pedro; Bani Hashemian, Seyed Mehdi; Pensabene-Bellavia, Giovanni; Gago, Selma; Duran-Vila, Núria

    2009-07-01

    The recently described Citrus viroid V (CVd-V) induces, in Etrog citron, mild stunting and very small necrotic lesions and cracks, sometimes filled with gum. As Etrog citron plants co-infected with Citrus dwarfing viroid (CDVd) and CVd-V show synergistic interactions, these host-viroid combinations provide a convenient model to identify the pathogenicity determinant(s). The biological effects of replacing limited portions of the rod-like structure of CVd-V with the corresponding portions of CDVd are reported. Chimeric constructs were synthesized using a novel polymerase chain reaction-based approach, much more flexible than those based on restriction enzymes used in previous studies. Of the seven chimeras (Ch) tested, only one (Ch5) proved to be infectious. Plants infected with Ch5 showed no symptoms and, although this novel chimera was able to replicate to relatively high titres in singly infected plants, it was rapidly displaced by either CVd-V or CDVd in doubly infected plants. The results demonstrate that direct interaction(s) between structural elements in the viroid RNA (in this case, the terminal left domain) and as yet unidentified host factors play an important role in modulating viroid pathogenicity. This is the first pathogenic determinant mapped in species of the genus Apscaviroid.

  14. Antennal sensilla of the pine weevil Pissodes nitidus Roel. (Coleoptera: Curculionidae).

    PubMed

    Yan, Shan-Chun; Meng, Zhao-Jun; Peng, Lu; Liu, Dan

    2011-05-01

    The antennal sensilla of the pine weevil (Pissodes nitidus Roel.) were observed with scanning electron microscopy and transmission electron microscopy (TEM). The weevil antenna consists of a long scape, a pedicel, and a flagellum with 10 segments; the last four flagellum segments are fused, forming the antennal club, which is densely covered by various sensilla. In both sexes, six types of sensilla, sensilla palmate 1-4, sensilla chaetica, sensilla trichoid, sensilla basiconic 1-2, sensilla rod-like 1-3, sensilla falciform, were identified. Sensilla palmate represent a unique sensillum type in the Pissodes genus, and named here after their palmate shape, also represent the most abundant sensillum type. The TEM analysis of sensilla palmate represents the first such analysis of this sensillum type, and we speculate that the sensilla have an olfactory function. The sensilla trichoid and chaetica were evenly distributed on the three or four hair bands of the club, with much lower numbers than the palmate sensilla. No significant sexual differences in the types, numbers, and distribution of the antennal sensilla were found except for the size. TEM observation indicated that sensilla chaetica and trichoid may function as olfactory sensors. The putative functions of other sensilla type were also discussed with reference to their morphology, distribution, and ultrastructure.

  15. Sharpening the surface of magnetic paranematic droplets.

    PubMed

    Tokarev, Alexander; Lee, Wah-Keat; Sevonkaev, Igor; Goia, Dan; Kornev, Konstantin G

    2014-03-28

    In a non-uniform magnetic field, the droplets of colloids of nickel nanorods and nanobeads aggregate to form a cusp at the droplet surface not deforming the entire droplet shape. When the field is removed, nanorods diffuse away and the cusp disappears. Spherical particles can form cusps in a similar way, but they stay aggregated after the release of the field; finally, the aggregates settle down to the bottom of the drop. The X-ray phase contrast imaging reveals that nanorods in the cusps stay parallel to each other without visible spatial order of their centers of mass. The formation of cusps can be explained with a model that includes magnetostatic and surface tension forces. The discovered possibility of controlled assembly and quenching of nanorod orientation under the cusped liquid surface offers vast opportunities for alignment of carbon nanotubes, nanowires and nanoscrolls, prior to spinning them into superstrong and multifunctional fibers. Magnetostatic and electrostatic analogies suggest that a similar ideal alignment can be achieved with the rod-like dipoles subject to a strong electric field. PMID:24800272

  16. Giant Raman scattering from J-aggregated dyes inside carbon nanotubes for multispectral imaging

    NASA Astrophysics Data System (ADS)

    Gaufrès, E.; Tang, N. Y.-Wa; Lapointe, F.; Cabana, J.; Nadon, M.-A.; Cottenye, N.; Raymond, F.; Szkopek, T.; Martel, R.

    2014-01-01

    Raman spectroscopy uses visible light to acquire vibrational fingerprints of molecules, thus making it a powerful tool for chemical analysis in a wide range of media. However, its potential for optical imaging at high resolution is severely limited by the fact that the Raman effect is weak. Here, we report the discovery of a giant Raman scattering effect from encapsulated and aggregated dye molecules inside single-walled carbon nanotubes. Measurements performed on rod-like dyes such as α-sexithiophene and β-carotene, assembled inside single-walled carbon nanotubes as highly polarizable J-aggregates, indicate a resonant Raman cross-section of (3 +/- 2) × 10-21 cm2 sr-1, which is well above the cross-section required for detecting individual aggregates at the highest optical resolution. Free from fluorescence background and photobleaching, this giant Raman effect allows the realization of a library of functionalized nanoprobe labels for Raman imaging with robust detection using multispectral analysis.

  17. Study on the resonance Raman scattering properties of β-carotene incorporated into SBA-15

    NASA Astrophysics Data System (ADS)

    Tan, Shishi; Zhang, Guannan; Shen, Aiguo; Hu, Juncheng; Hu, Jiming

    2010-10-01

    In this study, β-carotene, a resonance Raman active substance, was introduced into the large pore channel of rod-like SBA-15 for the first time. This novel resonance Raman active material has been characterized by small angle X-ray scattering (SAXS) and Brunauer-Emmett-Teller (BET) surface area analysis. The adsorption process did not show any influence on the microstructure of SBA-15 as well as its physicochemical characters. Excited by 514.5 nm laser, the resonance Raman signals of the products were demonstrated as well-defined Raman peaks at 1009, 1158 and 1514 cm -1, which should be assigned to the methyl rock (C-CH 3), carbon single-bond stretch (C-C) and carbon double-bond stretch (C dbnd C) normal modes, respectively. In addition, the internal standard method was utilized by resonance Raman spectroscopy to determine the adsorption capacity of mesoporous silicas for β-carotene using the results of UV-vis spectroscopy as a reference.

  18. Angiostrongylus cantonensis: morphological and behavioral investigation within the freshwater snail Pomacea canaliculata.

    PubMed

    Lv, Shan; Zhang, Yi; Liu, He-Xiang; Zhang, Chao-Wei; Steinmann, Peter; Zhou, Xiao-Nong; Utzinger, Jürg

    2009-06-01

    An infection with Angiostrongylus cantonensis, the main causative agent for human eosinophilic encephalitis, can be acquired through the consumption of the freshwater snail Pomacea canaliculata. This snail also provides a suitable model to study the developmental morphology and behavior of A. cantonensis larvae, facilitated by the snail's distinct lung structure. We used microanatomy for studying the natural appearance and behavior of A. cantonensis larvae while developing within P. canaliculata. The distribution of refractile granules in the larval body and characteristic head structures changed during the developmental cycle. Two well-developed, rod-like structures with expanded knob-like tips at the anterior part were observed under the buccal cavity as early as the late second developmental stage. A "T"-shaped structure at the anterior end and its tenacity distinguished the outer sheath from that shed during the second molting. Early first-stage larvae obtained from fresh rat feces are free moving and characterized by a coiled tail, whereas a mellifluous "Q"-movement was the behavioral trait of third-stage A. cantonensis larvae outside the host tissue. In combination, the distribution of refractive granules, distinct head features, variations in sheaths, and behavioral characteristics can be utilized for differentiation of larval stages, and for distinguishing A. cantonensis larvae from those of other free-living nematodes. PMID:19172296

  19. Growth and characterization of epitaxially stabilized ceria(001) nanostructures on Ru(0001)

    NASA Astrophysics Data System (ADS)

    Flege, Jan Ingo; Höcker, Jan; Kaemena, Björn; Menteş, T. Onur; Sala, Alessandro; Locatelli, Andrea; Gangopadhyay, Subhashis; Sadowski, Jerzy T.; Senanayake, Sanjaya D.; Falta, Jens

    2016-05-01

    We have studied (001) surface terminated cerium oxide nanoparticles grown on a ruthenium substrate using physical vapor deposition. Their morphology, shape, crystal structure, and chemical state are determined by low-energy electron microscopy and micro-diffraction, scanning probe microscopy, and synchrotron-based X-ray absorption spectroscopy. Square islands are identified as CeO2 nanocrystals exhibiting a (001) oriented top facet of varying size; they have a height of about 7 to 10 nm and a side length between about 50 and 500 nm, and are terminated with a p(2 × 2) surface reconstruction. Micro-illumination electron diffraction reveals the existence of a coincidence lattice at the interface to the ruthenium substrate. The orientation of the side facets of the rod-like particles is identified as (111); the square particles are most likely of cuboidal shape, exhibiting (100) oriented side facets. The square and needle-like islands are predominantly found at step bunches and may be grown exclusively at temperatures exceeding 1000 °C.

  20. Mineralogical comparisons of experimental results investigating the biological impacts on rock transport processes.

    PubMed

    Wagner, Doris; Milodowski, Antoni E; West, Julia M; Wragg, Joanna; Yoshikawa, Hideki

    2013-08-01

    This study investigates the influence of microbes on fluid transport in sedimentary and igneous host rock environments. It particularly focuses on granodiorite rock (Äspö; Sweden) and mudstone (Horonobe; Japan) that were utilised during laboratory-based column experiments. The results showed that biofilms form on both rock types in low nutrient conditions. Cryogenic scanning electron microscopy showed that the morphology of biofilaments varied from filamentous meshwork (in crushed granodiorite column experiments) to clusters of rod-like cells (fracture surfaces in mudstone). X-ray diffraction analysis of the fine fractions (<5 µm) revealed the formation of secondary clay mineral phases within the crushed Äspö granodiorite rock substrate only. The formation of secondary clay minerals appears to be enhanced when bacteria are present. All experiments showed biofilm formation, bacterial enhanced trapping of fines blocking off pore throats and/or secondary clay mineral formation. These observations illustrate the importance of bacteria on rock transport properties which will impact on the containment and migration of contaminants. PMID:23770916

  1. Development of a novel electrochemical DNA biosensor based on elongated hexagonal-pyramid CdS and poly-isonicotinic acid composite film.

    PubMed

    Zheng, Delun; Wang, Qingxiang; Gao, Feng; Wang, Qinghua; Qiu, Weiwei; Gao, Fei

    2014-10-15

    Three CdS materials with different shapes (i.e., irregular, rod-like, and elongated hexagonal-pyramid) were hydrothermally synthesized through controlling the molar ratio of Cd(2+) to thiourea. Electrochemical experiments showed that the elongated hexagonal-pyramid CdS (eh-CdS) modified on glassy carbon electrode (GCE) had the higher electrical conductivity than the other two forms. Then the eh-CdS modified GCE was further modified with a layer of poly-isonicotinic acid (PIA) through electro-polymerization in IA solution to enhance the stability and functionality of the interface. The layer-by-layer modification process was characterized by atomic force microscopy and electrochemistry. Then 5'-amino functionalized DNA was immobilized on the electrode surface through coupling with the carboxylic groups derived from PIA-eh-CdS composite film. The hybridization performance of the developed biosensor was evaluated using methylene blue as redox indicator, and the results showed that the peak currents of methylene blue varied with target concentrations in a wide linear range from 1.0 × 10(-14)M to 1.0 × 10(-9)M with a low detection limit of 3.9 × 10(-15)M. The biosensor also showed high stability and good discrimination ability to the one-base, three-base mismatched and non-complementary sequence.

  2. On the adsorption of magnetite nanoparticles on lysozyme amyloid fibrils.

    PubMed

    Majorosova, Jozefina; Petrenko, Viktor I; Siposova, Katarina; Timko, Milan; Tomasovicova, Natalia; Garamus, Vasil M; Koralewski, Marceli; Avdeev, Mikhail V; Leszczynski, Błażej; Jurga, Stefan; Gazova, Zuzana; Hayryan, Shura; Hu, Chin-Kun; Kopcansky, Peter

    2016-10-01

    An adsorption of magnetic nanoparticles (MNP) from electrostatically stabilized aqueous ferrofluids on amyloid fibrils of hen egg white lysozyme (HEWL) in 2mg/mL acidic dispersions have been detected for the MNP concentration range of 0.01-0.1vol.%. The association of the MNP with amyloid fibrils has been characterized by transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS) and magneto-optical measurements. It has been observed that the extent of adsorption is determined by the MNP concentration. When increasing the MNP concentration the formed aggregates of magnetic particles repeat the general rod-like structure of the fibrils. The effect is not observed when MNP are mixed with the solution of lysozyme monomers. The adsorption has been investigated with the aim to clarify previously found disaggregation activity of MNP in amyloid fibrils dispersions and to get deeper insight into interaction processes between amyloids and MNP. The observed effect is also discussed with respect to potential applications for ordering lysozyme amyloid fibrils in a liquid crystal phase under external magnetic fields. PMID:27451367

  3. Template-free synthesis of ZnWO{sub 4} powders via hydrothermal process in a wide pH range

    SciTech Connect

    Hojamberdiev, Mirabbos; Zhu, Gangqiang; Xu, Yunhua

    2010-12-15

    ZnWO{sub 4} powders with different morphologies were fabricated through a template-free hydrothermal method at 180 {sup o}C for 8 h in a wide pH range. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible and luminescence spectrophotometers were applied to study the effects of pH values on crystallinity, morphology, optical and luminescence properties. The XRD results showed that the WO{sub 3} + ZnWO{sub 4}, ZnWO{sub 4}, and ZnO phases could form after hydrothermal processing at 180 {sup o}C for 8 h with the pH values of 1, 3-11, and 13, respectively. The SEM and TEM observation revealed that the morphological transformation of ZnWO{sub 4} powders occurred with an increase in pH values as follows: star anise-, peony-, and desert rose-like microstructures and soya bean- and rod-like nanostructures. The highest luminescence intensity was found to be in sample consisting of star anise-like crystallites among all the samples due to the presence of larger particles with high crystallinity resulted from the favorable pH under the current hydrothermal conditions.

  4. Flow-induced anisotropy in the susceptibility of a particle suspension.

    PubMed

    Karis, T E; Jhon, M S

    1986-07-01

    The initial susceptibility, or low-field high-frequency permeability, of a rod-like particle suspension or polymer solution can become anisotropic when the particles or molecules interact with a magnetic field in a directional manner and are nonrandomly oriented by certain types of flow field. This is the alignment that leads to thixotropy and deviatoric stresses during rheological measurements on these fluids. A general expression for the particle order parameter and the fluid permeability in terms of Legendre polynomials is derived by calculating the ensemble average over all possible orientation angles. This is an integral containing the orientation angle-dependent orientation probability function. The example case of single-domain magnetic particles suspended in extensional flow of a newtonian fluid is examined by using the following well-known models: chain-of-spheres model for the magnetic properties of a particle and the Kirkwood-Auer theory for the orientation probability function. From this, the particle orientation in the flow direction downstream from a sharp circular convergence is predicted to dramatically increase with an increase in the ratio of the extension rate to the particle rotary diffusion coefficient. Consequently, the measured permeability of the fluid is predicted to decrease parallel to, and to increase perpendicular to, the flow direction. PMID:16593725

  5. Structural Insights into SraP-Mediated Staphylococcus aureus Adhesion to Host Cells

    PubMed Central

    Zhang, Juan; Wang, Lei; Bai, Xiao-Hui; Zhang, Shi-Jie; Ren, Yan-Min; Li, Na; Zhang, Yong-Hui; Zhang, Zhiyong; Gong, Qingguo; Mei, Yide; Xue, Ting; Zhang, Jing-Ren; Chen, Yuxing; Zhou, Cong-Zhao

    2014-01-01

    Staphylococcus aureus, a Gram-positive bacterium causes a number of devastating human diseases, such as infective endocarditis, osteomyelitis, septic arthritis and sepsis. S. aureus SraP, a surface-exposed serine-rich repeat glycoprotein (SRRP), is required for the pathogenesis of human infective endocarditis via its ligand-binding region (BR) adhering to human platelets. It remains unclear how SraP interacts with human host. Here we report the 2.05 Å crystal structure of the BR of SraP, revealing an extended rod-like architecture of four discrete modules. The N-terminal legume lectin-like module specifically binds to N-acetylneuraminic acid. The second module adopts a β-grasp fold similar to Ig-binding proteins, whereas the last two tandem repetitive modules resemble eukaryotic cadherins but differ in calcium coordination pattern. Under the conditions tested, small-angle X-ray scattering and molecular dynamic simulation indicated that the three C-terminal modules function as a relatively rigid stem to extend the N-terminal lectin module outwards. Structure-guided mutagenesis analyses, in addition to a recently identified trisaccharide ligand of SraP, enabled us to elucidate that SraP binding to sialylated receptors promotes S. aureus adhesion to and invasion into host epithelial cells. Our findings have thus provided novel structural and functional insights into the SraP-mediated host-pathogen interaction of S. aureus. PMID:24901708

  6. Synthesis of nanostructured methotrexate/hydroxyapatite: Morphology control, growth mechanism, and bioassay explore.

    PubMed

    Dai, Chao-Fan; Li, Shu-Ping; Li, Xiao-Dong

    2015-12-01

    In this study, a new structure of methotrexate/hydroxyapatite (MTX/HAp) nanorods via a facile hydrothermal route was reported. The as-synthesized samples were then characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric (TG) and differential scanning calorimetry (DSC) analysis. In order to explore the formation mechanism, the effects of reaction time, MTX concentrations and addition of ethylene glycol (PEG) were emphatically examined. The results indicated that, with the increase in reaction time, the fibrous nanoparticles turned to needle-like and then to rod-like. Our study also proved that reaction time of 12h was enough for the full-growth of the nanostructure. Drug-loading capacities (AIn) rose dramatically in the first 12h and reached a plateau afterwards. Importantly, MTX played a critical role in the longitudinal growth of MTX/HAp nanostructure and polyethylene glyco (PEG) was a good dispersing agent to improve the monodispersity. As expected, the functional agent of MTX was served as both the target anticancer drug loaded in HAp and effective complex agents to modify and control the morphologies of MTX/HAp. Lastly, in vitro bioassay tests gave us evidence that obvious tumor inhibition can be achieved when MTX was hybridized with HAp.

  7. Bactofilins, a ubiquitous class of cytoskeletal proteins mediating polar localization of a cell wall synthase in Caulobacter crescentus.

    PubMed

    Kühn, Juliane; Briegel, Ariane; Mörschel, Erhard; Kahnt, Jörg; Leser, Katja; Wick, Stephanie; Jensen, Grant J; Thanbichler, Martin

    2010-01-20

    The cytoskeleton has a key function in the temporal and spatial organization of both prokaryotic and eukaryotic cells. Here, we report the identification of a new class of polymer-forming proteins, termed bactofilins, that are widely conserved among bacteria. In Caulobacter crescentus, two bactofilin paralogues cooperate to form a sheet-like structure lining the cytoplasmic membrane in proximity of the stalked cell pole. These assemblies mediate polar localization of a peptidoglycan synthase involved in stalk morphogenesis, thus complementing the function of the actin-like cytoskeleton and the cell division machinery in the regulation of cell wall biogenesis. In other bacteria, bactofilins can establish rod-shaped filaments or associate with the cell division apparatus, indicating considerable structural and functional flexibility. Bactofilins polymerize spontaneously in the absence of additional cofactors in vitro, forming stable ribbon- or rod-like filament bundles. Our results suggest that these structures have evolved as an alternative to intermediate filaments, serving as versatile molecular scaffolds in a variety of cellular pathways.

  8. FtsZ-Dependent Elongation of a Coccoid Bacterium

    PubMed Central

    Pereira, Ana R.; Hsin, Jen; Król, Ewa; Tavares, Andreia C.; Flores, Pierre; Hoiczyk, Egbert; Ng, Natalie; Dajkovic, Alex; Brun, Yves V.; VanNieuwenhze, Michael S.; Roemer, Terry; Carballido-Lopez, Rut; Huang, Kerwyn Casey

    2016-01-01

    ABSTRACT A mechanistic understanding of the determination and maintenance of the simplest bacterial cell shape, a sphere, remains elusive compared with that of more complex shapes. Cocci seem to lack a dedicated elongation machinery, and a spherical shape has been considered an evolutionary dead-end morphology, as a transition from a spherical to a rod-like shape has never been observed in bacteria. Here we show that a Staphylococcus aureus mutant (M5) expressing the ftsZG193D allele exhibits elongated cells. Molecular dynamics simulations and in vitro studies indicate that FtsZG193D filaments are more twisted and shorter than wild-type filaments. In vivo, M5 cell wall deposition is initiated asymmetrically, only on one side of the cell, and progresses into a helical pattern rather than into a constricting ring as in wild-type cells. This helical pattern of wall insertion leads to elongation, as in rod-shaped cells. Thus, structural flexibility of FtsZ filaments can result in an FtsZ-dependent mechanism for generating elongated cells from cocci. PMID:27601570

  9. Infrared and infrared emission spectroscopy of gallium oxide alpha-GaO(OH) nanostructures.

    PubMed

    Yang, Jing Jeanne; Zhao, Yanyan; Frost, Ray L

    2009-10-01

    Infrared spectroscopy has been used to study nano- to micro-sized gallium oxyhydroxide alpha-GaO(OH), prepared using a low temperature hydrothermal route. Rod-like alpha-GaO(OH) crystals with average length of approximately 2.5 microm and width of 1.5 microm were prepared when the initial molar ratio of Ga to OH was 1:3. beta-Ga(2)O(3) nano and micro-rods were prepared through the calcination of alpha-GaO(OH). The initial morphology of alpha-GaO(OH) is retained in the beta-Ga(2)O(3) nanorods. The combination of infrared and infrared emission spectroscopy complimented with dynamic thermal analysis were used to characterise the alpha-GaO(OH) nanotubes and the formation of beta-Ga(2)O(3) nanorods. Bands at around 2903 and 2836 cm(-1) are assigned to the -OH stretching vibration of alpha-GaO(OH) nanorods. Infrared bands at around 952 and 1026 cm(-1) are assigned to the Ga-OH deformation modes of alpha-GaO(OH). A significant number of bands are observed in the 620-725 cm(-1) region and are assigned to GaO stretching vibrations.

  10. Mechanical Motion of Chiral Azobenzene Crystals with Twisting upon Photoirradiation.

    PubMed

    Taniguchi, Takuya; Fujisawa, Juri; Shiro, Motoo; Koshima, Hideko; Asahi, Toru

    2016-06-01

    The photomechanical motion of chiral crystals of trans-azobenzene derivatives with an (S)- and (R)-phenylethylamide group was investigated and compared with a racemic crystal. Changes in the UV/Vis absorption spectra of the powdered crystals before and after UV irradiation were measured by using an optical waveguide spectrometer, showing that the lifetime of the cis-to-trans thermal back-isomerization of the chiral crystals was faster than that of the racemic crystals. Upon UV irradiation, a long plate-like chiral microcrystal bent away from the light source with a twisting motion. A square-like chiral microcrystal curled toward the light with some twisting. Reversible bending of a rod-like chiral microcrystal was repeatable over twenty-five cycles. In contrast, bending of a plate-like racemic microcrystal was small. A possible mechanism for the bending and twisting motion was discussed based on the optimized cis conformer determined by using calculations, showing that the bending motion with twisting is caused by elongation along the b axis and shrinkage along the a axis.

  11. Study of synthesis of nano-hydroxyapatite using a silk fibroin template.

    PubMed

    Wang, Jing; Yu, Feng; Qu, Lijie; Meng, Xiangcai; Wen, G

    2010-08-01

    Nano-hydroxyapatite (HA) was directly synthesized on a silk fibroin (SF) template using the property of SF being soluble in a concentrated CaCl(2) solution as a HA source of calcium at pH 7.4 and room temperature. The microstructure and bonding state were investigated by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry-thermogravimetry analysis (DSC-TG) and transmission electron microscopy (TEM). The results indicated that the HA crystals were poorly crystallized with a rod-like shape of 20-60 nm length and 10-20 nm diameter. Strong molecular interactions and chemical bonds might be present between SF and HA. There were other nucleation sites such as carbonyl (-C-O) and amine (-N-H-) groups on SF molecules besides the carboxyl (-COOH) and hydroxyl (-OH) groups previously reported. During the formation of HA, the coordination action between specific functional groups on SF and calcium ions (Ca(2+)) played an important role. The crystallinity of HA was improved and had an orientation growth along (0 0 2) at the presence of SF, resulting in a structure similar to natural bone. It was concluded that SF could regulate the structure and morphology of HA effectively.

  12. Coherent collective precession of molecular rotors with chiral propellers.

    PubMed

    Tabe, Yuka; Yokoyama, Hiroshi

    2003-12-01

    Successful attempts to manufacture synthetic molecular motors have recently been reported. However, compared with natural systems such as motor proteins, synthetic motors are smaller molecules and are therefore subject to thermal fluctuations that prevent them from performing any useful function. A mechanism is needed to amplify the single molecular motion to such a level that it becomes distinguishable from the thermal background. Condensation of molecular motors into soft ordered phases (such as liquid crystals) will be a feasible approach, because there is evidence that they support molecularly driven non-equilibrium motions. Here we show that a chiral liquid-crystalline monolayer spread on a glycerol surface acts as a condensed layer of molecular rotors, which undergo a coherent molecular precession driven by the transmembrane transfer of water molecules. Composed of simple rod-like molecules with chiral propellers, the monolayer exhibits a spatiotemporal pattern in molecular orientations that closely resembles 'target patterns' in Belousov-Zhabotinsky reactions. Inversion of either the molecular chirality or the transfer direction of water molecules reverses the rotation direction associated with switching from expanding to converging target patterns. Endowed only with the soft directional order, the liquid crystal is an optimal medium that helps molecular motors to manifest their individual motions collectively.

  13. In vitro assessment of the biological response to nano-sized hydroxyapatite.

    PubMed

    Huang, J; Best, S M; Bonfield, W; Brooks, R A; Rushton, N; Jayasinghe, S N; Edirisinghe, M J

    2004-04-01

    Nano-sized, rod-like hydroxyapatite (nHA) crystals were produced and shown to be phasepure by X-ray diffraction analysis, as no secondary phases were observed. The nHA suspension was electrosprayed onto glass substrates using a novel processing routine to maintain nanocrystals of hydroxyapatite. The biocompatibility of nHAwas determined using human monocyte-derived macrophages and human osteoblast-like (HOB) cell models. The release of lactate dehydrogenase (LDH) from human monocyte-derived macrophages was measured as an indicator of cytotoxicity. The release of the inflammatory cytokine, tumour necrosis factor alpha (TNF-alpha) from cells in the presence of nHA crystallites was used as a measure of the inflammatory response. Although there was some evidence of LDH release from human monocyte-derived macrophages when in contact with high concentrations of nHA crystals, there was no significant release of TNF-alpha. Moreover, nHA-sprayed substrates were able to support the attachment and the growth of HOB cells. These results indicate that nHA crystals may be suitable for intraosseous implantation and offers the potential to formulate enhanced composites for biomedical applications.

  14. Supramolecular barrels from amphiphilic rigid-flexible macrocycles.

    PubMed

    Yang, Won-Young; Ahn, Jong-Hyun; Yoo, Yong-Sik; Oh, Nam-Keun; Lee, Myongsoo

    2005-05-01

    Precise control of supramolecular objects requires the rational design of molecular components, because the information determining their specific assembly should be encoded in their molecular architecture. In this context, diverse self-assembling molecules including liquid crystals, dendrimers, block copolymers, hydrogen-bonded complexes and rigid macrocycles are being created as a means of manipulating supramolecular structure. Incorporation of a stiff rod-like building block into an amphiphilic molecular architecture leads to another class of self-assembling molecules. Aggregation of rod building blocks can generate various nanoscale objects including bundles, ribbons, tubules and vesicles, depending on the molecular structure and/or the presence of a selective solvent. We present here an unusual example of supramolecular barrels in the solid and in aqueous solution, based on the self-assembly of amphiphilic rigid-flexible macrocycles driven by non-covalent interactions. Preliminary experiments show that these amphiphilic macrocycles are membrane-active. The amphiphilic macrocycles might thus lead to an excellent model system for exploring biological processes in supramolecular materials.

  15. A liquid-crystalline hexagonal columnar phase in highly-dilute suspensions of imogolite nanotubes.

    PubMed

    Paineau, Erwan; Krapf, Marie-Eve M; Amara, Mohamed-Salah; Matskova, Natalia V; Dozov, Ivan; Rouzière, Stéphan; Thill, Antoine; Launois, Pascale; Davidson, Patrick

    2016-01-01

    Liquid crystals have found wide applications in many fields ranging from detergents to information displays and they are also increasingly being used in the 'bottom-up' self-assembly approach of material nano-structuration. Moreover, liquid-crystalline organizations are frequently observed by biologists. Here we show that one of the four major lyotropic liquid-crystal phases, the columnar one, is much more stable on dilution than reported so far in literature. Indeed, aqueous suspensions of imogolite nanotubes, at low ionic strength, display the columnar liquid-crystal phase at volume fractions as low as ∼ 0.2%. Consequently, due to its low visco-elasticity, this columnar phase is easily aligned in an alternating current electric field, in contrast with usual columnar liquid-crystal phases. These findings should have important implications for the statistical physics of the suspensions of charged rods and could also be exploited in materials science to prepare ordered nanocomposites and in biophysics to better understand solutions of rod-like biopolymers.

  16. Diatom Mimics: Directing the Formation of Biosilica Nanoparticles by Controlled Folding of Lysine-Leucine Peptides

    PubMed Central

    Baio, Joe E.; Zane, Ariel; Jaeger, Vance; Roehrich, Adrienne M.; Lutz, Helmut; Pfaendtner, Jim; Drobny, Gary P.; Weidner, Tobias

    2015-01-01

    Silaffins, long chain polyamines, and other biomolecules found in diatoms are involved in the assembly of a large number of silica nanostructures under mild, ambient conditions. Nanofabrication researchers have sought to mimic the diatom's biosilica production capabilities by engineering proteins to resemble aspects of naturally occurring biomolecules. Such mimics can produce monodisperse biosilica nanospheres, but in vitro production of the variety of intricate biosilica nanostructures that compose the diatom frustule is not yet possible. In this study we demonstrate how LK peptides, composed solely of lysine (K) and leucine (L) amino acids arranged with varying hydrophobic periodicities, initiate the formation of different biosilica nanostructures in vitro. When L and K residues are arranged with a periodicity of 3.5 the α-helical form of the LK peptide produces monodisperse biosilica nanospheres. However, when the LK periodicity is changed to 3.0, corresponding to a 310 helix, the morphology of the nanoparticles changes to elongated rod-like structures. β-strand LK peptides with a periodicity of 2.0 induce wire-like silica morphologies. This study illustrates how the morphology of biosilica can be changed simply by varying the periodicity of polar and nonpolar amino acids. PMID:25285787

  17. Diatom mimics: directing the formation of biosilica nanoparticles by controlled folding of lysine-leucine peptides.

    PubMed

    Baio, Joe E; Zane, Ariel; Jaeger, Vance; Roehrich, Adrienne M; Lutz, Helmut; Pfaendtner, Jim; Drobny, Gary P; Weidner, Tobias

    2014-10-29

    Silaffins, long chain polyamines, and other biomolecules found in diatoms are involved in the assembly of a large number of silica nanostructures under mild, ambient conditions. Nanofabrication researchers have sought to mimic the diatom's biosilica production capabilities by engineering proteins to resemble aspects of naturally occurring biomolecules. Such mimics can produce monodisperse biosilica nanospheres, but in vitro production of the variety of intricate biosilica nanostructures that compose the diatom frustule is not yet possible. In this study we demonstrate how LK peptides, composed solely of lysine (K) and leucine (L) amino acids arranged with varying hydrophobic periodicities, initiate the formation of different biosilica nanostructures in vitro. When L and K residues are arranged with a periodicity of 3.5 the α-helical form of the LK peptide produces monodisperse biosilica nanospheres. However, when the LK periodicity is changed to 3.0, corresponding to a 310 helix, the morphology of the nanoparticles changes to elongated rod-like structures. β-strand LK peptides with a periodicity of 2.0 induce wire-like silica morphologies. This study illustrates how the morphology of biosilica can be changed simply by varying the periodicity of polar and nonpolar amino acids.

  18. Biosilica structures obtained from Nitzschia, Ditylum, Skeletonema, and Coscinodiscus diatom by a filtration-aided acid cleaning method.

    PubMed

    Wang, Yu; Zhang, Deyuan; Cai, Jun; Pan, Junfeng; Chen, Mingli; Li, Aobo; Jiang, Yonggang

    2012-09-01

    A filtration-aided acid cleaning method was used to collect biosilica structures from a diatom culture medium, natural seawater, or water bloom. Cell extraction, acid cleaning, and acid removal were all performed on a polytetrafluoroethylene (PTFE) filter cloth, significantly improving the treatment capacity and efficiency of the traditional acid wash method. Five typical diatoms were cultivated in the laboratory for acid cleaning. Different growth speeds were introduced, and different process parameters for acid cleaning were utilized. After the acid cleaning, biosilica structures were collected from the frustules of diatoms using different methods. Girdle bands and valves of Coscinodiscus sp. were separated by floating of the valves. Central spines of Ditylum brightwellii and valves of Skeletonema costatum were separately collected by settling or filtration. Rod-like frustules, such as those of Bacillaris paradoxa, are not suitable for large quantities of acid wash. The silica structures were observed and tested using an AFM-calibrated glass needle to determine their elasticity. Elasticity tests showed that ringent girdle bands are more flexible than complete ones (Coscinodiscus sp.) and that both long-chain clusters of Nitzschia palea and central spines of D. brightwellii have certain elasticities. The required pressure for deforming or breaking the biosilica structures of diatoms was also determined.

  19. Kinetic Study on the Isothermal and Nonisothermal Crystallization of Monoglyceride Organogels

    PubMed Central

    Meng, Zong; Yang, Lijun; Geng, Wenxin; Yao, Yubo; Wang, Xingguo; Liu, Yuanfa

    2014-01-01

    The isothermal and nonisothermal crystallization kinetics of monoglyceride (MAG) organogels were studied by pulsed nuclear magnetic resonance (pNMR) and differential scanning calorimetry (DSC), respectively. The Avrami equation was used to describe the isothermal crystallization kinetics and experimental data fitted the equation fairly well. Results showed that the crystal growth of MAG organogels was a rod-like growth of instantaneous nuclei at higher degrees of supercooling and a plate-like form with high nucleation rate at lower degrees of supercooling. The exothermic peak in nonisothermal DSC curves for the MAG organogels became wider and shifted to lower temperature when the cooling rate increased, and nonisothermal crystallization was analyzed by Mo equation. Results indicated that at the same crystallization time, to get a higher degree of relative crystallinity, a higher cooling rate was necessary. The activation energy of nonisothermal crystallization was calculated as 739.59 kJ/mol according to the Kissinger method. Therefore, as the results of the isothermal and nonisothermal crystallization kinetics for the MAG organogels obtained, the crystallization rate, crystal nucleation, and growth during the crystallization process could be preliminarily monitored through temperature and cooling rate regulation, which laid the foundation for the real industrial manufacture and application of the MAG organogels. PMID:24701138

  20. Development of Polysorbate 80/Phospholipid mixed micellar formation for docetaxel and assessment of its in vivo distribution in animal models

    NASA Astrophysics Data System (ADS)

    Song, Hua; Geng, Hongquan; Ruan, Jing; Wang, Kan; Bao, Chenchen; Wang, Juan; Peng, Xia; Zhang, Xueqing; Cui, Daxiang

    2011-04-01

    Docetaxel (DTX) is a very important member of taxoid family. Despite several alternative delivery systems reported recently, DTX formulated by Polysorbate 80 and alcohol (Taxotere®) is still the most frequent administration in clinical practice. In this study, we incorporated DTX into Polysorbate 80/Phospholipid mixed micelles and compared its structural characteristics, pharmacokinetics, biodistribution, and blood compatibility with its conventional counterparts. Results showed that the mixed micelles loaded DTX possessed a mean size of approximately 13 nm with narrow size distribution and a rod-like micelle shape. In the pharmacokinetics assessment, there was no significant difference between the two preparations ( P > 0.05), which demonstrated that the DTX in the two preparations may share a similar pharmacokinetic process. However, the Polysorbate 80/Phospholipid mixed micelles can increase the drug residence amount of DTX in kidney, spleen, ovary and uterus, heart, and liver. The blood compatibility assessment study revealed that the mixed micelles were safe for intravenous injection. In conclusion, Polysorbate 80/Phospholipid mixed micelle is safe, can improve the tumor therapeutic effects of DTX in the chosen organs, and may be a potential alternative dosage form for clinical intravenous administration of DTX.

  1. Morphological variations of Haemophilus parasuis strains.

    PubMed Central

    Morozumi, T; Nicolet, J

    1986-01-01

    Haemophilus parasuis strains isolated from the noses of apparently healthy animals and from animals with pathological conditions were examined for the presence of a capsule, for their ability to agglutinate in acriflavine or after boiling, and for their peptide profile after polyacrylamide gel electrophoresis (PAGE). The capsule was identified by precipitation against hexadecyl trimethylammonium bromide (Cetavlon), by demonstration of iridescence, and by means of a capsule-staining method. We found a group of capsulated strains showing a rather coccobacillary morphology compared with the morphology with polymorphism, varying from rod-like to filamentous, in strains without detectable capsules. The strains of the latter group were agglutinated by acriflavine or by boiling. Soluble antigens of capsulated strains reacting with Cetavlon were thermostable and resisted proteolytic enzymes, thus suggesting the presence of an acidic polysaccharide. A few of the capsulated strains did not precipitate with Cetavlon, which indicated that their chemical composition was different. Acriflavine-positive strains belonging to a definite PAGE pattern (type II) seemed to be associated with pathological conditions more frequently than were capsulated strains which were mostly isolated from nasal cavities of apparently healthy pigs. We put forward the hypothesis that the agglutinability in acriflavine, together with the PAGE profile type II, may be associated with particular structures responsible for virulence. Images PMID:3700597

  2. Characteristics of ZnO thin films doped by various elements

    NASA Astrophysics Data System (ADS)

    Kahraman, S.; Çakmak, H. M.; Çetinkaya, S.; Bayansal, F.; Çetinkara, H. A.; Güder, H. S.

    2013-01-01

    We have investigated the effects of Al, K and Co dopant elements on the properties of ZnO thin films deposited by CBD method on glass substrates. Changing in morphology, structural parameters, ionization energies of impurity levels, absorption behavior and optical band gap values were investigated through scanning electron microscopy (SEM), X-Ray diffraction (XRD), resistance-temperature measurement (R-T) and ultraviolet-visible spectroscopy (UV-vis) techniques. From the SEM observations, various morphologies (rod-like, flower-like and rice-like) were observed. Those morphological variations were attributed to the change in stable growth mechanism of intrinsic ZnO, induced by different atomic radius and different electronegativity of dopants. XRD results indicated that all orientations are well indexed to hexagonal phase crystalline ZnO. The impurity level ionization energy values (ΔE) were estimated as 0.32/0.13/0.07 eV; 0.34/0.15 eV; 0.40/0.13 eV and 0.48/0.22 eV for the Al, K, Co doped samples and i-ZnO, respectively. Optical band gap values were found that the doped samples' were higher than the intrinsic one's. This increasing (blue shift) was attributed to a deterioration which occurred in the lattice of the structures after doping. This effect was also supported by the structural results.

  3. Paramagnetic behavior of Co doped TiO2 nanocrystals controlled by self-purification mechanism

    NASA Astrophysics Data System (ADS)

    Anitha, B.; Khadar, M. Abdul; Banerjee, Alok

    2016-07-01

    Doping in nanocrystals is a challenging process because of the self- purification mechanism which tends to segregate out the dopants resulting in a greater dopant concentration near the surface than at the interior of nanocrystals. In the present work nanocrystals of TiO2 doped with different atom % of Co were synthesized by peroxide gel method. XRD analysis confirmed the tetragonal anatase structure and HRTEM images showed the rod-like morphology of the samples. Raman modes of anatase phase of TiO2 along with weak intensity peaks of Co3O4 for higher Co dopant concentrations were observed for the samples. EPR measurements revealed the presence of cobalt in +2 oxidation state in the TiO2 matrix. SQUID measurements indicated paramagnetic behavior of the Co doped TiO2 nanocrystals. The paramagnetic behavior is attributed to an increased concentration of Co2+ ions and an increased presence of Co3O4 phase near the surface of the TiO2 nanocrystals due to self-purification mechanism.

  4. Random Packings Of Rod-Sphere Mixtures Simulated By Mechanical Contraction

    NASA Astrophysics Data System (ADS)

    Kyrylyuk, Andriy V.; Wouterse, Alan; Philipse, Albert P.

    2009-06-01

    We study the random close packing of a binary mixture of spheres and rod-like particles (spherocylinders) by the mechanical contraction computer simulation. We investigate the universality in packing of near-spheres by monitoring the position and the value of the maximum in the mixture packing density as a function of the mixture composition and the rod aspect ratio. We find that independently of the mixture composition the particles pack more efficiently/densely as the rod aspect ratio is perturbed slightly from zero and the maximum density is always reached at one unique rod aspect ratio of about 0.45. The dependence of the value of the maximum packing fraction on the mixture composition (the relative rod volume fraction) is linear, exhibiting some ideality in packing of near-spheres. This counter-intuitive finding suggests that even for high rod concentrations in a rod-sphere mixture the packing is governed by local contacts between the neighboring particles, which is usually observed for dilute colloidal suspensions and granular gases, where there is no correlation between the particles. The plausible explanation for this intriguing behavior is that the correlations between the particles are completely lost in the range of distances of several particle diameters, which can be originated from the decoupling of the orientational and translational degrees of freedom of the nearly spherical rods. This gives rise to the universality and locality of random close packing of the rod-sphere mixtures.

  5. Iron oxide nanorods as high-performance magnetic resonance imaging contrast agents.

    PubMed

    Mohapatra, Jeotikanta; Mitra, Arijit; Tyagi, Himanshu; Bahadur, D; Aslam, M

    2015-01-01

    An efficient magnetic resonance imaging (MRI) contrast agent with a high R2 relaxivity value is achieved by controlling the shape of iron oxide to rod like morphology with a length of 30-70 nm and diameter of 4-12 nm. Fe3O4 nanorods of 70 nm length, encapsulated with polyethyleneimine show a very high R2 relaxivity value of 608 mM(-1) s(-1). The enhanced MRI contrast of nanorods is attributed to their higher surface area and anisotropic morphology. The higher surface area induces a stronger magnetic field perturbation over a larger volume more effectively for the outer sphere protons. The shape anisotropy contribution is understood by calculating the local magnetic field of nanorods and spherical nanoparticles under an applied magnetic field (3 Tesla). As compared to spherical geometry, the induced magnetic field of a rod is stronger and hence the stronger magnetic field over a large volume leads to a higher R2 relaxivity of nanorods.

  6. Synthesis and Tribological Properties of WSe2 Nanorods

    NASA Astrophysics Data System (ADS)

    Yang, Jinghai; Yao, Haixia; Liu, Yanqing; Zhang, Yongjun

    2008-12-01

    The WSe2 nanorods were synthesized via solid-state reaction method and characterized by X-ray diffractometer, TEM, and HRTEM. The results indicated the WSe2 compounds had rod-like structures with diameters of 10-50 nm and lengths of 100-400 nm, and the growth process of WSe2 nanorods was discussed on the basis of the experimental facts. The tribological properties of WSe2 nanorods as additives in HVI500 base oil were investigated by UMT-2 multispecimen tribotester. Under the determinate conditions, the friction coefficient of the base oil containing WSe2 nanorods was lower than that of the base oil, and decreased with increasing mass fraction of WSe2 nanorods when it was <7 wt.%. Moreover, the base oil with the additives was rather suited to high load and high rotating speed. A combination of rolling friction, sliding friction, and stable tribofilm on the rubbing surface could explain the good friction and wear properties of WSe2 nanorods as additives.

  7. Structural, optical and magnetic properties of Co-doped ZnO nanorods with hidden secondary phases

    NASA Astrophysics Data System (ADS)

    Wang, Xuefeng; Zheng, Rongkun; Liu, Zongwen; Ho, Ho-pui; Xu, Jianbin; Ringer, Simon P.

    2008-11-01

    Co-doped ZnO nanorods (composition: Zn0.955Co0.045O) were grown by a simple surfactant-assisted hydrothermal technique. The morphological, structural, optical and magnetic properties of the as-prepared nanorods were investigated by means of scanning electron microscopy, high-resolution transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, micro-Raman spectroscopy, micro-cathodoluminescence, and vibrating sample magnetometry (VSM). The results showed that the sample had rod-like morphology and that the preferential growth direction was along the c axis. While Co was successfully doped into the ZnO wurtzite lattice structure as revealed by several characterization techniques, hidden secondary phases of ZnyCo3-yO4 (0<=y<=1) were also clearly detected by the micro-Raman spectroscopic technique. We propose that the predominant diffusion-limited Ostwald ripening crystal growth mechanism under the hydrothermal coarsening yielded such phase segregation. VSM results showed that the nanorods displayed relatively weak room-temperature ferromagnetism. We suggest that the origin of the ferromagnetism is probably due to the presence of the mixed cation valence of Co via a d-d double-exchange mechanism rather than the real doping effect. It is essential to control the crystal growth mechanism and defect states associated with the ferromagnetism in order to realize the intrinsic diluted magnetic semiconductors.

  8. NTB-A Receptor Crystal Structure: Insights into Homophilic Interactions in the Signaling Lymphocytic Activation Molecule Receptor Family

    SciTech Connect

    Cao,E.; Ramagopal, U.; Fedorov, A.; Fedorov, E.; Yan, Q.; Lary, J.; Cole, J.; Nathenson, S.; Almo, S.

    2006-01-01

    The signaling lymphocytic activation molecule (SLAM) family includes homophilic and heterophilic receptors that regulate both innate and adaptive immunity. The ectodomains of most SLAM family members are composed of an N-terminal IgV domain and a C-terminal IgC2 domain. NK-T-B-antigen (NTB-A) is a homophilic receptor that stimulates cytotoxicity in natural killer (NK) cells, regulates bactericidal activities in neutrophils, and potentiates T helper 2 (Th2) responses. The 3.0 {angstrom} crystal structure of the complete NTB-A ectodomain revealed a rod-like monomer that self-associates to form a highly kinked dimer spanning an end-to-end distance of {approx}100 {angstrom}. The NTB-A homophilic and CD2-CD58 heterophilic dimers show overall structural similarities but differ in detailed organization and physicochemical properties of their respective interfaces. The NTB-A structure suggests a mechanism responsible for binding specificity within the SLAM family and imposes physical constraints relevant to the colocalization of SLAM-family proteins with other signaling molecules in the immunological synapse.

  9. Kinetic study on the isothermal and nonisothermal crystallization of monoglyceride organogels.

    PubMed

    Meng, Zong; Yang, Lijun; Geng, Wenxin; Yao, Yubo; Wang, Xingguo; Liu, Yuanfa

    2014-01-01

    The isothermal and nonisothermal crystallization kinetics of monoglyceride (MAG) organogels were studied by pulsed nuclear magnetic resonance (pNMR) and differential scanning calorimetry (DSC), respectively. The Avrami equation was used to describe the isothermal crystallization kinetics and experimental data fitted the equation fairly well. Results showed that the crystal growth of MAG organogels was a rod-like growth of instantaneous nuclei at higher degrees of supercooling and a plate-like form with high nucleation rate at lower degrees of supercooling. The exothermic peak in nonisothermal DSC curves for the MAG organogels became wider and shifted to lower temperature when the cooling rate increased, and nonisothermal crystallization was analyzed by Mo equation. Results indicated that at the same crystallization time, to get a higher degree of relative crystallinity, a higher cooling rate was necessary. The activation energy of nonisothermal crystallization was calculated as 739.59 kJ/mol according to the Kissinger method. Therefore, as the results of the isothermal and nonisothermal crystallization kinetics for the MAG organogels obtained, the crystallization rate, crystal nucleation, and growth during the crystallization process could be preliminarily monitored through temperature and cooling rate regulation, which laid the foundation for the real industrial manufacture and application of the MAG organogels.

  10. Characterization of the solution structure of a neuroligin/beta-neurexin complex.

    PubMed

    Comoletti, Davide; Grishaev, Alexander; Whitten, Andrew E; Taylor, Palmer; Trewhella, Jill

    2008-09-25

    Neuroligins are post-synaptic cell adhesion molecules that promote synaptic maturation and stabilization upon binding with pre-synaptic partners, the alpha- and beta-neurexins. Using a combination of analytical ultracentrifugation, small angle X-ray, and neutron scattering, we have characterized the low-resolution three-dimensional structure of the extracellular domain of the neuroligins, free in solution, and in complex with beta-neurexin. The globular extracellular domain of the neuroligins forms stable homodimers through a four-helix bundle typical of the cholinesterases and other members of the alpha/beta-hydrolase fold family. The presence of the stalk region adds to the extracellular domain of neuroligin-1 an elongated structure, suggesting a rod-like nature of the stalk domain. Sedimentation equilibrium coupled with solution scattering data of the beta-neurexin/neuroligin-1 complex indicated a 2:2 stoichiometry where two beta-neurexin molecules bind to a neuroligin-1 dimer. Deuteration of neurexin allowed us to collect neutron scattering data that, in combination with other biochemical techniques, provide a basis for optimizing the positioning of each component in a detailed computational model of the neuroligin/neurexin complex. As several mutations of both neurexin and neuroligin genes have been linked to autism spectrum disorders and mental retardation, these new structures provide an important framework for the study of altered structure and function of these synaptic proteins.

  11. Linked topological colloids in a nematic host

    PubMed Central

    Martinez, Angel; Hermosillo, Leonardo; Tasinkevych, Mykola; Smalyukh, Ivan I.

    2015-01-01

    Geometric shape and topology of constituent particles can alter many colloidal properties such as Brownian motion, self-assembly, and phase behavior. Thus far, only single-component building blocks of colloids with connected surfaces have been studied, although topological colloids, with constituent particles shaped as freestanding knots and handlebodies of different genus, have been recently introduced. Here we develop a topological class of colloids shaped as multicomponent links. Using two-photon photopolymerization, we fabricate colloidal microparticle analogs of the classic examples of links studied in the field of topology, the Hopf and Solomon links, which we disperse in nematic fluids that possess orientational ordering of anisotropic rod-like molecules. The surfaces of these particles are treated to impose tangential or perpendicular boundary conditions for the alignment of liquid crystal molecules, so that they generate a host of topologically nontrivial field and defect structures in the dispersing nematic medium, resulting in an elastic coupling between the linked constituents. The interplay between the topologies of surfaces of linked colloids and the molecular alignment field of the nematic host reveals that linking of particle rings with perpendicular boundary conditions is commonly accompanied by linking of closed singular defect loops, laying the foundations for fabricating complex composite materials with interlinking-based structural organization. PMID:25825765

  12. Photocatalytic direct conversion of ethanol to 1,1- diethoxyethane over noble-metal-loaded TiO2 nanotubes and nanorods.

    PubMed

    Zhang, Hongxia; Wu, Yupeng; Li, Li; Zhu, Zhenping

    2015-04-13

    As one of the most important biomass platform molecules, ethanol needs to have its product chain chemically extended to meet future demands in renewable fuels and chemicals. Additionally, chemical conversion of ethanol under mild and green conditions is still a major challenge. In this work, ethanol is directly converted into 1,1-diethoxyethane (DEE) and H2 under mild photocatalytic conditions over platinum-loaded TiO2 nanotubes and nanorods. The reaction follows a tandem dehydrogenation-acetalization mechanism, in which ethanol is first dehydrogenated into acetaldehyde and H(+) ion by photogenerated holes, and then acetalization between acetaldehyde and ethanol proceeds through promotion by H(+) ions formed in real time. Excess H(+) ions are simultaneously reduced into H2 by photogenerated electrons. This photocatalytic process has a very high reaction rate over nanosized tubular and rod-like TiO2 photocatalysts, reaching 157.7 mmol g(-1)  h(-1) in relatively low photocatalyst feeding. More importantly, the reaction is highly selective, with a nearly stoichiometric conversion of reacted ethanol into DEE. This photocatalytic dehydrogenation CO coupling of ethanol is a new green approach to the direct efficient conversion of ethanol into DEE and provides a promising channel for sustainable bioethanol applications. PMID:25755072

  13. Rotationally Molded Liquid Crystalline Polymers

    NASA Technical Reports Server (NTRS)

    Rogers, Martin; Scribben, Eric; Baird, Donald; Hulcher, Bruce

    2002-01-01

    Rotational molding is a unique process for producing hollow plastic parts. Rotational molding offers low cost tooling and can produce very large parts with complicated shapes. Products made by rotational molding include water tanks with capacities up to 20,000 gallons, truck bed liners, playground equipment, air ducts, Nylon fuel tanks, pipes, toys, stretchers, kayaks, pallets, and many others. Thermotropic liquid crystalline polymers are an important class of engineering resins employed in a wide variety of applications. Thermotropic liquid crystalline polymers resins are composed of semirigid, nearly linear polymeric chains resulting in an ordered mesomorphic phase between the crystalline solid and the isotropic liquid. Ordering of the rigid rod-like polymers in the melt phase yields microfibrous, self-reinforcing polymer structures with outstanding mechanical and thermal properties. Rotational molding of liquid crystalline polymer resins results in high strength and high temperature hollow structures useful in a variety of applications. Various fillers and reinforcements can potentially be added to improve properties of the hollow structures. This paper focuses on the process and properties of rotationally molded liquid crystalline polymers. This paper will also highlight the interactions between academia and small businesses in developing new products and processes.

  14. Identification of extensin protein associated with sugar beet pectin.

    PubMed

    Nuñez, Alberto; Fishman, Marshall L; Fortis, Laurie L; Cooke, Peter H; Hotchkiss, Arland T

    2009-11-25

    Several studies have suggested that the emulsification properties associated with pectin obtained from sugar beet (Beta vulgaris) are due to the presence of a protein-pectin complex. Nevertheless, the identity of the protein has remained elusive. Pectin, extracted from sugar beet pulp by microwave-assisted extraction, and a commercial sample were both subjected to protease digestion with trypsin. The resulting peptides were separated from the pectin solution by ultrafiltration using a 3 kDa molecular weight cutoff (MWCO) membrane and analyzed using matrix-assisted laser desorption ionization with tandem time-of-flight mass spectrometry. The partial sequences derived from the mass spectrometry analyses of the resulting tryptic peptides are found to be highly consistent with extensin protein matched from the B. vulgaris Genetic Index database and also correspond to previously reported extensin peptides found in sugar beet cell suspension cultures. Further attempts were made to disassociate the protein from pectin using 1 M NaCl and a 100 kDa MWCO membrane; however, no peptides were observed following trypsin digestion of the permeate solution. This evidence suggests the existence of a complex between the pectin and extensin that is not due to ionic interactions. Trypsin digestion of commercial sugar beet pectin also produced the peptide profile observed with the microwave-assisted extracted pectin sample. Atomic force microscopy established that the number of rod-like elements decreased following protease treatment compared to the untreated sample.

  15. Nanoporous Ag prepared from the melt-spun Cu-Ag alloys

    NASA Astrophysics Data System (ADS)

    Li, Guijing; Song, Xiaoping; Sun, Zhanbo; Yang, Shengchun; Ding, Bingjun; Yang, Sen; Yang, Zhimao; Wang, Fei

    2011-07-01

    Nanoporous Ag ribbons with different morphology and porosity were achieved by the electrochemical corrosion of the melt-spun Cu-Ag alloys. The Cu-rich phase in the alloys was removed, resulting in the formation of the nanopores distributed across the whole ribbon. It is found that the structures, morphology and porosity of the nanoporous Ag ribbons were dependent on the microstructures of the parent alloys. The most of ligaments presented a rod-like shape due to the formation of pseudoeutectic microstructure in the melt-spun Cu 55Ag 45 and Cu 70Ag 30 alloys. For nanoporous Ag prepared from Cu 85Ag 15 alloys, the ligaments were camber-like because of the appearance of the divorced microstructures. Especially, a novel bamboo-grove-like structure could be observed at the cross-section of the nanoporous Ag ribbons. The experiment reveals that nanoporous Ag ribbons exhibited excellent enhancement of surface-enhanced Raman scattering (SERS) effect, but a slight difference existed due to the discrepancy of their morphology.

  16. Evaluation of an experimental dental porcelain.

    PubMed

    Hamouda, Ibrahim M; El-Waseffy, Noha A; Hasan, Ahmed M; El-Falal, Abeer A

    2010-11-01

    The aim of this study was to evaluate fracture toughness, hardness, ceramic/metal bond strength and microstructure of experimental dental porcelain and compare it with commercial type. Specimens of specific dimensions were prepared. Fracture toughness was assessed by a three-point bending test. The Vickers hardness was measured using a microhardness tester. The ceramometal bond strength was measured using a universal testing machine. The load was applied at the porcelain/metal interface via a chisel edged blade with a crosshead speed of 2.0 mm/min until fracture. The polished specimens of dental porcelain were chemically etched and the microstructure was analyzed with a scanning electron microscope. The results showed comparable fracture toughness and bond strength for both materials, while the experimental porcelain exhibited higher hardness. The experimental porcelain showed uniform cohesive failure while the commercial type showed mixed mode of failure. The microstructure of the experimental porcelain was tetragonal leucite crystals dispersed randomly in a glass matrix. The leucite crystals exist in two forms, acicular and rod like structures. It was concluded that the experimental porcelain has adequate fracture toughness and ceramic/metal bond strength that can resist the rapid crack propagation and its consequent catastrophic failure, which indicates a material serviceability in the oral cavity.

  17. Label-free potentiometry for detecting DNA hybridization using peptide nucleic acid and DNA probes.

    PubMed

    Goda, Tatsuro; Singi, Ankit Balram; Maeda, Yasuhiro; Matsumoto, Akira; Torimura, Masaki; Aoki, Hiroshi; Miyahara, Yuji

    2013-02-07

    Peptide nucleic acid (PNA) has outstanding affinity over DNA for complementary nucleic acid sequences by forming a PNA-DNA heterodimer upon hybridization via Watson-Crick base-pairing. To verify whether PNA probes on an electrode surface enhance sensitivity for potentiometric DNA detection or not, we conducted a comparative study on the hybridization of PNA and DNA probes on the surface of a 10-channel gold electrodes microarray. Changes in the charge density as a result of hybridization at the solution/electrode interface on the self-assembled monolayer (SAM)-formed microelectrodes were directly transformed into potentiometric signals using a high input impedance electrometer. The charge readout allows label-free, reagent-less, and multi-parallel detection of target oligonucleotides without any optical assistance. The differences in the probe lengths between 15- to 22-mer dramatically influenced on the sensitivity of the PNA and DNA sensors. Molecular type of the capturing probe did not affect the degree of potential shift. Theoretical model for charged rod-like duplex using the Gouy-Chapman equation indicates the dominant effect of electrostatic attractive forces between anionic DNA and underlying electrode at the electrolyte/electrode interface in the potentiometry.

  18. Overexpression, purification, crystallization and preliminary X-ray analysis of Rv2780 from Mycobacterium tuberculosis H37Rv

    SciTech Connect

    Tripathi, Sarvind Mani; Ramachandran, Ravishankar

    2008-05-01

    Rv2780, an alanine dehydrogenase from M. tuberculosis, has been crystallized in apo and NAD/pyruvate-bound forms. Preliminary crystallographic analysis shows that there is a hexamer and trimer in the asymmetric units of the apo and ternary complex forms, respectively. Rv2780, an alanine dehydrogenase from Mycobacterium tuberculosis (MtAlaDH), catalyzes the NAD-dependent interconversion of alanine and pyruvate. Alanine dehydrogenase is released into the culture medium in substantial amounts by virulent strains of mycobacteria and is not found in the vaccine strain of tuberculosis. Crystals of recombinant MtAlaDH were grown from 2 M ammonium sulfate solution at ∼12 mg ml{sup −1} protein concentration in two crystal forms which occur in the presence and absence of NAD/pyruvate, respectively. Diffraction data extending to 2.6 Å were collected at room temperature from both apo and ternary complex crystals. Crystals of the apoenzyme have unit-cell parameters a = 173.89, b = 127.07, c = 135.95 Å. They are rod-like in shape and belong to space group C2. They contain a hexamer in the asymmetric unit. Crystals of the ternary complex belong to space group P4{sub 3}2{sub 1}2 and have unit-cell parameters a = b = 88.99, c = 373.85 Å. There are three subunits in the asymmetric unit of the holoenzyme crystals.

  19. Hydrothermal synthesis of zinc oxide nanoparticles using rice as soft biotemplate

    PubMed Central

    2013-01-01

    Background Rice as a renewable, abundant bio-resource with unique characteristics can be used as a bio-template to synthesize various functional nanomaterials. Therefore, the effect of uncooked rice flour as bio-template on physico-chemical properties, especially the morphology of zinc oxide nanostructures was investigated in this study. The ZnO particles were synthesized through hydrothermal-biotemplate method using zinc acetate-sodium hydroxide and uncooked rice flour at various ratios as precursors at 120°C for 18 hours. Results The results indicate that rice as a bio-template can be used to modify the shape and size of zinc oxide particles. Different morphologies, namely flake-, flower-, rose-, star- and rod-like structures were obtained with particle size at micro- and nanometer range. Pore size and texture of the resulting zinc oxide particles were found to be template-dependent and the resulting specific surface area enhanced compared to the zinc oxide synthesized without rice under the same conditions. However, optical property particularly the band gap energy is generally quite similar. Conclusion Pure zinc oxide crystals were successfully synthesized using rice flour as biotemplate at various ratios of zinc salt to rice. The size- and shape-controlled capability of rice to assemble the ZnO particles can be employed for further useful practical applications. PMID:23919386

  20. Synthesis and characterization of WO{sub 3} spherical nanoparticles and nanorods

    SciTech Connect

    Adhikari, Sangeeta; Sarkar, Debasish Maiti, Himadri Sekhar

    2014-01-01

    Graphical abstract: Two different morphology WO{sub 3} nanoparticles are synthesized by a simple and new wet chemical route through control over pH, temperature and structure directing agents. Reaction mechanism has been proposed for the formation of different morphologies. Nanorod WO{sub 3} has better crystallinity with less specific surface area compared to the spherical nanoparticles. Comparable band gaps are obtained for both the nanoparticles. - Highlights: • Spherical WO{sub 3} nanoparticle and nanorod synthesis mechanisms proposed. • Thermal analysis and spectroscopy confirms the intermediate reactions. • Both of the morphology has pure and monoclinic phase with identical band gap energy. - Abstract: Simple and new wet chemical routes are adopted for the synthesis of tungsten trioxide (WO{sub 3}) nanopowders having two different morphologies such as spherical and rod-like. Acid catalyzed exothermic reaction and a structure directing reagent have been used to control the formation of spherical and rod shaped nanoparticles, respectively. Thermal analysis and FTIR spectral data have been used to confirm the formation of the intermediate and the ultimate reaction products. X-ray and Raman spectroscopic data indicate the monoclinic structure of both forms of the particles. Rod shaped WO{sub 3} particles exhibit better crystallinity and low specific surface area compared to those exhibited by spherical particles. Band gaps are found to be nearly identical irrespective of the morphology.