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Sample records for temperature-sensitive poly-n-isopropylacrylamide-poly-n-isopropylmethacrylamide core-shell

  1. Engineered Magnetic Core-Shell Structures.

    Science.gov (United States)

    Alavi Nikje, Mir Mohammad; Vakili, Maryam

    2015-01-01

    In recent years, engineered magnetic core-shell structures are playing an important role in the wide range of various applications. These magnetic core-shell structures have attracted considerable attention because of their unique properties and various applications. Also, the synthesis of engineered magnetic core-shell structures has attracted practical interest because of potential applications in areas such as ferrofluids, medical imaging, drug targeting and delivery, cancer therapy, separations, and catalysis. So far a large number of engineered magnetic core-shell structures have been successfully synthesized. This review article focuses on the recent progress in synthesis and characterization of engineered magnetic core-shell structures. Also, this review gives a brief description of the various application of these structures. It is hoped that this review will play some small part in helping future developments in important field.

  2. Engineered inorganic core/shell nanoparticles

    International Nuclear Information System (INIS)

    Mélinon, Patrice; Begin-Colin, Sylvie; Duvail, Jean Luc; Gauffre, Fabienne; Boime, Nathalie Herlin; Ledoux, Gilles; Plain, Jérôme; Reiss, Peter; Silly, Fabien; Warot-Fonrose, Bénédicte

    2014-01-01

    It has been for a long time recognized that nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic structures. At first, size effects occurring in single elements have been studied. More recently, progress in chemical and physical synthesis routes permitted the preparation of more complex structures. Such structures take advantages of new adjustable parameters including stoichiometry, chemical ordering, shape and segregation opening new fields with tailored materials for biology, mechanics, optics magnetism, chemistry catalysis, solar cells and microelectronics. Among them, core/shell structures are a particular class of nanoparticles made with an inorganic core and one or several inorganic shell layer(s). In earlier work, the shell was merely used as a protective coating for the core. More recently, it has been shown that it is possible to tune the physical properties in a larger range than that of each material taken separately. The goal of the present review is to discuss the basic properties of the different types of core/shell nanoparticles including a large variety of heterostructures. We restrict ourselves on all inorganic (on inorganic/inorganic) core/shell structures. In the light of recent developments, the applications of inorganic core/shell particles are found in many fields including biology, chemistry, physics and engineering. In addition to a representative overview of the properties, general concepts based on solid state physics are considered for material selection and for identifying criteria linking the core/shell structure and its resulting properties. Chemical and physical routes for the synthesis and specific methods for the study of core/shell nanoparticle are briefly discussed

  3. Engineered inorganic core/shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Mélinon, Patrice, E-mail: patrice.melinon@univ-lyon1.fr [Institut Lumière matière Université Claude Bernard Lyon 1 et CNRS et OMNT, Domaine Scientifique de la Doua, Bâtiment Léon Brillouin, 43 Boulevard du 11 Novembre 1918, F 69622 Villeurbanne (France); Begin-Colin, Sylvie [IPCMS et OMNT, 23 rue du Loess BP 43, 67034 STRASBOURG Cedex 2 (France); Duvail, Jean Luc [IMN UMR 6502 et OMNT Campus Sciences : 2 rue de la Houssinire, BP32229, 44322 Nantes Cedex3 (France); Gauffre, Fabienne [SPM et OMNT : Institut des sciences chimiques de Rennes - UMR 6226, 263 Avenue du General Leclerc, CS 74205, 35042 RENNES Cedex (France); Boime, Nathalie Herlin [IRAMIS-NIMBE, Laboratoire Francis Perrin (CEA CNRS URA 2453) et OMNT, Bat 522, CEA Saclay, 91191 Gif sur Yvette Cedex (France); Ledoux, Gilles [Institut Lumière Matière Université Claude Bernard Lyon 1 et CNRS et OMNT, Domaine Scientifique de la Doua, Bâtiment Alfred Kastler 43 Boulevard du 11 Novembre 1918 F 69622 Villeurbanne (France); Plain, Jérôme [Universit de technologie de Troyes LNIO-ICD, CNRS et OMNT 12 rue Marie Curie - CS 42060 - 10004 Troyes cedex (France); Reiss, Peter [CEA Grenoble, INAC-SPrAM, UMR 5819 CEA-CNRS-UJF et OMNT, Grenoble cedex 9 (France); Silly, Fabien [CEA, IRAMIS, SPEC, TITANS, CNRS 2464 et OMNT, F-91191 Gif sur Yvette (France); Warot-Fonrose, Bénédicte [CEMES-CNRS, Université de Toulouse et OMNT, 29 rue Jeanne Marvig F 31055 Toulouse (France)

    2014-10-20

    It has been for a long time recognized that nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic structures. At first, size effects occurring in single elements have been studied. More recently, progress in chemical and physical synthesis routes permitted the preparation of more complex structures. Such structures take advantages of new adjustable parameters including stoichiometry, chemical ordering, shape and segregation opening new fields with tailored materials for biology, mechanics, optics magnetism, chemistry catalysis, solar cells and microelectronics. Among them, core/shell structures are a particular class of nanoparticles made with an inorganic core and one or several inorganic shell layer(s). In earlier work, the shell was merely used as a protective coating for the core. More recently, it has been shown that it is possible to tune the physical properties in a larger range than that of each material taken separately. The goal of the present review is to discuss the basic properties of the different types of core/shell nanoparticles including a large variety of heterostructures. We restrict ourselves on all inorganic (on inorganic/inorganic) core/shell structures. In the light of recent developments, the applications of inorganic core/shell particles are found in many fields including biology, chemistry, physics and engineering. In addition to a representative overview of the properties, general concepts based on solid state physics are considered for material selection and for identifying criteria linking the core/shell structure and its resulting properties. Chemical and physical routes for the synthesis and specific methods for the study of core/shell nanoparticle are briefly discussed.

  4. Magnetic core-shell silica particles

    NARCIS (Netherlands)

    Claesson, E.M.

    2007-01-01

    This thesis deals with magnetic silica core-shell colloids and related functionalized silica structures. Synthesis routes have been developed and optimized. The physical properties of these colloids have been investigated, such as the magnetic dipole moment, dipolar structure formation and

  5. Nanostructured core-shell electrode materials for electrochemical capacitors

    Science.gov (United States)

    Jiang, Long-bo; Yuan, Xing-zhong; Liang, Jie; Zhang, Jin; Wang, Hou; Zeng, Guang-ming

    2016-11-01

    Core-shell nanostructure represents a unique system for applications in electrochemical energy storage devices. Owing to the unique characteristics featuring high power delivery and long-term cycling stability, electrochemical capacitors (ECs) have emerged as one of the most attractive electrochemical storage systems since they can complement or even replace batteries in the energy storage field, especially when high power delivery or uptake is needed. This review aims to summarize recent progress on core-shell nanostructures for advanced supercapacitor applications in view of their hierarchical architecture which not only create the desired hierarchical porous channels, but also possess higher electrical conductivity and better structural mechanical stability. The core-shell nanostructures include carbon/carbon, carbon/metal oxide, carbon/conducting polymer, metal oxide/metal oxide, metal oxide/conducting polymer, conducting polymer/conducting polymer, and even more complex ternary core-shell nanoparticles. The preparation strategies, electrochemical performances, and structural stabilities of core-shell materials for ECs are summarized. The relationship between core-shell nanostructure and electrochemical performance is discussed in detail. In addition, the challenges and new trends in core-shell nanomaterials development have also been proposed.

  6. Graded core/shell semiconductor nanorods and nanorod barcodes

    Science.gov (United States)

    Alivisatos, A. Paul; Scher, Erik C.; Manna, Liberato

    2010-12-14

    Graded core/shell semiconductor nanorods and shaped nanorods are disclosed comprising Group II-VI, Group III-V and Group IV semiconductors and methods of making the same. Also disclosed are nanorod barcodes using core/shell nanorods where the core is a semiconductor or metal material, and with or without a shell. Methods of labeling analytes using the nanorod barcodes are also disclosed.

  7. Ab initio no core shell model

    Energy Technology Data Exchange (ETDEWEB)

    Barrett, Bruce R. [Univ. of Arizona, Tucson, AZ (United States); Navrátil, Petr [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Vary, James P. [Ames Lab. and Iowa State Univ., Ames, IA (United States)

    2012-11-17

    resulting NN and NNN interactions, characterized by the order of the expansion retained (e.g. 'next-to-next-to leading order' is NNLO), provide a high-quality fit to the NN data and the A = 3 ground-state (g.s.) properties. The derivations of NN, NNN, etc. interactions within meson-exchange and {chi}EFT are well-established but are not subjects of this review. Our focus is solution of the non-relativistic quantum many-body Hamiltonian that includes these interactions using our no core shell model (NCSM) formalism. In the next section we will briefly outline the NCSM formalism and then present applications, results and extensions in later sections.

  8. Electron energy spectrum in core-shell elliptic quantum wire

    Directory of Open Access Journals (Sweden)

    V.Holovatsky

    2007-01-01

    Full Text Available The electron energy spectrum in core-shell elliptic quantum wire and elliptic semiconductor nanotubes are investigated within the effective mass approximation. The solution of Schrodinger equation based on the Mathieu functions is obtained in elliptic coordinates. The dependencies of the electron size quantization spectrum on the size and shape of the core-shell nanowire and nanotube are calculated. It is shown that the ellipticity of a quantum wire leads to break of degeneration of quasiparticle energy spectrum. The dependences of the energy of odd and even electron states on the ratio between semiaxes are of a nonmonotonous character. The anticrosing effects are observed at the dependencies of electron energy spectrum on the transversal size of the core-shell nanowire.

  9. Electrochemical synthesis of CORE-shell magnetic nanowires

    KAUST Repository

    Ovejero, Jesús G.

    2015-04-16

    (Fe, Ni, CoFe) @ Au core-shell magnetic nanowires have been synthesized by optimized two-step potentiostatic electrodeposition inside self-assembled nanopores of anodic aluminium templates. The optimal electrochemical parameters (e.g., potential) have been firstly determined for the growth of continuous Au nanotubes at the inner wall of pores. Then, a magnetic core was synthesized inside the Au shells under suitable electrochemical conditions for a wide spectrum of single elements and alloy compositions (e.g., Fe, Ni and CoFe alloys). Novel opportunities offered by such nanowires are discussed particularly the magnetic behavior of (Fe, Ni, CoFe) @ Au core-shell nanowires was tested and compared with that of bare TM nanowires. These core-shell nanowires can be released from the template so, opening novel opportunities for biofunctionalization of individual nanowires.

  10. Tailored Core Shell Cathode Powders for Solid Oxide Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Swartz, Scott [NexTech Materials, Ltd.,Lewis Center, OH (United States)

    2015-03-23

    In this Phase I SBIR project, a “core-shell” composite cathode approach was evaluated for improving SOFC performance and reducing degradation of lanthanum strontium cobalt ferrite (LSCF) cathode materials, following previous successful demonstrations of infiltration approaches for achieving the same goals. The intent was to establish core-shell cathode powders that enabled high performance to be obtained with “drop-in” process capability for SOFC manufacturing (i.e., rather than adding an infiltration step to the SOFC manufacturing process). Milling, precipitation and hetero-coagulation methods were evaluated for making core-shell composite cathode powders comprised of coarse LSCF “core” particles and nanoscale “shell” particles of lanthanum strontium manganite (LSM) or praseodymium strontium manganite (PSM). Precipitation and hetero-coagulation methods were successful for obtaining the targeted core-shell morphology, although perfect coverage of the LSCF core particles by the LSM and PSM particles was not obtained. Electrochemical characterization of core-shell cathode powders and conventional (baseline) cathode powders was performed via electrochemical impedance spectroscopy (EIS) half-cell measurements and single-cell SOFC testing. Reliable EIS testing methods were established, which enabled comparative area-specific resistance measurements to be obtained. A single-cell SOFC testing approach also was established that enabled cathode resistance to be separated from overall cell resistance, and for cathode degradation to be separated from overall cell degradation. The results of these EIS and SOFC tests conclusively determined that the core-shell cathode powders resulted in significant lowering of performance, compared to the baseline cathodes. Based on the results of this project, it was concluded that the core-shell cathode approach did not warrant further investigation.

  11. Current directions in core-shell nanoparticle design

    Science.gov (United States)

    Schärtl, Wolfgang

    2010-06-01

    Ten years ago I wrote a review about the important field of core-shell nanoparticles, focussing mainly on our own work about tracer systems, and briefly addressing polymer-coated nanoparticles as fillers for homogeneous polymer-colloid composites. Since then, the potential use of core-shell nanoparticles as multifunctional sensors or potential smart drug-delivery vehicles in biology and medicine has gained more and more importance, affording special types of multi-functionalized and bio-compatible nanoparticles. In this new review article, I try to address the most important developments during the last ten years. This overview is mainly based on frequently cited and more specialized recent review articles from leaders in their respective field. We will consider a variety of nanoscopic core-shell architectures from highly fluorescent nanoparticles (NPs), protected magnetic NPs, multifunctional NPs, thermoresponsive NPs and biocompatible systems to, finally, smart drug-delivery systems.Ten years ago I wrote a review about the important field of core-shell nanoparticles, focussing mainly on our own work about tracer systems, and briefly addressing polymer-coated nanoparticles as fillers for homogeneous polymer-colloid composites. Since then, the potential use of core-shell nanoparticles as multifunctional sensors or potential smart drug-delivery vehicles in biology and medicine has gained more and more importance, affording special types of multi-functionalized and bio-compatible nanoparticles. In this new review article, I try to address the most important developments during the last ten years. This overview is mainly based on frequently cited and more specialized recent review articles from leaders in their respective field. We will consider a variety of nanoscopic core-shell architectures from highly fluorescent nanoparticles (NPs), protected magnetic NPs, multifunctional NPs, thermoresponsive NPs and biocompatible systems to, finally, smart drug-delivery systems

  12. Fabrication of Magnetite/Silica/Titania Core-Shell Nanoparticles

    Directory of Open Access Journals (Sweden)

    Suh Cem Pang

    2012-01-01

    Full Text Available Fe3O4/SiO2/TiO2 core-shell nanoparticles were synthesized via a sol-gel method with the aid of sonication. Fe3O4 nanoparticles were being encapsulated within discrete silica nanospheres, and a layer of TiO2 shell was then coated directly onto each silica nanosphere. As-synthesized Fe3O4/SiO2/TiO2 core-shell nanoparticles showed enhanced photocatalytic properties as evidenced by the enhanced photodegradation of methylene blue under UV light irradiation.

  13. Core-shell Au@Pd nanoparticles with enhanced catalytic activity for oxygen reduction reaction via core-shell Au@Ag/Pd constructions

    OpenAIRE

    Chen, Dong; Li, Chengyin; Liu, Hui; Ye, Feng; Yang, Jun

    2015-01-01

    Core-shell nanoparticles often exhibit improved catalytic properties due to the lattice strain created in these core-shell particles. Herein, we demonstrate the synthesis of core-shell Au@Pd nanoparticles from their core-shell Au@Ag/Pd parents. This strategy begins with the preparation of core-shell Au@Ag nanoparticles in an organic solvent. Then, the pure Ag shells are converted into the shells made of Ag/Pd alloy by galvanic replacement reaction between the Ag shells and Pd2+ precursors. Su...

  14. Optical absorption of carbon-gold core-shell nanoparticles

    Science.gov (United States)

    Wang, Zhaolong; Quan, Xiaojun; Zhang, Zhuomin; Cheng, Ping

    2018-01-01

    In order to enhance the solar thermal energy conversion efficiency, we propose to use carbon-gold core-shell nanoparticles dispersed in liquid water. This work demonstrates theoretically that an absorbing carbon (C) core enclosed in a plasmonic gold (Au) nanoshell can enhance the absorption peak while broadening the absorption band; giving rise to a much higher solar absorption than most previously studied core-shell combinations. The exact Mie solution is used to evaluate the absorption efficiency factor of spherical nanoparticles in the wavelength region from 300 nm to 1100 nm as well as the electric field and power dissipation profiles inside the nanoparticles at specified wavelengths (mostly at the localized surface plasmon resonance wavelength). The field enhancement by the localized plasmons at the gold surfaces boosts the absorption of the carbon particle, resulting in a redshift of the absorption peak with increased peak height and bandwidth. In addition to spherical nanoparticles, we use the finite-difference time-domain method to calculate the absorption of cubic core-shell nanoparticles. Even stronger enhancement can be achieved with cubic C-Au core-shell structures due to the localized plasmonic resonances at the sharp edges of the Au shell. The solar absorption efficiency factor can exceed 1.5 in the spherical case and reach 2.3 in the cubic case with a shell thickness of 10 nm. Such broadband absorption enhancement is in great demand for solar thermal applications including steam generation.

  15. First Principles Study of Core-Shell Semiconductor Nanocrystals

    Science.gov (United States)

    Vasiliev, Igor

    2011-03-01

    Core-shell nanocrystals composed of two different semiconductors have recently attracted considerable attention. These structures provide enhanced functionality and possess more degrees of freedom than single-component semiconductor nanocrystals and quantum dots. I present the results of ab initio density functional calculations for the structures, electronic densities of states, and optical absorption gaps of core-shell nanocrystals composed of group II-VI semiconductors, such as CdSe, CdTe, ZnSe, and ZnTe. The outer surfaces of the nanocrystals are passivated using partially charged hydrogen atoms. The calculations are performed for ``traditional'' core-shell nanocrystals, in which a core a narrow gap semiconductor is covered with a shell of a wide gap material, and ``inverted'' core-shell nanocrystals, in which a wide-gap core is enclosed in a narrow-gap shell. Supported by the Donors of the American Chemical Society Petroleum Research Fund under Grant No. PRF-48556-AC10 and by the U. S. Department of Energy under Grant No. DE-FG36-08GO88008.

  16. Core-shell iron-iron oxide nanoparticles

    DEFF Research Database (Denmark)

    Kuhn, Luise Theil; Bojesen, A.; Timmermann, L.

    2004-01-01

    We present studies of the magnetic properties of core-shell iron-iron oxide nanoparticles. By combining Mossbauer and X-ray absorption spectroscopy we have been able to measure the change from a Fe3O4-like to a gamma-Fe2O3-like composition from the interface to the surface. Furthermore, we have o...

  17. Synthesis of Cationic Core-Shell Latex Particles

    NARCIS (Netherlands)

    Dziomkina, N.; Hempenius, Mark A.; Vancso, Gyula J.

    2006-01-01

    Surfactant-free seeded (core-shell) polymerization of cationic polymer colloids is presented. Polystyrene core particles with sizes between 200 nm and 500 nm were synthesized. The number average diameter of the colloidal core particles increased with increasing monomer concentration. Cationic shells

  18. Electroless deposition of Gold-Platinum Core@ Shell Nanoparticles ...

    Indian Academy of Sciences (India)

    platinum nanoparticlesz (Au@PtNPs) with core@shell structure fabricated on glassy carbon electrode (GCE) by electroless depositionmethod. Initially, gold nanoparticles (AuNPs) were deposited on GCE by reducing HAuCl4 in the presence of ...

  19. Electroless deposition of Gold-Platinum Core@Shell Nanoparticles ...

    Indian Academy of Sciences (India)

    @platinum nanoparticles. (Au@PtNPs) with core@shell structure fabricated on glassy carbon electrode (GCE) by electroless deposition method. Initially, gold nanoparticles (AuNPs) were deposited on GCE by reducing HAuCl4 in the presence ...

  20. Tuning upconversion through energy migration in core-shell nanoparticles

    KAUST Repository

    Wang, Feng

    2011-10-23

    Photon upconversion is promising for applications such as biological imaging, data storage or solar cells. Here, we have investigated upconversion processes in a broad range of gadolinium-based nanoparticles of varying composition. We show that by rational design of a core-shell structure with a set of lanthanide ions incorporated into separated layers at precisely defined concentrations, efficient upconversion emission can be realized through gadolinium sublattice-mediated energy migration for a wide range of lanthanide activators without long-lived intermediary energy states. Furthermore, the use of the core-shell structure allows the elimination of deleterious cross-relaxation. This effect enables fine-tuning of upconversion emission through trapping of the migrating energy by the activators. Indeed, the findings described here suggest a general approach to constructing a new class of luminescent materials with tunable upconversion emissions by controlled manipulation of energy transfer within a nanoscopic region. © 2011 Macmillan Publishers Limited. All rights reserved.

  1. Process to make core-shell structured nanoparticles

    Science.gov (United States)

    Luhrs, Claudia; Phillips, Jonathan; Richard, Monique N

    2014-01-07

    Disclosed is a process for making a composite material that contains core-shell structured nanoparticles. The process includes providing a precursor in the form of a powder a liquid and/or a vapor of a liquid that contains a core material and a shell material, and suspending the precursor in an aerosol gas to produce an aerosol containing the precursor. In addition, the process includes providing a plasma that has a hot zone and passing the aerosol through the hot zone of the plasma. As the aerosol passes through the hot zone of the plasma, at least part of the core material and at least part of the shell material in the aerosol is vaporized. Vapor that contains the core material and the shell material that has been vaporized is removed from the hot zone of the plasma and allowed to condense into core-shell structured nanoparticles.

  2. Core-shell magnetic nanowires fabrication and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Kalska-Szostko, B., E-mail: kalska@uwb.edu.pl [Institute of Chemistry, University of Bialystok, Ciolkowskiego 1K, 15-245 Bialystok (Poland); Faculty of Physics, University of Bialystok, Ciolkowskiego 1L, 15-245 Bialystok, Poland (Poland); Klekotka, U.; Satuła, D. [Institute of Chemistry, University of Bialystok, Ciolkowskiego 1K, 15-245 Bialystok (Poland); Faculty of Physics, University of Bialystok, Ciolkowskiego 1L, 15-245 Bialystok, Poland (Poland)

    2017-02-28

    Highlights: • New approach for nanowires modification are presented. • Physical and chemical characterization of the nanowires are shown. • Properties modulations as an effect of the surface layer composition are discussed. - Abstract: In this paper, a new way of the preparation of core-shell magnetic nanowires has been proposed. For the modification Fe nanowires were prepared by electrodeposition in anodic aluminium oxide matrixes, in first step. In second, by wetting chemical deposition, shell layers of Ag, Au or Cu were obtained. Resultant core-shell nanowires structure was characterized by X-ray diffraction, infrared spectroscopy, transmission electron microscopy, and energy dispersive x-ray. Whereas magnetic properties by Mössbauer spectroscopy.

  3. Smart Core-Shell Nanowire Architectures for Multifunctional Nanoscale Devices

    Science.gov (United States)

    2014-02-16

    in Orlando, FL USA. “Electronic landscapes near semiconductor nanowire heterostructures ”, Department of Chemistry, Washington University of...Core-Shell Nanowire Architectures for Multifunctional Nanoscale Devices W911NF-08-1-0067 611103 Jonathan E Spanier Drexel University Office of...Hadas Shtrikman, Patrick Kung, Tsachi Livneh, Jonathan E. Spanier. Direct Measurement of Band Edge Discontinuity in Individual Core–Shell Nanowires by

  4. Core-shell Au@Pd nanoparticles with enhanced catalytic activity for oxygen reduction reaction via core-shell Au@Ag/Pd constructions

    Science.gov (United States)

    Chen, Dong; Li, Chengyin; Liu, Hui; Ye, Feng; Yang, Jun

    2015-01-01

    Core-shell nanoparticles often exhibit improved catalytic properties due to the lattice strain created in these core-shell particles. Herein, we demonstrate the synthesis of core-shell Au@Pd nanoparticles from their core-shell Au@Ag/Pd parents. This strategy begins with the preparation of core-shell Au@Ag nanoparticles in an organic solvent. Then, the pure Ag shells are converted into the shells made of Ag/Pd alloy by galvanic replacement reaction between the Ag shells and Pd2+ precursors. Subsequently, the Ag component is removed from the alloy shell using saturated NaCl solution to form core-shell Au@Pd nanoparticles with an Au core and a Pd shell. In comparison with the core-shell Au@Pd nanoparticles upon directly depositing Pd shell on the Au seeds and commercial Pd/C catalysts, the core-shell Au@Pd nanoparticles via their core-shell Au@Ag/Pd templates display superior activity and durability in catalyzing oxygen reduction reaction, mainly due to the larger lattice tensile effect in Pd shell induced by the Au core and Ag removal. PMID:26144550

  5. Core-shell Au@Pd nanoparticles with enhanced catalytic activity for oxygen reduction reaction via core-shell Au@Ag/Pd constructions

    Science.gov (United States)

    Chen, Dong; Li, Chengyin; Liu, Hui; Ye, Feng; Yang, Jun

    2015-07-01

    Core-shell nanoparticles often exhibit improved catalytic properties due to the lattice strain created in these core-shell particles. Herein, we demonstrate the synthesis of core-shell Au@Pd nanoparticles from their core-shell Au@Ag/Pd parents. This strategy begins with the preparation of core-shell Au@Ag nanoparticles in an organic solvent. Then, the pure Ag shells are converted into the shells made of Ag/Pd alloy by galvanic replacement reaction between the Ag shells and Pd2+ precursors. Subsequently, the Ag component is removed from the alloy shell using saturated NaCl solution to form core-shell Au@Pd nanoparticles with an Au core and a Pd shell. In comparison with the core-shell Au@Pd nanoparticles upon directly depositing Pd shell on the Au seeds and commercial Pd/C catalysts, the core-shell Au@Pd nanoparticles via their core-shell Au@Ag/Pd templates display superior activity and durability in catalyzing oxygen reduction reaction, mainly due to the larger lattice tensile effect in Pd shell induced by the Au core and Ag removal.

  6. Porous Core-Shell Nanostructures for Catalytic Applications

    Science.gov (United States)

    Ewers, Trevor David

    Porous core-shell nanostructures have recently received much attention for their enhanced thermal stability. They show great potential in the field of catalysis, as reactant gases can diffuse in and out of the porous shell while the core particle is protected from sintering, a process in which particles coalesce to form larger particles. Sintering is a large problem in industry and is the primary cause of irreversible deactivation. Despite the obvious advantages of high thermal stability, porous core-shell nanoparticles can be developed to have additional interactive properties from the combination of the core and shell together, rather than just the core particle alone. This dissertation focuses on developing new porous core-shell systems in which both the core and shell take part in catalysis. Two types of systems are explored; (1) yolk-shell nanostructures with reducible oxide shells formed using the Kirkendall effect and (2) ceramic-based porous oxide shells formed using sol-gel chemistry. Of the Kirkendall-based systems, Au FexOy and Cu CoO were synthesized and studied for catalytic applications. Additionally, ZnO was explored as a potential shelling material. Sol-gel work focused on optimizing synthetic methods to allow for coating of small gold particles, which remains a challenge today. Mixed metal oxides were explored as a shelling material to make dual catalysts in which the product of a reaction on the core particle becomes a reactant within the shell.

  7. Core/Shell Structured Magnetic Nanoparticles for Biological Applications

    International Nuclear Information System (INIS)

    Park, Jeong Chan; Jung, Myung Hwan

    2013-01-01

    Magnetic nanoparticles have been widely used for biomedical applications, such as magnetic resonance imaging (MRI), hyperthermia, drug delivery and cell signaling. The surface modification of the nanomaterials is required for biomedical use to give physiogical stability, surface reactivity and targeting properties. Among many approaches for the surface modification with materials, such as polymers, organic ligands and metals, one of the most attractive ways is using metals. The fabrication of metal-based, monolayer-coated magnetic nanoparticles has been intensively studied. However, the synthesis of metal-capped magnetic nanoparticles with monodispersities and controllable sizes is still challenged. Recently, gold-capped magnetic nanoparticles have been reported to increase stability and to provide biocompatibility. Magnetic nanoparticle with gold coating is an attractive system, which can be stabilized in biological conditions and readily functionalized in biological conditions and readily functionalized through well-established surface modification (Au-S) chemistry. The Au coating offers plasmonic properties to magnetic nanoparticles. This makes the magnetic/Au core/shell combinations interesting for magnetic and optical applications. Herein, the synthesis and characterization of gold capped-magnetic core structured nanomaterials with different gold sources, such as gold acetate and chloroauric acid have been reported. The core/shell nanoparticles were transferred from organic to aqueous solutions for biomedical applications. Magnetic core/shell structured nanoparticles have been prepared and transferred from organic phase to aqueous solutions. The resulting Au-coated magnetic core nanoparticles might be an attractive system for biomedical applications, which are needed both magnetic resonance imaging and optical imaging

  8. Core-shell hydrogel microcapsules for improved islets encapsulation.

    Science.gov (United States)

    Ma, Minglin; Chiu, Alan; Sahay, Gaurav; Doloff, Joshua C; Dholakia, Nimit; Thakrar, Raj; Cohen, Joshua; Vegas, Arturo; Chen, Delai; Bratlie, Kaitlin M; Dang, Tram; York, Roger L; Hollister-Lock, Jennifer; Weir, Gordon C; Anderson, Daniel G

    2013-05-01

    Islets microencapsulation holds great promise to treat type 1 diabetes. Currently used alginate microcapsules often have islets protruding outside capsules, leading to inadequate immuno-protection. A novel design of microcapsules with core-shell structures using a two-fluid co-axial electro-jetting is reported. Improved encapsulation and diabetes correction is achieved in a single step by simply confining the islets in the core region of the capsules. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Synthesis and characterization of mesoporous silica core-shell particles

    Directory of Open Access Journals (Sweden)

    Milan Nikolić

    2010-06-01

    Full Text Available Core-shell particles were formed by deposition of primary silica particles synthesized from sodium silicate solution on functionalized silica core particles (having size of ~0.5 µm prepared by hydrolysis and condensation of tetraethylortosilicate. The obtained mesoporous shell has thickness of about 60 nm and consists of primary silica particles with average size of ~21 nm. Scanning electron microscopy and zeta potential measurements showed that continuous silica shell exists around functionalized core particles which was additionally proved by FTIR and TEM results.

  10. Core-shell colloidal particles with dynamically tunable scattering properties.

    Science.gov (United States)

    Meng, Guangnan; Manoharan, Vinothan N; Perro, Adeline

    2017-09-27

    We design polystyrene-poly(N'-isopropylacrylamide-co-acrylic acid) core-shell particles that exhibit dynamically tunable scattering. We show that under normal solvent conditions the shell is nearly index-matched to pure water, and the particle scattering is dominated by Rayleigh scattering from the core. As the temperature or salt concentration increases, both the scattering cross-section and the forward scattering increase, characteristic of Mie scatterers. The magnitude of the change in the scattering cross-section and scattering anisotropy can be controlled through the solvent conditions and the size of the core. Such particles may find use as optical switches or optical filters with tunable opacity.

  11. Biocompatible core-shell magnetic nanoparticles for cancer treatment

    Science.gov (United States)

    Sharma, Amit; Qiang, You; Meyer, Daniel; Souza, Ryan; Mcconnaughoy, Alan; Muldoon, Leslie; Baer, Donald

    2008-04-01

    Nontoxic magnetic nanoparticles (MNPs) have expanded treatment delivery options in the medical world. With a size range from 2to200nm, MNPs can be compiled with most of the small cells and tissues in the living body. Monodispersive iron-iron oxide core-shell nanoparticles were prepared by our novel cluster deposition system. This unique method of preparing core-shell MNPs gives the nanoparticles a very high magnetic moment. We tested the nontoxicity and uptake of MNPs coated with/without dextrin by incubating them with rat LX-1 small cell lung cancer cells. Since core iron enhances the heating effect [L. Baker, Q. Zeing, W. Li, and S. Sullivan, J. Appl. Phys. 99, 08H106 (2006)], the rate of oxidation of iron nanoparticles was also tested in de-ionized water at a certain time interval. Both coated and noncoated MNPs were successfully uptaken by the cells, indicating that the nanoparticles were not toxic. The stability of MNPs was verified by x-ray diffraction scan after 0, 24, 48, 96, and 204h. Due to the high magnetic moment offered by MNPs produced in our laboratory, we predict that even at low applied external alternating field, the desired temperature could be reached in cancer cells in comparison to the commercially available nanoparticles. Moreover our MNPs do not require additional transfection agent, providing a cost effective means of treatment with significantly lower dosage in the body in comparison to commercially available nanoparticles.

  12. Biocompatible core-shell magnetic nanoparticles for cancer treatment

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Amit M.; Qiang, You; Meyer, Daniel R.; Souza, Ryan; Mcconnaughoy, Alan; Muldoon, Leslie; Baer, Donald R.

    2008-04-01

    Non-toxic magnetic nanoparticles (MNPs) have expanded the treatment delivery options in the medical world. With a size range from 2 to 200 nm MNPs can be compiled with most of the small cells and tissues in living body. Monodispersive iron-iron oxide core shell nanoparticles were prepared in our novel cluster deposition system. This unique method of preparing the core shell MNPs gives nanoparticles very high magnetic moment. We tested the nontoxicity and uptake of MNPs coated with/without dextrin by incubating them with rat LX-1 small cell lung cancer cells (SCLC). Since core iron enhances the heating effect [7] the rate of oxidation of iron nanoparticles was tested in deionized water at certain time interval. Both coated and noncoated MNPs were successfully uptaken by the cells, indicating that the nanoparticles were not toxic. The stability of MNPs was verified by X-ray diffraction (XRD) scan after 0, 24, 48, 96, 204 hours. Due to the high magnetic moment offered by MNPs produced in our lab, we predict that even in low applied external alternating field desired temperature can be reached in cancer cells in comparison to the commercially available nanoparticles. Moreover, our MNPs do not require additional anti-coagulating agents and provide a cost effective means of treatment with significantly lower dosage in the body in comparison to commercially available nanoparticles.

  13. Organized thiol functional groups in mesoporous core shell colloids

    Energy Technology Data Exchange (ETDEWEB)

    Marchena, Martin H. [Gerencia Quimica, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), Avda. Gral. Paz 1499, B1650KNA Buenos Aires (Argentina); Granada, Mara [Centro Atomico Bariloche-CNEA, 8400 San Carlos de Bariloche (Argentina); Instituto Balseiro-Centro Atomico Bariloche-CNEA, San Carlos de Bariloche 8400 (Argentina); Bordoni, Andrea V. [Gerencia Quimica, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), Avda. Gral. Paz 1499, B1650KNA Buenos Aires (Argentina); Joselevich, Maria [Asociacion Civil Expedicion Ciencia, Cabrera 4948, C1414BGP Buenos Aires (Argentina); Troiani, Horacio [Centro Atomico Bariloche-CNEA, 8400 San Carlos de Bariloche (Argentina); Instituto Balseiro-Centro Atomico Bariloche-CNEA, San Carlos de Bariloche 8400 (Argentina); Williams, Federico J. [DQIAQyF-INQUIMAE FCEN, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon II, C1428EHA Buenos Aires (Argentina); Wolosiuk, Alejandro, E-mail: wolosiuk@cnea.gov.ar [Gerencia Quimica, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), Avda. Gral. Paz 1499, B1650KNA Buenos Aires (Argentina)

    2012-03-15

    The co-condensation in situ of tetraethoxysilane (TEOS) and mercaptopropyltrimethoxysilane (MPTMS) using cetyltrimethylammonium bromide (CTAB) as a template results in the synthesis of multilayered mesoporous structured SiO{sub 2} colloids with 'onion-like' chemical environments. Thiol groups were anchored to an inner selected SiO{sub 2} porous layer in a bilayered core shell particle producing different chemical regions inside the colloidal layered structure. X-Ray Photoelectron Spectroscopy (XPS) shows a preferential anchoring of the -SH groups in the double layer shell system, while porosimetry and simple chemical modifications confirm that pores are accessible. We can envision the synthesis of interesting colloidal objects with defined chemical environments with highly controlled properties. - Graphical abstract: Mesoporous core shell SiO{sub 2} colloids with organized thiol groups. Highlights: Black-Right-Pointing-Pointer Double shell mesoporous silica colloids templated with CTAB. Black-Right-Pointing-Pointer Sequential deposition of mesoporous SiO{sub 2} layers with different chemistries. Black-Right-Pointing-Pointer XPS shows the selective functionalization of mesoporous layers with thiol groups.

  14. Light guiding and switching using eccentric core-shell geometries.

    Science.gov (United States)

    Barreda, Ángela I; Gutiérrez, Yael; Sanz, Juan M; González, Francisco; Moreno, Fernando

    2017-09-11

    High Refractive Index (HRI) dielectric nanoparticles have been proposed as an alternative to metallic ones due to their low absorption and magnetodielectric response in the VIS and NIR ranges. For the latter, important scattering directionality effects can be obtained. Also, systems constituted by dimers of HRI dielectric nanoparticles have shown to produce switching effects by playing with the polarization, frequency or intensity of the incident radiation. Here, we show that scattering directionality effects can be achieved with a single eccentric metallo-HRI dielectric core-shell nanoparticle. As an example, the effect of the metallic core displacements for a single Ag-Si core-shell nanoparticle has been analyzed. We report rotation of the main scattering lobe either clockwise or counterclockwise depending on the polarization of the incident radiation leading to new scattering configurations for switching purposes. Also, the efficiency of the scattering directionality can be enhanced. Finally, chains of these scattering units have shown good radiation guiding effects, and for 1D periodic arrays, redirection of diffracted intensity can be observed as a consequence of blazing effects. The proposed scattering units constitute new blocks for building systems for optical communications, solar energy harvesting devices and light guiding at the nanoscale level.

  15. Size-Dependent Specific Surface Area of Nanoporous Film Assembled by Core-Shell Iron Nanoclusters

    Directory of Open Access Journals (Sweden)

    Jiji Antony

    2006-01-01

    Full Text Available Nanoporous films of core-shell iron nanoclusters have improved possibilities for remediation, chemical reactivity rate, and environmentally favorable reaction pathways. Conventional methods often have difficulties to yield stable monodispersed core-shell nanoparticles. We produced core-shell nanoclusters by a cluster source that utilizes combination of Fe target sputtering along with gas aggregations in an inert atmosphere at 7∘C. Sizes of core-shell iron-iron oxide nanoclusters are observed with transmission electron microscopy (TEM. The specific surface areas of the porous films obtained from Brunauer-Emmett-Teller (BET process are size-dependent and compared with the calculated data.

  16. Symplectic ab initio no-core shell model

    Energy Technology Data Exchange (ETDEWEB)

    Draayer, J. P.; Dytrych, T.; Sviratcheva, K. D.; Bahri, C. [Department of Physics and Astronomy, Lousiana State University, Baton Rouge, 70803 Lousiana (United States); Vary, J. P. [Department of Physics and Astronomy, Iowa State University, Ames, 50011 Iowa (United States)

    2008-12-15

    The present study confirms the significance of the symplectic Sp(3,R) symmetry in nuclear dynamics as unveiled, for the first time, by examinations of realistic nucleon-nucleon interactions as well as of eigenstates calculated in the framework of the ab initio No-Core Shell Model (NCSM). The results reveal that the NCSM wave functions for light nuclei highly overlap (at the {approx} 90% level) with only a few of the most deformed Sp(3,R)-symmetric basis states. This points to the possibility of achieving convergence of higher-lying collective modes and reaching heavier nuclei by expanding the NCSM basis space beyond its current limits through Sp(3,R) basis states. Furthermore the symplectic symmetry is found to be favored by the JISP 16 and CD-Bonn realistic nucleon-nucleon interactions, which points to a more fundamental origin of the symplectic symmetry. (Author)

  17. Magnetization processes in core/shell exchange-spring structures.

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, J. S.

    2015-03-27

    The magnetization reversal processes in cylindrical and spherical soft core/hard shell exchange-spring structures are investigated via the analytical nucleation theory, and are verified with numerical micromagnetic simulations. At small core sizes, the nucleation of magnetic reversal proceeds via the modified bulging mode, where the transverse component of the magnetization is only semi-coherent in direction and the nucleation field contains a contribution from self-demagnetization. For large core sizes, the modified curling mode, where the magnetization configuration is vortex-like, is favored at nucleation. The preference for the modified curling mode is beneficial in that the fluxclosure allows cylindrical and spherical core/shell exchange-spring elements to be densely packed into bulk permanent magnets without affecting the nucleation field, thereby offering the potential for high energy product.

  18. Optical Bistability in Graded Core-Shell Granular Composites

    International Nuclear Information System (INIS)

    Wu Ya-Min; Chen Guo-Qing; Xue Si-Zhong; Zhu Zhuo-Wei; Ma Chao-Qun

    2012-01-01

    The intrinsic optical bistability (OB) of graded core-shell granular composites is investigated. The coated particles are made of cores with gradient dielectric function in c (r) = A(r/a) k and nonlinear shells. In view of the exponential distribution of the core dielectric constant, the potential functions of each region are obtained by solving the Maxwell equations, and the mathematical expressions of electric field in the shells and cores are determined. Numerical study reveals that the optical bistable threshold and the threshold width of the composite medium are dependent on the shell thickness, core dielectric exponent, and power function coefficient. The optical bistable width increases with the decreasing shell thickness and the power exponent and with the increasing power function coefficient

  19. Stability of core-shell nanowires in selected model solutions

    Science.gov (United States)

    Kalska-Szostko, B.; Wykowska, U.; Basa, A.; Zambrzycka, E.

    2015-03-01

    This paper presents the studies of stability of magnetic core-shell nanowires prepared by electrochemical deposition from an acidic solution containing iron in the core and modified surface layer. The obtained nanowires were tested according to their durability in distilled water, 0.01 M citric acid, 0.9% NaCl, and commercial white wine (12% alcohol). The proposed solutions were chosen in such a way as to mimic food related environment due to a possible application of nanowires as additives to, for example, packages. After 1, 2 and 3 weeks wetting in the solutions, nanoparticles were tested by Infrared Spectroscopy, Atomic Absorption Spectroscopy, Transmission Electron Microscopy and X-ray diffraction methods.

  20. Vertical Ge/Si Core/Shell Nanowire Junctionless Transistor.

    Science.gov (United States)

    Chen, Lin; Cai, Fuxi; Otuonye, Ugo; Lu, Wei D

    2016-01-13

    Vertical junctionless transistors with a gate-all-around (GAA) structure based on Ge/Si core/shell nanowires epitaxially grown and integrated on a ⟨111⟩ Si substrate were fabricated and analyzed. Because of efficient gate coupling in the nanowire-GAA transistor structure and the high density one-dimensional hole gas formed in the Ge nanowire core, excellent P-type transistor behaviors with Ion of 750 μA/μm were obtained at a moderate gate length of 544 nm with minimal short-channel effects. The experimental data can be quantitatively modeled by a GAA junctionless transistor model with few fitting parameters, suggesting the nanowire transistors can be fabricated reliably without introducing additional factors that can degrade device performance. Devices with different gate lengths were readily obtained by tuning the thickness of an etching mask film. Analysis of the histogram of different devices yielded a single dominate peak in device parameter distribution, indicating excellent uniformity and high confidence of single nanowire operation. Using two vertical nanowire junctionless transistors, a PMOS-logic inverter with near rail-to-rail output voltage was demonstrated, and device matching in the logic can be conveniently obtained by controlling the number of nanowires employed in different devices rather than modifying device geometry. These studies show that junctionless transistors based on vertical Ge/Si core/shell nanowires can be fabricated in a controlled fashion with excellent performance and may be used in future hybrid, high-performance circuits where bottom-up grown nanowire devices with different functionalities can be directly integrated with an existing Si platform.

  1. Synthesis of eccentric titania-silica core-shell and composite particles

    NARCIS (Netherlands)

    Demirors, A.F.|info:eu-repo/dai/nl/30483176X; van Blaaderen, A.|info:eu-repo/dai/nl/092946488; Imhof, A.|info:eu-repo/dai/nl/145641600

    2009-01-01

    We describe a novel method to synthesize colloidal particles with an eccentric core-shell structure. Titania-silica core-shell particles were synthesized by silica coating of porous titania particles under Sto¨ber (Sto¨ber et al. J. Colloid Interface Sci. 1968, 26, 62) conditions. We can control

  2. Core-shell Au/Ag nanoparticles embedded in silicate sol-gel ...

    Indian Academy of Sciences (India)

    The electrocatalytic activity of core-shell Au100-Ag ( = 15, 27, 46, and 60) bimetallic nanoparticles embedded in methyl functionalized silicate MTMOS network towards the reduction of hydrogen peroxide was investigated by using cyclic voltammetry and chronoamperometric techniques. Core-shell Au/Ag bimetallic ...

  3. Preparation and Characterization of Porous Core-Shell Fibers for Slow Release of Tea Polyphenols

    Directory of Open Access Journals (Sweden)

    Yaru Wang

    2018-02-01

    Full Text Available This study focused on the fabrication, characterization, and release properties of electrospun tea polyphenol (TPP loaded porous core-shell structured fibers. The morphology, structure and properties of the electrospun TPP loaded porous core-shell fibers were investigated by a combination of Fourier transformation infrared spectroscopy (FTIR, scanning electron microscopy (SEM, contact angle (CA measurements, transmission electron microscopy (TEM, etc. In addition, the cumulative drug release rate of TPP loaded porous core-shell fibers was determined by ultraviolet (UV spectrophotometer, and the release mechanism was investigated using Fickian diffusion equation, which would provide the theoretical basis for future study. The results showed TPP loaded porous core-shell structured fibers were successfully prepared by coaxial electrospinning, and the porous structure of the core-shell fibers could further enlarge the specific surface area, enhance the hydrophobic properties, and improve the drug release properties.

  4. Facile fabrication of siloxane @ poly (methylacrylic acid) core-shell microparticles with different functional groups

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Zheng-Bai; Tai, Li; Zhang, Da-Ming; Jiang, Yong, E-mail: yj@seu.edu.cn [Southeast University, School of Chemistry and Chemical Engineering (China)

    2017-02-15

    Siloxane @ poly (methylacrylic acid) core-shell microparticles with functional groups were prepared by a facile hydrolysis-condensation method in this work. Three different silane coupling agents 3-methacryloxypropyltrimethoxysilane (MPS), 3-triethoxysilylpropylamine (APTES), and 3-glycidoxypropyltrimethoxysilane (GPTMS) were added along with tetraethoxysilane (TEOS) into the polymethylacrylic acid (PMAA) microparticle ethanol dispersion to form the Si@PMAA core-shell microparticles with different functional groups. The core-shell structure and the surface special functional groups of the resulting microparticles were measured by transmission electron microscopy and FTIR. The sizes of these core-shell microparticles were about 350–400 nm. The corresponding preparation conditions and mechanism were discussed in detail. This hydrolysis-condensation method also could be used to functionalize other microparticles which contain active groups on the surface. Meanwhile, the Si@PMAA core-shell microparticles with carbon-carbon double bonds and amino groups have further been applied to prepare hydrophobic coatings.

  5. Electronic properties of core-shell nanowire resonant tunneling diodes

    Science.gov (United States)

    2014-01-01

    The electronic sub-band structure of InAs/InP/InAs/InP/InAs core-shell nanowire resonant tunneling diodes has been investigated in the effective mass approximation by varying the core radius and the thickness of the InP barriers and InAs shells. A top-hat, double-barrier potential profile and optimal energy configuration are obtained for core radii and surface shells >10 nm, InAs middle shells barriers. In this case, two sub-bands exist above the Fermi level in the InAs middle shell which belongs to the m = 0 and m = 1 ladder of states that have similar wave functions and energies. On the other hand, the lowest m = 0 sub-band in the core falls below the Fermi level but the m = 1 states do not contribute to the current transport since they reside energetically well above the Fermi level. We compare the case of GaAs/AlGaAs/GaAs/AlGaAs/GaAs which may conduct current with smaller applied voltages due to the larger effective mass of electrons in GaAs and discuss the need for doping. PMID:25288912

  6. Recent Developments in No-Core Shell-Model Calculations

    Energy Technology Data Exchange (ETDEWEB)

    Navratil, P; Quaglioni, S; Stetcu, I; Barrett, B R

    2009-03-20

    We present an overview of recent results and developments of the no-core shell model (NCSM), an ab initio approach to the nuclear many-body problem for light nuclei. In this aproach, we start from realistic two-nucleon or two- plus three-nucleon interactions. Many-body calculations are performed using a finite harmonic-oscillator (HO) basis. To facilitate convergence for realistic inter-nucleon interactions that generate strong short-range correlations, we derive effective interactions by unitary transformations that are tailored to the HO basis truncation. For soft realistic interactions this might not be necessary. If that is the case, the NCSM calculations are variational. In either case, the ab initio NCSM preserves translational invariance of the nuclear many-body problem. In this review, we, in particular, highlight results obtained with the chiral two- plus three-nucleon interactions. We discuss efforts to extend the applicability of the NCSM to heavier nuclei and larger model spaces using importance-truncation schemes and/or use of effective interactions with a core. We outline an extension of the ab initio NCSM to the description of nuclear reactions by the resonating group method technique. A future direction of the approach, the ab initio NCSM with continuum, which will provide a complete description of nuclei as open systems with coupling of bound and continuum states is given in the concluding part of the review.

  7. Homogeneous protein analysis by magnetic core-shell nanorod probes

    KAUST Repository

    Schrittwieser, Stefan

    2016-03-29

    Studying protein interactions is of vital importance both to fundamental biology research and to medical applications. Here, we report on the experimental proof of a universally applicable label-free homogeneous platform for rapid protein analysis. It is based on optically detecting changes in the rotational dynamics of magnetically agitated core-shell nanorods upon their specific interaction with proteins. By adjusting the excitation frequency, we are able to optimize the measurement signal for each analyte protein size. In addition, due to the locking of the optical signal to the magnetic excitation frequency, background signals are suppressed, thus allowing exclusive studies of processes at the nanoprobe surface only. We study target proteins (soluble domain of the human epidermal growth factor receptor 2 - sHER2) specifically binding to antibodies (trastuzumab) immobilized on the surface of our nanoprobes and demonstrate direct deduction of their respective sizes. Additionally, we examine the dependence of our measurement signal on the concentration of the analyte protein, and deduce a minimally detectable sHER2 concentration of 440 pM. For our homogeneous measurement platform, good dispersion stability of the applied nanoprobes under physiological conditions is of vital importance. To that end, we support our measurement data by theoretical modeling of the total particle-particle interaction energies. The successful implementation of our platform offers scope for applications in biomarker-based diagnostics as well as for answering basic biology questions.

  8. Variable solar control using thermotropic core/shell particles

    Energy Technology Data Exchange (ETDEWEB)

    Muehling, Olaf; Seeboth, Arno; Ruhmann, Ralf; Potechius, Elvira; Vetter, Renate [Fraunhofer Institute for Applied Polymer Research (IAP), Department of Chromogenic Polymers, Volmerstr. 7B, 12489 Berlin (Germany); Haeusler, Tobias [Brandenburg University of Technology (BTU Cottbus), Chair of Applied Physics/Thermophysics, Konrad-Zuse-Str. 1, 03046 Cottbus (Germany)

    2009-09-15

    Subject of our recent investigations is the utilization of a reversible thermotropic material for a self-regulating sun protection glazing that controls the solar energy input in order to avoid overheating. Based on the well-established UV curing technology for laminated glass a superior thermotropic material with tunable switching characteristics and of low material costs was developed. The polymer layer contains core/shell particles homogeneously dispersed in a UV-cured resin. The particle core in turn consists of an n-alkane mixture that is responsible for the temperature-induced clear/opaque switching. To obtain particles of well-defined size and with a narrow size distribution, the miniemulsion polymerization technique was used. The visible and solar optical properties (normal-normal, normal-hemispherical, and normal-diffuse transmittance) in the off (clear) and in the on state (opaque) were determined by UV/Vis/NIR spectroscopy. Samples containing particles of high median diameter (>800 nm) primarily scatter in the forward direction. However, with smaller particles (300-600 nm) a higher backscattering (reflection) efficiency was achieved. The largest difference in the normal-hemispherical transmittance could be found with a particle amount of 6% and a median scattering domain diameter of {proportional_to}380 nm. (author)

  9. Core-shell hexacyanoferrate for superior Na-ion batteries

    Science.gov (United States)

    Wan, Min; Tang, Yang; Wang, Lili; Xiang, Xinghua; Li, Xiaocheng; Chen, Kongyao; Xue, Lihong; Zhang, Wuxing; Huang, Yunhui

    2016-10-01

    Sodium iron hexacyanoferrate (Fe-HCF) is regarded as a potential cathode material for sodium-ion batteries (SIBs) due to its high specific capacity, low cost, facile synthesis and environmentally friendly. However, Fe-HCF always suffers from poor electronic conductivity, low crystallinity and side reactions with electrolyte, leading to poor rate performance, low coulombic efficiency and deterioration of cycling stability. Herein, we report a green and facile synthesis to encapsulate Fe-HCF microcubes with potassium nickel hexacyanoferrate (Ni-HCF). The core-shell Fe-HCF@Ni-HCF composite delivers a reversible capacity of 79.7 mAh g-1 at 200 mA g-1 after 800 cycles and a high coulombic efficiency of 99.3%. In addition, Fe-HCF@Ni-HCF exhibits excellent rate performance, retaining 60 mAh g-1 at 2000 mA g-1. The results show that Fe-HCF@Ni-HCF integrates the advantages of both Fe-HCF and Ni-HCF, making it electrochemically stable as cathode material for SIBs.

  10. Silica@layered double hydroxide core-shell hybrid materials.

    Science.gov (United States)

    Kwok, Wing L J; Crivoi, Dana-Georgiana; Chen, Chunping; Buffet, Jean-Charles; O'Hare, Dermot

    2017-12-19

    A series of silica@layered double hydroxides (SiO 2 @Mg 2 Al-CO 3 -AMO-LDHs) have been synthesised by in situ precipitation of Mg 2 Al-CO 3 -LDH at room temperature in the presence of amorphous spherical silica particles (∼500 nm). We have systematically investigated a number of synthetic parameters in order to evaluate their effects on the composition, morphological and physical properties of the isolated materials. Syntheses carried out at moderate stirring speeds (e.g. 500 rpm) were found to promote the formation of vertically aligned LDH platelets with respect to the silica surface. Addition rates of the metal solutions slower than 0.43 mmol h -1 were found to create a thicker LDH shell consisting of vertically aligned LDH platelets. When the metal solutions were added rapidly (0.86 mmol h -1 ), we observed that for both slow and fast stirring speeds the synthesised core-shell materials had thin LDH shells and the majority of the LDH precipitated independent of the silica, forming unbound "free" LDH.

  11. Supramolecular core-shell nanoparticles for photoconductive device applications

    Science.gov (United States)

    Cheng, Chih-Chia; Chen, Jem-Kun; Shieh, Yeong-Tarng; Lee, Duu-Jong

    2016-08-01

    We report a breakthrough discovery involving supramolecular-based strategies to construct novel core-shell heterojunction nanoparticles with hydrophilic adenine-functionalized polythiophene (PAT) as the core and hydrophobic phenyl-C61-butyric acid methyl ester (PCBM) as the shell, which enables the conception of new functional supramolecular assemblies for constructing functional nanomaterials for applications in optoelectronic devices. The generated nanoparticles exhibit uniform spherical shape, well-controlled tuning of particle size with narrow size distributions, and excellent electrochemical stability in solution and the solid state owing to highly efficient energy transfer from PAT to PCBM. When the PAT/PCBM nanoparticles were fabricated into a photoconducting layer in an electronic device, the resulting device showed excellent electric conduction characteristics, including an electrically-tunable voltage-controlled switch, and high short-circuit current and open-circuit voltage. These observations demonstrate how the self-assembly of PAT/PCBM into specific nanostructures may help to promote efficient charge generation and transport processes, suggesting potential for a wide variety of applications as a promising candidate material for bulk heterojunction polymer devices.

  12. Impact Resistance Enhancement by Adding Core-Shell Particle to Epoxy Resin Modified with Hyperbranched Polymer

    Directory of Open Access Journals (Sweden)

    Shuiping Li

    2017-12-01

    Full Text Available A core-shell particle was fabricated by grafting amino-terminated hyperbranched polymer to the surface of silica nanoparticles. The influences of core-shell particle contents on the tensile and impact strength of the epoxy thermosets modified with amino-terminated hyperbranched polymer were discussed in detail. For comparison, core-shell particle was added into the epoxy/polyamide system for toughness improvement. Results from tensile and impact tests are provided. The introduction of core-shell particle into the epoxy/polyamide systems just slightly enhanced the tensile and impact strength. The incorporation of 3 wt % core-shell particle could substantially improve the tensile and impact strength of epoxy/amino-terminated hyperbranched polymer thermosets. Field emission-scanning electron microscope images of the impact fracture surfaces showed that the excellent impact resistance of epoxy/amino-terminated hyperbranched polymer/core-shell particle thermosets may be attributed to the synergistic effect of shearing deformation and crack pinning/propagation, which is induced by the good compatibility between epoxy matrix and core-shell particle in the presence of amino-terminated hyperbranched polymer.

  13. Core-shell particles: preparation, fundamentals and applications in high performance liquid chromatography.

    Science.gov (United States)

    Hayes, Richard; Ahmed, Adham; Edge, Tony; Zhang, Haifei

    2014-08-29

    The challenges in HPLC are fast and efficient separation for a wide range of samples. Fast separation often results in very high operating pressure, which places a huge burden on HPLC instrumentation. In recent years, core-shell silica microspheres (with a solid core and a porous shell, also known as fused-core or superficially porous microspheres) have been widely investigated and used for highly efficient and fast separation with reasonably low pressure for separation of small molecules, large molecules and complex samples. In this review, we firstly show the types of core-shell particles and how they are generally prepared, focusing on the methods used to produce core-shell silica particles for chromatographic applications. The fundamentals are discussed on why core-shell particles can perform better with low back pressure, in terms of van Deemter equation and kinetic plots. The core-shell particles are compared with totally porous silica particles and also monolithic columns. The use of columns packed with core-shell particles in different types of liquid chromatography is then discussed, followed by illustrating example applications of such columns for separation of various types of samples. The review is completed with conclusion and a brief perspective on future development of core-shell particles in chromatography. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

  14. Core-Shell Structured Electro- and Magneto-Responsive Materials: Fabrication and Characteristics

    Directory of Open Access Journals (Sweden)

    Hyoung Jin Choi

    2014-11-01

    Full Text Available Core-shell structured electrorheological (ER and magnetorheological (MR particles have attracted increasing interest owing to their outstanding field-responsive properties, including morphology, chemical and dispersion stability, and rheological characteristics of shear stress and yield stress. This study covers recent progress in the preparation of core-shell structured materials as well as their critical characteristics and advantages. Broad emphasises from the synthetic strategy of various core-shell particles to their feature behaviours in the magnetic and electric fields have been elaborated.

  15. Cadmium Telluride, Cadmium Telluride/Cadmium Sulfide Core/Shell, and Cadmium Telluride/Cadmium Sulfide/Zinc Sulfide Core/Shell/Shell Quantum Dots Study

    Science.gov (United States)

    Yan, Yueran

    CdTe, CdTe/CdS core/shell, and CdTe/CdS/ZnS core/shell/shell quantum dots (QDs) are potential candidates for bio-imaging and solar cell applications because of some special physical properties in these nano materials. For example, the band gap energy of the bulk CdTe is about 1.5 eV, so that principally they can emit 790 nm light, which is in the near-infrared range (also called biological window). Moreover, theoretically hot exciton generated by QDs is possible to be caught since the exciton relaxation process in QDs is slower than in bulk materials due to the large intraband energy gap in QDs. In this dissertation, we have synthesized the CdTe and CdTe/CdS core/shell QDs, characterized their structure, and analyzed their photophysical properties. We used organometallic methods to synthesize the CdTe QDs in a noncoordinating solvent. To avoid being quenched by air, ligands, solvent, or other compounds, CdS shell was successfully deposited on the CdTe QDs by different methods, including the slow injection method, the successive ion layer adsorption and reaction (SILAR) method, and thermal-cycling coupled single precursor method (TC-SP). Our final product, quasi-type- II CdTe/CdS core/shell QDs were able to emit at 770 nm with a fluorescence quantum yield as high as 70%. We also tried to deposit a second shell ZnS on CdTe/CdS core/shell QDs since some compounds can quench CdTe/CdS core/shell QDs. Even though different methods were used to deposit ZnS shell on the CdTe/CdS core/shell QDs, CdTe/CdS/ZnS core/shell/shell QDs still can be quenched. Furthermore, the CdTe/CdS core/shell and CdTe/CdS/ZnS core/shell/shell QDs were transferred into aqueous phase, phosphate buffered saline or deionized water, by switching the hydrophilic ligands (thiol or PEG ligands). The thioglycolic acid (TGA)-capped CdTe/CdS core/shell QDs can be kept in aqueous phase with high fluorescence quantum yield (60%--70%) for more than two months. However, some other compounds in organic or

  16. Engineered magnetic core shell nanoprobes: Synthesis and applications to cancer imaging and therapeutics.

    Science.gov (United States)

    Mandal, Samir; Chaudhuri, Keya

    2016-02-26

    Magnetic core shell nanoparticles are composed of a highly magnetic core material surrounded by a thin shell of desired drug, polymer or metal oxide. These magnetic core shell nanoparticles have a wide range of applications in biomedical research, more specifically in tissue imaging, drug delivery and therapeutics. The present review discusses the up-to-date knowledge on the various procedures for synthesis of magnetic core shell nanoparticles along with their applications in cancer imaging, drug delivery and hyperthermia or cancer therapeutics. Literature in this area shows that magnetic core shell nanoparticle-based imaging, drug targeting and therapy through hyperthermia can potentially be a powerful tool for the advanced diagnosis and treatment of various cancers.

  17. Core-shell polymer nanorods by a two-step template wetting process

    International Nuclear Information System (INIS)

    Dougherty, S; Liang, J

    2009-01-01

    One-dimensional core-shell polymer nanowires offer many advantages and great potential for many different applications. In this paper we introduce a highly versatile two-step template wetting process to fabricate two-component core-shell polymer nanowires with controllable shell thickness. PLLA and PMMA were chosen as model polymers to demonstrate the feasibility of this process. Solution wetting with different concentrations of polymer solutions was used to fabricate the shell layer and melt wetting was used to fill the shell with the core polymer. The shell thickness was analyzed as a function of the polymer solution concentration and viscosity, and the core-shell morphology was observed with TEM. This paper demonstrates the feasibility of fabricating polymer core-shell nanostructures using our two-step template wetting process and opens the arena for optimization and future experiments with polymers that are desirable for specific applications.

  18. Cr/alpha-Cr2O3 monodispersed spherical core-shell particles based solar absorbers

    CSIR Research Space (South Africa)

    Khamlich, S

    2011-07-01

    Full Text Available Monodispersed spherical core-shell particles of Cr/alpha-Cr2O3 cermet ACG coatings investigated within this contribution could be successfully employed in thermal converters. Their selectivity depends on their chemical, physical and structural...

  19. Multiple-shell ZnSe core-shell spheres and their improved photocatalytic activity.

    Science.gov (United States)

    Zhao, Lijuan; Sun, Chengcheng; Tian, Gang; Pang, Qi

    2017-09-15

    Multiple-shell ZnSe core-shell microspheres were synthesized on a large scale by a facile solvothermal method in ethylene glycol (EG) with ethylene diamine tetraacetic acid (EDTA) assisted. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis absorption spectroscopy and photoluminescence (PL) were used to characterize the structures and optical properties of these core-shell spheres with multiple shells. XRD and SEM analyses show that the as-grown ZnSe samples are zinc-blende core-shell structures with multiple shells. The possible growth mechanism is investigated. The results of photocatalysis of methyl red (MR) indicate that the multiple-shell ZnSe core-shell microspheres possess remarkable photocatalytic activity. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Coaxial electrospun polyurethane core-shell nanofibers for shape memory and antibacterial nanomaterials

    Directory of Open Access Journals (Sweden)

    2011-02-01

    Full Text Available A novel kind of shape memory polyurethane (SMPU nanofibers with core-shell nanostructure is fabricated using coaxial electrospinning. Transmission electron microscopy (TEM and scanning electron microscopy (SEM results show that nanofibers with core-shell structure or bead-on-string structure can be electrospun successfully from the core solution of polycaprolactone based SMPU (CLSMPU and shell solution of pyridine containing polyurethane (PySMPU. In addition to the excellent shape memory effect with good shape fixity, excellent antibacterial activity against both gramnegative bacteria and gram-positive bacteria are achieved in the CLSMPU-PySMPU core-shell nanofiber. Finally, it is proposed that the antibacterial mechanism should be resulted from the PySMPU shell materials containing amido group in γ position and the high surface area per unit mass of nanofibers. Thus, the CLSMPU-PySMPU core shell nanofibers can be used as both shape memory nanomaterials and antibacterial nanomaterials.

  1. Synthesis and cytotoxicity study of magnesium ferrite-gold core-shell nanoparticles.

    Science.gov (United States)

    Nonkumwong, Jeeranan; Pakawanit, Phakkhananan; Wipatanawin, Angkana; Jantaratana, Pongsakorn; Ananta, Supon; Srisombat, Laongnuan

    2016-04-01

    In this work, the core-magnesium ferrite (MgFe2O4) nanoparticles were prepared by hydrothermal technique. Completed gold (Au) shell coating on the surfaces of MgFe2O4 nanoparticles was obtained by varying core/shell ratios via a reduction method. Phase identification, morphological evolution, optical properties, magnetic properties and cytotoxicity to mammalian cells of these MgFe2O4 core coated with Au nanoparticles were examined by using a combination of X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy, UV-visible spectroscopy (UV-vis), vibrating sample magnetometry and resazurin microplate assay techniques. In general, TEM images revealed different sizes of the core-shell nanoparticles generated from various core/shell ratios and confirmed the completed Au shell coating on MgFe2O4 core nanoparticles via suitable core/shell ratio with particle size less than 100 nm. The core-shell nanoparticle size and the quality of coating influence the optical properties of the products. The UV-vis spectra of complete coated MgFe2O4-Au core-shell nanoparticles exhibit the absorption bands in the near-Infrared (NIR) region indicating high potential for therapeutic applications. Based on the magnetic property measurement, it was found that the obtained MgFe2O4-Au core-shell nanoparticles still exhibit superparamagnetism with lower saturation magnetization value, compared with MgFe2O4 core. Both of MgFe2O4 and MgFe2O4-Au core-shell also showed in vitro non-cytotoxicity to mouse areola fibroblast (L-929) cell line. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Synthesis, structural, optical and photocatalytic properties of CdS/ZnS core/shell nanoparticles

    Science.gov (United States)

    Reddy, Ch. Venkata; Shim, Jaesool; Cho, Migyung

    2017-04-01

    CdS, ZnS and CdS/ZnS core/shell nanoparticles were successfully synthesized via two-step synthesis method. The as-prepared CdS, ZnS and CdS/ZnS core/shell nanoparticles were used to study the structural, morphological, and optical properties by PXRD, TEM, HRTEM, UV-vis spectroscopy, N2 adsorption-desorption, FT-IR, PL and Raman spectroscopy measurements. The XRD pattern confirms the crystal structure of the prepared ZnS, CdS, and CdS/ZnS core/shell nanoparticles. The crystallinity of the as-prepared samples is confirmed by PXRD, TEM and HRTEM analysis. The BET analysis showed that the CdS/ZnS core/shell nanoparticles had larger surface area and pore diameter than CdS and ZnS. The Raman and FT-IR spectra confirm the fundamental vibrational modes of CdS and ZnS respectively. Compared to pure CdS and ZnS, CdS/ZnS core/shell nanoparticles exhibited higher photocatalytic activity for the degradation of methyl orange (MO). The enhancement of photocatalytic activity in the CdS/ZnS core/shell nanoparticles is due to the interface actions between CdS and ZnS, which greatly reduces the recombination of photogenerated electrons-holes pair. The proposed mechanism for degradation of MO dye is discussed in detail.

  3. Core/shell nano-structuring of metal oxide semiconductors and their photocatalytic studies

    Science.gov (United States)

    Balakumar, S.; Rakkesh, R. Ajay

    2013-02-01

    Core/Shell Nanostructures of Metal Oxide Semiconductors (MOS) have attracted much attention because of their most fascinating tunable applications. These core shell morphologies can be easily engineered to enhance the unique properties of the metal-oxide nanostructures, which make them suitable as photocatalyst due to their high catalytic activity, substantial stability, and brilliant perspective in applications. This paper provides an overview on our work on the synthesis of some interesting core/ shell nanostructures of MOS such as ZnO-TiO2, ZnO-MoO3, and V2O5-TiO2 using a low temperature wet chemical route and hydrothermal techniques and their photocatalytic properties from the aspects of different shell materials and shell thicknesses. The effect of process parameters such as pH, temperature, and ratio of core and shell materials, was systematically studied. Here the evidence for the core shell formation with different shell thicknesses came from the X-ray diffraction peak intensities. The shell thickness variation was also confirmed by Transmission Electron Microscopic studies. Effect of shell thickness on optical band gap of the core shell fabricated was also investigated using DRS UV-Visible spectroscopy. A comprehensive study was carried out for the photocatalytic efficiency of core shell nanostructures by evaluating the photo-degradation of Acridine Orange (AO) dye in aqueous solution under visible and solar light irradiations. These results offered simple approaches to the nanoscale engineering and synthesis of MOS hybrid systems to serve as better photocatalytic materials.

  4. High quality ZnO-TiO2 core-shell nanowires for efficient ultraviolet sensing

    Science.gov (United States)

    Shao, Dali; Sun, Hongtao; Xin, Guoqing; Lian, Jie; Sawyer, Shayla

    2014-09-01

    High quality ZnO-TiO2 core-shell nanowires (NWs) have been fabricated via a facile two-step method: growth of ZnO nanowires by hydrothermal synthesis and then coating of highly uniform TiO2 shell using atomic layer deposition (ALD) technique. The ultraviolet (UV) emission intensity of the ZnO-TiO2 core-shell NWs is largely quenched due to an efficient electron-hole separation that reduces the band-to-band recombinations. To the contrary, the absorption of the ZnO-TiO2 core-shell NWs in both UV and visible region is enhanced, which is attributed to the antireflection properties of the TiO2 shell. An UV photodetector fabricated from the ZnO-TiO2 core-shell NWs showed a maximum photoresponsivity as high as 495 A/W at 373 nm under -10 V, which is ∼8 times higher than that of the photodetector fabricated from bare ZnO NWs. In addition, the transient response of the ZnO-TiO2 core-shell NWs is improved by 6 times as compared to that of the bare ZnO NWs. The results presented in this work suggest that ZnO-TiO2 core-shell NWs may be promising for various optoelectronics applications including: UV photodetectors, optical switches, optical fibers and solar cells.

  5. Ultrafast light matter interaction in CdSe/ZnS core-shell quantum dots

    Science.gov (United States)

    Yadav, Rajesh Kumar; Sharma, Rituraj; Mondal, Anirban; Adarsh, K. V.

    2018-04-01

    Core-shell quantum dot are imperative for carrier (electron and holes) confinement in core/shell, which provides a stage to explore the linear and nonlinear optical phenomena at the nanoscalelimit. Here we present a comprehensive study of ultrafast excitation dynamics and nonlinear optical absorption of CdSe/ZnS core shell quantum dot with the help of ultrafast spectroscopy. Pump-probe and time-resolved measurements revealed the drop of trapping at CdSe surface due to the presence of the ZnS shell, which makes more efficient photoluminescence. We have carried out femtosecond transient absorption studies of the CdSe/ZnS core-shell quantum dot by irradiation with 400 nm laser light, monitoring the transients in the visible region. The optical nonlinearity of the core-shell quantum dot studied by using the Z-scan technique with 120 fs pulses at the wavelengths of 800 nm. The value of two photon absorption coefficients (β) of core-shell QDs extracted as80cm/GW, and it shows excellent benchmark for the optical limiting onset of 2.5GW/cm2 with the low limiting differential transmittance of 0.10, that is an order of magnitude better than graphene based materials.

  6. Cu-Ag core-shell nanoparticles with enhanced oxidation stability for printed electronics.

    Science.gov (United States)

    Lee, Changsoo; Kim, Na Rae; Koo, Jahyun; Lee, Yung Jong; Lee, Hyuck Mo

    2015-11-13

    In this work, we synthesized uniform Cu-Ag core-shell nanoparticles using a facile two-step process that consists of thermal decomposition and galvanic displacement methods. The core-shell structure of these nanoparticles was confirmed through characterization using transmission electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction. Furthermore, we investigated the oxidation stability of the Cu-Ag core-shell nanoparticles in detail. Both qualitative and quantitative x-ray photoelectron spectroscopy analyses confirm that the Cu-Ag core-shell nanoparticles have considerably higher oxidation stability than Cu nanoparticles. Finally, we formulated a conductive ink using the synthesized nanoparticles and coated it onto glass substrates. Following the sintering process, we compared the resistivity of the Cu-Ag core-shell nanoparticles with that of the Cu nanoparticles. The results of this study clearly show that the Cu-Ag core-shell nanoparticles can potentially be used as an alternative to Ag nanoparticles because of their superior oxidation stability and electrical properties.

  7. Core-shell microspheres with porous nanostructured shells for liquid chromatography.

    Science.gov (United States)

    Ahmed, Adham; Skinley, Kevin; Herodotou, Stephanie; Zhang, Haifei

    2018-01-01

    The development of new stationary phases has been the key aspect for fast and efficient high-performance liquid chromatography separation with relatively low backpressure. Core-shell particles, with a solid core and porous shell, have been extensively investigated and commercially manufactured in the last decade. The excellent performance of core-shell particles columns has been recorded for a wide range of analytes, covering small and large molecules, neutral and ionic (acidic and basic), biomolecules and metabolites. In this review, we first introduce the advance and advantages of core-shell particles (or more widely known as superficially porous particles) against non-porous particles and fully porous particles. This is followed by the detailed description of various methods used to fabricate core-shell particles. We then discuss the applications of common silica core-shell particles (mostly commercially manufactured), spheres-on-sphere particles and core-shell particles with a non-silica shell. This review concludes with a summary and perspective on the development of stationary phase materials for high-performance liquid chromatography applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Magnetite and magnetite/silver core/shell nanoparticles with diluted magnet-like behavior

    International Nuclear Information System (INIS)

    Garza-Navarro, Marco; Torres-Castro, Alejandro; Gonzalez, Virgilio; Ortiz, Ubaldo; De la Rosa, Elder

    2010-01-01

    In the present work is reported the use of the biopolymer chitosan as template for the preparation of magnetite and magnetite/silver core/shell nanoparticles systems, following a two step procedure of magnetite nanoparticles in situ precipitation and subsequent silver ions reduction. The crystalline and morphological characteristics of both magnetite and magnetite/silver core/shell nanoparticles systems were analyzed by high resolution transmission electron microscopy (HRTEM) and nanobeam diffraction patterns (NBD). The results of these studies corroborate the core/shell morphology and the crystalline structure of the magnetite core and the silver shell. Moreover, magnetization temperature dependent, M(T), measurements show an unusual diluted magnetic behavior attributed to the dilution of the magnetic ordering in the magnetite and magnetite/silver core/shell nanoparticles systems. - Graphical abstract: Biopolymer chitosan was used as stabilization media to synthesize both magnetite and magnetite/silver core/shell nanoparticles. Results of HRTEM and NBD patterns confirm core/shell morphology of the obtained nanoparticles. It was found that the composites show diluted magnet-like behavior.

  9. Magnetic core-shell nanoparticles for drug delivery by nebulization

    LENUS (Irish Health Repository)

    Verma, Navin Kumar

    2013-01-23

    AbstractBackgroundAerosolized therapeutics hold great potential for effective treatment of various diseases including lung cancer. In this context, there is an urgent need to develop novel nanocarriers suitable for drug delivery by nebulization. To address this need, we synthesized and characterized a biocompatible drug delivery vehicle following surface coating of Fe3O4 magnetic nanoparticles (MNPs) with a polymer poly(lactic-co-glycolic acid) (PLGA). The polymeric shell of these engineered nanoparticles was loaded with a potential anti-cancer drug quercetin and their suitability for targeting lung cancer cells via nebulization was evaluated.ResultsAverage particle size of the developed MNPs and PLGA-MNPs as measured by electron microscopy was 9.6 and 53.2 nm, whereas their hydrodynamic swelling as determined using dynamic light scattering was 54.3 nm and 293.4 nm respectively. Utilizing a series of standardized biological tests incorporating a cell-based automated image acquisition and analysis procedure in combination with real-time impedance sensing, we confirmed that the developed MNP-based nanocarrier system was biocompatible, as no cytotoxicity was observed when up to 100 mug\\/ml PLGA-MNP was applied to the cultured human lung epithelial cells. Moreover, the PLGA-MNP preparation was well-tolerated in vivo in mice when applied intranasally as measured by glutathione and IL-6 secretion assays after 1, 4, or 7 days post-treatment. To imitate aerosol formation for drug delivery to the lungs, we applied quercitin loaded PLGA-MNPs to the human lung carcinoma cell line A549 following a single round of nebulization. The drug-loaded PLGA-MNPs significantly reduced the number of viable A549 cells, which was comparable when applied either by nebulization or by direct pipetting.ConclusionWe have developed a magnetic core-shell nanoparticle-based nanocarrier system and evaluated the feasibility of its drug delivery capability via aerosol administration. This study has

  10. Magnetic core-shell nanoparticles for drug delivery by nebulization

    Directory of Open Access Journals (Sweden)

    Verma Navin Kumar

    2013-01-01

    Full Text Available Abstract Background Aerosolized therapeutics hold great potential for effective treatment of various diseases including lung cancer. In this context, there is an urgent need to develop novel nanocarriers suitable for drug delivery by nebulization. To address this need, we synthesized and characterized a biocompatible drug delivery vehicle following surface coating of Fe3O4 magnetic nanoparticles (MNPs with a polymer poly(lactic-co-glycolic acid (PLGA. The polymeric shell of these engineered nanoparticles was loaded with a potential anti-cancer drug quercetin and their suitability for targeting lung cancer cells via nebulization was evaluated. Results Average particle size of the developed MNPs and PLGA-MNPs as measured by electron microscopy was 9.6 and 53.2 nm, whereas their hydrodynamic swelling as determined using dynamic light scattering was 54.3 nm and 293.4 nm respectively. Utilizing a series of standardized biological tests incorporating a cell-based automated image acquisition and analysis procedure in combination with real-time impedance sensing, we confirmed that the developed MNP-based nanocarrier system was biocompatible, as no cytotoxicity was observed when up to 100 μg/ml PLGA-MNP was applied to the cultured human lung epithelial cells. Moreover, the PLGA-MNP preparation was well-tolerated in vivo in mice when applied intranasally as measured by glutathione and IL-6 secretion assays after 1, 4, or 7 days post-treatment. To imitate aerosol formation for drug delivery to the lungs, we applied quercitin loaded PLGA-MNPs to the human lung carcinoma cell line A549 following a single round of nebulization. The drug-loaded PLGA-MNPs significantly reduced the number of viable A549 cells, which was comparable when applied either by nebulization or by direct pipetting. Conclusion We have developed a magnetic core-shell nanoparticle-based nanocarrier system and evaluated the feasibility of its drug delivery capability via aerosol

  11. Synthesis and cytotoxicity study of magnesium ferrite-gold core-shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Nonkumwong, Jeeranan [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Pakawanit, Phakkhananan [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Wipatanawin, Angkana [Division of Biochemistry and Biochemical Technology, Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Jantaratana, Pongsakorn [Department of Physics, Faculty of Science, Kasetsart University, Bangkok 11900 (Thailand); Ananta, Supon [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Srisombat, Laongnuan, E-mail: slaongnuan@yahoo.com [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand)

    2016-04-01

    In this work, the core-magnesium ferrite (MgFe{sub 2}O{sub 4}) nanoparticles were prepared by hydrothermal technique. Completed gold (Au) shell coating on the surfaces of MgFe{sub 2}O{sub 4} nanoparticles was obtained by varying core/shell ratios via a reduction method. Phase identification, morphological evolution, optical properties, magnetic properties and cytotoxicity to mammalian cells of these MgFe{sub 2}O{sub 4} core coated with Au nanoparticles were examined by using a combination of X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy, UV–visible spectroscopy (UV–vis), vibrating sample magnetometry and resazurin microplate assay techniques. In general, TEM images revealed different sizes of the core-shell nanoparticles generated from various core/shell ratios and confirmed the completed Au shell coating on MgFe{sub 2}O{sub 4} core nanoparticles via suitable core/shell ratio with particle size less than 100 nm. The core-shell nanoparticle size and the quality of coating influence the optical properties of the products. The UV–vis spectra of complete coated MgFe{sub 2}O{sub 4}-Au core-shell nanoparticles exhibit the absorption bands in the near-Infrared (NIR) region indicating high potential for therapeutic applications. Based on the magnetic property measurement, it was found that the obtained MgFe{sub 2}O{sub 4}-Au core-shell nanoparticles still exhibit superparamagnetism with lower saturation magnetization value, compared with MgFe{sub 2}O{sub 4} core. Both of MgFe{sub 2}O{sub 4} and MgFe{sub 2}O{sub 4}-Au core-shell also showed in vitro non-cytotoxicity to mouse areola fibroblast (L-929) cell line. - Highlights: • Synthesis of MgFe{sub 2}O{sub 4}-Au core-shell nanoparticles with particle size < 100 nm • Complete Au shell coating on the surfaces of MgFe{sub 2}O{sub 4} nanoparticles • In vitro cytotoxicity study of complete coated MgFe{sub 2}O{sub 4}-Au core-shell

  12. Core-shell microparticles for protein sequestration and controlled release of a protein-laden core.

    Science.gov (United States)

    Rinker, Torri E; Philbrick, Brandon D; Temenoff, Johnna S

    2017-07-01

    Development of multifunctional biomaterials that sequester, isolate, and redeliver cell-secreted proteins at a specific timepoint may be required to achieve the level of temporal control needed to more fully regulate tissue regeneration and repair. In response, we fabricated core-shell heparin-poly(ethylene-glycol) (PEG) microparticles (MPs) with a degradable PEG-based shell that can temporally control delivery of protein-laden heparin MPs. Core-shell MPs were fabricated via a re-emulsification technique and the number of heparin MPs per PEG-based shell could be tuned by varying the mass of heparin MPs in the precursor PEG phase. When heparin MPs were loaded with bone morphogenetic protein-2 (BMP-2) and then encapsulated into core-shell MPs, degradable core-shell MPs initiated similar C2C12 cell alkaline phosphatase (ALP) activity as the soluble control, while non-degradable core-shell MPs initiated a significantly lower response (85+19% vs. 9.0+4.8% of the soluble control, respectively). Similarly, when degradable core-shell MPs were formed and then loaded with BMP-2, they induced a ∼7-fold higher C2C12 ALP activity than the soluble control. As C2C12 ALP activity was enhanced by BMP-2, these studies indicated that degradable core-shell MPs were able to deliver a bioactive, BMP-2-laden heparin MP core. Overall, these dynamic core-shell MPs have the potential to sequester, isolate, and then redeliver proteins attached to a heparin core to initiate a cell response, which could be of great benefit to tissue regeneration applications requiring tight temporal control over protein presentation. Tissue repair requires temporally controlled presentation of potent proteins. Recently, biomaterial-mediated binding (sequestration) of cell-secreted proteins has emerged as a strategy to harness the regenerative potential of naturally produced proteins, but this strategy currently only allows immediate amplification and re-delivery of these signals. The multifunctional, dynamic

  13. Core-shell column Tanaka characterization and additional tests using active pharmaceutical ingredients.

    Science.gov (United States)

    Ludvigsson, Jufang Wu; Karlsson, Anders; Kjellberg, Viktor

    2016-12-01

    In the last decade, core-shell particles have gained more and more attention in fast liquid chromatography separations due to their comparable performance with fully porous sub-2 μm particles and their significantly lower back pressure. Core-shell particles are made of a solid core surrounded by a shell of classic fully porous material. To embrace the developed core-shell column market and use these columns in pharmaceutical analytical applications, 17 core-shell C 18 columns purchased from various vendors with various dimensions (50 mm × 2.1 mm to 100 mm × 3 mm) and particle sizes (1.6-2.7 μm) were characterized using Tanaka test protocols. Furthermore, four selected active pharmaceutical ingredients were chosen as test probes to investigate the batch to batch reproducibility for core-shell columns of particle size 2.6-2.7 μm, with dimension of 100 × 3 mm and columns of particle size 1.6 μm, with dimension 100 × 2.1 mm under isocratic elution. Columns of particle size 2.6-2.7 μm were also tested under gradient elution conditions. To confirm the claimed comparable efficiency of 2.6 μm core-shell particles as sub-2 μm fully porous particles, column performances of the selected core-shell columns were compared with BEH C 18 , 1.7 μm, a fully porous column material as well. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. In vitro hyperthermia with improved colloidal stability and enhanced SAR of magnetic core/shell nanostructures.

    Science.gov (United States)

    Patil, R M; Thorat, N D; Shete, P B; Otari, S V; Tiwale, B M; Pawar, S H

    2016-02-01

    Magnetic core/shell nanostructures of Fe3O4 nanoparticles coated with oleic acid and betaine-HCl were studied for their possible use in magnetic fluid hyperthermia (MFH). Their colloidal stability and heat induction ability were studied in different media viz. phosphate buffer solution (PBS), saline solution and glucose solution with different physiological conditions and in human serum. The results showed enhanced colloidal stability in these media owing to their high zeta potential values. Heat induction studies showed that specific absorption rates (SAR) of core/shells were 82-94W/g at different pH of PBS and concentrations of NaCl and glucose. Interestingly, core/shells showed 78.45±3.90W/g SAR in human serum. The cytotoxicity of core/shells done on L929 and HeLa cell lines using 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl tetrazolium bromide and trypan blue dye exclusion assays showed >89% and >80% cell viability for 24 and 48h respectively. Core/shell structures were also found to be very efficient for in vitro MFH on cancer cell line. About 95% cell death was occurred in 90min after hyperthermia treatment. The mechanism of cell death was found to be elevated ROS generation in cells after exposure to core/shells in external magnetic field. This study showed that these core/shells have a great potential to be used in in vivo MFH. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Editorial Core-Shell Nano structures: Modeling, Fabrication, Properties, and Applications

    International Nuclear Information System (INIS)

    Qi, W.; Luo, L.; Qian, H.; Ouyang, G.; Nanda, K.K.; Obare, S.O.

    2012-01-01

    Core-shell nano structures, a family of nano materials, have attracted increasing research interest due to their unique structural features that consist of an inner core and an external shell of different chemical compositions. These structural features allow the possibility of combining distinctive properties of varied materials. Comparatively, core-shell nano structures have exhibited improved physical and chemical properties relative to their single-component counterparts. The inherent emergent chemical and physical properties of core-shell nano structures are of great importance to a potentially broader range of applications including electronics, magnetism, optics, and catalysis. So far a large number of core-shell nano structures have been successfully fabricated using approaches ranging from laser ablation and high-temperature evaporation to carbothermal reduction and hydrothermal methods. Structural characterization of these nano structures and determination of their unique properties for various applications have been well documented. This special issue is devoted to describing a number of unique properties and applications of core-shell nano structures by introducing a few research papers in this field.

  16. Microwave absorbing materials using Ag-NiZn ferrite core-shell nanopowders as fillers

    International Nuclear Information System (INIS)

    Peng, C.-H.; Wang, H.-W.; Kan, S.-W.; Shen, M.-Z.; Wei, Y.-M.; Chen, S.-Y.

    2004-01-01

    Silver nanoparticles coated with Ni 0.5 Zn 0.5 Fe 2 O 4 spinel ferrites, forming a core-shell structure, were synthesized by utilizing hydrothermal method at different ferrite/silver ratio (ferrite/silver=6/1, 4/1, 2/1, 1/1, 1/6) and introduced into polyurethane matrix to be a microwave absorber. The complex permittivity (ε',ε'') and permeability (μ',μ'') of absorbing composite materials consisted of ferrite/silver core-shell nanopowders and polyurethane were measured in the frequency range of 2-15GHz. The reflection loss and matching frequency were calculated from measured data using theory of the absorbing wall for different ferrite/silver ratios. It was found that the matching frequency for reflection loss exceeded a satisfactory -25dB at 9.0GHz for using NiZn ferrite as a filler shifts to higher frequencies (10.9-13.7GHz) as the ferrite/silver ratio of core-shell nano-filler decreased from 6/1 to 2/1. The present result demonstrates that microwave absorbers using ferrite/silver core-shell filler can be fabricated for the applications over 9GHz, with reflection loss more than-25dB for specific frequencies, by controlling the ferrite/silver ratio of the core-shell nano-fillers in the composites

  17. Hypersonic vibrations of Ag@SiO2 (cubic core)-shell nanospheres.

    Science.gov (United States)

    Sun, Jing Ya; Wang, Zhi Kui; Lim, Hock Siah; Ng, Ser Choon; Kuok, Meng Hau; Tran, Toan Trong; Lu, Xianmao

    2010-12-28

    The intriguing optical and catalytic properties of metal-silica core-shell nanoparticles, inherited from their plasmonic metallic cores together with the rich surface chemistry and increased stability offered by their silica shells, have enabled a wide variety of applications. In this work, we investigate the confined vibrational modes of a series of monodisperse Ag@SiO(2) (cubic core)-shell nanospheres synthesized using a modified Stöber sol-gel method. The particle-size dependence of their mode frequencies has been mapped by Brillouin light scattering, a powerful tool for probing hypersonic vibrations. Unlike the larger particles, the observed spheroidal-like mode frequencies of the smaller ones do not scale with inverse diameter. Interestingly, the onset of the deviation from this linearity occurs at a smaller particle size for higher-energy modes than for lower-energy ones. Finite element simulations show that the mode displacement profiles of the Ag@SiO(2) core-shells closely resemble those of a homogeneous SiO(2) sphere. Simulations have also been performed to ascertain the effects that the core shape and the relative hardness of the core and shell materials have on the vibrations of the core-shell as a whole. As the vibrational modes of a particle have a bearing on its thermal and mechanical properties, the findings would be of value in designing core-shell nanostructures with customized thermal and mechanical characteristics.

  18. Sensitive detection of DNA based on the optical properties of core-shell gold nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Huang Haowen, E-mail: hhwn09@163.com; Li Chunhui; Qu Caiting; Huang Shaowen; Liu Fang; Zeng Yunlong [Hunan University of Science and Technology, Laboratory of Theoretical Chemistry and Molecular Simulation of Ministry of Education, School of Chemistry and Chemical Engineering (China)

    2012-03-15

    In this article, a type of core-shell nanostructure, Au{sub 2}S/AuAgS/Ag{sub 3}AuS{sub 2}-coated gold nanorods (GNRs) with unique optical properties was used as a sensing platform to detect fish sperm DNA (fsDNA). The prepared core-shell nanorods are positively charged due to the adsorption of the positively charged cetyltrimethylammonium bromide (CTAB) cations on their surface. fsDNA can form ternary fsDNA-CTAB-nanorod complexes together with CTAB and nanorod, which provides a useful platform to detect fsDNA through absorption spectra and resonance light scattering (RLS) spectroscopy. In this sensitive core-shell nanorod sensor, CTAB concentration and the nanoparticle dosage play important roles and have been investigated. Moreover, the fsDNA-CTAB-nanorod complexes induce a great enhancement of RLS intensity of the core-shell GNRs and directly proportional to the concentration of fsDNA, reaching a detection limit of about 10{sup -9} mg/mL. This study will be significant for as-prepared core-shell GNRs for future application in biological systems.

  19. Preparation and Characterization of SiO2/SiCN Core-shell Ceramic Microspheres

    Directory of Open Access Journals (Sweden)

    ZHANG Hai-yuan

    2017-05-01

    Full Text Available The SiO2/PSN core-shell microspheres were prepared via an emulsion reaction combined with the polymer-derived ceramics (PDCs method using polysilazane (PSN in situ polymerization on the surface of SiO2 modified by silane coupling agents MPS, followed by pyrolysis process to obtain SiO2/SiCN core-shell ceramic microspheres. The effects of raw mass ratio, curing time and pyrolysis temperature on the formation and the morphology of core-shell microspheres were studied. The morphology, chemical composition and phase transformation were characterized by SEM, EDS, TEM, FT-IR and XRD. The results show that after reaction for 4h at 200℃, SiO2 completely coated PSN forms a core-shell microsphere with rough surface when the mass ratio of SiO2 and PSN is 1:4; when pyrolysis temperature is at 800-1200℃, amorphous SiO2/SiCN core-shell ceramic microspheres are prepared; at 1400℃, the amorphous phase partially crystallizes to produce SiO2, SiC and Si3N4 phase.

  20. Nonpolar InGaN/GaN Core-Shell Single Nanowire Lasers.

    Science.gov (United States)

    Li, Changyi; Wright, Jeremy B; Liu, Sheng; Lu, Ping; Figiel, Jeffrey J; Leung, Benjamin; Chow, Weng W; Brener, Igal; Koleske, Daniel D; Luk, Ting-Shan; Feezell, Daniel F; Brueck, S R J; Wang, George T

    2017-02-08

    We report lasing from nonpolar p-i-n InGaN/GaN multi-quantum well core-shell single-nanowire lasers by optical pumping at room temperature. The nanowire lasers were fabricated using a hybrid approach consisting of a top-down two-step etch process followed by a bottom-up regrowth process, enabling precise geometrical control and high material gain and optical confinement. The modal gain spectra and the gain curves of the core-shell nanowire lasers were measured using micro-photoluminescence and analyzed using the Hakki-Paoli method. Significantly lower lasing thresholds due to high optical gain were measured compared to previously reported semipolar InGaN/GaN core-shell nanowires, despite significantly shorter cavity lengths and reduced active region volume. Mode simulations show that due to the core-shell architecture, annular-shaped modes have higher optical confinement than solid transverse modes. The results show the viability of this p-i-n nonpolar core-shell nanowire architecture, previously investigated for next-generation light-emitting diodes, as low-threshold, coherent UV-visible nanoscale light emitters, and open a route toward monolithic, integrable, electrically injected single-nanowire lasers operating at room temperature.

  1. Facile synthesis and excellent microwave absorption properties of FeCo-C core-shell nanoparticles

    Science.gov (United States)

    Liang, Bingbing; Wang, Shiliang; Kuang, Daitao; Hou, Lizhen; Yu, Bowen; Lin, Liangwu; Deng, Lianwen; Huang, Han; He, Jun

    2018-02-01

    FeCo-C core-shell nanoparticles (NPs) with diameters of 10-50 nm have been fabricated on a large scale by one-step metal-organic chemical vapor deposition using the mixture of cobalt acetylacetonate and iron acetylacetonate as the precursor. The Fe/Co molar ratio of the alloy nanocores and graphitization degree of C shells, and thus the magnetic and electric properties of the core-shell NPs, can be tuned by the deposition temperature ranging from 700 °C to 900 °C. Comparative tests reveal that a relatively high Fe/Co molar ratio and low graphitization degree benefit the microwave absorption (MA) performance of the core-shell NPs. The composite with 20 wt% core-shell NP obtained at 800 °C and 80 wt% paraffin exhibits an optimal reflection loss ({{R}}{{L}}) of -60.4 dB at 7.5 GHz with a thickness of 3.3 mm, and an effective absorption bandwidth (frequency range for RL ≤10 dB) of 9.2 GHz (8.8-18.0 GHz) under an absorber thickness of 2.5 mm. Our study provides a facile route for the fabrication of alloy-C core-shell nanostructures with high MA performance.

  2. Room temperature ferromagnetic Cr doped Ge/GeOx core-shell nanowires.

    Science.gov (United States)

    Katkar, Amar S; Gupta, Shobhnath P; Seikh, Md Motin; Chen, Lih-Juann; Walke, Pravin S

    2018-03-19

    The Cr doped tunable thickness core-shell Ge/GeOx nanowires were synthesized and characterized using X-ray diffraction, FESEM, TEM, EDS, XPS and magnetization studies. The shell thickness increases with the increase in synthesis temperature. The presence of metallic Cr and Cr3+ in core-shell structure was confirmed from XPS study. The magnetic property is highly sensitive to the core-shell thickness and intriguing room temperature ferromagnetism is realized only in core-shell nanowires. The magnetization decreases with increase in shell thickness and practically ceases to exist when there is no core. These nanowires shows high Curie temperature (TC>300 K) remarkably with the dominating values of its magnetic remanence (MR) and coercivity (HC) as compared to germanium dilute magnetic semiconductor nanomaterials. We believe that our finding on these Cr doped Ge/GeOX core-shell nanowires have potential to use as a hard magnet for forthcoming spintronic devices, owing to their higher characteristic values of FM ordering. © 2018 IOP Publishing Ltd.

  3. Macroporous polymer from core-shell particle-stabilized Pickering emulsions.

    Science.gov (United States)

    Li, Zifu; Ngai, To

    2010-04-06

    Poly(styrene-co-N-isopropylacrylamide) (PS-co-PNIPAM) core-shell particles were synthesized and used as particulate emulsifiers in the preparation of particle-stabilized (Pickering) emulsions. Highly concentrated oil-in-water emulsions with an internal phase up to 80 vol % can be produced using PS-co-PNIPAM core-shell particles along as the emulsifiers in emulsions. The core-shell particles are adsorbed at the liquid interface, acting as a barrier against oil droplet coalescence. In addition, it is likely that excess particles simultaneously form a gel in the continuous phase to trap oil droplets in the gel matrix, in turn inhibiting creaming and phase inversion. Evaporation in air of such a core-shell particle-stabilized emulsion directly leads to porous membranes in the absence of chemical reactions. The pore walls of the final structures are densely packed with layers of the core-shell particles. This provides great flexibility to prepare functionalized porous materials for opening up new applications.

  4. Electrosprayed core-shell polymer-lipid nanoparticles for active component delivery

    Science.gov (United States)

    Eltayeb, Megdi; Stride, Eleanor; Edirisinghe, Mohan

    2013-11-01

    A key challenge in the production of multicomponent nanoparticles for healthcare applications is obtaining reproducible monodisperse nanoparticles with the minimum number of preparation steps. This paper focus on the use of electrohydrodynamic (EHD) techniques to produce core-shell polymer-lipid structures with a narrow size distribution in a single step process. These nanoparticles are composed of a hydrophilic core for active component encapsulation and a lipid shell. It was found that core-shell nanoparticles with a tunable size range between 30 and 90 nm and a narrow size distribution could be reproducibly manufactured. The results indicate that the lipid component (stearic acid) stabilizes the nanoparticles against collapse and aggregation and improves entrapment of active components, in this case vanillin, ethylmaltol and maltol. The overall structure of the nanoparticles produced was examined by multiple methods, including transmission electron microscopy and differential scanning calorimetry, to confirm that they were of core-shell form.

  5. Highly responsive core-shell microactuator arrays for use in viscous and viscoelastic fluids

    International Nuclear Information System (INIS)

    Fiser, Briana L; Shields, Adam R; Falvo, M R; Superfine, R

    2015-01-01

    We present a new fabrication method to produce arrays of highly responsive polymer-metal core-shell magnetic microactuators. The core-shell fabrication method decouples the elastic and magnetic structural components such that the actuator response can be optimized by adjusting the core-shell geometry. Our microstructures are 10 µm long, 550 nm in diameter, and electrochemically fabricated in particle track-etched membranes, comprising a poly(dimethylsiloxane) core with a 100 nm Ni shell surrounding the upper 3–8 µm. The structures can achieve deflections of nearly 90° with moderate magnetic fields and are capable of driving fluid flow in a fluid 550 times more viscous than water. (paper)

  6. A study of the properties of core/shell/shell Ag/FeCo/Ag nanoparticles

    Science.gov (United States)

    Kamzin, A. S.; Takahashi, M.; Maenosono, S.; Valiullin, A. A.

    2017-10-01

    The properties of heterophase core/shell/shell Ag/FeCo/Ag nanoparticles synthesized via a plasma method that are promising for biological applications are studied. As is established, the core/shell/shell Ag/FeCo/Ag nanoparticles exhibit a superparamagnetic state at room temperature that allows one to manage the hyperthermia process. The magnetic characteristics of core/shell/shell Ag/FeCo/Ag nanoparticles are interpreted by assuming partial oxidation of the surface layer of a ferromagnetic FeCo shell and formation of the antiferromagnetic CoxFe1-xO layer on the FeCo surface. The interaction between the surface antiferromagnetic CoxFe1-xO layer and the ferromagnetic FeCo shell causes the emergence of the exchange bias in Ag/FeCo/Ag nanoparticles.

  7. Facile synthesis of Ag@ZIF-8 core-shell heterostructure nanowires for improved antibacterial activities

    Science.gov (United States)

    Guo, Yu-Feng; Fang, Wei-Jun; Fu, Jie-Ru; Wu, Yun; Zheng, Jun; Gao, Gui-Qi; Chen, Cheng; Yan, Rui-Wen; Huang, Shou-Guo; Wang, Chun-Chang

    2018-03-01

    Compared with pure MOFs, core-shell heterostructures of noble-metal@MOFs have attracted tremendous interest due to their unique structure and extensive applications. In the present study, we have successfully synthesized well-defined core-shell Ag@ZIF-8 nanowires. The products growth process has been investigated by examining the products obtained at different intervals and the thickness of ZIF-8 shell ranging from 30 to 100 nm can be technically obtained by tuning the quantity of Ag nanowires. Ag@ZIF-8 has been proven to possess large specific surfaces and high thermal stability. Additionally, the antibacterial activity of Ag@ZIF-8 is further tested against Bacillus subtilis and Escherichia coli BL21. The results reveal that Ag@ZIF-8 core-shell heterostructure nanowires have effective activities against the two types of bacterial strains.

  8. Mie scattering by soft core-shell particles and its applications to ellipsometric light scattering.

    Science.gov (United States)

    Ross, Daniel J; Sigel, Reinhard

    2012-05-01

    Through the use of Mie theory generalized to multiple spheres, the derivatives of the scattering matrix elements and ellipsometric scattering variables are found as a function of shell thickness and nonconcentricity for core-shell particles. In particular, for the case of a core-shell sphere system where the centers are not concentric, the derivatives are taken with respect to the line segment describing the distance between spherical centers. The derivatives of the scattering matrix elements can be used to calculate the changes in ellipsometric light scattering, allowing for sensitivity and precision in quantitative models of fluctuations in core-shell systems. Computed results giving model contrast for a variety of sizes and fluctuation modes are used to design and guide novel light-scattering experiments currently underway.

  9. Subwavelength core/shell cylindrical nanostructures for novel plasmonic and metamaterial devices

    Science.gov (United States)

    Kim, Kyoung-Ho; No, You-Shin

    2017-12-01

    In this review, we introduce novel plasmonic and metamaterial devices based on one-dimensional subwavelength nanostructures with cylindrical symmetry. Individual single devices with semiconductor/metal core/shell or dielectric/metal core/multi-shell structures experience strong light-matter interaction and yield unique optical properties with a variety of functions, e.g., invisibility cloaking, super-scattering/super-absorption, enhanced luminescence and nonlinear optical activities, and deep subwavelength-scale optical waveguiding. We describe the rational design of core/shell cylindrical nanostructures and the proper choice of appropriate constituent materials, which allow the efficient manipulation of electromagnetic waves and help to overcome the limitations of conventional homogeneous nanostructures. The recent developments of bottom-up synthesis combined with the top-down fabrication technologies for the practical applications and the experimental realizations of 1D subwavelength core/shell nanostructure devices are briefly discussed.

  10. Research advances in polymer emulsion based on "core-shell" structure particle design.

    Science.gov (United States)

    Ma, Jian-zhong; Liu, Yi-hong; Bao, Yan; Liu, Jun-li; Zhang, Jing

    2013-09-01

    In recent years, quite many studies on polymer emulsions with unique core-shell structure have emerged at the frontier between material chemistry and many other fields because of their singular morphology, properties and wide range of potential applications. Organic substance as a coating material onto either inorganic or organic internal core materials promises an unparalleled opportunity for enhancement of final functions through rational designs. This contribution provides a brief overview of recent progress in the synthesis, characterization, and applications of both inorganic-organic and organic-organic polymer emulsions with core-shell structure. In addition, future research trends in polymer composites with core-shell structure are also discussed in this review. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. Study of core-shell platinum-based catalyst for methanol and ethylene glycol oxidation

    Science.gov (United States)

    Kaplan, D.; Alon, M.; Burstein, L.; Rosenberg, Yu.; Peled, E.

    A Ru core-Pt shell, XC72-supported catalyst was synthesized in a two-step process: first, by deposition of Ru on XC72 by the polyol process and then by deposition of Pt on the XC72-supported Ru, with NaBH 4 as reducing agent. The structure and composition of this core-shell catalyst were determined by EDS, XPS, TEM and XRD. Electrochemical characterization was determined with the use of cyclic voltammetry and chronoamperometry. The methanol and ethylene glycol oxidation activities of the core-shell catalyst were studied at 80 °C and compared to those of a commercial catalyst. It was found to be significantly better (in terms of A g -1 of Pt) in the case of methanol oxidation and worse in the case of ethylene glycol oxidation. Possible reasons for the lower ethylene glycol oxidation activity of the core-shell catalyst are discussed.

  12. Highly responsive core-shell microactuator arrays for use in viscous and viscoelastic fluids

    Science.gov (United States)

    Fiser, Briana L.; Shields, Adam R.; Falvo, M. R.; Superfine, R.

    2015-01-01

    We present a new fabrication method to produce arrays of highly responsive polymer-metal core-shell magnetic microactuators. The core-shell fabrication method decouples the elastic and magnetic structural components such that the actuator response can be optimized by adjusting the core-shell geometry. Our microstructures are 10 μm long, 550 nm in diameter, and electrochemically fabricated in particle track-etched membranes, comprising a poly(dimethylsiloxane) core with a 100 nm Ni shell surrounding the upper 3–8 μm. The structures can achieve deflections of nearly 90° with moderate magnetic fields and are capable of driving fluid flow in a fluid 550 times more viscous than water. PMID:26405376

  13. Polyethylenimine-immobilized core-shell nanoparticles: synthesis, characterization, and biocompatibility test.

    Science.gov (United States)

    Ratanajanchai, Montri; Soodvilai, Sunhapas; Pimpha, Nuttaporn; Sunintaboon, Panya

    2014-01-01

    Herein, we prepared PEI-immobilized core-shell particles possessing various types of polymer cores via a visible light-induced surfactant-free emulsion polymerization (SFEP) of three vinyl monomers: styrene (St), methyl methacrylate (MMA), and 2-hydroxyethyl methacrylate (HEMA). An effect of monomers on the polymerization and characteristics of resulting products was investigated. Monomers with high polarity can provide high monomer conversion, high percentage of grafted PEI, stable particles with uniform size distribution but less amino groups per particles. All prepared nanoparticles exhibited a core-shell nanostructure, containing PEI on the shell with hydrodynamic size around 140-230nm. For in-vitro study in Caco-2 cells, we found that the incorporation of PEI into these core-shell nanoparticles can significantly reduce its cytotoxic effect and also be able to internalized within the cells. Accordingly, these biocompatible particles would be useful for various biomedical applications, including gene transfection and intracellular drug delivery. © 2013.

  14. Polymer-inorganic core-shell nanofibers by electrospinning and atomic layer deposition: flexible nylon-ZnO core-shell nanofiber mats and their photocatalytic activity.

    Science.gov (United States)

    Kayaci, Fatma; Ozgit-Akgun, Cagla; Donmez, Inci; Biyikli, Necmi; Uyar, Tamer

    2012-11-01

    Polymer-inorganic core-shell nanofibers were produced by two-step approach; electrospinning and atomic layer deposition (ALD). First, nylon 6,6 (polymeric core) nanofibers were obtained by electrospinning, and then zinc oxide (ZnO) (inorganic shell) with precise thickness control was deposited onto electrospun nylon 6,6 nanofibers using ALD technique. The bead-free and uniform nylon 6,6 nanofibers having different average fiber diameters (∼80, ∼240 and ∼650 nm) were achieved by using two different solvent systems and polymer concentrations. ZnO layer about 90 nm, having uniform thickness around the fiber structure, was successfully deposited onto the nylon 6,6 nanofibers. Because of the low deposition temperature utilized (200 °C), ALD process did not deform the polymeric fiber structure, and highly conformal ZnO layer with precise thickness and composition over a large scale were accomplished regardless of the differences in fiber diameters. ZnO shell layer was found to have a polycrystalline nature with hexagonal wurtzite structure. The core-shell nylon 6,6-ZnO nanofiber mats were flexible because of the polymeric core component. Photocatalytic activity of the core-shell nylon 6,6-ZnO nanofiber mats were tested by following the photocatalytic decomposition of rhodamine-B dye. The nylon 6,6-ZnO nanofiber mat, having thinner fiber diameter, has shown better photocatalytic efficiency due to higher surface area of this sample. These nylon 6,6-ZnO nanofiber mats have also shown structural stability and kept their photocatalytic activity for the second cycle test. Our findings suggest that core-shell nylon 6,6-ZnO nanofiber mat can be a very good candidate as a filter material for water purification and organic waste treatment because of their photocatalytic properties along with structural flexibility and stability.

  15. Acetone sensing of multi-networked WO3-NiO core-shell nanorod sensors

    Science.gov (United States)

    Choi, Seungbok; Lee, Jae Kyung; Lee, Woo Seok; Lee, Chongmu; Lee, Wan In

    2017-10-01

    WO3-NiO core-shell nanorods were synthesized by thermal evaporation of a mixture of WO3 and graphite powders and immersion of the synthesized WO3 nanorods in an 20 mM of nickel(II) acetate tetrahydrate (Ni(OCOCH3)2·4H2O) solution followed by UV irradiation and annealing. Subsequently, multi-networked nanorod sensors were fabricated by connecting these nanostructures with electrodes. The sensing properties of pristine WO3 nanorod and WO3-NiO core-shell nanorod sensors toward acetone were examined. Subsequently, multi-networked nanorod sensors were fabricated by connecting these nanostructures with electrodes. The WO3-NiO core-shell nanorod sensor exhibited a stronger response to acetone gas and shorter response/recovery times than the pristine WO3 nanorod sensor. The pristine WO3 nanorods showed responses of approximately 1.36 to 200 ppm of CH3COCH3 at 300 °C. On the other hand, the WO3-NiO core-shell nanorods showed responses of 4.4 to the same concentration of CH3COCH3 at the same temperature. The core-shell nanorods exhibited response and recovery times of 51 s and 59 s, respectively for 200 ppm of CH3COCH3. On the other hand, the pristine WO3 nanorods exhibited response and recovery times of 51 s and 59 s, respectively, for the same concentration of CH3COCH3. NiO coating enhanced the selectivity of the WO3 nanorods for acetone as well as the sensitivity of the WO3 nanorods. The underlying mechanism of the enhanced response of the WO3-NiO core-shell nanorod sensor is also discussed in detail.

  16. Sub-nanometer dimensions control of core/shell nanoparticles prepared by atomic layer deposition.

    Science.gov (United States)

    Weber, M J; Verheijen, M A; Bol, A A; Kessels, W M M

    2015-03-06

    Bimetallic core/shell nanoparticles (NPs) are the subject of intense research due to their unique electronic, optical and catalytic properties. Accurate and independent control over the dimensions of both core and shell would allow for unprecedented catalytic performance. Here, we demonstrate that both core and shell dimensions of Pd/Pt core/shell nanoparticles (NPs) supported on Al2O3 substrates can be controlled at the sub-nanometer level by using a novel strategy based on atomic layer deposition (ALD). From the results it is derived that the main conditions for accurate dimension control of these core/shell NPs are: (i) a difference in surface energy between the deposited core metal and the substrate to obtain island growth; (ii) a process yielding linear growth of the NP cores with ALD cycles to obtain monodispersed NPs with a narrow size distribution; (iii) a selective ALD process for the shell metal yielding a linearly increasing thickness to obtain controllable shell growth exclusively on the cores. For Pd/Pt core/shell NPs it is found that a minimum core diameter of 1 nm exists above which the NP cores are able to catalytically dissociate the precursor molecules for shell growth. In addition, initial studies on the stability of these core/shell NPs have been carried out, and it has been demonstrated that core/shell NPs can be deposited by ALD on high aspect ratio substrates such as nanowire arrays. These achievements show therefore that ALD has significant potential for the preparation of tuneable heterogeneous catalyst systems.

  17. Core-shell silk hydrogels with spatially tuned conformations as drug-delivery system.

    Science.gov (United States)

    Yan, Le-Ping; Oliveira, Joaquim M; Oliveira, Ana L; Reis, Rui L

    2017-11-01

    Hydrogels of spatially controlled physicochemical properties are appealing platforms for tissue engineering and drug delivery. In this study, core-shell silk fibroin (SF) hydrogels of spatially controlled conformation were developed. The core-shell structure in the hydrogels was formed by means of soaking the preformed (enzymatically crosslinked) random coil SF hydrogels in methanol. When increasing the methanol treatment time from 1 to 10 min, the thickness of the shell layer can be tuned from about 200 to about 850 μm as measured in wet status. After lyophilization of the rehydrated core-shell hydrogels, the shell layer displayed compact morphology and the core layer presented porous structure, when observed by scanning electron microscopy. The conformation of the hydrogels was evaluated by Fourier transform infrared spectroscopy in wet status. The results revealed that the shell layer possessed dominant β-sheet conformation and the core layer maintained mainly random coil conformation. Enzymatic degradation data showed that the shell layers presented superior stability to the core layer. The mechanical analysis displayed that the compressive modulus of the core-shell hydrogels ranged from about 25 kPa to about 1.1 MPa by increasing the immersion time in methanol. When incorporated with albumin, the core-shell SF hydrogels demonstrated slower and more controllable release profiles compared with the non-treated hydrogel. These core-shell SF hydrogels of highly tuned properties are useful systems as drug-delivery system and may be applied as cartilage substitute. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  18. Silica-silver core-shell particles for antibacterial textile application.

    Science.gov (United States)

    Nischala, K; Rao, Tata N; Hebalkar, Neha

    2011-01-01

    The silica-silver core-shell particles were synthesized by simple one pot chemical method and were employed on the cotton fabric as an antibacterial agent. Extremely small (1-2 nm) silver nanoparticles were attached on silica core particles of average 270 nm size. The optimum density of the nano silver particles was found which was sufficient to show good antibacterial activity as well as the suppression in their surface plasmon resonance responsible for the colour of the core-shell particle for antibacterial textile application. The change in the density and size of the particles in the shell were monitored and confirmed by direct evidence of their transmission electron micrographs and by studying surface plasmon resonance characteristics. The colony counting method of antibacterial activity testing showed excellent results and even the least silver containing core-shell particles showed 100% activity against bacterial concentration of 10(4) colony counting units (cfu). The bonding between core-shell particles and cotton fabric was examined by X-ray photoelectron spectroscopy. The antibacterial activity test confirmed the firm attachment of core-shell particles to the cotton fabric as a result 10 times washed sample was as good antibacterial as that of unwashed sample. The bacterial growth was inhibited on and beneath the coated fabric, at the same time no zone of inhibition which occurs due to the migration of silver ions into the medium was observed indicating immobilization of silver nanoparticles on silica and core-shell particles on fabric by strong bonding. Copyright © 2010 Elsevier B.V. All rights reserved.

  19. Physical mechanism of surface roughening on the radial core-shell nanowire heterostructure with alloy shell

    Science.gov (United States)

    Cao, Yuanyuan; Diao, Dongfeng

    2017-05-01

    We proposed a quantitative thermodynamic theory to address the physical process of surface roughening during the epitaxial growth of core-shell NW with alloy layer. The surface roughening origins from the transformation of the Frank-van der Merwe (FM) mode to the Stranski-Krastanow (SK) mode. In addition to the radius of NW core, the composition and thickness of alloy shell could determine the growth behaviors due to their modulation to the strain. The established theoretical model not only explains the surface roughening caused by the alloy shell layer, but also provides a new way to control the growth of core-shell NW.

  20. Physical mechanism of surface roughening on the radial core-shell nanowire heterostructure with alloy shell

    Directory of Open Access Journals (Sweden)

    Yuanyuan Cao

    2017-05-01

    Full Text Available We proposed a quantitative thermodynamic theory to address the physical process of surface roughening during the epitaxial growth of core-shell NW with alloy layer. The surface roughening origins from the transformation of the Frank-van der Merwe (FM mode to the Stranski-Krastanow (SK mode. In addition to the radius of NW core, the composition and thickness of alloy shell could determine the growth behaviors due to their modulation to the strain. The established theoretical model not only explains the surface roughening caused by the alloy shell layer, but also provides a new way to control the growth of core-shell NW.

  1. Synthesis of SnS/In2S3 core-shell nanoparticles

    Science.gov (United States)

    Prastani, C.; Nanu, M.; Nanu, D.; Schropp, R. E. I.; Rath, J. K.

    2014-09-01

    In this letter a new type of core-shell structure is presented. The core is made of tin-sulfide by colloidal route. The shell, made of indium-sulfide, by chemical bath deposition. These core-shell nanoparticles have been characterized by transmission electron microscope to study the size and the shape. High resolution TEM has allowed to determine the structure of the core and the shell. The chemical composition has been analyzed by energy-dispersive X-ray spectroscopy. In the end the optical absorption investigated by UV-vis changing the deposition time and temperature. Finally, the influence of these parameters on the band gap has been investigated.

  2. Fabrication and Characterization of ZnS/Diamond-Like Carbon Core-Shell Nanowires

    OpenAIRE

    Kim, Jung Han; Kim, Seul Cham; Kim, Do Hyun; Oh, Kyu Hwan; Hong, Woong-Ki; Bae, Tae-Sung; Chung, Hee-Suk

    2016-01-01

    We fabricated ZnS/diamond-like carbon (DLC) core-shell heterostructure nanowire using a simple two-step process: the vapor-liquid-solid method combined with radio frequency plasma enhanced chemical vapor deposition (rf PECVD). As a core nanowire, ZnS nanowires with face-centered cubic structure were synthesized with a sputtered Au thin film, which exhibit a length and a diameter of ~10 μm and ~30–120 nm . After rf PECVD for DLC coating, The length and width of the dense ZnS/DLC core-shell nan...

  3. Symplectic symmetry and the ab initio no-core shell model

    Energy Technology Data Exchange (ETDEWEB)

    Draayer, J.P.; Dytrych, T.; Sviratcheva, K.D.; Bahri, C. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Vary, J.P. [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)

    2007-12-15

    The symplectic symmetry of eigenstates for the O{sub gs}{sup +} in {sup 16}O and the O{sub gs}{sup +}s and lowest 2{sup +} and 4{sup +} configurations of {sup 12}C that are well-converged within the framework of the no-core shell model with the JISP16 realistic interaction is examined. These states are found to project at the 85-90% level onto very few symplectic representations including the most deformed configuration, which confirms the importance of a symplectic no-core shell model and reaffirms the relevance of the Elliott SU(3) model upon which the symplectic scheme is built. (Author)

  4. Recent advances in the synthesis of Fe3O4@AU core/shell nanoparticles

    Science.gov (United States)

    Salihov, Sergei V.; Ivanenkov, Yan A.; Krechetov, Sergei P.; Veselov, Mark S.; Sviridenkova, Natalia V.; Savchenko, Alexander G.; Klyachko, Natalya L.; Golovin, Yury I.; Chufarova, Nina V.; Beloglazkina, Elena K.; Majouga, Alexander G.

    2015-11-01

    Fe3O4@Au core/shell nanoparticles have unique magnetic and optical properties. These nanoparticles are used for biomedical applications, such as magnetic resonance imaging, photothermal therapy, controlled drug delivery, protein separation, biosensors, DNA detection, and immunosensors. In this review, recent methods for the synthesis of core/shell nanoparticles are discussed. We divided all of the synthetic methods in two groups: methods of synthesis of bi-layer structures and methods of synthesis of multilayer composite structures. The latter methods have a layer of "glue" material between the core and the shell.

  5. Enhanced bifunctional fuel cell catalysis via Pd/PtCu core/shell nanoplates.

    Science.gov (United States)

    Lin, Fei; Wang, Kai; Tang, Yonghua; Lai, Jianping; Lou, Mingchuan; Huang, Minghua; Guo, Shaojun

    2018-02-01

    Depositing Pt atoms on nanoscale two-dimensional (2D) substrates resulting in the exposure of specific crystal facets is an effective strategy for reducing the Pt content without compromising the catalytic property. Herein, the Pd/PtCu core/shell nanoplates exhibit substantially improved ORR and MOR mass activities, 8.3 and 3.3 times higher than those of commercial Pt. The present work highlights the important role of designing a 2D core/shell nanostructure in enhancing fuel cell electrocatalysis.

  6. Structural and magnetic properties of core-shell iron-iron oxide nanoparticles

    DEFF Research Database (Denmark)

    Kuhn, Luise Theil; Bojesen, A.; Timmermann, L.

    2002-01-01

    We present studies of the structural and magnetic properties of core-shell iron-iron oxide nanoparticles. alpha-Fe nanoparticles were fabricated by sputtering and subsequently covered with a protective nanocrystalline oxide shell consisting of either maghaemite (gamma-Fe2O3) or partially oxidized...... magnetite (Fe3O4). We observed that the nanoparticles were stable against further oxidation, and Mossbauer spectroscopy at high applied magnetic fields and low temperatures revealed a stable form of partly oxidized magnetite. The nanocrystalline structure of the oxide shell results in strong canting...... of the spin structure in the oxide shell, which thereby modifies the magnetic properties of the core-shell nanoparticles....

  7. Graded index and randomly oriented core-shell silicon nanowires for broadband and wide angle antireflection

    Directory of Open Access Journals (Sweden)

    P. Pignalosa

    2011-09-01

    Full Text Available Antireflection with broadband and wide angle properties is important for a wide range of applications on photovoltaic cells and display. The SiOx shell layer provides a natural antireflection from air to the Si core absorption layer. In this work, we have demonstrated the random core-shell silicon nanowires with both broadband (from 400nm to 900nm and wide angle (from normal incidence to 60º antireflection characteristics within AM1.5 solar spectrum. The graded index structure from the randomly oriented core-shell (Air/SiOx/Si nanowires may provide a potential avenue to realize a broadband and wide angle antireflection layer.

  8. Fabrication of SiGe/Ge core-shell nanowires by oxidation of SiGe

    OpenAIRE

    Kløw, Frode

    2011-01-01

    As Si technology is reaching its limits in solar cell and transistor applications, ways to improve these devices are being investigated. This study looks at the fabrication process of SiGe/Ge core-shell nanowires (NWs). Larger SiGe column structures can be oxidized to reduce their size and create a SiGe/Ge core-shell structure with a layer of SiO2 on the outside. Initially, SiGe dry oxidation was investigated in epitaxially grown SiGe films with 15% and 20% Ge, focusing on the Ge pileup r...

  9. Symplectic Symmetry and the Ab Initio No-Core Shell Model

    Energy Technology Data Exchange (ETDEWEB)

    Draayer, Jerry P.; Dytrych, Tomas; Sviratcheva, Kristina D.; Bahri, Chairul; /Louisiana State U.; Vary, James P.; /Iowa State U. /LLNL, Livermore /SLAC

    2007-03-14

    The symplectic symmetry of eigenstates for the 0{sub gs}{sup +} in {sup 16}O and the 0{sub gs}{sup +} and lowest 2{sup +} and 4{sup +} configurations of {sup 12}C that are well-converged within the framework of the no-core shell model with the JISP16 realistic interaction is examined. These states are found to project at the 85-90% level onto very few symplectic representations including the most deformed configuration, which confirms the importance of a symplectic no-core shell model and reaffirms the relevance of the Elliott SU(3) model upon which the symplectic scheme is built.

  10. Synthesis of Core-Shell Si O /Carbon Nanofibers on Silicon Substrates by Ultrasonic Spray Pyrolysis

    OpenAIRE

    Zhang, Jianhui; Kishi, Naoki; Soga, Tetsuo; Jimbo, Takashi; Tanji, Takayoshi

    2012-01-01

    We synthesized the core-shell Si O /carbon nanofibers with diameters of 200–300 nm using ultrasonic spray pyrolysis with a phosphorus/ethanol mixture. High-resolution transmission electron microscopy (HRTEM) and energy-dispersive spectroscopy (EDS) investigations confirmed the core-shell structure, which consisted of a core of Si O and a shell of amorphous carbon. The phosphorus atoms corroded the entire silicon substrate surface, and the Si-P liquid-catalyzed the solid-liquid-solid mecha...

  11. Simple Synthesis and Growth Mechanism of Core/Shell CdSe/SiOx Nanowires

    Directory of Open Access Journals (Sweden)

    Guozhang Dai

    2010-01-01

    Full Text Available Core-shell-structured CdSe/SiOx nanowires were synthesized on an equilateral triangle Si (111 substrate through a simple one-step thermal evaporation process. SEM, TEM, and XRD investigations confirmed the core-shell structure; that is, the core zone is single crystalline CdSe and the shell zone is SiOx amorphous layer and CdSe core was grown along (001 direction. Two-stage growth process was present to explain the growth mechanism of the core/shell nanwires. The silicon substrate of designed equilateral triangle providing the silicon source is the key factor to form the core-shell nanowires, which is significant for fabrication of nanowire-core sheathed with a silica system. The PL of the product studied at room temperature showed two emission bands around 715 and 560 nm, which originate from the band-band transition of CdSe cores and the amorphous SiOx shells, respectively.

  12. PEGylated liposome coated QDs/mesoporous silica core-shell nanoparticles for molecular imaging.

    Science.gov (United States)

    Pan, Jie; Wan, Dong; Gong, Jinlong

    2011-03-28

    This paper describes the synthesis and application of PEGylated liposome-coated quantum dots (QDs)/mesoporous silica core-shell nanoparticles (NPs) for molecular imaging. This system increases biocompatibility and stability of QDs, thus improving the imaging effects in labeling of cancer cells.

  13. Electrospun core-shell fibers for robust silicon nanoparticle-based lithium ion battery anodes.

    Science.gov (United States)

    Hwang, Tae Hoon; Lee, Yong Min; Kong, Byung-Seon; Seo, Jin-Seok; Choi, Jang Wook

    2012-02-08

    Because of its unprecedented theoretical capacity near 4000 mAh/g, which is approximately 10-fold larger compared to those of the current commercial graphite anodes, silicon has been the most promising anode for lithium ion batteries, particularly targeting large-scale energy storage applications including electrical vehicles and utility grids. Nevertheless, Si suffers from its short cycle life as well as the limitation for scalable electrode fabrication. Herein, we develop an electrospinning process to produce core-shell fiber electrodes using a dual nozzle in a scalable manner. In the core-shell fibers, commercially available nanoparticles in the core are wrapped by the carbon shell. The unique core-shell structure resolves various issues of Si anode operations, such as pulverization, vulnerable contacts between Si and carbon conductors, and an unstable sold-electrolyte interphase, thereby exhibiting outstanding cell performance: a gravimetric capacity as high as 1384 mAh/g, a 5 min discharging rate capability while retaining 721 mAh/g, and cycle life of 300 cycles with almost no capacity loss. The electrospun core-shell one-dimensional fibers suggest a new design principle for robust and scalable lithium battery electrodes suffering from volume expansion. © 2011 American Chemical Society

  14. Synthesis of magnetically separable Sn doped magnetite/silica core-shell structure and photocatalytic property

    International Nuclear Information System (INIS)

    Wang, Wei-Wei; Yao, Jia-Liang

    2010-01-01

    Sn doped Fe 3 O 4 /SiO 2 core-shell structures with the magnetic and photocatalytic properties have been successfully synthesized using Fe 3 O 4 microspheres as the precursor. The morphology, phase and structure of the bifunctional products were investigated by X-ray powder diffraction, transmission electron microscopy, selected-area electron diffraction, high-resolution transmission electron microscopy, energy dispersive spectroscopy, and scanning electron microscopy. The effects of the amount and hydrolysis rate of tetraethyl orthosilicate on the preparation of the Fe 3 O 4 /SiO 2 core-shell structures were investigated. Low concentration and slow hydrolysis rate of tetraethyl orthosilicate were useful to obtain the uniform silica coated Fe 3 O 4 . The magnetic measurements indicated that the Sn doped Fe 3 O 4 /SiO 2 core-shell structures showed ferromagnetic property and the magnetic saturation value slightly decreased after coated the silica layer. The magnetic Sn doped Fe 3 O 4 /SiO 2 core-shell structures exhibited good photocatalytic activity in the degradation of methyl orange and could be separated by applying an appropriate magnetic field.

  15. Core-shell Au/Ag nanoparticles embedded in silicate sol-gel ...

    Indian Academy of Sciences (India)

    Core-shell Au/Ag nanoparticles embedded in silicate sol-gel network for sensor application towards hydrogen peroxide ... The present study highlights the influence of molar composition of Ag nanoparticles in the Au/Ag bimetallic composition towards the electrocatalytic reduction and sensing of hydrogen peroxide in ...

  16. Non-volatile transistor memory devices using charge storage cross-linked core-shell nanoparticles.

    Science.gov (United States)

    Lo, Chen-Tsyr; Watanabe, Yu; Oya, Hiroshi; Nakabayashi, Kazuhiro; Mori, Hideharu; Chen, Wen-Chang

    2016-06-07

    Solution processable cross-linked core-shell poly[poly(ethylene glycol)methylether methacrylate]-block-poly(2,5-dibromo-3-vinylthiophene) (poly(PEGMA)m-b-poly(DB3VT)n) nanoparticles are firstly explored as charge storage materials for transistor-type memory devices owing to their efficient and controllable ability in electric charge transfer and trapping.

  17. Structural and magnetic properties of CoO-Pt core-shell nanoparticles

    Czech Academy of Sciences Publication Activity Database

    Zeleňáková, A.; Zeleňák, V.; Michalik, Štefan; Kováč, J.; Meisel, M. W.

    2014-01-01

    Roč. 89, č. 10 (2014), "104417-1"-"104417-10" ISSN 1098-0121 Institutional support: RVO:68378271 Keywords : CoO-Pt core shell nanoparticles * superparamagnetism * superspin glass state * x-ray diffraction * x-ray absorption spectroscopy Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 3.736, year: 2014

  18. Morphology and film formation of poly(butyl methacrylate)-polypyrrole core-shell latex particles

    NARCIS (Netherlands)

    Huijs, F; Lang, J

    Core-shell latex particles made of a poly(butyl methacrylate) (PBMA) core and a thin polypyrrole (PPy) shell were synthesized by two-stage polymerization. In the first stage, PBMA latex particles were synthesized in a semicontinuous process by free-radical polymerization. PBMA latex particles were

  19. Nonthermal Plasma Synthesis of Core/Shell Quantum Dots: Strained Ge/Si Nanocrystals.

    Science.gov (United States)

    Hunter, Katharine I; Held, Jacob T; Mkhoyan, K Andre; Kortshagen, Uwe R

    2017-03-08

    In this work, we present an all-gas-phase approach for the synthesis of quantum-confined core/shell nanocrystals (NCs) as a promising alternative to traditional solution-based methods. Spherical quantum dots (QDs) are grown using a single-stage flow-through nonthermal plasma, yielding monodisperse NCs, with a concentric core/shell structure confirmed by electron microscopy. The in-flight negative charging of the NCs by plasma electrons keeps the NC cores separated during shell growth. The success of this gas-phase approach is demonstrated here through the study of Ge/Si core/shell QDs. We find that the epitaxial growth of a Si shell on the Ge QD core compressively strains the Ge lattice and affords the ability to manipulate the Ge band structure by modulation of the core and shell dimensions. This all-gas-phase approach to core/shell QD synthesis offers an effective method to produce high-quality heterostructured NCs with control over the core and shell dimensions.

  20. Fabrication of Core-Shell Nanotube Array for Artificial Photosynthesis Featuring an Ultrathin Composite Separation Membrane.

    Science.gov (United States)

    Edri, Eran; Aloni, Shaul; Frei, Heinz

    2018-01-23

    Macroscale arrays of cobalt oxide-silica core-shell nanotubes with high aspect ratio and ultrathin walls of less than 20 nm have been fabricated. The silica shells feature embedded oligo-para(phenylenevinylene) molecules for charge transport across the insulating silica layer, which is tightly controlled by their electronic properties. The assembly is based on the use of a sacrificial Si nanorod array template combined with atomic layer deposition, covalent anchoring of organic wire molecules, and dry cryo-etching. High-resolution TEM imaging of samples prepared by microtome affords structural details of single core-shell nanotubes. The integrity of silica-embedded organic wire molecules exposed to atomic layer deposition, thermal treatment, and harsh etching procedures is demonstrated by grazing angle ATR FT-IR, FT-Raman, and XPS spectroscopy. The inorganic oxide-based core-shell nanotubes with ultrathin gas-impermeable, proton-conducting silica shells functionalized by molecular wires enable complete nanoscale photosynthetic units for CO 2 reduction by H 2 O under membrane separation. Arrays of massive numbers of such core-shell nanotube units afford a design that extends the separation of the incompatible H 2 O oxidation and CO 2 reduction catalysis environments across the continuum of length scales from nanometers to centimeters.

  1. Controlled Synthesis of Pd/Pt Core Shell Nanoparticles Using Area-selective Atomic Layer Deposition.

    Science.gov (United States)

    Cao, Kun; Zhu, Qianqian; Shan, Bin; Chen, Rong

    2015-02-16

    We report an atomic scale controllable synthesis of Pd/Pt core shell nanoparticles (NPs) via area-selective atomic layer deposition (ALD) on a modified surface. The method involves utilizing octadecyltrichlorosilane (ODTS) self-assembled monolayers (SAMs) to modify the surface. Take the usage of pinholes on SAMs as active sites for the initial core nucleation, and subsequent selective deposition of the second metal as the shell layer. Since new nucleation sites can be effectively blocked by surface ODTS SAMs in the second deposition stage, we demonstrate the successful growth of Pd/Pt and Pt/Pd NPs with uniform core shell structures and narrow size distribution. The size, shell thickness and composition of the NPs can be controlled precisely by varying the ALD cycles. Such core shell structures can be realized by using regular ALD recipes without special adjustment. This SAMs assisted area-selective ALD method of core shell structure fabrication greatly expands the applicability of ALD in fabricating novel structures and can be readily applied to the growth of NPs with other compositions.

  2. Atmospherically relevant core-shell aerosol studied using optical trapping and Mie scattering.

    Science.gov (United States)

    Jones, S H; King, M D; Ward, A D

    2015-03-21

    Solid core-liquid shell aerosols have been trapped in a counter-propagating optical trap confirming potential core-shell morphology in the atmosphere. Mie spectroscopy can be used to measure the core radius and film thickness to 0.5 and 1 nm precision respectively and to measure the wavelength dependent refractive indices of silica (core) and oleic acid (shell).

  3. High thermal stability of core-shell structures dominated by negative interface energy.

    Science.gov (United States)

    Zhu, Yong-Fu; Zhao, Ning; Jin, Bo; Zhao, Ming; Jiang, Qing

    2017-03-29

    Nanoscale core/shell structures are of interest in catalysis due to their superior catalytic properties. Here we investigated the thermal stability of the coherent core-shell structures in a thermodynamic way by considering the impact from the core with the bulk melting point T m (∞) lower or higher than the shell. When a low-T m (∞) core is adopted, core-shell melting induced by the melting depression of the core does not occur upon heating because of the superheating, although the melting depression of the core can be triggered ultimately by the preferential melting of the high-T m (∞) shell for small cores. The superheating of the core is contributed by the negative solid-solid interface energy, while the depression is originated from the positive solid-liquid interface energy. Owing to the presence of the negative interface energy, moreover, the low-T m (∞)-core structure possesses a low difference in thermal expansion between the core and the shell, high activation energy of outward atomic diffusion from the core to shell, and low heat capacity. This result is beneficial for the core-shell structure design for its application in catalysis.

  4. Synthesis and characterization of ZnO/TiO2 composite core/shell ...

    Indian Academy of Sciences (India)

    The optical and electrical properties of the bare TiO2 thin film and core/shell composite were compared together. ... Department of Physics, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran, Iran; Nano Research Lab, Lahijan Branch, Islamic Azad University, P.O. Box 1616, Lahijan, Iran; Department of ...

  5. Core-Shell-structured Dendritic Mesoporous Silica Nanoparticles for Combined Photodynamic Therapy and Antibody Delivery.

    Science.gov (United States)

    Abbaraju, Prasanna Lakshmi; Yang, Yannan; Yu, Meihua; Fu, Jianye; Xu, Chun; Yu, Chengzhong

    2017-07-04

    Multifunctional core-shell-structured dendritic mesoporous silica nanoparticles with a fullerene-doped silica core, a dendritic silica shell and large pores have been prepared. The combination of photodynamic therapy and antibody therapeutics significantly inhibits the cancer cell growth by effectively reducing the level of anti-apoptotic proteins. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Piezoelectric constants for ZnO calculated using classical polarizable core-shell potentials

    International Nuclear Information System (INIS)

    Dai Shuangxing; Dunn, Martin L; Park, Harold S

    2010-01-01

    We demonstrate the feasibility of using classical atomistic simulations, i.e. molecular dynamics and molecular statics, to study the piezoelectric properties of ZnO using core-shell interatomic potentials. We accomplish this by reporting the piezoelectric constants for ZnO as calculated using two different classical interatomic core-shell potentials: that originally proposed by Binks and Grimes (1994 Solid State Commun. 89 921-4), and that proposed by Nyberg et al (1996 J. Phys. Chem. 100 9054-63). We demonstrate that the classical core-shell potentials are able to qualitatively reproduce the piezoelectric constants as compared to benchmark ab initio calculations. We further demonstrate that while the presence of the shell is required to capture the electron polarization effects that control the clamped ion part of the piezoelectric constant, the major shortcoming of the classical potentials is a significant underprediction of the clamped ion term as compared to previous ab initio results. However, the present results suggest that overall, these classical core-shell potentials are sufficiently accurate to be utilized for large scale atomistic simulations of the piezoelectric response of ZnO nanostructures.

  7. Analysis of Completely Prevaporized Spray Flames with Water/Octane Core/Shell Structured Droplets

    Directory of Open Access Journals (Sweden)

    Chung-Yao Hsuan

    2015-01-01

    Full Text Available A series of studies on laminar flame propagation in off-stoichiometric dilute sprays of monodispersed inert or fuel drops had been investigated by large activation energy asymptotics. The present study extends previous theoretical model to consider water/octane core/shell structured drops instead of single-phase drops. The core/shell structured drops are composed of core fluid (water encased by a layer of shell fluid (n-octane. In this study, we only deal with the case that core/shell structured drops are vaporized completely just at flame location. Namely, the discussions of this paper are restricted to the completely prevaporized mode. By varying parameters of core water radius, core-to-shell ratio, the amount of liquid loading, and the stoichiometric ratio (lean or rich burning, we examine the gasification of core water and shell fuel of core/shell structured drops upstream of the bulk flame and its relation to the internal heat transfer. The effects of drop radius, core-to-shell ratio, liquid loading, and overall heat loss or gain on flame propagation flux are reported and discussed.

  8. Core-Shell Composite Fibers for High-Performance Flexible Supercapacitor Electrodes.

    Science.gov (United States)

    Lu, Xiaoyan; Shen, Chen; Zhang, Zeyang; Barrios, Elizabeth; Zhai, Lei

    2018-01-31

    Core-shell nanofibers containing poly(acrylic acid) (PAA) and manganese oxide nanoparticles as the core and polypyrrole (PPy) as the shell were fabricated through electrospinning the solution of PAA and manganese ions (PAA/Mn 2+ ). The obtained nanofibers were stabilized by Fe 3+ through the interaction between Fe 3+ ions and carboxylate groups. Subsequent oxidation of Mn 2+ by KMnO 4 produced uniform manganese dioxide (MnO 2 ) nanoparticles in the fibers. A PPy shell was created on the fibers by immersing the fibers in a pyrrole solution where the Fe 3+ ions in the fiber polymerized the pyrrole on the fiber surfaces. In the MnO 2 @PAA/PPy core-shell composite fibers, MnO 2 nanoparticles function as high-capacity materials, while the PPy shell prevents the loss of MnO 2 during the charge/discharge process. Such a unique structure makes the composite fibers efficient electrode materials for supercapacitors. The gravimetric specific capacity of the MnO 2 @PAA/PPy core-shell composite fibers was 564 F/g based on cyclic voltammetry curves at 10 mV/s and 580 F/g based on galvanostatic charge/discharge studies at 5 A/g. The MnO 2 @PAA/PPy core-shell composite fibers also present stable cycling performance with 100% capacitance retention after 5000 cycles.

  9. Shell morphology of core-shell latexes based on conductive polymers

    NARCIS (Netherlands)

    Huijs, F.M; Vercauteren, F.F.; de Ruiter, B.; Kalicharan, D; Hadziioannou, G

    Core-shell latexes with a conductive shell can be used to prepare transparent conducting layers. We have focussed on the relation between the conducting polymer content and the shell morphology and on its influence on conductivity. At low polypyrrole (PPy) concentrations the shell has a smooth

  10. Synthesis and characterization of ZnO/TiO2 composite core/shell ...

    Indian Academy of Sciences (India)

    Abstract. ZnO/TiO2 core/shell nanorod arrays were deposited on indium tin oxide (ITO) substrate via a facile sol–gel dip-coating process. Effects of solution pH for ZnO, annealing temperature, growth time and temperature on the physical properties of nanorods have been investigated. X-ray diffraction (XRD) analysis and ...

  11. Strippable core-shell polymer emulsion for decontamination of radioactive surface contamination

    International Nuclear Information System (INIS)

    Hwang, Ho-Sang; Seo, Bum-Kyoung; Lee, Kune-Woo

    2011-01-01

    In this study, the core-shell composite polymer for decontamination from the surface contamination was synthesized by the method of emulsion polymerization and blends of polymers. The strippable polymer emulsion is composed of the poly(styrene-ethyl acrylate) [poly(St-EA)] composite polymer, poly(vinyl alcohol) (PVA) and polyvinylpyrrolidone (PVP). The morphology of the poly(St-EA) composite emulsion particle was core-shell structure, with polystyrene (PS) as the core and poly(ethyl acrylate) (PEA) as the shell. Core-shell polymers of styrene (St)/ethyl acrylate (EA) pair were prepared by sequential emulsion polymerization in the presence of sodium dodecyl sulfate (SDS) as an emulsifier using ammonium persulfate (APS) as an initiator. Related tests and analysis confirmed the success in synthesis of composite polymer. The products are characterized by FT-IR spectroscopy, TGA that were used, respectively, to show the structure, the thermal stability of the prepared polymer. Two-phase particles with a core-shell structure were obtained in experiments where the estimated glass transition temperature and the morphologies of emulsion particles. Decontamination factors of the strippable polymeric emulsion were evaluated with the polymer blend contents. (author)

  12. Synthesis and characterization of silica–gold core-shell (SiO2@Au ...

    Indian Academy of Sciences (India)

    Synthesis and characterization of silica–gold core-shell (SiO2@Au) nanoparticles. DEEPIKA KANDPAL. 1,∗. , SUCHITA KALELE. 2 and S K KULKARNI. 2. 1. Department of Physics, G.B. Pant University of Agriculture & Technology,. Pantnagar 263 145, India. 2. Department of Physics, University of Pune, Pune 411 007, ...

  13. Synthesis and Characterization of Core-Shell Acrylate Based Latex and Study of Its Reactive Blends

    Directory of Open Access Journals (Sweden)

    Ying Nie

    2008-03-01

    Full Text Available Techniques in resin blending are simple and efficient method for improving the properties of polymers, and have been used widely in polymer modification field. However, polymer latex blends such as the combination of latexes, especially the latexes with water-soluble polymers, were rarely reported. Here, we report a core-shell composite latex synthesized using methyl methacrylate (MMA, butyl acrylate (BA, 2-ethylhexyl acrylate (EHA and glycidyl methacrylate (GMA as monomers and ammonium persulfate and sodium bisulfite redox system as the initiator. Two stages seeded semi-continuous emulsion polymerization were employed for constructing a core-shell structure with P(MMA-co-BA component as the core and P(EHA-co-GMA component as the shell. Results of Transmission Electron Microscopy (TEM and Dynamics Light Scattering (DLS tests confirmed that the particles obtained are indeed possessing a desired core-shell structural character. Stable reactive latex blends were prepared by adding the latex with waterborne melamine-formaldehyde resin (MF or urea-formaldehyde resin (UF. It was found that the glass transition temperature, the mechanical strength and the hygroscopic property of films cast from the latex blends present marked enhancements under higher thermal treatment temperature. It was revealed that the physical properties of chemically reactive latexes with core-shell structure could be altered via the change of crosslinking density both from the addition of crosslinkers and the thermal treatment.

  14. Comparison of methanol and ethylene glycol oxidation by alloy and Core-Shell platinum based catalysts

    Science.gov (United States)

    Kaplan, D.; Burstein, L.; Rosenberg, Yu.; Peled, E.

    2011-10-01

    Two Core-Shell, RuCore-PtShell and IrNiCore-PtRuShell, XC72-supported catalyst were synthesized in a two-step deposition process with NaBH4 as reducing agent. The structure and composition of the Core-Shell catalysts were determined by EDS, XPS and XRD. Electrochemical characterization was performed with the use of cyclic voltammetry. Methanol and ethylene glycol oxidation activities of the Core-Shell catalysts (in terms of surface and mass activities) were studied at 80 °C and compared to those of a commercial Pt-Ru alloy catalyst. The surface activity of the alloy based catalyst, in the case of methanol oxidation, was found to be superior as a result of optimized surface Pt:Ru composition. However, the mass activity of the PtRu/IrNi/XC72 was higher than that of the alloy based catalyst by ∼50%. Regarding ethylene glycol oxidation, while the surface activity of the alloy based catalyst was slightly higher than that of the Pt/Ru/XC72 catalyst, the latter showed ∼66% higher activities in terms of A g-1 of Pt. These results show the potential of Core-Shell catalysts for reducing the cost of catalysts for DMFC and DEGFC.

  15. Aqueous-Based Coaxial Electrospinning of Genetically Engineered Silk Elastin Core-Shell Nanofibers

    Directory of Open Access Journals (Sweden)

    Jingxin Zhu

    2016-03-01

    Full Text Available A nanofabrication method for the production of flexible core-shell structured silk elastin nanofibers is presented, based on an all-aqueous coaxial electrospinning process. In this process, silk fibroin (SF and silk-elastin-like protein polymer (SELP, both in aqueous solution, with high and low viscosity, respectively, were used as the inner (core and outer (shell layers of the nanofibers. The electrospinnable SF core solution served as a spinning aid for the nonelectrospinnable SELP shell solution. Uniform nanofibers with average diameter from 301 ± 108 nm to 408 ± 150 nm were obtained through adjusting the processing parameters. The core-shell structures of the nanofibers were confirmed by fluorescence and electron microscopy. In order to modulate the mechanical properties and provide stability in water, the as-spun SF-SELP nanofiber mats were treated with methanol vapor to induce β-sheet physical crosslinks. FTIR confirmed the conversion of the secondary structure from a random coil to β-sheets after the methanol treatment. Tensile tests of SF-SELP core-shell structured nanofibers showed good flexibility with elongation at break of 5.20% ± 0.57%, compared with SF nanofibers with an elongation at break of 1.38% ± 0.22%. The SF-SELP core-shell structured nanofibers should provide useful options to explore in the field of biomaterials due to the improved flexibility of the fibrous mats and the presence of a dynamic SELP layer on the outer surface.

  16. Simultaneous inhibition of aberrant cancer kinome using rationally designed polymer-protein core-shell nanomedicine.

    Science.gov (United States)

    Chandran, Parwathy; Gupta, Neha; Retnakumari, Archana Payickattu; Malarvizhi, Giridharan Loghanathan; Keechilat, Pavithran; Nair, Shantikumar; Koyakutty, Manzoor

    2013-11-01

    Simultaneous inhibition of deregulated cancer kinome using rationally designed nanomedicine is an advanced therapeutic approach. Herein, we have developed a polymer-protein core-shell nanomedicine to inhibit critically aberrant pro-survival kinases (mTOR, MAPK and STAT5) in primitive (CD34(+)/CD38(-)) Acute Myeloid Leukemia (AML) cells. The nanomedicine consists of poly-lactide-co-glycolide core (~250 nm) loaded with mTOR inhibitor, everolimus, and albumin shell (~25 nm thick) loaded with MAPK/STAT5 inhibitor, sorafenib and the whole construct was surface conjugated with monoclonal antibody against CD33 receptor overexpressed in AML. Electron microscopy confirmed formation of core-shell nanostructure (~290 nm) and flow cytometry and confocal studies showed enhanced cellular uptake of targeted nanomedicine. Simultaneous inhibition of critical kinases causing synergistic lethality against leukemic cells, without affecting healthy blood cells, was demonstrated using immunoblotting, cytotoxicity and apoptosis assays. This cell receptor plus multi-kinase targeted core-shell nanomedicine was found better specific and tolerable compared to current clinical regime of cytarabine and daunorubicin. These authors demonstrate simultaneous inhibition of critical kinases causing synergistic lethality against leukemic cells, without affecting healthy blood cells by using rationally designed polymer-protein core-shell nanomedicine, provoding an advanced method to eliminate cancer cells, with the hope of future therapeutic use. Copyright © 2013 Elsevier Inc. All rights reserved.

  17. Transferrin targeted core-shell nanomedicine for combinatorial delivery of doxorubicin and sorafenib against hepatocellular carcinoma.

    Science.gov (United States)

    Malarvizhi, Giridharan Loghanathan; Retnakumari, Archana Payickattu; Nair, Shantikumar; Koyakutty, Manzoor

    2014-11-01

    Combinatorial drug delivery is an attractive, but challenging requirement of next generation cancer nanomedicines. Here, we report a transferrin-targeted core-shell nanomedicine formed by encapsulating two clinically used single-agent drugs, doxorubicin and sorafenib against liver cancer. Doxorubicin was loaded in poly(vinyl alcohol) nano-core and sorafenib in albumin nano-shell, both formed by a sequential freeze-thaw/coacervation method. While sorafenib from the nano-shell inhibited aberrant oncogenic signaling involved in cell proliferation, doxorubicin from the nano-core evoked DNA intercalation thereby killing >75% of cancer cells. Upon targeting using transferrin ligands, the nanoparticles showed enhanced cellular uptake and synergistic cytotoxicity in ~92% of cells, particularly in iron-deficient microenvironment. Studies using 3D spheroids of liver tumor indicated efficient penetration of targeted core-shell nanoparticles throughout the tissue causing uniform cell killing. Thus, we show that rationally designed core-shell nanoparticles can effectively combine clinically relevant single-agent drugs for exerting synergistic activity against liver cancer. Transferrin-targeted core-shell nanomedicine encapsulating doxorubicin and sorafenib was studied as a drug delivery system against hepatocellular carcinoma, resulting in enhanced and synergistic therapeutic effects, paving the way towards potential future clinical applications of similar techniques. Copyright © 2014 Elsevier Inc. All rights reserved.

  18. Toward "Green" Hybrid Materials: Core-Shell Particles with Enhanced Impact Energy Absorbing Ability.

    Science.gov (United States)

    Arias, Veluska; Odent, Jeremy; Raquez, Jean-Marie; Dubois, Philippe; Odelius, Karin; Albertsson, Ann-Christine

    2016-07-05

    Restrained properties of "green" degradable products drive the creation of materials with innovative structures and retained eco-attributes. Herein, we introduce the creation of impact modifiers in the form of core-shell (CS) particles toward the creation of "green" composite materials. Particles with CS structure constituted of PLA stereocomplex (PLASC) and a rubbery phase of poly(ε-caprolactone- co -d,l-lactide) (P[CL- co -LA]) were successfully achieved by spray droplet atomization. A synergistic association of the soft P[CL- co -LA] and hard PLASC domains in the core-shell structure induced unique thermo-mechanical effects on the PLA-based composites. The core-shell particles enhanced the crystallization of PLA matrices by acting as nucleating agents. The core-shell particles functioned efficiently as impact modifiers with minimal effect on the composites stiffness and strength. These findings provide a new platform for scalable design of polymeric-based structures to be used in the creation of advanced degradable materials.

  19. In Situ Synthesis of Catalytic Active Au Nanoparticles onto Gibbsite-Polydopamine Core-Shell Nanoplates.

    Science.gov (United States)

    Cao, Jie; Mei, Shilin; Jia, He; Ott, Andreas; Ballauff, Matthias; Lu, Yan

    2015-09-01

    We report a facile method to synthesize anisotropic platelike gibbsite-polymer core-shell particles. Dopamine is self-polymerized on the surface of gibbsite nanoplates and forms a homogeneous layer on it. Transmission electron microscopy characterization of the resulting latexes demonstrates the formation of well-defined platelike core-shell particles. Reaction time and ultrasonification are found to be important factors to control the thickness of the polymer shell and avoid aggregation. Good control over the platelike morphology and 100% encapsulation efficiency have been achieved via this novel route. The resulting well-defined gibbsite-polydamine (G-PDA) core-shell nanoplates show excellent colloidal stability and can form opal-like columnar crystal with iridescent Bragg reflection after modest centrifugation. In addition, G-PDA core-shell nanoplates can serve both as reductant and stabilizer for the generation of Au nanoparticles (NPs) in situ. Au NPs with tunable size have been formed on the G-PDA particle surface, which show efficient catalytic activity for the reduction of 4-nitrophenol and Rhodamine B (RhB) in the presence of borohydride. Such nanocatalysts can be easily deposited on silicon substrate by spin-coating due to the large contact area of platelike G-PDA particles and the strong adhesive behavior of the PDA layer. The substrate-deposited nanocatalyst can be easily recycled which show excellent reusability for the reduction of RhB.

  20. Blends of polyamide-6 with acrylic core-shell impact modifiers

    NARCIS (Netherlands)

    Gaymans, R.J.; van der Werff, J.W.

    1994-01-01

    Blends of polyamide-6 (PA6) and acrylic core-shell impact modifiers (CSIM) were made by an extruder process as well as a reactor process. On the extruder blends, the impact behaviour was studied as a function of temperature while changing the type of CSIM, the CSIM concentration (0¿40%) and the

  1. Facile microfluidic production of composite polymer core-shell microcapsules and crescent-shaped microparticles.

    Science.gov (United States)

    Ekanem, Ekanem E; Zhang, Zilin; Vladisavljević, Goran T

    2017-07-15

    Core-shell microcapsules and crescent-shaped microparticles can be used as picolitre bioreactors for cell culture and microwells for cell trapping/immobilisation, respectively. Monodisperse polylactic acid (PLA) core-shell microcapsules with a diameter above 200μm, a shell thickness of 10μm, and 96% water entrapment efficiency were produced by solvent evaporation from microfluidically generated W/O/W emulsion drops with core-shell structure, and used to encapsulate Saccharomyces cerevisiae yeast cells in their aqueous cores. The morphological changes of the capsules stained with Nile red were studied over 14days under different osmotic pressure and pH gradients. The shell retained its integrity under isotonic conditions, but buckling and particle crumbling occurred in a hypertonic solution. When the capsules containing 5wt% aqueous Eudragit® S 100 solution in the core were incubated in 10 -4 M HCl solution, H + diffused through the PLA film into the core causing an ionic gelation of the inner phase and its phase separation into polymer-rich and water-rich regions, due to the transition of Eudragit from a hydrophilic to hydrophobic state. Crescent-shaped composite microparticles with Eudragit cores and PLA shells were fabricated by drying core-shell microcapsules with gelled cores, due to the collapse of PLA shells encompassing water-rich crescent regions. Copyright © 2017 Elsevier Inc. All rights reserved.

  2. Microfluidic production of perfluorocarbon-alginate core-shell microparticles for ultrasound therapeutic applications.

    Science.gov (United States)

    Duarte, Ana Rita C; Ünal, Barış; Mano, João F; Reis, Rui L; Jensen, Klavs F

    2014-10-21

    The fabrication of micrometer-sized core-shell particles for ultrasound-triggered delivery offers a variety of applications in medical research. In this work, we report the design and development of a glass capillary microfluidic system containing three concentric glass capillary tubes for the development of core-shell particles. The setup enables the preparation of perfluorocarbon-alginate core-shell microspheres in a single process, avoiding the requirement for further extensive purification steps. Core-shell microspheres in the range of 110-130 μm are prepared and are demonstrated to be stable up to 21 days upon immersion in calcium chloride solution or water. The mechanical stability of the particles is tested by injecting them through a 23 gauge needle into a polyacrylamide gel to mimic the tissue matrix. The integrity of the particles is maintained after the injection process and is disrupted after ultrasound exposure for 15 min. The results suggest that the perfluorcarbon-alginate microparticles could be a promising system for the delivery of compounds, such as proteins, peptides, and small-molecule drugs in ultrasound-based therapies.

  3. In vitro release profiles of PLGA core-shell composite particles loaded with theophylline and budesonide.

    Science.gov (United States)

    Yeh, Hsi-Wei; Chen, Da-Ren

    2017-08-07

    We investigated the effects of drug loading location, matrix material and shell thickness on the in vitro release of combinational drugs from core-shell PLGA (i.e., poly(lactic-co-glycolic acid)) particles. Budesonide and Theophylline were selected as highly hydrophobic and hydrophilic model drugs, respectively. The dual-capillary electrospray (ES) technique, operated at the cone-jet mode, was used to produce samples of drug-loaded core-shell composite particles with selected overall sizes, polymer materials, and shell thicknesses. Theophylline and Budesonide were loaded at different locations in a PLGA composite particle. This study illustrated how the aforementioned factors affect the release rates of Budesonide and Theophylline loaded in core-shell PLGA composites. We further identified that core-shell composite particles with both model drugs loaded in the core and with matrix PLGA polymers of low molecular weights and low LA/GA ratios are the best formulation for the sustained release of highly hydrophilic and hydrophobic active pharmaceutical ingredients from PLGA composite particles. The formulation strategy obtained in this study can be in principle generalized for biopharmaceutical applications in fixed-dose combination therapy. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Platinum-coated non-noble metal-noble metal core-shell electrocatalysts

    Science.gov (United States)

    Adzic, Radoslav; Zhang, Junliang; Mo, Yibo; Vukmirovic, Miomir

    2015-04-14

    Core-shell particles encapsulated by a thin film of a catalytically active metal are described. The particles are preferably nanoparticles comprising a non-noble core with a noble metal shell which preferably do not include Pt. The non-noble metal-noble metal core-shell nanoparticles are encapsulated by a catalytically active metal which is preferably Pt. The core-shell nanoparticles are preferably formed by prolonged elevated-temperature annealing of nanoparticle alloys in an inert environment. This causes the noble metal component to surface segregate and form an atomically thin shell. The Pt overlayer is formed by a process involving the underpotential deposition of a monolayer of a non-noble metal followed by immersion in a solution comprising a Pt salt. A thin Pt layer forms via the galvanic displacement of non-noble surface atoms by more noble Pt atoms in the salt. The overall process is a robust and cost-efficient method for forming Pt-coated non-noble metal-noble metal core-shell nanoparticles.

  5. Synthesis of core-shell Y2O3 nanoparticles for enhanced luminescence efficiency

    Science.gov (United States)

    Choi, Ju H.; Hyun, Jae Y.; Kim, Ki H.; Kim, Jae P.

    2013-09-01

    In this works, rare earth ion doped core and core-shell Y2O3 phosphors have been extensively studied for many applications due to the high stability and emission range and intensity. The core-shell Y2O3: (RE= Eu, Dy, Tb) nanoparticles are synthesized using a two-step process in which 100-150 nm Y2O3 core particles are synthesized using a molten salt synthesis and the shell is deposited using a sol-gel process The core-shell architecture was designed for enhanced luminescence efficiency with long emission lifetimes. Specifically, a multi-shell architecture was necessary to spatially separate Dy3+, Eu3+ and Tb3+ within the phosphor to circumvent the energy transfer to the surface quenching sites. First, the crystallinity of Y2O3nanophosphors was characterized using X-ray analysis. RE-doped Y2O3 core nanoparticles have a good compositional homogeneity. We have also recorded emission spectra and measured fluorescence lifetime. After coating passive shell layer, emission spectra and measured emission lifetimes were compared with those form Y2O3 nanophosphor core system and the effectiveness of these core-shell phosphors were successfully assessed.

  6. Rayleigh like scattering from silica–titania core-shell particles and ...

    Indian Academy of Sciences (India)

    of light with these kind of particles. 2. Theory of scattering of light from core-shell particles. Interaction of electromagnetic radiation with particles is well studied. The classical theory by Mie (1908) gives an analy- tical solution for scattering from homogenous particles. Theoretical studies to characterize the optical properties of.

  7. Peptide Microencapsulation by Core-Shell Printing Technology for Edible Film Application

    NARCIS (Netherlands)

    Blanco-Pascual, N.; Koldeweij, R.B.J.; Stevens, R.S.A.; Montero, M.P.; Gómez-Guillén, M.C.; Cate, A.T.T.

    2014-01-01

    This paper presents a new microencapsulation methodology for incorporation of functional ingredients in edible films. Core-shell microcapsules filled with demineralized water (C) or 1 % (w/v) peptide solution (Cp) were prepared using the microencapsulation printer technology. Shell material,

  8. First-Principles Modeling of Core/Shell Quantum Dot Sensitized Solar Cells

    NARCIS (Netherlands)

    Azpiroz, Jon Mikel; Infante, Ivan; De Angelis, Filippo

    2015-01-01

    We report on the density functional theory (DFT) modeling of core/shell quantum dot (QD) sensitized solar cells (QDSSCs), a device architecture that holds great potential in photovoltaics but has not been fully exploited so far. To understand the working mechanisms of this kind of solar cells, we

  9. Tunable Band Gap and Conductivity Type of ZnSe/Si Core-Shell Nanowire Heterostructures

    Directory of Open Access Journals (Sweden)

    Yijie Zeng

    2014-10-01

    Full Text Available The electronic properties of zincblende ZnSe/Si core-shell nanowires (NWs with a diameter of 1.1–2.8 nm are calculated by means of the first principle calculation. Band gaps of both ZnSe-core/Si-shell and Si-core/ZnSe-shell NWs are much smaller than those of pure ZnSe or Si NWs. Band alignment analysis reveals that the small band gaps of ZnSe/Si core-shell NWs are caused by the interface state. Fixing the ZnSe core size and enlarging the Si shell would turn the NWs from intrinsic to p-type, then to metallic. However, Fixing the Si core and enlarging the ZnSe shell would not change the band gap significantly. The partial charge distribution diagram shows that the conduction band maximum (CBM is confined in Si, while the valence band maximum (VBM is mainly distributed around the interface. Our findings also show that the band gap and conductivity type of ZnSe/Si core-shell NWs can be tuned by the concentration and diameter of the core-shell material, respectively.

  10. CuO/ZnO core/shell heterostructure nanowire arrays: synthesis, optical property, and energy application.

    Science.gov (United States)

    Zhao, Xinhong; Wang, Peng; Li, Baojun

    2010-09-28

    Aligned CuO nanowires (NWs) were synthesized by a simple cost-effective oxidation method. They act as cores; high density CuO/ZnO core/shell heterostructure NWs were fabricated by thermal decomposition. Using the core/shell heterostructure NWs as a photoelectrode, a 0.71% photo-to-hydrogen conversion efficiency was obtained from photoelectrochemical water decomposition.

  11. Electrochemical Performance of GeO2/C Core Shell based Electrodes for Li-ion Batteries

    DEFF Research Database (Denmark)

    Ngo, Duc Tung; Kalubarme, Ramchandra S.; Chourashiya, M. G.

    2014-01-01

    In the present study, a nanocrystalline GeO2/C core shell was synthesized by a cost-effective and simple citric-gel method for various parameters, and the effects of these parameters on the microstructural and electrochemical properties of the GeO2/C core shell were investigated. Thermo-gravimetr...

  12. Shape-controlled synthesis of Au@Pd core-shell nanoparticles and their corresponding electrochemical properties

    KAUST Repository

    Song, Hyon Min

    2012-01-01

    The shape-controlled synthesis of Au@Pd core-shell nanoparticles (NPs) was successfully achieved through the emulsion phase generated during the phase transfer from organic to aqueous medium. Contrary to conventional epitaxial growth for obtaining core-shell structures, this method does not require high temperatures and does not have shape restrictions. © 2012 The Royal Society of Chemistry.

  13. Processing effects on core-shell grain formation in zirconium dioxide-modified barium titanate ceramics

    Science.gov (United States)

    Zhou, Lei

    2001-07-01

    Formation of core-shell grains in BaTiO3 based dielectric ceramics is essential to achieve stable dielectric temperature characteristic. This grain core-shell structure consists of a grain core, which is high purity BaTiO3, ferroelectric, and a paraelectric grain shell, where there is a concentration gradient of dopant. Most commonly core-shell additives are ZrO2, CeO2, Nb2O5+CO 2O3. As a result, internal stress is generated due to this dopant inhomogeneity within the grain and the normally sharp phase transition at Curie point becomes diffused. Up to now understanding and control of core-shell grains in BaTiO3 ceramics is still far from satisfying, which is the basis of this thesis work. In this work, processing influences on core-shell grain formation were investigated in the terms of powder size, stoichiometry, particle surface modification by slurry pH and leached Ba2+, pressing pressure and additive effects such as ZrO2, Nd2O3, BaO and flux CuO, BaCuO2, followed by multiple regression analysis to identify significant variables so as to form core-shell grains in a controller manner. It is found that ZrO2 amount; powder size, stoichiometry and temperature/time are most significant in control of core-shell characteristic (low Deltaepsilon% slurry pH; with adequate eutectic liquid phase, uniformly distributed fine grain morphology was achieved with high sintered densities. A dielectric formulation of 0.8˜1.3 wt% ZrO2, and 3 m/o BaCuO2 and 0.1˜0.3 m/o Nd2 O3 was successfully developed to be sintered at 1055˜1085°C/45˜90 min with Deltaepsilon% < 25%. This formulation has the potential to be co-fired with base metal electrodes.

  14. Core-shell nanophosphor architecture: toward efficient energy transport in inorganic/organic hybrid solar cells.

    Science.gov (United States)

    Li, Qinghua; Yuan, Yongbiao; Chen, Zihan; Jin, Xiao; Wei, Tai-huei; Li, Yue; Qin, Yuancheng; Sun, Weifu

    2014-08-13

    In this work, a core-shell nanostructure of samarium phosphates encapsulated into a Eu(3+)-doped silica shell has been successfully fabricated, which has been confirmed by X-ray diffraction, transmission electron microscopy (TEM), and high-resolution TEM. Moreover, we report the energy transfer process from the Sm(3+) to emitters Eu(3+) that widens the light absorption range of the hybrid solar cells (HSCs) and the strong enhancement of the electron-transport of TiO2/poly(3-hexylthiophene) (P3HT) bulk heterojunction (BHJ) HSCs by introducing the unique core-shell nanoarchitecture. Furthermore, by applying femtosecond transient absorption spectroscopy, we successfully obtain the electron transport lifetimes of BHJ systems with or without incorporating the core-shell nanophosphors (NPs). Concrete evidence has been provided that the doping of core-shell NPs improves the efficiency of electron transfers from donor to acceptor, but the hole transport almost remains unchanged. In particular, the hot electron transfer lifetime was shortened from 30.2 to 16.7 ps, i.e., more than 44% faster than pure TiO2 acceptor. Consequently, a notable power conversion efficiency of 3.30% for SmPO4@Eu(3+):SiO2 blended TiO2/P3HT HSCs is achieved at 5 wt % as compared to 1.98% of pure TiO2/P3HT HSCs. This work indicates that the core-shell NPs can efficiently broaden the absorption region, facilitate electron-transport of BHJ, and enhance photovoltaic performance of inorganic/organic HSCs.

  15. Design and intestinal mucus penetration mechanism of core-shell nanocomplex.

    Science.gov (United States)

    Zhang, Xin; Cheng, Hongbo; Dong, Wei; Zhang, Meixia; Liu, Qiaoyu; Wang, Xiuhua; Guan, Jian; Wu, Haiyang; Mao, Shirui

    2018-02-28

    The objective of this study was to design intestinal mucus-penetrating core-shell nanocomplex by functionally mimicking the surface of virus, which can be used as the carrier for peroral delivery of macromolecules, and further understand the influence of nanocomplex surface properties on the mucosal permeation capacity. Taking insulin as a model drug, the core was formed by the self-assembly among positively charged chitosan, insulin and negatively charged sodium tripolyphosphate, different types of alginates were used as the shell forming material. The nanocomplex was characterized by dynamic light scattering (DLS), atomic force microscopy (AFM) and FTIR. Nanocomplex movement in mucus was recorded using multiple particle tracking (MPT) method. Permeation and uptake of different nanocomplex were studied in rat intestine. It was demonstrated that alginate coating layer was successfully formed on the core and the core-shell nanocomplex showed a good physical stability and improved enzymatic degradation protection. The mucus penetration and MPT study showed that the mucus penetration capacity of the nanocomplex was surface charge and coating polymer structure dependent, nanocomplex with negative alginate coating had 1.6-2.5 times higher mucus penetration ability than that of positively charged chitosan-insulin nanocomplex. Moreover, the mucus penetration ability of the core-shell nanocomplex was alginate structure dependent, whereas alginate with lower G content and lower molecular weight showed the best permeation enhancing ability. The improvement of intestine permeation and intestinal villi uptake of the core-shell nanocomplex were further confirmed in rat intestine and multiple uptake mechanisms were involved in the transport process. In conclusion, core-shell nanocomplex composed of oppositely charged materials could provide a strategy to overcome the mucus barrier and enhance the mucosal permeability. Copyright © 2018 Elsevier B.V. All rights reserved.

  16. Lithography-free shell-substrate isolation for core-shell GaAs nanowires.

    Science.gov (United States)

    Haggren, Tuomas; Perros, Alexander Pyymaki; Jiang, Hua; Huhtio, Teppo; Kakko, Joona-Pekko; Dhaka, Veer; Kauppinen, Esko; Lipsanen, Harri

    2016-07-08

    A facile and scalable lithography-free technique(5) for the rapid construction of GaAs core-shell nanowires incorporating shell isolation from the substrate is reported. The process is based on interrupting NW growth and applying a thin spin-on-glass (SOG) layer to the base of the NWs and resuming core-shell NW growth. NW growth occurred in an atmospheric pressure metalorganic vapour phase epitaxy (MOVPE) system with gold nanoparticles used as catalysts for the vapour-liquid-solid growth. It is shown that NW axial core growth and radial shell growth can be resumed after interruption and even exposure to air. The SOG residues and native oxide layer that forms on the NW surface are shown to prevent or perturb resumption of epitaxial NW growth if not removed. Both HF etching and in situ annealing of the air-exposed NWs in the MOVPE were shown to remove the SOG residues and native oxide layer. While both procedures are shown capable of removing the native oxide and enabling resumption of epitaxial NW growth, in situ annealing produced the best results and allowed construction of pristine core-shell NWs. No growth occurred on SOG and it was observed that axial NW growth was more rapid when a SOG layer covered the substrate. The fabricated p-core/n-shell NWs exhibited diode behaviour upon electrical testing. The isolation of the NW shells from the substrate was confirmed by scanning electron microscopy and electrical measurements. The crystal quality of the regrown core-shell NWs was verified with a high resolution transmission electron microscope. The reported technique potentially provides a pathway using MOVPE for scalable and high-throughput production of shell-substrate isolated core-shell NWs on an industrial scale.

  17. Fabrication and Characterization of ZnS/Diamond-Like Carbon Core-Shell Nanowires

    Directory of Open Access Journals (Sweden)

    Jung Han Kim

    2016-01-01

    Full Text Available We fabricated ZnS/diamond-like carbon (DLC core-shell heterostructure nanowire using a simple two-step process: the vapor-liquid-solid method combined with radio frequency plasma enhanced chemical vapor deposition (rf PECVD. As a core nanowire, ZnS nanowires with face-centered cubic structure were synthesized with a sputtered Au thin film, which exhibit a length and a diameter of ~10 μm and ~30–120 nm . After rf PECVD for DLC coating, The length and width of the dense ZnS/DLC core-shell nanowires were a range of ~10 μm  and 50–150 nm , respectively. In addition, ZnS/DLC core-shell nanowires were characterized with scanning transmission electron microscopy. From the results, the products have flat and uniform DLC coating layer on ZnS nanowire in spite of high residual stress induced by the high sp3 fraction. To further understanding of the DLC coating layer, Raman spectroscopy was employed with ZnS/DLC core-shell nanowires, which reveals two Raman bands at 1550 cm−1 (G peak and 1330 cm−1 (D peak. Finally, we investigated the optical properties from ultraviolet to infrared wavelength region using ultraviolet-visible (UV-Vis and Fourier transform infrared (FT-IR spectrometry. Related to optical properties, ZnS/DLC core-shell nanowires exhibit relatively lower absorbance and higher IR transmittance than that of ZnS nanowires.

  18. Spherical core-shell magnetic particles constructed by main-chain palladium N-heterocyclic carbenes

    Science.gov (United States)

    Zhao, Huaixia; Li, Liuyi; Wang, Jinyun; Wang, Ruihu

    2015-02-01

    The encapsulation of the functional species on magnetic core is a facile approach for the synthesis of core-shell magnetic materials, and surface encapsulating matrices play crucial roles in regulating their properties and applications. In this study, two core-shell palladium N-heterocyclic carbene (NHC) particles (Fe3O4@PNP1 and Fe3O4@PNP2) were prepared by a one-pot reaction of semi-rigid tripodal imidazolium salts and palladium acetate in the presence of magnetite nanoparticles. The magnetite nanoparticles are encapsulated inside the main-chain palladium, which act as cores. The conjugated effects of triphenyltriazine and triphenylbenzene in the imidazolium salts have important influence on their physical properties and catalytic performances. Fe3O4@PNP2 shows better recyclability than Fe3O4@PNP1. Unexpectedly, Pd(ii) is well maintained after six consecutive catalytic runs in Fe3O4@PNP2, and Pd(0) and Pd(ii) coexist in Fe3O4@PNP1 under the same conditions; moreover, the morphologies of these spherical core-shell particles show no significant variation after six consecutive catalytic runs.The encapsulation of the functional species on magnetic core is a facile approach for the synthesis of core-shell magnetic materials, and surface encapsulating matrices play crucial roles in regulating their properties and applications. In this study, two core-shell palladium N-heterocyclic carbene (NHC) particles (Fe3O4@PNP1 and Fe3O4@PNP2) were prepared by a one-pot reaction of semi-rigid tripodal imidazolium salts and palladium acetate in the presence of magnetite nanoparticles. The magnetite nanoparticles are encapsulated inside the main-chain palladium, which act as cores. The conjugated effects of triphenyltriazine and triphenylbenzene in the imidazolium salts have important influence on their physical properties and catalytic performances. Fe3O4@PNP2 shows better recyclability than Fe3O4@PNP1. Unexpectedly, Pd(ii) is well maintained after six consecutive catalytic runs in

  19. Effective Role of Magnetic Core-Shell Nanocomposites in Removing Organic and Inorganic Wastes from Water.

    Science.gov (United States)

    Shah, Nasrullah; Claessyns, Frederick; Rimmer, Stephen; Arain, Muhammad Balal; Rehan, Touseef; Wazwaz, Aref; Ahmad, Mohammad Wasi; Ul-Islam, Mazhar

    2016-01-01

    Affordable and efficient water treatment process to produce water free from various contaminants is a big challenge. The presence of toxic heavy metals, dyes, hazardous chemicals and other toxins causes contamination of water sources and our food chain and make them hazardous to living organisms. The current water treatment processes are no longer sustainable due to high cost and low efficiency. Due to advantageous properties, nanotechnology based materials can play a great role in increasing the efficiency of water treatment processes. Magnetic nanocomposites use nano as well as magnetic properties and have the potential to provide a sophisticated system to overcome most of the impurities present in water. There is a diversity of magnetic nanocomposites, however presently we have focussed the core-shell magnetic nanocomposites because they have excellent magnetic and separation properties, stability, and good biocompatibility. We collected systematically the bibliographic data bases for peer-reviewed research literature focusing on the theme of our review. The quality of the included research papers are selected by standard tools. A conceptual frame work is designed to arrange the topics and extracted the interventions and findings of the included studies. The overall study was divided into sections and each section incorporated the most appropriate literature citation. Total one hundred and eight references were included of which 32 references were used for basic description/introduction of core-shell magnetic nanocomposites. One review paper containing the synthesis methods for core shell magnetic nanocomposites is included while majority (76) of the references are included for comprehensive description of applications of the core-shell nanocomposites among which 25 were for dyes removal, 27 for hazardous metals, 07 for hazardous chemicals, 12 for pesticides and biological contaminants removal and five other including patents were added as miscellaneous

  20. Effective Role of Magnetic Core-Shell Nanocomposites in Removing Organic Wastes from Water.

    Science.gov (United States)

    Shah, Nasrullah; Claessyns, Frederick; Rimmer, Stephen; Arain, Muhammad Balal; Rehan, Touseef; Wazwaz, Aref; Ahmad, Md Wasi; Ul-Islam, Mazhar

    2016-04-29

    Affordable and efficient water treatment process to produce water free from various contaminants is a big challenge. The presence of toxic heavy metals, dyes, hazardous chemicals and other toxins cause contamination of water sources and our food chain and make them hazardous to living organisms. The current water treatment processes are no longer sustainable due to high cost and low efficiency. Due to advantageous properties, nanotechnology based materials can play a great role in increasing the efficiency of water treatment processes. Magnetic nanocomposites use nano as well as magnetic properties and have the potential to provide a sophisticated system to overcome most of the impurities present in water. There is diversity of magnetic nanocomposites, however presently we have focussed the core-shell magnetic nanocomposites because they have excellent magnetic and separation properties, stability, and good biocompatibility. We collected systematically the bibliographic data bases for peer-reviewed research literature focusing on the theme of our review. The Quality of the included research papers are selected by standard tools. A conceptual frame work is designed to arrange the topics and extracted the interventions and findings of the included studies. The overall study was divided in sections and each section incorporated the most appropriate literature citation. Total one hundred and eight references were included of which 32 references were used for basic description/introduction of core-shell magnetic nanocomposites. One review paper containing the synthesis methods for core shell magnetic nanocomposites is included while majority (76) of the references are included for comprehensive description of applications of the core-shell nanocomposites among which 25 were for dyes removal, 27 for hazardous metals, 07 for hazardous chemicals, 12 for pesticides and biological contaminants removal and five other including patents were added as miscellaneous substances

  1. Modeling of absorption and scattering properties of core -shell nanoparticles for application as nanoantenna in optical domain

    International Nuclear Information System (INIS)

    Devi, Jutika; Datta, Pranayee; Saikia, Rashmi

    2016-01-01

    The present paper describes the study of core-shell nanoparticles for application as nanoantenna in the optical domain. To obtain the absorption and extinction efficiencies as well as the angular distribution of the far field radiation pattern and the resonance wavelengths for these metal-dielectric, dielectric-metal and metal-metal core-shell nanoparticles in optical domain, we have used Finite Element Method based COMSOL Multiphysics Software and Mie Theory. From the comparative study of the extinction efficiencies of core-shell nanoparticles of different materials, it is found that for silica - gold core - shell nanoparticles, the resonant wavelength is greater than that of the gold - silver, silver-gold and gold-silica core - shell nanoparticles and also the radiation pattern of the silica-gold core-shell nanoparticle is the most suitable one from the point of view of directivity. The dielectric functions of the core and shell material as well as of the embedded matrix are extremely important and plays a very major role to tune the directivity and resonance wavelength. Such highly controllable parameters of the dielectric - metal core - shell nanoparticles make them suitable for efficient coupling of optical radiation into nanoscale structures for a broad range of applications in the field of communications. (paper)

  2. Development and characterization of cores-shell poly(lactide-co-glycolide)-chitosan microparticles for sustained release of GDNF.

    Science.gov (United States)

    Zeng, Wen; Liu, Zhongyang; Li, Yuqian; Zhu, Shu; Ma, Jie; Li, Weixin; Gao, Guodong

    2017-11-01

    The microencapsulation of bioactive neurotrophic factors in biodegradable poly(lactide-co-glycolide) (PLGA) microspheres has been a promising tool in the treatment of various nervous system disorders. However, challenges still exist; the PLGA burst drug release and acidic degradation products often limit clinical application. In this study, cores-shell PLGA-chitosan microparticles (MPs) were fabricated with a single shell of chitosan and multi-cores of PLGA using a re-emulsification method. The glial cell line-derived neurotrophic factor (GDNF) was encapsulated at the PLGA cores of the cores-shell MPs. The cores-shell MPs prepared by different chitosan concentrations showed a rough surface, and the particle mean size varied between 32.3 and 45.2μm. The fluorescence images indicated that Nile red-stained PLGA microspheres were uniformly distributed in the cores-shell MPs. Compared with PLGA microspheres, the cores-shell MPs were able to reduce the initial burst release of GDNF and neutralize the acidity of PLGA degradation products, which could be modulated by changing the chitosan concentrations. Further differentiation of PC12 cells toward a neuronal phenotype in vitro indicated that the cores-shell MPs were capable of maintaining the bioactivity of GDNF during preparation. Taken together, these findings highlight the possibility of using cores-shell PLGA-chitosan MPs for the sustained release of GDNF, which offers potential applications in nerve injury repair. Copyright © 2017. Published by Elsevier B.V.

  3. Controlled Release from Core-Shell Nanoporous Silica Particles for Corrosion Inhibition of Aluminum Alloys

    Directory of Open Access Journals (Sweden)

    Xingmao Jiang

    2011-01-01

    Full Text Available Cerium (Ce corrosion inhibitors were encapsulated into hexagonally ordered nanoporous silica particles via single-step aerosol-assisted self-assembly. The core/shell structured particles are effective for corrosion inhibition of aluminum alloy AA2024-T3. Numerical simulation proved that the core-shell nanostructure delays the release process. The effective diffusion coefficient elucidated from release data for monodisperse particles in water was 1.0×10−14 m2s for Ce3+ compared to 2.5×10−13 m2s for NaCl. The pore size, pore surface chemistry, and the inhibitor solubility are crucial factors for the application. Microporous hydrophobic particles encapsulating a less soluble corrosion inhibitor are desirable for long-term corrosion inhibition.

  4. Electrical transport and photovoltaic effects of core-shell CuO/C60 nanowire heterostructure.

    Science.gov (United States)

    Bao, Qiaoliang; Li, Chang Ming; Liao, Lei; Yang, Hongbin; Wang, Wei; Ke, Chang; Song, Qunliang; Bao, Haifeng; Yu, Ting; Loh, Kian Ping; Guo, Jun

    2009-02-11

    An organic/inorganic hybrid heterostructure consisting of p-type CuO nanowire core and n-type C(60) shell was fabricated and its electrical transport properties were studied for the first time. It was found that the devices with contacts on shell-shell show an ohmic behavior but the devices with contacts on core-shell forms a single p-n junction and display a rectifying behavior. Logarithmic current-voltage curves at various temperatures show that the tunneling transport plays a critical role in the electrical transport. Photovoltaic effects were observed in the core-shell contacted CuO/C(60) junctions under illumination. This work demonstrates that an inorganic/organic coaxial nanowire can provide potential in nanoelectronic devices and could further stack high density hybrid nanowires array as a renewable power source.

  5. Direct measurement of band edge discontinuity in individual core-shell nanowires by photocurrent spectroscopy.

    Science.gov (United States)

    Chen, Guannan; Sun, Guan; Ding, Yujie J; Prete, Paola; Miccoli, Ilio; Lovergine, Nico; Shtrikman, Hadas; Kung, Patrick; Livneh, Tsachi; Spanier, Jonathan E

    2013-09-11

    Group III-V coaxial core-shell semiconducting nanowire heterostructures possess unique advantages over their planar counterparts in logic, photovoltaic, and light-emitting devices. Dimensional confinement of electronic carriers and interface complexity in nanowires are known to produce local electronic potential landscapes along the radial direction that deviate from those along the normal to planar heterojunction interfaces. However, understanding of selected electronic and optoelectronic carrier transport properties and device characteristics remains lacking without a direct measurement of band alignment in individual nanowires. Here, we report on, in the GaAs/AlxGa1-xAs and GaAs/AlAs core-shell nanowire systems, how photocurrent and photoluminescence spectroscopies can be used together to construct a band diagram of an individual heterostructure nanowire with high spectral resolution, enabling quantification of conduction band offsets.

  6. Synthesis and characterization of ZnO/ZnS/MoS2 core-shell nanowires

    Science.gov (United States)

    Butanovs, Edgars; Kuzmin, Alexei; Butikova, Jelena; Vlassov, Sergei; Polyakov, Boris

    2017-02-01

    Hybrid nanostructures composed of layered materials have recently attracted a lot of attention due to their promising electronic and catalytic properties. In this study, we describe a novel synthesis strategy of ZnO/ZnS/MoS2 core-shell nanowire growth using a three-step route. First, ZnO nanowire array was grown on a silicon wafer. Second, the sample was immersed in ammonium molybdate solution and dried. At the third step, the sample was annealed in a sulfur atmosphere at 700 °C. Two solid state chemical reactions occur simultaneously during the annealing and result in a formation of ZnS and MoS2 phases. Produced ZnO/ZnS/MoS2 core-shell nanowires were characterized by scanning and transmission electron microscopy, whereas their chemical composition was confirmed by selected area electron diffraction and micro-Raman spectroscopy.

  7. Enhanced photocatalytic activity of C@ZnO core-shell nanostructures and its photoluminescence property

    Science.gov (United States)

    Chen, Tao; Yu, Shanwen; Fang, Xiaoxin; Huang, Honghong; Li, Lun; Wang, Xiuyuan; Wang, Huihu

    2016-12-01

    An ultrathin layer of amorphous carbon coated C@ZnO core-shell nanostructures were synthesized via a facile hydrothermal carbonization process using glucose as precursor in this work. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance UV-vis spectroscopy (DRS) were used for the characterization of as-prepared samples. Photoluminescence (PL) properties of C@ZnO samples were investigated using PL spectroscopy. The microstructure analysis results show that the glucose content has a great influence on the size, morphology, crystallinity and surface chemical states of C@ZnO nanostructures. Moreover, the as-prepared C@ZnO core-shell nanostructures exhibit the enhanced photocatalytic activity and good photostability for methyl orange dye degradation due to its high adsorption ability and its improved optical characteristics.

  8. A phase transfer identification of core-shell structures in Au-Ru nanoparticles

    International Nuclear Information System (INIS)

    Yang, J.; Lee, Jim Yang; Too, Heng-Phon

    2005-01-01

    The difference between the transfer of citrate-stabilized Au and Ru nanoparticles from the aqueous phase to toluene was used to develop a simple experimental procedure that can positively identify the formation of bimetallic Au-Ru nanoparticles with the core-shell structure formed in the seed-mediated growth process. The procedure was independently verified by UV-vis spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS). The experimental results clearly showed that core-shell nanoparticles of Au-Ru were formed by the seed mediated growth method using Au nanoparticle seeds. The reverse order of using Ru nanoparticles as the seeds, on the contrary, could only produce a physical mixture of isolated nanoparticles of Ru and Au under the same experimental conditions

  9. Core-shell magnetic nanoparticles for on-chip RF inductors

    KAUST Repository

    Koh, Kisik

    2013-01-01

    FeNi3 based core-shell magnetic nanoparticles are demonstrated as the magnetic core material for on-chip, radio frequency (RF) inductors. FeNi3 nanoparticles with 50-150 nm in diameter with 15-20 nm-thick SiO2 coating are chemically synthesized and deposited on a planar inductor as the magnetic core to enhance both inductance (L) and quality factor (Q) of the inductor. Experimentally, the ferromagnetic resonant frequency of the on-chip inductors based on FeNi3 core-shell nanoparticles has been shown to be over several GHz. A post-CMOS process has been developed to integrate the magnetic nanoparticles to a planar inductor and inductance enhancements up to 50% of the original magnitude with slightly enhanced Q-factor up to 1 GHz have been achieved. © 2013 IEEE.

  10. Synthesis and characterization of conductive core-shell polyacrylonitrile-polypyrrole nanofibers.

    Science.gov (United States)

    Jun, Tae-Sun; Nguyen, Tuan-Anh; Jung, Yongju; Kim, Yong Shin

    2012-07-01

    Nonwoven polyacrylonitrile-polypyrrole (PAN-PPy) core-shell nanofiber mats were prepared through the growth of PPy layers on electrospun PAN nanofibers via a two-step vapor-phase polymerization, i.e., the wet-coating of ferric tosylate (FeTos) oxidants on PAN nanofibers followed by exposure to pyrrole monomers in the gas phase. Under the conditions ([FeTos] = 10 wt%, reaction time = 15 min, temperature = 15 degrees C), the PPy polymerization procedure led to both a uniform coating over the PAN surface with an average thickness of 18 nm and cross-linkages among the nanofibers without a noticeable change in the highly porous nanofibrous structures. The oxidant concentration and polymerization time were found to be key parameters for achieving a good nanostructured core-shell fiber mat. FT-IR, XPS, XRD and conductivity measurements confirmed the synthesis of Tos-doped PPy with some degree of crystallinity and a high conductivity.

  11. Electrical transport and photovoltaic effects of core-shell CuO/C60 nanowire heterostructure

    International Nuclear Information System (INIS)

    Bao Qiaoliang; Li Changming; Yang Hongbin; Wang Wei; Song Qunliang; Bao Haifeng; Liao Lei; Yu Ting; Ke Chang; Loh, K P; Guo Jun

    2009-01-01

    An organic/inorganic hybrid heterostructure consisting of p-type CuO nanowire core and n-type C 60 shell was fabricated and its electrical transport properties were studied for the first time. It was found that the devices with contacts on shell-shell show an ohmic behavior but the devices with contacts on core-shell forms a single p-n junction and display a rectifying behavior. Logarithmic current-voltage curves at various temperatures show that the tunneling transport plays a critical role in the electrical transport. Photovoltaic effects were observed in the core-shell contacted CuO/C 60 junctions under illumination. This work demonstrates that an inorganic/organic coaxial nanowire can provide potential in nanoelectronic devices and could further stack high density hybrid nanowires array as a renewable power source.

  12. Alternating current dielectrophoresis of core-shell nanoparticles: Experiments and comparison with theory

    Science.gov (United States)

    Yang, Chungja

    Nanoparticles are fascinating where physical and optical properties are related to size. Highly controllable synthesis methods and nanoparticle assembly are essential for highly innovative technological applications. Well-defined shaped and sized nanoparticles enable comparisons between experiments, theory and subsequent new models to explain experimentally observed phenomena. Among nanoparticles, nonhomogeneous core-shell nanoparticles (CSnp) have new properties that arise when varying the relative dimensions of the core and the shell. This CSnp structure enables various optical resonances, and engineered energy barriers, in addition to the high charge to surface ratio. Assembly of homogeneous nanoparticles into functional structures has become ubiquitous in biosensors (i.e. optical labeling), nanocoatings, and electrical circuits. Limited nonhomogenous nanoparticle assembly has only been explored. Many conventional nanoparticle assembly methods exist, but this work explores dielectrophoresis (DEP) as a new method. DEP is particle polarization via non-uniform electric fields while suspended in conductive fluids. Most prior DEP efforts involve microscale particles. Prior work on core-shell nanoparticle assemblies and separately, nanoparticle characterizations with dielectrophoresis and electrorotation, did not systematically explore particle size, dielectric properties (permittivity and electrical conductivity), shell thickness, particle concentration, medium conductivity, and frequency. This work is the first, to the best of our knowledge, to systematically examine these dielectrophoretic properties for core-shell nanoparticles. Further, we conduct a parametric fitting to traditional core-shell models. These biocompatible core-shell nanoparticles were studied to fill a knowledge gap in the DEP field. Experimental results (chapter 5) first examine medium conductivity, size and shell material dependencies of dielectrophoretic behaviors of spherical CSnp into 2D and

  13. Polyaniline Coated Core-Shell Typed Stimuli-Responsive Microspheres and Their Electrorheology

    Directory of Open Access Journals (Sweden)

    Yu Zhen Dong

    2018-03-01

    Full Text Available Functional core-shell-structured particles have attracted considerable attention recently. This paper reviews the synthetic methods and morphologies of various electro-stimuli responsive polyaniline (PANI-coated core-shell-type microspheres, including PANI-coated Fe3O4, SiO2, Fe2O3, TiO2, poly(methyl methacrylate, poly(glycidyl methacrylate, and polystyrene along with their electrorheological (ER characteristics when prepared by dispersing these particles in an insulating medium. In addition to the various rheological characteristics and their analysis, such as shear stress and yield stress of their ER fluids, this paper summarizes some of the mechanisms proposed for ER fluids to further understand the responses of ER fluids to an externally applied electric field.

  14. III-nitride core-shell nanorod array on quartz substrates

    Science.gov (United States)

    Bae, Si-Young; Min, Jung-Wook; Hwang, Hyeong-Yong; Lekhal, Kaddour; Lee, Ho-Jun; Jho, Young-Dahl; Lee, Dong-Seon; Lee, Yong-Tak; Ikarashi, Nobuyuki; Honda, Yoshio; Amano, Hiroshi

    2017-03-01

    We report the fabrication of near-vertically elongated GaN nanorods on quartz substrates. To control the preferred orientation and length of individual GaN nanorods, we combined molecular beam epitaxy (MBE) with pulsed-mode metal-organic chemical vapor deposition (MOCVD). The MBE-grown buffer layer was composed of GaN nanograins exhibiting an ordered surface and preferred orientation along the surface normal direction. Position-controlled growth of the GaN nanorods was achieved by selective-area growth using MOCVD. Simultaneously, the GaN nanorods were elongated by the pulsed-mode growth. The microstructural and optical properties of both GaN nanorods and InGaN/GaN core-shell nanorods were then investigated. The nanorods were highly crystalline and the core-shell structures exhibited optical emission properties, indicating the feasibility of fabricating III-nitride nano-optoelectronic devices on amorphous substrates.

  15. Synthesis of Plasmonic Cu2-x Se@ZnS Core@Shell Nanoparticles.

    Science.gov (United States)

    Wolf, Andreas; Härtling, Thomas; Hinrichs, Dominik; Dorfs, Dirk

    2016-03-03

    We report the synthesis of plasmonic Cu2-x Se@ZnS core@shell nanoparticles (NPs). We used a shell growth approach, starting from Cu2-x Se NPs that have been shown before to exhibit a localized surface plasmon resonance (LSPR). By careful synthesis planning we avoided cation exchange reactions and received core@shell nanoparticles that, after oxidation under air, exhibit a strong LSPR in the NIR. Interestingly, the crystalline, closed ZnS shell that we grew with variable thickness still allowed a slow oxidation of the core under ambient conditions, while the core was effectively protected from reduction, even in the presence of reducing agents such as borane tert-butyamine complex and diisobutylaluminum hydride, giving rise to a stable particle LSPR, also under strongly reducing conditions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Silver-nickel oxide core-shell nanoparticle array electrode with enhanced lithium-storage performance

    International Nuclear Information System (INIS)

    Zhao, Wenjia; Du, Ning; Zhang, Hui; Yang, Deren

    2015-01-01

    We demonstrate the synthesis of Ag-NiO core-shell nanoparticle arrays via a one-step solution-immersion process and subsequent RF-sputtering technique. The Ag nanoparticle arrays on copper substrate are firstly prepared by a displacement reaction at mild temperature of 303K. Then, a NiO layer is deposited onto the surface of the Ag nanoparticles via RF-sputtering technique. When evaluated as an anode for lithium-ion batteries, the Ag-NiO core-shell electrode shows higher capacity and better cycling performance than the planar NiO electrode. The in-situ synthesized Ag nanoparticles can enhance the interfacial strength between the active material and substrate, andimprove the electrical conductivity of the electrode, which may be responsible for the enhanced performance

  17. Electrical transport and photovoltaic effects of core-shell CuO/C60 nanowire heterostructure

    Science.gov (United States)

    Bao, Qiaoliang; Li, Chang Ming; Liao, Lei; Yang, Hongbin; Wang, Wei; Ke, Chang; Song, Qunliang; Bao, Haifeng; Yu, Ting; Loh, Kian Ping; Guo, Jun

    2009-02-01

    An organic/inorganic hybrid heterostructure consisting of p-type CuO nanowire core and n-type C60 shell was fabricated and its electrical transport properties were studied for the first time. It was found that the devices with contacts on shell-shell show an ohmic behavior but the devices with contacts on core-shell forms a single p-n junction and display a rectifying behavior. Logarithmic current-voltage curves at various temperatures show that the tunneling transport plays a critical role in the electrical transport. Photovoltaic effects were observed in the core-shell contacted CuO/C60 junctions under illumination. This work demonstrates that an inorganic/organic coaxial nanowire can provide potential in nanoelectronic devices and could further stack high density hybrid nanowires array as a renewable power source.

  18. Exciton states and optical absorption in core/shell/shell spherical quantum dot

    Science.gov (United States)

    Hayrapetyan, D. B.; Baghdasaryan, D. A.; Kazaryan, E. M.; Pokutnyi, S. I.; Sarkisyan, H. A.

    2018-04-01

    The exciton states in core/shell/shell spherical quantum dot with three-dimensional Winternitz-Smorodinsky confinement potential are considered. The problem is discussed in the framework of adiabatic approximation when the heavy hole is situated in the effective potential well caused by the electron. The interband optical transitions caused by incident light polarized in z-direction have been considered in such systems. The oscillator strengths and selection rules for the quantum transitions have been obtained. The ensemble of quantum dots and their size dispersion have been taken into account in the calculations. The Gaussian distribution has been chosen to describe the size dispersion of the core/shell/shell quantum dots thickness. The dependence of the absorption coefficient and photoluminescence spectra on the energy of incident light of interband transitions have been obtained.

  19. Porous core-shell carbon fibers derived from lignin and cellulose nanofibrils

    KAUST Repository

    Xu, Xuezhu

    2013-10-01

    This letter reports a method to produce lignin and cellulose nanofibrils (CNFs) based porous core-shell carbon fibers via co-electrospinning followed by controlled carbonization. Lignin formed the shell of the fiber while CNF network formed the porous core. Polyacrylonitrile (PAN) was added to the lignin solution to increase its electrospinability. CNFs were surface acetylated and dispersed in silicon oil to obtain a homogenous dispersion for electrospinning the porous core. Hollow lignin fibers were also electrospun using glycerin as the core material. FT-IR measurements confirmed the CNF acetylation. SEM micrographs showed the core-shell and hollow fiber nanostructures before and after carbonization. The novel carbon fibers synthesized in this study exhibited increased surface area and porosity that are promising for many advanced applications. © 2013 Elsevier B.V.

  20. Controlled Release from Core-Shell Nano porous Silica Particles for Corrosion Inhibition of Aluminum Alloys

    International Nuclear Information System (INIS)

    Jiang, X.; Rathod, Sh.; Shah, P.; Brinker, C.J.; Jiang, X.; Jiang, Y.; Liu, N.; Xu, H.; Brinker, C.J.

    2011-01-01

    Cerium (Ce) corrosion inhibitors were encapsulated into hexagonally ordered nanoporous silica particles via single-step aerosol-assisted self-assembly. The core/shell structured particles are effective for corrosion inhibition of aluminum alloy AA2024-T3. Numerical simulation proved that the core-shell nanostructure delays the release process. The effective diffusion coefficient elucidated from release data for monodisperse particles in water was 1.0x10-14 m 2 s for Ce 3+ compared to 2.5x10-13 m 2 s for NaCl. The pore size, pore surface chemistry, and the inhibitor solubility are crucial factors for the application. Microporous hydrophobic particles encapsulating a less soluble corrosion inhibitor are desirable for long-term corrosion inhibition.

  1. Polydopamine and MnO2 core-shell composites for high-performance supercapacitors

    Science.gov (United States)

    Hou, Ding; Tao, Haisheng; Zhu, Xuezhen; Li, Maoguo

    2017-10-01

    Polydopamine and MnO2 core-shell composites (PDA@MnO2) for high-performance supercapacitors had been successfully synthesized by a facile and fast method. The morphology, crystalline phase and chemical composition of PDA@MnO2 composites are characterized using SEM, TEM, XRD, EDS and XPS. The performance of PDA@MnO2 composites are further investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy in 1 M Na2SO4 electrolyte. The PDA@MnO2 core-shell nanostructure composites exhibit a high capacitance of 193 F g-1 at the current density of 1A g-1 and retained over 81.2% of its initial capacitance after 2500 cycles of charge-discharge at 2 A g-1. The results manifest that the PDA@MnO2 composites can be potentially applied in supercapacitors.

  2. Core-Shell Structure in Doped Inorganic Nanoparticles: Approaches for Optimizing Luminescence Properties

    Directory of Open Access Journals (Sweden)

    Dini Xie

    2013-01-01

    Full Text Available Doped inorganic luminescent nanoparticles (NPs have been widely used in both research and application fields due to their distinctive properties. However, there is an urgent demand to improve their luminescence efficiency, which is greatly reduced by surface effects. In this paper, we review recent advances in optimizing luminescence properties of doped NPs based on core-shell structure, which are basically classified into two categories: one is by use of surface coating with nonmetal materials to weaken the influence of surface effect and the other is with metal shell via metal enhanced luminescence. Different materials used to coat NPs are surveyed, and their advantages and disadvantages are both commented on. Moreover, problems in current core-shell structured luminescent NPs are pointed out and strategies furthering the optimization of luminescence properties are suggested.

  3. Determining the size of nanoparticles in the example of magnetic iron oxide core-shell systems

    Science.gov (United States)

    Jarzębski, Maciej; Kościński, Mikołaj; Białopiotrowicz, Tomasz

    2017-08-01

    The size of nanoparticles is one of the most important factors for their possible applications. Various techniques for the nanoparticle size characterization are available. In this paper selected techniques will be considered base on the prepared core-shell magnetite nanoparticles. Magnetite is one of the most investigated and developed magnetic material. It shows interesting magnetic properties which can be used for biomedical applications, such as drug delivery, hypothermia and also as a contrast agent. To reduce the toxic effects of Fe3O4, magnetic core was covered by dextran and gelatin. Moreover, the shell was doped by fluorescent dye for confocal microscopy investigation. The main investigation focused on the methods for particles size determination of modified magnetite nanoparticles prepared with different techniques. The size distribution were obtained by nanoparticle tracking analysis, dynamic light scattering and transmission electron microscopy. Furthermore, fluorescent correlation spectroscopy (FCS) and confocal microscopy were used to compare the results for particle size determination of core-shell systems.

  4. Ab Initio Study of 40Ca with an Importance Truncated No-Core Shell Model

    Energy Technology Data Exchange (ETDEWEB)

    Roth, R; Navratil, P

    2007-05-22

    We propose an importance truncation scheme for the no-core shell model, which enables converged calculations for nuclei well beyond the p-shell. It is based on an a priori measure for the importance of individual basis states constructed by means of many-body perturbation theory. Only the physically relevant states of the no-core model space are considered, which leads to a dramatic reduction of the basis dimension. We analyze the validity and efficiency of this truncation scheme using different realistic nucleon-nucleon interactions and compare to conventional no-core shell model calculations for {sup 4}He and {sup 16}O. Then, we present the first converged calculations for the ground state of {sup 40}Ca within no-core model spaces including up to 16{h_bar}{Omega}-excitations using realistic low-momentum interactions. The scheme is universal and can be easily applied to other quantum many-body problems.

  5. Ultrathin Interface Regime of Core-Shell Magnetic Nanoparticles for Effective Magnetism Tailoring.

    Science.gov (United States)

    Moon, Seung Ho; Noh, Seung-Hyun; Lee, Jae-Hyun; Shin, Tae-Hyun; Lim, Yongjun; Cheon, Jinwoo

    2017-02-08

    The magnetic exchange coupling interaction between hard and soft magnetic phases has been important for tailoring nanoscale magnetism, but spin interactions at the core-shell interface have not been well studied. Here, we systematically investigated a new interface phenomenon termed enhanced spin canting (ESC), which is operative when the shell thickness becomes ultrathin, a few atomic layers, and exhibits a large enhancement of magnetic coercivity (H C ). We found that ESC arises not from the typical hard-soft exchange coupling but rather from the large magnetic surface anisotropy (K S ) of the ultrathin interface. Due to this large increase in magnetism, ultrathin core-shell nanoparticles overreach the theoretical limit of magnetic energy product ((BH) max ) and exhibit one of the largest values of specific loss power (SLP), which testifies to their potential capability as an effective mediator of magnetic energy conversion.

  6. Evidence for Symplectic Symmetry in Ab Initio No-Core Shell Model Results for Light Nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Dytrych, Tomas; Sviratcheva, Kristina D.; Bahri, Chairul; Draayer, Jerry P.; /Louisiana State U.; Vary, James P.; /Iowa State U. /LLNL, Livermore /SLAC

    2007-04-24

    Clear evidence for symplectic symmetry in low-lying states of {sup 12}C and {sup 16}O is reported. Eigenstates of {sup 12}C and {sup 16}O, determined within the framework of the no-core shell model using the JISP16 NN realistic interaction, typically project at the 85-90% level onto a few of the most deformed symplectic basis states that span only a small fraction of the full model space. The results are nearly independent of whether the bare or renormalized effective interactions are used in the analysis. The outcome confirms Elliott's SU(3) model which underpins the symplectic scheme, and above all, points to the relevance of a symplectic no-core shell model that can reproduce experimental B(E2) values without effective charges as well as deformed spatial modes associated with clustering phenomena in nuclei.

  7. Lowering of ground state induced by core-shell structure in strontium titanate

    Science.gov (United States)

    Kiat, J. M.; Hehlen, B.; Anoufa, M.; Bogicevic, C.; Curfs, C.; Boyer, B.; Al-Sabbagh, M.; Porcher, F.; Al-Zein, A.

    2016-04-01

    A new ground state of textbook compound strontium titanate (SrTi O3) is obtained by inducing a specific core-shell structure of the particles. Using a combination of high energy synchrotron and neutron diffraction, we demonstrate a lowering of the ferroelastic ground state towards a new antiferrodistortive phase, accompanied with strong shifts of the critical temperature. This new phase is discussed within the Landau theory and compared with the situation in thin films and during pressure experiments. The crucial competition between particle shape anisotropy, surface tension, and shear strain is analyzed. Inducing a specific core-shell structure is therefore an easy way to tailor structural properties and to stabilize new phases that cannot exist in bulk material, just like film deposition on a substrate.

  8. Progress in High-Capacity Core-Shell Cathode Materials for Rechargeable Lithium Batteries.

    Science.gov (United States)

    Myung, Seung-Taek; Noh, Hyung-Joo; Yoon, Sung-June; Lee, Eung-Ju; Sun, Yang-Kook

    2014-02-20

    High-energy-density rechargeable batteries are needed to fulfill various demands such as self-monitoring analysis and reporting technology (SMART) devices, energy storage systems, and (hybrid) electric vehicles. As a result, high-energy electrode materials enabling a long cycle life and reliable safety need to be developed. To ensure these requirements, new material chemistries can be derived from combinations of at least two compounds in a secondary particle with varying chemical composition and primary particle morphologies having a core-shell structure and spherical cathode-active materials, specifically a nanoparticle core and shell, nanoparticle core and nanorod shell, and nanorod core and shell. To this end, several layer core-shell cathode materials were developed to ensure high capacity, reliability, and safety.

  9. Three-dimensional atomic imaging of colloidal core-shell nanocrystals.

    Science.gov (United States)

    Bals, Sara; Casavola, Marianna; van Huis, Marijn A; Van Aert, Sandra; Batenburg, K Joost; Van Tendeloo, Gustaaf; Vanmaekelbergh, Daniël

    2011-08-10

    Colloidal core-shell semiconductor nanocrystals form an important class of optoelectronic materials, in which the exciton wave functions can be tailored by the atomic configuration of the core, the interfacial layers, and the shell. Here, we provide a trustful 3D characterization at the atomic scale of a free-standing PbSe(core)-CdSe(shell) nanocrystal by combining electron microscopy and discrete tomography. Our results yield unique insights for understanding the process of cation exchange, which is widely employed in the synthesis of core-shell nanocrystals. The study that we present is generally applicable to the broad range of colloidal heteronanocrystals that currently emerge as a new class of materials with technological importance.

  10. Au@Ag core/shell nanoparticles as colorimetric probes for cyanide sensing

    Science.gov (United States)

    Zeng, Jing-Bin; Cao, Ying-Ying; Chen, Jing-Jing; Wang, Xu-Dong; Yu, Jian-Feng; Yu, Bin-Bin; Yan, Zi-Feng; Chen, Xi

    2014-08-01

    We synthesize Au@Ag core/shell nanoparticles (NPs) using a Au NP assisted Tollens reaction. The as-synthesized NPs are used for the colorimetric cyanide sensing with a detection limit of 0.4 μM. The bimetallic NPs are immobilized into agarose gels as portable ``test strips''.We synthesize Au@Ag core/shell nanoparticles (NPs) using a Au NP assisted Tollens reaction. The as-synthesized NPs are used for the colorimetric cyanide sensing with a detection limit of 0.4 μM. The bimetallic NPs are immobilized into agarose gels as portable ``test strips''. Electronic supplementary information (ESI) available: Experimental procedures and Fig. S1-S14. See DOI: 10.1039/c4nr02560a

  11. Hydrothermal core-shell carbon nanoparticle films: thinning the shell leads to dramatic pH response.

    Science.gov (United States)

    Xia, Fengjie; Pan, Mu; Mu, Shichun; Xiong, Yuli; Edler, Karen J; Idini, Ilaria; Jones, Matthew D; Tsang, Shik Chi; Marken, Frank

    2012-12-05

    Carbon nanoparticles with phenylsulfonate negative surface functionality (Emperor 2000, Cabot Corp.) are coated with positive chitosan followed by hydrothermal carbonization to give highly pH-responsive core-shell nanocarbon composite materials. With optimised core-shell ratio (resulting in an average shell thickness of ca. 4 nm, estimated from SANS data) modified electrodes exhibit highly pH-sensitive resistance, capacitance, and Faradaic electron transfer responses (solution based, covalently bound, or hydrothermally embedded). A shell "double layer exclusion" mechanism is discussed to explain the observed pH switching effects. Based on this mechanism, a broader range of future applications of responsive core-shell nanoparticles are envisaged.

  12. Synthesis of Core-Shell SiO/Carbon Nanofibers on Silicon Substrates by Ultrasonic Spray Pyrolysis

    Directory of Open Access Journals (Sweden)

    Jianhui Zhang

    2012-01-01

    Full Text Available We synthesized the core-shell SiO/carbon nanofibers with diameters of 200–300 nm using ultrasonic spray pyrolysis with a phosphorus/ethanol mixture. High-resolution transmission electron microscopy (HRTEM and energy-dispersive spectroscopy (EDS investigations confirmed the core-shell structure, which consisted of a core of SiO and a shell of amorphous carbon. The phosphorus atoms corroded the entire silicon substrate surface, and the Si-P liquid-catalyzed the solid-liquid-solid mechanism is proposed to explain the growth of the core-shell SiO/carbon nanofibers.

  13. Controlled Synthesis of Pd/Pt Core Shell Nanoparticles Using Area-selective Atomic Layer Deposition

    OpenAIRE

    Cao, Kun; Zhu, Qianqian; Shan, Bin; Chen, Rong

    2015-01-01

    We report an atomic scale controllable synthesis of Pd/Pt core shell nanoparticles (NPs) via area-selective atomic layer deposition (ALD) on a modified surface. The method involves utilizing octadecyltrichlorosilane (ODTS) self-assembled monolayers (SAMs) to modify the surface. Take the usage of pinholes on SAMs as active sites for the initial core nucleation, and subsequent selective deposition of the second metal as the shell layer. Since new nucleation sites can be effectively blocked by s...

  14. How to Determine the Core-Shell Nature in Bimetallic Catalyst Particles?

    Directory of Open Access Journals (Sweden)

    Emma Westsson

    2014-11-01

    Full Text Available Nanometer-sized materials have significantly different chemical and physical properties compared to bulk material. However, these properties do not only depend on the elemental composition but also on the structure, shape, size and arrangement. Hence, it is not only of great importance to develop synthesis routes that enable control over the final structure but also characterization strategies that verify the exact nature of the nanoparticles obtained. Here, we consider the verification of contemporary synthesis strategies for the preparation of bimetallic core-shell particles in particular in relation to potential particle structures, such as partial absence of core, alloying and raspberry-like surface. It is discussed what properties must be investigated in order to fully confirm a covering, pin-hole free shell and which characterization techniques can provide such information. Not uncommonly, characterization strategies of core-shell particles rely heavily on visual imaging like transmission electron microscopy. The strengths and weaknesses of various techniques based on scattering, diffraction, transmission and absorption for investigating core-shell particles are discussed and, in particular, cases where structural ambiguities still remain will be highlighted. Our main conclusion is that for particles with extremely thin or mono-layered shells—i.e., structures outside the limitation of most imaging techniques—other strategies, not involving spectroscopy or imaging, are to be employed. We will provide a specific example of Fe-Pt core-shell particles prepared in bicontinuous microemulsion and point out the difficulties that arise in the characterization process of such particles.

  15. High Frequency Magneto Dielectric Effects In Self Assembled Ferrite Ferroelectric Core Shell Nanoparticles

    Science.gov (United States)

    2014-09-10

    magneto-electric interactions Appl. Phys. Lett. 105, 072905 (2014); 10.1063/1.4893699 Magnetic field assisted self-assembly of ferrite -ferroelectric...10.1063/1.4795820 Co- ferrite spinel and FeCo alloy core shell nanocomposites and mesoporous systems for multifunctional applications J. Appl. Phys...1. The stress in the ferrite phase is assumed to be produced by applied magnetic field and transferred to ferroelectric shell. Strain and stress

  16. Lanthanide modification of CdSe/ZnS core/shell quantum dots

    DEFF Research Database (Denmark)

    Dethlefsen, Johannes Rytter; Mikhailovsky, Alexander A.; Burks, Peter T.

    2012-01-01

    Lanthanide-modified CdSe quantum dots (CdSe(Ln) QDs) have been prepared by heating a solution of Cd(oleate)(2), SeO2, and Ln(bipy)(S2CNEt2)(3) (bipy = 2,2'-bipyridine) to 180-190 degrees C for 10-15 min. The elemental compositions of the resulting CdSe(Ln) cores and CdSe(Ln)/ZnS core/shell QDs show...

  17. Magnetoresistance of individual ferromagnetic GaAs/(Ga,Mn)As core-shell nanowires

    OpenAIRE

    Butschkow, Christian H.; Reiger, Elisabeth; Geißler, Stefan; Rudolph, Andreas; Soda, Marcello; Schuh, Dieter; Woltersdorf, Georg; Wegscheider, Werner; Weiss, Dieter

    2011-01-01

    We investigate, angle dependent, the magnetoresistance (MR) of individual self-assembled ferromagnetic GaAs/(Ga,Mn)As core-shell nanowires at cryogenic temperatures. The shape of the MR traces and the observed strong anisotropies in transport can be ascribed to the interplay of the negative magnetoresistance effect and a strong uniaxial anisotropy with the magnetic easy direction pointing along the wire axis. The magnetoresistance can be well described by a quantitative analysis based on the ...

  18. Determination of Core-Shell Structures in Pd-Hg Nanoparticles by STEM-EDX

    DEFF Research Database (Denmark)

    Deiana, Davide; Verdaguer Casadevall, Arnau; Malacrida, Paolo

    2015-01-01

    The structural and elemental configuration of a high-performing Pd-Hg electrocatalyst for oxygen reduction to hydrogen peroxide has been studied by means of high-resolution scanning transmission electron microscopy. Pd-Hg nanoparticles are shown to have a crystalline core-shell structure, with a Pd...... core and a Pd-Hg ordered alloy shell. The ordered shell is responsible for the high oxygen reduction selectivity to H2O2....

  19. Process Development of Gallium Nitride Phosphide Core-Shell Nanowire Array Solar Cell

    Science.gov (United States)

    Chuang, Chen

    Dilute Nitride GaNP is a promising materials for opto-electronic applications due to its band gap tunability. The efficiency of GaNxP1-x /GaNyP1-y core-shell nanowire solar cell (NWSC) is expected to reach as high as 44% by 1% N and 9% N in the core and shell, respectively. By developing such high efficiency NWSCs on silicon substrate, a further reduction of the cost of solar photovoltaic can be further reduced to 61$/MWh, which is competitive to levelized cost of electricity (LCOE) of fossil fuels. Therefore, a suitable NWSC structure and fabrication process need to be developed to achieve this promising NWSC. This thesis is devoted to the study on the development of fabrication process of GaNxP 1-x/GaNyP1-y core-shell Nanowire solar cell. The thesis is divided into two major parts. In the first parts, previously grown GaP/GaNyP1-y core-shell nanowire samples are used to develop the fabrication process of Gallium Nitride Phosphide nanowire solar cell. The design for nanowire arrays, passivation layer, polymeric filler spacer, transparent col- lecting layer and metal contact are discussed and fabricated. The property of these NWSCs are also characterized to point out the future development of Gal- lium Nitride Phosphide NWSC. In the second part, a nano-hole template made by nanosphere lithography is studied for selective area growth of nanowires to improve the structure of core-shell NWSC. The fabrication process of nano-hole templates and the results are presented. To have a consistent features of nano-hole tem- plate, the Taguchi Method is used to optimize the fabrication process of nano-hole templates.

  20. Enhancement of curcumin water dispersibility and antioxidant activity using core-shell protein-polysaccharide nanoparticles.

    Science.gov (United States)

    Huang, Xiaoxia; Huang, Xulin; Gong, Yushi; Xiao, Hang; McClements, David Julian; Hu, Kun

    2016-09-01

    Curcumin has strong antioxidant activity, but poor water-solubility and chemical stability, which limits its utilization as a nutraceutical in many applications. Previously, we developed a core-shell (zein-pectin) nanoparticle delivery system with high curcumin loading efficiency, high particle yield, and good water dispersibility. However, this system was unstable to aggregation around neutral pH and moderate ionic strengths due to weakening of electrostatic repulsion between nanoparticles. In the current study, we used a combination of alginate (high charge density) and pectin (low charge density) to form the shell around zein nanoparticles. Replacement of 30% of pectin with alginate greatly improved aggregation stability at pH 5 to 7 and at high ionic strengths (2000mM NaCl). Curcumin encapsulated within these core-shell nanoparticles exhibited higher antioxidant and radical scavenging activities than curcumin solubilized in ethanol solutions as determined by Fe (III) reducing power, 1, 1-Diphenyl-2-picrylhydrazyl free radical (DPPH·), and 2, 2'-azinobis-(3-ethylbenzothiazoline)-6-sulfonic acid radical cation (ABTS· + ) scavenging analysis. These core-shell nanoparticles may be useful for incorporating chemically unstable hydrophobic nutraceuticals such as curcumin into functional foods, dietary supplements, and pharmaceuticals. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Synthesis and Photocatalytic Activity of Magnetically Recoverable Core-Shell Nanoparticles

    Directory of Open Access Journals (Sweden)

    Zhen Peng

    2014-01-01

    Full Text Available TiO2/SiO2/Fe3O4 (TSF core-shell nanoparticles with good photocatalytic activity that are capable of fast magnetic separation have been successfully prepared by chemical coprecipitation and two-step sol-gel process. The as-prepared TSF nanoparticles were calcined at high temperature in order to transform the amorphous titanium dioxide into a photoactive crystalline phase. The calcined nanoparticles are composed of a Fe3O4 core with a strong response to external magnetic fields, a SiO2 intermediary layer, and a TiO2 outshell. Vibration sample magnetometer (VSM analysis confirms the superparamagnetism of calcined nanoparticles, which can enhance the recoverable properties of the novel photocatalyst. When the TiO2/SiO2/Fe3O4 core-shell nanoparticles are added to the crude oily wastewater, they exhibit high photocatalytic activity in the degradation of crude oily wastewater. The oil concentration could be reduced to lower than 30 ppm within 20 minutes for the case of initial oil concentration less than 350 ppm. It has been found that the TSF nanoparticles could be easily separated from the wastewater and withdrawn by using an external magnetic field. The recovered TSF nanoparticles possess high efficiency in the degradation of crude oily wastewater even after three times successive reuse. The present results indicate that TSF core-shell nanoparticles possess great application perspectives in the degradation of crude oily wastewater.

  2. Engineered core-shell nanofibers for electron transport study in dye-sensitized solar cells

    Directory of Open Access Journals (Sweden)

    Y. Shabdan

    2017-06-01

    Full Text Available In this study, a unique approach was developed to synthesize 1-D core-shell nanofibers of carbon nanotubes (CNTs and TiO2 using combination of coaxial electrospinning and sol-gel technique. Diameters of the fabricated core-shell single wall carbon nanotube-TiO2 (SWCNT-TiO2 and multi wall carbon nanotube-TiO2 (MWCNT-TiO2 nano-composite fibers were between 50-100nm. Energy dispersive spectroscopy (EDS and X-ray photon spectroscopy (XPS were applied to confirm encapsulation of carbon nanotube (CNT in the core-shell structure. Electron transport properties of both SWCNT-TiO2 and MWCNT-TiO2 in the Dye-sensitized solar cells (DSSCs were studied for the first time. It was found that SWCNT-TiO2 based DSSC provided higher short circuit current relative to MWCNT-TiO2, which was explained by I-V and bode plots. These findings were further illustrated by semi-conductive properties of SWCNT.

  3. Localized surface plasmon mediated energy transfer in the vicinity of core-shell nanoparticle

    Energy Technology Data Exchange (ETDEWEB)

    Shishodia, Manmohan Singh, E-mail: manmohan@gbu.ac.in; Juneja, Soniya [Department of Applied Physics, School of Vocational Studies and Applied Sciences, Gautam Buddha University, Greater Noida 201308 (India)

    2016-05-28

    Multipole spectral expansion based theory of energy transfer interactions between a donor and an acceptor molecule in the vicinity of a core-shell (nanoshell or core@shell) based plasmonic nanostructure is developed. In view of the diverse applications and rich plasmonic features such as tuning capability of surface plasmon (SP) frequencies, greater sensitivity to the change of dielectric environment, controllable redirection of electromagnetic radiation, closed form expressions for Energy Transfer Rate Enhancement Factor (ETREF) near core-shell particle are reported. The dependence of ETREF on different parameters is established through fitting equations, perceived to be of key importance for developing appropriate designs. The theoretical approach developed in the present work is capable of treating higher order multipoles, which, in turn, are also shown to play a crucial role in the present context. Moreover, closed form expressions derived in the present work can directly be used as formula, e.g., for designing SP based biosensors and estimating energy exchange between proteins and excitonic interactions in quantum dots.

  4. Synthesis and characterization of core-shell Fe3O4-gold-chitosan nanostructure

    Directory of Open Access Journals (Sweden)

    Salehizadeh Hossein

    2012-01-01

    Full Text Available Abstract Background Fe3O4-gold-chitosan core-shell nanostructure can be used in biotechnological and biomedical applications such as magnetic bioseparation, water and wastewater treatment, biodetection and bioimaging, drug delivery, and cancer treatment. Results Magnetite nanoparticles with an average size of 9.8 nm in diameter were synthesized using the chemical co-precipitation method. A gold-coated Fe3O4 monotonous core-shell nanostructure was produced with an average size of 15 nm in diameter by glucose reduction of Au3+ which is then stabilized with a chitosan cross linked by formaldehyde. The results of analyses with X-ray diffraction (XRD, Fourier Transformed Infrared Spectroscopy (FTIR, Transmission Electron Microscopy (TEM, and Atomic Force Microscopy (AFM indicated that the nanoparticles were regularly shaped, and agglomerate-free, with a narrow size distribution. Conclusions A rapid, mild method for synthesizing Fe3O4-gold nanoparticles using chitosan was investigated. A magnetic core-shell-chitosan nanocomposite, including both the supermagnetic properties of iron oxide and the optical characteristics of colloidal gold nanoparticles, was synthesized.

  5. Design and optimization of Ag-dielectric core-shell nanostructures for silicon solar cells

    Directory of Open Access Journals (Sweden)

    Feng-Xiang Chen

    2015-09-01

    Full Text Available Metal-dielectric core-shell nanostructures have been proposed as a light trapping scheme for enhancing the optical absorption of silicon solar cells. As a potential application of such enhanced effects, the scattering efficiencies of three core-shell structures (Ag@SiO2, Ag@TiO2, and Ag@ZrO2 are discussed using the Mie Scattering theory. For compatibility with experiment results, the core diameter and shell thickness are limited to 100 and 30 nm, respectively, and a weighted scattering efficiency is introduced to evaluate the scattering abilities of different nanoparticles under the solar spectrum AM 1.5. The simulated results indicate that the shell material and thickness are two key parameters affecting the weighted scattering efficiency. The SiO2 is found to be an unsuitable shell medium because of its low refractive index. However, using the high refractive index mediumTiO2 in Ag@TiO2 nanoparticles, only the thicker shell (30 nm is more beneficial for light scattering. The ZrO2 is an intermediate refractive index material, so Ag@ZrO2 nanoparticles are the most effective core-shell nanostructures in these silicon solar cells applications.

  6. Synthesis of SiCN@TiO2 core-shell ceramic microspheres via PDCs method

    Science.gov (United States)

    Liu, Hongli; Wei, Ning; Li, Jing; Zhang, Haiyuan; Chu, Peng

    2018-02-01

    A facile and effective polymer-derived ceramics (PDCs) emulsification-crosslinking-pyrolysis method was developed to fabricate SiCN@TiO2 core-shell ceramic microspheres with polyvinylsilazane (PVSZ) and tetrabutyl titanate (TBT) as precursors. The TBT: PVSZ mass ratios, emulsifier concentrations and the pyrolysis temperature were examined as control parameters to tune the size and morphology of microspheres. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed the synthesized SiCN@TiO2 microspheres to be comprised of SiCN core coated with TiO2 crystals, with an average size of 0.88 μm when pyrolyzed at 1400 °C. The analysis of Fourier transform infrared spectroscopy (FT-IR), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) ensured that SiCN@TiO2 core-shell ceramic microspheres composed of rutile TiO2, β-SiC and Si3N4 crystalline phases, The thermal properties were characterized by thermogravimetric analysis (TGA). The obtained SiCN@TiO2 core-shell ceramic microspheres were the promising candidate of the infrared opacifier in silica aerogels and this technique can be extended to other preceramic polymers.

  7. One-Step Synthesis of Hybrid Core-Shell Metal-Organic Frameworks.

    Science.gov (United States)

    Yang, Xinyu; Yuan, Shuai; Zou, Lanfang; Drake, Hannah; Zhang, Yingmu; Qin, Junsheng; Alsalme, Ali; Zhou, Hongcai

    2018-02-16

    Epitaxial growth of MOF-on-MOF composite is an evolving research topic. In current methods, the core-shell MOFs are synthesized via a stepwise strategy which involves growing the shell-MOFs on top of the preformed core-MOFs with matched lattice parameters. However, the inconvenient stepwise synthesis and the strict lattice-matching requirement have limited the development of core-shell MOFs. Herein, we demonstrate that hybrid core-shell MOFs with mismatching lattices can be synthesized under the guidance of nucleation kinetics. A series of MOF composites with mesoporous core and microporous shell were constructed and characterized by optical microscopy, powder X-ray diffraction, gas sorption measurement, and scanning electron microscopy. Isoreticular expansion of microporous shells and orthogonal modification of the core was realized to produce multifunctional MOF composites, which acted as size selective catalysts for olefin epoxidation with high activity and selectivity. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Novel Organically Modified Core-Shell Clay for Epoxy Composites-"SOBM Filler 1".

    Science.gov (United States)

    Iheaturu, Nnamdi Chibuike; Madufor, Innocent Chimezie

    2014-01-01

    Preparation of a novel organically modified clay from spent oil base drilling mud (SOBM) that could serve as core-shell clay filler for polymers is herein reported. Due to the hydrophilic nature of clay, its compatibility with polymer matrix was made possible through modification of the surface of the core clay sample with 3-aminopropyltriethoxysilane (3-APTES) compound prior to its use. Fourier transform infrared (FT-IR) spectroscopy was used to characterize clay surface modification. Electron dispersive X-ray diffraction (EDX) and scanning electron microscopy (SEM) were used to expose filler chemical composition and morphology, while electrophoresis measurement was used to examine level of filler dispersion. Results show an agglomerated core clay powder after high temperature treatment, while EDX analysis shows that the organically modified clay is composed of chemical inhomogeneities, wherein elemental compositions in weight percent vary from one point to the other in a probe of two points. Micrographs of the 3-APTES coupled SOBM core-shell clay filler clearly show cloudy appearance, while FT-IR indicates 25% and 5% increases in fundamental vibrations band at 1014 cm(-1) and 1435 cm(-1), respectively. Furthermore, 3-APTES coupled core-shell clay was used to prepare epoxy composites and tested for mechanical properties.

  9. Morphological and compositional characteristics of bimetallic core@shell nanoparticles revealed by MEIS

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, Dario F., E-mail: dario.f.sanchez@gmail.com [Instituto de Física, Universidade Federal do Rio Grande do Sul, Porto Alegre (Brazil); Moiraghi, Raquel; Cometto, Fernando P.; Pérez, Manuel A. [INFIQC, Departamento de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba (Argentina); Fichtner, Paulo F.P. [Instituto de Física, Universidade Federal do Rio Grande do Sul, Porto Alegre (Brazil); Department of Metallurgy, Engineering School UFRGS, Porto Alegre (Brazil); Grande, Pedro L. [Instituto de Física, Universidade Federal do Rio Grande do Sul, Porto Alegre (Brazil)

    2015-03-01

    Highlights: • Characterization of the morphology, structure and composition of Au@Ag core@shell nanoparticles, high polydispersity in the shell thickness. • Subnanometer resolution with a representative sampling achieved through the combination of Medium Energy Ion Scattering with Transmission Electron Microscopy. • For samples synthesized with baths of different AgNO{sub 3} concentrations, determination of the nanoparticles’ Ag shell thicknesses distribution of about a few nanometers around the Au core. - Abstract: In this paper we report the application of a suitable methodology to study the morphology, structure and composition of core@shell nanoparticles (NPs) systems with polydispersity in the shell thickness, with subnanometer resolution and good sampling. Through the combination of Medium Energy Ion Scattering with Transmission Electron Microscopy, we perform a systematic investigation on core@shell Au@Ag NPs synthesized by an original wet chemical method. For samples synthesized with baths of different AgNO{sub 3} concentrations, the present approach allowed us to determine the NP's Ag shell thicknesses distribution of about a few nanometers around the Au core.

  10. Non-resonant Mie scattering: emergent optical properties of core-shell polymer nanowires.

    Science.gov (United States)

    Khudiyev, Tural; Huseyinoglu, Ersin; Bayindir, Mehmet

    2014-04-09

    We provide the in-depth characterization of light-polymer nanowire interactions in the context of an effective Mie scattering regime associated with low refractive index materials. Properties of this regime sharply contrast with these of resonant Mie scattering, and involve the formation of strictly forward-scattered and coupling-free optical fields in the vicinity of core-shell polymer nanowires. Scattering from these optical fields is shown to be non-resonant in nature and independent from incident polarization. In order to demonstrate the potential utility of this scattering regime in one-dimensional (1D) polymeric nanostructures, we fabricate polycarbonate (PC) - polyvinylidene difluoride (PVDF) core-shell nanowires using a novel iterative thermal drawing process that yields uniform and indefinitely long core-shell nanostructures. These nanowires are successfully engineered for novel nanophotonics applications, including size-dependent structural coloration, efficient light capture on thin-film solar cells, optical nano-sensors with ultrahigh sensitivity and a mask-free photolithography method suitable for the straightforward production of 1D nanopatterns.

  11. Preparation and characteristics of core-shell structure cobalt/silica nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Fu Wuyou [National Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Yang Haibin [National Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China) and Henan Polytechnic University, Hennan Jiaozuo 454000 (China)]. E-mail: yanghb@jlu.edu.cn; Hari-Bala [College of Chemistry, Jilin University, Changchun 130023 (China); Liu Shikai [Henan Polytechnic University, Hennan Jiaozuo 454000 (China); Li, Minghui [National Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Zou Guangtian [National Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China)

    2006-12-10

    The silica nanolayer with different thickness was coated on the spherical cobalt nanoparticles (an average diameter of 67 nm) to form core-shell structure by the controlled hydrolysis and condensation of tetraethyl orthosilicate (TEOS). This coating process was based on the use of silane coupling agent 3-mercaptopropyltrimethoxysilane (HS-(CH{sub 2}){sub 3}Si(OCH{sub 3}){sub 3}, MPTS) as a primer to render the cobalt surface vitreophilic, thus rendering cobalt surface compatible with silica. The control over the silica coating layer thickness can be achieved by varying the reaction time. The cobalt nanoparticles and the cobalt coated with silica shell were confirmed by transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS) was used to gain insight into the way in which the MPTS is bound to the surface of the cobalt nanoparticles. Result of the thermogravimetric analysis (TGA) and differential thermal analysis (DTA) indicate that the thermal stability of cobalt/silica is better than that of pure cobalt nanoparticles. Magnetic properties of these powders have been evaluated. These cobalt/silica core-shell nanoparticles can be utilized as precursors for making property-tunable magnetic nanoparticles, thin films, and multilayered core-shell structure nanocomposites.

  12. Hierarchical Mesoporous Organosilica/Silica Core-Shell Nanoparticles Capable of Controlled Fungicide Release.

    Science.gov (United States)

    Anwander, Reiner; Liang, Yucang; Luo, Leilei; Erichsen, Egil

    2018-03-23

    A new class of hierarchically structured mesoporous silica core-shell nanoparticles (HSMSCSNs) with a periodic mesoporous organosilica (PMO) core and a mesoporous silica (MS) shell is reported. The applied one-pot two-step strategy allows for a rational control over the core/shell chemical composition, topology and pore/particle size, simply by adjusting the reaction conditions in the presence of CTAB as a structure directing agent under basic conditions. The spherical ethylene- or methylene-bridged PMO cores feature hexagonal (p6mm) or cage-like cubic symmetry (Pm-3n) depending on the organosilica precursor. The hexagonal MS shell was obtained by an n-hexane-induced controlled hydrolysis of TEOS followed by a directional co-assembly/condensation process of silicate/CTAB composites at the PMO cores. The HSMSCSN feature a hierarchical pore structure with pore diameters in the range of ca. 2.7 nm and 5.6 nm in the core and shell domains, respectively. The core sizes and shell thicknesses are adjustable in the range of 90-275 nm and 15-50 nm, respectively, and the surface areas (max. 1300 m2/g) and pore volumes (1.83 cm3/g) belong to highest ones reported for core-shell nanoparticles. The adsorption and controlled release of fungicide propiconazole on the HSMSCSN revealed a three-stage release profile. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Direct Correlation of Excitonics with Efficiency in a Core-Shell Quantum Dot Solar Cell.

    Science.gov (United States)

    Dana, Jayanta; Maiti, Sourav; Tripathi, Vaidehi S; Ghosh, Hirendra N

    2018-02-16

    Shell thickness dependent band-gap engineering of quasi type II core-shell material with higher carrier cooling time, lower interfacial defect states, and longer charge carrier recombination time can be a promising candidate for both photocatalysis and solar cell. In the present investigation, colloidal CdSe@CdS core-shells with different shell thickness (2, 4 and 6 monolayer CdS) were synthesized through hot injection method and have been characterized by high resolution transmission electron microscope (HRTEM) followed by steady state absorption and luminescence techniques. Ultrafast transient absorption (TA) studies suggest longer carrier cooling, lower interfacial surface states, and slower carrier recombination time in CdSe@CdS core-shell with increasing shell thickness. By TA spectroscopy, the role of CdS shell in power conversion efficiency (PCE) has been explained in detail. The measured PCE was found to initially increase and then decrease with increasing shell thickness. Shell thickness has been optimized to maximize the efficiency after correlating the shell controlled carrier cooling and recombination with PCE values and a maximum PCE of 3.88 % was obtained with 4 monolayers of CdS shell, which is found to be 57 % higher than compared to bare CdSe QDs. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Core-shell structured high-k polymer nanocomposites for energy storage and dielectric applications.

    Science.gov (United States)

    Huang, Xingyi; Jiang, Pingkai

    2015-01-21

    High-k polymer nanocomposites have considerable potential in energy storage and dielectric applications because of their ease of processing, flexibility, and low cost. Core-shell nanoarchitecture strategies are versatile and powerful tools for the design and synthesis of advanced high-k polymer nanocomposites. Recent and in-progress state-of-the-art advancements in the application of core-shell nanoarchitecture strategies to design and prepare high-k polymer nanocomposites are summarized. Special focus is directed to emphasizing their advantages over conventional melt-mixing and solution-mixing methods: first, homogeneous nanoparticle dispersion can be easily achieved even in highly loaded nanocomposites; second, the dielectric constant of the nanocomposites can be effectively enhanced and meanwhile the high breakdown strength can be well-preserved; third, for nanocomposites filled with electrically conductive nanoparticles, dielectric loss can be effectively surpressed, and meanwhile a high dielectric constant can be achieved. In addition, fundamental insights into the roles of the interfaces on the dielectric properties of the nanocomposites can be probed. The last part of the article is concluded with current problems and future perspectives of utilizing the core-shell nanoarchitecture strategies for the development of high-k polymer nanocomposites. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Nanocellulose Derivative/Silica Hybrid Core-Shell Chiral Stationary Phase: Preparation and Enantioseparation Performance

    Directory of Open Access Journals (Sweden)

    Xiaoli Zhang

    2016-05-01

    Full Text Available Core-shell silica microspheres with a nanocellulose derivative in the hybrid shell were successfully prepared as a chiral stationary phase by a layer-by-layer self-assembly method. The hybrid shell assembled on the silica core was formed using a surfactant as template by the copolymerization reaction of tetraethyl orthosilicate and the nanocellulose derivative bearing triethoxysilyl and 3,5-dimethylphenyl groups. The resulting nanocellulose hybrid core-shell chiral packing materials (CPMs were characterized and packed into columns, and their enantioseparation performance was evaluated by high performance liquid chromatography. The results showed that CPMs exhibited uniform surface morphology and core-shell structures. Various types of chiral compounds were efficiently separated under normal and reversed phase mode. Moreover, chloroform and tetrahydrofuran as mobile phase additives could obviously improve the resolution during the chiral separation processes. CPMs still have good chiral separation property when eluted with solvent systems with a high content of tetrahydrofuran and chloroform, which proved the high solvent resistance of this new material.

  16. Crystalline-amorphous core-shell silicon nanowires for high capacity and high current battery electrodes.

    Science.gov (United States)

    Cui, Li-Feng; Ruffo, Riccardo; Chan, Candace K; Peng, Hailin; Cui, Yi

    2009-01-01

    Silicon is an attractive alloy-type anode material for lithium ion batteries because of its highest known capacity (4200 mAh/g). However silicon's large volume change upon lithium insertion and extraction, which causes pulverization and capacity fading, has limited its applications. Designing nanoscale hierarchical structures is a novel approach to address the issues associated with the large volume changes. In this letter, we introduce a core-shell design of silicon nanowires for highpower and long-life lithium battery electrodes. Silicon crystalline-amorphous core-shell nanowires were grown directly on stainless steel current collectors by a simple one-step synthesis. Amorphous Si shells instead of crystalline Si cores can be selected to be electrochemically active due to the difference of their lithiation potentials. Therefore, crystalline Si cores function as a stable mechanical support and an efficient electrical conducting pathway while amorphous shells store Li(+) ions. We demonstrate here that these core-shell nanowires have high charge storage capacity ( approximately 1000 mAh/g, 3 times of carbon) with approximately 90% capacity retention over 100 cycles. They also show excellent electrochemical performance at high rate charging and discharging (6.8 A/g, approximately 20 times of carbon at 1 h rate).

  17. The impact of core-shell nanotube structures on fracture in ceramic nanocomposites

    International Nuclear Information System (INIS)

    Liang, Xin; Yang, Yingchao; Lou, Jun; Sheldon, Brian W.

    2017-01-01

    Multi-wall carbon nanotubes (MWCNTs) can be used to create ceramic nanocomposites with improved fracture toughness. In the present work, atomic layer deposition (ALD) was employed to deposit thin oxide layers on MWCNTs. These core-shell structures were then used to create nanocomposites by using a polymer derived ceramic (PDC) to produce the matrix. Variations in both the initial MWCNT structure and the oxide layers led to substantial differences in fiber-pullout behavior. Single tube pullout tests also showed that the oxide coatings led to stronger bonding with the ceramic matrix. With high defect density MWCNTs, this led to shorter pull-out lengths which is consistent with the conventional understanding of fracture in ceramic matrix composites. However, with low defect density MWCNTs longer pullout lengths were observed with the oxide layers. To interpret the different trends that were observed, we believe that the ALD coatings should not be viewed simply as a means of altering the interfacial properties. Instead, the coated MWCNTs should be viewed as more complex core-shell fibers where both interface and internal properties can be controlled with the ALD layers. - Graphical abstract: Fracture properties of core-shell nanotubes reinforced ceramic nanocomposites.

  18. Two-way actuation behavior of shape memory polymer/elastomer core/shell composites

    International Nuclear Information System (INIS)

    Kang, Tae-Hyung; Lee, Jeong-Min; Yu, Woong-Ryeol; Youk, Ji Ho; Ryu, Hee Wook

    2012-01-01

    Semi-crystalline shape memory polymers (SMPs) show net two-way shape memory (2W-SM) behavior under constant stresses by the recoverable creep strain upon heating and stress-induced crystallization under the application of creep stress upon cooling. The applied constant stress is the key factor in this 2W-SM behavior. A core/shell structure is manufactured for the purpose of imparting a constant stress upon SMPs. An SMP in film or fiber form is dipped into a solution of an elastomer, photoinitiator, and curing agent and then dried out. After this dip coating process is repeatedly carried out, the SMP/elastomer core/shell composite is deformed into a temporary shape after being heated up above the transition temperature of the SMP. Under constant strain conditions, the composite is cooled down, after which the shell elastomer is cured using ultraviolet light. Then, the SMP/elastomer core/shell composite extends and contracts upon cooling and heating, respectively, without any external load. This cyclic deformation behavior is characterized, demonstrating that the current method offers a simple macroscopic processing technique to manufacture 2W-SM polymer composites. (paper)

  19. Synthesis and characterization of ZnSe:Fe/ZnSe core/shell nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Lin; Zhu, Jianguo, E-mail: yanglin_1028@163.com; Xiao, Dingquan

    2014-04-15

    High-quality ZnSe:Fe/ZnSe core/shell nanocrystals were prepared via a hydrothermal microemulsion technique. Effective surface passivation of monodisperse ZnSe:Fe nanocrystals is achieved by overcoating them with a ZnSe shell. The samples were characterized by means of XRD, EDX, TEM, PSD, XPS, photoluminescence, and Raman spectrum. The results show that the as-synthesized nanocrystals are cubic zinc blende ZnSe structure with high purity and the average particle size of ZnSe:Fe/ZnSe core/shell nanocrystal is larger than that of ZnSe:Fe core. The growth of ZnSe shell causes a small red shift in PL spectra, and then the PL quantum yield (QY) increases from 16% before shell growth to the maximum of 37% after increasing shell thickness up to 1.2 monolayers (ML). Moreover, both transverse optic (TO) and longitudinal optic (LO) phonon modes of ZnSe are shifted toward lower frequency as compared with the reported ones. -- Highlights: • ZnSe:Fe/ZnSe core/shell QDs were prepared by a hydrothermal microemulsion method. • ZnSe shell efficiently passivates surface defects by serving as a physical barrier. • The particle size and PL properties can be turned with the growth of ZnSe shell. • The luminescence efficiency and stability of QDs could be improved in this manner.

  20. Core-shell catalysts consisting of nanoporous cores for oxygen reduction reaction.

    Science.gov (United States)

    Shao, Minhua; Smith, Brandon H; Guerrero, Sandra; Protsailo, Lesia; Su, Dong; Kaneko, Keiichi; Odell, Jonathan H; Humbert, Michael P; Sasaki, Kotaro; Marzullo, Jesse; Darling, Robert M

    2013-09-28

    A comprehensive experimental study was conducted on the dealloying of PdNi6 nanoparticles under various conditions. A two-stage dealloying protocol was developed to leach >95% of Ni while minimizing the dissolution of Pd. The final structure of the dealloyed particle was strongly dependent on the acid used and temperature. When H2SO4 and HNO3 solutions were used in the first stage of dealloying, solid and porous particles were generated, respectively. The porous particles have a 3-fold higher electrochemical surface area per Pd mass than the solid ones. The dealloyed PdNi6 nanoparticles were then used as a core material for the synthesis of core-shell catalysts. These catalysts were synthesized in gram-size batches and involved Pt displacement of an underpotentially deposited (UPD) Cu monolayer. The resulting materials were characterized by scanning transmission electron microscopy (STEM) and in situ X-ray diffraction (XRD). The oxygen reduction reaction (ORR) activity of the core-shell catalysts is 7-fold higher than the state-of-the-art Pt/C. The high activity was confirmed by a more than 40 mV improvement in fuel cell performance with a Pt loading of 0.1 mg cm(-2) by using the core-shell catalysts.

  1. Tunable core-shell particles generated from smart water-soluble chitosan seeds.

    Science.gov (United States)

    Xiao, Congming; You, Rongrui; Dong, Yanrui; Zhang, Zhongxin

    2016-05-20

    A chain-like route was presented to create various core-shell particles with soft, aqueous or inorganic cores respectively. Water-soluble chitosan (WSC) gel particles were obtained through gelating the aqueous WSC solution of 0.02 g/mL at its isoelectric point. Then, polyelectrolyte complexes were formed and surrounded on the outer surfaces of WSC gel particles by immersing the particles in 2 wt% aqueous sodium alginate. Soft WSC cores in these core-shell particles disappeared after maintaining the particles in 1M HCl for 6h. The cores of obtained particles at this step became aqueous, and could be further transformed into inorganic ones via contacting the particles with copper sulfate and sodium sulfide aqueous solutions successively. The composition of the shell was verified with Fourier transform infrared spectroscopy. The formation of various core-shell particles was confirmed with digital photographic observation, thermogravimetric and fluorescence analyses. The whole process was a chain-like one and was able to stop at any stage to harvest a corresponding target. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Biphasic synthesis of Au@SiO2 core-shell particles with stepwise ligand exchange.

    Science.gov (United States)

    Schulzendorf, Mathias; Cavelius, Christian; Born, Philip; Murray, Eoin; Kraus, Tobias

    2011-01-18

    We report the synthesis of well-dispersed core-shell Au@SiO(2) nanoparticles with minimal extraneous silica particle growth. Agglomeration was suppressed through consecutive exchange of the stabilizing ligands on the gold cores from citrate to L-arginine and finally (3-mercaptopropyl)triethoxysilane. The result was a vitreophilic, stable gold suspension that could be coated with silica in a biphasic mixture through controlled hydrolysis of tetraethoxysilane under L-arginine catalysis. Unwanted condensation of silica particles without gold cores was limited by slowing the transfer across the liquid-liquid interface and reducing the concentration of the L-arginine catalyst. In-situ dynamic light scattering and optical transmission spectroscopy revealed the growth and dispersion states during synthesis. The resulting core-shell particles were characterized via dynamic light scattering, optical spectroscopy, and electron microscopy. Their cores were typically 19 nm in diameter, with a narrow size distribution, and could be coated with a silica shell in multiple steps to yield core-shell particles with diameters up to 40 nm. The approach was sufficiently controllable to allow us to target a shell thickness by choosing appropriate precursor concentrations.

  3. Nanomagnetism of Core-Shell Magnetic Nanoparticles and Application in Spent Nuclear Fuel Separation

    Science.gov (United States)

    Tarsem Singh, Maninder Kaur

    This dissertation presents the study on novel core-shell magnetic nanoparticles (NPs) with unique magnetic properties. Understanding the fundamental physics of antiferromagnetic - ferromagnetic interactions is essential to apply in different applications. Chromium (Cr) doped and undoped core-shell iron/iron-oxide NPs have been synthesized using cluster deposition system and studied with respect to their nanostructures, morphologies, sizes, chemical composition and magnetic properties. The room-temperature magnetic properties of Fe based NPs shows the strong dependence of intra/inter-particle interaction on NP size. The Cr-doped Fe NP shows the origin of sigma-FeCr phase at very low Cr concentration (2 at.%) unlike others reported at high Cr content and interaction reversal from dipolar to exchange interaction. A theoretical model of watermelon is constructed based on the experimental results and core-shell NP system in order to explain the physics of exchange interaction in Cr-doped Fe particles. The magnetic nanoparticle---chelator separation nanotechnology is investigated for spent nuclear fuel recycling and is reported 97% and 80% of extraction for Am(III) and Pu(IV) actinides respectively. If the long-term heat generating actinides such as Am(III) can be efficiently removed from the used fuel raffinates, the volume of material that can be placed in a given amount of repository space can be significantly increased. As it is a simple, versatile, compact, and cost efficient process that minimizes secondary waste and improves storage performance.

  4. Development of a particle nanoimprinting technique by core-shell particles.

    Science.gov (United States)

    Watanabe, H; Nishimura, M; Fukui, Y; Fujimoto, K

    2014-02-18

    We developed a particle nanoimprinting technique assisted by the array of core-shell particles. Core-shell particles composed of a solid core of polystyrene and a soft shell were prepared by soap-free emulsion polymerization and subsequently seeded polymerization. By the Langmuir-Blodgett method, particles were arranged into a closely packed 2D array over the water surface and transferred onto a polystyrene (PS) substrate at a regular interval. The PS substrate was heated up above its glass transition temperature (Tg) by either UV irradiation using a high-pressure Hg lamp or heat treatment in a temperature-controlled incubator. It could be observed that a nanopatterned indented surface was formed through the denting of particles into the PS substrate (particle nanoindenting). By the detachment of particles from the substrate by ultrasonication in ethanol, nanoholes were produced over the surface (particle nanoimprinting). The depth and the wall of nanoholes and their interval were tunable by the shell thickness and the 2D packing ratio of core-shell particle monolayers. The contact angle decreased from 70 degrees of the pristine particle monolayer to 13 degrees by the particle nanoindenting, and again increased to 50 degrees by detaching the particles from the substrate to create the nanoholes. The use of nanoholes as zepto-litter volume vessels enabled us to produce and arrange nanocrystals, such as NaCl and CaCO3 (zepto-reactor).

  5. PMMA/PMMA core-shell particles with ellipsoidal, fluorescent cores: accessing rotational dynamics.

    Science.gov (United States)

    Klein, Matthias K; Klinkenberg, Nele; Schuetter, Stefan; Saenger, Nicolai; Pfleiderer, Patrick; Zumbusch, Andreas

    2015-03-10

    For several decades, nonaqueous dispersions of PMMA particles have played an important role in colloid research. They have found application as colloidal model systems, which are used to probe glassy dynamics or to explore crystal nucleation. To date, most research has focused on spherical particles, in which only translational motion can be investigated. Recently, however, there has been a surge of interest in analyzing also rotational dynamics. In this contribution, we introduce a new class of core-shell particles, which can be used as rotational probes. The colloids described herein are composed of shape anisotropic, fluorescent cores covered with nonfluorescent PMMA shells. The core-shell particles are built up in four steps. In a first step, we produce fluorescent and photo-cross-linkable PMMA colloids. In the second step, these particles are thermomechanically elongated and fixed in defined ellipsoidal shapes by photo-cross-linking. Subsequently, we cover the cross-linked, fluorescent core with a nonfluorescent PMMA shell. The shape of the resulting core-shell colloids is tunable between the initial anisotropic and perfect spherical shape. For shaping, we apply a simple solvent swelling procedure. As one option, this method yields perfect PMMA spheres with ellipsoidal, fluorescent centers. We also report morphological particle characterization using various fluorescence microscopy techniques. Finally, we demonstrate that the rotational dynamics of individual colloids can be tracked and analyzed.

  6. One-pot synthesis and characterization of rhodamine derivative-loaded magnetic core-shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Jin, E-mail: jzhang@eng.uwo.ca; Li Jiaxin [University of Western Ontario, Department of Chemical and Biochemical Engineering (Canada); Razavi, Fereidoon S. [Brock University, Department of Physics (Canada); Mumin, Abdul Md. [University of Western Ontario, Department of Chemical and Biochemical Engineering (Canada)

    2011-05-15

    A new method to produce elaborate nanostructure with magnetic and fluorescent properties in one entity is reported in this article. Magnetite (Fe{sub 3}O{sub 4}) coated with fluorescent silica (SiO{sub 2}) shell was produced through the one-pot reaction, in which one reactor was utilized to realize the synthesis of superparamagnetic core of Fe{sub 3}O{sub 4}, the formation of SiO{sub 2} coating through the condensation and polymerization of tetraethylorthosilicate (TEOS), and the encapsulation of tetramethyl rhodamine isothiocyanate-dextran (TRITC-dextran) within silica shell. Transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, and X-ray diffraction (XRD) were carried out to investigate the core-shell structure. The magnetic core of the core-shell nanoparticles is 60 {+-} 10 nm in diameter. The thickness of the fluorescent SiO{sub 2} shell is estimated at 15 {+-} 5 nm. In addition, the fluorescent signal of the SiO{sub 2} shell has been detected by the laser confocal scanning microscopy (LCSM) with emission wavelength ({lambda}{sub em}) at 566 nm. In addition, the magnetic properties of TRITC-dextran loaded silica-coating iron oxide nanoparticles (Fe{sub 3}O{sub 4}-SiO{sub 2} NPs) were studied. The hysteresis loop of the core-shell NPs measured at room temperature shows that the saturation magnetization (M{sub s}) is not reached even at the field of 70 kOe (7T). Meanwhile, the very low coercivity (H{sub c}) and remanent magnetization (M{sub r}) are 0.375 kOe and 6.6 emu/g, respectively, at room temperature. It indicates that the core-shell particles have the superparamagnetic properties. The measured blocking temperature (T{sub B}) of the TRITC-dextran loaded Fe{sub 3}O{sub 4}-SiO{sub 2} NPs is about 122.5 K. It is expected that the multifunctional core-shell nanoparticles can be used in bio-imaging.

  7. Ultrasonic approach to the synthesis of HMX@TATB core-shell microparticles with improved mechanical sensitivity.

    Science.gov (United States)

    Huang, Bing; Hao, Xiaofei; Zhang, Haobin; Yang, Zhijian; Ma, Zhigang; Li, Hongzhen; Nie, Fude; Huang, Hui

    2014-07-01

    To improve the safety of sensitive explosive HMX while maintaining explosion performance, a moderately powerful but insensitive explosive TATB was used to coat HMX microparticles via a facile ultrasonic method. By using Estane as surface modifier and nano-sized TATB as the shell layer, the HMX@TATB core-shell microparticles with a monodisperse size and compact shell structure were successfully constructed. Both scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) results confirmed the formation of perfect core-shell structured composites. Based on a systematic and comparative study of the effect of experimental conditions, a possible formation mechanism of core-shell structure was proposed in detail. Moreover, the perfect core-shell HMX@TATB microparticles exhibited a unique thermal behavior and significantly improved mechanical sensitivity compared with that of the physical mixture. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Synthesis and morphology of iron-iron oxide core-shell nanoparticles produced by high pressure gas condensation

    NARCIS (Netherlands)

    Xing, Lijuan; ten Brink, Gert H.; Chen, Bin; Schmidt, Franz P.; Haberfehlner, Georg; Hofer, Ferdinand; Kooi, Bart J.; Palasantzas, Georgios

    2016-01-01

    Core-shell structured Fe nanoparticles (NPs) produced by high pressure magnetron sputtering gas condensation were studied using transmission electron microscopy (TEM) techniques, electron diffraction, electron energy-loss spectroscopy (EELS), tomographic reconstruction, and Wulff shape construction

  9. The radiative decays of excited states of transition elements located inside and near core-shell nanoparticles

    Science.gov (United States)

    Pukhov, Konstantin K.

    2017-12-01

    Here we discuss the radiative decays of excited states of transition elements located inside and outside of the subwavelength core-shell nanoparticles embedded in dielectric medium. Based on the quantum mechanics and quantum electrodynamics, the general analytical expressions are derived for the probability of the spontaneous transitions in the luminescent centers (emitter) inside and outside the subwavelength core-shell nanoparticle. Obtained expressions holds for arbitrary orientation of the dipole moment and the principal axes of the quadrupole moment of the emitter with respect to the radius-vector r connecting the center of the emitter with the center of the nanoparticle. They have simple form and show how the spontaneous emission in core-shell NPs can be controlled and engineered due to the dependence of the emission rates on core-shell sizes, radius-vector r and permittivities of the surrounding medium, shell, and core.

  10. Highly Stretchable and Transparent Supercapacitor by Ag-Au Core-Shell Nanowire Network with High Electrochemical Stability.

    Science.gov (United States)

    Lee, Habeom; Hong, Sukjoon; Lee, Jinhwan; Suh, Young Duk; Kwon, Jinhyeong; Moon, Hyunjin; Kim, Hyeonseok; Yeo, Junyeob; Ko, Seung Hwan

    2016-06-22

    Stretchable and transparent electronics have steadily attracted huge attention in wearable devices. Although Ag nanowire is the one of the most promising candidates for transparent and stretchable electronics, its electrochemical instability has forbidden its application to the development of electrochemical energy devices such as supercapacitors. Here, we introduce a highly stretchable and transparent supercapacitor based on electrochemically stable Ag-Au core-shell nanowire percolation network electrode. We developed a simple solution process to synthesize the Ag-Au core-shell nanowire with excellent electrical conductivity as well as greatly enhanced chemical and electrochemical stabilities compared to pristine Ag nanowire. The proposed core-shell nanowire-based supercapacitor still possesses fine optical transmittance and outstanding mechanical stability up to 60% strain. The Ag-Au core-shell nanowire can be a strong candidate for future wearable electrochemical energy devices.

  11. Study of Charge Transport in Vertically Aligned Nitride Nanowire Based Core Shell P-I-N Junctions

    Science.gov (United States)

    2016-07-01

    realize these structures. Vertically-aligned, radial core-shell architecture allows for significant defect reduction, strain engineering, polarity...fabrication with various process optimization for enhanced detector performance 6) Studying the photodetector performance and reliability ( parametric

  12. Core-shell and asymmetric polystyrene-gold composite particles via one-step Pickering emulsion polymerization.

    Science.gov (United States)

    Zhang, Mingmeng; Ngo, Thao H; Rabiah, Noelle I; Otanicar, Todd P; Phelan, Patrick E; Swaminathan, Raja; Dai, Lenore L

    2014-01-14

    Core-shell structured polystyrene-gold composite particles are synthesized from one-step Pickering emulsion polymerization. The surface coverage of the core-shell composite particles is improved with increasing gold nanoparticle (AuNP) hydrophobicity and concentration. At high surface coverage, the AuNPs exhibit an ordered hexagonal pattern, likely due to electrostatic repulsion during the emulsion polymerization process. In addition to core-shell structured polystyrene-gold composite particles, an intriguing observation is that at low AuNP concentrations, asymmetric polystyrene-gold nanocomposite particles are simultaneously formed, where a single gold nanoparticle is attached onto each polystyrene particle. It is found that these asymmetric particles are formed via a "seeded-growth" mechanism. The core-shell and asymmetric polystyrene-gold composite particles prove to be efficient catalysts as they successfully catalyze the Rhodamine B reduction reaction with stable performance and show high recyclability as catalysts.

  13. Synthesis and optical study of green light emitting polymer coated CdSe/ZnSe core/shell nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Tripathi, S.K., E-mail: surya@pu.ac.in [Department of Physics, Center of Advanced Study in Physics, Panjab University, Chandigarh 160 014 (India); Sharma, Mamta [Department of Physics, Center of Advanced Study in Physics, Panjab University, Chandigarh 160 014 (India)

    2013-05-15

    Highlights: ► Synthesis of Polymer coated core CdSe and CdSe/ZnSe core/shell NCs. ► From TEM image, the spherical nature of CdSe and CdSe/ZnSe is obtained. ► Exhibiting green band photoemission peak at 541 nm and 549 nm for CdSe core and CdSe/ZnSe core/shell NCs. ► The shell thickness has been calculated by using superposition of quantum confinement energy model. - Abstract: CdSe/ZnSe Core/Shell NCs dispersed in PVA are synthesized by chemical method at room temperature. This is characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV/Vis spectra and photoluminescence spectroscopy (PL). TEM image shows the spherical nature of CdSe/ZnSe core/shell NCs. The red shift of absorption and emission peak of CdSe/ZnSe core/shell NCs as compared to CdSe core confirmed the formation of core/shell. The superposition of quantum confinement energy model is used for calculation of thickness of ZnSe shell.

  14. In situ atomic-scale observation of oxygen-driven core-shell formation in Pt3Co nanoparticles.

    Science.gov (United States)

    Dai, Sheng; You, Yuan; Zhang, Shuyi; Cai, Wei; Xu, Mingjie; Xie, Lin; Wu, Ruqian; Graham, George W; Pan, Xiaoqing

    2017-08-07

    The catalytic performance of core-shell platinum alloy nanoparticles is typically superior to that of pure platinum nanoparticles for the oxygen reduction reaction in fuel cell cathodes. Thorough understanding of core-shell formation is critical for atomic-scale design and control of the platinum shell, which is known to be the structural feature responsible for the enhancement. Here we reveal details of a counter-intuitive core-shell formation process in platinum-cobalt nanoparticles at elevated temperature under oxygen at atmospheric pressure, by using advanced in situ electron microscopy. Initial segregation of a thin platinum, rather than cobalt oxide, surface layer occurs concurrently with ordering of the intermetallic core, followed by the layer-by-layer growth of a platinum shell via Ostwald ripening during the oxygen annealing treatment. Calculations based on density functional theory demonstrate that this process follows an energetically favourable path. These findings are expected to be useful for the future design of structured platinum alloy nanocatalysts.Core-shell platinum alloy nanoparticles are promising catalysts for oxygen reduction, however a deeper understanding of core-shell formation is still required. Here the authors report oxygen-driven formation of core-shell Pt 3 Co nanoparticles, seen at the atomic scale with in situ electron microscopy at ambient pressure.

  15. Synthesis of 3D Printable Cu-Ag Core-Shell Materials: Kinetics of CuO Film Removal

    Science.gov (United States)

    Hong, Seongik; Kim, Namsoo

    2015-03-01

    In this research, Cu-Ag core-shell particles were synthesized as a functional and 3D printable material. Using the solid-liquid method, Cu-Ag core-shell particles were simply synthesized, and different particle sizes of 100 nm and 2 μm were used to confirm the size effect in the synthesis and reaction control of the Cu-Ag core-shell particles. In addition, highly viscous Cu-Ag core-shell particle paste was also prepared, and its electrical conductivity was measured. As a result, the reaction rate in the case of the 2 μm Cu particles was controlled by film diffusion, whereas for the 100 nm Cu particles, the reaction rate was controlled by CuO film produced before reacting with Ag ions in solution, and limited by chemical reaction control. Through the solid-liquid method, dendrite-shaped Cu-Ag core-shell particles were formed. Also, the electrical conductivity increased with increasing sintering temperature and core-shell particle concentration.

  16. Synthesis of fly ash based core-shell composites for use as functional pigment in paints

    Science.gov (United States)

    Sharma, Richa; Tiwari, Sangeeta

    2016-04-01

    Fly ash is a combustion residue, mainly composed of silica, alumina and iron oxides. It is produced by the power industries in very large amounts and usually disposed in landfills, which have represented an environmental problem in recent years1. The need to generate a market for fly ash consumption is the main reason why alternative applications have been studied. It has been applied as an additive in construction materials like cement and pavements2. The present work describes the synthesis of Flyash-Titania core-shell particles by precipitation technique using Titanium tetra isopropoxide (TTIP) which can be used for variety of applications such as NIR reflecting materials for cool coatings, Photocatalysis etc. In this work, Fly ash is used in core and Nano -TiO2 is coated as shell on it. Surfactants are used to improve the adhesion of Nano Titania shell on fly ash core. Effect on adhesion of TiO2 on Fly ash is studied by using different types of surfactant. The preparation of core shells was carried out in absence of surfactant as well as using anionic and non-ionic surfactants. The percentage of surfactant was varied to study the effect of amount of surfactant on the uniformity and size of particles in the shell using Kubelka-Munk transformed reflectance spectra. The morphology of core shell structures was studied using SEM technique. Use of anionic surfactant results in more uniform coating with reduced particle size of the shell material. The composite particles prepared by using anionic surfactant are having good pigment properties and also shows good reflectance in Near Infrared region and hence can be used as a pigment in cool coatings.

  17. Preparation of hollow core/shell microspheres of hematite and its adsorption ability for samarium.

    Science.gov (United States)

    Yu, Sheng-Hui; Yao, Qi-Zhi; Zhou, Gen-Tao; Fu, Sheng-Quan

    2014-07-09

    Hollow core/shell hematite microspheres with diameter of ca. 1-2 μm have been successfully achieved by calcining the precursor composite microspheres of pyrite and polyvinylpyrrolidone (PVP) in air. The synthesized products were characterized by a wide range of techniques including powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and Brunauer-Emmett-Teller (BET) gas sorptometry. Temperature- and time-dependent experiments unveil that the precursor pyrite-PVP composite microspheres finally transform into hollow core/shell hematite microspheres in air through a multistep process including the oxidation and sulfation of pyrite, combustion of PVP occluded in the precursor, desulfation, aggregation, and fusion of nanosized hematite as well as mass transportation from the interior to the exterior of the microspheres. The formation of the hollow core/shell microspheres dominantly depends on the calcination temperature under current experimental conditions, and the aggregation of hematite nanocrystals and the core shrinking during the oxidation of pyrite are responsible for the formation of the hollow structures. Moreover, the adsorption ability of the hematite for Sm(III) was also tested. The results exhibit that the hematite microspheres have good adsorption activity for trivalent samarium, and that its adsorption capacity strongly depends on the pH of the solution, and the maximum adsorption capacity for Sm(III) is 14.48 mg/g at neutral pH. As samarium is a typical member of the lanthanide series, our results suggest that the hollow hematite microspheres have potential application in removal of rare earth elements (REEs) entering the water environment.

  18. Core-shell titanium dioxide-titanium nitride nanotube arrays with near-infrared plasmon resonances

    Science.gov (United States)

    Farsinezhad, Samira; Shanavas, Thariq; Mahdi, Najia; Askar, Abdelrahman M.; Kar, Piyush; Sharma, Himani; Shankar, Karthik

    2018-04-01

    Titanium nitride (TiN) is a ceramic with high electrical conductivity which in nanoparticle form, exhibits localized surface plasmon resonances (LSPRs) in the visible region of the solar spectrum. The ceramic nature of TiN coupled with its dielectric loss factor being comparable to that of gold, render it attractive for CMOS polarizers, refractory plasmonics, surface-enhanced Raman scattering and a whole host of sensing applications. We report core-shell TiO2-TiN nanotube arrays exhibiting LSPR peaks in the range 775-830 nm achieved by a simple, solution-based, low cost, large area-compatible fabrication route that does not involve laser-writing or lithography. Self-organized, highly ordered TiO2 nanotube arrays were grown by electrochemical anodization of Ti thin films on fluorine-doped tin oxide-coated glass substrates and then conformally coated with a thin layer of TiN using atomic layer deposition. The effects of varying the TiN layer thickness and thermal annealing on the LSPR profiles were also investigated. Modeling the TiO2-TiN core-shell nanotube structure using two different approaches, one employing effective medium approximations coupled with Fresnel coefficients, resulted in calculated optical spectra that closely matched the experimentally measured spectra. Modeling provided the insight that the observed near-infrared resonance was not collective in nature, and was mainly attributable to the longitudinal resonance of annular nanotube-like TiN particles redshifted due to the presence of the higher permittivity TiO2 matrix. The resulting TiO2-TiN core-shell nanotube structures also function as visible light responsive photocatalysts, as evidenced by their photoelectrochemical water-splitting performance under light emitting diode illumination using 400, 430 and 500 nm photons.

  19. Material dimensionality effects on the nanoindentation behavior of Al/a-Si core-shell nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Fleming, Robert A. [Department of Mechanical Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); Center for Advanced Surface Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); Goss, Josue A. [Center for Advanced Surface Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); Zou, Min, E-mail: mzou@uark.edu [Department of Mechanical Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); Center for Advanced Surface Engineering, University of Arkansas, Fayetteville, AR 72701 (United States)

    2017-08-01

    Highlights: • Nanoindentation behavior of Al/a-Si core-shell nanostructures were studied. • 3D core confinement enables significant deformation recovery beyond elastic limit. • As the confinement is reduced, the deformation recovery is reduced or suppressed. • Atomistic simulations suggest core confinement affects dislocation dynamics. • 3D confinement has the highest percentage of dislocation removal after unloading. - Abstract: The nanoindentation behavior of hemispherical Al/a-Si core-shell nanostructures (CSNs), horizontally-aligned Al/a-Si core-shell nanorods (CSRs) with various lengths, and an Al/a-Si layered thin film has been studied to understand the effects of geometrical confinement of the Al core on the CSN deformation behavior. When loaded beyond the elastic limit, the CSNs have an unconventional load-displacement behavior with no residual displacement after unloading, resulting in no net shape change after indentation. This behavior is enabled by dislocation activities within the confined Al core, as indicated by discontinuous indentation signatures (load-drops and load-jumps) observed in the load-displacement data. When the geometrical confinement of the core is slightly reduced, as in the case of CSRs with the shortest rod length, the discontinuous indentation signatures and deformation resistance are heavily reduced. Further decreases in core confinement result in conventional nanoindentation behavior, regardless of geometry. Supporting molecular dynamics simulations show that dislocations nucleated in the core of a CSN are more effectively removed during unloading compared to CSRs, which supports the hypothesis that the unique deformation resistance of Al/a-Si CSNs are enabled by 3-dimensional confinement of the Al core.

  20. Core-Shell Gold Nanorod@Metal-Organic Framework Nanoprobes for Multimodality Diagnosis of Glioma.

    Science.gov (United States)

    Shang, Wenting; Zeng, Chaoting; Du, Yang; Hui, Hui; Liang, Xiao; Chi, Chongwei; Wang, Kun; Wang, Zhongliang; Tian, Jie

    2017-01-01

    One of the most significant challenges in the diagnosis of brain cancer is efficient in vivo imaging using nontoxic nanoprobes. Core-shell gold nanorod@MIL-88(Fe) nanostars are successfully constructed as triple-modality imaging (computed tomography/magnetic-resonance imaging/photoacoustic imaging) nanoprobes that show low cytotoxicity, high contrast, high penetration depth, and high spatial resolution for accurate and noninvasive imaging and diagnosis of gliomas. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Dynamics of Green AuNP Formation and Their Application in Core-Shell Nanostructures

    DEFF Research Database (Denmark)

    Engelbrekt, Christian; Zhang, Jingdong; Jensen, Palle Skovhus

    The formation of gold nanoparticles in our optimized synthesis is achieved through reduction of tetrachloroauric acid in 2 - (N - morpholino)ethanesulphonic acid (MES) buffered glucose and stabilization by starch at room temperature. The formation has been followed by measuring the electrochemical...... potential, conductivity, pH, turbidity, UV - Vis extinction , core size and hydrodynamic diameter . The synthesized AuNPs have been employed as core particles in advanced core - shell structures with highly porous platinum nanoparticle coating or copper oxide shells. These hold poten- tials as effective...

  2. SISGR - Design and Characterization of Novel Photocatalysts With Core-Shell Nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Zaera, Francisco [Univ. of California, Riverside, CA (United States). Dept. of Chemistry; Bardeen, Christopher J. [Univ. of California, Riverside, CA (United States). Dept. of Chemistry; Yin, Yadong [Univ. of California, Riverside, CA (United States). Dept. of Chemistry

    2017-03-15

    The overall goal of this project has been to develop new a new and novel class of well-characterized nanostructured Metal@TiO2 core-shell and yolk-shell photocatalysts to address two fundamental issues presently limiting this field: (1) the fast recombination of electron-hole pairs once generated by light absorption, and (2) the recombination of H2 and O2 on the metal surface once produced. These model samples are also used to study the fundamentals of the photocatalytic processes.

  3. Exchange bias and asymmetric hysteresis loops from a microscopic model of core/shell nanoparticles

    International Nuclear Information System (INIS)

    Iglesias, Oscar; Batlle, Xavier; Labarta, Amilcar

    2007-01-01

    We present Monte Carlo simulations of hysteresis loops of a model of a magnetic nanoparticle with a ferromagnetic core and an antiferromagnetic shell with varying values of the core/shell interface exchange coupling which aim to clarify the microscopic origin of exchange bias observed experimentally. We have found loop shifts in the field direction as well as displacements along the magnetization axis that increase in magnitude when increasing the interfacial exchange coupling. Overlap functions computed from the spin configurations along the loops have been obtained to explain the origin and magnitude of these features microscopically

  4. Glass transition of poly (methyl methacrylate) filled with nanosilica and core-shell structured silica

    DEFF Research Database (Denmark)

    Song, Yihu; Bu, Jing; Zuo, Min

    2017-01-01

    Core-shell (CS) nanocomposite particles with 53.4 wt% cross-linked poly (methyl methacrylate) (PMMA) shell of 11.6 nm in thickness were fabricated via miniemulsion polymerization of methyl methacrylate in the presence of modified nanosilica. The influence of nanosilica and CS nanoparticles on glass...... transition and segmental dynamics of PMMA in the nanocomposites prepared via solution casting was compared. The remarkable depression (≥10 °C) of glass transition temperature (Tg) induced by the incorporation of SiO2 and CS was both observed at low loadings. Here, different mechanisms were responsible...

  5. Uniform silver/polypyrrole core-shell nanoparticles synthesized by hydrothermal reaction

    Energy Technology Data Exchange (ETDEWEB)

    Wang Shibin [Department of Chemistry, Tsinghua University, Beijing 100084 (China); Shi Gaoquan [Department of Chemistry, Tsinghua University, Beijing 100084 (China)]. E-mail: gshi@tsinghua.edu.cn

    2007-04-15

    Uniformly sized silver/polypyrrole (Ag/PPy) core-shell nanoparticles were synthesized by one-step hydrothermal reaction of pyrrole and silver nitrate in the presence of polyvinyl pyrrolidone (PVP) as protection agent. The morphology and structures of the nanoparticles have been studied by scanning and transmission electronic microscopes, X-ray diffractometer and Raman spectroscopy. The experimental results indicated that the particles had 120 nm silver cores with 20 nm polypyrrole (PPy) coatings. The reaction conditions have strong effects on the morphology of the nanoparticles.

  6. Uniform silver/polypyrrole core-shell nanoparticles synthesized by hydrothermal reaction

    International Nuclear Information System (INIS)

    Wang Shibin; Shi Gaoquan

    2007-01-01

    Uniformly sized silver/polypyrrole (Ag/PPy) core-shell nanoparticles were synthesized by one-step hydrothermal reaction of pyrrole and silver nitrate in the presence of polyvinyl pyrrolidone (PVP) as protection agent. The morphology and structures of the nanoparticles have been studied by scanning and transmission electronic microscopes, X-ray diffractometer and Raman spectroscopy. The experimental results indicated that the particles had 120 nm silver cores with 20 nm polypyrrole (PPy) coatings. The reaction conditions have strong effects on the morphology of the nanoparticles

  7. Probing inhomogeneous composition in core/shell nanowires by Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Amaduzzi, F.; Alarcón-Lladó, E.; Russo-Averchi, E.; Matteini, F.; Heiß, M.; Tütüncüoglu, G.; Conesa-Boj, S.; Fontcuberta i Morral, A. [Laboratoire des Matériaux Semiconducteurs, École Polytechnique Fédérale de Lausanne, 1015 Lausanne (Switzerland); Mata, M. de la [Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193 Bellaterra, CAT (Spain); Arbiol, J. [Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193 Bellaterra, CAT (Spain); Institució Catalana de Recerca i Estudis Avançats (ICREA), 08019 Barcelona, CAT (Spain)

    2014-11-14

    Due to its non-destructive and its micro-spatial resolution, Raman spectroscopy is a powerful tool for a rapid structural and compositional characterization of nanoscale materials. Here, by combining the compositional dependence of the Raman peaks with the existence of photonic modes in the nanowires, we address the composition inhomogeneities of Al{sub x}Ga{sub 1−x}As/GaAs core/shell structures. The experimental results are validated with complementary chemical composition maps of the nanowire cross-sections and finite-difference time-domain simulations of the photonic modes.

  8. Poly(acrylonitrile-co-vinylacetate ) /fe2o3@pedot Core-shell Nanocapsules And Nanofibers

    OpenAIRE

    Satıcı, Mehmet Tolga

    2014-01-01

    Conducting polymers could not be directly deposited onto the surface of magnetic particles due to flocculation and the hydrophilic surfaces of magnetic particles. Therefore, P(AN-co-VAc)/Fe2O3 core-shell nanocapsules with uniform size and morphology was firstly constituted by mini-emulsion polymerization technique that comprises of coating of P(AN-co-VAc) as shell onto Fe2O3 nanoparticles using as core. Because this method facilitates fabricating homogeneously nanofibers including Fe2O3 by el...

  9. Doping GaP core-shell nanowire pn-junctions

    DEFF Research Database (Denmark)

    Yazdi, Sadegh; Berg, Alexander; Borgström, Magnus T.

    2015-01-01

    The doping process in GaP core-shell nanowire pn-junctions using different precursors is evaluated by mapping the nanowires' electrostatic potential distribution by means of off-axis electron holography. Three precursors, triethyltin (TESn), ditertiarybutylselenide, and silane are investigated......, ditertiarybutylselenide and silane for n-type doping of the shell and that the concentration of p-type dopants is higher in the region of core grown parasitically by vapor-solid mechanism due to unintentional carbon doping from trimethylgallium precursor....

  10. Electrospun core/shell nanofibers: a promising system for cartilage and tissue engineering?

    Czech Academy of Sciences Publication Activity Database

    Amler, Evžen; Míčková, Andrea; Buzgo, Matej

    2013-01-01

    Roč. 8, č. 4 (2013), s. 509-512 ISSN 1743-5889 Grant - others:GA UK(CZ) 330611; GA UK(CZ) 384311; GA UK(CZ) 626012; GA UK(CZ) 648112; GA MŠk(CZ) ME10145; GA MZd(CZ) NT12156 Institutional research plan: CEZ:AV0Z50390512; CEZ:AV0Z50390703 Keywords : core-shell nanofibers * electrospinning * drug delivery Subject RIV: FP - Other Medical Disciplines Impact factor: 5.824, year: 2013

  11. Radiative Properties of Carriers in Cdse-Cds Core-Shell Heterostructured Nanocrystals of Various Geometries

    Science.gov (United States)

    Zhou, S.; Dong, L.; Popov, S.; Friberg, A. T.

    2013-07-01

    We report a model on core-shell heterostructured nanocrystals with CdSe as the core and CdS as the shell. The model is based on one-band Schrödinger equation. Three different geometries, nanodot, nanorod, and nanobone, are implemented. The carrier localization regimes with these structures are simulated, compared, and analyzed. Based on the electron and hole wave functions, the carrier overlap integral that has a great impact on stimulated emission is further investigated numerically by a novel approach. Furthermore, the relation between the nanocrystal size and electron-hole recombination energy is also examined.

  12. Investigation of Ni@CoO core-shell nanoparticle films synthesized by sequential layer deposition

    International Nuclear Information System (INIS)

    Spadaro, M.C.; Luches, P.; Benedetti, F.; Valeri, S.; Turchini, S.; Bertoni, G.; Ferretti, A.M.; Capetti, E.; Ponti, A.; D’Addato, S.

    2017-01-01

    Highlights: • We studied Ni/CoO core-shell nanoparticles (NP) obtained with a gas aggregation source. • The NP oxide shells were produced bye reactive deposition of Co in Oxygen atmosphere (p O2 ≈ 10 −7 mbar). • XPS, SEM, STEM were used to obtain information on Ni chemical state and NP structure and morphology. • XMCD result showed evidence of remanent magnetization at room temperature. • We interpret XMCD results as due to stabilization induced by exchange bias due to AFM/FM coupling at the core/shell interface. - Abstract: Films of Ni@CoO core-shell nanoparticles (NP Ni core size d ≈ 11 nm) have been grown on Si/SiO x and lacey carbon supports, by a sequential layer deposition method: a first layer of CoO was evaporated on the substrate, followed by the deposition of a layer of pre-formed, mass-selected Ni NPs, and finally an overlayer of CoO was added. The Ni NPs were formed by a magnetron gas aggregation source, and mass selected with a quadrupole mass filter. The morphology of the films was investigated with Scanning Electron Microscopy and Scanning Transmission Electron Microscopy. The Ni NP cores have a shape compatible with McKay icosahedron, caused by multitwinning occurring during their growth in the source, and the Ni NP layer shows the typical random paving growth mode. After the deposition of the CoO overlayer, CoO islands are observed, gradually extending and tending to merge with each other, with the formation of shells that enclose the Ni NP cores. In situ X-ray Photoelectron Spectroscopy showed that a few Ni atomic layers localized at the core-shell interface are oxidized, hinting at the possibility of creating an intermediate NiO shell between Ni and CoO, depending on the deposition conditions. Finally, X-ray Magnetic Circular Dichroism at the Ni L 2,3 absorption edge showed the presence of magnetization at room temperature even at remanence, revealing the possibility of magnetic stabilization of the NP film.

  13. Investigation of Ni@CoO core-shell nanoparticle films synthesized by sequential layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Spadaro, M.C., E-mail: mariachiara.spadaro@unimore.it [CNR-NANO, via G. Campi 213/a, 41125 Modena (Italy); Dipartimento FIM, Università di Modena e Reggio Emilia, via G. Campi 213/a, 41125 Modena (Italy); Luches, P. [Dipartimento FIM, Università di Modena e Reggio Emilia, via G. Campi 213/a, 41125 Modena (Italy); Benedetti, F.; Valeri, S. [CNR-NANO, via G. Campi 213/a, 41125 Modena (Italy); Dipartimento FIM, Università di Modena e Reggio Emilia, via G. Campi 213/a, 41125 Modena (Italy); Turchini, S. [CNR-ISM, Via Fosso del Cavaliere 100, 00133 Roma (Italy); Bertoni, G. [CNR-IMEM, Parco Area delle Scienze 37/a, 43124 Parma (Italy); Ferretti, A.M.; Capetti, E.; Ponti, A. [Laboratorio di Nanotecnologie, Istituto di Scienze e Tecnologie Molecolari, Consiglio Nazionale delle Ricerche, via G. Fantoli 16/15, 20138 Milano (Italy); D’Addato, S. [CNR-NANO, via G. Campi 213/a, 41125 Modena (Italy); Dipartimento FIM, Università di Modena e Reggio Emilia, via G. Campi 213/a, 41125 Modena (Italy)

    2017-02-28

    Highlights: • We studied Ni/CoO core-shell nanoparticles (NP) obtained with a gas aggregation source. • The NP oxide shells were produced bye reactive deposition of Co in Oxygen atmosphere (p{sub O2} ≈ 10{sup −7} mbar). • XPS, SEM, STEM were used to obtain information on Ni chemical state and NP structure and morphology. • XMCD result showed evidence of remanent magnetization at room temperature. • We interpret XMCD results as due to stabilization induced by exchange bias due to AFM/FM coupling at the core/shell interface. - Abstract: Films of Ni@CoO core-shell nanoparticles (NP Ni core size d ≈ 11 nm) have been grown on Si/SiO{sub x} and lacey carbon supports, by a sequential layer deposition method: a first layer of CoO was evaporated on the substrate, followed by the deposition of a layer of pre-formed, mass-selected Ni NPs, and finally an overlayer of CoO was added. The Ni NPs were formed by a magnetron gas aggregation source, and mass selected with a quadrupole mass filter. The morphology of the films was investigated with Scanning Electron Microscopy and Scanning Transmission Electron Microscopy. The Ni NP cores have a shape compatible with McKay icosahedron, caused by multitwinning occurring during their growth in the source, and the Ni NP layer shows the typical random paving growth mode. After the deposition of the CoO overlayer, CoO islands are observed, gradually extending and tending to merge with each other, with the formation of shells that enclose the Ni NP cores. In situ X-ray Photoelectron Spectroscopy showed that a few Ni atomic layers localized at the core-shell interface are oxidized, hinting at the possibility of creating an intermediate NiO shell between Ni and CoO, depending on the deposition conditions. Finally, X-ray Magnetic Circular Dichroism at the Ni L{sub 2,3} absorption edge showed the presence of magnetization at room temperature even at remanence, revealing the possibility of magnetic stabilization of the NP film.

  14. Shape evolution of a core-shell spherical particle under hydrostatic pressure.

    Science.gov (United States)

    Colin, Jérôme

    2012-03-01

    The morphological evolution by surface diffusion of a core-shell spherical particle has been investigated theoretically under hydrostatic pressure when the shear modulii of the core and shell are different. A linear stability analysis has demonstrated that depending on the pressure, shear modulii, and radii of both phases, the free surface of the composite particle may be unstable with respect to a shape perturbation. A stability diagram finally emphasizes that the roughness development is favored in the case of a hard shell with a soft core.

  15. Immobilization of α-Chymotrypsin on the Surface of Magnetic/Gold Core/Shell Nanoparticles

    International Nuclear Information System (INIS)

    Ahmadi, M.K.; Vossoughi, M.

    2013-01-01

    Over the last decade, nanoparticles used as protein carriers have opened new avenues for a variety of biomedical applications. The main concern for these applications is changes in biological activity of immobilized proteins due to conformational changes on the surface of the carrier. To evaluate this concern, the preparation and bio catalyst activity of α-chymotrypsin-Fe 3 O 4 Au core/shell nanoparticles were investigated. First, Fe 3 O 4 Au core/shell nanoparticles were synthesized by coprecipitation method and citrate reduction of HAuCl 4 . TEM imaging revealed a core size of 13 ± 3 nm and a shell thickness of 4 ± 1 nm for synthesized nanoparticles. X-ray diffraction (XRD) was used to study the crystalline structure of the nanoparticles. Next, the enzyme was immobilized on the surface of synthesized nanoparticles by covalent bonding of Au shell with thiol and amine groups present in the protein structure (e.g., cysteine and histidine residues). FTIR and fluorescence spectroscopy were utilized to study secondary and tertiary structures of the immobilized enzyme. Results show that the secondary and tertiary structures of the enzyme remain virtually unchanged after immobilization on the nanoparticles surface. However, the bio catalyst activity of the enzyme was reduced by thirty percent, indicating possible conformational changes or active site occlusion

  16. Room temperature nanojoining of Cu-Ag core-shell nanoparticles and nanowires

    International Nuclear Information System (INIS)

    Wang, Jiaqi; Shin, Seungha

    2017-01-01

    Room temperature (T room , 300 K) nanojoining of Ag has been widely employed in fabrication of microelectronic applications where the shapes and structures of microelectronic components must be maintained. In this research, the joining processes of pure Ag nanoparticles (NPs), Cu-Ag core-shell NPs, and nanowires (NWs) are studied using molecular dynamics simulations at T room . The evolution of densification, potential energy, and structural deformation during joining process are analyzed to identify joining mechanisms. Depending on geometry, different joining mechanisms including crystallization-amorphization, reorientation, Shockley partial dislocation are determined. A three-stage joining scenario is observed in both joining process of NPs and NWs. Besides, the Cu core does not participate in all joining processes, however, it enhances the mobility of Ag shell atoms, contributing to a higher densification and bonding strength at T room , compared with pure Ag nanomaterials. The tensile test shows that the nanojoint bears higher rupture strength than the core-shell NW itself. This study deepens understanding in the underlying joining mechanisms and thus nanojoint with desirable thermal, electrical, and mechanical properties could be potentially achieved.

  17. New method to evaluate optical properties of core-shell nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Renteria-Tapia, V. [Universidad de Guadalajara, Ameca, Departamento de Ciencias Naturales y Exactas, Centro Universitario de Los Valles (Mexico); Franco, A., E-mail: alfredofranco@fisica.unam.mx; Garcia-Macedo, J. [Universidad Nacional Autonoma de Mexico, Departamento de Estado Solido, Instituto de Fisica (Mexico)

    2012-06-15

    A new method is presented to calculate, for metallic core-dielectric shell nanostructures, the local refractive index, resonance condition, maximum spectral shift, plasma wavelength, and the sensitivity of the wavelength maximum to variations in the refractive index of the environment. The equations that describe these properties are directly related to the surface plasmon peak position, refractive index of the shell, and to the surrounding medium. The method is based on the approach that a layered core dispersed in a dielectric environment (core-shell model) can be figured out as an uncoated sphere dispersed in a medium with a local refractive index (local refractive index model). Thus, in the Mie theory, the same spectral position of the surface plasmon resonance peak can be obtained by varying the volume fraction of the shell or by varying the local refractive index. The assumed equivalence between plasmon resonance wavelengths enable us to show that the local refractive index depends geometrically on the shell volume fraction. Hence, simple relationships between optical and geometrical properties of these core-shell nanostructures are obtained. Furthermore, good agreement is observed between the new relationships and experimental data corresponding to gold nanoparticles (radius = 7.5 nm) covered with silica shells (with thicknesses up to 29.19 nm), which insured that the equivalence hypothesis is correct.

  18. Monolithic and core-shell columns in comprehensive two-dimensional HPLC: a review.

    Science.gov (United States)

    Jandera, Pavel; Hájek, Tomáš; Staňková, Magda

    2015-01-01

    The crucial point affecting the separation time in comprehensive two-dimensional liquid chromatography is the performance of the column used in the second dimension, which should allow highly efficient fast chromatographic separations in the short time available for the analysis of fractions transferred from the first to the second dimension (often 1 min or less). This can be accomplished on short columns packed with sub-2-μm particles, at the cost of very high operation pressure. Core-shell or silica monolithic columns have better permeability, and their use in the second dimension of comprehensive two-dimensional liquid chromatography with conventional liquid chromatography instrumentation is continuously increasing. Monolithic columns based on organic polymer matrices offer a wide selection of stationary phase chemistries, including new hydrophilic interaction liquid chromatography materials, which can be used in the design of novel two-dimensional separations. Some organic polymer monolithic materials offer a dual retention mechanism (reversed-phase hydrophilic interaction liquid chromatography), so a single column can be used in alternating runs for highly orthogonal off-line two-dimensional and even three-dimensional separations. In the present work, the properties of core-shell and silica gel monolithic columns are briefly summarized and their applications in two-dimensional separations of peptides, proteins, oligomer surfactants, fats and oils, carotenoids, phenolic and flavone compounds in plant extracts, food, and beverages are reviewed.

  19. Preparation and enhanced capacitance of core-shell polypyrrole/polyaniline composite electrode for supercapacitors

    Science.gov (United States)

    Mi, Hongyu; Zhang, Xiaogang; Ye, Xiangguo; Yang, Sudong

    Polypyrrole (PPy) nanotubes were synthesized by using the complex of methyl orange (MO)/FeCl 3 as a template. Then the core-shell polypyrrole/polyaniline (PPy/PANI) composite was prepared by in situ chemical oxidation polymerization of aniline on the surface of PPy nanotubes. The morphology and molecular structure were characterized by transmission electron microscopy (TEM), infrared spectroscopy (IR) and X-ray diffraction (XRD). TEM images confirmed that the composite was core-shell nanotubes. The electrochemical properties of the PPy/PANI composite electrode were investigated by cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS). The electrochemical experiments showed that the specific capacitance of the PPy/PANI composite was 416 F g -1 in 1 M H 2SO 4 electrolyte and 291 F g -1 in 1 M KCl electrolyte. Furthermore, the composite electrode exhibited a good rate capability and maintained 91% of initial capacity at a current density of 15 mA cm -2 in 1 M H 2SO 4 electrolyte.

  20. Anisotropic phase coherence in GaAs/InAs core/shell nanowires

    Science.gov (United States)

    Haas, Fabian; Zellekens, Patrick; Wenz, Tobias; Demarina, Nataliya; Rieger, Torsten; Lepsa, Mihail I.; Grützmacher, Detlev; Lüth, Hans; Schäpers, Thomas

    2017-11-01

    Low-temperature transport in nanowires is accompanied by phase-coherent effects, which are observed as modulation of the conductance in an external magnetic field. In the GaAs/InAs core/shell nanowires investigated here, these are h/e flux periodic oscillations in a magnetic field aligned parallel to the nanowire axis and aperiodic universal conductance fluctuations in a field aligned perpendicularly to the nanowire axis. Both electron interference effects are used to analyse the phase coherence of the system. Temperature-dependent measurements are carried out, in order to derive the phase coherence lengths in the cross-sectional plane as well as along the nanowire sidewalls. It is found that these values show a strong anisotropy, which can be explained by the crystal structure of the GaAs/InAs core/shell nanowire. For nanowires with a radius as low as 45 nm, flux periodic oscillations were observed up to a temperature of 55 K.

  1. Effect of core-shell structure on optical properties of Au-Cu2O nanoparticles

    Science.gov (United States)

    Sai, Cong Doanh; Ngac, An Bang

    2018-03-01

    Solid Au-Cu2O core-shell nanoparticles were synthesized using gold nanoparticles of 16.6 nm in size as the core. The core-shell structure of the synthesized particles was confirmed and characterized by TEM and HRTEM images. Due to their similar crystal structure, the (111) planes of Cu2O are nucleated and grown epitaxially on the {111} facets of Au nanoparticles with the lattice mismatch of about 4.3% resulting in a polycrystallized Cu2O shell covering the Au nanocore. Due to the quantum confinement effect, the band gap energy Eg of the synthesized Cu2O shells is blue-shifted from 2.35 to 2.70 eV as the shell thickness decreases from of 24.6±3.6 to 9.0±1.7 nm. The localized SPR (Surface Plasmon Resonance) peak of the Au nanocore undergoes a large red shift of the order of a hundred of nm due to both the high refractive index and the increase of the thickness of Cu2O shell. Theoretical models within the Drude framework significantly underestimate the experimental data and predict a wrong rate of change of the SPR peak position with respect to the shell thickness.

  2. Synthesis of Pt-Sn core-shell nanoparticles deposited on SBA-15 modified

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez-Contreras, L.; Alonso-Lemus, I. [Centro de Investigacion en Materiales Avanzados S.C., Laboratorio Nacional de Nanotecnologia (Mexico); Botte, G. G. [Ohio University, Center for Electrochemical Engineering Research, Department of Chemical and Biomolecular Engineering (United States); Verde-Gomez, Y., E-mail: ysmaelverde@yahoo.com [Instituto Tecnologico de Cancun (Mexico)

    2013-07-15

    A novel one-step synthesis method to prepare Pt-Sn bimetallic nanoparticles supported on mesoporous silica with high surface area (SBA-15, 700 m{sup 2}/g) and narrow pore size distribution (around 9.5 nm) was developed. Tin incorporation plays an important dual role, to create active sites into the silica walls that serve as particles anchors center, and to grow Pt-Sn core-shell nanoparticles. High-resolution transmission and scanning electron microscopy, and X-ray diffraction pattern confirm the formation of the Pt-Sn core-shell type nanoparticles ( Almost-Equal-To 1-10 nm). The metal loading was 2.2 and 2.3 wt% for Pt and Sn, respectively. Electron microscopy results show that the metal nanoparticles were deposited not only on the matrix, but also inside of it. Structural, textural, and morphological features of the SBA-15 were slightly affected after the nanoparticles deposition, maintaining its high surface area. The results obtained suggest that Pt-Sn on SBA-15 could be attractive material for several catalytic applications, due to the narrow particle size distribution achieved (from 1 to 10 nm) the high dispersion on the support, as well as the Pt-Sn alloy developed.Graphical Abstract.

  3. Shell thickness-dependent microwave absorption of core-shell Fe3O4@C composites.

    Science.gov (United States)

    Du, Yunchen; Liu, Wenwen; Qiang, Rong; Wang, Ying; Han, Xijiang; Ma, Jun; Xu, Ping

    2014-08-13

    Core-shell composites, Fe3O4@C, with 500 nm Fe3O4 microspheres as cores have been successfully prepared through in situ polymerization of phenolic resin on the Fe3O4 surface and subsequent high-temperature carbonization. The thickness of carbon shell, from 20 to 70 nm, can be well controlled by modulating the weight ratio of resorcinol and Fe3O4 microspheres. Carbothermic reduction has not been triggered at present conditions, thus the crystalline phase and magnetic property of Fe3O4 micropsheres can be well preserved during the carbonization process. Although carbon shells display amorphous nature, Raman spectra reveal that the presence of Fe3O4 micropsheres can promote their graphitization degree to a certain extent. Coating Fe3O4 microspheres with carbon shells will not only increase the complex permittivity but also improve characteristic impedance, leading to multiple relaxation processes in these composites, thus the microwave absorption properties of these composites are greatly enhanced. Very interestingly, a critical thickness of carbon shells leads to an unusual dielectric behavior of the core-shell structure, which endows these composites with strong reflection loss, especially in the high frequency range. By considering good chemical homogeneity and microwave absorption, we believe the as-fabricated Fe3O4@C composites can be promising candidates as highly effective microwave absorbers.

  4. Analysis of Chemical Bonding and Structural Network of Gold Silicide in Core-Shell Silicon Nanowire

    Science.gov (United States)

    Swain, Bibhu P.; Swain, Bhabani S.

    2018-02-01

    The Au-catalyzed core-shell silicon nanowires (Si-NWs) were synthesized by chemical vapor deposition by using SiH4 and H2 precursor gases. The TEM and FTIR studies revealed that the Si-NWs consist of core silicon surrounded by a thick oxide sheath and Au distributed at the a-SiOx/Si interface. The x-ray photoelectron spectroscopy (XPS) was used to study the chemical composition and electronic environments of gold silicide in the a-SiO x /Si-NWs. The elemental analysis and chemical network of gold silicide of core-shell Si-NWs were explained on the basis of the random atomic distribution of Si, O and Au atoms. The Raman spectra and XRD peak reveal the crystalline core of Si-NWs. The individual contribution to the Au (4d) core orbital was deconvoluted to Au-Si-Au, Au-Si-O, Au-Au, Au-O-Au, Au-O-Si and Au=O/Au-O2 bonding structure. The analysis shows that the O linked with Si and Au has also contributed to growth of Si-NWs.

  5. Polarization effects on spectra of spherical core/shell nanostructures: Perturbation theory against finite difference approach

    International Nuclear Information System (INIS)

    Ibral, Asmaa; Zouitine, Asmaa; Assaid, El Mahdi

    2015-01-01

    Poisson equation is solved analytically in the case of a point charge placed anywhere in a spherical core/shell nanostructure, immersed in aqueous or organic solution or embedded in semiconducting or insulating matrix. Conduction and valence band-edge alignments between core and shell are described by finite height barriers. Influence of polarization charges induced at the surfaces where two adjacent materials meet is taken into account. Original expressions of electrostatic potential created everywhere in the space by a source point charge are derived. Expressions of self-polarization potential describing the interaction of a point charge with its own image–charge are deduced. Contributions of double dielectric constant mismatch to electron and hole ground state energies as well as nanostructure effective gap are calculated via first order perturbation theory and also by finite difference approach. Dependencies of electron, hole and gap energies against core to shell radii ratio are determined in the case of ZnS/CdSe core/shell nanostructure immersed in water or in toluene. It appears that finite difference approach is more efficient than first order perturbation method and that the effect of polarization charge may in no case be neglected as its contribution can reach a significant proportion of the value of nanostructure gap

  6. A novel approach to preparing magnetic protein microspheres with core-shell structure

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Wei, E-mail: climentjw@126.co [National Special Superfine Powder Engineering Research Center, Nanjing University of Science and Technology, Nanjing 210094 (China); Sun Zhendong; Li Fengsheng [National Special Superfine Powder Engineering Research Center, Nanjing University of Science and Technology, Nanjing 210094 (China); Chen Kai; Liu Tianyu; Liu Jialing [Department of Physics, Nanjing University of Science and Technology, Nanjing 210094 (China); Zhou Tianle [Department of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Guo Rui [Department of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China)

    2011-03-15

    Magnetic protein microspheres with core-shell structure were prepared through a novel approach based on the sonochemical method and the emulsion solvent evaporation method. The microspheres are composed of the oleic acid and undecylenic acid modified Fe{sub 3}O{sub 4} cores and coated with globular bovine serum albumin (BSA). Under an optimized condition, up to 57.8 wt% of approximately 10 nm superparamagnetic Fe{sub 3}O{sub 4} nanoparticles could be uniformly encapsulated into the BSA microspheres with the diameter of approximately 160 nm and the high saturation magnetization of 38.5 emu/g, besides of the abundant functional groups. The possible formation mechanism of magnetic microspheres was discussed in detail. - Research Highlights: Magnetic protein microspheres with core-shell structure were prepared through a novel approach based on the sonochemical method and the emulsion solvent evaporation method. The microspheres are composed of the oleic acid and undecylenic acid modified Fe{sub 3}O{sub 4} cores and coated with globular bovine serum albumin (BSA). 57.8 wt% of approximately 10 nm superparamagnetic Fe{sub 3}O{sub 4} nanoparticles could be uniformly encapsulated into the BSA microspheres with the diameter of approximately 160 nm and the high saturation magnetization of 38.5 emu/g, besides the abundant functional groups.

  7. Fast-dissolving core-shell composite microparticles of quercetin fabricated using a coaxial electrospray process.

    Directory of Open Access Journals (Sweden)

    Chen Li

    Full Text Available This study reports on novel fast-dissolving core-shell composite microparticles of quercetin fabricated using coaxial electrospraying. A PVC-coated concentric spinneret was developed to conduct the electrospray process. A series of analyses were undertaken to characterize the resultant particles in terms of their morphology, the physical form of their components, and their functional performance. Scanning and transmission electron microscopies revealed that the microparticles had spherical morphologies with clear core-shell structure visible. Differential scanning calorimetry and X-ray diffraction verified that the quercetin active ingredient in the core and sucralose and sodium dodecyl sulfate (SDS excipients in the shell existed in the amorphous state. This is believed to be a result of second-order interactions between the components; these could be observed by Fourier transform infrared spectroscopy. In vitro dissolution and permeation studies showed that the microparticles rapidly released the incorporated quercetin within one minute, and had permeation rates across the sublingual mucosa around 10 times faster than raw quercetin.

  8. Fabry-Perot Microcavity Modes in Single GaP/GaNP Core/Shell Nanowires.

    Science.gov (United States)

    Dobrovolsky, Alexander; Stehr, Jan E; Sukrittanon, Supanee; Kuang, Yanjin; Tu, Charles W; Chen, Weimin M; Buyanova, Irina A

    2015-12-16

    Semiconductor nanowires (NWs) are attracting increasing interest as nanobuilding blocks for optoelectronics and photonics. A novel material system that is highly suitable for these applications are GaNP NWs. In this article, we show that individual GaP/GaNP core/shell nanowires (NWs) grown by molecular beam epitaxy on Si substrates can act as Fabry-Perot (FP) microcavities. This conclusion is based on results of microphotoluminescence (μ-PL) measurements performed on individual NWs, which reveal periodic undulations of the PL intensity that follow an expected pattern of FP cavity modes. The cavity is concluded to be formed along the NW axis with the end facets acting as reflecting mirrors. The formation of the FP modes is shown to be facilitated by an increasing index contrast with the surrounding media. Spectral dependence of the group refractive index is also determined for the studied NWs. The observation of the FP microcavity modes in the GaP/GaNP core/shell NWs can be considered as a first step toward achieving lasing in this quasidirect bandgap semiconductor in the NW geometry. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Simulations of the Light Scattering Properties of Metal/Oxide Core/Shell Nanospheres

    Directory of Open Access Journals (Sweden)

    F. Ruffino

    2014-01-01

    Full Text Available Given the importance of the optical properties of metal/dielectric core/shell nanoparticles, in this work we focus our attention on the light scattering properties, within the Mie framework, of some specific categories of these noteworthy nanostructures. In particular, we report theoretical results of angle-dependent light scattering intensity and scattering efficiency for Ag/Ag2O, Al/Al2O2, Cu/Cu2O, Pd/PdO, and Ti/TiO2 core/shell nanoparticles as a function of the core radius/shell thickness ratio and on a relative comparison. The results highlight the light scattering characteristics of these systems as a function of the radius/shell thickness ratio, helping in the choice of the more suitable materials and sizes for specific applications (i.e., dynamic light scattering for biological and molecular recognition, increasing light trapping in thin-film silicon, organic solar cells for achieving a higher photocurrent.

  10. Core-shell PLA-PVA porous microparticles as carriers for bacteriocin nisin.

    Science.gov (United States)

    Holcapkova, Pavlina; Hrabalikova, Martina; Stoplova, Petra; Sedlarik, Vladimir

    2017-05-01

    This work is focused on preparation of novel porous type of core-shell-structured microparticles based on polylactide (shell) and poly(vinyl alcohol) cross-linked with glutaric acid (GA) (core) prepared by water-in-oil-in-water solvent evaporation technique. The microparticle systems were used as delivery systems for immobilisation of model antibacterial agent - nisin. The effect of cross-linking and the initial amount of nisin on their morphology was investigated using scanning electron microscopy, BET analysis, zeta potential measurement and Fourier transform infra-red spectroscopy. Encapsulation efficiency and release profile of nisin from the microparticles were studied by high performance liquid chromatography. Antibacterial activity of the prepared systems was tested by dilution and spread plate technique. Results showed the microparticles in the size range of 9-16 μm in diameter with spherical multi-hollow core-shell structure. The presence of cross-linking agent GA influences the release profile of the peptide and has synergistic effect on Listeria monocytogenes growth reduction.

  11. Gold/silver core-shell 20 nm nanoparticles extracted from citrate solution examined by XPS

    Energy Technology Data Exchange (ETDEWEB)

    Engelhard, Mark H.; Smith, Jordan N.; Baer, Donald R.

    2016-06-01

    Silver nanoparticles of many types are widely used in consumer and medical products. The surface chemistry of particles and the coatings that form during synthesis or use in many types of media can significantly impact the behaviors of particles including dissolution, transformation and biological or environmental impact. Consequently it is useful to be able to extract information about the thickness of surface coatings and other attributes of nanoparticles produced in a variety of ways. It has been demonstrated that X-ray Photoelectron Spectroscopy (XPS) can be reliably used to determine the thickness of organic and other nanoparticles coatings and shells. However, care is required to produce reliable and consistent information. Here we report the XPS spectra from gold/silver core-shell nanoparticles of nominal size 20 nm removed from a citrate saturated solution after one and two washing cycles. The Simulation of Electron Spectra for Surface Analysis (SESSA) program had been used to model peak amplitudes to obtain information on citrate coatings that remain after washing and demonstrate the presence of the gold core. This data is provided so that others can compare use of SESSA or other modeling approaches to quantify the nature of coatings to those already published and to explore the impacts particle non-uniformities on XPS signals from core-shell nanoparticles.

  12. Preparation and Characterization of WS₂@SiO₂ and WS₂@PANI Core-Shell Nanocomposites.

    Science.gov (United States)

    Sade, Hagit; Lellouche, Jean-Paul

    2018-03-10

    Two tungsten disulfide (WS₂)-based core-shell nanocomposites were fabricated using readily available reagents and simple procedures. The surface was pre-treated with a surfactant couple in a layer-by-layer approach, enabling good dispersion of the WS₂ nanostructures in aqueous media and providing a template for the polymerization of a silica (SiO₂) shell. After a Stöber-like reaction, a conformal silica coating was achieved. Inspired by the resulting nanocomposite, a second one was prepared by reacting the surfactant-modified WS₂ nanostructures with aniline and an oxidizing agent in an aqueous medium. Here too, a conformal coating of polyaniline (PANI) was obtained, giving a WS₂@PANI nanocomposite. Both nanocomposites were analyzed by electron microscopy, energy dispersive X-ray spectroscopy (EDS) and FTIR, verifying the core-shell structure and the character of shells. The silica shell was amorphous and mesoporous and the surface area of the composite increases with shell thickness. Polyaniline shells slightly differ in their morphologies dependent on the acid used in the polymerization process and are amorphous like the silica shell. Electron paramagnetic resonance (EPR) spectroscopy of the WS₂@PANI nanocomposite showed variation between bulk PANI and the PANI shell. These two nanocomposites have great potential to expand the use of transition metals dichalcogenides (TMDCs) for new applications in different fields.

  13. Estimation of sensing characteristics for refractory nitrides based gain assisted core-shell plasmonic nanoparticles

    Science.gov (United States)

    Shishodia, Manmohan Singh; Pathania, Pankaj

    2018-04-01

    Refractory transition metal nitrides such as zirconium nitride (ZrN), hafnium nitride (HfN) and titanium nitride (TiN) have emerged as viable alternatives to coinage metals based plasmonic materials, e.g., gold (Au) and silver (Ag). The present work assesses the suitability of gain assisted ZrN-, HfN- and TiN-based conventional core-shell nanoparticles (CCSNPs) and multilayered core-shell nanoparticles (MCSNPs) for refractive index sensing. We report that the optical gain incorporation in the dielectric layer leads to multifold enhancement of the scattering efficiency (Qsca), substantial reduction of the spectral full width at half maximum, and a higher figure of merit (FOM). In comparison with CCSNPs, the MCSNP system exhibits superior sensing characteristics such as higher FOM, ˜ 45% reduction in the critical optical gain, response shift towards the biological window, and higher degree of tunability. Inherent biocompatibility, growth compatibility, chemical stability and flexible spectral tuning of refractory nitrides augmented by superior sensing properties in the present work may pave the way for refractory nitrides based low cost sensing.

  14. Highly stable supercapacitors with conducting polymer core-shell electrodes for energy storage applications

    KAUST Repository

    Xia, Chuan

    2015-01-14

    Conducting polymers such as polyaniline (PAni) show a great potential as pseudocapacitor materials for electrochemical energy storage applications. Yet, the cycling instability of PAni resulting from structural alteration is a major hurdle to its commercial application. Here, the development of nanostructured PAni-RuO2 core-shell arrays as electrodes for highly stable pseudocapacitors with excellent energy storage performance is reported. A thin layer of RuO2 grown by atomic layer deposition (ALD) on PAni nanofibers plays a crucial role in stabilizing the PAni pseudocapacitors and improving their energy density. The pseudocapacitors, which are based on optimized PAni-RuO2 core-shell nanostructured electrodes, exhibit very high specific capacitance (710 F g-1 at 5 mV s-1) and power density (42.2 kW kg-1) at an energy density of 10 Wh kg-1. Furthermore, they exhibit remarkable capacitance retention of ≈88% after 10 000 cycles at very high current density of 20 A g-1, superior to that of pristine PAni-based pseudocapacitors. This prominently enhanced electrochemical stability successfully demonstrates the buffering effect of ALD coating on PAni, which provides a new approach for the preparation of metal-oxide/conducting polymer hybrid electrodes with excellent electrochemical performance.

  15. Multifunctional core-shell nanoparticles as highly efficient imaging and photosensitizing agents.

    Science.gov (United States)

    Zhang, Ruirui; Wu, Chuanliu; Tong, Lili; Tang, Bo; Xu, Qing-Hua

    2009-09-01

    Here we report the preparation of a novel multifunctional core-shell nanocomposite material that contains a nonporous dye-doped silica core and a mesoporous silica shell containing photosensitizer molecules, hematoporphyrin (HP). This architecture allows simultaneous fluorescence imaging and photosensitization treatment. The photosensitizer molecules are covalently linked to the mesoporous silica shell and exhibit excellent photo-oxidation efficiency. The efficiency of photo-oxidation of the core-shell hybrid nanoparticles was demonstrated to be significantly improved over that in the homogeneous solution. The mesoporous silica nanovehicle acts not only as a carrier for the photosensitizers but also as a nanoreactor to facilitate the photo-oxidation reaction. The doping of fluorescence dyes into the nonporous core endows the imaging capability, which has been demonstrated with cell imaging experiments. This approach could be easily extended to conjugate other functional regents if necessary. These multifunctional nanovehicles possess unique advantages in acting as nanocarriers in photodynamic therapy to allow simultaneous high-resolution targeting and treatment.

  16. A novel approach to preparing magnetic protein microspheres with core-shell structure

    International Nuclear Information System (INIS)

    Jiang Wei; Sun Zhendong; Li Fengsheng; Chen Kai; Liu Tianyu; Liu Jialing; Zhou Tianle; Guo Rui

    2011-01-01

    Magnetic protein microspheres with core-shell structure were prepared through a novel approach based on the sonochemical method and the emulsion solvent evaporation method. The microspheres are composed of the oleic acid and undecylenic acid modified Fe 3 O 4 cores and coated with globular bovine serum albumin (BSA). Under an optimized condition, up to 57.8 wt% of approximately 10 nm superparamagnetic Fe 3 O 4 nanoparticles could be uniformly encapsulated into the BSA microspheres with the diameter of approximately 160 nm and the high saturation magnetization of 38.5 emu/g, besides of the abundant functional groups. The possible formation mechanism of magnetic microspheres was discussed in detail. - Research Highlights: → Magnetic protein microspheres with core-shell structure were prepared through a novel approach based on the sonochemical method and the emulsion solvent evaporation method.→ The microspheres are composed of the oleic acid and undecylenic acid modified Fe 3 O 4 cores and coated with globular bovine serum albumin (BSA).→ 57.8 wt% of approximately 10 nm superparamagnetic Fe 3 O 4 nanoparticles could be uniformly encapsulated into the BSA microspheres with the diameter of approximately 160 nm and the high saturation magnetization of 38.5 emu/g, besides the abundant functional groups.

  17. Structural characterization of Pt-Pd core-shell nanoparticles by Cs-corrected STEM

    Energy Technology Data Exchange (ETDEWEB)

    Esparza, R., E-mail: resparza@fata.unam.mx [Universidad Nacional Autonoma de Mexico, Centro de Fisica Aplicada y Tecnologia Avanzada (Mexico); Garcia-Ruiz, Amado F. [UPIICSA-COFAA, Instituto Politecnico Nacional (Mexico); Velazquez Salazar, J. J. [University of Texas at San Antonio, Department of Physics and Astronomy (United States); Perez, R. [Universidad Nacional Autonoma de Mexico, Centro de Fisica Aplicada y Tecnologia Avanzada (Mexico); Jose-Yacaman, M. [The University of Texas at San Antonio, Department of Physics and Astronomy (United States)

    2013-01-15

    Pt-Pd core-shell nanoparticles were synthesized using a modified polyol method. A thermal method under refluxing, carrying on the reaction up to 285 Degree-Sign C, has been performed to reduce metallic salts using ethylene glycol as reducer and poly(N-vinyl-2-pyrrolidone) as protective reagent of the formed bimetallic nanoparticles. According to other works, this type of structure has been studied and utilized to successfully increase the catalytic properties of monometallic nanoparticles Pt or Pd. Core-shell bimetallic nanoparticles were structurally characterized using aberration-corrected scanning transmission electron microscopy (Cs-STEM) equipped with a high-angle annular dark field detector, energy-dispersive X-ray spectrometry (EDS), and electron energy-loss spectroscopy (EELS). The high-resolution elemental line scan and mappings were carried out using a combination of STEM-EDS and STEM-EELS. The obtained results show the growth of the Pd shell on the Pt core with polyhedral morphology. The average size of the bimetallic nanoparticles was 13.5 nm and the average size of the core was 8.5 nm; consequently, the thickness of the shell was around 2.5 nm. The growth of the Pd shell on the Pt core is layer by layer, suggesting a Frank-van der Merwe growth mechanism.

  18. Renewable Decyl-alcohol Templated Synthesis of Si-Cu Core-Shell Nanocomposite

    International Nuclear Information System (INIS)

    Salim, M A; Misran, H; Othman, S Z; Shah, N N H; Razak, N A A; Manap, A

    2013-01-01

    Monodispersed silica spheres with particles size of ca. 450 nm were successfully synthesized using a modified Stöber method. The synthesized monodispersed silica spheres were successfully coated with copper using modified sol-gel method employing nonsurfactant surface modifiers and catalyst. A renewable palm oil based decyl-alcohol (C10) as nonsurfactant surface modifiers and catalyst were used to modify the silica surfaces prior to coating with copper. The X-ray diffraction patterns of Si-Cu core-shell exhibited a broad peak corresponding to amorphous silica networks and monoclinic CuO phase. It was found that samples modified in the presence of 1 ml catalyst exhibited homogeneous deposition. The surface area of core materials (SiO2) was at ca. 7.04 m 2 /g and Si-Cu core-shell was at ca. 8.21 m 2 /g. The band gap of samples prepared with and without catalyst was calculated to be ca. 2.45 eV and ca. 3.90 eV respectively based on the UV-vis absorption spectrum of the product.

  19. Chemical and Colloidal Stability of Carboxylated Core-Shell Magnetite Nanoparticles Designed for Biomedical Applications

    Directory of Open Access Journals (Sweden)

    László Tiszlavicz

    2013-07-01

    Full Text Available Despite the large efforts to prepare super paramagnetic iron oxide nanoparticles (MNPs for biomedical applications, the number of FDA or EMA approved formulations is few. It is not known commonly that the approved formulations in many instances have already been withdrawn or discontinued by the producers; at present, hardly any approved formulations are produced and marketed. Literature survey reveals that there is a lack for a commonly accepted physicochemical practice in designing and qualifying formulations before they enter in vitro and in vivo biological testing. Such a standard procedure would exclude inadequate formulations from clinical trials thus improving their outcome. Here we present a straightforward route to assess eligibility of carboxylated MNPs for biomedical tests applied for a series of our core-shell products, i.e., citric acid, gallic acid, poly(acrylic acid and poly(acrylic acid-co-maleic acid coated MNPs. The discussion is based on physicochemical studies (carboxylate adsorption/desorption, FTIR-ATR, iron dissolution, zeta potential, particle size, coagulation kinetics and magnetization measurements and involves in vitro and in vivo tests. Our procedure can serve as an example to construct adequate physico-chemical selection strategies for preparation of other types of core-shell nanoparticles as well.

  20. Core-shell nanospheres Pt@SiO2 for catalytic hydrogen production

    Science.gov (United States)

    Hu, Yujuan; Wang, Yuqing; Lu, Zhang-Hui; Chen, Xiangshu; Xiong, Lihua

    2015-06-01

    Ultrafine platinum nanoparticles (NPs) embedded in silica nanospheres (Pt@SiO2) have been synthesized in a NP-5/cyclohexane reversed-micelle system followed by NaBH4 reduction. The as-synthesized core-shell nanocatalysts Pt@SiO2 were characterized by scanning electron microscopy, transmission electron microscopes, X-ray powder diffraction analysis, energy dispersive X-ray spectrometer and nitrogen adsorption-desorption investigations. Interestingly, the as-synthesized core-shell nanocatalysts Pt@SiO2 showed an excellent catalytic performance in hydrogen generation from the hydrolysis of ammonia borane (BH3NH3, AB) at room temperature. Especially, the catalytic performance of the Pt@SiO2 remained almost unchanged after the five recycles and even after the heat treatment (673 K), because the silica shells inhibit aggregation or deformation of the metal cores. Besides, the kinetic studies showed that the catalytic hydrolysis of AB was first order with respect to the catalyst concentration and zero order with respect to the substrate concentration, respectively. The excellent catalytic activity and stability of Pt@SiO2 can make it have a bright future in the practical application.

  1. Fulde-Ferrell state in superconducting core/shell nanowires: role of the orbital effect

    Science.gov (United States)

    Mika, Marek; Wójcik, Paweł

    2017-11-01

    The orbital effect on the Fulde-Ferrell (FF) phase is investigated in superconducting core/shell nanowires subjected to the axial magnetic field. Confinement in the radial direction results in quantization of the electron motion with energies determined by the radial j and orbital m quantum numbers. In the external magnetic field, the twofold degeneracy with respect to the orbital magnetic quantum number m is lifted which leads to the Fermi wave vector mismatch between the paired electrons, (k, j, m, \\uparrow) ≤ftrightarrow (-k, j, -m, \\downarrow) . This mismatch is transferred to the nonzero total momentum of the Cooper pairs, which results in a formation of the FF phase occurring sequentially with increasing magnetic field. By changing the nanowire radius R and the superconducting shell thickness d, we discuss the role of the orbital effect in the FF phase formation in both the nanowire-like (R/d \\ll 1 ) and nanofilm-like (R/d \\gg 1 ) regime. We have found that the irregular pattern of the FF phase which appears for the case of the nanowire-like regime, for the nanofilm-like geometry evolves towards the regular distribution in which the FF phase stability regions emerge periodically between the BCS states. The transition between these two different phase diagrams is explained as resulting from the orbital effect and the multigap character of superconductivity in the core/shell nanowires.

  2. Preparation and Properties of PTFE-PMMA Core-Shell Nanoparticles and Nanocomposites

    Directory of Open Access Journals (Sweden)

    Diego Antonioli

    2012-01-01

    Full Text Available The preparation of polytetrafluoroethylene-poly(methyl methacrylate (PTFE-PMMA core-shell particles was described, featuring controlled size and narrow size distribution over a wide compositional range, through a seeded emulsion polymerization starting from a PTFE seed of 26 nanometers. Over the entire MMA/PTFE range, the particle size increases as the MMA/PTFE ratio increases. A very precise control over the particle size can be exerted by properly adjusting the ratio between the monomer and the PTFE seed. Particles in the 80–240 nm range can be prepared with uniformity indexes suited to build 2D and 3D colloidal crystals. These core-shell particles were employed to prepare nanocomposites with different compositions, through an annealing procedure at a temperature higher than the glass transition temperature of the shell forming polymer. A perfect dispersion of the PTFE particles within the PMMA matrix was obtained and optically transparent nanocomposites were prepared containing a very high PTFE amount.

  3. Room temperature nanojoining of Cu-Ag core-shell nanoparticles and nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jiaqi; Shin, Seungha, E-mail: sshin@utk.edu [The University of Tennessee, Department of Mechanical, Aerospace and Biomedical Engineering (United States)

    2017-02-15

    Room temperature (T{sub room}, 300 K) nanojoining of Ag has been widely employed in fabrication of microelectronic applications where the shapes and structures of microelectronic components must be maintained. In this research, the joining processes of pure Ag nanoparticles (NPs), Cu-Ag core-shell NPs, and nanowires (NWs) are studied using molecular dynamics simulations at T{sub room}. The evolution of densification, potential energy, and structural deformation during joining process are analyzed to identify joining mechanisms. Depending on geometry, different joining mechanisms including crystallization-amorphization, reorientation, Shockley partial dislocation are determined. A three-stage joining scenario is observed in both joining process of NPs and NWs. Besides, the Cu core does not participate in all joining processes, however, it enhances the mobility of Ag shell atoms, contributing to a higher densification and bonding strength at T{sub room}, compared with pure Ag nanomaterials. The tensile test shows that the nanojoint bears higher rupture strength than the core-shell NW itself. This study deepens understanding in the underlying joining mechanisms and thus nanojoint with desirable thermal, electrical, and mechanical properties could be potentially achieved.

  4. Stabilization of Palladium Nanoparticles on Nanodiamond-Graphene Core-Shell Supports for CO Oxidation.

    Science.gov (United States)

    Zhang, Liyun; Liu, Hongyang; Huang, Xing; Sun, Xueping; Jiang, Zheng; Schlögl, Robert; Su, Dangsheng

    2015-12-21

    Nanodiamond-graphene core-shell materials have several unique properties compared with purely sp(2) -bonded nanocarbons and perform remarkably well as metal-free catalysts. In this work, we report that palladium nanoparticles supported on nanodiamond-graphene core-shell materials (Pd/ND@G) exhibit superior catalytic activity in CO oxidation compared to Pd NPs supported on an sp(2) -bonded onion-like carbon (Pd/OLC) material. Characterization revealed that the Pd NPs in Pd/ND@G have a special morphology with reduced crystallinity and are more stable towards sintering at high temperature than the Pd NPs in Pd/OLC. The electronic structure of Pd is changed in Pd/ND@G, resulting in weak CO chemisorption on the Pd NPs. Our work indicates that strong metal-support interactions can be achieved on a non-reducible support, as exemplified for nanocarbon, by carefully tuning the surface structure of the support, thus providing a good example for designing a high-performance nanostructured catalyst. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Core-shell microstructured nanocomposites for synergistic adjustment of environmental temperature and humidity

    Science.gov (United States)

    Zhang, Haiquan; Yuan, Yanping; Zhang, Nan; Sun, Qingrong; Cao, Xiaoling

    2016-11-01

    The adjustment of temperature and humidity is of great importance in a variety of fields. Composites that can perform both functions are prepared by mixing phase change materials (PCMs) with hygroscopic materials. However, the contact area between the adsorbent and humid air is inevitably decreased in such structures, which reduces the number of mass transfer channels for water vapor. An approach entailing the increase in the mass ratio of the adsorbent is presented here to improve the adsorption capacity. A core-shell CuSO4/polyethylene glycol (PEG) nanomaterial was developed to satisfy the conflicting requirements of temperature control and dehumidification. The results show that the equilibrium adsorption capacity of the PEG coating layer was enhanced by a factor of 188 compared with that of the pure PEG powder. The coating layer easily concentrates vapor, providing better adsorption properties for the composite. Furthermore, the volume modification of the CuSO4 matrix was reduced by 80% by the PEG coated layer, a factor that increases the stability of the composite. For the phase change process, the crystallization temperature of the coating layer was adjusted between 37.2 and 46.3 °C by interfacial tension. The core-shell CuSO4/PEG composite reported here provides a new general approach for the simultaneous control of temperature and humidity.

  6. Synthesis and characterization of PEG-iron oxide core-shell composite nanoparticles for thermal therapy

    Energy Technology Data Exchange (ETDEWEB)

    Wydra, Robert J.; Kruse, Anastasia M. [Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506 (United States); Bae, Younsoo [Department of Pharmaceutical Sciences, University of Kentucky, Lexington, KY 40506 (United States); Anderson, Kimberly W. [Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506 (United States); Hilt, J. Zach, E-mail: hilt@engr.uky.edu [Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506 (United States)

    2013-12-01

    In this study, core-shell nanoparticles were developed to achieve thermal therapy that can ablate cancer cells in a remotely controlled manner. The core-shell nanoparticles were prepared using atomic transfer radical polymerization (ATRP) to coat iron oxide (Fe{sub 3}O{sub 4}) nanoparticles with a poly(ethylene glycol) (PEG) based polymer shell. The iron oxide core allows for the remote heating of the particles in an alternating magnetic field (AMF). The coating of iron oxide with PEG was verified through Fourier transform infrared spectroscopy and thermal gravimetric analysis. A thermoablation (55 °C) study was performed on A549 lung carcinoma cells exposed to nanoparticles and over a 10 min AMF exposure. The successful thermoablation of A549 demonstrates the potential use of polymer coated particles for thermal therapy. - Highlights: • Utilized atomic transfer radical polymerization (ATRP) to coat iron oxide nanoparticles with PEG • Investigated the surface coating by surface characterization methods • Demonstrated the potential use of nanoparticles for cancer therapy applications.

  7. Epoxy-acrylic core-shell particles by seeded emulsion polymerization.

    Science.gov (United States)

    Chen, Liang; Hong, Liang; Lin, Jui-Ching; Meyers, Greg; Harris, Joseph; Radler, Michael

    2016-07-01

    We developed a novel method for synthesizing epoxy-acrylic hybrid latexes. We first prepared an aqueous dispersion of high molecular weight solid epoxy prepolymers using a mechanical dispersion process at elevated temperatures, and we subsequently used the epoxy dispersion as a seed in the emulsion polymerization of acrylic monomers comprising methyl methacrylate (MMA) and methacrylic acid (MAA). Advanced analytical techniques, such as scanning transmission X-ray microscopy (STXM) and peak force tapping atomic force microscopy (PFT-AFM), have elucidated a unique core-shell morphology of the epoxy-acrylic hybrid particles. Moreover, the formation of the core-shell morphology in the seeded emulsion polymerization process is primarily attributed to kinetic trapping of the acrylic phase at the exterior of the epoxy particles. By this new method, we are able to design the epoxy and acrylic polymers in two separate steps, and we can potentially synthesize epoxy-acrylic hybrid latexes with a broad range of compositions. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. Design of Gas-phase Synthesis of Core-Shell Particles by Computational Fluid - Aerosol Dynamics.

    Science.gov (United States)

    Buesser, B; Pratsinis, S E

    2011-11-01

    Core-shell particles preserve the bulk properties (e.g. magnetic, optical) of the core while its surface is modified by a shell material. Continuous aerosol coating of core TiO 2 nanoparticles with nanothin silicon dioxide shells by jet injection of hexamethyldisiloxane precursor vapor downstream of titania particle formation is elucidated by combining computational fluid and aerosol dynamics. The effect of inlet coating vapor concentration and mixing intensity on product shell thickness distribution is presented. Rapid mixing of the core aerosol with the shell precursor vapor facilitates efficient synthesis of hermetically coated core-shell nanoparticles. The predicted extent of hermetic coating shells is compared to the measured photocatalytic oxidation of isopropanol by such particles as hermetic SiO 2 shells prevent the photocatalytic activity of titania. Finally the performance of a simpler, plug-flow coating model is assessed by comparisons to the present detailed CFD model in terms of coating efficiency and silica average shell thickness and texture.

  9. Mechanical Fracturing of Core-Shell Undercooled Metal Particles for Heat-Free Soldering

    Science.gov (United States)

    Çınar, Simge; Tevis, Ian D.; Chen, Jiahao; Thuo, Martin

    2016-02-01

    Phase-change materials, such as meta-stable undercooled (supercooled) liquids, have been widely recognized as a suitable route for complex fabrication and engineering. Despite comprehensive studies on the undercooling phenomenon, little progress has been made in the use of undercooled metals, primarily due to low yields and poor stability. This paper reports the use of an extension of droplet emulsion technique (SLICE) to produce undercooled core-shell particles of structure; metal/oxide shell-acetate (‘/’ = physisorbed, ‘-’ = chemisorbed), from molten Field’s metal (Bi-In-Sn) and Bi-Sn alloys. These particles exhibit stability against solidification at ambient conditions. Besides synthesis, we report the use of these undercooled metal, liquid core-shell, particles for heat free joining and manufacturing at ambient conditions. Our approach incorporates gentle etching and/or fracturing of outer oxide-acetate layers through mechanical stressing or shearing, thus initiating a cascade entailing fluid flow with concomitant deformation, combination/alloying, shaping, and solidification. This simple and low cost technique for soldering and fabrication enables formation of complex shapes and joining at the meso- and micro-scale at ambient conditions without heat or electricity.

  10. Mechanical Fracturing of Core-Shell Undercooled Metal Particles for Heat-Free Soldering.

    Science.gov (United States)

    Çınar, Simge; Tevis, Ian D; Chen, Jiahao; Thuo, Martin

    2016-02-23

    Phase-change materials, such as meta-stable undercooled (supercooled) liquids, have been widely recognized as a suitable route for complex fabrication and engineering. Despite comprehensive studies on the undercooling phenomenon, little progress has been made in the use of undercooled metals, primarily due to low yields and poor stability. This paper reports the use of an extension of droplet emulsion technique (SLICE) to produce undercooled core-shell particles of structure; metal/oxide shell-acetate ('/' = physisorbed, '-' = chemisorbed), from molten Field's metal (Bi-In-Sn) and Bi-Sn alloys. These particles exhibit stability against solidification at ambient conditions. Besides synthesis, we report the use of these undercooled metal, liquid core-shell, particles for heat free joining and manufacturing at ambient conditions. Our approach incorporates gentle etching and/or fracturing of outer oxide-acetate layers through mechanical stressing or shearing, thus initiating a cascade entailing fluid flow with concomitant deformation, combination/alloying, shaping, and solidification. This simple and low cost technique for soldering and fabrication enables formation of complex shapes and joining at the meso- and micro-scale at ambient conditions without heat or electricity.

  11. Synthesis of Core-shell Structured Amorphous Si Nanoparticles by Induction Thermal Plasmas

    Science.gov (United States)

    Okamoto, Daisuke; Kageyama, Takuya; Tanaka, Manabu; Sone, Hirotaka; Watanabe, Takayuki

    2015-09-01

    Core-shell structured amorphous Si nanoparticles were synthesized by induction thermal plasma. Crystalline Si powder with 3 μm of average diameter was injected into the induction thermal plasma at 4 MHz. The Si raw materials immediately evaporate in the high temperature plasma region and nanoparticles were produced through the quenching process. Counterflow quenching gas was injected from downstream of the torch with its direction against the plasma flow. The effect of the operating parameter such as flow rate of quenching gas and input power was investigated. Collected particles were characterized by X-ray diffraction, transmission electron microscopy, electron energy-loss spectroscopy, and Raman spectroscopy. Obtained results indicate that amorphization degree of the synthesized nanoparticles is more than 90% when additional quenching gas of 20 L/min is injected. The quenching rate of the prepared nanoparticles in the growth region have an important role on determining the amorphization degree. Moreover, EELS and Raman analyses showed the synthesized nanoparticles were coated by the SiO2 shell with thickness of 2-4 nm. These findings indicated that amorphous Si/SiO2 core-shell structured nanoparticles were successfully synthesized by induction thermal plasma in single step.

  12. Porous Ni@Pt core-shell nanotube array electrocatalyst with high activity and stability for methanol oxidation.

    Science.gov (United States)

    Ding, Liang-Xin; Li, Gao-Ren; Wang, Zi-Long; Liu, Zhao-Qing; Liu, Hong; Tong, Ye-Xiang

    2012-07-02

    Bimetallic core-shell nanostructures are emerging as more important materials than monometallic nanostructures, and have much more interesting potential applications in various fields, including catalysis and electronics. In this work, we demonstrate the facile synthesis of core-shell nanotube array catalysts consisting of Pt thin layers as the shells and Ni nanotubes as the cores. The porous Ni@Pt core-shell nanotube arrays were fabricated by ZnO nanorod-array template-assisted electrodeposition, and they represent a new class of nanostructures with a high electrochemically active surface area of 50.08 m(2)  (g Pt)(-1), which is close to the value of 59.44 m(2)  (g Pt)(-1) for commercial Pt/C catalysts. The porous Ni@Pt core-shell nanotube arrays also show markedly enhanced electrocatalytic activity and stability for methanol oxidation compared with the commercial Pt/C catalysts. The attractive performances exhibited by these prepared porous Ni@Pt core-shell nanotube arrays make them promising candidates as future high-performance catalysts for methanol electrooxidation. The facile method described herein is suitable for large-scale, low-cost production, and significantly lowers the Pt loading, and thus, the cost of the catalysts. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. High ink absorption performance of inkjet printing based on SiO2@Al13 core-shell composites

    Science.gov (United States)

    Chen, YiFan; Jiang, Bo; Liu, Li; Du, Yunzhe; Zhang, Tong; Zhao, LiWei; Huang, YuDong

    2018-04-01

    The increasing growth of the inkjet market makes the inkjet printing more necessary. A composite material based on core-shell structure has been developed and applied to prepare inkjet printing layer. In this contribution, the ink printing record layers based on SiO2@Al13 core-shell composite was elaborated. The prepared core-shell composite materials were characterized by X-ray photoelectron spectroscopy (XPS), zeta potential, X-ray diffraction (XRD), scanning electron microscopy (SEM). The results proved the presence of electrostatic adsorption between SiO2 molecules and Al13 molecules with the formation of the well-dispersed system. In addition, based on the adsorption and the liquid permeability analysis, SiO2@Al13 ink printing record layer achieved a relatively high ink uptake (2.5 gmm-1) and permeability (87%), respectively. The smoothness and glossiness of SiO2@Al13 record layers were higher than SiO2 record layers. The core-shell structure facilitated the dispersion of the silica, thereby improved its ink absorption performance and made the clear printed image. Thus, the proposed procedure based on SiO2@Al13 core-shell structure of dye particles could be applied as a promising strategy for inkjet printing.

  14. NaF-loaded core-shell PAN-PMMA nanofibers as reinforcements for Bis-GMA/TEGDMA restorative resins.

    Science.gov (United States)

    Cheng, Liyuan; Zhou, Xuegang; Zhong, Hong; Deng, Xuliang; Cai, Qing; Yang, Xiaoping

    2014-01-01

    A kind of core-shell nanofibers containing sodium fluoride (NaF) was produced and used as reinforcing materials for dimethacrylate-based dental restorative resins in this study. The core-shell nanofibers were prepared by coaxial-electrospinning with polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) solutions as core and shell fluids, respectively. The produced PAN-PMMA nanofibers varied in fiber diameter and the thickness of PMMA shell depending on electrospinning parameters. NaF-loaded nanofibers were obtained by incorporating NaF nanocrystals into the core fluid at two loadings (0.8 or 1.0wt.%). Embedment of NaF nanocrystals into the PAN core did not damage the core-shell structure. The addition of PAN-PMMA nanofibers into Bis-GMA/TEGDMA clearly showed the reinforcement due to the good interfacial adhesion between fibers and resin. The flexural strength (Fs) and flexural modulus (Ey) of the composites decreased slightly as the thickness of PMMA shell increasing. Sustained fluoride releases with minor initial burst release were achieved from NaF-loaded core-shell nanofibers and the corresponding composites, which was quite different from the case of embedding NaF nanocrystals into the dental resin directly. The study demonstrated that NaF-loaded PAN-PMMA core-shell nanofibers were not only able to improve the mechanical properties of restorative resin, but also able to provide sustained fluoride release to help in preventing secondary caries. © 2013.

  15. Unlocking the Origin of Superior Performance of a Si-Ge Core-Shell Nanowire Quantum Dot Field Effect Transistor.

    Science.gov (United States)

    Dhungana, Kamal B; Jaishi, Meghnath; Pati, Ranjit

    2016-07-13

    The sustained advancement in semiconducting core-shell nanowire technology has unlocked a tantalizing route for making next generation field effect transistor (FET). Understanding how to control carrier mobility of these nanowire channels by applying a gate field is the key to developing a high performance FET. Herein, we have identified the switching mechanism responsible for the superior performance of a Si-Ge core-shell nanowire quantum dot FET over its homogeneous Si counterpart. A quantum transport approach is used to investigate the gate-field modulated switching behavior in electronic current for ultranarrow Si and Si-Ge core-shell nanowire quantum dot FETs. Our calculations reveal that for the ON state, the gate-field induced transverse localization of the wave function restricts the carrier transport to the outer (shell) layer with the pz orbitals providing the pathway for tunneling of electrons in the channels. The higher ON state current in the Si-Ge core-shell nanowire FET is attributed to the pz orbitals that are distributed over the entire channel; in the case of Si nanowire, the participating pz orbital is restricted to a few Si atoms in the channel resulting in a smaller tunneling current. Within the gate bias range considered here, the transconductance is found to be substantially higher in the case of a Si-Ge core-shell nanowire FET than in a Si nanowire FET, which suggests a much higher mobility in the Si-Ge nanowire device.

  16. Core-Shell Structuring of Pure Metallic Aerogels towards Highly Efficient Platinum Utilization for the Oxygen Reduction Reaction.

    Science.gov (United States)

    Cai, Bin; Hübner, René; Sasaki, Kotaro; Zhang, Yuanzhe; Su, Dong; Ziegler, Christoph; Vukmirovic, Miomir B; Rellinghaus, Bernd; Adzic, Radoslav R; Eychmüller, Alexander

    2018-03-05

    The development of core-shell structures remains a fundamental challenge for pure metallic aerogels. Here we report the synthesis of Pd x Au-Pt core-shell aerogels composed of an ultrathin Pt shell and a composition-tunable Pd x Au alloy core. The universality of this strategy ensures the extension of core compositions to Pd transition-metal alloys. The core-shell aerogels exhibited largely improved Pt utilization efficiencies for the oxygen reduction reaction and their activities show a volcano-type relationship as a function of the lattice parameter of the core substrate. The maximum mass and specific activities are 5.25 A mg Pt -1 and 2.53 mA cm -2 , which are 18.7 and 4.1 times higher than those of Pt/C, respectively, demonstrating the superiority of the core-shell metallic aerogels. The proposed core-based activity descriptor provides a new possible strategy for the design of future core-shell electrocatalysts. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Enhancing oxidative stability in heated oils using core/shell structures of collagen and α-tocopherol complex.

    Science.gov (United States)

    Gim, Seo Yeong; Hong, Seungmi; Kim, Jisu; Kwon, YongJun; Kim, Mi-Ja; Kim, GeunHyung; Lee, JaeHwan

    2017-11-15

    In this study, collagen mesh structure was prepared by carrying α-tocopherol in the form of core/shell complex. Antioxidant properties of α-tocopherol loaded carriers were tested in moisture added bulk oils at 140°C. From one gram of collagen core/shell complex, 138mg α-tocopherol was released in medium chain triacylglycerol (MCT). α-Tocopherol was substantially protected against heat treatment when α-tocopherol was complexed in collagen core/shell. Oxidative stability in bulk oil was significantly enhanced by added collagen mesh structure or collagen core/shell complex with α-tocopherol compared to that in control bulk oils (pshell with α-tocopherol (p>0.05). Results of DPPH loss in methanol demonstrated that collagen core/shell with α-tocopherol had significantly (pshell complex is a promising way to enhance the stability of α-tocopherol and oxidative stability in oil-rich foods prepared at high temperature. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. A comparative study of absorption in vertically and laterally oriented InP core-shell nanowire photovoltaic devices.

    Science.gov (United States)

    Nowzari, Ali; Heurlin, Magnus; Jain, Vishal; Storm, Kristian; Hosseinnia, Ali; Anttu, Nicklas; Borgström, Magnus T; Pettersson, Håkan; Samuelson, Lars

    2015-03-11

    We have compared the absorption in InP core-shell nanowire p-i-n junctions in lateral and vertical orientation. Arrays of vertical core-shell nanowires with 400 nm pitch and 280 nm diameter, as well as corresponding lateral single core-shell nanowires, were configured as photovoltaic devices. The photovoltaic characteristics of the samples, measured under 1 sun illumination, showed a higher absorption in lateral single nanowires compared to that in individual vertical nanowires, arranged in arrays with 400 nm pitch. Electromagnetic modeling of the structures confirmed the experimental observations and showed that the absorption in a vertical nanowire in an array depends strongly on the array pitch. The modeling demonstrated that, depending on the array pitch, absorption in a vertical nanowire can be lower or higher than that in a lateral nanowire with equal absorption predicted at a pitch of 510 nm for our nanowire geometry. The technology described in this Letter facilitates quantitative comparison of absorption in laterally and vertically oriented core-shell nanowire p-i-n junctions and can aid in the design, optimization, and performance evaluation of nanowire-based core-shell photovoltaic devices.

  19. One-pot synthesis of stable water soluble Mn:ZnSe/ZnS core/shell quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Hao; Gao Xue; Liu Siyu; Su Xingguang, E-mail: suxg@jlu.edu.cn [College of Chemistry, Jilin University, Department of Analytical Chemistry (China)

    2013-06-15

    In this paper, Mn:ZnSe/ZnS core/shell-doped quantum dots (d-dots) with 3-mercaptopropionic acid as the stabilizer are successfully synthesized through a simple one-pot synthesis procedure in aqueous solution. The average diameter of Mn:ZnSe/ZnS core/shell d-dots is about 2.9 nm, which is lager than that of Mn:ZnSe cores (about 1.9 nm). The optical features and structure of the obtained Mn:ZnSe/ZnS core/shell quantum dots have been characterized by UV-Vis and fluorescence spectroscopy, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The photostability against UV irradiation and chemical stability against H{sub 2}O{sub 2} etching have been studied, and the results showed that the prepared Mn:ZnSe/ZnS core/shell d-dots are more stable than CdTe quantum dots prepared in aqueous solution. Finally, the resulting core/shell quantum dots are used as fluorescent label in human osteoblast-like HepG2 cell imaging.

  20. High-efficient production of SiC/SiO2 core-shell nanowires for effective microwave absorption

    KAUST Repository

    Zhong, Bo

    2017-02-21

    In the current report, we have demonstrated that the high-efficient production of SiC/SiO2 core-shell nanowires can be achieved through the introduction of trace of water vapor during the chemical vapor deposition process. The yield of the SiC/SiO2 core-shell nanowires is dramatically improved due to the introduction of water vapor. The SiC/SiO2 core-shell nanowires exhibit an excellent microwave absorption property in the frequency range of 2.0–18.0GHz with a very low weight percentage of 0.50wt.% in the absorbers. A minimum reflection loss value of −32.72dB (>99.99% attenuation) at 13.84GHz has been observed with the absorber thickness of 3.0mm. Moreover, the SiC/SiO2 core-shell nanowires based absorber can reach an effective absorption bandwidth (<−10dB) of 5.32GHz with the absorber thickness of 3.5mm. Furthermore, a possible absorption mechanism is also proposed in detail for such effective attenuation of microwave which can be attributed to the dielectric loss and magnetic loss of SiC/SiO2 core-shell nanowires.

  1. Synthesis of Au@Ag core-shell nanocubes containing varying shaped cores and their localized surface plasmon resonances.

    Science.gov (United States)

    Gong, Jianxiao; Zhou, Fei; Li, Zhiyuan; Tang, Zhiyong

    2012-06-19

    We have synthesized Au@Ag core-shell nanocubes containing Au cores with varying shapes and sizes through modified seed-mediated methods. Bromide ions are found to be crucial in the epitaxial growth of Ag atoms onto Au cores and in the formation of the shell's cubic shape. The Au@Ag core-shell nanocubes exhibit very abundant and distinct localized surface plasmon resonance (LSPR) properties, which are core-shape and size-dependent. With the help of theoretical calculation, the physical origin and the resonance mode profile of each LSPR peak are identified and studied. The core-shell nanocrystals with varying shaped cores offer a new rich category for LSPR control through the plasmonic coupling effect between core and shell materials.

  2. Fabrication of In2O3@In2S3 core-shell nanocubes for enhanced photoelectrochemical performance

    Science.gov (United States)

    Li, Haohua; Chen, Cong; Huang, Xinyou; Leng, Yang; Hou, Mengnan; Xiao, Xiaogu; Bao, Jie; You, Jiali; Zhang, Wenwen; Wang, Yukun; Song, Juan; Wang, Yaping; Liu, Qinqin; Hope, Gregory A.

    2014-02-01

    Herein, we report the facile synthesis of In2O3@In2S3 core-shell nanocubes and their improved photoelectrochemical property. In2O3@In2S3 core-shell nanocubes are grown on a F-doped SnO2 (FTO) glass substrate by a two-step process, which involves the electrodeposition of In2O3 nanocubes and a subsequent ion-exchange treatment. The improved light-harvesting ability and the suitable band alignment of the In2O3@In2S3 core-shell nanocubes generate a remarkable photocurrent density of 6.19 mA cm-2 (at 0 V vs. Ag/AgCl), which is substantially higher than the pristine In2O3 nanocubes. These results provide a new insight into the design of a high-performance photoanode for photoelectrochemical water splitting.

  3. Core-Shell Zn/ZnO Structures with Improved Photocatalytic Properties Synthesized by Aqueous Solution Method

    Science.gov (United States)

    Huang, Yuan Ming; Ma, Qing-Lan; Zhai, Bao-Gai

    2013-08-01

    A facile and green method was utilized to synthesize core-shelled Zn/ZnO microspheres by boiling Zn microparticles in water for improving the photocatalytic activity of ZnO. The synthesized Zn/ZnO core-shells were investigated by means of scanning electron microscope, X-ray diffractometer and photoluminescence spectrometer, respectively. The morphology analysis showed that the metallic Zn core was about 6 μm in diameter while the ZnO shell was about 600 nm in thickness. Compared to ZnO nanoparticles, the core-shelled Zn/ZnO microspheres exhibited improved photocatalytic activity in degrading methyl orange in water. Our results suggest that the metal-semiconductor junction formed at the Zn/ZnO interface is responsible for the enhanced photocatalytic activity of ZnO.

  4. Strong 1.54 μm cathodoluminescence from core-shell structures of silicon nanoparticles and erbium

    Science.gov (United States)

    Hoang, Tuan; Elhalawany, Noha; Enders, Brian; Bahceci, Ersin; Abuhassan, Laila; Nayfeh, Munir H.

    2016-12-01

    We report on the development of efficient infrared-active core-shell Er2O3-Si nanoparticle architecture. Sub 3-nm H-terminated Si nanoparticles are used to reduce/deposit Er3+ ions on the nanoparticles, which in an aqueous environment simultaneously oxidize to produce the core-shells. Our results show strong cathodoluminance at 1543 nm while being able to resolve the Stark splitting. The strong luminescence afforded by the core-shell architecture in which the Si-Er interspacing drops appreciably supports a sensitive interspacing-dependent dipole-dipole energy transfer interaction model, while the hydrogenated silicon-core allows increased loading and reduced segregation of Er as in amorphous silicon material. The room temperature-wet procedure, with pre-prepared and -sorted Si nanostructures affords promising applications in electronic and optical technologies.

  5. Design and characterization of core-shell mPEG-PLGA composite microparticles for development of cell-scaffold constructs

    DEFF Research Database (Denmark)

    Wen, Yanhong; Gallego, Monica Ramos; Nielsen, Lene Feldskov

    2013-01-01

    /DS or Alg/CS/DS particles in the mPEG-PLGA microparticles were significantly dependent on the operating conditions, including the flow rate ratio (Qout/Qin) and the viscosity of the polymer solutions (Vout, Vin) between the outer and the inner feeding channels. The core-shell composite microparticles.......e. more sustainable cell growth was induced by the DS released from the core-shell composite microparticles comprising Alg/CS/DS particles. After seeding fibroblasts onto the composite microparticles, excellent cell adhesion was observed, and a successful assembly of the cell-scaffold constructs...... was induced within 7 days. Therefore, the present study demonstrates a novel strategy for fabrication of core-shell composite microparticles comprising additional particulate drug carriers in the core, which provides controlled delivery of DS and favorable cell biocompatibility; an approach to potentially...

  6. Silver-nickel oxide core-shell nanoflower arrays as high-performance anode for lithium-ion batteries

    Science.gov (United States)

    Zhao, Wenjia; Du, Ning; Zhang, Hui; Yang, Deren

    2015-07-01

    We demonstrate the synthesis of Ag-NiO core-shell nanoflower arrays via a one-step solution-immersion process and subsequent RF-sputtering method. The aligned Ag nanoflower arrays on copper substrate are prepared by a facile displacement reaction in absence of any surfactant at a mild temperature. When used as anode materials for lithium-ion batteries, the Ag-NiO core-shell nanoflower arrays show better cycling performance and higher capacity than the planar NiO electrodes. The improved performance should be attributed to the core-shell structures that can enhance the conductivity and accommodate the volume change during the charge-discharge process.

  7. Synthesis of Ni-SiO2/silicalite-1 core-shell micromembrane reactors and their reaction/diffusion performance

    KAUST Repository

    Khan, Easir A.

    2010-12-15

    Core-shell micromembrane reactors are a novel class of materials where a catalyst and a shape-selective membrane are synergistically housed in a single particle. In this work, we report the synthesis of micrometer -sized core-shell particles containing a catalyst core and a thin permselective zeolite shell and their application as a micromembrane reactor for the selective hydrogenation of the 1-hexene and 3,3-dimethyl-1-butene isomers. The bare catalyst, which is made from porous silica loaded with catalytically active nickel, showed no reactant selectivity between hexene isomers, but the core-shell particles showed high selectivities up to 300 for a 1-hexene conversion of 90%. © 2010 American Chemical Society.

  8. Mercaptoethanol capped CdSe quantum dots and CdSe/ZnS core/shell: synthesis, characterization and cytotoxicity evaluation.

    Science.gov (United States)

    Painuly, Diksha; Bhatt, Anugya; Krishnan, V Kalliyana

    2013-02-01

    CdSe Quantum dots (Q-dots) and CdSe/ZnS core/shell have been synthesized by wet chemical route using mercaptoethanol (ME) as cappant. The synthesized Q-dots and core/shell were characterized using X-ray diffraction (XRD), Transmission electron microscopy (TEM), Energy dispersive X-ray analysis (EDS), Dynamic Light Scattering (DLS), Optical absorption and luminescence spectroscopy. The core/shell formation was confirmed by both XRD and TEM analysis. The luminescence was shown to be considerably enhanced in the core/shell sample. Effect of dialysis process on the optical properties of the Q-dots and core/shell has also been discussed. Cytotoxicity studies have been carried out for Q-dots and core/shell. CdSe/ZnS core/shell was found to be non-cytotoxic as compared to CdSe Q-dots up to a certain concentration range. Polyethylene glycol (PEG) coating enhances the non-cytotoxic nature of CdSe/ZnS core/shell when compared with bare core/shell.

  9. Hollow Au@Pd and Au@Pt core-shell nanoparticles as electrocatalysts for ethanol oxidation reactions

    KAUST Repository

    Song, Hyon Min

    2012-09-27

    Hybrid alloys among gold, palladium and platinum become a new category of catalysts primarily due to their enhanced catalytic effects. Enhancement means not only their effectiveness, but also their uniqueness as catalysts for the reactions that individual metals may not catalyze. Here, preparation of hollow Au@Pd and Au@Pt core-shell nanoparticles (NPs) and their use as electrocatalysts are reported. Galvanic displacement with Ag NPs is used to obtain hollow NPs, and higher reduction potential of Au compared to Ag, Pd, and Pt helps to produce hollow Au cores first, followed by Pd or Pt shell growth. Continuous and highly crystalline shell growth was observed in Au@Pd core-shell NPs, but the sporadic and porous-like structure was observed in Au@Pt core-shell NPs. Along with hollow core-shell NPs, hollow porous Pt and hollow Au NPs are also prepared from Ag seed NPs. Twin boundaries which are typically observed in large size (>20 nm) Au NPs were not observed in hollow Au NPs. This absence is believed to be due to the role of the hollows, which significantly reduce the strain energy of edges where the two lattice planes meet. In ethanol oxidation reactions in alkaline medium, hollow Au@Pd core-shell NPs show highest current density in forward scan. Hollow Au@Pt core-shell NPs maintain better catalytic activities than metallic Pt, which is thought to be due to the better crystallinity of Pt shells as well as the alloy effect of Au cores. © 2012 The Royal Society of Chemistry.

  10. Interface Engineering of Mn-Doped ZnSe-Based Core/Shell Nanowires for Tunable Host-Dopant Coupling.

    Science.gov (United States)

    Li, Zhi-Jun; Hofman, Elan; Blaker, Amanda; Davis, Andrew Hunter; Dzikovski, Boris; Ma, De-Kun; Zheng, Weiwei

    2017-12-26

    Transition metal ion doped one-dimensional (1-D) nanocrystals (NCs) have advantages of larger absorption cross sections and polarized absorption and emissions in comparison to 0-D NCs. However, direct synthesis of doped 1-D nanorods (NRs) or nanowires (NWs) has proven challenging. In this study, we report the synthesis of 1-D Mn-doped ZnSe NWs using a colloidal hot-injection method and shell passivation for core/shell NWs with tunable optical properties. Experimental results show optical properties of the NWs are controlled by the composition and thickness of the shell lattice. It was found that both the host-Mn energy transfer and Mn-Mn coupling are strongly dependent on the type of alloy at the interface of doped core/shell NWs. For Mn-doped type I ZnSe/ZnS core/shell NWs, the ZnS shell passivation can enhance florescence quantum yield with little effect on the location of the incorporated Mn dopant due to the identical cationic Zn 2+ site available for Mn dopants throughout the core/shell NWs. However, for Mn-doped quasi type II ZnSe/CdS NWs and ZnSe/CdS/ZnS core/shell NWs, the cation alloying (Zn 1-x Cd x S(e)) can lead to metal dopant migration from the core to the alloyed interface and tunable host-dopant energy transfer efficiencies and Mn-Mn coupling. As a result, a tunable dual-band emission can be achieved for the doped NWs with the cation-alloyed interface. The interfacial alloying mediated energy transfer and Mn-Mn coupling provides a method to control the optical properties of the doped 1-D core/shell NWs.

  11. Process-Dependent Properties in Colloidally Synthesized “Giant” Core/Shell Nanocrystal Quantum Dots

    Energy Technology Data Exchange (ETDEWEB)

    Hollingsworth, Jennifer A. [Los Alamos National Laboratory; Ghosh, Yagnaseni [Los Alamos National Laboratory; Dennis, Allison M. [Los Alamos National Laboratory; Mangum, Benjamin D. [Los Alamos National Laboratory; Park, Young-Shin [Los Alamos National Laboratory; Kundu, Janardan [Los Alamos National Laboratory; Htoon, Han [Los Alamos National Laboratory

    2012-06-07

    Due to their characteristic bright and stable photoluminescence, semiconductor nanocrystal quantum dots (NQDs) have attracted much interest as efficient light emitters for applications from single-particle tracking to solid-state lighting. Despite their numerous enabling traits, however, NQD optical properties are frustratingly sensitive to their chemical environment, exhibit fluorescence intermittency ('blinking'), and are susceptible to Auger recombination, an efficient nonradiative decay process. Previously, we showed for the first time that colloidal CdSe/CdS core/shell nanocrystal quantum dots (NQDs) comprising ultrathick shells (number of shell monolayers, n, > 10) grown by protracted successive ionic layer adsorption and reaction (SILAR) leads to remarkable photostability and significantly suppressed blinking behavior as a function of increasing shell thickness. We have also shown that these so-called 'giant' NQDs (g-NQDs) afford nearly complete suppression of non-radiative Auger recombination, revealed in our studies as long biexciton lifetimes and efficient multiexciton emission. The unique behavior of this core/shell system prompted us to assess correlations between specific physicochemical properties - beyond shell thickness - and functionality. Here, we demonstrate the ability of particle shape/faceting, crystalline phase, and core size to determine ensemble and single-particle optical properties (quantum yield/brightness, blinking, radiative lifetimes). Significantly, we show how reaction process parameters (surface-stabilizing ligands, ligand:NQD ratio, choice of 'inert' solvent, and modifications to the SILAR method itself) can be tuned to modify these function-dictating NQD physical properties, ultimately leading to an optimized synthetic approach that results in the complete suppression of blinking. We find that the resulting 'guiding principles' can be applied to other NQD compositions, allowing us to

  12. Metal oxide core shell nanostructures as building blocks for efficient light emission (SISGR)

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Jane P [Univ. of California, Los Angeles, CA (United States); Dorman, James [Univ. of California, Los Angeles, CA (United States); Cheung, Cyrus [Univ. of California, Los Angeles, CA (United States)

    2016-01-12

    The objective of this research is to synthesize core-shell nano-structured metal oxide materials and investigate their structural, electronic and optical properties to understand the microscopic pathways governing the energy conversion process, thereby controlling and improving their efficiency. Specifically, the goal is to use a single metal oxide core-shell nanostructure and a single excitation source to generate photons with long emission lifetime over the entire visible spectrum and when controlled at the right ratio, generating white light. In order to achieve this goal, we need to control the energy transfer between light emitting elements, which dictates the control of their interatomic spacing and spatial distribution. We developed an economical wet chemical process to form the nanostructured core and to control the thickness and composition of the shell layers. With the help from using DOE funded synchrotron radiation facility, we delineated the growth mechanism of the nano-structured core and the shell layers, thereby enhancing our understanding of structure-property relation in these materials. Using the upconversion luminescence and the lifetime measurements as effective feedback to materials sysnthes is and integration, we demonstrated improved luminescence lifetimes of the core-shell nano-structures and quantified the optimal core-multi-shell structure with optimum shell thickness and composition. We developed a rare-earths co-doped LaPO4 core-multishell structure in order to produce a single white light source. It was decided that the mutli-shell method would produce the largest increase in luminescence efficiency while limiting any energy transfer that may occur between the dopant ions. All samples resulted in emission spectra within the accepted range of white light generation based on the converted CIE color coordinates. The white light obtained varied between warm and cool white depending on the layering architecture, allowing for the

  13. Size-controlled, magnetic, and core-shell nanoparticles synthesized by inert-gas condensation

    Science.gov (United States)

    Koten, Mark A.

    Interest in nanoparticles (2 to 100 nm in diameter) and clusters of atoms (0.5 to 2 nm in diameter) has heightened over the past two and a half decades on both fundamental and functional levels. Nanoparticles and clusters of atoms are an exciting branch of materials science because they do not behave like normal bulk matter, nor do they act like molecules. They can have shockingly different physical, chemical, optical, or magnetic properties from the same material at a larger scale. In the case of nanoparticles, the surface-to-volume ratio can change fundamental properties like melting temperature, binding energy, or electron affinity. The definitions of markers used to distinguish between metallic, semiconducting, and insulating bulk condensed matter, such as the band gap and polarizability, can even be blurred or confused on the nanoscale. Similarly, clusters of atoms can form in structures that are only stable at finite sizes, and do not translate to bulk condensed matter. Thermodynamics of finite systems changes dramatically in nanovolumes such as wires, rods, cubes, and spheres, which can lead to complex core-shell and onion-like nanostructures. Consequently, these changes in properties and structure have led to many new possibilities in the field of materials engineering. Inert-gas condensation (IGC) is a well-established method of producing nanoparticles that condense from the gas phase. Its first use dates back to the early 1990s, and it has been used to fabricate nanoparticles both commercially and in research and development for applications in magnetism, biomedicine, and catalysts. In this dissertation, IGC was used to produce a wide variety of nanoparticles. First, control over the size distributions of Cu nanoparticles and how it relates to the plasma properties inside the nucleation chamber was investigated. Next, the formation of phase pure WFe2 nanoparticles revealed that this Laves phase is ferromagnetic instead of non-magnetic. Finally, core-shell

  14. Large enhanced dielectric permittivity in polyaniline passivated core-shell nano magnetic iron oxide by plasma polymerization

    International Nuclear Information System (INIS)

    Joy, Lija K.; Sooraj, V.; Sethulakshmi, N.; Anantharaman, M. R.; Sajeev, U. S.; Nair, Swapna S.; Narayanan, T. N.; Ajayan, P. M.

    2014-01-01

    Commercial samples of Magnetite with size ranging from 25–30 nm were coated with polyaniline by using radio frequency plasma polymerization to achieve a core shell structure of magnetic nanoparticle (core)–Polyaniline (shell). High resolution transmission electron microscopy images confirm the core shell architecture of polyaniline coated iron oxide. The dielectric properties of the material were studied before and after plasma treatment. The polymer coated magnetite particles exhibited a large dielectric permittivity with respect to uncoated samples. The dielectric behavior was modeled using a Maxwell–Wagner capacitor model. A plausible mechanism for the enhancement of dielectric permittivity is proposed

  15. Spatially-resolved study of the luminescence from ZnO/MgO core-shell nanocrystal structures

    International Nuclear Information System (INIS)

    Panin, Gennady; Baranov, Andrey; Kapitanova, Olesya; Kang, Taewon

    2012-01-01

    The luminescent properties of core-shell nanocrystal structures were investigated with high spatial resolution. The composites consisting of ZnO/MgO core/shell nanoheteroparticles showed an increase in the relative intensity of the green luminescence after annealing while a suppression of green luminescence from samples of ZnO tetrapods in a MgO nanoparticle matrix was observed. Combined spatially-resolved combined through-the-lens-detector (TLD) and cathodoluminescence (CL) measurements revealed that the depletion of electrons in the ZnO nanocrystals could lead to a suppression of the luminescence.

  16. An improved way to prepare superparamagnetic magnetite-silica core-shell nanoparticles for possible biological application

    International Nuclear Information System (INIS)

    Sun Yongkang; Duan Lei; Guo Zhirui; Duanmu Yun; Ma Ming; Xu Lina; Zhang Yu; Gu Ning

    2005-01-01

    This paper describes an improved approach for the coating of superparamagnetic magnetite nanoparticles with shells of amorphous silica. Magnetite (Fe 3 O 4 ) nanoparticles are prepared by partial reduction coprecipitation method and modified by adding citric acid. The silica coating is conveniently controlled by a dilute silicate solution pretreatment and subsequent Saboteur process directly in ethanol. Transmission electron microscopy, photon correlation spectroscopy and zeta-potential analysis results show that the attractions between the superparamagnetic nanoparticles are screened by the silica coating. With enough tetraethyl orthosilicate added, the stable core-shell colloid was obtained. Vibrating sample magnetometer characterization shows that the magnetic core-shell structure is superparamagnetic

  17. Core-shell heterostructured metal oxide arrays enable superior light-harvesting and hysteresis-free mesoscopic perovskite solar cells

    Science.gov (United States)

    Mahmood, Khalid; Swain, Bhabani Sankar; Amassian, Aram

    2015-07-01

    To achieve highly efficient mesoscopic perovskite solar cells (PSCs), the structure and properties of an electron transport layer (ETL) or material (ETM) have been shown to be of supreme importance. Particularly, the core-shell heterostructured mesoscopic ETM architecture has been recognized as a successful electrode design, because of its large internal surface area, superior light-harvesting efficiency and its ability to achieve fast charge transport. Here we report the successful fabrication of a hysteresis-free, 15.3% efficient PSC using vertically aligned ZnO nanorod/TiO2 shell (ZNR/TS) core-shell heterostructured ETMs for the first time. We have also added a conjugated polyelectrolyte polymer into the growth solution to promote the growth of high aspect ratio (AR) ZNRs and substantially improve the infiltration of the perovskite light absorber into the ETM. The PSCs based on the as-synthesized core-shell ZnO/TiO2 heterostructured ETMs exhibited excellent performance enhancement credited to the superior light harvesting capability, larger surface area, prolonged charge-transport pathways and lower recombination rate. The unique ETM design together with minimal hysteresis introduces core-shell ZnO/TiO2 heterostructures as a promising mesoscopic electrode approach for the fabrication of efficient PSCs.To achieve highly efficient mesoscopic perovskite solar cells (PSCs), the structure and properties of an electron transport layer (ETL) or material (ETM) have been shown to be of supreme importance. Particularly, the core-shell heterostructured mesoscopic ETM architecture has been recognized as a successful electrode design, because of its large internal surface area, superior light-harvesting efficiency and its ability to achieve fast charge transport. Here we report the successful fabrication of a hysteresis-free, 15.3% efficient PSC using vertically aligned ZnO nanorod/TiO2 shell (ZNR/TS) core-shell heterostructured ETMs for the first time. We have also added a

  18. One-pot reverse microemulsion synthesis of core-shell structured YVO4:Eu3+@SiO2 nanocomposites

    Science.gov (United States)

    Liu, Lina; Yue, Surong; Zhang, Yongsheng; Qin, Ruifei; Liu, Lishuang; Zhang, Dongmei; Sun, Ruirui; Chen, Linfeng

    2015-01-01

    Core-shell structured YVO4:Eu3+@SiO2 nanocomposite particles were synthesized using a one-pot reverse microemulsion method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV absorption spectra, and photoluminescent spectra. The nanocomposite particles are well-dispersed and about 20 nm in average size. The synthesis method is of one-pot, simplifying the preparation of this kind of core-shell structured nanocomposites. The formation process of these nanocomposite particles is suggested and the photoluminescence properties of them are studied and compared with those of uncoated YVO4:Eu3+ sample.

  19. Preparation and Application of Temperature Sensitive Paintings

    Science.gov (United States)

    Li, Chi

    2015-11-01

    Temperature sensitive painting (TSP) is a rapidly developing surface optical measurement technology, which uses temperature sensitive fluorescent probe molecular to obtain the temperature distribution on the surface of the model. Two different types of TSP material are prepared to apply in fluid mechanical experiments. Rhodamine is used as fluorescer and acetone as solvent for the first recipe, while rare earth material as fluorescer and zirconia as solvent for the second recipe. With proper calibration, surface temperature nephogram and temperature gradient nephogram is obtained based on the measured light intensity data, and transition location and heat flux is analyzed. Double layer - multi component TSP measurement technology and more strict calibration will be developed in the near future to get more precise heat flux distribution.

  20. Influences of composition on Raman scattering from GeSi alloy core-shell nanowire heterostructures

    Science.gov (United States)

    Han, Delong; Ye, Han; Yu, Zhongyuan; Zhang, Yunzhen; Liu, Yumin; Li, Yinfeng

    2017-10-01

    In this paper, the influences of composition on Raman scattering from Ge/Si-GeSi core-shell nanowire heterostructures standing along [011] and [111] crystal directions are numerically investigated. Uniform, linear and spontaneous nonlinear composition profiles (CPs) in GeSi alloy shell are taken into consideration. In uniform CP case, clear double peaks in Raman spectra contributed by core and shell are observed. The strain-induced shift follows linear relation with Ge concentration and nonlinear relation with shell thickness. Larger strain-induced shifts are obtained in nanowires along [111] direction. In linear CP case, the peaks contributed by shell cannot be distinguished in the total spectra and plateaus are formed on the low frequency side. Moreover, the nonlinear CP accounts for the spontaneous composition transition near heterointerface during lateral epitaxy of GeSi shell. Due to the rapid Ge concentration transition, Raman spectra are shown nearly identical to uniform CP cases.

  1. CdTe-HgTe core-shell nanowire growth controlled by RHEED

    Science.gov (United States)

    Kessel, M.; Hajer, J.; Karczewski, G.; Schumacher, C.; Brüne, C.; Buhmann, H.; Molenkamp, L. W.

    2017-07-01

    We present results on the growth of CdTe-HgTe core-shell nanowires, a realization of a quasi-one-dimensional heterostructure of the topological insulator HgTe. The growth is a two step process consisting of the growth of single crystalline zinc blende CdTe nanowires with the vapor-liquid-solid method and the overgrowth of these wires with HgTe such that a closed shell is formed around the CdTe core structure. The CdTe wire growth is monitored by RHEED allowing us to infer information on the crystal properties from the electron diffraction pattern. This information is used to find and control the optimal growth temperature. High quality single crystal CdTe nanowires grow with a preferred orientation. For the growth of the conductive HgTe shell structure we find that the supplied Hg:Te ratio is the crucial parameter to facilitate growth on all surface facets.

  2. Protective agent-free synthesis of Ni-Ag core-shell nanoparticles

    International Nuclear Information System (INIS)

    Chen, D.-H.; Wang, S.-R.

    2006-01-01

    Ni-Ag core-shell nanoparticles have been prepared by successive hydrazine reduction in ethylene glycol in the absence of protective agents. TEM analysis indicated the product was very fine and the thickness of Ag nanoshells could be controlled by the added silver nitrate concentration. The analyses of electron diffraction pattern and XRD revealed that both Ni cores and Ag shells had a fcc structure. The surface composition analysis by XPS indicated that Ni cores were fully covered by Ag nanoshells. Because of the absence of protective agent, the appropriate nickel concentration for the coating of Ag nanoshells should be less than 1.0 mM to avoid particle agglomeration. The product possessed the surface character of Ag and the magnetic property of Ni, and may have many potential applications in optical, magnetic, catalytic, biochemical, and biomedical fields

  3. Interface bond relaxation on the thermal conductivity of Si/Ge core-shell nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Weifeng; He, Yan; Ouyang, Gang, E-mail: gangouy@hunnu.edu.cn [Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education, Synergetic Innovation Center for Quantum Effects and Applications(SICQEA), Hunan Normal University, Changsha 410081 (China); Sun, Changqing [School of Electrical & Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

    2016-01-15

    The thermal conductivity of Si/Ge core-shell nanowires (CSNWs) is investigated on the basis of atomic-bond-relaxation consideration and continuum mechanics. An analytical model is developed to clarify the interface bond relaxation of Si/Ge CSNWs. It is found that the thermal conductivity of Si core can be modulated through covering with Ge epitaxial layers. The change of thermal conductivity in Si/Ge CSNWs should be attributed to the surface relaxation and interface mismatch between inner Si nanowire and outer Ge epitaxial layer. Our results are in well agreement with the experimental measurements and simulations, suggesting that the presented method provides a fundamental insight of the thermal conductivity of CSNWs from the atomistic origin.

  4. Preparation and characterization of titania/ZnS core-shell nanotubes.

    Science.gov (United States)

    Kim, Mee Rahn; Ahn, Shin Ja; Jang, Du-Jeon

    2006-01-01

    Core-shell nanocomposites of titania nanotubes/ZnS quantum dots have been prepared by using a hydrothermal synthetic method and characterized by using various microscopic and spectroscopic methods. ZnS quantum dots surround the outsides of titania nanotubes having the inner and the outer diameters of 15 and 30 nm, respectively, with a thickness of 2 nm. The nanocomposites suspended in water show a broader absorption spectrum shifted to a longer wavelength by 20 nm and emit substantially stronger ZnS luminescence having significantly slower decay kinetics than bare ZnS nanoparticles in water. The support of TiO2 nanotubes is found to enhance the optical properties of ZnS considerably.

  5. Monodisperse core-shell particles composed of magnetite and dye-functionalized mesoporous silica

    Science.gov (United States)

    Eurov, D. A.; Kurdyukov, D. A.; Medvedev, A. V.; Kirilenko, D. A.; Yakovlev, D. R.; Golubev, V. G.

    2017-08-01

    Hybrid particles with a core-shell structure have been obtained in the form of monodisperse spherical mesoporous silica particles filled with magnetite and covered with a mesoporous silica shell functionalized with a luminescent dye. The particles have a small root-mean-square size deviation (at most 10%), possess a specific surface area and specific pore volume of up to 250 m2/g and 0.15 cm3/g, respectively, and exhibit visible luminescence peaked at a wavelength of 530 nm. The particles can be used in diagnostics of cancerous diseases, serving simultaneously for therapeutic (magnetic hyperthermia and targeted drug delivery) and diagnostic (contrast agent for magnetic-resonance tomography and luminescent marker) purposes.

  6. Hiding the interior region of core-shell nanoparticles with quantum invisible cloaks

    Science.gov (United States)

    Lee, Jeng Yi; Lee, Ray-Kuang

    2014-04-01

    Based on the scattering cancellation, we provide a method not only making a nanoparticle nearly invisible, but also hiding its interior region from the outside probing matter wave. By applying the interplay among the nodal points of partial waves along with the concept of streamline in fluid dynamics for probability flux, a quantum invisible cloak to the electron transport in a host semiconductor is demonstrated by simultaneously guiding the probability flux outside a hidden region and keeping the total scattering cross section negligible. As the probability flux vanishes in the interior region, one can embed any materials inside a multiple core-shell nanoparticle without affecting physical observables from the outside. Our results reveal the possibility to design a protection shield layer for fragile interior parts from the impact of transport electrons.

  7. Facile Synthesis of Au Nanocube-CdS Core-Shell Nanocomposites with Enhanced Photocatalytic Activity

    Science.gov (United States)

    Liu, Xiao-Li; Liang, Shan; Li, Min; Yu, Xue-Feng; Zhou, Li; Wang, Qu-Qua

    2014-06-01

    Au nanocube-CdS core-shell nanocomposites are prepared by using a one-pot method in aqueous phase with cetyltrimethylammonium bromide as the surfactant. The extinction properties and photocatalytic activity of Au-CdS nanocomposites are investigated. Compared with the pure Au nanocubes, the Au-CdS nanocomposites exhibit enhanced extinction intensity. Compared with CdS nanoparticles, the Au-CdS nanocomposites exhibit improved photocatalytic activity. Furthermore, the photocatalytic efficiency is even better with the increase in the core size of the Au-CdS nanocomposites. Typically, the photocatalytic efficiency of the Au-CdS with 62 nm sized Au nanocubes is about two times higher than that of the pure CdS. It is believed that the Au-CdS nanocomposites may find potential applications in environmental fields, and this synthesis method can be extended to prepare a wide variety of functional composites with Au cores.

  8. Reversible Rayleight-to-MIe Scattering Transition in a Core-Shell Colloidal System

    Science.gov (United States)

    Meng, Guangnan; Perro, Adeline; Manoharan, Vinothan

    2009-03-01

    We present a study of light scattering from colloidal particles with small polystyrene cores and large shells of poly(N'-isopropylacrylamide-co-acrylic acid). When swollen in deionize water at room temperature, the shell is nearly index-matched to pure water, and the scattering is dominated by Rayleigh scattering from the polystyrene cores. As we change the solvent condition by increasing temperature or salt concentration, the shell starts to shrink and scatter light. Both the scattering cross section and the forward scattering of the particles increase, characteristic of Mie scatterers. We use optical microscopy, static light scattering and turbidimetry to study this optical transition. Such core-shell particles might be used as aqueous index-matched tracer colloids, as model scatterers for self-assembly studies, or as optical filters with tunable opacity.

  9. Synthesis and magnetic properties of inverted core-shell polyaniline-ferrite composite

    Energy Technology Data Exchange (ETDEWEB)

    Donescu, Dan [National Institute for Research & Development in Chemistry and Petrochemistry - ICECHIM, 202 Spl. Independentei, 060021, Bucharest (Romania); Fierascu, Radu Claudiu, E-mail: radu_claudiu_fierascu@yahoo.com [National Institute for Research & Development in Chemistry and Petrochemistry - ICECHIM, 202 Spl. Independentei, 060021, Bucharest (Romania); Ghiurea, Marius [National Institute for Research & Development in Chemistry and Petrochemistry - ICECHIM, 202 Spl. Independentei, 060021, Bucharest (Romania); Manaila-Maximean, Doina [University Politehnica of Bucharest, Department of Physics, 313 Spl. Independentei, 060042, Bucharest (Romania); Nicolae, Cristian Andi; Somoghi, Raluca; Spataru, Catalin Ilie [National Institute for Research & Development in Chemistry and Petrochemistry - ICECHIM, 202 Spl. Independentei, 060021, Bucharest (Romania); Stanica, Nicolae [Institute of Physical Chemistry “Ilie Murgulescu”, 202 Spl. Independentei, 060021, Bucharest (Romania); Raditoiu, Valentin [National Institute for Research & Development in Chemistry and Petrochemistry - ICECHIM, 202 Spl. Independentei, 060021, Bucharest (Romania); Vasile, Eugeniu [SC METAV – CD SA, 31 C. A. Rosetti Str., 021051, Bucharest (Romania)

    2017-08-31

    The present paper studies the effect of polyaniline grafting on magnetite functionalized with aminopropyltrimethoxysilane. All the compounds were characterized by analytical techniques (X-ray fluorescence, X-ray diffraction, Fourier transform infrared spectroscopy, thermal analysis, Transmission electron microscopy), as well as by determining their magnetic properties. The electron microscopy analysis of the hybrids shows similar morphologies for all the samples. The presence of the iron atoms on the surface of the final product supports the idea of the existence of an inverted core-shell type structure, the more polar ferrite orienting itself towards water. The correlation between the maximum grafting probability and the maximum magnetization is evidenced, demonstrating the importance of the polymer grafting method on the magnetic properties.

  10. Silver, gold and the corresponding core shell nanoparticles: synthesis and characterization

    International Nuclear Information System (INIS)

    Douglas, Fraser; Yanez, Ramon; Ros, Josep; Marin, Sergio; Escosura-Muniz, Alfredo de la; Alegret, Salvador; Merkoci, Arben

    2008-01-01

    Simple strategies for producing silver and gold nanoparticles (AgNP and AuNP) along with the corresponding core shell nanoparticles (Au-Ag and Ag-Au) by reduction of the metal salts AgBF 4 and HAuCl 4 by NaBH 4 in water will be presented. The morphologies of the obtained nanoparticles are determined by the order of addition of reactants. The obtained NPs, with sizes in the range 3-40 nm, are characterized by transmission electronic microscopy (TEM) and UV-Vis absorption spectroscopy, so as to evaluate their qualities. Moreover, a direct electrochemical detection protocol based on a cyclic voltammetry in water solution that involves the use of glassy carbon electrode is also applied to characterize the prepared NPs. The developed NPs and the related electroanalytical method seem to be with interest for future sensing and biosensing applications including DNA sensors and immunosensors.

  11. Control of Microbial Growth in Alginate/Polydopamine Core/Shell Microbeads.

    Science.gov (United States)

    Kim, Beom Jin; Park, Taegyun; Park, So-Young; Han, Sang Woo; Lee, Hee-Seung; Kim, Yang-Gyun; Choi, Insung S

    2015-10-01

    Microbial microencapsulation not only protects microorganisms from harmful environments by physically isolating them from the outside media but also has the potential to tailor the release profile of the encapsulated cells. However, the microbial release has not yet been controlled tightly, leading to undesired detrimental exposure of microorganisms to the outside. In this work, we suggest a simple method for controlling the cell release by suppressing the microbial growth in the microbeads. Alginate microbeads, encapsulating yeast cells, were coated with ultrathin but robust polydopamine shells, and the resulting core/shell structures effectively reduced the growth rate, while maintaining the cell viability. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Preparation and Characterization of Nickel Ferrite-SiO2/Ag Core/Shell Nanocomposites

    Directory of Open Access Journals (Sweden)

    I. G. Blanco-Esqueda

    2015-01-01

    Full Text Available Magnetic composites with silver nanoparticles bonded to their surface were successfully prepared using a simple chemical method. By means of a sol-gel technique, nickel ferrite nanoparticles have been prepared and coated with silica to control and avoid their magnetic agglomeration. The structural and magnetic properties of the nanoparticles were studied in function of the annealing temperature. Then, silver nanoparticles were incorporated by hydrolysis-condensation of tetraethyl orthosilicate, which contains silver nitrate on the surface of the nickel ferrite-SiO2 core/shell. Samples were characterized using X-ray diffraction, IR spectroscopy, SEM, and magnetometry. Results show that the silica covered the nickel ferrite nanoparticles and the silver nanoparticles remain stable in the surface of the composite.

  13. A novel approach to preparing magnetic protein microspheres with core-shell structure

    Science.gov (United States)

    Jiang, Wei; Sun, Zhendong; Li, Fengsheng; Chen, Kai; Liu, Tianyu; Liu, Jialing; Zhou, Tianle; Guo, Rui

    2011-03-01

    Magnetic protein microspheres with core-shell structure were prepared through a novel approach based on the sonochemical method and the emulsion solvent evaporation method. The microspheres are composed of the oleic acid and undecylenic acid modified Fe 3O 4 cores and coated with globular bovine serum albumin (BSA). Under an optimized condition, up to 57.8 wt% of approximately 10 nm superparamagnetic Fe 3O 4 nanoparticles could be uniformly encapsulated into the BSA microspheres with the diameter of approximately 160 nm and the high saturation magnetization of 38.5 emu/g, besides of the abundant functional groups. The possible formation mechanism of magnetic microspheres was discussed in detail.

  14. Growth of Au@Ag core-shell pentatwinned nanorods: tuning the end facets.

    Science.gov (United States)

    Zhang, Weiqing; Goh, Hao Ying Johnny; Firdoz, Shaik; Lu, Xianmao

    2013-09-16

    Au@Ag core-shell nanorods with tunable end facets are obtained by coating Au bipyramids (BPs) with Ag. The resultant nanorods exhibit a pentatwinned crystal structure with tips terminated with either {110} or {111} facets. The control over the end facets is achieved by varying the capping agents and tuning the reduction rate of Ag. Specifically, when Ag is reduced slowly, Au@Ag nanorods with flat {110} end facets are formed with cetyltrimethylammonium bromide (CTAB) as the capping agent. If CTAB is replaced with cetyltrimethylammonium chloride (CTAC), Au@Ag nanorods with tips terminated with {111} facets are obtained. However, at a high Ag reduction rate, dumbbell-shaped Au@Ag nanorods are formed, with either CTAB or CTAC as the capping agent. The morphological evolution of the nanorods in each case is closely followed and a growth mechanism is proposed. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Evaluation of iron-cobalt/ferrite core-shell nanoparticles for cancer thermotherapy

    Science.gov (United States)

    Habib, A. H.; Ondeck, C. L.; Chaudhary, P.; Bockstaller, M. R.; McHenry, M. E.

    2008-04-01

    Magnetic nanoparticles (MNPs) offer promise for local hyperthermia or thermoablative cancer therapy. Magnetic hyperthermia uses MNPs to heat cancerous regions in an rf field. Metallic MNPs have larger magnetic moments than iron oxides, allowing similar heating at lower concentrations. By tuning the magnetic anisotropy in alloys, the heating rate at a particular particle size can be optimized. Fe-Co core-shell MNPs have protective CoFe2O4 shell which prevents oxidation. The oxide coating also aids in functionalization and improves biocompatibility of the MNPs. We predict the specific loss power (SLP) for FeCo (SLP ˜450W /g) at biocompatible fields to be significantly larger in comparision to oxide materials. The anisotropy of Fe-Co MNPs may be tuned by composition and/or shape variation to achieve the maximum SLP at a desired particle size.

  16. Lattice-Strain Control of the Activity in Dealloyed Core-Shell Fuel Cell Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Strasser, P. [Berlin Institute of Technology (Technische Universitat Berlin); Koh, Shirlaine [University of Houston, Houston; Anniyev, Toyli [SLAC National Accelerator Laboratory; Greeley, Jeff [Argonne National Laboratory (ANL); More, Karren Leslie [ORNL; Yu, Chengfei [University of Houston, Houston; Liu, Zengcai [University of Houston, Houston; Kaya, Sarpa [SLAC National Accelerator Laboratory; Nordlund, Dennis [SLAC National Accelerator Laboratory; Ogasawara, Hirohito [SLAC National Accelerator Laboratory; Toney, Michael F. [SLAC National Accelerator Laboratory; Anders, Nilsson [SLAC National Accelerator Laboratory

    2010-01-01

    Electrocatalysis will play a key role in future energy conversion and storage technologies, such as water electrolysers, fuel cells and metal-air batteries. Molecular interactions between chemical reactants and the catalytic surface control the activity and efficiency, and hence need to be optimized; however, generalized experimental strategies to do so are scarce. Here we show how lattice strain can be used experimentally to tune the catalytic activity of dealloyed bimetallic nanoparticles for the oxygen-reduction reaction, a key barrier to the application of fuel cells and metal-air batteries. We demonstrate the core-shell structure of the catalyst and clarify the mechanistic origin of its activity. The platinum-rich shell exhibits compressive strain, which results in a shift of the electronic band structure of platinum and weakening chemisorption of oxygenated species. We combine synthesis, measurements and an understanding of strain from theory to generate a reactivity-strain relationship that provides guidelines for tuning electrocatalytic activity.

  17. Si/PEDOT hybrid core/shell nanowire arrays as photoelectrodes for photoelectrochemical water-splitting.

    Science.gov (United States)

    Li, Xiaojuan; Lu, Wenhui; Dong, Weiling; Chen, Qi; Wu, Dan; Zhou, Wenzheng; Chen, Liwei

    2013-06-21

    Si/poly(3,4-ethylenedioxythiophene) (PEDOT) core/shell nanowire arrays have been prepared by chemical etching of Si nanowires followed by vapor-phase polymerization of PEDOT as hybrid photoanodes for photoelectrochemical water-splitting. The PEDOT layer is employed as a multi-functional coating to prevent photocorrosion of Si nanowires, collect photogenerated holes and catalyze the water oxidation reaction. The amino silane modified Si nanowire surface improves PEDOT layer adhesion, and the resulting photoanode exhibits better photoresponse and improved stability. By tuning the length of the nanowires, we identify that the competition between the carrier recombination and catalytic water oxidation reaction is the primary factor determining the photoelectrocatalytic activity of the hybrid photoanode.

  18. Preparation of novel magnetic polyurethane foam nanocomposites by using core-shell nanoparticles

    Directory of Open Access Journals (Sweden)

    Mir Mohammad Alavi Nikje

    Full Text Available Abstract Iron oxide magnetic nanoparticles (NP's converted to the core- shell structres by reacting with by n-(2-aminoethyl-3-aminopropyl trimethoxysilane (AEAP incorporated in polyurethane flexible (PUF foam formulations. Fourier transform spectra, thermal gravimetric analysis, scanning electron images, thermo-mechanical analysis and magnetic properties of the prepared nanocomposites were studied. Obtained data shown that by the increasing of the amine modified magnetic iron oxide NP's up to 3% in the polymer matrix, thermal and magnetic properties improved in comparison with pristine foams. In addition, due to the presence of functional groups on the magnetic NP's surface, hard phases formation decrease in the bulk polymer and cause decreasing of glass transition temperature.

  19. Core/shell magnetic mesoporous silica nanoparticles with radially oriented wide mesopores

    Directory of Open Access Journals (Sweden)

    Nikola Ž. Knežević

    2014-06-01

    Full Text Available Core/shell nanoparticles, containing magnetic iron-oxide (maghemite core and mesoporous shell with radial porous structure, were prepared by dispersing magnetite nanoparticles and adding tetraethylorthosilicate to a basic aqueous solution containing structure-templating cetyltrimethylammonium bromide and a pore-swelling mesithylene. The material is characterized by SEM and TEM imaging, nitrogen sorption and powder X-ray diffraction. Distinctive features of the prepared material are its high surface area (959 m2/g, wide average pore diameter (12.4 nm and large pore volume (2.3 cm3/g. The material exhibits radial pore structure and the high angle XRD pattern characteristic for maghemite nanoparticles, which are obtained upon calcination of the magnetite-containing material. The observed properties of the prepared material may render the material applicable in separation, drug delivery, sensing and heterogeneous catalysis.

  20. Core/Shell Conjugated Polymer/Quantum Dot Composite Nanofibers through Orthogonal Non-Covalent Interactions

    Directory of Open Access Journals (Sweden)

    Brad W. Watson

    2016-11-01

    Full Text Available Nanostructuring organic polymers and organic/inorganic hybrid materials and controlling blend morphologies at the molecular level are the prerequisites for modern electronic devices including biological sensors, light emitting diodes, memory devices and solar cells. To achieve all-around high performance, multiple organic and inorganic entities, each designed for specific functions, are commonly incorporated into a single device. Accurate arrangement of these components is a crucial goal in order to achieve the overall synergistic effects. We describe here a facile methodology of nanostructuring conjugated polymers and inorganic quantum dots into well-ordered core/shell composite nanofibers through cooperation of several orthogonal non-covalent interactions including conjugated polymer crystallization, block copolymer self-assembly and coordination interactions. Our methods provide precise control on the spatial arrangements among the various building blocks that are otherwise incompatible with one another, and should find applications in modern organic electronic devices such as solar cells.

  1. Core/shell fluorescent magnetic silica-coated composite nanoparticles for bioconjugation

    Science.gov (United States)

    He, Rong; You, Xiaogang; Shao, Jun; Gao, Feng; Pan, Bifeng; Cui, Daxiang

    2007-08-01

    A new class of highly fluorescent, photostable, and magnetic core/shell nanoparticles has been synthesized from a reverse microemulsion method. The obtained bifunctional nanocomposites were characterized by transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) spectrometry, photoluminescence (PL) spectrometry, and fluorescence microscopy in a magnetic field. To further improve their biocompatibility, the silica-coated nanoparticles were functionalized with amino groups. The fluorescent magnetic composite nanoparticles (FMCNPs) had a typical diameter of 50 ± 5 nm and a saturation magnetization of 3.21 emu g-1 at room temperature, and exhibited strong excitonic photoluminescence. Through activation with glutaraldehyde, the FMCNPs were successfully conjugated with goat anti-mouse immunoglobin G (GM IgG), and the bioactivity and binding specificity of the as-prepared FMCNPs-GM IgG were confirmed via immunofluorescence assays, commonly used in bioanalysis. So they are potentially useful for many applications in biolabelling, imaging, drug targeting, bioseparation and bioassays.

  2. Core/shell fluorescent magnetic silica-coated composite nanoparticles for bioconjugation

    International Nuclear Information System (INIS)

    He Rong; You Xiaogang; Shao Jun; Gao Feng; Pan Bifeng; Cui Daxiang

    2007-01-01

    A new class of highly fluorescent, photostable, and magnetic core/shell nanoparticles has been synthesized from a reverse microemulsion method. The obtained bifunctional nanocomposites were characterized by transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) spectrometry, photoluminescence (PL) spectrometry, and fluorescence microscopy in a magnetic field. To further improve their biocompatibility, the silica-coated nanoparticles were functionalized with amino groups. The fluorescent magnetic composite nanoparticles (FMCNPs) had a typical diameter of 50 ± 5 nm and a saturation magnetization of 3.21 emu g -1 at room temperature, and exhibited strong excitonic photoluminescence. Through activation with glutaraldehyde, the FMCNPs were successfully conjugated with goat anti-mouse immunoglobin G (GM IgG), and the bioactivity and binding specificity of the as-prepared FMCNPs-GM IgG were confirmed via immunofluorescence assays, commonly used in bioanalysis. So they are potentially useful for many applications in biolabelling, imaging, drug targeting, bioseparation and bioassays

  3. Significant Broadband Photocurrent Enhancement by Au-CZTS Core-Shell Nanostructured Photocathodes

    Science.gov (United States)

    Zhang, Xuemei; Wu, Xu; Centeno, Anthony; Ryan, Mary P.; Alford, Neil M.; Riley, D. Jason; Xie, Fang

    2016-03-01

    Copper zinc tin sulfide (CZTS) is a promising material for harvesting solar energy due to its abundance and non-toxicity. However, its poor performance hinders their wide application. In this paper gold (Au) nanoparticles are successfully incorporated into CZTS to form Au@CZTS core-shell nanostructures. The photocathode of Au@CZTS nanostructures exhibits enhanced optical absorption characteristics and improved incident photon-to-current efficiency (IPCE) performance. It is demonstrated that using this photocathode there is a significant increase of the power conversion efficiency (PCE) of a photoelectrochemical solar cell of 100% compared to using a CZTS without Au core. More importantly, the PCE of Au@CZTS photocathode improved by 15.8% compared to standard platinum (Pt) counter electrode. The increased efficiency is attributed to plasmon resonance energy transfer (PRET) between the Au nanoparticle core and the CZTS shell at wavelengths shorter than the localized surface plasmon resonance (LSPR) peak of the Au and the semiconductor bandgap.

  4. Au@Pd core-shell nanobricks with concave structures and their catalysis of ethanol oxidation.

    Science.gov (United States)

    Wang, Wenjin; Zhang, Jie; Yang, Shengchun; Ding, Bingjun; Song, Xiaoping

    2013-10-01

    Au@Pd core-shell nanobricks (CNBs) with concave surfaces and Pd shells with a thickness of approximately 5 nm were synthesized by co-reduction of HAuCl4 and H2 PdCl4 in the presence of Au seeds and Ag ions. These as-synthesized concave CNBs exhibit significantly enhanced catalytic activity for the electrooxidation of ethanol in alkaline media compared to the commercially-used Pd black. The improved performance of the Au@Pd CNBs can be attributed to the exposed stepped surfaces, high-index facets, and the synergistic effects of the core and shell metals. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Plasmonic Nanodiamonds – Targeted Core-shell Type Nanoparticles for Cancer Cell Thermoablation

    Science.gov (United States)

    Rehor, Ivan; Lee, Karin L.; Chen, Kevin; Hajek, Miroslav; Havlik, Jan; Lokajova, Jana; Masat, Milan; Slegerova, Jitka; Shukla, Sourabh; Heidari, Hamed; Bals, Sara

    2015-01-01

    Targeted biocompatible nanostructures with controlled plasmonic and morphological parameters are promising materials for cancer treatment based on selective thermal ablation of cells. Here, core-shell plasmonic nanodiamonds consisting of a silica-encapsulated diamond nanocrystal coated in a gold shell is designed and synthesized. The architecture of particles is analyzed and confirmed in detail using 3-dimensional transmission electron microscope tomography. The particles are biocompatibilized using a PEG polymer terminated with bioorthogonally reactive alkyne groups. Azide-modified transferrin is attached to these particles, and their high colloidal stability and successful targeting to cancer cells overexpressing the transferrin receptor is demonstrated. The particles are nontoxic to the cells and they are readily internalized upon binding to the transferrin receptor. The high plasmonic cross section of the particles in the near-infrared region is utilized to quantitatively ablate the cancer cells with a short, one-minute irradiation by a pulse 750-nm laser. PMID:25336437

  6. Long Wavelength Plasmonic Absorption Enhancement in Silicon Using Optical Lithography Compatible Core-Shell-Type Nanowires

    Directory of Open Access Journals (Sweden)

    Mohammed Shahriar Sabuktagin

    2014-01-01

    Full Text Available Plasmonic properties of rectangular core-shell type nanowires embedded in thin film silicon solar cell structure were characterized using FDTD simulations. Plasmon resonance of these nanowires showed tunability from  nm. However this absorption was significantly smaller than the Ohmic loss in the silver shell due to very low near-bandgap absorption properties of silicon. Prospect of improving enhanced absorption in silicon to Ohmic loss ratio by utilizing dual capability of these nanowires in boosting impurity photovoltaic effect and efficient extraction of the photogenerated carriers was discussed. Our results indicate that high volume fabrication capacity of optical lithography techniques can be utilized for plasmonic absorption enhancement in thin film silicon solar cells over the entire long wavelength range of solar radiation.

  7. Defect-tuning exchange bias of ferromagnet/antiferromagnet core/shell nanoparticles by numerical study

    International Nuclear Information System (INIS)

    Mao Zhongquan; Chen Xi; Zhan Xiaozhi

    2012-01-01

    The influence of non-magnetic defects on the exchange bias (EB) of ferromagnet (FM)/antiferromagnet (AFM) core/shell nanoparticles is studied by Monte Carlo simulations. It is found that the EB can be tuned by defects in different positions. Defects at both the AFM and FM interfaces reduce the EB field while they enhance the coercive field by decreasing the effective interface coupling. However, the EB field and the coercive field show respectively a non-monotonic and a monotonic dependence on the defect concentration when the defects are located inside the AFM shell, indicating a similar microscopic mechanism to that proposed in the domain state model. These results suggest a way to optimize the EB effect for applications. (paper)

  8. Chemical resistance of core-shell particles (PS/PMMA) polymerized by seeded suspension

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, Luiz Fernando Belchior; Machado, Ricardo Antonio Francisco, E-mail: ricardo.machado@ufsc.br [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil). Departamento de Engenharia de Materiais; Gonçalves, Odinei Hess [Universidade Técnológica Federal do Paraná(UTFPR), Campo Mourão, PR (Brazil); Marangoni, Cintia [Universidade Federal de Santa Catarina (UFSC), Blumenau, SC (Brazil); Motz, Günter [Lehrstuhl Keramische Werkstoffe, Universität Bayreuth (Germany)

    2017-07-01

    Core-shell particles were produced on seeded suspension polymerization by using polystyrene (PS) as polymer core, or seed, and methyl methacrylate (MMA) as the shell forming monomer. Two synthesis routes were evaluated by varying the PS seed conversion before MMA addition. The main purpose of this work was to investigate the influence of synthesis routes on the morphology and chemical resistance of the resulting particles. {sup 1}H NMR spectroscopy showed that the use of PS seeds with lower conversion led to the formation of higher amount of poly(styrene-co-MMA). The copolymer acted as a compatibilizer, decreasing the interfacial energy between both homopolymers. As a consequence, a larger amount of reduced PMMA cluster were formed, as was revealed by TEM measurements. Samples in this system showed enhanced resistance to cyclohexane attack compared with pure PS, with a PS extraction of only 37% after 54 hours test. (author)

  9. Chemical resistance of core-shell particles (PS/PMMA polymerized by seeded suspension

    Directory of Open Access Journals (Sweden)

    Luiz Fernando Belchior Ribeiro

    2017-09-01

    Full Text Available Abstract Core-shell particles were produced on seeded suspension polymerization by using polystyrene (PS as polymer core, or seed, and methyl methacrylate (MMA as the shell forming monomer. Two synthesis routes were evaluated by varying the PS seed conversion before MMA addition. The main purpose of this work was to investigate the influence of synthesis routes on the morphology and chemical resistance of the resulting particles. 1H NMR spectroscopy showed that the use of PS seeds with lower conversion led to the formation of higher amount of poly(styrene-co-MMA. The copolymer acted as a compatibilizer, decreasing the interfacial energy between both homopolymers. As a consequence, a larger amount of reduced PMMA cluster were formed, as was revealed by TEM measurements. Samples in this system showed enhanced resistance to cyclohexane attack compared with pure PS, with a PS extraction of only 37% after 54 hours test.

  10. ZnO-nanocarbon core-shell type hybrid quantum dots

    CERN Document Server

    Choi, Won Kook

    2017-01-01

    This book offers a comprehensive overview of ZnO-nano carbon core shell hybrid issues. There is significant interest in metal oxide/nanocarbon hybrid functional materials in the field of energy conversion and storage as electrode materials for supercapacitors, Li ion secondary battery, electrocatalysts for water splitting, and optoelectronic devices such as light emitting diodes and solar photovoltaic cells. Despite efforts to manipulate more uniform metal oxide-nanocarbon nanocomposite structures, they have shown poor performance because they are randomly scattered and non-uniformly attached to the nanocarbon surface. For higher and more effective performance of the hybrid structure, 3D conformal coating on metal oxides are highly desirable. In the first part of the book, the physical and chemical properties of ZnO and nanocarbons and the state-of-the-art in related research are briefly summarized. In the next part, the 3D conformal coating synthetic processes of ZnO templated nanocarbon hybrid materials suc...

  11. Signature of snaking states in the conductance of core-shell nanowires.

    Science.gov (United States)

    Rosdahl, Tomas Orn; Manolescu, Andrei; Gudmundsson, Vidar

    2015-01-14

    We model a core-shell nanowire (CSN) by a cylindrical surface of finite length. A uniform magnetic field perpendicular to the axis of the cylinder forms electron states along the lines of zero radial field projection, which can classically be described as snaking states. In a strong field, these states converge pairwise to quasidegenerate levels, which are situated at the bottom of the energy spectrum. We calculate the conductance of the CSN by coupling it to leads and predict that the snaking states govern transport at low chemical potential, forming isolated peaks, each of which may be split in two by applying a transverse electric field. If the contacts with the leads do not completely surround the CSN, as is usually the case in experiments, the amplitude of the snaking peaks changes when the magnetic field is rotated, determined by the overlap of the contacts with the snaking states.

  12. Differential response of macrophages to core-shell Fe3O4@Au nanoparticles and nanostars

    Science.gov (United States)

    Xia, Wei; Song, Hyon-Min; Wei, Qingshan; Wei, Alexander

    2012-10-01

    Murine RAW 264.7 cells were exposed to spheroidal core-shell Fe3O4@Au nanoparticles (SCS-NPs, ca. 34 nm) or nanostars (NSTs, ca. 100 nm) in the presence of bovine serum albumin, with variable effects observed after macrophagocytosis. Uptake of SCS-NPs caused macrophages to adopt a rounded, amoeboid form, accompanied by an increase in surface detachment. In contrast, the uptake of multibranched NSTs did not induce gross changes in macrophage shape or adhesion, but correlated instead with cell enlargement and signatures of macrophage activation such as TNF-α and ROS. MTT assays indicate a low cytotoxic response to either SCS-NPs or NSTs despite differences in macrophage behavior. These observations show that differences in NP size and shape are sufficient to produce diverse responses in macrophages following uptake.Murine RAW 264.7 cells were exposed to spheroidal core-shell Fe3O4@Au nanoparticles (SCS-NPs, ca. 34 nm) or nanostars (NSTs, ca. 100 nm) in the presence of bovine serum albumin, with variable effects observed after macrophagocytosis. Uptake of SCS-NPs caused macrophages to adopt a rounded, amoeboid form, accompanied by an increase in surface detachment. In contrast, the uptake of multibranched NSTs did not induce gross changes in macrophage shape or adhesion, but correlated instead with cell enlargement and signatures of macrophage activation such as TNF-α and ROS. MTT assays indicate a low cytotoxic response to either SCS-NPs or NSTs despite differences in macrophage behavior. These observations show that differences in NP size and shape are sufficient to produce diverse responses in macrophages following uptake. Electronic supplementary information (ESI) available: Synthetic details, additional TEM images, absorbance spectra, and DLS analysis of SCS-NPs and NSTs, negative and positive control images of ROS imaging, and the effect of magnetic field gradient on ROS production. See DOI: 10.1039/c2nr32070c

  13. HIPS-GLAD core shell nanorod array photodetectors with enhanced photocurrent and reduced dark current

    Science.gov (United States)

    Keles, Filiz; Cansizoglu, Hilal; Badraddin, Emad O.; Brozak, Matthew P.; Watanabe, Fumiya; Karabacak, Tansel

    2016-10-01

    Vertically aligned core/shell nanorod array photodetectors were fabricated by high pressure sputter (HIPS) deposition of copper indium sulfide (CIS) films on glancing angle deposited (GLAD) indium sulfide (In2S3) nanorods. For comparison, we also studied nanorod photodetectors with conventional low pressure sputtered (LPS) CIS film coatings and counterpart thin film devices incorporating HIPS or LPS-CIS on In2S3 films. HIPS-GLAD core/shell photodetectors have shown a superior photocurrent density response along with lowest dark current density. Photoresponsivity defined with the photocurrent density/dark current density ratio γ = |J ph/J dark| was about ˜1820 for HIPS-GLAD nanorod devices, which is several orders of magnitude higher compared to those of LPS-CIS thin film (γ ˜ 2) and HIPS-CIS thin film (γ ˜ 9) devices, and also about four-fold higher than LPS-CIS nanorod devices (γ ˜ 490). Enhanced photoresponsivity is attributed to the porous microstructure and improved conformality of HIPS-CIS film around the In2S3 nanorods confirmed by SEM and EDS measurements. Due to randomization of the sputtered flux at higher working gas pressures, HIPS can provide a more conformal while at the same time a voidy low-density film around nanostructured surfaces. Reduced interelectrode distance and improved p-n junction interface due to the more uniform conformality of HIPS-CIS result in a higher photocurrent in our HIPS-GLAD devices. In addition, the voids in HIPS-CIS film as a result of its porous nature can behave as highly resistive spots that lower the dark current. Therefore, we have demonstrated that by utilizing a simple and low-temperature HIPS-GLAD method, high-photocurrent and low-dark-current photodetectors can be achieved by controlling the conformality and microstructure of a shell layer around nanorod arrays. HIPS shell coating method can be extended to almost any type of nanostructured substrate.

  14. Synthesis and Growth Mechanism of Multimetallic Core-Shell and Hollow-Like Nanoparticles

    Science.gov (United States)

    Londono-Calderon, Alejandra

    A thorough control of nanoscale systems is crucial for developing and improving their activity in a variety of application fields. These range from nanocatalysis, plasmonics, nanosensors, nanomedicine, communications, and others. Controlling and understanding the growth and spatial distribution of multi metallic systems allow us to explore the correlation between the characteristics of the nanoparticle (composition, surface chemistry, crystallinity, etc.) and their properties (mechanical, optical, structural, etc.). In this dissertation bimetallic and multi-metallic nanoparticles were obtained by a seed mediated method and galvanic replacement. Combinations of the type core shell of Au Ag, Au Pd and Au Pd-Au Au multi-metallic systems were studied. A galvanic replacement method was used to obtain hollow-like Au/Pt nanoboxes and Au AgM (M = Au, Pd or Pt) yolk-shell structures with voids in the middle shell. Characterization regarding composition, morphology, optical properties and atomic structures was performed. The mechanical properties of Au Pd nanocubes were studied in situ by the use of a TEM-AFM nanomechanical holder. The nanoparticles strengthening mechanism relies on the Au core resistance to the motion of partial dislocations. The catalytic efficiency of core-shell and nanorattles structures were tested with a model reaction for the decomposition of 4-ntp to 4-amp. Yolk-shell systems exhibit an enhancement in the catalytic decomposition rate in comparison with solid and bimetallic system. Finally, the development of an Electrospray assisted Langmuir Blodgett technique was successfully employed for the deposition of nanoparticles monolayer on a substrate. High particle density and coverage of the substrate makes this a promising technique to finely tune nanoparticles self-assembly.

  15. Gold nanorod@iron oxide core-shell heterostructures: synthesis, characterization, and photocatalytic performance.

    Science.gov (United States)

    Li, Yue; Zhao, Junwei; You, Wenlong; Cheng, Danhong; Ni, Weihai

    2017-03-17

    Iron oxides are directly coated on the surface of cetyl-trimethylammonium bromide (CTAB)-capped gold nanorods (AuNRs) in aqueous solutions at room temperature, which results in AuNR@Fe 2 O 3 , AuNR@Fe 3 O 4 , and AuNR@Fe 2 O 3 @Fe 3 O 4 core-shell heterostructures. The iron oxide shells are uniform, smooth, with characteristic porous structure, and their thickness can be readily tuned. The shell formation is highly dependent on the reaction parameters including pH and CTAB concentration. The Fe 2 O 3 shell is amorphous and exhibits nearly zero remanence and coercivity, while the Fe 3 O 4 shell is ferromagnetic with a low saturation magnetization of about 0.5 emu g -1 due to its low crystallinity and the porous structure. At elevated temperatures achieved by plasmonic heating of the Au core, the Fe 2 O 3 shell transforms from amorphous to γ-Fe 2 O 3 and α-Fe 2 O 3 phases, while the Fe 3 O 4 phase disappears because of the oxidation of Fe 2+ . A 1.4-fold increase of photocatalytic performance is observed due to the plasmonic resonance provided by the Au core. The photocatalytic efficiency of Fe 3 O 4 is about 1.7-fold higher than Fe 2 O 3 as more surface defects are present on the Fe 3 O 4 shell, promoting the adsorption and activation of reagents on the surface during the catalytic reactions. This approach can be readily extended to other nanostructures including Au spherical nanoparticles and nanostars. These highly uniform and multifunctional core-shell heterostructures can be of great potential in a variety of energy, magnetic, and environment applications.

  16. Preparation and application of core-shell Fe3O4/polythiophene nanoparticles

    Science.gov (United States)

    Liu, Hanbin; Zhuang, Jia; Yang, Jie

    2011-12-01

    The Fe3O4/polythiophene nanoparticles, possessing core-shell structure, were prepared by two-step method. In the first step, the Fe3O4 particles were synthesized via co-precipitation of FeCl3 and FeSO4, using the NH3·H2O and N2H4·H2O as precipitant system. In the second step, the thiophene adsorbed and polymerized on the surface of the Fe3O4 in the solvent of chloroform. Raman, FTIR, EDS, XRD, TEM, Zeta potential measurement and TG-SDTA were employed to characterize the composition and structure of the products. The results showed that the Fe3O4/polythiophene nanoparticles were successfully synthesized with good dispersion and stable core-shell structure, provided with average particle size of approximately 20 nm, in which the diameter of Fe3O4 core was approximately 14 nm and the thickness of polythiophene shell was approximately 3-4 nm. Then, the nanoparticles were added into alkyd varnish to prepare a composite coating. The neutral salt spray test, paraffin control test and mechanical test were carried out to identify the properties of the composite coating. It was found that the composite coating had good performances of anticorrosion and paraffin controlling when the mass fraction of the nanoparticles was 0.8-1 wt% in alkyd varnish. As a multifunctional material, the Fe3O4/polythiophene nanoparticles can be used in the internal coating of pipeline and have great potential application in crude oil pipeline transportation.

  17. Germanium-silicon alloy and core-shell nanocrystals by gas phase synthesis.

    Science.gov (United States)

    Mehringer, Christian; Kloner, Christian; Butz, Benjamin; Winter, Benjamin; Spiecker, Erdmann; Peukert, Wolfgang

    2015-03-12

    In this work we present a novel route to synthesize well defined germanium-silicon alloy (GexSi1-x) and core-shell nanocrystals (NCs) employing monosilane (SiH4) and monogermane (GeH4) as precursors in a continuously operated two-stage hot-wall aerosol reactor setup. The first hot-wall reactor stage (HWR I) is used to produce silicon (Si) seed particles from SiH4 pyrolysis in Argon (Ar). The resulting seeding aerosol is fed into the second reactor stage (HWR II) and a mixture of SiH4 and GeH4 is added. The ratio of the precursors in the feed, their partial pressures, the synthesis temperature in HWR II and the overall pressure are varied depending on the desired morphology and composition. Alloy particle production is achieved in the heterogeneous surface reaction regime, meaning that germanium (Ge) and Si are deposited on the seed surface simultaneously. The NCs can be synthesized with any desired composition, whilst maintaining a mean diameter around 30 nm with a geometric standard deviation (GSD) around 1.25. The absorption behavior and the related fundamental optical band gap energy in dependence on the alloy composition are exemplarily presented. They prove the possibility to tailor NC properties for electronical and opto-electronical applications. In the homogeneous gas phase reaction regime facetted Ge-Si core-shell structures are accessible. The Ge deposition on the seeds precedes the Si deposition due to different gas phase reaction kinetics of the precursors. The Si layer grows epitaxially on the Ge core and is around 5 nm thick.

  18. Template-assisted nano-patterning of magnetic core-shell particles in gradient fields.

    Science.gov (United States)

    Xue, Xiaozheng; Furlani, Edward P

    2014-07-14

    A method is proposed for controlling the assembly of colloidal magnetic core-shell nanoparticles into patterned monolayer structures with nanoscale feature resolution. The method is based on magnetic field-directed self-assembly that is enhanced using soft-magnetic template elements. The elements are embedded in a nonmagnetic substrate and magnetized using a uniform bias field. A key feature of this approach is the combined use of a uniform field with induced gradient-fields produced by the template elements. This enables the customization of a force field with localized regions of attractive and repulsive magnetic forces that provide extraordinary control of particle motion during assembly. The method is demonstrated using a computational model that simulates the assembly process taking into account magnetic and hydrodynamic forces including interparticle interactions, Brownian diffusion, van der Waals force and effects of surfactants. The analysis shows that extended geometric patterns of particles can be assembled with nanoscale resolution, beyond that of the template elements, within milliseconds. This is achieved by tailoring key parameters including the template geometry to produce a force field that focuses the particles into prescribed patterns; the thickness of the dielectric particle shell to control the magnetic dipole-dipole force upon contact and the particle volume fraction to suppress undesired aggregation during assembly. The proposed method broadly applies to arbitrary template geometries and multi-layered core-shell particles with at least one magnetic component. It can enable the self-assembly of complex patterns of nanoparticles and open up opportunities for the scalable fabrication of multifunctional nanostructured materials for a broad range of applications.

  19. Formation and some properties of Fe core-shell powders with experimental parameters of the chemical vapor condensation process

    International Nuclear Information System (INIS)

    Kim, J.C.; Kim, S.J.; Kim, Y.D.; Kim, J.S.; Choi, C.J.

    2009-01-01

    Core-shell powders, recently, have aroused interest because of their potential applications in various areas such as electronics, optics, catalysis, ferrofluids, and magnetic data storage. Their unique properties and superior performances are determined by their powder size, shell thickness and surface structure, phase and powder interaction. In this study, carbon-coated Fe core-shell powders were prepared by chemical vapor condensation (CVC) process using Fe metal-organic (Fe(CO) 5 ) precursor and carbon containing carrier gases such as carbon monoxide and methane. Effects of experimental parameters on the properties of the as-produced core-shell powders were studied by X-ray diffractometer, Brunauer-Emitter-Teller analyzer, high resolution transmission electron microscope and X-ray photoelectron spectrometer. The microstructures and phases of the synthesized core-shell powders varied with the decomposition temperature of the precursors and the flow rate of the carrier gases. CVC Fe powders showed intricate long stand-like structure because of intrinsic magnetic properties of Fe.

  20. Comparison of antibacterial activities of Ag@TiO2 and Ag@SiO2 core-shell nanoparticles

    Science.gov (United States)

    Dhanalekshmi, K. I.; Meena, K. S.

    2014-07-01

    Core-shell type Ag@TiO2 nanoparticles were prepared by one pot simultaneous reduction of AgNO3 and hydrolysis of Ti (IV) isopropoxide and Ag@SiO2 core-shell nanoparticles were prepared by Stober's method. They were characterized by absorption, XRD, and HR-TEM techniques. XRD patterns show the presence of anatase form of TiO2 and amorphous form of SiO2 and the noble metal (Ag). High resolution transmission electron microscopy measurements revealed that their size is below 50 nm. The antibacterial properties of Ag@TiO2 and Ag@SiO2 core-shell nanoparticles against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were examined by the agar diffusion method. As a result E. coli and S. aureus were shown to be substantially inhibited by Ag@TiO2 and Ag@SiO2 core-shell nanoparticles. These results demonstrated that TiO2 and SiO2 supported on the surface of Ag NPs without aggregation was proved to have enhanced antibacterial activity.

  1. High performance of SDC and GDC core shell type composite electrolytes using methane as a fuel for low temperature SOFC

    Energy Technology Data Exchange (ETDEWEB)

    Irshad, Muneeb; Siraj, Khurram, E-mail: razahussaini786@gmail.com, E-mail: khurram.uet@gmail.com; Javed, Fayyaz; Ahsan, Muhammad; Rafique, Muhammad Shahid [Department of Physics, University of Engineering and Technology, Lahore (Pakistan); Raza, Rizwan, E-mail: razahussaini786@gmail.com, E-mail: khurram.uet@gmail.com [Department of Physics, COMSATS Institute of Information Technology, Lahore (Pakistan); Shakir, Imran [Deanship of scientific research, College of Engineering, PO Box 800, King Saud University, Riyadh 11421 (Saudi Arabia)

    2016-02-15

    Nanocomposites Samarium doped Ceria (SDC), Gadolinium doped Ceria (GDC), core shell SDC amorphous Na{sub 2}CO{sub 3} (SDCC) and GDC amorphous Na{sub 2}CO{sub 3} (GDCC) were synthesized using co-precipitation method and then compared to obtain better solid oxide electrolytes materials for low temperature Solid Oxide Fuel Cell (SOFCs). The comparison is done in terms of structure, crystallanity, thermal stability, conductivity and cell performance. In present work, XRD analysis confirmed proper doping of Sm and Gd in both single phase (SDC, GDC) and dual phase core shell (SDCC, GDCC) electrolyte materials. EDX analysis validated the presence of Sm and Gd in both single and dual phase electrolyte materials; also confirming the presence of amorphous Na{sub 2}CO{sub 3} in SDCC and GDCC. From TGA analysis a steep weight loss is observed in case of SDCC and GDCC when temperature rises above 725 °C while SDC and GDC do not show any loss. The ionic conductivity and cell performance of single phase SDC and GDC nanocomposite were compared with core shell GDC/amorphous Na{sub 2}CO{sub 3} and SDC/ amorphous Na{sub 2}CO{sub 3} nanocomposites using methane fuel. It is observed that dual phase core shell electrolytes materials (SDCC, GDCC) show better performance in low temperature range than their corresponding single phase electrolyte materials (SDC, GDC) with methane fuel.

  2. High performance of SDC and GDC core shell type composite electrolytes using methane as a fuel for low temperature SOFC

    Science.gov (United States)

    Irshad, Muneeb; Siraj, Khurram; Raza, Rizwan; Javed, Fayyaz; Ahsan, Muhammad; Shakir, Imran; Rafique, Muhammad Shahid

    2016-02-01

    Nanocomposites Samarium doped Ceria (SDC), Gadolinium doped Ceria (GDC), core shell SDC amorphous Na2CO3 (SDCC) and GDC amorphous Na2CO3 (GDCC) were synthesized using co-precipitation method and then compared to obtain better solid oxide electrolytes materials for low temperature Solid Oxide Fuel Cell (SOFCs). The comparison is done in terms of structure, crystallanity, thermal stability, conductivity and cell performance. In present work, XRD analysis confirmed proper doping of Sm and Gd in both single phase (SDC, GDC) and dual phase core shell (SDCC, GDCC) electrolyte materials. EDX analysis validated the presence of Sm and Gd in both single and dual phase electrolyte materials; also confirming the presence of amorphous Na2CO3 in SDCC and GDCC. From TGA analysis a steep weight loss is observed in case of SDCC and GDCC when temperature rises above 725 °C while SDC and GDC do not show any loss. The ionic conductivity and cell performance of single phase SDC and GDC nanocomposite were compared with core shell GDC/amorphous Na2CO3 and SDC/ amorphous Na2CO3 nanocomposites using methane fuel. It is observed that dual phase core shell electrolytes materials (SDCC, GDCC) show better performance in low temperature range than their corresponding single phase electrolyte materials (SDC, GDC) with methane fuel.

  3. High performance of SDC and GDC core shell type composite electrolytes using methane as a fuel for low temperature SOFC

    Directory of Open Access Journals (Sweden)

    Muneeb Irshad

    2016-02-01

    Full Text Available Nanocomposites Samarium doped Ceria (SDC, Gadolinium doped Ceria (GDC, core shell SDC amorphous Na2CO3 (SDCC and GDC amorphous Na2CO3 (GDCC were synthesized using co-precipitation method and then compared to obtain better solid oxide electrolytes materials for low temperature Solid Oxide Fuel Cell (SOFCs. The comparison is done in terms of structure, crystallanity, thermal stability, conductivity and cell performance. In present work, XRD analysis confirmed proper doping of Sm and Gd in both single phase (SDC, GDC and dual phase core shell (SDCC, GDCC electrolyte materials. EDX analysis validated the presence of Sm and Gd in both single and dual phase electrolyte materials; also confirming the presence of amorphous Na2CO3 in SDCC and GDCC. From TGA analysis a steep weight loss is observed in case of SDCC and GDCC when temperature rises above 725 °C while SDC and GDC do not show any loss. The ionic conductivity and cell performance of single phase SDC and GDC nanocomposite were compared with core shell GDC/amorphous Na2CO3 and SDC/ amorphous Na2CO3 nanocomposites using methane fuel. It is observed that dual phase core shell electrolytes materials (SDCC, GDCC show better performance in low temperature range than their corresponding single phase electrolyte materials (SDC, GDC with methane fuel.

  4. Synthesis and optical characterization of single phased ZnS:Mn²⁺/CdS core-shell nanoparticles.

    Science.gov (United States)

    Murugadoss, G; Ramasamy, V

    2012-07-01

    Uncoated ZnS, ZnS:Mn(2+), CdS and different thickness of CdS coated ZnS:Mn(2+) core-shell nanoparticles were successfully synthesized by a simple chemical method in an air atmosphere. X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques were used to characterize the uncoated and the novel ZnS:Mn(2+)/CdS core-shell nanoparticles. The results show that the size of the ZnS:Mn(2+)/CdS core-shell nanoparticles is less than the bare ZnS:Mn(2+). The PL study of ZnS:Mn(2+)/CdS core-shell nanoparticles shows an enhanced intensity than ZnS:Mn(2+). The coating of CdS layer over ZnS:Mn(2+) tuned the PL emission in the visible region. Addition of cadmium acetate (Cd 4 and 5M) in ZnS:Mn(2+) shows a distinct PL peak centered at 542 nm. The presence of Mn(2+) ions in ZnS lattice and the growth of the CdS on ZnS:Mn(2+) nanoparticles were confirmed by the ESR spectra. Copyright © 2012 Elsevier B.V. All rights reserved.

  5. Pt@Ag and Pd@Ag core/shell nanoparticles for catalytic degradation of Congo red in aqueous solution.

    Science.gov (United States)

    Salem, Mohamed A; Bakr, Eman A; El-Attar, Heba G

    2018-01-05

    Platinum/silver (Pt@Ag) and palladium/silver (Pd@Ag) core/shell NPs have been synthesized in two steps reaction using the citrate method. The progress of nanoparticle formation was followed by the UV/Vis spectroscopy. Transmission electron microscopy revealed spherical shaped core/shell nanoparticles with average particle diameter 32.17nm for Pt@Ag and 8.8nm for Pd@Ag. The core/shell NPs were further characterized by FT-IR and XRD. Reductive degradation of the Congo red dye was chosen to demonstrate the excellent catalytic activity of these core/shell nanostructures. The nanocatalysts act as electron mediators for the transfer of electrons from the reducing agent (NaBH 4 ) to the dye molecules. Effect of reaction parameters such as nanocatalyst dose, dye and NaBH 4 concentrations on the dye degradation was investigated. A comparison between the catalytic activities of both nanocatalysts was made to realize which of them the best in catalytic performance. Pd@Ag was the higher in catalytic activity over Pt@Ag. Such greater activity is originated from the smaller particle size and larger surface area. Pd@Ag nanocatalyst was catalytically stable through four subsequent reaction runs under the utilized reaction conditions. These findings can thus be considered as possible economical alternative for environmental safety against water pollution by dyes. Copyright © 2017. Published by Elsevier B.V.

  6. Monte Carlo simulation of dynamic phase transitions and frequency dispersions of hysteresis curves in core/shell ferrimagnetic cubic nanoparticle

    Energy Technology Data Exchange (ETDEWEB)

    Vatansever, Erol, E-mail: erol.vatansever@deu.edu.tr

    2017-05-10

    By means of Monte Carlo simulation method with Metropolis algorithm, we elucidate the thermal and magnetic phase transition behaviors of a ferrimagnetic core/shell nanocubic system driven by a time dependent magnetic field. The particle core is composed of ferromagnetic spins, and it is surrounded by an antiferromagnetic shell. At the interface of the core/shell particle, we use antiferromagnetic spin–spin coupling. We simulate the nanoparticle using classical Heisenberg spins. After a detailed analysis, our Monte Carlo simulation results suggest that present system exhibits unusual and interesting magnetic behaviors. For example, at the relatively lower temperature regions, an increment in the amplitude of the external field destroys the antiferromagnetism in the shell part of the nanoparticle, leading to a ground state with ferromagnetic character. Moreover, particular attention has been dedicated to the hysteresis behaviors of the system. For the first time, we show that frequency dispersions can be categorized into three groups for a fixed temperature for finite core/shell systems, as in the case of the conventional bulk systems under the influence of an oscillating magnetic field. - Highlights: • Cubic core/shell nanoparticle is considered. • Monte-Carlo simulation with Metropolis algorithm is used. • The particle is subjected to time dependent oscillating magnetic field. • External field destroys the antiferromagnetism in the shell part of particle. • Frequency dispersions of hysteresis loop areas can be categorized into three groups.

  7. In situ oxidation synthesis of Ag/AgCl core-shell nanowires and their photocatalytic properties.

    Science.gov (United States)

    Bi, Yingpu; Ye, Jinhua

    2009-11-21

    Ag/AgCl core-shell nanowires with uniform structure have been synthesized in large quantities via an in situ oxidation reaction between pentagonal Ag nanowires and FeCl(3) solution at room temperature, which exhibit excellent photocatalytic performance for decomposition of methylene orange under visible-light irradiation.

  8. Three-Dimensional Self-Assembly of Core/Shell-Like Nanostructures for High-Performance Nanocomposite Permanent Magnets.

    Science.gov (United States)

    Li, Hailing; Li, Xiaohong; Guo, Defeng; Lou, Li; Li, Wei; Zhang, Xiangyi

    2016-09-14

    Core/shell nanostructures are fascinating for many advanced applications including strong permanent magnets, magnetic recording, and biotechnology. They are generally achieved via chemical approaches, but these techniques limit them to nanoparticles. Here, we describe a three-dimensional (3D) self-assembly of core/shell-like nanocomposite magnets, with hard-magnetic Nd2Fe14B core of ∼45 nm and soft-magnetic α-Fe shell of ∼13 nm, through a physical route. The resulting Nd2Fe14B/α-Fe core/shell-like nanostructure allows both large remanent magnetization and high coercivity, leading to a record-high energy product of 25 MGOe which reaches the theoretical limit for isotropic Nd2Fe14B/α-Fe nanocomposite magnets. Our approach is based on a sequential growth of the core and shell nanocrystals in an alloy melt. These results make an important step toward fabricating core/shell-like nanostructure in 3D materials.

  9. Atomic layer deposition synthesis of platinum-tungsten carbide core-shell catalysts for the hydrogen evolution reaction.

    Science.gov (United States)

    Hsu, Irene J; Kimmel, Yannick C; Jiang, Xiaoqiang; Willis, Brian G; Chen, Jingguang G

    2012-01-25

    Pt was deposited onto tungsten carbide powders using atomic layer deposition to produce core-shell catalysts for the hydrogen evolution reaction (HER). The Pt loading on these catalysts was reduced nearly ten-fold compared to a bulk Pt catalyst while equivalent HER activities were observed. This journal is © The Royal Society of Chemistry 2012

  10. Development of silane grafted ZnO core shell nanoparticles loaded diglycidyl epoxy nanocomposites film for antimicrobial applications.

    Science.gov (United States)

    Suresh, S; Saravanan, P; Jayamoorthy, K; Ananda Kumar, S; Karthikeyan, S

    2016-07-01

    In this article a series of epoxy nanocomposites film were developed using amine functionalized (ZnO-APTES) core shell nanoparticles as the dispersed phase and a commercially available epoxy resin as the matrix phase. The functional group of the samples was characterized using FT-IR spectra. The most prominent peaks of epoxy resin were found in bare epoxy and in all the functionalized ZnO dispersed epoxy nanocomposites (ZnO-APTES-DGEBA). The XRD analysis of all the samples exhibits considerable shift in 2θ, intensity and d-spacing values but the best and optimum concentration is found to be 3% ZnO-APTES core shell nanoparticles loaded epoxy nanocomposites supported by FT-IR results. From TGA measurements, 100wt% residue is obtained in bare ZnO nanoparticles whereas in ZnO core shell nanoparticles grafted DGEBA residue percentages are 37, 41, 45, 46 and 52% for 0, 1, 3, 5 and 7% ZnO-APTES-DGEBA respectively, which is confirmed with ICP-OES analysis. From antimicrobial activity test, it was notable that antimicrobial activity of 7% ZnO-APTES core shell nanoparticles loaded epoxy nanocomposite film has best inhibition zone effect against all pathogens under study. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Preparation, and Luminescence Properties of SiO2@Sm(MABA-Siphen Core-Shell Structure Nanometer Composite

    Directory of Open Access Journals (Sweden)

    Feng Li-Na

    2018-01-01

    Full Text Available A novel ternary samarium complex was prepared using HOOCC6H4N(CONH(CH23Si- (OCH2CH332 (MABA-Si as first ligand, and phen as second ligand. The corresponding SiO2@Sm(MABA-Siphen core-shell structure nanometer composite was synthesized as well, and the silica spheres was the core, and the ternary samarium complex was the shell layer. The ternary samarium complex has been characterized by element analysis, molar conductivity and IR spectra. The results show that the chemical formula of the complex is Sm(MABA-Si(phen2(ClO43·2H2O. The fluorescent spectra illustrat that the luminescence properties of the samarium complex are superior. The core-shell structure of SiO2@Sm(MABA-Siphen nanometer composite is characterized by SEM, TEM and IR spectra. The SiO2@Sm(MABA-Siphen core-shell structure composites exhibit stronger emission intensity than the ternary samarium complex. The fluorescence lifetime of the complex and core-shell structure composite is measured as well.

  12. One pot synthesis of Pb S/Cu{sub 2}S core-shell nanoparticles and their optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Serrano, T.; Gomez, I., E-mail: maria.gomez@uanl.edu.mx [Universidad Autonoma de Nuevo Leon, Facultad de Ciencias Quimicas, Laboratorio de Materiales, Pedro de Alba, Ciudad Universitaria, San Nicolas de los Garza, Nuevo Leon (Mexico)

    2014-07-01

    The synthesis of Pb S/Cu{sub 2}S core-shell nanoparticles with emission on the visible range and with improved luminescence properties was carried out by the colloidal solution-phase growth method by using simple stabilizers such as trisodium citrate and 3-mercaptopropionic acid. The core shell arrangement for particles with different crystalline structure was achieved, in addition this is the first report related to the synthesis Pb S/C{sub 2}S core-shell system. The data obtained from absorption spectra, Pl spectra, and HRTEM image provided direct proof of the formation of Pb S core with size around 11 nm and Cu{sub 2}S shell of 5 nm thickness. According to the UV-vis absorption and Pl spectrum the optical characteristics observed in the synthesized material correspond to a Pb S/Cu{sub 2}S system that has a higher confinement effect than the pure Pb S nanoparticles. The Q Y was improved in 15% from Pb S/C{sub 2}S nanoparticles. The estimated band (Homo-Lumo) alignment determined by C V measurements corresponds to a type-I core shell arrangement. The synthesized material was studied with different techniques. The size and dispersion of the particles were determined by ultraviolet-visible (UV-Vis), photoluminescence and quantum yield, Dynamic Light Scattering method and X-ray diffraction with copper radiation (λ = 0.15418 nm). (Author)

  13. Spinel Ferrite Core-Shell Nanostructures by a Versatile Solvothermal Seed-Mediated Growth Approach and Study of Their Nanointerfaces

    Czech Academy of Sciences Publication Activity Database

    Angotzi, M. S.; Musinu, A.; Mameli, V.; Ardu, A.; Cara, C.; Nižňanský, Daniel; Xin, H. L.; Cannas, C.

    2017-01-01

    Roč. 11, č. 8 (2017), s. 7889-7900 ISSN 1936-0851 Institutional support: RVO:61388980 Keywords : ferrite * core-shell nanoparticles * cofe2o4/nife2o4 * EELS * EDX Subject RIV: CA - Inorganic Chemistry OBOR OECD: Inorganic and nuclear chemistry Impact factor: 13.942, year: 2016

  14. Core-shell rhodium sulfide catalyst for hydrogen evolution reaction / hydrogen oxidation reaction in hydrogen-bromine reversible fuel cell

    Science.gov (United States)

    Li, Yuanchao; Nguyen, Trung Van

    2018-04-01

    Synthesis and characterization of high electrochemical active surface area (ECSA) core-shell RhxSy catalysts for hydrogen evolution oxidation (HER)/hydrogen oxidation reaction (HOR) in H2-Br2 fuel cell are discussed. Catalysts with RhxSy as shell and different percentages (5%, 10%, and 20%) of platinum on carbon as core materials are synthesized. Cyclic voltammetry is used to evaluate the Pt-equivalent mass specific ECSA and durability of these catalysts. Transmission electron microscopy (TEM), X-ray Photoelectron spectroscopy (XPS) and Energy-dispersive X-ray spectroscopy (EDX) techniques are utilized to characterize the bulk and surface compositions and to confirm the core-shell structure of the catalysts, respectively. Cycling test and polarization curve measurements in the H2-Br2 fuel cell are used to assess the catalyst stability and performance in a fuel cell. The results show that the catalysts with core-shell structure have higher mass specific ECSA (50 m2 gm-Rh-1) compared to a commercial catalyst (RhxSy/C catalyst from BASF, 6.9 m2 gm-Rh-1). It also shows better HOR/HER performance in the fuel cell. Compared to the platinum catalyst, the core-shell catalysts show more stable performance in the fuel cell cycling test.

  15. Investigation of plasmonic gold-silica core-shell nanoparticle stability in dye-sensitized solar cell applications.

    Science.gov (United States)

    Törngren, Björn; Akitsu, Kenta; Ylinen, Anne; Sandén, Simon; Jiang, Hua; Ruokolainen, Janne; Komatsu, Makoto; Hamamura, Tomofumi; Nakazaki, Jotaro; Kubo, Takaya; Segawa, Hiroshi; Österbacka, Ronald; Smått, Jan-Henrik

    2014-08-01

    Plasmonic core-shell Au@SiO2 nanoparticles have previously been shown to enhance the performance of dye-sensitized solar cells (DSSCs). A thin silica coating can provide a better stability during thermal processing and chemical stability to survive the corrosive electrolyte used in DSSCs. However, the thickness and completeness of the silica shell has proven crucial for the performance of the plasmonic particles and is largely controlled by the linking chemistry between the gold core and silica shell. We have evaluated four different silica coating procedures of ∼15 nm gold nanoparticles for usage in DSSCs. The chemical stability of these core-shell nanoparticles was assessed by dispersing the particles in iodide/triiodide electrolyte solution and the thermal stability by heating the particles up to 500°C. In order to maintain stable gold cores a complete silica coating was required, which was best obtained by using a mercaptosilane as a linker. In situ TEM characterization indicated that the heating process only had minor effects on the core-shell particles. The final step was to evaluate how the stable Au@SiO2 nanoparticles were influencing a real DSSC device when mixed into the TiO2 photoanode. The plasmon-incorporated DSSCs showed a ∼10% increase in efficiency compared to devices without core-shell nanoparticles. Copyright © 2013 Elsevier Inc. All rights reserved.

  16. Core/shell CdS/ZnS nanoparticles: Molecular modelling and characterization by photocatalytic decomposition of Methylene Blue

    Czech Academy of Sciences Publication Activity Database

    Praus, P.; Svoboda, L.; Tokarský, J.; Hospodková, Alice; Klemm, V.

    2014-01-01

    Roč. 292, Feb (2014), s. 813-822 ISSN 0169-4332 Institutional support: RVO:68378271 Keywords : core/shell nanoparticles * CdS/ZnS * molecular modelling * electron tunnelling * photocatalysis Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.711, year: 2014

  17. Morphological control of Ni/NiO core/shell nanoparticles and production of hollow NiO nanostructures

    International Nuclear Information System (INIS)

    Chopra, Nitin; Claypoole, Leslie; Bachas, Leonidas G.

    2010-01-01

    Chemical synthesis coupled with a microwave irradiation process allowed for the control of size (6-40 nm), shape, and shell thickness of Ni/NiO core/shell nanoparticles. In this unique synthetic route, the size of Ni nanoparticles (NiNPs) was strongly influenced by the nickel salt-to-stabilizer ratio and the amount of the stabilizer. Interestingly, it was observed that the shape of the nanoparticles was altered by varying the reaction time, where longer reaction times resulted in annealing effects and rupture of the stabilizer micelle leading to distinct shapes of Ni/NiO core/shell nanostructures. Product cooling rate was another important parameter identified in this study that not only affected the shape, but also the crystal structure of the core/shell nanoparticles. In addition, a simple and cost-effective method of microwave irradiation of NiNPs led to the formation of distinctly shaped hollow NiO nanoparticles. These high surface area core/shell nanoparticles with well-controlled morphologies are important and can lead to significant advancement in the design of improved fuel cells, electrochromic display devices, and catalysis systems.

  18. Separative analyses of a chromatographic column packed with a core-shell adsorbent for lithium isotope separation

    International Nuclear Information System (INIS)

    Sugiyama, T.; Sugura, K.; Enokida, Y.; Yamamoto, I.

    2015-01-01

    Lithium-6 is used as a blanket material for sufficient tritium production in DT fueled fusion reactors. A core-shell type adsorbent was proposed for lithium isotope separation by chromatography. The mass transfer model in a chromatographic column consisted of 4 steps, such as convection and dispersion in the column, transfer through liquid films, intra-particle diffusion and and adsorption or desorption at the local adsorption sites. A model was developed and concentration profiles and time variation in the column were numerically simulated. It became clear that core-shell type adsorbents with thin porous shell were saturated rapidly relatively to fully porous one and established a sharp edge of adsorption band. This is very important feature because lithium isotope separation requires long-distance development of adsorption band. The values of HETP (Height Equivalent of a Theoretical Plate) for core-shell adsorbent packed column were estimated by statistical moments of the step response curve. The value of HETP decreased with the thickness of the porous shell. A core-shell type adsorbent is, then, useful for lithium isotope separation. (authors)

  19. Phase-change core/shell structured nanofibers based on eicosane/poly(vinylidene fluoride) for thermal storage applications

    Energy Technology Data Exchange (ETDEWEB)

    Do, Cong Van [Vietnam Academy of Science and Technology, Hanoi (Viet Nam); Nguyen, Thuy Thu Thi; Park, Jun Seo [Hankyong National University, Anseong (Korea, Republic of)

    2013-07-15

    We fabricated eicosane/poly(vinylidene fluoride) (PVDF) core/shell nanofibers by melt coaxial electrospinning as potential heat-storage applications. Eicosane, a hydrocarbon with melting point near the human body temperature and high latent heat, was chosen as the core material. Melted eicosane and PVDF solutions were coaxially electrospun using a double spinneret, in which melted eicosane was fed at 0.090-0.210 mL/h while the feeding rate of PVDF solution was maintained constant at 1.500 mL/h. The applied voltage and working distance were maintained constant at 12 kV and 17 cm, respectively. Good core/shell structure of nanofibers was observed at core feed rates of 0.090-0.180mL/h by transmission electron microscopy. Differential scanning calorimetry and thermogravimetric analysis values indicated good thermal stability and high energy-storage capacity of the obtained nanofibers. The highest amount of eicosane encapsulated in the electrospun core/shell nanofibers reached 32.5 wt% at core feed rate 0.180 mL/h and had a latent heat of 77 J/g at melting point 39.2 .deg. C. These shape-stabilized core/shell composite nanofibers showed good thermoregulating properties and had sufficiently high tensile strength for potential energy-storage applications, especially in smart textiles.

  20. Core-shell conjugated microporous polymers: a new strategy for exploring color-tunable and -controllable light emissions.

    Science.gov (United States)

    Xu, Yanhong; Nagai, Atsushi; Jiang, Donglin

    2013-02-25

    A core-shell strategy is demonstrated for designing a conjugated microporous polymer that allows the tuning of light emission over a wide wavelength range in a controlled manner. The polymers not only emit efficiently with an eight-fold enhanced luminescence but also sustain light emissions, irrespective of solvent and state.

  1. Preparation and characterization of water-soluble ZnSe:Cu/ZnS core/shell quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lei; Cao, Lixin, E-mail: caolixin@ouc.edu.cn; Su, Ge; Liu, Wei; Xia, Chenghui; Zhou, Huajian

    2013-09-01

    The synthesis and luminescent properties of water-soluble ZnSe:Cu/ZnS core/shell quantum dots (QDs) with different shell thickness are reported in this paper. X-ray powder diffraction (XRD) studies present that the ZnSe:Cu/ZnS core/shell QDs with different shell thickness have a cubic zinc-blende structure. The tests of transmission electron microscope (TEM) pictures exhibit that the QDs obtained are spherical-shaped particles and the average grain size increased from 2.7 to 3.8 nm with the growth of ZnS shell. The emission peak position of QDs has a small redshift from 461 to 475 nm with the growth of ZnS shell within the blue spectral window. The photoluminescence (PL) emission intensity and stability of the ZnSe:Cu core d-dots are both enhanced by coating ZnS shell on the surface of core d-dots. The largest PL intensity of the core/shell QDs is almost 3 times larger than that of Cu doped ZnSe quantum dots (ZnSe:Cu d-dots). The redshift of core/shell QDs compared with the core QDs are observed in both the absorption and the photoluminescence excitation spectra.

  2. Synthesis, Optical Properties, and Photocatalytic Activity of One-Dimensional CdS@ZnS Core-Shell Nanocomposites

    Directory of Open Access Journals (Sweden)

    Wang Le

    2009-01-01

    Full Text Available Abstract One-dimensional (1D CdS@ZnS core-shell nanocomposites were successfully synthesized via a two-step solvothermal method. Preformed CdS nanowires with a diameter of ca. 45 nm and a length up to several tens of micrometers were coated with a layer of ZnS shell by the reaction of zinc acetate and thiourea at 180 °C for 10 h. It was found that uniform ZnS shell was composed of ZnS nanoparticles with a diameter of ca. 4 nm, which anchored on the nanowires without any surface pretreatment. The 1D CdS@ZnS core-shell nanocomposites were confirmed by XRD, SEM, TEM, HR-TEM, ED, and EDS techniques. The optical properties and photocatalytic activities of the 1D CdS@ZnS core-shell nanocomposites towards methylene blue (MB and 4-chlorophenol (4CP under visible light (λ > 420 nm were separately investigated. The results show that the ZnS shell can effectively passivate the surface electronic states of the CdS cores, which accounts for the enhanced photocatalytic activities of the 1D CdS@ZnS core-shell nanocomposites compared to that of the uncoated CdS nanowires.

  3. Magnetization measurements and XMCD studies on ion irradiated iron oxide and core-shell iron/iron-oxide nanomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Maninder; Qiang, You; Jiang, Weilin; Pearce, Carolyn; McCloy, John S.

    2014-12-02

    Magnetite (Fe3O4) and core-shell iron/iron-oxide (Fe/Fe3O4) nanomaterials prepared by a cluster deposition system were irradiated with 5.5 MeV Si2+ ions and the structures determined by x-ray diffraction as consisting of 100% magnetite and 36/64 wt% Fe/FeO, respectively. However, x-ray magnetic circular dichroism (XMCD) indicates similar surfaces in the two samples, slightly oxidized and so having more Fe3+ than the expected magnetite structure, with XMCD intensity much lower for the irradiated core-shell samples indicating weaker magnetism. X-ray absorption spectroscopy (XAS) data lack the signature for FeO, but the irradiated core-shell system consists of Fe-cores with ~13 nm of separating oxide crystallite, so it is likely that FeO exists deeper than the probe depth of the XAS (~5 nm). Exchange bias (Hex) for both samples becomes increasingly negative as temperature is lowered, but the irradiated Fe3O4 sample shows greater sensitivity of cooling field on Hex. Loop asymmetries and Hex sensitivities of the irradiated Fe3O4 sample are due to interfaces and interactions between grains which were not present in samples before irradiation as well as surface oxidation. Asymmetries in the hysteresis curves of the irradiated core/shell sample are related to the reversal mechanism of the antiferromagnetic FeO and possibly some near surface oxidation.

  4. Methanol oxidation reaction on core-shell structured Ruthenium-Palladium nanoparticles: Relationship between structure and electrochemical behavior

    Science.gov (United States)

    Kübler, Markus; Jurzinsky, Tilman; Ziegenbalg, Dirk; Cremers, Carsten

    2018-01-01

    In this work the relationship between structural composition and electrochemical characteristics of Palladium(Pd)-Ruthenium(Ru) nanoparticles during alkaline methanol oxidation reaction is investigated. The comparative study of a standard alloyed and a precisely Ru-core-Pd-shell structured catalyst allows for a distinct investigation of the electronic effect and the bifunctional mechanism. Core-shell catalysts benefit from a strong electronic effect and an efficient Pd utilization. It is found that core-shell nanoparticles are highly active towards methanol oxidation reaction for potentials ≥0.6 V, whereas alloyed catalysts show higher current outputs in the lower potential range. However, differential electrochemical mass spectrometry (DEMS) experiments reveal that the methanol oxidation reaction on core-shell structured catalysts proceeds via the incomplete oxidation pathway yielding formaldehyde, formic acid or methyl formate. Contrary, the alloyed catalyst benefits from the Ru atoms at its surface. Those are found to be responsible for high methanol oxidation activity at lower potentials as well as for complete oxidation of CH3OH to CO2 via the bifunctional mechanism. Based on these findings a new Ru-core-Pd-shell-Ru-terrace catalyst was synthesized, which combines the advantages of the core-shell structure and the alloy. This novel catalyst shows high methanol electrooxidation activity as well as excellent selectivity for the complete oxidation pathway.

  5. Coaxial Electrospinning and Characterization of Core-Shell Structured Cellulose Nanocrystal Reinforced PMMA/PAN Composite Fibers

    Science.gov (United States)

    Li, Chao; Li, Qingde; Ni, Xiaohui; Liu, Guoxiang; Cheng, Wanli; Han, Guangping

    2017-01-01

    A modified coaxial electrospinning process was used to prepare composite nanofibrous mats from a poly(methyl methacrylate) (PMMA) solution with the addition of different cellulose nanocrystals (CNCs) as the sheath fluid and polyacrylonitrile (PAN) solution as the core fluid. This study investigated the conductivity of the as-spun solutions that increased significantly with increasing CNCs addition, which favors forming uniform fibers. This study discussed the effect of different CNCs addition on the morphology, thermal behavior, and the multilevel structure of the coaxial electrospun PMMA + CNCs/PAN composite nanofibers. A morphology analysis of the nanofibrous mats clearly demonstrated that the CNCs facilitated the production of the composite nanofibers with a core-shell structure. The diameter of the composite nanofibers decreased and the uniformity increased with increasing CNCs concentrations in the shell fluid. The composite nanofibrous mats had the maximum thermal decomposition temperature that was substantially higher than electrospun pure PMMA, PAN, as well as the core-shell PMMA/PAN nanocomposite. The BET (Brunauer, Emmett and Teller) formula results showed that the specific surface area of the CNCs reinforced core-shell composite significantly increased with increasing CNCs content. The specific surface area of the composite with 20% CNCs loading rose to 9.62 m2/g from 3.76 m2/g for the control. A dense porous structure was formed on the surface of the electrospun core-shell fibers. PMID:28772933

  6. Recent advances in the synthesis of Fe{sub 3}O{sub 4}@AU core/shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Salihov, Sergei V. [National University of Science and Technology MISiS, Leninskiy, Building 9, Moscow, 119049, Russian Federation, (Russian Federation); Ivanenkov, Yan A.; Krechetov, Sergei P.; Veselov, Mark S. [Moscow Institute of Physics and Technology (State University), 9 Institutskiy lane, Dolgoprudny City, Moscow Region, 141700 (Russian Federation); Sviridenkova, Natalia V.; Savchenko, Alexander G. [National University of Science and Technology MISiS, Leninskiy, Building 9, Moscow, 119049, Russian Federation, (Russian Federation); Klyachko, Natalya L. [National University of Science and Technology MISiS, Leninskiy, Building 9, Moscow, 119049, Russian Federation, (Russian Federation); Moscow State University, Chemistry Department, Lenins kie gory, Building 1/3, GSP-1, Moscow, 119991 (Russian Federation); Golovin, Yury I. [Moscow State University, Chemistry Department, Lenins kie gory, Building 1/3, GSP-1, Moscow, 119991 (Russian Federation); Chufarova, Nina V., E-mail: chnv@pharmcluster.ru [Moscow Institute of Physics and Technology (State University), 9 Institutskiy lane, Dolgoprudny City, Moscow Region, 141700 (Russian Federation); Beloglazkina, Elena K. [National University of Science and Technology MISiS, Leninskiy, Building 9, Moscow, 119049, Russian Federation, (Russian Federation); Moscow State University, Chemistry Department, Lenins kie gory, Building 1/3, GSP-1, Moscow, 119991 (Russian Federation); Majouga, Alexander G., E-mail: majouga@org.chem.msu.ru [National University of Science and Technology MISiS, Leninskiy, Building 9, Moscow, 119049, Russian Federation, (Russian Federation); Moscow State University, Chemistry Department, Lenins kie gory, Building 1/3, GSP-1, Moscow, 119991 (Russian Federation)

    2015-11-15

    Fe{sub 3}O{sub 4}@Au core/shell nanoparticles have unique magnetic and optical properties. These nanoparticles are used for biomedical applications, such as magnetic resonance imaging, photothermal therapy, controlled drug delivery, protein separation, biosensors, DNA detection, and immunosensors. In this review, recent methods for the synthesis of core/shell nanoparticles are discussed. We divided all of the synthetic methods in two groups: methods of synthesis of bi-layer structures and methods of synthesis of multilayer composite structures. The latter methods have a layer of “glue” material between the core and the shell. - Highlights: • Fe{sub 3}O{sub 4} nanoparticles are promising for biomedical applications but have some disadvantages. • Covering Fe{sub 3}O{sub 4} nanoparticles with Au shell leads to better stability and biocompatibility. • Core/shell nanoparticles are widely used for biomedical applications. • There are two types of Fe{sub 3}O{sub 4}@Au core/shell nanoparticles structures: bi-layer and multilayer composite. • Different synthetic methods enable production of nanoparticles of different sizes.

  7. Coaxial Electrospinning and Characterization of Core-Shell Structured Cellulose Nanocrystal Reinforced PMMA/PAN Composite Fibers.

    Science.gov (United States)

    Li, Chao; Li, Qingde; Ni, Xiaohui; Liu, Guoxiang; Cheng, Wanli; Han, Guangping

    2017-05-24

    A modified coaxial electrospinning process was used to prepare composite nanofibrous mats from a poly(methyl methacrylate) (PMMA) solution with the addition of different cellulose nanocrystals (CNCs) as the sheath fluid and polyacrylonitrile (PAN) solution as the core fluid. This study investigated the conductivity of the as-spun solutions that increased significantly with increasing CNCs addition, which favors forming uniform fibers. This study discussed the effect of different CNCs addition on the morphology, thermal behavior, and the multilevel structure of the coaxial electrospun PMMA + CNCs/PAN composite nanofibers. A morphology analysis of the nanofibrous mats clearly demonstrated that the CNCs facilitated the production of the composite nanofibers with a core-shell structure. The diameter of the composite nanofibers decreased and the uniformity increased with increasing CNCs concentrations in the shell fluid. The composite nanofibrous mats had the maximum thermal decomposition temperature that was substantially higher than electrospun pure PMMA, PAN, as well as the core-shell PMMA/PAN nanocomposite. The BET (Brunauer, Emmett and Teller) formula results showed that the specific surface area of the CNCs reinforced core-shell composite significantly increased with increasing CNCs content. The specific surface area of the composite with 20% CNCs loading rose to 9.62 m²/g from 3.76 m²/g for the control. A dense porous structure was formed on the surface of the electrospun core-shell fibers.

  8. Ag/TiO2 core-shell nanocables prepared with a one-step polyol process

    Science.gov (United States)

    Jiu, Jinting; Nogi, Masaya; Sugahara, Tohru; Suganuma, Katsuaki; Tsujimoto, Masahiko; Isoda, Seiji

    2012-11-01

    One-dimensional (1D) Ag/TiO2 core-shell nanocables have been synthesized with a facile polyol process by reducing AgNO3 and hydrolysis of titanium tetraisopropoxide without the need for any templates and capping agents under atmospheric conditions. The morphology of the Ag/TiO2 core-shell nanocables produced in this way is as either linear or spiral particles. The former are composed of an Ag rod core, and the later are aggregates of Ag nanoparticles which are aligned into an ID structure. The nanocables are about 50 and 150 nm in diameter for the linear and spiral particles, respectively, and over 30 μm in length. The absorption peaks of these Ag/TiO2 core-shell nanocables are significantly red-shifted comparing with those of uncoated pure silver nanowires. On the basis of the experimental results, a micro-reactor oxide template mechanism has been proposed to explain the growth of Ag/TiO2 core-shell nanocables.

  9. Synthesis and characterization of core-shell nanoparticles and their influence on the mechanical behavior of acrylic bone cements.

    Science.gov (United States)

    Gutiérrez-Mejía, A; Herrera-Kao, W; Duarte-Aranda, S; Loría-Bastarrachea, M I; Canché-Escamilla, G; Moscoso-Sánchez, F J; Cauich-Rodríguez, J V; Cervantes-Uc, J M

    2013-04-01

    Core-shell nanoparticles consisting of polybutyl acrylate (PBA) rubbery core and a polymethyl methacrylate (PMMA) shell, with different core-shell ratios, were synthesized in order to enhance the fracture toughness of the acrylic bone cements prepared with them. It was observed by TEM and SEM that the core-shell nanoparticles exhibited a spherical morphology with ca. 120 nm in diameter and that both modulus and tensile strength decreased by increasing the PBA content; the desired structuring pattern in the synthesized particles was confirmed by DMA. Also, experimental bone cements were prepared with variable amounts (0, 5, 10 and 20 wt.%) of nanoparticles with a core-shell ratio of 30/70 in order to study the influence of these nanostructured particles on the physicochemical, mechanical and fracture properties of bone cements. It was found that the addition of nanostructured particles to bone cements caused a significant reduction in the peak temperature and setting time while the glass transition temperature (Tg) of cements increased with increasing particles content. On the other hand, modulus and strength of bone cements decreased when particles were incorporated but fracture toughness was increased. Copyright © 2012 Elsevier B.V. All rights reserved.

  10. Generation of nano-sized core-shell particles using a coaxial tri-capillary electrospray-template removal method.

    Science.gov (United States)

    Cao, Lihua; Luo, Jun; Tu, Kehua; Wang, Li-Qun; Jiang, Hongliang

    2014-03-01

    This study proposed a new strategy based on a coaxial tri-capillary electrospray-template removal process for producing nanosized polylactide-b-polyethylene glycol (PLA-PEG) particles with a core-shell structure. Microparticles with core-shell-corona structures were first fabricated by coaxial tri-capillary electrospray, and core-shell nanoparticles less than 200 nm in size were subsequently obtained by removing the PEG template from the core-shell-corona microparticles. The nanoparticle size could be modulated by adjusting the flow rate of corona fluid, and nanoparticles with an average diameter of 106±5 nm were obtained. The nanoparticles displayed excellent dispersion stability in aqueous media and very low cytotoxicity. Paclitaxel was used as a model drug to be incorporated into the core section of the nanoparticles. A drug loading content in the nanoparticles as high as 50.7±1.5 wt% with an encapsulation efficiency of greater than 70% could be achieved by simply increasing the feed rate of the drug solution. Paclitaxel exhibited sustained release from the nanoparticles for more than 40 days. The location of the paclitaxel in the nanoparticles, i.e., in the core or shell layer, did not have a significant effect on its release. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. Highly luminescent CdSe/ZnSe core-shell quantum dots of one-pot preparation in octadecene

    NARCIS (Netherlands)

    Zeng, Q.; Kong, X.; Zhang, Y.; Zhang, H.

    2008-01-01

    CdSe/ZnSe core-shell quantum dots were synthesized using a new one-pot procedure where the core was prepared in octadecene. A ZnSe shell around a CdSe nanoparticle was formed by the reaction of selenium-richness on the surfaces of CdSe nanoparticles with Zn2+ from the injected zinc stearate

  12. The measurement of electrostatic potentials in core/shell GaN nanowires using off-axis electron holography

    DEFF Research Database (Denmark)

    Yazdi, Sadegh; Kasama, Takeshi; Ciechonski, R

    2013-01-01

    Core-shell GaN nanowires are expected to be building blocks of future light emitting devices. Here we apply off-axis electron holography to map the electrostatic potential distributions in such nanowires. To access the cross-section of selected individual nanowires, focused ion beam (FIB) milling...

  13. Pt@Ag and Pd@Ag core/shell nanoparticles for catalytic degradation of Congo red in aqueous solution

    Science.gov (United States)

    Salem, Mohamed A.; Bakr, Eman A.; El-Attar, Heba G.

    2018-01-01

    Platinum/silver (Pt@Ag) and palladium/silver (Pd@Ag) core/shell NPs have been synthesized in two steps reaction using the citrate method. The progress of nanoparticle formation was followed by the UV/Vis spectroscopy. Transmission electron microscopy revealed spherical shaped core/shell nanoparticles with average particle diameter 32.17 nm for Pt@Ag and 8.8 nm for Pd@Ag. The core/shell NPs were further characterized by FT-IR and XRD. Reductive degradation of the Congo red dye was chosen to demonstrate the excellent catalytic activity of these core/shell nanostructures. The nanocatalysts act as electron mediators for the transfer of electrons from the reducing agent (NaBH4) to the dye molecules. Effect of reaction parameters such as nanocatalyst dose, dye and NaBH4 concentrations on the dye degradation was investigated. A comparison between the catalytic activities of both nanocatalysts was made to realize which of them the best in catalytic performance. Pd@Ag was the higher in catalytic activity over Pt@Ag. Such greater activity is originated from the smaller particle size and larger surface area. Pd@Ag nanocatalyst was catalytically stable through four subsequent reaction runs under the utilized reaction conditions. These findings can thus be considered as possible economical alternative for environmental safety against water pollution by dyes.

  14. A novel biomaterial — Fe 3O 4:TiO 2 core-shell nano particle with magnetic performance and high visible light photocatalytic activity

    Science.gov (United States)

    He, Qinghang; Zhang, Zhenxi; Xiong, Jianwen; Xiong, Yuying; Xiao, Hua

    2008-10-01

    Aiming at some disadvantages of TiO 2 nano particle (TiO 2 NP), this paper successfully prepared Fe 3O 4:TiO 2 core-shell nano particle (Fe 3O 4:TiO 2 core-shell NP) using homogeneous precipitation method. The prepared Fe 3O 4:TiO 2 core-shell NP was characterized using XRD, TEM, UV-vis DRS, FT-IR, and VSM, respectively; the results show that Fe 3O 4:TiO 2 core-shell NP is single dispersed with the diameter of 20 nm on average. In contrast to the traditional TiO 2 NP, Fe 3O 4:TiO 2 core-shell NP generates red shift, and has higher absorption in visible region and greater photocatalytic activity, plus additional superparamagetism. In order to demonstrate the benefits of Fe 3O 4:TiO 2 core-shell NP, we adopted Hela cells as a model to investigate the killing efficiency. The results show that Fe 3O 4:TiO 2 core-shell NP is non-toxic, and much more efficient than traditional TiO 2 NP combined with extra magnetic field. This shows that Fe 3O 4:TiO 2 core-shell NP is a novel biomaterial with magnetic performance and high visible light photocatalytic activity. It would be a promising candidate in the field of malignant tumor therapy in future.

  15. A solar-thermal energy harvesting scheme: enhanced heat capacity of molten HITEC salt mixed with Sn/SiO(x) core-shell nanoparticles.

    Science.gov (United States)

    Lai, Chih-Chung; Chang, Wen-Chih; Hu, Wen-Liang; Wang, Zhiming M; Lu, Ming-Chang; Chueh, Yu-Lun

    2014-05-07

    We demonstrated enhanced solar-thermal storage by releasing the latent heat of Sn/SiO(x) core-shell nanoparticles (NPs) embedded in a eutectic salt. The microstructures and chemical compositions of Sn/SiO(x) core-shell NPs were characterized. In situ heating XRD provides dynamic crystalline information about the Sn/SiO(x) core-shell NPs during cyclic heating processes. The latent heat of ∼29 J g(-1) for Sn/SiO(x) core-shell NPs was measured, and 30% enhanced heat capacity was achieved from 1.57 to 2.03 J g(-1) K(-1) for the HITEC solar salt without and with, respectively, a mixture of 5% Sn/SiO(x) core-shell NPs. In addition, an endurance cycle test was performed to prove a stable operation in practical applications. The approach provides a method to enhance energy storage in solar-thermal power plants.

  16. A hot topic: temperature sensitive sodium channelopathies.

    Science.gov (United States)

    Egri, Csilla; Ruben, Peter C

    2012-01-01

    Perturbations to body temperature affect almost all cellular processes and, within certain limits, results in minimal effects on overall physiology. Genetic mutations to ion channels, or channelopathies, can shift the fine homeostatic balance resulting in a decreased threshold to temperature induced disturbances. This review summarizes the functional consequences of currently identified voltage-gated sodium (NaV) channelopathies that lead to disorders with a temperature sensitive phenotype. A comprehensive knowledge of the relationships between genotype and environment is not only important for understanding the etiology of disease, but also for developing safe and effective treatment paradigms.

  17. Fabrication of ammonium perchlorate/copper-chromium oxides core-shell nanocomposites for catalytic thermal decomposition of ammonium perchlorate

    Energy Technology Data Exchange (ETDEWEB)

    Eslami, Abbas, E-mail: eslami@umz.ac.ir [Department of Inorganic Chemistry, Faculty of Chemistry, University of Mazandaran, P.O.Box 47416-95447, Babolsar (Iran, Islamic Republic of); Juibari, Nafise Modanlou [Department of Inorganic Chemistry, Faculty of Chemistry, University of Mazandaran, P.O.Box 47416-95447, Babolsar (Iran, Islamic Republic of); Hosseini, Seyed Ghorban [Department of Chemistry, Malek Ashtar University of Technology, P.O. Box 16765-3454, Tehran (Iran, Islamic Republic of)

    2016-09-15

    The ammonium perchlorate/Cu(II)-Cr(III)-oxides(AP/Cu-Cr-O) core-shell nanocomposites were in-situ prepared by deposition of copper and chromium oxides on suspended ammonium perchlorate particles in ethyl acetate as solvent. The results of differential scanning calorimetery (DSC) and thermal gravimetric analysis (TGA) experiments showed that the nanocomposites have excellent catalytic effect on the thermal decomposition of AP, so that the released heat increases up to about 3-fold over initial values, changing from 450 J/g for pure AP to 1510 J/g for most appropriate mixture. For better comparison, single metal oxide/AP core-shell nanocomposite have also been prepared and the results showed that they have less catalytic effect respect to mixed metal oxides system. Scanning electron microscopy (SEM) results revealed homogenous deposition of nanoparticles on the surface of AP and fabrication of core-shell structures. The kinetic parameters of thermal decomposition of both pure AP and AP/Cu-Cr-O samples have been calculated by Kissinger method and the results showed that the values of pre-exponential factor and activation energy are higher for AP/Cu-Cr-O nanocomposite. The better catalytic effect of Cu-Cr-O nanocomposites is probably attributed to the synergistic effect between Cu{sup 2+} and Cr{sup 3+} in the nanocomposites, smaller particle size and more crystal defect. - Highlights: • The Cu-Cr-O nanoparticles were synthesized by chemical liquid deposition method. • Then, the AP/Cu-Cr-O core-shell nanocomposites were prepared. • The core-shell samples showed high catalytic activity for AP decomposition. • Thermal decomposition of samples occurs at lower temperature range.

  18. Fabrication of ammonium perchlorate/copper-chromium oxides core-shell nanocomposites for catalytic thermal decomposition of ammonium perchlorate

    International Nuclear Information System (INIS)

    Eslami, Abbas; Juibari, Nafise Modanlou; Hosseini, Seyed Ghorban

    2016-01-01

    The ammonium perchlorate/Cu(II)-Cr(III)-oxides(AP/Cu-Cr-O) core-shell nanocomposites were in-situ prepared by deposition of copper and chromium oxides on suspended ammonium perchlorate particles in ethyl acetate as solvent. The results of differential scanning calorimetery (DSC) and thermal gravimetric analysis (TGA) experiments showed that the nanocomposites have excellent catalytic effect on the thermal decomposition of AP, so that the released heat increases up to about 3-fold over initial values, changing from 450 J/g for pure AP to 1510 J/g for most appropriate mixture. For better comparison, single metal oxide/AP core-shell nanocomposite have also been prepared and the results showed that they have less catalytic effect respect to mixed metal oxides system. Scanning electron microscopy (SEM) results revealed homogenous deposition of nanoparticles on the surface of AP and fabrication of core-shell structures. The kinetic parameters of thermal decomposition of both pure AP and AP/Cu-Cr-O samples have been calculated by Kissinger method and the results showed that the values of pre-exponential factor and activation energy are higher for AP/Cu-Cr-O nanocomposite. The better catalytic effect of Cu-Cr-O nanocomposites is probably attributed to the synergistic effect between Cu 2+ and Cr 3+ in the nanocomposites, smaller particle size and more crystal defect. - Highlights: • The Cu-Cr-O nanoparticles were synthesized by chemical liquid deposition method. • Then, the AP/Cu-Cr-O core-shell nanocomposites were prepared. • The core-shell samples showed high catalytic activity for AP decomposition. • Thermal decomposition of samples occurs at lower temperature range.

  19. Core-Shell Diamond as a Support for Solid-Phase Extraction and High-Performance Liquid Chromatography

    International Nuclear Information System (INIS)

    Saini, Gaurav; Jensen, David S.; Wiest, Landon A.; Vail, Michael A.; Dadson, Andrew; Lee, Milton L.; Shutthanandan, V.; Linford, Matthew R.

    2010-01-01

    We report the formation of core-shell diamond particles for solid phase extraction (SPE) and high performance liquid chromatography (HPLC) made by layer-by-layer (LbL) deposition. Their synthesis begins with the amine functionalization of microdiamond by its immersion in an aqueous solution of a primary amine-containing polymer (polyallylamine (PAAm)). The amine-terminated microdiamond is then immersed in an aqueous suspension of nanodiamond, which leads to adsorption of the nanodiamond. Alternating (self-limiting) immersions in the solutions of the amine-containing polymer and the suspension of nanodiamond are continued until the desired number of nanodiamond layers is formed around the microdiamond. Finally, the core-shell particles are cross-linked with 1,2,5,6-diepoxycyclooctane or reacted with 1,2-epoxyoctadecane. Layer-by-layer deposition of PAAm and nanodiamond is also studied on planar Si/SiO2 surfaces, which were characterized by SEM, Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA). Core-shell particles are characterized by diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), environmental scanning electron microscopy (ESEM), and Brunauer Emmett Teller (BET) surface area and pore size measurements. Larger (ca. 50 ?m) core-shell diamond particles have much higher surface areas, and analyte loading capacities in SPE than nonporous solid diamond particles. Smaller (ca. 3 ?m), normal and reversed phase, core-shell diamond particles have been used for HPLC, with 36,300 plates per meter for mesitylene in a separation of benzene and alkyl benzenes on a C18 adsorbent, and 54,800 plates per meter for diazinon in a similar separation of two pesticides.

  20. Origin of luminescence from ZnO/CdS core/shell nanowire arrays

    Science.gov (United States)

    Wang, Zhiqiang; Wang, Jian; Sham, Tsun-Kong; Yang, Shaoguang

    2014-07-01

    Chemical imaging, electronic structure and optical properties of ZnO/CdS nano-composites have been investigated using scanning transmission X-ray microscopy (STXM), X-ray absorption near-edge structure (XANES) and X-ray excited optical luminescence (XEOL) spectroscopy. STXM and XANES results confirm that the as-prepared product is ZnO/CdS core/shell nanowires (NWs), and further indicate that ZnS was formed on the surface of ZnO NWs as the interface between ZnO and CdS. The XEOL from ZnO/CdS NW arrays exhibits one weak ultraviolet (UV) emission at 375 nm, one strong green emission at 512 nm, and two broad infrared (IR) emissions at 750 and 900 nm. Combining XANES and XEOL, it is concluded that the UV luminescence is the near band gap emission (BGE) of ZnO; the green luminescence comes from both the BGE of CdS and defect emission (DE, zinc vacancies) of ZnO; the IR luminescence is attributed to the DE (bulk defect related to the S site) of CdS; ZnS contributes little to the luminescence of the ZnO/CdS NW arrays. Interestingly, the BGE and DE from oxygen vacancies of ZnO in the ZnO/CdS nano-composites are almost entirely quenched, while DE from zinc vacancies changes little.Chemical imaging, electronic structure and optical properties of ZnO/CdS nano-composites have been investigated using scanning transmission X-ray microscopy (STXM), X-ray absorption near-edge structure (XANES) and X-ray excited optical luminescence (XEOL) spectroscopy. STXM and XANES results confirm that the as-prepared product is ZnO/CdS core/shell nanowires (NWs), and further indicate that ZnS was formed on the surface of ZnO NWs as the interface between ZnO and CdS. The XEOL from ZnO/CdS NW arrays exhibits one weak ultraviolet (UV) emission at 375 nm, one strong green emission at 512 nm, and two broad infrared (IR) emissions at 750 and 900 nm. Combining XANES and XEOL, it is concluded that the UV luminescence is the near band gap emission (BGE) of ZnO; the green luminescence comes from both the

  1. Immobilization of cholesterol oxidase on magnetic fluorescent core-shell-structured nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Jun, E-mail: hjun@whut.edu.cn; Liu, Huichao; Zhang, Peipei; Zhang, Pengfei; Li, Mengshi; Ding, Liyun

    2015-12-01

    The magnetic fluorescent core-shell structured nanoparticles, Fe{sub 3}O{sub 4}@SiO{sub 2}(F)@meso–SiO{sub 2} nanoparticles, were prepared. Cholesterol oxidase (COD) was immobilized on their surface to form Fe{sub 3}O{sub 4}@SiO{sub 2}(F)@meso–SiO{sub 2}@COD nanoparticles. Optimal immobilization was achieved with 2.5% (v/v) APTES, 2.0% (v/v) GA, 10 mg COD (in 15 mg carrier) and solution pH of 7.0. Fe{sub 3}O{sub 4}@SiO{sub 2}(F)@meso–SiO{sub 2}@COD nanoparticles showed maximal catalytic activity at pH 7.0 and 50 °C. The thermal, storage and operational stabilities of COD were improved greatly after its immobilization. After the incubation at 50 °C for 5 h, the nanoparticles and free COD retained 80% and 46% of its initial activity, respectively. After kept at 4 °C for 30 days, the nanoparticles and free COD maintained 86% and 65% of initial activity, respectively. The nanoparticles retained 71% of its initial activity after 7 consecutive operations. Since Fe{sub 3}O{sub 4}@SiO{sub 2}(F)@meso–SiO{sub 2}@COD nanoparticles contained tris(2,2-bipyridyl)dichloro-ruthenium(II) hexahydrate (Ru(bpy){sub 3}Cl{sub 2}) and were optical sensitive to oxygen in solution, it might be used as the sensing material and has the application potential in multi parameter fiber optic biosensor based on enzyme catalysis and oxygen consumption. - Highlights: • COD was immobilized on magnetic fluorescent core-shell structured nanoparticles. • The nanoparticles were optical sensitive to oxygen in water solution. • The nanoparticles have remarkable improved stability compared with free COD. • The nanoparticles can probably be used in multi parameter fiber optic Biosensor.

  2. Electrochemical reduction of trinitrotoluene on core-shell tin-carbon electrodes

    International Nuclear Information System (INIS)

    Grigoriants, Irena; Markovsky, Boris; Persky, Rachel; Perelshtein, Ilana; Gedanken, Aharon; Aurbach, Doron; Filanovsky, Boris; Bourenko, Tatiana; Felner, Israel

    2008-01-01

    In this work, we studied the electrochemical process of 2,4,6-trinitrotoluene (TNT) reduction on a new type of electrodes based on a core-shell tin-carbon Sn(C) structure. The Sn(C) composite was prepared from the precursor tetramethyl-tin Sn(CH 3 ) 4 , and the product contained a core of submicron-sized tin particles uniformly enveloped with carbon shells. Cyclic voltammograms of Sn(C) electrodes in aqueous sodium chloride solutions containing TNT show three well-pronounced reduction waves in the potential range of -0.50 to -0.80 V (vs. an Ag/AgCl/Cl - reference electrode) that correspond to the multistep process of TNT reduction. Electrodes containing Sn(C) particles annealed at 800 deg. C under argon develop higher voltammetric currents of TNT reduction (comparing to the as-prepared tin-carbon material) due to stabilization of the carbon shell. It is suggested that the reduction of TNT on core-shell tin-carbon electrodes is an electrochemically irreversible process. A partial oxidation of the TNT reduction products occurred at around -0.20 V. The electrochemical response of TNT reduction shows that it is not controlled by the diffusion of the active species to/from the electrodes but rather by interfacial charge transfer and possible adsorption phenomena. The tin-carbon electrodes demonstrate significantly stable behavior for TNT reduction in NaCl solutions and provide sufficient reproducibility with no surface fouling through prolonged voltammetric cycling. It is presumed that tin nanoparticles, which constitute the core, are electrochemically inactive towards TNT reduction, but Sn or SnO 2 formed on the electrodes during TNT reduction may participate in this reaction as catalysts or carbon-modifying agents. The nitro-groups of TNT can be reduced irreversibly (via two possible paths) by three six-electron transfers, to 2,4,6-triaminotoluene, as follows from mass-spectrometric studies. The tin-carbon electrodes described herein may serve as amperometric sensors

  3. XNBR-grafted halloysite nanotube core-shell as a potential compatibilizer for immiscible polymer systems

    International Nuclear Information System (INIS)

    Paran, S.M.R.; Naderi, G.; Ghoreishy, M.H.R.

    2016-01-01

    Highlights: • Attached an utilitarian silane coupling agent to the HNT via a sol-gel method. • Developed and analyzed the HNT/XNBR core-shell particles via sol-gel technique. • Enhanced the reactivity of the surface of HNT through XNBR grafting. • The act of HNT/XNBR as a compatibilizer in PA6/NBR TPEs. • Immiscible Polymer System with a good balanced physical and mechanical properties. - Abstract: Halloysite nanotubes (HNTs) grafted with carboxylated nitrile byutadiene rubber (XNBR) were synthesized via a sol-gel method. The HNTs as an inorganic cores were pre-treated with 3-Glycidoxypropyl trimethoxysilane, then successfully coated with the XNBR as an organic shell. The properties of XNBR-grafted HNTs were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results suggested that the XNBR grafted to the surfaces of HNTs successfully. Then the TPE nanocomposites based on polyamide-6 (PA6) and nitrile butadiene rubber (NBR) containing various XNBR-grafted and pristine HNTs were prepared via a direct melt mixing method. The morphology, mechanical, dynamic mechanical and rheological properties of the prepared TPE nanocomposites were investigated. The results show that the XNBR-grafted HNTs can effectively improve the morphology and mechanical properties of the PA6/NBR TPEs. The morphology study of the prepared nanocomposites show that the effect of XNBR-grafted HNTs on the size reduction of NBR phase is markedly more effective than the pristine HNTs and rose by 50% in the same concentrations. Mechanical measurements show that the Young’s modulus of the TPE nanocomposites rose by 60% in just 7 wt% of XNBR-grafted HNT loading. The results indicate that the introduction of HNT/XNBR core-shells into the PA6/NBR TPEs can enhances the interfacial interactions

  4. XNBR-grafted halloysite nanotube core-shell as a potential compatibilizer for immiscible polymer systems

    Energy Technology Data Exchange (ETDEWEB)

    Paran, S.M.R.; Naderi, G., E-mail: g.naderi@ippi.ac.ir; Ghoreishy, M.H.R.

    2016-09-30

    Highlights: • Attached an utilitarian silane coupling agent to the HNT via a sol-gel method. • Developed and analyzed the HNT/XNBR core-shell particles via sol-gel technique. • Enhanced the reactivity of the surface of HNT through XNBR grafting. • The act of HNT/XNBR as a compatibilizer in PA6/NBR TPEs. • Immiscible Polymer System with a good balanced physical and mechanical properties. - Abstract: Halloysite nanotubes (HNTs) grafted with carboxylated nitrile byutadiene rubber (XNBR) were synthesized via a sol-gel method. The HNTs as an inorganic cores were pre-treated with 3-Glycidoxypropyl trimethoxysilane, then successfully coated with the XNBR as an organic shell. The properties of XNBR-grafted HNTs were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results suggested that the XNBR grafted to the surfaces of HNTs successfully. Then the TPE nanocomposites based on polyamide-6 (PA6) and nitrile butadiene rubber (NBR) containing various XNBR-grafted and pristine HNTs were prepared via a direct melt mixing method. The morphology, mechanical, dynamic mechanical and rheological properties of the prepared TPE nanocomposites were investigated. The results show that the XNBR-grafted HNTs can effectively improve the morphology and mechanical properties of the PA6/NBR TPEs. The morphology study of the prepared nanocomposites show that the effect of XNBR-grafted HNTs on the size reduction of NBR phase is markedly more effective than the pristine HNTs and rose by 50% in the same concentrations. Mechanical measurements show that the Young’s modulus of the TPE nanocomposites rose by 60% in just 7 wt% of XNBR-grafted HNT loading. The results indicate that the introduction of HNT/XNBR core-shells into the PA6/NBR TPEs can enhances the interfacial interactions

  5. Microfluidic conceived pH sensitive core-shell particles for dual drug delivery.

    Science.gov (United States)

    Khan, Ikram Ullah; Stolch, Lukas; Serra, Christophe A; Anton, Nicolas; Akasov, Roman; Vandamme, Thierry F

    2015-01-15

    In current study, we report on the synthesis of core-shell microparticles for dual drug delivery by means of a two co-axial microfluidic device and online UV assisted free radical polymerization. Before developing pH-sensitive particles, ketoprofen loaded poly(methyl acrylate) core-ranitidine HCl loaded poly(acrylamide) shell particles were produced. Influence of inner and outer phases flow rates on particle size, shape, core diameter, shell thickness, and drug release properties was studied. All the particles were monodispersed with coefficient of variation below 5%. Furthermore, their diameter ranged from 100 to 151 μm by increasing continuous (Qc) to middle (Qm) phase flow rate ratio (Qc/Qm). Core diameter varied from 58 to 115 μm by decreasing middle (Qm) to inner (Qi) phase flow rate ratio (Qm/Qi) at constant continuous phase flow rate as confirmed by SEM images. It was observed that an optimum concentration of acrylamide (30 wt%) and an appropriate combination of surfactants were necessary to get core-shell particles otherwise Janus structure was obtained. FTIR confirmed the complete polymerization of core and shell phases. MTT assay showed variation in viability of cells under non-contact and contact conditions with less cytotoxicity for the former. Under non-contact conditions LD50 was 3.1mg/mL. Release studies in USP phosphate buffer solution showed simultaneously release of ketoprofen and ranitidine HCl for non pH-sensitive particles. However, release rates of ranitidine HCl and ketoprofen were higher at low and high pH respectively. To develop pH-sensitive particles for colon targeting, the previous shell phase was admixed with few weight percentage of pH sensitive carboxyethyl acrylate monomer. Core and shell contained the same hydrophobic and hydrophilic model drugs as in previous case. The pH-sensitive shell prevented the release of the two entrapped molecules at low pH while increasing significantly their release rate at higher pH with a maximum

  6. Dually Fluorescent Core-Shell Microgels for Ratiometric Imaging in Live Antigen-Presenting Cells

    Science.gov (United States)

    Zhou, Xianfeng; Su, Fengyu; Tian, Yanqing; Meldrum, Deirdre R.

    2014-01-01

    Core-shell microgels containing sensors/dyes in a matrix were fabricated by two-stage free radical precipitation polymerization method for ratiometric sensing/imaging. The microgels composing of poly(N-isopropylacrylamide) (PNIPAm) shell exhibits a low critical solution temperature (LCST), underwent an entropically driven transition from a swollen state to a deswollen state, which exhibit a hydrodynamic radius of ∼450 nm at 25°C (in vitro) and ∼190 nm at 37°C (in vivo). The microgel’s ability of escaping from lysosome into cytosol makes the microgel be a potential candidate for cytosolic delivery of sensors/probes. Non-invasive imaging/sensing in Antigen-presenting cells (APCs) was feasible by monitoring the changes of fluorescence intensity ratios. Thus, these biocompatible microgels-based imaging/sensing agents may be expected to expand current molecular imaging/sensing techniques into methods applicable to studies in vivo, which could further drive APC-based treatments. PMID:24505422

  7. Electrical breakdown and nanogap formation of indium oxide core/shell heterostructure nanowires.

    Science.gov (United States)

    Jung, Minkyung; Song, Woon; Sung Lee, Joon; Kim, Nam; Kim, Jinhee; Park, Jeunghee; Lee, Hyoyoung; Hirakawa, Kazuhiko

    2008-12-10

    We report the electrical breakdown behavior and subsequent nanogap formation of In(2)O(3)/InO(x) core/shell heterostructure nanowires with substrate-supported and suspended structures. The radial heterostructure nanowires, composed of crystalline In(2)O(3) cores and amorphous In-rich shells, are grown by chemical vapor deposition. As the nanowires broke down, they exhibited two distinct current drops in the current-voltage characteristics. The tips of the broken nanowires were found to have a cone or a volcano shape depending on the width of the nanowire. The shape, the size, and the position of the nanogap depend strongly on the device structure and the nanowire dimensions. The substrate-supported and the suspended devices exhibit distinct breakdown behavior which can be explained by the diffusive thermal transport model. The breakdown temperature of the nanowire is estimated to be about 450 K, close to the melting temperature of indium. We demonstrated the usefulness of this technique by successful fabrication of working pentacene field-effect transistors.

  8. GaAs-AlGaAs core-shell nanowire lasers on silicon: invited review

    Science.gov (United States)

    Koblmüller, Gregor; Mayer, Benedikt; Stettner, Thomas; Abstreiter, Gerhard; Finley, Jonathan J.

    2017-05-01

    Semiconductor nanowire (NW) lasers provide significant potential to create a new generation of lasers and on-chip coherent light sources by virtue of their ability to operate as single mode optical waveguides at the nanoscale. Due to their unique geometry, a major benefit lies also in the feasibility for direct integration on silicon (Si), enabling III-V-on-Si NW lasers that could fuel applications in optical interconnects and data communication. In this review, we describe the state-of-the-art and recent progress in GaAs-AlGaAs based NW lasers emitting in the near infrared (NIR) spectral region, with a specific emphasis on integration on a Si platform. First, we explore design rules for the photonic properties in GaAs NW waveguides based on finite difference time domain calculations. The lasing characteristics of GaAs-AlGaAs core-shell NW lasers are then investigated under various different optical pumping schemes ranging from pulsed to continuous wave excitation. We further review recent activities on the realization of low-dimensional quantum heterostructures inside NW cavities as a means to tune lasing wavelength, gain and threshold properties. Ultimately, we describe schemes for monolithic integration of GaAs-based NW lasers directly on Si and show how such vertical nanocavity lasers are excellent candidates for low-threshold lasing, high spontaneous emission coupling (high β-factor lasers), and ultrafast emission characteristics.

  9. Core-Shell-Yarn-Based Triboelectric Nanogenerator Textiles as Power Cloths.

    Science.gov (United States)

    Yu, Aifang; Pu, Xiong; Wen, Rongmei; Liu, Mengmeng; Zhou, Tao; Zhang, Ke; Zhang, Yang; Zhai, Junyi; Hu, Weiguo; Wang, Zhong Lin

    2017-12-26

    Although textile-based triboelectric nanogenerators (TENGs) are highly promising because they scavenge energy from their working environment to sustainably power wearable/mobile electronics, the challenge of simultaneously possessing the qualities of cloth remains. In this work, we propose a strategy for TENG textiles as power cloths in which core-shell yarns with core conductive fibers as the electrode and artificial polymer fibers or natural fibrous materials tightly twined around core conductive fibers are applied as the building blocks. The resulting TENG textiles are comfortable, flexible, and fashionable, and their production processes are compatible with industrial, large-scale textile manufacturing. More importantly, the comfortable TENG textiles demonstrate excellent washability and tailorability and can be fully applied in further garment processing. TENG textiles worn under the arm or foot have also been demonstrated to scavenge various types of energy from human motion, such as patting, walking, and running. All of these merits of proposed TENG textiles for clothing uses suggest their great potentials for viable applications in wearable electronics or smart textiles in the near future.

  10. Solution-processed core-shell nanowires for efficient photovoltaic cells.

    Science.gov (United States)

    Tang, Jinyao; Huo, Ziyang; Brittman, Sarah; Gao, Hanwei; Yang, Peidong

    2011-08-21

    Semiconductor nanowires are promising for photovoltaic applications, but, so far, nanowire-based solar cells have had lower efficiencies than planar cells made from the same materials, even allowing for the generally lower light absorption of nanowires. It is not clear, therefore, if the benefits of the nanowire structure, including better charge collection and transport and the possibility of enhanced absorption through light trapping, can outweigh the reductions in performance caused by recombination at the surface of the nanowires and at p-n junctions. Here, we fabricate core-shell nanowire solar cells with open-circuit voltage and fill factor values superior to those reported for equivalent planar cells, and an energy conversion efficiency of ∼5.4%, which is comparable to that of equivalent planar cells despite low light absorption levels. The device is made using a low-temperature solution-based cation exchange reaction that creates a heteroepitaxial junction between a single-crystalline CdS core and single-crystalline Cu2S shell. We integrate multiple cells on single nanowires in both series and parallel configurations for high output voltages and currents, respectively. The ability to produce efficient nanowire-based solar cells with a solution-based process and Earth-abundant elements could significantly reduce fabrication costs relative to existing high-temperature bulk material approaches.

  11. Synthesis and Characterization of ZnO/ZnS Core/Shell Nanowires

    Directory of Open Access Journals (Sweden)

    Taher Ghrib

    2014-01-01

    Full Text Available ZnO nanowires of approximately 3 µm length and 200 nm diameter are prepared and implanted vertically on substrate glass which is coated with thin layer of ITO which is too covered with bulk ZnO thin layer via electrodeposition process by cyclic voltammetry-chronoamperometry and with a chemical process that is described later; we have synthesized a ZnS nanolayer. ZnO/ZnS core/shell nanowires are formed by ZnO nanowires core surrounded by a very thin layer of porous ZnS shell principally constituted with a crystal which is about 15–20 nm in diameter. In the method, ZnS nanoparticles were prepared by reaction of ZnO nanowires with Na2S in aqueous solution at low temperature and also we have discussed the growth mechanism of ZnO/ZnS nanowires. The morphology, structure, and composition of the obtained nanostructures were obtained by using X-ray diffraction (XRD, scanning electron microscopy (SEM, transmission electron microscopy (TEM, and X-ray photoelectron spectroscopy (XPS. For the structure, SEM and XRD measurements indicated that the as-grown ZnO nanowires microscale was of hexagonal wurtzite phase with a high crystalline quality, and TEM shows that the ZnS is uniformly distributed on the surface of the ZnO nanowires.

  12. Development of Novel 3-D Printed Scaffolds With Core-Shell Nanoparticles for Nerve Regeneration.

    Science.gov (United States)

    Lee, Se-Jun; Zhu, Wei; Heyburn, Lanier; Nowicki, Margaret; Harris, Brent; Zhang, Lijie Grace

    2017-02-01

    A traumatic injury of peripheral nerves is serious clinical problem that may lead to major loss of nerve function, affecting quality of patient's life. Currently, nerve autograft is widely used to reconstruct the nerve gap. However, such surgical procedure suffers from many disadvantages including donor site morbidity and limited availability. In order to address these issues, neural tissue engineering has focused on the development of synthetic nerve scaffolds to support bridging a larger gap and improving nerve generation. For this purpose, we fabricated a novel 3-D biomimetic scaffold, which has tunable porous structure and embedded core-shell nanoparticles with sustained neurogenic factor delivery system, using stereolithography based 3-D printing and coaxial electrospraying techniques. Our results showed that scaffolds with larger porosity significantly improve PC-12 neural cell adhesion compared to ones with smaller porosity. Furthermore, scaffolds embedded with bovine serum albumin containing nanoparticles showed an enhancement in cell proliferation relative to bared control scaffolds. More importantly, confocal microscopy images illustrated that the scaffold with nerve growth factor nanoparticles greatly increased the length of neurites and directed neurite extension of PC-12 cells along the fiber. In addition, the 3-D printed nanocomposite scaffolds also improved the average neurite length of primary cortical neurons. The results in this study demonstrate the potential of this 3-D printed scaffold in improving neural cell function and nerve growth.

  13. Single-step generation of fluorophore-encapsulated gold nanoparticle core-shell materials

    International Nuclear Information System (INIS)

    Sardar, R; Shem, P M; Pecchia-Bekkum, C; Bjorge, N S; Shumaker-Parry, J S

    2010-01-01

    We report a simple route to produce fluorophore-encapsulated gold nanoparticles (AuNPs) in a single step under aqueous conditions using the fluorophore 1-pyrenemethylamine (PMA). Different amounts of PMA were used and the resulting core-shell gold nanoparticles were analyzed using UV-visible absorption spectroscopy, fluorescence spectroscopy, and transmission and scanning electron microscopy. Electron microscopy analysis shows nanoparticles consisting of a gold nanoparticle core which is encapsulated with a lower contrast shell. In the UV-visible spectra, we observed a significant red shift (37 nm) of the localized surface plasmon resonance (LSPR) absorption maximum (λ max ) compared to citrate-stabilized AuNPs of a similar size. We attribute the prominent LSPR wavelength shift for PMA-AuNP conjugates to the increase in the local dielectric environment near the gold nanoparticles due to the shell formation. This simple, aqueous-based synthesis is a new approach to the production of fluorophore-encapsulated AuNPs that could be applicable in biological sensing systems and photonic device fabrication.

  14. Structure-property relationship in core-shell rubber toughened epoxy nanocomposites

    Science.gov (United States)

    Gam, Ki Tak

    The structure-property relationships of epoxy nanocomposites with inorganic layer-structure nanofillers have been studied to obtain the fundamental understanding of the role of nanofillers and the physics of polymer nanocomposites in this dissertation. Several polymer nanocomposite systems with modified montmorillonite (MMT) or alpha-zirconium phosphate (ZrP) nanofillers were prepared with epoxy matrices of different ductility and properties. The successful nanofiller's exfoliations were confirmed with X-ray diffraction and transmission electronic microscopy (TEM). Dynamic mechanical analysis (DMA) on the prepared epoxy nanocomposites revealed the significant increase in rubbery plateau moduli of the epoxy nanocomposite systems above Tg, as high as 4.5 times, and tensile test results showed improved modulus by the nanofiller addition, while the fracture toughness was not affected or slightly decreased by nanofillers. The brittle epoxy nanocomposite systems were toughened with core shell rubber (CSR) particles and showed remarkable increase in fracture toughness (KIC) value up to 270%. The CSR toughening is more effective at ductile matrices, and TEM observation indicates that major toughening mechanisms induced by the CSR addition involve a large scale CSR cavitation, followed by massive shear deformation of the matrix.

  15. Enhanced electronic and electrochemical properties of core-shelled V2O5-Pt nanowires

    Science.gov (United States)

    Pan, Ko-Ying; Wei, Da-Hua

    2018-01-01

    Platinum nanoparticles (Pt NPs) were decorated on vanadium pentoxide nanowires (V2O5 NWs) to form the core-shelled vanadium-platinum nanowires (Pt@V2O5 NWs) and their electrochemical activities for methanol oxidation were investigated. The synthetic procedure involved the synthesis of abundant vanadium pentoxide nanowires (V2O5 NWs) by a direct vapor-solid growth process (VS method), followed by atomic layer depositions (ALD) of platinum nanoparticles (Pt NPs) onto the V2O5 NWs. After the physical examinations, three designed deposition parameters (50, 100 and 150 cycles) of Pt NPs onto the V2O5 NWs by ALD process were successful. From the measurements of current-voltage (I-V) and cyclic voltammetry (CV) curves respectively, both the conductivity and the ratio of the forward anodic peak current (IF) to the reverse anodic peak current (IR) are enhancing proportionately to the deposition cycles of ALD process, which denotes that coating Pt atomic layers onto V2O5 nanowires indeed improves the catalytic performances than that of pure V2O5 nanowires.

  16. Core-shell homojunction silicon vertical nanowire tunneling field-effect transistors

    Science.gov (United States)

    Yoon, Jun-Sik; Kim, Kihyun; Baek, Chang-Ki

    2017-01-01

    We propose three-terminal core-shell (CS) silicon vertical nanowire tunneling field-effect transistors (TFETs), which can be fabricated by conventional CMOS technology. CS TFETs show lower subthreshold swing (SS) and higher on-state current than conventional TFETs through their high surface-to-volume ratio, which increases carrier-tunneling region with no additional device area. The on-state current can be enhanced by increasing the nanowire height, decreasing equivalent oxide thickness (EOT) or creating a nanowire array. The off-state current is also manageable for power saving through selective epitaxial growth at the top-side nanowire region. CS TFETs with an EOT of 0.8 nm and an aspect ratio of 20 for the core nanowire region provide the largest drain current ranges with point SS values below 60 mV/dec and superior on/off current ratio under all operation voltages of 0.5, 0.7, and 1.0 V. These devices are promising for low-power applications at low fabrication cost and high device density. PMID:28112273

  17. Probing atomic structure in magnetic core/shell nanoparticles using synchrotron radiation.

    Science.gov (United States)

    Baker, S H; Roy, M; Thornton, S C; Qureshi, M; Binns, C

    2010-09-29

    Core/shell Fe/Cu and Fe/Au nanoparticles were prepared directly by deposition from the gas phase. A detailed study of the atomic structure in both the cores and shells of the nanoparticles was undertaken by means of extended absorption fine structure (EXAFS) measurements. For Fe/Cu nanoparticles, a Cu shell ∼ 20 monolayers thick appears similar in structure to bulk Cu and is sufficient to cause the structure in the Fe core to switch from body centred cubic (bcc; as in bulk Fe) to face centred cubic. This is not the case for thinner Cu shells, 1-2 monolayers in thickness, in which there is a considerable contraction in nearest-neighbour interatomic distance as the shell structure changes to bcc. In Fe/Au nanoparticles, the crystal structure in the Fe core remains bcc for all Au thicknesses although there is some stretching of the lattice. In thin Au shells ∼ 2 monolayers thick, there is strong contraction in interatomic distances. There does not appear to be significant alloying at the Fe/Au interface.

  18. Strained lattice with persistent atomic order in Pt3Fe2 intermetallic core-shell nanocatalysts.

    Science.gov (United States)

    Prabhudev, Sagar; Bugnet, Matthieu; Bock, Christina; Botton, Gianluigi A

    2013-07-23

    Fine-tuning nanocatalysts to enhance their catalytic activity and durability is crucial to commercialize proton exchange membrane fuel cells. The structural ordering and time evolution of ordered Pt3Fe2 intermetallic core-shell nanocatalysts for the oxygen reduction reaction that exhibit increased mass activity (228%) and an enhanced catalytic activity (155%) compared to Pt/C has been quantified using aberration-corrected scanning transmission electron microscopy. These catalysts were found to exhibit a static core-dynamic shell regime wherein, despite treating over 10,000 cycles, there is negligible decrease (9%) in catalytic activity and the ordered Pt3Fe2 core remained virtually intact while the Pt shell suffered a continuous enrichment. The existence of this regime was further confirmed by X-ray diffraction and the compositional analyses using energy-dispersive spectroscopy. With atomic-scale two-dimensional (2-D) surface relaxation mapping, we demonstrate that the Pt atoms on the surface are slightly relaxed with respect to bulk. The cycled nanocatalysts were found to exhibit a greater surface relaxation compared to noncycled catalysts. With 2-D lattice strain mapping, we show that the particle was about -3% strained with respect to pure Pt. While the observed enhancement in their activity is ascribed to such a strained lattice, our findings on the degradation kinetics establish that their extended catalytic durability is attributable to a sustained atomic order.

  19. Fermi energy dependence of the optical emission in core/shell InAs nanowire homostructures

    Science.gov (United States)

    Möller, M.; Oliveira, D. S.; Sahoo, P. K.; Cotta, M. A.; Iikawa, F.; Motisuke, P.; Molina-Sánchez, A.; de Lima, M. M., Jr.; García-Cristóbal, A.; Cantarero, A.

    2017-07-01

    InAs nanowires grown by vapor-liquid-solid (VLS) method are investigated by photoluminescence. We observe that the Fermi energy of all samples is reduced by ˜20 meV when the size of the Au nanoparticle used for catalysis is increased from 5 to 20 nm. Additional capping with a thin InP shell enhances the optical emission and does not affect the Fermi energy. The unexpected behavior of the Fermi energy is attributed to the differences in the residual donor (likely carbon) incorporation in the axial (low) and lateral (high incorporation) growth in the VLS and vapor-solid (VS) methods, respectively. The different impurity incorporation rate in these two regions leads to a core/shell InAs homostructure. In this case, the minority carriers (holes) diffuse to the core due to the built-in electric field created by the radial impurity distribution. As a result, the optical emission is dominated by the core region rather than by the more heavily doped InAs shell. Thus, the photoluminescence spectra and the Fermi energy become sensitive to the core diameter. These results are corroborated by a theoretical model using a self-consistent method to calculate the radial carrier distribution and Fermi energy for distinct diameters of Au nanoparticles.

  20. Dually fluorescent core-shell microgels for ratiometric imaging in live antigen-presenting cells.

    Directory of Open Access Journals (Sweden)

    Xianfeng Zhou

    Full Text Available Core-shell microgels containing sensors/dyes in a matrix were fabricated by two-stage free radical precipitation polymerization method for ratiometric sensing/imaging. The microgels composing of poly(N-isopropylacrylamide (PNIPAm shell exhibits a low critical solution temperature (LCST, underwent an entropically driven transition from a swollen state to a deswollen state, which exhibit a hydrodynamic radius of ∼ 450 nm at 25 °C (in vitro and ∼ 190 nm at 37 °C (in vivo. The microgel's ability of escaping from lysosome into cytosol makes the microgel be a potential candidate for cytosolic delivery of sensors/probes. Non-invasive imaging/sensing in Antigen-presenting cells (APCs was feasible by monitoring the changes of fluorescence intensity ratios. Thus, these biocompatible microgels-based imaging/sensing agents may be expected to expand current molecular imaging/sensing techniques into methods applicable to studies in vivo, which could further drive APC-based treatments.

  1. Novel highly dispersible, thermally stable core/shell proppants for geothermal applications

    Energy Technology Data Exchange (ETDEWEB)

    Childers, Ian M.; Endres, Mackenzie; Burns, Carolyne; Garcia, Benjamin J.; Liu, Jian; Wietsma, Thomas W.; Bonneville, Alain; Moore, Joseph; Leavy, Ian I.; Zhong, Lirong; Schaef, Herbert T.; Fu, Li; Wang, Hong-Fei; Fernandez, Carlos A.

    2017-11-01

    The use of proppants during reservoir stimulation in tight oil and gas plays requires the introduction of highly viscous fluids to transport the proppants (µm–mm) with the fracturing fluid. The highly viscous fluids required result in increased pump loads and energy costs. Furthermore, although proppant deployment with fracturing fluids is a standard practice for unconventional oil and gas stimulation operations, there are only a few examples in the US of the applying proppant technology to geothermal energy production. This is due to proppant dissolution, proppant flowback and loss of permeability associated with the extreme temperatures found in enhanced geothermal systems (EGS). This work demonstrates proof-of-concept of a novel, CO2-responsive, lightweight sintered-bauxite/polymer core/shell proppant. The polymer shell has two main roles; 1) increase the stability of the proppant dispersion in water without the addition of rheology modifiers, and 2) once at the fracture network react with CO2 to promote particle aggregation and prop fractures open. In this work, both of these roles are demonstrated together with the thermal and chemical stability of the materials showing the potential of these CO2-responsive proppants as an alternative proppant technology for geothermal and unconventional oil/gas applications.

  2. Core-Shell Microneedle Gel for Self-Regulated Insulin Delivery.

    Science.gov (United States)

    Wang, Jinqiang; Ye, Yanqi; Yu, Jicheng; Kahkoska, Anna R; Zhang, Xudong; Wang, Chao; Sun, Wujin; Corder, Ria D; Chen, Zhaowei; Khan, Saad A; Buse, John B; Gu, Zhen

    2018-03-27

    A bioinspired glucose-responsive insulin delivery system for self-regulation of blood glucose levels is desirable for improving health and quality of life outcomes for patients with type 1 and advanced type 2 diabetes. Here we describe a painless core-shell microneedle array patch consisting of degradable cross-linked gel for smart insulin delivery with rapid responsiveness and excellent biocompatibility. This gel-based device can partially dissociate and subsequently release insulin when triggered by hydrogen peroxide (H 2 O 2 ) generated during the oxidation of glucose by a glucose-specific enzyme covalently attached inside the gel. Importantly, the H 2 O 2 -responsive microneedles are coated with a thin-layer embedding H 2 O 2 -scavenging enzyme, thus mimicking the complementary function of enzymes in peroxisomes to protect normal tissues from injury caused by oxidative stress. Utilizing a chemically induced type 1 diabetic mouse model, we demonstrated that this smart insulin patch with a bioresponsive core and protective shell could effectively regulate the blood glucose levels within a normal range with improved biocompatibility.

  3. Multifunctional antitumor magnetite/chitosan-l-glutamic acid (core/shell) nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Daniela P. [University of Sao Paulo State, UNESP, Institute of Chemistry (Brazil); Ruiz, M. Adolfina; Gallardo, Visitacion [University of Granada, Department of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy (Spain); Zanoni, Maria Valnice B. [University of Sao Paulo State, UNESP, Institute of Chemistry (Brazil); Arias, Jose L., E-mail: jlarias@ugr.es [University of Granada, Department of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy (Spain)

    2011-09-15

    The development of anticancer drug delivery systems based on biodegradable nanoparticles has been intended to maximize the localization of chemotherapy agents within tumor interstitium, along with negligible drug distribution into healthy tissues. Interestingly, passive and active drug targeting strategies to cancer have led to improved nanomedicines with great tumor specificity and efficient chemotherapy effect. One of the most promising areas in the formulation of such nanoplatforms is the engineering of magnetically responsive nanoparticles. In this way, we have followed a chemical modification method for the synthesis of magnetite/chitosan-l-glutamic acid (core/shell) nanostructures. These magnetic nanocomposites (average size Almost-Equal-To 340 nm) exhibited multifunctional properties based on its capability to load the antitumor drug doxorubicin (along with an adequate sustained release) and its potential for hyperthermia applications. Compared to drug surface adsorption, doxorubicin entrapment into the nanocomposites matrix yielded a higher drug loading and a slower drug release profile. Heating characteristics of the magnetic nanocomposites were investigated in a high-frequency alternating magnetic gradient: a stable maximum temperature of 46 Degree-Sign C was successfully achieved within 40 min. To our knowledge, this is the first time that such kind of stimuli-sensitive nanoformulation with very important properties (i.e., magnetic targeting capabilities, hyperthermia, high drug loading, and little burst drug release) has been formulated for combined antitumor therapy against cancer.

  4. Reaction-Driven Restructuring of Rh-Pd and Pt-Pd Core-Shell Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Feng; Grass, Michael E.; Zhang, Yawen; Butcher, Derek R.; Renzas, James R.; Liu, Zhi; Chung, Jen Y.; Mun, Bongjin S.; Salmeron, Miquel; Somorjai, Gabor A.

    2009-06-17

    The structure and composition of core-shell Rh{sub 0.5}Pd{sub 0.5} and Pt{sub 0.5}Pd{sub 0.5} nanoparticle catalysts were studied in situ, during oxidizing, reducing, and catalytic reactions involving NO, O{sub 2}, CO, and H{sub 2} using X-ray photoelectron spectroscopy in the Torr pressure range. The Rh{sub 0.5}Pd{sub 0.5} nanoparticles undergo dramatic and reversible changes in composition and chemical state in response to oxidizing or reducing conditions. Under oxidizing conditions the Rh atoms segregate to the shell region while in reducing atmospheres the Pd atoms diffuse to the shell region. In contrast no significant segregation of Pd or Pt atoms was found in Pt{sub 0.5}Pd{sub 0.5} nanoparticles. The distinct behavior in restructuring and chemical response of Rh{sub 0.5}Pd{sub 0.5} and Pt{sub 0.5}Pd{sub 0.5} nanoparticle catalysts under the same reaction conditions illustrates the flexibility and tunability of the structure of bimetallic nanoparticle catalysts during catalytic reactions.

  5. Modifying Cement Hydration with NS@PCE Core-Shell Nanoparticles

    Directory of Open Access Journals (Sweden)

    Yue Gu

    2017-01-01

    Full Text Available It is generally accepted that fine particles could accelerate cement hydration process, or, more specifically, this accelerating effect can be attributed to additional surface area introduced by fine particles. In addition to this view, the surface state of fine particles is also an important factor, especially for nanoparticles. In the previous study, a series of nano-SiO2-polycarboxylate superplasticizer core-shell nanoparticles (NS@PCE were synthesized, which have a similar particle size distribution but different surface properties. In this study, the impact of NS@PCE on cement hydration was investigated by heat flow calorimetry, mechanical property measurement, XRD, and SEM. Results show that, among a series of NS@PCE, NS@PCE-2 with a moderate shell-core ratio appeared to be more effective in accelerating cement hydration. As dosage increases, the efficiency of NS@PCE-2 would reach a plateau which is quantified by various characteristic values. Compressive strength results indicate that strength has a linear correlation with cumulative heat release. A hypothesis was proposed to explain the modification effect of NS@PCE, which highlights a balance between initial dispersion and pozzolanic reactivity. This paper provides a new understanding for the surface modification of supplementary cementitious materials and their application and also sheds a new light on nano-SiO2 for optimizing cement-based materials.

  6. Organic-Inorganic Hydrophobic Nanocomposite Film with a Core-Shell Structure

    Directory of Open Access Journals (Sweden)

    Peng Liu

    2016-12-01

    Full Text Available A method to prepare novel organic-inorganic hydrophobic nanocomposite films was proposed by a site-specific polymerization process. The inorganic part, the core of the nanocomposite, is a ternary SiO2–Al2O3–TiO2 nanoparticles, which is grafted with methacryloxy propyl trimethoxyl silane (KH570, and wrapped by fluoride and siloxane polymers. The synthesized samples are characterized by transmission electron microscopy (TEM, Fourier transform infrared (FTIR spectrscopy, X-ray diffractometry (XRD, contact angle meter (CA, and scanning electron microscope (SEM. The results indicate that the novel organic-inorganic hydrophobic nanocomposite with a core-shell structure was synthesized successfully. XRD analysis reveals the nanocomposite film has an amorphous structure, and FTIR analysis indicates the nanoparticles react with a silane coupling agent (methacryloxy propyl trimethoxyl silane KH570. Interestingly, the morphology of the nanoparticle film is influenced by the composition of the core. Further, comparing with the film synthesized by silica nanoparticles, the film formed from SiO2–Al2O3–TiO2 nanoparticles has higher hydrophobic performance, i.e., the contact angle is greater than 101.7°. In addition, the TEM analysis reveals that the crystal structure of the particles can be changed at high temperatures.

  7. Core-shell homojunction silicon vertical nanowire tunneling field-effect transistors

    Science.gov (United States)

    Yoon, Jun-Sik; Kim, Kihyun; Baek, Chang-Ki

    2017-01-01

    We propose three-terminal core-shell (CS) silicon vertical nanowire tunneling field-effect transistors (TFETs), which can be fabricated by conventional CMOS technology. CS TFETs show lower subthreshold swing (SS) and higher on-state current than conventional TFETs through their high surface-to-volume ratio, which increases carrier-tunneling region with no additional device area. The on-state current can be enhanced by increasing the nanowire height, decreasing equivalent oxide thickness (EOT) or creating a nanowire array. The off-state current is also manageable for power saving through selective epitaxial growth at the top-side nanowire region. CS TFETs with an EOT of 0.8 nm and an aspect ratio of 20 for the core nanowire region provide the largest drain current ranges with point SS values below 60 mV/dec and superior on/off current ratio under all operation voltages of 0.5, 0.7, and 1.0 V. These devices are promising for low-power applications at low fabrication cost and high device density.

  8. Core/shell poly(ethylene oxide)/Eudragit fibers for site-specific release.

    Science.gov (United States)

    Jia, Dong; Gao, Yanshan; Williams, Gareth R

    2017-05-15

    Electrospinning was used to prepare core/shell fibers containing the active pharmaceutical ingredients indomethacin (IMC) or mebeverine hydrochloride (MB-HCl). The shell of the fibers was fabricated from the pH sensitive Eudragit S100 polymer, while the drug-loaded core was based on the mucoadhesive poly(ethylene oxide) (PEO). Three different drug loadings (from 9 to 23% (w/w) of the core mass) were prepared, and for MB-HCl two different molecular weights of PEO were explored. The resultant fibers generally comprise smooth cylinders, although in some cases defects such as surface particles or flattened or merged fibers were visible. Transmission electron microscopy showed all the systems to have clear core and shell compartments. The drugs are present in the amorphous physical form in the fibers. Dissolution tests found that the fibers can effectively prevent release in acidic conditions representative of the stomach, particularly for the acidic indomethacin. After transfer to a pH 7.4 medium, sustained release over between 6 and 22h is observed. Given the mucoadhesive nature of the PEO core, after dissolution of the shell the fibers will be able to adhere to the walls of the intestinal tract and give sustained local drug release. This renders them promising for the treatment of conditions such as irritable bowel disease and colon cancer. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Metal (Hydr)oxides@Polymer Core-Shell Strategy to Metal Single-Atom Materials.

    Science.gov (United States)

    Zhang, Maolin; Wang, Yang-Gang; Chen, Wenxing; Dong, Juncai; Zheng, Lirong; Luo, Jun; Wan, Jiawei; Tian, Shubo; Cheong, Weng-Chon; Wang, Dingsheng; Li, Yadong

    2017-08-16

    Preparing metal single-atom materials is currently attracting tremendous attention and remains a significant challenge. Herein, we report a novel core-shell strategy to synthesize single-atom materials. In this strategy, metal hydroxides or oxides are coated with polymers, followed by high-temperature pyrolysis and acid leaching, metal single atoms are anchored on the inner wall of hollow nitrogen-doped carbon (CN) materials. By changing metal precursors or polymers, we demonstrate the successful synthesis of different metal single atoms dispersed on CN materials (SA-M/CN, M = Fe, Co, Ni, Mn, FeCo, FeNi, etc.). Interestingly, the obtained SA-Fe/CN exhibits much higher catalytic activity for hydroxylation of benzene to phenol than Fe nanoparticles/CN (45% vs 5% benzene conversion). First-principle calculations further reveal that the high reactivity originates from the easier formation of activated oxygen species at the single Fe site. Our methodology provides a convenient route to prepare a variety of metal single-atom materials representing a new class of catalysts.

  10. Synthesis, morphology and rheology of core-shell silicone acrylic emulsion stabilized with polymerisable surfactant

    Directory of Open Access Journals (Sweden)

    2010-11-01

    Full Text Available Core-shell silicone acrylic emulsions with 3-methacryloxypropyl trimethoxysilane (MPTS in the shell were prepared by seeded polymerization with the assistance of polymerisable maleate surfactant (MT. Fourier transform infrared (FT-IR demonstrated the incorporation of polymerisable surfactant in copolymer. It was found that small amount of octadecyl acrylate was beneficial to emulsion stability with decreasing the particle size from 194.6 to 165.7 nm. It was also found that the particle size increased from 165.7 to 242.9 nm with the increase of MPTS concentration. Furthermore, rheological measurement indicated that the emulsion was endowed with pseudoplasticity. At low shear rate, marginal reduction in viscosity was detected when MPTS concentration increased to 2%, while great increase in viscosity was observed with higher MPTS concentration, the interaction force among emulsion particles became the predominant factor instead of particle size. In addition, better water resistance was observed when MT concentration was lower than 1.5%, and MPTS concentration higher than 2%. Moreover, surface roughness was increased with MPTS addition, the crosslinking among core and shell reconstructed the surface morphology of film.

  11. Preparation, Properties, and Self-Assembly Behavior of PTFE-Based Core-Shell Nanospheres

    Directory of Open Access Journals (Sweden)

    Katia Sparnacci

    2012-01-01

    Full Text Available Nanosized PTFE-based core-shell particles can be prepared by emulsifier-free seed emulsion polymerization technique starting from spherical or rod-like PTFE seeds of different size. The shell can be constituted by the relatively high Tg polystyrene and polymethylmethacrylate as well as by low Tg polyacrylic copolymers. Peculiar thermal behavior of the PTFE component is observed due to the high degree of PTFE compartmentalization. A very precise control over the particle size can be exerted by properly adjusting the ratio between the monomers and the PTFE seed. In addition, the particle size distribution self-sharpens as the ratio monomer/PTFE increases. Samples with uniformity ratios suited to build 2D and 3D colloidal crystals are easily prepared. In particular, 2D colloidal crystal of spheres leads to very small 2D nanostructuration, useful for the preparation of masks with a combination of nanosphere lithography and reactive ion etching. 3D colloidal crystals were also obtained featuring excellent opal quality, which is a direct consequence of the monodispersity of colloids used for their growth.

  12. Facile and green synthesis of core-shell structured magnetic chitosan submicrospheres and their surface functionalization.

    Science.gov (United States)

    Li, Yiya; Yuan, Dongying; Dong, Mingjie; Chai, Zhihua; Fu, Guoqi

    2013-09-17

    Submicrometer-sized magnetite colloid nanocrystal clusters (MCNCs) provide a new avenue for constructing uniformly sized and highly magnetic composite submicrospheres. Herein, a facile and eco-friendly method is described for the synthesis of Fe3O4@poly(acrylic acid) (PAA)/chitosan (CS) core-shell submicrospheres using MCNCs bearing carboxyl groups as the magnetic cores. It is based on the self-assembly of positively charged CS chains on the surface of the oppositely charged MCNCs dispersed in the aqueous solution containing acrylic acid (AA) and a cross-linker N,N'-methylenebis(acrylamide) (MBA), followed by radical induced cross-linking copolymerization of AA and MBA along the CS chains. The resulting polymer shell comprises a medium shell of cross-linked PAA/CS polyelectrolyte complexes and an outer shell of protonated CS chains. It was found that the shell thickness could be tuned by varying either the concentration of radical initiator or the molar ratio of AA to aminoglucoside units of CS. To the surface of thus obtained Fe3O4@PAA/CS particles, Au nanoparticles, a variety of functional groups such as fluorescein, carboxyl, quaternary ammonium, and aliphatic bromide, and even functional polymer chains were successfully introduced. Therefore, such Fe3O4@PAA/CS submicrospheres may be used as versatile magnetic functional scaffolds in biorelated areas like bioseparation and medical assay, considering the unique features of CS like nontoxicity and biocompatibility.

  13. Lattice-Strain Control of Exceptional Activity in Dealloyed Core-Shell Fuel Cell Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Strasser, Peter

    2011-08-19

    We present a combined experimental and theoretical approach to demonstrate how lattice strain can be used to continuously tune the catalytic activity of the oxygen reduction reaction (ORR) on bimetallic nanoparticles that have been dealloyed. The sluggish kinetics of the ORR is a key barrier to the adaptation of fuel cells and currently limits their widespread use. Dealloyed Pt-Cu bimetallic nanoparticles, however, have been shown to exhibit uniquely high reactivity for this reaction. We first present evidence for the formation of a core-shell structure during dealloying, which involves removal of Cu from the surface and subsurface of the precursor nanoparticles. We then show that the resulting Pt-rich surface shell exhibits compressive strain that depends on the composition of the precursor alloy. We next demonstrate the existence of a downward shift of the Pt d-band, resulting in weakening of the bond strength of intermediate oxygenated species due to strain. Finally, we combine synthesis, strain, and catalytic reactivity in an experimental/theoretical reactivity-strain relationship which provides guidelines for the rational design of strained oxygen reduction electrocatalysts. The stoichiometry of the precursor, together with the dealloying conditions, provides experimental control over the resulting surface strain and thereby allows continuous tuning of the surface electrocatalytic reactivity - a concept that can be generalized to other catalytic reactions.

  14. In-vitro cytotoxicity and cellular uptake studies of luminescent functionalized core-shell nanospheres

    Directory of Open Access Journals (Sweden)

    Anees A. Ansari

    2017-09-01

    Full Text Available Monodispersed luminescent functionalized core-shell nanospheres (LFCSNs were successfully synthesized and investigated for their cyto-toxic effect on human liver hepatocellular carcinoma cell line (HepG2 cells by adopting MTT, DNA Ladder, TUNEL assay and qPCR based gene expressions through mRNA quantifications. The TUNEL and DNA ladder assays suggested an insignificant apoptosis in HepG2 cells due to the LFCSNs treatment. Further, the qPCR results also show that the mRNA expressions of cell cycle checkpoint gene p53 and apoptosis related gene (caspase-9 was up-regulated, while the antiapoptotic gene BCl-2 and apoptosis related genes FADD and CAS-3 (apoptosis effecter gene were down-regulated in the LFCSNs treated cells. The nanospheres that were loaded into the cells confirm their intracellular uptake by light and fluorescent spectro-photometry and microscopy imaging analysis. The loaded nanospheres demonstrate an absolute resistance to photo-bleaching, which were applied for dynamic imaging to real-time tracking in-vitro cell migratory activity for continuous 24 and 48 h durations using a time-lapsed fluorescent microscope. These properties of LFCSNs could therefore promote applications in the area of fluorescent protein biolabeling and drug-delivery.

  15. Light neutron-rich hypernuclei from the importance-truncated no-core shell model

    Science.gov (United States)

    Wirth, Roland; Roth, Robert

    2018-04-01

    We explore the systematics of ground-state and excitation energies in singly-strange hypernuclei throughout the helium and lithium isotopic chains - from He5Λ to He11Λ and from Li7Λ to Li12Λ - in the ab initio no-core shell model with importance truncation. All calculations are based on two- and three-baryon interaction from chiral effective field theory and we employ a similarity renormalization group transformation consistently up to the three-baryon level to improve the model-space convergence. While the absolute energies of hypernuclear states show a systematic variation with the regulator cutoff of the hyperon-nucleon interaction, the resulting neutron separation energies are very stable and in good agreement with available data for both nucleonic parents and their daughter hypernuclei. We provide predictions for the neutron separation energies and the spectra of neutron-rich hypernuclei that have not yet been observed experimentally. Furthermore, we find that the neutron drip lines in the helium and lithium isotopic chains are not changed by the addition of a hyperon.

  16. Investigation of Photovoltaic Properties of Single Core-Shell GaN/InGaN Wires.

    Science.gov (United States)

    Messanvi, A; Zhang, H; Neplokh, V; Julien, F H; Bayle, F; Foldyna, M; Bougerol, C; Gautier, E; Babichev, A; Durand, C; Eymery, J; Tchernycheva, M

    2015-10-07

    We report the investigation of the photovoltaic properties of core-shell GaN/InGaN wires. The radial structure is grown on m-plane {11̅00} facets of self-assembled c̅-axis GaN wires elaborated by metal-organic vapor phase epitaxy (MOVPE) on sapphire substrates. The conversion efficiency of wires with radial shell composed of thick In0.1Ga0.9N layers and of 30× In0.18Ga0.82N/GaN quantum wells are compared. We also investigate the impact of the contact nature and layout on the carrier collection and photovoltaic performances. The contact optimization results in an improved conversion efficiency of 0.33% and a fill factor of 83% under 1 sun (AM1.5G) on single wires with a quantum well-based active region. Photocurrent spectroscopy demonstrates that the response ascribed to the absorption of InGaN/GaN quantum wells appears at wavelengths shorter than 440 nm.

  17. Preparation, Properties, and Self-Assembly Behavior of PTFE-Based Core-Shell Nanospheres

    International Nuclear Information System (INIS)

    Sparnacci, K.; Antonioli, D.; Deregibus, S.; Laus, M.; Zuccheri, G.; Boarino, L.; De Leo, N.; Comoretto, D.

    2012-01-01

    Nano sized PTFE-based core-shell particles can be prepared by emulsifier-free seed emulsion polymerization technique starting from spherical or rod-like PTFE seeds of different size. The shell can be constituted by the relatively high Tg polystyrene and polymethylmethacrylate as well as by low Tg polyacrylic copolymers. Peculiar thermal behavior of the PTFE component is observed due to the high degree of PTFE compartmentalization. A very precise control over the particle size can be exerted by properly adjusting the ratio between the monomers and the PTFE seed. In addition, the particle size distribution self-sharpens as the ratio monomer/PTFE increases. Samples with uniformity ratios suited to build 2D and 3D colloidal crystals are easily prepared. In particular, 2D colloidal crystal of spheres leads to very small 2D nanostructuration, useful for the preparation of masks with a combination of nanosphere lithography and reactive ion etching. 3D colloidal crystals were also obtained featuring excellent opal quality, which is a direct consequence of the monodispersity of colloids used for their growth.

  18. Synthesis of CeO2-based core/shell nanoparticles with high oxygen storage capacity

    Science.gov (United States)

    Uzunoglu, Aytekin; Kose, Dursun Ali; Stanciu, Lia A.

    2017-07-01

    Ceria plays a key role in various applications including sensing and catalysis owing to its high oxygen storage capacity (OSC). The aim of this work is to prepare novel MO x /CeO2 (M: Zr, Ti, Cu) metal oxide systems with core/shell structures using a facile two-step chemical precipitation method. The synthesized nanoparticles were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and N2 adsorption methods. The OSC property of the samples was evaluated using TGA analysis conducted at 600 °C under reductive (5% H2/Ar) and oxidative (synthetic air) environments. The OSCs of the samples were found to be 130, 253, and 2098 µmol-O2/g for ZrO2/CeO2, TiO2/CeO2, and CuO/CeO2, respectively. Effects of heat treatment on the physical and redox properties of the samples were also evaluated. In this regard, the samples were exposed to 500 °C for 5 h under ambient environment. It was observed that the heat treatment induced the formation of mixed metal oxide alloys and the BET surface area of the samples diminished significantly. The OSC of the samples, however, did not experience any significant chance, which was attributed to the compensation of the loss in the surface area by the alloy formation after the heat treatment.

  19. Reaction rate of a composite core-shell nanoreactor with multiple nanocatalysts.

    Science.gov (United States)

    Galanti, Marta; Fanelli, Duccio; Angioletti-Uberti, Stefano; Ballauff, Matthias; Dzubiella, Joachim; Piazza, Francesco

    2016-07-27

    We present a detailed theory for the total reaction rate constant of a composite core-shell nanoreactor, consisting of a central solid core surrounded by a hydrogel layer of variable thickness, where a given number of small catalytic nanoparticles are embedded at prescribed positions and are endowed with a prescribed surface reaction rate constant. Besides the precise geometry of the assembly, our theory accounts explicitly for the diffusion coefficients of the reactants in the hydrogel and in the bulk as well as for their transfer free energy jump upon entering the hydrogel shell. Moreover, we work out an approximate analytical formula for the overall rate constant, which is valid in the physically relevant range of geometrical and chemical parameters. We discuss in depth how the diffusion-controlled part of the rate depends on the essential variables, including the size of the central core. In particular, we derive some simple rules for estimating the number of nanocatalysts per nanoreactor for an efficient catalytic performance in the case of small to intermediate core sizes. Our theoretical treatment promises to provide a very useful and flexible tool for the design of superior performing nanoreactor geometries with optimized nanoparticle load.

  20. Förster Resonance Energy Transfer between Core/Shell Quantum Dots and Bacteriorhodopsin

    Directory of Open Access Journals (Sweden)

    Mark H. Griep

    2012-01-01

    Full Text Available An energy transfer relationship between core-shell CdSe/ZnS quantum dots (QDs and the optical protein bacteriorhodopsin (bR is shown, demonstrating a distance-dependent energy transfer with 88.2% and 51.1% of the QD energy being transferred to the bR monomer at separation distances of 3.5 nm and 8.5 nm, respectively. Fluorescence lifetime measurements isolate nonradiative energy transfer, other than optical absorptive mechanisms, with the effective QD excited state lifetime reducing from 18.0 ns to 13.3 ns with bR integration, demonstrating the Förster resonance energy transfer contributes to 26.1% of the transferred QD energy at the 3.5 nm separation distance. The established direct energy transfer mechanism holds the potential to enhance the bR spectral range and sensitivity of energies that the protein can utilize, increasing its subsequent photocurrent generation, a significant potential expansion of the applicability of bR in solar cell, biosensing, biocomputing, optoelectronic, and imaging technologies.

  1. Comprehensive analyses of core-shell InGaN/GaN single nanowire photodiodes

    Science.gov (United States)

    Zhang, H.; Guan, N.; Piazza, V.; Kapoor, A.; Bougerol, C.; Julien, F. H.; Babichev, A. V.; Cavassilas, N.; Bescond, M.; Michelini, F.; Foldyna, M.; Gautier, E.; Durand, C.; Eymery, J.; Tchernycheva, M.

    2017-12-01

    Single nitride nanowire core/shell n-p photodetectors are fabricated and analyzed. Nanowires consisting of an n-doped GaN stem, a radial InGaN/GaN multiple quantum well system and a p-doped GaN external shell were grown by catalyst-free metal-organic vapour phase epitaxy on sapphire substrates. Single nanowires were dispersed and the core and the shell regions were contacted with a metal and an ITO deposition, respectively, defined using electron beam lithography. The single wire photodiodes present a response in the visible to UV spectral range under zero external bias. The detector operation speed has been analyzed under different bias conditions. Under zero bias, the  -3 dB cut-off frequency is ~200 Hz for small light modulations. The current generation was modeled using non-equilibrium Green function formalism, which evidenced the importance of phonon scattering for carrier extraction from the quantum wells.

  2. SANS study of PLA-mPEG core-shell structured nanoparticles for targeted drug delivery

    International Nuclear Information System (INIS)

    Wang, Yichao; Li, Puwang; Kong, Lingxue

    2009-01-01

    Full text: Colorectal cancer (CRC), referring to cancers that affect the colon and the rectum, is the third most common form of cancer and second leading cause of cancer-related death in the western world (Fortina et al 2007). Currently there are many therapeutic methods, however, most of the traditional methods have enormous side effects, partly because they significantly damage the healthy cells. Therefore, there is an urgent demand to develop a more effective drug delivery mechanism to alleviate these side effects. PLA-mPEG core-shell nanoparticles will be used to deliver the therapeutic agent to the specific area. Materials preparation will include the deuteration of L-Iactic acid monomer and ring opening polymerization to prepare the block copolymer. The drug loaded nanoparticles will be fabricated by double emulsion and solvent evaporation method. The processing parameters will be varied and optimized to maximize the encapsulation efficiency and drug loading. With SANS, we will identify the internal structure of PLA-mPEG nanoparticles with a diameter of 50- 1 00 n m, an important aspect to control the release of the drugs. At the same time, we will relate how the different process parameters affect the core size. The relationship between drug release profile and structure of the encapsulation materials will also be studied using the data from SANS.

  3. Characterization of core-shell nanoparticles by small angle neutron scattering

    International Nuclear Information System (INIS)

    Strunz, P.; Mukherji, D.; Pigozzi, G.; Gilles, R.; Geue, T.; Pranzas, K.

    2007-01-01

    The Ni 3 Si-type nanoparticles dispersed in a mixture of H 2 O/D 2 O were characterised by SANS using the contrast variation method. The existence of a core-shell structure in the nanoparticles with a Ni 3 Si(Al) core and amorphous SiO x shell is confirmed by the SANS measurements. The nanoparticles were produced by extracting precipitates from a bulk Ni-13.3Si-2Al (at. %) alloy using electrochemical phase separation technique and were pre-characterised by X-ray diffraction and transmission electron microscopy. By comparing the precipitate morphology in the Ni-Si-Al alloy with the extracted nanoparticles in the SANS measurements, it is clearly established that the precipitates shape and size are unaffected by the extraction process and that the amorphous shell forms on top of the particle core. However, the present measurement could not confirm or exclude the presence of H atoms in the shell structure. (orig.)

  4. Self-Assembly of Fluorescent Hybrid Core-Shell Nanoparticles and Their Application.

    Science.gov (United States)

    Wang, Chun; Tang, Fu; Wang, Xiaoyu; Li, Lidong

    2015-06-24

    In this work, a fluorescent hybrid core-shell nanoparticle was prepared by coating a functional polymer shell onto silver nanoparticles via a facile one-pot method. The biomolecule poly-L-lysine (PLL) was chosen as the polymer shell and assembled onto the silver core via the amine-reactive cross-linker, 3,3'-dithiobis(sulfosuccinimidylpropionate). The fluorescent anticancer drug, doxorubicin, was incorporated into the PLL shell through the same linkage. As the cross-linker possesses a thiol-cleavable disulfide bond, disassembly of the PLL shell was observed in the presence of glutathione, leading to controllable doxorubicin release. The silver core there provided an easily modified surface to facilitate the shell coating and ensures the efficient separation of as-prepared nanoparticles from their reaction mixture through centrifugation. Cell assays show that the prepared hybrid fluorescent nanoparticles can internalize into cells possessing excellent biocompatibility prior to the release of doxorubicin, terminating cancer cells efficiently as the doxorubicin is released at the intracellular glutathione level. Such properties are important for designing smart containers for target drug delivery and cellular imaging.

  5. A novel method to make regenerable core-shell calcium-based sorbents

    Energy Technology Data Exchange (ETDEWEB)

    F.J. Liu; K.S. Chou; Y.K. Huang [National United University, Miao-Li (Taiwan). Department of Chemical Engineering

    2006-04-15

    A sorbent having a calcium oxide core and a clay shell was prepared and shown to be capable of reusable applications in absorption and desorption processes for carbon dioxide. The novelty of this sorbent is that only calcium carbonate and clay are used for its preparation with water as a binder. A two-step granulation procedure is used to get the core and then another step to coat the shell layer with the clay powder. A repeated wet-and-dry procedure probably makes the core porous yet strong enough to serve as a sorbent. The pellet is then calcined at 1200{sup o}C for 2 h to reach its final structure. The core-shell pellets have an overall diameter of 4.4 mm with average shell thickness of 0.45 mm, crush load of 35 N and attrition index of 0.035 wt%/h. These results indicate that the pellets will probably be capable of withstanding the stress in future applications. Carbon dioxide absorption at or below 300{sup o}C showed a maximum weight gain of 38% for our pellets. Finally, desorption in nitrogen at 80{sup o}C can restore the pellet to its original state and hence it is ready for re-use as a sorbent.

  6. PbSe-Based Colloidal Core/Shell Heterostructures for Optoelectronic Applications

    Science.gov (United States)

    Zaiats, Gary; Yanover, Diana; Vaxenburg, Roman; Tilchin, Jenya; Sashchiuk, Aldona; Lifshitz, Efrat

    2014-01-01

    Lead-based (IV–VI) colloidal quantum dots (QDs) are of widespread scientific and technological interest owing to their size-tunable band-gap energy in the near-infrared optical region. This article reviews the synthesis of PbSe-based heterostructures and their structural and optical investigations at various temperatures. The review focuses on the structures consisting of a PbSe core coated with a PbSexS1–x (0 ≤ x ≤ 1) or CdSe shell. The former-type shells were epitaxially grown on the PbSe core, while the latter-type shells were synthesized using partial cation-exchange. The influence of the QD composition and the ambient conditions, i.e., exposure to oxygen, on the QD optical properties, such as radiative lifetime, Stokes shift, and other temperature-dependent characteristics, was investigated. The study revealed unique properties of core/shell heterostructures of various compositions, which offer the opportunity of fine-tuning the QD electronic structure by changing their architecture. A theoretical model of the QD electronic band structure was developed and correlated with the results of the optical studies. The review also outlines the challenges related to potential applications of colloidal PbSe-based heterostructures. PMID:28788244

  7. Plasmonic nanodiamonds: targeted core-shell type nanoparticles for cancer cell thermoablation.

    Science.gov (United States)

    Rehor, Ivan; Lee, Karin L; Chen, Kevin; Hajek, Miroslav; Havlik, Jan; Lokajova, Jana; Masat, Milan; Slegerova, Jitka; Shukla, Sourabh; Heidari, Hamed; Bals, Sara; Steinmetz, Nicole F; Cigler, Petr

    2015-02-18

    Targeted biocompatible nanostructures with controlled plasmonic and morphological parameters are promising materials for cancer treatment based on selective thermal ablation of cells. Here, core-shell plasmonic nanodiamonds consisting of a silica-encapsulated diamond nanocrystal coated in a gold shell are designed and synthesized. The architecture of particles is analyzed and confirmed in detail using electron tomography. The particles are biocompatibilized using a PEG polymer terminated with bioorthogonally reactive alkyne groups. Azide-modified transferrin is attached to these particles, and their high colloidal stability and successful targeting to cancer cells overexpressing the transferrin receptor are demonstrated. The particles are nontoxic to the cells and they are readily internalized upon binding to the transferrin receptor. The high plasmonic cross section of the particles in the near-infrared region is utilized to quantitatively ablate the cancer cells with a short, one-minute irradiation by a pulse 750-nm laser. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Rough surface Au@Ag core-shell nanoparticles to fabricating high sensitivity SERS immunochromatographic sensors.

    Science.gov (United States)

    Fu, Qiangqiang; Liu, Hongwu Liu; Wu, Ze; Liu, An; Yao, Cuize; Li, Xiuqing; Xiao, Wei; Yu, Shiting; Luo, Zhi; Tang, Yong

    2015-11-14

    Immunochromatographic sensors (ICSs) are inexpensive, simple, portable, and robust, thus making ICSs commonplace in clinical diagnoses, food testing, and environmental monitoring. However, commonly used gold nanoparticles (AuNPs) ICSs have low sensitivity. Therefore, we developed highly sensitive surface enhanced Raman scattering (SERS) ICSs. To enhance the sensitivity of SERS ICSs, rough surface core-shell Au@Ag nanoparticles (RSAu@AgNPs) were prepared by coating silver on the surface of gold nanoflowers (AuNFs). Then these nanoparticles were used as SERS substrate in the SERS ICSs, after which the SERS ICSs were implemented to detect haemoglobin and heavy metal cadmium ion (Cd(2+)). The limit of detection (LOD) of the SERS ICSs for detecting haemoglobin was 8 ng/mL, and the linear range of the SERS ICSs was from 31.3 to 2000 ng/mL. The LOD of the SERS ICSs for detecting Cd(2+) was 0.05 ng/mL and the linear analysis range was from 0.05 to 25 ng/mL. The cross reactivity of the SERS ICSs was studied and results showed that the SERS ICSs exhibited highly specific for detection of haemoglobin and Cd(2+), respectively. The SERS ICSs were then used to detect haemoglobin (spiked in serum and in stool) and Cd(2+) (spiked in tap water, river water, and soil leaching water), and the results showed high recovery. These characteristics indicated that SERS ICSs were ideal tools for clinical diagnosis and environmental pollution monitoring.

  9. Nanoscale semiconductor-insulator-metal core/shell heterostructures: facile synthesis and light emission.

    Science.gov (United States)

    Li, Gong Ping; Chen, Rui; Guo, Dong Lai; Wong, Lai Mun; Wang, Shi Jie; Sun, Han Dong; Wu, Tom

    2011-08-01

    Controllably constructing hierarchical nanostructures with distinct components and designed architectures is an important theme of research in nanoscience, entailing novel but reliable approaches of bottom-up synthesis. Here, we report a facile method to reproducibly create semiconductor-insulator-metal core/shell nanostructures, which involves first coating uniform MgO shells onto metal oxide nanostructures in solution and then decorating them with Au nanoparticles. The semiconductor nanowire core can be almost any material and, herein, ZnO, SnO(2) and In(2)O(3) are used as examples. We also show that linear chains of short ZnO nanorods embedded in MgO nanotubes and porous MgO nanotubes can be obtained by taking advantage of the reduced thermal stability of the ZnO core. Furthermore, after MgO shell-coating and the appropriate annealing treatment, the intensity of the ZnO near-band-edge UV emission becomes much stronger, showing a 25-fold enhancement. The intensity ratio of the UV/visible emission can be increased further by decorating the surface of the ZnO/MgO nanowires with high-density plasmonic Au nanoparticles. These heterostructured semiconductor-insulator-metal nanowires with tailored morphologies and enhanced functionalities have great potential for use as nanoscale building blocks in photonic and electronic applications. This journal is © The Royal Society of Chemistry 2011

  10. Core-shell nanocarriers with high paclitaxel loading for passive and active targeting

    Science.gov (United States)

    Jin, Zhu; Lv, Yaqi; Cao, Hui; Yao, Jing; Zhou, Jianping; He, Wei; Yin, Lifang

    2016-06-01

    Rapid blood clearance and premature burst release are inherent drawbacks of conventional nanoparticles, resulting in poor tumor selectivity. iRGD peptide is widely recognized as an efficient cell membrane penetration peptide homing to αVβ3 integrins. Herein, core-shell nanocapsules (NCs) and iRGD-modified NCs (iRGD-NCs) with high drug payload for paclitaxel (PTX) were prepared to enhance the antitumor activities of chemotherapy agents with poor water solubility. Improved in vitro and in vivo tumor targeting and penetration were observed with NCs and iRGD-NCs; the latter exhibited better antitumor activity because iRGD enhanced the accumulation and penetration of NCs in tumors. The NCs were cytocompatible, histocompatible, and non-toxic to other healthy tissues. The endocytosis of NCs was mediated by lipid rafts in an energy-dependent manner, leading to better cytotoxicity of PTX against cancer cells. In contrast with commercial product, PTX-loaded NCs (PTX-NCs) increased area under concentration-time curve (AUC) by about 4-fold, prolonged mean resident time (MRT) by more than 8-fold and reduced the elimination rate constant by greater than 68-fold. In conclusion, the present nanocarriers with high drug-loading capacity represent an efficient tumor-targeting drug delivery system with promising potential for cancer therapy.

  11. Catalysts characteristics of Ni/YSZ core-shell according to plating conditions using electroless plating

    Science.gov (United States)

    Park, Hyun-Wook; Jang, Jae-Won; Lee, Young-Jin; Kim, Jin-Ho; Jeon, Dae-Woo; Lee, Jong-Heun; Hwang, Hae-jin; Lee, Mi-Jai

    2017-11-01

    This study aims to develop an anode catalyst for a solid oxide fuel cell (SOFC) using electroless nickel plating. We have proposed a new method for electroless plating of Ni metal on yttria-stabilized zirconia (YSZ) particles. We examine the uniformity of the Ni layer on the plated core-shell powder, in addition to the content of Ni and the reproducibility of the plating. We have also evaluated the carbon deposition rate and characteristics of the SOFC anode catalyst. To synthesize Ni-plated YSZ particles, the plated powder is heat-treated at 1200 °C. The resultant particles, which have an average size of 50 μm, were subsequently used in the experiment. The size of the Ni particles and the Ni content both increase with increasing plating temperature and plating time. The X-ray diffraction pattern reveals the growth of Ni particles. After heat-treatment, Ni is oxidized to NiO, leading to the co-existence of Ni and NiO; Ni3P is also observed due to the presence of phosphorous in the plating solution. Following heat treatment for 1 h at 1200 °C, Ni is mostly oxidized to NiO. The carbon deposition rate of the reference YSZ powder is 135%, while that of the Ni-plated YSZ is 1%-6%.

  12. Reinforcement of Natural Rubber with Core-Shell Structure Silica-Poly(Methyl Methacrylate Nanoparticles

    Directory of Open Access Journals (Sweden)

    Qinghuang Wang

    2012-01-01

    Full Text Available A highly performing natural rubber/silica (NR/SiO2 nanocomposite with a SiO2 loading of 2 wt% was prepared by combining similar dissolve mutually theory with latex compounding techniques. Before polymerization, double bonds were introduced onto the surface of the SiO2 particles with the silane-coupling agent. The core-shell structure silica-poly(methyl methacrylate, SiO2-PMMA, nanoparticles were formed by grafting polymerization of MMA on the surface of the modified SiO2 particles via in situ emulsion, and then NR/SiO2 nanocomposite was prepared by blending SiO2-PMMA and PMMA-modified NR (NR-PMMA. The Fourier transform infrared spectroscopy results show that PMMA has been successfully introduced onto the surface of SiO2, which can be well dispersed in NR matrix and present good interfacial adhesion with NR phase. Compared with those of pure NR, the thermal resistance and tensile properties of NR/SiO2 nanocomposite are significantly improved.

  13. No-Core Shell Model for A = 47 and A = 49

    Energy Technology Data Exchange (ETDEWEB)

    Vary, J P; Negoita, A G; Stoica, S

    2006-11-13

    We apply the no-core shell model to the nuclear structure of odd-mass nuclei straddling {sup 48}Ca. Starting with the NN interaction, that fits two-body scattering and bound state data, we evaluate the nuclear properties of A = 47 and A = 49 nuclei while preserving all the underlying symmetries. Due to model space limitations and the absence of three-body interactions, we incorporate phenomenological interaction terms determined by fits to A = 48 nuclei in a previous effort. Our modified Hamiltonian produces reasonable spectra for these odd-mass nuclei. In addition to the differences in single-particle basis states, the absence of a single-particle Hamiltonian in our no-core approach complicates comparisons with valence effective NN interactions. We focus on purely off-diagonal two-body matrix elements since they are not affected by ambiguities in the different roles for one-body potentials and we compare selected sets of fp-shell matrix elements of our initial and modified Hamiltonians in the harmonic oscillator basis with those of a recent model fp-shell interaction, the GXPF1 interaction of Honma et al. While some significant differences emerge from these comparisons, there is an overall reasonably good correlation between our off-diagonal matrix elements and those of GXPF1.

  14. Light Nuclei in the Framework of the Symplectic No-Core Shell Model

    Energy Technology Data Exchange (ETDEWEB)

    Draayer, Jerry P.; Dytrych, Tomas; Sviratcheva, Kristina D.; Bahri, Chairul; /Louisiana State U.; Vary, James P.; /Iowa State U. /LLNL, Livermore /SLAC

    2007-04-02

    A symplectic no-core shell model (Sp-NCSM) is constructed with the goal of extending the ab-initio NCSM to include strongly deformed higher-oscillator-shell configurations and to reach heavier nuclei that cannot be studied currently because the spaces encountered are too large to handle, even with the best of modern-day computers. This goal is achieved by integrating two powerful concepts: the ab-initio NCSM with that of the Sp(3,R) {contains} SU(3) group-theoretical approach. The NCSM uses modern realistic nuclear interactions in model spaces that consists of many-body configurations up to a given number of {h_bar}{Upsilon} excitations together with modern high-performance parallel computing techniques. The symplectic theory extends this picture by recognizing that when deformed configurations dominate, which they often do, the model space can be better selected so less relevant low-lying {h_bar}{Upsilon} configurations yield to more relevant high-lying {h_bar}{Upsilon} configurations, ones that respect a near symplectic symmetry found in the Hamiltonian. Results from an application of the Sp-NCSM to light nuclei are compared with those for the NCSM and with experiment.

  15. Core/shell cellulose-based microspheres for oral administration of Ketoprofen Lysinate.

    Science.gov (United States)

    Guarino, Vincenzo; Caputo, Tania; Calcagnile, Paola; Altobelli, Rosaria; Demitri, Christian; Ambrosio, Luigi

    2018-01-26

    Herein, we propose the fabrication of a new carrier with core/shell structure-inner core of cellulose acetate (CA) coated by a micrometric layer of chitosan (CS)-fabricated through an integrated process, which combines Electro Dynamic Atomization (EDA) and layer-by-layer (LbL) technique. We demonstrate that CA based microspheres possess a unique capability to relevantly retain the drugs-that is, Ketoprofen Lysinate (KL)-along the gastric tract, while providing a massive release along the intestine. CS shell slightly influences the morphology and water retention under different pH conditions, improving drug encapsulation without compromising drug release kinetics. In vitro studies in simulated gastric and intestine fluids (SGF, SIF) with physiological enzymes, show a moderate release of LSK during the first 2 h (ca. 20% at pH 2), followed by a sustained release during the next 6 h (ca. 80% at pH 7). The obtained results demonstrate that CA-based microspheres hold strong potential to be used as carriers for a delayed oral administration of anti-inflammatory drugs. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc.

  16. Ab initio many-body perturbation theory and no-core shell model

    Science.gov (United States)

    Hu, B. S.; Wu, Q.; Xu, F. R.

    2017-10-01

    In many-body perturbation theory (MBPT) we always introduce a parameter N shell to measure the maximal allowed major harmonic-oscillator (HO) shells for the single-particle basis, while the no-core shell model (NCSM) uses N maxℏΩ HO excitation truncation above the lowest HO configuration for the many-body basis. It is worth comparing the two different methods. Starting from “bare” and Okubo-Lee-Suzuki renormalized modern nucleon-nucleon interactions, NNLOopt and JISP16, we show that MBPT within Hartree-Fock bases is in reasonable agreement with NCSM within harmonic oscillator bases for 4He and 16O in “close” model space. In addition, we compare the results using “bare” force with the Okubo-Lee-Suzuki renormalized force. Supported by National Key Basic Research Program of China (2013CB834402), National Natural Science Foundation of China (11235001, 11320101004, 11575007) and the CUSTIPEN (China-U.S. Theory Institute for Physics with Exotic Nuclei) funded by the U.S. Department of Energy, Office of Science (DE-SC0009971)

  17. Hydrogen peroxide sensing using ultrathin platinum-coated gold nanoparticles with core@shell structure.

    Science.gov (United States)

    Li, Yongxin; Lu, Qiufang; Wu, Shengnan; Wang, Lun; Shi, Xianming

    2013-03-15

    Ultrathin platinum-coated gold (Pt@Au) nanoparticles with core@shell structure have been developed by under-potential deposition (UPD) redox replacement technique. A single UPD Cu replacement with Pt(2+) produced a uniform Pt monolayer on the surface of gold nanoparticles, which are immobilized on glassy carbon electrode (GCE) surface based on electrostatic interaction. The ultrathin Pt@Au nanoparticles were confirmed by cyclic voltammetry and X-ray photoelectron spectroscopy (XPS). Voltammetry and amperometric methodologies were used to evaluate the electrocatalytic activity of the Pt@Au nanoparticles modified electrode towards the reduction of hydrogen peroxide under the physiological condition. The present results show that ultrathin Pt coating greatly enhances the electrocatalytic activity towards the reduction of hydrogen peroxide, which can be utilized to fabricate the hydrogen peroxide sensor. Chronoamperometric experiments showed that at an applied potential of 0.08 V (vs. Ag/AgCl), the current reduction of hydrogen peroxide was linear to its concentration in the range of 1-450 μΜ, and the detection limit was found to be 0.18 μM (signal-to-noise ratio, S/N=3). Copyright © 2012 Elsevier B.V. All rights reserved.

  18. HPLC method for rapidly following biodiesel fuel transesterification reaction progress using a core-shell column.

    Science.gov (United States)

    Allen, Samuel J; Ott, Lisa S

    2012-07-01

    There are a wide and growing variety of feedstocks for biodiesel fuel. Most commonly, these feedstocks contain triglycerides which are transesterified into the fatty acid alkyl esters (FAAEs) which comprise biodiesel fuel. While the tranesterification reaction itself is simple, monitoring the reaction progress and reaction products is not. Gas chromatography-mass spectrometry is useful for assessing the FAAE products, but does not directly address either the tri-, di-, or monoglycerides present from incomplete transesterification or the free fatty acids which may also be present. Analysis of the biodiesel reaction mixture is complicated by the solubility and physical property differences among the components of the tranesterification reaction mixture. In this contribution, we present a simple, rapid HPLC method which allows for monitoring all of the main components in a biodiesel fuel transesterification reaction, with specific emphasis on the ability to monitor the reaction as a function of time. The utilization of a relatively new, core-shell stationary phase for the HPLC column allows for efficient separation of peaks with short elution times, saving both time and solvent.

  19. Quantitative detection of antibiotic resistance genes using magnetic/luminescent core-shell nanoparticles

    Science.gov (United States)

    Son, Ahjeong; Hristova, Krassimira R.; Dosev, Dosi; Kennedy, Ian M.

    2008-02-01

    Nanoscale magnetic/luminescent core-shell particles were used for DNA quantification in a hybridization-in-solution format. We demonstrated a simple, high-throughput, and non-PCR based DNA assay for quantifying antibiotic resistance gene tetQ. Fe 3O 4/Eu:Gd IIO 3 nanoparticles (NPs) synthesized by spray pyrolysis were biofunctionalized by passive adsorption of NeutrAvidin. Following immobilization of biotinylated probe DNA on the particles' surfaces, target dsDNA and signaling probe DNA labeled with Cy3 were hybridized with NPs-probe DNA. Hybridized DNA complexes were separated from solution by a magnet, while non-hybridized DNA remained in solution. A linear quantification (R2 = 0.99) of a target tetQ gene was achieved based on the normalized fluorescence (Cy3/NPs) of DNANP hybrids. A real-time qPCR assay was used for evaluation of the NPs assay sensitivity and range of quantification. The quantity of antibiotic resistance tetQ genes in activated sludge microcosms, with and without addition of tetracycline or triclosan has been determined, indicating the potential of the optimized assay for monitoring the level of antibiotic resistance in environmental samples. In addition, the tetQ gene copy numbers in microcosms determined by NPhybridization were well correlated with the numbers measured by real-time qPCR assay (R2 = 0.92).

  20. Microbial synthesis of core/shell gold/palladium nanoparticles for applications in green chemistry.

    Science.gov (United States)

    Deplanche, Kevin; Merroun, Mohamed L; Casadesus, Merixtell; Tran, Dung T; Mikheenko, Iryna P; Bennett, James A; Zhu, Ju; Jones, Ian P; Attard, Gary A; Wood, J; Selenska-Pobell, Sonja; Macaskie, Lynne E

    2012-07-07

    We report a novel biochemical method based on the sacrificial hydrogen strategy to synthesize bimetallic gold (Au)-palladium (Pd) nanoparticles (NPs) with a core/shell configuration. The ability of Escherichia coli cells supplied with H(2) as electron donor to rapidly precipitate Pd(II) ions from solution is used to promote the reduction of soluble Au(III). Pre-coating cells with Pd(0) (bioPd) dramatically accelerated Au(III) reduction, with the Au(III) reduction rate being dependent upon the initial Pd loading by mass on the cells. Following Au(III) addition, the bioPd-Au(III) mixture rapidly turned purple, indicating the formation of colloidal gold. Mapping of bio-NPs by energy dispersive X-ray microanalysis suggested Au-dense core regions and peripheral Pd but only Au was detected by X-ray diffraction (XRD) analysis. However, surface analysis of cleaned NPs by cyclic voltammetry revealed large Pd surface sites, suggesting, since XRD shows no crystalline Pd component, that layers of Pd atoms surround Au NPs. Characterization of the bimetallic particles using X-ray absorption spectroscopy confirmed the existence of Au-rich core and Pd-rich shell type bimetallic biogenic NPs. These showed comparable catalytic activity to chemical counterparts with respect to the oxidation of benzyl alcohol, in air, and at a low temperature (90°C).

  1. High-performance polyimide nanocomposites with core-shell AgNWs@BN for electronic packagings

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Yongcun; Liu, Feng, E-mail: liufeng@nwpu.edu.cn [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an Shaanxi 710072 (China)

    2016-08-22

    The increasing density of electronic devices underscores the need for efficient thermal management. Silver nanowires (AgNWs), as one-dimensional nanostructures, possess a high aspect ratio and intrinsic thermal conductivity. However, high electrical conductivity of AgNWs limits their application for electronic packaging. We synthesized boron nitride-coated silver nanowires (AgNWs@BN) using a flexible and fast method followed by incorporation into synthetic polyimide (PI) for enhanced thermal conductivity and dielectric properties of nanocomposites. The thinner boron nitride intermediate nanolayer on AgNWs not only alleviated the mismatch between AgNWs and PI but also enhanced their interfacial interaction. Hence, the maximum thermal conductivity of an AgNWs@BN/PI composite with a filler loading up to 20% volume was increased to 4.33 W/m K, which is an enhancement by nearly 23.3 times compared with that of the PI matrix. The relative permittivity and dielectric loss were about 9.89 and 0.015 at 1 MHz, respectively. Compared with AgNWs@SiO{sub 2}/PI and Ag@BN/PI composites, boron nitride-coated core-shell structures effectively increased the thermal conductivity and reduced the permittivity of nanocomposites. The relative mechanism was studied and discussed. This study enables the identification of appropriate modifier fillers for polymer matrix nanocomposites.

  2. Synthesis and Characterization of Polyvinylpyrrolidone Silica Core-Shell Nanocomposite Particles.

    Science.gov (United States)

    Chen, Lian-Xi; Li, Jie; Li, Xi; Zhang, Zhong-Min; Jiao, Cai-Bin

    2015-03-01

    In this work, a novel and facile strategy for making a new type of polymer/silica nanocomposte particle was proposed. Colloidally stable polyvinypyrrolidone (PVP)/silica core-shell nanocomposite particles have been successfully synthesized using an azo initiator via seed polymerization of N-vinyl-2-pyrrolidone (NVP) and VFSs (VFSs) that were derived from vinyl triethoxysilane (VTES). It was suggested from the FTIR and TGA analysis that the copolymerization reaction of NVP with VFSs has been thoroughly carried out. In addition, SEM images showed that PVP/silica nanocomposite particles have relatively rough surface due to surface polymerization in comparison with VFSs. Furthermore, TEM results proved that the size of VFSs had considerable effects on the appearance of PVP/silica nanocomposite particles. Generally, it presented that several silica nanoparticle cores with an average size of 78 nm mainly pack together within each nanocomposite particle after seed polymerization. Interestingly, the average shell thickness was 59 nm for most PVP/silica nanocomposite particles with cores about 242 nm. However, when the core size was large enough to about 504 nm, a series of PVP/silica nanocomposite particles with a relative thin shell were observed.

  3. Strain-Driven Stacking Faults in CdSe/CdS Core/Shell Nanorods.

    Science.gov (United States)

    Demortière, Arnaud; Leonard, Donovan N; Petkov, Valeri; Chapman, Karena; Chattopadhyay, Soma; She, Chunxing; Cullen, David A; Shibata, Tomohiro; Pelton, Matthew; Shevchenko, Elena V

    2018-04-19

    Colloidal semiconductor nanocrystals are commonly grown with a shell of a second semiconductor material to obtain desired physical properties, such as increased photoluminescence quantum yield. However, the growth of a lattice-mismatched shell results in strain within the nanocrystal, and this strain has the potential to produce crystalline defects. Here, we study CdSe/CdS core/shell nanorods as a model system to investigate the influence of core size and shape on the formation of stacking faults in the nanocrystal. Using a combination of high-angle annular dark-field scanning transmission electron microscopy and pair-distribution-function analysis of synchrotron X-ray scattering, we show that growth of the CdS shell on smaller, spherical CdSe cores results in relatively small strain and few stacking faults. By contrast, growth of the shell on larger, prolate spheroidal cores leads to significant strain in the CdS lattice, resulting in a high density of stacking faults.

  4. One-pot preparation of nanoporous Ag-Cu@Ag core-shell alloy with enhanced oxidative stability and robust antibacterial activity.

    Science.gov (United States)

    Liu, Xue; Du, Jing; Shao, Yang; Zhao, Shao-Fan; Yao, Ke-Fu

    2017-08-31

    Metallic core-shell nanostructures have inspired prominent research interests due to their better performances in catalytic, optical, electric, and magnetic applications as well as the less cost of noble metal than monometallic nanostructures, but limited by the complicated and expensive synthesis approaches. Development of one-pot and inexpensive method for metallic core-shell nanostructures' synthesis is therefore of great significance. A novel Cu network supported nanoporous Ag-Cu alloy with an Ag shell and an Ag-Cu core was successfully synthesized by one-pot chemical dealloying of Zr-Cu-Ag-Al-O amorphous/crystalline composite, which provides a new way to prepare metallic core-shell nanostructures by a simple method. The prepared nanoporous Ag-Cu@Ag core-shell alloy demonstrates excellent air-stability at room temperature and enhanced oxidative stability even compared with other reported Cu@Ag core-shell micro-particles. In addition, the nanoporous Ag-Cu@Ag core-shell alloy also possesses robust antibacterial activity against E. Coli DH5α. The simple and low-cost synthesis method as well as the excellent oxidative stability promises the nanoporous Ag-Cu@Ag core-shell alloy potentially wide applications.

  5. Fabrication of Fe{sub 3}O{sub 4}@CuO core-shell from MOF based materials and its antibacterial activity

    Energy Technology Data Exchange (ETDEWEB)

    Rajabi, S.K. [Department of Chemistry, University of Guilan, University Campus 2, Rasht (Iran, Islamic Republic of); Sohrabnezhad, Sh., E-mail: sohrabnezhad@guilan.ac.ir [Department of Chemistry, Faculty of Science, University of Guilan, P.O. Box 1914, Rasht (Iran, Islamic Republic of); Ghafourian, S. [Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam (Iran, Islamic Republic of)

    2016-12-15

    Magnetic Fe{sub 3}O{sub 4}@CuO nanocomposite with a core/shell structure was successfully synthesized via direct calcinations of magnetic Fe{sub 3}O{sub 4}@HKUST-1 in air atmosphere. The morphology, structure, magnetic and porous properties of the as-synthesized nano composites were characterized by using scanning electron microscope (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), and vibration sample magnetometer (VSM). The results showed that the nanocomposite material included a Fe{sub 3}O{sub 4} core and a CuO shell. The Fe{sub 3}O{sub 4}@CuO core-shell can be separated easily from the medium by a small magnet. The antibacterial activity of Fe{sub 3}O{sub 4}-CuO core-shell was investigated against gram-positive and gram-negative bacteria. A new mechanism was proposed for inactivation of bacteria over the prepared sample. It was demonstrated that the core-shell exhibit recyclable antibacterial activity, acting as an ideal long-acting antibacterial agent. - Graphical abstract: Fe{sub 3}O{sub 4}@CuO core-shell release of copper ions. These Cu{sup 2+} ions were responsible for the exhibited antibacterial activity. - Highlights: • The Fe{sub 3}O{sub 4}@CuO core-shell was prepared by MOF method. • This is the first study of antibacterial activity of core-shell consist of CuO and Fe{sub 3}O{sub 4}. • The core-shell can be reused effectively. • Core-shell was separated from the reaction solution by external magnetic field.

  6. High magnetic field reveals the nature of excitons in a single GaAs/AlAs core/shell nanowire.

    Science.gov (United States)

    Plochocka, P; Mitioglu, A A; Maude, D K; Rikken, G L J A; del Águila, A Granados; Christianen, P C M; Kacman, P; Shtrikman, Hadas

    2013-06-12

    Magneto-photoluminescence measurements of individual zinc-blende GaAs/AlAs core/shell nanowires are reported. At low temperature, a strong emission line at 1.507 eV is observed under low power (nW) excitation. Measurements performed in high magnetic field allowed us to detect in this emission several lines associated with excitons bound to defect pairs. Such lines were observed before in epitaxial GaAs of very high quality, as reported by Kunzel and Ploog. This demonstrates that the optical quality of our GaAs/AlAs core/shell nanowires is comparable to the best GaAs layers grown by molecular beam epitaxy. Moreover, strong free exciton emission is observed even at room temperature. The bright optical emission of our nanowires in room temperature should open the way for numerous optoelectronic device applications.

  7. Stepwise synthesis of cubic Au-AgCdS core-shell nanostructures with tunable plasmon resonances and fluorescence.

    Science.gov (United States)

    Liu, Xiao-Li; Liang, Shan; Nan, Fan; Pan, Yue-Yue; Shi, Jun-Jun; Zhou, Li; Jia, Shuang-Feng; Wang, Jian-Bo; Yu, Xue-Feng; Wang, Qu-Quan

    2013-10-21

    Cubic Au-AgCdS core-shell nanostructures were synthesized through cation exchange method assisted by tributylphosphine (TBP) as a phase-transfer agent. Among intermediate products, Au-Ag core-shell nanocubes exhibited many high-order plasmon resonance modes related to the special cubic shape, and these plasmon bands red-shifted along with the increasing of particle size. The plasmon band of Au core first red-shifted and broadened at the step of Au-Ag₂S and then blue-shifted and narrowed at the step of Au-AgCdS. Since TBP was very crucial for the efficient conversion from Ag₂S to CdS, we found that both absorption and fluorescence of the final products could be controlled by TBP.

  8. Influence of coating and annealing on the optical properties of ZnSe/CdO core-shell nanorods

    Science.gov (United States)

    Kim, Hyunsu; Jin, Changhyun; Hong, Chanseok; Lee, Chongmu

    2011-12-01

    We prepared ZnSe/CdO coaxial nanorods on Si(100) substrates by using a two step process comprising the thermal evaporation of ZnSe powders and the sputter-deposition of CdO. PL measurements show that the ZnSe-core/CdO-shell nanorods have a strong emission band centered at around 605 nm in the orange region. The PL emission of the core-shell nanrods can be significantly enhanced by CdO coating and subsequent annealing. Annealing in a reducing atmosphere is more efficient in enhancing the PL emission of the core-shell nanorods than annealing in an oxidative atmosphere owing to the generation of Zn interstitials during annealing.

  9. CoO/NiSi(x) core-shell nanowire arrays as lithium-ion anodes with high rate capabilities.

    Science.gov (United States)

    Qi, Yue; Du, Ning; Zhang, Hui; Fan, Xing; Yang, Yang; Yang, Deren

    2012-02-07

    This paper describes a facile chemical vapor deposition (CVD) and subsequent radio-frequency (RF)-sputtering approach for the synthesis of CoO/NiSi(x) core-shell nanowire (NW) arrays on Ni foams. The metallic core (i.e., NiSi(x)) with high conductivity acts as a nanostructured current collector. The as-synthesized CoO/NiSi(x) core-shell NW arrays have been applied as anode materials for lithium-ion batteries, which deliver high cycle life and enhanced power performance compared to planar CoO electrodes on Ni foams. The high surface-to-volume ratio and improved electronic/ionic conductivity of the nanostructured electrodes may be responsible for the improved performance. This journal is © The Royal Society of Chemistry 2012

  10. Synthesis and characterization of silver-copper core-shell nanoparticles using polyol method for antimicrobial agent

    Science.gov (United States)

    Hikmah, N.; Idrus, N. F.; Jai, J.; Hadi, A.

    2016-06-01

    Silver and copper nanoparticles are well-known as the good antimicrobial agent. The nano-size of particles influences in enhancing the antimicrobial activity. This paper discusses the effect of molarity on the microstructure and morphology of silver-copper core-shell nanoparticles prepared by a polyol method. In this study, silver-copper nanoparticles are synthesized through the green approach of polyol method using ethylene glycol (EG) as green solvent and reductant, and polyoxyethylene-(80)-sorbitan monooleate (Tween 80) as a nontoxic stabilizer. The phase and morphology of silver-copper nanoparticles are characterized by X-ray diffraction (XRD) and Field emission scanning electron microscope (FESEM) and Transmission electron microscope (TEM). The results XRD confirm the pure crystalline of silver and copper nanoparticles with face-centered cubic (FCC) structure. FESEM and TEM analysis confirm the existence of Ag and Cu nanoparticles in core-shell shape.

  11. Spontaneous formation of GaN/AlN core-shell nanowires on sapphire by hydride vapor phase epitaxy

    Science.gov (United States)

    Trassoudaine, Agnès; Roche, Elissa; Bougerol, Catherine; André, Yamina; Avit, Geoffrey; Monier, Guillaume; Ramdani, Mohammed Réda; Gil, Evelyne; Castelluci, Dominique; Dubrovskii, Vladimir G.

    2016-11-01

    Spontaneous GaN/AlN core-shell nanowires with high crystal quality were synthesized on sapphire substrates by vapor-liquid-solid hydride vapor phase epitaxy (VLS-HVPE) without any voluntary aluminum source. Deposition of aluminum is difficult to achieve in this growth technique which uses metal-chloride gaseous precursors: the strong interaction between the AlCl gaseous molecules and the quartz reactor yields a huge parasitic nucleation on the walls of the reactor upstream the substrate. We open up an innovative method to produce GaN/AlN structures by HVPE, thanks to aluminum etching from the sapphire substrate followed by redeposition onto the sidewalls of the GaN core. The paper presents the structural characterization of GaN/AlN core-shell nanowires, speculates on the growth mechanism and discusses a model which describes this unexpected behavior.

  12. Hybrid core shell nanoparticles entrapping Gd-DTPA and18F-FDG for simultaneous PET/MRI acquisitions.

    Science.gov (United States)

    Vecchione, Donatella; Aiello, Marco; Cavaliere, Carlo; Nicolai, Emanuele; Netti, Paolo Antonio; Torino, Enza

    2017-09-01

    Although there has been an improvement in the hardware and software of the PET/MRI system, the development of the nanoprobes exploiting the simultaneous acquisition of the bimodal data is still under investigation. Moreover, few studies on biocompatible and clinically relevant probes are available. This work presents a core-shell polymeric nanocarrier with improved relaxometric properties for simultaneous PET/MRI acquisitions. Core-shell nanoparticles entrapping the Gd-DTPA and 18 F-FDG are obtained by a complex coacervation. The boosting of r 1 of the entrapped Gd-DTPA up to five-times compared with 'free Gd-DTPA', is confirmed by the PET/MRI scan. The sorption of 18 F-FDG into the nanoparticles is studied and designed to be integrated downstream for the production of the tracer.

  13. Synthesis of robust water-soluble ZnS:Mn/SiO{sub 2} core/shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Sun Jing; Zhuang Jiaqi; Guan Shaowei; Yang Wensheng [Jilin University, Key Laboratory of Surface and Interface Chemistry of Jilin Province, College of Chemistry (China)], E-mail: wsyang@jlu.edu.cn

    2008-04-15

    Water-soluble Mn doped ZnS (ZnS:Mn) nanocrystals synthesized by using 3-mercaptopropionic acid (MPA) as stabilizer were homogeneously coated with a dense silica shell through a multi-step procedure. First, 3-mercaptopropyl triethoxy silane (MPS) was used to replace MPA on the particle surface to form a vitreophilic layer for further silica deposition under optimal experimental conditions. Then a two-step silica deposition was performed to form the final water-soluble ZnS:Mn/SiO{sub 2} core/shell nanoparticles. The as-prepared core/shell nanoparticles show little change in fluorescence intensity in a wide range of pH value.

  14. Characterization of core-shell GaAs/AlGaAs nanowire heterostructures using advanced electron microscopy

    International Nuclear Information System (INIS)

    Tambe, M J; Gradecak, S; Allard, L F

    2010-01-01

    To explore the unique properties of the nanoscale, advanced fabrication and characterization techniques are required. Specifically analyses in two orthogonal directions, plan-view and cross-section, were used to prove the core-shell morphology of GaAs/AlGaAs nanowires and determine their cross-section to be hexagonal. High-resolution transmission electron microscopy and high angle annular dark field scanning transmission electron microscopy confirmed the core-shell interface to be defect-free, coherent, and sharp ( 0.9 Ga 0.1 As uniformly along the length of the nanowire. These results demonstrate the power of electron microscopy to aid the development of semiconductor nanotechnology.

  15. Synthesis of Lutetium Phosphate/Apoferritin Core-Shell Nanoparticles for Potential Applications in Radioimmunoimaging and Radioimmunotherapy of Cancers

    International Nuclear Information System (INIS)

    Wu, Hong; Engelhard, Mark H.; Wang, Jun; Fisher, Darrell R.; Lin, Yuehe

    2008-01-01

    We report a novel approach for synthesizing LuPO4/apoferritin core-shell nanoparticles based on an apoferritin template, conjugated to the protein biotin. To prepare the nanoparticle conjugates, we used non-radioactive lutetium as a model target or surrogate for radiolutetium (177Lu). The central cavity, multi-channel structure, and chemical properties of apoferritin are well-suited for sequentially diffusing lutetium and phosphate ions into the cavity--resulting in a stable core-shell composite. We characterized the synthesized LuPO4/apoferritin nanoparticle using transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS). We tested the pre-targeting capability of biotin-modified lutetium/apoferritin nanoparticle using streptavidin-modified magnetic beads and streptavidin-modified fluorescein isothiocyanate (FITC) tracer. This paper presents a simple, fast, and efficient method for synthesizing LuPO4/apoferritin nanoparticle conjugates with biotin for potential applications in radioimmunotherapy and radioimmunoimaging of cancer

  16. Electrochemical characterization of core@shell CoFe{sub 2}O{sub 4}/Au composite

    Energy Technology Data Exchange (ETDEWEB)

    Carla, Francesco [' Ugo Schiff' , Universita degli Studi di Firenze, Dipartimento di Chimica (Italy); Campo, Giulio; Sangregorio, Claudio; Caneschi, Andrea; Julian Fernandez, Cesar de; Cabrera, Lourdes I., E-mail: lourisa_cabrera@yahoo.com [Universita degli Studi di Firenze, Laboratorio di Magnetismo Molecolare, INSTM, Dipartimento di Chimica (Italy)

    2013-08-15

    In this paper, we address the synthesis and characterization of the core@shell composite magneto-plasmonic cobalt ferrite-gold (Co-ferrite/Au) nanosystem. The synthesis Co-ferrite/Au nanocomposite is not obvious, hence it was of interest to generate it in a simple straightforward method. Co-ferrite/Au nanocomposite was generated by synthesizing first by thermal decomposition Co-ferrite nanoparticles (NPs). On a second step, ionic gold (Au{sup 3+}) was reduced at the surface of Co-ferrite NPs by ultrasound, to obtain the metallic Au shell. The characterization of the nanomaterial was achieved by microscopy, spectroscopy, and performing magnetic measurements. However, what is attractive about our work is the use of electrochemical techniques as analytical tools. The key technique was cyclic voltammetry, which provided information about the nature and structure of the nanocomposite, allowing us to confirm the core@shell structure.

  17. Facile synthesis of core-shell Cu2O@ ZnO structure with enhanced photocatalytic H2 production

    Science.gov (United States)

    Zhang, Yong-Hui; Jiu, Bei-Bei; Gong, Fei-Long; Lu, Kuan; Jiang, Nan; Zhang, Hao-Li; Chen, Jun-Li

    2018-05-01

    Core-shell Cu2O@ZnO composites were synthesized successfully based on a one-pot hydrothermal method in the presence of dioctyl sulfosuccinate sodium salt (AOT) surfactant. The Cu2O can be converted to rough core-shell Cu2O@ZnO structure by adjusting the amount of zinc powder added. The as-synthesized Cu2O@ZnO composites exhibited excellent photocatalytic activity and the amount of H2 generated using these composites was 4.5-fold more than that produced with Cu2O cubes. A possible photocatalytic mechanism for the Cu2O@ZnO composites with enhanced photocatalytic activity could be the separation by ZnO of the effective charge carriers.

  18. Antiviral effect of gold/copper sulfide core-shell nanoparticles on GI.1 human norovirus virus like particles (VLPS)

    Science.gov (United States)

    Alston, Brittny C.

    This research studied the effects of the Au/CuS core shell nanoparticles on norovirus (NoV) VLPs in efforts to disrupt the capsids and ultimately inactivate the virus. The results of the study showed that treatment of the GI.1 norovirus VLP ranging from 0.37-5.6ug/mL5.6 microg/mL with Au/CuS core shell nanoparticle concentrations ranging from 1%-25% (v/v) was effective in altering and completely inactivating the viral capsid of the VLP. The likely mechanism of action of the nanoparticles was that the particles degraded the capsid protein and disrupted the viral capsids. This mechanism of action has been supported by the TEM imaging results and Western blotting analysis of capsid protein which showed that the viral capsids were compromised and the major capsid protein degraded.

  19. Polyacrylonitrile/polyaniline core/shell nanofiber mat for removal of hexavalent chromium from aqueous solution: mechanism and applications

    KAUST Repository

    Wang, Jianqiang

    2013-01-01

    Polyacrylonitrile/polyaniline core/shell nanofibers were prepared via electrospinning followed by in situ polymerization of aniline. Nanofibers with different morphology were obtained by changing the polymerization temperature. When used as absorbent for Cr(vi) ions, the core/shell nanofiber mats exhibit excellent adsorption capability. The equilibrium capacity is 24.96, 37.24, and 52.00 mg g-1 for 105, 156, and 207 mg L-1 initial Cr(vi) solution, respectively, and the adsorption capacity increases with temperature. The adsorption follows a pseudo second order kinetics model and is best fit using the Langmuir isotherm model. The mats show excellent selectivity towards Cr(vi) ions in the presence of competing ions albeit a small decrease in adsorption is observed. The mats can be regenerated and reused after treatment with NaOH making them promising candidates as practical adsorbents for Cr(vi) removal. © The Royal Society of Chemistry 2013.

  20. Synthesis of suitable SiO2 nano particles as the core in core-shell nanostructured materials.

    Science.gov (United States)

    Ghahari, Mehdi; Aghababazadeh, Roya; Ebadzadeh, Touradj; Mirhabibi, Alireza; Brydson, Rik; Fabbri, Paola; Najafi, Farhod

    2011-06-01

    The effect of surfactant on the luminescent intensity of SiO2 @Y2O3:Eu3+ particles with a core shell structure is described. Core-shell particles are used in phosphor materials and employing spherical particles with a narrow size distribution is vital for the enhancement of luminescent properties. Three kinds of different surfactants were used to synthesis SiO2 nano particles via a sol gel process. The results demonstrated that comb polycarboxylic acid surfactant had a significant influence on the morphology and particle size distribution. Somehow, particles with 100 nm size and narrow size distribution were produced. These particles had relatively uniform packing, unlike particles produced with other surfactants or without surfactant which had irregular assembly. The photoluminescence intensity of SiO2 @Y2O3:Eu3+ particles that was synthesized by comb polycarboxylic acid surfactant was higher than those which were produced without surfactant.

  1. Synthesis of liquid core-shell particles and solid patchy multicomponent particles by shearing liquids into complex particles (SLICE).

    Science.gov (United States)

    Tevis, Ian D; Newcomb, Lucas B; Thuo, Martin

    2014-12-02

    We report a simple method that uses (i) emulsion shearing with oxidation to make core-shell particles, and (ii) emulsion shearing with surface-tension driven phase segregation to synthesize particles with complex surface compositions and morphologies. Subjecting eutectic gallium-indium, a liquid metal, to shear in an acidic carrier fluid we synthesized smooth liquid core-shell particles 6.4 nm to over 10 μm in diameter. Aggregates of these liquid particles can be reconfigured into larger structures using a focused ion beam. Using Field's metal melts we synthesized homogeneous nanoparticles and solid microparticles with different surface roughness and/or composition through shearing and phase separation. This extension of droplet emulsion technique, SLICE, applies fluidic shear to create micro- and nanoparticles in a tunable, green, and low-cost approach.

  2. Microwave-assisted synthesis and characterization of poly(acrylic)/SiO2-TiO2 core-shell nanoparticle hybrid thin films

    International Nuclear Information System (INIS)

    Chien, Wen-Chen; Yu, Yang-Yen; Chen, Po-Kan; Yu, Hui-Huan

    2011-01-01

    In this study, poly(acrylic)/SiO 2 -TiO 2 core-shell nanoparticle hybrid thin films were successfully synthesized by microwave-assisted polymerization. The coupling agent 3-(trimethoxysilyl) propyl methacrylate (MSMA) was hydrolyzed with colloidal SiO 2 -TiO 2 core-shell nanoparticles, and then polymerized with two acrylic monomers and initiator to form a precursor solution. The results of this study showed that the spin-coated hybrid films had relatively good surface planarity, high thermal stability, a tunable refractive index (1.525 2 -TiO 2 core-shell nanoparticle hybrid thin films, for potential use in optical applications.

  3. LaF{sub 3} core/shell nanoparticles for subcutaneous heating and thermal sensing in the second biological-window

    Energy Technology Data Exchange (ETDEWEB)

    Ximendes, Erving Clayton [Grupo de Fotônica e Fluidos Complexos, Instituto de Física, Universidade Federal de Alagoas, 57072-970 Maceió, Alagoas (Brazil); Fluorescence Imaging Group, Departamento de Física de Materiales C-04, Facultad de Ciencias, Instituto Nicolás Cabrera, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Rocha, Uéslen; Jaque, Daniel, E-mail: daniel.jaque@uam.es [Fluorescence Imaging Group, Departamento de Física de Materiales C-04, Facultad de Ciencias, Instituto Nicolás Cabrera, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Kumar, Kagola Upendra; Jacinto, Carlos [Grupo de Fotônica e Fluidos Complexos, Instituto de Física, Universidade Federal de Alagoas, 57072-970 Maceió, Alagoas (Brazil)

    2016-06-20

    We report on Ytterbium and Neodymium codoped LaF{sub 3} core/shell nanoparticles capable of simultaneous heating and thermal sensing under single beam infrared laser excitation. Efficient light-to-heat conversion is produced at the Neodymium highly doped shell due to non-radiative de-excitations. Thermal sensing is provided by the temperature dependent Nd{sup 3+} → Yb{sup 3+} energy transfer processes taking place at the core/shell interface. The potential application of these core/shell multifunctional nanoparticles for controlled photothermal subcutaneous treatments is also demonstrated.

  4. (FeCo)3Si-SiOx core-shell nanoparticles fabricated in the gas phase

    International Nuclear Information System (INIS)

    Bai Jianmin; Xu Yunhao; Thomas, John; Wang Jianping

    2007-01-01

    A method of fabricating core-shell nanoparticles by using an integrated nanoparticle deposition technique in the gas phase is reported. The principle of the method is based on nanoparticle growth from the vapour phase, during which elements showing lower surface energies prefer to form the shells and elements showing higher surface energies prefer to stay in the cores. This method was applied successfully to the Fe-Co-Si ternary system to fabricate core-shell-type nanoparticles. The nanoparticles were exposed in air after collection to achieve oxidation. The analysis results based on transmission electron microscopy (TEM), Auger electron spectroscopy (AES), x-ray diffraction (XRD), and a superconducting quantum interference device (SQUID) showed that the core parts are magnetic materials of body-centred cubic (bcc) structured (FeCo) 3 Si of 15 nm in diameter, and the shell parts are amorphous SiO x of 2 nm in thickness. These core-shell-type nanoparticles show a magnetic anisotropy constant of about 7 x 10 5 erg cm -3 and a saturation magnetization of around 1160 emu cm -3 , which is much higher than that of iron oxide. After annealing at 300 deg. C in air (FeCo) 3 Si-SiO x core-shell-type nanoparticles showed a little bit of a drop in magnetic moment, while pure FeCo nanopariticles totally lost their magnetic moment. This means that the shells of SiO x are dense enough to prevent the magnetic cores from oxidation

  5. Transmission electron microscopy and ab initio calculations to relate interfacial intermixing and the magnetism of core/shell nanoparticles

    International Nuclear Information System (INIS)

    Chi, C.-C.; Hsiao, C.-H.; Ouyang, Chuenhou; Skoropata, E.; Lierop, J. van

    2015-01-01

    Significant efforts towards understanding bi-magnetic core-shell nanoparticles are underway currently as they provide a pathway towards properties unavailable with single-phased systems. Recently, we have demonstrated that the magnetism of γ-Fe2O3/CoO core-shell nanoparticles, in particular, at high temperatures, originates essentially from an interfacial doped iron-oxide layer that is formed by the migration of Co 2+ from the CoO shell into the surface layers of the γ-Fe2O3 core [Skoropata et al., Phys. Rev. B 89, 024410 (2014)]. To examine directly the nature of the intermixed layer, we have used high-resolution transmission electron microscopy (HRTEM) and first-principles calculations to examine the impact of the core-shell intermixing at the atomic level. By analyzing the HRTEM images and energy dispersive spectra, the level and nature of intermixing was confirmed, mainly as doping of Co into the octahedral site vacancies of γ-Fe2O3. The average Co doping depths for different processing temperatures (150 °C and 235 °C) were 0.56 nm and 0.78 nm (determined to within 5% through simulation), respectively, establishing that the amount of core-shell intermixing can be altered purposefully with an appropriate change in synthesis conditions. Through first-principles calculations, we find that the intermixing phase of γ-Fe2O3 with Co doping is ferromagnetic, with even higher magnetization as compared to that of pure γ-Fe2O3. In addition, we show that Co doping into different octahedral sites can cause different magnetizations. This was reflected in a change in overall nanoparticle magnetization, where we observed a 25% reduction in magnetization for the 235 °C versus the 150 °C sample, despite a thicker intermixed layer

  6. Au@Ag core-shell nanocubes with finely tuned and well-controlled sizes, shell thicknesses, and optical properties.

    Science.gov (United States)

    Ma, Yanyun; Li, Weiyang; Cho, Eun Chul; Li, Zhiyuan; Yu, Taekyung; Zeng, Jie; Xie, Zhaoxiong; Xia, Younan

    2010-11-23

    This paper describes a facile method for generating Au@Ag core-shell nanocubes with edge lengths controllable in the range of 13.4-50 nm. The synthesis involved the use of single-crystal, spherical Au nanocrystals of 11 nm in size as the seeds in an aqueous system, with ascorbic acid serving as the reductant and cetyltrimethylammonium chloride (CTAC) as the capping agent. The thickness of the Ag shells could be finely tuned from 1.2 to 20 nm by varying the ratio of AgNO(3) precursor to Au seeds. We also investigated the growth mechanism by examining the effects of seeds (capped by CTAC or cetyltrimethylammonium bromide(CTAB)) and capping agent (CTAC vs CTAB) on both size and shape of the resultant core-shell nanocrystals. Our results clearly indicate that CTAC worked much better than CTAB as a capping agent in both the syntheses of Au seeds and Au@Ag core-shell nanocubes. We further studied the localized surface plasmon resonance properties of the Au@Ag nanocubes as a function of the Ag shell thickness. By comparing with the extinction spectra obtained from theoretical calculations, we derived a critical value of ca. 3 nm for the shell thickness at which the plasmon excitation of the Au cores would be completely screened by the Ag shells. Moreover, these Au@Ag core-shell nanocubes could be converted into Au-based hollow nanostructures containing the original Au seeds in the interiors through a galvanic replacement reaction.

  7. Giant exchange bias and its angular dependence in Co/CoO core-shell nanowire assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Gandha, Kinjal; Chaudhary, Rakesh P.; Mohapatra, Jeotikanta; Koymen, Ali R.; Liu, J. Ping, E-mail: pliu@uta.edu

    2017-07-12

    The exchange-bias field (H{sub EB}) and its angular dependence are systematically investigated in Co/CoO core-shell nanowire assemblies (∼15 nm in diameter and ∼200 nm in length) consisting of single-crystalline Co core and polycrystalline CoO shell. Giant exchange-bias field (H{sub EB}) up to 2.4 kOe is observed below a blocking temperature (T{sub EB} ∼150 K) in the aligned Co/CoO nanowire assemblies. It is also found that there is an angular dependence between the H{sub EB} and the applied magnetization direction. The H{sub EB} showed a peak at 30° between the applied field and the nanowire aligned direction, which may be attributed to the noncollinear spin orientations at the interface between the ferromagnetic core and the antiferromagnetic shell. This behavior is quantitatively supported by an analytical calculation based on Stoner–Wohlfarth model. This study underlines the importance of the competing magnetic anisotropies at the interface of Co/CoO core-shell nanowires. - Highlights: • Giant exchange bias is observed in oriented Co/CoO core-shell nanowire assemblies. • Study of angular and temperature dependence of the exchange bias effect. • Competing magnetic anisotropies at the interface of Co/CoO core-shell nanowires. • Effect of misaligned spins in FM/AFM interface on angular dependence of exchange bias. • We explain the analytical model that accounts for experimental results.

  8. Preparation and characterization of core-shell electrodes for application in gel electrolyte-based dye-sensitized solar cells

    International Nuclear Information System (INIS)

    Avellaneda, Cesar O.; Goncalves, Agnaldo D.; Benedetti, Joao E.; Nogueira, Ana F.

    2010-01-01

    Core-shell electrodes based on TiO 2 covered with different oxides were prepared and characterized. These electrodes were applied in gel electrolyte-based dye-sensitized solar cells (DSSC). The TiO 2 electrodes were prepared from TiO 2 powder (P25 Degussa) and coated with thin layers of Al 2 O 3 , MgO, Nb 2 O 5 , and SrTiO 3 prepared by the sol-gel method. The core-shell electrodes were characterized by X-ray diffraction, scanning electron microscopy and atomic force microscopy measurements. J-V curves in the dark and under standard AM 1.5 conditions and photovoltage decay measurements under open-circuit conditions were carried out in order to evaluate the influence of the oxide layer on the charge recombination dynamics and on the device's performance. The results indicated an improvement in the conversion efficiency as a result of an increase in the open circuit voltage. The photovoltage decay curves under open-circuit conditions showed that the core-shell electrodes provide longer electron lifetime values compared to uncoated TiO 2 electrodes, corroborating with a minimization in the recombination losses at the nanoparticle surface/electrolyte interface. This is the first time that a study has been applied to DSSC based on gel polymer electrolyte. The optimum performance was achieved by solar cells based on TiO 2 /MgO core-shell electrodes: fill factor of ∼0.60, short-circuit current density J sc of 12 mA cm -2 , open-circuit voltage V oc of 0.78 V and overall energy conversion efficiency of ∼5% (under illumination of 100 mW cm -2 ).

  9. Understanding emergent collectivity and clustering in nuclei from a symmetry-based no-core shell-model perspective

    Czech Academy of Sciences Publication Activity Database

    Dreyfuss, A. C.; Launey, K. D.; Dytrych, Tomáš; Draayer, J. P.; Baker, R. B.; Deibel, C. M.; Bahri, C.

    2017-01-01

    Roč. 95, č. 4 (2017), č. článku 044312. ISSN 2469-9985 R&D Projects: GA ČR GA16-16772S Institutional support: RVO:61389005 Keywords : C-12 * no-core shell-model * resonance Subject RIV: BE - Theoretical Physics OBOR OECD: Atomic, molecular and chemical physics (physics of atoms and molecules including collision, interaction with radiation, magnetic resonances, Mössbauer effect) Impact factor: 3.820, year: 2016

  10. Mechanical properties of zirconia core-shell rods with porous core and dense shell prepared by thermoplastic co-extrusion

    Czech Academy of Sciences Publication Activity Database

    Kaštyl, J.; Chlup, Zdeněk; Clemen, F.; Trunec, M.

    2017-01-01

    Roč. 37, č. 6 (2017), s. 2439-2447 ISSN 0955-2219 R&D Projects: GA MŠk(CZ) LQ1601 Institutional support: RVO:68081723 Keywords : ceramic injection moldings * oxide fuel-cells * electrophoretic deposition * large pores * alumina * fabrication * behavior * tubes * bioceramics * composites * Zirconia * Co-extrusion * Core-shell * Porous structure * Mechanical properties Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass OBOR OECD: Ceramics Impact factor: 3.411, year: 2016

  11. Highly selective anticancer activity of core shell particles based on hydroxyapatite, chitosan lactate and different androstane derivatives

    OpenAIRE

    Ignjatović, Nenad; Penov Gaši, Katarina; Ajduković, Jovana; Sakač, Marija; Kuzminac, Ivana; Kojić, Vesna V.; Marković, Smilja; Uskoković, Dragan

    2017-01-01

    Hybrid systems based on nano hydroxyapatites (HAp) are the subject of numerous studies in preventive and regenerative medicine. Special interests are directed towards the creation of a system based on HAp for use in a nano-oncology. The main objective of this research is directed towards the creation of a system with cytotoxic properties towards the cancer cells with the same time, minimum side effects. Carriers base on core shell of HAp/chitosan-poly(D,L)-lactide-coglycolide (PLGA) loaded wi...

  12. Quantifying the Impact of Nanoparticle Coatings and Nonuniformities on XPS Analysis: Gold/Silver Core-Shell Nanoparticles.

    Science.gov (United States)

    Wang, Yung-Chen; Engelhard, Mark H; Baer, Donald R; Castner, David G

    2016-04-05

    Spectral modeling of photoelectrons can serve as a valuable tool when combined with X-ray photoelectron spectroscopy (XPS) analysis. Herein, a new version of the NIST Simulation of Electron Spectra for Surface Analysis (SESSA 2.0) software, capable of directly simulating spherical multilayer NPs, was applied to model citrate stabilized Au/Ag-core/shell nanoparticles (NPs). The NPs were characterized using XPS and scanning transmission electron microscopy (STEM) to determine the composition and morphology of the NPs. The Au/Ag-core/shell NPs were observed to be polydispersed in size, nonspherical, and contain off-centered Au-cores. Using the average NP dimensions determined from STEM analysis, SESSA spectral modeling indicated that washed Au/Ag-core-shell NPs were stabilized with a 0.8 nm layer of sodium citrate and a 0.05 nm (one wash) or 0.025 nm (two wash) layer of adventitious hydrocarbon, but did not fully account for the observed XPS signal from the Au-core. This was addressed by a series of simulations and normalizations to account for contributions of NP nonsphericity and off-centered Au-cores. Both of these nonuniformities reduce the effective Ag-shell thickness, which effect the Au-core photoelectron intensity. The off-centered cores had the greatest impact for the particles in this study. When the contributions from the geometrical nonuniformities are included in the simulations, the SESSA generated elemental compositions that matched the XPS elemental compositions. This work demonstrates how spectral modeling software such as SESSA, when combined with experimental XPS and STEM measurements, advances the ability to quantitatively assess overlayer thicknesses for multilayer core-shell NPs and deal with complex, nonideal geometrical properties.

  13. Bandgap- and Radial-Position-Dependent Mn-Doped Zn-Cu-In-S/ZnS Core/Shell Nanocrystals.

    Science.gov (United States)

    Peng, Lucheng; Huang, Keke; Zhang, Zhuolei; Zhang, Ying; Shi, Zhan; Xie, Renguo; Yang, Wensheng

    2016-03-03

    This paper presents a mechanistic study on the doping of Zn-Cu-In-S/ZnS core/shell quantum dots (QDs) with Mn by changing the Zn-Cu-In-S QD bandgap and dopant position inside the samples (Zn-Cu-In-S core and ZnS shell). Results show that for the Mn:Zn-Cu-In-S/ZnS system, a Mn-doped emission can be obtained when the bandgap value of the QDs is larger than the energy of Mn-doped emission. Conversely, a bandgap emission is only observed for the doped system when the bandgap value of QDs is smaller than the energy gap of the Mn-doped emission. In the Zn-Cu-In-S/Mn:ZnS systems, doped QDs show dual emissions, consisting of bandgap and Mn dopant emissions, instead of one emission band when the value of the host bandgap is larger than the energy of the Mn-doped emission. These findings indicate that the emission from Mn-doped Zn-Cu-In-S/ZnS core/shell QDs depends on the bandgap of the QDs and the dopant position inside the core/shell material. The critical bandgap of the host materials is estimated to have the same value as the energy of the Mn d-d transition. Subsequently, the mechanism of photoluminescence properties of the Mn:Zn-Cu-In-S/ZnS and Zn-Cu-In-S/Mn:ZnS core/shell QD systems is proposed. Control experiments are then carried out by preparing Mn-doped Zn(Cu)-In-S QDs with various bandgaps, and the results confirm the reliability of the suggested mechanism. Therefore, the proposed mechanism can aid the design and synthesis of novel host materials in fabricating doped QDs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Green and facile synthesis of water-soluble Cu-In-S/ZnS core/shell quantum dots.

    Science.gov (United States)

    Chen, Yanyan; Li, Shenjie; Huang, Lijian; Pan, Daocheng

    2013-07-15

    Water-soluble Cu-In-S/ZnS core/shell quantum dots with a photoluminescence quantum yield up to 38% and an emission peak tunable from 543 to 625 nm have been successfully synthesized. All of the synthetic procedures were conducted in an aqueous solution at 95 °C under open-air conditions. L-Glutathione and sodium citrate were used as the dual stabilizing agents to balance the reactivity between copper and indium ions.

  15. Enhancing photocatalytic activity by using TiO2-MgO core-shell-structured nanoparticles

    International Nuclear Information System (INIS)

    Jung, Hyun Suk; Lee, Jung-Kun; Nastasi, Michael; Kim, Jeong-Ryeol; Lee, Sang-Wook; Kim, Jin Young; Park, Jong-Sung; Hong, Kug Sun; Shin, Hyunho

    2006-01-01

    Hygroscopic Mg(OH) 2 gel was topotactically decomposed on TiO 2 particle surfaces, resulting in highly nanoporous MgO-coated TiO 2 particles. The highly hygroscopic and nanoporous MgO shell absorbed more water molecules and hydroxyl groups from the environment to yield an improved photocatalytic property of the core-shell particles as compared to the uncoated TiO 2 counterpart

  16. Functionalized porous silica&maghemite core-shell nanoparticles for applications in medicine: design, synthesis and immunotoxicity

    Czech Academy of Sciences Publication Activity Database

    Zasońska, Beata Anna; Líšková, A.; Kuricová, M.; Tulinská, J.; Pop-Georgievski, Ognen; Čiampor, F.; Vávra, I.; Dušinská, M.; Ilavská, S.; Horváthová, M.; Horák, Daniel

    2016-01-01

    Roč. 57, č. 2 (2016), s. 165-178 ISSN 0353-9504 R&D Projects: GA ČR(CZ) GC16-01128J Institutional support: RVO:61389013 Keywords : core-shell maghemite nanoparticles * proliferative activity of lymphocytes * phagocytic activity Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.619, year: 2016 http://www.cmj.hr/2016/57/2/27106358.htm

  17. Kinetic evaluation of new generation of column packed with 1.3 μm core-shell particles.

    Science.gov (United States)

    Fekete, Szabolcs; Guillarme, Davy

    2013-09-20

    The goal of this study was to critically evaluate a new generation of columns packed with 1.3 μm core-shell particles. The practical possibilities and limitations of this column technology were assessed and performance was compared with other reference columns packed with 1.7, 2.6 and 5 μm core-shell particles. The column efficiency achieved with 1.3 μm core-shell particles was indeed impressive, Hmin value of only 1.95 μm was achieved, this would correspond to an efficiency of more than 500,000 plates/m. The separation impedance of this column was particularly low, Emin=2000, mostly due to a reduced plate height, h of 1.50. Comparing the kinetic performance of 1.3 μm core-shell particles to that of other particle dimensions tested in this study revealed that the 1.3 μm material could provide systematically the shortest analysis time in a range of below 30,000 theoretical plates (Ncore shell particles, which is mandatory for performing fast-analysis and preventing the influence of frictional heat on column performance in UHPLC, it was observed that the extra-column band broadening could have a major impact on the apparent kinetic performance. In the present work, significant plate count loss was noticed for retention factors of less than 5, even with the best system on the market (σ(2)ec=2 μL(2)). Copyright © 2013 Elsevier B.V. All rights reserved.

  18. Continuous one-pot synthesis of sandwich structured core-shell particles and transformation to yolk-shell particles.

    Science.gov (United States)

    Ko, You Na; Kang, Yun Chan; Park, Seung Bin

    2013-05-10

    Scalable continuous ultrasonic spray pyrolysis is used to develop a facile one-pot method of synthesizing sandwich structured core-shell particles consisting of a Pd core, a V2O5 inner layer, and a porous SiO2 outer layer. Pd@SiO2 yolk-shell particles are easily formed by removing the V2O5 inner layer.

  19. Synthesis and magnetic properties of core/shell FeO/Fe3O4 nano-octopods

    Science.gov (United States)

    Khurshid, Hafsa; Chandra, Sayan; Li, Wanfeng; Phan, M. H.; Hadjipanayis, G. C.; Mukherjee, P.; Srikanth, H.

    2013-05-01

    We report the synthesis and magnetic properties of core/shell FeO/Fe3O4 nanoparticles with an average size of 30 nm in a complex quasi-octopod shape. FeO nanoparticles were synthesized by a wet chemical synthesis route followed by partial oxidation to form core/shell structured FeO/Fe3O4 octopods. X-ray diffraction and transmission electron microscopy confirmed the presence of iron oxide phases and the formed core/shell FeO/Fe3O4 morphology. Magnetic measurements revealed two distinct temperatures corresponding to the thermally activated Verwey transition (TV ˜ 120 K) of the ferrimagnetic Fe3O4 shell and the Neel temperature (TN ˜ 230 K) of the antiferromagnetic FeO core. The nanoparticles exhibited a strong horizontal shift in the field-cooled hysteresis loop (the so-called exchange bias (EB) effect) accompanied by enhanced coercivity. The Meiklejohn-Bean model has been implemented to quantify the amount of frozen spins that locate at the interface between FeO and Fe3O4 and are responsible for the observed EB effect.

  20. Pd@Au core-shell nanocrystals with concave cubic shapes: kinetically controlled synthesis and electrocatalytic properties.

    Science.gov (United States)

    Zhang, Ling; Niu, Wenxin; Zhao, Jianming; Zhu, Shuyun; Yuan, Yali; Hua, Lianzhe; Xu, Guobao

    2013-01-01

    A new type of concave cubic Pd@Au core-shell nanocrystals is synthesized through a kinetically controlled growth process. Pd nanocubes of 56 nm are used as the inner core, and CTAC and Br(-) are used as the capping agent and selective adsorbent, respectively. A suitable ratio of HAuCl4 and cubic Pd seeds and the presence of Br(-) anions are critical to the growth of the concave cubic Pd@Au core-shell nanocrystals. The fast deposition rate on the corners of the cubic Pd seeds promotes the overgrowth of the Au outer shell along the direction, leading to the formation of concave cubic nanostructures. The reduction process is monitored by the surface plasmon resonance spectra of the nanocrystals, and the extinction band became broader and red shifted as the nanocrystals became larger. The electrocatalytic properties of the concave cubic Pd@Au core-shell nanocrystals were investigated with the cathodic electrochemiluminescence reaction of luminol and H2O2. A possible electrocatalytic mechanism was proposed and analyzed.