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.

Synthesis and Plasmonic Understanding of Core/Satellite and Core Shell Nanostructures

Science.gov (United States)

Ruan, Qifeng

Localized surface plasmon resonance, which stems from the collective oscillations of conduction-band electrons, endows Au nanocrystals with unique optical properties. Au nanocrystals possess extremely large scattering/absorption cross-sections and enhanced local electromagnetic field, both of which are synthetically tunable. Moreover, when Au nanocrystals are closely placed or hybridized with semiconductors, the coupling and interaction between the individual components bring about more fascinating phenomena and promising applications, including plasmon-enhanced spectroscopies, solar energy harvesting, and cancer therapy. The continuous development in the field of plasmonics calls for further advancements in the preparation of high-quality plasmonic nanocrystals, the facile construction of hybrid plasmonic nanostructures with desired functionalities, as well as deeper understanding and efficient utilization of the interaction between plasmonic nanocrystals and semiconductor components. In this thesis, I developed a seed-mediated growth method for producing size-controlled Au nanospheres with high monodispersity and assembled Au nanospheres of different sizes into core/satellite nanostructures for enhancing Raman signals. For investigating the interactions between Au nanocrystals and semiconductors, I first prepared (Au core) (TiO2 shell) nanostructures, and then studied their synthetically controlled plasmonic properties and light-harvesting applications. Au nanocrystals with spherical shapes are desirable in plasmon-coupled systems owing to their high geometrical symmetry, which facilitates the analysis of electrodynamic responses in a classical electromagnetic framework and the investigation of quantum tunneling and nonlocal effects. I prepared remarkably uniform Au nanospheres with diameters ranging from 20 nm to 220 nm using a simple seed-mediated growth method associated with mild oxidation. Core/satellite nanostructures were assembled out of differently sized

Large-scale shell model calculations for the N=126 isotones Po-Pu

International Nuclear Information System (INIS)

Caurier, E.; Rejmund, M.; Grawe, H.

2003-04-01

Large-scale shell model calculations were performed in the full Z=82-126 proton model space π(Oh 9/2 , 1f 7/2 , Oi 13/2 , 2p 3/2 , 1f 5/2 , 2p 1/2 ) employing the code NATHAN. The modified Kuo-Herling interaction was used, no truncation was applied up to protactinium (Z=91) and seniority truncation beyond. The results are compared to experimental data including binding energies, level schemes and electromagnetic transition rates. An overall excellent agreement is obtained for states that can be described in this model space. Limitations of the approach with respect to excitations across the Z=82 and N=126 shells and deficiencies of the interaction are discussed. (orig.)

Fabrication, characterization and screen printing of conductive ink based on carbon@Ag core-shell nanoparticles.

Science.gov (United States)

Wu, Wei; Yang, Shuanglei; Zhang, Shaofeng; Zhang, Hongbo; Jiang, Changzhong

2014-08-01

The large-scale synthesis and characterization of carbon-core/Ag-shell (C@Ag) nanoparticles by the successive reduction of silver ammonia are described. The resultant C@Ag nanoparticles had a mean core diameter of 360 nm and a controllable shell thickness from 10 to 40 nm by simple adjustments of repeat coating times. Various analysis techniques confirmed that the carbon cores were fully covered by Ag nanoshells. The results also show that C/Ag composite nanomaterials-based conductive inks, which can be easily produced on a large scale and possess outstanding electronic properties, have great potential for the convenient fabrication of flexible and low-cost carbon-based electronic devices and replace the traditional pure silver paste, by using a simple screen printing technique. Copyright © 2013 Elsevier Inc. All rights reserved.

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.

Anisotropic deformation of metallo-dielectric core-shell colloids under MeV ion irradiation

International Nuclear Information System (INIS)

Penninkhof, J.J.; Dillen, T. van; Roorda, S.; Graf, C.; Blaaderen, A. van; Vredenberg, A.M.; Polman, A.

2006-01-01

We have studied the deformation of metallo-dielectric core-shell colloids under 4 MeV Xe, 6 and 16 MeV Au, 30 MeV Si and 30 MeV Cu ion irradiation. Colloids of silica surrounded by a gold shell, with a typical diameter of 400 nm, show anisotropic plastic deformation under MeV ion irradiation, with the metal flowing conform the anisotropically deforming silica core. The 20 nm thick metal shell imposes a mechanical constraint on the deforming silica core, reducing the net deformation strain rate compared to that of pure silica. In colloids consisting of a Au core and a silica shell, the silica expands perpendicular to the ion beam, while the metal core shows a large elongation along the ion beam direction, provided the silica shell is thick enough (>40 nm). A minimum electronic energy loss of 3.3 keV/nm is required for shape transformation of the metal core. Silver cores embedded in a silica shell show no elongation, but rather disintegrate. Also in planar SiO 2 films, Au and Ag colloids show entirely different behavior under MeV irradiation. We conclude that the deformation model of core-shell colloids must include ion-induced particle disintegration in combination with thermodynamical effects, possibly in combination with mechanical effects driven by stresses around the ion tracks

Anisotropic deformation of metallo-dielectric core shell colloids under MeV ion irradiation

Science.gov (United States)

Penninkhof, J. J.; van Dillen, T.; Roorda, S.; Graf, C.; van Blaaderen, A.; Vredenberg, A. M.; Polman, A.

2006-01-01

We have studied the deformation of metallo-dielectric core-shell colloids under 4 MeV Xe, 6 and 16 MeV Au, 30 MeV Si and 30 MeV Cu ion irradiation. Colloids of silica surrounded by a gold shell, with a typical diameter of 400 nm, show anisotropic plastic deformation under MeV ion irradiation, with the metal flowing conform the anisotropically deforming silica core. The 20 nm thick metal shell imposes a mechanical constraint on the deforming silica core, reducing the net deformation strain rate compared to that of pure silica. In colloids consisting of a Au core and a silica shell, the silica expands perpendicular to the ion beam, while the metal core shows a large elongation along the ion beam direction, provided the silica shell is thick enough (>40 nm). A minimum electronic energy loss of 3.3 keV/nm is required for shape transformation of the metal core. Silver cores embedded in a silica shell show no elongation, but rather disintegrate. Also in planar SiO2 films, Au and Ag colloids show entirely different behavior under MeV irradiation. We conclude that the deformation model of core-shell colloids must include ion-induced particle disintegration in combination with thermodynamical effects, possibly in combination with mechanical effects driven by stresses around the ion tracks.

Influence of Shell Thickness on the Colloidal Stability of Magnetic Core-Shell Particle Suspensions.

Science.gov (United States)

Neville, Frances; Moreno-Atanasio, Roberto

2018-01-01

We present a Discrete Element study of the behavior of magnetic core-shell particles in which the properties of the core and the shell are explicitly defined. Particle cores were considered to be made of pure iron and thus possessed ferromagnetic properties, while particle shells were considered to be made of silica. Core sizes ranged between 0.5 and 4.0 μm with the actual particle size of the core-shell particles in the range between 0.6 and 21 μm. The magnetic cores were considered to have a magnetization of one tenth of the saturation magnetization of iron. This study aimed to understand how the thickness of the shell hinders the formation of particle chains. Chain formation was studied with different shell thicknesses and particle sizes in the presence and absence of an electrical double layer force in order to investigate the effect of surface charge density on the magnetic core-shell particle interactions. For core sizes of 0.5 and 4.0 μm the relative shell thicknesses needed to hinder the aggregation process were approximately 0.4 and 0.6 respectively, indicating that larger core sizes are detrimental to be used in applications in which no flocculation is needed. In addition, the presence of an electrical double layer, for values of surface charge density of less than 20 mC/m 2 , could stop the contact between particles without hindering their vertical alignment. Only when the shell thickness was considerably larger, was the electrical double layer able to contribute to the full disruption of the magnetic flocculation process.

One-step synthesis of gold-polyaniline core-shell particles

International Nuclear Information System (INIS)

Wang Zhijuan; Yuan Junhua; Han Dongxue; Niu Li; Ivaska, Ari

2007-01-01

A one-step method has been developed for synthesizing gold-polyaniline (Au-PANI) core-shell particles by using chlorauric acid (HAuCl 4 ) to oxidize aniline in the presence of acetic acid and Tween 40 at room temperature. SEM images indicated that the resulting core-shell particles were composed of submicrometre-scale Au particles and PANI shells with an average thickness of 25 nm. Furthermore, a possible mechanism concerning the growth of Au-PANI particles was also proposed based on the results of control experiments

On the core-mass-shell-luminosity relation for shell-burning stars

International Nuclear Information System (INIS)

Jeffery, C.S.; Saint Andrews Univ.

1988-01-01

Core-mass-shell-luminosity relations for several types of shell-burning star have been calculated using simultaneous differential equations derived from simple homology approximations. The principal objective of obtaining a mass-luminosity relation for helium giants was achieved. This relation gives substantially higher luminosities than the equivalent relation for H-shell stars with core masses greater than 1 solar mass. The algorithm for calculating mass-luminosity relations in this fashion was investigated in detail. Most of the assumptions regarding the physics in the shell do not play a critical role in determining the core-mass-shell-luminosity relation. The behaviour of the core-mass-core-radius relation for a growing degenerate core as a single unique function of mass and growth rate needs to be defined before a single core-mass-shell-luminosity relation for all H-shell stars can be obtained directly from the homology approximations. (author)

Sidewall coring shell

Energy Technology Data Exchange (ETDEWEB)

Edelman, Ya A; Konstantinov, L P; Martyshin, A N

1966-12-12

A sidewall coring shell consists of a housing and a detachable core catcher. The core lifter is provided with projections, the ends of which are situated in another plane, along the longitudinal axis of the lifter. The chamber has corresponding projections.

Enhanced linear photonic nanojet generated by core-shell optical microfibers

Science.gov (United States)

Liu, Cheng-Yang; Yen, Tzu-Ping; Chen, Chien-Wen

2017-05-01

The generation of linear photonic nanojet using core-shell optical microfiber is demonstrated numerically and experimentally in the visible light region. The power flow patterns for the core-shell optical microfiber are calculated by using the finite-difference time-domain method. The focusing properties of linear photonic nanojet are evaluated in terms of length and width along propagation and transversal directions. In experiment, the silica optical fiber is etched chemically down to 6 μm diameter and coated with metallic thin film by using glancing angle deposition. We show that the linear photonic nanojet is enhanced clearly by metallic shell due to surface plasmon polaritons. The large-area superresolution imaging can be performed by using a core-shell optical microfiber in the far-field system. The potential applications of this core-shell optical microfiber include micro-fluidics and nano-structure measurements.

Ge/Si core/shell quantum dots in alumina: tuning the optical absorption by the core and shell size

Directory of Open Access Journals (Sweden)

Nekić Nikolina

2017-03-01

Full Text Available Ge/Si core/shell quantum dots (QDs recently received extensive attention due to their specific properties induced by the confinement effects of the core and shell structure. They have a type II confinement resulting in spatially separated charge carriers, the electronic structure strongly dependent on the core and shell size. Herein, the experimental realization of Ge/Si core/shell QDs with strongly tunable optical properties is demonstrated. QDs embedded in an amorphous alumina glass matrix are produced by simple magnetron sputtering deposition. In addition, they are regularly arranged within the matrix due to their self-assembled growth regime. QDs with different Ge core and Si shell sizes are made. These core/shell structures have a significantly stronger absorption compared to pure Ge QDs and a highly tunable absorption peak dependent on the size of the core and shell. The optical properties are in agreement with recent theoretical predictions showing the dramatic influence of the shell size on optical gap, resulting in 0.7 eV blue shift for only 0.4 nm decrease at the shell thickness. Therefore, these materials are very promising for light-harvesting applications.

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.

Comparison of prestellar core elongations and large-scale molecular cloud structures in the Lupus I region

Energy Technology Data Exchange (ETDEWEB)

Poidevin, Frédérick [UCL, KLB, Department of Physics and Astronomy, Gower Place, London WC1E 6BT (United Kingdom); Ade, Peter A. R.; Hargrave, Peter C.; Nutter, David [School of Physics and Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA (United Kingdom); Angile, Francesco E.; Devlin, Mark J.; Klein, Jeffrey [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Benton, Steven J.; Netterfield, Calvin B. [Department of Physics, University of Toronto, 60 St. George Street, Toronto, ON M5S 1A7 (Canada); Chapin, Edward L. [XMM SOC, ESAC, Apartado 78, E-28691 Villanueva de la Canãda, Madrid (Spain); Fissel, Laura M.; Gandilo, Natalie N. [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada); Fukui, Yasuo [Department of Physics, Nagoya University, Chikusa-ku, Nagoya, Aichi 464-8601 (Japan); Gundersen, Joshua O. [Department of Physics, University of Miami, 1320 Campo Sano Drive, Coral Gables, FL 33146 (United States); Korotkov, Andrei L. [Department of Physics, Brown University, 182 Hope Street, Providence, RI 02912 (United States); Matthews, Tristan G.; Novak, Giles [Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Moncelsi, Lorenzo; Mroczkowski, Tony K. [California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Olmi, Luca, E-mail: fpoidevin@iac.es [Physics Department, University of Puerto Rico, Rio Piedras Campus, Box 23343, UPR station, San Juan, PR 00931 (United States); and others

2014-08-10

Turbulence and magnetic fields are expected to be important for regulating molecular cloud formation and evolution. However, their effects on sub-parsec to 100 parsec scales, leading to the formation of starless cores, are not well understood. We investigate the prestellar core structure morphologies obtained from analysis of the Herschel-SPIRE 350 μm maps of the Lupus I cloud. This distribution is first compared on a statistical basis to the large-scale shape of the main filament. We find the distribution of the elongation position angle of the cores to be consistent with a random distribution, which means no specific orientation of the morphology of the cores is observed with respect to the mean orientation of the large-scale filament in Lupus I, nor relative to a large-scale bent filament model. This distribution is also compared to the mean orientation of the large-scale magnetic fields probed at 350 μm with the Balloon-borne Large Aperture Telescope for Polarimetry during its 2010 campaign. Here again we do not find any correlation between the core morphology distribution and the average orientation of the magnetic fields on parsec scales. Our main conclusion is that the local filament dynamics—including secondary filaments that often run orthogonally to the primary filament—and possibly small-scale variations in the local magnetic field direction, could be the dominant factors for explaining the final orientation of each core.

Core–shell interaction and its impact on the optical absorption of pure and doped core-shell CdSe/ZnSe nanoclusters

Energy Technology Data Exchange (ETDEWEB)

Wang, Xinqin; Cui, Yingqi; Zeng, Qun; Yang, Mingli, E-mail: myang@scu.edu.cn [Institute of Atomic and Molecular Physics, Key Laboratory of High Energy Density Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610065 (China); Yu, Shengping [College of Chemistry and Environment Protection Engineering, Southwest University for Nationalities, Chengdu 610041 (China)

2016-04-07

The structural, electronic, and optical properties of core-shell nanoclusters, (CdSe){sub x}@(CdSe){sub y} and their Zn-substituted complexes of x = 2–4 and y = 16–28, were studied with density functional theory calculations. The substitution was applied in the cores, the shells, and/or the whole clusters. All these clusters are characterized by their core-shell structures in which the core-shell interaction was found different from those in core or in shell, as reflected by their bondlengths, volumes, and binding energies. Moreover, the core and shell combine together to compose a new cluster with electronic and optical properties different from those of separated individuals, as reflected by their HOMO-LUMO gaps and optical absorptions. With the substitution of Cd by Zn, the structural, electronic, and optical properties of clusters change regularly. The binding energy increases with Zn content, attributed to the strong Zn–Se bonding. For the same core/shell, the structure with a CdSe shell/core has a narrower gap than that with a ZnSe shell/core. The optical absorption spectra also change accordingly with Zn substitution. The peaks blueshift with increasing Zn concentration, accompanying with shape variations in case large number of Cd atoms are substituted. Our calculations reveal the core-shell interaction and its influence on the electronic and optical properties of the core-shell clusters, suggesting a composition–structure–property relationship for the design of core-shell CdSe and ZnSe nanoclusters.

Recent Developments in No-Core Shell-Model Calculations

International Nuclear Information System (INIS)

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

2009-01-01

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.

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.

Core excitations across the neutron shell gap in 207Tl

Directory of Open Access Journals (Sweden)

E. Wilson

2015-07-01

Full Text Available The single closed-neutron-shell, one proton–hole nucleus 207Tl was populated in deep-inelastic collisions of a 208Pb beam with a 208Pb target. The yrast and near-yrast level scheme has been established up to high excitation energy, comprising an octupole phonon state and a large number of core excited states. Based on shell-model calculations, all observed single core excitations were established to arise from the breaking of the N=126 neutron core. While the shell-model calculations correctly predict the ordering of these states, their energies are compressed at high spins. It is concluded that this compression is an intrinsic feature of shell-model calculations using two-body matrix elements developed for the description of two-body states, and that multiple core excitations need to be considered in order to accurately calculate the energy spacings of the predominantly three-quasiparticle states.

Synthesis of parallel and antiparallel core-shell triangular nanoparticles

Science.gov (United States)

Bhattacharjee, Gourab; Satpati, Biswarup

2018-04-01

Core-shell triangular nanoparticles were synthesized by seed mediated growth. Using triangular gold (Au) nanoparticle as template, we have grown silver (Ag) shellto get core-shell nanoparticle. Here by changing the chemistry we have grown two types of core-shell structures where core and shell is having same symmetry and also having opposite symmetry. Both core and core-shell nanoparticles were characterized using transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) to know the crystal structure and composition of these synthesized core-shell nanoparticles. From diffraction pattern analysis and energy filtered TEM (EFTEM) we have confirmed the crystal facet in core is responsible for such two dimensional growth of core-shell nanostructures.

Fixed-bed adsorption separation of xylene isomers over sio2/silicallite-1 core-shell adsorbents

KAUST Repository

Khan, Easir A.

2013-12-29

SiO2/Silicalite-1 core-shell material has been demonstrated as potential shape selective adsorbent in gas phase separation of p-xylene from a mixture of p/o-xylene isomers. The core-shell composite comprised of large silica core and thin polycrystalline silicalite-1 shell which was synthesized via a self-assembly of silicalite-1 nanocrystals on core silica surface followed by a secondary seeded growth method. The core materials, SiO2 used in this study has mesoporosity with an average pore diameter of 60Å and hence offers no shape selectivity for xylene isomers. However, the shell, silicalite-1 contains rigid pore structures and preferentially adsorbs p-xylene from their isomers mixtures. A series of adsorption fixed bed breakthrough adsorption/desorption experiment was performed to obtain the equilibrium isotherms and adsorption isotherm parameters of xylene isomers. The equilibrium isotherms of xylene isomers follow the Langmuir\\'s model. A chromatographic adsorption model has been used to describe the fixed-bed breakthrough profiles of xylene isomers. The model has successfully predicted the responses of the binary mixtures of p/o-xylene isomers. The SiO2/silicalite-1 core-shell adsorbents have shown para-selectivity as high as 15. © Bangladesh Uni. of Engg. & Tech.

Nitride stabilized core/shell nanoparticles

Science.gov (United States)

Kuttiyiel, Kurian Abraham; Sasaki, Kotaro; Adzic, Radoslav R.

2018-01-30

Nitride stabilized metal nanoparticles and methods for their manufacture are disclosed. In one embodiment the metal nanoparticles have a continuous and nonporous noble metal shell with a nitride-stabilized non-noble metal core. The nitride-stabilized core provides a stabilizing effect under high oxidizing conditions suppressing the noble metal dissolution during potential cycling. The nitride stabilized nanoparticles may be fabricated by a process in which a core is coated with a shell layer that encapsulates the entire core. Introduction of nitrogen into the core by annealing produces metal nitride(s) that are less susceptible to dissolution during potential cycling under high oxidizing conditions.

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.

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.

In-medium no-core shell model for ab initio nuclear structure calculations

International Nuclear Information System (INIS)

Gebrerufael, Eskendr

2017-01-01

In this work, we merge two successful ab initio nuclear-structure methods, the no-core shell model (NCSM) and the multi-reference in-medium similarity renormalization group (IM-SRG), to define a novel many-body approach for the comprehensive description of ground and excited states of closed- and open-shell medium-mass nuclei. Building on the key advantages of the two methods - the decoupling of excitations at the many-body level in the IM-SRG, and the exact diagonalization in the NCSM applicable up to medium-light nuclei - their combination enables fully converged no-core calculations for an unprecedented range of nuclei and observables at moderate computational cost. The efficiency and rapid model-space convergence of the new approach make it ideally suited for ab initio studies of ground and low-lying excited states of nuclei up to the medium-mass regime. Interactions constructed within the framework of chiral effective field theory provide an excellent opportunity to describe properties of nuclei from first principles, i.e., rooted in quantum chromodynamics, they overcome the lack of predictive power of phenomenological potentials. The hard core of these interactions causes strong short-range correlations, which we soften by using the similarity-renormalization-group transformation that accelerates the model-space convergence of many-body calculations. Three-nucleon effects, which are mandatory for the correct description of bulk properties of nuclei, are included in our calculations by using the normal-ordered two-body approximation, which has been shown to be sufficient to capture the main effects of the three-nucleon interaction. Using these interactions, we analyze energies of ground and excited states in the carbon and oxygen isotopic chains, where conventional NCSM calculations are still feasible and provide an important benchmark. Furthermore, we study the Hoyle state in 12 C - a three-alpha cluster state that cannot be converged in standard NCSM

Fixed-bed adsorption separation of xylene isomers over sio2/silicallite-1 core-shell adsorbents

KAUST Repository

Khan, Easir A.; Rajendran, Arvind; Lai, Zhiping

2013-01-01

SiO2/Silicalite-1 core-shell material has been demonstrated as potential shape selective adsorbent in gas phase separation of p-xylene from a mixture of p/o-xylene isomers. The core-shell composite comprised of large silica core and thin

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

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.

Ni@Ru and NiCo@Ru Core-Shell Hexagonal Nanosandwiches with a Compositionally Tunable Core and a Regioselectively Grown Shell.

Science.gov (United States)

Hwang, Hyeyoun; Kwon, Taehyun; Kim, Ho Young; Park, Jongsik; Oh, Aram; Kim, Byeongyoon; Baik, Hionsuck; Joo, Sang Hoon; Lee, Kwangyeol

2018-01-01

The development of highly active electrocatalysts is crucial for the advancement of renewable energy conversion devices. The design of core-shell nanoparticle catalysts represents a promising approach to boost catalytic activity as well as save the use of expensive precious metals. Here, a simple, one-step synthetic route is reported to prepare hexagonal nanosandwich-shaped Ni@Ru core-shell nanoparticles (Ni@Ru HNS), in which Ru shell layers are overgrown in a regioselective manner on the top and bottom, and around the center section of a hexagonal Ni nanoplate core. Notably, the synthesis can be extended to NiCo@Ru core-shell nanoparticles with tunable core compositions (Ni 3 Co x @Ru HNS). Core-shell HNS structures show superior electrocatalytic activity for the oxygen evolution reaction (OER) to a commercial RuO 2 black catalyst, with their OER activity being dependent on their core compositions. The observed trend in OER activity is correlated to the population of Ru oxide (Ru 4+ ) species, which can be modulated by the core compositions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Soft shell hard core concept for aircraft impact resistant design

International Nuclear Information System (INIS)

Chen, C.; Rieck, P.J.

1978-01-01

For nuclear power plants sited in the vicinity of airports, the hypothetical events of aircraft impact have to be designed for. The conventional design concept is to strengthen the exterior structure to resist the impact induced force. The stiffened structures have two (2) disadvantages; one is the high construction cost, and the other is the high reaction force induced as well as the vibrational effects on the interior equipment and piping systems. This new soft shell hard core concept can relieve the above shortcomings. In this concept, the essential equipment required for safety are installed inside the hard core area for protection and the non-essential equipment are maintained between the hard core and soft shell area. During a hypothetical impact event, the soft shell will collapse locally and absorb large amounts of kinetic energy; hence, it reduces the reaction force and the vibrational effects. The design and analysis of the soft shell concept are discussed. (Author)

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

Short-Range Correlated Magnetic Core-Shell CrO₂/Cr₂O₃ Nanorods: Experimental Observations and Theoretical Considerations.

Science.gov (United States)

Gandhi, Ashish C; Li, Tai-Yue; Chan, Ting Shan; Wu, Sheng Yun

2018-05-09

With the evolution of synthesis and the critical characterization of core-shell nanostructures, short-range magnetic correlation is of prime interest in employing their properties to develop novel devices and widespread applications. In this regard, a novel approach of the magnetic core-shell saturated magnetization (CSSM) cylinder model solely based on the contribution of saturated magnetization in one-dimensional CrO₂/Cr₂O₃ core-shell nanorods (NRs) has been developed and applied for the determination of core-diameter and shell-thickness. The nanosized effect leads to a short-range magnetic correlation of ferromagnetic core-CrO₂ extracted from CSSM, which can be explained using finite size scaling method. The outcome of this study is important in terms of utilizing magnetic properties for the critical characterization of core-shell nanomagnetic materials.

Construction of carbon nanoflakes shell on CuO nanowires core as enhanced core/shell arrays anode of lithium ion batteries

International Nuclear Information System (INIS)

Cao, F.; Xia, X.H.; Pan, G.X.; Chen, J.; Zhang, Y.J.

2015-01-01

Highlights: • CuO/C core/shell nanowire arrays are prepared by electro-deposition + ALD method. • Carbon shell is favorable for structural stability. • CuO/C core/shell arrays show enhanced cycle stability and high capacity. - Abstract: Tailored metal oxide/carbon composite structures have attracted great attention due to potential synergistic effects and enhanced properties. In this work, novel CuO/C core/shell nanowire arrays are prepared by the combination of electro-deposition of CuO and atomic-layer-deposition-assisted formation of carbon nanoflakes shell. The CuO nanowires with diameters of ∼200 nm are homogenously coated by carbon nanoflakes shell. When evaluated as anode materials for lithium ion batteries (LIBs), compared to the unmodified CuO nanowire arrays, the CuO/C core/shell nanowire arrays exhibit improved electrochemical performances with higher capacity, better electrochemical reactivity and high-rate capability as well as superior cycling life (610 mAh g"−"1 at 0.5C after 290 cycles). The enhanced electrochemical performance is mainly attributed to the introduction of carbon flake shell in the core/shell nanowire arrays structure, which provides higher active material-electrolyte contact area, improved electrical conductivity, and better accommodation of volume change. The proposed method provides a new way for fabrication of high-performance metal oxides anodes of LIBs.

Dehydration of core/shell fruits

OpenAIRE

Liu, Y.; Yang, Xiaosong; Cao, Y.; Wang, Z.; Chen, B.; Zhang, Jian J.; Zhang, H.

2015-01-01

Dehydrated core/shell fruits, such as jujubes, raisins and plums, show very complex buckles and wrinkles on their exocarp. It is a challenging task to model such complicated patterns and their evolution in a virtual environment even for professional animators. This paper presents a unified physically-based approach to simulate the morphological transformation for the core/shell fruits in the dehydration process. A finite element method (FEM), which is based on the multiplicative decomposition...

Isocratic and gradient impedance plot analysis and comparison of some recently introduced large size core-shell and fully porous particles.

Science.gov (United States)

Vanderheyden, Yoachim; Cabooter, Deirdre; Desmet, Gert; Broeckhoven, Ken

2013-10-18

The intrinsic kinetic performance of three recently commercialized large size (≥4μm) core-shell particles packed in columns with different lengths has been measured and compared with that of standard fully porous particles of similar and smaller size (5 and 3.5μm, respectively). The kinetic performance is compared in both absolute (plot of t0 versus the plate count N or the peak capacity np for isocratic and gradient elution, respectively) and dimensionless units. The latter is realized by switching to so-called impedance plots, a format which has been previously introduced (as a plot of t0/N(2) or E0 versus Nopt/N) and has in the present study been extended from isocratic to gradient elution (where the impedance plot corresponds to a plot of t0/np(4) versus np,opt(2)/np(2)). Both the isocratic and gradient impedance plot yielded a very similar picture: the clustered impedance plot curves divide into two distinct groups, one for the core-shell particles (lowest values, i.e. best performance) and one for the fully porous particles (highest values), confirming the clear intrinsic kinetic advantage of core-shell particles. If used around their optimal flow rate, the core-shell particles displayed a minimal separation impedance that is about 40% lower than the fully porous particles. Even larger gains in separation speed can be achieved in the C-term regime. Copyright © 2013 Elsevier B.V. All rights reserved.

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.

Core-shell architectures as nano-size transporters

International Nuclear Information System (INIS)

Adeli, M.; Zarnegar, Z.; Kabiri, R.; Salimi, F.; Dadkah, A.

2006-01-01

Core-shell architectures containing poly (ethylene imine) (PEI) as a core and poly (lactide) (PLA) as arms were prepared. PEI was used as macro initiator for ring opening polymerization of lactide. PEI-PLA core-shell architectures were able to encapsulate guest molecules. Size of the core-shell architectures was between 10- 100 nm, hence they can be considered as nano carriers to transport the guest molecules. Transport capacity of nano carriers depends on their nano-environments and type of self-assembly in solvent. In solid state nano carriers self-assemble as long structures with nano-size diameter or they form network structures. Aggregations type depends on the concentration of nano carriers in solution. Effect of the shell thickness and aggregation type on the release rate are also investigated

Wave Function Engineering in CdSe/PbS Core/Shell Quantum Dots.

Science.gov (United States)

Wieliczka, Brian M; Kaledin, Alexey L; Buhro, William E; Loomis, Richard A

2018-05-25

The synthesis of epitaxial CdSe/PbS core/shell quantum dots (QDs) is reported. The PbS shell grows in a rock salt structure on the zinc blende CdSe core, thereby creating a crystal structure mismatch through additive growth. Absorption and photoluminescence (PL) band edge features shift to lower energies with increasing shell thickness, but remain above the CdSe bulk band gap. Nevertheless, the profiles of the absorption spectra vary with shell growth, indicating that the overlap of the electron and hole wave functions is changing significantly. This leads to over an order of magnitude reduction of absorption near the band gap and a large, tunable energy shift, of up to 550 meV, between the onset of strong absorption and the band edge PL. While the bulk valence and conduction bands adopt an inverse type-I alignment, the observed spectroscopic behavior is consistent with a transition between quasi-type-I and quasi-type-II behavior depending on shell thickness. Three effective mass approximation models support this hypothesis and suggest that the large difference in effective masses between the core and shell results in hole localization in the CdSe core and a delocalization of the electron across the entire QD. These results show the tuning of wave functions and transition energies in CdSe/PbS nanoheterostructures with prospects for use in optoelectronic devices for luminescent solar concentration or multiexciton generation.

Core/shell particles containing liquid cores : morphology prediction, synthesis and characterization

NARCIS (Netherlands)

Zyl, van A.J.P.; Sanderson, R.D.; Wet-Roos, de D.; Klumperman, B.

2003-01-01

The ability to synthesize core/shell particles with distinct geometries is becoming increasingly important due to their potential applications. In this study structured particles with liquid cores and polymeric shells were synthesized by an in situ miniemulsion polymerization reaction. The resulting

Core-Shell-Corona Micelles with a Responsive Shell.

Science.gov (United States)

Gohy, Jean-François; Willet, Nicolas; Varshney, Sunil; Zhang, Jian-Xin; Jérôme, Robert

2001-09-03

A reactor for the synthesis of gold nanoparticles is one of the uses of a poly(styrene)-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) triblock copolymer (PS-b-P2VP-b-PEO) which forms core-shell-corona micelles in water. Very low polydispersity spherical micelles are observed that consist of a PS core surrounded by a pH-sensitive P2VP shell and a corona of PEO chains end-capped by a hydroxyl group. The corona can act as a site for attaching responsive or sensing molecules. © 2001 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.

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.

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

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.

Shell model in large spaces and statistical spectroscopy

International Nuclear Information System (INIS)

Kota, V.K.B.

1996-01-01

For many nuclear structure problems of current interest it is essential to deal with shell model in large spaces. For this, three different approaches are now in use and two of them are: (i) the conventional shell model diagonalization approach but taking into account new advances in computer technology; (ii) the shell model Monte Carlo method. A brief overview of these two methods is given. Large space shell model studies raise fundamental questions regarding the information content of the shell model spectrum of complex nuclei. This led to the third approach- the statistical spectroscopy methods. The principles of statistical spectroscopy have their basis in nuclear quantum chaos and they are described (which are substantiated by large scale shell model calculations) in some detail. (author)

Axial strain in GaAs/InAs core-shell nanowires

Energy Technology Data Exchange (ETDEWEB)

Biermanns, Andreas; Pietsch, Ullrich [Universitaet Siegen, Festkoerperphysik, 57068 Siegen (Germany); Rieger, Torsten; Gruetzmacher, Detlev; Ion Lepsa, Mihail [Peter Gruenberg Institute (PGI-9), Forschungszentrum, 52425 Juelich (Germany); JARA-Fundamentals of Future Information Technology, 52425 Juelich (Germany); Bussone, Genziana [Universitaet Siegen, Festkoerperphysik, 57068 Siegen (Germany); ESRF, 6 rue Jules Horowitz, BP220, F-38043 Grenoble Cedex (France)

2013-01-28

We study the axial strain relaxation in GaAs/InAs core-shell nanowire heterostructures grown by molecular beam epitaxy. Besides a gradual strain relaxation of the shell material, we find a significant strain in the GaAs core, increasing with shell thickness. This strain is explained by a saturation of the dislocation density at the core-shell interface. Independent measurements of core and shell lattice parameters by x-ray diffraction reveal a relaxation of 93% in a 35 nm thick InAs shell surrounding cores of 80 nm diameter. The compressive strain of -0.5% compared to bulk InAs is accompanied by a tensile strain up to 0.9% in the GaAs core.

Size-exclusion chromatography using core-shell particles.

Science.gov (United States)

Pirok, Bob W J; Breuer, Pascal; Hoppe, Serafine J M; Chitty, Mike; Welch, Emmet; Farkas, Tivadar; van der Wal, Sjoerd; Peters, Ron; Schoenmakers, Peter J

2017-02-24

Size-exclusion chromatography (SEC) is an indispensable technique for the separation of high-molecular-weight analytes and for determining molar-mass distributions. The potential application of SEC as second-dimension separation in comprehensive two-dimensional liquid chromatography demands very short analysis times. Liquid chromatography benefits from the advent of highly efficient core-shell packing materials, but because of the reduced total pore volume these materials have so far not been explored in SEC. The feasibility of using core-shell particles in SEC has been investigated and contemporary core-shell materials were compared with conventional packing materials for SEC. Columns packed with very small core-shell particles showed excellent resolution in specific molar-mass ranges, depending on the pore size. The analysis times were about an order of magnitude shorter than what could be achieved using conventional SEC columns. Copyright © 2016 Elsevier B.V. All rights reserved.

Distinction of neurochemistry between the cores and their shells of auditory nuclei in tetrapod species.

Science.gov (United States)

Zeng, ShaoJu; Li, Jia; Zhang, XinWen; Zuo, MingXue

2007-01-01

The distribution of Met-enkephalin (ENK), substance P (SP) and serotonin (5-HT) differs between the core and shell regions of the mesencephalic and diencephalic auditory nuclei of the turtle [Belekhova et al., 2002]. These neurochemical distinctions are also found in other tetrapods (mammals, birds and amphibians). The distribution of ENK, SP and 5-HT was examined in the core and shell regions of both mesencephalic and diencephalic auditory nuclei, and in the telencephalic auditory areas of Bengalese finches (Lonchura striata) and mice (Mus musculus), as well as in corresponding auditory areas in toads (Bufo bufo). ENK, SP and 5-HT immunoreactive fibers and perikarya were largely absent from the core regions of both mesencephalic and diencephalic auditory nuclei, in comparison with the shell regions of mice and Bengalese finches. In the toad, however, this pattern was observed in the mesencephalic auditory nucleus, but not in the diencephalic auditory areas. ENK and SP immunoreactive perikarya were detected in the telencephalic auditory area of mice, whereas no ENK, SP or 5-HT immunolabeling was observed in the telencephalic auditory area (Field L) of Bengalese finches. These findings are discussed in terms of the evolution of the core-and-shell organization of auditory nuclei of tetrapods. Copyright 2007 S. Karger AG, Basel.

Gold-Pluronic core-shell nanoparticles: synthesis, characterization and biological evaluation

Energy Technology Data Exchange (ETDEWEB)

Simon, Timea; Boca, Sanda [Babes-Bolyai University, Nanobiophotonics and Laser Microspectroscopy Center, Interdisciplinary Research Institute on Bio-Nano-Sciences and Faculty of Physics (Romania); Biro, Dominic [Sapientia University, Department of Mechanical Engineering, Faculty of Technical and Human Sciences (Romania); Baldeck, Patrice [Universite Joseph Fourier and CNRS, Laboratoire Interdisciplinaire de Physique, UMR 5588, CNRS (France); Astilean, Simion, E-mail: simion.astilean@phys.ubbcluj.ro [Babes-Bolyai University, Nanobiophotonics and Laser Microspectroscopy Center, Interdisciplinary Research Institute on Bio-Nano-Sciences and Faculty of Physics (Romania)

2013-04-15

This study presents the synthesis of gold-Pluronic core-shell nanoparticles by a two-step method and investigates their biological impact on cancer cells, specifically nanoparticle internalization and cytotoxicity. Uniform, 9-10-nm-sized, hydrophobic gold nanoparticles were synthesized in organic phase by reducing gold salt with oleylamine, after which oleylamine-protected gold nanoparticles were phase-transferred into aqueous medium using Pluronic F127 block copolymer, resulting in gold-Pluronic core-shell nanoparticles with a mean hydrodynamic diameter of {approx}35 nm. The formation and phase-transfer of gold nanoparticles were analyzed by UV-Vis absorption spectroscopy, transmission electron microscopy, and dynamic light scattering. The obtained gold-Pluronic core-shell nanoparticles proved to be highly stable in salted solution. Cytotoxicity tests showed no modification of cellular viability in the presence of properly purified particles. Furthermore, dark-field cellular imaging demonstrated that gold-Pluronic nanoparticles were able to be efficiently uptaken by cells, being internalized through nonspecific endocytosis. The high stability, proven biocompatibility, and imaging properties of gold-Pluronic core-shell nanoparticles hold promise for relevant intracellular applications, with such a design providing the feasibility to combine all multiple functionalities in one nanoparticle for simultaneous detection and imaging.

Ni3Si(Al)/a-SiOx core shell nanoparticles: characterization, shell formation, and stability

Science.gov (United States)

Pigozzi, G.; Mukherji, D.; Gilles, R.; Barbier, B.; Kostorz, G.

2006-08-01

We have used an electrochemical selective phase dissolution method to extract nanoprecipitates of the Ni3Si-type intermetallic phase from two-phase Ni-Si and Ni-Si-Al alloys by dissolving the matrix phase. The extracted nanoparticles are characterized by transmission electron microscopy, energy-dispersive x-ray spectrometry, x-ray powder diffraction, and electron powder diffraction. It is found that the Ni3Si-type nanoparticles have a core-shell structure. The core maintains the size, the shape, and the crystal structure of the precipitates that existed in the bulk alloys, while the shell is an amorphous phase, containing only Si and O (SiOx). The shell forms around the precipitates during the extraction process. After annealing the nanoparticles in nitrogen at 700 °C, the tridymite phase recrystallizes within the shell, which remains partially amorphous. In contrast, on annealing in air at 1000 °C, no changes in the composition or the structure of the nanoparticles occur. It is suggested that the shell forms after dealloying of the matrix phase, where Si atoms, the main constituents of the shell, migrate to the surface of the precipitates.

Efficacy of the SU(3) scheme for ab initio large-scale calculations beyond the lightest nuclei

Energy Technology Data Exchange (ETDEWEB)

Dytrych, T. [Academy of Sciences of the Czech Republic (ASCR), Prague (Czech Republic); Louisiana State Univ., Baton Rouge, LA (United States); Maris, Pieter [Iowa State Univ., Ames, IA (United States); Launey, K. D. [Louisiana State Univ., Baton Rouge, LA (United States); Draayer, J. P. [Louisiana State Univ., Baton Rouge, LA (United States); Vary, James [Iowa State Univ., Ames, IA (United States); Langr, D. [Czech Technical Univ., Prague (Czech Republic); Aerospace Research and Test Establishment, Prague (Czech Republic); Saule, E. [Univ. of North Carolina, Charlotte, NC (United States); Caprio, M. A. [Univ. of Notre Dame, IN (United States); Catalyurek, U. [The Ohio State Univ., Columbus, OH (United States). Dept. of Electrical and Computer Engineering; Sosonkina, M. [Old Dominion Univ., Norfolk, VA (United States)

2016-06-09

We report on the computational characteristics of ab initio nuclear structure calculations in a symmetry-adapted no-core shell model (SA-NCSM) framework. We examine the computational complexity of the current implementation of the SA-NCSM approach, dubbed LSU3shell, by analyzing ab initio results for ⁶Li and ¹²C in large harmonic oscillator model spaces and SU(3)-selected subspaces. We demonstrate LSU3shell's strong-scaling properties achieved with highly-parallel methods for computing the many-body matrix elements. Results compare favorably with complete model space calculations and signi cant memory savings are achieved in physically important applications. In particular, a well-chosen symmetry-adapted basis a ords memory savings in calculations of states with a fixed total angular momentum in large model spaces while exactly preserving translational invariance.

Importance-truncated no-core shell model for fermionic many-body systems

Energy Technology Data Exchange (ETDEWEB)

Spies, Helena

2017-03-15

The exact solution of quantum mechanical many-body problems is only possible for few particles. Therefore, numerical methods were developed in the fields of quantum physics and quantum chemistry for larger particle numbers. Configuration Interaction (CI) methods or the No-Core Shell Model (NCSM) allow ab initio calculations for light and intermediate-mass nuclei, without resorting to phenomenology. An extension of the NCSM is the Importance-Truncated No-Core Shell Model, which uses an a priori selection of the most important basis states. The importance truncation was first developed and applied in quantum chemistry in the 1970s and latter successfully applied to models of light and intermediate mass nuclei. Other numerical methods for calculations for ultra-cold fermionic many-body systems are the Fixed-Node Diffusion Monte Carlo method (FN-DMC) and the stochastic variational approach with Correlated Gaussian basis functions (CG). There are also such method as the Coupled-Cluster method, Green's Function Monte Carlo (GFMC) method, et cetera, used for calculation of many-body systems. In this thesis, we adopt the IT-NCSM for the calculation of ultra-cold Fermi gases at unitarity. Ultracold gases are dilute, strongly correlated systems, in which the average interparticle distance is much larger than the range of the interaction. Therefore, the detailed radial dependence of the potential is not resolved, and the potential can be replaced by an effective contact interaction. At low energy, s-wave scattering dominates and the interaction can be described by the s-wave scattering length. If the scattering length is small and negative, Cooper-pairs are formed in the Bardeen-Cooper-Schrieffer (BCS) regime. If the scattering length is small and positive, these Cooper-pairs become strongly bound molecules in a Bose-Einstein-Condensate (BEC). In between (for large scattering lengths) is the unitary limit with universal properties. Calculations of the energy spectra

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

Geometric screening of core/shell hydrogel microcapsules using a tapered microchannel with interdigitated electrodes.

Science.gov (United States)

Niu, Ye; Qi, Lin; Zhang, Fen; Zhao, Yi

2018-07-30

Core/shell hydrogel microcapsules attract increasing research attention due to their potentials in tissue engineering, food engineering, and drug delivery. Current approaches for generating core/shell hydrogel microcapsules suffer from large geometric variations. Geometrically defective core/shell microcapsules need to be removed before further use. High-throughput geometric characterization of such core/shell microcapsules is therefore necessary. In this work, a continuous-flow device was developed to measure the geometric properties of microcapsules with a hydrogel shell and an aqueous core. The microcapsules were pumped through a tapered microchannel patterned with an array of interdigitated microelectrodes. The geometric parameters (the shell thickness and the diameter) were derived from the displacement profiles of the microcapsules. The results show that this approach can successfully distinguish all unencapsulated microparticles. The geometric properties of core/shell microcapsules can be determined with high accuracy. The efficacy of this method was demonstrated through a drug releasing experiment where the optimization of the electrospray process based on geometric screening can lead to controlled and extended drug releasing profiles. This method does not require high-speed optical systems, simplifying the system configuration and making it an indeed miniaturized device. The throughput of up to 584 microcapsules per minute was achieved. This study provides a powerful tool for screening core/shell hydrogel microcapsules and is expected to facilitate the applications of these microcapsules in various fields. Copyright © 2018 Elsevier B.V. All rights reserved.

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

Exfoliated BN shell-based high-frequency magnetic core-shell materials.

Science.gov (United States)

Zhang, Wei; Patel, Ketan; Ren, Shenqiang

2017-09-14

The miniaturization of electric machines demands high frequency magnetic materials with large magnetic-flux density and low energy loss to achieve a decreased dimension of high rotational speed motors. Herein, we report a solution-processed high frequency magnetic composite (containing a nanometal FeCo core and a boron nitride (BN) shell) that simultaneously exhibits high electrical resistivity and magnetic permeability. The frequency dependent complex initial permeability and the mechanical robustness of nanocomposites are intensely dependent on the content of BN insulating phase. The results shown here suggest that insulating magnetic nanocomposites have potential for application in next-generation high-frequency electric machines with large electrical resistivity and permeability.

Development of Special Tools for the Straightness Measurement of JRTR Core Inner Shell

International Nuclear Information System (INIS)

Sinjlawi, Abdullah; Cho, Yeong-Garp; Chung, Jong-Ha

2014-01-01

Jordan Research and Training Reactor (JRTR) is an open pool type nuclear research reactor, 5 MW power, JRTR core made from Zircaloy. The JRTR will be used for nuclear applications such as isotopes production, nuclear researches, neutron transmutation doping (NTD), and training. JRTR core structures will be exposed to a large amount of neutron irradiation during the life time of the reactor. The core inner shell also will be exposed to a pressure that comes from heavy water system. JRTR core inner shell will deform due to the neutron irradiation and the mechanical stress. Therefore, the dimensional change of the core inner shell should be periodically (every 10 years) measured as an in-service inspection to confirm the structural integrity. As a result of neutron irradiation, pressure difference of the heavy water vessel, and the mechanical stress, the reactor core will deform as shown in figure 2 to figure 4. The maximum deformation to the normal direction of inner shell wall is 0.75 mm as shown in figure 3. This study discusses development of special tools that will be used for pre-service and in-service inspection of JRTR inner shell. The performance and procedure for the measurements tools will be verified using by the real inner shell of the heavy water vessel at factory before shipping to Jordan.. There will be very delicate working procedure for the measurement in the limited space in JRTR core. Therefore, we will develop the detail procedures to cover the removal of the core components, installation of the measurement tools, measurement, and re-installation of the core components. The measurement of the inner shell at JAEC site during commissioning stage will be the first remote measurement at the same conditions of pool water and heavy water system

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

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

International Nuclear Information System (INIS)

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

2016-01-01

In this work, the core-magnesium ferrite (MgFe_2O_4) nanoparticles were prepared by hydrothermal technique. Completed gold (Au) shell coating on the surfaces of MgFe_2O_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_2O_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_2O_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_2O_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_2O_4-Au core-shell nanoparticles still exhibit superparamagnetism with lower saturation magnetization value, compared with MgFe_2O_4 core. Both of MgFe_2O_4 and MgFe_2O_4-Au core-shell also showed in vitro non-cytotoxicity to mouse areola fibroblast (L-929) cell line. - Highlights: • Synthesis of MgFe_2O_4-Au core-shell nanoparticles with particle size < 100 nm • Complete Au shell coating on the surfaces of MgFe_2O_4 nanoparticles • In vitro cytotoxicity study of complete coated MgFe_2O_4-Au core-shell nanoparticles

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

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.

Laser Heating of the Core-Shell Nanowires

Science.gov (United States)

Astefanoaei, Iordana; Dumitru, Ioan; Stancu, Alexandru

2016-12-01

The induced thermal stress in a heating process is an important parameter to be known and controlled in the magnetization process of core-shell nanowires. This paper analyses the stress produced by a laser heating source placed at one end of a core-shell type structure. The thermal field was computed with the non-Fourier heat transport equation using a finite element method (FEM) implemented in Comsol Multiphysics. The internal stresses are essentially due to thermal gradients and different expansion characteristics of core and shell materials. The stress values were computed using the thermo elastic formalism and are depending on the laser beam parameters (spot size, power etc.) and system characteristics (dimensions, thermal characteristics). Stresses in the GPa range were estimated and consequently we find that the magnetic state of the system can be influenced significantly. A shell material as the glass which is a good thermal insulator induces in the magnetic core, the smaller stresses and consequently the smaller magnetoelastic energy. These results lead to a better understanding of the switching process in the magnetic materials.

Template-free synthesis of ordered ZnO@ZnS core-shell arrays for high performance supercapacitors.

Science.gov (United States)

Yan, Hailong; Li, Tong; Lu, Yang; Cheng, Jinbing; Peng, Tao; Xu, Jinyou; Yang, Linying; Hua, Xiangqiang; Liu, Yunxin; Luo, Yongsong

2016-11-28

In this article, ordered ZnO@ZnS core-shell structures have been produced on a stainless mesh by a two-step approach without using a template. ZnO nanorods fabricated by a chemical vapor method are transferred into a 50 ml autoclave for a second stage ion-exchange reaction followed by heating at 120 °C for 4-16 h. The ZnO core is prepared as the conducting channel and ZnS as the active material. Such unique architecture exhibits remarkable electrochemical performance with high capacitance and desirable cycle life. When evaluating as the electrode for supercapacitors, the ZnO@ZnS core-shell structure delivers a high specific capacitance of 603.8 F g -1 at a current density of 2 A g -1 , with 9.4% capacitance loss after cycling 3000 times. The fabrication strategy presented here is simple and cost-effective, which can open new avenues for large-scale applications of the novel materials in energy storage.

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.

Ni(3)Si(Al)/a-SiO(x) core-shell nanoparticles: characterization, shell formation, and stability.

Science.gov (United States)

Pigozzi, G; Mukherji, D; Gilles, R; Barbier, B; Kostorz, G

2006-08-28

We have used an electrochemical selective phase dissolution method to extract nanoprecipitates of the Ni(3)Si-type intermetallic phase from two-phase Ni-Si and Ni-Si-Al alloys by dissolving the matrix phase. The extracted nanoparticles are characterized by transmission electron microscopy, energy-dispersive x-ray spectrometry, x-ray powder diffraction, and electron powder diffraction. It is found that the Ni(3)Si-type nanoparticles have a core-shell structure. The core maintains the size, the shape, and the crystal structure of the precipitates that existed in the bulk alloys, while the shell is an amorphous phase, containing only Si and O (SiO(x)). The shell forms around the precipitates during the extraction process. After annealing the nanoparticles in nitrogen at 700 °C, the tridymite phase recrystallizes within the shell, which remains partially amorphous. In contrast, on annealing in air at 1000 °C, no changes in the composition or the structure of the nanoparticles occur. It is suggested that the shell forms after dealloying of the matrix phase, where Si atoms, the main constituents of the shell, migrate to the surface of the precipitates.

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.

Synthesis of triangular Au core-Ag shell nanoparticles

International Nuclear Information System (INIS)

Rai, Akhilesh; Chaudhary, Minakshi; Ahmad, Absar; Bhargava, Suresh; Sastry, Murali

2007-01-01

In this paper, we demonstrate a simple and reproducible method for the synthesis of triangular Au core-Ag shell nanoparticles. The triangular gold core is obtained by the reduction of gold ions by lemongrass extract. Utilizing the negative charge on the gold nanotriangles, silver ions are bound to their surface and thereafter reduced by ascorbic acid under alkaline conditions. The thickness of the silver shell may be modulated by varying the pH of the reaction medium. The formation of the Au core-Ag shell triangular nanostructures has been followed by UV-vis-NIR Spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM) measurements. The sharp vertices of the triangles coupled with the core-shell structure is expected to have potential for application in surface enhanced Raman spectroscopy and in the sensitive detection of biomolecules

Controlling interface characteristics by adjusting core-shell structure

International Nuclear Information System (INIS)

Chang, H.Y.; Cheng, S.Y.; Sheu, C.I.

2004-01-01

Most grain boundary layer ceramics comprise semiconductive/conductive grains and insulated grain boundaries. Such a structure can be theoretically regarded as a shell (grain boundary layer) surrounds a core (conductive or semiconductive grain). The core-shell structure of titanium (Ti)-strontium titanate (ST) is composed of three zones - ST, non-stoichiometric strontium-titanium oxide and Ti, in order from shell to core. It was successfully prepared using a hydrothermal method. The Ti-ST core-shell structure was sintered in a reducing atmosphere and then annealed in air to achieve the metal-insulator-metal structure (MIM structure). The resulting MIM structure, annealed in air, changes with the oxygen stoichiometry of the ST shell (insulator layer) at various temperatures, which is thus used to tune its electrical characteristics. The characteristics exhibit nonlinear behavior. Accordingly, the thickness of the insulator layer can be adjusted in various annealing atmospheres and at various temperatures to develop various interfacial devices, such as varistors, capacitors and thermistors, without the use of complex donor/acceptor doping technology

Super-paramagnetic core-shell material with tunable magnetic behavior by regulating electron transfer efficiency and structure stability of the shell

Directory of Open Access Journals (Sweden)

Wenyan Zhang

Full Text Available In this work, a spherical nano core-shell material was constructed by encapsulating Fe3O4 microsphere into conductive polymer-metal composite shell. The Fe3O4 microspheres were fabricated by assembling large amounts of Fe3O4 nano-crystals, which endowed the microspheres with super-paramagnetic property and high saturation magnetization. The polymer-metal composite shell was constructed by inserting Pt nano-particles (NPs into the conductive polymer polypyrrole (PPy. As size and dispersion of the Pt NPs has an important influence on their surface area and surface energy, it was effective to enlarge the interface area between PPy and Pt NPs, enhance the electron transfer efficiency of PPy/Pt composite shell, and reinforced the shell’s structural stability just by tuning the size and dispersion of Pt NPs. Moreover, core-shell structure of the materials made it convenient to investigate the PPy/Pt shell’s shielding effect on the Fe3O4 core’s magnetic response to external magnetic fields. It was found that the saturation magnetization of Fe3O4/PPy/Pt core-shell material could be reduced by 20.5% by regulating the conductivity of the PPy/Pt shell. Keywords: Super-paramagnetic, Conductivity, Magnetic shielding, Structural stability

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.

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.

Preparation and characterization of antibacterial Au/C core-shell composite

Energy Technology Data Exchange (ETDEWEB)

Gao Yanhong [Department of Chemistry and Institute of Nanochemistry, Jinan University, 601 Huangpudadaoxi Road, Guangzhou 510632, Guangdong (China); Centers for Disease Control and Prevention of Guangdong Province, Guangzhou 510300, Guangdong (China); Zhang Nianchun [Department of Chemistry and Institute of Nanochemistry, Jinan University, 601 Huangpudadaoxi Road, Guangzhou 510632, Guangdong (China); Zhong Yuwen [Centers for Disease Control and Prevention of Guangdong Province, Guangzhou 510300, Guangdong (China); Cai Huaihong [Department of Chemistry and Institute of Nanochemistry, Jinan University, 601 Huangpudadaoxi Road, Guangzhou 510632, Guangdong (China); Liu Yingliang, E-mail: tliuyl@jnu.edu.cn [Department of Chemistry and Institute of Nanochemistry, Jinan University, 601 Huangpudadaoxi Road, Guangzhou 510632, Guangdong (China)

2010-09-01

An environment-friendly oxidation-reduction method was used to prepare Au/C core-shell composite using carbon as core and gold as shell. The chemical structures and morphologies of Au/C core-shell composite and carbon sphere were characterized by X-ray diffraction, transmission electron microscope, energy dispersion X-ray spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS). The antibacterial properties of the Au/C core-shell composite against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans) were examined by the disk diffusion assay and minimal inhibition concentration (MIC) methods. In addition, antibacterial ability of Au/C core-shell composite was observed by atomic force microscope. Results demonstrated that gold homogeneously supported on the surface of carbon spheres without aggregation and showed efficient antibacterial abilities.

Short-Range Correlated Magnetic Core-Shell CrO2/Cr2O3 Nanorods: Experimental Observations and Theoretical Considerations

Directory of Open Access Journals (Sweden)

Ashish C. Gandhi

2018-05-01

Full Text Available With the evolution of synthesis and the critical characterization of core-shell nanostructures, short-range magnetic correlation is of prime interest in employing their properties to develop novel devices and widespread applications. In this regard, a novel approach of the magnetic core-shell saturated magnetization (CSSM cylinder model solely based on the contribution of saturated magnetization in one-dimensional CrO2/Cr2O3 core-shell nanorods (NRs has been developed and applied for the determination of core-diameter and shell-thickness. The nanosized effect leads to a short-range magnetic correlation of ferromagnetic core-CrO2 extracted from CSSM, which can be explained using finite size scaling method. The outcome of this study is important in terms of utilizing magnetic properties for the critical characterization of core-shell nanomagnetic materials.

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.

Plasma-activated core-shell gold nanoparticle films with enhanced catalytic properties

Energy Technology Data Exchange (ETDEWEB)

Llorca, Jordi, E-mail: jordi.llorca@upc.edu; Casanovas, Albert; Dominguez, Montserrat; Casanova, Ignasi [Universitat Politecnica de Catalunya, Institut de Tecniques Energetiques (Spain); Angurell, Inmaculada; Seco, Miquel; Rossell, Oriol [Universitat de Barcelona, Departament de Quimica Inorganica (Spain)

2008-03-15

Catalytically active gold nanoparticle films have been prepared from core-shell nanoparticles by plasma-activation and characterized by high-resolution transmission electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Methane can be selectively oxidized into formic acid with an O{sub 2}-H{sub 2} mixture in a catalytic wall reactor functionalized with plasma-activated gold nanoparticle films containing well-defined Au particles of about 3.5 nm in diameter. No catalytic activity was recorded over gold nanoparticle films prepared by thermal decomposition of core-shell nanoparticles due to particle agglomeration.

Plasma-activated core-shell gold nanoparticle films with enhanced catalytic properties

International Nuclear Information System (INIS)

Llorca, Jordi; Casanovas, Albert; Dominguez, Montserrat; Casanova, Ignasi; Angurell, Inmaculada; Seco, Miquel; Rossell, Oriol

2008-01-01

Catalytically active gold nanoparticle films have been prepared from core-shell nanoparticles by plasma-activation and characterized by high-resolution transmission electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Methane can be selectively oxidized into formic acid with an O 2 -H 2 mixture in a catalytic wall reactor functionalized with plasma-activated gold nanoparticle films containing well-defined Au particles of about 3.5 nm in diameter. No catalytic activity was recorded over gold nanoparticle films prepared by thermal decomposition of core-shell nanoparticles due to particle agglomeration

Controllable synthesis and characterization of novel copper-carbon core-shell structured nanoparticles

International Nuclear Information System (INIS)

Zhai, Jing; Tao, Xia; Pu, Yuan; Zeng, Xiao-Fei; Chen, Jian-Feng

2011-01-01

Highlights: → We reported a facile, green and cheap hydrothermal method to obtain novel copper-carbon core-shell nanoparticles. → The as-formed particles with controllable size and morphology are antioxidant. → The particles with organic-group-loaded surfaces and protective shells are expected to be applied in fields of medicine, electronics, sensors and lubricant. -- Abstract: A facile hydrothermal method was developed for preparing copper-carbon core-shell structured particles through a reaction at 160 o C in which glucose, copper sulfate pentahydrate and cetyltrimethylammonium bromide were used as starting materials. The original copper-carbon core-shell structured particles obtained were sized of 100-250 nm. The thickness of carbonaceous shells was controlled ranging from 25 to 100 nm by adjusting the hydrothermal duration time and the concentrations of glucose in the process. Products were characterized with transmission electron microscopy, X-ray diffraction, energy dispersive spectroscopy, Fourier transform infrared spectroscopy. Since no toxic materials were involved in the preparation, particles with stable carbonaceous framework and reactive surface also showed promising applications in medicine, electronics, sensors, lubricant, etc.

Controllable synthesis and characterization of novel copper-carbon core-shell structured nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Zhai, Jing [Sin-China Nano Technology Center, Key Lab for Nanomaterials, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China); Research Center of the Ministry of Education for High Gravity Engineering and Technology, Beijing University of Chemical Technology, No. 15 Beisanhuan Dong Lu, Beijing 100029 (China); Tao, Xia; Pu, Yuan; Zeng, Xiao-Fei [Sin-China Nano Technology Center, Key Lab for Nanomaterials, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China); Chen, Jian-Feng, E-mail: chenjf@mail.buct.edu.cn [Research Center of the Ministry of Education for High Gravity Engineering and Technology, Beijing University of Chemical Technology, No. 15 Beisanhuan Dong Lu, Beijing 100029 (China)

2011-06-15

Highlights: {yields} We reported a facile, green and cheap hydrothermal method to obtain novel copper-carbon core-shell nanoparticles. {yields} The as-formed particles with controllable size and morphology are antioxidant. {yields} The particles with organic-group-loaded surfaces and protective shells are expected to be applied in fields of medicine, electronics, sensors and lubricant. -- Abstract: A facile hydrothermal method was developed for preparing copper-carbon core-shell structured particles through a reaction at 160 {sup o}C in which glucose, copper sulfate pentahydrate and cetyltrimethylammonium bromide were used as starting materials. The original copper-carbon core-shell structured particles obtained were sized of 100-250 nm. The thickness of carbonaceous shells was controlled ranging from 25 to 100 nm by adjusting the hydrothermal duration time and the concentrations of glucose in the process. Products were characterized with transmission electron microscopy, X-ray diffraction, energy dispersive spectroscopy, Fourier transform infrared spectroscopy. Since no toxic materials were involved in the preparation, particles with stable carbonaceous framework and reactive surface also showed promising applications in medicine, electronics, sensors, lubricant, etc.

Core-shell particle composition by liquid phase infrared spectroscopy

International Nuclear Information System (INIS)

Ribeiro, Luiz F.B.; Machado, Ricardo A.F.; Goncalves, Odinei H.; Bona, Evandro

2011-01-01

Polymeric particles with core-shell morphology can offer advantages over conventional particles improving properties like mechanical and chemical resistance. However, particle composition must be known due to its influence on the final properties. In this work liquid phase infrared spectroscopy was used to determine the overall composition of core-shell particles composed by polystyrene (core) and poly(methyl methacrylate) (shell). Results were in agreement with those obtained with H 1 Nuclear Magnetic Resonance data (Goncalves et al, 2008). (author)

Energy transfers in large-scale and small-scale dynamos

Science.gov (United States)

Samtaney, Ravi; Kumar, Rohit; Verma, Mahendra

2015-11-01

We present the energy transfers, mainly energy fluxes and shell-to-shell energy transfers in small-scale dynamo (SSD) and large-scale dynamo (LSD) using numerical simulations of MHD turbulence for Pm = 20 (SSD) and for Pm = 0.2 on 10243 grid. For SSD, we demonstrate that the magnetic energy growth is caused by nonlocal energy transfers from the large-scale or forcing-scale velocity field to small-scale magnetic field. The peak of these energy transfers move towards lower wavenumbers as dynamo evolves, which is the reason for the growth of the magnetic fields at the large scales. The energy transfers U2U (velocity to velocity) and B2B (magnetic to magnetic) are forward and local. For LSD, we show that the magnetic energy growth takes place via energy transfers from large-scale velocity field to large-scale magnetic field. We observe forward U2U and B2B energy flux, similar to SSD.

In-situ observation of Cu-Pt core-shell nanoparticles in the atomic scale by XAFS

International Nuclear Information System (INIS)

Zheng, Xusheng; Liu, Shoujie; Chen, Xing; Cheng, Jie; Ye, Qing; Pan, Zhiyun; Chu, Wangsheng; Wu, Ziyu; Marcelli, Augosto

2013-01-01

Bimetallic nanoparticles play an important role in potential industrial applications, such as catalysis, optoelectronics, information storage and biological labeling. Herein, homogeneous Cu-Pt core-shell nanoparticles with the averaged size of 8 nm have been synthesized by chemical methods. Cu atoms diffusion process, which motivated by heating, was observed in-situ by using temperature-dependent x-ray absorption fine-structure (XAFS) spectroscopy. Results show that Cu diffuse gradually from Cu core to Pt shell in these nanoparticles with increasing temperature. We also found the surface ligand (O) bonded Pt at the room temperature and were removed gradually by heating the sample. The analysis of the diffusion process in bimetallic nanoparticles will provide important guideline for their designing and tuning.

Coherently Strained Si-SixGe1-x Core-Shell Nanowire Heterostructures.

Science.gov (United States)

Dillen, David C; Wen, Feng; Kim, Kyounghwan; Tutuc, Emanuel

2016-01-13

Coherently strained Si-SixGe1-x core-shell nanowire heterostructures are expected to possess a positive shell-to-core conduction band offset, allowing for quantum confinement of electrons in the Si core. We report the growth of epitaxial, coherently strained Si-SixGe1-x core-shell heterostructures through the vapor-liquid-solid mechanism for the Si core, followed in situ by the epitaxial SixGe1-x shell growth using ultrahigh vacuum chemical vapor deposition. The Raman spectra of individual nanowires reveal peaks associated with the Si-Si optical phonon mode in the Si core and the Si-Si, Si-Ge, and Ge-Ge vibrational modes of the SixGe1-x shell. The core Si-Si mode displays a clear red-shift compared to unstrained, bare Si nanowires thanks to the lattice mismatch-induced tensile strain, in agreement with calculated values using a finite-element continuum elasticity model combined with lattice dynamic theory. N-type field-effect transistors using Si-SixGe1-x core-shell nanowires as channel are demonstrated.

Strongly luminescent InP/ZnS core-shell nanoparticles.

Science.gov (United States)

Haubold, S; Haase, M; Kornowski, A; Weller, H

2001-05-18

The wide-bandgap semiconducting material, zinc sulfide, has been coated on indium phosphide nanoclusters to a 1-2-Å thickness. The resulting InP-ZnS core-shell particle (as shown in the TEM image; scale 1 cm=5 nm) exhibits bright luminescence at room temperature with quantum efficiencies as high as 23 %. © 2001 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.

Comparison of Large eddy dynamo simulation using dynamic sub-grid scale (SGS) model with a fully resolved direct simulation in a rotating spherical shell

Science.gov (United States)

Matsui, H.; Buffett, B. A.

2017-12-01

The flow in the Earth's outer core is expected to have vast length scale from the geometry of the outer core to the thickness of the boundary layer. Because of the limitation of the spatial resolution in the numerical simulations, sub-grid scale (SGS) modeling is required to model the effects of the unresolved field on the large-scale fields. We model the effects of sub-grid scale flow and magnetic field using a dynamic scale similarity model. Four terms are introduced for the momentum flux, heat flux, Lorentz force and magnetic induction. The model was previously used in the convection-driven dynamo in a rotating plane layer and spherical shell using the Finite Element Methods. In the present study, we perform large eddy simulations (LES) using the dynamic scale similarity model. The scale similarity model is implement in Calypso, which is a numerical dynamo model using spherical harmonics expansion. To obtain the SGS terms, the spatial filtering in the horizontal directions is done by taking the convolution of a Gaussian filter expressed in terms of a spherical harmonic expansion, following Jekeli (1981). A Gaussian field is also applied in the radial direction. To verify the present model, we perform a fully resolved direct numerical simulation (DNS) with the truncation of the spherical harmonics L = 255 as a reference. And, we perform unresolved DNS and LES with SGS model on coarser resolution (L= 127, 84, and 63) using the same control parameter as the resolved DNS. We will discuss the verification results by comparison among these simulations and role of small scale fields to large scale fields through the role of the SGS terms in LES.

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.

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.

Synthesis of CuO-NiO core-shell nanoparticles by homogeneous precipitation method

International Nuclear Information System (INIS)

Bayal, Nisha; Jeevanandam, P.

2012-01-01

Highlights: ► CuO-NiO core-shell nanoparticles have been synthesized using a simple homogeneous precipitation method for the first time. ► Mechanism of the formation of core-shell nanoparticles has been investigated. ► The synthesis route may be extended for the synthesis of other mixed metal oxide core-shell nanoparticles. - Abstract: Core-shell CuO–NiO mixed metal oxide nanoparticles in which CuO is the core and NiO is the shell have been successfully synthesized using homogeneous precipitation method. This is a simple synthetic method which produces first a layered double hydroxide precursor with core-shell morphology which on calcination at 350 °C yields the mixed metal oxide nanoparticles with the retention of core-shell morphology. The CuO–NiO mixed metal oxide precursor and the core-shell nanoparticles were characterized by powder X-ray diffraction, FT-IR spectroscopy, thermal gravimetric analysis, elemental analysis, scanning electron microscopy, transmission electron microscopy, and diffuse reflectance spectroscopy. The chemical reactivity of the core-shell nanoparticles was tested using catalytic reduction of 4-nitrophenol with NaBH 4 . The possible growth mechanism of the particles with core-shell morphology has also been investigated.

Development of SiO2@TiO2 core-shell nanospheres for catalytic applications

Science.gov (United States)

Kitsou, I.; Panagopoulos, P.; Maggos, Th.; Arkas, M.; Tsetsekou, A.

2018-05-01

Silica-titania core-shell nanospheres, CSNp, were prepared via a simple and environmentally friendly two step route. First, silica cores were prepared through the hydrolysis-condensation reaction of silicic acid in the presence of hyperbranched poly(ethylene)imine (HBPEI) followed by repeating washing, centrifugation and, finally, calcination steps. To create the core-shell structure, various amounts of titanium isopropoxide were added to the cores and after that a HBPEI-water solution was added to hydrolyze the titanium precursor. Washing with ethanol and heat treatment followed. The optimization of processing parameters led to well-developed core-shell structures bearing a homogeneous nanocrystalline anatase coating over each silica core. The photocatalytic activity for NO was examined in a continuous flux photocatalytic reactor under real environmental conditions. The results revealed a very potent photocatalyst as the degradation percentage reached 84.27% for the core-shell material compared to the 82% of pure titania with the photodecomposition rates measured at 0.62 and 0.55 μg·m-2·s-1, respectively. In addition, catalytic activities of the CSNp and pure titania were investigated by monitoring the reduction of 4-nitrophenol to 4-aminophenol by an excess of NaBH4. Both materials exhibited excellent catalytic activity (100%), making the core-shell material a promising alternative catalyst to pure titania for various applications.

Experimental and numerical modelling of ductile crack propagation in large-scale shell structures

DEFF Research Database (Denmark)

Simonsen, Bo Cerup; Törnquist, R.

2004-01-01

plastic and controlled conditions. The test specimen can be deformed either in combined in-plane bending and extension or in pure extension. Experimental results are described for 5 and 10 mm thick aluminium and steel plates. By performing an inverse finite-element analysis of the experimental results......This paper presents a combined experimental-numerical procedure for development and calibration of macroscopic crack propagation criteria in large-scale shell structures. A novel experimental set-up is described in which a mode-I crack can be driven 400 mm through a 20(+) mm thick plate under fully...... for steel and aluminium plates, mainly as curves showing the critical element deformation versus the shell element size. These derived crack propagation criteria are then validated against a separate set of experiments considering centre crack specimens (CCS) which have a different crack-tip constraint...

Modified ferrite core-shell nanoparticles magneto-structural characterization

Science.gov (United States)

Klekotka, Urszula; Piotrowska, Beata; Satuła, Dariusz; Kalska-Szostko, Beata

2018-06-01

In this study, ferrite nanoparticles with core-shell structures and different chemical compositions of both the core and shell were prepared with success. Proposed nanoparticles have in the first and second series magnetite core, and the shell is composed of a mixture of ferrites with Fe3+, Fe2+ and M ions (where M = Co2+, Mn2+ or Ni2+) with a general composition of M0.5Fe2.5O4. In the third series, the composition is inverted, the core is composed of a mixture of ferrites and as a shell magnetite is placed. Morphology and structural characterization of nanoparticles were done using Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), and Infrared spectroscopy (IR). While room temperature magnetic properties were measured using Mössbauer spectroscopy (MS). It is seen from Mössbauer measurements that Co always increases hyperfine magnetic field on Fe atoms at RT, while Ni and Mn have opposite influences in comparison to pure Fe ferrite, regardless of the nanoparticles structure.

Enhanced thermoelectric transport in modulation-doped GaN/AlGaN core/shell nanowires.

Science.gov (United States)

Song, Erdong; Li, Qiming; Swartzentruber, Brian; Pan, Wei; Wang, George T; Martinez, Julio A

2016-01-08

The thermoelectric properties of unintentionally n-doped core GaN/AlGaN core/shell N-face nanowires are reported. We found that the temperature dependence of the electrical conductivity is consistent with thermally activated carriers with two distinctive donor energies. The Seebeck coefficient of GaN/AlGaN nanowires is more than twice as large as that for the GaN nanowires alone. However, an outer layer of GaN deposited onto the GaN/AlGaN core/shell nanowires decreases the Seebeck coefficient at room temperature, while the temperature dependence of the electrical conductivity remains the same. We attribute these observations to the formation of an electron gas channel within the heavily-doped GaN core of the GaN/AlGaN nanowires. The room-temperature thermoelectric power factor for the GaN/AlGaN nanowires can be four times higher than the GaN nanowires. Selective doping in bandgap engineered core/shell nanowires is proposed for enhancing the thermoelectric power.

Directed self-assembly of hybrid oxide/polymer core/shell nanowires with transport optimized morphology for photovoltaics

Energy Technology Data Exchange (ETDEWEB)

Zhang, Shanju; Pelligra, Candice I.; Keskar, Gayatri; Majewski, Pawel W.; Taylor, Andre D.; Pfefferle, Lisa D.; Osuji, Chinedum O. [Department of Chemical and Environmental Engineering, Yale University, New Haven, CT (United States); Jiang, Jie; Ismail-Beigi, Sohrab [Department of Applied Physics, Yale University, New Haven, CT (United States)

2012-01-03

An entirely bottom-up approach for the preparation of liquid crystalline suspensions of core-shell nanowires for ordered bulk heterojunction photovoltaics is demonstrated. Side-on attachment of polythiophene derivatives to ZnO nanowires promotes a co-axial polymer backbone-nanowire arrangement which favors high hole mobility. This strategy offers structural control over multiple length scales and a viable means of fabricating ordered films over large areas. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

DNA nanoparticles with core-shell morphology.

Science.gov (United States)

Chandran, Preethi L; Dimitriadis, Emilios K; Lisziewicz, Julianna; Speransky, Vlad; Horkay, Ferenc

2014-10-14

Mannobiose-modified polyethylenimines (PEI) are used in gene therapy to generate nanoparticles of DNA that can be targeted to the antigen-presenting cells of the immune system. We report that the sugar modification alters the DNA organization within the nanoparticles from homogenous to shell-like packing. The depth-dependent packing of DNA within the nanoparticles was probed using AFM nano-indentation. Unmodified PEI-DNA nanoparticles display linear elastic properties and depth-independent mechanics, characteristic of homogenous materials. Mannobiose-modified nanoparticles, however, showed distinct force regimes that were dependent on indentation depth, with 'buckling'-like response that is reproducible and not due to particle failure. By comparison with theoretical studies of spherical shell mechanics, the structure of mannobiosylated particles was deduced to be a thin shell with wall thickness in the order of few nanometers, and a fluid-filled core. The shell-core structure is also consistent with observations of nanoparticle denting in altered solution conditions, with measurements of nanoparticle water content from AFM images, and with images of DNA distribution in Transmission Electron Microscopy.

Ge/Si core/multi shell heterostructure FETs

Energy Technology Data Exchange (ETDEWEB)

Picraux, Samuel T [Los Alamos National Laboratory; Dayeh, Shadi A [Los Alamos National Laboratory

2010-01-01

Concentric heterostructured materials provide numerous design opportunities for engineering strain and interfaces, as well as tailoring energy band-edge combinations for optimal device performance. Key to the realization of such novel device concepts is the complete understanding and full control over their growth, crystal structure, and hetero-epitaxy. We report here on a new route for synthesizing Ge/Si core/multi-shell heterostructure nanowires that eliminate Au seed diffusion on the nanowire sidewalls by engineering the interface energy density difference. We show that such control over core/shell synthesis enable experimental realization of heterostructure FET devices beyond those available in the literature with enhanced transport characteristics. We provide a side-by-side comparison on the transport properties of Ge/Si core/multi-shell nanowires grown with and without Au diffusion and demonstrate heterostructure FETs with drive currents that are {approx} 2X higher than record results for p-type FETs.

Core-shell designed scaffolds for drug delivery and tissue engineering.

Science.gov (United States)

Perez, Roman A; Kim, Hae-Won

2015-07-01

Scaffolds that secure and deliver therapeutic ingredients like signaling molecules and stem cells hold great promise for drug delivery and tissue engineering. Employing a core-shell design for scaffolds provides a promising solution. Some unique methods, such as co-concentric nozzle extrusion, microfluidics generation, and chemical confinement reactions, have been successful in producing core-shelled nano/microfibers and nano/microspheres. Signaling molecules and drugs, spatially allocated to the core and/or shell part, can be delivered in a controllable and sequential manner for optimal therapeutic effects. Stem cells can be loaded within the core part on-demand, safely protected from the environments, which ultimately affords ex vivo culture and in vivo tissue engineering. The encapsulated cells experience three-dimensional tissue-mimic microenvironments in which therapeutic molecules are secreted to the surrounding tissues through the semi-permeable shell. Tuning the material properties of the core and shell, changing the geometrical parameters, and shaping them into proper forms significantly influence the release behaviors of biomolecules and the fate of the cells. This topical issue highlights the immense usefulness of core-shell designs for the therapeutic actions of scaffolds in the delivery of signaling molecules and stem cells for tissue regeneration and disease treatment. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Core-in-shell sorbent for hot coal gas desulfurization

Science.gov (United States)

Wheelock, Thomas D.; Akiti, Jr., Tetteh T.

2004-02-10

A core-in-shell sorbent is described herein. The core is reactive to the compounds of interest, and is preferably calcium-based, such as limestone for hot gas desulfurization. The shell is a porous protective layer, preferably inert, which allows the reactive core to remove the desired compounds while maintaining the desired physical characteristics to withstand the conditions of use.

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.

Multiple Fano resonances in single-layer nonconcentric core-shell nanostructures

DEFF Research Database (Denmark)

Zhang, Jingjing; Zayats, Anatoly

2013-01-01

where the multiple dark modes appear due to the geometrical symmetry breaking induced by axial offset of the core. Both dielectric-core-metal-shell (DCMS) and metal-core-dielectric-shell (MCDS) configurations have been studied. Compared to the MCDS structure, the DCMS configuration provides higher...

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.

Characterization of spherical core–shell particles by static light scattering. Estimation of the core- and particle-size distributions

International Nuclear Information System (INIS)

Clementi, Luis A.; Vega, Jorge R.; Gugliotta, Luis M.; Quirantes, Arturo

2012-01-01

A numerical method is proposed for the characterization of core–shell spherical particles from static light scattering (SLS) measurements. The method is able to estimate the core size distribution (CSD) and the particle size distribution (PSD), through the following two-step procedure: (i) the estimation of the bivariate core–particle size distribution (C–PSD), by solving a linear ill-conditioned inverse problem through a generalized Tikhonov regularization strategy, and (ii) the calculation of the CSD and the PSD from the estimated C–PSD. First, the method was evaluated on the basis of several simulated examples, with polystyrene–poly(methyl methacrylate) core–shell particles of different CSDs and PSDs. Then, two samples of hematite–Yttrium basic carbonate core–shell particles were successfully characterized. In all analyzed examples, acceptable estimates of the PSD and the average diameter of the CSD were obtained. Based on the single-scattering Mie theory, the proposed method is an effective tool for characterizing core–shell colloidal particles larger than their Rayleigh limits without requiring any a-priori assumption on the shapes of the size distributions. Under such conditions, the PSDs can always be adequately estimated, while acceptable CSD estimates are obtained when the core/shell particles exhibit either a high optical contrast, or a moderate optical contrast but with a high ‘average core diameter’/‘average particle diameter’ ratio. -- Highlights: ► Particles with core–shell morphology are characterized by static light scattering. ► Core size distribution and particle size distribution are successfully estimated. ► Simulated and experimental examples are used to validate the numerical method. ► The positive effect of a large core/shell optical contrast is investigated. ► No a-priori assumption on the shapes of the size distributions is required.

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.

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.

Strain relaxation and ambipolar electrical transport in GaAs/InSb core-shell nanowires.

Science.gov (United States)

Rieger, Torsten; Zellekens, Patrick; Demarina, Natalia; Hassan, Ali Al; Hackemüller, Franz Josef; Lüth, Hans; Pietsch, Ullrich; Schäpers, Thomas; Grützmacher, Detlev; Lepsa, Mihail Ion

2017-11-30

The growth, crystal structure, strain relaxation and room temperature transport characteristics of GaAs/InSb core-shell nanowires grown using molecular beam epitaxy are investigated. Due to the large lattice mismatch between GaAs and InSb of 14%, a transition from island-based to layer-like growth occurs during the formation of the shell. High resolution transmission electron microscopy in combination with geometric phase analyses as well as X-ray diffraction with synchrotron radiation are used to investigate the strain relaxation and prove the existence of different dislocations relaxing the strain on zinc blende and wurtzite core-shell nanowire segments. While on the wurtzite phase only Frank partial dislocations are found, the strain on the zinc blende phase is relaxed by dislocations with perfect, Shockley partial and Frank partial dislocations. Even for ultrathin shells of about 2 nm thickness, the strain caused by the high lattice mismatch between GaAs and InSb is relaxed almost completely. Transfer characteristics of the core-shell nanowires show an ambipolar conductance behavior whose strength strongly depends on the dimensions of the nanowires. The interpretation is given based on an electronic band profile which is calculated for completely relaxed core/shell structures. The peculiarities of the band alignment in this situation implies simultaneously occupied electron and hole channels in the InSb shell. The ambipolar behavior is then explained by the change of carrier concentration in both channels by the gate voltage.

Novel three-dimensional tin/carbon hybrid core/shell architecture with large amount of solid cross-linked micro/nanochannels for lithium ion battery application

International Nuclear Information System (INIS)

Yang, Zunxian; Meng, Qing; Yan, Wenhuan; Lv, Jun; Guo, Zaiping; Yu, Xuebin; Chen, Zhixin; Guo, Tailiang; Zeng, Rong

2015-01-01

Uniform Sn/C hybrid core/shell nanocomposites were synthesized by a combination of electrospinning and subsequent thermal treatment in a reducing atmosphere. The particular three-dimensional architecture, consisting of a Sn@C nanoparticle core and porous hollow carbon nanofiber shell, is characterized by many micro/nanochannels, enhanced mechanical support from the three-dimensional hollow carbon shell, and the abundant porous carbon matrix. The as-prepared Sn/C core/shell nanomaterials exhibit excellent electrochemical performance. They display a reversible capacity of 546.7 mAhg −1 up to 100 cycles at the current density of 40 mAg −1 and good rate capability of 181.8 mAhg −1 at 4000 mAg −1 . These results indicate that the composite could be a promising anode candidate for lithium ion batteries. - Highlights: • Sn/C core/shell composites were synthesized by an electrospinning, a hydrothermal process, and further thermal treatment. • The best-performing 3D composite consists of a Sn@C nanoparticle core and porous hollow carbon nanofiber shell. • The Sn/C composite electrode exhibit excellent Li ion storage capacity and cycling stability

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.

Enhanced Oxidation-Resistant Cu@Ni Core-Shell Nanoparticles for Printed Flexible Electrodes.

Science.gov (United States)

Kim, Tae Gon; Park, Hye Jin; Woo, Kyoohee; Jeong, Sunho; Choi, Youngmin; Lee, Su Yeon

2018-01-10

In this work, the fabrication and application of highly conductive, robust, flexible, and oxidation-resistant Cu-Ni core-shell nanoparticle (NP)-based electrodes have been reported. Cu@Ni core-shell NPs with a tunable Ni shell thickness were synthesized by varying the Cu/Ni molar ratios in the precursor solution. Through continuous spray coating and flash photonic sintering without an inert atmosphere, large-area Cu@Ni NP-based conductors were fabricated on various polymer substrates. These NP-based electrodes demonstrate a low sheet resistance of 1.3 Ω sq -1 under an optical energy dose of 1.5 J cm -2 . In addition, they exhibit highly stable sheet resistances (ΔR/R 0 flexible heater fabricated from the Cu@Ni film is demonstrated, which shows uniform heat distribution and stable temperature compared to those of a pure Cu film.

The influence of MOVPE growth conditions on the shell of core-shell GaN microrod structures

Science.gov (United States)

Schimpke, Tilman; Avramescu, Adrian; Koller, Andreas; Fernando-Saavedra, Amalia; Hartmann, Jana; Ledig, Johannes; Waag, Andreas; Strassburg, Martin; Lugauer, Hans-Jürgen

2017-05-01

A core-shell geometry is employed for most next-generation, three-dimensional opto-electric devices based on III-V semiconductors and grown by metal organic vapor phase epitaxy (MOVPE). Controlling the shape of the shell layers is fundamental for device optimization, however no detailed analysis of the influence of growth conditions has been published to date. We study homogeneous arrays of gallium nitride core-shell microrods with height and diameter in the micrometer range and grown in a two-step selective area MOVPE process. Changes in shell shape and homogeneity effected by deliberately altered shell growth conditions were accurately assessed by digital analysis of high-resolution scanning electron microscope images. Most notably, two temperature regimes could be established, which show a significantly different behavior with regard to material distribution. Above 900 °C of wafer carrier temperature, the shell thickness along the growth axis of the rods was very homogeneous, however variations between vicinal rods increase. In contrast, below 830 °C the shell thickness is higher close to the microrod tip than at the base of the rods, while the lateral homogeneity between neighboring microrods is very uniform. This temperature effect could be either amplified or attenuated by changing the remaining growth parameters such as reactor pressure, structure distance, gallium precursor, carrier gas composition and dopant materials. Possible reasons for these findings are discussed with respect to GaN decomposition as well as the surface and gas phase diffusion of growth species, leading to an improved control of the functional layers in next-generation 3D V-III devices.

Core-Shell Columns in High-Performance Liquid Chromatography: Food Analysis Applications

Science.gov (United States)

Preti, Raffaella

2016-01-01

The increased separation efficiency provided by the new technology of column packed with core-shell particles in high-performance liquid chromatography (HPLC) has resulted in their widespread diffusion in several analytical fields: from pharmaceutical, biological, environmental, and toxicological. The present paper presents their most recent applications in food analysis. Their use has proved to be particularly advantageous for the determination of compounds at trace levels or when a large amount of samples must be analyzed fast using reliable and solvent-saving apparatus. The literature hereby described shows how the outstanding performances provided by core-shell particles column on a traditional HPLC instruments are comparable to those obtained with a costly UHPLC instrumentation, making this novel column a promising key tool in food analysis. PMID:27143972

Enhanced thermoelectric transport in modulation-doped GaN/AlGaN core/shell nanowires

International Nuclear Information System (INIS)

Song, Erdong; Martinez, Julio A; Li, Qiming; Pan, Wei; Wang, George T; Swartzentruber, Brian

2016-01-01

The thermoelectric properties of unintentionally n-doped core GaN/AlGaN core/shell N-face nanowires are reported. We found that the temperature dependence of the electrical conductivity is consistent with thermally activated carriers with two distinctive donor energies. The Seebeck coefficient of GaN/AlGaN nanowires is more than twice as large as that for the GaN nanowires alone. However, an outer layer of GaN deposited onto the GaN/AlGaN core/shell nanowires decreases the Seebeck coefficient at room temperature, while the temperature dependence of the electrical conductivity remains the same. We attribute these observations to the formation of an electron gas channel within the heavily-doped GaN core of the GaN/AlGaN nanowires. The room-temperature thermoelectric power factor for the GaN/AlGaN nanowires can be four times higher than the GaN nanowires. Selective doping in bandgap engineered core/shell nanowires is proposed for enhancing the thermoelectric power. (paper)

Shape-controlled synthesis of Pt-Pd core-shell nanoparticles exhibiting polyhedral morphologies by modified polyol method

International Nuclear Information System (INIS)

Long, Nguyen Viet; Asaka, Toru; Matsubara, Takashi; Nogami, Masayuki

2011-01-01

Pt-Pd core-shell nanoparticles were synthesized by a simple synthetic method. First, Pt nanoparticles were synthesized in a controlled manner via the reduction of chloroplantinic acid hexahydrate in ethylene glycol (EG) at 160 deg. C in the presence of silver nitrate and the stabilization of polyvinylpyrrolidon. AgNO 3 used acts as a structure-modifying agent to the morphology of the Pt nanoparticles. These Pt nanoparticles function as the seeds for the successive reduction of sodium tetrachloropalladate (II) hydrate in EG under stirring for 15 min at 160 deg. C in order to synthesize Pt-Pd core-shell nanoparticles. To characterize the as-prepared Pt-Pd nanoparticles, transmission electron microscopy (TEM) and high-resolution TEM are used. The high-resolution elemental mappings were carried out using the combination of scanning TEM and X-ray energy-dispersive spectroscopy. The results also demonstrate the homogeneous nucleation and growth of the Pd metal shell on the definite Pt core. The synthesized Pt-Pd core-shell nanoparticles exhibit a sharp and polyhedral morphology. The epitaxial growth of the controlled Pd shells on the Pt cores via a polyol method was observed. It is suggested that Frank-van der Merwe and Stranski-Krastanov growth modes coexisted in the nucleation and growth of Pt-Pd core-shell nanoparticles.

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.

Large-scale exact diagonalizations reveal low-momentum scales of nuclei

Science.gov (United States)

Forssén, C.; Carlsson, B. D.; Johansson, H. T.; Sääf, D.; Bansal, A.; Hagen, G.; Papenbrock, T.

2018-03-01

Ab initio methods aim to solve the nuclear many-body problem with controlled approximations. Virtually exact numerical solutions for realistic interactions can only be obtained for certain special cases such as few-nucleon systems. Here we extend the reach of exact diagonalization methods to handle model spaces with dimension exceeding 1010 on a single compute node. This allows us to perform no-core shell model (NCSM) calculations for 6Li in model spaces up to Nmax=22 and to reveal the 4He+d halo structure of this nucleus. Still, the use of a finite harmonic-oscillator basis implies truncations in both infrared (IR) and ultraviolet (UV) length scales. These truncations impose finite-size corrections on observables computed in this basis. We perform IR extrapolations of energies and radii computed in the NCSM and with the coupled-cluster method at several fixed UV cutoffs. It is shown that this strategy enables information gain also from data that is not fully UV converged. IR extrapolations improve the accuracy of relevant bound-state observables for a range of UV cutoffs, thus making them profitable tools. We relate the momentum scale that governs the exponential IR convergence to the threshold energy for the first open decay channel. Using large-scale NCSM calculations we numerically verify this small-momentum scale of finite nuclei.

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

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.

Core and shell sizing of small silver-coated nanospheres by optical extinction spectroscopy

International Nuclear Information System (INIS)

Schinca, D C; Scaffardi, L B

2008-01-01

Silver metal nanoparticles (Nps) are extensively used in different areas of research and technology due to their interesting optical, thermal and electric properties, especially for bare core and core-shell nanostructures with sizes smaller than 10 nm. Since these properties are core-shell size-dependent, size measurement is important in manipulating their potential functionalization and applications. Bare and coated small silver Nps fabricated by physical and chemical methods present specific characteristics in their extinction spectra that are potentially useful for sizing purposes. This work presents a novel procedure to size mean core radius smaller than 10 nm and mean shell thickness of silver core-shell Nps based on a comparative study of the characteristics in their optical extinction spectra in different media as a function of core radii, shell thickness and coating refractive index. From the regularities derived from these relationships, it can be concluded that plasmon full width at half-maximum (FWHM) is sensitive to core size but not to coating thickness, while plasmon resonance wavelength (PRW) is related to shell thickness and mostly independent of core radius. These facts, which allow sizing simultaneously both mean core radius and shell thickness, can also be used to size bare silver Nps as a special case of core-shell Nps with zero shell thickness. The proposed method was applied to size experimental samples and the results show good agreement with conventional TEM microscopy.

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.

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

International Nuclear Information System (INIS)

Fleming, Robert A.; Goss, Josue A.; Zou, Min

2017-01-01

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.

Novel method for the preparation of core-shell nanoparticles with movable Ag core and polystyrene loop shell

International Nuclear Information System (INIS)

Liu Weijun; Zhang Zhicheng; He Weidong; Zheng Cheng; Ge Xuewu; Li, Jian; Liu Huarong; Jiang Hao

2006-01-01

Core/shell nanoparticles with movable silver (Ag) core and polystyrene (PSt) shell (Ag at PSt nanoparticle) were successfully synthesized at room temperature and under ambient pressure via two steps: γ-irradiation and interfacial-initiated polymerization. Firstly, mono-dispersed Ag nanoparticles with diameters 20 nm were synthesized in inversed microemulsion by reducing silver nitrate under γ-irradiation. Then, Ag nanoparticles were coated with PSt via interfacial-initiated polymerization with cumene hydroperoxide/ferrous sulfate/disodium ethylenediaminetetraacetate/sodium formaldehyde sulfoxylate (CHPO-Fe 2+ -EDTA-SFS) as the redox initiation pair. The resulted Ag at PSt nanoparticles were identified by transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS)

Human nitric oxide biomarker as potential NO donor in conjunction with superparamagnetic iron oxide @ gold core shell nanoparticles for cancer therapeutics.

Science.gov (United States)

Singh, Nimisha; Patel, Khushbu; Sahoo, Suban K; Kumar, Rajender

2018-03-01

Nitric oxide releasing superparamagnetic (Fe 3 O 4 -Au@NTHP) nanoparticles were synthesized by conjugation of human biomarker of nitric oxide, N-nitrosothioproline with iron oxide-gold (Fe 3 O 4 -Au) core shell nanoparticles. The structure and morphology of the prepared nanoparticles were confirmed by ATR-FTIR, HR-TEM, EDAX, XPS, DLS and VSM measurements. N-nitrosothioproline is a natural molecule and nontoxic to humans. Thus, the core shell nanoparticles prepared were highly biocompatible. The prepared Fe 3 O 4 -Au@NTHP nanoparticles also provided an excellent release of nitric oxide in dark and upon light irradiation for cancer treatment. The amount of NO release was controllable with the wavelength of light and time of irradiation. The developed nanoparticles provided efficient cellular uptake and good cytotoxicity in picomolar range when tested on HeLa cancerous cells. These nanoparticles on account of their controllable NO release can also be used to release small amount of NO for killing cancerous cells without any toxic effect. Furthermore, the magnetic and photochemical properties of these nanoparticles provides dual platform for magneto therapy and phototherapy for cancer treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

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.

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.

Synthesis of Aqueous CdTe/CdS/ZnS Core/shell/shell Quantum Dots by a Chemical Aerosol Flow Method

Directory of Open Access Journals (Sweden)

Chen Dong

2009-01-01

Full Text Available Abstract This work described a continuous method to synthesize CdTe/CdS/ZnS core/shell/shell quantum dots. In an integrated system by flawlessly combining the chemical aerosol flow system working at high temperature (200–300°C to generate CdTe/CdS intermediate products and an additional heat-up setup at relatively low temperature to overcoat the ZnS shells, the CdTe/CdS/ZnS multishell structures were realized. The as-synthesized CdTe/CdS/ZnS core/shell/shell quantum dots are characterized by photoluminescence spectra, X-ray diffraction (XRD, energy-dispersive X-ray spectra (EDS, transmission electron microscopy (TEM, and high-resolution transmission electron microscopy (HRTEM. Fluorescence and XRD results confirm that the obtained quantum dots have a core/shell/shell structure. It shows the highest quantum yield above 45% when compared to the rhodamine 6G. The core/shell/shell QDs were more stable via the oxidation experiment by H2O2.

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

Science.gov (United States)

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

2018-05-17

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 rational control over the core/shell chemical composition, topology, and pore/particle size, simply by adjusting the reaction conditions in the presence of cetyltrimethylammonium bromide (CTAB) as structure-directing agent under basic conditions. The spherical, ethylene- or methylene-bridged PMO cores feature hexagonal (p6mm) or cage-like cubic symmetry (Pm3‾ n) depending on the organosilica precursor. The hexagonal MS shell was obtained by n-hexane-induced controlled hydrolysis of TEOS followed by directional co-assembly/condensation of silicate/CTAB composites at the PMO cores. The HSMSCSNs feature a hierarchical pore structure with pore diameters of about 2.7 and 5.6 nm in the core and shell domains, respectively. The core sizes and shell thicknesses are adjustable in the ranges of 90-275 and 15-50 nm, respectively, and the surface areas (max. 1300 m 2  g -1 ) and pore volumes (max. 1.83 cm 3  g -1 ) are among the highest reported for core-shell nanoparticles. The adsorption and controlled release of the fungicide propiconazole by the HSMSCSNs showed a three-stage release profile. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrostatically assisted fabrication of silver-dielectric core/shell nanoparticles thin film capacitor with uniform metal nanoparticle distribution and controlled spacing.

Science.gov (United States)

Li, Xue; Niitsoo, Olivia; Couzis, Alexander

2016-03-01

An electrostatically-assisted strategy for fabrication of thin film composite capacitors with controllable dielectric constant (k) has been developed. The capacitor is composed of metal-dielectric core/shell nanoparticle (silver/silica, Ag@SiO2) multilayer films, and a backfilling polymer. Compared with the simple metal particle-polymer mixtures where the metal nanoparticles (NP) are randomly dispersed in the polymer matrix, the metal volume fraction in our capacitor was significantly increased, owing to the densely packed NP multilayers formed by the electrostatically assisted assembly process. Moreover, the insulating layer of silica shell provides a potential barrier that reduces the tunneling current between neighboring Ag cores, endowing the core/shell nanocomposites with a stable and relatively high dielectric constant (k) and low dielectric loss (D). Our work also shows that the thickness of the SiO2 shell plays a dominant role in controlling the dielectric properties of the nanocomposites. Control over metal NP separation distance was realized not only by variation the shell thickness of the core/shell NPs but also by introducing a high k nanoparticle, barium strontium titanate (BST) of relatively smaller size (∼8nm) compared to 80-160nm of the core/shell Ag@SiO2 NPs. The BST assemble between the Ag@SiO2 and fill the void space between the closely packed core/shell NPs leading to significant enhancement of the dielectric constant. This electrostatically assisted assembly method is promising for generating multilayer films of a large variety of NPs over large areas at low cost. Copyright © 2015 Elsevier Inc. All rights reserved.

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.

Core - shell upconversion nanoparticle - semiconductor heterostructures for photodynamic therapy

Science.gov (United States)

Dou, Qing Qing; Rengaramchandran, Adith; Selvan, Subramanian Tamil; Paulmurugan, Ramasamy; Zhang, Yong

2015-02-01

Core-shell nanoparticles (CSNPs) with diverse chemical compositions have been attracting greater attention in recent years. However, it has been a challenge to develop CSNPs with different crystal structures due to the lattice mismatch of the nanocrystals. Here we report a rational design of core-shell heterostructure consisting of NaYF4:Yb,Tm upconversion nanoparticle (UCN) as the core and ZnO semiconductor as the shell for potential application in photodynamic therapy (PDT). The core-shell architecture (confirmed by TEM and STEM) enables for improving the loading efficiency of photosensitizer (ZnO) as the semiconductor is directly coated on the UCN core. Importantly, UCN acts as a transducer to sensitize ZnO and trigger the generation of cytotoxic reactive oxygen species (ROS) to induce cancer cell death. We also present a firefly luciferase (FLuc) reporter gene based molecular biosensor (ARE-FLuc) to measure the antioxidant signaling response activated in cells during the release of ROS in response to the exposure of CSNPs under 980 nm NIR light. The breast cancer cells (MDA-MB-231 and 4T1) exposed to CSNPs showed significant release of ROS as measured by aminophenyl fluorescein (APF) and ARE-FLuc luciferase assays, and ~45% cancer cell death as measured by MTT assay, when illuminated with 980 nm NIR light.

HTGR Metallic Reactor Internals Core Shell Cutting & Machining Antideformation Technique Study

International Nuclear Information System (INIS)

Xing Huiping; Xue Song

2014-01-01

The reactor shell assembly of HTGR nuclear power station demonstration project metallic reactor internals is key components of reactor, remains with high-precision large component with large-sized thin-walled straight cylinder-shaped structure, and is the first manufacture in China. As compared with other reactor shell, it has a larger ID (Φ5360mm), a longer length (19000mm), a smaller wall thickness (40mm) and a higher precision requirement. During the process of manufacture, the deformation due to cutting & machining will directly affect the final result of manufacture, the control of structural deformation and cutting deformation shall be throughout total manufacture process of such assembly. To realize the control of entire core shell assembly geometry, the key is to innovate and make breakthroughs on anti-deformation technique and then provide reliable technological foundations for the manufacture of HTGR metallic reactor internals. (author)

Majorana states in prismatic core-shell nanowires

Science.gov (United States)

Manolescu, Andrei; Sitek, Anna; Osca, Javier; Serra, Llorenç; Gudmundsson, Vidar; Stanescu, Tudor Dan

2017-09-01

We consider core-shell nanowires with conductive shell and insulating core and with polygonal cross section. We investigate the implications of this geometry on Majorana states expected in the presence of proximity-induced superconductivity and an external magnetic field. A typical prismatic nanowire has a hexagonal profile, but square and triangular shapes can also be obtained. The low-energy states are localized at the corners of the cross section, i.e., along the prism edges, and are separated by a gap from higher energy states localized on the sides. The corner localization depends on the details of the shell geometry, i.e., thickness, diameter, and sharpness of the corners. We study systematically the low-energy spectrum of prismatic shells using numerical methods and derive the topological phase diagram as a function of magnetic field and chemical potential for triangular, square, and hexagonal geometries. A strong corner localization enhances the stability of Majorana modes to various perturbations, including the orbital effect of the magnetic field, whereas a weaker localization favorizes orbital effects and reduces the critical magnetic field. The prismatic geometry allows the Majorana zero-energy modes to be accompanied by low-energy states, which we call pseudo Majorana, and which converge to real Majoranas in the limit of small shell thickness. We include the Rashba spin-orbit coupling in a phenomenological manner, assuming a radial electric field across the shell.

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

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.

Fabrication of Ni@Ti core-shell nanoparticles by modified gas aggregation source

Science.gov (United States)

Hanuš, J.; Vaidulych, M.; Kylián, O.; Choukourov, A.; Kousal, J.; Khalakhan, I.; Cieslar, M.; Solař, P.; Biederman, H.

2017-11-01

Ni@Ti core-shell nanoparticles were prepared by a vacuum based method using the gas aggregation source (GAS) of nanoparticles. Ni nanoparticles fabricated in the GAS were afterwards coated by a Ti shell. The Ti shell was deposited by means of magnetron sputtering. The Ni nanoparticles were decelerated in the vicinity of the magnetron to the Ar drift velocity in the second deposition chamber. X-ray photoelectron spectroscopy and energy dispersive x-ray spectroscopy analysis of the nanoparticles showed the core-shell structure. It was shown that the thickness of the shell can be easily tuned by the process parameters with a maximum achieved thickness of the Ti shell ~2.5 nm. The core-shell structure was confirmed by the STEM analysis of the particles.

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.

Synthesis and characterization of aligned ZnO/BeO core/shell nanocable arrays on glass substrate

Directory of Open Access Journals (Sweden)

Zhou Minjie

2011-01-01

Full Text Available Abstract By sequential hydrothermal growth of ZnO nanowire arrays and thermal evaporation of Be, large-scale vertically aligned ZnO/BeO core/shell nanocable arrays on glass substrate have been successfully synthesized without further heat treatment. Detailed characterizations on the sample morphologies, compositions, and microstructures were systematically carried out, which results disclose the growth behaviors of the ZnO/BeO nanocable. Furthermore, incorporation of BeO shell onto ZnO core resulted in distinct improvement of optical properties of ZnO nanowire, i.e., significant enhancement of near band edge (NBE emission as well as effective suppression of defects emission in ZnO. In particular, the NBE emission of nanocable sample shows a noticeable blue-shift compared with that of pristine ZnO nanowire, which characteristics most likely originate from Be alloying into ZnO. Consequently, the integration of ZnO and BeO into nanoscale heterostructure could bring up new opportunities in developing ZnO-based device for application in deep ultraviolet region. PACS 61.46.K; 78.67.Uh; 81.07.Gf.

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.

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.

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.

Au@Ag Core-Shell Nanocubes with Finely Tuned and Well-Controlled Sizes, Shell Thicknesses, and Optical Properties

OpenAIRE

Ma, Yanyun; Li, Weiyang; Cho, Eun Chul; Li, Zhiyuan; Yu, Taekyung; Zeng, Jie; Xie, Zhaoxiong; Xia, Younan

2010-01-01

This paper describes a facile method for generating Au@Ag core-shell nanocubes with edge lengths controllable in the range of 13.4 to 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 AgNO3 precursor to Au se...

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.

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

NARCIS (Netherlands)

Demirors, A.F.; van Blaaderen, A.; Imhof, A.

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

Multi-core MgO NPs(at)C core-shell nanospheres for selective CO2 capture under mild conditions

International Nuclear Information System (INIS)

Tae Kyung Kim; Kyung Joo Lee; Hoi Ri Moon; Junhan Yuh; Sang Kyu Kwak

2014-01-01

The core-shell structures have attracted attention in catalysis, because the outer shells isolate the catalytically active NP cores and prevent the possibility of sintering of core particles during catalytic reaction under physically and chemically harsh conditions. We aimed to adopt this core-shell system for CO 2 sorption materials. In this study, a composite material of multi-core 3 nm-sized magnesium oxide nanoparticles embedded in porous carbon nanospheres (MgO NPs(at)C) was synthesized by a gas phase reaction via a solvent-free process. It showed selective CO 2 adsorption capacity over N 2 under mild regeneration conditions. (authors)

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.

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.

Facile synthesis of silver immobilized-poly(methyl methacrylate)/polyethyleneimine core-shell particle composites

Energy Technology Data Exchange (ETDEWEB)

Jenjob, Somkieath [Department of Chemistry, Faculty of Science, Mahidol University, 999 Phuttamonthon 4 Road, Salaya, Nakhon Pathom 73170 (Thailand); Center of Excellence for Innovation in Chemistry (PERCH-CIC), Department of Chemistry, Faculty of Science, Mahidol University, Rama 6 Road, Ratchathewi, Bangkok 10400 (Thailand); Tharawut, Teeralak [Department of Chemistry, Faculty of Science, Mahidol University, 999 Phuttamonthon 4 Road, Salaya, Nakhon Pathom 73170 (Thailand); Sunintaboon, Panya, E-mail: panya.sun@mahidol.ac.th [Department of Chemistry, Faculty of Science, Mahidol University, 999 Phuttamonthon 4 Road, Salaya, Nakhon Pathom 73170 (Thailand); Center of Excellence for Innovation in Chemistry (PERCH-CIC), Department of Chemistry, Faculty of Science, Mahidol University, Rama 6 Road, Ratchathewi, Bangkok 10400 (Thailand); Center for Alternative Energy, Faculty of Science, Mahidol University, 999 Phuttamonthon 4 Road, Salaya, Nakhon Pathom 73170 (Thailand)

2012-10-01

A facile route to synthesize silver-embedded-poly(methyl methacrylate)/polyethyleneimine (PMMA/PEI-Ag) core-shell particle composites was illustrated in this present work. PMMA/PEI core-shell particle templates were first prepared by a surfactant-free emulsion polymerization. PEI on the templates' surface was further used to complex and reduce Ag{sup +} ions (from silver nitrate solution) to silver nanoparticles (AgNPs) at ambient temperature, resulting in the PMMA/PEI-Ag particle composites. The formation of AgNPs was affected by the pHs of the reaction medium. The pH of reaction medium at 6.5 was optimal for the formation of PMMA/PEI-Ag with good colloidal stability, which was confirmed by size and size distribution, FTIR spectroscopy, UV-vis spectroscopy and X-ray diffraction. Moreover, the amount of AgNO{sub 3} solution (4.17-12.50 g) was found to affect the formation of AgNPs. Transmission electron microscopy (TEM) indicated that the AgNPs were incorporated in the PMMA/PEI core-shell matrix, and had 6-10 nm in diameter. AgNPs immobilized on PMMA/PEI core-shell particles were also investigated by energy dispersive X-ray spectroscopy analysis mode extended from scanning electron microscopy (SEM/EDS). Furthermore, the presence of AgNPs was found to influence the thermal degradation behavior of PMMA/PEI particle composites as observed through thermogravimetric analysis (TGA). Highlights: Black-Right-Pointing-Pointer A 2-step synthesis of Ag immobilized-PMMA/PEI particle composites was shown. Black-Right-Pointing-Pointer PMMA/PEI core-shell templates were first formed and PEI assisted AgNP formation. Black-Right-Pointing-Pointer Formation of PMMA/PEI-Ag was affected by pH of medium and amount of AgNO{sub 3}. Black-Right-Pointing-Pointer PMMA/PEI-Ag can be confirmed by color change, UV-vis, TEM, SEM with EDS, and X-ray. Black-Right-Pointing-Pointer Effect of AgNPs on thermal degradation of PMMA/PEI-Ag can be observed through TGA.

Study of the effect of varying core diameter, shell thickness and strain velocity on the tensile properties of single crystals of Cu-Ag core-shell nanowire using molecular dynamics simulations

Science.gov (United States)

Sarkar, Jit; Das, D. K.

2018-01-01

Core-shell type nanostructures show exceptional properties due to their unique structure having a central solid core of one type and an outer thin shell of another type which draw immense attention among researchers. In this study, molecular dynamics simulations are carried out on single crystals of copper-silver core-shell nanowires having wire diameter ranging from 9 to 30 nm with varying core diameter, shell thickness, and strain velocity. The tensile properties like yield strength, ultimate tensile strength, and Young's modulus are studied and correlated by varying one parameter at a time and keeping the other two parameters constant. The results obtained for a fixed wire size and different strain velocities were extrapolated to calculate the tensile properties like yield strength and Young's modulus at standard strain rate of 1 mm/min. The results show ultra-high tensile properties of copper-silver core-shell nanowires, several times than that of bulk copper and silver. These copper-silver core-shell nanowires can be used as a reinforcing agent in bulk metal matrix for developing ultra-high strength nanocomposites.

Modified solvothermal synthesis and characterization of CdS/ZnS core/shell nanorods

International Nuclear Information System (INIS)

Baby Suganthi, A.R.; Sagayaraj, P.

2013-01-01

Core/shell CdS/ZnS nanorods were synthesized using a two-step solvothermal approach. The first step is the formation of CdS nanoparticles initiated using nucleation followed by growth through coalescence-exchange and particle coagulation. The second step leads to the formation of ZnS and further coalescence-exchange leading to deposition and growth of a ZnS shell around CdS nanoparticles. The structural, morphological and chemical studies were performed using X-ray diffraction, Energy Dispersive X-ray spectroscopy (EDX) Scanning electron Microscopy (SEM), UV–vis absorption spectra and Transmission Electron Microscopy (TEM), provide direct evidence for shell growth. The present synthesis provides a rational approach to the design of novel core/shell nanomaterials with appealing applications in optoelectronic devices. - Graphical abstract: From the resulting TEM images, the formation of core/shell could be observed. The apparent microscopy contrast between the CdS core and the ZnS shell offers evidence for the formation of CdS/ZnS core/shell nanostructures. It is clearly evident that the surfaces of the nanorods became rough after coating and also the diameter of the nanorod is seen increased up to 40–50 nm. Highlights: ► CdS/ZnS core/shell nanorods were synthesized using two-step solvothermal approach. ► The nanoparticles were characterized by XRD, EDX, SEM, UV–vis and TEM. ► SEM images revealed the surface roughness after ZnS shell growth. ► TEM microscopy offers evidence for the formation of core/shell nanostructures

Amplification of large-scale magnetic field in nonhelical magnetohydrodynamics

KAUST Repository

Kumar, Rohit

2017-08-11

It is typically assumed that the kinetic and magnetic helicities play a crucial role in the growth of large-scale dynamo. In this paper, we demonstrate that helicity is not essential for the amplification of large-scale magnetic field. For this purpose, we perform nonhelical magnetohydrodynamic (MHD) simulation, and show that the large-scale magnetic field can grow in nonhelical MHD when random external forcing is employed at scale 1/10 the box size. The energy fluxes and shell-to-shell transfer rates computed using the numerical data show that the large-scale magnetic energy grows due to the energy transfers from the velocity field at the forcing scales.

Predictable Particle Engineering: Programming the Energy Level, Carrier Generation, and Conductivity of Core-Shell Particles.

Science.gov (United States)

Yuan, Conghui; Wu, Tong; Mao, Jie; Chen, Ting; Li, Yuntong; Li, Min; Xu, Yiting; Zeng, Birong; Luo, Weiang; Yu, Lingke; Zheng, Gaofeng; Dai, Lizong

2018-06-20

Core-shell structures are of particular interest in the development of advanced composite materials as they can efficiently bring different components together at nanoscale. The advantage of this structure greatly relies on the crucial design of both core and shell, thus achieving an intercomponent synergistic effect. In this report, we show that decorating semiconductor nanocrystals with a boronate polymer shell can easily achieve programmable core-shell interactions. Taking ZnO and anatase TiO 2 nanocrystals as inner core examples, the effective core-shell interactions can narrow the band gap of semiconductor nanocrystals, change the HOMO and LUMO levels of boronate polymer shell, and significantly improve the carrier density of core-shell particles. The hole mobility of core-shell particles can be improved by almost 9 orders of magnitude in comparison with net boronate polymer, while the conductivity of core-shell particles is at most 30-fold of nanocrystals. The particle engineering strategy is based on two driving forces: catechol-surface binding and B-N dative bonding and having a high ability to control and predict the shell thickness. Also, this approach is applicable to various inorganic nanoparticles with different components, sizes, and shapes.

Enhanced energy storage and suppressed dielectric loss in oxide core-shell-polyolefin nanocomposites by moderating internal surface area and increasing shell thickness

Energy Technology Data Exchange (ETDEWEB)

Fredin, Lisa A.; Li, Zhong; Ratner, Mark A.; Marks, Tobin J. [Department of Chemistry Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Lanagan, Michael T. [Center for Dielectric Studies, Materials Research Institute, The Pennsylvania State University, University Park, PA 16802-4800 (United States)

2012-11-20

Dielectric loss in metal oxide core/Al{sub 2}O{sub 3} shell polypropylene nanocomposites scales with the particle surface area. By moderating the interfacial surface area between the phases and using increasing shell thicknesses, dielectric loss is significantly reduced, and thus the energy stored within, and recoverable from, capacitors fabricated from these materials is significantly increased, to as high as 2.05 J/cm{sup 3}. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

High-resolution TEM characterization of ZnO core-shell nanowires for dye-sensitized solar cells

Energy Technology Data Exchange (ETDEWEB)

Divitini, G; Ducati, C [Department of Materials Science, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom); Plank, N O V; Welland, M E [Nanoscience Centre, Department of Engineering, University of Cambridge, CB3 0FF (United Kingdom); Snaith, H J, E-mail: gd322@cam.ac.u [Clarendon Laboratory, Department of Physics, University of Oxford, OX1 3PU (United Kingdom)

2010-07-01

Recently ZnO nanowire films have been used in very promising and inexpensive dye-sensitized solar cells (DSSC). It was found that the performance of the devices can be enhanced by functionalising the nanowires with a thin metal oxide coating. This nm-scale shell is believed to tailor the electronic structure of the nanowire, and help the absorption of the dye. Core-shell ZnO nanowire structures are synthesised at low temperature (below 120{sup 0}C) by consecutive hydrothermal growth steps. Different materials are investigated for the coating, including Mg, Al, Cs and Zr oxides. High resolution TEM is used to characterise the quality of both the nanowire core and the shell, and to monitor the thickness and the degree of crystallisation of the oxide coating. The interface between the nanowire core and the outer shell is investigated in order to understand the adhesion of the coating, and give valuable feedback for the synthesis process. Nanowire films are packaged into dye-sensitised solar cell prototypes; samples coated with ZrO{sub 2} and MgO show the largest enhancement in the photocurrent and open-circuit voltage and look very promising for further improvement.

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)

Synthesis of magnetic CoPt/SiO{sub 2} core-shell nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Seto, Takafumi [Research Consortium for Synthetic Nano-Function Materials Project (SYNAF), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Koga, Kenji [Research Consortium for Synthetic Nano-Function Materials Project (SYNAF), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Takano, Fumiyoshi [Research Consortium for Synthetic Nano-Function Materials Project (SYNAF), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Akinaga, Hiroyuki [Research Consortium for Synthetic Nano-Function Materials Project (SYNAF), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Orii, Takaaki [Research Consortium for Synthetic Nano-Function Materials Project (SYNAF), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Hirasawa, Makoto [Research Consortium for Synthetic Nano-Function Materials Project (SYNAF), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Murayama, Mitsuhiro [National Institute for Material Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan)

2007-04-15

Core-shell nanoparticles composed of ferromagnetic cobalt platinum cores covered by non-magnetic silica shells were synthesized by laser ablating a composite target in a helium background gas. The average diameter of the CoPt core was controlled by adjusting the CoPt/SiO{sub 2} ratio of the ablation target. The particles were also classified in the gas phase using an electrical mobility classifier. The present method successfully synthesized nearly monodispersed nanoparticles with an average core diameter of 2.5nm. This article describes the synthesis of the core-shell nanoparticles and investigates their magnetic properties.

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.

Construction of CdS@UIO-66-NH2 core-shell nanorods for enhanced photocatalytic activity with excellent photostability.

Science.gov (United States)

Liang, Qian; Cui, Sainan; Liu, Changhai; Xu, Song; Yao, Chao; Li, Zhongyu

2018-08-15

A novel class of CdS@UIO-66-NH 2 core shell heterojunction was fabricated by the facile in-situ solvothermal method. Characterizations show that porous UIO-66-NH 2 shell not only allows the visible light to be absorbed on CdS nanorod core, but also provides abundant catalytic active sites as well as an intimate heterojunction interface between UIO-66-NH 2 shell and CdS nanorod core. By taking advantage of this property, the core-shell composite presents highly solar-driven photocatalytic performance compared with pristine UIO-66-NH 2 and CdS nanorod for the degradation of organic dyes including malachite green (MG) and methyl orange (MO), and displays superior photostability after four recycles. Furthermore, the photoelectrochemical performance of CdS@UIO-66-NH 2 can be measured by the UV-vis spectra, Mott-Schottky plots and photocurrent. The remarkably enhanced photocatalytic activity of CdS@UIO-66-NH 2 can be ascribed to high surface areas, intimate interaction on molecular scale and the formation of one-dimensional heterojunction with n-n type. What's more, the core-shell heterostructural CdS@UIO-66-NH 2 can facilitate the effective separation and transfer of the photoinduced interfacial electron-hole pairs and protect CdS nanorod core from photocorrosion. Copyright © 2018 Elsevier Inc. All rights reserved.

Development of magnetic luminescent core/shell nanocomplex particles with fluorescence using Rhodamine 6G

Energy Technology Data Exchange (ETDEWEB)

Lee, Hee Uk; Song, Yoon Seok [Department of Chemical and Biological Engineering, Korea University, 5 Ga, Anam-Dong, Sungbuk-Gu, Seoul 136-701 (Korea, Republic of); Park, Chulhwan [Department of Chemical Engineering, Kwangwoon University, 447-1 Wolgye-Dong, Nowon-Gu, Seoul 139-701 (Korea, Republic of); Kim, Seung Wook, E-mail: kimsw@korea.ac.kr [Department of Chemical and Biological Engineering, Korea University, 5 Ga, Anam-Dong, Sungbuk-Gu, Seoul 136-701 (Korea, Republic of)

2012-12-15

Graphical abstract: Display Omitted Highlights: ► A simple method was developed to synthesize Co-B/SiO{sub 2}/dye/SiO{sub 2} composite particles. ► The magnetic particle shows that highly luminescent and core/shell particles are formed. ► Such core/shell particles can be easily suspended in water. ► The magnetic particles could detect fluorescence for the application of biosensor. -- Abstract: A simple and reproducible method was developed to synthesize a novel class of Co-B/SiO{sub 2}/dye/SiO{sub 2} composite core/shell particles. Using a single cobalt core, Rhodamine 6G of organic dye molecules was entrapped in a silica shell, resulting in core/shell particles of ∼200 nm diameter. Analyses using a variety of techniques such as transmission electron microscopy, X-ray photoelectron spectroscopy, vibration sample magnetometry, confocal laser scanning microscopy, and fluorescence intensity demonstrated that dye molecules were trapped inside the core/shell particles. A photoluminescence investigation showed that highly luminescent and photostable core/shell particles were formed. Such core/shell particles can be easily suspended in water. The synthesized magnetic particles could be used to detect fluorescence on glass substrate arrays for bioassay and biosensor applications.

Ionic bonding of lanthanides, as influenced by d- and f-atomic orbitals, by core-shells and by relativity.

Science.gov (United States)

Ji, Wen-Xin; Xu, Wei; Schwarz, W H Eugen; Wang, Shu-Guang

2015-03-15

Lanthanide trihalide molecules LnX3 (X = F, Cl, Br, I) were quantum chemically investigated, in particular detail for Ln = Lu (lutetium). We applied density functional theory (DFT) at the nonrelativistic and scalar and SO-coupled relativistic levels, and also the ab initio coupled cluster approach. The chemically active electron shells of the lanthanide atoms comprise the 5d and 6s (and 6p) valence atomic orbitals (AO) and also the filled inner 4f semivalence and outer 5p semicore shells. Four different frozen-core approximations for Lu were compared: the (1s(2) -4d(10) ) [Pd] medium core, the [Pd+5s(2) 5p(6) = Xe] and [Pd+4f(14) ] large cores, and the [Pd+4f(14) +5s(2) 5p(6) ] very large core. The errors of LuX bonding are more serious on freezing the 5p(6) shell than the 4f(14) shell, more serious upon core-freezing than on the effective-core-potential approximation. The LnX distances correlate linearly with the AO radii of the ionic outer shells, Ln(3+) -5p(6) and X(-) -np(6) , characteristic for dominantly ionic Ln(3+) -X(-) binding. The heavier halogen atoms also bind covalently with the Ln-5d shell. Scalar relativistic effects contract and destabilize the LuX bonds, spin orbit coupling hardly affects the geometries but the bond energies, owing to SO effects in the free atoms. The relativistic changes of bond energy BE, bond length Re , bond force k, and bond stretching frequency vs do not follow the simple rules of Badger and Gordy (Re ∼BE∼k∼vs ). The so-called degeneracy-driven covalence, meaning strong mixing of accidentally near-degenerate, nearly nonoverlapping AOs without BE contribution is critically discussed. © 2015 Wiley Periodicals, Inc.

Application of microwaves for incinerating waste shell moulds and cores

Directory of Open Access Journals (Sweden)

K. Granat

2008-08-01

Full Text Available In the paper, investigation results of microwave heating application for incinerating waste shell moulds and cores made of moulding sands with thermosetting resins are presented. It was found that waste shell cores or shell moulds left after casting, separated from moulding sand, can be effectively incinerated. It was evidenced that microwave heating allows effective control of this process and its results. Incineration of waste moulds and cores made of commercial grades of resin-coated moulding sand using microwave heating was found to be an effective way of their utilisation. It was determined that the optimum burning time of these wastes (except those insufficiently disintegrated and not mixed with an activating agent is maximum 240 s at the used magnetron power of 650 W. It was noticed that proper disintegration of the wastes and use of suitable additives to intensify the microwave heating process guarantee significant reduction of the process time and its full stabilisation. Application of microwave heating for incinerating waste shell moulds and cores ensure substantial and measurable economic profits due to shorter process time and lower energy consumption.

Synthesis of bimetallic Pt-Pd core-shell nanocrystals and their high electrocatalytic activity modulated by Pd shell thickness

Science.gov (United States)

Li, Yujing; Wang, Zhi Wei; Chiu, Chin-Yi; Ruan, Lingyan; Yang, Wenbing; Yang, Yang; Palmer, Richard E.; Huang, Yu

2012-01-01

Bimetallic Pt-Pd core-shell nanocrystals (NCs) are synthesized through a two-step process with controlled Pd thickness from sub-monolayer to multiple atomic layers. The oxygen reduction reaction (ORR) catalytic activity and methanol oxidation reactivity of the core-shell NCs for fuel cell applications in alkaline solution are systematically studied and compared based on different Pd thickness. It is found that the Pd shell helps to reduce the over-potential of ORR by up to 50mV when compared to commercial Pd black, while generating up to 3-fold higher kinetic current density. The carbon monoxide poisoning test shows that the bimetallic NCs are more resistant to the CO poisoning than Pt NCs and Pt black. It is also demonstrated that the bimetallic Pt-Pd core-shell NCs can enhance the current density of the methanol oxidation reaction, lowering the over-potential by 35 mV with respect to the Pt core NCs. Further investigation reveals that the Pd/Pt ratio of 1/3, which corresponds to nearly monolayer Pd deposition on Pt core NCs, gives the highest oxidation current density and lowest over-potential. This study shows for the first time the systematic investigation of effects of Pd atomic shells on Pt-Pd bimetallic nanocatalysts, providing valuable guidelines for designing high-performance catalysts for fuel cell applications.Bimetallic Pt-Pd core-shell nanocrystals (NCs) are synthesized through a two-step process with controlled Pd thickness from sub-monolayer to multiple atomic layers. The oxygen reduction reaction (ORR) catalytic activity and methanol oxidation reactivity of the core-shell NCs for fuel cell applications in alkaline solution are systematically studied and compared based on different Pd thickness. It is found that the Pd shell helps to reduce the over-potential of ORR by up to 50mV when compared to commercial Pd black, while generating up to 3-fold higher kinetic current density. The carbon monoxide poisoning test shows that the bimetallic NCs are more

Bioprinting Using Mechanically Robust Core-Shell Cell-Laden Hydrogel Strands.

Science.gov (United States)

Mistry, Pritesh; Aied, Ahmed; Alexander, Morgan; Shakesheff, Kevin; Bennett, Andrew; Yang, Jing

2017-06-01

The strand material in extrusion-based bioprinting determines the microenvironments of the embedded cells and the initial mechanical properties of the constructs. One unmet challenge is the combination of optimal biological and mechanical properties in bioprinted constructs. Here, a novel bioprinting method that utilizes core-shell cell-laden strands with a mechanically robust shell and an extracellular matrix-like core has been developed. Cells encapsulated in the strands demonstrate high cell viability and tissue-like functions during cultivation. This process of bioprinting using core-shell strands with optimal biochemical and biomechanical properties represents a new strategy for fabricating functional human tissues and organs. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Atomistic tight-binding computations of the structural and optical properties of CdTe/CdX (X=S and Se)/ZnS core/shell/shell nanocrystals

Science.gov (United States)

Sukkabot, Worasak

2018-05-01

A study of CdTe/CdX (X=S and Se)/ZnS core/shell/shell nanocrystals is carried out using atomistic tight-binding theory and the configuration interaction method to provide information for applications in bioimaging, biolabeling, display devices and near-infrared electronic instruments. The calculations yield the dependences of the internal and external passivated shells on the natural behaviours of CdTe/CdX (X=S and Se)/ZnS core/shell/shell nanocrystals. The reduction of the optical band gaps is observed with increasing numbers of monolayers in the external ZnS shell due to quantum confinement. Interestingly, the optical band gaps of CdTe/CdS/ZnS core/shell/shell nanocrystals are greater than those of CdTe/CdSe/ZnS core/shell/shell nanocrystals. In the presence of an external ZnS-coated shell, electron-hole wave function overlaps, oscillation strengths, ground-state exchange energies and Stokes shift are improved, whereas ground-state coulomb energies and fine-structure splitting are reduced. The oscillation strengths, Stokes shift and fine-structure splitting are reduced with the increase in external ZnS shell thickness. The oscillation strengths, Stokes shift and fine-structure splitting of CdTe/CdS/ZnS core/shell/shell nanocrystals are larger than those of CdTe/CdSe/ZnS core/shell/shell nanocrystals. Reduction of the atomistic electron-hole interactions is observed with increasing external ZnS shell size. The strong electron-hole interactions are more probed in CdTe/CdS/ZnS core/shell/shell nanocrystals than in CdTe/CdSe/ZnS core/shell/shell nanocrystals.

Development of core-shell coaxially electrospun composite PCL/chitosan scaffolds.

Science.gov (United States)

Surucu, Seda; Turkoglu Sasmazel, Hilal

2016-11-01

This study was related to combining of synthetic Poly (ε-caprolactone) (PCL) and natural chitosan polymers to develop three dimensional (3D) PCL/chitosan core-shell scaffolds for tissue engineering applications. The scaffolds were fabricated with coaxial electrospinning technique and the characterizations of the samples were done by thickness and contact angle (CA) measurements, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-Ray Photoelectron Spectroscopy (XPS) analyses, mechanical and PBS absorption and shrinkage tests. The average inter-fiber diameter values were calculated for PCL (0.717±0.001μm), chitosan (0.660±0.007μm) and PCL/chitosan core-shell scaffolds (0.412±0.003μm), also the average inter-fiber pore size values exhibited decreases of 66.91% and 61.90% for the PCL and chitosan scaffolds respectively, compared to PCL/chitosan core-shell ones. XPS analysis of the PCL/chitosan core-shell structures exhibited the characteristic peaks of PCL and chitosan polymers. The cell culture studies (MTT assay, Confocal Laser Scanning Microscope (CLSM) and SEM analyses) carried out with L929 ATCC CCL-1 mouse fibroblast cell line proved that the biocompatibility performance of the scaffolds. The obtained results showed that the created micro/nano fibrous structure of the PCL/chitosan core-shell scaffolds in this study increased the cell viability and proliferation on/within scaffolds. Copyright © 2016 Elsevier B.V. All rights reserved.

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.

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

KAUST Repository

Xu, Xuezhu; Zhou, Jian; Jiang, Long; Lubineau, Gilles; Chen, Ye; Wu, Xiangfa; Piere, Robert

2013-01-01

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.

Fabrication of Te@Au core-shell hybrids for efficient ethanol oxidation

Science.gov (United States)

Jin, Huile; Wang, Demeng; Zhao, Yuewu; Zhou, Huan; Wang, Shun; Wang, Jichang

2012-10-01

Using Au nanoparticles to catalyze the oxidation of alcohols has garnered increasing attention due to its potential application in direct alcohol fuel cells. In this research Te@Au core-shell hybrids were fabricated for the catalytic oxidation of ethanol, where the preparation procedure involved the initial production of Te crystals with different microstructures and the subsequent utilization of the Te crystal as a template and reducing agent for the production of Te@Au hybrids. The as-prepared core-shell hybrids were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction techniques. Electrochemical measurements illustrate that the hybrids have great electrocatalytic activity and stability toward ethanol oxidation in alkaline media. The enhanced electrocatalytic property may be attributed to the cooperative effects between the metal and semiconductor and the presence of a large number of active sites on the hybrids surface.

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....

Shell morphology and Raman spectra of epitaxial Ge-SixGe1-x and Si-SixGe1-x core-shell nanowires

Science.gov (United States)

Wen, Feng; Dillen, David C.; Kim, Kyounghwan; Tutuc, Emanuel

2017-06-01

We investigate the shell morphology and Raman spectra of epitaxial Ge-SixGe1-x and Si-SixGe1-x core-shell nanowire heterostructures grown using a combination of a vapor-liquid-solid (VLS) growth mechanism for the core, followed by in-situ epitaxial shell growth using ultra-high vacuum chemical vapor deposition. Cross-sectional transmission electron microscopy reveals that the VLS growth yields cylindrical Ge, and Si nanowire cores grown along the ⟨111⟩, and ⟨110⟩ or ⟨112⟩ directions, respectively. A hexagonal cross-sectional morphology is observed for Ge-SixGe1-x core-shell nanowires terminated by six {112} facets. Two distinct morphologies are observed for Si-SixGe1-x core-shell nanowires that are either terminated by four {111} and two {100} planes associated with the ⟨110⟩ growth direction or four {113} and two {111} planes associated with the ⟨112⟩ growth direction. We show that the Raman spectra of Si- SixGe1-x are correlated with the shell morphology thanks to epitaxial growth-induced strain, with the core Si-Si mode showing a larger red shift in ⟨112⟩ core-shell nanowires compared to their ⟨110⟩ counterparts. We compare the Si-Si Raman mode value with calculations based on a continuum elasticity model coupled with the lattice dynamic theory.

Core@shell@shell structured carbon-based magnetic ternary nanohybrids: Synthesis and their enhanced microwave absorption properties

Science.gov (United States)

Yang, Erqi; Qi, Xiaosi; Xie, Ren; Bai, Zhongchen; Jiang, Yang; Qin, Shuijie; Zhong, Wei; Du, Youwei

2018-05-01

High encapsulation efficiency of core@shell@shell structured carbon-based magnetic ternary nanohybrids have been synthesized in high yield by chemical vapor deposition of acetylene directly over octahedral-shaped Fe2O3 nanoparticles. By controlling the pyrolysis temperature, Fe3O4@Fe3C@carbon nanotubes (CNTs) and Fe@Fe3C@CNTs ternary nanohybrids could be selectively produced. The optimal RL values for the as-prepared ternary nanohybrids could reach up to ca. -46.7, -52.7 and -29.5 dB, respectively. The excellent microwave absorption properties of the obtaiend ternary nanohybrids were proved to ascribe to the quarter-wavelength matching model. Moreover, the as-prepared Fe@Fe3C@CNTs ternary nanohybrids displayed remarkably enhanced EM wave absorption capabilities compared to Fe3O4@Fe3C@CNTs due to their excellent dielectric loss abilities, good complementarities between the dielectric loss and the magnetic loss, and high attenuation constant. Generally, this strategy can be extended to explore other categories of core@shell or core@shell@shell structured carbon-based nanohybrids, which is very beneficial to accelerate the advancements of high performance MAMs.

Large-Scale Trade in Legally Protected Marine Mollusc Shells from Java and Bali, Indonesia.

Science.gov (United States)

Nijman, Vincent; Spaan, Denise; Nekaris, K Anne-Isola

2015-01-01

Tropical marine molluscs are traded globally. Larger species with slow life histories are under threat from over-exploitation. We report on the trade in protected marine mollusc shells in and from Java and Bali, Indonesia. Since 1987 twelve species of marine molluscs are protected under Indonesian law to shield them from overexploitation. Despite this protection they are traded openly in large volumes. We collected data on species composition, origins, volumes and prices at two large open markets (2013), collected data from wholesale traders (2013), and compiled seizure data by the Indonesian authorities (2008-2013). All twelve protected species were observed in trade. Smaller species were traded for Java and Bali, but the trade involves networks stretching hundreds of kilometres throughout Indonesia. Wholesale traders offer protected marine mollusc shells for the export market by the container or by the metric ton. Data from 20 confiscated shipments show an on-going trade in these molluscs. Over 42,000 shells were seized over a 5-year period, with a retail value of USD700,000 within Indonesia; horned helmet (Cassis cornuta) (>32,000 shells valued at USD500,000), chambered nautilus (Nautilus pompilius) (>3,000 shells, USD60,000) and giant clams (Tridacna spp.) (>2,000 shells, USD45,000) were traded in largest volumes. Two-thirds of this trade was destined for international markets, including in the USA and Asia-Pacific region. We demonstrated that the trade in protected marine mollusc shells in Indonesia is not controlled nor monitored, that it involves large volumes, and that networks of shell collectors, traders, middlemen and exporters span the globe. This impedes protection of these species on the ground and calls into question the effectiveness of protected species management in Indonesia; solutions are unlikely to be found only in Indonesia and must involve the cooperation of importing countries.

Large-Scale Trade in Legally Protected Marine Mollusc Shells from Java and Bali, Indonesia

Science.gov (United States)

Nijman, Vincent; Spaan, Denise; Nekaris, K. Anne-Isola

2015-01-01

Background Tropical marine molluscs are traded globally. Larger species with slow life histories are under threat from over-exploitation. We report on the trade in protected marine mollusc shells in and from Java and Bali, Indonesia. Since 1987 twelve species of marine molluscs are protected under Indonesian law to shield them from overexploitation. Despite this protection they are traded openly in large volumes. Methodology/Principal Findings We collected data on species composition, origins, volumes and prices at two large open markets (2013), collected data from wholesale traders (2013), and compiled seizure data by the Indonesian authorities (2008–2013). All twelve protected species were observed in trade. Smaller species were traded for trade involves networks stretching hundreds of kilometres throughout Indonesia. Wholesale traders offer protected marine mollusc shells for the export market by the container or by the metric ton. Data from 20 confiscated shipments show an on-going trade in these molluscs. Over 42,000 shells were seized over a 5-year period, with a retail value of USD700,000 within Indonesia; horned helmet (Cassis cornuta) (>32,000 shells valued at USD500,000), chambered nautilus (Nautilus pompilius) (>3,000 shells, USD60,000) and giant clams (Tridacna spp.) (>2,000 shells, USD45,000) were traded in largest volumes. Two-thirds of this trade was destined for international markets, including in the USA and Asia-Pacific region. Conclusions/Significance We demonstrated that the trade in protected marine mollusc shells in Indonesia is not controlled nor monitored, that it involves large volumes, and that networks of shell collectors, traders, middlemen and exporters span the globe. This impedes protection of these species on the ground and calls into question the effectiveness of protected species management in Indonesia; solutions are unlikely to be found only in Indonesia and must involve the cooperation of importing countries. PMID:26717021

Preparation of water-soluble CdTe/CdS core/shell quantum dots with enhanced photostability

International Nuclear Information System (INIS)

Peng Hui; Zhang Lijuan; Soeller, Christian; Travas-Sejdic, Jadranka

2007-01-01

CdTe/CdS core/shell quantum dots (QDs) have been synthesized in an aqueous phase using thioacetamide as a sulfur source. The quantum yield was greatly enhanced by the epitaxial growth of a CdS shell, which was confirmed by X-ray photoelectron spectroscopy (XPS) results. The quantum yield of as-prepared CdTe/CdS core/shell QDs without any post-preparative processing reached 58%. The experimental results illustrate that the QDs with core/shell structure show better photostability than thioglycolic acid (TGA)-capped CdTe QDs. The cyclic voltammograms reveal higher oxidation potentials for CdTe/CdS core/shell QDs than for TGA-capped CdTe QDs, which explains the superior photostability of QDs with a core/shell structure. This enhanced photostability makes these QDs with core/shell structure more suitable for bio-labeling and imaging

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.

Light neutron-rich hypernuclei from the importance-truncated no-core shell model

Directory of Open Access Journals (Sweden)

Roland Wirth

2018-04-01

Full Text Available We explore the systematics of ground-state and excitation energies in singly-strange hypernuclei throughout the helium and lithium isotopic chains — from HeΛ5 to HeΛ11 and from LiΛ7 to LiΛ12 — 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. Keywords: Hypernuclei, Ab-initio methods, Neutron-rich nuclei, Neutron separation energies, Neutron drip line

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.

Large-Scale Trade in Legally Protected Marine Mollusc Shells from Java and Bali, Indonesia.

Directory of Open Access Journals (Sweden)

Vincent Nijman

Full Text Available Tropical marine molluscs are traded globally. Larger species with slow life histories are under threat from over-exploitation. We report on the trade in protected marine mollusc shells in and from Java and Bali, Indonesia. Since 1987 twelve species of marine molluscs are protected under Indonesian law to shield them from overexploitation. Despite this protection they are traded openly in large volumes.We collected data on species composition, origins, volumes and prices at two large open markets (2013, collected data from wholesale traders (2013, and compiled seizure data by the Indonesian authorities (2008-2013. All twelve protected species were observed in trade. Smaller species were traded for 32,000 shells valued at USD500,000, chambered nautilus (Nautilus pompilius (>3,000 shells, USD60,000 and giant clams (Tridacna spp. (>2,000 shells, USD45,000 were traded in largest volumes. Two-thirds of this trade was destined for international markets, including in the USA and Asia-Pacific region.We demonstrated that the trade in protected marine mollusc shells in Indonesia is not controlled nor monitored, that it involves large volumes, and that networks of shell collectors, traders, middlemen and exporters span the globe. This impedes protection of these species on the ground and calls into question the effectiveness of protected species management in Indonesia; solutions are unlikely to be found only in Indonesia and must involve the cooperation of importing countries.

Large-Scale Assessment, Rationality, and Scientific Management: The Case of No Child Left Behind

Science.gov (United States)

Roach, Andrew T.; Frank, Jennifer

2007-01-01

This article examines the ways in which NCLB and the movement towards large-scale assessment systems are based on Weber's concept of formal rationality and tradition of scientific management. Building on these ideas, the authors use Ritzer's McDonaldization thesis to examine some of the core features of large-scale assessment and accountability…

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.

Characterization of core-shell nanoparticles by small angle neutron scattering

Energy Technology Data Exchange (ETDEWEB)

Strunz, P. [Nuclear Physics Institute (NPI), Rez (Czech Republic); Research Centre Rez, Rez (Czech Republic); Mukherji, D. [TU Braunschweig, IfW, Braunschweig (Germany); Pigozzi, G. [ETH Zuerich, Laboratory for Nanometallurgy, Zuerich (Switzerland); Gilles, R. [TU Muenchen, ZWE FRM-II, Garching (Germany); Geue, T. [PSI and ETH Zuerich, Laboratory for Neutron Scattering, Villigen PSI (Switzerland); Pranzas, K. [GKSS Research Centre, Institute of Materials Research, Geesthacht (Germany)

2007-08-15

The Ni{sub 3}Si-type nanoparticles dispersed in a mixture of H{sub 2}O/D{sub 2}O were characterised by SANS using the contrast variation method. The existence of a core-shell structure in the nanoparticles with a Ni{sub 3}Si(Al) core and amorphous SiO{sub 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.)

Magnetic response of hybrid ferromagnetic and antiferromagnetic core-shell nanostructures.

Science.gov (United States)

Khan, U; Li, W J; Adeela, N; Irfan, M; Javed, K; Wan, C H; Riaz, S; Han, X F

2016-03-21

The synthesis of FeTiO3-Ni(Ni80Fe20) core-shell nanostructures by a two-step method (sol-gel and DC electrodeposition) has been demonstrated. XRD analysis confirms the rhombohedral crystal structure of FeTiO3(FTO) with space group R3[combining macron]. Transmission electron microscopy clearly depicts better morphology of nanostructures with shell thicknesses of ∼25 nm. Room temperature magnetic measurements showed significant enhancement of magnetic anisotropy for the permalloy (Ni80Fe20)-FTO over Ni-FTO core-shell nanostructures. Low temperature magnetic measurements of permalloy-FeTiO3 core-shell structure indicated a strong exchange bias mechanism with magnetic coercivity below the antiferromagnetic Neel temperature (TN = 59 K). The exchange bias is attributed to the alignment of magnetic moments in the antiferromagnetic material at low temperature. Our scheme opens a path towards optimum automotive systems and wireless communications wherein broader bandwidths and smaller sizes are required.

Deriving the nuclear shell model from first principles

Science.gov (United States)

Barrett, Bruce R.; Dikmen, Erdal; Vary, James P.; Maris, Pieter; Shirokov, Andrey M.; Lisetskiy, Alexander F.

2014-09-01

The results of an 18-nucleon No Core Shell Model calculation, performed in a large basis space using a bare, soft NN interaction, can be projected into the 0 ℏω space, i.e., the sd -shell. Because the 16 nucleons in the 16O core are frozen in the 0 ℏω space, all the correlations of the 18-nucleon system are captured by the two valence, sd -shell nucleons. By the projection, we obtain microscopically the sd -shell 2-body effective interactions, the core energy and the sd -shell s.p. energies. Thus, the input for standard shell-model calculations can be determined microscopically by this approach. If the same procedure is then applied to 19-nucleon systems, the sd -shell 3-body effective interactions can also be obtained, indicating the importance of these 3-body effective interactions relative to the 2-body effective interactions. Applications to A = 19 and heavier nuclei with different intrinsic NN interactions will be presented and discussed. The results of an 18-nucleon No Core Shell Model calculation, performed in a large basis space using a bare, soft NN interaction, can be projected into the 0 ℏω space, i.e., the sd -shell. Because the 16 nucleons in the 16O core are frozen in the 0 ℏω space, all the correlations of the 18-nucleon system are captured by the two valence, sd -shell nucleons. By the projection, we obtain microscopically the sd -shell 2-body effective interactions, the core energy and the sd -shell s.p. energies. Thus, the input for standard shell-model calculations can be determined microscopically by this approach. If the same procedure is then applied to 19-nucleon systems, the sd -shell 3-body effective interactions can also be obtained, indicating the importance of these 3-body effective interactions relative to the 2-body effective interactions. Applications to A = 19 and heavier nuclei with different intrinsic NN interactions will be presented and discussed. Supported by the US NSF under Grant No. 0854912, the US DOE under

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.

Nano-sized LiFePO4/C composite with core-shell structure as cathode material for lithium ion battery

International Nuclear Information System (INIS)

Liu, Yang; Zhang, Min; Li, Ying; Hu, Yemin; Zhu, Mingyuan; Jin, Hongming; Li, Wenxian

2015-01-01

Graphical abstract: Nano-sized LiFePO4/C composite with core-shell structure was fabricated via a well-designed approach as cathode material forlithium ion battery. The nano-sized LiFePO4/C composite with whole carbon shell coating layer showed an excellent electrical performance. - Abstract: Nano-sized composite with LiFePO 4 -core and carbon-shell was synthesized via a facile route followed by heat treatment at 650 °C. X-ray diffraction (XRD) shows that the core is well crystallized LiFePO 4 . The electron microscopy (SEM and TEM) observations show that the core-shell structured LiFePO 4 /C composite coating with whole carbon shell layer of ∼2.8 nm, possesses a specific surface area of 51 m 2 g −1 . As cathode material for lithium ion battery, the core-shell LiFePO 4 /C composite exhibits high initial capacity of 161 mAh g −1 at 0.1 C, excellent high-rate discharge capacity of 135 mAh g −1 at 5 C and perfect cycling retention of 99.6% at 100 th cycle. All these promising results should be contributed to the core-shell nanostructure which prevents collapse of the particle structure in the long-term charge and discharge cycles, as well as the large surface area of the nano-sized LiFePO 4 /C composite which enhances the electronic conductivity and shortens the distance of lithium ion diffusion

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

Chemical and thermal stability of core-shelled magnetite nanoparticles and solid silica

Science.gov (United States)

Cendrowski, Krzysztof; Sikora, Pawel; Zielinska, Beata; Horszczaruk, Elzbieta; Mijowska, Ewa

2017-06-01

Pristine nanoparticles of magnetite were coated by solid silica shell forming core/shell structure. 20 nm thick silica coating significantly enhanced the chemical and thermal stability of the iron oxide. Chemical and thermal stability of this structure has been compared to the magnetite coated by mesoporous shell and pristine magnetite nanoparticles. It is assumed that six-membered silica rings in a solid silica shell limit the rate of oxygen diffusion during thermal treatment in air and prevent the access of HCl molecules to the core during chemical etching. Therefore, the core/shell structure with a solid shell requires a longer time to induce the oxidation of iron oxide to a higher oxidation state and, basically, even strong concentrated acid such as HCl is not able to dissolve it totally in one month. This leads to the desired performance of the material in potential applications such as catalysis and environmental protection.

The diamagnetic susceptibility of a donor in a semiconductor core shell quantum dot

Energy Technology Data Exchange (ETDEWEB)

Sudharshan, M. S.; Subhash, P.; Shaik, Nagoor Babu [Department of Mechanical Engineering, Saveetha School of Engineering, Saveetha University, Thandalam, Chennai – 602105 (India); Kalpana, P.; Jayakumar, K. [Department of Physics, Gandhigram Rural University, Gandhigram, Tamilnadu-624302 (India); Reuben, A. Merwyn Jasper D., E-mail: merwyn@gmail.com [Department of Physics, Saveetha School of Engineering, Saveetha University, Thandalam, Chennai – 602105 (India)

2015-06-24

The effect of Aluminium concentration, shell thickness and size of the core shell Quantum Dot on the Diamagnetic Susceptibility of a donor in the Core Shell Quantum Dot is calculated in the effective mass approximation using the variational method. The results are presented and discussed.

The diamagnetic susceptibility of a donor in a semiconductor core shell quantum dot

Science.gov (United States)

Sudharshan, M. S.; Subhash, P.; Shaik, Nagoor Babu; Kalpana, P.; Jayakumar, K.; Reuben, A. Merwyn Jasper D.

2015-06-01

The effect of Aluminium concentration, shell thickness and size of the core shell Quantum Dot on the Diamagnetic Susceptibility of a donor in the Core Shell Quantum Dot is calculated in the effective mass approximation using the variational method. The results are presented and discussed.

PLGA-lecithin-PEG core-shell nanoparticles for controlled drug delivery.

Science.gov (United States)

Chan, Juliana M; Zhang, Liangfang; Yuet, Kai P; Liao, Grace; Rhee, June-Wha; Langer, Robert; Farokhzad, Omid C

2009-03-01

Current approaches to encapsulate and deliver therapeutic compounds have focused on developing liposomal and biodegradable polymeric nanoparticles (NPs), resulting in clinically approved therapeutics such as Doxil/Caelyx and Genexol-PM, respectively. Our group recently reported the development of biodegradable core-shell NP systems that combined the beneficial properties of liposomal and polymeric NPs for controlled drug delivery. Herein we report the parameters that alter the biological and physicochemical characteristics, stability, drug release properties and cytotoxicity of these core-shell NPs. We further define scalable processes for the formulation of these NPs in a reproducible manner. These core-shell NPs consist of (i) a poly(D,L-lactide-co-glycolide) hydrophobic core, (ii) a soybean lecithin monolayer, and (iii) a poly(ethylene glycol) shell, and were synthesized by a modified nanoprecipitation method combined with self-assembly. Preparation of the NPs showed that various formulation parameters such as the lipid/polymer mass ratio and lipid/lipid-PEG molar ratio controlled NP physical stability and size. We encapsulated a model chemotherapy drug, docetaxel, in the NPs and showed that the amount of lipid coverage affected its drug release kinetics. Next, we demonstrated a potentially scalable process for the formulation, purification, and storage of NPs. Finally, we tested the cytotoxicity using MTT assays on two model human cell lines, HeLa and HepG2, and demonstrated the biocompatibility of these particles in vitro. Our data suggest that the PLGA-lecithin-PEG core-shell NPs may be a useful new controlled release drug delivery system.

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

Ag@ZnO core-shell nanoparticles study by first principle: The structural, magnetic and optical properties

Energy Technology Data Exchange (ETDEWEB)

Cheng, Hai-Xia [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China); Wang, Xiao-Xu [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China); Beijing Computing Center, Beijing 100094 (China); Hu, Yao-Wen [Department of Physics, Tsinghua University, Beijing 100084 (China); Song, Hong-Quan; Huo, Jin-Rong; Li, Lu [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China); Qian, Ping, E-mail: ustbqianp@163.com [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China); Song, Yu-Jun [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China)

2016-12-15

Ag@ZnO core-shell nanoparticles of around 72 atoms have been investigated by the density functional theory, revealing proving for the first time that the core-shell structure exhibits a shrinkage phenomenon from outer shell in agreement with the other studies in literatures. Our calculations predict that the Ag@ZnO core-shell structure is a ferromagnetic spin polarized state, and the magnetism mainly stems from the spin splitting of 2p electrons of O atoms. In addition, the total and partial DOS of Ag@ZnO indicate that the nanostructure is a half-metallic nanoparticle and has the characters of the p-type semiconductor. Furthermore, the optical properties calculations show that the absorption edge of Ag@ZnO have a red shift and good photocatalysis compare to that of the bulk ZnO. These results of the Ag@ZnO core-shell structure obtain a well agreement with the experimental measurement. - Graphical abstract: Geometric structure of (a) Ag@ZnO core-shell nanostructure; (b) the core of Ag; (c) the shell of ZnO The core-shell nanoparticle Ag@ZnO contains Ag inner core of radius of 4 Å and ZnO outer shell with thickness of 2 Å. Ag@ZnO core-shell nanoparticles of around 72 atoms have been proved for the first time that the core-shell structure exhibit a shrinkage phenomenon from outer shell. Our calculations predict that the Ag@ZnO core-shell structure is a half-metallic nanoparticle and has the characters of the p-type semiconductor. The absorption edge of Ag@ZnO have a red shift and get good photo-catalysis compare to that of the bulk ZnO.

Ab initio translationally invariant nonlocal one-body densities from no-core shell-model theory

Science.gov (United States)

Burrows, M.; Elster, Ch.; Popa, G.; Launey, K. D.; Nogga, A.; Maris, P.

2018-02-01

Background: It is well known that effective nuclear interactions are in general nonlocal. Thus if nuclear densities obtained from ab initio no-core shell-model (NCSM) calculations are to be used in reaction calculations, translationally invariant nonlocal densities must be available. Purpose: Though it is standard to extract translationally invariant one-body local densities from NCSM calculations to calculate local nuclear observables like radii and transition amplitudes, the corresponding nonlocal one-body densities have not been considered so far. A major reason for this is that the procedure for removing the center-of-mass component from NCSM wave functions up to now has only been developed for local densities. Results: A formulation for removing center-of-mass contributions from nonlocal one-body densities obtained from NCSM and symmetry-adapted NCSM (SA-NCSM) calculations is derived, and applied to the ground state densities of 4He, 6Li, 12C, and 16O. The nonlocality is studied as a function of angular momentum components in momentum as well as coordinate space. Conclusions: We find that the nonlocality for the ground state densities of the nuclei under consideration increases as a function of the angular momentum. The relative magnitude of those contributions decreases with increasing angular momentum. In general, the nonlocal structure of the one-body density matrices we studied is given by the shell structure of the nucleus, and cannot be described with simple functional forms.

Electrochemical synthesis of CORE-shell magnetic nanowires

KAUST Repository

Ovejero, Jesú s G.; Bran, Cristina; Vidal, Enrique Vilanova; Kosel, Jü rgen; Morales, Marí a P.; Vazquez, Manuel

2015-01-01

(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

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.

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

International Nuclear Information System (INIS)

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.

2015-01-01

Fe 3 O 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 3 O 4 nanoparticles are promising for biomedical applications but have some disadvantages. • Covering Fe 3 O 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 3 O 4 @Au core/shell nanoparticles structures: bi-layer and multilayer composite. • Different synthetic methods enable production of nanoparticles of different sizes

Iridium-decorated palladium-platinum core-shell catalysts for oxygen reduction reaction in proton exchange membrane fuel cell.

Science.gov (United States)

Wang, Chen-Hao; Hsu, Hsin-Cheng; Wang, Kai-Ching

2014-08-01

Carbon-supported Pt, Pd, Pd-Pt core-shell (Pt(shell)-Pd(core)/C) and Ir-decorated Pd-Pt core-shell (Ir-decorated Pt(shell)-Pd(core)/C) catalysts were synthesized, and their physical properties, electrochemical behaviors, oxygen reduction reaction (ORR) characteristics and proton exchange membrane fuel cell (PEMFC) performances were investigated herein. From the XRD patterns and TEM images, Ir-decorated Pt(shell)-Pd(core)/C has been confirmed that Pt was deposited on the Pd nanoparticle which had the core-shell structure. Ir-decorated Pt(shell)-Pd(core)/C has more positive OH reduction peak than Pt/C, which is beneficial to weaken the binding energy of Pt-OH during the ORR. Thus, Ir-decorated Pt(shell)-Pd(core)/C has higher ORR activity than Pt/C. The maximum power density of H2-O2 PEMFC using Ir-decorated Pt(shell)-Pd(core)/C is 792.2 mW cm(-2) at 70°C, which is 24% higher than that using Pt/C. The single-cell accelerated degradation test of PEMFC using Ir-decorated Pt(shell)-Pd(core)/C shows good durability by the potential cycling of 40,000 cycles. This study concludes that Ir-decorated Pt(shell)-Pd(core)/C has the low Pt content, but it can facilitate the low-cost and high-efficient PEMFC. Copyright © 2013 Elsevier Inc. All rights reserved.

Composition-dependent photoluminescence properties of CuInS_2/ZnS core/shell quantum dots

International Nuclear Information System (INIS)

Hua, Jie; Du, Yuwei; Wei, Qi; Yuan, Xi; Wang, Jin; Zhao, Jialong; Li, Haibo

2016-01-01

CuInS_2/ZnS (CIS/ZnS) core/shell quantum dots (QDs) with various Cu/In ratios were synthesized using the hot-injection method, and their photoluminescence (PL) properties were investigated by measuring steady-state and time-resolved PL spectroscopy. The emission peak of the CIS/ZnS QDs were tuned from 680 to 580 nm by decreasing the Cu/In precursor ratio from 1/1 to 1/9. As the Cu/In ratio decreases, the PL lifetimes and PL quantum yields (QYs) of CIS/ZnS core/shell QDs increased firstly and then decreased. Two dominant radiative recombination processes were postulated to analyze composition-dependent PL properties, including the recombination from a quantized conduction band to deep defects state and donor-acceptor pair (DAP) recombination. The decrease of PL efficiency resulted from high density defects and traps, which formed at the interface between CIS core and ZnS shell due to the large off-stoichiometry composition. The PL intensity and peak energy for CIS/ZnS core/shell QDs as a function of temperature were also provided. The thermal quenching further confirmed that the PL emission of CIS/ZnS QDs did not come from the recombination of excitons but from the recombination of many kinds of intrinsic defects inside the QDs as emission centers.

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.

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

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

Energy Technology Data Exchange (ETDEWEB)

Ibral, Asmaa [Equipe d' Optique et Electronique du Solide, Département de Physique, Faculté des Sciences, Université Chouaïb Doukkali, B. P. 20 El Jadida principale, El Jadida, Royaume du Maroc (Morocco); Laboratoire d' Instrumentation, Mesure et Contrôle, Département de Physique, Faculté des Sciences, Université Chouaïb Doukkali, B. P. 20 El Jadida principale, El Jadida, Royaume du Maroc (Morocco); Zouitine, Asmaa [Département de Physique, Ecole Nationale Supérieure d' Enseignement Technique, Université Mohammed V Souissi, B. P. 6207 Rabat-Instituts, Rabat, Royaume du Maroc (Morocco); Assaid, El Mahdi, E-mail: eassaid@yahoo.fr [Equipe d' Optique et Electronique du Solide, Département de Physique, Faculté des Sciences, Université Chouaïb Doukkali, B. P. 20 El Jadida principale, El Jadida, Royaume du Maroc (Morocco); Laboratoire d' Instrumentation, Mesure et Contrôle, Département de Physique, Faculté des Sciences, Université Chouaïb Doukkali, B. P. 20 El Jadida principale, El Jadida, Royaume du Maroc (Morocco); and others

2015-02-01

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.

Successive and large-scale synthesis of InP/ZnS quantum dots in a hybrid reactor and their application to white LEDs

Science.gov (United States)

Kim, Kyungnam; Jeong, Sohee; Woo, Ju Yeon; Han, Chang-Soo

2012-02-01

We report successive and large-scale synthesis of InP/ZnS core/shell nanocrystal quantum dots (QDs) using a customized hybrid flow reactor, which is based on serial combination of a batch-type mixer and a flow-type furnace. InP cores and InP/ZnS core/shell QDs were successively synthesized in the hybrid reactor in a simple one-step process. In this reactor, the flow rate of the solutions was typically 1 ml min-1, 100 times larger than that of conventional microfluidic reactors. In order to synthesize high-quality InP/ZnS QDs, we controlled both the flow rate and the crystal growth temperature. Finally, we obtained high-quality InP/ZnS QDs in colors from bluish green to red, and we demonstrated that these core/shell QDs could be incorporated into white-light-emitting diode (LED) devices to improve color rendering performance.

Titanium dioxide@polypyrrole core-shell nanowires for all solid-state flexible supercapacitors

Science.gov (United States)

Yu, Minghao; Zeng, Yinxiang; Zhang, Chong; Lu, Xihong; Zeng, Chenghui; Yao, Chenzhong; Yang, Yangyi; Tong, Yexiang

2013-10-01

Herein, we developed a facile two-step process to synthesize TiO2@PPy core-shell nanowires (NWs) on carbon cloth and reported their improved electrochemical performance for flexible supercapacitors (SCs). The fabricated solid-state SC device based on TiO2@PPy core-shell NWs not only has excellent flexibility, but also exhibits remarkable electrochemical performance.Herein, we developed a facile two-step process to synthesize TiO2@PPy core-shell nanowires (NWs) on carbon cloth and reported their improved electrochemical performance for flexible supercapacitors (SCs). The fabricated solid-state SC device based on TiO2@PPy core-shell NWs not only has excellent flexibility, but also exhibits remarkable electrochemical performance. Electronic supplementary information (ESI) available: Experimental details, XRD pattern, FT-IR absorption spectrum and CV curves of TiO2@PPy NWs, and SEM images of the PPy. See DOI: 10.1039/c3nr03578f

Seaurchin-like hierarchical NiCo2O4@NiMoO4 core-shell nanomaterials for high performance supercapacitors.

Science.gov (United States)

Zhang, Qiang; Deng, Yanghua; Hu, Zhonghua; Liu, Yafei; Yao, Mingming; Liu, Peipei

2014-11-14

A novel electrode material of the three-dimensional (3D) multicomponent oxide NiCo2O4@NiMoO4 core-shell was synthesized via a facile two-step hydrothermal method using a post-annealing procedure. The uniform NiMoO4 nanosheets were grown on the seaurchin-like NiCo2O4 backbone to form a NiCo2O4@NiMoO4 core-shell material constructed by interconnected ultrathin nanosheets, so as to produce hierarchical mesopores with a large specific surface area of 100.3 m(2) g(-1). The porous feature and core-shell structure can facilitate the penetration of electrolytic ions and increases the number of electroactive sites. Hence, the NiCo2O4@NiMoO4 material exhibited a high specific capacitance of 2474 F g(-1) and 2080 F g(-1) at current densities of 1 A g(-1) and 20 A g(-1) respectively, suggesting that it has not only a very large specific capacitance, but also a good rate performance. In addition, the capacitance loss was only 5.0% after 1000 cycles of charge and discharge tests at the current density of 10 A g(-1), indicating high stability. The excellent electrochemical performance is mainly attributed to its 3D core-shell and hierarchical mesoporous structures which can provide unobstructed pathways for the fast diffusion and transportation of ions and electrons, a large number of active sites and good strain accommodation.

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....

Core-Shell Columns in High-Performance Liquid Chromatography: Food Analysis Applications

OpenAIRE

Preti, Raffaella

2016-01-01

The increased separation efficiency provided by the new technology of column packed with core-shell particles in high-performance liquid chromatography (HPLC) has resulted in their widespread diffusion in several analytical fields: from pharmaceutical, biological, environmental, and toxicological. The present paper presents their most recent applications in food analysis. Their use has proved to be particularly advantageous for the determination of compounds at trace levels or when a large am...

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.

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.

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.

Cluster form factor calculation in the ab initio no-core shell model

International Nuclear Information System (INIS)

Navratil, Petr

2004-01-01

We derive expressions for cluster overlap integrals or channel cluster form factors for ab initio no-core shell model (NCSM) wave functions. These are used to obtain the spectroscopic factors and can serve as a starting point for the description of low-energy nuclear reactions. We consider the composite system and the target nucleus to be described in the Slater determinant (SD) harmonic oscillator (HO) basis while the projectile eigenstate to be expanded in the Jacobi coordinate HO basis. This is the most practical case. The spurious center of mass components present in the SD bases are removed exactly. The calculated cluster overlap integrals are translationally invariant. As an illustration, we present results of cluster form factor calculations for 5 He vertical bar 4 He+n>, 5 He vertical bar 3 H+d>, 6 Li vertical bar 4 He+d>, 6 Be vertical bar 3 He+ 3 He>, 7 Li vertical bar 4 He+ 3 H>, 7 Li vertical bar 6 Li+n>, 8 Be vertical bar 6 Li+d>, 8 Be vertical bar 7 Li+p>, 9 Li vertical bar 8 Li+n>, and 13 C vertical bar 12 C+n>, with all the nuclei described by multi-(ℎ/2π)Ω NCSM wave functions

Coercivity enhancement in Ce-Fe-B based magnets by core-shell grain structuring

Directory of Open Access Journals (Sweden)

M. Ito

2016-05-01

Full Text Available Ce-based R2Fe14B (R= rare-earth nano-structured permanent magnets consisting of (Ce,Nd2Fe14B core-shell grains separated by a non-magnetic grain boundary phase, in which the relative amount of Nd to Ce is higher in the shell of the magnetic grain than in its core, were fabricated by Nd-Cu infiltration into (Ce,Nd2Fe14B hot-deformed magnets. The coercivity values of infiltrated core-shell structured magnets are superior to those of as-hot-deformed magnets with the same overall Nd content. This is attributed to the higher value of magnetocrystalline anisotropy of the shell phase in the core-shell structured infiltrated magnets compared to the homogeneous R2Fe14B grains of the as-hot-deformed magnets, and to magnetic isolation of R2Fe14B grains by the infiltrated grain boundary phase. First order reversal curve (FORC diagrams suggest that the higher anisotropy shell suppresses initial magnetization reversal at the edges and corners of the R2Fe14B grains.

Strain in GaAs / InAs core-shell nanowire heterostructures grown on GaAs

Energy Technology Data Exchange (ETDEWEB)

Biermanns, Andreas; Davydok, Anton; Pietsch, Ullrich [Universitaet Siegen, Festkoerperphysik (Germany); Rieger, Torsten; Lepsa, Mihail Ion [Peter Gruenberg Institut 9, Forschungszentrum Juelich (Germany); JARA - Fundamentals of Future Information Technology (Germany)

2012-07-01

The growth of semiconductor nanowires (NWs) has attracted significant interest in recent years due to the possible fabrication of novel semiconductor devices for future electronic and opto-electronic applications. Compared to planar heterostructures, the nanowire approach offers an advantage regarding the possibility to form heterostructures between highly lattice mismatched systems, because the free surface of the nanowires allows to relieve the strain more efficiently. One particular way to form heterostructures in the NW geometry, is the fabrication of core-shell devices, in which a NW core is surrounded by a shell of different material. The understanding of the mutual strain between core and shell, as well as the relaxation behavior of the system are crucial for the fabrication of functional devices. In this contribution we report on first X-ray diffraction measurements of GaAs-core/InAs-shell nanowires grown on GaAs(111) by molecular beam epitaxy. Using symmetric- and grazing-incidence X-ray diffraction, the relaxation state of the InAs shell as well as the strain in the GaAs core are measured as function of the InAs shell thickness, showing a gradual relaxation behavior of the shell.

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.

Nuclear spins, magnetic moments and quadrupole moments of Cu isotopes from N = 28 to N = 46: probes for core polarization effects

CERN Document Server

Vingerhoets, P; Avgoulea, M; Billowes, J; Bissell, M L; Blaum, K; Brown, B A; Cheal, B; De Rydt, M; Forest, D H; Geppert, Ch; Honma, M; Kowalska, M; Kramer, J; Krieger, A; Mane, E; Neugart, R; Neyens, G; Nortershauser, W; Otsuka, T; Schug, M; Stroke, H H; Tungate, G; Yordanov, D T

2010-01-01

Measurements of the ground-state nuclear spins, magnetic and quadrupole moments of the copper isotopes from 61Cu up to 75Cu are reported. The experiments were performed at the ISOLDE facility, using the technique of collinear laser spectroscopy. The trend in the magnetic moments between the N=28 and N=50 shell closures is reasonably reproduced by large-scale shell-model calculations starting from a 56Ni core. The quadrupole moments reveal a strong polarization of the underlying Ni core when the neutron shell is opened, which is however strongly reduced at N=40 due to the parity change between the $pf$ and $g$ orbits. No enhanced core polarization is seen beyond N=40. Deviations between measured and calculated moments are attributed to the softness of the 56Ni core and weakening of the Z=28 and N=28 shell gaps.

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.

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

International Nuclear Information System (INIS)

Zhao, Zheng-Bai; Tai, Li; Zhang, Da-Ming; Jiang, Yong

2017-01-01

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.

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.

Luminescence study of Eu3+ doped GdVO4 nanoparticles: Concentration, particle size, and core/shell effects

Science.gov (United States)

Singh, N. Shanta; Ningthoujam, R. S.; Devi, L. Romila; Yaiphaba, N.; Sudarsan, V.; Singh, S. Dorendrajit; Vatsa, R. K.; Tewari, R.

2008-11-01

Nanoparticles of GdVO4 doped with Eu3+ and core/shell of GdVO4:Eu3+/GdVO4 are prepared by urea hydrolysis method using ethylene glycol as capping agent as well as reaction medium at 130 °C. Unit cell volume increases when GdVO4 is doped with Eu3+ indicating the substitution of Gd3+ lattice sites by Eu3+. From luminescence study, it is confirmed that there is no particle size effect on emission positions of Eu3+. Optimum luminescence intensity is found to be in 5-10 at. % Eu3+. Above these concentrations, luminescence intensity decreases due to concentration quenching effect. There is an enhancement in luminescence intensity of core/shell nanoparticles. This has been attributed to the reduction in surface inhomogenities of Eu3+ surroundings by bonding to GdVO4 shell. The lifetime for D50 level increases with annealing and core/shell formation.

The Synthesis and Characterization of Gold-Core/LDH-Shell Nanoparticles

Science.gov (United States)

Rearick, Colton

In recent years, the field of nanomedicine has progressed at an astonishing rate, particularly with respect to applications in cancer treatment and molecular imaging. Although organic systems have been the frontrunners, inorganic systems have also begun to show promise, especially those based upon silica and magnetic nanoparticles (NPs). Many of these systems are being designed for simultaneous therapeutic and diagnostic capabilities, thus coining the term, theranostics. A unique class of inorganic systems that shows great promise as theranostics is that of layered double hydroxides (LDH). By synthesis of a core/shell structures, e.g. a gold nanoparticle (NP) core and LDH shell, the multifunctional theranostic may be developed without a drastic increase in the structural complexity. To demonstrate initial proof-of-concept of a potential (inorganic) theranostic platform, a Au-core/LDH-shell nanovector has been synthesized and characterized. The LDH shell was heterogeneously nucleated and grown on the surface of silica coated gold NPs via a coprecipitation method. Polyethylene glycol (PEG) was introduced in the initial synthesis steps to improve crystallinity and colloidal stability. Additionally, during synthesis, fluorescein isothiocyanate (FITC) was intercalated into the interlayer spacing of the LDH. In contrast to the PEG stabilization, a post synthesis citric acid treatment was used as a method to control the size and short-term stability. The heterogeneous core-shell system was characterized with scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), dynamic light scattering (DLS), and powder x-ray diffraction (PXRD). A preliminary in vitro study carried out with the assistance of Dr. Kaushal Rege's group at Arizona State University was to demonstrate the endocytosis capability of homogeneously-grown LDH NPs. The DLS measurements of the core-shell NPs indicated an average particle size of 212nm. The PXRD analysis showed that PEG

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

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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.

A Core-Shell Fe/Fe2 O3 Nanowire as a High-Performance Anode Material for Lithium-Ion Batteries.

Science.gov (United States)

Na, Zhaolin; Huang, Gang; Liang, Fei; Yin, Dongming; Wang, Limin

2016-08-16

The preparation of novel one-dimensional core-shell Fe/Fe2 O3 nanowires as anodes for high-performance lithium-ion batteries (LIBs) is reported. The nanowires are prepared in a facile synthetic process in aqueous solution under ambient conditions with subsequent annealing treatment that could tune the capacity for lithium storage. When this hybrid is used as an anode material for LIBs, the outer Fe2 O3 shell can act as an electrochemically active material to store and release lithium ions, whereas the highly conductive and inactive Fe core functions as nothing more than an efficient electrical conducting pathway and a remarkable buffer to tolerate volume changes of the electrode materials during the insertion and extraction of lithium ions. The core-shell Fe/Fe2 O3 nanowire maintains an excellent reversible capacity of over 767 mA h g(-1) at 500 mA g(-1) after 200 cycles with a high average Coulombic efficiency of 98.6 %. Even at 2000 mA g(-1) , a stable capacity as high as 538 mA h g(-1) could be obtained. The unique composition and nanostructure of this electrode material contribute to this enhanced electrochemical performance. Due to the ease of large-scale fabrication and superior electrochemical performance, these hybrid nanowires are promising anode materials for the next generation of high-performance LIBs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dynamo Scaling Laws for Uranus and Neptune: The Role of Convective Shell Thickness on Dipolarity

Science.gov (United States)

Stanley, Sabine; Yunsheng Tian, Bob

2017-10-01

Previous dynamo scaling law studies (Christensen and Aubert, 2006) have demonstrated that the morphology of a planet’s magnetic field is determined by the local Rossby number (Ro_l): a non-dimensional diagnostic variable that quantifies the ratio of inertial forces to Coriolis forces on the average length scale of the flow. Dynamos with Ro_l ~ 0.1 produce multipolar magnetic fields. Scaling studies have also determined the dependence of the local Rossby number on non-dimensional parameters governing the system - specifically the Ekman, Prandtl, magnetic Prandtl and flux-based Rayleigh numbers (Olson and Christensen, 2006). When these scaling laws are applied to the planets, it appears that Uranus and Neptune should have dipole-dominated fields, contrary to observations. However, those scaling laws were derived using the specific convective shell thickness of the Earth’s core. Here we investigate the role of convective shell thickness on dynamo scaling laws. We find that the local Rossby number depends exponentially on the convective shell thickness. Including this new dependence on convective shell thickness, we find that the dynamo scaling laws now predict that Uranus and Neptune reside deeply in the multipolar regime, thereby resolving the previous contradiction with observations.

(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

Eco-friendly microwave-assisted green and rapid synthesis of well-stabilized gold and core-shell silver-gold nanoparticles.

Science.gov (United States)

El-Naggar, Mehrez E; Shaheen, Tharwat I; Fouda, Moustafa M G; Hebeish, Ali A

2016-01-20

Herein, we present a new approach for the synthesis of gold nanoparticles (AuNPs) individually and as bimetallic core-shell nanoparticles (AgNPs-AuNPs). The novelty of the approach is further maximized by using curdlan (CRD) biopolymer to perform the dual role of reducing and capping agents and microwave-aided technology for affecting the said nanoparticles with varying concentrations in addition to those affected by precursor concentrations. Thus, for preparation of AuNPs, curdlan was solubilized in alkali solution followed by an addition of tetrachloroauric acid (HAuCl4). The curdlan solution containing HAuCl4 was then subjected to microwave radiation for up to 10 min. The optimum conditions obtained with the synthesis of AuNPs were employed for preparation of core-shell silver-gold nanoparticles by replacing definite portion of HAuCl4 with an equivalent portion of silver nitrate (AgNO3). The portion of AgNO3 was added initially and allowed to be reduced by virtue of the dual role of curdlan under microwave radiation. The corresponding portion of HAuCl4 was then added and allowed to complete the reaction. Characterization of AuNPs and AgNPs-AuNPs core-shell were made using UV-vis spectra, TEM, FTIR, XRD, zeta potential, and AFM analysis. Accordingly, strong peaks of the colloidal particles show surface plasmon resonance (SPR) at maximum wavelength of 540 nm, proving the formation of well-stabilized gold nanoparticles. TEM investigations reveal that the major size of AuNPs formed at different Au(+3)concentration lie below 20 nm with narrow size distribution. Whilst, the SPR bands of AgNPs-AuNPs core-shell differ than those obtained from original AgNPs (420 nm) and AuNPs (540 nm). Such shifting due to SPR of Au nanoshell deposited onto AgNPs core was significantly affected by the variation of bimetallic ratios applied. TEM micrographs show variation in contrast between dark silver core and the lighter gold shell. Increasing the ratio of silver ions leads to

Magnetic Behavior of Ni-Fe Core-Shell and Alloy Nanowires

Science.gov (United States)

Tripathy, Jagnyaseni; Vargas, Jose; Spinu, Leonard; Wiley, John

2013-03-01

Template assisted synthesis was used to fabricate a series of Ni-Fe core-shell and alloy nanowires. By controlling reaction conditions as well as pore structure, both systems could be targeted and magnetic properties followed as a function of architectures. In the core-shell structure coercivity increases with decrease in shell thickness while for the alloys, coercivity squareness improve with increase pore diameter. Details on the systematic studies of these materials will be presented in terms of hysteretic measurements, including first order reversal curves (FORC), and FMR data. Magnetic variation as a function of structure and nanowire aspect ratios will be presented and the origins of these behaviors discussed. Advanced Material Research Institute

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...

Strain distribution of confined Ge/GeO2 core/shell nanoparticles engineered by growth environments

Science.gov (United States)

Wei, Wenyan; Yuan, Cailei; Luo, Xingfang; Yu, Ting; Wang, Gongping

2016-02-01

The strain distributions of Ge/GeO2 core/shell nanoparticles confined in different host matrix grown by surface oxidation are investigated. The simulated results by finite element method demonstrated that the strains of the Ge core and the GeO2 shell strongly depend on the growth environments of the nanoparticles. Moreover, it can be found that there is a transformation of the strain on Ge core from tensile to compressive strain during the growth of Ge/GeO2 core/shell nanoparticles. And, the transformation of the strain is closely related with the Young's modulus of surrounding materials of Ge/GeO2 core/shell nanoparticles.

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.

Control of the Speed of a Light-Induced Spin Transition through Mesoscale Core-Shell Architecture.

Science.gov (United States)

Felts, Ashley C; Slimani, Ahmed; Cain, John M; Andrus, Matthew J; Ahir, Akhil R; Abboud, Khalil A; Meisel, Mark W; Boukheddaden, Kamel; Talham, Daniel R

2018-05-02

The rate of the light-induced spin transition in a coordination polymer network solid dramatically increases when included as the core in mesoscale core-shell particles. A series of photomagnetic coordination polymer core-shell heterostructures, based on the light-switchable Rb a Co b [Fe(CN) 6 ] c · mH 2 O (RbCoFe-PBA) as core with the isostructural K j Ni k [Cr(CN) 6 ] l · nH 2 O (KNiCr-PBA) as shell, are studied using temperature-dependent powder X-ray diffraction and SQUID magnetometry. The core RbCoFe-PBA exhibits a charge transfer-induced spin transition (CTIST), which can be thermally and optically induced. When coupled to the shell, the rate of the optically induced transition from low spin to high spin increases. Isothermal relaxation from the optically induced high spin state of the core back to the low spin state and activation energies associated with the transition between these states were measured. The presence of a shell decreases the activation energy, which is associated with the elastic properties of the core. Numerical simulations using an electro-elastic model for the spin transition in core-shell particles supports the findings, demonstrating how coupling of the core to the shell changes the elastic properties of the system. The ability to tune the rate of optically induced magnetic and structural phase transitions through control of mesoscale architecture presents a new approach to the development of photoswitchable materials with tailored properties.

Successive and large-scale synthesis of InP/ZnS quantum dots in a hybrid reactor and their application to white LEDs

International Nuclear Information System (INIS)

Kim, Kyungnam; Jeong, Sohee; Woo, Ju Yeon; Han, Chang-Soo

2012-01-01

We report successive and large-scale synthesis of InP/ZnS core/shell nanocrystal quantum dots (QDs) using a customized hybrid flow reactor, which is based on serial combination of a batch-type mixer and a flow-type furnace. InP cores and InP/ZnS core/shell QDs were successively synthesized in the hybrid reactor in a simple one-step process. In this reactor, the flow rate of the solutions was typically 1 ml min −1 , 100 times larger than that of conventional microfluidic reactors. In order to synthesize high-quality InP/ZnS QDs, we controlled both the flow rate and the crystal growth temperature. Finally, we obtained high-quality InP/ZnS QDs in colors from bluish green to red, and we demonstrated that these core/shell QDs could be incorporated into white-light-emitting diode (LED) devices to improve color rendering performance. (paper)

Hierarchical α-MnO2 nanowires@Ni1-x Mnx Oy nanoflakes core-shell nanostructures for supercapacitors.

Science.gov (United States)

Wang, Hsin-Yi; Xiao, Fang-Xing; Yu, Le; Liu, Bin; Lou, Xiong Wen David

2014-08-13

A facile two-step solution-phase method has been developed for the preparation of hierarchical α-MnO2 nanowires@Ni1-x Mnx Oy nanoflakes core-shell nanostructures. Ultralong α-MnO2 nanowires were synthesized by a hydrothermal method in the first step. Subsequently, Ni1-x Mnx Oy nanoflakes were grown on α-MnO2 nanowires to form core-shell nanostructures using chemical bath deposition followed by thermal annealing. Both solution-phase methods can be easily scaled up for mass production. We have evaluated their application in supercapacitors. The ultralong one-dimensional (1D) α-MnO2 nanowires in hierarchical core-shell nanostructures offer a stable and efficient backbone for charge transport; while the two-dimensional (2D) Ni1-x Mnx Oy nanoflakes on α-MnO2 nanowires provide high accessible surface to ions in the electrolyte. These beneficial features enable the electrode with high capacitance and reliable stability. The capacitance of the core-shell α-MnO2 @Ni1-x Mnx Oy nanostructures (x = 0.75) is as high as 657 F g(-1) at a current density of 250 mA g(-1) , and stable charging-discharging cycling over 1000 times at a current density of 2000 mA g(-1) has been realized. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Improved microbial growth inhibition activity of bio-surfactant induced Ag–TiO{sub 2} core shell nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Nithyadevi, D. [Department of Nanoscience and Technology, Bharathiar University, Coimbatore 641 046 (India); Kumar, P. Suresh [Thin Film and Nanomaterials Laboratory, Department of Physics, Bharathiar University, Coimbatore 641 046 (India); Mangalaraj, D., E-mail: dmraj800@yahoo.com [Department of Nanoscience and Technology, Bharathiar University, Coimbatore 641 046 (India); Ponpandian, N.; Viswanathan, C. [Department of Nanoscience and Technology, Bharathiar University, Coimbatore 641 046 (India); Meena, P. [Department of Physics, PSGR Krishnammal college for women, Coimbatore 641 004 (India)

2015-02-01

Graphical abstract: - Highlights: • TiO{sub 2} nanoparticles were synthesized by hydrolysis process and Ag nanoparticles were prepared by using hydrazine reduction method. • Ag–TiO{sub 2} core shell nanoparticles were synthesized by reverse micelle method. • Coatings of TiO{sub 2} shell leads to decrease the usage of silver particles and also it reduces the release of silver ions from the matrix. • Optimum ratio of TiO{sub 2} particles: Ag atoms are needed for better antibacterial activity. • Sodium alginate (Bio-copolymer) induced core shell nanoparticles results 100% cell growth inhibition toward Staphylococcus aureus. - Abstract: Surfactant induced silver–titanium dioxide core shell nanoparticles within the size range of 10–50 nm were applied in the antibacterial agent to inhibit the growth of bacterial cells. The single crystalline silver was located in the core part of the composite powder and the titanium dioxide components were uniformly distributed in the shell part. HRTEM and XRD results indicated that silver was completely covered by titanium dioxide and its crystal structure was not affected after being coated by titanium dioxide. The effect of silver–titanium dioxide nanoparticles in the inhibition of bacterial cell growth was studied by means of disk diffusion method. The inhibition zone results reveal that sodium alginate induced silver–titanium dioxide nanoparticles exhibit 100% more antibacterial activity than that with cetyltrimethylbromide or without surfactant. UV–vis spectroscopic analysis showed a large concentration of silver was rapidly released into phosphate buffer solution (PBS) within a period of 1 day, with a much smaller concentration being released after this 1-day period. It was concluded that sodium alginate induced silver–titanium dioxide core shell nanoparticles could enhance long term cell growth inhibition in comparison with cetyltrimethylbromide or without surfactant. The surfactant mediated core shell

Rapid Synthesis and Formation Mechanism of Core-Shell-Structured La-Doped SrTiO3 with a Nb-Doped Shell

Directory of Open Access Journals (Sweden)

Nam-Hee Park

2015-07-01

Full Text Available To provide a convenient and practical synthesis process for metal ion doping on the surface of nanoparticles in an assembled nanostructure, core-shell-structured La-doped SrTiO3 nanocubes with a Nb-doped surface layer were synthesized via a rapid synthesis combining a rapid sol-precipitation and hydrothermal process. The La-doped SrTiO3 nanocubes were formed at room temperature by a rapid dissolution of NaOH pellets during the rapid sol-precipitation process, and the Nb-doped surface (shell along with Nb-rich edges formed on the core nanocubes via the hydrothermal process. The formation mechanism of the core-shell-structured nanocubes and their shape evolution as a function of the Nb doping level were investigated. The synthesized core-shell-structured nanocubes could be arranged face-to-face on a SiO2/Si substrate by a slow evaporation process, and this nanostructured 10 μm thick thin film showed a smooth surface.

CuO-In2O3 Core-Shell Nanowire Based Chemical Gas Sensors

Directory of Open Access Journals (Sweden)

Xiaoxin Li

2014-01-01

Full Text Available The CuO-In2O3 core-shell nanowire was fabricated by a two-step method. The CuO nanowire core (NWs was firstly grown by the conventional thermal oxidation of Cu meshes at 500°C for 5 hours. Then, the CuO nanowires were immersed into the suspension of amorphous indium hydroxide deposited from the In(AC3 solution by ammonia. The CuO nanowires coated with In(OH3 were subsequently heated at 600°C to form the crystalline CuO-In2O3 core-shell structure, with In2O3 nanocrystals uniformly anchored on the CuO nanowires. The gas sensing properties of the formed CuO-In2O3 core-shell nanowires were investigated by various reducing gases such as hydrogen, carbon monoxide, and propane at elevated temperature. The sensors using the CuO-In2O3 nanowires show improved sensing performance to hydrogen and propane but a suppressed response to carbon monoxide, which could be attributed to the enhanced catalytic properties of CuO with the coated porous In2O3 shell and the p-n junction formed at the core-shell interface.

Surface characterization of hydrophobic core-shell QDs using NMR techniques

Science.gov (United States)

Zhang, Chengqi; Zeng, Birong; Palui, Goutam; Mattoussi, Hedi

2018-02-01

Using a few solution phase NMR spectroscopy techniques, including 1H NMR and 31P NMR, we have characterized the organic shell on CdSe-ZnS core-shell quantum dots and tracked changes in its composition when the QD dispersions are subjected to varying degrees of purification. Combining solution phase NMR with diffusion ordered spectroscopy (DOSY), we were able to distinguish between freely diffusing ligands in the sample from those bound on the surfaces. Additionally, matrix assisted laser desorption ionization (MALDI) and FTIR measurements were used to provide complementary and supporting information on the organic ligand coating for these nanocrystals. We found that the organic shell is dominated by monomeric or oligomeric n-hexylphosphonic acid (HPA), along with small portion of 1-hexadecyl amine (HDA). The presence of TOP/TOPO (tri-n-octylphosphine / tri-noctylphosphine oxide) molecules is much smaller, even though large excess of TOP/TOPO were used during the QD growth. These results indicate that HPA (alkyl phosphonate) exhibits the strongest coordination affinity to ZnS-rich QD surfaces grown using the high temperature injection route.

Elastic stability of cylindrical shells with soft elastic cores: Biomimicking natural tubular structures

Science.gov (United States)

Karam, Gebran Nizar

1994-01-01

Thin walled cylindrical shell structures are widespread in nature: examples include plant stems, porcupine quills, and hedgehog spines. All have an outer shell of almost fully dense material supported by a low density, cellular core. In nature, all are loaded in combination of axial compression and bending: failure is typically by buckling. Natural structures are often optimized. Here we have analyzed the elastic buckling of a thin cylindrical shell supported by an elastic core to show that this structural configuration achieves significant weight saving over a hollow cylinder. The results of the analysis are compared with data from an extensive experimental program on uniaxial compression and four point bending tests on silicone rubber shells with and without compliant foam cores. The analysis describes the results of the mechanical tests well. Characterization of the microstructures of several natural tubular structures with foamlike cores (plant stems, quills, and spines) revealed them to be close to the optimal configurations predicted by the analytical model. Biomimicking of natural cylindrical shell structures and evolutionary design processes may offer the potential to increase the mechanical efficiency of engineering cylindrical shells.

Aqueous-phase synthesis and color-tuning of core/shell/shell inorganic nanocrystals consisting of ZnSe, (Cu, Mn)-doped ZnS, and ZnS

Energy Technology Data Exchange (ETDEWEB)

Choi, Jongwan; Yoon, Sujin [Department of Chemistry and Research Institute for Natural Science, Hanyang University, Seoul, 133-791 (Korea, Republic of); Kim, Felix Sunjoo, E-mail: fskim@cau.ac.kr [School of Chemical Engineering and Materials Science, Chung-Ang University, Seoul, 156-756 (Korea, Republic of); Kim, Nakjoong, E-mail: kimnj@hanyang.ac.kr [Department of Chemistry and Research Institute for Natural Science, Hanyang University, Seoul, 133-791 (Korea, Republic of)

2016-06-25

We report synthesis of colloidal nanocrystals based on ZnSe core, (Cu,Mn)-doped ZnS inner-shell, and ZnS outer-shell by using an eco-friendly method and their optical properties. Synthesis of core/shell/shell nanocrystals was performed by using a one-pot/three-step colloidal method with 3-mercaptopropionic acid as a stabilizer in aqueous phase at low temperature. A double-shell structure was employed with inner-shell as a host for doping and outer-shell as a passivation layer for covering surface defects. Copper and manganese were introduced as single- or co-dopants during inner-shell formation, providing an effective means to control the emission color of the nanocrystals. The synthesized nanocrystals showed fluorescent emission ranging from blue to green, to white, and to orange, adjusted by doping components, amounts, and ratios. The photoluminescence quantum yields of the core/doped-shell/shell nanocrystals approached 36%. - Highlights: • ZnSe/ZnS:(Cu,Ms)/ZnS core/(doped)shell/shell nanocrystals were synthesized in an aqueous phase. • Emission color of nanocrystals was controlled from blue to white to orange by adjusting the atomic ratio of Cu and Mn co-dopants. • Photoluminescence quantum yields of the colloidal nanocrystals approached 36%.

A general and high-yield galvanic displacement approach to Au-M (M = Au, Pd, and Pt) core-shell nanostructures with porous shells and enhanced electrocatalytic performances.

Science.gov (United States)

Kuai, Long; Geng, Baoyou; Wang, Shaozhen; Sang, Yan

2012-07-23

In this work, we utilize the galvanic displacement synthesis and make it a general and efficient method for the preparation of Au-M (M = Au, Pd, and Pt) core-shell nanostructures with porous shells, which consist of multilayer nanoparticles. The method is generally applicable to the preparation of Au-Au, Au-Pd, and Au-Pt core-shell nanostructures with typical porous shells. Moreover, the Au-Au isomeric core-shell nanostructure is reported for the first time. The lower oxidation states of Au(I), Pd(II), and Pt(II) are supposed to contribute to the formation of porous core-shell nanostructures instead of yolk-shell nanostructures. The electrocatalytic ethanol oxidation and oxygen reduction reaction (ORR) performance of porous Au-Pd core-shell nanostructures are assessed as a typical example for the investigation of the advantages of the obtained core-shell nanostructures. As expected, the Au-Pd core-shell nanostructure indeed exhibits a significantly reduced overpotential (the peak potential is shifted in the positive direction by 44 mV and 32 mV), a much improved CO tolerance (I(f)/I(b) is 3.6 and 1.63 times higher), and an enhanced catalytic stability in comparison with Pd nanoparticles and Pt/C catalysts. Thus, porous Au-M (M = Au, Pd, and Pt) core-shell nanostructures may provide many opportunities in the fields of organic catalysis, direct alcohol fuel cells, surface-enhanced Raman scattering, and so forth. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Core-shell particles as model compound for studying fouling

DEFF Research Database (Denmark)

Christensen, Morten Lykkegaard; Nielsen, Troels Bach; Andersen, Morten Boel Overgaard

2008-01-01

Synthetic colloidal particles with hard cores and soft, water-swollen shells were used to study cake formation during ultrafiltration. The total cake resistance was lowest for particles with thick shells, which indicates that interparticular forces between particles (steric hindrance...... and electrostatic repulsion) influenced cake formation. At low pressure the specific cake resistance could be predicted from the Kozeny-Carman equation. At higher pressures, the resistance increased due to cake compression. Both cake formation and compression were reversible. For particles with thick shells...

Fabrication and characterization of optical sensors using metallic core-shell thin film nanoislands for ozone detection

Science.gov (United States)

Addanki, Satish; Nedumaran, D.

2017-07-01

Core-Shell nanostructures play a vital role in the sensor field owing to their performance improvements in sensing characteristics and well-established synthesis procedures. These nanostructures can be ingeniously tuned to achieve tailored properties for a particular application of interest. In this work, an Ag-Au core-shell thin film nanoislands with APTMS (3-Aminopropyl trimethoxysilane) and PVA (Polyvinyl alcohol) binding agents was modeled, synthesized and characterized. The simulation results were used to fabricate the sensor through chemical route. The results of this study confirmed that the APTMS based Ag-Au core-shell thin film nanoislands offered a better performance over the PVA based Ag-Au core-shell thin film nanoislands. Also, the APTMS based Ag-Au core-shell thin film nanoislands exhibited better sensitivity towards ozone sensing over the other types, viz., APTMS/PVA based Au-Ag core-shell and standalone Au/Ag thin film nanoislands.

THE LAST MINUTES OF OXYGEN SHELL BURNING IN A MASSIVE STAR

Energy Technology Data Exchange (ETDEWEB)

Müller, Bernhard [Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, Belfast, BT7 1NN (United Kingdom); Viallet, Maxime; Janka, Hans-Thomas [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching (Germany); Heger, Alexander, E-mail: b.mueller@qub.ac.uk [Monash Centre for Astrophysics, School of Physics and Astronomy, Monash University, Victoria 3800 (Australia)

2016-12-10

We present the first  4 π– three-dimensional (3D) simulation of the last minutes of oxygen shell burning in an 18 M {sub ⊙} supernova progenitor up to the onset of core collapse. A moving inner boundary is used to accurately model the contraction of the silicon and iron core according to a one-dimensional stellar evolution model with a self-consistent treatment of core deleptonization and nuclear quasi-equilibrium. The simulation covers the full solid angle to allow the emergence of large-scale convective modes. Due to core contraction and the concomitant acceleration of nuclear burning, the convective Mach number increases to ∼0.1 at collapse, and an ℓ  = 2 mode emerges shortly before the end of the simulation. Aside from a growth of the oxygen shell from 0.51 M {sub ⊙} to 0.56 M {sub ⊙} due to entrainment from the carbon shell, the convective flow is reasonably well described by mixing-length theory, and the dominant scales are compatible with estimates from linear stability analysis. We deduce that artificial changes in the physics, such as accelerated core contraction, can have precarious consequences for the state of convection at collapse. We argue that scaling laws for the convective velocities and eddy sizes furnish good estimates for the state of shell convection at collapse and develop a simple analytic theory for the impact of convective seed perturbations on shock revival in the ensuing supernova. We predict a reduction of the critical luminosity for explosion by 12% – 24% due to seed asphericities for our 3D progenitor model relative to the case without large seed perturbations.

Broadband absorption and enhanced photothermal conversion property of octopod-like Ag@Ag2S core@shell structures with gradually varying shell thickness.

Science.gov (United States)

Jiang, Qian; Zeng, Wenxia; Zhang, Canying; Meng, Zhaoguo; Wu, Jiawei; Zhu, Qunzhi; Wu, Daxiong; Zhu, Haitao

2017-12-19

Photothermal conversion materials have promising applications in many fields and therefore they have attracted tremendous attention. However, the multi-functionalization of a single nanostructure to meet the requirements of multiple photothermal applications is still a challenge. The difficulty is that most nanostructures have specific absoprtion band and are not flexible to different demands. In the current work, we reported the synthesis and multi-band photothermal conversion of Ag@Ag 2 S core@shell structures with gradually varying shell thickness. We synthesized the core@shell structures through the sulfidation of Ag nanocubes by taking the advantage of their spatially different reactivity. The resulting core@shell structures show an octopod-like mopgorlogy with a Ag 2 S bulge sitting at each corner of the Ag nanocubes. The thickness of the Ag 2 S shell gradually increases from the central surface towards the corners of the structure. The synthesized core@shell structures show a broad band absorption spectrum from 300 to 1100 nm. Enhanced photothermal conversion effect is observed under the illuminations of 635, 808, and 1064 nm lasers. The results indicate that the octopod-like Ag@Ag 2 S core@shell structures have characteristics of multi-band photothermal conversion. The current work might provide a guidance for the design and synthesis of multifunctional photothermal conversion materials.

Chemical insights into the roles of nanowire cores on the growth and supercapacitor performances of Ni-Co-O/Ni(OH)₂ core/shell electrodes.

Science.gov (United States)

Yin, Xuesong; Tang, Chunhua; Zhang, Liuyang; Yu, Zhi Gen; Gong, Hao

2016-02-09

Nanostructured core/shell electrodes have been experimentally demonstrated promising for high-performance electrochemical energy storage devices. However, chemical insights into the significant roles of nanowire cores on the growth of shells and their supercapacitor behaviors still remain as a research shortfall. In this work, by substituting 1/3 cobalt in the Co3O4 nanowire core with nickel, a 61% enhancement of the specific mass-loading of the Ni(OH)2 shell, a tremendous 93% increase of the volumetric capacitance and a superior cyclability were achieved in a novel NiCo2O4/Ni(OH)2 core/shell electrode in contrast to a Co3O4/Ni(OH)2 one. A comparative study suggested that not only the growth of Ni(OH)2 shells but also the contribution of cores were attributed to the overall performances. Importantly, their chemical origins were revealed through a theoretical simulation of the core/shell interfacial energy changes. Besides, asymmetric supercapacitor devices and applications were also explored. The scientific clues and practical potentials obtained in this work are helpful for the design and analysis of alternative core/shell electrode materials.

Synthesis of hydrophobic zeolite X-SiO{sub 2} core-shell composites

Energy Technology Data Exchange (ETDEWEB)

Liu Liying [School of Material and Metallurgy, Northeastern University, Shenyang, Liaoning 110004 (China); Cooperative Research Centre for Greenhouse Gas Technologies (CO-2CRC) (Australia); Singh, Ranjeet; Li Gang; Xiao Gongkui [Cooperative Research Centre for Greenhouse Gas Technologies (CO-2CRC) (Australia); Department of Chemical Engineering, Monash University, Clayton, Victoria 3800 (Australia); Webley, Paul A., E-mail: paul.webley@eng.monash.edu.au [Cooperative Research Centre for Greenhouse Gas Technologies (CO-2CRC) (Australia); Department of Chemical and Biomolecular Engineering, University of Melbourne, Victoria 3010 (Australia); Zhai Yuchun [School of Material and Metallurgy, Northeastern University, Shenyang, Liaoning 110004 (China)

2012-04-16

Highlights: Black-Right-Pointing-Pointer Hydrophobic 13X zeolite composites with silicalite and mesoporous silica shells are designed. Black-Right-Pointing-Pointer These core-shell composites are silynated and their hydrophobicity is tested. Black-Right-Pointing-Pointer Addition of silica layer increases the density of surface hydroxyl groups which makes the improvement of the hydrophobicity possible by further silynation. - Abstract: Core-shell structures of zeolite X coated with silicalite as well as mesoporous (MCM-41) have been synthesized. Furthermore, the surfaces of the silicalite and mesoporous silica shells were silylated using organosilanes. The materials were characterized by X-ray diffraction, nitrogen adsorption/desorption, scanning and transmission electron microscopy. The results show that the properties of zeolite 13X-silicalite and zeolite 13X-mesoporous silica core-shells composite structures are well maintained even after the modification. As expected, the shell thickness increased with increase in synthesis time, however, the micropore volume decreased. Silylation with smaller organosilanes (trimethyl chlorosilane) resulted in decrease in surface area as they diffused through the pores; however, bulkier silane reacted with surface hydroxyl groups and maintained the pore structure. Contact angle measurements revealed that hydrophobicity of zeolite 13X was enhanced by the microporous and mesoporous shell coating and was further improved by silylation.

Placement of the dam for the no. 2 kambaratinskaya HPP by large-scale blasting: some observations

International Nuclear Information System (INIS)

Shuifer, M. I.; Argal, É. S.

2011-01-01

Results of complex instrument observations of large-scale blasting during construction of the dam for the No. 2 Kambaratinskaya HPP on the Naryn River in the Republic of Kirgizia are analyzed. The purpose of these observations was: to determine the actual parameters of the seismic process, evaluate the effect of air and acoustic shock waves, and investigate the kinematics of the surface formed by the blast in its core region within the mass of fractured rocks.

Systematic investigation of the synthesis of core-shell poly(styrene-co-acrylic acid) colloids with varying shell thickness and core diameter

DEFF Research Database (Denmark)

Hinge, Mogens; Keiding, Kristian

2006-01-01

the morphology of the material for an specific application is going on. It is known from SFEP of styrene that the final colloidal size can be controlled by adjusting the ionic strength of the synthesis feed [1] and it is suggested that adding acrylic acid to the synthesis will result in a change...... in polymerization locus from the core to the surface [2]. There is at present not performed a systematically investigation in controlling the core size and shell thickness of poly(styrene-co-acrylic acid) core-shell colloids  (poly(ST-co-AA)).   Poly(ST-co-AA) colloids were synthesized by free-radical surfactant......-free emulsion co-polymerization (SFECP) at 70°C, using styrene as monomer and acrylic acid as co-monomer. Different batches of poly(ST-co-AA) colloids were synthesized with varying ionic strength and acrylic acid concentrations in the synthesis feed. The produced poly(ST-co-AA) colloids were analysed...

Dye-sensitized solar cells based on nanoparticle-decorated ZnO/TiO2 core/shell nanorod arrays

International Nuclear Information System (INIS)

Wang Meili; Huang Changgang; Cao Yongge; Deng Zhonghua; Liu Yuan; Huang Zhi; Huang Jiquan; Huang Qiufeng; Guo Wang; Liang Jingkui; Yu Qingjiang

2009-01-01

Nanoparticles (NPs) decorated ZnO/TiO 2 core/shell nanorod arrays were fabricated on transparent conductive glass substrates by sequential plasma deposition and post-annealing processes for dye-sensitized solar cells (DSSCs) applications. The NPs decorated ZnO/TiO 2 nanorods were composed of single-crystalline ZnO nanorods, homogeneously coated thin TiO 2 shells and entirely covered anatase TiO 2 NPs. The photocurrent density of the composite electrode was largely enhanced due to the enlarged surface area, the dark current was suppressed and the open-circuit voltage was increased because of the energy barrier formed at the interface between the ZnO core and the TiO 2 shell. The increased photocurrent and open-circuit voltage led to an improvement of twice the energy conversion efficiency.

Novel fluorescent core-shell nanocontainers for cell membrane transport.

Science.gov (United States)

Yin, Meizhen; Kuhlmann, Christoph R W; Sorokina, Ksenia; Li, Chen; Mihov, George; Pietrowski, Eweline; Koynov, Kaloian; Klapper, Markus; Luhmann, Heiko J; Müllen, Klaus; Weil, Tanja

2008-05-01

The synthesis and characterization of novel core-shell macromolecules consisting of a fluorescent perylene-3,4,9,10-tetracarboxdiimide chromophore in the center surrounded by a hydrophobic polyphenylene shell as a first and a flexible hydrophilic polymer shell as a second layer was presented. Following this strategy, several macromolecules bearing varying polymer chain lengths, different polymer shell densities, and increasing numbers of positive and negative charges were achieved. Because all of these macromolecules reveal a good water solubility, their ability to cross cellular membranes was investigated. In this way, a qualitative relationship between the molecular architecture of these macromolecules and the biological response was established.

Photoresponse and Field Effect Transport Studies in InAsP-InP Core-Shell Nanowires

Science.gov (United States)

Lee, Rochelle; Jo, Min Hyeok; Kim, TaeWan; Kim, Hyo Jin; Kim, Doo Gun; Shin, Jae Cheol

2018-05-01

A ternary InAsyP1-y alloy is suitable for an application to near-infrared (NIR) optical devices as their direct bandgap energy covers the entire NIR band. A nanowire (NW) system allows an epitaxial integration of InAsyP1-y alloy on any type of substrate since the lattice mismatch strain can be relieved through the NW sidewall. Nevertheless, the very large surface to volume ratio feature of the NWs leads to enormous surface states which are susceptible to surface recombination of free carriers. Here, ternary InAs0.75P0.25 NWs are grown with InP passivation layer (i.e., core-shell structure) to minimize the influence of the surface states, thus increasing their optical and electrical properties. A photoresponse study was achieved through the modeled band structure of the grown NWs. The model and experimental results suggest that 5-nm-thick InP shell efficiently passivates the surface states of the InAs0.75P0.25 NWs. The fabricated core-shell photodetectors and field-effect transistors exhibit improved photoresponse and transport properties compared to its counterpart core-only structure.

Photoresponse and Field Effect Transport Studies in InAsP-InP Core-Shell Nanowires

Science.gov (United States)

Lee, Rochelle; Jo, Min Hyeok; Kim, TaeWan; Kim, Hyo Jin; Kim, Doo Gun; Shin, Jae Cheol

2018-03-01

A ternary InAsyP1-y alloy is suitable for an application to near-infrared (NIR) optical devices as their direct bandgap energy covers the entire NIR band. A nanowire (NW) system allows an epitaxial integration of InAsyP1-y alloy on any type of substrate since the lattice mismatch strain can be relieved through the NW sidewall. Nevertheless, the very large surface to volume ratio feature of the NWs leads to enormous surface states which are susceptible to surface recombination of free carriers. Here, ternary InAs0.75P0.25 NWs are grown with InP passivation layer (i.e., core-shell structure) to minimize the influence of the surface states, thus increasing their optical and electrical properties. A photoresponse study was achieved through the modeled band structure of the grown NWs. The model and experimental results suggest that 5-nm-thick InP shell efficiently passivates the surface states of the InAs0.75P0.25 NWs. The fabricated core-shell photodetectors and field-effect transistors exhibit improved photoresponse and transport properties compared to its counterpart core-only structure.

Multi-photon excited luminescence of magnetic FePt core-shell nanoparticles.

Science.gov (United States)

Seemann, K M; Kuhn, B

2014-07-01

We present magnetic FePt nanoparticles with a hydrophilic, inert, and biocompatible silico-tungsten oxide shell. The particles can be functionalized, optically detected, and optically manipulated. To show the functionalization the fluorescent dye NOPS was bound to the FePt core-shell nanoparticles with propyl-triethoxy-silane linkers and fluorescence of the labeled particles were observed in ethanol (EtOH). In aqueous dispersion the NOPS fluorescence is quenched making them invisible using 1-photon excitation. However, we observe bright luminescence of labeled and even unlabeled magnetic core-shell nanoparticles with multi-photon excitation. Luminescence can be detected in the near ultraviolet and the full visible spectral range by near infrared multi-photon excitation. For optical manipulation, we were able to drag clusters of particles, and maybe also single particles, by a focused laser beam that acts as optical tweezers by inducing an electric dipole in the insulated metal nanoparticles. In a first application, we show that the luminescence of the core-shell nanoparticles is bright enough for in vivo multi-photon imaging in the mouse neocortex down to cortical layer 5.

Position-controlled MOVPE growth and electro-optical characterization of core-shell InGaN/GaN microrod LEDs

Science.gov (United States)

Schimpke, Tilman; Lugauer, H.-J.; Avramescu, A.; Varghese, T.; Koller, A.; Hartmann, J.; Ledig, J.; Waag, A.; Strassburg, M.

2016-03-01

Today's InGaN-based white LEDs still suffer from a significant efficiency reduction at elevated current densities, the so-called "Droop". Core-shell microrods, with quantum wells (QWs) covering their entire surface, enable a tremendous increase in active area scaling with the rod's aspect ratio. Enlarging the active area on a given footprint area is a viable and cost effective route to mitigate the droop by effectively reducing the local current density. Microrods were grown in a large volume metal-organic vapor phase epitaxy (MOVPE) reactor on GaN-on-sapphire substrates with a thin, patterned SiO2 mask for position control. Out of the mask openings, pencil-shaped n-doped GaN microrod cores were grown under conditions favoring 3D growth. In a second growth step, these cores are covered with a shell containing a quantum well and a p-n junction to form LED structures. The emission from the QWs on the different facets was studied using resonant temperature-dependent photoluminescence (PL) and cathodoluminescence (CL) measurements. The crystal quality of the structures was investigated by transmission electron microscopy (TEM) showing the absence of extended defects like threading dislocations in the 3D core. In order to fabricate LED chips, dedicated processes were developed to accommodate for the special requirements of the 3D geometry. The electrical and optical properties of ensembles of tens of thousands microrods connected in parallel are discussed.

Photo-physical properties enhancement of bare and core-shell quantum dots

Energy Technology Data Exchange (ETDEWEB)

Mumin, Md Abdul, E-mail: pcharpentier@eng.uwo.ca; Akhter, Kazi Farida, E-mail: pcharpentier@eng.uwo.ca; Charpentier, Paul A., E-mail: pcharpentier@eng.uwo.ca [Chemical and Biochemical Engineering, Western University, London Ontario (Canada)

2014-03-31

Semiconductor nanocrystals (NCs) (also known as quantum dots, QDs) have attracted immense attention for their size-tunable optical properties that makes them impressive candidates for solar cells, light emitting devices, lasers, as well as biomedical imaging. However monodispersity, high and consistent photoluminescence, photostability, and biocompatibility are still major challenges. This work focuses on optimizing the photophysical properties and biocompatibility of QDs by forming core-shell nanostructures and their encapsulation by a carrier. Highly luminescent CdS and CdS-ZnS core-shell QDs with 5 nm sizes were synthesized using a facile approach based on pyrolysis of the single molecule precursors. After capping the CdS QDs with a thin layer of ZnS to reduce toxicity, the photoluminescence and photostability of the core-shell QDs was significantly enhanced. To make both the bare and core/shell structure QDs more resistant against photochemical reactions, a mesoporous silica layer was grown on the QDs through a reverse microemulsion technique based on hydrophobic interaction. This encapsulation enhanced the quantum yield and photostability compared to the bare QDs by providing much stronger resistance to oxidation and Oswald ripening of QDs. Encapsulation also improved biocompatibility of QDs that was evaluated with human umbilical vein endothelial cell lines (HUVEC)

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

International Nuclear Information System (INIS)

Ruffino, F.; Piccitto, G.; Grimaldi, M.G.; Ruffino, F.; Grimaldi, M.G.

2014-01-01

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 nano structures. In particular, we report theoretical results of angle-dependent light scattering intensity and scattering efficiency for Ag/Ag 2 O, Al/Al 2 O 2 , Cu/Cu 2 O, Pd/PdO, and Ti/TiO 2 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).

Dependence of nonlinear optical properties of Ag2S@ZnS core-shells on Zinc precursor and capping agent

Science.gov (United States)

Dehghanipour, M.; Khanzadeh, M.; Karimipour, M.; Molaei, M.

2018-03-01

In this research, four different types of Ag2S@ZnS core-shells were synthesized and their nonlinear optical (NLO) properties were investigated using a Z-scan technique by a 532 nm laser diode. Here, Ag2S and ZnS nanoparticles were also synthesized and their NLO properties were compared with Ag2S@ZnS core-shells. It was observed that the NLO properties of Ag2S@ZnS quantum dots significantly increased by increasing the values of Zn(NO3)2 and thioglycolic acid (TGA). It was also observed that the NLO properties of Ag2S@ZnS core-shells for 0.1 g of Zn(NO3)2 and 7000 μl TGA is higher than sole Ag2S and ZnS nanoparticles. In open aperture Z-scan curve of ZnS sample, a saturable absorption peak was observed and this peak was seen also in type of Ag2S@ZnS nanoparticles which the value of Zn(NO3)2 much more.

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

Optimization and photomodification of extremely broadband optical response of plasmonic core-shell obscurants.

Science.gov (United States)

de Silva, Vashista C; Nyga, Piotr; Drachev, Vladimir P

2016-12-15

Plasmonic resonances of the metallic shells depend on their nanostructure and geometry of the core, which can be optimized for the broadband extinction normalized by mass. The fractal nanostructures can provide a broadband extinction. It allows as well for a laser photoburning of holes in the extinction spectra and consequently windows of transparency in a controlled manner. The studied core-shell microparticles synthesized using colloidal chemistry consist of gold fractal nanostructures grown on precipitated calcium carbonate (PCC) microparticles or silica (SiO 2 ) microspheres. The optimization includes different core sizes and shapes, and shell nanostructures. It shows that the rich surface of the PCC flakes is the best core for the fractal shells providing the highest mass normalized extinction over the extremely broad spectral range. The mass normalized extinction cross section up to 3m 2 /g has been demonstrated in the broad spectral range from the visible to mid-infrared. Essentially, the broadband response is a characteristic feature of each core-shell microparticle in contrast to a combination of several structures resonant at different wavelengths, for example nanorods with different aspect ratios. The photomodification at an IR wavelength makes the window of transparency at the longer wavelength side. Copyright © 2016 Elsevier Inc. All rights reserved.

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.

DESIGN AND CONTROL OF SOAP-FREE HYDROPHILIC-HYDROPHOBIC CORE-SHELL LATEX PARTICLES WITH HIGH CARBOXYL CONTENT IN THE CORE OF THE PARTICLES

Institute of Scientific and Technical Information of China (English)

Wen-jiao Ji; Yi-ming Jiang; Bo-tian Li; Wei Deng; Cheng-you Kan

2012-01-01

Soap-free hydrophilic-hydrophobic core-shell latex particles with high carboxyl content in the core of the particles were synthesized via the seeded emulsion polymerization using methyl methacrylate (MMA),butyl acrylate (BA),methacrylic acid (MAA),styrene (St) and ethylene glycol dimethacrylate (EGDMA) as monomers,and the influences of MMA content used in the core preparation on polymerization,particle size and morphology were investigated by transmission electron microscopy,dynamic light scattering and conductometric titration.The results showed that the seeded emulsion polymerization could be carried out smoothly using "starved monomer feeding process" when MAA content in the core preparation was equal to or less than 24 wt％,and the encapsulating efficiency of the hydrophilic P(MMA-BA-MAA-EGDMA) core with the hydrophobic PSt shell decreased with the increase in MAA content.When an interlayer of P(MMA-MAA-St) with moderate polarity was inserted between the P(MMA-BA-MAA-EGDMA) core and the PSt shell,well designed soap-free hydrophilic-hydrophobic core-shell latex particles with 24 wt％ MAA content in the core preparation were obtained.

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

Science.gov (United States)

Devi, Jutika; Saikia, Rashmi; Datta, Pranayee

2016-10-01

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.

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)

New-generation Monte Carlo shell model for the K computer era

International Nuclear Information System (INIS)

Shimizu, Noritaka; Abe, Takashi; Yoshida, Tooru; Otsuka, Takaharu; Tsunoda, Yusuke; Utsuno, Yutaka; Mizusaki, Takahiro; Honma, Michio

2012-01-01

We present a newly enhanced version of the Monte Carlo shell-model (MCSM) method by incorporating the conjugate gradient method and energy-variance extrapolation. This new method enables us to perform large-scale shell-model calculations that the direct diagonalization method cannot reach. This new-generation framework of the MCSM provides us with a powerful tool to perform very advanced large-scale shell-model calculations on current massively parallel computers such as the K computer. We discuss the validity of this method in ab initio calculations of light nuclei, and propose a new method to describe the intrinsic wave function in terms of the shell-model picture. We also apply this new MCSM to the study of neutron-rich Cr and Ni isotopes using conventional shell-model calculations with an inert 40 Ca core and discuss how the magicity of N = 28, 40, 50 remains or is broken. (author)

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.

Synthesis and detection the oxidization of Co cores of Co@SiO2 core-shell nanoparticles by in situ XRD and EXAFS.

Science.gov (United States)

Zhang, Kunhao; Zhao, Ziyan; Wu, Zhonghua; Zhou, Ying

2015-01-01

In this paper, the Co@SiO2 core-shell nanoparticles were prepared by the sol-gel method. The oxidization of Co core nanoparticles was studied by the synchrotron radiation-based techniques including in situ X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) up to 800°C in air and N2 protection conditions, respectively. It was found that the oxidization of Co cores is undergoing three steps regardless of being in air or in N2 protection condition. In the first step ranging from room temperature to 200°C, the Co cores were dominated by Co(0) state as well as small amount of Co(2+) ions. When temperature was above 300°C, the interface between Co cores and SiO2 shells was gradually oxidized into Co(2+), and the CoO layer was observed. As the temperature increasing to 800°C, the Co cores were oxidized to Co3O4 or Co3O4/CoO. Nevertheless, the oxidization kinetics of Co cores is different for the Co@SiO2 in air and N2 gas conditions. Generally, the O2 in the air could get through the SiO2 shells easily onto the Co core surface and induce the oxidization of the Co cores due to the mesoporous nature of the SiO2 shells. However, in N2 gas condition, the O atoms can only be from the SiO2 shells, so the diffusion effect of O atoms in the interface between Co core and SiO2 shell plays a key role.

Studies on II-VI and III-V semiconductor nanostructures. Introduction of the core/shell/shell structure and development of CdSe nanocrystals in an automatized procedure; Untersuchungen an II-VI und III-V Halbleiternanostrukturen. Einfuehrung der Core/shell/shell-Struktur und Darstellung von CdSe-Nanokristallen in einem automatisierten Verfahren

Energy Technology Data Exchange (ETDEWEB)

Mekis, I.

2005-11-15

The work in this dissertation is focused on the development and characterization of fluorescent II-VI and III-V-Nanomaterials. Highly luminescent and photostable Nanocrystals with narrow size distributions were prepared. It was shown that nearly monodisperse CdSe-Nanocrystals could be prepared from Cd(Ac){sub 2} and TOPSe in a mixture of TOPO/TOP/HDA/TDPA. Nearly monodisperse CdSe/CdS-Core/shell-Nanocrystals have been prepared in a one-pot-synthesis by injection of H{sub 2}S-Gas into a freshly prepared crude solution of CdSe. The passivation of the CdSe-core with an inorganic shell of CdS resulted in the drastic improvement of the photoluminescence-efficiency of the colloidal solution. Reproducible room-temperature quantum yields reached up to a value of 85%. Photostability investigations have proved the enhanced stability of CdSe/CdS-Nanocrystals compared to CdSe-Nanocrystals under illumination with UV-Light. A novel type of luminescent semiconductor nanocrystal structure has been developed, consisting of a CdSe core and two anorganic shells. Highly fluorescent and nearly monodisperse CdSe/CdS/ZnS- and CdSe/ZnSe/ZnS-Core/shell/shell-nanocrystals have been prepared via organometallic- and acetate-precursors. The Core/she ll/shell particles reached reproducible room-temperature quantum yields up to 85%. Photostability investigations among CdSe-core, CdSe/CdS-Core/shell- and CdSe/CdS/ZnS- Core/shell/-shell-nanocrystals under illumination with UV-light have proved the highest photostability of the Core/shell/shell-particles. The photostabilities of CdSe/ZnSe/ZnS-and CdSe/ZnS-nanocrystals were compared under illumination with intense laser-beam in air. Another part of this work focused on the development of an automated synthesis procedure of CdSe-nanocrystals by constructing and implementing a flow-reactor system. The size and structure of prepared nanocrystals depended considerably on the Cd:Se-precursorratio and the flow-rate. The preparation of CdSe using Cd(Ac)2

Photonic crystals of core-shell colloidal particles

NARCIS (Netherlands)

Velikov, K.P.; Moroz, A.; Blaaderen, A. van

2001-01-01

We report on the fabrication and optical transmission studies of thin three-dimensional (3D) photonic crystals of high-dielectric ZnS-core and low-dielectric SiO2-shell colloidal particles. These samples were fabricated using a vertical controlled drying method. The spectral position and width of a

Fabrication of Fe3O4@CuO core-shell from MOF based materials and its antibacterial activity

International Nuclear Information System (INIS)

Rajabi, S.K.; Sohrabnezhad, Sh.; Ghafourian, S.

2016-01-01

Magnetic Fe 3 O 4 @CuO nanocomposite with a core/shell structure was successfully synthesized via direct calcinations of magnetic Fe 3 O 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 3 O 4 core and a CuO shell. The Fe 3 O 4 @CuO core-shell can be separated easily from the medium by a small magnet. The antibacterial activity of Fe 3 O 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 3 O 4 @CuO core-shell release of copper ions. These Cu 2+ ions were responsible for the exhibited antibacterial activity. - Highlights: • The Fe 3 O 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 3 O 4 . • The core-shell can be reused effectively. • Core-shell was separated from the reaction solution by external magnetic field.

Synthesis and characterization of ZnO/TiO 2 composite core/shell ...

Indian Academy of Sciences (India)

Organic solar cells; ZnO/TiO2 core/shell; nanorod arrays; sol–gel. ... 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 ... The optical and electrical properties of the bare TiO2 thin film and core/shell composite ...

Significant efficiency enhancement of hybrid solar cells using core-shell nanowire geometry for energy harvesting.

Science.gov (United States)

Tsai, Shin-Hung; Chang, Hung-Chih; Wang, Hsin-Hua; Chen, Szu-Ying; Lin, Chin-An; Chen, Show-An; Chueh, Yu-Lun; He, Jr-Hau

2011-12-27

A novel strategy employing core-shell nanowire arrays (NWAs) consisting of Si/regioregular poly(3-hexylthiophene) (P3HT) was demonstrated to facilitate efficient light harvesting and exciton dissociation/charge collection for hybrid solar cells (HSCs). We experimentally demonstrate broadband and omnidirectional light-harvesting characteristics of core-shell NWA HSCs due to their subwavelength features, further supported by the simulation based on finite-difference time domain analysis. Meanwhile, core-shell geometry of NWA HSCs guarantees efficient charge separation since the thickness of the P3HT shells is comparable to the exciton diffusion length. Consequently, core-shell HSCs exhibit a 61% improvement of short-circuit current for a conversion efficiency (η) enhancement of 31.1% as compared to the P3HT-infiltrated Si NWA HSCs with layers forming a flat air/polymer cell interface. The improvement of crystal quality of P3HT shells due to the formation of ordering structure at Si interfaces after air mass 1.5 global (AM 1.5G) illumination was confirmed by transmission electron microscopy and Raman spectroscopy. The core-shell geometry with the interfacial improvement by AM 1.5G illumination promotes more efficient exciton dissociation and charge separation, leading to η improvement (∼140.6%) due to the considerable increase in V(oc) from 257 to 346 mV, J(sc) from 11.7 to 18.9 mA/cm(2), and FF from 32.2 to 35.2%, which is not observed in conventional P3HT-infiltrated Si NWA HSCs. The stability of the Si/P3HT core-shell NWA HSCs in air ambient was carefully examined. The core-shell geometry should be applicable to many other material systems of solar cells and thus holds high potential in third-generation solar cells.

Synthesis of composite nanoparticles using co-precipitation of a magnetic iron-oxide shell onto core nanoparticles

International Nuclear Information System (INIS)

Primc, Darinka; Belec, Blaž; Makovec, Darko

2016-01-01

Composite nanoparticles can be synthesized by coating a shell made of one material onto core nanoparticles made of another material. Here we report on a novel method for coating a magnetic iron oxide onto the surface of core nanoparticles in an aqueous suspension. The method is based on the heterogeneous nucleation of an initial product of Fe"3"+/Fe"2"+ co-precipitation on the core nanoparticles. The close control of the supersaturation of the precipitating species required for an exclusively heterogeneous nucleation and the growth of the shell were achieved by immobilizing the reactive Fe"3"+ ions in a nitrate complex with urea ([Fe((CO(NH_2)_2)_6](NO_3)_3) and by using solid Mg(OH)_2 as the precipitating reagent. The slow thermal decomposition of the complex at 60 °C homogeneously releases the reactive Fe"3"+ ions into the suspension of the core nanoparticles. The key stage of the process is the thermal hydrolysis of the released Fe"3"+ ions prior to the addition of Mg(OH)_2. The thermal hydrolysis results in the formation of γ-FeOOH, exclusively at the surfaces of the core nanoparticles. After the addition of the solid hydroxide Mg(OH)_2, the pH increases and at pH ~ 5.7 the Fe"2"+ precipitates and reacts with the γ-FeOOH to form magnetic iron oxide with a spinel structure (spinel ferrite) at the surfaces of the core nanoparticles. The proposed low-temperature method for the synthesis of composite nanoparticles is capable of forming well-defined interfaces between the two components, important for the coupling of the different properties. The procedure is environmentally friendly, inexpensive, and appropriate for scaling up to mass production.Graphical abstract

Fabrication and micro-photoluminescence property of CdSe/CdS core/shell nanowires

Energy Technology Data Exchange (ETDEWEB)

Dai, Guozhang; Gou, Guangyang; Wu, Zeming; Chen, Yu; Li, Hongjian [Central South University, Hunan Key Laboratory for Super-microstructure and Ultrafast Process, School of Physics and Electronics, Changsha, Hunan (China); Wan, Qiang [Hunan University, School of Physics and Electronics, Changsha (China); Zou, Bingsuo [Beijing Institute of Technology, Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems, School of Physics, Beijing (China)

2015-04-01

Hetero-epitaxial CdSe/CdS core/shell nanowires (NWs) were prepared by a source-controllable chemical vapor deposition method. A two-stage growth mechanism was proposed to the growth process of the core/shell NWs. Micro-photoluminescence (μ-PL) property of individual NW was studied by a confocal microscopy system. The pure CdSe NW emits a red light with peak at 712.3 nm, which is inconsistent with the CdSe band-edge emission. The CdSe/CdS core/shell NW emits two apparent peaks, one is an intensive red emission peak centered at 715.2 nm and the other is a weak green emission peak located at 516.2 nm. The room temperature μ-PL spectrum shows that the PL intensity of CdSe NW was evidently promoted by coating the CdS shell, and this is because CdS improves the surface state optimizing the energy band structure of CdSe NW. The as-synthesized CdSe/CdS core/shell NW has more efficient PL quantum yields than pure CdSe NW and may find potential applications in nanoscale photonic devices. (orig.)

Fabrication and micro-photoluminescence property of CdSe/CdS core/shell nanowires

International Nuclear Information System (INIS)

Dai, Guozhang; Gou, Guangyang; Wu, Zeming; Chen, Yu; Li, Hongjian; Wan, Qiang; Zou, Bingsuo

2015-01-01

Hetero-epitaxial CdSe/CdS core/shell nanowires (NWs) were prepared by a source-controllable chemical vapor deposition method. A two-stage growth mechanism was proposed to the growth process of the core/shell NWs. Micro-photoluminescence (μ-PL) property of individual NW was studied by a confocal microscopy system. The pure CdSe NW emits a red light with peak at 712.3 nm, which is inconsistent with the CdSe band-edge emission. The CdSe/CdS core/shell NW emits two apparent peaks, one is an intensive red emission peak centered at 715.2 nm and the other is a weak green emission peak located at 516.2 nm. The room temperature μ-PL spectrum shows that the PL intensity of CdSe NW was evidently promoted by coating the CdS shell, and this is because CdS improves the surface state optimizing the energy band structure of CdSe NW. The as-synthesized CdSe/CdS core/shell NW has more efficient PL quantum yields than pure CdSe NW and may find potential applications in nanoscale photonic devices. (orig.)

Controlled-release and preserved bioactivity of proteins from (self-assembled core-shell double-walled microspheres

Directory of Open Access Journals (Sweden)

Yuan W

2012-01-01

Full Text Available Weien Yuan1,2, Zhenguo Liu11Department of Neurology, Xinhua Hospital, affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 2School of Pharmacy, Shanghai Jiao Tong University, Shanghai, People’s Republic of ChinaAbstract: In order to address preserved protein bioactivities and protein sustained-release problems, a method for preparing double-walled microspheres with a core (protein-loaded nanoparticles with a polymer-suspended granule system-formed core and a second shell (a polymer-formed shell for controlled drug release and preserved protein bioactivities has been developed using (solid-in-oil phase-in-hydrophilic oil-in-water (S/O/Oh/W phases. The method, based on our previous microsphere preparation method (solid-in-oil phase-in-hydrophilic oil-in-water (S/O/Oh/W, employs different concentric poly(D,L-lactide-co-glycolide, poly(D,L-lactide, and protein-loaded nanoparticles to produce a suspended liquid which then self-assembles to form shell-core microspheres in the hydrophilic oil phase, which are then solidified in the water phase. Variations in the preparation parameters allowed complete encapsulation by the shell phase, including the efficient formation of a poly(D,L-lactide shell encapsulating a protein-loaded nanoparticle-based poly(D,L-lactide-co-glycolide core. This method produces core-shell double-walled microspheres that show controlled protein release and preserved protein bioactivities for 60 days. Based upon these results, we concluded that the core-shell double-walled microspheres might be applied for tissue engineering and therapy for chronic diseases, etc.Keywords: protein delivery, protein stability, core-shell microspheres, dextran nanoparticles

Synthesis of Various Metal/TiO2 Core/shell Nanorod Arrays

Science.gov (United States)

Zhu, Wei; Wang, Guan-zhong; Hong, Xun; Shen, Xiao-shuang

2011-02-01

We present a general approach to fabricate metal/TiO2 core/shell nanorod structures by two-step electrodeposition. Firstly, TiO2 nanotubes with uniform wall thickness are prepared in anodic aluminum oxide (AAO) membranes by electrodeposition. The wall thickness of the nanotubes could be easily controlled by modulating the deposition time, and their outer diameter and length are only limited by the channel diameter and the thickness of the AAO membranes, respectively. The nanotubes' tops prepared by this method are open, while the bottoms are connected directly with the Au film at the back of the AAO membranes. Secondly, Pd, Cu, and Fe elements are filled into the TiO2 nanotubes to form core/shell structures. The core/shell nanorods prepared by this two-step process are high density and free-standing, and their length is dependent on the deposition time.

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,

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.

Interface engineered ferrite@ferroelectric core-shell nanostructures: A facile approach to impart superior magneto-electric coupling

Science.gov (United States)

Abraham, Ann Rose; Raneesh, B.; Das, Dipankar; Oluwafemi, Oluwatobi Samuel; Thomas, Sabu; Kalarikkal, Nandakumar

2018-04-01

The electric field control of magnetism in multiferroics is attractive for the realization of ultra-fast and miniaturized low power device applications like nonvolatile memories. Room temperature hybrid multiferroic heterostructures with core-shell (0-0) architecture (ferrite core and ferroelectric shell) were developed via a two-step method. High-Resolution Transmission Electron Microscopy (HRTEM) images confirm the core-shell structure. The temperature dependant magnetization measurements and Mossbauer spectra reveal superparamagnetic nature of the core-shell sample. The ferroelectric hysteresis loops reveal leaky nature of the samples. The results indicate the promising applications of the samples for magneto-electric memories and spintronics.

From core/shell to hollow Fe/γ-Fe_2O_3 nanoparticles: evolution of the magnetic behavior

International Nuclear Information System (INIS)

Nemati, Z; Khurshid, H; Alonso, J; Phan, M H; Mukherjee, P; Srikanth, H

2015-01-01

High quality Fe/γ-Fe_2O_3 core/shell, core/void/shell, and hollow nanoparticles with two different sizes of 8 and 12 nm were synthesized, and the effect of morphology, surface and finite-size effects on their magnetic properties including the exchange bias (EB) effect were systematically investigated. We find a general trend for both systems that as the morphology changes from core/shell to core/void/shell, the magnetization of the system decays and inter-particle interactions become weaker, while the effective anisotropy and the EB effect increase. The changes are more drastic when the nanoparticles become completely hollow. Noticeably, the morphological change from core/shell to hollow increases the mean blocking temperature for the 12 nm particles but decreases for the 8 nm particles. The low-temperature magnetic behavior of the 12 nm particles changes from a collective super-spin-glass system mediated by dipolar interactions for the core/shell nanoparticles to a frustrated cluster glass-like state for the shell nanograins in the hollow morphology. On the other hand for the 8 nm nanoparticles core/shell and hollow particles the magnetic behavior is more similar, and a conventional spin glass-like transition is obtained at low temperatures. In the case of the hollow nanoparticles, the coupling between the inner and outer spin layers in the shell gives rise to an enhanced EB effect, which increases with increasing shell thickness. This indicates that the morphology of the shell plays a crucial role in this kind of exchange-biased systems. (paper)

Graphitic carbon nitride nanosheet@metal-organic framework core-shell nanoparticles for photo-chemo combination therapy

Science.gov (United States)

Chen, Rui; Zhang, Jinfeng; Wang, Yu; Chen, Xianfeng; Zapien, J. Antonio; Lee, Chun-Sing

2015-10-01

Recently, nanoscale metal-organic frameworks (NMOFs) have started to be developed as a promising platform for bioimaging and drug delivery. On the other hand, combination therapies using multiple approaches are demonstrated to achieve much enhanced efficacy. Herein, we report, for the first time, core-shell nanoparticles consisting of a photodynamic therapeutic (PDT) agent and a MOF shell while simultaneously carrying a chemotherapeutic drug for effective combination therapy. In this work, core-shell nanoparticles of zeolitic-imadazolate framework-8 (ZIF-8) as shell embedded with graphitic carbon nitride (g-C3N4) nanosheets as core are fabricated by growing ZIF-8 in the presence of g-C3N4 nanosheets. Doxorubicin hydrochloride (DOX) is then loaded into the ZIF-8 shell of the core-shell nanoparticles. The combination of the chemotherapeutic effects of DOX and the PDT effect of g-C3N4 nanosheets can lead to considerably enhanced efficacy. Furthermore, the red fluorescence of DOX and the blue fluorescence of g-C3N4 nanosheets provide the additional function of dual-color imaging for monitoring the drug release process.Recently, nanoscale metal-organic frameworks (NMOFs) have started to be developed as a promising platform for bioimaging and drug delivery. On the other hand, combination therapies using multiple approaches are demonstrated to achieve much enhanced efficacy. Herein, we report, for the first time, core-shell nanoparticles consisting of a photodynamic therapeutic (PDT) agent and a MOF shell while simultaneously carrying a chemotherapeutic drug for effective combination therapy. In this work, core-shell nanoparticles of zeolitic-imadazolate framework-8 (ZIF-8) as shell embedded with graphitic carbon nitride (g-C3N4) nanosheets as core are fabricated by growing ZIF-8 in the presence of g-C3N4 nanosheets. Doxorubicin hydrochloride (DOX) is then loaded into the ZIF-8 shell of the core-shell nanoparticles. The combination of the chemotherapeutic effects of DOX

Ellipsoidal all-dielectric Fano resonant core-shell metamaterials

Science.gov (United States)

Reena, Reena; Kalra, Yogita; Kumar, Ajeet

2018-06-01

In this paper, ellipsoidal core (Si) and shell (SiO2) metamaterial has been proposed for highly directional properties. At the wavelength of magnetic resonance, Fano dip occurs in the backward scattering cross section and forward scattering enhancement takes place at the same wavelength so that there is an increment in the directivity. Effect on the directivity by changing the length of ellipsoidal nanoparticle along semi-axes has been analyzed. Two Fano resonances have been observed by decreasing the length of the nanoparticle along the semi-axis having electric polarization, where first and second Fano resonances are attributed to the dipole and quadrupole moments, respectively. These Fano resonant wavelengths in ellipsoidal nanoparticle exhibit higher directivity than the Kerker's type scattering or forward scattering shown by symmetrical structures like sphere. So, this core-shell metamaterial can act as an efficient directional nanoantenna.

Optical properties of supported core-shell and alloy silver/gold nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Hubenthal, Frank; Traeger, Frank [Universitaet Kassel (Germany)

2008-07-01

For many applications like surface enhanced Raman scattering in which the optical field enhancement associated with surface plasmon excitation is exploited, tunability of this collective resonance over a wide range is required. For this purpose we have prepared core-shell and alloy nanoparticles consisting of Ag and Au. The core-shell nanoparticles were made by subsequent deposition of Ag and Au atoms and vice versa on dielectric substrates followed by diffusion and nucleation. One of the most interesting among the numerous results is that the plasmon frequency can be tuned from 2.8 eV (442 nm) to 2.1 eV (590 nm) depending on the Au shell thickness. Subsequent annealing of the core-shell nanoparticles causes a shift of the resonance frequency to 2.6 eV. Theoretical modelling allows us to attribute this observation to the formation of alloy nanoparticles. Finally, we have measured the dephasing time T{sub 2} of the alloy nanoparticles by means of spectral hole burning. T{sub 2} amounts to 8.1{+-}1.6 fs, in good agreement with the dephasing time T{sub 2}=8.9 fs that is included in the dielectric function of the bulk.

Core-shell polymer nanoparticles for prevention of GSH drug detoxification and cisplatin delivery to breast cancer cells

Science.gov (United States)

Surnar, Bapurao; Sharma, Kavita; Jayakannan, Manickam

2015-10-01

Platinum drug delivery against the detoxification of cytoplasmic thiols is urgently required for achieving efficacy in breast cancer treatment that is over expressed by glutathione (GSH, thiol-oligopeptide). GSH-resistant polymer-cisplatin core-shell nanoparticles were custom designed based on biodegradable carboxylic functional polycaprolactone (PCL)-block-poly(ethylene glycol) diblock copolymers. The core of the nanoparticle was fixed as 100 carboxylic units and the shell part was varied using various molecular weight poly(ethylene glycol) monomethyl ethers (MW of PEGs = 100-5000 g mol-1) as initiator in the ring-opening polymerization. The complexation of cisplatin aquo species with the diblocks produced core-shell nanoparticles of 75 nm core with precise size control the particles up to 190 nm. The core-shell nanoparticles were found to be stable in saline solution and PBS and they exhibited enhanced stability with increase in the PEG shell thickness at the periphery. The hydrophobic PCL layer on the periphery of the cisplatin core behaved as a protecting layer against the cytoplasmic thiol residues (GSH and cysteine) and exhibited embryonic fibroblast cells (Wt-MEFs), and breast cancer (MCF-7) and cervical cancer (HeLa) cell lines. Free cisplatin and polymer drug core-shell nanoparticles showed similar cytotoxicity effects in the HeLa cells. In MCF-7 cells, the free cisplatin drug exhibited 50% cell death whereas complete cell death (100%) was accomplished by the polymer-cisplatin core-shell nanoparticles. Confocal microscopic images confirmed that the core-shell nanoparticles were taken up by the MCF-7 and HeLa cells and they were accumulated both at the cytoplasm as well at peri-nuclear environments. The present investigation lays a new foundation for the polymer-based core-shell nanoparticles approach for overcoming detoxification in platinum drugs for the treatment of GSH over-expressed breast cancer cells.Platinum drug delivery against the detoxification

Atomistic Tight-Binding Theory of Electron-Hole Exchange Interaction in Morphological Evolution of CdSe/ZnS Core/Shell Nanodisk to CdSe/ZnS Core/Shell Nanorod

Directory of Open Access Journals (Sweden)

Worasak Sukkabot

2016-01-01

Full Text Available Based on the atomistic tight-binding theory (TB and a configuration interaction (CI description, the electron-hole exchange interaction in the morphological transformation of CdSe/ZnS core/shell nanodisk to CdSe/ZnS core/shell nanorod is described with the aim of understanding the impact of the structural shapes on the change of the electron-hole exchange interaction. Normally, the ground hole states confined in typical CdSe/ZnS core/shell nanocrystals are of heavy hole-like character. However, the atomistic tight-binding theory shows that a transition of the ground hole states from heavy hole-like to light hole-like contribution with the increasing aspect ratios of the CdSe/ZnS core/shell nanostructures is recognized. According to the change in the ground-state hole characters, the electron-hole exchange interaction is also significantly altered. To do so, optical band gaps, ground-state electron character, ground-state hole character, oscillation strengths, ground-state coulomb energies, ground-state exchange energies, and dark-bright (DB excitonic splitting (stoke shift are numerically demonstrated. These atomistic computations obviously show the sensitivity with the aspect ratios. Finally, the alteration in the hole character has a prominent effect on dark-bright (DB excitonic splitting.

Enhanced charge storage capability of Ge/GeO2 core/shell nanostructure

International Nuclear Information System (INIS)

Yuan, C L; Lee, P S

2008-01-01

A Ge/GeO 2 core/shell nanostructure embedded in an Al 2 O 3 gate dielectrics matrix was produced. A larger memory window with good data retention was observed in the fabricated metal-insulator-semiconductor (MIS) capacitor for Ge/GeO 2 core/shell nanoparticles compared to Ge nanoparticles only, which is due to the high percentage of defects located on the surface and grain boundaries of the GeO 2 shell. We believe that the findings presented here provide physical insight and offer useful guidelines to controllably modify the charge storage properties of indirect semiconductors through defect engineering

Enhanced charge storage capability of Ge/GeO(2) core/shell nanostructure.

Science.gov (United States)

Yuan, C L; Lee, P S

2008-09-03

A Ge/GeO(2) core/shell nanostructure embedded in an Al(2)O(3) gate dielectrics matrix was produced. A larger memory window with good data retention was observed in the fabricated metal-insulator-semiconductor (MIS) capacitor for Ge/GeO(2) core/shell nanoparticles compared to Ge nanoparticles only, which is due to the high percentage of defects located on the surface and grain boundaries of the GeO(2) shell. We believe that the findings presented here provide physical insight and offer useful guidelines to controllably modify the charge storage properties of indirect semiconductors through defect engineering.

Photocatalytic hydrogen generation from water under visible light using core/shell nano-catalysts.

Science.gov (United States)

Wang, X; Shih, K; Li, X Y

2010-01-01

A microemulsion technique was employed to synthesize nano-sized photocatalysts with a core (CdS)/shell (ZnS) structure. The primary particles of the photocatalysts were around 10 nm, and the mean size of the catalyst clusters in water was about 100 nm. The band gaps of the catalysts ranged from 2.25 to 2.46 eV. The experiments of photocatalytic H(2) generation showed that the catalysts (CdS)(x)/(ZnS)(1-x) with x ranging from 0.1 to 1 were able to produce hydrogen from water photolysis under visible light. The catalyst with x=0.9 had the highest rate of hydrogen production. The catalyst loading density also influenced the photo-hydrogen production rate, and the best catalyst concentration in water was 1 g L(-1). The stability of the nano-catalysts in terms of size, morphology and activity was satisfactory during an extended test period for a specific hydrogen production rate of 2.38 mmol g(-1) L(-1) h(-1) and a quantum yield of 16.1% under visible light (165 W Xe lamp, lambda>420 nm). The results demonstrate that the (CdS)/(ZnS) core/shell nano-particles are a novel photo-catalyst for renewable hydrogen generation from water under visible light. This is attributable to the large band-gap ZnS shell that separates the electron/hole pairs generated by the CdS core and hence reduces their recombinations.

Large-scale fluid motion in the earth's outer core estimated from non-dipole magnetic field data

International Nuclear Information System (INIS)

Matsushima, Masaki; Honkura, Yoshimori

1989-01-01

Fluid motions in the Earth's outer core can be estimated from magnetic field data at the Earth's surface based on some assumptions. The basic standpoint here is that the non-dipole magnetic field is generated by the interaction between a strong toroidal magnetic field, created by differential rotation, and the convective motion in the outer core. Large-scale convective motions are studied to express them in terms of the poloidal velocity field expanded into a series of spherical harmonics. The radial distribution of differential rotation is estimated from the balance between the effective couple due to angular momentum transfer and the electromagnetic couple. Then the radial dependence of the toroidal magnetic field is derived from the interaction between the differential rotation thus estimated and the dipole magnetic field within the outer core. Magnetic field data are applied to a secular variation model which takes into account the fluctuations of the standing and drifting parts of the non-zonal magnetic field. The velocity field in the outer core is estimated for two cases. It is revealed that the pattern of convective motions is generally characterized by large-scale motions in the quasi-steady case. In the non-steady case, the magnitude of the velocity field is much larger, indicating a more dynamic feature. (N.K.)

Efficient tungsten oxide/bismuth oxyiodide core/shell photoanode for photoelectrochemical water splitting

Science.gov (United States)

Ma, Haipeng; Zhang, Jing; Liu, Zhifeng

2017-11-01

The novel WO3 nanorods (NRs)/BiOI core/shell structure composite is used as an efficient photoanode applied in photoelectrochemical (PEC) water splitting for the first time. It is synthesized via facile hydrothermal method and, successive ionic layer adsorption and reaction (SILAR) process. This facile synthesis route can achieve uniform WO3/BiOI core/shell composite nanostructures and obtain varied BiOI morphologies simultaneously. The WO3 NRs/BiOI-20 composite exhibits enhanced PEC activity compared to pristine WO3 with a photocurrent density of 0.79 mA cm-2 measured at 0.8 V vs. RHE under AM 1.5G. This excellent performance benefits from the broader absorption spectrum and suppressed electron-hole recombination. This novel core/shell composite may provide insight in developing more efficient solar driven photoelectrodes.

Synthesis of Multicolor Core/Shell NaLuF4:Yb3+/Ln3+@CaF2 Upconversion Nanocrystals

Directory of Open Access Journals (Sweden)

Hui Li

2017-02-01

Full Text Available The ability to synthesize high-quality hierarchical core/shell nanocrystals from an efficient host lattice is important to realize efficacious photon upconversion for applications ranging from bioimaging to solar cells. Here, we describe a strategy to fabricate multicolor core @ shell α-NaLuF4:Yb3+/Ln3+@CaF2 (Ln = Er, Ho, Tm upconversion nanocrystals (UCNCs based on the newly established host lattice of sodium lutetium fluoride (NaLuF4. We exploited the liquid-solid-solution method to synthesize the NaLuF4 core of pure cubic phase and the thermal decomposition approach to expitaxially grow the calcium fluoride (CaF2 shell onto the core UCNCs, yielding cubic core/shell nanocrystals with a size of 15.6 ± 1.2 nm (the core ~9 ± 0.9 nm, the shell ~3.3 ± 0.3 nm. We showed that those core/shell UCNCs could emit activator-defined multicolor emissions up to about 772 times more efficient than the core nanocrystals due to effective suppression of surface-related quenching effects. Our results provide a new paradigm on heterogeneous core/shell structure for enhanced multicolor upconversion photoluminescence from colloidal nanocrystals.

Dependences of optical properties of spherical two-layered nanoparticles on parameters of gold core and material shell

International Nuclear Information System (INIS)

Pustovalov, V.K.; Astafyeva, L.G.; Zharov, V.P.

2013-01-01

Modeling of nonlinear dependences of optical properties of spherical two-layered gold core and some material shell nanoparticles (NPs) placed in water on parameters of core and shell was carried out on the basis of the extended Mie theory. Efficiency cross-sections of absorption, scattering and extinction of radiation with wavelength 532 nm by core–shell NPs in the ranges of core radii r 00 =5–40 nm and of relative NP radii r 1 /r 00 =1–8 were calculated (r 1 —radius of two-layered nanoparticle). Shell materials were used with optical indexes in the ranges of refraction n 1 =0.2–1.5 and absorption k 1 =0–3.5 for the presentation of optical properties of wide classes of shell materials (including dielectrics, metals, polymers, vapor shell around gold core). Results show nonlinear dependences of optical properties of two-layered NPs on optical indexes of shell material, core r 00 and relative NP r 1 /r 00 radii. Regions with sharp decrease and increase of absorption, scattering and extinction efficiency cross-sections with changing of core and shell parameters were investigated. These dependences should be taken into account for applications of two-layered NPs in laser nanomedicine and optical diagnostics of tissues. The results can be used for experimental investigation of shell formation on NP core and optical determination of geometrical parameters of core and shell of two-layered NPs. -- Highlights: • Absorption, scattering and extinction of two-layered nanoparticles are studied. • Shell materials change in wide regions of materials (metals, dielectrics, vapor). • Effect of sharp decrease and increase of optical characteristics is established. • Explanation of sharp decreasing and increasing optical characteristics is presented

Boronic Acid functionalized core-shell polymer nanoparticles prepared by distillation precipitation polymerization for glycopeptide enrichment.

Science.gov (United States)

Qu, Yanyan; Liu, Jianxi; Yang, Kaiguang; Liang, Zhen; Zhang, Lihua; Zhang, Yukui

2012-07-16

The boronic acid-functionalized core-shell polymer nanoparticles, poly(N,N-methylenebisacrylamide-co-methacrylic acid)@4-vinylphenylboronic acid (poly(MBA-co-MAA)@VPBA), were successfully synthesized for enriching glycosylated peptides. Such nanoparticles were composed of a hydrophilic polymer core prepared by distillation precipitation polymerization (DPP) and a boronic acid-functionalized shell designed for capturing glycopeptides. Owing to the relatively large amount of residual vinyl groups introduced by DPP on the core surface, the VPBA monomer was coated with high efficiency, working as the shell. Moreover, the overall polymerization route, especially the use of DPP, made the synthesis of nanoparticles facile and time-saving. With the poly(MBA-co-MAA)@VPBA nanoparticles, 18 glycopeptides from horseradish peroxidase (HRP) digest were captured and identified by MALDI-TOF mass spectrometric analysis, relative to eight glycopeptides enriched by using commercially available meta-aminophenylboronic acid agarose under the same conditions. When the concentration of the HRP digest was decreased to as low as 5 nmol, glycopeptides could still be selectively isolated by the prepared nanoparticles. Our results demonstrated that the synthetic poly(MBA-co-MAA)@VPBA nanoparticles might be a promising selective enrichment material for glycoproteome analysis. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Platinum-nanoparticle-supported core-shell polymer nanospheres with unexpected water stability and facile further modification

Science.gov (United States)

Yuan, Conghui; Xu, Yiting; Luo, Weiang; Zeng, Birong; Qiu, Wuhui; Liu, Jie; Huang, Huiling; Dai, Lizong

2012-05-01

Core-shell nanospheres (CSNSs) with hydrophobic cores and hydrophilic shells were fabricated via a simple mini-emulsion polymerization for the stabilization of platinum nanoparticles (Pt-NPs). The CSNSs showed extremely high loading capacity of Pt-NPs (the largest loading amount of the Pt-NPs was about 49.2 wt%). Importantly, the Pt-NPs/CSNSs nanocomposites had unexpected stability in aqueous solution. DLS results revealed that the CSNSs loaded with Pt-NPs exhibited almost no aggregation after standing for a long time . However, the Pt-NPs immobilized on the CSNSs were not straitlaced: they could transport and redistribute between CSNSs freely when the environmental temperature was higher than the melting point of the CSNS shell. Owing to their excellent stability in aqueous solution, the surface of the Pt-NPs/CSNSs nanocomposites could be further decorated easily. For example, polyaniline (PANI)-coated Pt-NPs/CSNSs, nickel (Ni)-coated Pt-NPs/CSNSs and PANI/Pt-NPs dual-layer hollow nanospheres were facilely fabricated from the Pt-NPs/CSNS nanocomposites.

Au@MnO2 core-shell nanomesh electrodes for transparent flexible supercapacitors.

Science.gov (United States)

Qiu, Tengfei; Luo, Bin; Giersig, Michael; Akinoglu, Eser Metin; Hao, Long; Wang, Xiangjun; Shi, Lin; Jin, Meihua; Zhi, Linjie

2014-10-29

A novel Au@MnO2 supercapacitor is presented. The sophisticated core-shell architecture combining an Au nanomesh core with a MnO2 shell on a flexible polymeric substrate is demonstrated as an electrode for high performance transparent flexible supercapacitors (TFSCs). Due to their unique structure, high areal/gravimetric capacitance and rate capability for TFSCs are achieved. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The influence of shell thickness of Au@TiO2 core-shell nanoparticles on the plasmonic enhancement effect in dye-sensitized solar cells.

Science.gov (United States)

Liu, Wei-Liang; Lin, Fan-Cheng; Yang, Yu-Chen; Huang, Chen-Hsien; Gwo, Shangjr; Huang, Michael H; Huang, Jer-Shing

2013-09-07

Plasmonic core-shell nanoparticles (PCSNPs) can function as nanoantennas and improve the efficiency of dye-sensitized solar cells (DSSCs). To achieve maximum enhancement, the morphology of PCSNPs needs to be optimized. Here we precisely control the morphology of Au@TiO2 PCSNPs and systematically study its influence on the plasmonic enhancement effect. The enhancement mechanism was found to vary with the thickness of the TiO2 shell. PCSNPs with a thinner shell mainly enhance the current, whereas particles with a thicker shell improve the voltage. While pronounced plasmonic enhancement was found in the near infrared regime, wavelength-independent enhancement in the visible range was observed and attributed to the plasmonic heating effect. Emission lifetime measurement confirms that N719 molecules neighboring nanoparticles with TiO2 shells exhibit a longer lifetime than those in contact with metal cores. Overall, PCSNPs with a 5 nm shell give the highest efficiency enhancement of 23%. Our work provides a new synthesis route for well-controlled Au@TiO2 core-shell nanoparticles and gains insight into the plasmonic enhancement in DSSCs.

Enhancement of the core near-band-edge emission induced by an amorphous shell in coaxial one-dimensional nanostructure: the case of SiC/SiO{sub 2} core/shell self-organized nanowires

Energy Technology Data Exchange (ETDEWEB)

Fabbri, Filippo; Rossi, Francesca; Attolini, Giovanni; Salviati, Giancarlo; Iannotta, Salvatore [IMEM-CNR Institute, Viale Usberti 37/A, I-43124 Parma (Italy); Aversa, Lucrezia; Verucchi, Roberto; Nardi, Marco [IFN-CNR Institute, Via alla Cascata 56/C-Povo, I-38123 Trento (Italy); Fukata, Naoki [International Center for Materials Nanoarchitectonics, National Institute for Materials Science and PRESTO JST, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Dierre, Benjamin; Sekiguchi, Takashi [Nano Device Characterization Group, Advanced Electronic Materials Center, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

2010-08-27

We report the influence of the native amorphous SiO{sub 2} shell on the cathodoluminescence emission of 3C-SiC/SiO{sub 2} core/shell nanowires. A shell-induced enhancement of the SiC near-band-edge emission is observed and studied as a function of the silicon dioxide thickness. Since the diameter of the investigated SiC cores rules out any direct bandgap optical transitions due to confinement effects, this enhancement is ascribed to a carrier diffusion from the shell to the core, promoted by the alignment of the SiO{sub 2} and SiC bands in a type I quantum well. An accurate correlation between the optical emission and structural and SiO{sub 2}-SiC interface properties is also reported.

Facile synthesis of hierarchical Co3O4@MnO2 core-shell arrays on Ni foam for asymmetric supercapacitors

Science.gov (United States)

Huang, Ming; Zhang, Yuxin; Li, Fei; Zhang, Lili; Wen, Zhiyu; Liu, Qing

2014-04-01

Hierarchical Co3O4@MnO2 core-shell arrays on Ni foam have been fabricated by a facile hydrothermal approach and further investigated as the electrode for high-performance supercapacitors. Owing to the high conductivity of the well-defined mesoporous Co3O4 nanowire arrays in combination with the large surface area provided by the ultrathin MnO2 nanosheets, the unique designed Co3O4@MnO2 core-shell arrays on Ni foam have exhibited a high specific capacitance (560 F g-1 at a current density of 0.2 A g-1), good rate capability, and excellent cycling stability (95% capacitance retention after 5000 cycles). An asymmetric supercapacitor with Co3O4@MnO2 core-shell nanostructure as the positive electrode and activated microwave exfoliated graphite oxide activated graphene (MEGO) as the negative electrode yielded an energy density of 17.7 Wh kg-1 and a maximum power density of 158 kW kg-1. The rational design of the unique core-shell array architectures demonstrated in this work provides a new and facile approach to fabricate high-performance electrode for supercapacitors.

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.

Simple and convenient preparation of Au-Pt core-shell nanoparticles on surface via a seed growth method

International Nuclear Information System (INIS)

Qian Lei; Sha Yufang; Yang Xiurong

2006-01-01

Au-Pt core-shell nanoparticles were prepared on glass surface by a seed growth method. Gold nanoparticles were used as seeds and ascorbic acid-H 2 PtCl 6 solutions as growth solutions to deposit Pt shell on the surface of gold nanoparticles. These core-shell nanoparticles and their growth process were examined by UV-Vis spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy and field-emission environmental scanning electron microscopy and the results indicated that the deposition speed was fast and nanoparticles with obvious core-shell structure could be obtained after 2 min. Moreover, this seed growth method for preparation of the core-shell nanoparticles is simple and convenient compared with other seed growth methods with NH 4 OH as a mild reductant. In addition, electrochemical experiments indicated that these Au-Pt core-shell nanoparticles had similar electrochemical properties to those of the bulk Pt electrode

Synthesis of Fe5C2@SiO2 core@shell nanoparticles as a potential candidate for biomedical application

Science.gov (United States)

Ahmadpoor, Fatemeh; Shojaosadati, Seyed Abbas; Delavari H, Hamid; Christiansen, Gunna; Saber, Reza

2018-05-01

A new strategy for water-dispersibility of hydrophobic carbide nanostructures was proposed. In this regard, hydrophobic Fe5C2 nanoparticles (NPs) with size ranging 25–40 nm were synthesized and coated with 12–15 nm silica shell for biomedical applications. X-ray diffraction (XRD) results revealed that Fe5C2 NPs with monoclinic structure were successfully prepared. The crystalline structure of Fe5C2 NPs was remained unchanged and saturation magnetization of core remained nearly constant after coating with silica shell. Moreover, Raman spectroscopy identified D-band of amorphous carbon shells which was also confirmed by transmission electron microscopy (TEM). Finally, Fe5C2@SiO2 core@shell NPs demonstrated no significant cytotoxicity and appropriate heat generating which makes them a promising candidate for magnetic fluid hyperthermia applications.

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

Silicon nanotube field effect transistor with core-shell gate stacks for enhanced high-performance operation and area scaling benefits

KAUST Repository

Fahad, Hossain M.; Smith, Casey; Rojas, Jhonathan Prieto; Hussain, Muhammad Mustafa

2011-01-01

We introduce the concept of a silicon nanotube field effect transistor whose unique core-shell gate stacks help achieve full volume inversion by giving a surge in minority carrier concentration in the near vicinity of the ultrathin channel and at the same time rapid roll-off at the source and drain junctions constituting velocity saturation-induced higher drive current-enhanced high performance per device with efficient real estate consumption. The core-shell gate stacks also provide superior short channel effects control than classical planar metal oxide semiconductor field effect transistor (MOSFET) and gate-all-around nanowire FET. The proposed device offers the true potential to be an ideal blend for quantum ballistic transport study of device property control by bottom-up approach and high-density integration compatibility using top-down state-of-the-art complementary metal oxide semiconductor flow. © 2011 American Chemical Society.

Silicon nanotube field effect transistor with core-shell gate stacks for enhanced high-performance operation and area scaling benefits

KAUST Repository

Fahad, Hossain M.

2011-10-12

We introduce the concept of a silicon nanotube field effect transistor whose unique core-shell gate stacks help achieve full volume inversion by giving a surge in minority carrier concentration in the near vicinity of the ultrathin channel and at the same time rapid roll-off at the source and drain junctions constituting velocity saturation-induced higher drive current-enhanced high performance per device with efficient real estate consumption. The core-shell gate stacks also provide superior short channel effects control than classical planar metal oxide semiconductor field effect transistor (MOSFET) and gate-all-around nanowire FET. The proposed device offers the true potential to be an ideal blend for quantum ballistic transport study of device property control by bottom-up approach and high-density integration compatibility using top-down state-of-the-art complementary metal oxide semiconductor flow. © 2011 American Chemical Society.

Centrifugal Deposited Au-Pd Core-Shell Nanoparticle Film for Room-Temperature Optical Detection of Hydrogen Gas.

Science.gov (United States)

Song, Han; Luo, Zhijie; Liu, Mingyao; Zhang, Gang; Peng, Wang; Wang, Boyi; Zhu, Yong

2018-05-06

In the present work, centrifugal deposited Au-Pd core-shell nanoparticle (NP) film was proposed for the room-temperature optical detection of hydrogen gas. The size dimension of 44, 48, 54, and 62 nm Au-Pd core-shell nanocubes with 40 nm Au core were synthesized following a solution-based seed-mediated growth method. Compared to a pure Pd NP, this core-shell structure with an inert Au core could decrease the H diffusion length in the Pd shell. Through a modified centrifugal deposition process, continues film samples with different core-shell NPs were deposited on 10 mm diameter quartz substrates. Under various hydrogen concentration conditions, the optical response properties of these samples were characterized by an intensity-based optical fiber bundle sensor. Experimental results show that the continues film that was composed of 62 nm Au-Pd core-shell NPs has achieved a stable and repeatable reflectance response with low zero drift in the range of 4 to 0.1% hydrogen after a stress relaxation mechanism at first few loading/unloading cycles. Because of the short H diffusion length due to the thinner Pd shell, the film sample composed of 44 nm Au-Pd NPs has achieved a dramatically decreased response/recovery time to 4 s/30 s. The experiments present the promising prospect of this simple method to fabricate optical hydrogen sensors with controllable high sensitivity and response rate at low cost.

Folding and unfolding of large-size shell construction for application in Earth orbit

Science.gov (United States)

Kondyurin, Alexey; Pestrenina, Irena; Pestrenin, Valery; Rusakov, Sergey

2016-07-01

financially supported by the Russian Fund for Basic Research (grants No. 15-01-07946_a and 14-08-96011_r_ural_a). 1. Briskman V., A.Kondyurin, K.Kostarev, V.Leontyev, M.Levkovich, A.Mashinsky, G.Nechitailo, T.Yudina, Polymerization in microgravity as a new process in space technology, Paper No IAA-97-IAA.12.1.07, 48th International Astronautical Congress, October 6-10, 1997, Turin Italy. 2. Kondyurin A., Pestrenina I., Pestrenin V., Kashin N., Naymushin A. Large-size deployable construction heated by solar irradiation free space, 40th COSPAR Scientific Assembly 2014. 3. V. M. Pestrenin, I. V. Pestrenina, S. V. Rusakov, and A. V. Kondyurin Deployment of large-size shell constructions by internal pressure, Mechanics of Composite Materials, 2015, Vol. 51, No 5, p. 629-636.

Intracellular ion monitoring using a gold-core polymer-shell nanosensor architecture

Energy Technology Data Exchange (ETDEWEB)

Stanca, S E; Cranfield, C G; Biskup, C [Biomolecular Photonics Group, University Hospital Jena, Teichgraben 8, 07743 Jena (Germany); Nietzsche, S [Centre for Electron Microscopy, University Hospital Jena, Ziegel-muehlenweg 1, 07743 Jena (Germany); Fritzsche, W, E-mail: sarmiza.stanca@mti.uni-jena.de, E-mail: charles.cranfield@mti.uni-jena.de, E-mail: christoph.biskup@mti.uni-jena.de [Institute of Photonic Technology, Albert-Einstein-Strasse 9, 07745 Jena (Germany)

2010-02-05

In this study, we describe the design of new ratiometric fluorescent nanosensors, whose architecture is based on a gold core surrounded by a poly(vinyl alcohol)-polyacetal shell. To the gold core, indicator dyes and reference dyes are attached via a cysteine linker. This nanosensor architecture is flexible with regards to the number and types of fluorophore linkages possible. The robust poly(vinyl alcohol)-polyacetal shell protects the fluorophores linked to the core from non-specific interactions with intracellular proteins. The nanosensors developed in this way are biocompatible and can be easily incorporated into mammalian cells without the use of transfection agents. Here, we show the application of these nanosensors for intracellular pH and sodium ion measurements.

Synthesis and properties MFe2O4 (M = Fe, Co) nanoparticles and core-shell structures

Science.gov (United States)

Yelenich, O. V.; Solopan, S. O.; Greneche, J. M.; Belous, A. G.

2015-08-01

Individual Fe3-xO4 and CoFe2O4 nanoparticles, as well as Fe3-xO4/CoFe2O4 core/shell structures were synthesized by the method of co-precipitation from diethylene glycol solutions. Core/shell structure were synthesized with CoFe2O4-shell thickness of 1.0, 2.5 and 3.5 nm. X-ray diffraction patterns of individual nanoparticles and core/shell are similar and indicate that all synthesized samples have a cubic spinel structure. Compares Mössbauer studies of CoFe2O4, Fe3-xO4 nanoparticles indicate superparamagnetic properties at 300 K. It was shown that individual magnetite nanoparticles are transformed into maghemite through oxidation during the synthesis procedure, wherein the smallest nanoparticles are completely oxidized while a magnetite core does occur in the case of the largest nanoparticles. The Mössbauer spectra of core/shell nanoparticles with increasing CoFe2O4-shell thickness show a gradual decrease in the relative intensity of the quadrupole doublet and significant decrease of the mean isomer shift value at both RT and 77 K indicating a decrease of the superparamagnetic relaxation phenomena. Specific loss power for the prepared ferrofluids was experimentally calculated and it was determined that under influence of ac-magnetic field magnetic fluid based on individual CoFe2O4 and Fe3-xO4 particles are characterized by very low heating temperature, when magnetic fluids based on core/shell nanoparticles demonstrate higher heating effect.

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.

Transfer of pharmacopoeial liquid chromatography reversedphase methods for determination of related compounds in diclofenac sodium and metamizole sodium from conventional to core-shell column

Directory of Open Access Journals (Sweden)

Katerina Brezovska

2015-04-01

Full Text Available Core-shell silica particles were developed as a new material for chromatographic stationary phases in order to provide fast and high efficiency separations of small and large molecules and complex samples, at pressures compatible with conventional HPLC equipment. The aim of our work was to show the applicability of the HPLC columns based on a core-shell technology for determination of related substances in diclofenac sodium and in metamizole sodium using the methods described in the corresponding monographs of the European pharmacopoeia. The obtained results have shown that the proposed methods can be successfully transferred on core shell column, with suitable adjustment of injection volume and flow rate. The advantage of using core-shell column is fast and highly efficient separation on conventional HPLC equipment with increased sensitivity of the method and high throughput of the analysis, providing enhanced lab productivity and reduced costs.

Iron/iron oxide core-shell nanoclusters for biomedical applications

International Nuclear Information System (INIS)

Qiang You; Antony, Jiji; Sharma, Amit; Nutting, Joseph; Sikes, Daniel; Meyer, Daniel

2006-01-01

Biocompatible magnetic nanoparticles have been found promising in several biomedical applications for tagging, imaging, sensing and separation in recent years. Most magnetic particles or beads currently used in biomedical applications are based on ferromagnetic iron oxides with very low specific magnetic moments of about 20-30 emu/g. Here we report a new approach to synthesize monodispersed core-shell nanostructured clusters with high specific magnetic moments above 200 emu/g. Iron nanoclusters with monodispersive size of diameters from 2 nm to 100 nm are produced by our newly developed nanocluster source and go to a deposition chamber, where a chemical reaction starts, and the nanoclusters are coated with iron oxides. HRTEM Images show the coatings are very uniform and stable. The core-shell nanoclusters are superparamagnetic at room temperature for sizes less than 15 nm, and then become ferromagnetic when the cluster size increases. The specific magnetic moment of core-shell nanoclusters is size dependent, and increases rapidly from about 80 emu/g at the cluster size of around 3 nm to over 200 emu/g up to the size of 100 nm. The use of high magnetic moment nanoclusters for biomedical applications could dramatically enhance the contrast for MRI, reduce the concentration of magnetic particle needs for cell separation, or make drug delivery possible with much lower magnetic field gradients

CdSe/AsS core-shell quantum dots: preparation and two-photon fluorescence.

Science.gov (United States)

Wang, Junzhong; Lin, Ming; Yan, Yongli; Wang, Zhe; Ho, Paul C; Loh, Kian Ping

2009-08-19

Arsenic(II) sulfide (AsS)-coated CdSe core-shell nanocrystals can be prepared by a cluster-complex deposition approach under mild conditions. At 60 degrees C, growth of an AsS shell onto a CdSe nanocrystal can be realized through the crystallization of a cluster complex of AsS/butylamine in a mixed solvent of isopropanol/chloroform. The new, type I core-shell nanocrystal exhibits markedly enhanced one-photon fluorescence as well two-photon upconversion fluorescence. The nanocrystals can be used for infrared-excited upconversion cellular labeling.

Dual-Channel, Molecular-Sieving Core/Shell ZIF@MOF Architectures as Engineered Fillers in Hybrid Membranes for Highly Selective CO2 Separation.

Science.gov (United States)

Song, Zhuonan; Qiu, Fen; Zaia, Edmond W; Wang, Zhongying; Kunz, Martin; Guo, Jinghua; Brady, Michael; Mi, Baoxia; Urban, Jeffrey J

2017-11-08

A novel core/shell porous crystalline structure was prepared using a large pore metal organic framework (MOF, UiO-66-NH 2 , pore size, ∼ 0.6 nm) as core surrounded by a small pore zeolitic imidazolate framework (ZIF, ZIF-8, pore size, ∼ 0.4 nm) through a layer-by-layer deposition method and subsequently used as an engineered filler to construct hybrid polysulfone (PSF) membranes for CO 2 capture. Compared to traditional fillers utilizing only one type of porous material with rigid channels (either large or small), our custom designed core/shell fillers possess clear advantages via pore engineering: the large internal channels of the UiO-66-NH 2 MOFs create molecular highways to accelerate molecular transport through the membrane, while the thin shells with small pores (ZIF-8) or even smaller pores generated at the interface by the imperfect registry between the overlapping pores of ZIF and MOF enhance molecular sieving thus serving to distinguish slightly larger N 2 molecules (kinetic diameter, 0.364 nm) from smaller CO 2 molecules (kinetic diameter, 0.33 nm). The resultant core/shell ZIF@MOF and as-prepared hybrid PSF membranes were characterized by transmission electron microscopy, X-ray diffraction, wide-angle X-ray scattering, scanning electron microscopy, Fourier transform infrared, thermogravimetric analysis, differential scanning calorimetry, and contact angle tests. The dependence of the separation performance of the membranes on the MOF/ZIF ratio was also studied by varying the number of layers of ZIF coatings. The integrated PSF-ZIF@MOF hybrid membrane (40 wt % loading) with optimized ZIF coating cycles showed improved hydrophobicity and excellent CO 2 separation performance by simultaneously increasing CO 2 permeability (CO 2 permeability of 45.2 barrer, 710% higher than PSF membrane) and CO 2 /N 2 selectivity (CO 2 /N 2 selectivity of 39, 50% higher than PSF membrane), which is superior to most reported hybrid PSF membranes. The strategy of using

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_O_2 ≈ 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.

High-performance asymmetric supercapacitors based on core/shell cobalt oxide/carbon nanowire arrays with enhanced electrochemical energy storage

International Nuclear Information System (INIS)

Pan, G.X.; Xia, X.H.; Cao, F.; Chen, J.; Tang, P.S.; Zhang, Y.J.; Chen, H.F.

2014-01-01

Graphical abstract: - Highlights: • We prepared a self-supported porous Co 3 O 4 /C core/shell nanowire array. • Core/shell nanowire array showed high pseudo-capacitive properties. • Core/shell array structure was favorable for fast ion and electron transfer. - Abstract: High-reactivity electrode materials are indispensible for developing high-performance electrochemical energy storage devices. Herein, we report self-supported core/shell Co 3 O 4 /C nanowire arrays by using hydrothermal synthesis and chemical vapor deposition methods. A uniform and thin carbon shell is coated on the surface of Co 3 O 4 nanowire forming core/shell nanowires with diameters of ∼100 nm. Asymmetric supercapacitors have been assembled with the core/shell Co 3 O 4 /C nanowire arrays as the positive electrode and activated carbon (AC) as the negative electrode. The core/shell Co 3 O 4 /C nanowire arrays exhibit a specific capacity of 116 mAh g −1 at the working current of 100 mA (4 A g −1 ), and a long cycle life along with ∼ 92% retention after 8000 cycles at 4 A g −1 , higher than the unmodified Co 3 O 4 nanowire arrays (81 mAh g −1 at 4 A g −1 ). The introduction of uniform carbon layer into the core/shell structure is favorable for the enhancement of supercapacitor due to the improved electrical conductivity and reaction kinetics

Influence of core size on the upconversion luminescence properties of spherical Gd2O3:Yb3+/Er3+@SiO2 particles with core-shell structures

International Nuclear Information System (INIS)

Zheng, Kezhi; Liu, Zhenyu; Liu, Ye; Song, Weiye; Qin, Weiping

2013-01-01

Spherical SiO 2 particles with different sizes (30, 80, 120, and 180 nm) have been coated with Gd 2 O 3 :Yb 3+ /Er 3+ layers by a heterogeneous precipitation method, leading to the formation of core-shell structural Gd 2 O 3 :Yb 3+ /Er 3+ @SiO 2 particles. The samples were characterized by using X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, upconversion (UC) emission spectra, and fluorescent dynamical analysis. The obtained core-shell particles have perfect spherical shape with narrow size distribution. Under the excitation of 980 nm diode laser, the core-shell samples showed size-dependent upconversion luminescence (UCL) properties. The inner SiO 2 cores in core-shell samples were proved to have limited effect on the total UCL intensities of Er 3+ ions. The UCL intensities of core-shell particles were demonstrated much higher than the values obtained in pure Gd 2 O 3 :Yb 3+ /Er 3+ with the same phosphor volume. The dependence of the specific area of a UCL shell on the size of its inner SiO 2 particle was calculated and analyzed for the first time. It was confirmed that the surface effect came from the outer surfaces of emitting shells is dominant in influencing the UCL property in the core-shell samples. Three-photon UC processes for the green emissions were observed in the samples with small sizes of SiO 2 cores. The results of dynamical analysis illustrated that more nonradiative relaxation occurred in the core-shell samples with smaller SiO 2 core sizes

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

KAUST Repository

Khan, Easir A.; Rajendran, Arvind; Lai, Zhiping

2010-01-01

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.

Protective agent-free synthesis of Ni-Ag core-shell nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Chen, D.-H. [Department of Chemical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China)]. E-mail: chendh@mail.ncku.edu.tw; Wang, S.-R. [Department of Chemical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China)

2006-12-10

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.

Physical property control in core/shell inorganic nanostructures for fluorescence and magnetic targeting applications

Science.gov (United States)

Roberts, Stephen K.

Nanomaterials show immense promise for the future in numerous areas of application. Properties that are unique from the bulk material and are tunable allow for innovation in material design. This thesis will focus on controlling the physical properties of core/shell nanostructures to enhance the utility of the materials. The first focus is on the impact of different solvent mixtures during the shell growth phase of SILAR based core/shell quantum dot synthesis is studied. Gaining insight into the mechanism for SILAR growth of core/shell nanoparticles allows improved synthetic yields and precursor binding, providing enhanced control to synthesis of core/shell nanoparticles. The second focus of this thesis is exploring the use of magnetic nanoparticles for magnetic drug targeting for cardiovascular conditions. Magnetic targeting for drug delivery enables increased local drug concentration, while minimizing non-specific interactions. In order to be effective for magnetic targeting, it must be shown that low magnetic strength is sufficient to capture flowing nanoparticles. By demonstrating the binding of a therapeutic agent to the surface at medicinal levels, the viability for use as a nanoparticle drug delivery system is improved.

Isostructural solid-solid phase transition in monolayers of soft core-shell particles at fluid interfaces: structure and mechanics.

Science.gov (United States)

Rey, Marcel; Fernández-Rodríguez, Miguel Ángel; Steinacher, Mathias; Scheidegger, Laura; Geisel, Karen; Richtering, Walter; Squires, Todd M; Isa, Lucio

2016-04-21

We have studied the complete two-dimensional phase diagram of a core-shell microgel-laden fluid interface by synchronizing its compression with the deposition of the interfacial monolayer. Applying a new protocol, different positions on the substrate correspond to different values of the monolayer surface pressure and specific area. Analyzing the microstructure of the deposited monolayers, we discovered an isostructural solid-solid phase transition between two crystalline phases with the same hexagonal symmetry, but with two different lattice constants. The two phases corresponded to shell-shell and core-core inter-particle contacts, respectively; with increasing surface pressure the former mechanically failed enabling the particle cores to come into contact. In the phase-transition region, clusters of particles in core-core contacts nucleate, melting the surrounding shell-shell crystal, until the whole monolayer moves into the second phase. We furthermore measured the interfacial rheology of the monolayers as a function of the surface pressure using an interfacial microdisk rheometer. The interfaces always showed a strong elastic response, with a dip in the shear elastic modulus in correspondence with the melting of the shell-shell phase, followed by a steep increase upon the formation of a percolating network of the core-core contacts. These results demonstrate that the core-shell nature of the particles leads to a rich mechanical and structural behavior that can be externally tuned by compressing the interface, indicating new routes for applications, e.g. in surface patterning or emulsion stabilization.

Investigation of novel inverted NiO@NixCo1-xO core-shell nanoparticles

Science.gov (United States)

Hasan, Samiul; Mayanovic, R. A.; Benamara, Mourad

2018-05-01

Inverse core-shell nanoparticles, comprised of an antiferromagnetic (AFM) core covered by a ferromagnetic (FM) or ferrimagnetic (FiM) shell, are of current interest due to their different potential application and due to the tunability of their magnetic properties. The antiferromagnetic nature of NiO and high Néel temperature (523 K) makes this material well suited for inverse core-shell nanoparticle applications. Our primary objective in this project has been to synthesize and characterize inverted core-shell nanoparticles (CSNs) comprised of a NiO (AFM) core and a shell consisting of a NixCo1-xO (FiM) compound. The synthesis of the CSNs was made using a two-step process. The NiO nanoparticles were synthesized using a chemical reaction method. Subsequently, the NiO nanoparticles were used to grow the NiO@NixCo1-xO CSNs using our hydrothermal nano-phase epitaxy method. XRD structural characterization shows that the NiO@NixCo1-xO CSNs have the rock salt cubic crystal structure. SEM-EDS data indicates the presence of Co in the CSNs. Magnetic measurements show that the CSNs exhibit AFM/FiM characteristics with a small coercivity field of 30 Oe at 5 K. The field cooled vs zero field cooled hysteresis loop measurements show a magnetization axis shift which is attributed to the exchange bias effect between the AFM NiO core and an FiM NixCo1-xO shell of the CSNs. Our ab initio based calculations of the NixCo1-xO rock salt structure confirm a weak FiM character and a charge transfer insulator property of the compound.

Investigation of novel inverted NiO@NixCo1-xO core-shell nanoparticles

Directory of Open Access Journals (Sweden)

Samiul Hasan

2018-05-01

Full Text Available Inverse core-shell nanoparticles, comprised of an antiferromagnetic (AFM core covered by a ferromagnetic (FM or ferrimagnetic (FiM shell, are of current interest due to their different potential application and due to the tunability of their magnetic properties. The antiferromagnetic nature of NiO and high Néel temperature (523 K makes this material well suited for inverse core-shell nanoparticle applications. Our primary objective in this project has been to synthesize and characterize inverted core-shell nanoparticles (CSNs comprised of a NiO (AFM core and a shell consisting of a NixCo1-xO (FiM compound. The synthesis of the CSNs was made using a two-step process. The NiO nanoparticles were synthesized using a chemical reaction method. Subsequently, the NiO nanoparticles were used to grow the NiO@NixCo1-xO CSNs using our hydrothermal nano-phase epitaxy method. XRD structural characterization shows that the NiO@NixCo1-xO CSNs have the rock salt cubic crystal structure. SEM-EDS data indicates the presence of Co in the CSNs. Magnetic measurements show that the CSNs exhibit AFM/FiM characteristics with a small coercivity field of 30 Oe at 5 K. The field cooled vs zero field cooled hysteresis loop measurements show a magnetization axis shift which is attributed to the exchange bias effect between the AFM NiO core and an FiM NixCo1-xO shell of the CSNs. Our ab initio based calculations of the NixCo1-xO rock salt structure confirm a weak FiM character and a charge transfer insulator property of the compound.

(Gold core)/(titania shell) nanostructures for plasmon-enhanced photon harvesting and generation of reactive oxygen species

KAUST Repository

Fang, Caihong; Jia, Henglei; Chang, Shuai; Ruan, Qifeng; Wang, Peng; Chen, Tao; Wang, Jianfang

2014-01-01

Integration of gold and titania in a nanoscale core/shell architecture can offer large active metal/semiconductor interfacial areas and avoid aggregation and reshaping of the metal nanocrystal core. Such hybrid nanostructures are very useful for studying plasmon-enhanced/enabled processes and have great potential in light-harvesting applications. Herein we report on a facile route to (gold nanocrystal core)/(titania shell) nanostructures with their plasmon band synthetically variable from ∼700 nm to over 1000 nm. The coating method has also been applied to other mono- and bi-metallic Pd, Pt, Au nanocrystals. The gold/titania nanostructures have been employed as the scattering layer in dye-sensitized solar cells, with the resultant cells exhibiting a 13.3% increase in the power conversion efficiency and a 75% decrease in the scattering-layer thickness. Moreover, under resonant excitation, the gold/titania nanostructures can efficiently utilize low-energy photons to generate reactive oxygen species, including singlet oxygen and hydroxyl radicals.

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.

Giant exchange bias and its angular dependence in Co/CoO core-shell nanowire assemblies

International Nuclear Information System (INIS)

Gandha, Kinjal; Chaudhary, Rakesh P.; Mohapatra, Jeotikanta; Koymen, Ali R.; Liu, J. Ping

2017-01-01

The exchange-bias field (H 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 EB ) up to 2.4 kOe is observed below a blocking temperature (T EB ∼150 K) in the aligned Co/CoO nanowire assemblies. It is also found that there is an angular dependence between the H EB and the applied magnetization direction. The H 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.

Effect of shell thickness on the exchange bias blocking temperature and coercivity in Co-CoO core-shell nanoparticles

Science.gov (United States)

Thomas, S.; Reethu, K.; Thanveer, T.; Myint, M. T. Z.; Al-Harthi, S. H.

2017-08-01

The exchange bias blocking temperature distribution of naturally oxidized Co-CoO core-shell nanoparticles exhibits two distinct signatures. These are associated with the existence of two magnetic entities which are responsible for the temperature dependence of an exchange bias field. One is from the CoO grains which undergo thermally activated magnetization reversal. The other is from the disordered spins at the Co-CoO interface which exhibits spin-glass-like behavior. We investigated the oxide shell thickness dependence of the exchange bias effect. For particles with a 3 nm thick CoO shell, the predominant contribution to the temperature dependence of exchange bias is the interfacial spin-glass layer. On increasing the shell thickness to 4 nm, the contribution from the spin-glass layer decreases, while upholding the antiferromagnetic grain contribution. For samples with a 4 nm CoO shell, the exchange bias training was minimal. On the other hand, 3 nm samples exhibited both the training effect and a peak in coercivity at an intermediate set temperature Ta. This is explained using a magnetic core-shell model including disordered spins at the interface.

Theoretical Study of Local Surface Plasmon Resonances on a Dielectric-Ag Core-Shell Nanosphere Using the Discrete-Dipole Approximation Method

International Nuclear Information System (INIS)

Ma Ye-Wan; Wu Zhao-Wang; Zhang Li-Hua; Liu Wan-Fang; Zhang Jie

2015-01-01

The local surface plasmon resonances (LSPRs) of dielectric-Ag core-shell nanospheres are studied by the discretedipole approximation method. The result shows that LSPRs are sensitive to the surrounding medium refractive index, which shows a clear red-shift with the increasing surrounding medium refractive index. A dielectric-Ag core-shell nanosphere exhibits a strong coupling between the core and shell plasmon resonance modes. LSPRs depend on the shell thickness and the composition of dielectric-core and metal-shell. LSPRs can be tuned over a longer wavelength range by changing the ratio of core to shell value. The lower energy mode ω_− shows a red-shift with the increasing dielectric-core value and the inner core radius, while blue-shifted with the increasing outer shell thickness. The underlying mechanisms are analyzed with the plasmon hybridization theory and the phase retardation effect. (paper)

Bandgap engineered reverse type-I CdTe/InP/ZnS core-shell nanocrystals for the near-infrared.

Science.gov (United States)

Kim, Sunghoon; Shim, Wooyoung; Seo, Heonjin; Hyun Bae, Je; Sung, Jaeyoung; Choi, Seung Hong; Moon, Woo Kyung; Lee, Gwang; Lee, Bunyeoul; Kim, Sang-Wook

2009-03-14

New quantum dots were fabricated with a core/shell/shell structure consisting of CdTe core/InP shell/ZnS shell of which the InP shell causes a red-shift to the NIR region and the ZnS shell imparts photo-stability; toxicity tests on mammalian cells and NIR imaging of a mouse highlight their potential applications in biomedical imaging.

Symmetry-guided large-scale shell-model theory

Czech Academy of Sciences Publication Activity Database

Launey, K. D.; Dytrych, Tomáš; Draayer, J. P.

2016-01-01

Roč. 89, JUL (2016), s. 101-136 ISSN 0146-6410 R&D Projects: GA ČR GA16-16772S Institutional support: RVO:61389005 Keywords : Ab intio shell -model theory * Symplectic symmetry * Collectivity * Clusters * Hoyle state * Orderly patterns in nuclei from first principles Subject RIV: BE - Theoretical Physics Impact factor: 11.229, year: 2016

Formation of core (polystyrene)-shell (polybenzimidazole) nanoparticles using sulfonated polystyrene as template.

Science.gov (United States)

Hazarika, Mousumi; Arunbabu, Dhamodaran; Jana, Tushar

2010-11-15

We report formation of core (polystyrene)-shell (polybenzimidazole) nanoparticles from a new blend system consisting of an amorphous polymer polybenzimidazole (PBI) and an ionomer sodium salt of sulfonated polystyrene (SPS-Na). The ionomer used for the blending is spherical in shape with sulfonate groups on the surface of the particles. An in depth investigation of the blends at various sulfonation degrees and compositions using Fourier transform infrared (FT-IR) spectroscopy provides direct evidence of specific hydrogen bonding interactions between the N-H groups of PBI and the sulfonate groups of SPS-Na. The disruption of PBI chains self association owing to the interaction between the functional groups of these polymer pairs is the driving force for the blending. Thermodynamical studies carried out by using differential scanning calorimeter (DSC) establish partially miscible phase separated blending of these polymers in a wider composition range. The two distinguishable glass transition temperatures (T(g)) which are different from the neat components and unaltered with the blends composition attribute that the domain size of heterogeneity (d(d)) of the blends is >20 nm since one of the blend component (SPS-Na particle) diameter is ∼70 nm. The diminish of PBI chains self association upon blending with SPS-Na particles and the presence of invariant T(g)'s of the blends suggest the wrapping of PBI chains over the SPS-Na spherical particle surface and hence resulting a core-shell morphology. Transmission electron microscopy (TEM) study provides direct evidence of core-shell nanoparticle formation; where core is the polystyrene and shell is the PBI. The sulfonation degree affects the blends phase separations. The higher degree of sulfonation favors the disruption of PBI self association and thus forms partially miscible two phases blends with core-shell morphology. Copyright © 2010 Elsevier Inc. All rights reserved.

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.

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.

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.

Facile in situ synthesis of wurtzite ZnS/ZnO core/shell heterostructure with highly efficient visible-light photocatalytic activity and photostability

Science.gov (United States)

Xiao, Jian-Hua; Huang, Wei-Qing; Hu, Yong-sheng; Zeng, Fan; Huang, Qin-Yi; Zhou, Bing-Xin; Pan, Anlian; Li, Kai; Huang, Gui-Fang

2018-02-01

High photocatalytic activity and photostability are the pursuit of the goal for designing promising photocatalysts. Herein, using ZnO to encapsulate ZnS nanoparticles is proposed as an effective strategy to enhance photocatalytic activity and anti-photocorrosion. The ZnS/ZnO core/shell heterostructures are obtained via an annealing treatment of ZnS nanoparticles produced by a facile wet chemical approach. Due to its small size, the nascent cubic sphalerite ZnS (s-ZnS) converts into a hexagonal wurtzite ZnS (w-ZnS)/ZnO core/shell structure after annealing treatment. In situ oxidation leads to increasing ZnO, simultaneously decreasing the w-ZnS content in the resultant w-ZnS/ZnO with thermal annealing time. The w-ZnS/ZnO core/shell heterostructures show high photocatalytic activity, demonstrated by the photodegradation rate of methylene blue being up to ten-fold and seven-fold higher than that of s-ZnS under UV and visible light irradiation, respectively, and the high capability of degrading rhodamine B. The enhanced photocatalytic activity may be attributed to the large specific surface and improved charge carrier separation at the core/shell interface. Moreover, it displays high photostability owing to the protection of the ZnO shell, greatly inhibiting the photocorrosion of ZnS. This facile in situ oxidation is effective and easily scalable, providing opportunities for developing novel core/shell structure photocatalysts with high activity and photostability.

Pt monolayer shell on hollow Pd core electrocatalysts: Scale up synthesis, structure, and activity for the oxygen reduction reaction

Directory of Open Access Journals (Sweden)

Vukmirovic Miomir B.

2013-01-01

Full Text Available We report on synthesis, characterization and the oxygen reduction reaction (ORR kinetics of Pt monolayer shell on Pd(hollow, or Pd-Au(hollow core electrocatalysts. Comparison between the ORR catalytic activity of the electrocatalysts with hollow cores and those of Pt solid and Pt hollow nanoparticles has been obtained using the rotating disk electrode technique. Hollow nanoparticles were made using Ni or Cu nanoparticles as sacrificial templates. The Pt ORR specific and mass activities of the electrocatalysts with hollow cores were found considerably higher than those of the electrocatalysts with the solid cores. We attribute this enhanced Pt activity to the smooth surface morphology and hollow-induced lattice contraction, in addition to the mass-saving geometry of hollow particles.

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.

Monolithic photonic crystals created by partial coalescence of core-shell particles.

Science.gov (United States)

Lee, Joon-Seok; Lim, Che Ho; Yang, Seung-Man; Kim, Shin-Hyun

2014-03-11

Colloidal crystals and their derivatives have been intensively studied and developed during the past two decades due to their unique photonic band gap properties. However, complex fabrication procedures and low mechanical stability severely limit their practical uses. Here, we report stable photonic structures created by using colloidal building blocks composed of an inorganic core and an organic shell. The core-shell particles are convectively assembled into an opal structure, which is then subjected to thermal annealing. During the heat treatment, the inorganic cores, which are insensitive to heat, retain their regular arrangement in a face-centered cubic lattice, while the organic shells are partially fused with their neighbors; this forms a monolithic structure with high mechanical stability. The interparticle distance and therefore stop band position are precisely controlled by the annealing time; the distance decreases and the stop band blue shifts during the annealing. The composite films can be further treated to give a high contrast in the refractive index. The inorganic cores are selectively removed from the composite by wet etching, thereby providing an organic film containing regular arrays of air cavities. The high refractive index contrast of the porous structure gives rise to pronounced structural colors and high reflectivity at the stop band position.

Ultrafast Dynamics of Metallo-Dielectric Core-Shell Particles

NARCIS (Netherlands)

Shan, X.

2008-01-01

Optical properties of metallic nano-structures have attracted a lot of attention in the past decades. In this thesis, we focus on nano-sized silica-core gold-shell particles, study the linear, nonlinear and acoustic vibrations of the particles. The linear optical properties in the visible range of

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)

Facile and controllable construction of vanadium pentoxide@conducting polymer core/shell nanostructures and their thickness-dependent synergistic energy storage properties

International Nuclear Information System (INIS)

Tong, Zhongqiu; Liu, Shikun; Li, Xingang; Ding, Yanbo; Zhao, Jiupeng; Li, Yao

2016-01-01

Graphical abstract: Here, we report a novel approach to prepare metal oxide@conducting polymer core/shell hybrids with controlled shell thickness and morphology, and the influence of PANI shell thickness on the electrochemical performance of V 2 O 5 @PANI core/shell hybrids is systematically investigated. Thickness-dependent synergistic electron transport, Li-ion diffusion distance, and shell mechanical strength mechanisms are proposed. - Highlights: • Thickness- and morphology-controlled V 2 O 5 /PANI core/shell hybrid nanofibers are fabricated. • The enhancement of energy storage performance of core/shell hybrids varies with the shell thickness. • Thickness-dependent synergistic electron transport, Li-ion diffusion distances, and shell mechanical strength mechanisms are proposed. - Abstract: Thickness- and morphology-controlled vanadium pentoxide/polyaniline (V 2 O 5 /PANI) core/shell hybrid nanofibers are fabricated by electropolymerization of PANI on V 2 O 5 nanofibers for enhanced energy storage. By simply adjusting the electrodeposition time, the thickness of the PANI shells can be controlled from 5 nm to 47 nm, and the morphology can be changed from coaxial to branched. The influence of shell thickness on the improved Li-ion storage performance of the V 2 O 5 /PANI core/shell nanofibers is systematically investigated, and this enhancement of charge capability and cycling stability strongly varies with the shell thickness. Thickness-dependent synergistic electron transport, Li-ion diffusion distances, and shell mechanical strength mechanisms are also proposed. These results provide meaningful references for developing new functional core/shell materials and high-performance energy storage composite materials.

Novel chiral core-shell silica microspheres with trans-(1R,2R)-diaminocyclohexane bridged in the mesoporous shell: synthesis, characterization and application in high performance liquid chromatography.

Science.gov (United States)

Wu, Xiabing; You, Linjun; Di, Bin; Hao, Weiqiang; Su, Mengxiang; Gu, Yu; Shen, Lingling

2013-07-19

Novel chiral core-shell silica microspheres with trans-(1R,2R)-diaminocyclohexane (DACH) moiety bridged in the mesoporous shell were synthesized using layer-by-layer method. The chiral mesoporous shell around the nonporous silica core was formed by the co-condensation of N,N'-bis-[(triethoxysilyl)propyl]-trans-(1R,2R)-bis-(ureido)-cyclohexane (DACH-BS) and tetraethoxysilane (TEOS) using octadecyltrimethylammonium chloride (C18TMACl) and triblock poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) copolymer (P123) as the templates. The functionalized core-shell silica microspheres were characterized and tested as chiral stationary phases for high performance liquid chromatography (HPLC). R/S-1,1'-bi-2,2'-naphthol, R/S-6,6'-dibromo-1,1'-bi-2-naphthol and R/S-1,1'-bi-2,2'-phenanthrol were enantioseparated rapidly on the column packed with the DACH core-shell silica particles. Moreover, the column packed with core-shell particles exhibited better performance than the column packed with the DACH functionalized periodic mesoporous organosilicas. Copyright © 2013 Elsevier B.V. All rights reserved.

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)

Synthesis of highly monodisperse particles composed of a magnetic core and fluorescent shell.

Science.gov (United States)

Nagao, Daisuke; Yokoyama, Mikio; Yamauchi, Noriko; Matsumoto, Hideki; Kobayashi, Yoshio; Konno, Mikio

2008-09-02

Highly monodisperse particles composed of a magnetic silica core and fluorescent polymer shell were synthesized with a combined technique of heterocoagulation and soap-free emulsion polymerization. Prior to heterocoagulation, monodisperse, submicrometer-sized silica particles were prepared with the Stober method, and magnetic nanoparticles were prepared with a modified Massart method in which a cationic silane coupling agent of N-trimethoxysilylpropyl- N, N, N-trimethylammonium chloride was added just after coprecipitation of Fe (2+) and Fe (3+). The silica particles with negative surface potential were heterocoagulated with the magnetic nanoparticles with positive surface potential. The magnetic silica particles obtained with the heterocoagulation were treated with sodium silicate to modify their surfaces with silica. In the formation of a fluorescent polymer shell onto the silica-coated magnetic silica cores, an amphoteric initiator of 2,2'-azobis[ N-(2-carboxyethyl)-2-2-methylpropionamidine] (VA-057) was used to control the colloidal stability of the magnetic cores during the polymer coating. The polymerization of St in the presence of a hydrophobic fluorophore of pyrene could coat the cores with fluorescent polymer shells, resulting in monodisperse particles with a magnetic silica core and fluorescent polymer shell. Measurements of zeta potential for the composite particles in different pH values indicated that the composite particles had an amphoteric property originating from VA-057 initiator.

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.

Catalyst-free fabrication of novel ZnO/CuO core-Shell nanowires heterojunction: Controlled growth, structural and optoelectronic properties

Science.gov (United States)

Khan, Muhammad Arif; Wahab, Yussof; Muhammad, Rosnita; Tahir, Muhammad; Sakrani, Samsudi

2018-03-01

Development of controlled growth and vertically aligned ZnO/CuO core-shell heterojunction nanowires (NWs) with large area by a catalyst free vapor deposition and oxidation approach has been investigated. Structural characterization reveals successful fabrication of a core ZnO nanowire having single crystalline hexagonal wurtzite structure along [002] direction and CuO nanostructure shell with thickness (8-10 nm) having polycrystalline monoclinic structure. The optical property analysis suggests that the reflectance spectrum of ZnO/CuO heterostructure nanowires is decreased by 18% in the visible range, which correspondingly shows high absorption in this region as compared to pristine ZnO nanowires. The current-voltage (I-V) characteristics of core-shell heterojunction nanowires measured by conductive atomic force microscopy (C-AFM) shows excellent rectifying behavior, which indicates the characteristics of a good p-n junction. The high-resolution transmission electron microscopy (HRTEM) has confirmed the sharp junction interface between the core-shell heterojunction nanowire arrays. The valence band offset and conduction band offset at ZnO/CuO heterointerfaces are measured to be 2.4 ± 0.05 and 0.23 ± 0.005 eV respectively, using X-ray photoelectron spectroscopy (XPS) and a type-II band alignment structure is found. The results of this study contribute to the development of new advanced device heterostructures for solar energy conversion and optoelectronics applications.

Largely improved the low temperature toughness of acrylonitrile-styrene-acrylate (ASA) resin: Fabricated a core-shell structure of two elastomers through the differences of interfacial tensions

Science.gov (United States)

Mao, Zepeng; Zhang, Jun

2018-06-01

The phase morphology of two elastomers (i.e., chlorinated polyethylene (CPE) and polybutadiene rubber (BR)) were devised to be a core-shell structure in acrylonitrile-styrene-acrylate (ASA) resin matrix, via the interfacial tension differences of polymer pairs. Selective extraction test and scanning electron microscopy (SEM) were utilized to verify this special phase morphology. The results demonstrated that the core-shell structure, BR core and CPE shell, significantly contributed to improve the low temperature toughness of ASA/CPE/BR ternary blends, which may be because the nonpolar BR core was segregated from polar ASA by the CPE shell. The CPE shell served dual functions: Not only did it play compatibilizing effect in the interface between BR and ASA matrix, but it also toughened the blends at 25 and 0 °C. The blends of ASA/CPE/BR (100/27/3, w/w/w) and ASA/CPE/BR (100/22/8, w/w/w) showed the peak impact strengths at about 28 and 9 kJ/m2 at 0 and -30 °C, respectively, which were higher than both that of ASA/CPE/BR (100/30/0, w/w/w) and ASA/CPE/BR (100/0/30, w/w/w). Moreover, the impact strength of ternary blends at room temperature kept at 40 kJ/m2 when BR content was lower than 10 phr. Other characterizations including contact angle measurement, dynamic mechanical thermal analysis (DMTA), morphology of impact-fractured surfaces, tensile properties, flexural properties, and Fourier transform infrared spectroscopy (FTIR) were measured as well.

Preparation of porous carbon particle with shell/core structure

Directory of Open Access Journals (Sweden)

2007-05-01

Full Text Available Porous carbon particles with a shell/core structure have been prepared successfully by controlled precipitation of the polymer from droplets of oil-in-water emulsion, followed by curing and carbonization. The droplets of the oil phase are composed of phenolic resin (PFR, a good solvent (ethyl acetate and porogen (Poly(methyl methacrylate, PMMA. The microstructure was characterized in detail by scanning electron microscopy (SEM, transmission electron microscopy (TEM, nitrogen adsorption, and thermo gravimetric analysis (TGA. The obtained carbon particles have a capsular structure with a microporous carbon shell and a mesoporous carbon core. The BET surface area and porous volume are calculated to be 499 m2g-1 and 0.56 cm3g-1, respectively. The effects of the amount of porogen (PMMA, co-solvent (acetone and surfactant on the resultant structure were studied in detail.

Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111) substrate

Science.gov (United States)

Sangeetha, P.; Jeganathan, K.; Ramakrishnan, V.

2013-06-01

The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE) on Si (111) substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E2 (high) and A1 (LO) phonon mode of InN core at 490 and 590 cm-1 respectively and E2 (high) phonon mode of GaN shell at 573 cm-1. The free carrier concentration of InN core is found to be low in the order ˜ 1016 cm-3 due to the screening of charge carriers by thin GaN shell. Diameter of InN core evaluated using the spatial correlation model is consistent with the transmission electron microscopic measurement of ˜15 nm. The phonon-life time of core-shell nanowire structure is estimated to be ˜0.4 ps. The micro-Raman mapping and its corresponding localised spectra for 325 nm excitation exhibit intense E2 (high) phonon mode of GaN shell at 573 cm-1 as the decrease of laser interaction length and the signal intensity is quenched at the voids due to high spacing of NWs.

Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111 substrate

Directory of Open Access Journals (Sweden)

P. Sangeetha

2013-06-01

Full Text Available The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE on Si (111 substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E2 (high and A1 (LO phonon mode of InN core at 490 and 590 cm−1 respectively and E2 (high phonon mode of GaN shell at 573 cm−1. The free carrier concentration of InN core is found to be low in the order ∼ 1016 cm−3 due to the screening of charge carriers by thin GaN shell. Diameter of InN core evaluated using the spatial correlation model is consistent with the transmission electron microscopic measurement of ∼15 nm. The phonon-life time of core-shell nanowire structure is estimated to be ∼0.4 ps. The micro-Raman mapping and its corresponding localised spectra for 325 nm excitation exhibit intense E2 (high phonon mode of GaN shell at 573 cm−1 as the decrease of laser interaction length and the signal intensity is quenched at the voids due to high spacing of NWs.

Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111) substrate

International Nuclear Information System (INIS)

Sangeetha, P.; Ramakrishnan, V.; Jeganathan, K.

2013-01-01

The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE) on Si (111) substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E 2 (high) and A 1 (LO) phonon mode of InN core at 490 and 590 cm −1 respectively and E 2 (high) phonon mode of GaN shell at 573 cm −1 . The free carrier concentration of InN core is found to be low in the order ∼ 10 16 cm −3 due to the screening of charge carriers by thin GaN shell. Diameter of InN core evaluated using the spatial correlation model is consistent with the transmission electron microscopic measurement of ∼15 nm. The phonon-life time of core-shell nanowire structure is estimated to be ∼0.4 ps. The micro-Raman mapping and its corresponding localised spectra for 325 nm excitation exhibit intense E 2 (high) phonon mode of GaN shell at 573 cm −1 as the decrease of laser interaction length and the signal intensity is quenched at the voids due to high spacing of NWs.

Synthesis and optical properties of core-multi-shell CdSe/CdS/ZnS quantum dots: Surface modifications

Science.gov (United States)

Ratnesh, R. K.; Mehata, Mohan Singh

2017-02-01

We report two port synthesis of CdSe/CdS/ZnS core-multi-shell quantum dots (Q-dots) and their structural properties. The multi-shell structures of Q-dots were developed by using successive ionic layer adsorption and reaction (SILAR) technique. The obtained Q-dots show high crystallinity with the step-wise adjustment of lattice parameters in the radial direction. The size of the core and core-shell Q-dots estimated by transmission electron microscopy images and absorption spectra is about 3.4 and 5.3 nm, respectively. The water soluble Q-dots (scheme-1) were prepared by using ligand exchange method, and the effect of pH was discussed regarding the variation of quantum yield (QY). The decrease of a lifetime of core-multi-shell Q-dots with respect to core CdSe indicates that the shell growth may be tuned by the lifetimes. Thus, the study clearly demonstrates that the core-shell approach can be used to substantially improve the optical properties of Q-dots desired for various applications.

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.

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.

Electronic structure and intersubband magnetoabsorption spectra of CdSe/CdS core-shell nanowires

Science.gov (United States)

Xiong, Wen

2016-10-01

The electronic structures of CdSe/CdS core-shell nanowires are calculated based on the effective-mass theory, and it is found that the hole states in CdSe/CdS core-shell nanowires are strongly mixed, which are very different from the hole states in CdSe or CdS nanowires. In addition, we find the three highest hole states at the Γ point are almost localized in the CdSe core and the energies of the hole states in CdSe/CdS core-shell nanowires can be enhanced greatly when the core radius Rc increases and the total radius R is fixed. The degenerate hole states are split by the magnetic field, and the split energies will increase when |Jh | increases from 1/2 to 7/2, while they are almost not influenced by the change of the core radius Rc. The absorption spectra of CdSe/CdS core-shell nanowires at the Γ point are also studied in the magnetic field when the temperature T is considered, and we find there are only two peaks will arise if the core radius Rc and the temperature T increase. The intensity of each optical absorption can be considerably enhanced by increasing the core radius Rc when the temperature T is fixed, it is due to the increase of their optical transition matrix element. Meanwhile, the intensity of each optical absorption can be decreased when the temperature T increases and the core radius Rc is fixed, and this is because the Fermi-Dirac distribution function of the corresponding hole states will increase as the increase of the temperature T.

Ru-core/Cu-shell bimetallic nanoparticles with controlled size formed in one-pot synthesis.

Science.gov (United States)

Helgadottir, I; Freychet, G; Arquillière, P; Maret, M; Gergaud, P; Haumesser, P H; Santini, C C

2014-12-21

Suspensions of bimetallic nanoparticles (NPs) of Ru and Cu have been synthesized by simultaneous decomposition of two organometallic compounds in an ionic liquid. These suspensions have been characterized by Anomalous Small-Angle X-ray Scattering (ASAXS) at energies slightly below the Ru K-edge. It is found that the NPs adopt a Ru-core, a Cu-shell structure, with a constant Ru core diameter of 1.9 nm for all Ru : Cu compositions, while the Cu shell thickness increases with Cu content up to 0.9 nm. The formation of RuCuNPs thus proceeds through rapid decomposition of the Ru precursor into RuNPs of constant size followed by the reaction of the Cu precursor and agglomeration as a Cu shell. Thus, the different decomposition kinetics of precursors make possible the elaboration of core-shell NPs composed of two metals without chemical affinity.

Core/shell structured ZnO/SiO2 nanoparticles: Preparation, characterization and photocatalytic property

International Nuclear Information System (INIS)

Zhai Jing; Tao Xia; Pu Yuan; Zeng Xiaofei; Chen Jianfeng

2010-01-01

ZnO nanoparticles were prepared by a simple chemical synthesis route. Subsequently, SiO 2 layers were successfully coated onto the surface of ZnO nanoparticles to modify the photocatalytic activity in acidic or alkaline solutions. The obtained particles were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectrometry (EDS) and zeta potential. It was found that ultrafine core/shell structured ZnO/SiO 2 nanoparticles were successfully obtained. The photocatalytic performance of ZnO/SiO 2 core/shell structured nanoparticles in Rhodamine B aqueous solution at varied pH value were also investigated. Compared with uncoated ZnO nanoparticles, core/shell structured ZnO/SiO 2 nanoparticles with thinner SiO 2 shell possess improved stability and relatively better photocatalytic activity in acidic or alkaline solutions, which would broaden its potential application in pollutant treatment.

Fabrication of the novel core-shell MCM-41@mTiO{sub 2} composite microspheres with large specific surface area for enhanced photocatalytic degradation of dinitro butyl phenol (DNBP)

Energy Technology Data Exchange (ETDEWEB)

Wei, Xiao-Na; Wang, Hui-Long, E-mail: hlwang@dlut.edu.cn; Li, Zhen-Duo; Huang, Zhi-Qiang; Qi, Hui-Ping; Jiang, Wen-Feng

2016-05-30

Graphical abstract: The mesoporous MCM-41@mTiO{sub 2} composite microspheres with core/shell structure, well-crystallized mesoporous TiO{sub 2} layer, high specific surface, large pore volume and excellent photocatalytic activity were synthesized by combining sol-gel and simple hydrothermal treatment. - Highlights: • The mesoporous MCM-41@mTiO{sub 2} composite was synthesized successfully. • The composite was facilely prepared by combining sol-gel and hydrothermal method. • The composite exhibited high photocatalytic degradation activity for DNBP. • The composite photocatalyst has excellent reproducibility. - Abstract: The mesoporous MCM-41@mTiO{sub 2} core-shell composite microspheres were synthesized successfully by combining sol-gel and simple hydrothermal treatment. The morphology and microstructure characteristics of the synthesized materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), N{sub 2} adsorption-desorption measurements, X-ray powder diffraction (XRD), UV–vis diffuse reflectance spectra (UV–vis/DRS) and Fourier transform infrared spectroscopy (FT-IR). The results indicate that the composite material possesses obvious core/shell structure, a pure mesoporous and well-crystallized TiO{sub 2} layer (mTiO{sub 2}), high specific surface area (316.8 m{sup 2}/g), large pore volume (0.42 cm{sup 3}/g) and two different pore sizes (2.6 nm and 11.0 nm). The photocatalytic activity of the novel MCM-41@mTiO{sub 2} composite was evaluated by degrading 2-sec-butyl-4,6-dinitrophenol (DNBP) in aqueous suspension under UV and visible light irradiation. The results were compared with commercial anatase TiO{sub 2} and Degussa P25 and the enhanced degradation were obtained with the synthesized MCM-41@mTiO{sub 2} composite under the same conditions, which meant that this material can serve as an efficient photocatalyst for the degradation of hazardous organic pollutants in wastewaters.

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.

ZnO@MnO2 Core-Shell Nanofiber Cathodes for High Performance Asymmetric Supercapacitors.

Science.gov (United States)

Radhamani, A V; Shareef, K M; Rao, M S Ramachandra

2016-11-09

Asymmetric supercapacitors (ASCs) with aqueous electrolyte medium have recently become the focus of increasing research. For high performance ASCs, selection of cathode materials play a crucial role, and core-shell nanostructures are found to be a good choice. We successfully synthesized, ZnO@MnO 2 core-shell nanofibers (NFs) by modification of high-aspect-ratio-electrospun ZnO NFs hydrothermally with MnO 2 nanoflakes. High conductivity of the ZnO NFs and the exceptionally high pseudocapacitive nature of MnO 2 nanoflakes coating delivered a specific capacitance of 907 Fg -1 at 0.6 Ag -1 for the core-shell NFs. A simple and cost-effective ASC construction was demonstrated with ZnO@MnO 2 NFs as a battery-type cathode material and a commercial-quality activated carbon as a capacitor-type anode material. The fabricated device functioned very well in a voltage window of 0-2.0 V, and a red-LED was illuminated using a single-celled fabricated ASC device. It was found to deliver a maximum energy density of 17 Whkg -1 and a power density of 6.5 kWkg -1 with capacitance retention of 94% and Coulombic efficiency of 100%. The novel architecture of the ZnO@MnO 2 core-shell nanofibrous material implies the importance of using simple design of fiber-based electrode material by mere changes of core and shell counterparts.

Electrical Conductivity of Ni-YSZ Anode for SOFCs According to the Ni Powder Size Variations in Core-shell Structure

International Nuclear Information System (INIS)

Kang, Young Jin; Jung, Sung-Hun; An, Yong-Tae; Choi, Byung-Hyun; Ji, Mi-Jung

2015-01-01

Ni-YSZ (Y_2O_3-stabilized ZrO_2) core-shell structures were prepared by a high-speed mixing method, starting from Ni particles of three different average sizes of 0.2, 0.4, and 1.8 μm. The Ni-YSZ core-shell structures prepared using Ni particles of size 0.2, 0.4, and 1.8 μm exhibited dense core, porous core, and random-morphology core, respectively. Subsequently, nano structured cermet anodes were fabricated using the prepared Ni-YSZ core-shell powders. During the formation of cermet, the heat treatment of Ni-YSZ core-shell powder results in the eruption of Ni core out of the YSZ shell layers, thereby facilitating the formation of nano structured Ni-YSZ cermet. Systematic studies indicated that the morphology and electrical conductivity of the prepared Ni-YSZ core-shell powders and the cermet anode varied, depending on the initial particle size of the Ni particles. Of the different samples prepared in this study, the Ni-YSZ cermet prepared using Ni particles of size 0.4 μm showed the highest electrical conductivity at 750 ℃.

Electrical Conductivity of Ni-YSZ Anode for SOFCs According to the Ni Powder Size Variations in Core-shell Structure

Energy Technology Data Exchange (ETDEWEB)

Kang, Young Jin; Jung, Sung-Hun; An, Yong-Tae; Choi, Byung-Hyun; Ji, Mi-Jung [Korea Institute of Ceramic Engineering and Technology (KICET), Seoul (Korea, Republic of)

2015-04-15

Ni-YSZ (Y{sub 2}O{sub 3}-stabilized ZrO{sub 2}) core-shell structures were prepared by a high-speed mixing method, starting from Ni particles of three different average sizes of 0.2, 0.4, and 1.8 μm. The Ni-YSZ core-shell structures prepared using Ni particles of size 0.2, 0.4, and 1.8 μm exhibited dense core, porous core, and random-morphology core, respectively. Subsequently, nano structured cermet anodes were fabricated using the prepared Ni-YSZ core-shell powders. During the formation of cermet, the heat treatment of Ni-YSZ core-shell powder results in the eruption of Ni core out of the YSZ shell layers, thereby facilitating the formation of nano structured Ni-YSZ cermet. Systematic studies indicated that the morphology and electrical conductivity of the prepared Ni-YSZ core-shell powders and the cermet anode varied, depending on the initial particle size of the Ni particles. Of the different samples prepared in this study, the Ni-YSZ cermet prepared using Ni particles of size 0.4 μm showed the highest electrical conductivity at 750 ℃.

Core-shell fluorescent silica nanoparticles for sensing near-neutral pH values

International Nuclear Information System (INIS)

Gao, F.; Chen, X.; Ye, Q.; Yao, Z.; Guo, X.; Wang, L.

2011-01-01

pH-responsive fluorescent core-shell silica nanoparticles (SiNPs) were prepared by encapsulating the pH-sensitive fluorophore 8-hydroxypyrene-1,3, 6-trisulfonate into their silica shell via a facile reverse microemulsion method. The resulting SiNPs were characterized by SEM, TEM, fluorescence lifetime spectroscopy, photobleaching experiments, and photoluminescence. The core-shell structure endows the SiNPs with reduced photobleaching, excellent photostability, minimized solvatachromic shift, and increased fluorescence efficiency compared to the free fluorophore in aqueous solution. The dynamic range for sensing pH ranges from 5. 5 to 9. 0. The nanosensors show excellent stability, are highly reproducible, and enable rapid detection of pH. The results obtained with the SiNPs are in good agreement with data obtained with a glass electrode. (author)

Epitaxial TiO 2/SnO 2 core-shell heterostructure by atomic layer deposition

KAUST Repository

Nie, Anmin

2012-01-01

Taking TiO 2/SnO 2 core-shell nanowires (NWs) as a model system, we systematically investigate the structure and the morphological evolution of this heterostructure synthesized by atomic layer deposition/epitaxy (ALD/ALE). All characterizations, by X-ray diffraction, high-resolution transmission electron microscopy, selected area electron diffraction and Raman spectra, reveal that single crystalline rutile TiO 2 shells can be epitaxially grown on SnO 2 NWs with an atomically sharp interface at low temperature (250 °C). The growth behavior of the TiO 2 shells highly depends on the surface orientations and the geometrical shape of the core SnO 2 NW cross-section. Atomically smooth surfaces are found for growth on the {110} surface. Rough surfaces develop on {100} surfaces due to (100) - (1 × 3) reconstruction, by introducing steps in the [010] direction as a continuation of {110} facets. Lattice mismatch induces superlattice structures in the TiO 2 shell and misfit dislocations along the interface. Conformal epitaxial growth has been observed for SnO 2 NW cores with an octagonal cross-section ({100} and {110} surfaces). However, for a rectangular core ({101} and {010} surfaces), the shell also derives an octagonal shape from the epitaxial growth, which was explained by a proposed model based on ALD kinetics. The surface steps and defects induced by the lattice mismatch likely lead to improved photoluminescence (PL) performance for the yellow emission. Compared to the pure SnO 2 NWs, the PL spectrum of the core-shell nanostructures exhibits a stronger emission peak, which suggests potential applications in optoelectronics. © The Royal Society of Chemistry 2012.

Effect of the shell material and confinement type on the conversion efficiency of core/shell quantum dot nanocrystal solar cells.

Science.gov (United States)

Sahin, Mehmet

2018-05-23

In this study, the effects of the shell material and confinement type on the conversion efficiency of core/shell quantum dot nanocrystal (QDNC) solar cells have been investigated in detail. For this purpose, the conventional, i.e. original, detailed balance model, developed by Shockley and Queisser to calculate an upper limit for the conversion efficiency of silicon p-n junction solar cells, is modified in a simple and effective way to calculate the conversion efficiency of core/shell QDNC solar cells. Since the existing model relies on the gap energy ([Formula: see text]) of the solar cell, it does not make an estimation about the effect of QDNC materials on the efficiency of the solar cells, and gives the same efficiency values for several QDNC solar cells with the same [Formula: see text]. The proposed modification, however, estimates a conversion efficiency in relation to the material properties and also the confinement type of the QDNCs. The results of the modified model show that, in contrast to the original one, the conversion efficiencies of different QDNC solar cells, even if they have the same [Formula: see text], become different depending upon the confinement type and shell material of the core/shell QDNCs, and this is crucial in the design and fabrication of the new generation solar cells to predict the confinement type and also appropriate QDNC materials for better efficiency.

Effect of the shell material and confinement type on the conversion efficiency of core/shell quantum dot nanocrystal solar cells

Science.gov (United States)

Sahin, Mehmet

2018-05-01

In this study, the effects of the shell material and confinement type on the conversion efficiency of core/shell quantum dot nanocrystal (QDNC) solar cells have been investigated in detail. For this purpose, the conventional, i.e. original, detailed balance model, developed by Shockley and Queisser to calculate an upper limit for the conversion efficiency of silicon p–n junction solar cells, is modified in a simple and effective way to calculate the conversion efficiency of core/shell QDNC solar cells. Since the existing model relies on the gap energy () of the solar cell, it does not make an estimation about the effect of QDNC materials on the efficiency of the solar cells, and gives the same efficiency values for several QDNC solar cells with the same . The proposed modification, however, estimates a conversion efficiency in relation to the material properties and also the confinement type of the QDNCs. The results of the modified model show that, in contrast to the original one, the conversion efficiencies of different QDNC solar cells, even if they have the same , become different depending upon the confinement type and shell material of the core/shell QDNCs, and this is crucial in the design and fabrication of the new generation solar cells to predict the confinement type and also appropriate QDNC materials for better efficiency.

Complete Au@ZnO core-shell nanoparticles with enhanced plasmonic absorption enabling significantly improved photocatalysis

Science.gov (United States)

Sun, Yiqiang; Sun, Yugang; Zhang, Tao; Chen, Guozhu; Zhang, Fengshou; Liu, Dilong; Cai, Weiping; Li, Yue; Yang, Xianfeng; Li, Cuncheng

2016-05-01

Nanostructured ZnO exhibits high chemical stability and unique optical properties, representing a promising candidate among photocatalysts in the field of environmental remediation and solar energy conversion. However, ZnO only absorbs the UV light, which accounts for less than 5% of total solar irradiation, significantly limiting its applications. In this article, we report a facile and efficient approach to overcome the poor wettability between ZnO and Au by carefully modulating the surface charge density on Au nanoparticles (NPs), enabling rapid synthesis of Au@ZnO core-shell NPs at room temperature. The resulting Au@ZnO core-shell NPs exhibit a significantly enhanced plasmonic absorption in the visible range due to the Au NP cores. They also show a significantly improved photocatalytic performance in comparison with their single-component counterparts, i.e., the Au NPs and ZnO NPs. Moreover, the high catalytic activity of the as-synthesized Au@ZnO core-shell NPs can be maintained even after many cycles of photocatalytic reaction. Our results shed light on the fact that the Au@ZnO core-shell NPs represent a promising class of candidates for applications in plasmonics, surface-enhanced spectroscopy, light harvest devices, solar energy conversion, and degradation of organic pollutants.Nanostructured ZnO exhibits high chemical stability and unique optical properties, representing a promising candidate among photocatalysts in the field of environmental remediation and solar energy conversion. However, ZnO only absorbs the UV light, which accounts for less than 5% of total solar irradiation, significantly limiting its applications. In this article, we report a facile and efficient approach to overcome the poor wettability between ZnO and Au by carefully modulating the surface charge density on Au nanoparticles (NPs), enabling rapid synthesis of Au@ZnO core-shell NPs at room temperature. The resulting Au@ZnO core-shell NPs exhibit a significantly enhanced plasmonic

Quantitative optical extinction-based parametric method for sizing a single core-shell Ag-Ag2O nanoparticle

International Nuclear Information System (INIS)

Santillan, J M J; Scaffardi, L B; Schinca, D C

2011-01-01

This paper develops a parametric method for determining the core radius and shell thickness in small silver-silver-oxide core-shell nanoparticles (Nps) based on single particle optical extinction spectroscopy. The method is based on the study of the relationship between plasmon peak wavelength, full width at half maximum (FWHM) and contrast of the extinction spectra as a function of core radius and shell thickness. This study reveals that plasmon peak wavelength is strongly dependent on shell thickness, whereas FWHM and contrast depend on both variables. These characteristics may be used for establishing an easy and fast stepwise procedure to size core-shell NPs from single particle absorption spectrum. The importance of the method lies in the possibility of monitoring the growth of the silver-oxide layer around small spherical silver Nps in real time. Using the electrostatic approximation of Mie theory, core-shell single particle extinction spectra were calculated for a silver particle's core size smaller than about 20 nm and different thicknesses of silver oxide around it. Analysis of the obtained curves shows a very particular characteristic of the plasmon peak of small silver-silver-oxide Nps, expressed in the fact that its position is strongly dependent on oxide thickness and weakly dependent on the core radius. Even a very thin oxide layer shifts the plasmon peak noticeably, enabling plasmon tuning with appropriate shell thickness. This characteristic, together with the behaviour of FWHM and contrast of the extinction spectra can be combined into a parametric method for sizing both core and shell of single silver Nps in a medium using only optical information. In turn, shell thickness can be related to oxygen content in the Np's surrounding media. The method proposed is applied to size silver Nps from single particle extinction spectrum. The results are compared with full optical spectrum fitting using the electrostatic approximation in Mie theory. The method

Tailored Synthesis of Core-Shell Mesoporous Silica Particles—Optimization of Dye Sorption Properties

Directory of Open Access Journals (Sweden)

Andrzej Baliś

2018-04-01

Full Text Available Monodisperse spherical silica particles, with solid cores and mesoporous shells (SCMS, were synthesized at various temperatures using a one-pot method utilizing a cationic surfactant template. The temperature of the synthesis was found to significantly affect the diameters of both the cores (ca. 170–800 nm and shells (ca. 11–80 nm of the particles, which can be tailored for specific applications that require a high specific surface area of the nanocarriers (mesoporous shells and simultaneously their mechanical robustness for, e.g., facile isolation from suspensions (dense cores. The applied method enabled the formation of the relatively thick mesoporous shells at conditions below room temperature. Radially ordered pores with narrow distributions of their sizes in 3–4 nm range were found in the shells. The adsorption ability of the SCMS particles was studied using rhodamine 6G as a model dye. Decolorization of the dye solution in the presence of the SCMS particles was correlated with their structure and specific surface area and reached its maximum for the particles synthesized at 15 °C. The presented strategy may be applied for the fine-tuning of the structure of SCMS particles and the enhancement of their adsorption capabilities.

Structural Color Palettes of Core-Shell Photonic Ink Capsules Containing Cholesteric Liquid Crystals.

Science.gov (United States)

Lee, Sang Seok; Seo, Hyeon Jin; Kim, Yun Ho; Kim, Shin-Hyun

2017-06-01

Photonic microcapsules with onion-like topology are microfluidically designed to have cholesteric liquid crystals with opposite handedness in their core and shell. The microcapsules exhibit structural colors caused by dual photonic bandgaps, resulting in a rich variety of color on the optical palette. Moreover, the microcapsules can switch the colors from either core or shell depending on the selection of light-handedness. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation and recognition of surface molecularly imprinted core-shell microbeads for protein in aqueous solutions

International Nuclear Information System (INIS)

Lu Yan; Yan Changling; Gao Shuyan

2009-01-01

In this paper, a surface molecular imprinting technique was reported for preparing core-shell microbeads of protein imprinting, and bovine hemoglobin or bovine serum albumin were used as model proteins for studying the imprinted core-shell microbeads. 3-Aminophenylboronic acid (APBA) was polymerized onto the surface of polystyrene microbead in the presence of the protein templates to create protein-imprinted core-shell microbeads. The various samples were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) methods. The effect of pH on rebinding of the template hemoglobin, the specific binding and selective recognition were studied for the imprinted microbeads. The results show that the bovine hemoglobin-imprinted core-shell microbeads were successfully created. The shell was a sort of imprinted thin films with porous structure and larger surface areas. The imprinted microbeads have good selectivity for templates and high stability. Due to the recognition sites locating at or closing to the surface, these imprinted microbeads have good property of mass-transport. Unfortunately, the imprint technology was not successfully applied to imprinting bovine serum albumin (BSA).

Preparation and recognition of surface molecularly imprinted core-shell microbeads for protein in aqueous solutions

Energy Technology Data Exchange (ETDEWEB)

Lu Yan, E-mail: yanlu2001@sohu.com [College of Chemistry and Environmental Science, Henan Normal University, 46 Jlanshe Road, Xinxiang 453007 (China); Yan Changling; Gao Shuyan [College of Chemistry and Environmental Science, Henan Normal University, 46 Jlanshe Road, Xinxiang 453007 (China)

2009-04-01

In this paper, a surface molecular imprinting technique was reported for preparing core-shell microbeads of protein imprinting, and bovine hemoglobin or bovine serum albumin were used as model proteins for studying the imprinted core-shell microbeads. 3-Aminophenylboronic acid (APBA) was polymerized onto the surface of polystyrene microbead in the presence of the protein templates to create protein-imprinted core-shell microbeads. The various samples were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) methods. The effect of pH on rebinding of the template hemoglobin, the specific binding and selective recognition were studied for the imprinted microbeads. The results show that the bovine hemoglobin-imprinted core-shell microbeads were successfully created. The shell was a sort of imprinted thin films with porous structure and larger surface areas. The imprinted microbeads have good selectivity for templates and high stability. Due to the recognition sites locating at or closing to the surface, these imprinted microbeads have good property of mass-transport. Unfortunately, the imprint technology was not successfully applied to imprinting bovine serum albumin (BSA).

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.

The linearly scaling 3D fragment method for large scale electronic structure calculations

Energy Technology Data Exchange (ETDEWEB)

Zhao Zhengji [National Energy Research Scientific Computing Center (NERSC) (United States); Meza, Juan; Shan Hongzhang; Strohmaier, Erich; Bailey, David; Wang Linwang [Computational Research Division, Lawrence Berkeley National Laboratory (United States); Lee, Byounghak, E-mail: ZZhao@lbl.go [Physics Department, Texas State University (United States)

2009-07-01

The linearly scaling three-dimensional fragment (LS3DF) method is an O(N) ab initio electronic structure method for large-scale nano material simulations. It is a divide-and-conquer approach with a novel patching scheme that effectively cancels out the artificial boundary effects, which exist in all divide-and-conquer schemes. This method has made ab initio simulations of thousand-atom nanosystems feasible in a couple of hours, while retaining essentially the same accuracy as the direct calculation methods. The LS3DF method won the 2008 ACM Gordon Bell Prize for algorithm innovation. Our code has reached 442 Tflop/s running on 147,456 processors on the Cray XT5 (Jaguar) at OLCF, and has been run on 163,840 processors on the Blue Gene/P (Intrepid) at ALCF, and has been applied to a system containing 36,000 atoms. In this paper, we will present the recent parallel performance results of this code, and will apply the method to asymmetric CdSe/CdS core/shell nanorods, which have potential applications in electronic devices and solar cells.

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

KAUST Repository

Zhong, Bo; Sai, Tianqi; Xia, Long; Yu, Yuanlie; Wen, Guangwu

2017-01-01

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.

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.

Preparation, process optimization and characterization of core-shell polyurethane/chitosan nanofibers as a potential platform for bioactive scaffolds.

Science.gov (United States)

Maleknia, Laleh; Dilamian, Mandana; Pilehrood, Mohammad Kazemi; Sadeghi-Aliabadi, Hojjat; Hekmati, Amir Houshang

2018-06-01

In this paper, polyurethane (PU), chitosan (Cs)/polyethylene oxide (PEO), and core-shell PU/Cs nanofibers were produced at the optimal processing conditions using electrospinning technique. Several methods including SEM, TEM, FTIR, XRD, DSC, TGA and image analysis were utilized to characterize these nanofibrous structures. SEM images exhibited that the core-shell PU/Cs nanofibers were spun without any structural imperfections at the optimized processing conditions. TEM image confirmed the PU/Cs core-shell nanofibers were formed apparently. It that seems the inclusion of Cs/PEO to the shell, did not induce the significant variations in the crystallinity in the core-shell nanofibers. DSC analysis showed that the inclusion of Cs/PEO led to the glass temperature of the composition increased significantly compared to those of neat PU nanofibers. The thermal degradation of core-shell PU/Cs was similar to PU nanofibers degradation due to the higher PU concentration compared to other components. It was hypothesized that the core-shell PU/Cs nanofibers can be used as a potential platform for the bioactive scaffolds in tissue engineering. Further biological tests should be conducted to evaluate this platform as a three dimensional scaffold with the capabilities of releasing the bioactive molecules in a sustained manner.

Large-scale Instability during Gravitational Collapse with Neutrino Transport and a Core-Collapse Supernova

Science.gov (United States)

Aksenov, A. G.; Chechetkin, V. M.

2018-04-01

Most of the energy released in the gravitational collapse of the cores of massive stars is carried away by neutrinos. Neutrinos play a pivotal role in explaining core-collape supernovae. Currently, mathematical models of the gravitational collapse are based on multi-dimensional gas dynamics and thermonuclear reactions, while neutrino transport is considered in a simplified way. Multidimensional gas dynamics is used with neutrino transport in the flux-limited diffusion approximation to study the role of multi-dimensional effects. The possibility of large-scale convection is discussed, which is interesting both for explaining SN II and for setting up observations to register possible high-energy (≳10MeV) neutrinos from the supernova. A new multi-dimensional, multi-temperature gas dynamics method with neutrino transport is presented.

Fabrication of core-shell nanostructures via silicon on insulator dewetting and germanium condensation: towards a strain tuning method for SiGe-based heterostructures in a three-dimensional geometry.

Science.gov (United States)

Naffouti, Meher; David, Thomas; Benkouider, Abdelmalek; Favre, Luc; Cabie, Martiane; Ronda, Antoine; Berbezier, Isabelle; Abbarchi, Marco

2016-07-29

We report on a novel method for the implementation of core-shell SiGe-based nanocrystals combining silicon on insulator dewetting in a molecular beam epitaxy reactor with an ex situ Ge condensation process. With an in situ two-step process (annealing and Ge deposition) we produce two families of islands on the same sample: Si-rich, formed during the first step and, all around them, Ge-rich formed after Ge deposition. By increasing the amount of Ge deposited on the annealed samples from 0 to 18 monolayers, the islands' shape in the Si-rich zones can be tuned from elongated and flat to more symmetric and with a larger vertical aspect ratio. At the same time, the spatial extension of the Ge-rich zones is progressively increased as well as the Ge content in the islands. Further processing by ex situ rapid thermal oxidation results in the formation of a core-shell composition profile in both Si and Ge-rich zones with atomically sharp heterointerfaces. The Ge condensation induces a Ge enrichment of the islands' shell of up to 50% while keeping a pure Si core in the Si-rich zones and a ∼25% SiGe alloy in the Ge-rich ones. The large lattice mismatch between core and shell, the absence of dislocations and the islands' monocrystalline nature render this novel class of nanostructures a promising device platform for strain-based band-gap engineering. Finally, this method can be used for the implementation of ultralarge scale meta-surfaces with dielectric Mie resonators for light manipulation at the nanoscale.

SUPERGIANT SHELLS AND MOLECULAR CLOUD FORMATION IN THE LARGE MAGELLANIC CLOUD

Energy Technology Data Exchange (ETDEWEB)

Dawson, J. R.; Dickey, John M. [School of Mathematics and Physics, University of Tasmania, Sandy Bay Campus, Churchill Avenue, Sandy Bay, TAS 7005 (Australia); McClure-Griffiths, N. M. [Australia Telescope National Facility, CSIRO Astronomy and Space Science, Marsfield NSW 2122 (Australia); Wong, T. [Astronomy Department, University of Illinois, Urbana, IL 61801 (United States); Hughes, A. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117, Heidelberg (Germany); Fukui, Y. [Department of Physics and Astrophysics, Nagoya University, Chikusa-ku, Nagoya (Japan); Kawamura, A., E-mail: joanne.dawson@utas.edu.au [National Astronomical Observatory of Japan, Tokyo 181-8588 (Japan)

2013-01-20

We investigate the influence of large-scale stellar feedback on the formation of molecular clouds in the Large Magellanic Cloud (LMC). Examining the relationship between H I and {sup 12}CO(J = 1-0) in supergiant shells (SGSs), we find that the molecular fraction in the total volume occupied by SGSs is not enhanced with respect to the rest of the LMC disk. However, the majority of objects ({approx}70% by mass) are more molecular than their local surroundings, implying that the presence of a supergiant shell does on average have a positive effect on the molecular gas fraction. Averaged over the full SGS sample, our results suggest that {approx}12%-25% of the molecular mass in supergiant shell systems was formed as a direct result of the stellar feedback that created the shells. This corresponds to {approx}4%-11% of the total molecular mass of the galaxy. These figures are an approximate lower limit to the total contribution of stellar feedback to molecular cloud formation in the LMC, and constitute one of the first quantitative measurements of feedback-triggered molecular cloud formation in a galactic system.

Magnetic properties of Ni/Au core/shell studied by Monte Carlo simulations

Energy Technology Data Exchange (ETDEWEB)

Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, Sidi Bouzid, Safi, 63 4600 (Morocco); LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Av. Ibn Batouta, B.P. 1014, Rabat (Morocco); Bahmad, L. [LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Av. Ibn Batouta, B.P. 1014, Rabat (Morocco); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Benyoussef, A. [LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Av. Ibn Batouta, B.P. 1014, Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble cedex 9 (France)

2014-01-10

The magnetic properties of ferromagnetic Ni/Au core/shell have been studied using Monte Carlo simulations within the Ising model framework. The considered Hamiltonian includes the exchange interactions between Ni–Ni, Au–Au and Ni–Au and the external magnetic field. The thermal total magnetizations and total magnetic susceptibilities of core/shell Ni/Au are computed. The critical temperature is deduced. The exchange interaction between Ni and Au atoms is obtained. In addition, the total magnetizations versus the external magnetic field and crystal filed for different temperature are also established.

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.

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.

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.

A broadening temperature sensitivity range with a core-shell YbEr@YbNd double ratiometric optical nanothermometer

Science.gov (United States)

Marciniak, L.; Prorok, K.; Francés-Soriano, L.; Pérez-Prieto, J.; Bednarkiewicz, A.

2016-02-01

The chemical architecture of lanthanide doped core-shell up-converting nanoparticles can be engineered to purposely design the properties of luminescent nanomaterials, which are typically inaccessible to their homogeneous counterparts. Such an approach allowed to shift the up-conversion excitation wavelength from ~980 to the more relevant ~808 nm or enable Tb or Eu up-conversion emission, which was previously impossible to obtain or inefficient. Here, we address the issue of limited temperature sensitivity range of optical lanthanide based nano-thermometers. By covering Yb-Er co-doped core nanoparticles with the Yb-Nd co-doped shell, we have intentionally combined temperature dependent Er up-conversion together with temperature dependent Nd --> Yb energy transfer, and thus have expanded the temperature response range ΔT of a single nanoparticle based optical nano-thermometer under single ~808 nm wavelength photo-excitation from around ΔT = 150 K to over ΔT = 300 K (150-450 K). Such engineered nanocrystals are suitable for remote optical temperature measurements in technology and biotechnology at the sub-micron scale.The chemical architecture of lanthanide doped core-shell up-converting nanoparticles can be engineered to purposely design the properties of luminescent nanomaterials, which are typically inaccessible to their homogeneous counterparts. Such an approach allowed to shift the up-conversion excitation wavelength from ~980 to the more relevant ~808 nm or enable Tb or Eu up-conversion emission, which was previously impossible to obtain or inefficient. Here, we address the issue of limited temperature sensitivity range of optical lanthanide based nano-thermometers. By covering Yb-Er co-doped core nanoparticles with the Yb-Nd co-doped shell, we have intentionally combined temperature dependent Er up-conversion together with temperature dependent Nd --> Yb energy transfer, and thus have expanded the temperature response range ΔT of a single nanoparticle

Controllable dielectric and electrical performance of polymer composites with novel core/shell-structured conductive particles through biomimetic method

International Nuclear Information System (INIS)

Yang, Dan; Tian, Ming; Wang, Wencai; Li, Dongdong; Li, Runyuan; Liu, Haoliang; Zhang, Liqun

2013-01-01

Highlights: ► Conductive core/shell-structured particles were synthesized by biomimetic method. ► These particles with silica/poly(dopamine)/silver core and poly(dopamine) shell. ► Dielectric composites were prepared with resulted particles and silicone elastomer. ► The dielectric properties of the composites can be controlled by shell thickness. ► This biomimetic method is simple, nontoxic, efficient and easy to control. - Abstract: Novel silica/poly(dopamine)/silver (from inner to outer) (denoted as SiO 2 /PDA/Ag) conductive micro-particles were first synthesized by biomimetic poly(dopamine) coating. These micro-particles were then coated with a poly(dopamine) layer to form core/shell-structured particles, with silica/poly(dopamine)/silver core and poly(dopamine) shell (denoted as SiO 2 /PDA/Ag/PDA). This multilayer core/shell micro-particles were confirmed by scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscope. Polymer composites were then prepared by mechanical blending of poly(dimethyl siloxane) and the core/shell-structured particles. It was found that the silver layer and the poly(dopamine) shell had good adhesion with substrate and they kept intact even under violent shearing stress during mechanical mixing. The effect of the thickness of outermost poly(dopamine) shell as well as the loading amount of this filler on the dielectric and electrical properties of the composites was further studied. The results showed that the dielectric constant, dielectric loss, and conductivity of the composites decreased with increasing shell thickness (10–53 nm) at the same loading level. And the maximal dielectric constant of composites was achieved in the composites filled with SiO 2 /PDA/Ag/PDA (with 10–15 nm PDA shell) particles, which was much larger than that of the composite filled with SiO 2 /PDA/Ag particles without insulative PDA shell. At the same time, the composites can change

Shell model in-water frequencies of the core barrel

International Nuclear Information System (INIS)

Takeuchi, K.; De Santo, D.F.

1980-01-01

Natural frequencies of a 1/24th-scale core barrel/vessel model in air and in water are measured by determining frequency responses to applied forces. The measured data are analyzed by the use of the one-dimensional fluid-structure computer code, MULTIFLEX, developed to calculate the hydraulic force. The fluid-structure interaction in the downcomer annulus is computed with a one-dimensional network model formed to be equivalent to two-dimensional fluid-structure interaction. The structural model incorporated in MULTIFLEX is substantially simpler than that necessary for structural analyses. Proposed for computation of structural dynamics is the projector method than can deal with the beam mode by modal analysis and the other shell modes by a direct integration method. Computed in-air and in-water frequencies agree fairly well with the experimental data, verifying the above MULTIFLEX technique

One-by-one imprinting in two eccentric layers of hollow core-shells: Sequential electroanalysis of anti-HIV drugs.

Science.gov (United States)

Singh, Kislay; Jaiswal, Swadha; Singh, Richa; Fatma, Sana; Prasad, Bhim Bali

2018-07-15

Double layered one-by-one imprinted hollow core-shells@ pencil graphite electrode was fabricated for sequential sensing of anti-HIV drugs. For this, two eccentric layers were developed on the surface of vinylated silica nanospheres to obtain double layered one-by-one imprinted solid core-shells. This yielded hollow core-shells on treatment with hydrofluoric acid. The modified hollow core-shells (single layered dual imprinted) evolved competitive diffusion of probe/analyte molecules. However, the corresponding double layered one-by-one imprinted hollow core-shells (outer layer imprinted with Zidovudine, and inner layer with Lamivudine) were found relatively better owing to their bilateral diffusions into molecular cavities, without any competition. The entire work is based on differential pulse anodic stripping voltammetry at double layered one-by-one imprinted hollow core-shells. This resulted in indirect detection of electro inactive targets with limits of detection as low as 0.91 and 0.12 (aqueous sample), 0.94 and 0.13 (blood serum), and 0.99 and 0.20 ng mL -1 (pharmaceutics) for lamivudine and zidovudine, respectively in anti-HIV drug combination. Copyright © 2018 Elsevier B.V. All rights reserved.

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.

Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111) substrate

Energy Technology Data Exchange (ETDEWEB)

Sangeetha, P.; Ramakrishnan, V. [Department of Laser Studies, School of Physics, Madurai Kamaraj University, Madurai-625 021 (India); Jeganathan, K. [Centre for Nanoscience and Nanotechnology, School of Physics, Bharathidasan University, Tiruchirappalli-620 024 (India)

2013-06-15

The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE) on Si (111) substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E{sub 2} (high) and A{sub 1} (LO) phonon mode of InN core at 490 and 590 cm{sup -1} respectively and E{sub 2} (high) phonon mode of GaN shell at 573 cm{sup -1}. The free carrier concentration of InN core is found to be low in the order {approx} 10{sup 16} cm{sup -3} due to the screening of charge carriers by thin GaN shell. Diameter of InN core evaluated using the spatial correlation model is consistent with the transmission electron microscopic measurement of {approx}15 nm. The phonon-life time of core-shell nanowire structure is estimated to be {approx}0.4 ps. The micro-Raman mapping and its corresponding localised spectra for 325 nm excitation exhibit intense E{sub 2} (high) phonon mode of GaN shell at 573 cm{sup -1} as the decrease of laser interaction length and the signal intensity is quenched at the voids due to high spacing of NWs.

Large scale nuclear structure studies

International Nuclear Information System (INIS)

Faessler, A.

1985-01-01

Results of large scale nuclear structure studies are reported. The starting point is the Hartree-Fock-Bogoliubov solution with angular momentum and proton and neutron number projection after variation. This model for number and spin projected two-quasiparticle excitations with realistic forces yields in sd-shell nuclei similar good results as the 'exact' shell-model calculations. Here the authors present results for a pf-shell nucleus 46 Ti and results for the A=130 mass region where they studied 58 different nuclei with the same single-particle energies and the same effective force derived from a meson exchange potential. They carried out a Hartree-Fock-Bogoliubov variation after mean field projection in realistic model spaces. In this way, they determine for each yrast state the optimal mean Hartree-Fock-Bogoliubov field. They apply this method to 130 Ce and 128 Ba using the same effective nucleon-nucleon interaction. (Auth.)

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.

Morphological control of Ni/NiO core/shell nanoparticles and production of hollow NiO nanostructures

Energy Technology Data Exchange (ETDEWEB)

Chopra, Nitin [University of Alabama, Department of Metallurgical and Materials Engineering, Center for Materials for Information Technology (MINT) (United States); Claypoole, Leslie [Fairmont State University (United States); Bachas, Leonidas G., E-mail: bachas@uky.ed [University of Kentucky, Department of Chemistry (United States)

2010-10-15

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.

pH-sensitive chitosan/alginate core-shell nanoparticles for efficient and safe oral insulin delivery.

Science.gov (United States)

Mukhopadhyay, Piyasi; Chakraborty, Souma; Bhattacharya, Sourav; Mishra, Roshnara; Kundu, P P

2015-01-01

Chitosan-alginate (CS/ALG) nanoparticles were prepared by formation of an ionotropic pre-gelation of an alginate (ALG) core entrapping insulin, followed by chitosan (CS) polyelectrolyte complexation, for successful oral insulin administration. Mild preparation process without harsh chemicals is aimed at improving insulin bio-efficiency in in vivo model. The nanoparticles showed an average particle size of 100-200 nm in dynamic light scattering (DLS), with almost spherical or sub-spherical shape and ∼ 85% of insulin encapsulation. Again, retention of almost entire amount of encapsulated insulin in simulated gastric buffer followed by its sustained release in simulated intestinal condition proved its pH sensitivity in in vitro release studies. Significant hypoglycemic effects with improved insulin-relative bioavailability (∼ 8.11%) in in vivo model revealed the efficacy of these core-shell nanoparticles of CS/ALG as an oral insulin carrier. No systemic toxicity was found after its peroral treatment, suggesting these core-shell nanoparticles as a promising device for potential oral insulin delivery. Copyright © 2014 Elsevier B.V. All rights reserved.

Phosphine-free synthesis and characterization of type-II ZnSe/CdS core-shell quantum dots

Science.gov (United States)

Ghasemzadeh, Roghayyeh; Armanmehr, Mohammad Hasan; Abedi, Mohammad; Fateh, Davood Sadeghi; Bahreini, Zaker

2018-01-01

A phosphine-free route for synthesis of type-II ZnSe/CdS core-shell quantum dots, using green, low cost and environmentally friendly reagents and phosphine-free solvents such as 1-octadecene (ODE) and liquid paraffin has been reported. Hot-injection technique has been used for the synthesis of ZnSe core quantum dots. The CdS shell quantum dots prepared by reaction of CdO precursor and S powder in 1-octadecene (ODE). The ZnSe/CdS core-shell quantum dots were synthesized via successive ion layer adsorption and reaction (SILAR) technique. The characterization of produced quantum dots were performed by absorption and fluorescence spectroscopy, X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). The results showed the formation of type-II ZnSe/CdS core-shell quantum dots with FWHM 32 nm and uniform size distribution.

Nanocrystalline p-hydroxyacetanilide (paracetamol) and gold core-shell structure as a model drug deliverable organic-inorganic hybrid nanostructure

Science.gov (United States)

Das, Subhojit; Paul, Anumita; Chattopadhyay, Arun

2013-09-01

We report on the generation of core-shell nanoparticles (NPs) having an organic nanocrystal (NC) core coated with an inorganic metallic shell, being dispersed in aqueous medium. First, NCs of p-hydroxyacetanilide (pHA)--known also as paracetamol--were generated in an aqueous medium. Transmission electron microscopy (TEM) and powder X-ray diffraction (XRD) evidenced the formation of pHA NCs and of their crystalline nature. The NCs were then coated with Au to form pHA@Au core-shell NPs, where the thickness of the Au shell was on the order of nanometers. The formation of Au nanoshell--surrounding pHA NC--was confirmed from its surface plasmon resonance (SPR) band in the UV/Vis spectrum and by TEM measurements. Further, on treatment of the core-shell particles with a solution comprising NaCl and HCl (pH paracetamol--were generated in an aqueous medium. Transmission electron microscopy (TEM) and powder X-ray diffraction (XRD) evidenced the formation of pHA NCs and of their crystalline nature. The NCs were then coated with Au to form pHA@Au core-shell NPs, where the thickness of the Au shell was on the order of nanometers. The formation of Au nanoshell--surrounding pHA NC--was confirmed from its surface plasmon resonance (SPR) band in the UV/Vis spectrum and by TEM measurements. Further, on treatment of the core-shell particles with a solution comprising NaCl and HCl (pH < 3), the Au shell could be dissolved, subsequently releasing pHA molecules. The dissolution of Au shell was marked by a gradual diminishing of its SPR band, while the release of pHA molecules in the solution was confirmed from TEM and FTIR studies. The findings suggest that the core-shell NP could be hypothesized to be a model for encapsulating drug molecules, in their crystalline forms, for slow as well as targeted release. Electronic supplementary information (ESI) available: See DOI: 10.1039/c3nr03566b

High performance of PbSe/PbS core/shell quantum dot heterojunction solar cells: short circuit current enhancement without the loss of open circuit voltage by shell thickness control.

Science.gov (United States)

Choi, Hyekyoung; Song, Jung Hoon; Jang, Jihoon; Mai, Xuan Dung; Kim, Sungwoo; Jeong, Sohee

2015-11-07

We fabricated heterojunction solar cells with PbSe/PbS core shell quantum dots and studied the precisely controlled PbS shell thickness dependency in terms of optical properties, electronic structure, and solar cell performances. When the PbS shell thickness increases, the short circuit current density (JSC) increases from 6.4 to 11.8 mA cm(-2) and the fill factor (FF) enhances from 30 to 49% while the open circuit voltage (VOC) remains unchanged at 0.46 V even with the decreased effective band gap. We found that the Fermi level and the valence band maximum level remain unchanged in both the PbSe core and PbSe/PbS core/shell with a less than 1 nm thick PbS shell as probed via ultraviolet photoelectron spectroscopy (UPS). The PbS shell reduces their surface trap density as confirmed by relative quantum yield measurements. Consequently, PbS shell formation on the PbSe core mitigates the trade-off relationship between the open circuit voltage and the short circuit current density. Finally, under the optimized conditions, the PbSe core with a 0.9 nm thick shell yielded a power conversion efficiency of 6.5% under AM 1.5.

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, SnO2 and In2O3 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.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, SnO2 and In2O3 are used as examples. We also show that linear chains of short ZnO nanorods embedded in

Drug release from core-shell PVA/silk fibroin nanoparticles fabricated by one-step electrospraying.

Science.gov (United States)

Cao, Yang; Liu, Fengqiu; Chen, Yuli; Yu, Tao; Lou, Deshuai; Guo, Yuan; Li, Pan; Wang, Zhigang; Ran, Haitao

2017-09-20

Silk fibroin (SF), a FDA-approved natural protein, is renowned for its great biocompatibility, biodegradability, and mechanical properties. SF-based nanoparticles provide new options for drug delivery with their tunable drug loading and release properties. To take advantage of the features of carrier polymers, we present a one-step electrospraying method that combines SF, polyvinyl alcohol (PVA) and therapeutic drugs without an emulsion process. A distinct core-shell structure was obtained with the PVA core and silk shell after the system was properly set up. The model drug, doxorubicin, was encapsulated in the core with a greater than 90% drug encapsulation efficiency. Controllable drug release profiles were achieved by alternating the PVA/SF ratio. Although the initial burst release of the drug was minimized by the SF coating, a large number of drug molecules remained entrapped by the carrier polymers. To promote and trigger drug release on demand, low intensity focused ultrasound (US) was applied. The US was especially advantageous for accelerating the drug diffusion and release. The apoptotic activity of MDA-MB-231 cells incubated with drug-loaded nanoparticles was found to increase with time. In addition, we also observed PVA/SF nanoparticles that could elicit a drug release in response to pH.

TiN/VN composites with core/shell structure for supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Dong, Shanmu; Chen, Xiao [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao 266101 (China); Gu, Lin [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 9808577 (Japan); Zhou, Xinhong [Qingdao University of Science and Technology, Qingdao 266101 (China); Wang, Haibo; Liu, Zhihong; Han, Pengxian; Yao, Jianhua; Wang, Li [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao 266101 (China); Cui, Guanglei, E-mail: cuigl@qibebt.ac.cn [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao 266101 (China); Chen, Liquan [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao 266101 (China); Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China)

2011-06-15

Research highlights: {yields} Vanadium and titanium nitride nanocomposite with core-shell structure was prepared. {yields} TiN/VN composites with different V:Ti molar ratios were obtained. {yields} TiN/VN composites can provide promising electronic conductivity and favorable capacity storage. -- Abstract: TiN/VN core-shell composites are prepared by a two-step strategy involving coating of commercial TiN nanoparticles with V{sub 2}O{sub 5}.nH{sub 2}O sols followed by ammonia reduction. The highest specific capacitance of 170 F g{sup -1} is obtained when scanned at 2 mV s{sup -1} and a promising rate capacity performance is maintained at higher voltage sweep rates. These results indicate that these composites with good electronic conductivity can deliver a favorable capacity performance.

Synthesis, characterization of Ag-Au core-shell bimetal nanoparticles and its application for electrocatalytic oxidation/sensing of L-methionine

Energy Technology Data Exchange (ETDEWEB)

Murugavelu, M.; Karthikeyan, B., E-mail: bkarthi_au@yahoo.com

2017-01-01

The Ag-Au core-shell bimetal nanoparticles (BNPs) was prepared using chemical reduction method. The prepared Ag-Au core-shell BNPs were characterized by UV–Visible (UV–Vis) spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) pattern. These results showed the Ag-Au BNPs exhibited core-shell shape. The Ag-Au core-shell BNPs was examined towards electrocatalytic oxidation of L-methionine (L-Met) by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry. According to the results, L-Met is determined with detection limit of 30 μM. Interference studies in biological buffer was also studied. - Highlights: • The Ag-Au core-shell BNPs are synthesized and characterized • Ag-Au core-shell BNPs modified (Ag-Au/GCE) has been examined for L-methionine oxidation/sensing by using electrochemical method. • The Ag-Au/GCE exhibited good performance for the detection of L-methionine.

Characterization of the core-shell interaction of differently stabilized transition-metal nanoparticles by means of X-ray absorption spectroscopy

International Nuclear Information System (INIS)

Bucher, S.

2002-05-01

Transition metal nanoparticles with different surfactants were investigated using X-ray absorption spectroscopy (XAS) to obtain information about the interaction between metal core and protecting shell. For tetraalkylammoniumchloride stabilized Pd- and Co-colloids, a detailed model of the interaction between the metal core and the stabilizing shell could be established, in which chlorine is the connecting element between the metal core and the organic protection cover. Different lengths of the alkyl-chains can cause different equilibrium positions for the chlorine atoms. At aluminum-organic stabilized Pt-colloids, Al K-XANES and Pt L III -XAS were carried out. In this case, it turned out that aluminum is the connecting element between metal core and protection shell. After modification of the shell by connecting different molecules to the outside of the shell, rearrangements of the shell could be observed. In contrast to the surfactant stabilized systems discussed above, metallic covers, especially gold coatings, of Co-particles did not lead to a complete protection shell. In all cases, the cobalt in the nanoparticles was oxidized. A core shell structure could not be verified for any of the metallic stabilized colloids. (orig.)

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.

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.