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Sample records for mediated polymeric core-shell

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

    PubMed

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

    2016-07-01

    We developed a novel method for synthesizing epoxy-acrylic hybrid latexes. We first prepared an aqueous dispersion of high molecular weight solid epoxy prepolymers using a mechanical dispersion process at elevated temperatures, and we subsequently used the epoxy dispersion as a seed in the emulsion polymerization of acrylic monomers comprising methyl methacrylate (MMA) and methacrylic acid (MAA). Advanced analytical techniques, such as scanning transmission X-ray microscopy (STXM) and peak force tapping atomic force microscopy (PFT-AFM), have elucidated a unique core-shell morphology of the epoxy-acrylic hybrid particles. Moreover, the formation of the core-shell morphology in the seeded emulsion polymerization process is primarily attributed to kinetic trapping of the acrylic phase at the exterior of the epoxy particles. By this new method, we are able to design the epoxy and acrylic polymers in two separate steps, and we can potentially synthesize epoxy-acrylic hybrid latexes with a broad range of compositions. PMID:27078740

  2. Multifunctional core-shell-corona-type polymeric micelles for anticancer drug-delivery and imaging.

    PubMed

    Bastakoti, Bishnu Prasad; Wu, Kevin C-W; Inoue, Masamichi; Yusa, Shin-ichi; Nakashima, Kenichi; Yamauchi, Yusuke

    2013-04-01

    We have developed core-shell-corona-type polymeric micelles that can integrate multiple functions in one system, including the capability of accommodating hydrophobic dyes into core and hydrophilic drug into the shell, as well as pH-triggered drug-release. The neutral and hydrophilic corona sterically stabilizes the multifunctional polymeric micelles in aqueous solution. The mineralization of calcium phosphate (CaP) on the PAA domain not only enhances the diagnostic efficacy of organic dyes, but also works as a diffusion barrier for the controlled release. PMID:23417774

  3. Core-shell polymeric microcapsules with superior thermal and solvent stability.

    PubMed

    Kang, Sen; Baginska, Marta; White, Scott R; Sottos, Nancy R

    2015-05-27

    A protective polydopamine (PDA) coating is applied to core-shell microcapsule surfaces by the polymerization of dopamine monomers. A neutral aqueous solution and the addition of an oxidant (i.e., ammonium persulfate) are crucial for microcapsule survival and the initiation of PDA polymerization, respectively. The resulting PDA coating is a dense and uniform layer approximately 50 nm thick. The PDA protective coating significantly increases capsule stability at an elevated temperature (180 °C) and in a variety of organic solvents and acidic/basic solutions that otherwise lead to deflation and loss of the core content of uncoated microcapsules. PMID:25923539

  4. Core/shell silicon/polyaniline particles via in-flight plasma-induced polymerization

    NASA Astrophysics Data System (ADS)

    Yasar-Inceoglu, Ozgul; Zhong, Lanlan; Mangolini, Lorenzo

    2015-08-01

    Although silicon nanoparticles have potential applications in many relevant fields, there is often the need for post-processing steps to tune the property of the nanomaterial and to optimize it for targeted applications. In particular surface modification is generally necessary to both tune dispersibility of the particles in desired solvents to achieve optimal coating conditions, and to interface the particles with other materials to realize functional heterostructures. In this contribution we discuss the realization of core/shell silicon/polymer nanoparticles realized using a plasma-initiated in-flight polymerization process. Silicon particles are produced in a non-thermal plasma reactor using silane as a precursor. After synthesis they are aerodynamically injected into a second plasma reactor into which aniline vapor is introduced. The second plasma initiates the polymerization reactor leading to the formation of a 3-4 nm thick polymer shell surrounding the silicon core. The role of processing conditions on the properties of the polymeric shell is discussed. Preliminary results on the testing of this material as an anode for lithium ion batteries are presented.

  5. Core-Shell Silver/Polymeric Nanoparticles-Based Combinatorial Therapy against Breast Cancer In-vitro

    NASA Astrophysics Data System (ADS)

    Elbaz, Nancy M.; Ziko, Laila; Siam, Rania; Mamdouh, Wael

    2016-08-01

    The current study aimed at preparing AgNPs and three different core-shell silver/polymeric NPs composed of Ag core and three different polymeric shells: polyvinyl alcohol (PVA), polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP). Thereafter, the core/shell NPs were loaded with a chemotherapeutic agent doxorubicin (DOX). Finally, the cytotoxic effects of the different core-shell Ag/polymeric NPs-based combinatorial therapeutics were tested in-vitro against breast cancer (MCF-7) and human fibroblast (1BR hTERT) cell lines. AgNPs, Ag/PVA and Ag/PVP NPs were more cytotoxic to MCF-7 cells than normal fibroblasts, as well as DOX-Ag, DOX-Ag/PVA, DOX-Ag/PEG and DOX-Ag/PVP nanocarriers (NCs). Notably, low dosage of core-shell DOX-loaded Ag/polymeric nanocarriers (NCs) exhibited a synergic anticancer activity, with DOX-Ag/PVP being the most cytotoxic. We believe that the prepared NPs-based combinatorial therapy showed a significant enhanced cytotoxic effect against breast cancer cells. Future studies on NPs-based combinatorial therapy may aid in formulating a novel and more effective cancer therapeutics.

  6. Core-Shell Silver/Polymeric Nanoparticles-Based Combinatorial Therapy against Breast Cancer In-vitro

    PubMed Central

    Elbaz, Nancy M.; Ziko, Laila; Siam, Rania; Mamdouh, Wael

    2016-01-01

    The current study aimed at preparing AgNPs and three different core-shell silver/polymeric NPs composed of Ag core and three different polymeric shells: polyvinyl alcohol (PVA), polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP). Thereafter, the core/shell NPs were loaded with a chemotherapeutic agent doxorubicin (DOX). Finally, the cytotoxic effects of the different core-shell Ag/polymeric NPs-based combinatorial therapeutics were tested in-vitro against breast cancer (MCF-7) and human fibroblast (1BR hTERT) cell lines. AgNPs, Ag/PVA and Ag/PVP NPs were more cytotoxic to MCF-7 cells than normal fibroblasts, as well as DOX-Ag, DOX-Ag/PVA, DOX-Ag/PEG and DOX-Ag/PVP nanocarriers (NCs). Notably, low dosage of core-shell DOX-loaded Ag/polymeric nanocarriers (NCs) exhibited a synergic anticancer activity, with DOX-Ag/PVP being the most cytotoxic. We believe that the prepared NPs-based combinatorial therapy showed a significant enhanced cytotoxic effect against breast cancer cells. Future studies on NPs-based combinatorial therapy may aid in formulating a novel and more effective cancer therapeutics. PMID:27491622

  7. Core-Shell Silver/Polymeric Nanoparticles-Based Combinatorial Therapy against Breast Cancer In-vitro.

    PubMed

    Elbaz, Nancy M; Ziko, Laila; Siam, Rania; Mamdouh, Wael

    2016-01-01

    The current study aimed at preparing AgNPs and three different core-shell silver/polymeric NPs composed of Ag core and three different polymeric shells: polyvinyl alcohol (PVA), polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP). Thereafter, the core/shell NPs were loaded with a chemotherapeutic agent doxorubicin (DOX). Finally, the cytotoxic effects of the different core-shell Ag/polymeric NPs-based combinatorial therapeutics were tested in-vitro against breast cancer (MCF-7) and human fibroblast (1BR hTERT) cell lines. AgNPs, Ag/PVA and Ag/PVP NPs were more cytotoxic to MCF-7 cells than normal fibroblasts, as well as DOX-Ag, DOX-Ag/PVA, DOX-Ag/PEG and DOX-Ag/PVP nanocarriers (NCs). Notably, low dosage of core-shell DOX-loaded Ag/polymeric nanocarriers (NCs) exhibited a synergic anticancer activity, with DOX-Ag/PVP being the most cytotoxic. We believe that the prepared NPs-based combinatorial therapy showed a significant enhanced cytotoxic effect against breast cancer cells. Future studies on NPs-based combinatorial therapy may aid in formulating a novel and more effective cancer therapeutics. PMID:27491622

  8. Large enhanced dielectric permittivity in polyaniline passivated core-shell nano magnetic iron oxide by plasma polymerization

    SciTech Connect

    Joy, Lija K.; Sooraj, V.; Sethulakshmi, N.; Anantharaman, M. R.; Sajeev, U. S.; Nair, Swapna S.; Narayanan, T. N.; Ajayan, P. M.

    2014-03-24

    Commercial samples of Magnetite with size ranging from 25–30 nm were coated with polyaniline by using radio frequency plasma polymerization to achieve a core shell structure of magnetic nanoparticle (core)–Polyaniline (shell). High resolution transmission electron microscopy images confirm the core shell architecture of polyaniline coated iron oxide. The dielectric properties of the material were studied before and after plasma treatment. The polymer coated magnetite particles exhibited a large dielectric permittivity with respect to uncoated samples. The dielectric behavior was modeled using a Maxwell–Wagner capacitor model. A plausible mechanism for the enhancement of dielectric permittivity is proposed.

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

    PubMed

    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. PMID:22707097

  10. An Assessment of a New Synthetic Procedure for Core-shell Polymeric Supports Based on the Amberlite XAD-4 Adsorbent.

    PubMed

    Cyganowski, Piotr; Jermakowicz-Bartkowiak, Dorota; Chęcmanowski, Jacek

    2015-01-01

    In pursuit for new reactive materials designed for synthesis of functional resins, the novel core-shell type polymeric supports with accessible chloromethyl groups were synthesized. The commercial Amberlite XAD-4 adsorbent was impregnated with different mixtures of vinylbenzylchloride and divinylbenzene, that were further polymerized in the structure of the polymer carrier. The syntheses have been evaluated by recording FT-IR spectra, capturing SEM micrographs as well as analyzing the sorption and desorption of nitrogen at 77 K. The amount of the introduced functionalities has been estimated by chlorine content determination. Based on the obtained results, the reactive chloromethyl groups were successfully introduced into XAD-4 structure. Captured SEM micrographs revealed that VBC/DVB copolymer has covered initial polymeric matrix of XAD-4 adsorbent. Based on the results we have determined conditions of the synthesis that allow us to receive that effect. PMID:26454602

  11. Strain-Mediated Interfacial Dynamics during Au-PbS Core-Shell Nanostructure Formation.

    PubMed

    Niu, Kai-Yang; Liu, Miao; Persson, Kristin A; Han, Yu; Zheng, Haimei

    2016-06-28

    An understanding of the hierarchical nanostructure formation is of significant importance for the design of advanced functional materials. Here, we report the in situ study of lead sulfide (PbS) growth on gold (Au) nanorod seeds using liquid cell transmission electron microscopy (TEM). By tracking the formation dynamics of Au-PbS core-shell nanoparticles, we found the preferential heterogeneous nucleation of PbS on the ends of a Au nanorod prior to the development of a complete PdS shell. During PbS shell growth, drastic sulfidation of Au nanorod was observed, leading to large volume shrinkage (up to 50%) of the initial Au nanorod seed. We also captured intriguing wavy interfacial behavior, which can be explained by our DFT calculation results that the local strain gradient at the core-shell interface facilitates the mass transport and mediates reversible phase transitions of Au ↔ Au2S during the PbS shell growth. PMID:27214625

  12. Novel core-shell cerium(IV)-immobilized magnetic polymeric microspheres for selective enrichment and rapid separation of phosphopeptides.

    PubMed

    Wang, Zhi-Gang; Cheng, Gong; Liu, Yan-Lin; Zhang, Ji-Lin; Sun, De-Hui; Ni, Jia-Zuan

    2014-03-01

    In this work, novel magnetic polymeric core-shell structured microspheres with immobilized Ce(IV), Fe3O4@SiO2@PVPA-Ce(IV), were designed rationally and synthesized successfully via a facile route for the first time. Magnetic Fe3O4@SiO2 microspheres were first prepared by directly coating a thin layer of silica onto Fe3O4 magnetic particles using a sol-gel method, a poly(vinylphosphonic acid) (PVPA) shell was then coated on the Fe3O4@SiO2 microspheres to form Fe3O4@SiO2@PVPA microspheres through a radical polymerization reaction, and finally Ce(IV) ions were robustly immobilized onto the Fe3O4@SiO2@PVPA microspheres through strong chelation between Ce(IV) ions and phosphate moieties in the PVPA. The applicability of the Fe3O4@SiO2@PVPA-Ce(IV) microspheres for selective enrichment and rapid separation of phosphopeptides from proteolytic digests of standard and real protein samples was investigated. The results demonstrated that the core-shell structured Fe3O4@SiO2@PVPA-Ce(IV) microspheres with abundant Ce(IV) affinity sites and excellent magnetic responsiveness can effectively purify phosphopeptides from complex biosamples for MS detection taking advantage of the rapid magnetic separation and the selective affinity between Ce(IV) ions and phosphate moieties of the phosphopeptides. Furthermore, they can be effectively recycled and show good reusability, and have better performance than commercial TiO2 beads and homemade Fe3O4@PMAA-Ce(IV) microspheres. Thus the Fe3O4@SiO2@PVPA-Ce(IV) microspheres can benefit greatly the mass spectrometric qualitative analysis of phosphopeptides in phosphoproteome research. PMID:24407680

  13. TiO2@C Core-Shell Nanoparticles Formed by Polymeric Nano-Encapsulation

    NASA Astrophysics Data System (ADS)

    Vasei, Mitra; Das, Paramita; Cherfouh, Hayet; Marsan, Benoit; Claverie, Jerome

    2014-07-01

    TiO2 semiconducting nanoparticles are known to be photocatalysts of moderate activity due to their high band-gap and high rate of electron-hole recombination. The formation of a shell of carbon around the core of TiO2, i.e. the formation of TiO2@C nanoparticles, is believed to partly alleviate these problems. It is usually achieved by a hydrothermal treatment in a presence of a sugar derivative. We present here a novel method for the formation of highly uniform C shell around TiO2 nanoparticles. For this purpose, TiO2 nanoparticles were dispersed in water using an oligomeric dispersant prepared by Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization. Then the nanoparticles were engaged into an emulsion polymerization of acrylonitrile, resulting in the formation of a shell of polyacrylonitrile (PAN) around each TiO2 nanoparticles. Upon pyrolisis, the PAN was transformed into carbon, resulting in the formation of TiO2@C nanoparticles. The structure of the resulting particles was elucidated by X-Ray diffraction, FTIR, UV-VIS and Raman spectroscopy as well as TEM microscopy. Preliminary results about the use of the TiO2@C particles as photocatalysts for the splitting of water are presented. They indicate that the presence of the C shell is responsible for a significant enhancement of the photocurrent.

  14. TiO2@C core-shell nanoparticles formed by polymeric nano-encapsulation

    PubMed Central

    Vasei, Mitra; Das, Paramita; Cherfouth, Hayet; Marsan, Benoît; Claverie, Jerome P.

    2014-01-01

    TiO2 semiconducting nanoparticles are known to be photocatalysts of moderate activity due to their high band-gap and high rate of electron-hole recombination. The formation of a shell of carbon around the core of TiO2, i.e., the formation of TiO2@C nanoparticles, is believed to partly alleviate these problems. It is usually achieved by a hydrothermal treatment in a presence of a sugar derivative. We present here a novel method for the formation of highly uniform C shell around TiO2 nanoparticles. For this purpose, TiO2 nanoparticles were dispersed in water using an oligomeric dispersant prepared by Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization. Then the nanoparticles were engaged into an emulsion polymerization of acrylonitrile, resulting in the formation of a shell of polyacrylonitrile (PAN) around each TiO2 nanoparticles. Upon pyrolysis, the PAN was transformed into carbon, resulting in the formation of TiO2@C nanoparticles. The structure of the resulting particles was elucidated by X-Ray diffraction, FTIR, UV-VIS and Raman spectroscopy as well as TEM microscopy. Preliminary results about the use of the TiO2@C particles as photocatalysts for the splitting of water are presented. They indicate that the presence of the C shell is responsible for a significant enhancement of the photocurrent. PMID:25072054

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

    NASA Astrophysics Data System (ADS)

    Shishodia, Manmohan Singh; Juneja, Soniya

    2016-05-01

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

  16. Synthesis of polystyrene/polysilsesquioxane core/shell composite particles via emulsion polymerization in the existence of poly(γ-methacryloxypropyl trimethoxysilane) sol.

    PubMed

    Yang, Shenglin; Song, Chunfeng; Qiu, Teng; Guo, Longhai; Li, Xiaoyu

    2013-01-01

    Here, we synthesized the polystyrene/polysilsesquioxane (PS/PSQ) core/shell latex particles via emulsion polymerization, which behave as an amusing morphology. First, the nanosized PSQ particles were prepared by the hydrolysis-condensation reaction of γ-methacryloxypropyl trimethoxysilane (MPTS) in ethanol medium. Subsequently, the as-obtained methacryloxypropylene functionalized PSQ (PMPTS) sol was directly added into the emulsion system of styrene (St) monomer, and PS/PSQ composite particles with core/shell structure were obtained through emulsion polymerization. We found that the structure of the composite particles can be affected by the synthesis parameters such as reaction time, content of PMPTS added in the reaction, amount of coemulsifier, and the pH value of emulsion system, which were systemically explored by transmission electron microscopy (TEM), scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), and thermogravimetric analysis (TGA) in this work. These results indicate that the PMPTS particles in the size of about 5 nm could first absorb onto the surface of PS latex particles so as to assemble in a strawberry-like morphology. The further coalescence among the PMPTS particles would result in a continuous PMPTS shell around the PS core. Moreover, the hollow PSQ capsules were prepared after extraction of the PS core by organic solvent, further confirming the core/shell structure of the as-synthesized PS/PMPTS particles. Meanwhile, we also explored the application of the PS/PSQ core/shell particles as a new kind of Pickering emulsifier in the emulsion polymerization of St, and composite particles with complex patchy morphologies have been obtained finally under different ratios of styrene monomer to PS/PMPTS colloidal emulsifier. PMID:23231420

  17. Optimizing LiFePO₄@C core-shell structures via the 3-aminophenol-formaldehyde polymerization for improved battery performance.

    PubMed

    Chi, Zi-xiang; Zhang, Wei; Wang, Xu-sheng; Cheng, Fu-quan; Chen, Ji-tao; Cao, An-min; Wan, Li-jun

    2014-12-24

    Polyanion-type cathode materials are well-known for their low electronic conductivity; accordingly, the addition of conductive carbon in the cathode materials becomes an indispensable step for their application in lithium ion batteries. To maximize the contribution of carbon, a core-shell structure with a full coverage of carbon should be favorable due to an improved electronic contact between different particles. Here, we report the formation of a uniform carbon nanoshell on a typical cathode material, LiFePO4, with the shell thickness precisely defined via the 3-aminophenol-formaldehyde polymerization process. In addition to the higher discharge capacity and the improved rate capability as expected from the carbon nanoshell, we identified that the core-shell configuration could lead to a much safer cathode material as revealed by the obviously reduced iron dissolution, much less heat released during the cycling, and better cyclability at high temperature. PMID:25453295

  18. Exchange bias in Fe/Fe{sub 3}O{sub 4} core-shell magnetic nanoparticles mediated by frozen interfacial spins.

    SciTech Connect

    Ong, Q. K.; Wei, A.; Lin, X.-M.; Center for Nanoscale Materials; Purdue Univ.

    2009-10-01

    The magnetization curves of monodisperse Fe/Fe{sub 3}O{sub 4} core-shell and Fe{sub 3}O{sub 4} hollow-shell nanoparticles reveal an unusual exchange-bias effect. Hysteresis measurements of core-shell particles at 5 K after field cooling exhibit a large loop shift associated with unidirectional anisotropy whereas Fe{sub 3}O{sub 4} hollow-shell nanoparticles support much smaller shifts. Both core-shell and hollow-shell particles exhibit sharp demagnetization jumps at low fields associated with a sudden switching of shell moments. Temperature-dependent magnetization of core-shell particles at high fields shows a deviation between field-cooled and zero-field-cooled curves below 30 K, suggesting the presence of frozen spins at the interface. These frozen interfacial spins play an important role in mediating the exchange coupling between the ferromagnetic core and ferrimagnetic shell.

  19. Preparation of SiC/SiO2 core-shell nanowires via molten salt mediated carbothermal reduction route

    NASA Astrophysics Data System (ADS)

    Zhang, Ju; Yan, Shuai; Jia, Quanli; Huang, Juntong; Lin, Liangxu; Zhang, Shaowei

    2016-06-01

    The growth of silicon carbide (SiC) crystal generally requires a high temperature, especially when low quality industrial wastes are used as the starting raw materials. In this work, SiC/SiO2 core-shell nanowires (NWs) were synthesized from low cost silica fume and sucrose via a molten salt mediated carbothermal reduction (CR) route. The molten salt was found to be effective in promoting the SiC growth and lowering the synthesis temperature. The resultant NWs exhibited a heterostructure composed of a 3C-SiC core of 100 nm in diameter and a 5-10 nm thick amorphous SiO2 shell layer. The photoluminescence spectrum of the achieved SiC NWs displayed a significant blue shift (a dominant luminescence at round 422 nm), which suggested that they were high quality and could be a promising candidate material for future optoelectronic applications.

  20. Preparation of (Ba,Sr)TiO3@polystrene core-shell nanoparticles by solvent-free surface-initiated atom transfer radical polymerization

    NASA Astrophysics Data System (ADS)

    Xiaowei, Yang; Yanwei, Zeng; Tongxiang, Cai; Zhenxing, Hu

    2012-07-01

    The polystyrene shells have been successfully grown on the barium strontium titanate (BST) nanocrystals, which were synthesized by microwave-activated glycothermal method, via a solvent-free surface-initiated atom transfer radical polymerization (SI-ATRP) after the 2-bromo-2-methylpropionic acid molecules (Br-MPA) were anchored at the surface of BST nanocrystals through ligand exchange with hydroxyl groups on their surfaces. These surface modified BST nanocrystals can then be perfectly dispersed in styrene monomer and act as macroinitiators for ATRP to yield BST@PS core-shell structured nanoparticles, which endow the BST nanocrystals with exceptionally good dispersibility and stability in hydrophobic solvents. The BST@PS core-shell structures were characterized by X-ray diffraction (XRD) technique and transmission electron microscopy (TEM). Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (Raman), differential scanning calorimetry (DSC) and gel permeation chromatography were also employed to probe the Br-MPA and PS on the BST nanocrystals. It has been shown that after the BST nanocrystals are surface-modified with Br-MPA, the polymerization of styrene can steadily occur at the surface of BST nanocrystals to form a uniform polystyrene shell and its thickness can reach ∼10 nm when the polymerization reaction is extended to 36 h, while no changes are found to take place with the BST nanocrystals. Compared with typical high molecular weight PS (Mn = 6700), the as-obtained PS possess a relatively low molecular weight (Mn = 5473) and a lower glass transition temperature (Tg ∼ 93 °C). The research results demonstrate a viable strategy for the preparation of polymer-coated functional metal oxides nanocrystals, potentially useful in biological and nanoelectronic applications.

  1. Immobilization of Ni-Pd/core-shell nanoparticles through thermal polymerization of acrylamide on glassy carbon electrode for highly stable and sensitive glutamate detection.

    PubMed

    Yu, Huicheng; Ma, Zhenzhen; Wu, Zhaoyang

    2015-10-01

    The preparation of a persistently stable and sensitive biosensor is highly important for practical applications. To improve the stability and sensitivity of glutamate sensors, an electrode modified with glutamate dehydrogenase (GDH)/Ni-Pd/core-shell nanoparticles was developed using the thermal polymerization of acrylamide (AM) to immobilize the synthesized Ni-Pd/core-shell nanoparticles onto a glassy carbon electrode (GCE). The modified electrode was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Electrochemical data showed that the prepared biosensor had remarkably enhanced electrocatalytic activity toward glutamate. Moreover, superior reproducibility and excellent stability were observed (relative average deviation was 2.96% after continuous use of the same sensor for 60 times, and current responses remained at 94.85% of the initial value after 60 d). The sensor also demonstrated highly sensitive amperometric detection of glutamate with a low limit of detection (0.052 μM, S/N = 3), high sensitivity (4.768 μA μM(-1) cm(-2)), and a wide, useful linear range (0.1-500 μM). No interference from potential interfering species such as l-cysteine, ascorbic acid, and l-aspartate were noted. The determination of glutamate levels in actual samples achieved good recovery percentages. PMID:26481997

  2. Photochemical internalization-mediated nonviral gene transfection: polyamine core-shell nanoparticles as gene carrier

    PubMed Central

    Zamora, Genesis; Wang, Frederick; Sun, Chung-Ho; Trinidad, Anthony; Kwon, Young Jik; Cho, Soo Kyung; Berg, Kristian; Madsen, Steen J.; Hirschberg, Henry

    2014-01-01

    Abstract. The overall objective of the research was to investigate the utility of photochemical internalization (PCI) for the enhanced nonviral transfection of genes into glioma cells. The PCI-mediated introduction of the tumor suppressor gene phosphatase and tensin homolog (PTEN) or the cytosine deaminase (CD) pro-drug activating gene into U87 or U251 glioma cell monolayers and multicell tumor spheroids were evaluated. In the study reported here, polyamine-DNA gene polyplexes were encapsulated in a nanoparticle (NP) with an acid degradable polyketal outer shell. These NP synthetically mimic the roles of viral capsid and envelope, which transport and release the gene, respectively. The effects of PCI-mediated suppressor and suicide genes transfection efficiency employing either “naked” polyplex cores alone or as NP-shelled cores were compared. PCI was performed with the photosensitizer AlPcS2a and λ=670-nm laser irradiance. The results clearly demonstrated that the PCI can enhance the delivery of both the PTEN or CD genes in human glioma cell monolayers and multicell tumor spheroids. The transfection efficiency, as measured by cell survival and inhibition of spheroid growth, was found to be significantly greater at suboptimal light and DNA levels for shelled NPs compared with polyamine-DNA polyplexes alone. PMID:25341069

  3. Photochemical internalization-mediated nonviral gene transfection: polyamine core-shell nanoparticles as gene carrier

    NASA Astrophysics Data System (ADS)

    Zamora, Genesis; Wang, Frederick; Sun, Chung-Ho; Trinidad, Anthony; Kwon, Young Jik; Cho, Soo Kyung; Berg, Kristian; Madsen, Steen J.; Hirschberg, Henry

    2014-10-01

    The overall objective of the research was to investigate the utility of photochemical internalization (PCI) for the enhanced nonviral transfection of genes into glioma cells. The PCI-mediated introduction of the tumor suppressor gene phosphatase and tensin homolog (PTEN) or the cytosine deaminase (CD) pro-drug activating gene into U87 or U251 glioma cell monolayers and multicell tumor spheroids were evaluated. In the study reported here, polyamine-DNA gene polyplexes were encapsulated in a nanoparticle (NP) with an acid degradable polyketal outer shell. These NP synthetically mimic the roles of viral capsid and envelope, which transport and release the gene, respectively. The effects of PCI-mediated suppressor and suicide genes transfection efficiency employing either "naked" polyplex cores alone or as NP-shelled cores were compared. PCI was performed with the photosensitizer AlPcS2a and λ=670-nm laser irradiance. The results clearly demonstrated that the PCI can enhance the delivery of both the PTEN or CD genes in human glioma cell monolayers and multicell tumor spheroids. The transfection efficiency, as measured by cell survival and inhibition of spheroid growth, was found to be significantly greater at suboptimal light and DNA levels for shelled NPs compared with polyamine-DNA polyplexes alone.

  4. Mechanism of in situ surface polymerization of gallic acid in an environmental-inspired preparation of carboxylated core-shell magnetite nanoparticles.

    PubMed

    Tóth, Ildikó Y; Szekeres, Márta; Turcu, Rodica; Sáringer, Szilárd; Illés, Erzsébet; Nesztor, Dániel; Tombácz, Etelka

    2014-12-30

    Magnetite nanoparticles (MNPs) with biocompatible coatings are good candidates for MRI (magnetic resonance imaging) contrasting, magnetic hyperthermia treatments, and drug delivery systems. The spontaneous surface induced polymerization of dissolved organic matter on environmental mineral particles inspired us to prepare carboxylated core-shell MNPs by using a ubiquitous polyphenolic precursor. Through the adsorption and in situ surface polymerization of gallic acid (GA), a polygallate (PGA) coating is formed on the nanoparticles (PGA@MNP) with possible antioxidant capacity. The present work explores the mechanism of polymerization with the help of potentiometric acid-base titration, dynamic light scattering (for particle size and zeta potential determination), UV-vis (UV-visible light spectroscopy), FTIR-ATR (Fourier-transformed infrared spectroscopy by attenuated total reflection), and XPS (X-ray photoelectron spectroscopy) techniques. We observed the formation of ester and ether linkages between gallate monomers both in solution and in the adsorbed state. Higher polymers were formed in the course of several weeks both on the surface of nanoparticles and in the dispersion medium. The ratio of the absorbances of PGA supernatants at 400 and 600 nm (i.e., the E4/E6 ratio commonly used to characterize the degree of polymerization of humic materials) was determined to be 4.3, similar to that of humic acids. Combined XPS, dynamic light scattering, and FTIR-ATR results revealed that, prior to polymerization, the GA monomers became oxidized to poly(carboxylic acid)s due to ring opening while Fe(3+) ions reduced to Fe(2+). Our published results on the colloidal and chemical stability of PGA@MNPs are referenced thoroughly in the present work. Detailed studies on biocompatibility, antioxidant property, and biomedical applicability of the particles will be published. PMID:25517214

  5. Fabrication of core-shell structured magnetic nanocellulose base polymeric ionic liquid for effective biosorption of Congo red dye.

    PubMed

    Beyki, Mostafa Hossein; Bayat, Mehrnoosh; Shemirani, Farzaneh

    2016-10-01

    Ionic liquids are considered to be a class of environmentally friendly compounds as combination of them with bioresource polymeric substances such as; cellulose, constitute emerging coating materials. Biosorption by polymeric ionic liquids exhibits an attractive green way that involves low cost and irrespective of toxicity. As a result, a novel polymeric ionic liquid has been developed by the reaction of one step synthesized Fe3O4-cellulose nanohybrid, epichlorohydrin and 1-methylimidazole and employed as a green sorbent for efficient biosorption of Congo red dye. Effective parameters on dye removing as well as their interactions were determined with response surface methodology (RSM). Congo red adsorption showed fast equilibrium time (11min) with maximum uptake of 131mgg(-1). Isotherm study revealed that Langmuir adsorption model can better describe dye adsorption behavior. Regeneration of the sorbent was performed with a mixture of methanol-acetone-NaOH (3.0molL(-1)) solution. PMID:27372013

  6. Holistic assessment of covalently labeled core-shell polymeric nanoparticles with fluorescent contrast agents for theranostic applications.

    PubMed

    Gustafson, Tiffany P; Lim, Young H; Flores, Jeniree A; Heo, Gyu Seong; Zhang, Fuwu; Zhang, Shiyi; Samarajeewa, Sandani; Raymond, Jeffery E; Wooley, Karen L

    2014-01-21

    The successful development of degradable polymeric nanostructures as optical probes for use in nanotheranostic applications requires the intelligent design of materials such that their surface response, degradation, drug delivery, and imaging properties are all optimized. In the case of imaging, optimization must result in materials that allow differentiation between unbound optical contrast agents and labeled polymeric materials as they undergo degradation. In this study, we have shown that use of traditional electrophoretic gel-plate assays for the determination of the purity of dye-conjugated degradable nanoparticles is limited by polymer degradation characteristics. To overcome these limitations, we have outlined a holistic approach to evaluating dye and peptide-polymer nanoparticle conjugation by utilizing steady-state fluorescence, anisotropy, and emission and anisotropy lifetime decay profiles, through which nanoparticle-dye binding can be assessed independently of perturbations, such as those presented during the execution of electrolyte gel-based assays. This approach has been demonstrated to provide an overall understanding of the spectral signature-structure-function relationship, ascertaining key information on interactions between the fluorophore, polymer, and solvent components that have a direct and measurable impact on the emissive properties of the optical probe. The use of these powerful techniques provides feedback that can be utilized to improve nanotheranostics by evaluating dye emissivity in degradable nanotheranostic systems, which has become increasingly important as modern platforms transition to architectures intentionally reliant on degradation and built-in environmental responses. PMID:24392760

  7. Facile synthesis of core-shell/hollow anisotropic particles via control of cross-linking during one-pot dispersion polymerization.

    PubMed

    Liu, Yanan; Ma, Yuhong; Liu, Lianying; Yang, Wantai

    2015-05-01

    Preparation of anisotropic particles based on seed phase separation involves multiple processes, and asymmetrical structures and surfaces cannot be produced when anisotropic shapes emerge. In conventional one-pot dispersion polymerization (Dis.P) using cross-linker, only spherical particles are prepared due to rapid and high cross-linking. Herein, monodisperse snowman-like particles with core-shell/hollow structures and partially rough surface were synthesized straightforward by a modified one-pot Dis.P, in which ethylene glycol and water (6/4, vol.) were used as medium, and ammonium persulfate (APS) aqueous solution, vinyl acetate (VA) and/or acrylic acid (AA), divinylbenzene (DVB) and styrene (St) were added at 6h. The cross-linking of growing particles was confined to exterior (forming cross-linked shell), and gel contents were low, leading to phase separation. Asymmetrical morphologies, structures, sizes and surface roughness were flexibly tuned by varying amounts of APS, VA and/or AA, water and DVB, and DVB adding speed. At low APS contents or high DVB amounts, the inhomogeneous cross-linking of head enabled its phase to separate, producing elongated head. With addition of VA and AA, phase separations inside head and body were induced, generating hollow structure. Adding DVB very slowly, nonlinear growth of third compartment occurred, forming bowed head. PMID:25626132

  8. Preparation and characterization of Phase change material microcapsules by a core-shell-like emulsion polymerization method

    NASA Astrophysics Data System (ADS)

    Ding, Li-ming; Pei, Guang-ling

    2015-07-01

    Phase change material microcapsules (MicroPCMs) were synthesized by a coreshell-like emulsion polymerization method. Styrene and methylacrylic acid copolymer (PS- MAA) was used as a wall material, and paraffin was used as a core material in order to prepare spherical, high resistance and high enthalpy MicroPCMs. Scanning Electron Microscope (SEM), laser particle size analyzer, Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetry (TG) and Differential Scanning Calorimeter (DSC) were employed to characterize the MicroPCMs. The results indicated that the average particle size of MicroPCMs was 42.29 μm, and the content of paraffin within microcapsules was 57.6%. The melting temperature and crystallization temperature were 30.7°C and 25.2°C.The melting enthalpy and crystallization enthalpy were -84.1 J/g and 91.3 J/g, respectively.

  9. Preparation of Core-Shell Hybrid Compounds by Atomic Transfer Radical Polymerization and Its Application to Plastic Lens of Headlamp.

    PubMed

    Noh, Seung-Man; Ahn, Jae-Beum; Choi, Ki-Hyun; Park, Seung-Kyu

    2015-09-01

    Nano silica ball (NSB) core polymethylmethacrylate (PMMA) shell hybrid nanocomposites were synthesized by atomic transfer radical polymerization (ATRP) method for the application to the clearcoat to enhance scratch resistance. The characteristics of the synthesized inorganic/organic hybrid material were examined by scanning electron microscope (SEM), particle size analysis, Fourier transform infrared (FTIR) spectroscopy and thermo gravimetric analysis-differential scanning calorimetry (TGA-DSC). The scratch resistance and light transmittance of the clearcoat were measured by a nano-scratch tester and UV-visible spectroscopy, respectively. The average particle size of the NSB-PMMA hybrid compounds was 30 nm with narrow size distribution. Even 0.1 wt% loading of NSB-PMMA in the clearcoat dramatically enhanced the scratch resistance, about 40% increase in the force of the first fracture, while slightly reduced the light transmittance, about 5% only. PMID:26716303

  10. Polymer-Mediated Self-Assembly of TiO2@Cu2O Core-Shell Nanowire Array for Highly Efficient Photoelectrochemical Water Oxidation.

    PubMed

    Yuan, Weiyong; Yuan, Jia; Xie, Jiale; Li, Chang Ming

    2016-03-01

    Phototoelectrochemical (PEC) water splitting represents a highly promising strategy to convert solar energy to chemical energy in the form of hydrogen, but its performance is severely limited by the water oxidation reaction. We conformally grew an ultrathin and continuous coating of Cu2O on TiO2 nanowire array (NWA) to form a truly core-shell TiO2@Cu2O NWA via a new facile, economical, and scalable polymer-mediated self-assembly approach, in which the polymer serves as a stabilizer, reductant, and linker simultaneously. This heteronanostructure was subsequently directly used as a photoanode for PEC water splitting, showing a photocurrent density of 4.66 mA cm(-2) at 1.23 V vs RHE in 0.5 M Na2SO4 solution and a maximum photoconversion efficiency of 0.71%, both of which are the highest reported for TiO2-based photoanodes measured under the same conditions (neutral conditions and without any sacrificial agent). The superior PEC performance of the TiO2@Cu2O NWA toward water oxidation is primarily due to much enhanced visible light collection and charge separation for high charge carrier density as well as greatly facilitated charge transfer and transport. This work not only offers a novel TiO2@Cu2O core-shell NWA photoanode for highly efficient PEC water oxidation and investigate its enhancement mechanism but also provides scientific insights into the mechanism of the polymer-mediated self-assembly, which can be further extended to fabricate various other core-shell nanoarchitectures for broad applications. PMID:26908094

  11. Radical-Mediated Enzymatic Polymerizations

    PubMed Central

    Zavada, Scott R.; Battsengel, Tsatsral; Scott, Timothy F.

    2016-01-01

    Polymerization reactions are commonly effected by exposing monomer formulations to some initiation stimulus such as elevated temperature, light, or a chemical reactant. Increasingly, these polymerization reactions are mediated by enzymes―catalytic proteins―owing to their reaction efficiency under mild conditions as well as their environmental friendliness. The utilization of enzymes, particularly oxidases and peroxidases, for generating radicals via reduction-oxidation mechanisms is especially common for initiating radical-mediated polymerization reactions, including vinyl chain-growth polymerization, atom transfer radical polymerization, thiol–ene step-growth polymerization, and polymerization via oxidative coupling. While enzyme-mediated polymerization is useful for the production of materials intended for subsequent use, it is especially well-suited for in situ polymerizations, where the polymer is formed in the place where it will be utilized. Such polymerizations are especially useful for biomedical adhesives and for sensing applications. PMID:26848652

  12. Radical-Mediated Enzymatic Polymerizations.

    PubMed

    Zavada, Scott R; Battsengel, Tsatsral; Scott, Timothy F

    2016-01-01

    Polymerization reactions are commonly effected by exposing monomer formulations to some initiation stimulus such as elevated temperature, light, or a chemical reactant. Increasingly, these polymerization reactions are mediated by enzymes--catalytic proteins--owing to their reaction efficiency under mild conditions as well as their environmental friendliness. The utilization of enzymes, particularly oxidases and peroxidases, for generating radicals via reduction-oxidation mechanisms is especially common for initiating radical-mediated polymerization reactions, including vinyl chain-growth polymerization, atom transfer radical polymerization, thiol-ene step-growth polymerization, and polymerization via oxidative coupling. While enzyme-mediated polymerization is useful for the production of materials intended for subsequent use, it is especially well-suited for in situ polymerizations, where the polymer is formed in the place where it will be utilized. Such polymerizations are especially useful for biomedical adhesives and for sensing applications. PMID:26848652

  13. Preparations and properties of a tunable void with shell thickness SiO2@SiO2 core-shell structures via activators generated by electron transfer for atom transfer radical polymerization

    NASA Astrophysics Data System (ADS)

    Ren, Yi-xian; Zhou, Guo-wei; Cao, Pei

    2016-02-01

    Core-shell structure nanoparticles are attracting considerable attention because of their applications in drug delivery, catalysis carrier, and nanomedicine. In this study, SiO2@SiO2 core-shell structure with tunable void and shell thickness was successfully prepared for the first time using SiO2-poly(buty acrylate) (PBA)-poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) (SiO2-PBA-b-PDMAEMA) as the template and tetraethoxysilane (TEOS) as the silica source. An amphiphilic copolymer PBA-b-PDMAEMA was first grafted onto the SiO2 nanosphere surface through activators regenerated by electron transfer for atom transfer radical polymerization. TEOS was hydrolyzed along with the PDMAEMA chain through hydrogen bonding, and the core-shell structure of SiO2@SiO2 was obtained through calcination to remove the copolymer. The gradient hydrophilicity of the PBA-b-PDMAEMA copolymer template facilitated the hydrolysis of TEOS molecules along the PDMAEMA to PBA segments, thereby tuning the voids between the SiO2 core and SiO2 shell, as well as the SiO2 shell thickness. The voids were about 10-15 nm and the shell thicknesses were about 4-11 nm when adding different amounts of DMAEMA monomer. SiO2@SiO2 core-shell structures with tunable void and shell thickness were employed as supports for the loading and release of doxorubicin hydrochloride (DOX) in PBS (pH 4.0). The samples demonstrated good loading capacity and controlled release rate of DOX.

  14. Brain tumor-targeted therapy by systemic delivery of siRNA with Transferrin receptor-mediated core-shell nanoparticles.

    PubMed

    Wei, Lin; Guo, Xi-Ying; Yang, Ting; Yu, Min-Zhi; Chen, Da-Wei; Wang, Jian-Cheng

    2016-08-20

    Treatment of brain tumor remains a great challenge worldwide. Development of a stable, safe, and effective siRNA delivery system which is able to cross the impermeable blood-brain barrier (BBB) and target glioma cells is necessary. This study aims to investigate the therapeutic effects of intravenous administration of T7 peptide modified core-shell nanoparticles (named T7-LPC/siRNA NPs) on brain tumors. Layer-by-layer assembling of protamine/chondroitin sulfate/siRNA/cationic liposomes followed by T7 peptide modification has been carried out in order to obtain a targeted siRNA delivery system. In vitro cellular uptake experiments demonstrated a higher intracellular fluorescence intensity of siRNA in brain microvascular endothelial cells (BMVECs) and U87 glioma cells when treated with T7-LPC/siRNA NPs compared with PEG-LPC/siRNA NPs. In the co-culture model of BMVECs and U87 cells, a significant down-regulation of EGFR protein expression occurred in the U87 glioma cells after treatment with the T7-LPC/siEGFR NPs. Moreover, the T7-LPC/siRNA NPs had an advantage in penetrating into a deep region of the tumor spheroid compared with PEG-LPC/siRNA NPs. In vivo imaging revealed that T7-LPC/siRNA NPs accumulated more specifically in brain tumor tissues than the non-targeted NPs. Also, in vivo tumor therapy experiments demonstrated that the longest survival period along with the greatest downregulation of EGFR expression in tumor tissues was observed in mice with an intracranial U87 glioma treated with T7-LPC/siEGFR NPs compared with mice receiving other formulations. Therefore, we believe that these transferrin receptor-mediated core-shell nanoparticles are an important potential siRNA delivery system for brain tumor-targeted therapy. PMID:27374198

  15. Core-Shell Composite Nanoparticles: Synthesis, Characterization, and Applications

    NASA Astrophysics Data System (ADS)

    Sanyal, Sriya

    Nanoparticles are ubiquitous in various fields due to their unique properties not seen in similar bulk materials. Among them, core-shell composite nanoparticles are an important class of materials which are attractive for their applications in catalysis, sensing, electromagnetic shielding, drug delivery, and environmental remediation. This dissertation focuses on the study of core-shell type of nanoparticles where a polymer serves as the core and inorganic nanoparticles are the shell. This is an interesting class of supramolecular building blocks and can "exhibit unusual, possibly unique, properties which cannot be obtained simply by co-mixing polymer and inorganic particles". The one-step Pickering emulsion polymerization method was successfully developed and applied to synthesize polystyrene-silica core-shell composite particles. Possible mechanisms of the Pickering emulsion polymerization were also explored. The silica nanoparticles were thermodynamically favorable to self-assemble at liquid-liquid interfaces at the initial stage of polymerization and remained at the interface to finally form the shells of the composite particles. More importantly, Pickering emulsion polymerization was employed to synthesize polystyrene/poly(N-isopropylacrylamide) (PNIPAAm)-silica core-shell nanoparticles with N-isopropylacrylamide incorporated into the core as a co-monomer. The composite nanoparticles were temperature sensitive and could be up-taken by human prostate cancer cells and demonstrated effectiveness in drug delivery and cancer therapy. Similarly, by incorporating poly-2-(N,N)-dimethylamino)ethyl methacrylate (PDMA) into the core, pH sensitive core-shell composite nanoparticles were synthesized and applied as effective carriers to release a rheological modifier upon a pH change. Finally, the research focuses on facile approaches to engineer the transition of the temperature-sensitive particles and develop composite core-shell nanoparticles with a metallic shell.

  16. Core-shell nanostructured catalysts.

    PubMed

    Zhang, Qiao; Lee, Ilkeun; Joo, Ji Bong; Zaera, Francisco; Yin, Yadong

    2013-08-20

    Novel nanotechnologies have allowed great improvements in the syn-thesis of catalysts with well-controlled size, shape, and surface properties. Transition metal nanostructures with specific sizes and shapes, for instance, have shown great promise as catalysts with high selectivities and relative ease of recycling. Researchers have already demonstrated new selective catalysis with solution-dispersed or supported-metal nanocatalysts, in some cases applied to new types of reactions. Several challenges remain, however, particularly in improving the structural stability of the catalytic active phase. Core-shell nanostructures are nanoparticles encapsulated and protected by an outer shell that isolates the nanoparticles and prevents their migration and coalescence during the catalytic reactions. The synthesis and characterization of effective core-shell catalysts has been at the center of our research efforts and is the focus of this Account. Efficient core-shell catalysts require porous shells that allow free access of chemical species from the outside to the surface of nanocatalysts. For this purpose, we have developed a surface-protected etching process to prepare mesoporous silica and titania shells with controllable porosity. In certain cases, we can tune catalytic reaction rates by adjusting the porosity of the outer shell. We also designed and successfully applied a silica-protected calcination method to prepare crystalline shells with high surface area, using anatase titania as a model system. We achieved a high degree of control over the crystallinity and porosity of the anatase shells, allowing for the systematic optimization of their photocatalytic activity. Core-shell nanostructures also provide a great opportunity for controlling the interaction among the different components in ways that might boost structural stability or catalytic activity. For example, we fabricated a SiO₂/Au/N-doped TiO₂ core-shell photocatalyst with a sandwich structure that showed

  17. Defect-mediated of Cu@TiO2 core-shell nanoparticles with oxygen vacancies for photocatalytic degradation 2,4-DCP under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Wang, Zhen; Zang, Ling; Fan, Xiaoyun; Jia, Hanzhong; Li, Li; Deng, Wenye; Wang, Chuanyi

    2015-12-01

    Cu @TiO2 core-shell nanoparticles with different mass ratios of Cu to TiO2 were facilely synthesized via wet chemical approaches, and were characterized by transmission electron microscopy, scanning electron microscopy, UV-vis diffuse reflection absorption spectroscopy, X-ray photoelectron spectroscopy and electron paramagnetic resonance. The photocatalytic efficiency of Cu@TiO2 nanoparticles was evaluated by degradation of 2,4-dichlorophenol, a typical persistent organic pollutant, under visible light irradiation. The results show that the oxygen vacancy creation obviously enhances the visible-light absorption of TiO2. Meanwhile, the Cu nanoparticle incorporation into the TiO2 can effectively improve charge-separation efficiency of Cu@TiO2 under visible-light irradiation, thereby enhancing the photoactivity.

  18. A novel approach to the construction of core shell gold polyaniline nanoparticles

    NASA Astrophysics Data System (ADS)

    Dong, Yang; Ma, Ying; Zhai, Tianyou; Zeng, Yi; Fu, Hongbing; Yao, Jiannian

    2007-11-01

    Uniform core-shell gold-polyaniline (Au-PANI) nanoparticles were successfully fabricated by in situ polymerization of aniline using poly(N-isopropylacrylamide)-co-poly(acrylic acid) (PNIPAM-co-PAA)/AuNP hybrid microgel particles as a template. TEM images gave direct evidence of the core-shell nanostructure of Au-PANI particles, which were composed of gold nanoparticles as the core and polyaniline as the shell. The shell thickness of as-prepared core-shell Au-PANI nanoparticles can be easily tuned by controlling the reaction time. A possible mechanism for the formation of core-shell Au-PANI nanostructures was proposed. This novel synthetic method may be extended to the synthesis of other core-shell nanostructures with diverse functionality and high colloidal stability.

  19. Synthesis of core-shell composites using an inverse surfmer.

    PubMed

    Armando Zaragoza-Contreras, E; Stockton-Leal, Margarita; Hernández-Escobar, Claudia A; Hoshina, Yusuke; Guzmán-Lozano, Josué F; Kobayashi, Takaomi

    2012-07-01

    Anilinium dodecylsulfate was prepared from aniline and sodium dodecylsulfate. The critical micellar concentration of the salt was determined using electrical conductimetry, which revealed that the change of countercation, sodium by anilinium, reduced the critical micellar concentration with respect to the conventional counterpart, sodium dodecylsulfate. The anilinium dodecylsulfate was used as the surfmer in the synthesis of polystyrene/polyaniline core-shell composites, first performing as the surfactant to stabilize the emulsion polymerization of styrene, and later as the monomer to synthesize polyaniline via oxidative polymerization. Here, the surfmer function was directed toward the external phase instead of to the internal phase, as with conventional surfmers with carbon-carbon double bonds. Consequently, the term inverse surfmer is proposed. Analyses of its composite microstructure using electron microscopy and thermogravimetric analysis confirmed the core-shell arrangement. PMID:22520709

  20. Silica-metal core-shell nanostructures.

    PubMed

    Jankiewicz, B J; Jamiola, D; Choma, J; Jaroniec, M

    2012-01-15

    Silica-metal nanostructures consisting of silica cores and metal nanoshells attract a lot of attention because of their unique properties and potential applications ranging from catalysis and biosensing to optical devices and medicine. The important feature of these nanostructures is the possibility of controlling their properties by the variation of their geometry, shell morphology and shell material. This review is devoted to silica-noble metal core-shell nanostructures; specifically, it outlines the main methods used for the preparation and surface modification of silica particles and presents the major strategies for the formation of metal nanoshells on the modified silica particles. A special emphasis is given to the Stöber method, which is relatively simple, effective and well verified for the synthesis of large and highly uniform silica particles (with diameters from 100 nm to a few microns). Next, the surface chemistry of these particles is discussed with a special focus on the attachment of specific organic groups such as aminopropyl or mercaptopropyl groups, which interact strongly with metal species. Finally, the synthesis, characterization and application of various silica-metal core-shell nanostructures are reviewed, especially in relation to the siliceous cores with gold or silver nanoshells. Nowadays, gold is most often used metal for the formation of nanoshells due to its beneficial properties for many applications. However, other metals such as silver, platinum, palladium, nickel and copper were also used for fabrication of core-shell nanostructures. Silica-metal nanostructures can be prepared using various methods, for instance, (i) growth of metal nanoshells on the siliceous cores with deposited metal nanoparticles, (ii) reduction of metal species accompanied by precipitation of metal nanoparticles on the modified silica cores, and (iii) formation of metal nanoshells under ultrasonic conditions. A special emphasis is given to the seed-mediated

  1. Biocompatible magnetic core-shell nanocomposites for engineered magnetic tissues

    NASA Astrophysics Data System (ADS)

    Rodriguez-Arco, Laura; Rodriguez, Ismael A.; Carriel, Victor; Bonhome-Espinosa, Ana B.; Campos, Fernando; Kuzhir, Pavel; Duran, Juan D. G.; Lopez-Lopez, Modesto T.

    2016-04-01

    The inclusion of magnetic nanoparticles into biopolymer matrixes enables the preparation of magnetic field-responsive engineered tissues. Here we describe a synthetic route to prepare biocompatible core-shell nanostructures consisting of a polymeric core and a magnetic shell, which are used for this purpose. We show that using a core-shell architecture is doubly advantageous. First, gravitational settling for core-shell nanocomposites is slower because of the reduction of the composite average density connected to the light polymer core. Second, the magnetic response of core-shell nanocomposites can be tuned by changing the thickness of the magnetic layer. The incorporation of the composites into biopolymer hydrogels containing cells results in magnetic field-responsive engineered tissues whose mechanical properties can be controlled by external magnetic forces. Indeed, we obtain a significant increase of the viscoelastic moduli of the engineered tissues when exposed to an external magnetic field. Because the composites are functionalized with polyethylene glycol, the prepared bio-artificial tissue-like constructs also display excellent ex vivo cell viability and proliferation. When implanted in vivo, the engineered tissues show good biocompatibility and outstanding interaction with the host tissue. Actually, they only cause a localized transitory inflammatory reaction at the implantation site, without any effect on other organs. Altogether, our results suggest that the inclusion of magnetic core-shell nanocomposites into biomaterials would enable tissue engineering of artificial substitutes whose mechanical properties could be tuned to match those of the potential target tissue. In a wider perspective, the good biocompatibility and magnetic behavior of the composites could be beneficial for many other applications.The inclusion of magnetic nanoparticles into biopolymer matrixes enables the preparation of magnetic field-responsive engineered tissues. Here we

  2. Biocompatible magnetic core-shell nanocomposites for engineered magnetic tissues.

    PubMed

    Rodriguez-Arco, Laura; Rodriguez, Ismael A; Carriel, Victor; Bonhome-Espinosa, Ana B; Campos, Fernando; Kuzhir, Pavel; Duran, Juan D G; Lopez-Lopez, Modesto T

    2016-04-14

    The inclusion of magnetic nanoparticles into biopolymer matrixes enables the preparation of magnetic field-responsive engineered tissues. Here we describe a synthetic route to prepare biocompatible core-shell nanostructures consisting of a polymeric core and a magnetic shell, which are used for this purpose. We show that using a core-shell architecture is doubly advantageous. First, gravitational settling for core-shell nanocomposites is slower because of the reduction of the composite average density connected to the light polymer core. Second, the magnetic response of core-shell nanocomposites can be tuned by changing the thickness of the magnetic layer. The incorporation of the composites into biopolymer hydrogels containing cells results in magnetic field-responsive engineered tissues whose mechanical properties can be controlled by external magnetic forces. Indeed, we obtain a significant increase of the viscoelastic moduli of the engineered tissues when exposed to an external magnetic field. Because the composites are functionalized with polyethylene glycol, the prepared bio-artificial tissue-like constructs also display excellent ex vivo cell viability and proliferation. When implanted in vivo, the engineered tissues show good biocompatibility and outstanding interaction with the host tissue. Actually, they only cause a localized transitory inflammatory reaction at the implantation site, without any effect on other organs. Altogether, our results suggest that the inclusion of magnetic core-shell nanocomposites into biomaterials would enable tissue engineering of artificial substitutes whose mechanical properties could be tuned to match those of the potential target tissue. In a wider perspective, the good biocompatibility and magnetic behavior of the composites could be beneficial for many other applications. PMID:27029891

  3. Engineered Magnetic Core-Shell Structures.

    PubMed

    Alavi Nikje, Mir Mohammad; Vakili, Maryam

    2015-01-01

    In recent years, engineered magnetic core-shell structures are playing an important role in the wide range of various applications. These magnetic core-shell structures have attracted considerable attention because of their unique properties and various applications. Also, the synthesis of engineered magnetic core-shell structures has attracted practical interest because of potential applications in areas such as ferrofluids, medical imaging, drug targeting and delivery, cancer therapy, separations, and catalysis. So far a large number of engineered magnetic core-shell structures have been successfully synthesized. This review article focuses on the recent progress in synthesis and characterization of engineered magnetic core-shell structures. Also, this review gives a brief description of the various application of these structures. It is hoped that this review will play some small part in helping future developments in important field. PMID:26377655

  4. Ultrasound-Mediated Polymeric Micelle Drug Delivery.

    PubMed

    Xia, Hesheng; Zhao, Yue; Tong, Rui

    2016-01-01

    The synthesis of multi-functional nanocarriers and the design of new stimuli-responsive means are equally important for drug delivery. Ultrasound can be used as a remote, non-invasive and controllable trigger for the stimuli-responsive release of nanocarriers. Polymeric micelles are one kind of potential drug nanocarrier. By combining ultrasound and polymeric micelles, a new modality (i.e., ultrasound-mediated polymeric micelle drug delivery) has been developed and has recently received increasing attention. A major challenge remaining in developing ultrasound-responsive polymeric micelles is the improvement of the sensitivity or responsiveness of polymeric micelles to ultrasound. This chapter reviews the recent advance in this field. In order to understand the interaction mechanism between ultrasound stimulus and polymeric micelles, ultrasound effects, such as thermal effect, cavitation effect, ultrasound sonochemistry (including ultrasonic degradation, ultrasound-initiated polymerization, ultrasonic in-situ polymerization and ultrasound site-specific degradation), as well as basic micellar knowledge are introduced. Ultrasound-mediated polymeric micelle drug delivery has been classified into two main streams based on the different interaction mechanism between ultrasound and polymeric micelles; one is based on the ultrasound-induced physical disruption of the micelle and reversible release of payload. The other is based on micellar ultrasound mechanochemical disruption and irreversible release of payload. PMID:26486348

  5. Polymeric microspheres

    DOEpatents

    Walt, David R.; Mandal, Tarun K.; Fleming, Michael S.

    2004-04-13

    The invention features core-shell microsphere compositions, hollow polymeric microspheres, and methods for making the microspheres. The microspheres are characterized as having a polymeric shell with consistent shell thickness.

  6. Photon upconversion in core-shell nanoparticles.

    PubMed

    Chen, Xian; Peng, Denfeng; Ju, Qiang; Wang, Feng

    2015-03-21

    Photon upconversion generally results from a series of successive electronic transitions within complex energy levels of lanthanide ions that are embedded in the lattice of a crystalline solid. In conventional lanthanide-doped upconversion nanoparticles, the dopant ions homogeneously distributed in the host lattice are readily accessible to surface quenchers and lose their excitation energy, giving rise to weak and susceptible emissions. Therefore, present studies on upconversion are mainly focused on core-shell nanoparticles comprising spatially confined dopant ions. By doping upconverting lanthanide ions in the interior of a core-shell nanoparticle, the upconversion emission can be substantially enhanced, and the optical integrity of the nanoparticles can be largely preserved. Optically active shells are also frequently employed to impart multiple functionalities to upconversion nanoparticles. Intriguingly, the core-shell design introduces the possibility of constructing novel upconversion nanoparticles by exploiting the energy exchange interactions across the core-shell interface. In this tutorial review, we highlight recent advances in the development of upconversion core-shell nanoparticles, with particular emphasis on the emerging strategies for regulating the interplay of dopant interactions through core-shell nanostructural engineering that leads to unprecedented upconversion properties. The improved control over photon energy conversion will open up new opportunities for biological and energy applications. PMID:25058157

  7. Core-Shell Structured Magnetic Ternary Nanocubes

    SciTech Connect

    Wang, Lingyan; Wang, Xin; Luo, Jin; Wanjala, Bridgid N.; Wang, Chong M.; Chernova, Natalya; Engelhard, Mark H.; Liu, Yao; Bae, In-Tae; Zhong, Chuan-Jian

    2010-12-01

    While transition metal-doped ferrite nanoparticles constitute an important class of soft magnetic nanomaterials with spinel structures, the ability to control the shape and composition would enable a wide range of applications in homogeneous or heterogeneous reactions such as catalysis and magnetic separation of biomolecules. This report describes novel findings of an investigation of core-shell structured MnZn ferrite nanocubes synthesized in organic solvents by manipulating the reaction temperature and capping agent composition in the absence of the conventionally-used reducing agents. The core-shell structure of the highly-monodispersed nanocubes (~20 nm) are shown to consist of an Fe3O4 core and an (Mn0.5Zn0.5)(Fe0.9, Mn1.1)O4 shell. In comparison with Fe3O4 and other binary ferrite nanoparticles, the core-shell structured nanocubes were shown to display magnetic properties regulated by a combination of the core-shell composition, leading to a higher coercivity (~350 Oe) and field-cool/zero-field-cool characteristics drastically different from many regular MnZn ferrite nanoparticles. The findings are discussed in terms of the unique core-shell composition, the understanding of which has important implication to the exploration of this class of soft magnetic nanomaterials in many potential applications such as magnetic resonance imaging, fuel cells, and batteries.

  8. Folate-targeting magnetic core-shell nanocarriers for selective drug release and imaging.

    PubMed

    Wang, Hanjie; Wang, Sheng; Liao, Zhenyu; Zhao, Peiqi; Su, Wenya; Niu, Ruifang; Chang, Jin

    2012-07-01

    One of the most urgent medical requirements for cancer diagnosis and treatment is how to construct a multifunctional vesicle for simultaneous diagnostic imaging and therapeutic applications. In our study, superparamagnetic iron oxide nanocrystals (SPIONs) and doxorubicin hydrochloride (DOX) are co-encapsulated into PLGA/polymeric liposome core-shell nanocarriers for achieving simultaneous magnetic resonance imaging and targeting drug delivery. The core-shell nanocarrier was self-assembled from a hydrophobic PLGA core and a hydrophilic folate coated PEGlated lipid shell. The experiment showed that folate-targeting magnetic core-shell nanocarriers show clear core-shell structure, excellent magnetism and controlled drug release behavior. Importantly, the core-shell nanoparticles achieve the possibility of co-delivering drugs and SPIONs to the same cells for enhancing magnetic resonance imaging (MRI) effect and improving drug delivery efficiency simultaneously. Our data suggests that the folate-targeting magnetic core-shell nanocarriers (FMNs) could provide effective cancer-targeting and MRI as well as drug delivery. The FMNs may become a useful nanomedical carrier system for cancer diagnosis and treatment. PMID:22525087

  9. Comparison of Fe2O3 and Fe2CoO4 core-shell plasmonic nanoparticles for aptamer mediated SERS assays

    NASA Astrophysics Data System (ADS)

    Marks, Haley; Mabbott, Samuel; Huang, Po-Jung; Jackson, George W.; Kameoka, Jun; Graham, Duncan; Coté, Gerard L.

    2016-03-01

    Conjugation of oligonucleotides or aptamers and their corresponding analytes onto plasmonic nanoparticles mediates the formation of nanoparticle assemblies: molecularly bound bundles of nanoparticles which cause a measurable change in the colloid's optical properties. Here, we present further optimization of a "SERS off" competitive binding assay utilizing plasmonic and magnetic nanoparticles for the detection of the toxin bisphenol A (BPA). The assay involves 1) a `target' silver nanoparticle functionalized with a Raman reporter dye and PEGylated BPA-binding DNA aptamers, and 2) a version of the toxin BPA, bisphenol A diglycidyl ether (BADGE), PEGylated and immobilized onto a silver coated magnetic 'probe' nanoparticle. When mixed, these target and probe nanoparticles cluster into magnetic dimers and trimers and an enhancement in their SERS spectra is observed. Upon introduction of free BPA in its native form, target AgNPs are competitively freed; reversing the nanoparticle assembly and causing the SERS signal to "turn-off" and decrease in response to the competitive binding event. The assay particles were housed inside two types of optofluidic chips containing magnetically active nickel pads, in either a straight or spotted pattern, and both Fe2O3 and Fe2CoO4 were compared as magnetic cores for the silver coated probe nanoparticle. We found that the Ag@ Fe2O3 particles were, on average, more uniform in size and more stable than Ag@ Fe2CoO4, while the addition of cobalt significantly improved the collection time of particles within the magnetic chips. Using 3D Raman mapping, we found that the straight channel design with the Ag@ Fe2O3 particles provided the most uniform nanoparticle organization, while the spotted channel design with Ag@ Fe2CoO4 demonstrated a larger SERS enhancement, and thus a lower limit of detection.

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

    PubMed

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

    2014-01-01

    Herein, we prepared PEI-immobilized core-shell particles possessing various types of polymer cores via a visible light-induced surfactant-free emulsion polymerization (SFEP) of three vinyl monomers: styrene (St), methyl methacrylate (MMA), and 2-hydroxyethyl methacrylate (HEMA). An effect of monomers on the polymerization and characteristics of resulting products was investigated. Monomers with high polarity can provide high monomer conversion, high percentage of grafted PEI, stable particles with uniform size distribution but less amino groups per particles. All prepared nanoparticles exhibited a core-shell nanostructure, containing PEI on the shell with hydrodynamic size around 140-230nm. For in-vitro study in Caco-2 cells, we found that the incorporation of PEI into these core-shell nanoparticles can significantly reduce its cytotoxic effect and also be able to internalized within the cells. Accordingly, these biocompatible particles would be useful for various biomedical applications, including gene transfection and intracellular drug delivery. PMID:24268272

  11. Preparation and Biocompatibility of Gold@ Polypyrrole-Chitosan with Core-Shell Nanostructure.

    PubMed

    Wu, Yun; Wang, Yanyan; Chen, Hui; Ge, Shanshan; Zhang, Jinling; Mao, Chun; Ding, Hongyan; Shen, Jian

    2016-03-01

    A two-step method for preparing Au@polypyrrole-chitosan core-shell nanoparticles (Au @ PPy-CS NPs) was fabricated by in situ polymerization of pyrrole monomer on the surface of Au spheres in chitosan solution. Transmission electron microscopy (TEM) images showed the presence of core-shell structure of nanoparticles. Energy-Dispersive Spectroscopy (EDS) and Fourier transform infrared (FTIR) spectroscopy were adopted to verify the shell is polypyrrole-chitosan. Ultraviolet-visible (UV-vis) and X-ray diffraction (XRD) showed that Au was present in the core-shell nanoparticles. The biocompatibility of Au @ PPy-CS NPs was characterized by in vitro for hemolysis assay and cytotoxicity experiments. Results indicated the Au @ PPy-CS NPs had good blood compatibility and low cytotoxicity. The Au @ PPy-CS NPs we proposed provide a promising platform of blood circulation system for early illness diagnosis and therapy. PMID:27455639

  12. Core-shell morphology and characterization of carbon nanotube nanowires click coupled with polypyrrole

    NASA Astrophysics Data System (ADS)

    Rana, Sravendra; Cho, Jae Whan

    2011-07-01

    Core-shell nanowires having multiwalled carbon nanotubes (MWNT) as a core and polypyrrole (PPy) as a shell were synthesized using Cu(I)-catalyzed azide-alkyne cycloaddition click chemistry. According to transmission electron microscopy measurements, the uniform PPy layers of 10-20 nm in thickness were formed well on the MWNT's surface. In particular 'grafting from' click coupling was more effective in obtaining uniform and stable core-shell nanowires as well as in the reaction yield, compared to 'grafting to' click coupling. This is due to chemical bond formation between PPy and MWNT in equal intervals along the longitudinal direction of the MWNT, achieved by 'grafting from' click coupling. As a result, the core-shell nanowires were very stable even in the sonication of nanowires and showed an enhanced electrical conductivity of 80 S cm - 1, due to the synergetic interaction between MWNTs and PPy, which is higher than the conductivity of pure MWNTs and pure PPy. In addition, the core-shell nanowires could show better NO2 gas sensing properties compared to pure MWNTs and pure PPy as well as MWNT/PPy composites prepared by in situ polymerization. The synthesized core-shell nanowires would play an important role in preparing electrical and sensing devices.

  13. Core/shell colloidal semiconductor nanoplatelets.

    PubMed

    Mahler, Benoit; Nadal, Brice; Bouet, Cecile; Patriarche, Gilles; Dubertret, Benoit

    2012-11-14

    We have recently synthesized atomically flat semiconductor colloidal nanoplatelets with quasi 2D geometry. Here, we show that core/shell nanoplatelets can be obtained with a 2D geometry that is conserved. The epitaxial growth of the shell semiconductor is performed at room temperature. We report the detailed synthesis of CdSe/CdS and CdSe/CdZnS structures with different shell thicknesses. The shell growth is characterized both spectroscopically and structurally. In particular, the core/shell structure appears very clearly on high-resolution, high-angle annular dark-field transmission electron microscope images, thanks to the difference of atomic density between the core and the shell. When the nanoplatelets stand on their edge, we can precisely count the number of atomic planes forming the core and the shell. This provides a direct measurement, with atomic precision, of the core nanoplatelets thickness. The constraints exerted by the shell growth on the core is analyzed using global phase analysis. The core/shell nanoplatelets we obtained have narrow emission spectra with full-width at half-maximum close to 20 nm, and quantum yield that can reach 60%. PMID:23057684

  14. Thermo-responsive and aqueous dispersible ZnO/PNIPAM core/shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Alem, Halima; Schejn, Aleksandra; Roques-Carmes, Thibault; Ghanbaja, Jaafar; Schneider, Raphaël

    2015-08-01

    In this work, we developed a new process to covalently graft a thermoresponsive polymer on the surface of fluorescent nanocrystals in order to synthesize materials that combine both responsive and fluorescent properties. For the first time, poly(N-isopropylacrylamide) (PNIPAM) was grown by activator regenerated by electron transfer-atom transfer radical polymerization (ARGET-ATRP) from ZnO quantum dots (QDs) by surface-initiated polymerization. This process allowed the formation of fluorescent and responsive ZnO/PNIPAM core/shell QDs while only requiring the use of a ppm amount of copper for the synthesis. The influence of the nature of the silanized layer and the polymerization time on the properties of the final nanomaterials were investigated. Results clearly evidence that both the PNIPAM layer thickness and the temperature affected the luminescence properties of the core/shell nanoparticles, but also that the PNIPAM layer, when it is thick enough, could stabilize the QDs’ optical properties.

  15. Magnetic-Plasmonic Core-Shell Nanoparticles

    PubMed Central

    Levin, Carly S.; Hofmann, Cristina; Ali, Tamer A.; Kelly, Anna T.; Morosan, Emilia; Nordlander, Peter; Whitmire, Kenton H.; Halas, Naomi J.

    2013-01-01

    Nanoparticles composed of magnetic cores with continuous Au shell layers simultaneously possess both magnetic and plasmonic properties. Faceted and tetracubic nanocrystals consisting of wüstite with magnetite-rich corners and edges retain magnetic properties when coated with an Au shell layer, with the composite nanostructures showing ferrimagnetic behavior. The plasmonic properties are profoundly influenced by the high dielectric constant of the mixed-iron-oxide nanocrystalline core. A comprehensive theoretical analysis that examines the geometric plasmon tunability over a range of core permittivities enables us to identify the dielectric properties of the mixed-oxide magnetic core directly from the plasmonic behavior of the core-shell nanoparticle. PMID:19441794

  16. Hydrogel Nanofilaments via Core-Shell Electrospinning.

    PubMed

    Nakielski, Paweł; Pawłowska, Sylwia; Pierini, Filippo; Liwińska, Wioletta; Hejduk, Patryk; Zembrzycki, Krzysztof; Zabost, Ewelina; Kowalewski, Tomasz A

    2015-01-01

    Recent biomedical hydrogels applications require the development of nanostructures with controlled diameter and adjustable mechanical properties. Here we present a technique for the production of flexible nanofilaments to be used as drug carriers or in microfluidics, with deformability and elasticity resembling those of long DNA chains. The fabrication method is based on the core-shell electrospinning technique with core solution polymerisation post electrospinning. Produced from the nanofibers highly deformable hydrogel nanofilaments are characterised by their Brownian motion and bending dynamics. The evaluated mechanical properties are compared with AFM nanoindentation tests. PMID:26091487

  17. Real-Time Imaging of the Formation of Au-Ag Core-Shell Nanoparticles.

    PubMed

    Tan, Shu Fen; Chee, See Wee; Lin, Guanhua; Bosman, Michel; Lin, Ming; Mirsaidov, Utkur; Nijhuis, Christian A

    2016-04-27

    We study the overgrowth process of silver-on-gold nanocubes in dilute, aqueous silver nitrate solution in the presence of a reducing agent, ascorbic acid, using in situ liquid-cell electron microscopy. Au-Ag core-shell nanostructures were formed via two mechanistic pathways: (1) nuclei coalescence, where the Ag nanoparticles absorbed onto the Au nanocubes, and (2) monomer attachment, where the Ag atoms epitaxially deposited onto the Au nanocubes. Both pathways lead to the same Au-Ag core-shell nanostructures. Analysis of the Ag deposition rate reveals the growth modes of this process and shows that this reaction is chemically mediated by the reducing agent. PMID:27043921

  18. Core-shell diodes for particle detectors

    NASA Astrophysics Data System (ADS)

    Jia, Guobin; Plentz, Jonathan; Höger, Ingmar; Dellith, Jan; Dellith, Andrea; Falk, Fritz

    2016-02-01

    High performance particle detectors are needed for fundamental research in high energy physics in the exploration of the Higgs boson, dark matter, anti-matter, gravitational waves and proof of the standard model, which will extend the understanding of our Universe. Future particle detectors should have ultrahigh radiation hardness, low power consumption, high spatial resolution and fast signal response. Unfortunately, some of these properties are counter-influencing for the conventional silicon drift detectors (SDDs), so that they cannot be optimized simultaneously. In this paper, the main issues of conventional SDDs have been analyzed, and a novel core-shell detector design based on micro- and nano-structures etched into Si-wafers is proposed. It is expected to simultaneously reach ultrahigh radiation hardness, low power consumption, fast signal response and high spatial resolution down to the sub-micrometer range, which will probably meet the requirements for the most powerful particle accelerators in the near future. A prototype core-shell detector was fabricated using modern silicon nanotechnology and the functionality was tested using electron-beam-induced current measurements. Such a high performance detector will open many new applications in extreme radiation environments such as high energy physics, astrophysics, high resolution (bio-) imaging and crystallography, which will push these fields beyond their current boundaries.

  19. Heterogeneous core/shell fluoride nanocrystals with enhanced upconversion photoluminescence for in vivo bioimaging

    NASA Astrophysics Data System (ADS)

    Hao, Shuwei; Yang, Liming; Qiu, Hailong; Fan, Rongwei; Yang, Chunhui; Chen, Guanying

    2015-06-01

    We report on heterogeneous core/shell CaF2:Yb3+/Ho3+@NaGdF4 nanocrystals of 17 nm with efficient upconversion (UC) photoluminescence (PL) for in vivo bioimaging. Monodisperse core/shell nanostructures were synthesized using a seed-mediated growth process involving two quite different approaches of liquid-solid-solution and thermal decomposition. They exhibit green emission with a sharp band around 540 nm when excited at ~980 nm, which is about 39 times brighter than the core CaF2:Yb3+/Ho3+ nanoparticles. PL decays at 540 nm revealed that such an enhancement arises from efficient suppression of surface-related deactivation from the core nanocrystals. In vivo bioimaging employing water-dispersed core/shell nanoparticles displayed high contrast against the background.We report on heterogeneous core/shell CaF2:Yb3+/Ho3+@NaGdF4 nanocrystals of 17 nm with efficient upconversion (UC) photoluminescence (PL) for in vivo bioimaging. Monodisperse core/shell nanostructures were synthesized using a seed-mediated growth process involving two quite different approaches of liquid-solid-solution and thermal decomposition. They exhibit green emission with a sharp band around 540 nm when excited at ~980 nm, which is about 39 times brighter than the core CaF2:Yb3+/Ho3+ nanoparticles. PL decays at 540 nm revealed that such an enhancement arises from efficient suppression of surface-related deactivation from the core nanocrystals. In vivo bioimaging employing water-dispersed core/shell nanoparticles displayed high contrast against the background. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02287h

  20. Synthesis and characterization of core-shell acrylate based latex and study of its reactive blends.

    PubMed

    Liu, Xiang; Fan, Xiao-Dong; Tang, Min-Feng; Nie, Ying

    2008-03-01

    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. PMID:19325753

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

    PubMed Central

    Liu, Xiang; Fan, Xiao-Dong; Tang, Min-Feng; Nie, Ying

    2008-01-01

    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. PMID:19325753

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

    PubMed

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

    2015-09-01

    We report a facile method to synthesize anisotropic platelike gibbsite-polymer core-shell particles. Dopamine is self-polymerized on the surface of gibbsite nanoplates and forms a homogeneous layer on it. Transmission electron microscopy characterization of the resulting latexes demonstrates the formation of well-defined platelike core-shell particles. Reaction time and ultrasonification are found to be important factors to control the thickness of the polymer shell and avoid aggregation. Good control over the platelike morphology and 100% encapsulation efficiency have been achieved via this novel route. The resulting well-defined gibbsite-polydamine (G-PDA) core-shell nanoplates show excellent colloidal stability and can form opal-like columnar crystal with iridescent Bragg reflection after modest centrifugation. In addition, G-PDA core-shell nanoplates can serve both as reductant and stabilizer for the generation of Au nanoparticles (NPs) in situ. Au NPs with tunable size have been formed on the G-PDA particle surface, which show efficient catalytic activity for the reduction of 4-nitrophenol and Rhodamine B (RhB) in the presence of borohydride. Such nanocatalysts can be easily deposited on silicon substrate by spin-coating due to the large contact area of platelike G-PDA particles and the strong adhesive behavior of the PDA layer. The substrate-deposited nanocatalyst can be easily recycled which show excellent reusability for the reduction of RhB. PMID:26266398

  3. Synthesis and characterization of dual-functionalized core-shell fluorescent microspheres for bioconjugation and cellular delivery.

    PubMed

    Behrendt, Jonathan M; Nagel, David; Chundoo, Evita; Alexander, Lois M; Dupin, Damien; Hine, Anna V; Bradley, Mark; Sutherland, Andrew J

    2013-01-01

    The efficient transport of micron-sized beads into cells, via a non-endocytosis mediated mechanism, has only recently been described. As such there is considerable scope for optimization and exploitation of this procedure to enable imaging and sensing applications to be realized. Herein, we report the design, synthesis and characterization of fluorescent microsphere-based cellular delivery agents that can also carry biological cargoes. These core-shell polymer microspheres possess two distinct chemical environments; the core is hydrophobic and can be labeled with fluorescent dye, to permit visual tracking of the microsphere during and after cellular delivery, whilst the outer shell renders the external surfaces of the microspheres hydrophilic, thus facilitating both bioconjugation and cellular compatibility. Cross-linked core particles were prepared in a dispersion polymerization reaction employing styrene, divinylbenzene and a thiol-functionalized co-monomer. These core particles were then shelled in a seeded emulsion polymerization reaction, employing styrene, divinylbenzene and methacrylic acid, to generate orthogonally functionalized core-shell microspheres which were internally labeled via the core thiol moieties through reaction with a thiol reactive dye (DY630-maleimide). Following internal labeling, bioconjugation of green fluorescent protein (GFP) to their carboxyl-functionalized surfaces was successfully accomplished using standard coupling protocols. The resultant dual-labeled microspheres were visualized by both of the fully resolvable fluorescence emissions of their cores (DY630) and shells (GFP). In vitro cellular uptake of these microspheres by HeLa cells was demonstrated conventionally by fluorescence-based flow cytometry, whilst MTT assays demonstrated that 92% of HeLa cells remained viable after uptake. Due to their size and surface functionalities, these far-red-labeled microspheres are ideal candidates for in vitro, cellular delivery of proteins

  4. No-Core Shell Model and Reactions

    SciTech Connect

    Navratil, Petr; Ormand, W. Erich; Caurier, Etienne; Bertulani, Carlos

    2005-10-14

    There has been a significant progress in ab initio approaches to the structure of light nuclei. Starting from realistic two- and three-nucleon interactions the ab initio no-core shell model (NCSM) can predict low-lying levels in p-shell nuclei. It is a challenging task to extend ab initio methods to describe nuclear reactions. In this contribution, we present a brief overview of the NCSM with examples of recent applications as well as the first steps taken toward nuclear reaction applications. In particular, we discuss cross section calculations of p+6Li and 6He+p scattering as well as a calculation of the astrophysically important 7Be(p,{gamma})8B S-factor.

  5. Multifunctional composite core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Wei, Suying; Wang, Qiang; Zhu, Jiahua; Sun, Luyi; Lin, Hongfei; Guo, Zhanhu

    2011-11-01

    In this review paper, the state-of-the-art knowledge of the core-shell multifunctional nanoparticles (MNPs), especially with unique physiochemical properties, is presented. The synthesis methods were summarized from the aspects of both the advantages and the demerits. The core includes the inexpensive and easily oxidized metals and the noble shells include the relatively noble metals, carbon, silica, other oxides, and polymers. The properties including magnetic, optical, anti-corrosion and the surface chemistry of the NPs are thoroughly reviewed. The current status of the applications is reviewed with the detailed examples including the catalysis, giant magnetoresistance (GMR) sensing, electromagnetic interface shielding or microwave absorption, biomedical drug delivery, and the environmental remediation.

  6. No-Core Shell Model and Reactions

    SciTech Connect

    Navratil, P; Ormand, W E; Caurier, E; Bertulani, C

    2005-04-29

    There has been a significant progress in ab initio approaches to the structure of light nuclei. Starting from realistic two- and three-nucleon interactions the ab initio no-core shell model (NCSM) can predict low-lying levels in p-shell nuclei. It is a challenging task to extend ab initio methods to describe nuclear reactions. In this contribution, we present a brief overview of the NCSM with examples of recent applications as well as the first steps taken toward nuclear reaction applications. In particular, we discuss cross section calculations of p+{sup 6}Li and {sup 6}He+p scattering as well as a calculation of the astrophysically important {sup 7}Be(p, {gamma}){sup 8}B S-factor.

  7. Enhancement of Electrochromic Durability of a Film Made of Silica-Polyaniline Core-Shell Nanoparticles

    NASA Astrophysics Data System (ADS)

    Hwang, Taejin; Lee, Heungyeol; Kim, Hohyeong; Kim, Gyuntak; Mun, Gyeongjin

    Enhancing the operation life time or the electrochemical durability is one of the key issues in electrochromic material studies. It is generally accepted that the inorganic-organic hybrid structure is one of the effective ways to enhance the chemical stability of the material. In this study, an electrochromic film made of silica-polyaniline core-shell composite nanoparticles was tested. The composite particles were prepared through a chemical dispersion polymerization of aniline in an aqueous colloidal solution of silica. The synthesized particles were then dispersed into ethanol and the solution was deposited onto an Indium Tin Oxide (ITO)-coated glass substrate. The electrochromic characterization on the prepared films was performed using the cyclovoltammetry and the optical response to a switching potential. The results showed that the inorganic-organic core-shell hybrid nanoparticle could be a promising choice for the enhancement of electrochromic durability.

  8. Controlled self-assembly of multiferroic core-shell nanoparticles exhibiting strong magneto-electric effects

    SciTech Connect

    Sreenivasulu, Gollapudi; Hamilton, Sean L.; Lehto, Piper R.; Srinivasan, Gopalan; Popov, Maksym; Chavez, Ferman A.

    2014-02-03

    Ferromagnetic-ferroelectric composites show strain mediated coupling between the magnetic and electric sub-systems due to magnetostriction and piezoelectric effects associated with the ferroic phases. We have synthesized core-shell multiferroic nano-composites by functionalizing 10–100 nm barium titanate and nickel ferrite nanoparticles with complementary coupling groups and allowing them to self-assemble in the presence of a catalyst. The core-shell structure was confirmed by electron microscopy and magnetic force microscopy. Evidence for strong strain mediated magneto-electric coupling was obtained by static magnetic field induced variations in the permittivity over 16–18 GHz and polarization and by electric field induced by low-frequency ac magnetic fields.

  9. Tegafur loading and release properties of magnetite/poly(alkylcyanoacrylate) (core/shell) nanoparticles.

    PubMed

    Arias, José L; Ruiz, M Adolfina; Gallardo, Visitación; Delgado, Angel V

    2008-01-01

    In this work, we describe a reproducible method to prepare polymeric colloidal nanospheres of poly(ethyl-2-cyanoacrylate), poly(butylcyanoacrylate), poly(hexylcyanoacrylate) and poly(octylcyanoacrylate) with a magnetite core, and loaded with the anticancer drug Tegafur. The method is based on the emulsion polymerization procedure, often used in the synthesis of poly(alkylcyanoacrylate) nanospheres for drug delivery. The heterogeneous structure of the particles confer them both magnetic-field responsiveness and potential applicability as drug carriers. In order to investigate to what extent is this target achieved, we compare the surface electrical properties of the core/shell particles with those of both the nucleus and the coating material. The hysteresis cycles of both magnetite and composite particles demonstrate that the polymer shell reduces the magnetic responsiveness of the particles, but keeps their soft ferrimagnetic character unchanged. A detailed investigation of the capabilities of the core/shell particles to load this drug is shown. We found, by means of spectrophotometric and electrophoretic measurements, the existence of two drug loading mechanisms: absorption or entrapment in the polymeric network, and surface adsorption. The type of polymer, the pH and the drug concentration are the main factors determining the drug incorporation to the nanoparticles. The release studies showed a biphasic profile affected by the type of polymeric shell, the type of drug incorporation and the amount of drug loaded. PMID:17949844

  10. Core@shell bimetallic nanoparticle synthesis via anion coordination

    NASA Astrophysics Data System (ADS)

    Serpell, Christopher J.; Cookson, James; Ozkaya, Dogan; Beer, Paul D.

    2011-06-01

    Core@shell structured bimetallic nanoparticles are currently of immense interest due to their unique electronic, optical and catalytic properties. However, their synthesis is non-trivial. We report a new supramolecular route for the synthesis of core@shell nanoparticles, based on an anion coordination protocol—the first to function by binding the shell metal to the surface of the pre-formed primary metal core before reduction. The resultant gold/palladium and platinum/palladium core@shell nanoparticles have been characterized by aberration-corrected scanning transmission electron microscopy (as well as other techniques), giving striking atomic-resolution images of the core@shell architecture, and the unique catalytic properties of the structured nanoparticles have been demonstrated in a remarkable improvement of the selective production of industrially valuable chloroaniline from chloronitrobenzene.

  11. Graded core/shell semiconductor nanorods and nanorod barcodes

    DOEpatents

    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.

  12. Graded core/shell semiconductor nanorods and nanorod barcodes

    DOEpatents

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

    2013-03-26

    Graded core/shell semiconductor nanorods and shapped 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.

  13. Solution-Blown Core-Shell Self-Healing Nano- and Microfibers.

    PubMed

    Lee, Min Wook; Yoon, Sam S; Yarin, Alexander L

    2016-02-24

    Self-healing microfibers with core-shell geometry were studied. A commercial binary epoxy was encased in solution-blown polymer nano-/microfibers in the 0.2-2.6 μm diameter range. The core-shell microfibers were formed by coaxial nozzles, which encapsulated the epoxy resin and its hardener in separate cores. Solution blowing, the fiber-forming process used in this work, was at least 30 times faster than the electrospinning method used previously and has already been scaled up to the industrial level. These core-shell microfibers show self-healing capability, in which epoxy and hardener are released from the cores of damaged fibers, resulting in polymerization. The epoxy used had a higher strength and shorter solidification time than poly(dimethylsiloxane) (PDMS) used previously. Also, the larger fiber diameters in the present study facilitated faster release of the epoxy resin and its hardener from the fiber cores, shortening the solidification time in comparison to the previous studies. Blister tests were conducted, which measured the adhesion energy of microfiber mats to substrates and the cohesion energy between layers of microfiber mats before and after fatigue damage followed by self-healing. PMID:26836581

  14. Non-resonant Mie scattering: Emergent optical properties of core-shell polymer nanowires

    PubMed Central

    Khudiyev, Tural; Huseyinoglu, Ersin; Bayindir, Mehmet

    2014-01-01

    We provide the in-depth characterization of light-polymer nanowire interactions in the context of an effective Mie scattering regime associated with low refractive index materials. Properties of this regime sharply contrast with these of resonant Mie scattering, and involve the formation of strictly forward-scattered and coupling-free optical fields in the vicinity of core-shell polymer nanowires. Scattering from these optical fields is shown to be non-resonant in nature and independent from incident polarization. In order to demonstrate the potential utility of this scattering regime in one-dimensional (1D) polymeric nanostructures, we fabricate polycarbonate (PC) - polyvinylidene difluoride (PVDF) core-shell nanowires using a novel iterative thermal drawing process that yields uniform and indefinitely long core-shell nanostructures. These nanowires are successfully engineered for novel nanophotonics applications, including size-dependent structural coloration, efficient light capture on thin-film solar cells, optical nano-sensors with ultrahigh sensitivity and a mask-free photolithography method suitable for the straightforward production of 1D nanopatterns. PMID:24714206

  15. Ab Initio No-Core Shell Model

    SciTech Connect

    Barrett, B R; Navratil, P; Vary, J P

    2011-04-11

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

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

    NASA Astrophysics Data System (ADS)

    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.

  17. Core/shell structural transformation and brittle-to-ductile transition in nanowires

    NASA Astrophysics Data System (ADS)

    Yuan, Zaoshi; Nomura, Ken-ichi; Nakano, Aiichiro

    2012-04-01

    Nanowires (NWs) exhibit thermo-mechanical properties that are distinct from their bulk properties, and their understanding is critical for the reliability, manufacturability, and optimization of a wide range of devices consisting of NWs. Here, molecular-dynamics simulation reveals a rich size-temperature "phase diagram" for the mechanical response of a zinc-oxide NW under tension. For smaller diameters and higher temperatures, transitions are found from brittle cleavage to structural transformation-mediated brittle cleavage to ductile failure. Atomistic mechanisms of the unique nano-thermo-mechanical behavior are elucidated as a consequence of surface-structural relaxation, which in particular predicts spontaneous formation of a core/shell structure under tension. The nano-thermo-mechanical phase diagram resolves controversies between previous experiments and theory, and the predicted "intrinsic" core/shell structure may find device applications.

  18. Simulated evolution process of core-shell microstructures

    NASA Astrophysics Data System (ADS)

    Qin, Tao; Wang, Haipeng; Wei, Bingbo

    2007-08-01

    The evolution process of core-shell microstructures formed in monotectic alloys under the space environment condition was investigated by the numerical simulation method. In order to account for the effect of surface segregation on phase separation, Model H was modified by introducing a surface free energy term into the total free energy of alloy droplet. Three Fe-Cu alloys were taken as simulated examples, which usually exhibit metastable phase separation in undercooled and microgravity states. It was revealed by the dynamic simulation process that the formation of core-shell microstructures depends mainly on surface segregation and Marangoni convection. The phase separation of Fe65Cu35 alloy starts from a dispersed structure and gradually evolves into a triple-layer core-shell micro-structure. Similarly, Fe50Cu50 alloy experiences a structural evolution process of “bicontinuous phase → quadruple-layer core-shell → triple-layer core-shell”, while the microstructures of Fe35Cu65 alloy transfer from the dispersed structure into the final double-layer core-shell morphology. The Cu-rich phase always forms the outer layer because of surface segregation, whereas the internal microstructural evolution is controlled mainly by the Marangoni convection resulting from the temperature gradient.

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

    PubMed

    Surnar, Bapurao; Sharma, Kavita; Jayakannan, Manickam

    2015-11-14

    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 <5% of drug detoxification. In vitro drug-release studies revealed that the core-shell nanoparticles were ruptured upon exposure to lysosomal enzymes like esterase at the intracellular compartments. Cytotoxicity studies were performed both in normal wild-type mouse 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

  20. Core-shell and segmented polymer-metal composite nanostructures.

    PubMed

    Lahav, Michal; Weiss, Emily A; Xu, Qiaobing; Whitesides, George M

    2006-09-01

    Composite nanostructures (approximately 200 nm wide and several micrometers long) of metal and polyaniline (PANI) in two new variations of core-shell (PANI-Au) and segmented (Au-PANI and Ni-Au-PANI) architectures were fabricated electrochemically within anodized aluminum oxide (AAO) membranes. Control over the structure of these composites (including the length of the gold shells in the core-shell structures) was accomplished by adjusting the time and rate of electrodeposition and the pH of the solution from which the materials were grown. Exposure of the core-shell structures to oxygen plasma removed the PANI and yielded aligned gold nanotubes. In the segmented structures, a self-assembled monolayer (SAM) of thioaniline nucleated the growth of PANI on top of metal nanorods and acted as an adhesion layer between the metal and PANI components. PMID:16968046

  1. Electrochemical synthesis of core-shell magnetic nanowires

    NASA Astrophysics Data System (ADS)

    Ovejero, Jesús G.; Bran, Cristina; Vilanova, Enrique; Kosel, Jürgen; Morales, María P.; Vazquez, Manuel

    2015-09-01

    (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) 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 alloy). 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 nanowires. These core-shell nanowires can be released from the template thereby opening novel opportunities for biofunctionalization of individual nanowires.

  2. Fully Crystalline Faceted Fe-Au Core-Shell Nanoparticles.

    PubMed

    Langlois, C; Benzo, P; Arenal, R; Benoit, M; Nicolai, J; Combe, N; Ponchet, A; Casanove, M J

    2015-08-12

    Fe-Au core-shell nanoparticles displaying an original polyhedral morphology have been successfully synthesized through a physical route. Analyses using transmission electron microscopy show that the Au shell forms truncated pyramids epitaxially grown on the (100) facets of the iron cubic core. The evolution of the elastic energy and strain field in the nanoparticles as a function of their geometry and composition is calculated using the finite-element method. The stability of the remarkable centered core-shell morphology experimentally observed is attributed to the weak elastic energy resulting from the low misfit at the Fe/Au (100) interface compared to the surface energy contribution. PMID:26146846

  3. Optimized optical "tractor beam" for core-shell nanoparticles.

    PubMed

    Wang, Neng; Lu, Wanli; Ng, Jack; Lin, Zhifang

    2014-04-15

    It is known that core-shell subwavelength nanoparticles consisting of a dielectric shell and a metallic core can simultaneously support electric and magnetic dipolar resonances, which enhance forward scattering and suppress backward scattering. This creates favorable conditions for optical tractor beam applications. Using the generalized Lorenz-Mie theory and Maxwell stress tensor formulation, we demonstrate how optical pulling forces can be induced and optimized by first-order Bessel beams with appropriate polarization. The transverse stability of the core-shell nanoparticle under ambient damping is also verified by linear stability analysis and dynamical simulation. PMID:24979003

  4. Lithium Intercalation in Core-Shell Materials-Theoretical Analysis

    SciTech Connect

    Suthar, B; Subramanian, VR

    2014-03-04

    Core-shell composite structures are potential candidates for Li-ion battery electrodes as they can take advantage of materials with higher energy density and materials with higher cyclability. This paper derives an analytical solution for isotropic 1-dimensional diffusion with galvanostatic boundary condition in composite slab, cylinder and sphere using separation of variables method. A general interfacial condition has been used to represent the dynamics at the interface of the composite material rendering the solution useful for wide variety of battery materials. Using the derived analytical solution for diffusion, intercalation induced stresses were estimated for spherical core-shell materials. (C) 2014 The Electrochemical Society. All rights reserved.

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

    NASA Astrophysics Data System (ADS)

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

    2007-03-01

    A one-step method has been developed for synthesizing gold-polyaniline (Au@PANI) core-shell particles by using chlorauric acid (HAuCl4) 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.

  6. Surface zwitterionicalization of poly(vinylidene fluoride) membranes from the entrapped reactive core-shell silica nanoparticles.

    PubMed

    Zhu, Li-Jing; Zhu, Li-Ping; Zhang, Pei-Bin; Zhu, Bao-Ku; Xu, You-Yi

    2016-04-15

    We demonstrate the preparation and properties of poly(vinylidene fluoride) (PVDF) filtration membranes modified via surface zwitterionicalization mediated by reactive core-shell silica nanoparticles (SiO2 NPs). The organic/inorganic hybrid SiO2 NPs grafted with poly(methyl meth acrylate)-block-poly(2-dimethylaminoethyl methacrylate) copolymer (PMMA-b-PDMAEMA) shell were prepared by surface-initiated reversible addition fragmentation chain transfer (SI-RAFT) polymerization and then used as a membrane-making additive of PVDF membranes. The PDMAEMA exposed on membrane surface and pore walls were quaternized into zwitterionic poly(sulfobetaine methacrylate) (PSBMA) using 1,3-propane sultone (1,3-PS) as the quaternization agent. The membrane surface chemistry and morphology were analyzed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. The hydrophilicity, permeability and antifouling ability of the investigated membranes were evaluated in detail. It was found that the PSBMA chains brought highly-hydrophilic and strong fouling resistant characteristics to PVDF membranes due to the powerful hydration of zwitterionic surface. The SiO2 cores and PMMA chains in the hybrid NPs play a role of anchors for the linking of PSBMA chains to membrane surface. Compared to the traditional strategies for membrane hydrophilic modification, the developed method in this work combined the advantages of both blending and surface reaction. PMID:26835581

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

    PubMed Central

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

    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 <5% of drug detoxification. In vitro drug-release studies revealed that the core-shell nanoparticles were ruptured upon exposure to lysosomal enzymes like esterase at the intracellular compartments. Cytotoxicity studies were performed both in normal wild-type mouse 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

  9. Chemoenzymatic Synthesis of Amphiphilic Core-Shell TMP-(PCL-b-PGMA2)3 Star-Block Copolymer.

    PubMed

    Wang, Shuwei; Li, Yapeng; Zhang, Xiaonan; Chen, Xuesi; Wang, Jingyuan; Zhang, He-Xin; Yoon, Keun-Byoung

    2015-06-01

    A novel well-defined amphiphilic Core-Shell star-block copolymer was synthesized from trimethylolpropane, ε-caprolactone, and glycidyl methacrylate by a combination of enzymatic ring-opening polymerization and atom transfer radical polymerization. The structure and molecular weight of the macroinitiator and the star-block copolymer were confirmed by means of nuclear magnetic resonance and gel permeation chromatography. The effects of the glycidyl methacrylate sequence length on the hydrodynamic diameter and morphology of the polymer micelles were investigated by dynamic light scattering and transmission electron microscopy, respectively. PMID:26369103

  10. Metal enhanced fluorescence in rare earth doped plasmonic core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Derom, S.; Berthelot, A.; Pillonnet, A.; Benamara, O.; Jurdyc, A. M.; Girard, C.; Colas des Francs, G.

    2013-12-01

    We theoretically and numerically investigate metal enhanced fluorescence of plasmonic core-shell nanoparticles doped with rare earth (RE) ions. Particle shape and size are engineered to maximize the average enhancement factor (AEF) of the overall doped shell. We show that the highest enhancement (11 in the visible and 7 in the near-infrared) is achieved by tuning either the dipolar or the quadrupolar particle resonance to the rare earth ion’s excitation wavelength. Additionally, the calculated AEFs are compared to experimental data reported in the literature, obtained in similar conditions (plasmon mediated enhancement) or when a metal-RE energy transfer mechanism is involved.

  11. Core-shell composite particles composed of biodegradable polymer particles and magnetic iron oxide nanoparticles for targeted drug delivery

    NASA Astrophysics Data System (ADS)

    Oka, Chiemi; Ushimaru, Kazunori; Horiishi, Nanao; Tsuge, Takeharu; Kitamoto, Yoshitaka

    2015-05-01

    Core-shell composite particles with biodegradability and superparamagnetic behavior were prepared using a Pickering emulsion for targeted drug delivery based on magnetic guidance. The composite particles were composed of a core of biodegradable polymer and a shell of assembled magnetic iron oxide nanoparticles. It was found that the dispersibility of the nanoparticles is crucial for controlling the core-shell structure. The addition of a small amount of dispersant into the nanoparticle's suspension could improve the dispersibility and led to the formation of composite particles with a thin magnetic shell covering a polymeric core. The composite particles were also fabricated with a model drug loaded into the core, which was released via hydrolysis of the core under strong alkaline conditions. Because the core can also be biodegraded by lipase, this result suggests that the slow release of the drug from the composite particles should occur inside the body.

  12. Enhanced performance of core-shell structured polyaniline at helical carbon nanotube hybrids for ammonia gas sensor

    SciTech Connect

    Tian, Xin; Wang, Qiang; Chen, Xiangnan; Yang, Weiqing; Xu, Xiaoling E-mail: bihan-2001@163.com; Jiang, Man; Zhou, Zuowan E-mail: bihan-2001@163.com; Wu, Zuquan

    2014-11-17

    A core-shell structured hybrid of polyaniline at helical carbon nanotubes was synthesized using in situ polymerization, which the helical carbon nanotubes were uniformly surrounded by a layer of polyaniline nanorods array. More interestingly, repeatable responses were experimentally observed that the sensitivity to ammonia gas of the as-prepared helical shaped core-shell hybrid displays an enhancement of more than two times compared to those of only polyaniline or helical carbon nanotubes sensors because of the peculiar structures with high surface area. This kind of hybrid comprising nanorod arrays of conductive polymers covering carbon nanotubes and related structures provide a potential in sensors of trace gas detection for environmental monitoring and safety forecasting.

  13. Magnetism of iron oxide based core-shell nanoparticles from interface mixing with enhanced spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Skoropata, E.; Desautels, R. D.; Chi, C.-C.; Ouyang, H.; Freeland, J. W.; van Lierop, J.

    2014-01-01

    We show that the magnetism of core-shell nanoparticles (made of maghemite, γ-Fe2O3, cores and transition-metal and metal-oxide shells) is altered substantially by the interface, which is a doped iron-oxide layer formed naturally during the seed-mediated synthesis process, a route used typically to produce core-shell nanoparticles. Characteristics fundamental to useful applications, such as the anisotropy and superparamagnetic blocking temperature, were altered substantially with Cu, CoO, MnO, and NiO shells. To ascertain the origin of this behavior, the prototype γ-Fe2O3/CoO core-shell nanoparticles are described in detail. We show that the magnetism originates essentially from an interfacial doped iron-oxide layer formed via migration of shell ions, e.g., Co2+, into octahedral site vacancies in the surface layers of the γ-Fe2O3 core. For this system, an overall Fe morb/mspin=0.15±0.03 is measured (morb˜0 for the Fe-oxides) and an enhanced Co morb/mspin=0.65±0.03 elucidates the origin of the unexpectedly high overall anisotropy of the nanoparticle. This interfacial layer is responsible for the overall (e.g., bulk) magnetism and provides a perspective on how the magnetism of core-shell nanoparticles manifests from the selected core and shell materials.

  14. Engineering of Superparamagnetic Core-Shell Iron Oxide/N-Chloramine Nanoparticles for Water Purification.

    PubMed

    Haham, Hai; Natan, Michal; Gutman, Ori; Kolitz-Domb, Michal; Banin, Ehud; Margel, Shlomo

    2016-07-20

    In this study, we describe the synthesis and characterization of superparamagnetic core-shell iron oxide (IO)/N-halamine antibacterial nanoparticles (NPs). For this purpose, superparamagnetic IO core NPs were coated with cross-linked polymethacrylamide (PMAA) by surfactant-free dispersion copolymerization of methacrylamide and N,N-methylenebis(acrylamide) in an aqueous continuous phase. The effect of the polymerization process on the chemical composition, size, shape, crystallinity, and magnetic properties of the IO/PMAA NPs was elucidated. Conversion of the core-shell IO/PMAA NPs into their N-halamine form, IO/PMAA-Cl, was accomplished using a chlorination reaction with sodium hypochlorite. The influence of chlorination on the shape, crystallinity, and magnetic properties of the IO/PMAA NPs was studied. The IO/PMAA-Cl NPs demonstrated excellent antibacterial activity against Gram-negative and Gram-positive bacteria. Finally, the chlorination recharging capabilities of the NPs and their potential for use in the purification of water containing bacteria were demonstrated with magnetic columns packed with the IO/PMAA-Cl NPs. PMID:27348740

  15. Dual-responsive magnetic core-shell nanoparticles for nonviral gene delivery and cell separation.

    PubMed

    Majewski, Alexander P; Schallon, Anja; Jérôme, Valérie; Freitag, Ruth; Müller, Axel H E; Schmalz, Holger

    2012-03-12

    We present the synthesis of dual-responsive (pH and temperature) magnetic core-shell nanoparticles utilizing the grafting-from approach. First, oleic acid stabilized superparamagnetic maghemite (γ-Fe(2)O(3)) nanoparticles (NPs), prepared by thermal decomposition of iron pentacarbonyl, were surface-functionalized with ATRP initiating sites bearing a dopamine anchor group via ligand exchange. Subsequently, 2-(dimethylamino)ethyl methacrylate (DMAEMA) was polymerized from the surface by ATRP, yielding dual-responsive magnetic core-shell NPs (γ-Fe(2)O(3)@PDMAEMA). The attachment of the dopamine anchor group on the nanoparticle's surface is shown to be reversible to a certain extent, resulting in a grafting density of 0.15 chains per nm(2) after purification. Nevertheless, the grafted NPs show excellent long-term stability in water over a wide pH range and exhibit a pH- and temperature-dependent reversible agglomeration, as revealed by turbidimetry. The efficiency of γ-Fe(2)O(3)@PDMAEMA hybrid nanoparticles as a potential transfection agent was explored under standard conditions in CHO-K1 cells. Remarkably, γ-Fe(2)O(3)@PDMAEMA led to a 2-fold increase in the transfection efficiency without increasing the cytotoxicity, as compared to polyethyleneimine (PEI), and yielded on average more than 50% transfected cells. Moreover, after transfection with the hybrid nanoparticles, the cells acquired magnetic properties that could be used for selective isolation of transfected cells. PMID:22296556

  16. Atrazine adsorption removal with nylon6/polypyrrole core-shell nanofibers mat: possible mechanism and characteristics

    NASA Astrophysics Data System (ADS)

    Yang, Bi-Yi; Cao, Yang; Qi, Fei-Fei; Li, Xiao-Qing; Xu, Qian

    2015-05-01

    A functionalized nylon6/polypyrrole core-shell nanofibers mat (PA6/PPy NFM) was prepared via situ polymerization on nylon6 electrospun nanofibers mat (PA6 NFM) template and used as an adsorbent to remove atrazine from aqueous solutions. The core-shell structure of PA6/PPy NFM can be clearly proved under scanning electron microscope (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The effects of initial solution pH and ionic strength, as well as the comparison of the adsorption capacity of functionalized (PA6/PPy NFM) and non-functionalized (PA6 NFM) adsorbent, were examined to reveal the possible adsorption mechanism. The results indicated that π-π interaction and electrostatic interaction should play a key role in the adsorption process. The kinetics and thermodynamics studies also further elucidated the detailed adsorption characteristics of atrazine removal by PA6/PPy NFM. The adsorption of atrazine could be well described by the pseudo-second-order equation. The adsorption equilibrium data was well fitted with the Freundlich isotherm model with a maximum adsorption capacity value of 14.8 mg/g. In addition, the increase of adsorption rate caused by a temperature increase could be felicitously explained by the endothermic reaction. The desorption results showed that the adsorption capacity remained almost unchanged after six adsorption/desorption cycles. These results suggest that PA6/PPy NFM could be employed as an efficient adsorbent for removing atrazine from contaminated water sources.

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

    NASA Astrophysics Data System (ADS)

    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 <5% of drug detoxification. In vitro drug-release studies revealed that the core-shell nanoparticles were ruptured upon exposure to lysosomal enzymes like esterase at the intracellular compartments. Cytotoxicity studies were performed both in normal wild-type mouse 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

  18. Nanocomposite plasmonic fluorescence emitters with core/shell configurations.

    SciTech Connect

    Brener, Igal; Luk, Ting Shan; Miao, Xiaoyu

    2010-06-01

    This paper is focused on the optical properties of nanocomposite plasmonic emitters with core/shell configurations, where a fluorescence emitter is located inside a metal nanoshell. Systematic theoretical investigations are presented for the influence of material type, core radius, shell thickness, and excitation wavelength on the internal optical intensity, radiative quantum yield, and fluorescence enhancement of the nanocomposite emitter. It is our conclusion that: (i) an optimal ratio between the core radius and shell thickness is required to maximize the absorption rate of fluorescence emitters, and (ii) a large core radius is desired to minimize the non-radiative damping and avoid significant quantum yield degradation of light emitters. Several experimental approaches to synthesize these nanocomposite emitters are also discussed. Furthermore, our theoretical results are successfully used to explain several reported experimental observations and should prove useful for designing ultra-bright core/shell nanocomposite emitters.

  19. Process to make core-shell structured nanoparticles

    DOEpatents

    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.

  20. Rare Earth core/shell nanobarcodes for multiplexed trace biodetection.

    PubMed

    Chen, Lei; Li, Xiaomin; Shen, Dengke; Zhou, Lei; Zhu, Dan; Fan, Chunhai; Zhang, Fan

    2015-06-01

    Multiplexed detection technology has been attractive for its simultaneous assay of several analytes, which play significant roles in applications such as screening for combinatorial chemistry, genetic analysis, and clinical diagnostics. This work reports a novel and potentially powerful encoding system based upon dispersible suspension arrays of multilayer rare earth core/shell nanoparticles that are capable of multiplexed, high-sensitivity reporting for biomolecule detection by the Z-contrast imaging. These nanobarcode arrays are encoded by nanostructure design based on different atomic numbers. With the well-resolved high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) decoding technique, many thousands of unique nanobarcodes can be identified by multilayer core/shell nanostructure. Their applications to multiplexed biodetection of DNA demonstrated the highly sensitive (picomole) features of this novel nanobarcode system. PMID:25951110

  1. Synthesis of fullerene@gold core-shell nanostructures.

    PubMed

    Ren, Yupeng; Paira, Priyankar; Nayak, Tapas Ranjan; Ang, Wee Han; Pastorin, Giorgia

    2011-07-21

    A "direct encapsulation" method was developed for the synthesis of highly stable water-soluble fullerene@gold core-shell nanostructures, with gold nanoshells showing either closed or porous morphology. This gold nano-shell coating formed a "nano-oven", capable of decomposing encapsulated fullerene molecules rapidly when irradiated by laser. We envisaged this being a useful tool for chemical reactions as well as a novel scaffold for nano-material synthesis. PMID:21655582

  2. Isolation and Characterization of Monodisperse Core-Shell Nanoparticle Fractions.

    PubMed

    Sánchez-Ferrer, Antoni; Carney, Randy P; Stellacci, Francesco; Mezzenga, Raffaele; Isa, Lucio

    2015-10-20

    Monodispersity is a key property to control the self-assembly of colloidal particles, and is typically reached after fine-tuning of the synthesis conditions. Monodisperse particle fractions can also be separated from polydisperse suspensions via ultracentrifugation. This paper demonstrates the capability of isolating and characterizing suspensions of core-shell iron oxide-polymer nanoparticles with extremely low polydispersity (p < 0.01) and, thus, of complementing nanoparticle synthetic approaches in the pursuit of highly monodisperse materials. PMID:26406563

  3. Radial modulation doping in core-shell nanowires

    NASA Astrophysics Data System (ADS)

    Dillen, David C.; Kim, Kyounghwan; Liu, En-Shao; Tutuc, Emanuel

    2014-02-01

    Semiconductor nanowires are potential candidates for applications in quantum information processing, Josephson junctions and field-effect transistors and provide a unique test bed for low-dimensional physical phenomena. The ability to fabricate nanowire heterostructures with atomically flat, defect-free interfaces enables energy band engineering in both axial and radial directions. The design of radial, or core-shell, nanowire heterostructures relies on energy band offsets that confine charge carriers into the core region, potentially reducing scattering from charged impurities on the nanowire surface. Key to the design of such nanoscale heterostructures is a fundamental understanding of the heterointerface properties, particularly energy band offsets and strain. The charge-transfer and confinement mechanism can be used to achieve modulation doping in core-shell structures. By selectively doping the shell, which has a larger bandgap, charge carriers are donated and confined in the core, generating a quasi-one-dimensional electron system with higher mobility. Here, we demonstrate radial modulation doping in coherently strained Ge-SixGe1-x core-shell nanowires and a technique to directly measure their valence band offset. Radial modulation doping is achieved by incorporating a B-doped layer during epitaxial shell growth. In contrast to previous work showing site-selective doping in Ge-Si core-shell nanowires, we find both an enhancement in peak hole mobility compared with undoped nanowires and observe a decoupling of electron transport in the core and shell regions. This decoupling stems from the higher carrier mobility in the core than in the shell and allows a direct measurement of the valence band offset for nanowires of various shell compositions.

  4. Graded core/shell semiconductor nanorods and nanorod barcodes

    DOEpatents

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

    2009-05-19

    Disclosed herein is a graded core/shell semiconductor nanorod having at least a first segment of a core of a Group II-VI, Group III-V or a Group IV semiconductor, a graded shell overlying the core, wherein the graded shell comprises at least two monolayers, wherein the at least two monolayers each independently comprise a Group II-VI, Group III-V or a Group IV semiconductor.

  5. Au-Cu2O core-shell nanowire photovoltaics

    NASA Astrophysics Data System (ADS)

    Oener, S. Z.; Mann, S. A.; Sciacca, B.; Sfiligoj, C.; Hoang, J.; Garnett, E. C.

    2015-01-01

    Semiconductor nanowires are among the most promising candidates for next generation photovoltaics. This is due to their outstanding optical and electrical properties which provide large optical cross sections while simultaneously decoupling the photon absorption and charge carrier extraction length scales. These effects relax the requirements for both the minority carrier diffusion length and the amount of semiconductor needed. Metal-semiconductor core-shell nanowires have previously been predicted to show even better optical absorption than solid semiconductor nanowires and offer the additional advantage of a local metal core contact. Here, we fabricate and analyze such a geometry using a single Au-Cu2O core-shell nanowire photovoltaic cell as a model system. Spatially resolved photocurrent maps reveal that although the minority carrier diffusion length in the Cu2O shell is less than 1 μm, the radial contact geometry with the incorporated metal electrode still allows for photogenerated carrier collection along an entire nanowire. Current-voltage measurements yield an open-circuit voltage of 600 mV under laser illumination and a dark diode turn-on voltage of 1 V. This study suggests the metal-semiconductor core-shell nanowire concept could be extended to low-cost, large-scale photovoltaic devices, utilizing for example, metal nanowire electrode grids coated with epitaxially grown semiconductor shells.

  6. Porous Core-Shell Nanostructures for Catalytic Applications

    NASA Astrophysics Data System (ADS)

    Ewers, Trevor David

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

  7. Thermal conductivity modeling of core-shell and tubular nanowires.

    PubMed

    Yang, Ronggui; Chen, Gang; Dresselhaus, Mildred S

    2005-06-01

    The heteroepitaxial growth of crystalline core-shell nanostructures of a variety of materials has become possible in recent years, allowing the realization of various novel nanoscale electronic and optoelectronic devices. The increased surface or interface area will decrease the thermal conductivity of such nanostructures and impose challenges for the thermal management of such devices. In the meantime, the decreased thermal conductivity might benefit the thermoelectric conversion efficiency. In this paper, we present modeling results on the lattice thermal conductivity of core-shell and tubular nanowires along the wire axis direction using the phonon Boltzmann equation. We report the dependence of the thermal conductivity on the surface conditions and the core-shell geometry for silicon core-germanium shell and tubular silicon nanowires at room temperature. The results show that the effective thermal conductivity changes not only with the composition of the constituents but also with the radius of the nanowires and nanopores due to the nature of the ballistic phonon transport. The results in this work have implications for the design and operation of a variety of nanoelectronic devices, optoelectronic devices, and thermoelectric materials and devices. PMID:15943452

  8. Core-shell upconversion nanoparticle - semiconductor heterostructures for photodynamic therapy.

    PubMed

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

    2015-01-01

    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. PMID:25652742

  9. Core - shell upconversion nanoparticle - semiconductor heterostructures for photodynamic therapy

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed Central

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

    2015-01-01

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

  11. Thermoelectric properties of porous multi-walled carbon nanotube/polyaniline core/shell nanocomposites.

    PubMed

    Zhang, Kun; Davis, Marauo; Qiu, Jingjing; Hope-Weeks, Louisa; Wang, Shiren

    2012-09-28

    Porous polyaniline (PANI)-coated multi-walled carbon nanotube (MWNT) core/shell nanohybrids were fabricated through in situ polymerization and subsequently assembled into macroscopic composites. N(2) adsorption/desorption analysis indicated that the volume of nanopores increased significantly, which could make a significant contribution to phonon scattering. Thermal annealing was also carried out to improve the Seebeck coefficient of the as-produced nanocomposites. The optimal sample showed electrical conductivity of 14.1 S cm(-1), a Seebeck coefficient of 79.8 μV K(-1) and thermal conductivity of 0.27 W mK(-1), resulting in a highest figure of merit (ZT) of 0.01 at a very low loading of MWNTs (<1 wt%). These results will provide a potential direction to enhance thermoelectric performance of organic materials and also facilitate the application of organic materials in thermal energy harvesting or cooling. PMID:22947620

  12. Thermoelectric properties of porous multi-walled carbon nanotube/polyaniline core/shell nanocomposites

    NASA Astrophysics Data System (ADS)

    Zhang, Kun; Davis, Marauo; Qiu, Jingjing; Hope-Weeks, Louisa; Wang, Shiren

    2012-09-01

    Porous polyaniline (PANI)-coated multi-walled carbon nanotube (MWNT) core/shell nanohybrids were fabricated through in situ polymerization and subsequently assembled into macroscopic composites. N2 adsorption/desorption analysis indicated that the volume of nanopores increased significantly, which could make a significant contribution to phonon scattering. Thermal annealing was also carried out to improve the Seebeck coefficient of the as-produced nanocomposites. The optimal sample showed electrical conductivity of 14.1 S cm-1, a Seebeck coefficient of 79.8 μV K-1 and thermal conductivity of 0.27 W mK-1, resulting in a highest figure of merit (ZT) of 0.01 at a very low loading of MWNTs (<1 wt%). These results will provide a potential direction to enhance thermoelectric performance of organic materials and also facilitate the application of organic materials in thermal energy harvesting or cooling.

  13. Structured superparamagnetic nanoparticles for high performance mediator of magnetic fluid hyperthermia: synthesis, colloidal stability and biocompatibility evaluation.

    PubMed

    Thorat, N D; Otari, S V; Bohara, R A; Yadav, H M; Khot, V M; Salunkhe, A B; Phadatare, M R; Prasad, A I; Ningthoujam, R S; Pawar, S H

    2014-09-01

    Core-shell structures with magnetic core and metal/polymer shell provide a new opportunity for constructing highly efficient mediator for magnetic fluid hyperthermia. Herein, a facile method is described for the synthesis of superparamagnetic LSMO@Pluronic F127 core-shell nanoparticles. Initially, the surface of the LSMO nanoparticles is functionalized with oleic acid and the polymeric shell formation is achieved through hydrophobic interactions with oleic acid. Each step is optimized to get good dispersion and less aggregation. This methodology results into core-shell formation, of average diameter less than 40 nm, which was stable under physiological conditions. After making a core-shell formulation, a significant increase of specific absorption rate (up to 300%) has been achieved with variation of the magnetization (<20%). Furthermore, this high heating capacity can be maintained in various simulated physiological conditions. The observed specific absorption rate is almost higher than Fe3O4. MTT assay is used to evaluate the toxicity of bare and core-shell MNPs. The mechanism of cell death by necrosis and apoptosis is studied with sequential staining of acridine orange and ethidium bromide using fluorescence and confocal microscopy. The present work reports a facile method for the synthesis of core-shell structure which significantly improves SAR and biocompatibility of bare LSMO MNPs, indicating potential application for hyperthermia. PMID:25063164

  14. Core-shell nanoparticle-based peptide therapeutics and combined hyperthermia for enhanced cancer cell apoptosis.

    PubMed

    Shah, Birju P; Pasquale, Nicholas; De, Gejing; Tan, Tao; Ma, Jianjie; Lee, Ki-Bum

    2014-09-23

    Mitochondria-targeting peptides have garnered immense interest as potential chemotherapeutics in recent years. However, there is a clear need to develop strategies to overcome the critical limitations of peptides, such as poor solubility and the lack of target specificity, which impede their clinical applications. To this end, we report magnetic core-shell nanoparticle (MCNP)-mediated delivery of a mitochondria-targeting pro-apoptotic amphipathic tail-anchoring peptide (ATAP) to malignant brain and metastatic breast cancer cells. Conjugation of ATAP to the MCNPs significantly enhanced the chemotherapeutic efficacy of ATAP, while the presence of targeting ligands afforded selective delivery to cancer cells. Induction of MCNP-mediated hyperthermia further potentiated the efficacy of ATAP. In summary, a combination of MCNP-mediated ATAP delivery and subsequent hyperthermia resulted in an enhanced effect on mitochondrial dysfunction, thus resulting in increased cancer cell apoptosis. PMID:25133971

  15. PDMAEMA-grafted core-shell-corona particles for nonviral gene delivery and magnetic cell separation.

    PubMed

    Majewski, Alexander P; Stahlschmidt, Ullrich; Jérôme, Valérie; Freitag, Ruth; Müller, Axel H E; Schmalz, Holger

    2013-09-01

    Monodisperse, magnetic nanoparticles as vectors for gene delivery were successfully synthesized via the grafting-from approach. First, oleic acid stabilized maghemite nanoparticles (γ-Fe2O3) were encapsulated with silica utilizing a reverse microemulsion process with simultaneous functionalization with initiating sites for atom transfer radical polymerization (ATRP). Polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA) from the core-shell nanoparticles led to core-shell-corona hybrid nanoparticles (γ-Fe2O3@silica@PDMAEMA) with an average grafting density of 91 polymer chains of DP(n) = 540 (PDMAEMA540) per particle. The permanent attachment of the arms was verified by field-flow fractionation. The dual-responsive behavior (pH and temperature) was confirmed by dynamic light scattering (DLS) and turbidity measurements. The interaction of the hybrid nanoparticles with plasmid DNA at various N/P ratios (polymer nitrogen/DNA phosphorus) was investigated by DLS and zeta-potential measurements, indicating that for N/P ≥ 7.5 the complexes bear a positive net charge and do not undergo secondary aggregation. The hybrids were tested as transfection agents under standard conditions in CHO-K1 and L929 cells, revealing transfection efficiencies >50% and low cytotoxicity at N/P ratios of 10 and 15, respectively. Due to the magnetic properties of the hybrid gene vector, it is possible to collect most of the cells that have incorporated a sufficient amount of magnetic material by using a magnetic activated cell sorting system (MACS). Afterward, cells were further cultivated and displayed a transfection efficiency of ca. 60% together with a high viability. PMID:23889326

  16. Synthesis and characterization of fluorinated magnetic core-shell nanoparticles for inhibition of insulin amyloid fibril formation

    NASA Astrophysics Data System (ADS)

    Skaat, Hadas; Belfort, Georges; Margel, Shlomo

    2009-06-01

    Maghemite (γ-Fe2O3) magnetic nanoparticles of 15.0 ± 2.1 nm are formed by nucleation followed by controlled growth of maghemite thin films on gelatin-iron oxide nuclei. Uniform magnetic γ-Fe2O3/poly (2,2,3,3,4,4,4-heptafluorobutyl acrylate) (γ-Fe2O3/PHFBA) core-shell nanoparticles are prepared by emulsion polymerization of the fluorinated monomer 2,2,3,3,4,4,4-heptafluorobutyl acrylate (HFBA) in the presence of the maghemite nanoparticles. The kinetics of the insulin fibrillation process in the absence and in the presence of the γ-Fe2O3/PHFBA core-shell nanoparticles are elucidated. A significant direct slow transition from α-helix to β-sheets during insulin fibril formation is observed in the presence of the γ-Fe2O3/PHFBA nanoparticles. This is in contradiction to our previous manuscript, which illustrated that the γ-Fe2O3 core nanoparticles do not affect the kinetics of the formation of the insulin fibrils, and to other previous publications that describe acceleration of the fibrillation process by using various types of nanoparticles. These core-shell nanoparticles may therefore be also useful for the inhibition of conformational changes of other amyloidogenic proteins that lead to neurodegenerative diseases such as Alzheimer's, Parkinson's, Huntington's, mad cow and prion diseases.

  17. Facile synthesis of core-shell structured PANI-Co3O4 nanocomposites with superior electrochemical performance in supercapacitors

    NASA Astrophysics Data System (ADS)

    Hai, Zhenyin; Gao, Libo; Zhang, Qiang; Xu, Hongyan; Cui, Danfeng; Zhang, Zengxing; Tsoukalas, Dimitris; Tang, Jun; Yan, Shubin; Xue, Chenyang

    2016-01-01

    Core-shell structured PANI-Co3O4 nanocomposites for supercapacitor applications were synthesized by combination of carbon-assisted method and in situ polymerization method. The crystalline structure, optical band gap, morphology, and hydrophilic property, as the major factors affecting the performances of supercapacitors, were investigated by X-ray diffraction (XRD), UV-vis spectrophotometry (UV-vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and water contact angle (WCA). The core-shell structured PANI-Co3O4 nanocomposites are characterized by amorphous PANI, small bandgaps, large surface area and favorable hydrophilicity, which indicates the superior electrochemical performances of the nanocomposites as electrode material for supercapacitors. Cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS) measurements were conducted in 6 M KOH aqueous solution to evaluate the electrochemical performances. The results shows that core-shell structured PANI-Co3O4 nanocomposites exhibit a high specific capacitance of 1184 F g-1 at 1.25 A g-1, excellent cycling stability of a capacitance retention of 84.9% after 1000 galvanostatic charge/discharge cycles, good electrical conductivity and ion diffusion behavior.

  18. Boronic acid-functionalized core-shell-shell magnetic composite microspheres for the selective enrichment of glycoprotein.

    PubMed

    Pan, Miaorong; Sun, Yangfei; Zheng, Jin; Yang, Wuli

    2013-09-11

    In this work, core-shell-shell-structured boronic acid-functionalized magnetic composite microspheres Fe3O4@SiO2@poly (methyl methacrylate-co-4-vinylphenylbornoic acid) (Fe3O4@SiO2@P(MMA-co-VPBA)) with a uniform size and fine morphology were synthesized. Here, Fe3O4 magnetic particles were prepared by a solvothermal reaction, whereas the Fe3O4@SiO2 microspheres with a core-shell structure were obtained by a sol-gel process. 3-(Trimethoxysilyl) propyl methacrylate (MPS)-modified Fe3O4@SiO2 was used as the seed in the emulsion polymerization of MMA and VPBA to form the core-shell-shell-structured magnetic composite microspheres. As the boronic acid groups on the surface of Fe3O4@SiO2@P(MMA-co-VPBA) could form tight yet reversible covalent bonds with the cis-1,2-diols groups of glycoproteins, the magnetic composite microspheres were applied to enrich a standard glycoprotein, horseradish peroxidase (HRP), and the results demonstrated that the composite microspheres have a higher affinity for the glycoproteins in the presence of the nonglycoprotein bovine serum albumin (BSA) over HRP. Additionally, different monomer mole ratios of MMA/VPBA were studied, and the results implied that using MMA as the major monomer could reduce the amount of VPBA with a similar glycoprotein enrichment efficiency but a lower cost. PMID:23924282

  19. Synthesis and characterization of Fe3O4-TiO2 core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Stefan, M.; Pana, O.; Leostean, C.; Bele, C.; Silipas, D.; Senila, M.; Gautron, E.

    2014-09-01

    Composite core-shell nanoparticles may have morpho-structural, magnetic, and optical (photoluminescence (PL)) properties different from each of the components considered separately. The properties of Fe3O4-TiO2 nanoparticles can be controlled by adjusting the titania amount (shell thinness). Core-shell nanoparticles were prepared by seed mediated growth of semiconductor (TiO2) through a modified sol-gel process onto preformed magnetite (Fe3O4) cores resulted from the co-precipitation method. The structure and morphology of samples were characterized by X-ray diffraction, transmission electron microscopy (TEM), and high resolution-TEM respectively. X-ray photoelectron spectroscopy was correlated with ICP-AES. Magnetic measurements, optical absorption spectra, as well as PL spectroscopy indicate the presence of a charge/spin transfer from the conduction band of magnetite into the band gap of titania nanocrystals. The process modifies both Fe3O4 and TiO2 magnetic and optical properties, respectively.

  20. Size effects in bimagnetic CoO/CoFe2O4 core/shell nanoparticles.

    PubMed

    Lavorato, Gabriel C; Lima, Enio; Tobia, Dina; Fiorani, Dino; Troiani, Horacio E; Zysler, Roberto D; Winkler, Elin L

    2014-09-01

    The control of the size of bimagnetic nanoparticles represents an important step toward the study of fundamental properties and the design of new nanostructured magnetic materials. We report the synthesis and the structural and magnetic characterization of bimagnetic CoO/CoFe2O4 core/shell nanoparticles. The material was fabricated by a seed-mediated growth high-temperature decomposition method with sizes in the range of 5-11 nm. We show that the core/shell morphology favours the crystallinity of the shell phase, and the reduction of the particle size leads to a remarkable increase of the magnetic hardening. When the size is reduced, the coercive field at 5 K increases from 21.5 kOe to 30.8 kOe, while the blocking temperature decreases from 388 K to 167 K. The size effects on the magnetic behaviour are described through a phenomenological model for strongly ferri-/antiferromagnetic coupled phases. PMID:25120018

  1. Synthesis and Characterization of Polyvinylpyrrolidone Silica Core-Shell Nanocomposite Particles.

    PubMed

    Chen, Lian-Xi; Li, Jie; Li, Xi; Zhang, Zhong-Min; Jiao, Cai-Bin

    2015-03-01

    In this work, a novel and facile strategy for making a new type of polymer/silica nanocomposte particle was proposed. Colloidally stable polyvinypyrrolidone (PVP)/silica core-shell nanocomposite particles have been successfully synthesized using an azo initiator via seed polymerization of N-vinyl-2-pyrrolidone (NVP) and VFSs (VFSs) that were derived from vinyl triethoxysilane (VTES). It was suggested from the FTIR and TGA analysis that the copolymerization reaction of NVP with VFSs has been thoroughly carried out. In addition, SEM images showed that PVP/silica nanocomposite particles have relatively rough surface due to surface polymerization in comparison with VFSs. Furthermore, TEM results proved that the size of VFSs had considerable effects on the appearance of PVP/silica nanocomposite particles. Generally, it presented that several silica nanoparticle cores with an average size of 78 nm mainly pack together within each nanocomposite particle after seed polymerization. Interestingly, the average shell thickness was 59 nm for most PVP/silica nanocomposite particles with cores about 242 nm. However, when the core size was large enough to about 504 nm, a series of PVP/silica nanocomposite particles with a relative thin shell were observed. PMID:26413650

  2. The growth and enhanced catalytic performance of Au@Pd core-shell nanodendrites

    NASA Astrophysics Data System (ADS)

    Wang, Haihua; Sun, Zhenhua; Yang, Yi; Su, Dangsheng

    2012-12-01

    Au@Pd core-shell nanodendrites were synthesized by reducing H2PdCl4 with ascorbic acid onto the surface of Au polyhedra at room temperature. The Au@Pd core-shell nanodendrites consisting of a Au core and nanoporous Pd shell, exhibited plasmonic properties and higher catalytic activity in comparison with Au@Pd core-shell nanocubes.Au@Pd core-shell nanodendrites were synthesized by reducing H2PdCl4 with ascorbic acid onto the surface of Au polyhedra at room temperature. The Au@Pd core-shell nanodendrites consisting of a Au core and nanoporous Pd shell, exhibited plasmonic properties and higher catalytic activity in comparison with Au@Pd core-shell nanocubes. Electronic supplementary information (ESI) available: Experimental details, characterization and catalytic performance measurement of Au nanopolyhedra and Au@Pd core-shell nanostructures, TEM image of Au nanopolyhedra and Au@Pd core-shell nanodendrites after four cycles of the Suzuki coupling reaction, TEM and high-resolution images of a single Au@Pd core-shell nanodendrite, and XRD pattern of Au@Pd core-shell nanodendrites, UV-vis spectrum of Au@Pd nanodendrites in the range 200-400 nm, references. See DOI: 10.1039/c2nr32849f

  3. Visible light-induced singlet oxygen-mediated intracellular disassembly of polymeric micelles co-loaded with a photosensitizer and an anticancer drug for enhanced photodynamic therapy.

    PubMed

    Saravanakumar, Gurusamy; Lee, Junseok; Kim, Jihoon; Kim, Won Jong

    2015-06-21

    Herein, we report a biocompatible amphiphilic block copolymer micelle bearing a singlet oxygen-sensitive vinyldithioether cleavable linker at the core-shell junction, which undergoes singlet oxygen-mediated photocleavage in the presence of visible light. The micelle facilitates the light-responsive release of singlet oxygen and an anticancer drug for enhanced photodynamic therapy. PMID:25998105

  4. Enhanced spin-orbit coupling in core/shell nanowires

    NASA Astrophysics Data System (ADS)

    Furthmeier, Stephan; Dirnberger, Florian; Gmitra, Martin; Bayer, Andreas; Forsch, Moritz; Hubmann, Joachim; Schüller, Christian; Reiger, Elisabeth; Fabian, Jaroslav; Korn, Tobias; Bougeard, Dominique

    2016-08-01

    The spin-orbit coupling (SOC) in semiconductors is strongly influenced by structural asymmetries, as prominently observed in bulk crystal structures that lack inversion symmetry. Here we study an additional effect on the SOC: the asymmetry induced by the large interface area between a nanowire core and its surrounding shell. Our experiments on purely wurtzite GaAs/AlGaAs core/shell nanowires demonstrate optical spin injection into a single free-standing nanowire and determine the effective electron g-factor of the hexagonal GaAs wurtzite phase. The spin relaxation is highly anisotropic in time-resolved micro-photoluminescence measurements on single nanowires, showing a significant increase of spin relaxation in external magnetic fields. This behaviour is counterintuitive compared with bulk wurtzite crystals. We present a model for the observed electron spin dynamics highlighting the dominant role of the interface-induced SOC in these core/shell nanowires. This enhanced SOC may represent an interesting tuning parameter for the implementation of spin-orbitronic concepts in semiconductor-based structures.

  5. Biocompatible core-shell magnetic nanoparticles for cancer treatment

    SciTech Connect

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

    2008-04-01

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

  6. Enhanced spin–orbit coupling in core/shell nanowires

    PubMed Central

    Furthmeier, Stephan; Dirnberger, Florian; Gmitra, Martin; Bayer, Andreas; Forsch, Moritz; Hubmann, Joachim; Schüller, Christian; Reiger, Elisabeth; Fabian, Jaroslav; Korn, Tobias; Bougeard, Dominique

    2016-01-01

    The spin–orbit coupling (SOC) in semiconductors is strongly influenced by structural asymmetries, as prominently observed in bulk crystal structures that lack inversion symmetry. Here we study an additional effect on the SOC: the asymmetry induced by the large interface area between a nanowire core and its surrounding shell. Our experiments on purely wurtzite GaAs/AlGaAs core/shell nanowires demonstrate optical spin injection into a single free-standing nanowire and determine the effective electron g-factor of the hexagonal GaAs wurtzite phase. The spin relaxation is highly anisotropic in time-resolved micro-photoluminescence measurements on single nanowires, showing a significant increase of spin relaxation in external magnetic fields. This behaviour is counterintuitive compared with bulk wurtzite crystals. We present a model for the observed electron spin dynamics highlighting the dominant role of the interface-induced SOC in these core/shell nanowires. This enhanced SOC may represent an interesting tuning parameter for the implementation of spin–orbitronic concepts in semiconductor-based structures. PMID:27491871

  7. Core-Shell Chitosan Microcapsules for Programmed Sequential Drug Release.

    PubMed

    Yang, Xiu-Lan; Ju, Xiao-Jie; Mu, Xiao-Ting; Wang, Wei; Xie, Rui; Liu, Zhuang; Chu, Liang-Yin

    2016-04-27

    A novel type of core-shell chitosan microcapsule with programmed sequential drug release is developed by the microfluidic technique for acute gastrosis therapy. The microcapsule is composed of a cross-linked chitosan hydrogel shell and an oily core containing both free drug molecules and drug-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles. Before exposure to acid stimulus, the resultant microcapsules can keep their structural integrity without leakage of the encapsulated substances. Upon acid-triggering, the microcapsules first achieve burst release due to the acid-induced decomposition of the chitosan shell. The encapsulated free drug molecules and drug-loaded PLGA nanoparticles are rapidly released within 60 s. Next, the drugs loaded in the PLGA nanoparticles are slowly released for several days to achieve sustained release based on the synergistic effect of drug diffusion and PLGA degradation. Such core-shell chitosan microcapsules with programmed sequential drug release are promising for rational drug delivery and controlled-release for the treatment of acute gastritis. In addition, the microcapsule systems with programmed sequential release provide more versatility for controlled release in biomedical applications. PMID:27052812

  8. Enhanced spin-orbit coupling in core/shell nanowires.

    PubMed

    Furthmeier, Stephan; Dirnberger, Florian; Gmitra, Martin; Bayer, Andreas; Forsch, Moritz; Hubmann, Joachim; Schüller, Christian; Reiger, Elisabeth; Fabian, Jaroslav; Korn, Tobias; Bougeard, Dominique

    2016-01-01

    The spin-orbit coupling (SOC) in semiconductors is strongly influenced by structural asymmetries, as prominently observed in bulk crystal structures that lack inversion symmetry. Here we study an additional effect on the SOC: the asymmetry induced by the large interface area between a nanowire core and its surrounding shell. Our experiments on purely wurtzite GaAs/AlGaAs core/shell nanowires demonstrate optical spin injection into a single free-standing nanowire and determine the effective electron g-factor of the hexagonal GaAs wurtzite phase. The spin relaxation is highly anisotropic in time-resolved micro-photoluminescence measurements on single nanowires, showing a significant increase of spin relaxation in external magnetic fields. This behaviour is counterintuitive compared with bulk wurtzite crystals. We present a model for the observed electron spin dynamics highlighting the dominant role of the interface-induced SOC in these core/shell nanowires. This enhanced SOC may represent an interesting tuning parameter for the implementation of spin-orbitronic concepts in semiconductor-based structures. PMID:27491871

  9. TOPICAL REVIEW: Ab initio symplectic no-core shell model

    NASA Astrophysics Data System (ADS)

    Dytrych, T.; Sviratcheva, K. D.; Draayer, J. P.; Bahri, C.; Vary, J. P.

    2008-12-01

    The no-core shell model (NCSM) is a prominent ab initio method that yields a good description of the low-lying states in few-nucleon systems as well as in more complex p-shell nuclei. Nevertheless, its applicability is limited by the rapid growth of the many-body basis with larger model spaces and increasing number of nucleons. The symplectic no-core shell model (Sp-NCSM) aspires to extend the scope of the NCSM beyond the p-shell region by augmenting the conventional spherical harmonic oscillator basis with the physically relevant symplectic \\SpR{3} symmetry-adapted configurations of the symplectic shell model that describe naturally the monopole-quadrupole vibrational and rotational modes, and also partially incorporate α-cluster correlations. In this review, the models underpinning the Sp-NCSM approach, namely, the NCSM, the Elliott SU(3) model and the symplectic shell model, are discussed. Following this, a prescription for constructing translationally invariant symplectic configurations in the spherical harmonic oscillator basis is given. This prescription is utilized to unveil the extent to which symplectic configurations enter into low-lying states in 12C and 16O nuclei calculated within the framework of the NCSM with the JISP16 realistic nucleon-nucleon interaction. The outcomes of this proof-of-principle study are presented in detail.

  10. Acoustic phonons and strain in core/shell nanowires

    NASA Astrophysics Data System (ADS)

    Kloeffel, Christoph; Trif, Mircea; Loss, Daniel

    2014-09-01

    We study theoretically the low-energy phonons and the static strain in cylindrical core/shell nanowires (NWs). Assuming pseudomorphic growth, isotropic media, and a force-free wire surface, we derive algebraic expressions for the dispersion relations, the displacement fields, and the stress and strain components from linear elasticity theory. Our results apply to NWs with arbitrary radii and arbitrary elastic constants for both core and shell. The expressions for the static strain are consistent with experiments, simulations, and previous analytical investigations; those for phonons are consistent with known results for homogeneous NWs. Among other things, we show that the dispersion relations of the torsional, longitudinal, and flexural modes change differently with the relative shell thickness, and we identify new terms in the corresponding strain tensors that are absent for uncapped NWs. We illustrate our results via the example of Ge/Si core/shell NWs and demonstrate that shell-induced strain has large effects on the hole spectrum of these systems.

  11. Organized thiol functional groups in mesoporous core shell colloids

    SciTech Connect

    Marchena, Martin H.; Granada, Mara; Bordoni, Andrea V.; Joselevich, Maria; Troiani, Horacio; Williams, Federico J.; Wolosiuk, Alejandro

    2012-03-15

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

  12. Hydrazide functionalized core-shell magnetic nanocomposites for highly specific enrichment of N-glycopeptides.

    PubMed

    Liu, Liting; Yu, Meng; Zhang, Ying; Wang, Changchun; Lu, Haojie

    2014-05-28

    In view of the biological significance of glycosylation for human health, profiling of glycoproteome from complex biological samples is highly inclined toward the discovery of disease biomarkers and clinical diagnosis. Nevertheless, because of the existence of glycopeptides at relatively low abundances compared with nonglycosylated peptides and glycan microheterogeneity, glycopeptides need to be highly selectively enriched from complex biological samples for mass spectrometry analysis. Herein, a new type of hydrazide functionalized core-shell magnetic nanocomposite has been synthesized for highly specific enrichment of N-glycopeptides. The nanocomposites with both the magnetic core and the polymer shell hanging high density of hydrazide groups were prepared by first functionalization of the magnetic core with polymethacrylic acid by reflux precipitation polymerization to obtain the Fe3O4@poly(methacrylic acid) (Fe3O4@PMAA) and then modification of the surface of Fe3O4@PMAA with adipic acid dihydrazide (ADH) to obtain Fe3O4@poly(methacrylic hydrazide) (Fe3O4@PMAH). The abundant hydrazide groups toward highly specific enrichment of glycopeptides and the magnetic core make it suitable for large-scale, high-throughput, and automated sample processing. In addition, the hydrophilic polymer surface can provide low nonspecific adsorption of other peptides. Compared to commercially available hydrazide resin, Fe3O4@PMAH improved more than 5 times the signal-to-noise ratio of standard glycopeptides. Finally, this nanocomposite was applied in the profiling of N-glycoproteome from the colorectal cancer patient serum. In total, 175 unique glycopeptides and 181 glycosylation sites corresponding to 63 unique glycoproteins were identified in three repeated experiments, with the specificities of the enriched glycopeptides and corresponding glycoproteins of 69.6% and 80.9%, respectively. Because of all these attractive features, we believe that this novel hydrazide functionalized

  13. Enhancement of Thermoelectric Performance by Reducing Phonon Thermal Conductance in Multiple Core-shell Nanowires

    PubMed Central

    Zhou, Wu-Xing; Chen, Ke-Qiu

    2014-01-01

    The thermoelectric properties of multiple core-shell nanowires are investigated by using nonequilibrium Green's function method and molecular dynamics simulations. The results show that the thermoelectric performance of multiple core-shell NWs can be improved observably with the increase of shell number compared with the single component NWs due to the significant reduction of phonon thermal conductance. The ZT value of multiple core-shell NWs can reach three times greater than that of the single component GaSb NWs at room temperature. Moreover, the ZT values of both the core-shell NWs and single component NWs are increased with the increasing temperature, but the ZT value of core-shell NWs increases more slowly than that of single component NWs. These results show that the single component NWs is suitable as thermoelectric material at much high temperature, but the multiple core-shell NWs is more suitable as thermoelectric material at room temperature. PMID:25413874

  14. Simultaneous in-situ synthesis and characterization of Co@Cu core-shell nanoparticle arrays

    DOE PAGESBeta

    McKeown, Joseph T.; Wu, Yueying; Fowlkes, Jason D.; Rack, Philip D.; Campbell, Geoffrey H.

    2014-12-23

    Core-shell nanostructures have attracted much attention due to their unique and tunable properties relative to bulk structures of the same materials, making core-shell nanoparticles candidates for a variety of applications with multiple functionalities.[1,2] Intriguing magnetic behavior can be tailored by variation of size, interface, crystal orientation, and composition, and core-shell nanostructures with noble-metal shells yield novel optical responses[3] and enhanced electrocatalytic activity.[4

  15. Synthesis of a 3D graphite microball using a microfluidic droplet generator and its polymer composite with core-shell structure.

    PubMed

    Han, Dong Ju; Jung, Jae Hwan; Choi, Jong Seob; Kim, Yong Tae; Seo, Tae Seok

    2013-10-21

    Spherical 3D graphite microballs (3D GMs) and their nanohybrids (3D GM-Fe3O4 nanoparticles) were synthesized by using a microfluidic droplet generator and a thermal evaporation-induced capillary compression method. Using the 3D GM-Fe3O4 nanoparticle as a support for polymerization, 3D GM-polypyrrole composites were produced with a unique core-shell structure. PMID:23921454

  16. Improved microbial growth inhibition activity of bio-surfactant induced Ag-TiO2 core shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Nithyadevi, D.; Kumar, P. Suresh; Mangalaraj, D.; Ponpandian, N.; Viswanathan, C.; Meena, P.

    2015-02-01

    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 nanoparticles have comparatively rapid, less expensive and wider applications in modern antibacterial therapy.

  17. Core-size-dependent catalytic properties of bimetallic Au/Ag core-shell nanoparticles.

    PubMed

    Haldar, Krishna Kanta; Kundu, Simanta; Patra, Amitava

    2014-12-24

    Bimetallic core-shell nanoparticles have recently emerged as a new class of functional materials because of their potential applications in catalysis, surface enhanced Raman scattering (SERS) substrate and photonics etc. Here, we have synthesized Au/Ag bimetallic core-shell nanoparticles with varying the core diameter. The red-shifting of the both plasmonic peaks of Ag and Au confirms the core-shell structure of the nanoparticles. Transmission electron microscopy (TEM) analysis, line scan EDS measurement and UV-vis study confirm the formation of core-shell nanoparticles. We have examined the catalytic activity of these core-shell nanostructures in the reaction between 4-nitrophenol (4-NP) and NaBH4 to form 4-aminophenol (4-AP) and the efficiency of the catalytic reaction is found to be increased with increasing the core size of Au/Ag core-shell nanocrystals. The catalytic efficiency varies from 41.8 to 96.5% with varying core size from 10 to 100 nm of Au/Ag core-shell nanoparticles, and the Au100/Ag bimetallic core-shell nanoparticle is found to be 12-fold more active than that of the pure Au nanoparticles with 100 nm diameter. Thus, the catalytic properties of the metal nanoparticles are significantly enhanced because of the Au/Ag core-shell structure, and the rate is dependent on the size of the core of the nanoparticles. PMID:25456348

  18. Highly temperature responsive core-shell magnetic particles: synthesis, characterization and colloidal properties.

    PubMed

    Rahman, Md Mahbubor; Chehimi, Mohamed M; Fessi, Hatem; Elaissari, Abdelhamid

    2011-08-15

    Temperature responsive magnetic polymer submicron particles were prepared by two step seed emulsion polymerization process. First, magnetic seed polymer particles were obtained by emulsion polymerization of styrene using potassium persulfate (KPS) as an initiator and divinylbenzne (DVB) as a cross-linker in the presence of oil-in-water magnetic emulsion (organic ferrofluid droplets). Thereafter, DVB cross-linked magnetic polymer particles were used as seed in the precipitation polymerization of N-isopropylacrylamide (NIPAM) to induce thermosensitive PNIPAM shell onto the hydrophobic polymer surface of the cross-linked magnetic polymer particles. To impart cationic functional groups in the thermosensitive PNIPAM backbone, the functional monomer aminoethylmethacrylate hydrochloride (AEMH) was used to polymerize with NIPAM while N,N'-methylenebisacrylamide (MBA) and 2, 2'-azobis (2-methylpropionamidine) dihydrochloride (V-50) were used as a cross-linker and as an initiator respectively. The effect of seed to monomer (w/w) ratio along with seed nature on the final particle morphology was investigated. Dynamic light scattering (DLS) results demonstrated particles swelling at below volume phase transition temperature (VPTT) and deswelling above the VPTT. The perfect core (magnetic) shell (polymer) structure of the particles prepared was confirmed by Transmission Electron Microscopy (TEM). The chemical composition of the particles were determined by thermogravimetric analysis (TGA). The effect of temperature, pH, ionic strength on the colloidal properties such as size and zeta potential of the micron sized thermo-sensitive magnetic particles were also studied. In addition, a short mechanistic discussion on the formation of core-shell morphology of magnetic polymer particles has also been discussed. PMID:21570083

  19. Synthesis and characterization of self-crosslinking fluorinated polyacrylate soap-free latices with core-shell structure

    NASA Astrophysics Data System (ADS)

    Xu, Wei; An, Qiufeng; Hao, Lifen; Zhang, Dan; Zhang, Min

    2013-03-01

    Novel self-crosslinking fluorinated polyacrylate soap-free latices (FMBN) with core-shell structure were synthesized by semicontinuous seeded emulsion polymerization method from dodecafluoroheptyl methacrylate (DFMA), methyl methacrylate (MMA), butyl acrylate (BA), and N-methylolamide (NMA) in the presence of a polymerizable emulsifier-ammonium allyloxtmethylate nonylphenol ethoxylates sulfate (DNS-86). Effects of the DNS-86 and DFMA amounts on stability and properties of the FMBN emulsions were studied. Besides, the latices and their film were characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (1H NMR) spectrum, scanning electron microscopy (SEM), transmission electron microscopy (TEM), laser particle size analyzer, differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), contact angle goniometer, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. FT-IR spectra and 1H NMR spectrum showed that DFMA successfully participated in soap-free emulsion polymerization and monomers formed the fluorinated acrylate copolymer. The resulted latex particles had the core-shell structure. The films formed from the FMBN latices thus had two Tg. Their thermal stability and Tg of the shell phase increased gradually with augment of DFMA amount in polymer. XPS, AFM and hydrophobicity analyses indicated the fluoroalkyl groups had the tendency to enrich at the film-air interface. This enrichment of fluorine at the film-air interface was more evident after the annealing process. Water contact angles of the FMBN film before and after the annealing process could attain 115.5° and 117.5°, individually.

  20. Facile synthesis of hairy core-shell structured magnetic polymer submicrospheres and their adsorption of bovine serum albumin.

    PubMed

    Yan, Xianming; Kong, Juan; Yang, Chongchong; Fu, Guoqi

    2015-05-01

    Highly magnetic polymer submicrospheres with a hairy core-shell structure were facilely synthesized by combining distillation-precipitation polymerization (DPP) with subsequent surface-initiated atom transfer radical polymerization (SI-ATRP), and then investigated for protein adsorption. A robust polymer shell consisting of poly(divinylbenzene-co-chloromethylstyrene) (P(DVB-co-CMS)) was coated on superparamagnetic submicrometer-sized magnetite colloid nanocrystal clusters (MCNCs) via DPP. With the benzyl chloride groups on the shell as initiator, poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) hairs were grafted by SI-ATRP approach. The resulting hairy core-shell structured Fe3O4@ P(DVB-co-CMS)-PDMAEMA microspheres showed pH- and temperature-sensitivity, and high-magnetization. The composite microspheres were further investigated for adsorption of a typical acidic protein, i.e. bovine serum albumin (BSA). They exhibited a high binding capacity up to over 660 mg/g (corresponding to 158 DMAEMA monomer units cooperating for binding one BSA molecule) and could rapidly reach binding equilibrium within 5 min. Moreover, the adsorption of BSA was found to be remarkably dependent on the pH and salt concentration of the protein solutions, and the bound protein could be quantitatively desorbed by washing with a medium with lowered pH or raised salt concentration. PMID:25594881

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    NASA Astrophysics Data System (ADS)

    Jiang, J. S.

    2015-05-01

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

  3. Photoacid-mediated ring opening polymerization driven by visible light.

    PubMed

    Fu, Changkui; Xu, Jiangtao; Boyer, Cyrille

    2016-06-01

    A novel methodology of visible light regulated ring opening polymerization in the presence of reversible merocyanine-based photoacid was reported for the first time. In combination with a photoinduced radical polymerization technique, a dual wavelength light controlled orthogonal polymerization system was investigated to switch the polymerization between two different monomers and for the preparation of block and graft copolymers in one pot. PMID:27167862

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

    PubMed

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

    2016-01-13

    Vertical junctionless transistors with a gate-all-around (GAA) structure based on Ge/Si core/shell nanowires epitaxially grown and integrated on a ⟨111⟩ Si substrate were fabricated and analyzed. Because of efficient gate coupling in the nanowire-GAA transistor structure and the high density one-dimensional hole gas formed in the Ge nanowire core, excellent P-type transistor behaviors with Ion of 750 μA/μm were obtained at a moderate gate length of 544 nm with minimal short-channel effects. The experimental data can be quantitatively modeled by a GAA junctionless transistor model with few fitting parameters, suggesting the nanowire transistors can be fabricated reliably without introducing additional factors that can degrade device performance. Devices with different gate lengths were readily obtained by tuning the thickness of an etching mask film. Analysis of the histogram of different devices yielded a single dominate peak in device parameter distribution, indicating excellent uniformity and high confidence of single nanowire operation. Using two vertical nanowire junctionless transistors, a PMOS-logic inverter with near rail-to-rail output voltage was demonstrated, and device matching in the logic can be conveniently obtained by controlling the number of nanowires employed in different devices rather than modifying device geometry. These studies show that junctionless transistors based on vertical Ge/Si core/shell nanowires can be fabricated in a controlled fashion with excellent performance and may be used in future hybrid, high-performance circuits where bottom-up grown nanowire devices with different functionalities can be directly integrated with an existing Si platform. PMID:26674542

  5. Controlling core/shell Au/FePt nanoparticle electrocatalysis via changing the core size and shell thickness

    NASA Astrophysics Data System (ADS)

    Sun, Xiaolian; Li, Dongguo; Guo, Shaojun; Zhu, Wenlei; Sun, Shouheng

    2016-01-01

    Using a modified seed-mediated method, we synthesized core/shell Au/FePt nanoparticles (NPs) with Au sizes of 4, 7, and 9 nm and the FePt shell was controlled to have similar FePt compositions and 0.5, 1, and 2 nm thickness. We studied both core and shell effects on electrochemical and electrocatalytic properties of the Au/FePt NPs, and found that the Au core did change the redox chemistry of the FePt shell and promoted its electrochemical oxidation of methanol. The catalytic activity was dependent on the FePt thicknesses, but not much on the Au core sizes, and the 1 nm FePt shell was found to be the optimal thickness for catalyzing methanol oxidation in 0.1 M HClO4 + 0.1 M methanol, offering not only high activity (1.19 mA cm-2 at 0.5 V vs. Ag/AgCl), but also enhanced stability. Our studies demonstrate a general approach to the design and tuning of shell catalysis in the core/shell structure to achieve optimal catalysis for important electrochemical reactions.Using a modified seed-mediated method, we synthesized core/shell Au/FePt nanoparticles (NPs) with Au sizes of 4, 7, and 9 nm and the FePt shell was controlled to have similar FePt compositions and 0.5, 1, and 2 nm thickness. We studied both core and shell effects on electrochemical and electrocatalytic properties of the Au/FePt NPs, and found that the Au core did change the redox chemistry of the FePt shell and promoted its electrochemical oxidation of methanol. The catalytic activity was dependent on the FePt thicknesses, but not much on the Au core sizes, and the 1 nm FePt shell was found to be the optimal thickness for catalyzing methanol oxidation in 0.1 M HClO4 + 0.1 M methanol, offering not only high activity (1.19 mA cm-2 at 0.5 V vs. Ag/AgCl), but also enhanced stability. Our studies demonstrate a general approach to the design and tuning of shell catalysis in the core/shell structure to achieve optimal catalysis for important electrochemical reactions. Electronic supplementary information (ESI

  6. Microgel coating of magnetic nanoparticles via bienzyme-mediated free-radical polymerization for colorimetric detection of glucose.

    PubMed

    Wu, Qing; Wang, Xia; Liao, Chuanan; Wei, Qingcong; Wang, Qigang

    2015-10-28

    This study describes a new strategy for the fabrication of magnetic core-shell microgels by free-radical polymerization triggered by the cascade reaction of glucose oxidase (GOx) and horseradish peroxidase (HRP). The mild polymerization around the interface of the magnetic nanoparticles permits the mild coating of the microgel layer with excellent characteristics for various applications in biocatalysis and medical diagnostics, as well as in clinical fields. The immobilized bienzyme within the microgel has a largely retained activity relative to the non-immobilized one. The confining effect of the microgel and the well designed distance between the two enzymes can benefit the diffusion of intermediates to the HRP active site. The final microgels can be incontestably employed as sensitive biosensors for colorimetric glucose detection. PMID:26412343

  7. Enzyme and Thermal Dual Responsive Amphiphilic Polymer Core-Shell Nanoparticle for Doxorubicin Delivery to Cancer Cells.

    PubMed

    Kashyap, Smita; Singh, Nitesh; Surnar, Bapurao; Jayakannan, Manickam

    2016-01-11

    Dual responsive polymer nanoscaffolds for administering anticancer drugs both at the tumor site and intracellular compartments are made for improving treatment in cancers. The present work reports the design and development of new thermo- and enzyme-responsive amphiphilic copolymer core-shell nanoparticles for doxorubicin delivery at extracellular and intracellular compartments, respectively. A hydrophobic acrylate monomer was tailor-made from 3-pentadecylphenol (PDP, a natural resource) and copolymerized with oligoethylene glycol acrylate (as a hydrophilic monomer) to make new classes of thermo and enzyme dual responsive polymeric amphiphiles. Both radical and reversible addition-fragmentation chain transfer (RAFT) methodologies were adapted for making the amphiphilic copolymers. These amphiphilic copolymers were self-assembled to produce spherical core-shell nanoparticles in water. Upon heating, the core-shell nanoparticles underwent segregation to produce larger sized aggregates above the lower critical solution temperature (LCST). The dual responsive polymer scaffold was found to be capable of loading water insoluble drug, such as doxorubicin (DOX), and fluorescent probe-like Nile Red. The drug release kinetics revealed that DOX was preserved in the core-shell assemblies at normal body temperature (below LCST, ≤ 37 °C). At closer to cancer tissue temperature (above LCST, ∼43 °C), the polymeric scaffold underwent burst release to deliver 90% of loaded drugs within 2 h. At the intracellular environment (pH 7.4, 37 °C) in the presence of esterase enzyme, the amphiphilic copolymer ruptured in a slow and controlled manner to release >95% of the drugs in 12 h. Thus, both burst release of cargo at the tumor microenvironment and control delivery at intracellular compartments were accomplished in a single polymer scaffold. Cytotoxicity assays of the nascent and DOX-loaded polymer were carried out in breast cancer (MCF-7) and cervical cancer (HeLa) cells. Among

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

    SciTech Connect

    Liu Weijun; Zhang Zhicheng . E-mail: lwj3600@ustc.edu; He Weidong; Zheng Cheng; Ge Xuewu; Li, Jian; Liu Huarong; Jiang Hao

    2006-04-15

    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: {gamma}-irradiation and interfacial-initiated polymerization. Firstly, mono-dispersed Ag nanoparticles with diameters 20 nm were synthesized in inversed microemulsion by reducing silver nitrate under {gamma}-irradiation. Then, Ag nanoparticles were coated with PSt via interfacial-initiated polymerization with cumene hydroperoxide/ferrous sulfate/disodium ethylenediaminetetraacetate/sodium formaldehyde sulfoxylate (CHPO-Fe {sup 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)

  9. Microgel coating of magnetic nanoparticles via bienzyme-mediated free-radical polymerization for colorimetric detection of glucose

    NASA Astrophysics Data System (ADS)

    Wu, Qing; Wang, Xia; Liao, Chuanan; Wei, Qingcong; Wang, Qigang

    2015-10-01

    This study describes a new strategy for the fabrication of magnetic core-shell microgels by free-radical polymerization triggered by the cascade reaction of glucose oxidase (GOx) and horseradish peroxidase (HRP). The mild polymerization around the interface of the magnetic nanoparticles permits the mild coating of the microgel layer with excellent characteristics for various applications in biocatalysis and medical diagnostics, as well as in clinical fields. The immobilized bienzyme within the microgel has a largely retained activity relative to the non-immobilized one. The confining effect of the microgel and the well designed distance between the two enzymes can benefit the diffusion of intermediates to the HRP active site. The final microgels can be incontestably employed as sensitive biosensors for colorimetric glucose detection.This study describes a new strategy for the fabrication of magnetic core-shell microgels by free-radical polymerization triggered by the cascade reaction of glucose oxidase (GOx) and horseradish peroxidase (HRP). The mild polymerization around the interface of the magnetic nanoparticles permits the mild coating of the microgel layer with excellent characteristics for various applications in biocatalysis and medical diagnostics, as well as in clinical fields. The immobilized bienzyme within the microgel has a largely retained activity relative to the non-immobilized one. The confining effect of the microgel and the well designed distance between the two enzymes can benefit the diffusion of intermediates to the HRP active site. The final microgels can be incontestably employed as sensitive biosensors for colorimetric glucose detection. Electronic supplementary information (ESI) available: Experimental details and ESI figures. See DOI: 10.1039/c5nr05716g

  10. Microfluidic conceived pH sensitive core-shell particles for dual drug delivery.

    PubMed

    Khan, Ikram Ullah; Stolch, Lukas; Serra, Christophe A; Anton, Nicolas; Akasov, Roman; Vandamme, Thierry F

    2015-01-15

    In current study, we report on the synthesis of core-shell microparticles for dual drug delivery by means of a two co-axial microfluidic device and online UV assisted free radical polymerization. Before developing pH-sensitive particles, ketoprofen loaded poly(methyl acrylate) core-ranitidine HCl loaded poly(acrylamide) shell particles were produced. Influence of inner and outer phases flow rates on particle size, shape, core diameter, shell thickness, and drug release properties was studied. All the particles were monodispersed with coefficient of variation below 5%. Furthermore, their diameter ranged from 100 to 151 μm by increasing continuous (Qc) to middle (Qm) phase flow rate ratio (Qc/Qm). Core diameter varied from 58 to 115 μm by decreasing middle (Qm) to inner (Qi) phase flow rate ratio (Qm/Qi) at constant continuous phase flow rate as confirmed by SEM images. It was observed that an optimum concentration of acrylamide (30 wt%) and an appropriate combination of surfactants were necessary to get core-shell particles otherwise Janus structure was obtained. FTIR confirmed the complete polymerization of core and shell phases. MTT assay showed variation in viability of cells under non-contact and contact conditions with less cytotoxicity for the former. Under non-contact conditions LD50 was 3.1mg/mL. Release studies in USP phosphate buffer solution showed simultaneously release of ketoprofen and ranitidine HCl for non pH-sensitive particles. However, release rates of ranitidine HCl and ketoprofen were higher at low and high pH respectively. To develop pH-sensitive particles for colon targeting, the previous shell phase was admixed with few weight percentage of pH sensitive carboxyethyl acrylate monomer. Core and shell contained the same hydrophobic and hydrophilic model drugs as in previous case. The pH-sensitive shell prevented the release of the two entrapped molecules at low pH while increasing significantly their release rate at higher pH with a maximum

  11. Horseradish peroxidase-catalyzed polymerization of cardanol in the presence of redox mediators.

    PubMed

    Won, Keehoon; Kim, Yong Hwan; An, Eun Suk; Lee, Yeon Soo; Song, Bong Keun

    2004-01-01

    Horseradish peroxidase-catalyzed polymerization of cardanol in aqueous organic solvent was investigated in the presence of a redox mediator. Cardanol is a phenol derivative from a renewable resource mainly having a C15 unsaturated hydrocarbon chain with mostly 1-3 double bonds at a meta position. Unlike soybean peroxidase (SBP), it has been shown that horseradish peroxidase (HRP) is not able to perform oxidative polymerization of phenol derivatives having a bulky meta substituent such as cardanol. For the first time, redox mediators have been applied to enable horseradish peroxidase to polymerize cardanol. Veratryl alcohol, N-ethyl phenothiazine, and phenothiazine-10-propionic acid were tested as a mediator. It is surprising that the horseradish peroxidase-catalyzed polymerization of cardanol took place in the presence of N-ethyl phenothiazine or phenothiazine-10-propionic acid. However, veratryl alcohol showed no effect. FT-IR and GPC analysis of the product revealed that the structure and properties of polycardanol formed by HRP with a mediator were similar to those by SBP. This is the first work to apply a redox mediator to enzyme-catalyzed oxidative polymerization. Our new finding that oxidative polymerization of a poor substrate, which the enzyme is not active with, can take place in the presence of an appropriate mediator will present more opportunities for the application of enzyme-catalyzed polymerization. PMID:14715000

  12. Iron(ii)-triazole core-shell nanocomposites: toward multistep spin crossover materials.

    PubMed

    Wang, Yu-Xia; Qiu, Dan; Xi, Sai-Fei; Ding, Zheng-Dong; Li, Zaijun; Li, Yunxing; Ren, Xuehong; Gu, Zhi-Guo

    2016-06-28

    The first SCO@SCO core-shell nanomaterials have been synthesized by the step-by-step microemulsion method. The observed gyroscopic core-shell nanocomposites exhibit three-step spin crossover behaviour with thermal hysteresis at around room temperature. This offers an efficient and novel strategy for the development of multistable SCO materials. PMID:27263855

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

    SciTech Connect

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

    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.

  14. Raman scattering from Zn/ZnO core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Bajaj, Geetika; Soni, R. K.

    2008-09-01

    We have synthesized Zn/ZnO core-shell nanoparticles by pulsed laser ablation in liquid (PLAL) media using nanosecond pulsed Nd:YAG laser. The formation of crystalline core-shell nanoparticles of varying core and shell thickness with varying SDS concentration is confirmed by HRTEM images. The optical absorption shows distinct features corresponding to ZnO exciton and Zn surface plasmon. Raman spectrum from Zn/ZnO core-shell nanoparticles shows E2(high) phonon modes of the bulk which are insensitive to the size and modes unique to the core-shell structures. Moreover, the surface optical mode is dominant feature of the nonresonant spectrum. We have also examined the wavelength dependence of the phonon modes in Zn/ZnO core-shell structure.

  15. Preparation and characterization of polystyrene/Ag core-shell microspheres--a bio-inspired poly(dopamine) approach.

    PubMed

    Wang, Wencai; Jiang, Yi; Wen, Shipeng; Liu, Li; Zhang, Liqun

    2012-02-15

    A facile and versatile method using a biopolymer as a chelating agent for silver ions and as a reducing agent for the formation of catalytic sites is proposed to prepare polystyrene (PS)/Ag core-shell microspheres. More specifically, the core-shell microspheres were fabricated by electroless plating after the formation of poly(dopamine) (PDA) on the surface of PS microspheres through insitu spontaneous oxidative polymerization of dopamine. The PS-PDA microspheres were characterized by SEM, XPS, and TGA. The results showed that a uniform PDA layer was formed on the PS microsphere surface and the thickness of the PDA layer could be well controlled by varying the concentration of dopamine solution. The PDA layer was used as a chelating agent for silver ions, as a reducing agent for the formation of catalytic sites by reducing the silver ions into silver nanoparticles, and as an adhesion layer between the PS microspheres and silver layer. SEM and XRD results indicate that the diameter of the silver nanoparticles decreased with the increase in the thickness of the PDA layer. The silver nanoparticles could form a continuous and compact silver layer on the surface of the PS microspheres. Furthermore, the PS-PDA/Ag core-shell microspheres showed a good conductivity of 10S/cm and a low effective density of 1.8 g/cm(3), much lower than the corresponding values for block silver. Finally, hollow silver microspheres could be prepared by removing the PS core through calcination. SEM images showed that the hollow Ag microspheres remained unbroken and retained the spherical shape. PMID:22104278

  16. Design, synthesis and applications of core-shell, hollow core, and nanorattle multifunctional nanostructures.

    PubMed

    El-Toni, Ahmed Mohamed; Habila, Mohamed A; Labis, Joselito Puzon; ALOthman, Zeid A; Alhoshan, Mansour; Elzatahry, Ahmed A; Zhang, Fan

    2016-02-01

    With the evolution of nanoscience and nanotechnology, studies have been focused on manipulating nanoparticle properties through the control of their size, composition, and morphology. As nanomaterial research has progressed, the foremost focus has gradually shifted from synthesis, morphology control, and characterization of properties to the investigation of function and the utility of integrating these materials and chemical sciences with the physical, biological, and medical fields, which therefore necessitates the development of novel materials that are capable of performing multiple tasks and functions. The construction of multifunctional nanomaterials that integrate two or more functions into a single geometry has been achieved through the surface-coating technique, which created a new class of substances designated as core-shell nanoparticles. Core-shell materials have growing and expanding applications due to the multifunctionality that is achieved through the formation of multiple shells as well as the manipulation of core/shell materials. Moreover, core removal from core-shell-based structures offers excellent opportunities to construct multifunctional hollow core architectures that possess huge storage capacities, low densities, and tunable optical properties. Furthermore, the fabrication of nanomaterials that have the combined properties of a core-shell structure with that of a hollow one has resulted in the creation of a new and important class of substances, known as the rattle core-shell nanoparticles, or nanorattles. The design strategies of these new multifunctional nanostructures (core-shell, hollow core, and nanorattle) are discussed in the first part of this review. In the second part, different synthesis and fabrication approaches for multifunctional core-shell, hollow core-shell and rattle core-shell architectures are highlighted. Finally, in the last part of the article, the versatile and diverse applications of these nanoarchitectures in

  17. Design, synthesis and applications of core-shell, hollow core, and nanorattle multifunctional nanostructures

    NASA Astrophysics Data System (ADS)

    El-Toni, Ahmed Mohamed; Habila, Mohamed A.; Labis, Joselito Puzon; Alothman, Zeid A.; Alhoshan, Mansour; Elzatahry, Ahmed A.; Zhang, Fan

    2016-01-01

    With the evolution of nanoscience and nanotechnology, studies have been focused on manipulating nanoparticle properties through the control of their size, composition, and morphology. As nanomaterial research has progressed, the foremost focus has gradually shifted from synthesis, morphology control, and characterization of properties to the investigation of function and the utility of integrating these materials and chemical sciences with the physical, biological, and medical fields, which therefore necessitates the development of novel materials that are capable of performing multiple tasks and functions. The construction of multifunctional nanomaterials that integrate two or more functions into a single geometry has been achieved through the surface-coating technique, which created a new class of substances designated as core-shell nanoparticles. Core-shell materials have growing and expanding applications due to the multifunctionality that is achieved through the formation of multiple shells as well as the manipulation of core/shell materials. Moreover, core removal from core-shell-based structures offers excellent opportunities to construct multifunctional hollow core architectures that possess huge storage capacities, low densities, and tunable optical properties. Furthermore, the fabrication of nanomaterials that have the combined properties of a core-shell structure with that of a hollow one has resulted in the creation of a new and important class of substances, known as the rattle core-shell nanoparticles, or nanorattles. The design strategies of these new multifunctional nanostructures (core-shell, hollow core, and nanorattle) are discussed in the first part of this review. In the second part, different synthesis and fabrication approaches for multifunctional core-shell, hollow core-shell and rattle core-shell architectures are highlighted. Finally, in the last part of the article, the versatile and diverse applications of these nanoarchitectures in

  18. Reduction-responsive core-shell-corona micelles based on triblock copolymers: novel synthetic strategy, characterization, and application as a tumor microenvironment-responsive drug delivery system.

    PubMed

    Zhao, Xubo; Liu, Peng

    2015-01-14

    A facile and effective approach was established for fabricating core-shell-corona micelles by self-assembly of poly(ethylene glycol)-b-poly(acrylic acid-co-tert-butyl acrylate)-poly(ε-caprolactone) (PEG43-b-P(AA30-co-tBA18)-b-PCL53) triblock copolymer, synthesized via a combination of ring-opening polymerization (ROP), atom transfer radical polymerization (ATRP), click chemistry, and hydrolyzation. The prenanovehicles with three different hydrolysis degrees from PEG43-b-PtBA48-b-PCL53 were developed to evaluate the drug loading capacity (DLC) and drug encapsulation efficiency (DEE). After cross-linking with a disulfide bond to regulate the drug release kinetics, the spherical core-shell-corona micelles with average diameter of 52 ± 4 nm were obtained in aqueous solution. The reduction-responsive cross-linked micelles showed a slow sustained release in normal physiological conditions and a rapid release upon exposure to simulated tumor intracellular conditions. In addition, the cytotoxic analysis and HepG2 cell growth inhibition assays demonstrated their remarkable biocompatibility and similar excellent anticancer activity as the free doxorubicin (DOX), which has also been revealed by the confocal laser scanning microscope (CLSM) analysis. So the reduction-sensitive core-shell-corona micelles are expected to be promising tumor microenvironment-responsive nanovehicles for hydrophobic drugs by glutathione (GSH) triggering. PMID:25394962

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

    NASA Astrophysics Data System (ADS)

    Wang, Xinqin; Cui, Yingqi; Yu, Shengping; Zeng, Qun; Yang, Mingli

    2016-04-01

    The structural, electronic, and optical properties of core-shell nanoclusters, (CdSe)x@(CdSe)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.

  20. Highly flexible transparent self-healing composite based on electrospun core-shell nanofibers produced by coaxial electrospinning for anti-corrosion and electrical insulation

    NASA Astrophysics Data System (ADS)

    An, Seongpil; Liou, Minho; Song, Kyo Yong; Jo, Hong Seok; Lee, Min Wook; Al-Deyab, Salem S.; Yarin, Alexander L.; Yoon, Sam S.

    2015-10-01

    Coaxial electrospinning was used to fabricate two types of core-shell fibers: the first type with liquid resin monomer in the core and polyacrylonitrile in the shell, and the second type with liquid curing agent in the core and polyacrylonitrile in the shell. These two types of core-shell fibers were mutually entangled and embedded into two flexible transparent matrices thus forming transparent flexible self-healing composite materials. Such materials could be formed before only using emulsion electrospinning, rather than coaxial electrospinning. The self-healing properties of such materials are associated with release of healing agents (resin monomer and cure) from nanofiber cores in damaged locations with the subsequent polymerization reaction filing the micro-crack with polydimethylsiloxane. Transparency of these materials is measured and the anti-corrosive protection provided by them is demonstrated in electrochemical experiments.

  1. Supramolecular core-shell nanoparticles for photoconductive device applications.

    PubMed

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

    2016-08-12

    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. PMID:27353003

  2. Mesoscale modeling of functional properties in core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Mangeri, John; Heinonen, Olle; Karpeev, Dmitry; Nakhmanson, Serge

    2015-03-01

    Core-shell nanoparticle systems of Zn-ZnO and ZnO-TiO2 are studied computationally using the highly scalable MOOSE finite-element framework, developed at Idaho National Lab. The elastic anisotropic mismatch of the core and shell create an imprinting effect within the shell that produces a wide variation of strains. Due to this diversity of strains, the sharp band gap edges of the bulk semiconductor are observed to be ``thinned-out'' much like amorphous silicon. We show that a variety of factors, such as particle size, core-to-shell volume ratio, applied hydrostatic pressure, shell microstructure, as well as the effect of surface elasticity, can influence the distribution of optical band-gap values within the particle, which may prove useful within the field of photovoltaics. Part of the work by O.H. was supported by Award 70NANB14H012 from U.S. Department of Commerce, National Institute of Standards and Technology as part of the Center for Hierarchical Material Design.

  3. Cloaking core-shell nanoparticles from conducting electrons in solids.

    PubMed

    Liao, Bolin; Zebarjadi, Mona; Esfarjani, Keivan; Chen, Gang

    2012-09-21

    In this Letter, we aim at making nanoparticles embedded in a host semiconductor with a size comparable to electronic wavelengths "invisible" to the electron transport. Inspired by the recent progress made in optics and working within the framework of the expansion of partial waves, we demonstrate that the opposite effects imposed by potential barriers and wells of a core-shell nanoparticle on the phase shifts associated with the scattered electron wave could make the scattering cross section of the first two partial waves vanish simultaneously. We show that this is sufficient to cloak the nanoparticle from being detected by electrons with specific energy in the sense that a total scattering cross section smaller than 0.01% of the physical cross section can be obtained and a 4 orders of magnitude difference in the total scattering cross section can be presented within an energy range of only 40 meV, indicating possible applications of the "electron cloaks" as novel electronic switches and sensors, and in efficient energy harvesting and conversion technologies. PMID:23005976

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

    SciTech Connect

    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.

  5. Nonlocal dielectric effects in core-shell nanowires.

    SciTech Connect

    McMahon, J. M.; Gray, S. K.; Schatz, G. C.

    2010-01-01

    We study the optical spectra and near fields of core-shell nanowires (nanoshells), using a recently developed finite-difference method that allows for a spatially nonlocal dielectric response. We first analyze the parameters of the nonlocal model by making comparisons with related experimental data and previous theoretical work. We then investigate how nonlocal effects are dependent on nanoshell features, such as shell thickness, overall size, and the ratio of core radius to shell radius. We demonstrate that the shell thickness along the longitudinal direction of the incident light is the primary controlling factor of nonlocal effects, which appear as anomalous absorption resonances and blueshifts in the localized surface plasmon resonance (LSPR) positions, relative to local theory. In addition, we show that the amount of blueshift depends on the order of the LSPR. The optical responses of nanoshells immersed in various refractive index (RI) environments are also studied. We show that the nonlocal anomalous absorption features are relatively insensitive to RI changes, but the blueshift of the dipolar LSPR varies nonlinearly.

  6. Cloaking Core-Shell Nanoparticles from Conducting Electrons in Solids

    NASA Astrophysics Data System (ADS)

    Liao, Bolin; Zebarjadi, Mona; Esfarjani, Keivan; Chen, Gang

    2012-09-01

    In this Letter, we aim at making nanoparticles embedded in a host semiconductor with a size comparable to electronic wavelengths “invisible” to the electron transport. Inspired by the recent progress made in optics and working within the framework of the expansion of partial waves, we demonstrate that the opposite effects imposed by potential barriers and wells of a core-shell nanoparticle on the phase shifts associated with the scattered electron wave could make the scattering cross section of the first two partial waves vanish simultaneously. We show that this is sufficient to cloak the nanoparticle from being detected by electrons with specific energy in the sense that a total scattering cross section smaller than 0.01% of the physical cross section can be obtained and a 4 orders of magnitude difference in the total scattering cross section can be presented within an energy range of only 40 meV, indicating possible applications of the “electron cloaks” as novel electronic switches and sensors, and in efficient energy harvesting and conversion technologies.

  7. Radial pressure measurement in core/shell nanocrystals

    NASA Astrophysics Data System (ADS)

    Ithurria, Sandrine; Guyot-Sionnest, Philippe; Mahler, Benoît; Dubertret, Benoît

    2009-02-01

    Quantum dots are nanometre-sized semiconductor particles exhibiting unique size-dependent electronic properties. In order to passivate the nanocrystals surface and to protect them from oxidation, we grow a shell composed of a second semiconductor with a larger bandgap on the core (for example a core / shell CdS / ZnS). However, the lattice mismatch between the two materials (typically 7% between ZnS and CdS) induces mechanical stress which can lead to dislocations. To better understand these mechanisms, it is important to be able to measure the pressure induced on the semiconductor core. We used a nanocrystal doped with manganese ions Mn2+, which provide a phosphorescence signal depending on the local pressure. A few dopant atoms per nanoparticle were placed at controlled radial positions in a ZnS shell formed layer by layer. The experimental pressure measurements are in very good agreement with a simple spherically symmetric elastic continuum model[1]. Using manganese as a pressure gauge could be used to better understand some structural phenomena observed in these nanocrystals, such as crystalline phases transition, or shell cracking.

  8. Band structure of core-shell semiconductor nanowires

    NASA Astrophysics Data System (ADS)

    Pistol, Mats-Erik; Pryor, Craig

    2009-03-01

    We present band structures of strained core-shell nanowires composed of zincblende III-V (binary) semiconductors. We consider all combinations of AlN, GaN, InN, and all combinations of AlP, GaP, AlAs, GaAs, InP, InAs, AlSb, GaSb, and InSb. We compute the γ- and X-conduction band minima as well as the valence band maximum, all as functions of the core and shell radii. The calculations were performed using continuum elasticity theory for the strain, eight-band strain-dependent k.p theory for the γ-point energies, and single band approximation for the X-point conduction minima. We identify structures with type-I, type-II and type-III band alignment, as well as systems in which one material becomes metallic due to a negative band-gap. We identify structures that may support exciton crystals with and without photoexcitation. We have also computed the effective masses, from which the confinement energy may be estimated. All the results [Pistol and Pryor, Phys. Rev. B 78, 115319] are available in graphical and tabular form at www.semiconductor.physics.uiowa.edu

  9. Homogeneous Protein Analysis by Magnetic Core-Shell Nanorod Probes.

    PubMed

    Schrittwieser, Stefan; Pelaz, Beatriz; Parak, Wolfgang J; Lentijo-Mozo, Sergio; Soulantica, Katerina; Dieckhoff, Jan; Ludwig, Frank; Altantzis, Thomas; Bals, Sara; Schotter, Joerg

    2016-04-13

    Studying protein interactions is of vital importance both to fundamental biology research and to medical applications. Here, we report on the experimental proof of a universally applicable label-free homogeneous platform for rapid protein analysis. It is based on optically detecting changes in the rotational dynamics of magnetically agitated core-shell nanorods upon their specific interaction with proteins. By adjusting the excitation frequency, we are able to optimize the measurement signal for each analyte protein size. In addition, due to the locking of the optical signal to the magnetic excitation frequency, background signals are suppressed, thus allowing exclusive studies of processes at the nanoprobe surface only. We study target proteins (soluble domain of the human epidermal growth factor receptor 2 - sHER2) specifically binding to antibodies (trastuzumab) immobilized on the surface of our nanoprobes and demonstrate direct deduction of their respective sizes. Additionally, we examine the dependence of our measurement signal on the concentration of the analyte protein, and deduce a minimally detectable sHER2 concentration of 440 pM. For our homogeneous measurement platform, good dispersion stability of the applied nanoprobes under physiological conditions is of vital importance. To that end, we support our measurement data by theoretical modeling of the total particle-particle interaction energies. The successful implementation of our platform offers scope for applications in biomarker-based diagnostics as well as for answering basic biology questions. PMID:27023370

  10. Core-shell nanostructured hybrid composites for volatile organic compound detection

    PubMed Central

    Tung, Tran Thanh; Losic, Dusan; Park, Seung Jun; Feller, Jean-Francois; Kim, TaeYoung

    2015-01-01

    We report a high-performance chemiresistive sensor for detection of volatile organic compound (VOC) vapors based on core-shell hybridized nanostructures of Fe3O4 magnetic nanoparticles (MNPs) and poly(3,4-ethylenedioxythiophene) (PEDOT)-conducting polymers. The MNPs were prepared using microwave-assisted synthesis in the presence of polymerized ionic liquids (PILs), which were used as a linker to couple the MNP and PEDOT. The resulting PEDOT–PIL-modified Fe3O4 hybrids were then explored as a sensing channel material for a chemiresistive sensor to detect VOC vapors. The PEDOT–PIL-modified Fe3O4 sensor exhibited a tunable response, with high sensitivity (down to a concentration of 1 ppm) and low noise level, to VOCs; these VOCs include acetone vapor, which is present in the exhaled breath of potential lung cancer patients. The present sensor, based on the hybrid nanostructured sensing materials, exhibited a 38.8% higher sensitivity and an 11% lower noise level than its PEDOT–PIL-only counterpart. This approach of embedding MNPs in conducting polymers could lead to the development of new electronic noses, which have significant potential for the use in the early diagnosis of lung cancer via the detection of VOC biomarkers. PMID:26357471

  11. Controllable fabrication and characterization of biocompatible core-shell particles and hollow capsules as drug carrier

    NASA Astrophysics Data System (ADS)

    Hao, Lingyun; Gong, Xinglong; Xuan, Shouhu; Zhang, Hong; Gong, Xiuqing; Jiang, Wanquan; Chen, Zuyao

    2006-10-01

    SiO 2@CdSe core-shell particles were fabricated by controllable deposition CdSe nanoparticles on silica colloidal spheres. Step-wise coating process was tracked by the TEM and XRD measurements. In addition, SiO 2@CdSe/polypyrrole(PPy) multi-composite particles were synthesized based on the as-prepared SiO 2@CdSe particles by cationic polymerization. The direct electrochemistry of myoglobin (Mb) could be performed by immobilizing Mb on the surface of SiO 2@CdSe particles. Immobilized with Mb, SiO 2@CdSe/PPy-Mb also displayed good bioelectrochemical activity. It confirmed the good biocompatible property of the materials with protein. CdSe hollow capsules were further obtained as the removal of the cores of SiO 2@CdSe spheres. Hollow and porous character of CdSe sub-meter size capsules made them becoming hopeful candidates as drug carriers. Doxorubicin, a typical an antineoplastic drug, was introduced into the capsules. A good sustained drug release behavior of the loading capsules was discovered via performing a release test in the PBS buffer (pH 7.4) solution at 310 k. Furthermore, SiO 2@CdSe/PPy could be converted to various smart hollow capsules via selectively removal of their relevant components.

  12. Potentiometric glucose biosensor based on core-shell Fe3O4-enzyme-polypyrrole nanoparticles.

    PubMed

    Yang, Zhengpeng; Zhang, Chunjing; Zhang, Jianxin; Bai, Wanbei

    2014-01-15

    Core-shell Fe3O4-enzyme-polypyrrole (Ppy) nanoparticles with excellent magnetism and conductivity were successfully prepared via the surface modification and enzyme self-encapsulation within Ppy. A novel potentiometric glucose biosensor has been constructed by effectively attaching the proposed Fe3O4-enzyme-Ppy nanoparticles to the surface of the magnetic glassy carbon electrode (MGCE). The optimum biosensing conditions could be provided with polymerization time of pyrrole for 6h and 0.42 mg immobilization amount of Fe3O4-enzyme-Ppy nanoparticles on MGCE. The performance of the developed glucose biosensor was evaluated and the results indicated that a sensitive glucose biosensor could be fabricated. The obtained glucose biosensor presents shorter response time (6 s), wider linear range (0.5 μM to 34 mM), lower limit of detection (LOD, 0.3 μM), high-selectivity monitoring of glucose and good stability (with about 98.1% of the initial response signal retained after 20 days). The analytical application of the glucose biosensor confirms the feasibility of glucose detection in serum sample. PMID:23974157

  13. Core-shell nanostructured hybrid composites for volatile organic compound detection.

    PubMed

    Tung, Tran Thanh; Losic, Dusan; Park, Seung Jun; Feller, Jean-Francois; Kim, TaeYoung

    2015-01-01

    We report a high-performance chemiresistive sensor for detection of volatile organic compound (VOC) vapors based on core-shell hybridized nanostructures of Fe3O4 magnetic nanoparticles (MNPs) and poly(3,4-ethylenedioxythiophene) (PEDOT)-conducting polymers. The MNPs were prepared using microwave-assisted synthesis in the presence of polymerized ionic liquids (PILs), which were used as a linker to couple the MNP and PEDOT. The resulting PEDOT-PIL-modified Fe3O4 hybrids were then explored as a sensing channel material for a chemiresistive sensor to detect VOC vapors. The PEDOT-PIL-modified Fe3O4 sensor exhibited a tunable response, with high sensitivity (down to a concentration of 1 ppm) and low noise level, to VOCs; these VOCs include acetone vapor, which is present in the exhaled breath of potential lung cancer patients. The present sensor, based on the hybrid nanostructured sensing materials, exhibited a 38.8% higher sensitivity and an 11% lower noise level than its PEDOT-PIL-only counterpart. This approach of embedding MNPs in conducting polymers could lead to the development of new electronic noses, which have significant potential for the use in the early diagnosis of lung cancer via the detection of VOC biomarkers. PMID:26357471

  14. RTA-treated carbon fiber/copper core/shell hybrid for thermally conductive composites.

    PubMed

    Yu, Seunggun; Park, Bo-In; Park, Cheolmin; Hong, Soon Man; Han, Tae Hee; Koo, Chong Min

    2014-05-28

    In this paper, we demonstrate a facile route to produce epoxy/carbon fiber composites providing continuous heat conduction pathway of Cu with a high degree of crystal perfection via electroplating, followed by rapid thermal annealing (RTA) treatment and compression molding. Copper shells on carbon fibers were coated through electroplating method and post-treated via RTA technique to reduce the degree of imperfection in the Cu crystal. The epoxy/Cu-plated carbon fiber composites with Cu shell of 12.0 vol % prepared via simple compression molding, revealed 18 times larger thermal conductivity (47.2 W m(-1) K(-1)) in parallel direction and 6 times larger thermal conductivity (3.9 W m(-1) K(-1)) in perpendicular direction than epoxy/carbon fiber composite. Our novel composites with RTA-treated carbon fiber/Cu core/shell hybrid showed heat conduction behavior of an excellent polymeric composite thermal conductor with continuous heat conduction pathway, comparable to theoretical values obtained from Hatta and Taya model. PMID:24758290

  15. Hollow nitrogen-containing core/shell fibrous carbon nanomaterials as support to platinum nanocatalysts and their TEM tomography study

    NASA Astrophysics Data System (ADS)

    Zhou, Cuifeng; Liu, Zongwen; Du, Xusheng; Mitchell, David Richard Graham; Mai, Yiu-Wing; Yan, Yushan; Ringer, Simon

    2012-03-01

    Core/shell nanostructured carbon materials with carbon nanofiber (CNF) as the core and a nitrogen (N)-doped graphitic layer as the shell were synthesized by pyrolysis of CNF/polyaniline (CNF/PANI) composites prepared by in situ polymerization of aniline on CNFs. High-resolution transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared and Raman analyses indicated that the PANI shell was carbonized at 900°C. Platinum (Pt) nanoparticles were reduced by formic acid with catalyst supports. Compared to the untreated CNF/PANI composites, the carbonized composites were proven to be better supporting materials for the Pt nanocatalysts and showed superior performance as catalyst supports for methanol electrochemical oxidation. The current density of methanol oxidation on the catalyst with the core/shell nanostructured carbon materials is approximately seven times of that on the catalyst with CNF/PANI support. TEM tomography revealed that some Pt nanoparticles were embedded in the PANI shells of the CNF/PANI composites, which might decrease the electrocatalyst activity. TEM-energy dispersive spectroscopy mapping confirmed that the Pt nanoparticles in the inner tube of N-doped hollow CNFs could be accessed by the Nafion ionomer electrolyte, contributing to the catalytic oxidation of methanol.

  16. Hollow nitrogen-containing core/shell fibrous carbon nanomaterials as support to platinum nanocatalysts and their TEM tomography study

    PubMed Central

    2012-01-01

    Core/shell nanostructured carbon materials with carbon nanofiber (CNF) as the core and a nitrogen (N)-doped graphitic layer as the shell were synthesized by pyrolysis of CNF/polyaniline (CNF/PANI) composites prepared by in situ polymerization of aniline on CNFs. High-resolution transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared and Raman analyses indicated that the PANI shell was carbonized at 900°C. Platinum (Pt) nanoparticles were reduced by formic acid with catalyst supports. Compared to the untreated CNF/PANI composites, the carbonized composites were proven to be better supporting materials for the Pt nanocatalysts and showed superior performance as catalyst supports for methanol electrochemical oxidation. The current density of methanol oxidation on the catalyst with the core/shell nanostructured carbon materials is approximately seven times of that on the catalyst with CNF/PANI support. TEM tomography revealed that some Pt nanoparticles were embedded in the PANI shells of the CNF/PANI composites, which might decrease the electrocatalyst activity. TEM-energy dispersive spectroscopy mapping confirmed that the Pt nanoparticles in the inner tube of N-doped hollow CNFs could be accessed by the Nafion ionomer electrolyte, contributing to the catalytic oxidation of methanol. PMID:22385930

  17. Microwave absorption behavior of core-shell structured poly (3,4-ethylenedioxy thiophene)-barium ferrite nanocomposites.

    PubMed

    Ohlan, Anil; Singh, Kuldeep; Chandra, Amita; Dhawan, Sundeep K

    2010-03-01

    The present paper reports the complex permittivity, permeability, and microwave absorption properties of core shell type poly (3,4-ethylenedioxy thiophene) (PEDOT) nanocomposite with barium ferrite, synthesized by in situ emulsion polymerization, in the 12.4-18 GHz frequency range. High-resolution transmission electron microscopy (HRTEM) studies reveal the formation of core-shell type morphology with ferrite particles (60-80 nm) as the center while the polymer (PEDOT) formulates the outer shell of the composite. The presence of barium ferrite nanoparticles in the polymer matrix includes the magnetic losses, which mainly arise from the magnetic hysteresis, domain-wall displacement, and eddy current loss. The higher dielectric (epsilon'' = 23.5) and magnetic loss (micro'' = 0.22) contributes to the microwave absorption value of 22.5 dB (>99% attenuation) and are found to increase with the amount of ferrite constituents. The polymer was further characterized through Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). PMID:20356300

  18. Constructing Uniform Core-Shell PPy@PANI Composites with Tunable Shell Thickness toward Enhancement in Microwave Absorption.

    PubMed

    Tian, Chunhua; Du, Yunchen; Xu, Ping; Qiang, Rong; Wang, Ying; Ding, Ding; Xue, Jianlei; Ma, Jun; Zhao, Hongtao; Han, Xijiang

    2015-09-16

    Highly uniform core-shell composites, polypyrrole@polyaniline (PPy@PANI), have been successfully constructed by directing the polymerization of aniline on the surface of PPy microspheres. The thickness of PANI shells, from 30 to 120 nm, can be well controlled by modulating the weight ratio of aniline and PPy microspheres. PPy microspheres with abundant carbonyl groups have very strong affinity to the conjugated chains of PANI, which is responsible for the spontaneous formation of uniform core-shell microstructures. However, the strong affinity between PPy microspheres and PANI shells does not promote the diffusion or reassembly of two kinds of conjugated chains. Coating PPy microspheres with PANI shells increases the complex permittivity and creates the mechanism of interfacial polarization, where the latter plays an important role in increasing the dielectric loss of PPy@PANI composites. With a proper thickness of PANI shells, the moderate dielectric loss will produce well matched characteristic impedance, so that the microwave absorption properties of these composites can be greatly enhanced. Although PPy@PANI composites herein consume the incident electromagnetic wave by absolute dielectric loss, their performances are still superior or comparable to most PANI-based composites ever reported, indicating that they can be taken as a new kind of promising lightweight microwave absorbers. More importantly, microwave absorption of PPy@PANI composites can be simply modulated not only by the thickness of the absorbers, but also the shell thickness to satisfy the applications in different frequency bands. PMID:26322386

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

    PubMed

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

    2016-02-01

    Magnetic core/shell nanostructures of Fe3O4 nanoparticles coated with oleic acid and betaine-HCl were studied for their possible use in magnetic fluid hyperthermia (MFH). Their colloidal stability and heat induction ability were studied in different media viz. phosphate buffer solution (PBS), saline solution and glucose solution with different physiological conditions and in human serum. The results showed enhanced colloidal stability in these media owing to their high zeta potential values. Heat induction studies showed that specific absorption rates (SAR) of core/shells were 82-94W/g at different pH of PBS and concentrations of NaCl and glucose. Interestingly, core/shells showed 78.45±3.90W/g SAR in human serum. The cytotoxicity of core/shells done on L929 and HeLa cell lines using 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl tetrazolium bromide and trypan blue dye exclusion assays showed >89% and >80% cell viability for 24 and 48h respectively. Core/shell structures were also found to be very efficient for in vitro MFH on cancer cell line. About 95% cell death was occurred in 90min after hyperthermia treatment. The mechanism of cell death was found to be elevated ROS generation in cells after exposure to core/shells in external magnetic field. This study showed that these core/shells have a great potential to be used in in vivo MFH. PMID:26652424

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

    SciTech Connect

    Lee, Hee Uk; Song, Yoon Seok; Park, Chulhwan; Kim, Seung Wook

    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.

  1. Influences of external vs. core-shell mixing on aerosol optical properties at various relative humidities.

    PubMed

    Ramachandran, S; Srivastava, Rohit

    2013-05-01

    Aerosol optical properties of external and core-shell mixtures of aerosol species present in the atmosphere are calculated in this study for different relative humidities. Core-shell Mie calculations are performed using the values of radii, refractive indices and densities of aerosol species that act as core and shell, and the core-shell radius ratio. The single scattering albedo (SSA) is higher when the absorbing species (black carbon, BC) is the core, while for a sulfate core SSA does not vary significantly as the BC in the shell dominates the absorption. Absorption gets enhanced in core-shell mixing of absorbing and scattering aerosols when compared to their external mixture. Thus, SSA is significantly lower for a core-shell mixture than their external mixture. SSA is more sensitive to core-shell ratio than mode radius when BC is the core. The extinction coefficient, SSA and asymmetry parameter are higher for external mixing when compared to BC (core)-water soluble aerosol (shell), and water soluble aerosol (core)-BC (shell) mixtures in the relative humidity range of 0 to 90%. Spectral SSA exhibits the behaviour of the species which acts as a shell in core-shell mixing. The asymmetry parameter for an external mixture of water soluble aerosol and BC is higher than BC (core)-water soluble aerosol (shell) mixing and increases as function of relative humidity. The asymmetry parameter for the water soluble aerosol (core)-BC (shell) is independent of relative humidity as BC is hydrophobic. The asymmetry parameter of the core-shell mixture decreases when BC aerosols are involved in mixing, as the asymmetry parameter of BC is lower. Aerosol optical depth (AOD) of core-shell mixtures increases at a higher rate when the relative humidity exceeds 70% in continental clean and urban aerosol models, whereas AOD remains the same when the relative humidity exceeds 50% in maritime aerosol models. The SSA for continental aerosols varies for core-shell mixing of water soluble

  2. PVP induce self-seeding process for growth of Au@Ag core@shell nanocomposites

    NASA Astrophysics Data System (ADS)

    Eisa, Wael H.; Al-Ashkar, Emad; El-Mossalamy, S. M.; Ali, Safaa S. M.

    2016-05-01

    A novel self-seeding route is developed for fabrication of metallic nanocomposites of gold (core) and silver (shell) (Au@Ag core@shell). Herein, polyvinylpyrrolidone (PVP) is used as both reducing and stabilizing agent. The surface plasmon resonance (SPR) of Au@Ag core@shell can be tuned by controlling the thickness of the Ag shell. The different growth stages of the Au@Ag core@shell have been traced by in situ UV-vis absorption spectra. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy are used for the characterization of the prepared samples.

  3. Formation of core-shell structure in high entropy alloy coating by laser cladding

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Wu, Wanfei; He, Yizhu; Li, Mingxi; Guo, Sheng

    2016-02-01

    The formation of core-shell structure is an interesting phenomenon occurring during the solidification process, due to the liquid phase separation. The formation of core-shell structure in high-entropy alloys, a new class of advanced metallic materials, has not been reported previously, and thus constitutes an intriguing scientific question. Here, we firstly report the formation of core-shell structure in one laser cladded high-entropy alloy, where we show the nanosized-Y2O3 powder addition, serves as the catalyst for the liquid phase separation.

  4. Advanced piezoresistance of extended metal-insulator core-shell nanoparticle assemblies.

    PubMed

    Athanassiou, E K; Krumeich, F; Grass, R N; Stark, W J

    2008-10-17

    Assembled metal-insulator nanoparticles with a core-shell geometry provide access to materials containing a large number (>10(6)) of tunneling barriers. We demonstrate the production of ceramic coated metal nanoparticles exhibiting an exceptional pressure-sensitive conductivity. We further show that graphene bi- and trilayers on 20 nm copper nanoparticles are insulating in such a core-shell geometry and show a similar pressure-dependent conductivity. This demonstrates that core-shell metal-insulator assemblies offer a route to alternative sensing materials. PMID:18999701

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

    NASA Astrophysics Data System (ADS)

    Yan, Yueran

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

  6. Ab initio no-core shell model with continuum

    NASA Astrophysics Data System (ADS)

    Navratil, Petr

    2008-04-01

    The ab initio no-core shell model (NCSM) is a many-body approach to nuclear structure of light nuclei. The NCSM adopts an effective interaction theory to transform fundamental inter-nucleon interactions into effective interactions for a specified nucleus in a selected harmonic oscillator basis space [1]. The method is capable of predicting nuclear structure from inter-nucleon forces derived from quantum chromodynamics by means of chiral effective field theory [2]. NCSM extensions to the microscopic description of nuclear reactions are now under development. In my talk, I will first discuss our recent calculations of the ^4He total photo-absorption cross section using two- and three-nucleon interactions from chiral effective field theory [3]. I will then outline our effort to augment the NCSM by the resonating group method (RGM) technique to develop a new method capable of describing simultaneously both bound states and nuclear reactions on light nuclei [4]. This approach, which preserves translational symmetry and the Pauli principle, will allow us to calculate cross sections of reactions important for astrophysics and describe weakly-bound systems from first principles. I will present our first phase shift results for neutron scattering off ^3H, ^4He and ^7Li and proton scattering off ^3He, ^4He and ^7Be using realistic nucleon-nucleon potentials. 3mm [1] P. Navr'atil, J. P. Vary and B. R. Barrett, Phys. Rev. C 62, 054311 (2000). [2] P. Navr'atil and V. G. Gueorguiev and J. P. Vary, W. E. Ormand and A. Nogga, Phys. Rev. Lett. 99, 042501 (2007). [3] S. Quaglioni and P. Navr'atil, Phys. Lett. B 652, 370 (2007). [4] S. Quaglioni and P. Navr'atil, arXiv:0712.0855.

  7. Preparation of core-shell Ag@CeO2 nanocomposite by LSPR photothermal induced interface reaction

    NASA Astrophysics Data System (ADS)

    Zhong, H. X.; Wei, Y.; Yue, Y. Z.; Zhang, L. H.; Liu, Y.

    2016-04-01

    The core-shell structure of Ag@CeO2 was prepared by a novel and facile method, which was based on the photothermal effect of localized surface plasmon resonance (LSPR). Nanoparticles (NPs) of Ag were dispersed in a solution containing citric acid, ethylene glycol and cerium nitrate, then under irradiation, Ag NPs generated heat from LSPR and the heat-induced polymerization reaction in the interface between Ag and the sol resulted in cerium gel formation only on the surface of the Ag NPs. After calcination, Ag@CeO2 was successfully obtained, then Ag@CeO2/SiO2 was prepared by loading Ag@CeO2 on SiO2. The resultant catalyst exhibited favorable activity and stability for CO oxidation. The preparation method proposed here should be extendable to other composites with metallic cores and oxide shells in which the metallic nanoparticle possesses LSPR properties.

  8. Design of polyelectrolyte core-shells with DNA to control TMPyP binding.

    PubMed

    Serra, Vanda Vaz; Teixeira, Raquel; Andrade, Suzana M; Costa, Sílvia M B

    2016-10-01

    The interaction of DNA with 5,10,15,20-tetrakis(4-N-methylpyridiniumyl)porphyrin (TMPyP) in polyelectrolyte core-shells obtained via layer by layer adsorption of poly(sodium 4-styrenesulfonate), PSS, and poly(allylamine hydrochloride), PAH, polyelectrolytes was followed by steady state, time resolved fluorescence and by Fluorescence Lifetime Imaging Microscopy (FLIM). Our results show that DNA adsorption onto polyelectrolyte core-shell changes the TMPyP interaction within PSS/PAH core-shells structure and increase significantly the TMPyP uptake. Specific DNA/TMPyP interactions are also altered by DNA adsorption favouring porphyrin intercalation onto GC pair rich regions. Circular dichroism (CD) spectra reveal that DNA undergoes important conformational changes upon adsorption onto the core-shell surface, which are reverted upon TMPyP encapsulation. PMID:27285535

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

    PubMed Central

    Mandal, Samir; Chaudhuri, Keya

    2016-01-01

    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. PMID:26981204

  10. Study of photodynamic activity of Au@SiO2 core-shell nanoparticles in vitro.

    PubMed

    Meena, K S; Dhanalekshmi, K I; Jayamoorthy, K

    2016-06-01

    Metal-semiconductor core-shell type Au@SiO2 nanoparticles were prepared by Stober's method. They were characterized by absorption, XRD, HR-TEM and EDAX techniques. The resulting modified core-shell nanoparticles shows that the formation of singlet oxygen, which was confirmed by ESR technique. The photohemolysis studies were carried out under two different experimental conditions. It is observed that the photohemolysis increases with concentration as well as light dose. Cell viability of the core-shell nanoparticles against HeLa cell lines were studied by MTT assay method. The outcomes of the present study indicate that, the Au@SiO2 core-shell nanoparticles are extremely stable with a very high photodynamic efficiency under visible light illumination. PMID:27040225

  11. Water-soluble core/shell nanoparticles for proton therapy through particle-induced radiation

    NASA Astrophysics Data System (ADS)

    Park, Jeong Chan; Jung, Myung-Hwan; Kim, Maeng Jun; Kim, Kye-Ryung

    2015-02-01

    Metallic nanoparticles have been used in biomedical applications such as magnetic resonance imaging (MRI), therapy, and drug delivery systems. Metallic nanoparticles as therapeutic tools have been demonstrated using radio-frequency magnetic fields or near-infrared light. Recently, therapeutic applications of metallic nanomaterials combined with proton beams have been reported. Particle-induced radiation from metallic nanoparticles, which can enhance the therapeutic effects of proton therapy, was released when the nanoparticles were bombarded by a high-energy proton beam. Core/shell nanoparticles, especially Au-coated magnetic nanoparticles, have drawn attention in biological applications due to their attractive characteristics. However, studies on the phase transfer of organic-ligand-based core/shell nanoparticles into water are limited. Herein, we demonstrated that hydrophobic core/shell structured nanomaterials could be successfully dispersed in water through chloroform/surfactant mixtures. The effects of the core/shell nanomaterials and the proton irradiation on Escherichia coli (E. coli) were also explored.

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

    DOE PAGESBeta

    Antony, Jiji; Nutting, Joseph; Baer, Donald R.; Meyer, Daniel; Sharma, Amit; Qiang, You

    2006-01-01

    Nmore » anoporous 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.« less

  13. Coordination polymer core/shell structures: Preparation and up/down-conversion luminescence.

    PubMed

    Li, Bingmei; Xu, Hualan; Xiao, Chen; Shuai, Min; Chen, Weimin; Zhong, Shengliang

    2016-10-01

    Coordination polymer (CP) core-shell nanoparticles with Gd-based CP (GdCP) as core and Eu-based CP (EuCP) as shell have been successfully prepared. Allantoin was employed as the organic building block without the assistance of any template. The composition, size and structure of the core-shell nanospheres were well characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric analysis (TG). Results show that the resultant cores are uniform nanospheres with diameter of approximately 45nm, while the diameters of the core-shell nanospheres are increased to approximately 60nm. The core-shell products show enhanced luminescence efficiency than the core under 980nm laser excitation and decreased down-conversion luminescence when excited at 394nm. PMID:27344485

  14. Tunable mechanical and thermal properties of ZnS/CdS core/shell nanowires

    NASA Astrophysics Data System (ADS)

    Mandal, Taraknath; Dasgupta, Chandan; Maiti, Prabal K.

    2015-03-01

    Using all-atom molecular dynamics (MD) simulations, we have studied the mechanical properties of ZnS/CdS core/shell nanowires. Our results show that the coating of a few-atomic-layer CdS shell on the ZnS nanowire leads to a significant change in the stiffness of the core/shell nanowires compared to the stiffness of pure ZnS nanowires. The binding energy between the core and shell region decreases due to the lattice mismatch at the core-shell interface. This reduction in binding energy plays an important role in determining the stiffness of a core/shell nanowire. We have also investigated the effects of the shell on the thermal conductivity and melting behavior of the nanowires.

  15. Controllable fabrication of PS/Ag core-shell-shaped nanostructures

    PubMed Central

    2012-01-01

    In this paper, based on the previous steps, a facile in situ reduction method was developed to controllably prepare polystyrene/Ag (PS/Ag) core-shell-shaped nanostructures. The crucial procedure includes surface treatment of polystyrene core particles by cationic polyelectrolyte polyethyleneimine, in situ formation of Ag nanoparticles, and immobilization of the Ag nanoparticles onto the surface of the polystyrene colloids via functional group NH from the polyethyleneimine. The experimental parameters, such as the reaction temperature, the reaction time, and the silver precursors were optimized for improvement of dispersion and Ag coat coverage of the core-shell-shaped nanostructures. Ultimately, the optimum parameters were obtained through a series of experiments, and well-dispersed, uniformly coated PS/Ag core-shell-shaped nanostructures were successfully fabricated. The formation mechanism of the PS/Ag core-shell-shaped nanostructures was also explained. PMID:23092195

  16. One-pot aerosol synthesis of ordered hierarchical mesoporous core-shell silica nanoparticles.

    PubMed

    Areva, S; Boissière, C; Grosso, D; Asakawa, T; Sanchez, C; Lindén, M

    2004-07-21

    A mixed surfactant approach has been successfully employed in an aerosol-based synthesis of spherical silica particles exhibiting a new core-shell structure where the shell and the core exhibit different ordered mesoporosity and pore sizes. PMID:15263952

  17. Synthesis and characterization of Zn 3P 2/ZnS core/shell nanowires

    NASA Astrophysics Data System (ADS)

    Sun, T.; Wu, P. C.; Guo, Z. D.; Dai, Y.; Meng, H.; Fang, X. L.; Shi, Z. J.; Dai, L.; Qin, G. G.

    2011-05-01

    Fully-surrounded Zn3P2/ZnS core/shell nanowires (NWs) were synthesized for the first time via a two-step method: a catalyst free chemical vapor deposition followed by a low-pressure vulcanization process. Field emission scanning electron microscopy, high-resolution transmission electron microscopy, and high-angle angular dark field scanning transmission electron microscopy were used to characterize the morphologies, crystal structure, and element composition of the core/shell NWs. The band structure analysis demonstrates that the Zn3P2/ZnS core-shell NW type-II heterostructures have bright potential in photovoltaic nanodevice applications. The core/shell NW growth method used here can be extended to other material system.

  18. Introduction of biotin or folic acid into polypyrrole magnetite core-shell nanoparticles

    SciTech Connect

    Nan, Alexandrina; Turcu, Rodica; Liebscher, Jürgen

    2013-11-13

    In order to contribute to the trend in contemporary research to develop magnetic core shell nanoparticles with better properties (reduced toxicity, high colloidal and chemical stability, wide scope of application) in straightforward and reproducible methods new core shell magnetic nanoparticles were developed based on polypyrrole shells functionalized with biotin and folic acid. Magnetite nanoparticles stabilized by sebacic acid were used as magnetic cores. The morphology of magnetite was determined by transmission electron microscopy TEM, while the chemical structure investigated by FT-IR.

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

    PubMed

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

    2016-04-01

    In this work, the core-magnesium ferrite (MgFe2O4) nanoparticles were prepared by hydrothermal technique. Completed gold (Au) shell coating on the surfaces of MgFe2O4 nanoparticles was obtained by varying core/shell ratios via a reduction method. Phase identification, morphological evolution, optical properties, magnetic properties and cytotoxicity to mammalian cells of these MgFe2O4 core coated with Au nanoparticles were examined by using a combination of X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy, UV-visible spectroscopy (UV-vis), vibrating sample magnetometry and resazurin microplate assay techniques. In general, TEM images revealed different sizes of the core-shell nanoparticles generated from various core/shell ratios and confirmed the completed Au shell coating on MgFe2O4 core nanoparticles via suitable core/shell ratio with particle size less than 100nm. The core-shell nanoparticle size and the quality of coating influence the optical properties of the products. The UV-vis spectra of complete coated MgFe2O4-Au core-shell nanoparticles exhibit the absorption bands in the near-Infrared (NIR) region indicating high potential for therapeutic applications. Based on the magnetic property measurement, it was found that the obtained MgFe2O4-Au core-shell nanoparticles still exhibit superparamagnetism with lower saturation magnetization value, compared with MgFe2O4 core. Both of MgFe2O4 and MgFe2O4-Au core-shell also showed in vitro non-cytotoxicity to mouse areola fibroblast (L-929) cell line. PMID:26838832

  20. Synthesis and optical properties of three-dimensional porous core-shell nanoarchitectures.

    PubMed

    Qian, Li-Hua; Ding, Yi; Fujita, Takeshi; Chen, Ming-Wei

    2008-05-01

    Three-dimensional porous core-shell nanostructures consisting of gold skeletons and silver shells were fabricated by controllable electroless plating. Optical properties of the 3D nanocomposite with a heterogeneous interface exhibit a significant shell-thickness dependence. The porous core-shell structure with an optimized shell thickness of approximately 3-5 nm exhibits a considerable improvement in surface-enhanced Raman scattering. This study has important implications in the functionalization of nanoporous metals by surface modification. PMID:18355096

  1. Core-shell palladium nanoparticle@metal-organic frameworks as multifunctional catalysts for cascade reactions.

    PubMed

    Zhao, Meiting; Deng, Ke; He, Liangcan; Liu, Yong; Li, Guodong; Zhao, Huijun; Tang, Zhiyong

    2014-02-01

    Uniform core-shell Pd@IRMOF-3 nanostructures, where single Pd nanoparticle core is surrounded by amino-functionalized IRMOF-3 shell, are prepared by a facile mixed solvothermal method. When used as multifunctional catalysts, the Pd@IRMOF-3 nanocomposites exhibit high activity, enhanced selectivity, and excellent stability in the cascade reaction. Both experimental evidence and theoretical calculations reveal that the high catalytic performance of Pd@IRMOF-3 nanocomposites originates from their unique core-shell structures. PMID:24437922

  2. Fluorescent dye-labelled polymer synthesis by nitroxide mediated radical polymerization

    NASA Astrophysics Data System (ADS)

    Kollár, Jozef; Chmela, Štefan; Hrčková, Ľudmila; Hrdlovič, Pavol

    2012-07-01

    New applications of polymers at advanced technologies demand increased requirements on their properties. These properties are influenced by molecular as well as supramolecular structure. Controlled radical polymerization mediated by stable nitroxides (NMP) or substituted alkoxyamines offers simple method for preparation of polymers with programmable structure of macromolecules which possess remarkable better physical as well as chemical properties. They can be used as a macro initiators for the synthesis of block copolymers. At the present time it has been generally accepted that the extent of "livingness" is high for all conversions [1-4]. To verify this statement a series of fluorescent dye-labelled regulators has been synthesized, spectrally characterized and used as the mediators of styrene and n-butyl acrylate polymerization. Direct quantification of dormant species concentration (extent of livingness) and calculation of molar mass of marked polymers was performed by absorption and/or emission spectroscopy. Controlled radical polymerization mediated by stable nitroxides bearing fluorescence mark represents unconventional approach for monitoring and evaluation of mechanism and kinetics of polymerization process. Results indicate that the extent of livingness is strongly influenced by conversion as well as mediator concentration. There is a clear tendency toward to decreasing amount of dormant species with increasing monomer conversion. Moreover, lower mediator concentration decreases livingness of polymerization process.

  3. Environmentally responsive core/shell particles via electrohydrodynamic co-jetting of fully miscible polymer solutions.

    PubMed

    Kazemi, Abbass; Lahann, Joerg

    2008-10-01

    Herein it is demonstrated that electrohydrodynamic co-jetting is not limited to Janus-type particles, but can also be used for the preparation of core/shell particles. Using side-by-side flow of miscible polymer solutions, electrohydrodynamic co-jetting offers an elegant and scalable route towards preparation of core/shell particles with otherwise difficult-to-prepare particle architectures, including particles with hydrophilic shell and core. Throughout this study, electrohydrodynamic co-jetting of aqueous solutions consisting of a mixture of PAAm-co-AA and PAA is used, and a range of different types of particles with distinct compartments are observed. Transition from Janus particles to core/shell particles appears to be caused by changes in the relative conductivity of the two jetting solutions. After crosslinking, the core/shell particles are stable in aqueous solution and exhibit reproducible swelling behavior while maintaining the original core/shell geometry. In addition, the pH-responsiveness of the particles is demonstrated by repeatedly switching the environmental pH between 1.3 and 12. Moreover, the core/shell particles show surprising uptake selectivity. For instance, a 450% increase in uptake of 6-carboxyfluorescein over rhodamine B base is found. PMID:18819137

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

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

    SciTech Connect

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

    2010-01-15

    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.

  6. Core-shell nanocarriers with high paclitaxel loading for passive and active targeting

    NASA Astrophysics Data System (ADS)

    Jin, Zhu; Lv, Yaqi; Cao, Hui; Yao, Jing; Zhou, Jianping; He, Wei; Yin, Lifang

    2016-06-01

    Rapid blood clearance and premature burst release are inherent drawbacks of conventional nanoparticles, resulting in poor tumor selectivity. iRGD peptide is widely recognized as an efficient cell membrane penetration peptide homing to αVβ3 integrins. Herein, core-shell nanocapsules (NCs) and iRGD-modified NCs (iRGD-NCs) with high drug payload for paclitaxel (PTX) were prepared to enhance the antitumor activities of chemotherapy agents with poor water solubility. Improved in vitro and in vivo tumor targeting and penetration were observed with NCs and iRGD-NCs; the latter exhibited better antitumor activity because iRGD enhanced the accumulation and penetration of NCs in tumors. The NCs were cytocompatible, histocompatible, and non-toxic to other healthy tissues. The endocytosis of NCs was mediated by lipid rafts in an energy-dependent manner, leading to better cytotoxicity of PTX against cancer cells. In contrast with commercial product, PTX-loaded NCs (PTX-NCs) increased area under concentration-time curve (AUC) by about 4-fold, prolonged mean resident time (MRT) by more than 8-fold and reduced the elimination rate constant by greater than 68-fold. In conclusion, the present nanocarriers with high drug-loading capacity represent an efficient tumor-targeting drug delivery system with promising potential for cancer therapy.

  7. Core-shell nanocarriers with high paclitaxel loading for passive and active targeting

    PubMed Central

    Jin, Zhu; Lv, Yaqi; Cao, Hui; Yao, Jing; Zhou, Jianping; He, Wei; Yin, Lifang

    2016-01-01

    Rapid blood clearance and premature burst release are inherent drawbacks of conventional nanoparticles, resulting in poor tumor selectivity. iRGD peptide is widely recognized as an efficient cell membrane penetration peptide homing to αVβ3 integrins. Herein, core-shell nanocapsules (NCs) and iRGD-modified NCs (iRGD-NCs) with high drug payload for paclitaxel (PTX) were prepared to enhance the antitumor activities of chemotherapy agents with poor water solubility. Improved in vitro and in vivo tumor targeting and penetration were observed with NCs and iRGD-NCs; the latter exhibited better antitumor activity because iRGD enhanced the accumulation and penetration of NCs in tumors. The NCs were cytocompatible, histocompatible, and non-toxic to other healthy tissues. The endocytosis of NCs was mediated by lipid rafts in an energy-dependent manner, leading to better cytotoxicity of PTX against cancer cells. In contrast with commercial product, PTX-loaded NCs (PTX-NCs) increased area under concentration-time curve (AUC) by about 4-fold, prolonged mean resident time (MRT) by more than 8-fold and reduced the elimination rate constant by greater than 68-fold. In conclusion, the present nanocarriers with high drug-loading capacity represent an efficient tumor-targeting drug delivery system with promising potential for cancer therapy. PMID:27278751

  8. Core-shell nanocarriers with high paclitaxel loading for passive and active targeting.

    PubMed

    Jin, Zhu; Lv, Yaqi; Cao, Hui; Yao, Jing; Zhou, Jianping; He, Wei; Yin, Lifang

    2016-01-01

    Rapid blood clearance and premature burst release are inherent drawbacks of conventional nanoparticles, resulting in poor tumor selectivity. iRGD peptide is widely recognized as an efficient cell membrane penetration peptide homing to αVβ3 integrins. Herein, core-shell nanocapsules (NCs) and iRGD-modified NCs (iRGD-NCs) with high drug payload for paclitaxel (PTX) were prepared to enhance the antitumor activities of chemotherapy agents with poor water solubility. Improved in vitro and in vivo tumor targeting and penetration were observed with NCs and iRGD-NCs; the latter exhibited better antitumor activity because iRGD enhanced the accumulation and penetration of NCs in tumors. The NCs were cytocompatible, histocompatible, and non-toxic to other healthy tissues. The endocytosis of NCs was mediated by lipid rafts in an energy-dependent manner, leading to better cytotoxicity of PTX against cancer cells. In contrast with commercial product, PTX-loaded NCs (PTX-NCs) increased area under concentration-time curve (AUC) by about 4-fold, prolonged mean resident time (MRT) by more than 8-fold and reduced the elimination rate constant by greater than 68-fold. In conclusion, the present nanocarriers with high drug-loading capacity represent an efficient tumor-targeting drug delivery system with promising potential for cancer therapy. PMID:27278751

  9. Core-shell nanocarriers with ZnO quantum dots-conjugated Au nanoparticle for tumor-targeted drug delivery.

    PubMed

    Chen, Tong; Zhao, Tong; Wei, Dongfeng; Wei, Yanxia; Li, Yuanyuan; Zhang, Haixia

    2013-02-15

    Core-shell structured multifunctional nanocarriers (NCs) of ZnO quantum dots-conjugated gold nanoparticles (Au NPs) as core and amphiphilic hyperbranched block copolymer as shell were synthesized for targeted anticancer drug delivery. The amphiphilic hyperbranched block copolymer contained poly(l-lactide) (PLA) inner arm and folate (FA)-conjugated a sulfated polysaccharide from Gynostemma pentaphyllum Makino (GPPS-FA) outer arm. The structure and properties of core-shell structured multifunctional nanocarriers were characterized and determined by UV-visible spectra, FT-IR spectra, X-ray diffraction (XRD), fluorescence spectroscopy and TEM analyses. The release results indicated that camptothecin (CPT) release from NCs at pH 7.4 was much greater than that at pH 5.3. The cytotoxicity studies showed that both the blank NCs and the CPT-loaded NCs provided high anticancer activity against Hela cells. Furthermore, nanocarriers gained specificity to target model cancer cells in this study due to the enhanced cell uptake mediated by FA moiety. The results indicated that the NCs not only had great potential as tumor-targeted drug delivery nanocarrier, but also had an assistant role in the treatment of cancer. PMID:23399137

  10. Solar-photocatalytic disinfection of Vibrio cholerae by using Ag@ZnO core-shell structure nanocomposites.

    PubMed

    Das, Sourav; Sinha, Sayantan; Suar, Mrutyunjay; Yun, Soon-Il; Mishra, Amrita; Tripathy, Suraj K

    2015-01-01

    Disinfection of Gram-negative bacterium Vibrio cholerae 569B in aqueous matrix by solar-photocatalysis mediated by Ag@ZnO core-shell structure nanocomposite particles was investigated. Silver nanoparticles are synthesized by the reduction of silver perchlorate followed by precipitation of zinc oxide shell and are employed in the photocatalytic disinfection of the model pathogen. Effect of photocatalyst loading and reaction temperature on the disinfection kinetics was studied. Disinfection efficiency in laboratory as well as real water samples was compared with that of pure-ZnO and TiO2 (Degussa P25). Nanocomposite system has shown optimum disinfection (≈98%) at 40-60min of sun-light exposure with a catalyst loading of 0.5mg/L of the reaction solution. The reduction of aquatic bacterial densities by photocatalytically active Ag@ZnO core-shell nanocomposite in presence of natural sun-light may have potential ex situ application in water decontamination at ambient conditions. PMID:25523714

  11. Preparation, characterization, and photocatalytic performance of pear-shaped ZnO/Ag core-shell submicrospheres

    NASA Astrophysics Data System (ADS)

    Guo, Xiao-Hua; Ma, Jian-Qi; Ge, Hong-Guang

    2013-05-01

    Pear-shaped ZnO/Ag core-shell submicrospheres with good monodispersity were prepared via a seed-mediated particle growth procedure, where metal Ag (by reducing Ag+ with Sn2+) deposited on the as-prepared ZnO submicrospheres served as seeds (nucleation sites) for further growth of Ag nanoparticles. The as-prepared samples were characterized by X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, ultraviolet-visible and photoluminescence spectra. Structure characterization demonstrates that the ZnO/Ag composites are composed of pear-shaped wurtzite ZnO submicrosphere core and Ag nanoparticles (nanoshell). Photoluminescence indicates that Ag nanoshell can effectively inhibit the recombination of the photoinduced electrons and holes of ZnO. This is responsible for the higher photocatalytic activity of the ZnO/Ag core-shell composites. The photocatalytic performance of the prepared ZnO/Ag samples for degradation of Rhodamine B was evaluated with a comparative study. The relationship between the structure of the samples and their photocatalytic performance shows that Ag deposits can significantly enhance the photocatalytic efficiency of ZnO submicrospheres.

  12. Controlling core/shell Au/FePt nanoparticle electrocatalysis via changing the core size and shell thickness.

    PubMed

    Sun, Xiaolian; Li, Dongguo; Guo, Shaojun; Zhu, Wenlei; Sun, Shouheng

    2016-02-01

    Using a modified seed-mediated method, we synthesized core/shell Au/FePt nanoparticles (NPs) with Au sizes of 4, 7, and 9 nm and the FePt shell was controlled to have similar FePt compositions and 0.5, 1, and 2 nm thickness. We studied both core and shell effects on electrochemical and electrocatalytic properties of the Au/FePt NPs, and found that the Au core did change the redox chemistry of the FePt shell and promoted its electrochemical oxidation of methanol. The catalytic activity was dependent on the FePt thicknesses, but not much on the Au core sizes, and the 1 nm FePt shell was found to be the optimal thickness for catalyzing methanol oxidation in 0.1 M HClO4 + 0.1 M methanol, offering not only high activity (1.19 mA cm(-2) at 0.5 V vs. Ag/AgCl), but also enhanced stability. Our studies demonstrate a general approach to the design and tuning of shell catalysis in the core/shell structure to achieve optimal catalysis for important electrochemical reactions. PMID:26676367

  13. Enhanced antibacterial activity of bimetallic gold-silver core-shell nanoparticles at low silver concentration

    NASA Astrophysics Data System (ADS)

    Banerjee, Madhuchanda; Sharma, Shilpa; Chattopadhyay, Arun; Ghosh, Siddhartha Sankar

    2011-12-01

    Herein we report the development of bimetallic Au@Ag core-shell nanoparticles (NPs) where gold nanoparticles (Au NPs) served as the seeds for continuous deposition of silver atoms on its surface. The core-shell structure and morphology were examined by UV-Vis spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis and X-ray diffraction (XRD). The core-shell NPs showed antibacterial activity against both Gram negative (Escherichia coli and Pseudomonas aeruginosa) and Gram positive (Enterococcus faecalis and Pediococcus acidilactici) bacteria at low concentration of silver present in the shell, with more efficacy against Gram negative bacteria. TEM and flow cytometric studies showed that the core-shell NPs attached to the bacterial surface and caused membrane damage leading to cell death. The enhanced antibacterial properties of Au@Ag core-shell NPs was possibly due to the more active silver atoms in the shell surrounding gold core due to high surface free energy of the surface Ag atoms owing to shell thinness in the bimetallic NP structure.Herein we report the development of bimetallic Au@Ag core-shell nanoparticles (NPs) where gold nanoparticles (Au NPs) served as the seeds for continuous deposition of silver atoms on its surface. The core-shell structure and morphology were examined by UV-Vis spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis and X-ray diffraction (XRD). The core-shell NPs showed antibacterial activity against both Gram negative (Escherichia coli and Pseudomonas aeruginosa) and Gram positive (Enterococcus faecalis and Pediococcus acidilactici) bacteria at low concentration of silver present in the shell, with more efficacy against Gram negative bacteria. TEM and flow cytometric studies showed that the core-shell NPs attached to the bacterial surface and caused membrane damage leading to cell death. The enhanced antibacterial properties of Au@Ag core-shell NPs was

  14. Investigation of the deformation mechanisms of core-shell rubber-modified epoxy at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Brown, Hayley Rebecca

    The industrial demand for high strength-to-weight ratio materials is increasing due to the need for high performance components. Epoxy polymers, although often used in fiber-reinforced polymeric composites, have an inherent low toughness that further decreases with decreasing temperatures. Second-phase additives have been effective in increasing the toughness of epoxies at room temperature; however, the mechanisms at low temperatures are still not understood. In this study, the deformation mechanisms of a DGEBA epoxy modified with MX960 core-shell rubber (CSR) particles were investigated under quasi-static tensile and impact loads at room temperature (RT) and liquid nitrogen (LN 2) temperature. Overall, the CSR had little effect on the tensile properties at RT and LN2 temperature. The impact strength decreased from neat to 3 wt% but increased from neat to 5 wt% at RT and LN2 temperature, with a higher impact strength at RT at all CSR loadings. The CSR particles debonded in front of the crack tip, inducing voids into the matrix. It was found that an increase in shear deformation and void growth likely accounted for the higher impact strength at 5 wt% CSR loading at RT while the thermal stress fields due to the coefficient of thermal expansion mismatch between rubber and epoxy and an increase in secondary cracking is likely responsible for the higher impact strength at 5 wt% tested at LN2 temperature. While a large toughening effect was not seen in this study, the mechanisms analyzed herein will likely be of use for further material investigations at cryogenic temperatures.

  15. Magnetic field assisted self-assembly of ferrite-ferroelectric core-shell nanofibers and studies on magneto-electric interactions

    SciTech Connect

    Sreenivasulu, G.; Zhang, Ru; Sharma, K.; Janes, C.; Mukundan, A.; Srinivasan, G.; Popov, Maksym

    2014-02-03

    Core-shell nanofibers of nickel ferrite and lead zirconate titanate have been synthesized by electrospinning, assembled into superstructure in uniform or non-uniform magnetic fields, and have been characterized in terms of ferroic order parameters and strain mediated magneto-electric (ME) coupling. The core-shell structure was confirmed by electron microscopy and scanning probe microscopy. Studies on magnetic field induced polarization P in assembled samples showed a decrease or increase in P, depending on the nature of fibers and strengthening of ME coupling with change in remnant-P as high as 32%. Strong ME interactions were evident from H-induced variation in permittivity at 20–22 GHz.

  16. Controlled synthesis of magnetic iron oxides@SnO2 quasi-hollow core-shell heterostructures: formation mechanism, and enhanced photocatalytic activity.

    PubMed

    Wu, Wei; Zhang, Shaofeng; Ren, Feng; Xiao, Xiangheng; Zhou, Juan; Jiang, Changzhong

    2011-11-01

    Iron oxide/SnO(2) magnetic semiconductor core-shell heterostructures with high purity were synthesized by a low-cost, surfactant-free and environmentally friendly hydrothermal strategy via a seed-mediated method. The morphology and structure of the hybrid nanostructures were characterized by means of high-resolution transmission electron microscopy and X-ray diffraction. The morphology evolution investigations reveal that the Kirkendall effect directs the diffusion and causes the formation of iron oxide/SnO(2) quasi-hollow particles. Significantly, the as-obtained iron oxides/SnO(2) core-shell heterostructures exhibited enhanced visible light or UV photocatalytic abilities, remarkably superior to as-used α-Fe(2)O(3) seeds and commercial SnO(2) products, mainly owing to the effective electron hole separation at the iron oxides/SnO(2) interfaces. PMID:21947413

  17. Metal-organic framework-immobilized polyhedral metal nanocrystals: reduction at solid-gas interface, metal segregation, core-shell structure, and high catalytic activity.

    PubMed

    Aijaz, Arshad; Akita, Tomoki; Tsumori, Nobuko; Xu, Qiang

    2013-11-01

    For the first time, this work presents surfactant-free monometallic and bimetallic polyhedral metal nanocrystals (MNCs) immobilized to a metal-organic framework (MIL-101) by CO-directed reduction of metal precursors at the solid-gas interface. With this novel method, Pt cubes and Pd tetrahedra were formed by CO preferential bindings on their (100) and (111) facets, respectively. PtPd bimetallic nanocrystals showed metal segregation, leading to Pd-rich core and Pt-rich shell. Core-shell Pt@Pd nanocrystals were immobilized to MIL-101 by seed-mediated two-step reduction, representing the first example of core-shell MNCs formed using only gas-phase reducing agents. These MOF-supported MNCs exhibited high catalytic activities for CO oxidation. PMID:24138338

  18. Synthesis of monodisperse TiO2-paraffin core-shell nanoparticles for improved dielectric properties.

    PubMed

    Balasubramanian, Balamurugan; Kraemer, Kristin L; Reding, Nicholas A; Skomski, Ralph; Ducharme, Stephen; Sellmyer, David J

    2010-04-27

    Core-shell structures of oxide nanoparticles having a high dielectric constant, and organic shells with large breakdown field are attractive candidates for large electrical energy storage applications. A high growth temperature, however, is required to obtain the dielectric oxide nanoparticles, which affects the process of core-shell formation and also leads to poor control of size, shape, and size-distribution. In this communication, we report a new synthetic process to grow core-shell nanoparticles by means of an experimental method that can be easily adapted to synthesize core-shell structures from a variety of inorganic-organic or inorganic-inorganic materials. Monodisperse and spherical TiO2 nanoparticles were produced at room temperature as a collimated cluster beam in the gas phase using a cluster-deposition source and subsequently coated with uniform paraffin nanoshells using in situ thermal evaporation, prior to deposition on substrates for further characterization and device processing. The paraffin nanoshells prevent the TiO2 nanoparticles from contacting each other and also act as a matrix in which the volume fraction of TiO2 nanoparticles was varied by controlling the thickness of the nanoshells. Parallel-plate capacitors were fabricated using dielectric core-shell nanoparticles having different shell thicknesses. With respect to the bulk paraffin, the effective dielectric constant of TiO2-paraffin core-shell nanoparticles is greatly enhanced with a decrease in the shell thickness. The capacitors show a minimum dielectric dispersion and low dielectric losses in the frequency range of 100 Hz-1 MHz, which are highly desirable for exploiting these core-shell nanoparticles for potential applications. PMID:20359188

  19. Controlled synthesis of magnetic iron oxides@SnO2 quasi-hollow core-shell heterostructures: formation mechanism, and enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Wu, Wei; Zhang, Shaofeng; Ren, Feng; Xiao, Xiangheng; Zhou, Juan; Jiang, Changzhong

    2011-11-01

    Iron oxide/SnO2 magnetic semiconductor core-shell heterostructures with high purity were synthesized by a low-cost, surfactant-free and environmentally friendly hydrothermal strategy via a seed-mediated method. The morphology and structure of the hybrid nanostructures were characterized by means of high-resolution transmission electron microscopy and X-ray diffraction. The morphology evolution investigations reveal that the Kirkendall effect directs the diffusion and causes the formation of iron oxide/SnO2 quasi-hollow particles. Significantly, the as-obtained iron oxides/SnO2 core-shell heterostructures exhibited enhanced visible light or UV photocatalytic abilities, remarkably superior to as-used α-Fe2O3 seeds and commercial SnO2 products, mainly owing to the effective electron hole separation at the iron oxides/SnO2 interfaces.Iron oxide/SnO2 magnetic semiconductor core-shell heterostructures with high purity were synthesized by a low-cost, surfactant-free and environmentally friendly hydrothermal strategy via a seed-mediated method. The morphology and structure of the hybrid nanostructures were characterized by means of high-resolution transmission electron microscopy and X-ray diffraction. The morphology evolution investigations reveal that the Kirkendall effect directs the diffusion and causes the formation of iron oxide/SnO2 quasi-hollow particles. Significantly, the as-obtained iron oxides/SnO2 core-shell heterostructures exhibited enhanced visible light or UV photocatalytic abilities, remarkably superior to as-used α-Fe2O3 seeds and commercial SnO2 products, mainly owing to the effective electron hole separation at the iron oxides/SnO2 interfaces. Electronic supplementary information (ESI) available: TEM and HRTEM images of hematite seeds and iron oxide/SnO2 (12 h and 36 h). See DOI: 10.1039/c1nr10728c

  20. Spectroscopy of colloidal semiconductor core/shell nanoplatelets with high quantum yield.

    PubMed

    Tessier, M D; Mahler, B; Nadal, B; Heuclin, H; Pedetti, S; Dubertret, B

    2013-07-10

    Free standing two-dimensional materials appear as a novel class of structures. Recently, the first colloidal two-dimensional heterostructures have been synthesized. These core/shell nanoplatelets are the first step toward colloidal quantum wells. Here, we study in detail the spectroscopic properties of this novel generation of colloidal nanoparticles. We show that core/shell CdSe/CdZnS nanoplatelets with 80% quantum yield can be obtained. The emission time trace of single core/shell nanoplatelets exhibits reduced blinking compared to core nanoplatelets with a two level emission time trace. At cryogenic temperatures, these nanoplatelets have a quantum yield close to 100% and a stable emission time trace. A solution of core/shell nanoplatelets has emission spectra with a full width half-maximum close to 20 nm, a value much lower than corresponding spherical or rod-shaped heterostructures. Using single particle spectroscopy, we show that the broadening of the emission spectra upon the shell deposition is not due to dispersity between particles but is related to an intrinsic increased exciton-phonon coupling in the shell. We also demonstrate that optical spectroscopy is a relevant tool to investigate the presence of traps induced by shell deposition. The spectroscopic properties of the core/shell nanoplatelets presented here strongly suggest that this new generation of objects will be an interesting alternative to spherical or rod-shaped nanocrystals. PMID:23731211

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

    PubMed

    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. PMID:21087022

  2. Dual Drug Release Electrospun Core-Shell Nanofibers with Tunable Dose in the Second Phase

    PubMed Central

    Qian, Wei; Yu, Deng-Guang; Li, Ying; Liao, Yao-Zu; Wang, Xia; Wang, Lu

    2014-01-01

    This study reports a new type of drug-loaded core-shell nanofibers capable of providing dual controlled release with tunable dose in the second phase. The core-shell nanofibers were fabricated through a modified coaxial electrospinning using a Teflon-coated concentric spinneret. Poly(vinyl pyrrolidone) and ethyl cellulose were used as the shell and core polymer matrices respectively, and the content of active ingredient acetaminophen (APAP) in the core was programmed. The Teflon-coated concentric spinneret may facilitate the efficacious and stable preparation of core-shell nanofibers through the modified coaxial electrospinning, where the core fluids were electrospinnable and the shell fluid had no electrospinnability. The resultant nanofibers had linear morphologies and clear core-shell structures, as observed by the scanning and transmission electron microscopic images. APAP was amorphously distributed in the shell and core polymer matrices due to the favorite second-order interactions, as indicated by the X-ray diffraction and FTIR spectroscopic tests. The results from the in vitro dissolution tests demonstrated that the core-shell nanofibers were able to furnish the desired dual drug controlled-release profiles with a tunable drug release amount in the second phase. The modified coaxial electrospinning is a useful tool to generate nanostructures with a tailored components and compositions in their different parts, and thus to realize the desired functional performances. PMID:24406731

  3. Hydrogel Encapsulation of Cells in Core-Shell Microcapsules for Cell Delivery.

    PubMed

    Nguyen, Duy Khiem; Son, Young Min; Lee, Nae-Eung

    2015-07-15

    A newly designed 3D core-shell microcapsule structure composed of a cell-containing liquid core and an alginate hydrogel shell is fabricated using a coaxial dual-nozzle electrospinning system. Spherical alginate microcapsules are successfully generated with a core-shell structure and less than 300 μm in average diameter using this system. The thickness of the core and shell can be easily controlled by manipulating the core and shell flow rates. Cells encapsulated in core-shell microcapsules demonstrate better cell encapsulation and immune protection than those encapsulated in microbeads. The observation of a high percentage of live cells (≈80%) after encapsulation demonstrates that the voltage applied for generation of microcapsules does not significantly affect the viability of encapsulated cells. The viability of encapsulated cells does not change even after 3 d in culture, which suggests that the core-shell structure with culture medium in the core can maintain high cell survival by providing nutrients and oxygen to all cells. This newly designed core-shell structure can be extended to use in multifunctional platforms not only for delivery of cells but also for factor delivery, imaging, or diagnosis by loading other components in the core or shell. PMID:25963828

  4. Platinum Monolayer on IrFe Core-Shell Nanoparticle Electrocatalysts for the Oxygen Reduction Reaction

    SciTech Connect

    K Sasaki; K Kuttiyiel; D Su; R Adzic

    2011-12-31

    We synthesized high activity and stability platinum monolayer on IrFe core-shell nanoparticle electrocatalysts. Carbon-supported IrFe core-shell nanoparticles were synthesized by chemical reduction and subsequent thermal annealing. The formation of Ir shells on IrFe solid-solution alloy cores has been verified by scanning transmission electron microscopy coupled with energy-loss spectroscopy (EELS) and in situ X-ray absorption spectroscopy. The Pt monolayers were deposited on IrFe core-shell nanoparticles by galvanic replacement of underpotentially deposited Cu adatoms on the Ir shell surfaces. The specific and Pt mass activities for the ORR on the Pt monolayer on IrFe core-shell nanoparticle electrocatalyst are 0.46 mA/cm{sup 2} and 1.1 A/mg{sub Pt}, which are much higher than those on a commercial Pt/C electrocatalyst. High durability of Pt{sub ML}/IrFe/C has also been demonstrated by potential cycling tests. These high activity and durability observed can be ascribed to the structural and electronic interaction between the Pt monolayer and the IrFe core-shell nanoparticles.

  5. [Scattering properties of core-shell structure of mist wrapped dust particles].

    PubMed

    Feng, Shi-qi; Song, Wei; Wang, Yan; Miao, Xin-hui; Xu, Li-jun; Liu, Yu; Li, Cheng; Li Wen-long; Wang, Yi-ran; Cai, Hong-xing

    2014-12-01

    The authors have investigated the optical properties of core-shell structure of mist wrapped dust particles based on the method of discrete dipole approximation (DDA). The influence on the thickness of the elliptical core-shell structure were calculated which the ratio of long axis and short axis is 2:1, and the change of scattering angle for scattering characteristics. The results shows that the thickness of outer layer increase from 1.2 to 4.8 μm with the scattering and extinction coefficient of double core-shell layers particles decrease from 3.4 and 3.43 to 2.543 and 2.545, when the size of inner core isn't change. And scattering relative strength also increased obviously. The thickness of inner core increase from 0.6 to 2.4 μm with the of scattering and extinction coefficient change from 2.59 and 2.88 to 2.6 and 2.76 when thickness of outer remain constant. Effect of the thickness of visible outer layer on the scattering characteristics of double core-shell layers particles is greater, because of the interaction between scattering light and outer materials. The scattering relative intensity decrease with wavelength increased, while increased with the scale of core-shell structure increase. The results make a promotion on the study of the transportation characteristics of laser and scattering characteristics when the atmospheric aerosol and water mist interact together. PMID:25881412

  6. Development of polymer-biomolecule core-shell particles for biomedical applications

    NASA Astrophysics Data System (ADS)

    Suthiwangcharoen, Nisaraporn

    Developing efficient strategies to introduce biomolecules around polymeric nanoparticles (NPs) is critical for targeted delivery of therapeutic or diagnostic agents. Although polymeric NPs have been well established, problems such as toxicity, stability, and immunoresistance remain potential concerns. The first part of this dissertation focuses on the development of nanosized targeted drug delivery vehicle in cancer chemotherapy. The vehicle was created by the self-assembly of folate-grafted filamentous bacteriophage M13 with poly(caprolactone- b-2-vinylpyridine) while doxorubicin, the antitumor drugs, was successfully loaded in the interior of the vehicles. These particles offer unique properties of being able to selectively target tumor cells while appearing to be safe and non-toxic to normal cells. Although they have shown great prospects in many biomedical applications, less is known about the interactions between biomolecules and polymers. The next part of the dissertation focuses on the self-assembly of proteins and polymers to create polymer-protein core-shell nanoparticles (PPCS-NPs). Several proteins with different isoelectric points and molecular weights were employed to demonstrate a versatility of our assembly method while a series of esterified derivatives of poly(2-hydroxyethyl methacrylate) (pHEMA) were synthesized to evaluate the interaction between proteins and polymers. Our data indicated that the polymers containing pyridine residues can successfully assemble with proteins, and the mechanism is mainly governed by hydrogen bonding and the hydrophobic/hydrophilic interactions. This in turn helps retaining proteins' folding conformation and functionality, which are also demonstrated in the in vitro/in vivo cellular uptake of the PPCS-NPs in endothelial cells. The last part of the dissertation focuses on the self-assembly of the bienzyme-polymer NPs. Glucose oxidase (GOX) together with horseradish peroxidase (HRP) were employed to construct bienzyme

  7. Isoprene polymerization mediated by vanadium-[ONNO] complexes.

    PubMed

    Phuphuak, Yupin; Bonnet, Fanny; Vendier, Laure; Lorber, Christian; Zinck, Philippe

    2016-07-26

    A series of vanadium complexes bearing dianionic tetradentate amine-bisphenolate [ONNO] ligands, V([double bond, length as m-dash]O)X[ONNO(Me)] (X = Cl (1); O(i)Pr (2)), VCl2[ONNO(Me)] (3) and V(O(i)Pr)2[ONNO(R)] (R = Me (4), (t)Bu (5), Cl (6)), displaying various electronic and steric properties have been prepared. The molecular structures of two of these complexes, namely V[ONNO(R)](O(i)Pr)2 with R = (t)Bu (5) or Cl (6), are reported. Activated with dialkylmagnesium, all complexes lead to modest isoprene homo-polymerization activities at 50 °C. Quantitative polymerizations were observed using 4 and 6 as pre-catalysts combined with Al(i)Bu3. The resulting polyisoprene microstructure was composed of ca. 70% 3,4 enchainments, the remaining 30% 1,4 enchainments being a mixture of cis and trans stereoisomers. 6 leads to a more active catalyst than 4. β-Hydride abstraction occurs during the reaction. PMID:27396409

  8. Doxorubicin/gold-loaded core/shell nanoparticles for combination therapy to treat cancer through the enhanced tumor targeting.

    PubMed

    Kim, Kyungim; Oh, Keun Sang; Park, Dal Yong; Lee, Jae Young; Lee, Beom Suk; Kim, In San; Kim, Kwangmeyung; Kwon, Ick Chan; Sang, Yoon Kim; Yuk, Soon Hong

    2016-04-28

    A combination therapy consisting of radiotherapy and chemotherapy is performed using the core/shell nanoparticles (NPs) containing gold NPs and doxorubicin (DOX). Gold NPs in the core/shell NPs were utilized as a radiosensitizer. To examine the morphology and size distribution of the core/shell NPs, transmittance electron microscopy and dynamic light scattering were used. The in vitro release behavior, cellular uptake and toxicity were also observed to verify the functionality of the core/shell NPs as a nanocarrier. To demonstrate the advantage of the core/shell NPs over traditional gold NPs reported in the combination therapy, we evaluated the accumulation behavior of the core/shell NPs at the tumor site using the biodistribution. Antitumor efficacy was observed with and without radiation to evaluate the role of gold NPs as a radiosensitizer. PMID:26970205

  9. Core shell particles consisting of cobalt ferrite and silica as model ferrofluids [CoFe 2O 4-SiO 2 core shell particles

    NASA Astrophysics Data System (ADS)

    Wagner, Joachim; Autenrieth, Tina; Hempelmann, Rolf

    2002-11-01

    Nearly monodisperse core shell particles consisting of a magnetic core of cobalt ferrite (CoFe 2O 4) and a shell of silica (SiO 2) are prepared via a modified Stöber synthesis. The core shell structure is confirmed by TEM, the size distribution of the whole particles was determined by means of photon correlation spectroscopy and small angle X-ray scattering. Due to charged surface groups of the silica shells and the magnetic moments of the cores, these particles interact both via a screened Coulomb potential and via a magnetic dipole potential. If stray ions are removed in the presence of a mixed bed ion exchanger, the electrostatic repulsion induces colloidal crystallisation. The lattice constant is influenced by the interaction with a magnetic field gradient, indicated by a blue shift of the Laue spots towards increasing field gradient.

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

    NASA Astrophysics Data System (ADS)

    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.

  11. Production of Polymer Core-Shell Colloids with High Uniformity via Coaxial Electrospray

    NASA Astrophysics Data System (ADS)

    Hwang, Yoon Kyun; Jeong, Unyong

    2008-03-01

    Although nanofibers fabricated by electrospinning have been attracting wide interest, the production of colloids by electrospraying has not much studied so far. We have developed a simple method for the production of core-shell colloids with high uniformity by means of the coaxial electrospray. Contrary to usual coaxial setup, the inner nozzle was set to touch the inside wall of the outer nozzle for reproducible production. A polymer solution for the core was introduced through the outer nozzle and another solution for the shell was provided through the inner nozzle. The structure of the colloids was dependent on the polymer concentration, relative feed ratio between the polymer solutions. Especially, core-shell structured colloids are our primary interest due to their promising uses in drug-delivery systems, cosmetics, and food industries. This talk will present the production of core-shell colloids consisting of two polymer components.

  12. Platinum-Maghemite Core-Shell Nanoparticles Using a Sequential Synthesis

    SciTech Connect

    Teng, X.; Black, D.; Watkins, N.J.; Gao, Y.; Yang, H.

    2003-01-11

    OAK-B135 Pt{at}Fe2O3 core-shell nanoparticles have been made using a sequential synthetic method. Platinum nanoparticles were synthesized via reduction of platinum acetylacetonate in octyl ether, and layers of iron oxide were subsequently deposited on the surface of Pt nanoparticles through thermal decomposition of iron pentacarbonyl. The core-shell nanoparticles were characterized by powder X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoemission spectroscopy. Thickness of the shell can be controlled by changing concentrations of the reactants and the reaction conditions. These Pt{at}Fe2O3 core-shell nanoparticles could have potential applications in catalysis and as precursors for making property-tunable magnetic nanoparticles, thin films, and nanocomposites.

  13. Thermoelectric characteristic of the rough InN/GaN core-shell nanowires

    SciTech Connect

    Wu, Chao-Wei; Wu, Yuh-Renn

    2014-09-14

    An analysis to model the thermoelectric (TE) effects of the rough InN/GaN core-shell nanowires (NWs) with wire diameter ranging from 25 nm to 100 nm is proposed. The elastic continuum model is employed to calculate the phonon dispersion relation curves and the related phonon group velocity. Within the framework of Boltzmann transport equations and relaxation time approximation, the electrical conductivity, Seebeck coefficient, electronic thermal conductivity, and the lattice thermal conductivity is obtained. Simulation results indicate that TE properties of the rough InN/GaN core-shell NWs are strongly affected by the surface roughness and the diameter of NWs. The optimized condition of the proposed rough InN/GaN core-shell TE NWs is studied in this paper and the highest ZT obtained in the calculation is 0.8598 at 300 K and 1.713 at 1000 K.

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

    NASA Astrophysics Data System (ADS)

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

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

  15. Photonic bandgap of inverse opals prepared from core-shell spheres.

    PubMed

    Liu, Bo-Tau; Lin, Ya-Li; Huang, Shao-Xian

    2012-01-01

    In this study, we synthesized monodispersed polystyrene (PS)-silica core-shell spheres with various shell thicknesses for the fabrication of photonic crystals. The shell thickness of the spheres was controlled by various additions of tetraethyl orthosilicate during the shell growth process. The shrinkage ratio of the inverse opal photonic crystals prepared from the core-shell spheres was significantly reduced from 14.7% to within 3%. We suspected that the improvement resulted from the confinement of silica shell to the contraction of PS space during calcination. Due to the shell effect, the inverse opals prepared from the core-shell spheres have higher filling fraction and larger wavelength of stop band maximum. PMID:22894600

  16. Preparation of highly dispersed core/shell-type titania nanocapsules containing a single Ag nanoparticle.

    PubMed

    Sakai, Hideki; Kanda, Takashi; Shibata, Hirobumi; Ohkubo, Takahiro; Abe, Masahiko

    2006-04-19

    Core/shell-type titania nanocapsules containing a single Ag nanoparticle were prepared. Ag nanoparticles were prepared using the reduction of silver nitrate with hydrazine in the presence of cetyltrimethylammonium bromide (CTAB) as protective agent. The sol-gel reaction of titanium tetraisopropoxide (TTIP) was used to prepare core/shell-type titania nanocapsules with CTAB-coated Ag nanoparticles as the core. TEM observations revealed that the size of the core (Ag particle) and the thickness of the shell (titania) of the core/shell particles obtained are about 10 nm and 5-10 nm, respectively. In addition, the nanocapsules were found to be dispersed in the medium as individual particles without aggregation. Moreover, titania coating caused the surface plasmon absorption of Ag nanoparticles to shift toward the longer wavelength side. PMID:16608315

  17. A New Class of Silica Crosslinked Micellar Core-Shell /nanoparticles."

    SciTech Connect

    Huo, Qisheng; Liu, Jun; Wang, Li Q.; Jiang, Yingbing; Lambert, Timothy N.; Fang, Erica

    2006-05-17

    Micellar nanoparticles made of surfactants and polymers have attracted wide attention in the materials and biomedical community for controlled drug delivery, molecular imaging and sensing; however, their long-term stability remains a topic of intense study. Here we report a new class of robust, ultrafine (10nm) silica core-shell nanoparticles formed from silica crosslinked, individual block copolymer micelles. Compared with pure polymer micelles, the new core-shell nanoparticles have significantly improved stability and do not break down during dilution. They also achieve much higher loading capacity for a wide range of chemicals, with the entrapped molecules slowly released over a much longer period of time. A wide range of functional groups can be easily incorporated through co-condensation with the silica matrix. The potential to deliver hydrophobic agents into cancer cells has been demonstrated. Because of their unique properties, these novel core-shell nanoparticles could potentially provide a new nanomedicine platform for imaging, detection and treatment.

  18. Lithography-Free Fabrication of Core-Shell GaAs Nanowire Tunnel Diodes.

    PubMed

    Darbandi, A; Kavanagh, K L; Watkins, S P

    2015-08-12

    GaAs core-shell p-n junction tunnel diodes were demonstrated by combining vapor-liquid-solid growth with gallium oxide deposition by atomic layer deposition for electrical isolation. The characterization of an ensemble of core-shell structures was enabled by the use of a tungsten probe in a scanning electron microscope without the need for lithographic processing. Radial tunneling transport was observed, exhibiting negative differential resistance behavior with peak-to-valley current ratios of up to 3.1. Peak current densities of up to 2.1 kA/cm(2) point the way to applications in core-shell photovoltaics and tunnel field effect transistors. PMID:26189994

  19. A pathway for the growth of core-shell Pt-Pd nanoparticles

    SciTech Connect

    Narula, Chaitanya Kumar; Yang, Xiaofan; Li, Chen; Pennycook, Stephen J; Lupini, Andrew R

    2015-10-12

    In this study, the aging of both Pt-Pd nanoparticles and core-shell Pt-Pd nanoparticles has been reported to result in alloying of Pt with Pd. In comparison to monometallic Pt catalysts, the growth of Pd-Pt bimetallics is slower; however, the mechanism of growth of particles and the mechanism by which Pd improves the hydrothermal durability of bimetallic Pd-Pt particles remains uncertain. In our work on hydrothermal aging of core-shell Pt-Pd nanoparticles, synthesized by solution methods, with varying Pd:Pt ratio of 1:4, 1:1, and 4:1, we compare the growth of core-shell Pt-Pd nanoparticles and find that particles grow by migrating and joining together. The unique feature of the observed growth is that Pd shells from both particles open up and join, allowing the cores to merge. At high temperatures, alloying occurs in good agreement with reports by other workers.

  20. Nitride stabilized PtNi core-shell nanocatalyst for high oxygen reduction activity.

    PubMed

    Kuttiyiel, Kurian A; Sasaki, Kotaro; Choi, Yongman; Su, Dong; Liu, Ping; Adzic, Radoslav R

    2012-12-12

    We describe a route to the development of novel PtNiN core-shell catalysts with low Pt content shell and inexpensive NiN core having high activity and stability for the oxygen reduction reaction (ORR). The PtNiN synthesis involves nitriding Ni nanoparticles and simultaneously encapsulating it by 2-4 monolayer-thick Pt shell. The experimental data and the density functional theory calculations indicate nitride has the bifunctional effect that facilitates formation of the core-shell structures and improves the performance of the Pt shell by inducing both geometric and electronic effects. Synthesis of inexpensive NiN cores opens up possibilities for designing of various transition metal nitride based core-shell nanoparticles for a wide range of applications in energy conversion processes. PMID:23194259

  1. Controlled nanostructuring of multiphase core-shell nanowires by a template-assisted electrodeposition approach

    NASA Astrophysics Data System (ADS)

    Shi, Dawei; Chen, Junyang; Riaz, Saira; Zhou, Wenping; Han, Xiufeng

    2012-08-01

    Multiphase core-shell nanowires have been fabricated by controlling the ion transport processes of the microfluids in the nanochannels of the template. Both forced convection and pulsed potential induced migration can be applied to tune the morphologies of the nanostructures obtained by manipulating the ion transport during electrodeposition. The morphology and content of the core-shell structure were studied by field emission scanning electron microscope (FESEM) analysis, transmission electron microscope (TEM) analysis and energy dispersive spectrometry (EDS), respectively. The magnetic properties were analyzed by vibrating sample magnetometer (VSM) analysis. A magnetically hard core and soft shell constitutes the multiphase composite nanostructure. The unique magnetic hysteresis curve indicates the decoupled magnetic reversal processes of the two components. Our work provides deeper insights into the formation mechanisms of a new core-shell nanostructure, which may have potential applications in novel spintronics devices.

  2. Tuning g factors of core-shell nanoparticles by controlled positioning of magnetic impurities

    NASA Astrophysics Data System (ADS)

    Sanders, G. D.; Musfeldt, J. L.; Stanton, C. J.

    2016-02-01

    We present a theoretical platform for modeling the electronic and magneto-optic properties of magnetically doped core-shell nanoparticles that has, as a central prediction, a mechanism by which the g factors in these nanoparticles can be tuned over a wide range by controlled positioning of magnetic impurities. We illustrate this effect for wide-gap Mn-doped CdS-ZnS core-shell particles and point out several unexpected trends that merit extended experimental investigation. The ability to tune g factors will make core-shell nanostructures viable candidates for spintronic applications, and the comprehensive modeling approach outlined here will be a powerful tool for predicting their properties as well as for optimizing the design of novel spintronic devices.

  3. Cracking the Si Shell Growth in Hexagonal GaP-Si Core-Shell Nanowires.

    PubMed

    Conesa-Boj, S; Hauge, H I T; Verheijen, M A; Assali, S; Li, A; Bakkers, E P A M; Fontcuberta i Morral, A

    2015-05-13

    Semiconductor nanowires have increased the palette of possible heterostructures thanks to their more effective strain relaxation. Among these, core-shell heterostructures are much more sensitive to strain than axial ones. It is now accepted that the formation of misfit dislocations depends both on the lattice mismatch and relative dimensions of the core and the shell. Here, we show for the first time the existence of a new kind of defect in core-shell nanowires: cracks. These defects do not originate from a lattice mismatch (we demonstrate their appearance in an essentially zero-mismatch system) but from the thermal history during the growth of the nanowires. Crack defects lead to the development of secondary defects, such as type-I1 stacking faults and Frank-type dislocations. These results provide crucial information with important implications for the optimized synthesis of nanowire-based core-shell heterostructures. PMID:25922878

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

    PubMed Central

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

    2015-01-01

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

  5. Ethanol sensing of SnO2-WO3 core/shell nanowires

    NASA Astrophysics Data System (ADS)

    Park, Sunghoon; Kim, Soohyun; Sun, Gun-Joo; Choi, Seung-Bok; Lee, Sangmin; Lee, Chongmu

    2015-09-01

    SnO2-WO3 core/shell nanowires were synthesized by the thermal evaporation of Sn powders in an oxidizing ambient followed by the thermal evaporation of WO3 powders. Their C2H5OH gas sensing properties were then examined. The C2H5OH gas sensing properties were improved remarkably by formation of the SnO2-WO3 heterostructures. The SnO2-WO3 core/shell nanowire sensors showed a much stronger and faster response to C2H5OH gas than the pristine SnO2-nanowire sensors. The enhanced sensing performance of the SnO2-WO3 core/shell nanowires towards C2H5OH gas can be accounted for by the potential barrier-controlled carrier-transport mechanism combined with the surface-depletion mechanism. [Figure not available: see fulltext.

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

    PubMed

    Eltayeb, Megdi; Stride, Eleanor; Edirisinghe, Mohan

    2013-11-22

    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. PMID:24164775

  7. Controlled nanostructuring of multiphase core-shell nanowires by a template-assisted electrodeposition approach.

    PubMed

    Shi, Dawei; Chen, Junyang; Riaz, Saira; Zhou, Wenping; Han, Xiufeng

    2012-08-01

    Multiphase core-shell nanowires have been fabricated by controlling the ion transport processes of the microfluids in the nanochannels of the template. Both forced convection and pulsed potential induced migration can be applied to tune the morphologies of the nanostructures obtained by manipulating the ion transport during electrodeposition. The morphology and content of the core-shell structure were studied by field emission scanning electron microscope (FESEM) analysis, transmission electron microscope (TEM) analysis and energy dispersive spectrometry (EDS), respectively. The magnetic properties were analyzed by vibrating sample magnetometer (VSM) analysis. A magnetically hard core and soft shell constitutes the multiphase composite nanostructure. The unique magnetic hysteresis curve indicates the decoupled magnetic reversal processes of the two components. Our work provides deeper insights into the formation mechanisms of a new core-shell nanostructure, which may have potential applications in novel spintronics devices. PMID:22751156

  8. Solution-Processed Copper/Reduced-Graphene-Oxide Core/Shell Nanowire Transparent Conductors.

    PubMed

    Dou, Letian; Cui, Fan; Yu, Yi; Khanarian, Garo; Eaton, Samuel W; Yang, Qin; Resasco, Joaquin; Schildknecht, Christian; Schierle-Arndt, Kerstin; Yang, Peidong

    2016-02-23

    Copper nanowire (Cu NW) based transparent conductors are promising candidates to replace ITO (indium-tin-oxide) owing to the high electrical conductivity and low-cost of copper. However, the relatively low performance and poor stability of Cu NWs under ambient conditions limit the practical application of these devices. Here, we report a solution-based approach to wrap graphene oxide (GO) nanosheets on the surface of ultrathin copper nanowires. By mild thermal annealing, GO can be reduced and high quality Cu r-GO core-shell NWs can be obtained. High performance transparent conducting films were fabricated with these ultrathin core-shell nanowires and excellent optical and electric performance was achieved. The core-shell NW structure enables the production of highly stable conducting films (over 200 days stored in air), which have comparable performance to ITO and silver NW thin films (sheet resistance ∼28 Ω/sq, haze ∼2% at transmittance of ∼90%). PMID:26820809

  9. Synthesis of SiO{sub 2}/Y{sub 2}O{sub 3}:Eu core-shell materials and hollow spheres

    SciTech Connect

    Liu Guixia; Hong Guangyan . E-mail: gyhang@ns.ciac.jl.cn

    2005-05-15

    The SiO{sub 2}/Y{sub 2}O{sub 3}:Eu core-shell materials and hollow spheres were first synthesized by a template-mediated method. X-ray diffraction patterns indicated that the broadened diffraction peaks result from nanocrystals of Y{sub 2}O{sub 3}:Eu shells and hollow spheres. X-ray photoelectron spectra showed that the Y{sub 2}O{sub 3}:Eu shells are linked with silica cores by Si-O-Y chemical bond. SEM and TEM observations showed that the size of SiO{sub 2}/Y{sub 2}O{sub 3}:Eu core-shell structure is in the range of 140-180nm, and the thickness of Y{sub 2}O{sub 3}:Eu hollow spherical shell is about 20-40nm. The photoluminescence spectra of SiO{sub 2}/Y{sub 2}O{sub 3}:Eu core-shell materials and Y{sub 2}O{sub 3}:Eu hollow spheres have better red luminescent properties, and the broadened emission bands came from the size effects of nanocrystals composed of Y{sub 2}O{sub 3}:Eu shell.

  10. Monodisperse core/shell Ni/FePt nanoparticles and their con-version to Ni/Pt to catalyze oxygen reduction

    DOE PAGESBeta

    Zhang, Sen; Hao, Yizhou; Su, Dong; Doan-Nguyen, Vicky V. T.; Wu, Yaoting; Li, Jing; Sun, Shouheng; Murray, Christopher B.

    2014-10-28

    We report a size-controllable synthesis of monodisperse core/shell Ni/FePt nanoparticles (NPs) via a seed-mediated growth and their subsequent conversion to Ni/Pt NPs. Preventing surface oxidation of the Ni seeds is essential for the growth of uniform FePt shells. These Ni/FePt NPs have a thin (≈ 1 nm) FePt shell, and can be converted to Ni/Pt by acetic acid wash to yield active catalysts for oxygen reduction reaction (ORR). Tuning the core size allow for optimization of their electrocatalytic activity. The specific activity and mass activity of 4.2 nm/0.8 nm core/shell Ni/FePt reach 1.95 mA/cm² and 490 mA/mgPt at 0.9 Vmore » (vs. reversible hydrogen electrode, RHE), which are much higher than those of benchmark commercial Pt catalyst (0.34 mA/cm² and 92 mA/mgPt at 0.9 V). Our studies provide a robust approach to monodisperse core/shell NPs with non-precious metal core, making it possible to develop advanced NP catalysts with ultralow Pt content for ORR and many other heterogeneous reactions.« less

  11. Monodisperse core/shell Ni/FePt nanoparticles and their con-version to Ni/Pt to catalyze oxygen reduction

    SciTech Connect

    Zhang, Sen; Hao, Yizhou; Su, Dong; Doan-Nguyen, Vicky V. T.; Wu, Yaoting; Li, Jing; Sun, Shouheng; Murray, Christopher B.

    2014-10-28

    We report a size-controllable synthesis of monodisperse core/shell Ni/FePt nanoparticles (NPs) via a seed-mediated growth and their subsequent conversion to Ni/Pt NPs. Preventing surface oxidation of the Ni seeds is essential for the growth of uniform FePt shells. These Ni/FePt NPs have a thin (≈ 1 nm) FePt shell, and can be converted to Ni/Pt by acetic acid wash to yield active catalysts for oxygen reduction reaction (ORR). Tuning the core size allow for optimization of their electrocatalytic activity. The specific activity and mass activity of 4.2 nm/0.8 nm core/shell Ni/FePt reach 1.95 mA/cm² and 490 mA/mgPt at 0.9 V (vs. reversible hydrogen electrode, RHE), which are much higher than those of benchmark commercial Pt catalyst (0.34 mA/cm² and 92 mA/mgPt at 0.9 V). Our studies provide a robust approach to monodisperse core/shell NPs with non-precious metal core, making it possible to develop advanced NP catalysts with ultralow Pt content for ORR and many other heterogeneous reactions.

  12. Controllable synthesis, magnetic properties, and enhanced photocatalytic activity of spindlelike mesoporous α-Fe(2)O(3)/ZnO core-shell heterostructures.

    PubMed

    Wu, Wei; Zhang, Shaofeng; Xiao, Xiangheng; Zhou, Juan; Ren, Feng; Sun, Lingling; Jiang, Changzhong

    2012-07-25

    Mesoporous spindlelike iron oxide/ZnO core-shell heterostructures are successfully fabricated by a low-cost, surfactant-free, and environmentally friendly seed-mediate strategy with the help of postannealing treatment. The material composition and stoichiometry, as well as these magnetic and optical properties, have been examined and verified by means of high-resolution transmission electron microscopy and X-ray diffraction, the thickness of ZnO layer can be simply tailored by the concentration of zinc precursor. Considering that both α-Fe2O3 and ZnO are good photocatalytic materials, we have investigated the photodegradation performances of the core-shell heterostructures using organic dyes Rhodamin B (RhB). It is interesting to find that the as-obtained iron oxides/ZnO core-shell heterostructures exhibited enhanced visible light or UV photocatalytic abilities, remarkably superior to the as-used α-Fe2O3 seeds and commercial TiO2 products (P25), mainly owing to the synergistic effect between the narrow and wide bandgap semiconductors and effective electron-hole separation at the interfaces of iron oxides/ZnO. PMID:22692878

  13. Lipid and polymeric carrier-mediated nucleic acid delivery

    PubMed Central

    Zhu, Lin; Mahato, Ram I

    2010-01-01

    Importance of the field Nucleic acids such as plasmid DNA, antisense oligonucleotide, and RNA interference (RNAi) molecules, have a great potential to be used as therapeutics for the treatment of various genetic and acquired diseases. To design a successful nucleic acid delivery system, the pharmacological effect of nucleic acids, the physiological condition of the subjects or sites, and the physicochemical properties of nucleic acid and carriers have to be thoroughly examined. Areas covered in this review The commonly used lipids, polymers and corresponding delivery systems are reviewed in terms of their characteristics, applications, advantages and limitations. What the reader will gain This article aims to provide an overview of biological barriers and strategies to overcome these barriers by properly designing effective synthetic carriers for nucleic acid delivery. Take home message A thorough understanding of biological barriers and the structure–activity relationship of lipid and polymeric carriers is the key for effective nucleic acid therapy. PMID:20836625

  14. Highly stable multi-wall carbon nanotubes@poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) core-shell composites with three-dimensional porous nano-network for electrochemical capacitors

    NASA Astrophysics Data System (ADS)

    Zhou, Haihan; Han, Gaoyi; Chang, Yunzhen; Fu, Dongying; Xiao, Yaoming

    2015-01-01

    A facile and feasible electrochemical polymerization method has been used to construct the multi-wall carbon nanotubes@poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (MWCNTs@PEDOT/PSS) core-shell composites with three-dimensional (3D) porous nano-network microstructure. The composites are characterized with Fourier transform infrared spectroscopy, scanning electron microscope, and transmission electron microscopy. This special core-shell nanostructure can significantly reduce the ions diffusion distance and the 3D porous nano-network microstructure effectively enlarges the electrode/electrolyte interface. The electrochemical tests including cyclic voltammetry, galvanostatic charge/discharge measurements, and electrochemical impedance spectroscopy tests are performed, the results manifest the MWCNTs@PEDOT/PSS core-shell composites have superior capacitive behaviors and excellent cyclic stability, and a high areal capacitance of 98.1 mF cm-2 is achieved at 5 mV s-1 cyclic voltammetry scan. Furthermore, the MWCNTs@PEDOT/PSS composites exhibit obviously superior capacitive performance than that of PEDOT/PSS and PEDOT/Cl electrodes, indicating the effective composite of MWCNTs and PEDOT noticeably boosts the capacitive performance of PEDOT-based electrodes for electrochemical energy storage. Such a highly stable core-shell 3D network structural composite is very promising to be used as electrode materials for the high-performance electrochemical capacitors.

  15. Synthesis and Characterization of CoFe2O4/Ni0.5Zn0.5Fe2O4 Core/shell Magnetic Nanocomposite by the Wet Chemical Route

    NASA Astrophysics Data System (ADS)

    Honarbakhsh-Raouf, A.; Emamian, H. R.; Yourdkhani, A.; Ataie, A.

    A cobalt ferrite/nickel-zinc ferrite core/shell nanocomposite was synthesized by a polymerized complex method using iron citrate, cobalt nitrate, nickel nitrate, zinc nitrate, citric acid, ethylene glycol, benzoic acid and sodium citrate as starting materials. The XRD, TEM and VSM techniques were employed to evaluate the phase composition, morphology and magnetic properties of the samples. The XRD results indicated the coexistence of characteristic reflections of CoFe2O4 and Ni0.5Zn0.5Fe2 O4 spinel ferrites in the composite sample. The core/shell structure of the composite sample has been confirmed by TEM images. The size of obtained spherical core/shell nanoparticles was 20-40 nm in core diameter and about 10 nm in shell thickness. The VSM results showed that both the coercivity and the saturation magnetization of the resulting core/shell nanocomposite were decreased compared to those of the CoFe2O4 core, due to the interaction at the interface of CoFe2O4 and Ni0.5Zn0.5Fe2O4.

  16. Auger and Carrier Trapping Dynamics in Core/Shell Quantum Dots Having Sharp and Alloyed Interfaces.

    PubMed

    Beane, Gary A; Gong, Ke; Kelley, David F

    2016-03-22

    The role of interface sharpness in controlling the excited state dynamics in CdSe/ZnSe core/shell particles is examined here. Particles composed of CdSe/ZnSe with 2.4-4.0 nm diameter cores and approximately 4 monolayer shells are synthesized at relatively low temperature, ensuring a sharp core-shell interface. Subsequent annealing results in cadmium and zinc interdiffusion, softening the interface. TEM imaging and absorption spectra reveal that annealing results in no change in the particle sizes. Annealing results in a 5-10 nm blue shift in the absorption spectrum, which is compared to calculated spectral shifts to characterize the extent of metal interdiffusion. The one- and two-photon dynamics are measured using time-resolved absorption spectroscopy. We find that biexcitons undergo biexponential decays, with fast and slow decay times differing by about an order of magnitude. The relative magnitudes of the fast and slow components depend on the sharpness of the core-shell interface, with larger fast component amplitudes associated with a sharp core-shell interface. The slow component is assigned to Auger recombination of band edge carriers and the fast decay component to Auger recombination of holes that are trapped in defects produced by lattice strain. Annealing of these particles softens the core-shell interface and thereby reduces the amount of lattice strain and diminishes the magnitude of the fast decay component. The time constant of the slow biexciton Auger recombination component changes only slightly upon softening of the core-shell interface. PMID:26895220

  17. Rare Earth Metal-Mediated Precision Polymerization of Vinylphosphonates and Conjugated Nitrogen-Containing Vinyl Monomers.

    PubMed

    Soller, Benedikt S; Salzinger, Stephan; Rieger, Bernhard

    2016-02-24

    This review focuses on introducing and explaining the rare earth metal-mediated group transfer polymerization (REM-GTP) of polar monomers and is composed of three main sections: poly(vinylphosphonate)s, surface-initiated group transfer polymerization (SI-GTP), and extension to N-coordinating Michael-type monomers (2-vinylpridine (2VP), 2-isopropenyl-2-oxazoline (IPOx)). The poly(vinylphosphonate)s section is divided into two parts: radical, anionic, and silyl ketene acetal group transfer polymerization (SKA-GTP) of vinylphosphonates in comparison to REM-GTP, and properties of poly(vinylphosphonate)s. The mechanism of vinylphosphonate REM-GTP is discussed in detail for initiation and propagation including activation enthalpies ΔH(‡) and entropies ΔS(‡) according to the Eyring equation. SI-GTP is presented as a method for surface functionalization, and recent trends for 2VP and IPOx polymerization are summarized. This review will serve as a good resource or guideline for researchers who are currently working in the field of rare earth metal mediated polymerization catalysis as well as for those who are interested in beginning to employ rare earth metal complexes for the synthesis of new materials from polar monomers. PMID:26718632

  18. Anisotropic In distribution in InGaN core-shell nanowires

    SciTech Connect

    Leclere, C.; Renevier, H.; Katcho, N. A.; Tourbot, G.; Daudin, B.; Proietti, M. G.

    2014-07-07

    In this work, we investigate the local atomic structure of defect-free homogeneous and self-organized core-shell structure nanowires by means of X-ray Absorption Fine Structure (XAFS) Spectroscopy at the In L{sub III} and K edges and Multiwavelength Anomalous Diffraction. The results are interpreted by comparison of the experimental data with X-ray absorption calculations carried out with ab initio structural models. Extended-XAFS data analysis at In K-edge shows an anisotropic In distribution in the second nearest neighbors pointing out to a deviation from randomness in In distribution for the core-shell sample.

  19. Highly stable, luminescent core-shell type methylammonium-octylammonium lead bromide layered perovskite nanoparticles.

    PubMed

    Bhaumik, Saikat; Veldhuis, Sjoerd A; Ng, Yan Fong; Li, Mingjie; Muduli, Subas Kumar; Sum, Tze Chien; Damodaran, Bahulayan; Mhaisalkar, Subodh; Mathews, Nripan

    2016-06-01

    A new protocol for the synthesis of a highly stable (over 2 months under ambient conditions) solution-processed core-shell type structure of mixed methylammonium-octylammonium lead bromide perovskite nanoparticles (5-12 nm), having spherical shape, color tunability in the blue to green spectral region (438-521 nm) and a high photoluminescence quantum yield (PLQY) of up to 92% is described. The color tunability, high PLQY and stability are due to the quantum confinement imparted by the crystal engineering associated with core-shell nanoparticle formation during growth. PMID:27165565

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

    SciTech Connect

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

    2007-03-14

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

  1. Improved oxygen reduction activity on the Ih Cu@Pt core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Yang, Zongxian; Geng, Zhixia; Zhang, Yanxing; Wang, Jinlong; Ma, Shuhong

    2011-09-01

    The minimum energy path (MEP) for the dissociation of O 2 on the Ih Cu@Pt12 core-shell nanoparticle. Ih Cu@Pt12 is the most stable among the symmetric Cu@Pt12 core-shell isomers. O 2 prefers to be adsorbed on the Ih Cu@Pt12 with the t-b-t configuration. The Ih Cu@Pt12 has enhanced activity for O 2 dissociation and O diffusion. Ih Cu@Pt12 nanoparticle is a good candidate for being the ORR catalyst.

  2. Synthesis of AgatCrO2 core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Sharma, Preetam K.; Sharma, Priyanka; Biswas, S.; Nagawat, A. K.

    2013-06-01

    Half metallic ferromagnetic Chromium Oxide (CrO2) with 100% spin polarization is thought as an excellent candidate for magnetic nano-tag for Giant magnetoresistive biosensor. We have investigated the chemical synthesis and direct mixing approaches for the synthesis of Ag@CrO2 core shell nanoparticles. For chemical synthesis two mild reducing agents namely polyvinyl alcohol (PVA) and ethylene glycol (EG) were used. Our investigations suggest that the direct mixing and subsequent annealing at 300°C for 2 h is the better method to realize Ag@CrO2 core shell nanoparticles.

  3. Facile preparation of hybrid core-shell nanorods for photothermal and radiation combined therapy.

    PubMed

    Deng, Yaoyao; Li, Erdong; Cheng, Xiaju; Zhu, Jing; Lu, Shuanglong; Ge, Cuicui; Gu, Hongwei; Pan, Yue

    2016-02-11

    The hybrid platinum@iron oxide core-shell nanorods with high biocompatibility were synthesized and applied for combined therapy. These hybrid nanorods exhibit a good photothermal effect on cancer cells upon irradiation with a NIR laser. Furthermore, due to the presence of a high atomic number element (platinum core), the hybrid nanorods show a synergistic effect between photothermal and radiation therapy. Therefore, the as-prepared core-shell nanorods could play an important role in facilitating synergistic therapy between photothermal and radiation therapy to achieve better therapeutic efficacy. PMID:26818657

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  5. Smart multifunctional core-shell nanospheres with drug and gene co-loaded for enhancing the therapeutic effect in a rat intracranial tumor model.

    PubMed

    Wang, HanJie; Su, Wenya; Wang, Sheng; Wang, Xiaomin; Liao, Zhenyu; Kang, Chunsheng; Han, Lei; Chang, Jin; Wang, Guangxiu; Pu, Peiyu

    2012-10-21

    Glioblastoma with high mortality has been one of the most serious cancers threatening human health. Because of the present treatment limitations, there is an urgent need to construct a multifunctional vesicle for enhancing the treatment of in situ malignant glioblastoma. In our study, drug and gene co-loaded magnetic PLGA/multifunctional polymeric liposome (magnetic PLGA/MPLs) core-shell nanospheres were constructed. They were mainly self-assembled from two parts: hydrophobic PLGA cores that can load drugs and magnetic nanocrystals; and polymeric lipid shells anchored with functional molecules such as PEG chains, TAT peptides and RGD peptides that can help the vectors to condense the gene, prolong the circulation time, cross the blood brain barrier and target delivery to the cancer tissue. The results showed that the magnetic PLGA/MPLs nanosphere has a nanosized core-shell structure, can achieve sustained drug release and has good DNA binding abilities. Importantly, compared with the control group and other groups with single functionality, it can co-deliver the drug and gene into the same cell in vitro and show the strongest inhibiting effect on the growth of the in situ malignant glioblastoma in vivo. All of these results indicated that the different functional components of magnetic PLGA/MPLs, can form an organic whole and none of them can be dispensed with. The magnetic PLGA/MPLs nanosphere may be another option for treatment of glioblastoma. PMID:22961067

  6. In situ synthesis and characterization of LiNi0.5La0.08Fe1.92O4 polyaniline core shell nanocomposites

    NASA Astrophysics Data System (ADS)

    Jiang, Jing; Li, Liangchao; Xu, Feng

    2007-09-01

    Core shell-structured LiNi0.5La0.08Fe1.92O4 polyaniline (PANI) nanocomposites with magnetic behavior were synthesized by in situ polymerization of aniline in the presence of LiNi0.5La0.08Fe1.92O4 nanoparticles. The structure, morphology and magnetic properties of samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), UV vis absorption, transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) technique. The results of spectroanalysis indicated that there was interaction between PANI chains and ferrite particles. TEM study showed that LiNi0.5La0.08Fe1.92O4 PANI nanocomposites presented a core shell structure with a magnetic core of 30 50 nm diameter and an amorphous shell of 10 20 nm thickness. The nanocomposites under applied magnetic field exhibited the hysteresis loops of the ferromagnetic nature. The saturation magnetization and coercivity of nanocomposites decreased with decreasing content of LiNi0.5La0.08Fe1.92O4. The polymerization mechanism and bonding interaction in the nanocomposites have been discussed.

  7. Highly robust silicon nanowire/graphene core-shell electrodes without polymeric binders

    NASA Astrophysics Data System (ADS)

    Lee, Sang Eon; Kim, Han-Jung; Kim, Hwanjin; Park, Jong Hyeok; Choi, Dae-Geun

    2013-09-01

    A large theoretical charge storage capacity along with a low discharge working potential renders silicon a promising anode material for high energy density lithium ion batteries. However, up to 400% volume expansion during charge-discharge cycling coupled with a low intrinsic electronic conductivity causes pulverization and fracture, thus inhibiting silicon's widespread use in practical applications. We report herein on a low cost approach to fabricate hybrid silicon nanowire (SiNW)/graphene nanostructures that exhibit enhanced cycle performance with the capability of retaining more than 90% of their initial capacity after 50 cycles. We also demonstrate the use of hot-pressing in the absence of any common polymer binder such as PVDF to bind the hybrid structure to the current collector. The applied heat and pressure ensure strong adhesion between the SiNW/graphene nano-composite and current collector. This facile yet strong binding method is expected to find use in the further development of polymer-binder free anodes for lithium ion batteries.A large theoretical charge storage capacity along with a low discharge working potential renders silicon a promising anode material for high energy density lithium ion batteries. However, up to 400% volume expansion during charge-discharge cycling coupled with a low intrinsic electronic conductivity causes pulverization and fracture, thus inhibiting silicon's widespread use in practical applications. We report herein on a low cost approach to fabricate hybrid silicon nanowire (SiNW)/graphene nanostructures that exhibit enhanced cycle performance with the capability of retaining more than 90% of their initial capacity after 50 cycles. We also demonstrate the use of hot-pressing in the absence of any common polymer binder such as PVDF to bind the hybrid structure to the current collector. The applied heat and pressure ensure strong adhesion between the SiNW/graphene nano-composite and current collector. This facile yet strong binding method is expected to find use in the further development of polymer-binder free anodes for lithium ion batteries. Electronic supplementary information (ESI) available: Details of desired length of SiNWs and optimum thickness of graphene. See DOI: 10.1039/c3nr00852e

  8. Highly robust silicon nanowire/graphene core-shell electrodes without polymeric binders.

    PubMed

    Lee, Sang Eon; Kim, Han-Jung; Kim, Hwanjin; Park, Jong Hyeok; Choi, Dae-Geun

    2013-10-01

    A large theoretical charge storage capacity along with a low discharge working potential renders silicon a promising anode material for high energy density lithium ion batteries. However, up to 400% volume expansion during charge-discharge cycling coupled with a low intrinsic electronic conductivity causes pulverization and fracture, thus inhibiting silicon's widespread use in practical applications. We report herein on a low cost approach to fabricate hybrid silicon nanowire (SiNW)/graphene nanostructures that exhibit enhanced cycle performance with the capability of retaining more than 90% of their initial capacity after 50 cycles. We also demonstrate the use of hot-pressing in the absence of any common polymer binder such as PVDF to bind the hybrid structure to the current collector. The applied heat and pressure ensure strong adhesion between the SiNW/graphene nano-composite and current collector. This facile yet strong binding method is expected to find use in the further development of polymer-binder free anodes for lithium ion batteries. PMID:23760363

  9. A dual-emitting core-shell carbon dot-silica-phosphor composite for white light emission

    NASA Astrophysics Data System (ADS)

    Chen, Yonghao; Lei, Bingfu; Zheng, Mingtao; Zhang, Haoran; Zhuang, Jianle; Liu, Yingliang

    2015-11-01

    A unique dual-emitting core-shell carbon dot-silica-phosphor (CDSP) was constructed from carbon dots (CDs), tetraethoxysilane (TEOS) and Sr2Si5N8:Eu2+ phosphor through a one-pot sol-gel method. Blue emitting CDs uniformly disperse in the silica layer covering the orange emitting phosphor via a polymerization process, which makes CDSP achieve even white light emission. Tunable photoluminescence of CDSP is observed and the preferable white light emission is achieved through changing the excitation wavelength or controlling the mass ratio of the phosphor. When CDSP powders with a phosphor rate of 3.9% and 5.1% are excited at a wavelength of 400 nm, preferable white light emission is observed, with Commission Internationale de l'Eclairage (CIE) coordinates of (0.32, 0.32) and (0.34, 0.32), respectively. Furthermore, CDSP can mix well with epoxy resin to emit strong and even white light, and based on this, a CDSP-based white LED with a high colour rendering index (CRI) of 94 was fabricated.A unique dual-emitting core-shell carbon dot-silica-phosphor (CDSP) was constructed from carbon dots (CDs), tetraethoxysilane (TEOS) and Sr2Si5N8:Eu2+ phosphor through a one-pot sol-gel method. Blue emitting CDs uniformly disperse in the silica layer covering the orange emitting phosphor via a polymerization process, which makes CDSP achieve even white light emission. Tunable photoluminescence of CDSP is observed and the preferable white light emission is achieved through changing the excitation wavelength or controlling the mass ratio of the phosphor. When CDSP powders with a phosphor rate of 3.9% and 5.1% are excited at a wavelength of 400 nm, preferable white light emission is observed, with Commission Internationale de l'Eclairage (CIE) coordinates of (0.32, 0.32) and (0.34, 0.32), respectively. Furthermore, CDSP can mix well with epoxy resin to emit strong and even white light, and based on this, a CDSP-based white LED with a high colour rendering index (CRI) of 94 was fabricated

  10. A new class of PANI-Ag core-shell nanorods with sensing dimensions.

    PubMed

    Shukla, Vineet K; Yadav, Poonam; Yadav, Raghvendra S; Mishra, Priya; Pandey, Avinash C

    2012-07-01

    A single-step, cost-effective and eco-safe synthesis of a new class of homogeneous silver-polyaniline (PANI-Ag) core-shell nanorods is carried out via mild photolysis by ultraviolet radiation from sunlight (SUN UV-radiation). X-ray diffraction (XRD) of these core-shell nanorods gives two additional peaks from PANI centered at 2θ = 20.5° and 24. 9°. A validation of the core-shell structural information is given by transmission electron spectroscopy (TEM) whereas the tubular shape morphology is determined by scanning electron microscopy (SEM). UV-Vis. absorption shows a strong blue-shift along with photoluminescence emission. Fourier transform-infrared spectroscopy (FT-IR) and energy dispersive X-ray spectroscopy (EDX) also support the core-shell formation. Thermogravimetric analysis (TGA) shows good thermal stability and allows excellent detection of hydrogen peroxide and hydrazine. The cyclic voltammetry (CV) results show excellent electro-activation, indicating its promising potential in sensing of clinical and environmental analytes. PMID:22669315

  11. Poly(Glycerol sebacate)/gelatin core/shell fibrous structure for regeneration of myocardial infarction.

    PubMed

    Ravichandran, Rajeswari; Venugopal, Jayarama Reddy; Sundarrajan, Subramanian; Mukherjee, Shayanti; Ramakrishna, Seeram

    2011-05-01

    Heart failure remains the leading cause of death in many industrialized nations owing to the inability of the myocardial tissue to regenerate. The main objective of this work was to develop a cardiac patch that is biocompatible and matches the mechanical properties of the heart muscle for myocardial infarction. The present study was to fabricate poly (glycerol sebacate)/gelatin (PGS/gelatin) core/shell fibers and gelatin fibers alone by electrospinning for cardiac tissue engineering. PGS/gelatin core/shell fibers, PGS used as a core polymer to impart the mechanical properties and gelatin as a shell material to achieve favorable cell adhesion and proliferation. These core/shell fibers were characterized by scanning electron microscopy, contact angle, Fourier transform infrared spectroscopy, and tensile testing. The cell-scaffold interactions were analyzed by cell proliferation, confocal analysis for the expression of marker proteins like actinin, troponin-T, and platelet endothelial cell adhesion molecule, and scanning electron microscopy to analyze cell morphology. Dual immunofluorescent staining was performed to further confirm the cardiogenic differentiation of mesenchymal stem cells by employing mesenchymal stem cell-specific marker protein CD 105 and cardiac-specific marker protein actinin. The results observed that PGS/gelatin core/shell fibers have good potential biocompatibility and mechanical properties for fabricating nanofibrous cardiac patch and would be a prognosticating device for the restoration of myocardium. PMID:21247338

  12. Core-shell TiO2@ZnO nanorods for efficient ultraviolet photodetection.

    PubMed

    Panigrahi, Shrabani; Basak, Durga

    2011-05-01

    Core-shell TiO(2)@ZnO nanorods (NRs) have been fabricated by a simple two step method: growth of ZnO NRs' array by an aqueous chemical technique and then coating of the NRs with a solution of titanium isopropoxide [Ti(OC(3)H(7))(4)] followed by a heating step to form the shell. The core-shell nanocomposites are composed of single-crystalline ZnO NRs, coated with a thin TiO(2) shell layer obtained by varying the number of coatings (one, three and five times). The ultraviolet (UV) emission intensity of the nanocomposite is largely quenched due to an efficient electron-hole separation reducing the band-to-band recombinations. The UV photoconductivity of the core-shell structure with three times TiO(2) coating has been largely enhanced due to photoelectron transfer between the core and the shell. The UV photosensitivity of the nanocomposite becomes four times larger while the photocurrent decay during steady UV illumination has been decreased almost by 7 times compared to the as-grown ZnO NRs indicating high efficiency of these core-shell structures as UV sensors. PMID:21483939

  13. Core-shell TiO2@ZnO nanorods for efficient ultraviolet photodetection

    NASA Astrophysics Data System (ADS)

    Panigrahi, Shrabani; Basak, Durga

    2011-05-01

    Core-shell TiO2@ZnO nanorods (NRs) have been fabricated by a simple two step method: growth of ZnO NRs' array by an aqueous chemical technique and then coating of the NRs with a solution of titanium isopropoxide [Ti(OC3H7)4] followed by a heating step to form the shell. The core-shell nanocomposites are composed of single-crystalline ZnO NRs, coated with a thin TiO2 shell layer obtained by varying the number of coatings (one, three and five times). The ultraviolet (UV) emission intensity of the nanocomposite is largely quenched due to an efficient electron-hole separation reducing the band-to-band recombinations. The UV photoconductivity of the core-shell structure with three times TiO2 coating has been largely enhanced due to photoelectron transfer between the core and the shell. The UV photosensitivity of the nanocomposite becomes four times larger while the photocurrent decay during steady UV illumination has been decreased almost by 7 times compared to the as-grown ZnO NRs indicating high efficiency of these core-shell structures as UV sensors.

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

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

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

  15. Novel ZnO/Fe₂O₃ Core-Shell Nanowires for Photoelectrochemical Water Splitting.

    PubMed

    Hsu, Yu-Kuei; Chen, Ying-Chu; Lin, Yan-Gu

    2015-07-01

    A facile and simple fabrication of Fe2O3 as a shell layer on the surface of ZnO nanowires (NW) as a core-shell nanoelectrode is applied for the photoelectrochemical (PEC) splitting of water. An ZnO NW array of core diameter ∼80 nm was grown on a fluorine-doped tin-oxide (FTO) substrate with a hydrothermal method; subsequent deposition and annealing achieved a shell structure of the Fe2O3 layer of thickness a few nm. Fe2O3 in the α phase and ZnO in the wurtzite phase were identified as the structures of the shell and core, respectively, through analysis with X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The ZnO/Fe2O3 core-shell NW showed an excellent PEC response to the oxidation of water, and also benefited from a negative shift of onset potential because of an n/n heterojunction structure. A detailed energy diagram of the ZnO/Fe2O3 core-shell NW was investigated with a Mott-Schottky analysis. This novel core-shell nanostructure can hence not only exhibit a great potential for the solar generation of hydrogen, but also offer a blueprint for the future design of photocatalysts. PMID:26053274

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

    DOEpatents

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

    2015-04-14

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

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

    PubMed Central

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

    2015-01-01

    We report an atomic scale controllable synthesis of Pd/Pt core shell nanoparticles (NPs) via area-selective atomic layer deposition (ALD) on a modified surface. The method involves utilizing octadecyltrichlorosilane (ODTS) self-assembled monolayers (SAMs) to modify the surface. Take the usage of pinholes on SAMs as active sites for the initial core nucleation, and subsequent selective deposition of the second metal as the shell layer. Since new nucleation sites can be effectively blocked by surface ODTS SAMs in the second deposition stage, we demonstrate the successful growth of Pd/Pt and Pt/Pd NPs with uniform core shell structures and narrow size distribution. The size, shell thickness and composition of the NPs can be controlled precisely by varying the ALD cycles. Such core shell structures can be realized by using regular ALD recipes without special adjustment. This SAMs assisted area-selective ALD method of core shell structure fabrication greatly expands the applicability of ALD in fabricating novel structures and can be readily applied to the growth of NPs with other compositions. PMID:25683469

  18. Fluorescent core-shell silica nanoparticles: an alternative radiative materials platform

    NASA Astrophysics Data System (ADS)

    Herz, Erik; Burns, Andrew; Lee, Stephanie; Sengupta, Prabuddha; Bonner, Daniel; Ow, Hooisweng; Liddell, Chekesha; Baird, Barbara; Wiesner, Ulrich

    2006-02-01

    We report on monodisperse fluorescent core-shell silica nanoparticles (C dots) with enhanced brightness and photostability as compared to parent free dye in aqueous solution. Dots containing either tetramethylrhodamine or 7-nitrobenz-2-oxa-1,3-diazole dyes with diameters ranging from tens of nanometers to microns are discussed. The benefits of the core-shell architecture are described in terms of enhanced fluorescent yield of the fluorophores in the quasi-solid-state environment within the particle as compared with parent free dye in water. Several applications of these particles in the fields of photonics and the life sciences are discussed. Specifically, fluorescent core-shell silica nanoparticles are investigated as an active medium for photonic building blocks assembled on zinc sulfide-based seed particles. Initial assembly results for these composite raspberry structures are shown. Finally, applications in the life sciences are explored, including targeting of specific antibody receptors using these single-emission nanoparticles. We expand on single-emission core-shell architecture to incorporate environmentally-sensitive fluorophores to create quantitative ratiometric nanoscale sensors capable of interrogating chemical concentrations on the sub-cellular to molecular levels and demonstrate initial results of intracellular pH imaging. The concept of a single particle laboratory (SPL) is introduced as an active investigator of its environment.

  19. Enhanced functionalization of Mn2O3@SiO2 core-shell nanostructures

    NASA Astrophysics Data System (ADS)

    Vaidya, Sonalika; Thaplyal, Pallavi; Ganguli, Ashok Kumar

    2011-12-01

    Core-shell nanostructures of Mn2O3@SiO2, Mn2O3@amino-functionalized silica, Mn2O3@vinyl-functionalized silica, and Mn2O3@allyl-functionalized silica were synthesized using the hydrolysis of the respective organosilane precursor over Mn2O3 nanoparticles dispersed using colloidal solutions of Tergitol and cyclohexane. The synthetic methodology used is an improvement over the commonly used post-grafting or co-condensation method as it ensures a high density of functional groups over the core-shell nanostructures. The high density of functional groups can be useful in immobilization of biomolecules and drugs and thus can be used in targeted drug delivery. The high density of functional groups can be used for extraction of elements present in trace amounts. These functionalized core-shell nanostructures were characterized using TEM, IR, and zeta potential studies. The zeta potential study shows that the hydrolysis of organosilane to form the shell results in more number of functional groups on it as compared to the shell formed using post-grafting method. The amino-functionalized core-shell nanostructures were used for the immobilization of glucose and L -methionine and were characterized by zeta potential studies.

  20. In-situ Liquid Phase Epitaxy: Another Strategy to Synthesize Heterostructured Core-shell Composites

    NASA Astrophysics Data System (ADS)

    Wen, Zhongsheng; Wang, Guanqin

    2016-04-01

    Core-shell Nb2O5/TiO2 composite with hierarchical heterostructure is successfully synthesized In-situ by a facile template-free and acid-free solvothermal method based on the mechanism of liquid phase epitaxy. The chemical circumstance change induced by the alcoholysis of NbCl5 is utilized tactically to trigger core-shell assembling In-situ. The tentative mechanism for the self-assembling of core-shell structure and hierarchical structure is explored. The microstructure and morphology changes during synthesis process are investigated systematically by using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. The dramatic alcoholysis of NbCl5 has been demonstrated to be the fundamental factor for the formation of the spherical core, which changes the acid circumstance of the solution and induces the co-precipitation of TiO2. The homogeneous co-existence of Nb2O5/TiO2 in the core and the co-existence of Nb/Ti ions in the reaction solution facilitate the In-situ nucleation and epitaxial growth of the crystalline shell with the same composition as the core. In-situ liquid phase epitaxy can offer a different strategy for the core-shell assembling for oxide materials.

  1. In-situ Liquid Phase Epitaxy: Another Strategy to Synthesize Heterostructured Core-shell Composites

    PubMed Central

    Wen, Zhongsheng; Wang, Guanqin

    2016-01-01

    Core-shell Nb2O5/TiO2 composite with hierarchical heterostructure is successfully synthesized In-situ by a facile template-free and acid-free solvothermal method based on the mechanism of liquid phase epitaxy. The chemical circumstance change induced by the alcoholysis of NbCl5 is utilized tactically to trigger core-shell assembling In-situ. The tentative mechanism for the self-assembling of core-shell structure and hierarchical structure is explored. The microstructure and morphology changes during synthesis process are investigated systematically by using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. The dramatic alcoholysis of NbCl5 has been demonstrated to be the fundamental factor for the formation of the spherical core, which changes the acid circumstance of the solution and induces the co-precipitation of TiO2. The homogeneous co-existence of Nb2O5/TiO2 in the core and the co-existence of Nb/Ti ions in the reaction solution facilitate the In-situ nucleation and epitaxial growth of the crystalline shell with the same composition as the core. In-situ liquid phase epitaxy can offer a different strategy for the core-shell assembling for oxide materials. PMID:27121200

  2. In-situ Liquid Phase Epitaxy: Another Strategy to Synthesize Heterostructured Core-shell Composites.

    PubMed

    Wen, Zhongsheng; Wang, Guanqin

    2016-01-01

    Core-shell Nb2O5/TiO2 composite with hierarchical heterostructure is successfully synthesized In-situ by a facile template-free and acid-free solvothermal method based on the mechanism of liquid phase epitaxy. The chemical circumstance change induced by the alcoholysis of NbCl5 is utilized tactically to trigger core-shell assembling In-situ. The tentative mechanism for the self-assembling of core-shell structure and hierarchical structure is explored. The microstructure and morphology changes during synthesis process are investigated systematically by using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. The dramatic alcoholysis of NbCl5 has been demonstrated to be the fundamental factor for the formation of the spherical core, which changes the acid circumstance of the solution and induces the co-precipitation of TiO2. The homogeneous co-existence of Nb2O5/TiO2 in the core and the co-existence of Nb/Ti ions in the reaction solution facilitate the In-situ nucleation and epitaxial growth of the crystalline shell with the same composition as the core. In-situ liquid phase epitaxy can offer a different strategy for the core-shell assembling for oxide materials. PMID:27121200

  3. Liquid immiscibility and core-shell morphology formation in ternary Al–Bi–Sn alloys

    SciTech Connect

    Dai, R.; Zhang, J.F.; Zhang, S.G. Li, J.G.

    2013-07-15

    The effects of composition on liquid immiscibility, macroscopic morphology, microstructure and phase transformation in ternary Al–Bi–Sn alloys were investigated. Three types of morphology, the core-shell type, the stochastic droplet type and uniform dispersion type, of Al–Bi–Sn particles prepared by a jet breakup process were distinguished, and the relationships between which were discussed. The phase transformation behaviors of the Al–Bi–Sn alloys were studied by thermal analysis, in agreement with the microstructural observation and microanalysis. The liquid immiscibility and formation of the core-shell morphology in Al–Bi–Sn alloys are easily achieved when the composition lies in the liquid miscibility gap. The particles exhibit a high melting point Al-rich core with a low melting point Sn–Bi-rich solder shell, showing promise for application as high-density electronic packaging materials. - Highlights: • The liquid demixing, morphology and microstructure in Al–Bi–Sn alloys were studied. • Three types of morphology were classified and discussed. • The conditions for formation of the core-shell morphology were obtained. • The phase transition behaviors agree with the microstructure characterization. • The Al/Sn–Bi core-shell particles show promise for use in electronic packaging.

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

    NASA Astrophysics Data System (ADS)

    Mumin, Md Abdul; Akhter, Kazi Farida; Charpentier, Paul A.

    2014-03-01

    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).

  5. Copper nanowire-graphene core-shell nanostructure for highly stable transparent conducting electrodes.

    PubMed

    Ahn, Yumi; Jeong, Youngjun; Lee, Donghwa; Lee, Youngu

    2015-03-24

    A copper nanowire-graphene (CuNW-G) core-shell nanostructure was successfully synthesized using a low-temperature plasma-enhanced chemical vapor deposition process at temperatures as low as 400 °C for the first time. The CuNW-G core-shell nanostructure was systematically characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman, and X-ray photoelectron spectroscopy measurements. A transparent conducting electrode (TCE) based on the CuNW-G core-shell nanostructure exhibited excellent optical and electrical properties compared to a conventional indium tin oxide TCE. Moreover, it showed remarkable thermal oxidation and chemical stability because of the tight encapsulation of the CuNW with gas-impermeable graphene shells. The potential suitability of CuNW-G TCE was demonstrated by fabricating bulk heterojunction polymer solar cells. We anticipate that the CuNW-G core-shell nanostructure can be used as an alternative to conventional TCE materials for emerging optoelectronic devices such as flexible solar cells, displays, and touch panels. PMID:25712446

  6. Facile preparation of hybrid core-shell nanorods for photothermal and radiation combined therapy

    NASA Astrophysics Data System (ADS)

    Deng, Yaoyao; Li, Erdong; Cheng, Xiaju; Zhu, Jing; Lu, Shuanglong; Ge, Cuicui; Gu, Hongwei; Pan, Yue

    2016-02-01

    The hybrid platinum@iron oxide core-shell nanorods with high biocompatibility were synthesized and applied for combined therapy. These hybrid nanorods exhibit a good photothermal effect on cancer cells upon irradiation with a NIR laser. Furthermore, due to the presence of a high atomic number element (platinum core), the hybrid nanorods show a synergistic effect between photothermal and radiation therapy. Therefore, the as-prepared core-shell nanorods could play an important role in facilitating synergistic therapy between photothermal and radiation therapy to achieve better therapeutic efficacy.The hybrid platinum@iron oxide core-shell nanorods with high biocompatibility were synthesized and applied for combined therapy. These hybrid nanorods exhibit a good photothermal effect on cancer cells upon irradiation with a NIR laser. Furthermore, due to the presence of a high atomic number element (platinum core), the hybrid nanorods show a synergistic effect between photothermal and radiation therapy. Therefore, the as-prepared core-shell nanorods could play an important role in facilitating synergistic therapy between photothermal and radiation therapy to achieve better therapeutic efficacy. Electronic supplementary information (ESI) available: Details of general experimental procedures. See DOI: 10.1039/c5nr09102k

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

    SciTech Connect

    Mumin, Md Abdul Akhter, Kazi Farida Charpentier, Paul A.

    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)

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

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

    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.

  9. Role of the interfaces in multiple networked one-dimensional core-shell nanostructured gas sensors.

    PubMed

    Park, Sunghoon; Ko, Hyunsung; Kim, Soohyun; Lee, Chongmu

    2014-06-25

    This study examined the gas sensing mechanism of multiple networked core-shell nanowire sensors. The ethanol gas sensing properties of In2O3/ZnO core-shell nanowires synthesized by the thermal evaporation of indium powder in an oxidizing atmosphere followed by the atomic layer deposition of ZnO were examined as an example. The pristine In2O3 nanowires and In2O3-core/ZnO-shell nanowires exhibited responses of ∼30% and ∼196%, respectively, to 1000 ppm ethanol at 300 °C. The response of the core-shell nanostructures to ethanol also showed a strong dependence on the shell layer width. The strongest response to ethanol was obtained with a shell layer thickness of ∼44 nm corresponding to 2λD, where λD is the Debye length of ZnO. The enhanced sensing properties of the core-shell nanowires toward ethanol can be explained based on the potential barrier-controlled carrier transport model combined with the surface depletion model; the former is predominant over the latter. PMID:24850501

  10. Controlled Release of Ciprofloxacin from Core-Shell Nanofibers with Monolithic or Blended Core.

    PubMed

    Zupančič, Špela; Sinha-Ray, Sumit; Sinha-Ray, Suman; Kristl, Julijana; Yarin, Alexander L

    2016-04-01

    Sustained controlled drug release is one of the prominent contributions for more successful treatment outcomes in the case of several diseases. However, the incorporation of hydrophilic drugs into nanofibers, a promising novel delivery system, and achieving a long-term sustained release still pose a challenging task. In this work we demonstrated a robust method of avoiding burst release of drugs and achieving a sustained drug release from 2 to 4 weeks using core-shell nanofibers with poly(methyl methacrylate) (PMMA) shell and monolithic poly(vinyl alcohol) (PVA) core or a novel type of core-shell nanofibers with blended (PVA and PMMA) core loaded with ciprofloxacin hydrochloride (CIP). It is also shown that, for core-shell nanofibers with monolithic core, drug release can be manipulated by varying flow rate of the core PVA solution, whereas for core-shell nanofibers with blended core, drug release can be manipulated by varying the ratios between PMMA and PVA in the core. During coaxial electrospinning, when the solvent from the core evaporates in concert with the solvent from the shell, the interconnected pores spanning the core and the shell are formed. The release process is found to be desorption-limited and agrees with the two-stage desorption model. Ciprofloxacin-loaded nanofiber mats developed in the present work could be potentially used as local drug delivery systems for treatment of several medical conditions, including periodontal disease and skin, bone, and joint infections. PMID:26950163

  11. Hydrothermal synthesis of core-shell TiO2 to enhance the photocatalytic hydrogen evolution

    NASA Astrophysics Data System (ADS)

    Jiang, Jinghui; Zhou, Han; Zhang, Fan; Fan, Tongxiang; Zhang, Di

    2016-04-01

    A hydrothermal approach was designed to synthesize core-shell TiO2 with interior cavity by making sodium dodecyl sulfonate (SDS) as the surfactant and the mixture of water and ethanol as the solvent. The control experiment of solvent reveals ethanol and water are responsible for the formation of sphere and interior cavity, respectively. Besides, SDS can assist the growth of core-shell structure, and the sizes of sphere and interior cavity can be tuned by regulating the reaction time or temperature. UV-vis absorption proves core-shell structure with interior cavity can increase the absorption of incident light to enhance the optical activity of final product. The calculated bandgap and photoluminescence (PL) analyses reveal the coexistence of rutile in final product can optimize the bandgap to 3.03 eV and delay the charge recombination. As a result, an effective photocatalytic hydrogen evolution under full spectrum irradiation can be harvested by the as-synthesized core-shell spheres to reach a quantum yield, approximately 9.57% at 340 nm wavelength.

  12. Nanostructured core-shell Ni deposition on SiC particles by alkaline electroless coating

    NASA Astrophysics Data System (ADS)

    Uysal, M.; Karslioğlu, R.; Alp, A.; Akbulut, H.

    2011-10-01

    In this study, core-shell nanostructured nickel formation on silicon carbide (SiC) ceramic powders was achieved through the electroless deposition method using alkaline solutions. To produce a nano core-shell Ni deposition on the SiC surfaces, process parameters such as pH values, the type of reducer material, deposition temperature, stirring rate and activation procedure among others were determined. Full coverage of core-shell nickel structures on SiC surfaces was achieved with a grain size of between 100 and 300 nm, which was approximately the same deposition thickness on the SiC surfaces. The surface morphology of the coated SiC particles showed a homogenous distribution of nanostructured nickel grains characterized by scanning electron microscopy and X-ray diffraction techniques. The nanostructures of the crystalline Ni coatings were observed to be attractive for achieving both good bonding and dense structure. The thin core shell-structure of Ni on the SiC surfaces was assessed as a beneficial reinforcement for possible metal matrix composite manufacturing.

  13. Controllable synthesis of Cu-Ni core-shell nanoparticles and nanowires with tunable magnetic properties.

    PubMed

    Guo, Huizhang; Jin, Jiarui; Chen, Yuanzhi; Liu, Xiang; Zeng, Deqian; Wang, Laisen; Peng, Dong-Liang

    2016-05-25

    Cu seeds were used to direct the epitaxial growth of Ni shell to form Cu-Ni core-shell cubes, tetrahexahedrons and nanowires. The controllable epitaxial growth of Ni shells on Cu cores provided selectively exposed surfaces and morphologies as well as tunable magnetic properties. PMID:27147395

  14. Core-shell structured TiO2@polydopamine for highly active visible-light photocatalysis.

    PubMed

    Mao, Wen-Xin; Lin, Xi-Jie; Zhang, Wei; Chi, Zi-Xiang; Lyu, Rong-Wen; Cao, An-Min; Wan, Li-Jun

    2016-06-01

    This communication reports that the TiO2@polydopamine nanocomposite with a core-shell structure could be a highly active photocatalyst working under visible light. A very thin layer of polydopamine at around 1 nm was found to be critical for the degradation of Rhodamine B. PMID:27165843

  15. Core-shell potassium niobate nanowires for enhanced nonlinear optical effects.

    PubMed

    Richter, J; Steinbrück, A; Zilk, M; Sergeyev, A; Pertsch, T; Tünnermann, A; Grange, R

    2014-05-21

    We demonstrate the synthesis as well as the optical characterization of core-shell nanowires. The wires consist of a potassium niobate (KNbO3) core and a gold shell. The nonlinear optical properties of the core are combined with the plasmonic resonance of the shell and offer an enhanced optical signal in the near infrared spectral range. We compare two different functionalization schemes of the core material prior to the shell growth process: silanization and polyelectrolyte. We show that the latter leads to a smoother and complete core-shell nanostructure and an easier-to-use synthesis process. A Mie-theory based theoretical approach is presented to model the enhanced second-harmonic generated (SHG) signal of the core-shell wires, illustrating the influence of the fabrication-induced varying geometrical factors of wire radius and shell thickness. A spectroscopic measurement on a core-shell nanowire shows a strong localized surface plasmon resonance close to 900 nm, which matches with the SHG resonance obtained from nonlinear optical experiments with the same nanowire. According to the simulation, this corresponds to a wire radius of 35 nm and a shell thickness of 7.5 nm. By comparing SHG signals measured from an uncoated nanowire and the coated one, we obtain a 250 times enhancement factor. This is less than the calculated enhancement, which considers a cylindrical nanowire with a perfectly smooth shell. Thus, we explain this discrepancy mainly with the roughness of the synthesized gold shell. PMID:24675780

  16. Core-shell nanoreactors for efficient aqueous biphasic catalysis.

    PubMed

    Zhang, Xuewei; Cardozo, Andrés F; Chen, Si; Zhang, Wenjing; Julcour, Carine; Lansalot, Muriel; Blanco, Jean-François; Gayet, Florence; Delmas, Henri; Charleux, Bernadette; Manoury, Eric; D'Agosto, Franck; Poli, Rinaldo

    2014-11-17

    Water-borne phosphine-functionalized core-cross-linked micelles (CCM) consisting of a hydrophobic core and a hydrophilic shell were obtained as stable latexes by reversible addition-fragmentation chain transfer (RAFT) in water in a one-pot, three-step process. Initial homogeneous aqueous-phase copolymerization of methacrylic acid (MAA) and poly(ethylene oxide) methyl ether methacrylate (PEOMA) is followed by copolymerization of styrene (S) and 4-diphenylphosphinostyrene (DPPS), yielding P(MAA-co-PEOMA)-b-P(S-co-DPPS) amphiphilic block copolymer micelles (M) by polymerization-induced self-assembly (PISA), and final micellar cross-linking with a mixture of S and diethylene glycol dimethacrylate. The CCM were characterized by dynamic light scattering and NMR spectroscopy to evaluate size, dispersity, stability, and the swelling ability of various organic substrates. Coordination of [Rh(acac)(CO)2 ] (acac=acetylacetonate) to the core-confined phosphine groups was rapid and quantitative. The CCM and M latexes were then used, in combination with [Rh(acac)(CO)2 ], to catalyze the aqueous biphasic hydroformylation of 1-octene, in which they showed high activity, recyclability, protection of the activated Rh center by the polymer scaffold, and low Rh leaching. The CCM latex gave slightly lower catalytic activity but significantly less Rh leaching than the M latex. A control experiment conducted in the presence of the sulfoxantphos ligand pointed to the action of the CCM as catalytic nanoreactors with substrate and product transport into and out of the polymer core, rather than as a surfactant in interfacial catalysis. PMID:25284685

  17. A facile route to synthesize core/shell structured carbon/magnetic nanoparticles hybrid and their magnetic properties

    SciTech Connect

    Qi, Xiaosi; Xu, Jianle; Zhong, Wei; Du, Youwei

    2015-07-15

    Graphical abstract: Controllable synthesis of core/shell structured carbon/magnetic nanoparticles hybrid and their tunable magnetic properties. - Highlights: • The paper reports a simple route for core/shell structured carbon/magnetic nanoparticles hybrid. • By controlling the temperature, Fe{sub 3}O{sub 4}@CNCs, Fe@HCNTs and Fe@LCNTs were produced selectively. • The magnetic properties of the obtained core/shell structured hybrid could be tuned effectively. - Abstract: By controlling the pyrolysis temperature, core/shell structured Fe{sub 3}O{sub 4}/carbon nanocages, Fe/helical carbon nanotubes and Fe/low helicity of carbon nanotubes could be synthesized selectively over Fe{sub 2}O{sub 3} nanotubes generated by a hydrothermal method. The transmission electron microscopic and scanning electron microscopic investigations revealed that the efficiency of generating core/shell structured hybrid was high, exceeding 90%. Because of the magnetic nanoparticles tightly wrapped in graphitic layers, the obtained core/shell structured hybrids showed high stability and good magnetic properties. And the magnetic properties of the obtained core/shell structured hybrid could be tuned by the decomposition temperature and time. Therefore, a simple, inexpensive and environment-benign route was proposed to produce magnetism-tunable core/shell structured hybrid in large quantities.

  18. Determining the size distribution of core-shell spheres and other complex particles by laser diffraction.

    PubMed

    Lagasse, R R; Richards, D Wayne

    2003-11-01

    The goal of this work is to determine the size distribution of hollow glass spheres by laser diffraction, an experiment which involves measuring angle-dependent scattering of light from particles dispersed in a liquid. The proprietary software supplied with commercial instruments is not strictly applicable to our two-layer, glass-shell, hollow-core spheres because it requires that the particles have spatially homogeneous properties. We therefore developed Fortran code to compute the scattering from core-shell spherical particles. The results show that the scattering from representative hollow glass particles diverges from homogeneous sphere scattering when the radius decreases from 10 to 3 microm. Additionally, scattering measurements on two core-shell hollow glass powders were analyzed using the exact core-shell optical model and homogeneous sphere approximations. In both cases, the size distribution determined using the exact core-shell model differs from that determined using the homogeneous-sphere approximation when the distribution covers radii smaller than about 10 microm, as expected. The size distribution based on the exact core-shell optical model was determined using a new algorithm. Although the basic equations used in the algorithm have been published previously, they are developed here in a different form, which can be implemented using Fortran and MatLab routines available commercially and in the public domain. This algorithm could be used to determine the size distribution of other kinds of particles, such as cylindrical rods, as long as their angle-dependent scattering could be computed. PMID:14554168

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

    PubMed

    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. PMID:24967836

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

    PubMed

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

    2016-07-01

    A facile and scalable lithography-free technique(5) for the rapid construction of GaAs core-shell nanowires incorporating shell isolation from the substrate is reported. The process is based on interrupting NW growth and applying a thin spin-on-glass (SOG) layer to the base of the NWs and resuming core-shell NW growth. NW growth occurred in an atmospheric pressure metalorganic vapour phase epitaxy (MOVPE) system with gold nanoparticles used as catalysts for the vapour-liquid-solid growth. It is shown that NW axial core growth and radial shell growth can be resumed after interruption and even exposure to air. The SOG residues and native oxide layer that forms on the NW surface are shown to prevent or perturb resumption of epitaxial NW growth if not removed. Both HF etching and in situ annealing of the air-exposed NWs in the MOVPE were shown to remove the SOG residues and native oxide layer. While both procedures are shown capable of removing the native oxide and enabling resumption of epitaxial NW growth, in situ annealing produced the best results and allowed construction of pristine core-shell NWs. No growth occurred on SOG and it was observed that axial NW growth was more rapid when a SOG layer covered the substrate. The fabricated p-core/n-shell NWs exhibited diode behaviour upon electrical testing. The isolation of the NW shells from the substrate was confirmed by scanning electron microscopy and electrical measurements. The crystal quality of the regrown core-shell NWs was verified with a high resolution transmission electron microscope. The reported technique potentially provides a pathway using MOVPE for scalable and high-throughput production of shell-substrate isolated core-shell NWs on an industrial scale. PMID:27242347

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

    NASA Astrophysics Data System (ADS)

    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.

  2. Magnetic field directed assembly of superstructures of ferrite-ferroelectric core-shell nanoparticles and studies on magneto-electric interactions

    SciTech Connect

    Srinivasan, G. Sreenivasulu, G.; Benoit, Crystal; Petrov, V. M.; Chavez, F.

    2015-05-07

    Composites of ferromagnetic and ferroelectric are of interest for studies on mechanical strain mediated magneto-electric (ME) interactions and for useful technologies. Here, we report on magnetic-field-assisted-assembly of barium titanate (BTO)-nickel ferrite (NFO) core-shell particles into linear chains and 2D/3D arrays and measurements of ME effects in such assemblies. First, we synthesized the core-shell nano-particles with 50–600 nm BTO and 10–200 nm NFO by chemical self-assembly by coating the ferroic particles with complementary coupling groups and allowing them to self-assemble in the presence of a catalyst via the “click” reaction. The core-shell structure was confirmed with electron microscopy and scanning probe microscopy. We obtained superstructure of the core-shell particles by subjecting them to a magnetic field gradient that exerts an attractive force on the particles and align them toward the regions of high field strengths. At low particle concentration, linear chains were formed and they evolved into 2D and 3D arrays at high particle concentrations. Magnetoelectric characterization on unassembled films and assembled arrays has been performed through measurements of low-frequency ME voltage coefficient (MEVC) by subjecting the sample to a bias magnetic field and an ac magnetic field. The MEVC is higher for field-assembled samples than for unassembled films and is found to be sensitive to field orientation with a higher MEVC for magnetic fields parallel to the array direction than for magnetic fields perpendicular to the array. A maximum MEVC of 20 mV/cm Oe, one of the highest reported for any bulk nanocomposite, is measured across the array thickness. A model is provided for ME coupling in the superstructures of BTO-NFO particulate composites. First, we estimated the MEVC for a free-standing BTO-NFO core-shell particle and then extended the model to include an array of linear chains of the particles. The theoretical estimates are in

  3. Dynamic evolution process of multilayer core-shell microstructures within containerlessly solidifying Fe(50)Sn(50) immiscible alloy.

    PubMed

    Wang, W L; Wu, Y H; Li, L H; Geng, D L; Wei, B

    2016-03-01

    Multilayer core-shell structures are frequently formed in polymers and alloys when temperature and concentration fields are well symmetrical spatially. Here we report that two- to five-layer core-shell microstructures were the dominant structural morphology of a binary Fe(50)Sn(50) immiscible alloy solidified under the containerless and microgravity states within a drop tube. Three dimensional phase field simulation reveals that both the uniformly dispersive structure and the multilayer core-shells are the various metastable and transitional states of the liquid phase separation process. Only the two-layer core-shell is the most stable microstructure with the lowest chemical potential. Because of the suppression of Stokes motion, solutal Marangoni migration becomes important to drive the evolution of core-shell structures. PMID:27078410

  4. Dynamic evolution process of multilayer core-shell microstructures within containerlessly solidifying F e50S n50 immiscible alloy

    NASA Astrophysics Data System (ADS)

    Wang, W. L.; Wu, Y. H.; Li, L. H.; Geng, D. L.; Wei, B.

    2016-03-01

    Multilayer core-shell structures are frequently formed in polymers and alloys when temperature and concentration fields are well symmetrical spatially. Here we report that two- to five-layer core-shell microstructures were the dominant structural morphology of a binary F e50S n50 immiscible alloy solidified under the containerless and microgravity states within a drop tube. Three dimensional phase field simulation reveals that both the uniformly dispersive structure and the multilayer core-shells are the various metastable and transitional states of the liquid phase separation process. Only the two-layer core-shell is the most stable microstructure with the lowest chemical potential. Because of the suppression of Stokes motion, solutal Marangoni migration becomes important to drive the evolution of core-shell structures.

  5. Proteresis of Cu2O/CuO core-shell nanoparticles: Experimental observations and theoretical considerations

    NASA Astrophysics Data System (ADS)

    Wu, Sheng Yun; Ji, Jhong-Yi; Shih, Po-Hsun; Gandhi, Ashish Chhaganlal; Chan, Ting-Shan

    2014-11-01

    A study of "proteresis (inverted hysteresis)" in core-shell, Cu2O/CuO nanoparticles, is presented. Crystal and characteristic sizes are determined using the x-ray absorption near-edge structure method for the weak ferromagnetic core (Cu2O) and antiferromagnetic shell (CuO) nanoparticles. A core-shell anisotropic energy model is established to describe the observed proteretic behavior in Cu2O/CuO core-shell nanocrystals. The proteresis loop triggered by the applied magnetic field can be tentatively attributed to core-shell exchange coupling induced by the surface of the Cu2O core, hinting at a possible way to tune the strength of the exchange inter-coupling energy that can control the dynamic of proteresis and hysteresis in a core-shell system.

  6. Surface-imprinted core-shell Au nanoparticles for selective detection of bisphenol A based on surface-enhanced Raman scattering.

    PubMed

    Xue, Jin-Qun; Li, Da-Wei; Qu, Lu-Lu; Long, Yi-Tao

    2013-05-13

    Surface-imprinted core-shell Au nanoparticles (AuNPs) were explored for the highly selective detection of bisphenol A (BPA) by surface-enhanced Raman scattering (SERS). A triethoxysilane-template complex (BPA-Si) was synthesized and then utilized to fabricate a molecularly imprinted polymer (MIP) layer on the AuNPs via a sol-gel process. The imprinted BPA molecules were removed by a simple thermal treatment to generated the imprint-removed material, MIP-ir-AuNPs, with the desired recognition sites that could selectively rebind the BPA molecules. The morphological and polymeric characteristics of MIP-ir-AuNPs were investigated by transmission electron microscopy and Fourier-transform infrared spectroscopy. The results demonstrated that the MIP-ir-AuNPs were fabricated with a 2 nm MIP shell layer within which abundant amine groups were generated. The rebinding kinetics study showed that the MIP-ir-AuNPs could reach the equilibrium adsorption for BPA within 10 min owning to the advantage of ultrathin core-shell nanostructure. Moreover, a linear relationship between SERS intensity and the concentration of BPA on the MIP-ir-AuNPs was observed in the range of 0.5-22.8 mg L(-1), with a detection limit of 0.12 mg L(-1) (blank±3×s.d.). When applied to SERS detection, the developed surface-imprinted core-shell MIP-ir-AuNPs could recognize BPA and prevent interference from the structural analogues such as hexafluorobisphenol A (BPAF) and diethylstilbestrol (DES). These results revealed that the proposed method displayed significant potential utility in rapid and selective detection of BPA in real samples. PMID:23622965

  7. Surface Grafting via Photo-Induced Copper-Mediated Radical Polymerization at Extremely Low Catalyst Concentrations.

    PubMed

    Laun, Joachim; Vorobii, Mariia; de los Santos Pereira, Andres; Pop-Georgievski, Ognen; Trouillet, Vanessa; Welle, Alexander; Barner-Kowollik, Christopher; Rodriguez-Emmenegger, Cesar; Junkers, Thomas

    2015-09-01

    Surface-initiated photo-induced copper-mediated radical polymerization is employed to graft a wide range of polyacrylate brushes from silicon substrates at extremely low catalyst concentrations. This is the first time that the controlled nature of the reported process is demonstrated via block copolymer formation and re-initiation experiments. In addition to unmatched copper catalyst concentrations in the range of few ppb, film thicknesses up to almost 1 μm are achieved within only 1 h. PMID:26149622

  8. Structural basis for tandem L27 domain-mediated polymerization

    SciTech Connect

    Yang, Xue; Xie, Xingqiao; Chen, Liu; Zhou, Hao; Wang, Zheng; Zhao, Weijing; Tian, Ran; Zhang, Rongguang; Tian, Changlin; Long, Jiafu; Shen, Yuequan

    2010-12-01

    The establishment of epithelial cell polarity requires the assembly of multiprotein complexes and is crucial during epithelial morphogenesis. Three scaffolding proteins, Dlg1, MPP7, and Mals3, can be assembled to form a complex that functions in the establishment and maintenance of apicobasal polarity in epithelial tissues through their L27 domains. Here we report the crystal structure of a 4-L27-domain complex derived from the human tripartite complex Dlg1-MPP7-Mals3 in combination with paramagnetic relaxation enhancement measurements. The heterotrimer consists of 2 pairs of heterodimeric L27 domains. These 2 dimers are asymmetric due to the large difference between the N- and C-terminal tandem L27 domain of MPP7. Structural analysis combined with biochemical experiments further reveals that the loop {alpha}A-{alpha}B and helix {alpha}B of the C-terminal L27 domain of MPP7 play a critical role in assembling the entire tripartite complex, suggesting a synergistic tandem L27-mediated assembling event.

  9. Core-shell potassium niobate nanowires for enhanced nonlinear optical effects

    NASA Astrophysics Data System (ADS)

    Richter, J.; Steinbrück, A.; Zilk, M.; Sergeyev, A.; Pertsch, T.; Tünnermann, A.; Grange, R.

    2014-04-01

    We demonstrate the synthesis as well as the optical characterization of core-shell nanowires. The wires consist of a potassium niobate (KNbO3) core and a gold shell. The nonlinear optical properties of the core are combined with the plasmonic resonance of the shell and offer an enhanced optical signal in the near infrared spectral range. We compare two different functionalization schemes of the core material prior to the shell growth process: silanization and polyelectrolyte. We show that the latter leads to a smoother and complete core-shell nanostructure and an easier-to-use synthesis process. A Mie-theory based theoretical approach is presented to model the enhanced second-harmonic generated (SHG) signal of the core-shell wires, illustrating the influence of the fabrication-induced varying geometrical factors of wire radius and shell thickness. A spectroscopic measurement on a core-shell nanowire shows a strong localized surface plasmon resonance close to 900 nm, which matches with the SHG resonance obtained from nonlinear optical experiments with the same nanowire. According to the simulation, this corresponds to a wire radius of 35 nm and a shell thickness of 7.5 nm. By comparing SHG signals measured from an uncoated nanowire and the coated one, we obtain a 250 times enhancement factor. This is less than the calculated enhancement, which considers a cylindrical nanowire with a perfectly smooth shell. Thus, we explain this discrepancy mainly with the roughness of the synthesized gold shell.We demonstrate the synthesis as well as the optical characterization of core-shell nanowires. The wires consist of a potassium niobate (KNbO3) core and a gold shell. The nonlinear optical properties of the core are combined with the plasmonic resonance of the shell and offer an enhanced optical signal in the near infrared spectral range. We compare two different functionalization schemes of the core material prior to the shell growth process: silanization and polyelectrolyte

  10. Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst.

    PubMed

    Yeow, Jonathan; Xu, Jiangtao; Boyer, Cyrille

    2016-01-01

    Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins with the synthesis of a hydrophilic poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) homopolymer using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Under mild visible light irradiation (λ = 460 nm, 0.7 mW/cm(2)), this macro-chain transfer agent (macro-CTA) in the presence of a ruthenium based photoredox catalyst, Ru(bpy)3Cl2 can be chain extended with a second monomer to form a well-defined block copolymer in a process known as Photoinduced Electron Transfer RAFT (PET-RAFT). When PET-RAFT is used to chain extend POEGMA with benzyl methacrylate (BzMA) in ethanol (EtOH), polymeric nanoparticles with different morphologies are formed in situ according to a polymerization-induced self-assembly (PISA) mechanism. Self-assembly into nanoparticles presenting POEGMA chains at the corona and poly(benzyl methacrylate) (PBzMA) chains in the core occurs in situ due to the growing insolubility of the PBzMA block in ethanol. Interestingly, the formation of highly pure worm-like micelles can be readily monitored by observing the onset of a highly viscous gel in situ due to nanoparticle entanglements occurring during the polymerization. This process thereby allows for a more reproducible synthesis of worm-like micelles simply by monitoring the solution viscosity during the course of the polymerization. In addition, the light stimulus can be intermittently applied in an ON/OFF manner demonstrating temporal control over the nanoparticle morphology. PMID:27340940

  11. Synthesis and characterization of thermoresponsive polyamidoamine-polyethylene glycol-poly(D,L-lactide) core-shell nanoparticles.

    PubMed

    Kailasan, Arunvel; Yuan, Quan; Yang, Hu

    2010-03-01

    This work describes the synthesis and characterization of novel thermoresponsive highly branched polyamidoamine-polyethylene glycol-poly(D,L-lactide) (PAMAM-PEG-PDLLA) core-shell nanoparticles. A series of dendritic PEG-PDLLA nanoparticles were synthesized through conjugation of PEG of various chain lengths (1500, 6000 and 12,000 g mol(-1)) to polyamidoamine (PAMAM) dendrimer G3.0 and subsequent ring-opening polymerization of DLLA. The ninhydrin assay, (1)H NMR, Fourier transform infrared spectroscopy, dynamic light scattering and atomic force microscopy were used to characterize the structure and compositions of dendritic PEG-PDLLA nanoparticles. The sol-gel phase transition of aqueous dendritic PEG-PDLLA solutions was measured using UV-visual spectroscopy. According to our results dendritic PEG-PDLLA nanoparticles in aqueous solution can self-assemble into sub-micron/micron aggregates, the size of which is dependent on temperature and PEG-PDLLA chain length. Further, dendritic PEG-PDLLA solutions exhibit a sol-gel phase transition with increasing temperature. The constructed dendritic PEG-PDLLA nanoparticles possessed high cytocompatibility, which was significantly improved compared with PAMAM dendrimers. The potential of dendritic PEG-PDLLA nanoparticles for encapsulation of water-insoluble drugs such as camptothecin was demonstrated. The dendritic PEG-PDLLA nanoparticles we developed offer greater structural flexibility and provide a novel nanostructured thermoresponsive carrier for drug delivery. PMID:19716444

  12. Directly-Grown Hierarchical Carbon Nanotube@Polypyrrole Core-Shell Hybrid for High-Performance Flexible Supercapacitors.

    PubMed

    Yesi, Yesi; Shown, Indrajit; Ganguly, Abhijit; Ngo, Trung Truc; Chen, Li-Chyong; Chen, Kuei-Hsien

    2016-02-19

    A hierarchical carbon nanotube-polypyrrole (CNT-PPy) core-shell composite was fabricated by growing CNTs directly on carbon cloth (CC) as a skeleton followed by electropolymerization of PPy with controlled polymerization time. Direct fabrication of electroactive (CNT-PPy) materials on the flexible CC electrode could reduce the interfacial resistance between the electrode and electrolyte and improve the ion diffusion. The supercapacitor electrode based on optimized PPy/CNT-CC exhibits excellent electrochemical performance, with the highest gravimetric capacitance being roughly 1038 F g(-1) per active mass of PPy and up to 486.1 F g(-1) per active mass of the PPy/CNT composite. Notably, excellent flexibility and cycle stability up to 10 000 cycles with only 18 % capacitance loss was achieved. At the same time, the fabricated asymmetric supercapacitor (PPy/CNT-CC∥CNT-CC) shows the maximum power density of 10 962 W kg(-1) at an energy density of 3.9 Wh kg(-1) under the operating potential of 1.4 V. The overall high cycle stability and high performance of the fabricated PPy/CNT-CC flexible electrode is due to the novel binder-free direct growth process. PMID:26791424

  13. A core-shell-structured molecularly imprinted polymer on upconverting nanoparticles for selective and sensitive fluorescence sensing of sulfamethazine.

    PubMed

    Tian, Jinghan; Bai, Jialei; Peng, Yuan; Qie, Zhiwei; Zhao, Yufeng; Ning, Baoan; Xiao, Dan; Gao, Zhixian

    2015-08-01

    A core-shell structured molecularly imprinted polymer on upconverting nanoparticles (UCNPs@MIP) was synthesized for the fluorescence (FL) sensing of sulfamethazine (SMZ). Hexagonal UCNPs were synthesized by the solvothermal method, then coated with a thin silica shell and modified with vinyl groups. Finally, surface polymerization was initiated among the vinyl groups, the functional monomers and cross-linking agents by the initiator. The MIP synthesized by this procedure was anchored on the surface of UCNPs, possessed better site accessibility and lower transfer resistance for the target molecule compared to bulk imprinted materials. The obtained UCNPs@MIP showed good binding capacity, fast response, high selectivity and specificity to the SMZ. The FL intensity of the UCNPs@MIP decreased sensitively with the increasing concentration of SMZ in the range of 50-700 ng mL(-1), the detection limit was 34 ng mL(-1) (S/N = 3). The UCNPs@MIP was successfully applied to the detection of SMZ in chicken samples. Thanks to the unique near-infrared (NIR) excitation nature of UCNPs, the chicken meat only needed some simple extraction procedures before FL detection, no complex purifications were required. The average recoveries ranged from 96.01% to 98.90%, with relative standard deviations (RSDs) below 4.5%. This work offers a novel sensing system that combined the advantages of upconverting nanotechnology and molecularly imprinted technology. PMID:26075380

  14. Facile preparation of novel core-shell enzyme-Au-polydopamine-Fe₃O₄ magnetic bionanoparticles for glucosesensor.

    PubMed

    Peng, Hua-Ping; Liang, Ru-Ping; Zhang, Li; Qiu, Jian-Ding

    2013-04-15

    In this study, a novel biomolecule immobilization approach has been proposed to the synthesis of multi-functional core-shell glucose oxidase-Au-polydopamine-Fe₃O₄ magnetic bionanoparticles (GOx-Au-PDA-Fe₃O₄ MBNPs) using the one-pot chemical polymerization method. Then, a high performance biosensor has been constructed by effectively attaching the proposed GOx-Au-PDA-Fe₃O₄ MBNPs to the surface of the magnetic glassy carbon electrode. Scanning electron microscope, energy dispersive x-ray spectrometer, UV-vis spectroscopy, and electrochemical methods were used to characterize the GOx-Au-PDA-Fe₃O₄ MBNPs. The resultant GOx-Au-PDA-Fe₃O₄ MBNPs not only have the magnetism of Fe₃O₄ nanoparticles which makes them easily manipulated by an external magnetic field, but also have the excellent biocompatibility of PDA to maintain the native structure of the GOx, and good conductivity of Au nanoparticles which can facilitate the direct electrochemistry of GOx in the biofilm. Hence, the present GOx-Au-PDA-Fe₃O₄ biofilm displays good linear amperometric response to glucose concentration ranging from 0.02 to 1.875 mM. This efficient biomolecule immobilization platform is recommended for the preparation of many other MBNPs with interesting properties and application potentials in many fields, such as biosensing, biocatalysis, biofuel cells, and bioaffinity separation. PMID:23208101

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  16. One-pot synthesis of hematite@graphene core@shell nanostructures for superior lithium storage

    NASA Astrophysics Data System (ADS)

    Chen, Dezhi; Quan, Hongying; Liang, Junfei; Guo, Lin

    2013-09-01

    Novel hematite@graphene composites have been successfully synthesized by a one-pot surfactant governed approach under mild wet-chemical conditions. A series of characterizations including X-ray diffraction (XRD), Raman spectrum, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that the hematite nanoparticles with relatively uniform size were encapsulated by graphene layers and were able to form core-shell nanostructures. The electrochemical properties of hematite@graphene core-shell nanostructures as anodes for lithium-ion batteries were evaluated by galvanostatic charge-discharge and AC impedance spectroscopy techniques. The as-prepared hematite@graphene core-shell nanostructures exhibited a high reversible specific capacity of 1040 mA h g-1 at a current density of 200 mA g-1 (0.2 C) after 180 cycles and excellent rate capability and long cycle life. Furthermore, a reversible capacity as high as 500 mA h g-1 was still achieved after 200 cycles even at a high rate of 6 C. The electrochemical test results show that the hematite@graphene composites prepared by the one-pot wet chemical method are promising anode materials for lithium-ion batteries.Novel hematite@graphene composites have been successfully synthesized by a one-pot surfactant governed approach under mild wet-chemical conditions. A series of characterizations including X-ray diffraction (XRD), Raman spectrum, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that the hematite nanoparticles with relatively uniform size were encapsulated by graphene layers and were able to form core-shell nanostructures. The electrochemical properties of hematite@graphene core-shell nanostructures as anodes for lithium-ion batteries were evaluated by galvanostatic charge-discharge and AC impedance spectroscopy techniques. The as-prepared hematite@graphene core-shell nanostructures exhibited a high reversible specific capacity of 1040 mA h g-1 at a

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    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&cmb.macr;. 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.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&cmb.macr;. 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

  18. Smart micelle@polydopamine core-shell nanoparticles for highly effective chemo-photothermal combination therapy

    NASA Astrophysics Data System (ADS)

    Zhang, Ruirui; Su, Shishuai; Hu, Kelei; Shao, Leihou; Deng, Xiongwei; Sheng, Wang; Wu, Yan

    2015-11-01

    In this investigation, we have designed and synthesized a novel core-shell polymer nanoparticle system for highly effective chemo-photothermal combination therapy. A nanoscale DSPE-PEG micelle encapsulating doxorubicin (Dox-M) was designed as a core, and then modified by a polydopamine (PDA) shell for photothermal therapy and bortezomib (Btz) administration (Dox-M@PDA-Btz). The facile conjugation of Btz to the catechol-containing PDA shell can form a reversible pH-sensitive boronic acid-catechol conjugate to create a stimuli-responsive drug carrier system. As expected, the micelle@PDA core-shell nanoparticles exhibited satisfactory photothermal efficiency, which has potential for thermal ablation of malignant tissues. In addition, on account of the PDA modification, both Dox and Btz release processes were pH-dependent and NIR-dependent. Both in vitro and in vivo studies illustrated that the Dox-M@PDA-Btz nanoparticles coupled with laser irradiation could enhance the cytotoxicity, and thus combinational therapy efficacy was achieved when integrating Dox, Btz, and PDA into a single nanoplatform. Altogether, our current study indicated that the micelle@polydopamine core-shell nanoparticles could be applied for NIR/pH-responsive sustained-release and synergized chemo-photothermal therapy for breast cancer.In this investigation, we have designed and synthesized a novel core-shell polymer nanoparticle system for highly effective chemo-photothermal combination therapy. A nanoscale DSPE-PEG micelle encapsulating doxorubicin (Dox-M) was designed as a core, and then modified by a polydopamine (PDA) shell for photothermal therapy and bortezomib (Btz) administration (Dox-M@PDA-Btz). The facile conjugation of Btz to the catechol-containing PDA shell can form a reversible pH-sensitive boronic acid-catechol conjugate to create a stimuli-responsive drug carrier system. As expected, the micelle@PDA core-shell nanoparticles exhibited satisfactory photothermal efficiency, which has

  19. Core-shell nanoparticles based on pullulan and poly(β-amino) ester for hepatoma-targeted codelivery of gene and chemotherapy agent.

    PubMed

    Liu, Yuanyuan; Wang, Yan; Zhang, Cong; Zhou, Ping; Liu, Yang; An, Tong; Sun, Duxin; Zhang, Ning; Wang, Yinsong

    2014-01-01

    This study designs a novel nanoparticle system with core-shell structure based on pullulan and poly(β-amino) ester (PBAE) for the hepatoma-targeted codelivery of gene and chemotherapy agent. Plasmid DNA expressing green fluorescent protein (pEGFP), as a model gene, was fully condensed with cationic PBAE to form the inner core of PBAE/pEGFP polycomplex. Methotrexate (MTX), as a model chemotherapy agent, was conjugated to pullulan by ester bond to synthesize polymeric prodrug of MTX-PL. MTX-PL was then adsorbed on the surface of PBAE/pEGFP polycomplex to form MTX-PL/PBAE/pEGFP nanoparticles with a classic core-shell structure. MTX-PL was also used as a hepatoma targeting moiety, because of its specific binding affinity for asialoglycoprotein receptor (ASGPR) overexpressed by human hepatoma HepG2 cells. MTX-PL/PBAE/pEGFP nanoparticles realized the efficient transfection of pEGFP in HepG2 cells and exhibited significant inhibitory effect on the cell proliferation. In HepG2 tumor-bearing nude mice, MTX-PL/PBAE/pEGFP nanoparticles were mainly distributed in the tumor after 24 h postintravenous injection. Altogether, this novel codelivery system with a strong hepatoma-targeting property achieved simultaneous delivery of gene and chemotherapy agent into tumor at both cellular and animal levels. PMID:25289563

  20. Synthesis and characterization of surface-enhanced Raman scattering tags with Ag/SiO2 core-shell nanostructures using reverse micelle technology.

    PubMed

    Gong, Ji-Lai; Jiang, Jian-Hui; Liang, Yi; Shen, Guo-Li; Yu, Ru-Qin

    2006-06-15

    A novel simplified method for synthesis of surface-enhanced Raman scattering tags has been reported. This synthesis method is based on reverse micelle technique using Igepal CO-520 as a surfactant and the mixed solution of silver nitrate and rhodamine dyes with isothiocyanate group as water pool followed by hydrazine hydrate reduction and TEOS polymerization leading to the formation of silica layer surrounding the silver core. Compared to the method reported in literature, the proposed methodology eliminates the necessity of vitrophilic pretreatment and makes it possible to complete all different processes including the preparation of silver nanoparticles, the conjugation of dye molecules and the formation of silica shell in the microreactor. The nanoparticle-based surface-enhanced Raman tags obtained are composed of silver core conjugated with rhodamine dyes and an encasing silica shell. Both the dyes themselves and the Ag/SiO2 core-shell nanoparticles without the encapsulation of dyes exhibit no Raman signals. However, the Ag/SiO2 core-shell nanoparticles exhibit strong Raman signals when encapsulated with these dyes. This is due to the appearance of fluorescence quenching and surface-enhanced Raman scattering effect resulting from the conjugation of dyes and silver core. The Raman tags were characterized using transmission electron microscopy (TEM), UV-visible absorption spectrometry, and Raman spectrometry. PMID:16457836

  1. Preparation of monodisperse polystyrene/silica core-shell nano-composite abrasive with controllable size and its chemical mechanical polishing performance on copper

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Wang, Haibo; Zhang, Zefang; Qin, Fei; Liu, Weili; Song, Zhitang

    2011-11-01

    Monodisperse silica-coated polystyrene (PS) nano-composite abrasives with controllable size were prepared via a two-step process. Monodisperse positively charged PS colloids were synthesized via polymerization of styrene by using a cationic initiator. In the subsequent coating process, silica formed shell on the surfaces of core PS particles via the ammonia-catalyzed hydrolysis and condensation of tetraethoxysilane. Neither centrifugation/water wash/redispersion cycle process nor surface modification or addition surfactant was needed in the whole process. The morphology of the abrasives was characterized by scanning electron microscope. Transmission electron microscope and energy dispersive X-ray analysis results indicated that silica layer was successfully coated onto the surfaces of PS particles. Composite abrasive has a core-shell structure and smooth surface. The chemical mechanical polishing performances of the composite abrasive and conventional colloidal silica abrasive on blanket copper wafers were investigated. The root mean square roughness decreases from 4.27 nm to 0.56 nm using composite abrasive. The PS/SiO2 core-shell composite abrasives exhibited little higher material removal rate than silica abrasives.

  2. Novel ferroferric oxide/polystyrene/silver core-shell magnetic nanocomposite microspheres as regenerable substrates for surface-enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Liu, Bo; Bai, Chong; Zhao, Dan; Liu, Wei-Liang; Ren, Man-Man; Liu, Qin-Ze; Yang, Zhi-Zhou; Wang, Xin-Qiang; Duan, Xiu-Lan

    2016-02-01

    A novel Ag-coated Fe3O4@Polystyrene core-shell microsphere has been designed via fabrication of Fe3O4@Polystyrene core-shell magnetic microsphere through a seed emulsion polymerization, followed by deposition of Ag nanoparticles using in-situ reduction method. Such magnetic microspheres can be utilized as sensitive surface-enhanced Raman scattering (SERS) substrates, using Rhodamine 6G (R6G) as a probe molecule, with both stable and reproducible performances. The SERS detection limit of R6G decreased to 1 × 10-10 M and the enhancement factor of this substrate on the order of 106 was obtained. In addition, owing to possessing excellent magnetic properties, the resultant microspheres could be separated rapidly by an external magnetic field and utilized repeatedly for three times at least. Therefore, the unique renewable property suggests a new route to eliminate the single-use problem of traditional SERS substrates and will be promising for the practical application.

  3. Core-shell-structured silica/polyacrylate particles prepared by Pickering emulsion: influence of the nucleation model on particle interfacial organization and emulsion stability

    PubMed Central

    2014-01-01

    This work reports a new evidence of the versatility of silica sol as a stabilizer for Pickering emulsions. The organization of silica particles at the oil-water interface is a function of the nucleation model. The present results show that nucleation model, together with monomer hydrophobicity, can be used as a trigger to modify the packing density of silica particles at the oil-water interface: Less hydrophobic methylmethacrylate, more wettable with silica particles, favors the formation of core-shell-structured composite when the composite particles are prepared by miniemulsion polymerization in which monomers are fed in batch (droplet nucleation). By contrast, hydrophobic butylacrylate promotes the encapsulating efficiency of silica when monomers are fed dropwise (homogeneous nucleation). The morphologies of polyacrylate-nano-SiO2 composites prepared from different feed ratio of methylmethacrylate/butylacrylate (with different hydrophobicity) and by different feed processes are characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques. The results from SEM and TEM show that the morphologies of the as-prepared polyacrylate/nano-SiO2 composite can be a core-shell structure or a bare acrylic sphere. The stability of resulting emulsions composed of these composite particles is strongly dependent on the surface coverage of silica particles. The emulsion stability is improved by densely silica-packed composite particles. PMID:25313299

  4. Scalable synthesis of core-shell structured SiOx/nitrogen-doped carbon composite as a high-performance anode material for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Shi, Lu; Wang, Weikun; Wang, Anbang; Yuan, Keguo; Jin, Zhaoqing; Yang, Yusheng

    2016-06-01

    In this work, a novel core-shell structured SiOx/nitrogen-doped carbon composite has been prepared by simply dispersing the SiOx particles, which are synthesized by a thermal evaporation method from an equimolar mixture of Si and SiO2, into the dopamine solution, followed by a carbonization process. The SiOx core is well covered by the conformal and homogeneous nitrogen-doped carbon layer from the pyrolysis of polydopamine. By contrast with the bare SiOx, the electrochemical performance of the as-prepared core-shell structured SiOx/nitrogen-doped carbon composite has been improved significantly. It delivers a reversible capacity of 1514 mA h g-1 after 100 cycles at a current density of 100 mA g-1 and 933 mA h g-1 at 2 A g-1, much higher than those of commercial graphite anodes. The nitrogen-doped carbon layer ensures the excellent electrochemical performance of the SiOx/C composite. In addition, since dopamine can self-polymerize and coat virtually any surface, this versatile, facile and highly efficient coating process may be widely applicable to obtain various composites with uniform nitrogen-doped carbon coating layer.

  5. Investigation of linear optical absorption coefficients in core-shell quantum dot (QD) luminescent solar concentrators (LSCs)

    NASA Astrophysics Data System (ADS)

    Ebrahimipour, Bahareh Alsadat; Askari, Hassan Ranjbar; Ramezani, Ali Behjat

    2016-09-01

    The interlevel absorption coefficient of CdSe/ZnS and ZnS/CdSe core-shell Quantum Dot (QD) in luminescent solar concentrators (LSCs) is reported. By considering the quantum confinement effects, the wave functions and eigenenergies of electrons in the nonperturebative system consists of a core-shell QD have been numerically calculated under the frame work of effective-mass approximation by solving a three-dimensional Schrӧdinger equation. And then the absorption coefficient is obtained under density matrix approximation considering in the polymer sheets of the concentrator including the core-shell QDs. The effect of the hetero-structure geometry upon the energy spectrum and absorption coefficient associated to interlevel transitions was also considered. The results show that the core-shell QDs can absorb the photons with higher energy in solar spectrum as compared to the inverted core-shell. And with a small shell layer diameter, the core-shell QDs produce larger linear absorption coefficients and consequently higher efficiency values, however it is inversed for inverted core-shell QDs. The work described here gives a detailed insight into the promise of QD-based LSCs and the optoelectronic devices applications.

  6. Au@Ag core/shell cuboids and dumbbells: Optical properties and SERS response

    NASA Astrophysics Data System (ADS)

    Khlebtsov, Boris N.; Liu, Zhonghui; Ye, Jian; Khlebtsov, Nikolai G.

    2015-12-01

    Recent studies have conclusively shown that the plasmonic properties of Au nanorods can be finely controlled by Ag coating. Here, we investigate the effect of asymmetric silver overgrowth of Au nanorods on their extinction and surface-enhanced Raman scattering (SERS) properties for colloids and self-assembled monolayers. Au@Ag core/shell cuboids and dumbbells were fabricated through a seed-mediated anisotropic growth process, in which AgCl was reduced by use of Au nanorods with narrow size and shape distribution as seeds. Upon tailoring the reaction rate, monodisperse cuboids and dumbbells were synthesized and further transformed into water-soluble powders of PEGylated nanoparticles. The extinction spectra of AuNRs were in excellent agreement with T-matrix simulations based on size and shape distributions of randomly oriented particles. The multimodal plasmonic properties of the Au@Ag cuboids and dumbbells were investigated by comparing the experimental extinction spectra with finite-difference time-domain (FDTD) simulations. The SERS efficiencies of the Au@Ag cuboids and dumbbells were compared in two options: (1) individual SERS enhancers in colloids and (2) self-assembled monolayers formed on a silicon wafer by drop casting of nanopowder solutions mixed with a drop of Raman reporters. By using 1,4-aminothiophenol Raman reporter molecules, the analytical SERS enhancement factor (AEF) of the colloidal dumbbells was determined to be 5.1×106, which is an order of magnitude higher than the AEF=4.0×105 for the cuboids. This difference can be explained by better fitting of the dumbbell plasmon resonance to the excitation laser wavelength. In contrast to the colloidal measurements, the AEF=5×107 of self-assembled cuboid monolayers was almost twofold higher than that for dumbbell monolayers, as determined with rhodamine 6G Raman reporters. According to TEM data and electromagnetic simulations, the better SERS response of the self-assembled cuboids is due to uniform

  7. Facile synthesis 3D flexible core-shell graphene/glass fiber via chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Yang, Cheng; Xu, Yuanyuan; Zhang, Chao; Sun, Zhencui; Chen, Chuansong; Li, Xiuhua; Jiang, Shouzhen; Man, Baoyuan

    2014-08-01

    Direct deposition of graphene layers on the flexible glass fiber surface to form the three-dimensional (3D) core-shell structures is offered using a two-heating reactor chemical vapor deposition system. The two-heating reactor is utilized to offer sufficient, well-proportioned floating C atoms and provide a facile way for low-temperature deposition. Graphene layers, which are controlled by changing the growth time, can be grown on the surface of wire-type glass fiber with the diameter from 30 nm to 120 um. The core-shell graphene/glass fiber deposition mechanism is proposed, suggesting that the 3D graphene films can be deposited on any proper wire-type substrates. These results open a facile way for direct and high-efficiency deposition of the transfer-free graphene layers on the low-temperature dielectric wire-type substrates.

  8. Core-shell nanoparticles as scavengers for hydrophobic molecules in biological systems

    NASA Astrophysics Data System (ADS)

    Wong, Jeffrey

    2005-11-01

    Core-shell nanoparticles containing hydrophobic cores and hydrophilic shells were synthesized based on a tertiary microemulsion system. Due to their hydrophobic interior, this system is proposed to work as a scavenger of non polar species, like pesticides or drugs present in concentrations higher than what the body can tolerate. The ability to control the core and shell sizes using different molecules to fill the core was studied with different techniques. Hydrophobic fluorescent dyes were used as model non polar molecules to study the uptake abilities of the system synthesized. Derivatization of the surface of the core-shell particles with different groups, including biotin and poly(ethylene glycol) was performed to improve the biocompatibility of the system. Binding to streptavidin via the biotin units on the surface was performed to study the biocompatibility of the derivatized nanocapsules in biological relevant systems.

  9. Green synthesis and surface properties of Fe3O4@SA core-shell nanocomposites

    NASA Astrophysics Data System (ADS)

    Cao, Huimin; Li, Juchuan; Shen, Yuhua; Li, Shikuo; Huang, Fangzhi; Xie, Anjian

    2014-05-01

    In this paper, a one-step, economic and green approach was explored to prepare Fe3O4 nanoparticles by using L-cysteine as reducer and disperser without any inert gas protection. The Fe3O4 nanoparticles were then modified with stearic acid (SA) to form Fe3O4@SA core-shell nanocomposites. The experiment results indicate that the core-shell nanocomposites prepared could form monolayer on the water surface or films by means of Langmuir-Blodgett (LB) technology due to their hydrophobic and lipophilic properties. Also the composites exhibit paramagnetism, which make product dispersed stably in the oil medium to form magnetic fluid. Moreover, they are developed as sorbents to remove oil from water surface.

  10. Effect of guided resonance modes on emission from GaN core-shell nanorod arrays

    NASA Astrophysics Data System (ADS)

    Anderson, P. Duke; Lin, Chenxi; Povinelli, Michelle L.

    2014-12-01

    We model the process of incoherent emission from quantum wells in GaN core-shell nanorod arrays using finite-difference time-domain simulations. We find that high-intensity features in the emitted field correspond to guided resonance modes near the -point of the photonic band structure. We identify one -point mode whose electric field intensity profile is ideal for core-shell nanorod array geometries. Using this mode, we are able to simultaneously enhance the radiative recombination rate and extraction efficiency relative to an in-filled slab. We determine the conditions on radiative and nonradiative recombination rates for which the nanorod array has a higher internal and external quantum efficiency than a reference slab. We present one nanorod array geometry where the external quantum efficiency is enhanced up to a factor of 25.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Yang, Chungja

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

  13. Core-shell-type magnetic mesoporous silica nanocomposites for bioimaging and therapeutic agent delivery.

    PubMed

    Wang, Yao; Gu, Hongchen

    2015-01-21

    Advances in nanotechnology and nanomedicine offer great opportunities for the development of nanoscaled theranostic platforms. Among various multifunctional nanocarriers, magnetic mesoporous silica nanocomposites (M-MSNs) attract prominent research interest for their outstanding properties and potential biomedical applications. This Research News article highlights recent progress in the design of core-shell-type M-MSNs for both diagnostic and therapeutic applications. First, an overview of synthetic strategies for three representative core-shell-type M-MSNs with different morphologies and structures is presented. Then, the diagnostic functions of M-MSNs is illustrated for magnetic resonance imaging (MRI) applications. Next, magnetic targeted delivery and stimuli-responsive release of drugs, and effective package of DNA/siRNA inside mesopores using M-MSNs as therapeutic agent carriers are discussed. The article concludes with some important challenges that need to be overcome for further practical applications of M-MSNs in nanomedicine. PMID:25238634

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

    PubMed

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

    2016-03-01

    We report the synthesis of plasmonic Cu2-x Se@ZnS core@shell nanoparticles (NPs). We used a shell growth approach, starting from Cu2-x Se NPs that have been shown before to exhibit a localized surface plasmon resonance (LSPR). By careful synthesis planning we avoided cation exchange reactions and received core@shell nanoparticles that, after oxidation under air, exhibit a strong LSPR in the NIR. Interestingly, the crystalline, closed ZnS shell that we grew with variable thickness still allowed a slow oxidation of the core under ambient conditions, while the core was effectively protected from reduction, even in the presence of reducing agents such as borane tert-butyamine complex and diisobutylaluminum hydride, giving rise to a stable particle LSPR, also under strongly reducing conditions. PMID:26604183

  15. Structural investigations of core-shell nanowires using grazing incidence X-ray diffraction.

    PubMed

    Keplinger, Mario; Mårtensson, Thomas; Stangl, Julian; Wintersberger, Eugen; Mandl, Bernhard; Kriegner, Dominik; Holý, Václav; Bauer, Günther; Deppert, Knut; Samuelson, Lars

    2009-05-01

    The fabrication of core-shell structures is crucial for many nanowire device concepts. For the proper tailoring of their electronic properties, control of structural parameters such as shape, size, diameter of core and shell, their chemical composition, and information on their strain fields is mandatory. Using synchrotron X-ray diffraction studies and finite element simulations, we determined the chemical composition, dimensions, and strain distribution for series of InAs/InAsP core-shell wires grown on Si(111) with systematically varied growth parameters. In particular we detect initiation of plastic relaxation of these structures with increasing shell thickness and/or increasing phosphorus content. We establish a phase diagram, defining the region of parameters leading to pseudomorphic nanowire growth. This is important to avoid extended defects which are detrimental for their electronic properties. PMID:19320494

  16. Surface mode hybridization in the optical response of core-shell particles

    NASA Astrophysics Data System (ADS)

    Thiessen, E.; Heinisch, R. L.; Bronold, F. X.; Fehske, H.

    2016-03-01

    We present an exact rewriting of the Mie coefficients describing the scattering of light by a spherical core-shell particle which enables their interpretation in terms of a hybridization of the two surface modes arising, respectively, at the core-shell and the shell-medium interface. For this particular case, we thus obtain from the Mie theory—analytically for all multipole orders and hence for arbitrarily sized particles—the hybridization scenario, which so far has been employed primarily for small particles in the electrostatic approximation. To demonstrate the strength of the rewriting approach, we also extract the hybridization scenario for a stratified sphere directly from the expansion coefficients for the electromagnetic fields.

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

    PubMed Central

    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

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

    PubMed

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

    2014-02-20

    High-energy-density rechargeable batteries are needed to fulfill various demands such as self-monitoring analysis and reporting technology (SMART) devices, energy storage systems, and (hybrid) electric vehicles. As a result, high-energy electrode materials enabling a long cycle life and reliable safety need to be developed. To ensure these requirements, new material chemistries can be derived from combinations of at least two compounds in a secondary particle with varying chemical composition and primary particle morphologies having a core-shell structure and spherical cathode-active materials, specifically a nanoparticle core and shell, nanoparticle core and nanorod shell, and nanorod core and shell. To this end, several layer core-shell cathode materials were developed to ensure high capacity, reliability, and safety. PMID:26270835

  19. The preparation and properties of monodisperse core-shell silica magnetic microspheres.

    PubMed

    Lou, Min-yi; Jia, Qiu-ling; Wang, De-ping; Liu, Bing; Huang, Wen-hai

    2008-01-01

    The monodisperse core-shell silica magnetic microspheres (MMS) were synthesized by sol-gel method gelling in the emulsion. Optical microscope (OM), field emission scanning electron microscope (FESEM), nitrogen adsorption and desorption Brunauer Emmett Teller Procedure (BET) isotherms and Barrett-Joyner-Halenda (BJH) pore size distribution measurements, X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and vibrating sample magnetometer (VSM) were used to characterize the appearance, size distribution, phase, specific surface area, chemical composition and magnetic property of silica MMS. The results showed that silica MMS prepared through sol-gel method with acid-alkali two-step catalyze and gelling in emulsion exhibited the superior core-shell structure and size distribution of the microspheres concentrated in about 20 mum. The main phase of microspheres was amorphous silica and spinel ferroferric oxide. Meanwhile, the microspheres remained the superparamagnetic behavior and could be used as biomaterials. PMID:17597357

  20. The Core-Shell Approach to Formation of Ordered Nanoporous Materials

    SciTech Connect

    Chang, Jeong H.; Wang, Li Q.; Shin, Yongsoon; Jeong, Byeongmoon; Birnbaum, Jerome C.; Exarhos, Gregory J.

    2002-03-04

    This work describes a novel core-shell approach for the preparation of ordered nanoporous ceramic materials that involve a self-assembly process at the molecular level using MPEG-b-PDLLA bloack copolymers. This approach provides for rapid self-assembly and structural reorganization at room temperature. Selected MPEG-b-PDLLA block copolymers were synthesized with systematic variation of the chain lengths of the resident hydrophilic and hydrophobic blocks. This allows the micelle size to be systematically varied. Results from this work are used to understand the formation mechanism of nanoporous structures in which the pore size and wall thickness are closely dependent on the size of hydrophobic cores and hydrophilic shells of the block copolymer templates. The core-shell mechanism for nanoporous structure evolution is based on the size and contrasting micellar packing arrangements that are controlled by the copolymer.

  1. Controlled Growth of Ordered III-Nitride Core-Shell Nanostructure Arrays for Visible Optoelectronic Devices

    NASA Astrophysics Data System (ADS)

    Rishinaramangalam, Ashwin K.; Ul Masabih, Saadat Mishkat; Fairchild, Michael N.; Wright, Jeremy B.; Shima, Darryl M.; Balakrishnan, Ganesh; Brener, Igal; Brueck, S. R. J.; Feezell, Daniel F.

    2015-05-01

    We demonstrate the growth of ordered arrays of nonpolar core-shell nanowalls and semipolar core-shell pyramidal nanostripes on c-plane (0001) sapphire substrates using selective-area epitaxy and metal organic chemical vapor deposition. The nanostructure arrays are controllably patterned into LED mesa regions, demonstrating a technique to impart secondary lithography features into the arrays. We study the dependence of the nanostructure cores on the epitaxial growth conditions and show that the geometry and morphology are strongly influenced by growth temperature, V/III ratio, and pulse interruption time. We also demonstrate the growth of InGaN quantum well shells on the nanostructures and characterize the structures by using micro-photoluminescence and cross-section scanning tunneling electron microscopy.

  2. Intraband Luminescence from HgSe/CdS Core/Shell Quantum Dots.

    PubMed

    Deng, Zhiyou; Guyot-Sionnest, Philippe

    2016-02-23

    HgSe/CdS core/shell CQD are synthesized, and the changes in the optical absorption and luminescence are investigated. While HgSe quantum dots are naturally n-doped after synthesis, both as colloidal solutions and as films, the HgSe/CdS core/shell dots in solution lose the n-doping, as seen from the optical absorption in solution. However, n-doping is regained in films, and the intraband luminescence of the films of HgSe/CdS is greater than that of the cores. The shell also vastly improves the stability of the quantum dots films against sintering at 200 °C. After annealing at that temperature, the HgSe/CdS films retain a narrow intraband emission and sustain a higher laser power leading to brighter emission at 5 μm. PMID:26820380

  3. Template-Directed Synthesis of Porous and Protective Core-Shell Bionanoparticles.

    PubMed

    Li, Shaobo; Dharmarwardana, Madushani; Welch, Raymond P; Ren, Yixin; Thompson, Christina M; Smaldone, Ronald A; Gassensmith, Jeremiah J

    2016-08-26

    Metal-organic frameworks (MOFs) are promising high surface area coordination polymers with tunable pore structures and functionality; however, a lack of good size and morphological control over the as-prepared MOFs has persisted as an issue in their application. Herein, we show how a robust protein template, tobacco mosaic virus (TMV), can be used to regulate the size and shape of as-fabricated MOF materials. We were able to obtain discrete rod-shaped TMV@MOF core-shell hybrids with good uniformity, and their diameters could be tuned by adjusting the synthetic conditions, which can also significantly impact the stability of the core-shell composite. More interestingly, the virus particle underneath the MOF shell can be chemically modified using a standard bioconjugation reaction, showing mass transportation within the MOF shell. PMID:27485579

  4. TiN/VN composites with core/shell structure for supercapacitors

    SciTech Connect

    Dong, Shanmu; Chen, Xiao; Gu, Lin; Zhou, Xinhong; Wang, Haibo; Liu, Zhihong; Han, Pengxian; Yao, Jianhua; Wang, Li; Cui, Guanglei; Chen, Liquan

    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.

  5. Freestanding three-dimensional core-shell nanoarrays for lithium-ion battery anodes.

    PubMed

    Tan, Guoqiang; Wu, Feng; Yuan, Yifei; Chen, Renjie; Zhao, Teng; Yao, Ying; Qian, Ji; Liu, Jianrui; Ye, Yusheng; Shahbazian-Yassar, Reza; Lu, Jun; Amine, Khalil

    2016-01-01

    Structural degradation and low conductivity of transition-metal oxides lead to severe capacity fading in lithium-ion batteries. Recent efforts to solve this issue have mainly focused on using nanocomposites or hybrids by integrating nanosized metal oxides with conducting additives. Here we design specific hierarchical structures and demonstrate their use in flexible, large-area anode assemblies. Fabrication of these anodes is achieved via oxidative growth of copper oxide nanowires onto copper substrates followed by radio-frequency sputtering of carbon-nitride films, forming freestanding three-dimensional arrays with core-shell nano-architecture. Cable-like copper oxide/carbon-nitride core-shell nanostructures accommodate the volume change during lithiation-delithiation processes, the three-dimensional arrays provide abundant electroactive zones and electron/ion transport paths, and the monolithic sandwich-type configuration without additional binders or conductive agents improves energy/power densities of the whole electrode. PMID:27256920

  6. Potential of electrospun core-shell structured gelatin-chitosan nanofibers for biomedical applications.

    PubMed

    Jalaja, K; Naskar, Deboki; Kundu, Subhas C; James, Nirmala R

    2016-01-20

    Coaxial electrospinning is an upcoming technology that has emerged from the conventional electrospinning process in order to realize the production of nanofibers of less spinnable materials with potential applications. The present work focuses on the production of chitosan nanofibers in a benign route, using natural polymer as core template, mild solvent system and naturally derived cross-linkers. Nanofibers with chitosan as shell are fabricated by coaxial electrospinning with highly spinnable gelatin as core using aqueous acetic acid as solvent. For maintaining the biocompatibility and structural integrity of the core-shell nanofibers, cross-linking is carried out using naturally derived cross-linking agents, dextran aldehyde and sucrose aldehyde. The biological evaluation of gelatin/chitosan mat is carried out using human osteoblast like cells. The results show that the cross-linked core-shell nanofibers are excellent matrices for cell adhesion and proliferation. PMID:26572452

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

    SciTech Connect

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

    2007-04-24

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

  8. Transforming powder mechanical properties by core/shell structure: compressible sand.

    PubMed

    Shi, Limin; Sun, Changquan Calvin

    2010-11-01

    Some active pharmaceutical ingredients possess poor mechanical properties and are not suitable for tableting. Using fine sand (silicon dioxide), we show that a core/shell structure, where a core particle (sand) is coated with a thin layer of polyvinylpyrrolidone (PVP), can profoundly improve powder compaction properties. Sand coated with 5% PVP could be compressed into intact tablets. Under a given compaction pressure, tablet tensile strength increases dramatically with the amount of coating. This is in sharp contrast to poor compaction properties of physical mixtures, where intact tablets cannot be made when PVP content is 20% or less. The profoundly improved tabletability of core/shell particles is attributed to the formation of a continuous three-dimensional bonding network in the tablet. PMID:20845444

  9. The composition-dependent mechanical properties of Ge/Si core shell nanowires

    NASA Astrophysics Data System (ADS)

    Liu, X. W.; Hu, J.; Pan, B. C.

    2008-09-01

    The Stillinger-Weber potential is used to study the composition-dependent Young's modulus for Ge-core/Si-shell and Si-core/Ge-shell nanowires. Here, the composition is defined as a ratio of the number of atoms of the core to the number of atoms of a core-shell nanowire. For each concerned Ge-core/Si-shell nanowire with a specified diameter, we find that its Young's modulus increases to a maximal value and then decreases as the composition increases. Whereas Young's modulus of the Si-core/Ge-shell nanowires increase nonlinearly in a wide compositional range. Our calculations reveal that these observed trends of Young's modulus of core-shell nanowires are essentially attributed to the different components of the cores and the shells, as well as the different strains in the interfaces between the cores and the shells.

  10. Freestanding three-dimensional core-shell nanoarrays for lithium-ion battery anodes

    NASA Astrophysics Data System (ADS)

    Tan, Guoqiang; Wu, Feng; Yuan, Yifei; Chen, Renjie; Zhao, Teng; Yao, Ying; Qian, Ji; Liu, Jianrui; Ye, Yusheng; Shahbazian-Yassar, Reza; Lu, Jun; Amine, Khalil

    2016-06-01

    Structural degradation and low conductivity of transition-metal oxides lead to severe capacity fading in lithium-ion batteries. Recent efforts to solve this issue have mainly focused on using nanocomposites or hybrids by integrating nanosized metal oxides with conducting additives. Here we design specific hierarchical structures and demonstrate their use in flexible, large-area anode assemblies. Fabrication of these anodes is achieved via oxidative growth of copper oxide nanowires onto copper substrates followed by radio-frequency sputtering of carbon-nitride films, forming freestanding three-dimensional arrays with core-shell nano-architecture. Cable-like copper oxide/carbon-nitride core-shell nanostructures accommodate the volume change during lithiation-delithiation processes, the three-dimensional arrays provide abundant electroactive zones and electron/ion transport paths, and the monolithic sandwich-type configuration without additional binders or conductive agents improves energy/power densities of the whole electrode.

  11. Picomolar detection of mercuric ions by means of gold-silver core-shell nanorods

    NASA Astrophysics Data System (ADS)

    Chen, Shouhui; Liu, Dingbin; Wang, Zhihua; Sun, Xiaolian; Cui, Daxiang; Chen, Xiaoyuan

    2013-07-01

    We report an ultrasensitive and selective probe for detection of mercuric ions using gold-silver core-shell nanorods as the substrate of surface-enhanced Raman scattering. The detection limit of this probe for mercuric ions can be as low as 1 pM. The efficiency of this probe in complex samples was evaluated by allowing detection of spiked mercuric ions in river water and fish samples.We report an ultrasensitive and selective probe for detection of mercuric ions using gold-silver core-shell nanorods as the substrate of surface-enhanced Raman scattering. The detection limit of this probe for mercuric ions can be as low as 1 pM. The efficiency of this probe in complex samples was evaluated by allowing detection of spiked mercuric ions in river water and fish samples. Electronic supplementary information (ESI) available: See DOI: 10.1039/c3nr01603j

  12. General Method for the Synthesis of Ultrastable Core/Shell Quantum Dots by Aluminum Doping.

    PubMed

    Li, Zhichun; Yao, Wei; Kong, Long; Zhao, Yixin; Li, Liang

    2015-10-01

    Semiconductor quantum dots (QDs) have attracted extensive attention in various applications because of their unique optical and electronic properties. However, long-term photostability remains a challenge for their practical application. Here, we present a simple method to enhance the photostability of QDs against oxidation by doping aluminum into the shell of core/shell QDs. We demonstrate that Al in the coating shell can be oxidized to Al2O3, which can serve as a self-passivation layer on the surface of the core/shell QDs and effectively stop further photodegradation during long-term light irradiation. The prepared CdSe/CdS:Al QDs survived 24 h without significant degradation when they were subjected to intense illumination under LED light (450 nm, 0.35 W/cm(2)), whereas conventional CdSe/CdS QDs were bleached within 3 h. PMID:26389704

  13. Palladium–platinum core-shell icosahedra with substantially enhanced activity and durability towards oxygen reduction

    SciTech Connect

    Wang, Xue; Choi, Sang-Il; Roling, Luke T.; Luo, Ming; Ma, Cheng; Zhang, Lei; Chi, Miaofang; Liu, Jingyue; Xie, Zhaoxiong; Herron, Jeffrey A.; Mavrikakis, Manos; Xia, Younan

    2015-07-02

    Conformal deposition of platinum as ultrathin shells on facet-controlled palladium nanocrystals offers a great opportunity to enhance the catalytic performance while reducing its loading. Here we report such a system based on palladium icosahedra. Owing to lateral confinement imposed by twin boundaries and thus vertical relaxation only, the platinum overlayers evolve into a corrugated structure under compressive strain. For the core-shell nanocrystals with an average of 2.7 platinum overlayers, their specific and platinum mass activities towards oxygen reduction are enhanced by eight- and sevenfold, respectively, relative to a commercial catalyst. Density functional theory calculations indicate that the enhancement can be attributed to the weakened binding of hydroxyl to the compressed platinum surface supported on palladium. After 10,000 testing cycles, the mass activity of the core-shell nanocrystals is still four times higher than the commercial catalyst. Ultimately, these results demonstrate an effective approach to the development of electrocatalysts with greatly enhanced activity and durability.

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

    NASA Astrophysics Data System (ADS)

    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.

  15. Palladium-platinum core-shell icosahedra with substantially enhanced activity and durability towards oxygen reduction

    NASA Astrophysics Data System (ADS)

    Wang, Xue; Choi, Sang-Il; Roling, Luke T.; Luo, Ming; Ma, Cheng; Zhang, Lei; Chi, Miaofang; Liu, Jingyue; Xie, Zhaoxiong; Herron, Jeffrey A.; Mavrikakis, Manos; Xia, Younan

    2015-07-01

    Conformal deposition of platinum as ultrathin shells on facet-controlled palladium nanocrystals offers a great opportunity to enhance the catalytic performance while reducing its loading. Here we report such a system based on palladium icosahedra. Owing to lateral confinement imposed by twin boundaries and thus vertical relaxation only, the platinum overlayers evolve into a corrugated structure under compressive strain. For the core-shell nanocrystals with an average of 2.7 platinum overlayers, their specific and platinum mass activities towards oxygen reduction are enhanced by eight- and sevenfold, respectively, relative to a commercial catalyst. Density functional theory calculations indicate that the enhancement can be attributed to the weakened binding of hydroxyl to the compressed platinum surface supported on palladium. After 10,000 testing cycles, the mass activity of the core-shell nanocrystals is still four times higher than the commercial catalyst. These results demonstrate an effective approach to the development of electrocatalysts with greatly enhanced activity and durability.

  16. On axisymmetric/diamond-like mode transitions in axially compressed core-shell cylinders

    NASA Astrophysics Data System (ADS)

    Xu, Fan; Potier-Ferry, Michel

    2016-09-01

    Recent interests in curvature- and stress-induced pattern formation and pattern selection motivate the present study. Surface morphological wrinkling of a cylindrical shell supported by a soft core subjected to axial compression is investigated based on a nonlinear 3D finite element model. The post-buckling behavior of core-shell cylinders beyond the first bifurcation often leads to complicated responses with surface mode transitions. The proposed finite element framework allows predicting and tracing these bifurcation portraits from a quantitative standpoint. The occurrence and evolution of 3D instability modes including sinusoidally deformed axisymmetric patterns and non-axisymmetric diamond-like modes will be highlighted according to critical dimensionless parameters. Besides, the phase diagram obtained from dimensional analyses and numerical results could be used to guide the design of core-shell cylindrical systems to achieve the desired instability patterns.

  17. Tuning biexciton binding and antibinding in core/shell quantum dots

    NASA Astrophysics Data System (ADS)

    McDonald, Peter G.; Tyrrell, Edward J.; Shumway, John; Smith, Jason M.; Galbraith, Ian

    2012-09-01

    We use a path integral quantum Monte Carlo method to simulate excitons and biexcitons in core/shell nanocrystals with Type-I, Type-II, and quasi-Type-II band alignments. Quantum Monte Carlo techniques allow for all quantum correlations to be included when determining the thermal ground state, thus producing accurate predictions of biexciton binding. These subtle quantum correlations are found to cause the biexciton to be binding with Type-I carrier localization and strongly antibinding with Type-II carrier localization, in agreement with experiment for both core/shell nanocrystals and dot in rod nanocrystal structures. Simple treatments based on perturbative approaches are shown to miss this important transition in the biexciton binding. Understanding these correlations offers prospects to engineer strong biexciton antibinding, which is crucial to the design of nanocrystals for single-exciton lasing applications.

  18. Organic phase synthesis of noble metal-zinc chalcogenide core-shell nanostructures.

    PubMed

    Kumar, Prashant; Diab, Mahmud; Flomin, Kobi; Rukenstein, Pazit; Mokari, Taleb

    2016-10-15

    Multi-component nanostructures have been attracting tremendous attention due to their ability to form novel materials with unique chemical, optical and physical properties. Development of hybrid nanostructures that are composed of metal-semiconductor components using a simple approach is of interest. Herein, we report a robust and general organic phase synthesis of metal (Au or Ag)-Zinc chalcogenide (ZnS or ZnSe) core-shell nanostructures. This synthetic protocol also enabled the growth of more compositionally complex nanostructures of Au-ZnSxSe1-x alloys and Au-ZnS-ZnSe core-shell-shell. The optical and structural properties of these hybrid nanostructures are also presented. PMID:27428852

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

    DOE PAGESBeta

    Jiang, Xingmao; Jiang, Ying-Bing; Liu, Nanguo; Xu, Huifang; Rathod, Shailendra; Shah, Pratik; Brinker, C. Jeffrey

    2011-01-01

    Ceriumore » m (Ce) corrosion inhibitors were encapsulated into hexagonally ordered nanoporous silica particles via single-step aerosol-assisted self-assembly. The core/shell structured particles are effective for corrosion inhibition of aluminum alloy AA2024-T3. Numerical simulation proved that the core-shell nanostructure delays the release process. The effective diffusion coefficient elucidated from release data for monodisperse particles in water was 1.0 × 10 − 14  m 2 s for Ce 3+ compared to 2.5 × 10 − 13  m 2 s for NaCl. The pore size, pore surface chemistry, and the inhibitor solubility are crucial factors for the application. Microporous hydrophobic particles encapsulating a less soluble corrosion inhibitor are desirable for long-term corrosion inhibition.« less

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

    SciTech Connect

    Roth, R; Navratil, P

    2007-05-22

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

  1. Combination chemotherapy using core-shell nanoparticles through the self-assembly of HPMA-based copolymers and degradable polyester.

    PubMed

    Jäger, Eliézer; Jäger, Alessandro; Chytil, Petr; Etrych, Tomáš; Ríhová, Blanka; Giacomelli, Fernando Carlos; Stěpánek, Petr; Ulbrich, Karel

    2013-01-28

    The preparation of core-shell polymeric nanoparticles simultaneously loaded with docetaxel (DTXL) and doxorubicin (DOX) is reported herein. The self-assembly of the aliphatic biodegradable copolyester PBS/PBDL (poly(butylene succinate-co-butylene dilinoleate)) and HPMA-based copolymers (N-(2-hydroxypropyl)methacrylamide-based copolymers) hydrophobically modified by the incorporation of cholesterol led to the formation of narrow-size-distributed (PDI<0.10) sub-200-nm polymeric nanoparticles suitable for passive tumor-targeting drug delivery based on the size-dependent EPR (enhanced permeability and retention) effect. The PHPMA provided to the self-assembled nanoparticle stability against aggregation as evaluated in vitro. The highly hydrophobic drug docetaxel (DTXL) was physically entrapped within the PBS/PBDL copolyester core and the hydrophilic drug doxorubicin hydrochloride (DOX·HCl) was chemically conjugated to the reactive PHPMA copolymer shell via hydrazone bonding that allowed its pH-sensitive release. This strategy enabled the combination chemotherapy by the simultaneous DOX and DTXL drug delivery. The structure of the nanoparticles was characterized in detail using static (SLS), dynamic (DLS) and electrophoretic (ELS) light scattering besides transmission electron microscopy (TEM). The use of nanoparticles simultaneously loaded with DTXL and DOX provided a more efficient suppression of tumor-cell growth in mice bearing EL-4 T cell lymphoma when compared to the effect of nanoparticles loaded with either DTXL or DOX separately. Additionally, the obtained self-assembled nanoparticles enable further development of targeting strategies based on the use of multiple ligands attached to an HPMA copolymer on the particle surface for simultaneous passive and active targeting and different combination therapies. PMID:23178950

  2. Simultaneous in-situ synthesis and characterization of Co@Cu core-shell nanoparticle arrays

    SciTech Connect

    McKeown, Joseph T.; Wu, Yueying; Fowlkes, Jason D.; Rack, Philip D.; Campbell, Geoffrey H.

    2014-12-23

    Core-shell nanostructures have attracted much attention due to their unique and tunable properties relative to bulk structures of the same materials, making core-shell nanoparticles candidates for a variety of applications with multiple functionalities.[1,2] Intriguing magnetic behavior can be tailored by variation of size, interface, crystal orientation, and composition, and core-shell nanostructures with noble-metal shells yield novel optical responses[3] and enhanced electrocatalytic activity.[4]

  3. LaF3 core/shell nanoparticles for subcutaneous heating and thermal sensing in the second biological-window

    NASA Astrophysics Data System (ADS)

    Ximendes, Erving Clayton; Rocha, Uéslen; Kumar, Kagola Upendra; Jacinto, Carlos; Jaque, Daniel

    2016-06-01

    We report on Ytterbium and Neodymium codoped LaF3 core/shell nanoparticles capable of simultaneous heating and thermal sensing under single beam infrared laser excitation. Efficient light-to-heat conversion is produced at the Neodymium highly doped shell due to non-radiative de-excitations. Thermal sensing is provided by the temperature dependent Nd3+ → Yb3+ energy transfer processes taking place at the core/shell interface. The potential application of these core/shell multifunctional nanoparticles for controlled photothermal subcutaneous treatments is also demonstrated.

  4. Optical trapping of core-shell magnetic microparticles by cylindrical vector beams

    SciTech Connect

    Zhong, Min-Cheng; Gong, Lei; Li, Di; Zhou, Jin-Hua; Wang, Zi-Qiang; Li, Yin-Mei

    2014-11-03

    Optical trapping of core-shell magnetic microparticles is experimentally demonstrated by using cylindrical vector beams. Second, we investigate the optical trapping efficiencies. The results show that radially and azimuthally polarized beams exhibit higher axial trapping efficiencies than the Gaussian beam. Finally, a trapped particle is manipulated to kill a cancer cell. The results make possible utilizing magnetic particles for optical manipulation, which is an important advantage for magnetic particles as labeling agent in targeted medicine and biological analysis.

  5. Tailoring thermal conductivity of silicon/germanium nanowires utilizing core-shell architecture

    NASA Astrophysics Data System (ADS)

    Sarikurt, S.; Ozden, A.; Kandemir, A.; Sevik, C.; Kinaci, A.; Haskins, J. B.; Cagin, T.

    2016-04-01

    Low-dimensional nanostructured materials show large variations in their thermal transport properties. In this work, we investigate the influence of the core-shell architecture on nanowire (1D) thermal conductivity and evaluate its validity as a strategy to achieve a better thermoelectric performance. To obtain the thermal conductivity values, equilibrium molecular dynamics simulations are conducted for core-shell nanowires of silicon and germanium. To explore the parameter space, we have calculated thermal conductivity values of the Si-core/Ge-shell and Ge-core/Si-shell nanowires having different cross-sectional sizes and core contents at several temperatures. Our results indicate that (1) increasing the cross-sectional area of pristine Si and pristine Ge nanowires increases the thermal conductivity, (2) increasing the Ge core size in the Ge-core/Si-shell structure results in a decrease in the thermal conductivity at 300 K, (3) the thermal conductivity of the Si-core/Ge-shell nanowires demonstrates a minima at a specific core size, (4) no significant variation in the thermal conductivity is observed in nanowires for temperatures larger than 300 K, and (5) the predicted thermal conductivity within the frame of applied geometrical constraints is found to be around 10 W/(mK) for the Si and Ge core-shell architecture with a smooth interface. The value is still higher than the amorphous limit (1 W/(mK)). This represents a significant reduction in thermal conductivity with respect to their bulk crystalline and pristine nanowire forms. Furthermore, we observed additional suppression of thermal conductivity through the introduction of interface roughness to Si/Ge core-shell nanowires.

  6. Controllable synthesis of a novel hedgehog-like core/shell structure

    SciTech Connect

    Wang Shumin; Tian Hongwei; Pei Yanhui; Meng Qingnan; Chen Jianli; Wang Huan; Zeng Yi; Zheng Weitao; Liu Yichun

    2012-02-15

    A novel hedgehog-like core/shell structure, consisting of a high density of vertically aligned graphene sheets and a thin graphene shell/a copper core (VGs-GS/CC), has been synthesized via a simple one-step synthesis route using radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD). Scanning and transmission electron microscopy investigations show that the morphology of this core/shell material could be controlled by deposition time. For a short deposition time, only multilayer graphene shell tightly surrounds the copper particle, while as the deposition time is relative long, graphene sheets extend from the surface of GS/CC. The GS can protect CC particles from oxidation. The growth mechanism for the obtained GS/CC and VGs-GS/CC has been revealed. Compared to VGs, VGs-GS/CC material exhibits a better electron field emission property. This investigation opens a possibility for designing a core/shell structure of different carbon-metal hybrid materials for a wide variety of practical applications. - Graphical abstract: With increasing deposition time, graphene sheets extend from the surface of GS/CC, causing the multilayer graphene encapsulated copper to be converted into vertically aligned graphene sheets-graphene shell/copper core structure. Highlights: Black-Right-Pointing-Pointer A novel hedgehog-like core/shell structure has been synthesized. Black-Right-Pointing-Pointer The structure consists of vertical graphene sheets-graphene shell and copper core. Black-Right-Pointing-Pointer The morphology of VGs-GS/CC can be controlled by choosing a proper deposition time. Black-Right-Pointing-Pointer With increasing deposition time, graphene sheets extend from the surface of GS/CC. Black-Right-Pointing-Pointer VGs-GS/CC exhibits a better electron field emission property as compared with VGs.

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

    PubMed

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

    2016-06-01

    Solution processable cross-linked core-shell poly[poly(ethylene glycol)methylether methacrylate]-block-poly(2,5-dibromo-3-vinylthiophene) (poly(PEGMA)m-b-poly(DB3VT)n) nanoparticles are firstly explored as charge storage materials for transistor-type memory devices owing to their efficient and controllable ability in electric charge transfer and trapping. PMID:27180874

  8. Spatially resolved Raman spectroscopy on indium-catalyzed core-shell germanium nanowires: size effects.

    PubMed

    Xiang, Y; Zardo, I; Cao, L Y; Garma, T; Heiss, M; Morante, J R; Arbiol, J; Brongersma, M L; Fontcuberta I Morral, A

    2010-03-12

    The structure of indium-catalyzed germanium nanowires is investigated by atomic force microscopy, scanning confocal Raman spectroscopy and transmission electron microscopy. The nanowires are formed by a crystalline core and an amorphous shell. We find that the diameter of the crystalline core varies along the nanowire, down to few nanometers. Phonon confinement effects are observed in the regions where the crystalline region is the thinnest. The results are consistent with the thermally insulating behavior of the core-shell nanowires. PMID:20154375

  9. Gap state related blue light emitting boron-carbon core shell structures

    NASA Astrophysics Data System (ADS)

    Singh, Paviter; Kaur, Manpreet; Singh, Bikramjeet; Kaur, Gurpreet; Singh, Kulwinder; Kumar, Manjeet; Bala, Rajni; Thakur, Anup; Kumar, Akshay

    2016-05-01

    Boron- carbon core shell structures have been synthesized by solvo-thermal synthesis route. The synthesized material is highly pure. X-ray diffraction analysis confirms the reduction of reactants in to boron and carbon. Scanning Electron Microscopy (SEM) analysis showed that the shell is uniform with average thickness of 340 nm. Photo luminescence studies showed that the material is blue light emitting with CIE color coordinates: x=0.16085, y=0.07554.

  10. SYNTHESIS AND APPLICATIONS OF Fe3O4/SiO2 CORE-SHELL MATERIALS.

    PubMed

    Sonmez, Maria; Georgescu, Mihai; Alexandrescu, Laurentia; Gurau, Dana; Ficai, Anton; Ficai, Denisa; Andronescu, Ecaterina

    2015-01-01

    Multifunctional nanoparticles based on magnetite/silica core-shell, consisting of iron oxides coated with silica matrix doped with fluorescent components such as organic dyes (fluorescein isothiocyanate - FITC, Rhodamine 6G) or quantum dots, have drawn remarkable attention in the last years. Due to the bi-functionality of these types of nanoparticles (simultaneously having magnetic and fluorescent properties), they are successfully used in highly efficient human stem cell labeling, magnetic carrier for photodynamic therapy, drug delivery, hyperthermia and other biomedical applications. Another application of core-shell-based nanoparticles, in which the silica is functionalized with aminosilanes, is for immobilization and separation of various biological entities such as proteins, antibodies, enzymes etc. as well as in environmental applications, as adsorbents for heavy metal ions. In vitro tests on human cancerous cells, such as A549 (human lung carcinoma), breast, human cervical cancer, THP-1 (human acute monocytic leukaemia) etc. , were conducted to assess the potential cytotoxic effects that may occur upon contact of nanoparticles with cancerous tissue. Results show that core-shell nanoparticles doped with cytostatics (cisplatin, doxorubicin, etc.), are easily adsorbed by affected tissue and in some cases lead to an inhibition of cell proliferation and induce cell death by apoptosis. The goal of this review is to summarize the advances in the field of core-shell materials, particularly those based on magnetite/silica with applicability in medicine and environmental protection. This paper briefly describes synthesis methods of silica-coated magnetite nanoparticles (Stöber method and microemulsion), the method of encapsulating functional groups based on aminosilanes in silica shell, as well as applications in medicine of these types of simple or modified nanoparticles for cancer therapy, MRI, biomarker immobilization, drug delivery, biocatalysis etc., and in

  11. MAGNETIC CORE SHELL STRUCTURES: from 0D to 1D assembling.

    PubMed

    Ficai, Denisa; Ficai, Anton; Dinu, Elena; Oprea, Ovidiu; Sonmez, Maria; Keler, Memduh Kagan; Sahin, Yesim Muge; Ekren, Nazmi; Inan, Ahmet Talat; Daglilar, Sibel; Gunduz, Oguzhan

    2015-01-01

    Material research and development studies are focused on different techniques of bringing out nanomaterials with desired characteristics and properties. From the point of view of materials development, nowadays scientists are strongly focused on obtaining materials with predefined characteristics and properties. The morphology control seems to be a determinant factor and increasing attention is devoted to this aspect. At this moment it is possible to engineer the material's features by using different methods and materials combination for both medical and industrial applications. In the applications of chemistry and synthesis, biology, mechanics, optics solar cells and microelectronics tailoring the adjustable parameters of stoichiometry, chemical structure, shape and segregation are evaluated and opens new fields. Because of the magnetic features of nanoparticles and durable particle size, less than 100 nm, this study is aiming to describe their uses in practical applications. That's why the whole hydrodynamic magnetic core shell topic will be reviewed on this paper. Additionally, the properties acting in general sight in solid-state physics are utilized for material selection and for defining issue connecting the core, shell structure and their producing properties. Here, in the study of core/shell nanoparticle various physical and chemical synthesis routes and the effect of electrospun method are briefly discussed. Starting from a real void of the scientific literature, the existent data related to the 1D magnetic electrospun materials are reviewed. The perspectives in the medical, environmental or energetic sector is great and bring some real advantages related to the 0D core@shell structures because both mechanical and biological properties are dependent on the morphology of the materials. PMID:26377653

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

    PubMed

    Zhang, Xiaoli; Wang, Litao; Dong, Shuqing; Zhang, Xia; Wu, Qi; Zhao, Liang; Shi, Yanping

    2016-01-01

    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. PMID:27153055

  13. Modeling heterogeneous polymer-grafted nanoparticle networks having biomimetic core-shell structure

    NASA Astrophysics Data System (ADS)

    Mbanga, Badel L.; Yashin, Victor V.; Holten-Andersen, Niels; Balazs, Anna C.

    Inspired by the remarkable mechanical properties of such biological structures as mussel adhesive fibers, we use 3D computational modeling to study the behavior of heterogeneous polymer-grafted nanoparticle (PGN) networks under tensile deformation. The building block of a PGN network is a nanoparticle with grafted polymer chains whose free ends' reactive groups can form both permanent and labile bonds with the end chains on the nearby particles. The tunable behavior of cross-linked PGN networks makes them excellent candidates for designing novel materials with enhanced mechanical properties. Here, we consider the PGN networks having the core-shell structures, in which the type and strength of the inter-particle bonds in the outer shell differ from those in the core. Using the computer simulations, we obtain and compare the ultimate tensile properties (strength, toughness, ductility) and the strain recovery properties for the uniform samples and various core-shell structures. We demonstrate that the core-shell structures could be designed to obtain highly resilient self-healing materials

  14. Au-Cu{sub 2}O core-shell nanowire photovoltaics

    SciTech Connect

    Oener, S. Z.; Mann, S. A.; Sciacca, B.; Sfiligoj, C.; Hoang, J.; Garnett, E. C.

    2015-01-12

    Semiconductor nanowires are among the most promising candidates for next generation photovoltaics. This is due to their outstanding optical and electrical properties which provide large optical cross sections while simultaneously decoupling the photon absorption and charge carrier extraction length scales. These effects relax the requirements for both the minority carrier diffusion length and the amount of semiconductor needed. Metal-semiconductor core-shell nanowires have previously been predicted to show even better optical absorption than solid semiconductor nanowires and offer the additional advantage of a local metal core contact. Here, we fabricate and analyze such a geometry using a single Au-Cu{sub 2}O core-shell nanowire photovoltaic cell as a model system. Spatially resolved photocurrent maps reveal that although the minority carrier diffusion length in the Cu{sub 2}O shell is less than 1 μm, the radial contact geometry with the incorporated metal electrode still allows for photogenerated carrier collection along an entire nanowire. Current-voltage measurements yield an open-circuit voltage of 600 mV under laser illumination and a dark diode turn-on voltage of 1 V. This study suggests the metal-semiconductor core-shell nanowire concept could be extended to low-cost, large-scale photovoltaic devices, utilizing for example, metal nanowire electrode grids coated with epitaxially grown semiconductor shells.

  15. Microfluidic fabrication of cholesteric liquid crystal core-shell structures toward magnetically transportable microlasers.

    PubMed

    Chen, Lu-Jian; Gong, Ling-Li; Lin, Ya-Li; Jin, Xin-Yi; Li, Han-Ying; Li, Sen-Sen; Che, Kai-Jun; Cai, Zhi-Ping; Yang, Chaoyong James

    2016-04-01

    We report a magnetically transportable microlaser with cholesteric liquid crystal (CLC) core-shell structure, operating in band-edge mode. The dye doped CLC shells as a water-in-oil-in-water (W/O/W) double emulsion were fabricated by microfluidics. Water-dispersible Fe3O4 magnetic nanoparticles were incorporated in the inner aqueous phase by taking advantage of the immiscibility with the middle CLC oil phase. The influence of temperature and shell thickness on laser properties was discussed in detail. The non-invasive manipulation of microlasers was realized under a magnetic field. The dependence of velocity on the viscosity of the carrying fluid and size of the core-shell structure was theoretically analyzed and experimentally investigated using a prototype electromagnetic platform. We also discussed the design principles for this type of DDCLC core-shell structure. Such magnetically transportable microlasers offer promise in in-channel illumination applications requiring active control inside micro-channels. PMID:26923221

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

    PubMed

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

    2016-05-20

    A chain-like route was presented to create various core-shell particles with soft, aqueous or inorganic cores respectively. Water-soluble chitosan (WSC) gel particles were obtained through gelating the aqueous WSC solution of 0.02g/mL at its isoelectric point. Then, polyelectrolyte complexes were formed and surrounded on the outer surfaces of WSC gel particles by immersing the particles in 2wt% aqueous sodium alginate. Soft WSC cores in these core-shell particles disappeared after maintaining the particles in 1M HCl for 6h. The cores of obtained particles at this step became aqueous, and could be further transformed into inorganic ones via contacting the particles with copper sulfate and sodium sulfide aqueous solutions successively. The composition of the shell was verified with Fourier transform infrared spectroscopy. The formation of various core-shell particles was confirmed with digital photographic observation, thermogravimetric and fluorescence analyses. The whole process was a chain-like one and was able to stop at any stage to harvest a corresponding target. PMID:26917373

  17. Microstructure and electronic behavior of PtPd@Pt core-shell nanowires

    SciTech Connect

    Han, Wei-Qiang; Su, Dong; Murphy, Michael; Ward, Matthew; Sham, Tsun-Kong; Wu, Lijun; Zhu, Yimei; Hu, Yongfeng; Aoki, Toshihiro

    2010-07-19

    PtPd{at}Pt core-shell ultrathin nanowires were prepared using a one-step phase-transfer approach. The diameters of the nanowires range from 2 to 3 nm, and their lengths are up to hundreds of nanometers. Line scanning electron energy loss spectra showed that PtPd bimetallic nanowires have a core-shell structure, with a PtPd alloy core and a Pt monolayer shell. X-ray absorption near edge structure (XANES) spectra reveal that a strong Pt-Pd interaction exists in this nanowire system in that there is PtPd alloying and/or interfacial interaction. Extended x-ray absorption fine structures (EXAFS) further confirms the PtPd@Pt core-shell structure. The bimetallic nanowires were determined to be face-centered cubic structures. The long-chain organic molecules of n-dodecyl trimethylammonium bromide and octadecylamine, used as surfactants during synthesis, were clearly observed using aberration-corrected TEM operated at 80 KV. The interaction of Pt and surfactants was also revealed by EXAFS.

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

    NASA Astrophysics Data System (ADS)

    Tarsem Singh, Maninder Kaur

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

  19. Core-Shell CdS-Cu₂S Nanorod Array Solar Cells.

    PubMed

    Wong, Andrew Barnabas; Brittman, Sarah; Yu, Yi; Dasgupta, Neil P; Yang, Peidong

    2015-06-10

    As an earth-abundant p-type semiconductor, copper sulfide (Cu2S) is an attractive material for application in photovoltaic devices. However, it suffers from a minority carrier diffusion length that is less than the length required for complete light absorption. Core-shell nanowires and nanorods have the potential to alleviate this difficulty because they decouple the length scales of light absorption and charge collection. To achieve this geometry using Cu2S, cation exchange was applied to an array of CdS nanorods to produce well-defined CdS-Cu2S core-shell nanorods. Previous work has demonstrated single-nanowire photovoltaic devices from this material system, but in this work, the cation exchange chemistry has been applied to nanorod arrays to produce ensemble-level devices with microscale sizes. The core-shell nanorod array devices show power conversion efficiencies of up to 3.8%. In addition, these devices are stable when measured in air after nearly one month of storage in a desiccator. These results are a first step in the development of large-area nanostructured Cu2S-based photovoltaics that can be processed from solution. PMID:25993088

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

    PubMed

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

    2015-03-10

    For several decades, nonaqueous dispersions of PMMA particles have played an important role in colloid research. They have found application as colloidal model systems, which are used to probe glassy dynamics or to explore crystal nucleation. To date, most research has focused on spherical particles, in which only translational motion can be investigated. Recently, however, there has been a surge of interest in analyzing also rotational dynamics. In this contribution, we introduce a new class of core-shell particles, which can be used as rotational probes. The colloids described herein are composed of shape anisotropic, fluorescent cores covered with nonfluorescent PMMA shells. The core-shell particles are built up in four steps. In a first step, we produce fluorescent and photo-cross-linkable PMMA colloids. In the second step, these particles are thermomechanically elongated and fixed in defined ellipsoidal shapes by photo-cross-linking. Subsequently, we cover the cross-linked, fluorescent core with a nonfluorescent PMMA shell. The shape of the resulting core-shell colloids is tunable between the initial anisotropic and perfect spherical shape. For shaping, we apply a simple solvent swelling procedure. As one option, this method yields perfect PMMA spheres with ellipsoidal, fluorescent centers. We also report morphological particle characterization using various fluorescence microscopy techniques. Finally, we demonstrate that the rotational dynamics of individual colloids can be tracked and analyzed. PMID:25654438

  1. Vertically aligned P(VDF-TrFE) core-shell structures on flexible pillar arrays

    PubMed Central

    Choi, Yoon-Young; Yun, Tae Gwang; Qaiser, Nadeem; Paik, Haemin; Roh, Hee Seok; Hong, Jongin; Hong, Seungbum; Han, Seung Min; No, Kwangsoo

    2015-01-01

    PVDF and P(VDF-TrFE) nano- and micro- structures have been widely used due to their potential applications in several fields, including sensors, actuators, vital sign transducers, and energy harvesters. In this study, we developed vertically aligned P(VDF-TrFE) core-shell structures using high modulus polyurethane acrylate (PUA) pillars as the support structure to maintain the structural integrity. In addition, we were able to improve the piezoelectric effect by 1.85 times from 40 ± 2 to 74 ± 2 pm/V when compared to the thin film counterpart, which contributes to the more efficient current generation under a given stress, by making an effective use of the P(VDF-TrFE) thin top layer as well as the side walls. We attribute the enhancement of piezoelectric effects to the contributions from the shell component and the strain confinement effect, which was supported by our modeling results. We envision that these organic-based P(VDF-TrFE) core-shell structures will be used widely as 3D sensors and power generators because they are optimized for current generations by utilizing all surface areas, including the side walls of core-shell structures. PMID:26040539

  2. Gold/Copper Sulphide core/shell nanoparticles for Photothermal Therapy

    NASA Astrophysics Data System (ADS)

    Bala Lakshmanan, Santana; Zou, Xiaoju; Chen, Wei

    2011-10-01

    One of the biggest successes in photothermal therapy (PTT) is the use of gold (Au) nanoparticles. But its disadvantage is that it is too expensive and in addition the NIR absorption in gold nanostructures is from surface plasmon resonance which is dependent on the dielectric constant of the surrounding matrix. Thus the plasmon absorption maxima would shift for in-vivo observations compared to in-vitro. Alternatively, Copper sulphide (CuS) nanoparticles, developed recently, have also been used for PTT. Their advantage over gold nanostructures is that they have NIR absorption around 1100 nm which originates from the d-d transition of Cu2+ ions unlike surface plasmon resonance in gold nanostructures. Therefore, in this paper, we combined the above two nanoparticle systems and developed a new type of agent -Gold/Copper Sulphide (Au/CuS) core/shell nanostructure that has better photothermal conversion efficiency and also overcomes the limitations of the existing nanoparticle systems for PTT. The TEM results confirmed the core/shell structure of Au/CuS nanostructures. From UV-Vis-NIR spectrometer we obtained that these core/shell nanostructures have maximum absorbance at 1100 nm and absorption intensity much higher than only Au and only CuS nanoparticles systems. This, in turn attributed to the relatively high photothermal conversion efficiency of Au/CuS nanostructures.

  3. Directed Fluid Flow Produced by Arrays of Magnetically Actuated Core-Shell Biomimetic Cilia

    NASA Astrophysics Data System (ADS)

    Fiser, B. L.; Shields, A. R.; Evans, B. A.; Superfine, R.

    2010-03-01

    We have developed a novel core-shell microstructure that we use to fabricate arrays of flexible, magnetically actuated biomimetic cilia. Our biomimetic cilia mimic the size and beat shape of biological cilia in order to replicate the transport of fluid driven by cilia in many biological systems including the determination of left-right asymmetry in the vertebrate embryonic nodal plate and mucociliary clearance in the lung. Our core-shell structures consist of a flexible poly(dimethylsiloxane) (PDMS) core surrounded by a shell of nickel approximately forty nanometers thick; by using a core-shell structure, we can tune the mechanical and magnetic properties independently. We present the fabrication process and the long-range transport that occurs above the beating biomimetic cilia tips and will report on progress toward biomimetic cilia induced flow in viscoelastic fluids similar to mucus in the human airway. These flows may have applications in photonics and microfluidics, and our structures may be further useful as sensors or actuators in microelectromechanical systems.

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

    PubMed

    Iheaturu, Nnamdi Chibuike; Madufor, Innocent Chimezie

    2014-01-01

    Preparation of a novel organically modified clay from spent oil base drilling mud (SOBM) that could serve as core-shell clay filler for polymers is herein reported. Due to the hydrophilic nature of clay, its compatibility with polymer matrix was made possible through modification of the surface of the core clay sample with 3-aminopropyltriethoxysilane (3-APTES) compound prior to its use. Fourier transform infrared (FT-IR) spectroscopy was used to characterize clay surface modification. Electron dispersive X-ray diffraction (EDX) and scanning electron microscopy (SEM) were used to expose filler chemical composition and morphology, while electrophoresis measurement was used to examine level of filler dispersion. Results show an agglomerated core clay powder after high temperature treatment, while EDX analysis shows that the organically modified clay is composed of chemical inhomogeneities, wherein elemental compositions in weight percent vary from one point to the other in a probe of two points. Micrographs of the 3-APTES coupled SOBM core-shell clay filler clearly show cloudy appearance, while FT-IR indicates 25% and 5% increases in fundamental vibrations band at 1014 cm(-1) and 1435 cm(-1), respectively. Furthermore, 3-APTES coupled core-shell clay was used to prepare epoxy composites and tested for mechanical properties. PMID:27355022

  5. A pathway for the growth of core-shell Pt-Pd nanoparticles

    DOE PAGESBeta

    Narula, Chaitanya Kumar; Yang, Xiaofan; Li, Chen; Pennycook, Stephen J; Lupini, Andrew R

    2015-10-12

    In this study, the aging of both Pt-Pd nanoparticles and core-shell Pt-Pd nanoparticles has been reported to result in alloying of Pt with Pd. In comparison to monometallic Pt catalysts, the growth of Pd-Pt bimetallics is slower; however, the mechanism of growth of particles and the mechanism by which Pd improves the hydrothermal durability of bimetallic Pd-Pt particles remains uncertain. In our work on hydrothermal aging of core-shell Pt-Pd nanoparticles, synthesized by solution methods, with varying Pd:Pt ratio of 1:4, 1:1, and 4:1, we compare the growth of core-shell Pt-Pd nanoparticles and find that particles grow by migrating and joiningmore » together. The unique feature of the observed growth is that Pd shells from both particles open up and join, allowing the cores to merge. At high temperatures, alloying occurs in good agreement with reports by other workers.« less

  6. Computational Atomistic Modeling of Bi-Magnetic Core-Shell Nanoparticles

    NASA Astrophysics Data System (ADS)

    Sahay, Rahul; Peralta, Juan; Caruntu, Gabriel

    Since its discovery, there has been an increasing interest in the modeling of magnetic phenomena found in materials that present exchange bias. In particular, ferro-antiferromagnetic core-shell nanoparticles are an interesting case in which the magnetic properties of the nanostructure can be altered by adjusting their size, shape, and composition. Here we present a computational scheme that efficiently models the magnetic behavior of bi-magnetic core-shell nanostructures. Using a Heisenberg-Dirac-van Vleck Hamiltonian in combination with a continuous spin model, we simulate a wide range of hysteresis diagrams displaying exchange bias. Furthermore, we will demonstrate our efforts towards improving the efficiency of the simulation algorithms, aiming to afford magnetic atomistic simulations of large nanostructures by using a method based on a tessellated unit sphere to account for spin orientations. Our results allow for further semi-quantitative comparisons with existing experimental data and provide a means to discover new phenomena associated with these core-shell nanoparticles and other nanostructures. NSF DMR-1206920.

  7. Smart micelle@polydopamine core-shell nanoparticles for highly effective chemo-photothermal combination therapy.

    PubMed

    Zhang, Ruirui; Su, Shishuai; Hu, Kelei; Shao, Leihou; Deng, Xiongwei; Sheng, Wang; Wu, Yan

    2015-12-14

    In this investigation, we have designed and synthesized a novel core-shell polymer nanoparticle system for highly effective chemo-photothermal combination therapy. A nanoscale DSPE-PEG micelle encapsulating doxorubicin (Dox-M) was designed as a core, and then modified by a polydopamine (PDA) shell for photothermal therapy and bortezomib (Btz) administration (Dox-M@PDA-Btz). The facile conjugation of Btz to the catechol-containing PDA shell can form a reversible pH-sensitive boronic acid-catechol conjugate to create a stimuli-responsive drug carrier system. As expected, the micelle@PDA core-shell nanoparticles exhibited satisfactory photothermal efficiency, which has potential for thermal ablation of malignant tissues. In addition, on account of the PDA modification, both Dox and Btz release processes were pH-dependent and NIR-dependent. Both in vitro and in vivo studies illustrated that the Dox-M@PDA-Btz nanoparticles coupled with laser irradiation could enhance the cytotoxicity, and thus combinational therapy efficacy was achieved when integrating Dox, Btz, and PDA into a single nanoplatform. Altogether, our current study indicated that the micelle@polydopamine core-shell nanoparticles could be applied for NIR/pH-responsive sustained-release and synergized chemo-photothermal therapy for breast cancer. PMID:26556382

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

    PubMed Central

    Seemann, K.M.; Kuhn, B.

    2014-01-01

    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. PMID:25071977

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

    NASA Astrophysics Data System (ADS)

    Ito, M.; Yano, M.; Sakuma, N.; Kishimoto, H.; Manabe, A.; Shoji, T.; Kato, A.; Dempsey, N. M.; Givord, D.; Zimanyi, G. T.

    2016-05-01

    Ce-based R2Fe14B (R= rare-earth) nano-structured permanent magnets consisting of (Ce,Nd)2Fe14B 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,Nd)2Fe14B 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.

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

    PubMed

    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. PMID:26931335

  11. Agx@WO3 core-shell nanostructure for LSP enhanced chemical sensors

    PubMed Central

    Xu, Lijie; Yin, Ming-Li; (Frank) Liu, Shengzhong

    2014-01-01

    Exceptional properties of graphene have triggered intensive research on other 2D materials. Surface plasmon is another subject being actively explored for many applications. Herein we report a new class of core-shell nanostructure in which the shell is made of a 2D material for effective plasmonic propagation. We have designed a much enhanced chemical sensor made of plasmonic Agx@(2D-WO3) that combines above advantages. Specifically, the sensor response increases from 38 for Agx-WO3 mixture to 217 for the Agx@(2D-WO3) core-shell structure; response and recovery time are shortened considerably to 2 and 5 seconds; and optimum sensor working temperature is lowered from 370°C to 340°C. Light irradiation is found to increase the Agx@(2D-WO3) sensor response, particularly at blue wavelength where it resonates with the absorption of Ag nanoparticles. Raman scattering shows significantly enhanced intensity for both the 2D-WO3 shell and surface adsorbates. Both the resonance sensor enhancement and the Raman suggest that the improved sensor performance is due to nanoplasmonic mechanism. It is demonstrated that (1) 2D material can be used as the shell component of a core-shell nanostructure, and (2) surface plasmon can effectively boost sensor performance. PMID:25339285

  12. Enhanced Electrorheological Properties of Elastomers Containing TiO₂/Urea Core-Shell Particles.

    PubMed

    Niu, Chenguang; Dong, Xufeng; Qi, Min

    2015-11-11

    Polar molecule-coated core-shell particles have been used to prepare electrorheological (ER) fluids with high performance. Inspired by those studies, TiO2/urea core-shell structured particles were fabricated and used to prepare novel ER elastomers, whose properties were compared with the ER elastomers with bare TiO2 particles. Particles characterization results illustrate the TiO2/urea particles present little change in size, morphology and crystal structure with respect to the bare amorphous TiO2 particles, while clear core-shell structure is observed. Compared with the bare TiO2 particles filled elastomer, the TiO2/urea particles filled elastomer presents higher dielectric constant, indicating enhanced polarization. The viscoelastic properties of the two elastomers under different strain amplitude, frequency and electric field were tested. The results indicate that the TiO2/urea particles filled elastomer shows higher storage modulus G' and higher relative ER effect within the low field strength region from 0 to 2 kV/mm. Coating polar molecules is an effective method to improve the ER performance for ER elastomers. PMID:26492099

  13. Core-Shell Processing of Natural Pigment: Upper Palaeolithic Red Ochre from Lovas, Hungary.

    PubMed

    Sajó, István E; Kovács, János; Fitzsimmons, Kathryn E; Jáger, Viktor; Lengyel, György; Viola, Bence; Talamo, Sahra; Hublin, Jean-Jacques

    2015-01-01

    Ochre is the common archaeological term for prehistoric pigments. It is applied to a range of uses, from ritual burials to cave art to medications. While a substantial number of Palaeolithic paint mining pits have been identified across Europe, the link between ochre use and provenance, and their antiquity, has never yet been identified. Here we characterise the mineralogical signature of core-shell processed ochre from the Palaeolithic paint mining pits near Lovas in Hungary, using a novel integration of petrographic and mineralogical techniques. We present the first evidence for core-shell processed, natural pigment that was prepared by prehistoric people from hematitic red ochre. This involved combining the darker red outer shell with the less intensely coloured core to efficiently produce an economical, yet still strongly coloured, paint. We demonstrate the antiquity of the site as having operated between 14-13 kcal BP, during the Epigravettian period. This is based on new radiocarbon dating of bone artefacts associated with the quarry site. The dating results indicate the site to be the oldest known evidence for core-shell pigment processing. We show that the ochre mined at Lovas was exported from the site based on its characteristic signature at other archaeological sites in the region. Our discovery not only provides a methodological framework for future characterisation of ochre pigments, but also provides the earliest known evidence for "value-adding" of products for trade. PMID:26147808

  14. Energy-Cascaded Upconversion in an Organic Dye-Sensitized Core/Shell Fluoride Nanocrystal.

    PubMed

    Chen, Guanying; Damasco, Jossana; Qiu, Hailong; Shao, Wei; Ohulchanskyy, Tymish Y; Valiev, Rashid R; Wu, Xiang; Han, Gang; Wang, Yan; Yang, Chunhui; Ågren, Hans; Prasad, Paras N

    2015-11-11

    Lanthanide-doped upconversion nanoparticles hold promises for bioimaging, solar cells, and volumetric displays. However, their emission brightness and excitation wavelength range are limited by the weak and narrowband absorption of lanthanide ions. Here, we introduce a concept of multistep cascade energy transfer, from broadly infrared-harvesting organic dyes to sensitizer ions in the shell of an epitaxially designed core/shell inorganic nanostructure, with a sequential nonradiative energy transfer to upconverting ion pairs in the core. We show that this concept, when implemented in a core-shell architecture with suppressed surface-related luminescence quenching, yields multiphoton (three-, four-, and five-photon) upconversion quantum efficiency as high as 19% (upconversion energy conversion efficiency of 9.3%, upconversion quantum yield of 4.8%), which is about ~100 times higher than typically reported efficiency of upconversion at 800 nm in lanthanide-based nanostructures, along with a broad spectral range (over 150 nm) of infrared excitation and a large absorption cross-section of 1.47 × 10(-14) cm(2) per single nanoparticle. These features enable unprecedented three-photon upconversion (visible by naked eye as blue light) of an incoherent infrared light excitation with a power density comparable to that of solar irradiation at the Earth surface, having implications for broad applications of these organic-inorganic core/shell nanostructures with energy-cascaded upconversion. PMID:26487489

  15. Novel Organically Modified Core-Shell Clay for Epoxy Composites—“SOBM Filler 1”

    PubMed Central

    Iheaturu, Nnamdi Chibuike; Madufor, Innocent Chimezie

    2014-01-01

    Preparation of a novel organically modified clay from spent oil base drilling mud (SOBM) that could serve as core-shell clay filler for polymers is herein reported. Due to the hydrophilic nature of clay, its compatibility with polymer matrix was made possible through modification of the surface of the core clay sample with 3-aminopropyltriethoxysilane (3-APTES) compound prior to its use. Fourier transform infrared (FT-IR) spectroscopy was used to characterize clay surface modification. Electron dispersive X-ray diffraction (EDX) and scanning electron microscopy (SEM) were used to expose filler chemical composition and morphology, while electrophoresis measurement was used to examine level of filler dispersion. Results show an agglomerated core clay powder after high temperature treatment, while EDX analysis shows that the organically modified clay is composed of chemical inhomogeneities, wherein elemental compositions in weight percent vary from one point to the other in a probe of two points. Micrographs of the 3-APTES coupled SOBM core-shell clay filler clearly show cloudy appearance, while FT-IR indicates 25% and 5% increases in fundamental vibrations band at 1014 cm−1 and 1435 cm−1, respectively. Furthermore, 3-APTES coupled core-shell clay was used to prepare epoxy composites and tested for mechanical properties. PMID:27355022

  16. Nanowire-in-microtube structured core/shell fibers via multifluidic coaxial electrospinning.

    PubMed

    Chen, Hongyan; Wang, Nü; Di, Jiancheng; Zhao, Yong; Song, Yanlin; Jiang, Lei

    2010-07-01

    A multifluidic coaxial electrospinning approach is reported here to fabricate core/shell ultrathin fibers with a novel nanowire-in-microtube structure from more optional fluid pairs than routine coaxial electrospinning. The advantage of this approach lies in the fact that it introduces an extra middle fluid between the core and shell fluids of traditional coaxial electrospinning, which can work as an effective spacer to decrease the interaction of the other two fluids. Under the protection of a proper middle fluid, more fluid pairs, even mutually miscible fluids, can be operated to generate "sandwich"-structured ultrathin fibers with a sharp boundary between the core and shell materials. It thereby largely extends the scope of optional materials. Selectively removing the middle layer of the as-prepared fibers results in an interesting nanowire-in-microtube structure. Either homogeneous or heterogeneous fibers with well-tailored sandwich structures have been successfully fabricated. This method is an important extension of traditional co-electrospinning that affords a more universal avenue to preparing core/shell fibers; moreover, the special hollow cavity structure may introduce some extra properties into the conventional core/shell structure, which may find potential applications such as optical applications, microelectronics, and others. PMID:20337483

  17. Identification and characteristics of ZnO/MgO core-shell nanowires

    SciTech Connect

    Yang, S. Wang, L.; Wang, Y.; Li, L.; Wang, T.; Jiang, Z.

    2015-03-15

    In this paper, ZnO/MgO core-shell nanowires are synthesized based on a one-step chemical vapor deposition (CVD) method. The scanning electron microscopy (SEM) images of core-shell nanowires indicate that Mg addition has little influence on the morphology of the synthesizing products. High crystalline quality ZnO/MgO core-shell nanowires instead of ZnMgO ternary compounds are identified by X-ray diffraction (XRD) patterns, transmission electron microscopy (TEM) images, selected area electron diffraction (SAED) pattern and photoluminescence (PL) spectra. The experimental results show that the ultraviolet (UV) emission of these samples with MgO shell is 12 times higher than that of the corresponding bare ZnO nanowires, and the suppression of the green emission is only 1/45 of the bare ZnO nanowires. It is also found that PL properties are proportional to Mg ratio. The UV emission enhancement and green emission suppression are due to the passivation of surface defects and the improvement of ZnO crystalline quality. The results are very useful for the development of optical devices based on nanowires.

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

    PubMed Central

    2012-01-01

    Background Fe3O4-gold-chitosan core-shell nanostructure can be used in biotechnological and biomedical applications such as magnetic bioseparation, water and wastewater treatment, biodetection and bioimaging, drug delivery, and cancer treatment. Results Magnetite nanoparticles with an average size of 9.8 nm in diameter were synthesized using the chemical co-precipitation method. A gold-coated Fe3O4 monotonous core-shell nanostructure was produced with an average size of 15 nm in diameter by glucose reduction of Au3+ which is then stabilized with a chitosan cross linked by formaldehyde. The results of analyses with X-ray diffraction (XRD), Fourier Transformed Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), and Atomic Force Microscopy (AFM) indicated that the nanoparticles were regularly shaped, and agglomerate-free, with a narrow size distribution. Conclusions A rapid, mild method for synthesizing Fe3O4-gold nanoparticles using chitosan was investigated. A magnetic core-shell-chitosan nanocomposite, including both the supermagnetic properties of iron oxide and the optical characteristics of colloidal gold nanoparticles, was synthesized. PMID:22221555

  19. Vertically aligned P(VDF-TrFE) core-shell structures on flexible pillar arrays

    SciTech Connect

    Choi, Yoon-Young; Yun, Tae Gwang; Qaiser, Nadeem; Paik, Haemin; Roh, Hee Seok; Hong, Jongin; Hong, Seungbum; Han, Seung Min; No, Kwangsoo

    2015-06-04

    PVDF and P(VDF-TrFE) nano- and micro- structures are widely used due to their potential applications in several fields, including sensors, actuators, vital sign transducers, and energy harvesters. In this study, we developed vertically aligned P(VDF-TrFE) core-shell structures using high modulus polyurethane acrylate (PUA) pillars as the support structure to maintain the structural integrity. In addition, we were able to improve the piezoelectric effect by 1.85 times from 40 ± 2 to 74 ± 2 pm/V when compared to the thin film counterpart, which contributes to the more efficient current generation under a given stress, by making an effective use of the P(VDF-TrFE) thin top layer as well as the side walls. We attribute the enhancement of piezoelectric effects to the contributions from the shell component and the strain confinement effect, which was supported by our modeling results. We envision that these organic-based P(VDF-TrFE) core-shell structures will be used widely as 3D sensors and power generators because they are optimized for current generations by utilizing all surface areas, including the side walls of core-shell structures.

  20. Vertically aligned P(VDF-TrFE) core-shell structures on flexible pillar arrays

    DOE PAGESBeta

    Choi, Yoon-Young; Yun, Tae Gwang; Qaiser, Nadeem; Paik, Haemin; Roh, Hee Seok; Hong, Jongin; Hong, Seungbum; Han, Seung Min; No, Kwangsoo

    2015-06-04

    PVDF and P(VDF-TrFE) nano- and micro- structures are widely used due to their potential applications in several fields, including sensors, actuators, vital sign transducers, and energy harvesters. In this study, we developed vertically aligned P(VDF-TrFE) core-shell structures using high modulus polyurethane acrylate (PUA) pillars as the support structure to maintain the structural integrity. In addition, we were able to improve the piezoelectric effect by 1.85 times from 40 ± 2 to 74 ± 2 pm/V when compared to the thin film counterpart, which contributes to the more efficient current generation under a given stress, by making an effective use ofmore » the P(VDF-TrFE) thin top layer as well as the side walls. We attribute the enhancement of piezoelectric effects to the contributions from the shell component and the strain confinement effect, which was supported by our modeling results. We envision that these organic-based P(VDF-TrFE) core-shell structures will be used widely as 3D sensors and power generators because they are optimized for current generations by utilizing all surface areas, including the side walls of core-shell structures.« less

  1. Vertically aligned P(VDF-TrFE) core-shell structures on flexible pillar arrays.

    PubMed

    Choi, Yoon-Young; Yun, Tae Gwang; Qaiser, Nadeem; Paik, Haemin; Roh, Hee Seok; Hong, Jongin; Hong, Seungbum; Han, Seung Min; No, Kwangsoo

    2015-01-01

    PVDF and P(VDF-TrFE) nano- and micro- structures have been widely used due to their potential applications in several fields, including sensors, actuators, vital sign transducers, and energy harvesters. In this study, we developed vertically aligned P(VDF-TrFE) core-shell structures using high modulus polyurethane acrylate (PUA) pillars as the support structure to maintain the structural integrity. In addition, we were able to improve the piezoelectric effect by 1.85 times from 40 ± 2 to 74 ± 2 pm/V when compared to the thin film counterpart, which contributes to the more efficient current generation under a given stress, by making an effective use of the P(VDF-TrFE) thin top layer as well as the side walls. We attribute the enhancement of piezoelectric effects to the contributions from the shell component and the strain confinement effect, which was supported by our modeling results. We envision that these organic-based P(VDF-TrFE) core-shell structures will be used widely as 3D sensors and power generators because they are optimized for current generations by utilizing all surface areas, including the side walls of core-shell structures. PMID:26040539

  2. Core-Shell Processing of Natural Pigment: Upper Palaeolithic Red Ochre from Lovas, Hungary

    PubMed Central

    Sajó, István E.; Kovács, János; Fitzsimmons, Kathryn E.; Jáger, Viktor; Lengyel, György; Viola, Bence; Talamo, Sahra; Hublin, Jean-Jacques

    2015-01-01

    Ochre is the common archaeological term for prehistoric pigments. It is applied to a range of uses, from ritual burials to cave art to medications. While a substantial number of Palaeolithic paint mining pits have been identified across Europe, the link between ochre use and provenance, and their antiquity, has never yet been identified. Here we characterise the mineralogical signature of core-shell processed ochre from the Palaeolithic paint mining pits near Lovas in Hungary, using a novel integration of petrographic and mineralogical techniques. We present the first evidence for core-shell processed, natural pigment that was prepared by prehistoric people from hematitic red ochre. This involved combining the darker red outer shell with the less intensely coloured core to efficiently produce an economical, yet still strongly coloured, paint. We demonstrate the antiquity of the site as having operated between 14–13 kcal BP, during the Epigravettian period. This is based on new radiocarbon dating of bone artefacts associated with the quarry site. The dating results indicate the site to be the oldest known evidence for core-shell pigment processing. We show that the ochre mined at Lovas was exported from the site based on its characteristic signature at other archaeological sites in the region. Our discovery not only provides a methodological framework for future characterisation of ochre pigments, but also provides the earliest known evidence for “value-adding” of products for trade. PMID:26147808

  3. Controllable synthesis of a novel hedgehog-like core/shell structure

    NASA Astrophysics Data System (ADS)

    Wang, Shumin; Tian, Hongwei; Pei, Yanhui; Meng, Qingnan; Chen, Jianli; Wang, Huan; Zeng, Yi; Zheng, Weitao; Liu, Yichun

    2012-02-01

    A novel hedgehog-like core/shell structure, consisting of a high density of vertically aligned graphene sheets and a thin graphene shell/a copper core (VGs-GS/CC), has been synthesized via a simple one-step synthesis route using radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD). Scanning and transmission electron microscopy investigations show that the morphology of this core/shell material could be controlled by deposition time. For a short deposition time, only multilayer graphene shell tightly surrounds the copper particle, while as the deposition time is relative long, graphene sheets extend from the surface of GS/CC. The GS can protect CC particles from oxidation. The growth mechanism for the obtained GS/CC and VGs-GS/CC has been revealed. Compared to VGs, VGs-GS/CC material exhibits a better electron field emission property. This investigation opens a possibility for designing a core/shell structure of different carbon-metal hybrid materials for a wide variety of practical applications.

  4. Ablation characteristics of electrospun core-shell nanofiber by femtosecond laser.

    PubMed

    Park, ChangKyoo; Xue, Ruipeng; Lannutti, John J; Farson, Dave F

    2016-08-01

    This study examined the femtosecond laser ablation properties of core and shell polymers their relationship to the ablation characteristics of core-shell nanofibers. The single-pulse ablation threshold of bulk polycaprolactone (PCL) was measured to be 2.12J/cm(2) and that of bulk polydimethylsiloxane (PDMS) was 4.07J/cm(2). The incubation coefficients were measured to be 0.82±0.02 for PCL and 0.53±0.03 for PDMS. PDMS-PCL core-shell and pure PCL nanofibers were fabricated by electrospinning. The energy/volume of pure PCL and PDMS-PCL core-shell nanofiber ablation was investigated by measuring linear ablation grooves made at different scanning speeds. At large scanning speed, higher energy/volume was required for machining PDMS-PCL nanofiber than for PCL nanofiber. However, at small scanning speed, comparable energy/volume was measured for PDMS-PCL and PCL nanofiber ablation. Additionally, in linear scanned ablation of PDMS-PCL fibers at small laser pulse energy and large scanning speed, there were partially ablated fibers where the shell was ablated but the core remained. This was attributed to the lower ablation threshold of the shell material. PMID:27157748

  5. Core-shell nanoscale coordination polymers combine chemotherapy and photodynamic therapy to potentiate checkpoint blockade cancer immunotherapy.

    PubMed

    He, Chunbai; Duan, Xiaopin; Guo, Nining; Chan, Christina; Poon, Christopher; Weichselbaum, Ralph R; Lin, Wenbin

    2016-01-01

    Advanced colorectal cancer is one of the deadliest cancers, with a 5-year survival rate of only 12% for patients with the metastatic disease. Checkpoint inhibitors, such as the antibodies inhibiting the PD-1/PD-L1 axis, are among the most promising immunotherapies for patients with advanced colon cancer, but their durable response rate remains low. We herein report the use of immunogenic nanoparticles to augment the antitumour efficacy of PD-L1 antibody-mediated cancer immunotherapy. Nanoscale coordination polymer (NCP) core-shell nanoparticles carry oxaliplatin in the core and the photosensitizer pyropheophorbide-lipid conjugate (pyrolipid) in the shell (NCP@pyrolipid) for effective chemotherapy and photodynamic therapy (PDT). Synergy between oxaliplatin and pyrolipid-induced PDT kills tumour cells and provokes an immune response, resulting in calreticulin exposure on the cell surface, antitumour vaccination and an abscopal effect. When combined with anti-PD-L1 therapy, NCP@pyrolipid mediates regression of both light-irradiated primary tumours and non-irradiated distant tumours by inducing a strong tumour-specific immune response. PMID:27530650

  6. Core-shell nanoscale coordination polymers combine chemotherapy and photodynamic therapy to potentiate checkpoint blockade cancer immunotherapy

    PubMed Central

    He, Chunbai; Duan, Xiaopin; Guo, Nining; Chan, Christina; Poon, Christopher; Weichselbaum, Ralph R.; Lin, Wenbin

    2016-01-01

    Advanced colorectal cancer is one of the deadliest cancers, with a 5-year survival rate of only 12% for patients with the metastatic disease. Checkpoint inhibitors, such as the antibodies inhibiting the PD-1/PD-L1 axis, are among the most promising immunotherapies for patients with advanced colon cancer, but their durable response rate remains low. We herein report the use of immunogenic nanoparticles to augment the antitumour efficacy of PD-L1 antibody-mediated cancer immunotherapy. Nanoscale coordination polymer (NCP) core-shell nanoparticles carry oxaliplatin in the core and the photosensitizer pyropheophorbide-lipid conjugate (pyrolipid) in the shell (NCP@pyrolipid) for effective chemotherapy and photodynamic therapy (PDT). Synergy between oxaliplatin and pyrolipid-induced PDT kills tumour cells and provokes an immune response, resulting in calreticulin exposure on the cell surface, antitumour vaccination and an abscopal effect. When combined with anti-PD-L1 therapy, NCP@pyrolipid mediates regression of both light-irradiated primary tumours and non-irradiated distant tumours by inducing a strong tumour-specific immune response. PMID:27530650

  7. Exploring meso-/microporous composite molecular sieves with core-shell structures.

    PubMed

    Qian, Xufang F; Li, Bin; Hu, Yuanyuan Y; Niu, Guoxing X; Zhang, D Yahong H; Che, Renchao C; Tang, Yi; Su, Dangsheng S; Asiri, Abdullah M; Zhao, Dongyuan Y

    2012-01-16

    A series of core-shell-structured composite molecular sieves comprising zeolite single crystals (i.e., ZSM-5) as a core and ordered mesoporous silica as a shell were synthesized by means of a surfactant-directed sol-gel process in basic medium by using cetyltrimethylammonium bromide (CTAB) as a template and tetraethylorthosilicate (TEOS) as silica precursor. Through this coating method, uniform mesoporous silica shells closely grow around the anisotropic zeolite single crystals, the shell thickness of which can easily be tuned in the range of 15-100 nm by changing the ratio of TEOS/zeolite. The obtained composite molecular sieves have compact meso-/micropore junctions that form a hierarchical pore structure from ordered mesopore channels (2.4-3.0 nm in diameter) to zeolite micropores (≈0.51 nm). The short-time kinetic diffusion efficiency of benzene molecules within pristine ZSM-5 (≈7.88×10(-19)  m(2)  s(-1)) is almost retainable after covering with 75 nm-thick mesoporous silica shells (≈7.25×10(-19)  m(2)  s(-1)), which reflects the greatly opened junctions between closely connected mesopores (shell) and micropores (core). The core-shell composite shows greatly enhanced adsorption capacity (≈1.35 mmol  g(-1)) for large molecules such as 1,3,5-triisopropylbenzene relative to that of pristine ZSM-5 (≈0.4 mmol  g(-1)) owing to the mesoporous silica shells. When Al species are introduced during the coating process, the core-shell composite molecular sieves demonstrate a graded acidity distribution from weak acidity of mesopores (predominant Lewis acid sites) to accessible strong acidity of zeolite cores (Lewis and Brønsted acid sites). The probe catalytic cracking reaction of n-dodecane shows the superiority of the unique core-shell structure over pristine ZSM-5. Insight into the core-shell composite structure with hierarchical pore and graded acidity distribution show great potential for petroleum catalytic processes. PMID

  8. Preparation of Novel Poly(hydroxyethyl methacrylate-coglycidyl methacrylate)-Grafted Core-Shell Magnetic Chitosan Microspheres and Immobilization of Lactase

    PubMed Central

    Zhao, Wei; Yang, Rui-Jin; Qian, Ting-Ting; Hua, Xiao; Zhang, Wen-Bin; Katiyo, Wendy

    2013-01-01

    Poly(hydroxyethyl methacrylate-co-glycidyl methacrylate)-grafted magnetic chitosan microspheres (HG-MCM) were prepared using reversed-phase suspension polymerization method. The HG-MCM presented a core-shell structure and regular spherical shape with poly(hydroxyethyl methacrylate-co-glycidyl methacrylate) grafted onto the chitosan layer coating the Fe3O4 cores. The average diameter of the magnetic microspheres was 10.67 μm, within a narrow size distribution of 6.6–17.4 μm. The saturation magnetization and retentivity of the magnetic microspheres were 7.0033 emu/g and 0.6273 emu/g, respectively. The application of HG-MCM in immobilization of lactase showed that the immobilized enzyme presented higher storage, pH and thermal stability compared to the free enzyme. This indicates that HG-MCM have potential applications in bio-macromolecule immobilization. PMID:23743822

  9. Smart multifunctional core-shell nanospheres with drug and gene co-loaded for enhancing the therapeutic effect in a rat intracranial tumor model

    NASA Astrophysics Data System (ADS)

    Wang, Hanjie; Su, Wenya; Wang, Sheng; Wang, Xiaomin; Liao, Zhenyu; Kang, Chunsheng; Han, Lei; Chang, Jin; Wang, Guangxiu; Pu, Peiyu

    2012-09-01

    Glioblastoma with high mortality has been one of the most serious cancers threatening human health. Because of the present treatment limitations, there is an urgent need to construct a multifunctional vesicle for enhancing the treatment of in situ malignant glioblastoma. In our study, drug and gene co-loaded magnetic PLGA/multifunctional polymeric liposome (magnetic PLGA/MPLs) core-shell nanospheres were constructed. They were mainly self-assembled from two parts: hydrophobic PLGA cores that can load drugs and magnetic nanocrystals; and polymeric lipid shells anchored with functional molecules such as PEG chains, TAT peptides and RGD peptides that can help the vectors to condense the gene, prolong the circulation time, cross the blood brain barrier and target delivery to the cancer tissue. The results showed that the magnetic PLGA/MPLs nanosphere has a nanosized core-shell structure, can achieve sustained drug release and has good DNA binding abilities. Importantly, compared with the control group and other groups with single functionality, it can co-deliver the drug and gene into the same cell in vitro and show the strongest inhibiting effect on the growth of the in situ malignant glioblastoma in vivo. All of these results indicated that the different functional components of magnetic PLGA/MPLs, can form an organic whole and none of them can be dispensed with. The magnetic PLGA/MPLs nanosphere may be another option for treatment of glioblastoma.Glioblastoma with high mortality has been one of the most serious cancers threatening human health. Because of the present treatment limitations, there is an urgent need to construct a multifunctional vesicle for enhancing the treatment of in situ malignant glioblastoma. In our study, drug and gene co-loaded magnetic PLGA/multifunctional polymeric liposome (magnetic PLGA/MPLs) core-shell nanospheres were constructed. They were mainly self-assembled from two parts: hydrophobic PLGA cores that can load drugs and magnetic

  10. Monodisperse poly(2-methylaniline) coated polystyrene core-shell microspheres fabricated by controlled releasing process and their electrorheological stimuli-response under electric fields.

    PubMed

    Kwon, Seung Hyuk; Liu, Ying Dan; Choi, Hyoung Jin

    2015-02-15

    A core-shell structured electro-responsive electrorheological (ER) particle system comprised of monodisperse poly(2-methylaniline)-coated polystyrene (PS/PMAN) microspheres was fabricated by applying a controlled swelling-releasing technique to pre-fabricated micron-sized PS seeds using a dispersion polymerization method. Compact wrapping of the PS microparticles with semiconducting PMAN without a de-doping process was examined by scanning electron microscopy and transmission electron microscopy. Fourier-transform infrared spectroscopy and thermogravimetric analysis also confirmed the chemical composition and thermal stability of the particles, respectively. Rheological characteristics of the PS/PMAN microsphere based ER fluid dispersed in silicone oil at various electric field strengths revealed a typical ER response under both steady shear flow and dynamic oscillation, demonstrating its mechanism of a conductivity model with a slope of 1.5. PMID:25460683

  11. TEM Study of the Growth Mechanism, Phase Transformation, and Core/shell Structure of Semiconductor Nanowires

    NASA Astrophysics Data System (ADS)

    Wong, Tai Lun

    In this thesis, the fabrication and characterization of one-dimensional nanostructures have been studied systematically to understand the growth mechanism and structure transformation of one-dimensional nanostructures. The growth behavior of the ultrathin ZnSe nanowires with diameter less than 60 nm was found to be different from classical vapor-liquid-solid (VLS) process. The growth rate increases when the diameter of nanowires decreases, in contrast to the classical VLS process in which the growth rate increases with the diameter. The nucleation, initial growth, growth rates, defects, interface structures and growth direction of the nanowires were investigated by high resolution transmission electron microscopy (HRTEM). We found the structure and growth direction of ultra-thin nanowires are highly sensitive to growth temperatures and diameters of nanowires. At a low growth temperature (380°C), the growth direction for most nanowires is along <111>. Planar defects were found throughout the nanowires. At a high growth temperature (530°C), uniform nanowires with diameters around 10nm were grown along <110> and <112> directions, and the nanowires with diameters larger than 20nm were mainly grown along <111> direction. The possible growth mechanism of ultrathin nanowires was proposed by combining the solid catalytic growth with the interface diffusion theory, in order to explain how the growth temperature and the size of the catalysts influent the morphology, growth direction and growth rate of ultrathin nanowires. Structural and phase transformation of a nickel coated Si nanowire to NiSi2/SiC core-shell nanowire heterostructures has been investigated by the in-situ Transmission Electron Microscope (TEM). The phase transformation is a single-site nucleation process and therefore a single crystalline NiSi2 core resulted in the core-shell nanowire heterostructures. The transformation of the Si nanowire to NiSi2/SiC core-shell nanowire heterostructures was extremely

  12. Heteroaggregation assisted wet synthesis of core-shell silver-silica-cadmium selenide nanowires

    NASA Astrophysics Data System (ADS)

    Pita, Isabel A.; Singh, Shalini; Silien, Christophe; Ryan, Kevin M.; Liu, Ning

    2015-12-01

    A method has been developed for the wet solution synthesis of core shell heterogeneous nanowires. An ultrathin silica layer was first grown around plain silver nanowires to act as a suitable insulator. An outer nanoparticle layer was then attached through heteroaggregation by dispersing the un-functionalized nanowires in toluene solutions containing nanoparticles of CdSe or Au. Total coverage of nanoparticles on nanowires was found to increase with the nanoparticle size, which is attributed to the increase in the van der Waals interaction between the nanoparticles and the nanowire with the increasing size of nanoparticles. Using this method, we achieved over 79.5% coverage of CdSe nanoparticles (24 nm × 11 nm) on the nanowire surface. Although following the same trend, Au nanoparticles show an overall lower coverage than CdSe, with only 24.2% coverage at their largest particle size of 19 nm in diameter. This result is attributed to the increase in steric repulsion during attachment due to the increasing length of capping ligands. Investigation of the core-shell nanowire's optical properties yielded CdSe Raman peak enhancement by a factor of 2-3 due to the excitation of surface plasmon propagation. Our method can be applied to the attachment of a wide range of nanoparticles to nanowire materials in non-polar solution and the core-shell nanowires show great potential for incorporation into various microscopic and drug delivery applications.A method has been developed for the wet solution synthesis of core shell heterogeneous nanowires. An ultrathin silica layer was first grown around plain silver nanowires to act as a suitable insulator. An outer nanoparticle layer was then attached through heteroaggregation by dispersing the un-functionalized nanowires in toluene solutions containing nanoparticles of CdSe or Au. Total coverage of nanoparticles on nanowires was found to increase with the nanoparticle size, which is attributed to the increase in the van der Waals

  13. Single-step in situ synthesis of double bond-grafted yttrium-hydroxide nanotube core-shell structures.

    PubMed

    Li, Weijia; Wang, Xun; Li, Yadong

    2004-01-21

    Novel MMA-Y(OH)(3) nanotube core-shell structures have been successfully prepared with double bonds successfully grafted on the surface through a single-step in-situ hydrothermal method. PMID:14737530

  14. Core shell micron-scale composites of titanium oxide and carbide formed through controlled thermal-plasma oxidation

    NASA Astrophysics Data System (ADS)

    Li, Ya-Li; Ishigaki, Takamasa

    2003-01-01

    Core-shell structured micron-scale spheres of titanium oxide and carbide were prepared by the controlled in-flight oxidation of a powder of irregularly shaped titanium-carbide particles in an argon-oxygen thermal plasma. Mono-dispersed core-shell particles with rutile shells and TiC cores were formed by an intermediate-rate input of oxygen to the plasma gas. The partial oxidation of the TiC particles in the liquid phase was accompanied by spheroidization of the surface oxide melt, thus giving rise to a core-shell composite under rapid quenching. TiO 2-TiC core-shell composites have potential as new materials for roles such as light-scattering media, photo-catalysts, and electro-rheorogical fluids.

  15. One-pot synthesis of highly luminescent CdTe/CdS core/shell nanocrystals in aqueous phase

    NASA Astrophysics Data System (ADS)

    Gu, Zhenyu; Zou, Lei; Fang, Zheng; Zhu, Weihong; Zhong, Xinhua

    2008-04-01

    Surface passivation of nanocrystals with suitable organic or inorganic materials is key to improving the photoluminescence (PL) efficiency and stability of nanocrystals. Although the hot-injection organometallic approach is a powerful tool to achieve different kinds of core/shell structures, direct synthesis of such structures in aqueous phase, which bears many advantages such as biocompatibility, water-solubility, environment-friendliness, and cheapness, is less often reported. Herein we present a facile approach for the one-pot preparation of a water-soluble core/shell structure with CdTe cores packed in a CdS shell in aqueous phase. In comparison with plain CdTe nanocrystals, the PL efficiency of the obtained CdTe/CdS core/shell structure can approach about 75%. The stability of the core/shell structure to UV irradiation and oxidation is also improved.

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

    PubMed

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

    2016-06-22

    Stretchable and transparent electronics have steadily attracted huge attention in wearable devices. Although Ag nanowire is the one of the most promising candidates for transparent and stretchable electronics, its electrochemical instability has forbidden its application to the development of electrochemical energy devices such as supercapacitors. Here, we introduce a highly stretchable and transparent supercapacitor based on electrochemically stable Ag-Au core-shell nanowire percolation network electrode. We developed a simple solution process to synthesize the Ag-Au core-shell nanowire with excellent electrical conductivity as well as greatly enhanced chemical and electrochemical stabilities compared to pristine Ag nanowire. The proposed core-shell nanowire-based supercapacitor still possesses fine optical transmittance and outstanding mechanical stability up to 60% strain. The Ag-Au core-shell nanowire can be a strong candidate for future wearable electrochemical energy devices. PMID:27285849

  17. When cubic cobalt sulfide meets layered molybdenum disulfide: a core-shell system toward synergetic electrocatalytic water splitting.

    PubMed

    Zhu, Han; Zhang, Junfeng; Yanzhang, Ruoping; Du, Mingliang; Wang, Qingfa; Gao, Guohua; Wu, Jiandong; Wu, Guangming; Zhang, Ming; Liu, Bo; Yao, Juming; Zhang, Xiangwen

    2015-08-26

    A new class of Co9 S8 @MoS2 core-shell structures formed on carbon nanofibers composed of cubic Co9 S8 as cores and layered MoS2 as shells is described. The core-shell design of these nanostructures allows the advantages of MoS2 and Co9 S8 to be combined, serving as a bifunctional electrocatalyst for H2 and O2 evolution. PMID:26179503

  18. Polymerization Behavior and Polymer Properties of Eosin-Mediated Surface Modification Reactions.

    PubMed

    Avens, Heather J; Randle, Thomas James; Bowman, Christopher N

    2008-10-17

    Surface modification by surface-mediated polymerization necessitates control of the grafted polymer film thicknesses to achieve the desired property changes. Here, a microarray format is used to assess a range of reaction conditions and formulations rapidly in regards to the film thicknesses achieved and the polymerization behavior. Monomer formulations initiated by eosin conjugates with varying concentrations of poly(ethylene glycol) diacrylate (PEGDA), N-methyldiethanolamine (MDEA), and 1-vinyl-2-pyrrolidone (VP) were evaluated. Acrylamide with MDEA or ascorbic acid as a coinitiator was also investigated. The best formulation was found to be 40 wt% acrylamide with MDEA which yielded four to eight fold thicker films (maximum polymer thickness increased from 180 nm to 1420 nm) and generated visible films from 5-fold lower eosin surface densities (2.8 vs. 14 eosins/µm(2)) compared to a corresponding PEGDA formulation. Using a microarray format to assess multiple initiator surface densities enabled facile identification of a monomer formulation that yields the desired polymer properties and polymerization behavior across the requisite range of initiator surface densities. PMID:19838291

  19. Polymerization Behavior and Polymer Properties of Eosin-Mediated Surface Modification Reactions

    PubMed Central

    Avens, Heather J.; Randle, Thomas James; Bowman, Christopher N.

    2008-01-01

    Surface modification by surface-mediated polymerization necessitates control of the grafted polymer film thicknesses to achieve the desired property changes. Here, a microarray format is used to assess a range of reaction conditions and formulations rapidly in regards to the film thicknesses achieved and the polymerization behavior. Monomer formulations initiated by eosin conjugates with varying concentrations of poly(ethylene glycol) diacrylate (PEGDA), N-methyldiethanolamine (MDEA), and 1-vinyl-2-pyrrolidone (VP) were evaluated. Acrylamide with MDEA or ascorbic acid as a coinitiator was also investigated. The best formulation was found to be 40 wt% acrylamide with MDEA which yielded four to eight fold thicker films (maximum polymer thickness increased from 180 nm to 1420 nm) and generated visible films from 5-fold lower eosin surface densities (2.8 vs. 14 eosins/µm2) compared to a corresponding PEGDA formulation. Using a microarray format to assess multiple initiator surface densities enabled facile identification of a monomer formulation that yields the desired polymer properties and polymerization behavior across the requisite range of initiator surface densities. PMID:19838291

  20. Silicon nanowire array/Cu2O crystalline core-shell nanosystem for solar-driven photocatalytic water splitting.

    PubMed

    Xiong, Zuzhou; Zheng, Maojun; Liu, Sida; Ma, Li; Shen, Wenzhong

    2013-07-01

    P-type Cu2O nanocrystals were deposited on n-type silicon nanowire arrays (Si NWs) to form core-shell heterojunction arrays structure via a simple electroless deposition technique. Scanning electron microscopy, transmission electron microscope and x-ray diffraction were utilized to characterize the morphology and structure of the core-shell nanosystem. The reflectivity of the obtained core-shell structure measured by UV/vis spectrometry showed a comparatively low reflectivity in the visible-light region, which implied good optical absorption performance. The water splitting performance of the obtained Si NWs, planar Si/Cu2O structure and Si NW/Cu2O core-shell nanosystem were studied. Owing to the large specific surface area, heterojunctions formed between Cu2O nanocrystallites and Si NWs and the light trapping effect of the NW array structure, the photocatalytic performance of the Si NW/Cu2O core-shell nanosystem increased markedly compared with that of pure silicon NWs and a planar Si/Cu2O structure, which means excellent hydrogen production capacity under irradiation with simulated sunlight. In addition, the photocatalytic performance of the core-shell nanosystem was improved obviously after platinum nanoparticles were electrodeposited on it. PMID:23733303

  1. Silicon nanowire array/Cu2O crystalline core-shell nanosystem for solar-driven photocatalytic water splitting

    NASA Astrophysics Data System (ADS)

    Xiong, Zuzhou; Zheng, Maojun; Liu, Sida; Ma, Li; Shen, Wenzhong

    2013-07-01

    P-type Cu2O nanocrystals were deposited on n-type silicon nanowire arrays (Si NWs) to form core-shell heterojunction arrays structure via a simple electroless deposition technique. Scanning electron microscopy, transmission electron microscope and x-ray diffraction were utilized to characterize the morphology and structure of the core-shell nanosystem. The reflectivity of the obtained core-shell structure measured by UV/vis spectrometry showed a comparatively low reflectivity in the visible-light region, which implied good optical absorption performance. The water splitting performance of the obtained Si NWs, planar Si/Cu2O structure and Si NW/Cu2O core-shell nanosystem were studied. Owing to the large specific surface area, heterojunctions formed between Cu2O nanocrystallites and Si NWs and the light trapping effect of the NW array structure, the photocatalytic performance of the Si NW/Cu2O core-shell nanosystem increased markedly compared with that of pure silicon NWs and a planar Si/Cu2O structure, which means excellent hydrogen production capacity under irradiation with simulated sunlight. In addition, the photocatalytic performance of the core-shell nanosystem was improved obviously after platinum nanoparticles were electrodeposited on it.

  2. Global optimization and oxygen dissociation on polyicosahedral Ag32Cu6 core-shell cluster for alkaline fuel cells

    NASA Astrophysics Data System (ADS)

    Zhang, N.; Chen, F. Y.; Wu, X. Q.

    2015-07-01

    The structure of 38 atoms Ag-Cu cluster is studied by using a combination of a genetic algorithm global optimization technique and density functional theory (DFT) calculations. It is demonstrated that the truncated octahedral (TO) Ag32Cu6 core-shell cluster is less stable than the polyicosahedral (pIh) Ag32Cu6 core-shell cluster from the atomistic models and the DFT calculation shows an agreeable result, so the newfound pIh Ag32Cu6 core-shell cluster is further investigated for potential application for O2 dissociation in oxygen reduction reaction (ORR). The activation energy barrier for the O2 dissociation on pIh Ag32Cu6 core-shell cluster is 0.715 eV, where the d-band center is -3.395 eV and the density of states at the Fermi energy level is maximal for the favorable absorption site, indicating that the catalytic activity is attributed to a maximal charge transfer between an oxygen molecule and the pIh Ag32Cu6 core-shell cluster. This work revises the earlier idea that Ag32Cu6 core-shell nanoparticles are not suitable as ORR catalysts and confirms that Ag-Cu nanoalloy is a potential candidate to substitute noble Pt-based catalyst in alkaline fuel cells.

  3. Global optimization and oxygen dissociation on polyicosahedral Ag32Cu6 core-shell cluster for alkaline fuel cells

    PubMed Central

    Zhang, N.; Chen, F. Y.; Wu, X.Q.

    2015-01-01

    The structure of 38 atoms Ag-Cu cluster is studied by using a combination of a genetic algorithm global optimization technique and density functional theory (DFT) calculations. It is demonstrated that the truncated octahedral (TO) Ag32Cu6 core-shell cluster is less stable than the polyicosahedral (pIh) Ag32Cu6 core-shell cluster from the atomistic models and the DFT calculation shows an agreeable result, so the newfound pIh Ag32Cu6 core-shell cluster is further investigated for potential application for O2 dissociation in oxygen reduction reaction (ORR). The activation energy barrier for the O2 dissociation on pIh Ag32Cu6 core-shell cluster is 0.715 eV, where the d-band center is −3.395 eV and the density of states at the Fermi energy level is maximal for the favorable absorption site, indicating that the catalytic activity is attributed to a maximal charge transfer between an oxygen molecule and the pIh Ag32Cu6 core-shell cluster. This work revises the earlier idea that Ag32Cu6 core-shell nanoparticles are not suitable as ORR catalysts and confirms that Ag-Cu nanoalloy is a potential candidate to substitute noble Pt-based catalyst in alkaline fuel cells. PMID:26148904

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

    SciTech Connect

    Tripathi, S.K.; Sharma, Mamta

    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.

  5. Preparation and photocatalytic activity of eccentric Au-titania core-shell nanoparticles by block copolymer templates.

    PubMed

    Li, Xue; Fu, Xiaoning; Yang, Hui

    2011-02-21

    A novel route for a preparation of eccentric Au-titania core-shell nanoparticles using gold nanoparticles (AuNPs) with block copolymer shells as a template is reported. AuNPs with poly(2-vinyl pyridine)-block-poly(ethylene oxide) (PVP-b-PEO) block copolymer shells are first prepared by UV irradiation of the solution of PVP-b-PEO/HAuCl(4) complexes. Then the sol-gel reaction of titanium tetra-isopropoxide (TTIP) selectively on the surfaces of AuNPs leads to Au-titania core-shell composite nanoparticles. The eccentric Au-titania core-shell nanoparticles are obtained from the Au-titania core-shell composite nanoparticles by removal of organic interlayer by UV treatment. Photocatalytic activities of the resulting eccentric core-shell nanoparticles are investigated in terms of the degradation of methylene blue (MB). The results show that the eccentric core-shell structures endow the catalyst with greatly enhanced photocatalytic activity. PMID:21157597

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

    NASA Astrophysics Data System (ADS)

    Ruan, Qifeng

    Au nanospheres with molecular linkers. The plasmon resonances of the core/satellite nanostructures undergo red shifts in comparison to those of the sole Au cores, which is consistent with Mie theory analysis. As predicted by finite-difference time-domain simulations, the assembled core/satellite nanostructures exhibit large enhancements for Raman scattering. The facile growth of Au nanospheres and assembly of core/satellite nanostructures blaze a new way to the design of nanoarchitectures with desired plasmonic properties and functions. Coating semiconductors onto Au nanocrystals to form core shell configurations can increase the interactions between the two materials, benefiting from their large active interfacial area. The shell can also protect the Au nanocrystal core from aggregation, reshaping, and chemical corrosion. In this thesis, (Au nanocrystal core) (titania shell) nanostructures with tunable shell thicknesses were prepared by a facile wetchemistry method. Au nanocrystals with strong and tunable plasmon resonances in the visible and near-infrared regions can enhance and broaden the light utilization of TiO2 through the scattering/absorption enhancement, sensitization, and hot-electron injection. The integration of Au nanocrystals therefore hold the prospect of breaking the light-harvesting limit of TiO2 arising from its wide band gap. The resultant (Au core) (TiO2 shell) nanostructures were examined to be capable of efficiently generating reactive oxygen species under near-infrared resonant excitation. On the other hand, the transverse plasmon modes of Au nanorods, which are often too weak to be observed on scattering spectra, are enhanced by the TiO2 shell through energy transfer. With the increment of the shell thickness, the intensity of the transverse plasmon mode increases significantly and even becomes comparable with the longitudinal plasmon mode. Interestingly, both the transverse and longitudinal modes of the (Au core) (TiO2 shell) nanostructures

  7. Exciton-Plasmon Coupling in Metal-Nanoparticle-Decorated ZnO/MgO Core-Shell Nanowires

    NASA Astrophysics Data System (ADS)

    Mayo, Daniel; Marvinney, Claire; Bililign, Ephraim; McBride, James; Mu, Richard; Haglund, Richard

    2014-03-01

    Zinc oxide has emerged as one of the most promising optoelectronic materials due to its direct bandgap of 3.37 eV and large exciton binding energy of 60 meV. Room temperature photoluminescence (PL) spectra for ZnO exhibit a sharply defined exciton recombination peak centered at 3.3 eV and a broad visible defect peak centered around 2.3. A wide range of optoelectronic devices, including LEDs, lasers and sensors, have been developed by tuning ZnO emission through different growth, annealing, and doping conditions. However, one of the most effective methods for PL enhancement is through coupling of localized surface plasmons of metal nanoparticles to the ZnO luminescent centers. ZnO nanowires are decorated variously with Ag, Al, and Au nanoparticles, with an insulating MgO interlayer used to differentiate plasmon-mediated emission due to hot-electron transfer from that due to local field effects. In addition, at specific MgO thicknesses, Fabry-Perot resonators within the core-shell nanowires result in dramatic enhancement of the band-edge PL while the visible emission remains unaffected. A large variation in the band-edge emission occurs for the various nanoparticle species, with Al exhibiting the strongest plasmonic coupling and therefore the highest PL enhancement.

  8. Facile route to the synthesis and characterization of novel core-shell and Ag/Ru allied nanoparticles

    NASA Astrophysics Data System (ADS)

    Adekoya, Joseph Adeyemi; Dare, Enock Olugbenga; Adediran Mesubi, Michael; Revaprasadu, Neerish

    2015-07-01

    The synthesis of polyvinylpyrrolidone (PVP) and dodecanethiol (DT) seed mediated Ag/Ru allied bimetallic nanoparticles were successfully carried out by the simultaneous reduction of the metal ions in aqueous and non-aqueous solutions with ethylene glycol (EG), diethylene glycol (DEG), glycerol (GLY) and pentaerythritol (PET). The TEM images of the AgRu NPs passivated by DT/DEG; DT/GLY; DT/EG (200 °C, 3 h) and PVP/PET (90 °C, 4 h) revealed novel well-ordered core-shell structures with particle sizes in the range of 8.2±0.7, 10.0±3.2, 11.4±1.3 and 18.89±6.83 nm respectively. The analysis of the nanocomposites using X-ray photoelectron spectroscopy and X-ray diffraction suggests dominance of the face-centred cubic structure with 2θ reflections slightly shifted from the silver peaks.

  9. Virus-templated Au and Au/Pt Core/shell Nanowires and Their Electrocatalytic Activitives for Fuel Cell Applications

    PubMed Central

    LEE, YOUJIN; KIM, JUNHYUNG; YUN, DONG SOO; NAM, YOON SUNG; SHAO-HORN, YANG; BELCHER, ANGELA M.

    2014-01-01

    A facile synthetic route was developed to make Au nanowires (NWs) from surfactant-mediated bio-mineralization of a genetically engineered M13 phage with specific Au binding peptides. From the selective interaction between Au binding M13 phage and Au ions in aqueous solution, Au NWs with uniform diameter were synthesized at room temperature with yields greater than 98 % without the need for size selection. The diameters of Au NWs were controlled from 10 nm to 50 nm. The Au NWs were found to be active for electrocatalytic oxidation of CO molecules for all sizes, where the activity was highly dependent on the surface facets of Au NWs. This low-temperature high yield method of preparing Au NWs was further extended to the synthesis of Au/Pt core/shell NWs with controlled coverage of Pt shell layers. Electro-catalytic studies of ethanol oxidation with different Pt loading showed enhanced activity relative to a commercial supported Pt catalyst, indicative of the dual functionality of Pt for the ethanol oxidation and Au for the anti-poisoning component of Pt. These new one-dimensional noble metal NWs with controlled compositions could facilitate the design of new alloy materials with tunable properties. PMID:24910712

  10. Rational assembly of a biointerfaced core@shell nanocomplex towards selective and highly efficient synergistic photothermal/photodynamic therapy.

    PubMed

    Qin, Chenchen; Fei, Jinbo; Wang, Anhe; Yang, Yang; Li, Junbai

    2015-12-21

    To optimize synergistic cancer therapy, we rationally assemble an inorganic-organic nanocomplex using a folate-modified lipid bilayer spread on photosensitizer-entrapped mesoporous silica nanoparticle (MSN) coated gold nanorods (AuNRs). In this hybrid bioconjugate, the large specific surface area and pore size of AuNR@MSN guarantee a high loading capacity of small photosensitive molecules. The modification with selective mixed liposomes on the surface of AuNR@MSN enables faster cellular internalization and enhancement of endocytosis. Under one-time NIR two-photon illumination, AuNR-mediated hyperthermia can kill cancer cells directly. Meanwhile, the loaded photosensitizer, hypocrellin B, generates two kinds of reactive oxygen species (ROS) to induce cell apoptosis. Remarkably, hyperthermia can improve the yield of ROS. After intravenous injection of this bioconjugate into female BALB/c nude mice followed by laser irradiation (808 nm, 1.3 W cm(-2), 6 min), the tumor growth is suppressed completely. The tumors are not recurrent within the observation time (19 days), and the normal or main organs are not obviously pathological. Thus, such a simplified and selective cancer treatment, combining photothermal and photodynamic therapy in a synergistic manner, provides outstanding efficiency in vivo. This nanocomplex with well-defined core@shell nanostructures integrated with a two-photon technique holds great promise to improve cancer phototherapy with a high efficiency in the clinic. PMID:26574662

  11. Systemic delivery of siRNA by T7 peptide modified core-shell nanoparticles for targeted therapy of breast cancer.

    PubMed

    Yu, Min-Zhi; Pang, Wen-Hao; Yang, Ting; Wang, Jian-Cheng; Wei, Lin; Qiu, Chong; Wu, Yi-Fan; Liu, Wei-Zhong; Wei, Wei; Guo, Xi-Ying; Zhang, Qiang

    2016-09-20

    Systemic delivery of siRNA is the most challenging step to transfer RNAi to clinical application for breast cancer therapy. In this study, the tumor targeted, T7 peptide modified core-shell nanoparticles (named as T7-LPC/siRNA NPs) were constructed to achieve effective systemic delivery of siRNA. The core-shell structure of T7-LPC/siRNA NPs enables them to encapsulate siRNA in the core and protect it from RNase degradation during circulation. In vitro cellular uptake and gene silencing experiments demonstrated that T7-LPC/siEGFR NPs could deliver EGFR siRNA into breast cancer cells through receptor mediated endocytosis and effectively down-regulate the EGFR expression. In vivo distribution study proved the T7-LPC/siRNA NPs could deliver fluorescence labeled siRNA to the tumor site more efficiently than the non-targeted PEG-LPC/siRNA NPs after intravenous administration. Furthermore, the experiments of in vivo tumor therapy confirmed that intravenous administration of T7-LPC/siEGFR NPs led to an effective EGFR down-regulation and an obvious inhibition of breast tumor growth, with little activation of immune responses and negligible body weight loss. These results suggested that T7-LPC/siRNA NPs could be an effective and safe systemic siRNA delivery system for RNAi-based breast cancer therapy. PMID:27355138

  12. Engineering of Hollow Core-Shell Interlinked Carbon Spheres for Highly Stable Lithium-Sulfur Batteries.

    PubMed

    Sun, Qiang; He, Bin; Zhang, Xiang-Qian; Lu, An-Hui

    2015-08-25

    We report engineered hollow core-shell interlinked carbon spheres that consist of a mesoporous shell, a hollow void, and an anchored carbon core and are expected to be ideal sulfur hosts for overcoming the shortage of Li-S batteries. The hollow core-shell interlinked carbon spheres were obtained through solution synthesis of polymer spheres followed by a pyrolysis process that occurred in the hermetical silica shell. During the pyrolysis, the polymer sphere was transformed into the carbon core and the carbonaceous volatiles were self-deposited on the silica shell due to the blocking effect of the hermetical silica shell. The gravitational force and the natural driving force of lowering the surface energy tend to interlink the carbon core and carbon/silica shell, resulting in a core-shell interlinked structure. After the SiO2 shell was etched, the mesoporous carbon shell was generated. When used as the sulfur host for Li-S batteries, such a hierarchical structure provides access to Li(+) ingress/egress for reactivity with the sulfur and, meanwhile, can overcome the limitations of low sulfur loading and a severe shuttle effect in solid carbon-supported sulfur cathodes. Transmission electron microscopy and scanning transmission electron microscopy images provide visible evidence that sulfur is well-encapsulated in the hollow void. Importantly, such anchored-core carbon nanostructures can simultaneously serve as a physical buffer and an electronically connecting matrix, which helps to realize the full potential of the active materials. Based on the many merits, carbon-sulfur cathodes show a high utilization of sulfur with a sulfur loading of 70 wt % and exhibit excellent cycling stability (i.e., 960 mA h g(-1) after 200 cycles at a current density of 0.5 C). PMID:26182333

  13. A study of the compartmentalization of core-shell nanoparticles through fluorescence energy transfer of dopants.

    PubMed

    Chávez, Jorge L; Jiang, Hui; Duran, Randolph S

    2010-02-01

    Hybrid organic-inorganic templates and core-shell nanoparticles were used as models to study the communication between fluorescent probes placed inside nanoparticles. The hybrid templates were prepared on the basis of a mixed-surfactant system using octadecyltrimethoxysilane as a reactive amphiphile. The core-shell particles were obtained after coating of the templates with a siloxane shell, using the silanol groups on their surface. Atomic force microscopy imaging showed that the templates were made of a flexible material that flattened significantly after deposition on a substrate and evaporation of the solvent. Pyrene was sequestered by the templates in an aqueous suspension, which placed it in a nonpolar environment, as observed by its fluorescence response. Subsequently, double-doped templates were prepared by sequestering coumarin 153 (C153), with pyrene-doped hybrid templates. The communication between these probes was studied on the basis of their spectral properties, by means of fluorescence resonance energy transfer (FRET). Energy transfer between the dyes with efficiencies up to 55% was observed. Similarly, double-doped core-shell particles prepared on the basis of the hybrid templates were doped with this pair of dyes. Despite the presence of the shell, which was intended to increment the average separation between the probes, interaction of the dyes was observed, although with lower efficiencies. A similar study was performed with C153 and 4-(dicyanomethylene)-2-methyl-6-p-(dimethylamino)styryl-4H-pyran (DCM). FRET studies indicated that the probes were placed in proximity to each other. We confirmed these observations by means of fluorescence lifetime measurements, which showed a decrease in the lifetime of the donor upon addition of the acceptor. PMID:20023306

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

    SciTech Connect

    Hollingsworth, Jennifer A.; Ghosh, Yagnaseni; Dennis, Allison M.; Mangum, Benjamin D.; Park, Young-Shin; Kundu, Janardan; Htoon, Han

    2012-06-07

    Due to their characteristic bright and stable photoluminescence, semiconductor nanocrystal quantum dots (NQDs) have attracted much interest as efficient light emitters for applications from single-particle tracking to solid-state lighting. Despite their numerous enabling traits, however, NQD optical properties are frustratingly sensitive to their chemical environment, exhibit fluorescence intermittency ('blinking'), and are susceptible to Auger recombination, an efficient nonradiative decay process. Previously, we showed for the first time that colloidal CdSe/CdS core/shell nanocrystal quantum dots (NQDs) comprising ultrathick shells (number of shell monolayers, n, > 10) grown by protracted successive ionic layer adsorption and reaction (SILAR) leads to remarkable photostability and significantly suppressed blinking behavior as a function of increasing shell thickness. We have also shown that these so-called 'giant' NQDs (g-NQDs) afford nearly complete suppression of non-radiative Auger recombination, revealed in our studies as long biexciton lifetimes and efficient multiexciton emission. The unique behavior of this core/shell system prompted us to assess correlations between specific physicochemical properties - beyond shell thickness - and functionality. Here, we demonstrate the ability of particle shape/faceting, crystalline phase, and core size to determine ensemble and single-particle optical properties (quantum yield/brightness, blinking, radiative lifetimes). Significantly, we show how reaction process parameters (surface-stabilizing ligands, ligand:NQD ratio, choice of 'inert' solvent, and modifications to the SILAR method itself) can be tuned to modify these function-dictating NQD physical properties, ultimately leading to an optimized synthetic approach that results in the complete suppression of blinking. We find that the resulting 'guiding principles' can be applied to other NQD compositions, allowing us to achieve non-blinking behavior in the near

  15. Green synthesis and characterization of Au@Pt core-shell bimetallic nanoparticles using gallic acid

    NASA Astrophysics Data System (ADS)

    Zhang, Guojun; Zheng, Hongmei; Shen, Ming; Wang, Lei; Wang, Xiaosan

    2015-06-01

    In this study, we developed a facile and benign green synthesis approach for the successful fabrication of well-dispersed urchin-like Au@Pt core-shell nanoparticles (NPs) using gallic acid (GA) as both a reducing and protecting agent. The proposed one-step synthesis exploits the differences in the reduction potentials of AuCl4- and PtCl62-, where the AuCl4- ions are preferentially reduced to Au cores and the PtCl62- ions are then deposited continuously onto the Au core surface as a Pt shell. The as-prepared Au@Pt NPs were characterized by transmission electron microscope (TEM); high-resolution transmission electron microscope (HR-TEM); scanning electron microscope (SEM); UV-vis absorption spectra (UV-vis); X-ray diffraction (XRD); Fourier transmission infrared spectra (FT-IR). We systematically investigated the effects of some experimental parameters on the formation of the Au@Pt NPs, i.e., the reaction temperature, the molar ratios of HAuCl4/H2PtCl6, and the amount of GA. When polyvinylpyrrolidone K-30 (PVP) was used as a protecting agent, the Au@Pt core-shell NPs obtained using this green synthesis method were better dispersed and smaller in size. The as-prepared Au@Pt NPs exhibited better catalytic activity in the reaction where NaBH4 reduced p-nitrophenol to p-aminophenol. However, the results showed that the Au@Pt bimetallic NPs had a lower catalytic activity than the pure Au NPs obtained by the same method, which confirmed the formation of Au@Pt core-shell nanostructures because the active sites on the surfaces of the Au NPs were covered with a Pt shell.

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

    NASA Astrophysics Data System (ADS)

    Sharma, Richa; Tiwari, Sangeeta

    2016-04-01

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

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

    PubMed

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

    2014-07-01

    Hollow core/shell hematite microspheres with diameter of ca. 1-2 μm have been successfully achieved by calcining the precursor composite microspheres of pyrite and polyvinylpyrrolidone (PVP) in air. The synthesized products were characterized by a wide range of techniques including powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and Brunauer-Emmett-Teller (BET) gas sorptometry. Temperature- and time-dependent experiments unveil that the precursor pyrite-PVP composite microspheres finally transform into hollow core/shell hematite microspheres in air through a multistep process including the oxidation and sulfation of pyrite, combustion of PVP occluded in the precursor, desulfation, aggregation, and fusion of nanosized hematite as well as mass transportation from the interior to the exterior of the microspheres. The formation of the hollow core/shell microspheres dominantly depends on the calcination temperature under current experimental conditions, and the aggregation of hematite nanocrystals and the core shrinking during the oxidation of pyrite are responsible for the formation of the hollow structures. Moreover, the adsorption ability of the hematite for Sm(III) was also tested. The results exhibit that the hematite microspheres have good adsorption activity for trivalent samarium, and that its adsorption capacity strongly depends on the pH of the solution, and the maximum adsorption capacity for Sm(III) is 14.48 mg/g at neutral pH. As samarium is a typical member of the lanthanide series, our results suggest that the hollow hematite microspheres have potential application in removal of rare earth elements (REEs) entering the water environment. PMID:24892188

  18. Core-shell electrospun polybutylene terephthalate/polypyrrole hollow nanofibers for micro-solid phase extraction.

    PubMed

    Bagheri, Habib; Rezvani, Omid; Banihashemi, Solmaz

    2016-02-19

    In the present work, a new micro-solid phase extraction (μ-SPE) sorbent as an extracting medium based on core-shell nanofibers was synthesized by electrospinning. The core-shell nanofibers of polyvinylpyrrolidone-Polybutylene terephthalate/polypyrrole (PVP-PBT/PPy) were electrospun and subsequently, modified hollow nanofibers were prepared by removing the central PVP moiety. Moreover, conventional PBT/PPy was also prepared for the comparison purposes. The homogeneity and the porous surface structure of the core-shell nanofibers were confirmed by scanning electron microscopy (SEM). The applicability of the fabricated nanofibers-coating was examined by immersed μ-SPE of some selected triazine herbicides from aqueous samples and wheat grains. Subsequently, the extracted analytes were transferred into a gas chromatography (GC) after solvent desorption. Influencing parameters on the morphology of nanofiber such as elctrospinning parameters and the weight ratio of components were optimized. In addition, effects of different parameters influencing the extraction efficiency including extraction temperature, extraction time, ionic strength, sample pH, desorption temperature, and desorption time were investigated and optimized. Eventually, the developed method was validated by gas chromatography-mass spectrometry (GC-MS). At the optimum conditions, the relative standard deviation values for real water samples spiked with the selected triazines at 1 ng mL(-1) were 4-8% (n=3) and the limits of detection for the studied compounds were between 50 and 90 ng L(-1). The calibration curves for the selected triazines were in the range of 0.3-500 ng mL(-1) and regression coefficients (R(2)) were between 0.9985 and 0.9996. PMID:26810808

  19. Structural optical correlated properties of SnO2/Al2O3 core@ shell heterostructure

    NASA Astrophysics Data System (ADS)

    Heiba, Zein K.; Imam, N. G.; Bakr Mohamed, Mohamed

    2016-07-01

    Nano size polycrystalline samples of the core@shell heterostructure of SnO2 @ xAl2O3 (x = 0, 25, 50, 75 wt.%) were synthesized by sol-gel technique. The resulting samples were characterized with fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) and X-ray powder diffraction (XRD). The XRD patterns manifest diffraction peaks of SnO2 as main phase with weak peaks corresponding to Al2O3 phase. The formation of core@ shell structure is confirmed by TEM images and Rietveld quantitative phase analysis which revealed that small part of Al2O3 is incorporated into the SnO2 lattice while the main part (shell) remains as a separate phase segregated on the grain boundary surface of SnO2 (core). It is found that the grain size of the mixed oxides SnO2 @ xAl2O3 is below 10 nm while for pure SnO2 it is over 41 nm, indicating that alumina can effectively prevent SnO2 from further growing up in the process of calcination. This is confirmed by the large increase in the specific surface area for mixed oxide samples. The PL emission showed great dependence on the structure properties analyzed by XRD and FTIR. The PL results recommend Al2O3@SnO2 core@shell heterostructure to be a promising short-wavelength luminescent optoelectronic devices for blue, UV, and laser light-emitting diodes.

  20. Synthesis and microwave-absorbing properties of Co3Fe7@C core-shell nanostructure

    NASA Astrophysics Data System (ADS)

    Guo, Xiao Dang; Qiao, Xiao Jing; Ren, Qing Guo; Wan, Xiang; Li, Wang Chang; Sun, Zhi Gang

    2015-07-01

    Co3Fe7@C core-shell nanoparticles with high performance of microwave-absorbing properties were prepared by hydrothermal method and heat treatment. The transformation of structural, morphological and magnetic properties among the carbon-encapsulated composites, which were annealed at three different temperatures, were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). XRD analysis indicated the phase composition of Co3Fe7/CoFe2O4, Fe3C/Co3Fe7 and pure Co3Fe7 at different annealing temperatures. TEM confirmed the Co3Fe7@graphite core-shell nanostructure with an average particle size of 180 nm. The saturation magnetization ( M s) increased monotonically with the increase in temperature, which was attributed to the crystal growth and purity of metallic core. Co3Fe7@graphite nanoparticles exhibited the hysteretic loops of soft ferromagnetic behavior with high M s of 222.85 emu g-1, weak remanent magnetization ( M r) and coercivity ( H c). For Co3Fe7@graphite nanomaterial, a reflection loss exceeding -20 dB was obtained between 2.8 and 10.2 GHz, which almost covering from S-band to X-band. The maximum reflection loss is -26.8 dB at 9 GHz with 1.8 mm thickness. The excellent microwave absorption properties result from the proper electromagnetic match in core-shell nanostructure and the strong natural ferromagnetic resonance.

  1. pH sensitive core-shell magnetic nanoparticles for targeted drug delivery in cancer therapy.

    PubMed

    Lungu, Iulia Ioana; Rădulescu, Marius; Mogoşanu, George Dan; Grumezescu, Alexandru Mihai

    2016-01-01

    In the last decade, nanobiotechnology has evolved rapidly with an extensive impact on biomedical area. In order to improve bioavailability and minimize adverse effects, drug delivery systems based on magnetic nanocomposites are under development mainly for cancer imaging and antitumor therapy. In this regard, pH sensitive core-shell magnetic nanoparticles (NPs) with accurate controlled size and shape are synthesized by various modern methods, such as homogeneous precipitation, coprecipitation, microemulsion or polyol approaches, high temperature and hydrothermal reactions, sol-gel reactions, aerosol÷vapor processes and sonolysis. Due to their unique combined physico-chemical and biological properties (such as higher dispensability, chemical and thermal stability, biocompatibility), pH responsive core-shell magnetic NPs are widely investigated for controlled release of cytostatic drugs into the tumor site by means of pH change: magnetite@silicon dioxide (Fe3O4@SiO2), Fe3O4@titanium dioxide (TiO2), β-thiopropionate-polyethylene glycol (PEG)-modified Fe3O4@mSiO2, Fe3O4 NPs core coated with SiO2 with an imidazole group modified PEG-polypeptide (mPEG-poly-L-Asparagine), polyacrylic acid (PAA) and folic acid (FA) coating of the iron oxide NP core, methoxy polyethylene glycol-block-polymethacrylic acid-block-polyglycerol monomethacrylate (MPEG-b-PMAA-b-PGMA) attached by a PGMA block to a Fe3O4 core, PEG-modified polyamidoamine (PAMAM) dendrimer shell with Fe3O4 core and mesoporous silica coated on Fe3O4, mostly coated with an anticancer drug. This review paper highlights the modern research directions currently employed to demonstrate the utility of the pH responsive core-shell magnetic NPs in diagnosis and treatment of oncological diseases. PMID:27151685

  2. Preparation and characterization of polymer electrolyte membranes based on silicon-containing core-shell structured nanocomposite latex particles

    NASA Astrophysics Data System (ADS)

    Zhong, Shuangling; Sun, Chenggang; Gao, Yushan; Cui, Xuejun

    2015-09-01

    A series of silicon-containing core-shell structured polyacrylate/2-acrylamido-2-methyl-1-propanesulfonic acid (SiO2-CS-PA/A) nanocomposite latex particles are prepared by the emulsifier-free emulsion polymerization of acrylate monomers and various amount of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) with colloidal nanosilica particles as seed. The chemical and morphological structures of latex particles with high monomer conversion are determined using Fourier transform infrared (FTIR), dynamic light scattering (DLS) and transmission electron microscopy (TEM). The SiO2-CS-PA/A nanocomposite membranes are fabricated through pouring the latex onto a clean surface of glass and drying at 60 °C for 10 h and 120 °C for 2 h. The nanocomposite membranes possess good thermal and dimensional stability. In addition, in comparison to Nafion® 117, the nanocomposite membranes exhibit moderate proton conductivity, significantly better methanol barrier and selectivity. The methanol diffusion coefficient is in the range of 1.03 × 10-8 to 5.26 × 10-8 cm2 s-1 which is about two orders of magnitude lower than that of Nafion® 117 (2.36 × 10-6 cm2 s-1). The SiO2-CS-PA/A 5 membrane shows the highest selectivity value (2.34 × 105 S cm-3) which is approximately 11.0 times of that (2.13 × 104 S cm-3) of Nafion® 117. These results indicate that the nanocomposite membranes are promising candidates to be used as polymer electrolyte membranes in direct methanol fuel cells.

  3. Highly flexible binder-free core-shell nanofibrous electrode for lightweight electrochemical energy storage using recycled water bottles.

    PubMed

    Shi, HaoTian H; Naguib, Hani E

    2016-08-12

    The creation of a novel flexible nanocomposite fiber with conductive polymer polyaniline (PAni) coating on a polyethylene terephthalate (PET) substrate allowed for increased electrochemical performance while retaining ideal mechanical properties such as very high flexibility. Binder-free PAni-wrapped PET (PAni@PET) fiber with a core-shell structure was successfully fabricated through a novel technique. The PET nanofiber substrate was fabricated through an optimized electrospinning method, while the PAni shell was chemically polymerized onto the surface of the nanofibers. The PET substrate can be made directly from recycled PETE1 grade plastic water bottles. The resulting nanofiber with an average diameter of 121 nm ± 39 nm, with a specific surface area of 83.72 m(2) g(-1), led to better ionic interactions at the electrode/electrolyte interface. The PAni active layer coating was found to be 69 nm in average thickness. The specific capacitance was found to have increased dramatically from pure PAni with carbon binders. The specific capacitance was found to be 347 F g(-1) at a relatively high scan rate of 10 mV s(-1). The PAni/PET fiber also experienced very little degradation (4.4%) in capacitance after 1500 galvanostatic charge/discharge cycles at a specific current of 1.2 A g(-1). The mesoporous structure of the PAni@PET fibrous mat also allowed for tunable capacitance by controlling the pore sizes. This novel fabrication method offers insights for the utilization of recycled PETE1 based bottles as a high performance, low cost, highly flexible supercapacitor device. PMID:27354434

  4. Ising nanowires with simple core-shell structure; Their characteristic phenomena

    NASA Astrophysics Data System (ADS)

    Kaneyoshi, T.

    2016-09-01

    The phase diagrams and magnetizations of Ising nanowires with simple core-shell structure are investigated by the use of the effective field theory with correlations. A lot of characteristic behaviors observed in ferromagnetic and ferrimagnetic materials as well as novel phenomena have been obtained, although one section of the system is consisted of one spin-1/2 surface shell atom and one spin-1/2 core atom and they are coupled with a positive or a negative shell-core exchange interaction.

  5. Converging sequences in the ab initio no-core shell model

    SciTech Connect

    Forssen, C.; Vary, J. P.; Caurier, E.; Navratil, P.

    2008-02-15

    We demonstrate the existence of multiple converging sequences in the ab initio no-core shell model. By examining the underlying theory of effective operators, we expose the physical foundations for the alternative pathways to convergence. This leads us to propose a revised strategy for evaluating effective interactions for A-body calculations in restricted model spaces. We suggest that this strategy is particularly useful for applications to nuclear processes in which states of both parities are used simultaneously, such as for transition rates. We demonstrate the utility of our strategy with large-scale calculations in light nuclei.

  6. Widely tuning optical properties of nanoporous gold-titania core-shells.

    PubMed

    Qian, Lihua; Shen, Bo; Qin, Gaowu W; Das, Biswajit

    2011-01-01

    Widely shifting localized surface plasmon resonance (LSPR) bands of nanoporous metals is essential for light manipulation within small volumes. In this work, nanoporous gold-titania core-shells fabricated by atomic layer deposition exhibit tunable LSPR of gold skeletons in comparison with nanoporous gold-alumina developed before. Extremely large red-shift of LSPR band in nanoporous gold-titania from 537 to 751 nm results from high refractive index of titania and its dielectric medium dependence of LSPR, and the well-controlled thickness of titania shell at the nanometer scale will benefit to integrate optical nanodevices with supreme performances. PMID:21219020

  7. Tunable two types of Fano resonances in metal-dielectric core-shell nanoparticle clusters

    NASA Astrophysics Data System (ADS)

    Yang, Zhong-Jian; Wang, Qu-Quan; Lin, Hai-Qing

    2013-09-01

    We demonstrate that two types of Fano resonances could be observed in metal-dielectric core-shell nanoparticle heptamer clusters. The first kind of Fano resonance is caused by the coupling between electric dipolar plasmon modes. It still remains with high refractive index shells even though metal cores are separated by them. The second one is caused by the interference between scattering electromagnetic modes of dielectric shell and modified plasmon modes. The energy and line shape of these Fano resonances are highly tunable with shell index and particle geometry, which could find applications in nanophotonics.

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

    SciTech Connect

    Amaduzzi, F.; Alarcón-Lladó, E.; Russo-Averchi, E.; Matteini, F.; Heiß, M.; Tütüncüoglu, G.; Conesa-Boj, S.; Fontcuberta i Morral, A.; Mata, M. de la; Arbiol, J.

    2014-11-14

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

  9. Longitudinal versus polar wrinkling of core-shell fibers with anisotropic size mismatches

    NASA Astrophysics Data System (ADS)

    Patrício, P.; Teixeira, P. I. C.; Trindade, A. C.; Godinho, M. H.

    2014-01-01

    We consider a fiber made of a soft elastic material, encased in a stiff elastic shell (core-shell geometry). If the core and shell dimensions are mismatched, e.g., because the core shrinks while the shell does not, but the two remain attached, then an elastic instability is triggered whereby wrinkles may appear on the shell. The wrinkle orientation may be longitudinal (along the fiber axis), polar (along the fiber perimeter), or a mixture of both, depending on the fiber's geometrical and material parameters. Here we investigate under what conditions longitudinal or polar wrinkling will occur.

  10. Hybrid Ag@TiO2 core-shell nanostructures with highly enhanced photocatalytic performance.

    PubMed

    Yang, X H; Fu, H T; Wong, K; Jiang, X C; Yu, A B

    2013-10-18

    A new synthetic approach has been developed to prepare silver@titanium dioxide (Ag@TiO2) core-shell nanostructures with controllable size, shape, crystal phase and function at ambient conditions (e.g. in water, ≤100 ° C). This approach shows a few unique features, including short reaction time (a few minutes) for forming core-shell nanostructures, no requirement of high temperature calcinations for generating TiO2 (e.g. at ~100 ° C in our case), tunable TiO2 shell thickness, high yield and good reproducibility. The experimental results show that the Ag@TiO2 core-shell nanostructures exhibit excellent photocatalytic activity compared to the commercial TiO2 (P25) and Ag-doped TiO2 nanocomposite in the degradation of organic dye molecules (e.g. methyl orange) with ultraviolet (UV) irradiation. This could be attributed to the large surface area of TiO2 nanoparticles for maximum harvesting of UV light, mixed anatase and rutile crystalline phases in the TiO2 shell and the effective charge separation between Ag and TiO2 that can reduce the possible recombination of electron-hole (e(-)-h(+)) pairs within TiO2 generated under UV radiation. To further understand the charge separation situation within Ag-TiO2 composites, theoretical simulation (e.g. density functional theory, DFT) was employed in this study. The DFT simulation results indicate that for the Ag@TiO2 core-shell nanostructures, photo-generated electrons transfer readily from the external TiO2 layer to the internal Ag layer with heavy accumulation compared to those doping Ag on TiO2 surfaces, which may reduce the recombination of e(-)-h(+) pairs and thus enhance the photocatalytic efficiency. The findings may open a new strategy to synthesize TiO2-based photocatalysts with highly enhanced efficiency for environmental remediation applications. PMID:24045164

  11. Hybrid Ag@TiO2 core-shell nanostructures with highly enhanced photocatalytic performance

    NASA Astrophysics Data System (ADS)

    Yang, X. H.; Fu, H. T.; Wong, K.; Jiang, X. C.; Yu, A. B.

    2013-10-01

    A new synthetic approach has been developed to prepare silver@titanium dioxide (Ag@TiO2) core-shell nanostructures with controllable size, shape, crystal phase and function at ambient conditions (e.g. in water, ≤100 ° C). This approach shows a few unique features, including short reaction time (a few minutes) for forming core-shell nanostructures, no requirement of high temperature calcinations for generating TiO2 (e.g. at ˜100 ° C in our case), tunable TiO2 shell thickness, high yield and good reproducibility. The experimental results show that the Ag@TiO2 core-shell nanostructures exhibit excellent photocatalytic activity compared to the commercial TiO2 (P25) and Ag-doped TiO2 nanocomposite in the degradation of organic dye molecules (e.g. methyl orange) with ultraviolet (UV) irradiation. This could be attributed to the large surface area of TiO2 nanoparticles for maximum harvesting of UV light, mixed anatase and rutile crystalline phases in the TiO2 shell and the effective charge separation between Ag and TiO2 that can reduce the possible recombination of electron-hole (e--h+) pairs within TiO2 generated under UV radiation. To further understand the charge separation situation within Ag-TiO2 composites, theoretical simulation (e.g. density functional theory, DFT) was employed in this study. The DFT simulation results indicate that for the Ag@TiO2 core-shell nanostructures, photo-generated electrons transfer readily from the external TiO2 layer to the internal Ag layer with heavy accumulation compared to those doping Ag on TiO2 surfaces, which may reduce the recombination of e--h+ pairs and thus enhance the photocatalytic efficiency. The findings may open a new strategy to synthesize TiO2-based photocatalysts with highly enhanced efficiency for environmental remediation applications.

  12. Optimal design of hollow core-shell structural active materials for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Jiang, Wenjuan; Li, Tingting; Ma, Zengsheng; Lin, Jianguo; Lu, Chunsheng

    To mitigate mechanical and chemical degradation of active materials, hollow core-shell structures have been applied in lithium ion batteries. Without embedding of lithium ions, the rigid coating shell can constrain the inward volume deformation. In this paper, optimal conditions for the full use of inner hollow space are identified in terms of the critical ratio of shell thickness and inner size and the state of charge. It is shown that the critical ratios are 0.10 and 0.15 for Si particle and tube (0.12 and 0.18 for Sn particle and tube), and above which there is lack of space for further lithiation.

  13. No-Core Shell Model Calculations in Light Nuclei with Three-Nucleon Forces

    SciTech Connect

    Barrett, B R; Vary, J P; Nogga, A; Navratil, P; Ormand, W E

    2004-01-08

    The ab initio No-Core Shell Model (NCSM) has recently been expanded to include nucleon-nucleon (NN) and three-nucleon (3N) interactions at the three-body cluster level. Here it is used to predict binding energies and spectra of p-shell nuclei based on realistic NN and 3N interactions. It is shown that 3N force (3NF) properties can be studied in these nuclear systems. First results show that interactions based on chiral perturbation theory lead to a realistic description of {sup 6}Li.

  14. Preparation and optical properties of silica@Ag Cu alloy core-shell composite colloids

    NASA Astrophysics Data System (ADS)

    Zhang, Jianhui; Liu, Huaiyong; Wang, Zhenlin; Ming, Naiben

    2007-04-01

    The silica@Ag-Cu alloy core-shell composite colloids have been successfully synthesized by an electroless plating approach to explore the possibility of modifying the plasmon resonance at the nanoshell surface by varying the metal nanoshell composition for the first time. The surface plasmon resonance of the composite colloids increases in intensity and shifts towards longer, then shorter wavelengths as the Cu/Ag ratio in the alloy shell is increased. The variations in intensity of the surface plasmon resonance with the Cu/Ag ratio obviously affect the Raman bands of the silica colloid core. The report here may supply a new technique to effectively modify the surface plasmon resonance.

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

    PubMed

    Colin, Jérôme

    2012-03-01

    The morphological evolution by surface diffusion of a core-shell spherical particle has been investigated theoretically under hydrostatic pressure when the shear modulii of the core and shell are different. A linear stability analysis has demonstrated that depending on the pressure, shear modulii, and radii of both phases, the free surface of the composite particle may be unstable with respect to a shape perturbation. A stability diagram finally emphasizes that the roughness development is favored in the case of a hard shell with a soft core. PMID:22587137

  16. First-Principles Study on β-SiC/BNNT Core/shell Nanocable

    NASA Astrophysics Data System (ADS)

    Zou, X. C.; Ouyang, J.; Wu, M. S.; Liu, G.; Lei, X. L.; Ouyang, C. Y.; Xu, B.

    2013-09-01

    In this paper, we studied the structural and electronic properties of core/shell nanocables composed of cubic silicon carbide nanowires (β-SiCNW) and boron nitride nanotubes (BNNT) using first-principles pseudopotential plane wave method within density functional theory. Our results show that the β-SiC/BNNT heterojunction structures are metallic, which primarily originates from the contributions of the BNNTs and the surfaces of SiCNWs. The BNNTs exhibit metallic characters after the SiC nanowires are inserted. The transition of the BNNTs is attributed to the charge transfer between BNNTs and SiCNWs.

  17. Au@Pd core-shell nanobricks with concave structures and their catalysis of ethanol oxidation.

    PubMed

    Wang, Wenjin; Zhang, Jie; Yang, Shengchun; Ding, Bingjun; Song, Xiaoping

    2013-10-01

    Au@Pd core-shell nanobricks (CNBs) with concave surfaces and Pd shells with a thickness of approximately 5 nm were synthesized by co-reduction of HAuCl4 and H2 PdCl4 in the presence of Au seeds and Ag ions. These as-synthesized concave CNBs exhibit significantly enhanced catalytic activity for the electrooxidation of ethanol in alkaline media compared to the commercially-used Pd black. The improved performance of the Au@Pd CNBs can be attributed to the exposed stepped surfaces, high-index facets, and the synergistic effects of the core and shell metals. PMID:23929810

  18. Multilevel memristor effect in metal-semiconductor core-shell nanoparticles tested by scanning tunneling spectroscopy

    NASA Astrophysics Data System (ADS)

    Chakrabarti, Sudipto; Pal, Amlan J.

    2015-05-01

    We have grown gold (Au) and copper-zinc-tin-sulfide (CZTS) nanocrystals and Au-CZTS core-shell nanostructures, with gold in the core and the semiconductor in the shell layer, through a high-temperature colloidal synthetic approach. Following usual characterization, we formed ultrathin layers of these in order to characterize the nanostructures in an ultrahigh-vacuum scanning tunneling microscope. Scanning tunneling spectroscopy of individual nanostructures showed the memristor effect or resistive switching from a low- to a high-conducting state upon application of a suitable voltage pulse. The Au-CZTS core-shell nanostructures also show a multilevel memristor effect with the nanostructures undergoing two transitions in conductance at two magnitudes of voltage pulse. We have studied the reproducibility, reversibility, and retentivity of the multilevel memristors. From the normalized density of states (NDOS), we infer that the memristor effect is correlated to a decrease in the transport gap of the nanostructures. We also infer that the memristor effect occurs in the nanostructures due to an increase in the density of available states upon application of a voltage pulse.We have grown gold (Au) and copper-zinc-tin-sulfide (CZTS) nanocrystals and Au-CZTS core-shell nanostructures, with gold in the core and the semiconductor in the shell layer, through a high-temperature colloidal synthetic approach. Following usual characterization, we formed ultrathin layers of these in order to characterize the nanostructures in an ultrahigh-vacuum scanning tunneling microscope. Scanning tunneling spectroscopy of individual nanostructures showed the memristor effect or resistive switching from a low- to a high-conducting state upon application of a suitable voltage pulse. The Au-CZTS core-shell nanostructures also show a multilevel memristor effect with the nanostructures undergoing two transitions in conductance at two magnitudes of voltage pulse. We have studied the reproducibility

  19. Jacobi no-core shell model for p-shell nuclei

    NASA Astrophysics Data System (ADS)

    Liebig, S.; Meißner, U.-G.; Nogga, A.

    2016-04-01

    We introduce an algorithm to obtain coefficients of fractional parentage for light p-shell nuclei. The coefficients enable one to use Jacobi coordinates in no-core shell model calculations separating off the center-of-mass motion. Fully antisymmetrized basis states are given together with recoupling coefficients that allow one to apply two- and three-nucleon operators. As an example, we study the dependence on the harmonic oscillator frequency of 3H, 4He, 6He, 6Li and 7Li and extract their binding and excitation energies. The coefficients will be made openly accessible as HDF5 data files.

  20. Surface-engineered core-shell nano-size ferrites and their antimicrobial activity

    SciTech Connect

    Baraliya, Jagdish D. Joshi, Hiren H.

    2014-04-24

    We report the results of biological study on core-shell structured MFe{sub 2}O{sub 4} (where M = Co, Mn, Ni) nanoparticles and influence of silica- DEG dual coating on their antimicrobial activity. Spherical MFe{sub 2}O{sub 4} nanoparticles were prepared via a Co-precipitation method. The microstructures and morphologies of these nanoparticles were studied by x-ray diffraction and FTIR. The antimicrobial activity study carried out in nutrient agar medium with addition of antimicrobial synthesis compound which is tested for its activity against different types of bacteria.

  1. The Synthesis of Cellulose Graft Copolymers Using Cu(0)-Mediated Polymerization

    NASA Astrophysics Data System (ADS)

    Donaldson, Jason L.

    Cellulose is the most abundant renewable polymer on the planet and there is great interest in expanding its use beyond its traditional applications. However, its hydrophilicity and insolubility in most common solvent systems are obstacles to its widespread use in advanced materials. One way to counteract this is to attach hydrophobic polymer chains to cellulose: this allows the properties of the copolymer to be tailored by the molecular weight, density, and physical properties of the grafts. Two methods were used here to synthesize the graft copolymers: a 'grafting-from' approach, where synthetic chains were grown outward from bromoester moieties on cellulose (Cell-BiB) via Cu(0)-mediated polymerization; and a 'grafting-to' approach, where fully formed synthetic chains with terminal sulfide functionality were added to cellulose acetate with methacrylate functionality (CA-MAA) via thiol-ene Michael addition. The Cell-BiB was synthesized in the ionic liquid 1-butyl-3-methylimidazolium chloride and had a degree of substitution of 1.13. Polymerization from Cell-BiB proceeded at similar but slightly slower rate than an analogous non-polymeric initiator (EBiB). The average graft density of poly(methyl acrylate) chains was 0.71 chains/ring, with a maximum of 1.0 obtained. The graft density when grafting poly(methyl methacrylate) was only 0.15, and this appeared to be due to the slow initiation of BiB groups. Using EBiB to model the reaction and improve the design should allow this to be overcome. Chain extension experiments demonstrated the living behaviour of the polymer. The CA-MAA was synthesized by esterification with methacrylic acid. Reactions of CA-MAA with thiophenol and dodecanethiol resulted in quantitative addition of the thiol to the alkene. The grafts were synthesized by Cu(0)-mediated polymerization from a bifunctional initiator containing a disulfide bond, followed by reduction to sulfides. The synthetic polymers were successfully grafted to CA-MAA but the

  2. The important role of surface ligand on CdSe/CdS core/shell nanocrystals in affecting the efficiency of H2 photogeneration from water

    NASA Astrophysics Data System (ADS)

    Wang, Ping; Zhang, Jie; He, Haili; Xu, Xiaolong; Jin, Yongdong

    2015-03-01

    The use of colloidal semiconductor nanocrystals (NCs), especially those with a core/shell structure, for photocatalytic hydrogen (H2) production from water is currently one of the hottest research fields. Although the ligand on the semiconductor NC surface is crucial to the optical and optoelectronic properties of the NC, the study of the ligand effect on the photocatalytic activity of H2 generation is rarely reported. Herein, we employ nearly monodispersed CdSe/CdS core/shell NCs as a model photocatalytic system, and three kinds of ligands with different numbers of functional thiol groups (i.e., poly(acrylic acid), 3-mercaptopropionic acid and 2,3-dimercaptosuccinic acid) are selected as the ligands to investigate the effect of ligand on the efficiency of H2 photogeneration. The results show that the H2 photogeneration efficiency is highly dependent on the surface ligand of the NCs, and it increases with the increase of the number of the functional thiol groups in the ligand, and correspondingly, the photoluminescence intensity and average fluorescence lifetime, which are measured by steady state and time-resolved fluorescence measurements, are decreased. The surface trap-related charge separation efficiency, which is mediated by surface coating with different ligands, is supposed to cause the distinct ligand-dependent performance in the H2 evolution.The use of colloidal semiconductor nanocrystals (NCs), especially those with a core/shell structure, for photocatalytic hydrogen (H2) production from water is currently one of the hottest research fields. Although the ligand on the semiconductor NC surface is crucial to the optical and optoelectronic properties of the NC, the study of the ligand effect on the photocatalytic activity of H2 generation is rarely reported. Herein, we employ nearly monodispersed CdSe/CdS core/shell NCs as a model photocatalytic system, and three kinds of ligands with different numbers of functional thiol groups (i.e., poly(acrylic acid), 3

  3. Controllable synthesis of concave cubic gold core-shell nanoparticles for plasmon-enhanced photon harvesting.

    PubMed

    Bai, Yang; Butburee, Teera; Yu, Hua; Li, Zhen; Amal, Rose; Lu, G Q Max; Wang, Lianzhou

    2015-07-01

    Well-defined core-shell nanoparticles (NPs) containing concave cubic Au cores and TiO2 shells (CA@T) were synthesized in colloidal suspension. These CA@T NPs exhibit Localized Surface Plasmon Resonance (LSPR) absorption in the NIR region, which provides a unique property for utilizing the low energy range of the solar spectrum. In order to evaluate the plasmonic enhancement effect, a variety of CA@T NPs were incorporated into working electrodes of dye-sensitized solar cells (DSSCs). By adjusting the shell thickness of CA@T NPs, the plasmonic property can be tuned to achieve maximum photovoltaic improvement. Furthermore, the DSSC cells fabricated with the CA@T NPs exhibit a remarkably plasmonic assisted conversion efficiency enhancement (23.3%), compared to that (14.8%) of the reference cells assembled with spherical Au@TiO2 core-shell (SA@T) NPs under similar conditions. Various characterizations reveal that this performance improvement is attributed to the much stronger electromagnetic field generated at the hot spots of CA@T NPs, resulting in significantly higher light harvesting and more efficient charge separation. This study also provides new insights into maximizing the plasmonic enhancement, offering great potential in other applications including light-matter interaction, photocatalytic energy conversion and new-generation solar cells. PMID:25498878

  4. No-Core Shell Model for 48-Ca, 48-Sc and 48-Ti

    SciTech Connect

    Popescu, S; Stoica, S; Vary, J P; Navratil, P

    2004-10-26

    The authors report the first no-core shell model results for {sup 48}Ca, {sup 48}Sc and {sup 48}Ti with derived and modified two-body Hamiltonians. We use an oscillator basis with a limited {bar h}{Omega} range around 40/A{sup 1/3} = 11 MeV and a limited model space up to 1 {bar h}{Omega}. No single-particle energies are used. They find that the charge dependence of the bulk binding energy of eight A = 48 nuclei is reasonably described with an effective Hamiltonian derived from the CD-Bonn interaction while there is an overall underbinding by about 0.4 MeV/nucleon. However, resulting spectra exhibit deficiencies that are anticipated due to: (1) basis space limitations and/or the absence of effective many-body interactions; and, (2) the absence of genuine three-nucleon interactions. They introduce phenomenological modifications to obtain fits to total binding and low-lying spectra. The resulting no-core shell model opens a path for applications to experiments such as the double-beta ({beta}{beta}) decay process.

  5. Mechanisms of morphological evolution on faceted core-shell nanowire surfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Qian; Aqua, Jean-Noël; Voorhees, Peter W.; Davis, Stephen H.

    2016-06-01

    Core-shell nanowires with radial heterostructures hold great promise in photonic and electronic applications and controlling the formation of these heterostructures in the core-shell conguration remains a challenge. Recently, GaAs nanowires have been used as substrates to create AlGaAs shells. The deposition of the AlGaAs layer leads to the spontaneous formation of Al-rich stripes along certain crystallographic directions and quantum dots near the apexes of the shell. A general two-dimensional model has been developed for the motion of the faceted solid-vapor interfaces for pure materials that accounts for capillarity and deposition. With this model, the growth processes and morphological evolution of shells of nanowires around hexagonal cores (six small facets {112} in the corners of six equivalent facets {110}) are investigated in detail both analytically and numerically. It is found that deposition can yield facets that are not present on the Wulff shape. These small facets can have slowly time-varying sizes that can lead to stripe structures and quantum dots depending on the balances between diffusion and deposition. The effects of deposition rates and polarity (or asymmetry) on planes {112} on the development of the configurations of nanowires are discussed. The numerical results are compared with experimental results giving almost quantitative agreement, despite the fact that only pure materials are treated herein whereas the experiments deal with alloys.

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

    PubMed Central

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

    2016-01-01

    Phase-change materials, such as meta-stable undercooled (supercooled) liquids, have been widely recognized as a suitable route for complex fabrication and engineering. Despite comprehensive studies on the undercooling phenomenon, little progress has been made in the use of undercooled metals, primarily due to low yields and poor stability. This paper reports the use of an extension of droplet emulsion technique (SLICE) to produce undercooled core-shell particles of structure; metal/oxide shell-acetate (‘/’ = physisorbed, ‘-’ = chemisorbed), from molten Field’s metal (Bi-In-Sn) and Bi-Sn alloys. These particles exhibit stability against solidification at ambient conditions. Besides synthesis, we report the use of these undercooled metal, liquid core-shell, particles for heat free joining and manufacturing at ambient conditions. Our approach incorporates gentle etching and/or fracturing of outer oxide-acetate layers through mechanical stressing or shearing, thus initiating a cascade entailing fluid flow with concomitant deformation, combination/alloying, shaping, and solidification. This simple and low cost technique for soldering and fabrication enables formation of complex shapes and joining at the meso- and micro-scale at ambient conditions without heat or electricity. PMID:26902483

  7. Dynamics of Intraband and Interband Auger Processes in Colloidal Core-Shell Quantum Dots.

    PubMed

    Rabouw, Freddy T; Vaxenburg, Roman; Bakulin, Artem A; van Dijk-Moes, Relinde J A; Bakker, Huib J; Rodina, Anna; Lifshitz, Efrat; L Efros, Alexander; Koenderink, A Femius; Vanmaekelbergh, Daniël

    2015-10-27

    Conventional colloidal quantum dots (QDs) suffer from rapid energy losses by nonradiative (Auger) processes, leading to sub-ns lifetimes in all excited states but the lowest-energy single exciton. Suppression of interband Auger decay, such as biexciton Auger recombination, has been achieved with the design of heterostructured core-shell QDs. Auger-like processes are also believed to be responsible for rapid intraband hot-electron cooling in QDs. However, the simultaneous effect of shell growth on interband Auger recombination and intraband hot-electron cooling has not been addressed. Here we investigate how the growth of a CdS shell affects these two relaxation processes in CdSe/CdS core-shell QDs. Using a combination of ultrafast pump-push-probe spectroscopy on the QD ensemble and analysis of the photon statistics from single QDs, we find that Auger losses in the biexciton state are suppressed with increasing shell thickness, while hot-electron cooling remains unaffected. Calculations conducted within an eight-band k·p model confirm the experimental dependence of the biexciton Auger decay on the shell thickness, and provide insights into the factors determining the cooling rate of hot carriers. PMID:26389562

  8. Intrinsically core-shell plasmonic dielectric nanostructures with ultrahigh refractive index

    PubMed Central

    Yue, Zengji; Cai, Boyuan; Wang, Lan; Wang, Xiaolin; Gu, Min

    2016-01-01

    Topological insulators are a new class of quantum materials with metallic (edge) surface states and insulating bulk states. They demonstrate a variety of novel electronic and optical properties, which make them highly promising electronic, spintronic, and optoelectronic materials. We report on a novel conic plasmonic nanostructure that is made of bulk-insulating topological insulators and has an intrinsic core-shell formation. The insulating (dielectric) core of the nanocone displays an ultrahigh refractive index of up to 5.5 in the near-infrared frequency range. On the metallic shell, plasmonic response and strong backward light scattering were observed in the visible frequency range. Through integrating the nanocone arrays into a-Si thin film solar cells, up to 15% enhancement of light absorption was predicted in the ultraviolet and visible ranges. With these unique features, the intrinsically core-shell plasmonic nanostructure paves a new way for designing low-loss and high-performance visible to infrared optical devices. PMID:27051869

  9. Synthesis of zirconium tungstate-zirconia core-shell composite particles

    SciTech Connect

    Khazeni, Nasser; Mavis, Bora; Guenduez, Guengoer; Colak, Uner

    2011-11-15

    Highlights: {yields} ZrW{sub 2}O{sub 8}-ZrO{sub 2} core-shell particles to offer solutions for sintering problems. {yields} Core synthesis by a precursor based on tungstic acid and zirconium acetate. {yields} Shell phase by urea hydrolysis in the presence of zirconium ions. {yields} [Urea]/[ZrOCl{sub 2}] ratio controls the rate of shell precursor precipitation. -- Abstract: In this work, ZrW{sub 2}O{sub 8}-ZrO{sub 2} core-shell composite particles were synthesized. ZrW{sub 2}O{sub 8} that was used in the core is a material with negative coefficient of thermal expansion, and it was synthesized from a high-pH precursor based on use of tungstic acid and zirconium acetate. Shell layer was composed of ZrO{sub 2} nanocrystallites and precipitated from an aqueous solution by urea hydrolysis. While volume of the shell was effectively controlled by the initial zirconium ion concentration in the solutions, the rate of precipitation was a function of the ratio of initial concentrations of urea to zirconium ions. It is hypothesized that isolation of the ZrW{sub 2}O{sub 8} within a layer of ZrO{sub 2}, will be a key element in solving problems associated with reactivity of ZrW{sub 2}O{sub 8} towards other components in sintering of ceramic-ceramic composites with tuned or zero thermal expansion coefficient.

  10. Carboxymethyl chitosan-poly(amidoamine) dendrimer core-shell nanoparticles for intracellular lysozyme delivery.

    PubMed

    Zhang, Xiaoyang; Zhao, Jun; Wen, Yan; Zhu, Chuanshun; Yang, Jun; Yao, Fanglian

    2013-11-01

    Intracellular delivery of native, active proteins is challenging due to the fragility of most proteins. Herein, a novel polymer/protein polyion complex (PIC) nanoparticle with core-shell structure was prepared. Carboxymethyl chitosan-grafted-terminal carboxyl group-poly(amidoamine) (CM-chitosan-PAMAM) dendrimers were synthesized by amidation and saponification reactions. (1)H NMR was used to characterize CM-chitosan-PAMAM dendrimers. The TEM images and results of lysozyme loading efficiency indicated that CM-chitosan-PAMAM dendrimers could self-assemble into core-shell nanoparticles, and lysozyme was efficiently encapsulated inside the core of CM-chitosan-PAMAM dendrimer nanoparticles. Activity of lysozyme was completely inhibited by CM-chitosan-PAMAM Dendrimers at physiological pH, whereas it was released into the medium and exhibited a significant enzymatic activity in an acidic intracellular environment. Moreover, the CM-chitosan-PAMAM dendrimer nanoparticles did not exhibit significant cytotoxicity in the range of concentrations below 3.16 mg/ml. The results indicated that these CM-chitosan-PAMAM dendrimers have excellent properties as highly potent and non-toxic intracellular protein carriers, which would create opportunities for novel applications in protein delivery. PMID:24053810

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

    PubMed

    Li, Chen; Yu, Deng-Guang; Williams, Gareth R; Wang, Zhuan-Hua

    2014-01-01

    This study reports on novel fast-dissolving core-shell composite microparticles of quercetin fabricated using coaxial electrospraying. A PVC-coated concentric spinneret was developed to conduct the electrospray process. A series of analyses were undertaken to characterize the resultant particles in terms of their morphology, the physical form of their components, and their functional performance. Scanning and transmission electron microscopies revealed that the microparticles had spherical morphologies with clear core-shell structure visible. Differential scanning calorimetry and X-ray diffraction verified that the quercetin active ingredient in the core and sucralose and sodium dodecyl sulfate (SDS) excipients in the shell existed in the amorphous state. This is believed to be a result of second-order interactions between the components; these could be observed by Fourier transform infrared spectroscopy. In vitro dissolution and permeation studies showed that the microparticles rapidly released the incorporated quercetin within one minute, and had permeation rates across the sublingual mucosa around 10 times faster than raw quercetin. PMID:24643072

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

    PubMed

    Buesser, B; Pratsinis, S E

    2011-11-01

    Core-shell particles preserve the bulk properties (e.g. magnetic, optical) of the core while its surface is modified by a shell material. Continuous aerosol coating of core TiO2 nanoparticles with nanothin silicon dioxide shells by jet injection of hexamethyldisiloxane precursor vapor downstream of titania particle formation is elucidated by combining computational fluid and aerosol dynamics. The effect of inlet coating vapor concentration and mixing intensity on product shell thickness distribution is presented. Rapid mixing of the core aerosol with the shell precursor vapor facilitates efficient synthesis of hermetically coated core-shell nanoparticles. The predicted extent of hermetic coating shells is compared to the measured photocatalytic oxidation of isopropanol by such particles as hermetic SiO2 shells prevent the photocatalytic activity of titania. Finally the performance of a simpler, plug-flow coating model is assessed by comparisons to the present detailed CFD model in terms of coating efficiency and silica average shell thickness and texture. PMID:23729817

  13. Magnetic proximity effect in ferrimagnetic-ferromagnetic core-shell Prussian blue analogues molecular magnet

    NASA Astrophysics Data System (ADS)

    Bhatt, Pramod; Kumar, Amit; Meena, S. S.; Mukadam, M. D.; Yusuf, S. M.

    2016-05-01

    A magnetic proximity effect has been observed in core-shell structure of molecular magnet, Mn1.5[Cr(CN)6]·mH2O@Ni1.5[Cr(CN)6]·nH2O, synthesized using a ferrimagnetic core of Mn1.5[Cr(CN)6]·7.5H2O surrounded by a ferromagnetic shell of Ni1.5[Cr(CN)6]·7.5H2O. The values of Curie temperature (TC) are found to be of ∼65 and ∼60 K for the bare-core and bare-shell compounds, respectively. However, an enhanced TC (∼70 K) has been observed for the core-shell structure. The proximity effect (due to presence of interface exchange coupling) between core and shell is responsible for the observed enhancement of TC. A neutron depolarization study also confirms finite depolarization below ∼70 K.

  14. Effects of Nonlocal Exact Exchange on Electrons in Core/Shell Nanowires

    NASA Astrophysics Data System (ADS)

    Wong, Bryan; Long, Andrew

    2013-03-01

    The unique properties of semiconducting heterostructure nanowires hold great promise for their incorporation in next-generation transistors, circuits, and nanoscale devices. The reduction in dimensionality produced by confining electrons in these heterostructure nanowires results in a dramatic change in their electronic structure, leading to novel properties such as ballistic transport and conductance quantization. In order to understand the formation of electron gases in core-shell nanowires, we developed a new pseudospectral approach for incorporating many-body, nonlocal exact exchange interactions within a self-consistent Schrodinger-Poisson formalism. Our approach is efficiently implemented in the open-source software package PAMELA (Pseudospectral Analysis Method with Exchange & Local Approximations) that can calculate electronic energies, densities, wavefunctions, and band-bending diagrams. Furthermore, in order to present a general-purpose set of tools that both experimentalists and theorists can easily use to predict electron gas formation in core-shell nanowires, we document and provide our efficient and user-friendly PAMELA source code that is freely available at http://alum.mit.edu/www/usagi.

  15. Multilevel memristor effect in metal-semiconductor core-shell nanoparticles tested by scanning tunneling spectroscopy.

    PubMed

    Chakrabarti, Sudipto; Pal, Amlan J

    2015-06-01

    We have grown gold (Au) and copper-zinc-tin-sulfide (CZTS) nanocrystals and Au-CZTS core-shell nanostructures, with gold in the core and the semiconductor in the shell layer, through a high-temperature colloidal synthetic approach. Following usual characterization, we formed ultrathin layers of these in order to characterize the nanostructures in an ultrahigh-vacuum scanning tunneling microscope. Scanning tunneling spectroscopy of individual nanostructures showed the memristor effect or resistive switching from a low- to a high-conducting state upon application of a suitable voltage pulse. The Au-CZTS core-shell nanostructures also show a multilevel memristor effect with the nanostructures undergoing two transitions in conductance at two magnitudes of voltage pulse. We have studied the reproducibility, reversibility, and retentivity of the multilevel memristors. From the normalized density of states (NDOS), we infer that the memristor effect is correlated to a decrease in the transport gap of the nanostructures. We also infer that the memristor effect occurs in the nanostructures due to an increase in the density of available states upon application of a voltage pulse. PMID:25966930

  16. Intrinsically core-shell plasmonic dielectric nanostructures with ultrahigh refractive index.

    PubMed

    Yue, Zengji; Cai, Boyuan; Wang, Lan; Wang, Xiaolin; Gu, Min

    2016-03-01

    Topological insulators are a new class of quantum materials with metallic (edge) surface states and insulating bulk states. They demonstrate a variety of novel electronic and optical properties, which make them highly promising electronic, spintronic, and optoelectronic materials. We report on a novel conic plasmonic nanostructure that is made of bulk-insulating topological insulators and has an intrinsic core-shell formation. The insulating (dielectric) core of the nanocone displays an ultrahigh refractive index of up to 5.5 in the near-infrared frequency range. On the metallic shell, plasmonic response and strong backward light scattering were observed in the visible frequency range. Through integrating the nanocone arrays into a-Si thin film solar cells, up to 15% enhancement of light absorption was predicted in the ultraviolet and visible ranges. With these unique features, the intrinsically core-shell plasmonic nanostructure paves a new way for designing low-loss and high-performance visible to infrared optical devices. PMID:27051869

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

    PubMed

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

    2015-12-21

    Nanodiamond-graphene core-shell materials have several unique properties compared with purely sp(2) -bonded nanocarbons and perform remarkably well as metal-free catalysts. In this work, we report that palladium nanoparticles supported on nanodiamond-graphene core-shell materials (Pd/ND@G) exhibit superior catalytic activity in CO oxidation compared to Pd NPs supported on an sp(2) -bonded onion-like carbon (Pd/OLC) material. Characterization revealed that the Pd NPs in Pd/ND@G have a special morphology with reduced crystallinity and are more stable towards sintering at high temperature than the Pd NPs in Pd/OLC. The electronic structure of Pd is changed in Pd/ND@G, resulting in weak CO chemisorption on the Pd NPs. Our work indicates that strong metal-support interactions can be achieved on a non-reducible support, as exemplified for nanocarbon, by carefully tuning the surface structure of the support, thus providing a good example for designing a high-performance nanostructured catalyst. PMID:26568172

  18. Supported Core@Shell Electrocatalysts for Fuel Cells: Close Encounter with Reality

    PubMed Central

    Hwang, Seung Jun; Yoo, Sung Jong; Shin, Jungho; Cho, Yong-Hun; Jang, Jong Hyun; Cho, Eunae; Sung, Yung-Eun; Nam, Suk Woo; Lim, Tae-Hoon; Lee, Seung-Cheol; Kim, Soo-Kil

    2013-01-01

    Core@shell electrocatalysts for fuel cells have the advantages of a high utilization of Pt and the modification of its electronic structures toward enhancement of the activities. In this study, we suggest both a theoretical background for the design of highly active and stable core@shell/C and a novel facile synthetic strategy for their preparation. Using density functional theory calculations guided by the oxygen adsorption energy and vacancy formation energy, Pd3Cu1@Pt/C was selected as the most suitable candidate for the oxygen reduction reaction in terms of its activity and stability. These predictions were experimentally verified by the surfactant-free synthesis of Pd3Cu1/C cores and the selective Pt shell formation using a Hantzsch ester as a reducing agent. In a similar fashion, Pd@Pd4Ir6/C catalyst was also designed and synthesized for the hydrogen oxidation reaction. The developed catalysts exhibited high activity, high selectivity, and 4,000 h of long-term durability at the single-cell level. PMID:23419683

  19. Employing Core-Shell Quantum Dots as Triplet Sensitizers for Photon Upconversion.

    PubMed

    Okumura, Keisuke; Mase, Kazuma; Yanai, Nobuhiro; Kimizuka, Nobuo

    2016-06-01

    A new family of surface-functionalized CdSe/ZnS core-shell quantum dots (csQD) has been developed, which work as triplet sensitizers for triplet-triplet annihilation-based photon upconversion (TTA-UC). The surface modification of csQD with acceptor molecules plays a key role in the efficient relay of the excited energy of csQD to emitter molecules in the bulk solution, where the generated emitter triplets undergo triplet-triplet annihilation that leads to photon upconversion. Interestingly, improved UC properties were achieved with the core-shell QDs compared with core-only CdSe QDs (cQD). The threshold excitation intensity, which is defined as the necessary irradiance to achieve efficient TTA process, decreases by more than a factor of four. Furthermore, the total UC quantum yield is enhanced more than 50-fold. These enhancements should be derived from better optical properties of csQD, in which the non-radiative surface recombination sites are passivated by the shell layer with wider bandgap. PMID:27121225

  20. Core/Shell and High Aspect Ratio Magnetic Oxide Nanoparticles for Antenna Applications

    NASA Astrophysics Data System (ADS)

    Ekiert, Thomas F., Jr.; O'Malley, Matthew; Yocum, Brandon; Lippold, Jennifer; Lyle, Mallory; Griner, Angela; Flynn, Cory; Nickel, Anna; Alexander, Max D., Jr.

    2012-02-01

    Improved antenna gain, reduced antenna aperture size, and improved bandwidth are of interest to an increasingly mobile world. To obtain these improvements our efforts are directed at developing new magnetic oxide nanoparticle/polymer composites with modifiable permeability and permittivity and low electrical losses. Our approach consists of producing core/shell and shape controlled magnetic nanoparticles. Methods of synthesis utilize microwave and traditional heating to perform hydrothermal and solvothermal reactions. Decomposition of metal acetylacetonates is performed using various alcohols resulting in spherical nanoparticles with diameters of 8-16 nm and 3-7 nm for Fe3O4 and CoFe2O4, respectively. Microwave methods result in similar particles, but are produced in an hour or less as compared to 48 hrs via the traditional solvothermal method. Successive growths are used to produce larger monolithic particles as well as core/shell systems where exchange coupling between the core and shell is observed. Hexaferrite particles have been produced via hydrothermal synthesis, while high aspect ratio Fe3O4 nanoparticles ( 10-100 nm) produced via hydrothermal synthesis result in nanoneedles with high μr.

  1. A theoretical study on the advantage of core-shell particles with radially-oriented mesopores.

    PubMed

    Deridder, Sander; Catani, Martina; Cavazzini, Alberto; Desmet, Gert

    2016-07-22

    We report on a first-principles numerical study explaining the potential advantage of core-shell particles with strictly radially-oriented mesopores. Comparing the efficiency of these particles with fully porous and core-shell particles with a conventional (i.e., randomly oriented) mesopore network, the present numerical study shows a similar strong reduction in minimal reduced plate height (hmin) as was very recently observed in an experimental study by Wei et al. (respectively a hmin-reduction on the order of about 1 and 0.5 reduced plate height-units). As such, the present work provides a theoretical basis to understand and confirm their experimental findings and quantifies the general advantage of "radial-diffusion-only" particles. Determining the effective longitudinal diffusion (B-term contribution) in a series of dedicated, independent simulations, it was found that this contribution can be described by a very simple, yet fully exact mathematical expression for the case of "radial- diffusion-only" particles. Using this expression, the significant increase in efficiency of these particles can be fully attributed to their much smaller B-term band broadening, while their C-term band broadening (representing the mass transfer resistance) remains unaffected. PMID:27317003

  2. Core-Shell Coating Silicon Anode Interfaces with Coordination Complex for Stable Lithium-Ion Batteries.

    PubMed

    Zhou, Jinqiu; Qian, Tao; Wang, Mengfan; Xu, Na; Zhang, Qi; Li, Qun; Yan, Chenglin

    2016-03-01

    In situ core-shell coating was used to improve the electrochemical performance of Si-based anodes with polypyrrole-Fe coordination complex. The vast functional groups in the organometallic coordination complex easily formed hydrogen bonds when in situ modifying commercial Si nanoparticles. The incorporation of polypyrrole-Fe resulted in the conformal conductive coating surrounding each Si nanoparticle, not only providing good electrical connection to the particles but also promoting the formation of a stable solid-electrolyte-interface layer on the Si electrode surface, enhancing the cycling properties. As an anode material for Li-ion batteries, modified silicon powders exhibited high reversible capacity (3567 mAh/g at 0.3 A/g), good rate property (549.12 mAh/g at 12 A/g), and excellent cycling performance (reversible capacity of 1500 mAh/g after 800 cycles at 1.2 A/g). The constructed novel concept of core-shell coating Si particles presented a promising route for facile and large-scale production of Si-based anodes for extremely durable Li-ion batteries, which provided a wide range of applications in the field of energy storage of the renewable energy derived from the solar energy, hydropower, tidal energy, and geothermal heat. PMID:26863089

  3. Photosensitive and biomimetic core-shell nanofibrous scaffolds as wound dressing.

    PubMed

    Jin, Guorui; Prabhakaran, Molamma P; Ramakrishna, Seeram

    2014-01-01

    Tissue engineered skin grafts that mimic the native extracellular matrix of skin has gained huge popularity among clinicians since they increase the survival rate of the patients. Phototherapy shows promising results with respect to acute and chronic pain relief, treatment of inflammatory conditions and promotion of wound healing. Here, we encapsulated a photosensitive polymer poly (3-hexylthiophene) (P3HT) and epidermal growth factor in the core-shell-structured Gelatin/poly(L-lactic acid)-co-poly-(ε-caprolactone) nanofibers [Gel/PLLCL/P3GF(cs)] by coaxial spinning and studied the potential application of the Gel/PLLCL/P3GF(cs) nanofibrous scaffold as a novel skin graft. The proliferation of fibroblasts was significantly improved on Gel/PLLCL/P3GF(cs) under light stimulation compared to fibroblasts on the same scaffold under dark condition. Studies on the in vitro wound healing ability of Gel/PLLCL/P3GF(cs) showed complete closure of wound after 9 days under "light stimulation" too. Furthermore, the potential of adipose-derived stem cells (ASCs) to differentiate to epidermal cells on Gel/PLLCL/P3GF(cs) was evaluated. The differentiated ASCs with keratinocytes morphology were only found on the light stimulated Gel/PLLCL/P3GF(cs). Our results suggest that the photosensitive core-shell Gel/PLLCL/P3GF(cs) nanofibers could be a novel substrate to aid in the reestablishment of skin architecture. PMID:24417712

  4. Quantitative analysis of core-shell catalyst nanoparticles for industrial applications

    NASA Astrophysics Data System (ADS)

    E, H.; Nellist, P. D.; Lozano-Perez, S.; Ozkaya, D.

    2012-07-01

    Pd@Pt core-shell designed nanoparticle catalysts have been shown to dramatically increase the activity and selectivity of the oxygen reduction reaction in fuel cells. Aberration corrected electron microscopy offers the spatial resolution and chemical sensitivity to unlock these structures at the atomic scale. Understanding the particle size, shape and the exact nature of the shell coverage (whether it is full, partial or whether the particle is alloyed) is vital to understanding their behaviour. This paves the way for even more effective catalyst designs. We present a semi-statistical investigation into the size, morphology and bimetallic content of various core-shell particle designs, pre- and post- fuel cell cycling, using high resolution HAADF STEM and EDX. In addition, careful quantitative analysis of our datasets will allow us to extract information, not only of the morphology, but also the thickness and coverage of the particle shells. We compare this with chemical findings about activity and selectivity to understand how shell coverage and content affect catalytic activity.

  5. Magnetic behavior of Joule-heated magnetic core-shell nanowires with positive magnetostrictive core material

    NASA Astrophysics Data System (ADS)

    Dumitru, Ioan; Astefanoaei, Iordana; Cimpoesu, Dorin; Stancu, Alexandru

    2015-10-01

    Temperature field is an important parameter to be known and controlled in the magnetization process of the core-shell nanowires. The paper analyzes the temperature dependence of hysteretic process in a core-shell nanowire subjected to a dc Joule heating process. An electrical current that passes through the wire induces a temperature and a thermal stress field in the system. Spatial and temporal evolution of the temperature in system was analyzed using a model based on time-dependent heat conduction equation. The stresses determined by thermal gradients and different expansion characteristics of core and shell materials were computed. The temperature and stress depend on the size parameters of the system, dc Joule current and the initial temperature of the system. The magnetic behavior of the nanowire was analyzed using the Micromag application. The magnetic state of the core is influenced by the temperature field induced by a dc current applied to the system. For core materials with positive magnetostriction coefficient the coercive field increases at the increase of dc current intensity passed through the system.

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

    PubMed

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

    2016-01-01

    Phase-change materials, such as meta-stable undercooled (supercooled) liquids, have been widely recognized as a suitable route for complex fabrication and engineering. Despite comprehensive studies on the undercooling phenomenon, little progress has been made in the use of undercooled metals, primarily due to low yields and poor stability. This paper reports the use of an extension of droplet emulsion technique (SLICE) to produce undercooled core-shell particles of structure; metal/oxide shell-acetate ('/' = physisorbed, '-' = chemisorbed), from molten Field's metal (Bi-In-Sn) and Bi-Sn alloys. These particles exhibit stability against solidification at ambient conditions. Besides synthesis, we report the use of these undercooled metal, liquid core-shell, particles for heat free joining and manufacturing at ambient conditions. Our approach incorporates gentle etching and/or fracturing of outer oxide-acetate layers through mechanical stressing or shearing, thus initiating a cascade entailing fluid flow with concomitant deformation, combination/alloying, shaping, and solidification. This simple and low cost technique for soldering and fabrication enables formation of complex shapes and joining at the meso- and micro-scale at ambient conditions without heat or electricity. PMID:26902483

  7. Interfacial strain effect on type-I and type-II core/shell quantum dots

    NASA Astrophysics Data System (ADS)

    Gheshlaghi, Negar; Pisheh, Hadi Sedaghat; Karim, M. Rezaul; Malkoc, Derya; Ünlü, Hilmi

    2016-09-01

    A comparative experimental and theoretical study on the calculation of capped core diameter in ZnSe/ZnS, CdSe/Cd(Zn)S type-I and ZnSe/CdS type-II core/shell nanocrystals is presented. The lattice mismatch induced interface strain between core and shell was calculated from continuum elastic theory and applied in effective mass approximation method to obtain the corresponding capped core diameter. The calculated results were compared with diameter of bare cores (CdSe and ZnSe) from transmission electron microscopy images to obtain the amount of the stretched or squeezed core after deposition of tensile or compressive shells. The result of the study showed that the core is squeezed in ZnSe/ZnS and CdSe/Cd(Zn)S after compressive shell and stretched in ZnSe/CdS after tensile shell deposition. The stretched and squeezed amount of the capped core found to be in proportion with lattice mismatch amount in the core/shell structure.

  8. Synthesis of core-shell bioaffinity chitosan-TiO₂ composite and its environmental applications.

    PubMed

    Xiao, Gang; Su, Haijia; Tan, Tianwei

    2015-01-01

    Based on the coupling of molecular imprinting, chitosan biosorption, and nano TiO2 photocatalysis technologies, a novel core-shell organic-inorganic hybrid material of surface imprinted chitosan-TiO2 composite (SICT) was prepared with methyl orange as the template. SEM, EDS, AFM, pore size analysis, and FTIR characterization results illustrated that TiO2 nano powder was successfully coated on the surface of chitosan microparticles via intermolecular hydrogen bonds to form the core-shell organic-inorganic composites with rough and porous surface morphology. SICT showed enhanced photocatalytic selectivity for methyl orange (M.O.) compared with the non-imprinted chitosan-TiO2 composites because of the existing of more suitable sites generated by surface molecular imprinting. The removal of M.O. by SICT was mainly from the photocatalytic degradation rather than simple adsorption. SICT could be reused directly without further desorption and regeneration for 10 cycles with preserving 60% of its photocatalytic efficiency. The reusability of SICT would be beneficial for the simplification of the operating steps and the cost reduction which facilitated its practical applications in wastewater treatment concerning environmental organic pollutants. PMID:25464333

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

    Monodispersed silica spheres with particles size of ca. 450 nm were successfully synthesized using a modified Stöber method. The synthesized monodispersed silica spheres were successfully coated with copper using modified sol-gel method employing nonsurfactant surface modifiers and catalyst. A renewable palm oil based decyl-alcohol (C10) as nonsurfactant surface modifiers and catalyst were used to modify the silica surfaces prior to coating with copper. The X-ray diffraction patterns of Si-Cu core-shell exhibited a broad peak corresponding to amorphous silica networks and monoclinic CuO phase. It was found that samples modified in the presence of 1 ml catalyst exhibited homogeneous deposition. The surface area of core materials (SiO2) was at ca. 7.04 m2/g and Si-Cu core-shell was at ca. 8.21 m2/g. The band gap of samples prepared with and without catalyst was calculated to be ca. 2.45 eV and ca. 3.90 eV respectively based on the UV-vis absorption spectrum of the product.

  10. Synthesis and Characterization of Au@Cu Core-Shell Nanoparticles

    NASA Astrophysics Data System (ADS)

    Khanal, Subarna; Velazquez-Salazar, Jesus; Yacaman, Miguel Jose

    2011-10-01

    The synthesis of bimetallic nanoparticles has become so important in present times due to its diverse applications of nanotechnology. Particularly most of the bimetallic nanoparticles are focused to use in catalysis, plasmonic, magnetic, sensors, and many other applications. In Au/Cu case, the bulk Au and Cu are soluble at all compositions. But the structure of Au/Cu nanoparticles depends on the preparation methods. The structure might be the core shell, alloys or other morphology. Au- Cu core-shell nanocrystals were prepared using a two-step polyol reduction method. First, Au core seeds were prepared by reducing HAuCl4. 4H2O in ethylene glycol (EG) using oil-bath heating in the presence of polyvinylpyrrolidone (PVP) as a polymer surfactant. Then Cu shells were overgrown on Au core seeds by reducing Cu2(OAc)4 in EG with PVP again using oil-bath heating. The morphology is studied by STEM HITACHI S-5500.The resultant crystal structures were characterized using TEM, high-resolution (HR)-TEM and the STEM were using for the study of micro analysis.

  11. Synthesis, structural characterization and magnetic properties of Fe/Pt core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Pisane, K. L.; Singh, Sobhit; Seehra, M. S.

    2015-05-01

    Structural and magnetic properties of Fe/Pt core-shell nanostructure prepared by a sequential reduction process are reported. Transmission electron microscopy shows nearly spherical particles fitting a lognormal size distribution with Do = 3.0 nm and distribution width λD = 0.31. In x-ray diffraction, Bragg lines only from the Pt shell are clearly identified with line-widths yielding crystallite size = 3.1 nm. Measurements of magnetization M vs. T (2 K-350 K) in magnetic fields up to 90 kOe show a blocking temperature TB = 13 K below which hysteresis loops are observed with coercivity HC increasing with decreasing T reaching HC = 750 Oe at 2 K. Temperature dependence of the ac susceptibilities at frequencies fm = 10 Hz-5 kHz is measured to determine the change in TB with fm using the Vogel-Fulcher law. This analysis shows the presence of significant interparticle interaction, the Neel-Brown relaxation frequency fo = 5.3 × 1010 Hz and anisotropy constant Ka = 3.6 × 106 ergs/cm3. A fit of the M vs. H data up to H = 90 kOe for T > TB to the modified Langevin function taking particle size distribution into account yields magnetic moment per particle consistent with the proposed core-shell structure; Fe core of 2.2 nm diameter and Pt shell of 0.4 nm thickness.

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  13. The multifunctional wound dressing with core-shell structured fibers prepared by coaxial electrospinning

    NASA Astrophysics Data System (ADS)

    Wei, Qilin; Xu, Feiyang; Xu, Xingjian; Geng, Xue; Ye, Lin; Zhang, Aiying; Feng, Zengguo

    2016-04-01

    The non-woven wound dressing with core-shell structured fibers was prepared by coaxial electrospinning. The polycaprolactone (PCL) was electrospun as the fiber's core to provide mechanical strength whereas collagen was fabricated into the shell in order to utilize its good biocompatibility. Simultaneously, the silver nanoparticles (Ag- NPs) as anti-bacterial agent were loaded in the shell whereas the vitamin A palmitate (VA) as healing-promoting drug was encapsulated in the core. Resulting from the fiber's core-shell structure, the VA released from the core and Ag-NPs present in the shell can endow the dressing both heal-promoting and anti-bacteria ability simultaneously, which can greatly enhance the dressing's clinical therapeutic effect. The dressing can maintain high swelling ratio of 190% for 3 d indicating its potential application as wet dressing. Furthermore, the dressing's anti-bacteria ability against Staphylococcus aureus was proved by in vitro anti-bacteria test. The in vitro drug release test showed the sustainable release of VA within 72 h, while the cell attachment showed L929 cells can well attach on the dressing indicating its good biocompatibility. In conclusion, the fabricated nanofibrous dressing possesses multiple functions to benefit wound healing and shows promising potential for clinical application.

  14. Core-Shell Composite Hydrogels for Controlled Nanocrystal Formation and Release of Hydrophobic Active Pharmaceutical Ingredients.

    PubMed

    Badruddoza, Abu Zayed Md; Godfrin, P Douglas; Myerson, Allan S; Trout, Bernhardt L; Doyle, Patrick S

    2016-08-01

    Although roughly 40% of pharmaceuticals being developed are poorly water soluble, this class of drugs lacks a formulation strategy capable of producing high loads, fast dissolution kinetics, and low energy input. In this work, a novel bottom-up approach is developed for producing and formulating nanocrystals of poorly water-soluble active pharmaceutical ingredients (APIs) using core-shell composite hydrogel beads. Organic phase nanoemulsion droplets stabilized by polyvinyl alcohol (PVA) and containing a model hydrophobic API (fenofibrate) are embedded in the alginate hydrogel matrix and subsequently act as crystallization reactors. Controlled evaporation of this composite material produces core-shell structured alginate-PVA hydrogels with drug nanocrystals (500-650 nm) embedded within the core. Adjustable loading of API nanocrystals up to 83% by weight is achieved with dissolution (of 80% of the drug) occurring in as little as 30 min. A quantitative model is also developed and experimentally validated that the drug release patterns of the fenofibrate nanocrystals can be modulated by controlling the thickness of the PVA shell and drug loading. Thus, these composite materials offer a "designer" drug delivery system. Overall, our approach enables a novel means of simultaneous controlled crystallization and formulation of hydrophobic drugs that circumvents energy intensive top-down processes in traditional manufacturing. PMID:27249402

  15. The multifunctional wound dressing with core-shell structured fibers prepared by coaxial electrospinning

    NASA Astrophysics Data System (ADS)

    Wei, Qilin; Xu, Feiyang; Xu, Xingjian; Geng, Xue; Ye, Lin; Zhang, Aiying; Feng, Zengguo

    2016-06-01

    The non-woven wound dressing with core-shell structured fibers was prepared by coaxial electrospinning. The polycaprolactone (PCL) was electrospun as the fiber's core to provide mechanical strength whereas collagen was fabricated into the shell in order to utilize its good biocompatibility. Simultaneously, the silver nanoparticles (Ag-NPs) as anti-bacterial agent were loaded in the shell whereas the vitamin A palmitate (VA) as healing-promoting drug was encapsulated in the core. Resulting from the fiber's core-shell structure, the VA released from the core and Ag-NPs present in the shell can endow the dressing both heal-promoting and anti-bacteria ability simultaneously, which can greatly enhance the dressing's clinical therapeutic effect. The dressing can maintain high swelling ratio of 190% for 3 d indicating its potential application as wet dressing. Furthermore, the dressing's anti-bacteria ability against Staphylococcus aureus was proved by in vitro anti-bacteria test. The in vitro drug release test showed the sustainable release of VA within 72 h, while the cell attachment showed L929 cells can well attach on the dressing indicating its good biocompatibility. In conclusion, the fabricated nanofibrous dressing possesses multiple functions to benefit wound healing and shows promising potential for clinical application.

  16. Formation mechanism of monodispersed spherical core-shell ceria/polymer hybrid nanoparticles

    SciTech Connect

    Izu, Noriya; Uchida, Toshio; Matsubara, Ichiro; Itoh, Toshio; Shin, Woosuck; Nishibori, Maiko

    2011-08-15

    Graphical abstract: The formation mechanism for core-shell nanoparticles is considered to be as follows: nucleation and particle growth occur simultaneously (left square); very slow particle growth occurs (middle square). Highlights: {yields} The size of the resultant nanoparticles was strongly and complicatedly dependent on the set temperature used during reflux heating and the PVP molecular weight. {yields} The size of the nanoparticles increased by a 2-step process as the reflux heating time increased. {yields} The IR spectral changes with increasing reflux time indicated the increase in the number of cross-linked polymers in the shell. -- Abstract: Very unique core-shell ceria (cerium oxide)/polymer hybrid nanoparticles that have monodispersed spherical structures and are easily dispersed in water or alcohol without the need for a dispersant were reported recently. The formation mechanism of the unique nanoparticles, however, was not clear. In order to clarify the formation mechanism, these nanoparticles were prepared using a polyol method (reflux heating) under varied conditions of temperature, time, and concentration and molecular weight of added polymer (poly(vinylpyrrolidone)). The size of the resultant nanoparticles was strongly and complicatedly dependent on the set temperature used during reflux heating and the poly(vinylpyrrolidone) molecular weight. Furthermore, the size of the nanoparticles increased by a 2-step process as the reflux heating time increased. The IR spectral changes with increasing reflux time indicated the increase in the number of cross-linked polymers in the shell. From these results, the formation mechanism was discussed and proposed.

  17. Carbon-Supported IrNi Core-Shell Nanoparticles: Synthesis Characterization and Catalytic Activity

    SciTech Connect

    K Sasaki; K Kuttiyiel; L Barrio; D Su; A Frenkel; N Marinkovic; D Mahajan; R Adzic

    2011-12-31

    We synthesized carbon-supported IrNi core-shell nanoparticles by chemical reduction and subsequent thermal annealing in H{sub 2}, and verified the formation of Ir shells on IrNi solid solution alloy cores by various experimental methods. The EXAFS analysis is consistent with the model wherein the IrNi nanoparticles are composed of two-layer Ir shells and IrNi alloy cores. In situ XAS revealed that the Ir shells completely protect Ni atoms in the cores from oxidation or dissolution in an acid electrolyte under elevated potentials. The formation of Ir shell during annealing due to thermal segregation is monitored by time-resolved synchrotron XRD measurements, coupled with Rietveld refinement analyses. The H{sub 2} oxidation activity of the IrNi nanoparticles was found to be higher than that of a commercial Pt/C catalyst. This is predominantly due to Ni-core-induced Ir shell contraction that makes the surface less reactive for IrOH formation, and the resulting more metallic Ir surface becomes more active for H{sub 2} oxidation. This new class of core-shell nanoparticles appears promising for application as hydrogen anode fuel cell electrocatalysts.

  18. Magnetic properties of fluffy Fe@α-Fe2O3 core-shell nanowires

    PubMed Central

    2013-01-01

    Novel fluffy Fe@α-Fe2O3 core-shell nanowires have been synthesized using the chemical reaction of ferrous sulfate and sodium borohydride, as well as the post-annealing process in air. The coercivity of the as-synthesized nanowires is above 684 Oe in the temperature range of 5 to 300 K, which is significantly higher than that of the bulk Fe (approximately 0.9 Oe). Through the annealing process in air, the coercivity and the exchange field are evidently improved. Both the coercivity and the exchange field increase with increasing annealing time (TA) and reach their maximum values of 1,042 and 78 Oe, respectively, at TA = 4 h. The magnetic measurements show that the effective anisotropy is increased with increasing the thickness of theα-Fe2O3 by annealing. The large values of coercivity and exchange field, as well as the high surface area to volume ratio, may make the fluffy Fe@α-Fe2O3 core-shell nanowire a promising candidate for the applications of the magnetic drug delivery, electrochemical energy storage, gas sensors, photocatalysis, and so forth. PMID:24134440

  19. Exciton Formation and Quenching in a Au/CdS Core/Shell Nanostructure.

    PubMed

    Ziemannn, Dirk; May, Volkhard

    2015-10-15

    An atomistic description is presented of the excited state dynamics in spherical Au/CdS core/shell nanocrystals up to a diameter of 15 nm. Au-core excited states are considered in a multipole plasmon scheme, whereas a tight-binding description combined with a configuration interaction approach is used to compute single electron-hole pair excitations in the CdS-shell. The electron-hole pair energy-shift and screening due to an Au-core polarization is found of minor importance. For the studied system, the energy transfer coupling can be identified as the essential core-shell interaction. Characterizing the CdS-shell excitons by atomic centered transition charges and the Au-core by its multipole plasmon moments, an energy transfer coupling can be introduced that gives a complete microscopic description beyond any dipole-dipole approximation and with values around 10 meV. Together with a considerable plasmon-exciton energy mismatch, these coupling values explain the measured 300 ps lifetime of shell excitons due to energy transfer to the Au-core. PMID:26722776

  20. Direct Fabrication of Monodisperse Silica Nanorings from Hollow Spheres - A Template for Core-Shell Nanorings.

    PubMed

    Zhong, Kuo; Li, Jiaqi; Liu, Liwang; Brullot, Ward; Bloemen, Maarten; Volodin, Alexander; Song, Kai; Van Dorpe, Pol; Verellen, Niels; Clays, Koen

    2016-04-27

    We report a new type of nanosphere colloidal lithography to directly fabricate monodisperse silica (SiO2) nanorings by means of reactive ion etching of hollow SiO2 spheres. Detailed TEM, SEM, and AFM structural analysis is complemented by a model describing the geometrical transition from hollow sphere to ring during the etching process. The resulting silica nanorings can be readily redispersed in solution and subsequently serve as universal templates for the synthesis of ring-shaped core-shell nanostructures. As an example we used silica nanorings (with diameter of ∼200 nm) to create a novel plasmonic nanoparticle topology, a silica-Au core-shell nanoring, by self-assembly of Au nanoparticles (<20 nm) on the ring's surface. Spectroscopic measurements and finite difference time domain simulations reveal high quality factor multipolar and antibonding surface plasmon resonances in the near-infrared. By loading different types of nanoparticles on the silica core, hybrid and multifunctional composite nanoring structures could be realized for applications such as MRI contrast enhancement, catalysis, drug delivery, plasmonic and magnetic hyperthermia, photoacoustic imaging, and biochemical sensing. PMID:27031364