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Sample records for random nanowire composites

  1. Misfit dislocations in composites with nanowires

    CERN Document Server

    Gutkin, M Y; Sheinerman, A G

    2003-01-01

    A theoretical model is suggested which describes the generation and evolution of misfit dislocations in composite solids containing nanowires with rectangular cross-section. In the framework of the model, the ranges of the geometric parameters (nanowire sizes, misfit parameter, interspacing between the nanowire and the free surface of the composite) are calculated at which the generation of various misfit dislocation configurations (loops, semi-loops and dipoles) is energetically favourable. Transformations of these dislocation configurations and their specific features are discussed.

  2. Smooth Nanowire/Polymer Composite Transparent Electrodes

    KAUST Repository

    Gaynor, Whitney

    2011-04-29

    Smooth composite transparent electrodes are fabricated via lamination of silver nanowires into the polymer poly-(4,3-ethylene dioxythiophene): poly(styrene-sulfonate) (PEDOT:PSS). The surface roughness is dramatically reduced compared to bare nanowires. High-efficiency P3HT:PCBM organic photovoltaic cells can be fabricated using these composites, reproducing the performance of cells on indium tin oxide (ITO) on glass and improving the performance of cells on ITO on plastic. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Smooth nanowire/polymer composite transparent electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Gaynor, Whitney; McGehee, Michael D. [Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305 (United States); Burkhard, George F. [Department of Applied Physics, Stanford University, Stanford, CA 94305 (United States); Peumans, Peter [Department of Electrical Engineering, Stanford University, Stanford, CA 94305 (United States)

    2011-07-12

    Smooth composite transparent electrodes are fabricated via lamination of silver nanowires into the polymer poly-(4,3-ethylene dioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS). The surface roughness is dramatically reduced compared to bare nanowires. High-efficiency P3HT:PCBM organic photovoltaic cells can be fabricated using these composites, reproducing the performance of cells on indium tin oxide (ITO) on glass and improving the performance of cells on ITO on plastic. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Features of Random Metal Nanowire Networks with

    KAUST Repository

    Maloth, Thirupathi

    2017-05-01

    Among the alternatives to conventional Indium Tin Oxide (ITO) used in making transparent conducting electrodes, the random metal nanowire (NW) networks are considered to be superior offering performance at par with ITO. The performance is measured in terms of sheet resistance and optical transmittance. However, as the electrical properties of such random networks are achieved thanks to a percolation network, a minimum size of the electrodes is needed so it actually exceeds the representative volume element (RVE) of the material and the macroscopic electrical properties are achieved. There is not much information about the compatibility of this minimum RVE size with the resolution actually needed in electronic devices. Furthermore, the efficiency of NWs in terms of electrical conduction is overlooked. In this work, we address the above industrially relevant questions - 1) The minimum size of electrodes that can be made based on the dimensions of NWs and the material coverage. For this, we propose a morphology based classification in defining the RVE size and we also compare the same with that is based on macroscopic electrical properties stabilization. 2) The amount of NWs that do not participate in electrical conduction, hence of no practical use. The results presented in this thesis are a design guide to experimentalists to design transparent electrodes with more optimal usage of the material.

  5. Composition and bandgap-graded semiconductor alloy nanowires.

    Science.gov (United States)

    Zhuang, Xiujuan; Ning, C Z; Pan, Anlian

    2012-01-03

    Semiconductor alloy nanowires with spatially graded compositions (and bandgaps) provide a new material platform for many new multifunctional optoelectronic devices, such as broadly tunable lasers, multispectral photodetectors, broad-band light emitting diodes (LEDs) and high-efficiency solar cells. In this review, we will summarize the recent progress on composition graded semiconductor alloy nanowires with bandgaps graded in a wide range. Depending on different growth methods and material systems, two typical nanowire composition grading approaches will be presented in detail, including composition graded alloy nanowires along a single substrate and those along single nanowires. Furthermore, selected examples of applications of these composition graded semiconductor nanowires will be presented and discussed, including tunable nanolasers, multi-terminal on-nanowire photodetectors, full-spectrum solar cells, and white-light LEDs. Finally, we will make some concluding remarks with future perspectives including opportunities and challenges in this research area. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Strain analysis of nanowire interfaces in multiscale composites

    Science.gov (United States)

    Malakooti, Mohammad H.; Zhou, Zhi; Spears, John H.; Shankwitz, Timothy J.; Sodano, Henry A.

    2016-04-01

    Recently, the reinforcement-matrix interface of fiber reinforced polymers has been modified through grafting nanostructures - particularly carbon nanotubes and ZnO nanowires - on to the fiber surface. This type of interface engineering has made a great impact on the development of multiscale composites that have high stiffness, interfacial strength, toughness, and vibrational damping - qualities that are mutually exclusive to a degree in most raw materials. Although the efficacy of such nanostructured interfaces has been established, the reinforcement mechanisms of these multiscale composites have not been explored. Here, strain transfer across a nanowire interphase is studied in order to gain a heightened understanding of the working principles of physical interface modification and the formation of a functional gradient. This problem is studied using a functionally graded piezoelectric interface composed of vertically aligned lead zirconate titanate nanowires, as their piezoelectric properties can be utilized to precisely control the strain on one side of the interface. The displacement and strain across the nanowire interface is captured using digital image correlation. It is demonstrated that the material gradient created through nanowires cause a smooth strain transfer from reinforcement phase into matrix phase that eliminates the stress concentration between these phases, which have highly mismatched elasticity.

  7. Enhancing ionic conductivity in composite polymer electrolytes with well-aligned ceramic nanowires

    Science.gov (United States)

    Liu, Wei; Lee, Seok Woo; Lin, Dingchang; Shi, Feifei; Wang, Shuang; Sendek, Austin D.; Cui, Yi

    2017-04-01

    In contrast to conventional organic liquid electrolytes that have leakage, flammability and chemical stability issues, solid electrolytes are widely considered as a promising candidate for the development of next-generation safe lithium-ion batteries. In solid polymer electrolytes that contain polymers and lithium salts, inorganic nanoparticles are often used as fillers to improve electrochemical performance, structure stability, and mechanical strength. However, such composite polymer electrolytes generally have low ionic conductivity. Here we report that a composite polymer electrolyte with well-aligned inorganic Li+-conductive nanowires exhibits an ionic conductivity of 6.05 × 10-5 S cm-1 at 30 ∘C, which is one order of magnitude higher than previous polymer electrolytes with randomly aligned nanowires. The large conductivity enhancement is ascribed to a fast ion-conducting pathway without crossing junctions on the surfaces of the aligned nanowires. Moreover, the long-term structural stability of the polymer electrolyte is also improved by the use of nanowires.

  8. Cellulose-gold nanowire (GNW) composite for electronic applications

    Science.gov (United States)

    Kim, Joo-Hyung; Lim, Byungwook; Park, Seongsoon

    2012-04-01

    In recent years, regenerated cellulose has received much attention due to its huge industrial potentials and its feasibility for many industrial applications such as sensors and actuators. However, due to its insulating property, few results used for potential electronic applications have been reported. By modification of cellulose itself, nano-sized electrical inner paths can be formed by chemical bonding of metallic or semiconducting nanowires to cellulose fibrils during regenerated process. Already our earlier result of the chemical bonding between carbon nanotubes and the regenerated cellulose has been reported as a novel electronic material for potential paper transistor. In this paper, we study the cellulose-gold nanowire (GNW) composite for electronic application due to its huge potential for paper transistor and other applications such as biosensors and strain sensors due to its electrical response sensitivity. The detailed material properties of GNW cellulose composite and its potential for electrical applications will be demonstrated.

  9. Dynamics of graded-composition and graded-doping semiconductor nanowires under local carrier modulation.

    Science.gov (United States)

    Deng, Wenjuan; Zou, Jijun; Peng, Xincun; Zhang, Jianbing; Wang, Weilu; Zhang, Yijun; Zhang, Daoli

    2016-10-17

    Scanning photocurrent microscopy is a powerful tool for investigating charge transfer and internal fields, which strongly influence carrier statics and dynamics in semiconductor nanowires. We performed comprehensive numerical modeling of the carrier dynamics of graded-composition and graded-doping AlGaAs nanowires to achieve a greater understanding of these nanowires. The simulation results indicated that the built-in electric field changes the shape of the scanning photocurrent microscopy profiles, which helped us to judge the dopant level, Al composition range and doping type of the material. The simulation results also assess the potential of the scanning photocurrent techniques in graded-doping and graded-composition nanowire properties.

  10. Method for producing nanowire-polymer composite electrodes

    Science.gov (United States)

    Pei, Qibing; Yu, Zhibin

    2017-11-21

    A method for producing flexible, nanoparticle-polymer composite electrodes is described. Conductive nanoparticles, preferably metal nanowires or nanotubes, are deposited on a smooth surface of a platform to produce a porous conductive layer. A second application of conductive nanoparticles or a mixture of nanoparticles can also be deposited to form a porous conductive layer. The conductive layer is then coated with at least one coating of monomers that is polymerized to form a conductive layer-polymer composite film. Optionally, a protective coating can be applied to the top of the composite film. In one embodiment, the monomer coating includes light transducing particles to reduce the total internal reflection of light through the composite film or pigments that absorb light at one wavelength and re-emit light at a longer wavelength. The resulting composite film has an active side that is smooth with surface height variations of 100 nm or less.

  11. Understanding the vapor-liquid-solid growth and composition of ternary III-V nanowires and nanowire heterostructures

    Science.gov (United States)

    Dubrovskii, V. G.

    2017-11-01

    Based on the recent achievements in vapor-liquid-solid (VLS) synthesis, characterization and modeling of ternary III-V nanowires and axial heterostructures within such nanowires, we try to understand the major trends in their compositional evolution from a general theoretical perspective. Clearly, the VLS growth of ternary materials is much more complex than in standard vapor-solid epitaxy techniques, and even maintaining the necessary control over the composition of steady-state ternary nanowires is far from straightforward. On the other hand, VLS nanowires offer otherwise unattainable material combinations without introducing structural defects and hence are very promising for next-generation optoelectronic devices, in particular those integrated with a silicon electronic platform. In this review, we consider two main problems. First, we show how and by means of which parameters the steady-state composition of Au-catalyzed or self-catalyzed ternary III-V nanowires can be tuned to a desired value and why it is generally different from the vapor composition. Second, we present some experimental data and modeling results for the interfacial abruptness across axial nanowire heterostructures, both in Au-catalyzed and self-catalyzed VLS growth methods. Refined modeling allows us to formulate some general growth recipes for suppressing the unwanted reservoir effect in the droplet and sharpening the nanowire heterojunctions. We consider and refine two approaches developed to date, namely the regular crystallization model for a liquid alloy with a critical size of only one III-V pair at high supersaturations or classical binary nucleation theory with a macroscopic critical nucleus at modest supersaturations.

  12. Flexible, Transparent, and Conductive Film Based on Random Networks of Ag Nanowires

    Directory of Open Access Journals (Sweden)

    Shunhua Wang

    2013-01-01

    Full Text Available Flexible, transparent, and conductive films based on random networks of Ag nanowires were prepared by vacuum-filtrating method. The size of Ag nanowires prepared by hydrothermal method is uniform, with a relatively smaller diameter and a longer length, thereby achieving a high aspect ratio (>1000. The films fabricated by Ag nanowires exhibit the excellent transparency with a 92% optical transmittance and a low surface resistivity of 11 Ωsq−1. Importantly, both the transmittance and sheet resistance decrease with the increasing of the Ag nanowires contents. When the contents of Ag nanowires are up to 200 mg/m2 especially, the surface resistivity quickly falls below 5 Ωsq−1. Also, these films are robust, which have almost no change in sheet resistance after the repeating bends over 200 cycles. These encouraging results may have a potential application in flexible and transparent electronics and other heating systems.

  13. Zinc oxide nanowire interphase for enhanced interfacial strength in lightweight polymer fiber composites.

    Science.gov (United States)

    Ehlert, Gregory J; Sodano, Henry A

    2009-08-01

    A novel functionalization method for aramid fibers is developed to enhance the bonding of a ZnO nanowire interphase grown on the fiber surface for interfacial strength enhancement. The nanowire interphase functionally grades the typically discrete interface and reduces the stress concentration between the fiber and matrix. The functionalization process is developed to improve the bonding between the ZnO nanowires and the aramid fiber and is validated through Fourier transform IR and X-ray photoelectron spectroscopy studies. Mechanical testing shows significant improvement in the interfacial shear strength with no decrease in the base fiber strength. This is the only technique found in the literature for the growth of a nanowire interphase on polymer fibers for structural enhancement without degrading the in-plane properties of the bulk composite. Furthermore, it is firmly shown that the functionalization process is a necessary condition for enhanced interfacial strength, demonstrating that ZnO nanowires strongly interact with carboxylic acid functional groups.

  14. Synthesis and characterization of WO3 nanowires and metal nanoparticle-WO3 nanowire composites

    Science.gov (United States)

    Szabó, Mária; Pusztai, Péter; Leino, Anne-Riikka; Kordás, Krisztián; Kónya, Zoltán; Kukovecz, Ákos

    2013-07-01

    Tungsten-trioxide nanowire bundles were prepared using a simple hydrothermal method. Sodium-tungstate was used as precursor and sodium-sulfate as structure directing agent. All the reflections of the X-ray diffractogram of the synthesized wires belong to the hexagonal phase of the tungsten trioxide. The nanowires were successfully decorated with metal nanoparticles by wet impregnation. The TEM investigation showed that using different metal precursors resulted in different particle sizes and coverage on the surface.

  15. In situ-growth of silica nanowires in ceramic carbon composites

    Directory of Open Access Journals (Sweden)

    Rahul Kumar

    2017-09-01

    Full Text Available An understanding of the processing and microstructure of ceramic–carbon composites is critical to development of these composites for applications needing electrically conducting, thermal shock resistant ceramic materials. In the present study green compacts of carbon ceramic composites were prepared either by slurry processing or dry powder blending of one or more of the three — clay, glass, alumina and carbon black or graphite. The dried green compacts were sintered at 1400 °C in flowing argon. The ceramic carbon composites except the ones without clay addition showed formation of silica nanowires. The silica nanowire formation was observed in both samples prepared by slip casting and dry powder compaction containing either carbon black or graphite. TEM micrographs showed presence of carbon at the core of the silica nanowires indicating that carbon served the role of a catalyst. Selected area electron diffraction (SAED suggested that the silica nanowires are amorphous. Prior studies have reported formation of silica nanowires from silicon, silica, silicon carbide but this is the first report ever on formation of silica nanowires from clay.

  16. Composite continuous time random walks

    Science.gov (United States)

    Hilfer, Rudolf

    2017-12-01

    Random walks in composite continuous time are introduced. Composite time flow is the product of translational time flow and fractional time flow [see Chem. Phys. 84, 399 (2002)]. The continuum limit of composite continuous time random walks gives a diffusion equation where the infinitesimal generator of time flow is the sum of a first order and a fractional time derivative. The latter is specified as a generalized Riemann-Liouville derivative. Generalized and binomial Mittag-Leffler functions are found as the exact results for waiting time density and mean square displacement.

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

    Directory of Open Access Journals (Sweden)

    P. Pignalosa

    2011-09-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-11-14

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

  19. Al-doped ZnO/Ag-nanowire Composite Electrodes for Flexible 3-Dimensional Nanowire Solar Cells.

    Science.gov (United States)

    Pathirane, Minoli K; Hosseinzadeh Khaligh, Hadi; Goldthorpe, Irene A; Wong, William S

    2017-08-21

    Silver nanowires in conjunction with sputter-coated Al-doped ZnO (AZO) thin films were used as a composite transparent top electrode for hybrid radial-junction ZnO nanowire/a-Si:H p-i-n thin-film solar cells. Solar cells with the composite nanowire top contacts attained a short-circuit current density (Jsc) of 13.9 mA/cm2 and a fill factor (FF) of 62% on glass substrates while a Jsc of 13.0 mA/cm2 and FF of 62% was achieved on plastic substrates. The power conversion efficiency (PCE) of the 3-dimensional solar cells improved by up to 60% compared to using AZO electrodes alone due to enhanced coverage of the top electrode over the 3-D structures, decreasing the series resistance of the device by 5×. The composite layer also showed a 10× reduction in sheet resistance compared to the AZO thin-film contact under applied mechanical strain.

  20. Power generation from base excitation of a Kevlar composite beam with ZnO nanowires

    Science.gov (United States)

    Malakooti, Mohammad H.; Hwang, Hyun-Sik; Sodano, Henry A.

    2015-04-01

    One-dimensional nanostructures such as nanowires, nanorods, and nanotubes with piezoelectric properties have gained interest in the fabrication of small scale power harvesting systems. However, the practical applications of the nanoscale materials in structures with true mechanical strengths have not yet been demonstrated. In this paper, piezoelectric ZnO nanowires are integrated into the fiber reinforced polymer composites serving as an active phase to convert the induced strain energy from ambient vibration into electrical energy. Arrays of ZnO nanowires are grown vertically aligned on aramid fibers through a low-cost hydrothermal process. The modified fabrics with ZnO nanowires whiskers are then placed between two carbon fabrics as the top and the bottom electrodes. Finally, vacuum resin transfer molding technique is utilized to fabricate these multiscale composites. The fabricated composites are subjected to a base excitation using a shaker to generate charge due to the direct piezoelectric effect of ZnO nanowires. Measuring the generated potential difference between the two electrodes showed the energy harvesting application of these multiscale composites in addition to their superior mechanical properties. These results propose a new generation of power harvesting systems with enhanced mechanical properties.

  1. Development of multifunctional fiber reinforced polymer composites through ZnO nanowire arrays

    Science.gov (United States)

    Malakooti, Mohammad H.; Patterson, Brendan A.; Hwang, Hyun-Sik; Sodano, Henry A.

    2016-04-01

    Piezoelectric nanowires, in particular zinc oxide (ZnO) nanowires, have been vastly used in the fabrication of electromechanical devices to convert wasted mechanical energy into useful electrical energy. Over recent years, the growth of vertically aligned ZnO nanowires on various structural fibers has led to the development of fiber-based nanostructured energy harvesting devices. However, the development of more realistic energy harvesters that are capable of continuous power generation requires a sufficient mechanical strength to withstand typical structural loading conditions. Yet, a durable, multifunctional material system has not been developed thoroughly enough to generate electrical power without deteriorating the mechanical performance. Here, a hybrid composite energy harvester is fabricated in a hierarchical design that provides both efficient power generating capabilities while enhancing the structural properties of the fiber reinforced polymer composite. Through a simple and low-cost process, a modified aramid fabric with vertically aligned ZnO nanowires grown on the fiber surface is embedded between woven carbon fabrics, which serve as the structural reinforcement as well as the top and the bottom electrodes of the nanowire arrays. The performance of the developed multifunctional composite is characterized through direct vibration excitation and tensile strength examination.

  2. Thermal transport in epitaxial Si1-xGex alloy nanowires with varying composition and morphology.

    Science.gov (United States)

    El Sachat, Alexandros; Reparaz, Juan S; Spiece, Jean; Alonso, Maria Isabel; Goni, Alejandro R; Garriga, M; Vaccaro, Pablo Oscar; Wagner, M R; Kolosov, Oleg V; Sotomayor Torres, Clivia M; Alzina, Francesc

    2017-10-19

    We report on structural, compositional, and thermal characterization of self-assembled in-plane epitaxial Si1-xGex alloy nanowires grown by molecular beam epitaxy on Si (001) substrates. The thermal properties were studied by means of scanning thermal microscopy, while the microstructural characteristics, the spatial distribution of the elemental composition of the alloy nanowires and the sample surface were investigated by transmission electron microscopy and energy dispersive x-ray microanalysis. We provide new insights regarding the morphology of the in-plane nanostructures, their size-dependent gradient chemical composition, and the formation of a 5 nm thick wetting layer on the Si substrate surface. In addition, we directly probe heat transfer between a heated scanning probe sensor and Si1-xGex alloy nanowires of different morphological characteristics and we quantify their thermal resistance variations. We correlate the variations of the thermal signal to the dependence of the heat spreading with the cross-sectional geometry of the nanowires using finite element method simula-tions. With this method we determine the thermal conductivity of the nanowires with values in the range of 2-3 Wm-1K-1. These results provide valuable information in growth processes and show the great capability of the scanning thermal mi-croscopy technique in ambient environment for nanoscale thermal studies, otherwise not possible using conventional tech-niques. Creative Commons Attribution license.

  3. Development of a zinc oxide nanowire interphase for enhanced structural composites

    Science.gov (United States)

    Ehlert, Gregory John

    Continuous fiber reinforced polymers (CFRPs) form the backbone of the high strength, low density material systems that will be central to the next generation of transportation vehicles. CFRPs, with a compliant matrix between relatively stiff fibers, localize stress at the interface between the two different phases to cause the interface to dominate many bulk material properties. As such, the two phase composite design problem generally has three selections; fiber, matrix and the interface between the two. This work has developed a unique ZnO nanowire interphase to improve the properties of the interface. Whiskerization, the deposition of an array of whiskers on the surface of a fiber, enables enhancement of the interfacial properties by causing fibers to interlock thus allowing the formation of a graded interface to reduce the stress concentration between the two phases. Whiskerization techniques have existed for some time; however ZnO nanowires offer a radical departure from existing technologies because ZnO nanowires can be deposited at low temperatures (90 °C) aqueous solutions. The high performance afforded by ZnO nanowires is documented for the first time in this work. This work will demonstrate the ability of a ZnO nanowire interphase to reinforce the interface of both aramid and carbon fiber composites. The interfacial shear strength of single fiber aramid composites is enhanced by 41% and single carbon fiber composite are improved by 110% with this process. Lamina scale testing on unidirectional carbon fiber composites demonstrates a 37% increase in shear strength and a 38% increase in shear modulus for the affected fibers. Given that ZnO nanowires are grown directly onto the underlying fiber, the interface between the nanowires and fiber will have low surface area and minimal interlocking, which implies that the chemical adhesion of the nanowires is strong. This work develops new functionalization procedures that directly control the interface chemistry

  4. Thermal transport through Zn3P2 nanowire-BN microparticle/nanoparticle composites and hybrids

    Science.gov (United States)

    Vasiraju, Venkata; Norris, David; Vaddiraju, Sreeram

    2017-07-01

    Composites and hybrids of BN and Zn3P2 nanowires were made by consolidating respectively BN micropowder-Zn3P2 nanowire mixtures and non-conformally BN decorated Zn3P2 nanowires. The intent here is to study whether mere solid-state mixing of a thermal conductor and a thermal insulator leads to the engineering of the thermal conductivities of the resulting composites and hybrids. The results demonstrated that contrary to intuition, mere mixing of two materials, a thermal conductor (BN) and a thermal insulator (Zn3P2 nanowires), does not result in composites and hybrids that have thermal conductivities higher than those of the thermal insulator and lower than those of the thermal conductor. This contrary result is especially true in instances where microparticles or nanoparticles of a high thermal conductivity material are introduced into a matrix of the thermal insulator for achieving spatially uniform composites/hybrids and engineering the resulting materials’ thermal conductivities. Here, both the size of the filler material and the type of interfaces formed between the matrix and the filler material play a major role in determining the ultimate thermal conductivities of the composites/hybrids. Imperfect interface formed between materials that have high lattice mismatches lead to lowering of the thermal conductivities of the composites/hybrids.

  5. Band gap modulation of Si-C binary core/shell nanowires by composition and ratio.

    Science.gov (United States)

    Dong, Huilong; Guo, Zhenyu; Gilmore, Keith; Du, Chunmiao; Hou, Tingjun; Lee, Shuit-Tong; Li, Youyong

    2015-07-10

    Core/shell nanowires (CSNWs) composed of Si, C, and SiC are promising systems for optoelectronic devices. Through computational investigations, we find that the band gaps (Eg) of these nanowires can be controlled not only by changing their composition, but also by adjusting the core/shell thickness ratio. For Si/SiC or SiC/C CSNWs with a fixed total number of layers, the dependence of Eg on the core/shell thickness ratio shows a bowing effect. Eg can be tuned from a few eV all the way to zero. These investigations provide direction for designing optoelectronic devices based on Earth-abundant elements.

  6. Tribological Characterization of NiAl Self-Lubricating Composites Containing V2O5 Nanowires

    Science.gov (United States)

    Huang, Yuchun; Ibrahim, Ahmed Mohamed Mahmoud; Shi, Xiaoliang; Radwan, Amr Rady; Zhai, Wenzheng; Yang, Kang; Xue, Bing

    2016-11-01

    In order to improve the tribological properties of NiAl self-lubricating composites, V2O5 nanowires with average width of 39 nm were synthesized by hydrothermal method. Furthermore, NiAl self-lubricating composites containing V2O5 nanowires (NAV) were successfully fabricated using spark plasma sintering technique. The tribological characteristics and wear mechanisms of NAV were evaluated at different sliding speeds, counterface ball materials and elevated temperatures. The results revealed that the frictional properties of NAV improved slightly with adding V2O5 nanowires at room temperature if compared to NiAl self-lubricating composites without solid lubricant as investigated in previous studies, while the wear mechanisms of NAV change widely with the change of the counterface ball materials and sliding velocities. V2O5 nanowires showed a beneficial effect on tribological performance of NAV at high temperatures owing to the formation of the V2O5-enriched glaze film at temperatures above 700 °C, which acts as the lubricous and protective mask against the severe wear.

  7. Influences of composition on Raman scattering from GeSi alloy core-shell nanowire heterostructures

    Science.gov (United States)

    Han, Delong; Ye, Han; Yu, Zhongyuan; Zhang, Yunzhen; Liu, Yumin; Li, Yinfeng

    2017-10-01

    In this paper, the influences of composition on Raman scattering from Ge/Si-GeSi core-shell nanowire heterostructures standing along [011] and [111] crystal directions are numerically investigated. Uniform, linear and spontaneous nonlinear composition profiles (CPs) in GeSi alloy shell are taken into consideration. In uniform CP case, clear double peaks in Raman spectra contributed by core and shell are observed. The strain-induced shift follows linear relation with Ge concentration and nonlinear relation with shell thickness. Larger strain-induced shifts are obtained in nanowires along [111] direction. In linear CP case, the peaks contributed by shell cannot be distinguished in the total spectra and plateaus are formed on the low frequency side. Moreover, the nonlinear CP accounts for the spontaneous composition transition near heterointerface during lateral epitaxy of GeSi shell. Due to the rapid Ge concentration transition, Raman spectra are shown nearly identical to uniform CP cases.

  8. Zinc Oxide Nanowire Interphase for Enhanced Lightweight Polymer Fiber Composites

    Science.gov (United States)

    Sodano, Henry A.; Brett, Robert

    2011-01-01

    The objective of this work was to increase the interfacial strength between aramid fiber and epoxy matrix. This was achieved by functionalizing the aramid fiber followed by growth of a layer of ZnO nanowires on the fiber surface such that when embedded into the polymer, the load transfer and bonding area could be substantially enhanced. The functionalization procedure developed here created functional carboxylic acid surface groups that chemically interact with the ZnO and thus greatly enhance the strength of the interface between the fiber and the ZnO.

  9. Surface Plasmon Resonance Temperature Sensor Based on Photonic Crystal Fibers Randomly Filled with Silver Nanowires

    Directory of Open Access Journals (Sweden)

    Nannan Luan

    2014-08-01

    Full Text Available We propose a temperature sensor design based on surface plasmon resonances (SPRs supported by filling the holes of a six-hole photonic crystal fiber (PCF with a silver nanowire. A liquid mixture (ethanol and chloroform with a large thermo-optic coefficient is filled into the PCF holes as sensing medium. The filled silver nanowires can support resonance peaks and the peak will shift when temperature variations induce changes in the refractive indices of the mixture. By measuring the peak shift, the temperature change can be detected. The resonance peak is extremely sensitive to temperature because the refractive index of the filled mixture is close to that of the PCF material. Our numerical results indicate that a temperature sensitivity as high as 4 nm/K can be achieved and that the most sensitive range of the sensor can be tuned by changing the volume ratios of ethanol and chloroform. Moreover, the maximal sensitivity is relatively stable with random filled nanowires, which will be very convenient for the sensor fabrication.

  10. Broad compositional tunability of indium tin oxide nanowires grown by the vapor-liquid-solid mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Zervos, M., E-mail: zervos@ucy.ac.cy; Giapintzakis, J. [Nanotechnology Research Centre (NRC), University of Cyprus, P.O. Box 20537, Nicosia 1678 (Cyprus); Department of Mechanical and Manufacturing Engineering, University of Cyprus, P.O. Box 20537, Nicosia 1678 (Cyprus); Mihailescu, C. N. [Nanotechnology Research Centre (NRC), University of Cyprus, P.O. Box 20537, Nicosia 1678 (Cyprus); Department of Mechanical and Manufacturing Engineering, University of Cyprus, P.O. Box 20537, Nicosia 1678 (Cyprus); National Institute for Laser, Plasma and Radiation Physics, Str. Atomistilor, P.O. Box MG-36, 077125 Magurele (Romania); Luculescu, C. R. [Department of Mechanical and Manufacturing Engineering, University of Cyprus, P.O. Box 20537, Nicosia 1678 (Cyprus); National Institute for Laser, Plasma and Radiation Physics, Str. Atomistilor, P.O. Box MG-36, 077125 Magurele (Romania); Florini, N.; Komninou, Ph.; Kioseoglou, J. [Nanostructured Materials Microscopy Group (NMMG), Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece); Othonos, A. [Nanotechnology Research Centre (NRC), University of Cyprus, P.O. Box 20537, Nicosia 1678 (Cyprus); Research Center of Ultrafast Science, Department of Physics, University of Cyprus, P.O. Box 20537, Nicosia 1678 (Cyprus)

    2014-05-01

    Indium tin oxide nanowires were grown by the reaction of In and Sn with O{sub 2} at 800 °C via the vapor-liquid-solid mechanism on 1 nm Au/Si(001). We obtain Sn doped In{sub 2}O{sub 3} nanowires having a cubic bixbyite crystal structure by using In:Sn source weight ratios > 1:9 while below this we observe the emergence of tetragonal rutile SnO{sub 2} and suppression of In{sub 2}O{sub 3} permitting compositional and structural tuning from SnO{sub 2} to In{sub 2}O{sub 3} which is accompanied by a blue shift of the photoluminescence spectrum and increase in carrier lifetime attributed to a higher crystal quality and Fermi level position.

  11. Broad compositional tunability of indium tin oxide nanowires grown by the vapor-liquid-solid mechanism

    Science.gov (United States)

    Zervos, M.; Mihailescu, C. N.; Giapintzakis, J.; Luculescu, C. R.; Florini, N.; Komninou, Ph.; Kioseoglou, J.; Othonos, A.

    2014-05-01

    Indium tin oxide nanowires were grown by the reaction of In and Sn with O2 at 800 °C via the vapor-liquid-solid mechanism on 1 nm Au/Si(001). We obtain Sn doped In2O3 nanowires having a cubic bixbyite crystal structure by using In:Sn source weight ratios > 1:9 while below this we observe the emergence of tetragonal rutile SnO2 and suppression of In2O3 permitting compositional and structural tuning from SnO2 to In2O3 which is accompanied by a blue shift of the photoluminescence spectrum and increase in carrier lifetime attributed to a higher crystal quality and Fermi level position.

  12. Broad compositional tunability of indium tin oxide nanowires grown by the vapor-liquid-solid mechanism

    Directory of Open Access Journals (Sweden)

    M. Zervos

    2014-05-01

    Full Text Available Indium tin oxide nanowires were grown by the reaction of In and Sn with O2 at 800 °C via the vapor-liquid-solid mechanism on 1 nm Au/Si(001. We obtain Sn doped In2O3 nanowires having a cubic bixbyite crystal structure by using In:Sn source weight ratios > 1:9 while below this we observe the emergence of tetragonal rutile SnO2 and suppression of In2O3 permitting compositional and structural tuning from SnO2 to In2O3 which is accompanied by a blue shift of the photoluminescence spectrum and increase in carrier lifetime attributed to a higher crystal quality and Fermi level position.

  13. Quantum Dot-Like Behavior of Compositional Fluctuations in AlGaN Nanowires.

    Science.gov (United States)

    Belloeil, M; Gayral, B; Daudin, B

    2016-02-10

    We report on the structural and optical properties of AlxGa(1-x)N nanowire sections grown by plasma-assisted molecular beam epitaxy on GaN nanowire bases used as a template. Based on a combination of scanning electron microscopy, microphotoluminescence, time-resolved microphotoluminescence, and photon correlation experiments, it is shown that compositional fluctuations in AlxGa(1-x)N sections associated with carrier localization optically behave as quantum dots. Moreover, most of the micro-optical properties of such fluctuations are demonstrated to be very little dependent on kinetic growth parameters such as AlxGa(1-x)N growth temperature and AlN molar fraction in the alloy, which govern the macrostructural properties of AlxGa(1-x)N sections.

  14. Ultrathin Tungsten Oxide Nanowires/Reduced Graphene Oxide Composites for Toluene Sensing

    Directory of Open Access Journals (Sweden)

    Muhammad Hassan

    2017-09-01

    Full Text Available Graphene-based composites have gained great attention in the field of gas sensor fabrication due to their higher surface area with additional functional groups. Decorating one-dimensional (1D semiconductor nanomaterials on graphene also show potential benefits in gas sensing applications. Here we demonstrate the one-pot and low cost synthesis of W18O49 NWs/rGO composites with different amount of reduced graphene oxide (rGO which show excellent gas-sensing properties towards toluene and strong dependence on their chemical composition. As compared to pure W18O49 NWs, an improved gas sensing response (2.8 times higher was achieved in case of W18O49 NWs composite with 0.5 wt. % rGO. Promisingly, this strategy can be extended to prepare other nanowire based composites with excellent gas-sensing performance.

  15. Faceting, composition and crystal phase evolution in III-V antimonide nanowire heterostructures revealed by combining microscopy techniques

    Science.gov (United States)

    Xu, Tao; Dick, Kimberly A.; Plissard, Sébastien; Hai Nguyen, Thanh; Makoudi, Younes; Berthe, Maxime; Nys, Jean-Philippe; Wallart, Xavier; Grandidier, Bruno; Caroff, Philippe

    2012-03-01

    III-V antimonide nanowires are among the most interesting semiconductors for transport physics, nanoelectronics and long-wavelength optoelectronic devices due to their optimal material properties. In order to investigate their complex crystal structure evolution, faceting and composition, we report a combined scanning electron microscopy (SEM), transmission electron microscopy (TEM), and scanning tunneling microscopy (STM) study of gold-nucleated ternary InAs/InAs1-xSbx nanowire heterostructures grown by molecular beam epitaxy. SEM showed the general morphology and faceting, TEM revealed the internal crystal structure and ternary compositions, while STM was successfully applied to characterize the oxide-free nanowire sidewalls, in terms of nanofaceting morphology, atomic structure and surface composition. The complementary use of these techniques allows for correlation of the morphological and structural properties of the nanowires with the amount of Sb incorporated during growth. The addition of even a minute amount of Sb to InAs changes the crystal structure from perfect wurtzite to perfect zinc blende, via intermediate stacking fault and pseudo-periodic twinning regimes. Moreover, the addition of Sb during the axial growth of InAs/InAs1-xSbx heterostructure nanowires causes a significant conformal lateral overgrowth on both segments, leading to the spontaneous formation of a core-shell structure, with an Sb-rich shell.

  16. Thermal transport in epitaxial Si1‑x Ge x alloy nanowires with varying composition and morphology

    Science.gov (United States)

    El Sachat, A.; Reparaz, J. S.; Spiece, J.; Alonso, M. I.; Goñi, A. R.; Garriga, M.; Vaccaro, P. O.; Wagner, M. R.; Kolosov, O. V.; Sotomayor Torres, C. M.; Alzina, F.

    2017-12-01

    We report on structural, compositional, and thermal characterization of self-assembled in-plane epitaxial Si1‑x Ge x alloy nanowires grown by molecular beam epitaxy on Si (001) substrates. The thermal properties were studied by means of scanning thermal microscopy (SThM), while the microstructural characteristics, the spatial distribution of the elemental composition of the alloy nanowires and the sample surface were investigated by transmission electron microscopy and energy dispersive x-ray microanalysis. We provide new insights regarding the morphology of the in-plane nanostructures, their size-dependent gradient chemical composition, and the formation of a 5 nm thick wetting layer on the Si substrate surface. In addition, we directly probe heat transfer between a heated scanning probe sensor and Si1‑x Ge x alloy nanowires of different morphological characteristics and we quantify their thermal resistance variations. We correlate the variations of the thermal signal to the dependence of the heat spreading with the cross-sectional geometry of the nanowires using finite element method simulations. With this method we determine the thermal conductivity of the nanowires with values in the range of 2–3 W m‑1 K‑1. These results provide valuable information in growth processes and show the great capability of the SThM technique in ambient environment for nanoscale thermal studies, otherwise not possible using conventional techniques.

  17. Inuence of Gold-Copper Alloy Catalyst Composition on Crystal Growth and Dopant Distribution in Silicon and Germanium Nanowires

    Science.gov (United States)

    Connell, Justin G.

    A combination of local electrode atom probe tomography (LEAP) and transmission electron microscopy characterization were used to investigate growth of and dopant incorporation in silicon and germanium nanowires (Si and GeNWs) via the vapor-liquid- solid (VLS) mechanism. A sample structure was developed that enabled isolation of the catalyst-mediated contribution to doping in individual nanowires during LEAP analysis. As a result, the distribution coefficient - a thermodynamic quantity describing axial junction abruptness - was measured in nanowires for the first time, providing a fundamental framework for comparison of junction abruptness in nanowires. These investigations also enabled the identification of a previously unknown radial anisotropy in dopant incorporation through the catalyst, with variations in dopant concentration across the VLS-defined diameter of the nanowire as large as two orders of magnitude. Finite element modeling of the doping process, coupled with in situ TEM observations reported in the literature, suggests that this radially inhomogeneous dopant distribution is a direct consequence of growth from a faceted liquid-solid interface, rather than the commonly assumed planar interface. Au-Cu alloy catalysts were explored as alternatives to Au-catalyzed VLS nanowire growth as a means to alleviate or eliminate axial and radial doping gradients in nanowires. Both an aqueous solution and electron beam lithographic method for creating Au-Cu alloy catalysts of controlled composition were developed, and GeNW growth was demonstrated from both types of catalyst. LEAP characterization of Au-Cu alloy catalyzed P-doped GeNWs revealed that alloying with Cu results in more abrupt axial doping junctions, as well as a more homogeneous radial distribution of dopants within the VLS-defined diameter of the nanowire.

  18. Magnetic nanowires (Fe, Fe-Co, Fe-Ni – magnetic moment reorientation in respect of wires composition

    Directory of Open Access Journals (Sweden)

    Kalska-Szostko Beata

    2015-03-01

    Full Text Available Magnetic nanowires of Fe, Fe-Co, and Fe-Ni alloy and layered structure were prepared by electrochemical alternating current (AC deposition method. The morphology of the nanowires in and without the matrix was studied by energy dispersive X-ray spectroscopy (EDX, scanning electron microscopy (SEM, and X-ray diffraction (XRD, respectively. The wires either show strong dependence on the combination of elements deposition (alloy or layered or chemical composition (Co or Ni. The magnetic properties of the nanostructures were determined on the basis of Mössbauer spectroscopy (MS.

  19. The effects of random field at surface on the magnetic properties in the Ising nanotube and nanowire

    Science.gov (United States)

    Kaneyoshi, T.

    2016-12-01

    The phase diagrams and temperature dependences of total magnetization mT in two nanosystems (nanotube and nanowire) with a random magnetic field at the surface shell are studied by the uses of the effective-field theory with correlations. Some characteristic phenomena (reentrant phenomena and unconventional thermal variation of total magnetization) are found in the two systems. They are rather different between the two systems, which mainly come from the structural differences of the cores

  20. Great Thermal Conductivity Enhancement of Silicone Composite with Ultra-Long Copper Nanowires

    Science.gov (United States)

    Zhang, Liye; Yin, Junshan; Yu, Wei; Wang, Mingzhu; Xie, Huaqing

    2017-07-01

    In this paper, ultra-long copper nanowires (CuNWs) were successfully synthesized at a large scale by hydrothermal reduction of divalent copper ion using oleylamine and oleic acid as dual ligands. The characteristic of CuNWs is hard and linear, which is clearly different from graphene nanoplatelets (GNPs) and multi-wall carbon nanotubes (MWCNTs). The thermal properties and models of silicone composites with three nanomaterials have been mainly researched. The maximum of thermal conductivity enhancement is up to 215% with only 1.0 vol.% CuNW loading, which is much higher than GNPs and MWCNTs. It is due to the ultra-long CuNWs with a length of more than 100 μm, which facilitates the formation of effective thermal-conductive networks, resulting in great enhancement of thermal conductivity.

  1. Laser patterned polymer/nanotube composite electrodes for nanowire transistors on flexible substrates

    DEFF Research Database (Denmark)

    Beliatis, Michail

    2017-01-01

    almost four orders of magnitude after adding f-MWCNT. Work function of PEDOT:PSS/f-MWCNT films was ~ 0.5eV higher as compared to the work function of pure PEDOT:PSS films, determined by Kelvin probe method. Field-effect transistors source-drain electrodes were prepared on PET plastic substrates where...... transistors were completed by depositing parylene C as polymer gate dielectric and gold as the top-gate electrode. Transistor characteristics showed p-type conduction with excellent gate electrode coupling, with an ON/OFF ratio of ~ 200. Thereby, we demonstrate the feasibility of using high workfunction......, printable PEDOT:PSS/MWCNT composite inks for patterning source/drain electrodes for nanowire transistors on flexible substrates....

  2. Fully Printed Memristors from Cu-SiO2 Core-Shell Nanowire Composites

    Science.gov (United States)

    Catenacci, Matthew J.; Flowers, Patrick F.; Cao, Changyong; Andrews, Joseph B.; Franklin, Aaron D.; Wiley, Benjamin J.

    2017-07-01

    This article describes a fully printed memory in which a composite of Cu-SiO2 nanowires dispersed in ethylcellulose acts as a resistive switch between printed Cu and Au electrodes. A 16-cell crossbar array of these memristors was printed with an aerosol jet. The memristors exhibited moderate operating voltages (˜3 V), no degradation over 104 switching cycles, write speeds of 3 μs, and extrapolated retention times of 10 years. The low operating voltage enabled the programming of a fully printed 4-bit memristor array with an Arduino. The excellent performance of these fully printed memristors could help enable the creation of fully printed RFID tags and sensors with integrated data storage.

  3. Fabricating fast triggered electro-active shape memory graphite/silver nanowires/epoxy resin composite from polymer template.

    Science.gov (United States)

    Zhou, Jie; Li, Hua; Tian, Ran; Dugnani, Roberto; Lu, Huiyuan; Chen, Yujie; Guo, Yiping; Duan, Huanan; Liu, Hezhou

    2017-07-17

    In recent years shape-memory polymers have been under intense investigation due to their unique mechanical, thermal, and electrical properties that could potentially make them extremely valuable in numerous engineering applications. In this manuscript, we report a polymer-template-assisted assembly manufacturing strategy used to fabricate graphite/silver nanowires/epoxy resin (PGSE) composite. In the proposed method, the porous polymer foams work as the skeleton by forming three-dimensional graphite structure, whereas the silver nanowires act as the continuous conductive network. Preliminary testing on hybrid foams after vacuum infusion showed high electrical conductivity and excellent thermal stability. Furthermore, the composites were found to recover their original shape within 60 seconds from the application of a 0.8 V mm(-1) electric field. Notably, the reported shape-memory polymer composites are manufactured with readily-available raw materials, they are fast to manufacture, and are shape-controlled.

  4. Designed Quasi-1D Potential Structures Realized in Compositionally Graded InAs1-xPx Nanowires.

    Science.gov (United States)

    Nylund, Gustav; Storm, Kristian; Lehmann, Sebastian; Capasso, Federico; Samuelson, Lars

    2016-02-10

    III-V semiconductor heterostructures are important components of many solid-state optoelectronic devices, but the ability to control and tune the electrical and optical properties of these structures in conventional device geometries is fundamentally limited by the bulk dimensionality and the inability to accommodate lattice-mismatched material combinations. Here we demonstrate how semiconductor nanowires may enable the creation of arbitrarily shaped one-dimensional potential structures for new types of designed device functionality. We describe the controlled growth of stepwise compositionally graded InAs1-xPx heterostructures defined along the axes of InAs nanowires, and we show that nanowires with sawtooth-shaped composition profiles behave as near-ideal unipolar diodes with ratchet-like rectification of the electron transport through the nanowires, in excellent agreement with simulations. This new type of designed quasi-1D potential structure represents a significant advance in band gap engineering and may enable fundamental studies of low-dimensional hot-carrier dynamics, in addition to constituting a platform for implementing novel electronic and optoelectronic device concepts.

  5. Enhanced THz emission efficiency of composition-tunable InGaAs nanowire arrays

    Science.gov (United States)

    BeleckaitÄ--, I.; Treu, J.; Morkötter, S.; Döblinger, M.; Xu, X.; Adomavičius, R.; Finley, J. J.; Koblmüller, G.; Krotkus, A.

    2017-05-01

    We report the terahertz (THz) emission properties of composition-tunable, intrinsically n-type InGaAs nanowire (NW) arrays using THz time-domain spectroscopy. By tuning the alloy composition of In1-xGaxAs NWs from pure InAs (x(Ga)=0) up to the intermediate composition (x(Ga)˜0.5), a substantially enhanced (>3-fold) THz emission efficiency is found, which is ascribed to a reduction in electron accumulation at the NW surface and respective electron scattering at donor-type surface defects. These findings are also confirmed by photoexcitation wavelength dependent measurements, while the THz emission characteristics are further found to be different from corresponding bulk-type planar InGaAs. In particular, NWs exhibit no distinct maxima in THz excitation spectra as caused by electron scattering to subsidiary conduction band valleys and commonly observed in the majority of bulk semiconductors. The wavelength-dependent emission spectra further reveal distinct signatures of modified intervalley scattering, revealing the underlying polytypism of intermixed wurtzite and zincblende phases in the investigated InGaAs NWs.

  6. Temperature-controlled transparent-film heater based on silver nanowire-PMMA composite film

    Science.gov (United States)

    He, Xin; Liu, A.'lei; Hu, Xuyang; Song, Mingxia; Duan, Feng; Lan, Qiuming; Xiao, Jundong; Liu, Junyan; Zhang, Mei; Chen, Yeqing; Zeng, Qingguang

    2016-11-01

    We fabricated a high-performance film heater based on a silver nanowire and polymethyl methacrylate (Ag NW-PMMA) composite film, which was synthesized with the assistance of mechanical lamination and an in situ transfer method. The films exhibit excellent conductivity, high figure of merit, and strong adhesion of percolation network to substrate. By controlling NW density, we prepared the films with a transmittance of 44.9-85.0% at 550 nm and a sheet resistance of 0.13-1.40 Ω sq-1. A stable temperature ranging from 130 °C-40 °C was generated at 3.0 V within 10-30 s, indicating that the resulting film heaters show a rapid thermal response, low driving voltage and stable temperature recoverability. Furthermore, we demonstrated the applications of the film heater in defrosting and a physical therapeutic instrument. A fast defrosting on the composite film with a transmittance of 88% was observed by applying a 9 V driving voltage for 20 s. Meanwhile, we developed a physical therapeutic instrument with two modes of thermotherapy and electronic-pulse massage by using the composite films as two electrodes, greatly decreasing the weight and power consumption compared to a traditional instrument. Therefore, Ag NW-PMMA film can be a promising candidate for diversified heating applications.

  7. RANDOM VIBRATION ANALYSIS OF SANDWICH COMPOSITE BEAMS

    OpenAIRE

    K. Ravindranath Tagore, Rachumalla Pallavi

    2016-01-01

    In this thesis, a sandwich composite for Semi-monocoque construction in aircraft fuselage is analyzed for its strength under different loading conditions using different materials for Stringers balsa wood, syntactic foams, and honeycombs and Carbon Fiber reinforced thermoplastics is used as skin material. 3D modeling is done in Pro/Engineer. Static, Modal and Random Vibration analysis is done on the beam using finite element analysis software Ansys.

  8. Angiogenic Rg1 /Sr-Doped TiO2 Nanowire/Poly(Propylene Fumarate) Bone Cement Composites.

    Science.gov (United States)

    Salarian, Mehrnaz; Xu, William Z; Bohay, Richard; Lui, Edmund M K; Charpentier, Paul A

    2017-02-01

    A new approach is provided for preparing radiopaque and angiogenic poly(propylene fumarate) (PPF) bone cements by integrating Sr-doped n-TiO2 nanowires and ginsenoside Rg1 suitable for treating osteonecrosis. High aspect ratio radiopaque TiO2 -nanowires are synthesized by strontium doping in supercritical CO2 for the first time, showing a new phase, SrTiO3 . PPF is synthesized using a transesterification method by reacting diethyl fumarate and propylene glycol, then functionalized using maleic anhydride to produce terminal carboxyl groups, which are subsequently linked to the nanowires. The strong interfacial adhesion between functionalized PPF and nanowires is examined by scanning electron microscopy, Fourier transform infrared, X-ray photoelectron spectroscopy, thermal analysis, and mechanical testing. An angiogenic modulator, ginsenoside Rg1 , is integrated into the bone cement formulation with the mechanical properties, radiopacity, drug release, and angiogenesis behavior of the formed composites explored. The results show superior radiopacity and excellent release of ginsenoside Rg1 in vitro, as well as a dose-dependent increase in the branching point numbers. The present study suggests this new methodology provides sufficient mechanical properties, radiopacity, and angiogenic activity to be suitable for cementation of necrotic bone. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Direct nucleation, morphology and compositional tuning of InAs1-x Sb x nanowires on InAs (111) B substrates

    Science.gov (United States)

    Namazi, Luna; Gorji Ghalamestani, Sepideh; Lehmann, Sebastian; Zamani, Reza R.; Dick, Kimberly A.

    2017-04-01

    III-V ternary nanowires are interesting due to the possibility of modulating their physical and material properties by tuning their material composition. Amongst them InAs1-x Sb x nanowires are good candidates for applications such as Infrared detectors. However, this material has not been grown directly from substrates, in a large range of material compositions. Since the properties of ternaries are alterable by tuning their composition, it is beneficial to gain access to a wide range of composition tunability. Here we demonstrate direct nucleation and growth of InAs1-x Sb x nanowires from Au seed particles over a broad range of compositions (x = 0.08-0.75) for different diameters and surface densities by means of metalorganic vapor phase epitaxy. We investigate how the nucleation, morphology, solid phase Sb content, and growth rate of these nanowires depend on the particle dimensions, and on growth conditions such as the vapor phase composition, V/III ratio, and temperature. We show that the solid phase Sb content of the nanowires remains invariant towards changes of the In precursor flow. We also discuss that at relatively high In flows the growth mechanism alters from Au-seeded to what is referred to as semi In-seeded growth. This change enables growth of nanowires with a high solid phase Sb content of 0.75 that are not feasible via Au-seeded growth. Independent of the growth conditions and morphology, we report that the nanowire Sb content changes over their length, from lower Sb contents at the base, increasing to higher amounts towards the tip. We correlate the axial Sb content variations to the axial growth rate measured in situ. We also report spontaneous core-shell formation for Au-seeded nanowires, where the core is Sb-rich in comparison to the Sb-poor shell.

  10. Scalable integration of indium zinc oxide/photosensitive-nanowire composite thin-film transistors for transparent multicolor photodetectors array.

    Science.gov (United States)

    Liu, Xingqiang; Jiang, Lang; Zou, Xuming; Xiao, Xiangheng; Guo, Shishang; Jiang, Changzhong; Liu, Xi; Fan, Zhiyong; Hu, Weida; Chen, Xiaoshuang; Lu, Wei; Hu, Wenping; Liao, Lei

    2014-05-01

    By incorporating crystalline photosensitive nanowires (NWs), an amorphous InZnO (a-IZO) thin film is designed to be sensitive to the primary colors of light via a facile sol-gel approach. The mobility is also improved. The composite devices leverage the advantages of the transparency of a-IZO with the photosensitivity of CdS NWs. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Composition-graded nanowire solar cells fabricated in a single process for spectrum-splitting photovoltaic systems.

    Science.gov (United States)

    Caselli, Derek; Liu, Zhicheng; Shelhammer, David; Ning, Cun-Zheng

    2014-10-08

    Nanomaterials such as semiconductor nanowires have unique features that could enable novel optoelectronic applications such as novel solar cells. This paper aims to demonstrate one such recently proposed concept: Monolithically Integrated Laterally Arrayed Multiple Band gap (MILAMB) solar cells for spectrum-splitting photovoltaic systems. Two cells with different band gaps were fabricated simultaneously in the same process on a single substrate using spatially composition-graded CdSSe alloy nanowires grown by the Dual-Gradient Method in a chemical vapor deposition system. CdSSe nanowire ensemble devices tested under 1 sun AM1.5G illumination achieved open-circuit voltages up to 307 and 173 mV and short-circuit current densities as high as 0.091 and 0.974 mA/cm(2) for the CdS- and CdSe-rich cells, respectively. The open-circuit voltages were roughly three times those of similar CdSSe film cells fabricated for comparison due to the superior optical quality of the nanowires. I-V measurements were also performed using optical filters to simulate spectrum-splitting. The open-circuit voltages and fill factors of the CdS-rich subcells were uniformly larger than the corresponding CdSe-rich cells for similar photon flux, as expected. This suggests that if all wires can be contacted, the wide-gap cell is expected to have greater output power than the narrow-gap cell, which is the key to achieving high efficiencies with spectrum-splitting. This paper thus provides the first proof-of-concept demonstration of simultaneous fabrication of MILAMB solar cells. This approach to solar cell fabrication using single-crystal nanowires for spectrum-splitting photovoltaics could provide a future low-cost high-efficiency alternative to the conventional high-cost high-efficiency tandem cells.

  12. Characterization and properties of micro- and nanowires of controlled size, composition, and geometry fabricated by electrodeposition and ion-track technology

    Directory of Open Access Journals (Sweden)

    Maria Eugenia Toimil-Molares

    2012-12-01

    Full Text Available The combination of electrodeposition and polymeric templates created by heavy-ion irradiation followed by chemical track etching provides a large variety of poly- and single-crystalline nanowires of controlled size, geometry, composition, and surface morphology. Recent results obtained by our group on the fabrication, characterization and size-dependent properties of nanowires synthesized by this technique are reviewed, including investigations on electrical resistivity, surface plasmon resonances, and thermal instability.

  13. Preparation of Advanced CuO Nanowires/Functionalized Graphene Composite Anode Material for Lithium Ion Batteries

    Directory of Open Access Journals (Sweden)

    Jin Zhang

    2017-01-01

    Full Text Available The copper oxide (CuO nanowires/functionalized graphene (f-graphene composite material was successfully composed by a one-pot synthesis method. The f-graphene synthesized through the Birch reduction chemistry method was modified with functional group “–(CH25COOH”, and the CuO nanowires (NWs were well dispersed in the f-graphene sheets. When used as anode materials in lithium-ion batteries, the composite exhibited good cyclic stability and decent specific capacity of 677 mA·h·g−1 after 50 cycles. CuO NWs can enhance the lithium-ion storage of the composites while the f-graphene effectively resists the volume expansion of the CuO NWs during the galvanostatic charge/discharge cyclic process, and provide a conductive paths for charge transportation. The good electrochemical performance of the synthesized CuO/f-graphene composite suggests great potential of the composite materials for lithium-ion batteries anodes.

  14. Preparation of Advanced CuO Nanowires/Functionalized Graphene Composite Anode Material for Lithium Ion Batteries

    Science.gov (United States)

    Zhang, Jin; Wang, Beibei; Zhou, Jiachen; Xia, Ruoyu; Chu, Yingli; Huang, Jia

    2017-01-01

    The copper oxide (CuO) nanowires/functionalized graphene (f-graphene) composite material was successfully composed by a one-pot synthesis method. The f-graphene synthesized through the Birch reduction chemistry method was modified with functional group “–(CH2)5COOH”, and the CuO nanowires (NWs) were well dispersed in the f-graphene sheets. When used as anode materials in lithium-ion batteries, the composite exhibited good cyclic stability and decent specific capacity of 677 mA·h·g−1 after 50 cycles. CuO NWs can enhance the lithium-ion storage of the composites while the f-graphene effectively resists the volume expansion of the CuO NWs during the galvanostatic charge/discharge cyclic process, and provide a conductive paths for charge transportation. The good electrochemical performance of the synthesized CuO/f-graphene composite suggests great potential of the composite materials for lithium-ion batteries anodes. PMID:28772432

  15. Heterogeneous Configuration of a Ag Nanowire/Polymer Composite Structure for Selectively Stretchable Transparent Electrodes.

    Science.gov (United States)

    Kim, Youngmin; Jun, Sungwoo; Ju, Byeong-Kwon; Kim, Jong-Woong

    2017-03-01

    One of the most important aspects that we need to consider in the design of intrinsically stretchable electrodes is that most electronic devices that can be formed on them are not stretchable themselves. This discrepancy can induce severe stress singularities at the interfaces between stiff devices and stretchable electrodes, leading to catastrophic device delamination when the substrate is stretched. Here, we suggest a novel solution to this challenge which involves introducing a photolithography-based rigid-island approach to fabricate the heterogeneous configuration of a silver nanowire (AgNW)/polymer composite structure. For this, we designed two new transparent polymers: a photopatternable polymer that is rigid yet flexible, and a stretchable polymer, both of which have identical acrylate functional groups. Patterning of the rigid polymer and subsequent overcoating of the soft polymer formed rigid island disks embedded in the soft polymer, resulting in a selectively stretchable transparent film. Strong covalent bonds instead of weak physical interactions between the polymers strengthened the cohesive force at the interface of the rigid/soft polymers. Inverted-layer processing with a percolated AgNW network was used to form a heterogeneous AgNW/polymer composite structure that can be used as a selectively stretchable transparent electrode. An optimized structural configuration prevented the resistance of the rigid electrode from varying up to a lateral strain of 70%. A repeated stretch/release test with 60% strain for 5000 cycles did not cause any severe damage to the structure, revealing that the fabricated structure was mechanically stable and reliable.

  16. Fabrication and Synthesis of Highly Ordered Nickel Cobalt Sulfide Nanowire-Grown Woven Kevlar Fiber/Reduced Graphene Oxide/Polyester Composites.

    Science.gov (United States)

    Hazarika, Ankita; Deka, Biplab K; Kim, DoYoung; Roh, Hyung Doh; Park, Young-Bin; Park, Hyung Wook

    2017-10-18

    Well-aligned NiCo2S4 nanowires, synthesized hydrothermally on the surface of woven Kevlar fiber (WKF), were used to fabricate composites with reduced graphene oxide (rGO) dispersed in polyester resin (PES) by means of vacuum-assisted resin transfer molding. The NiCo2S4 nanowires were synthesized with three precursor concentrations. Nanowire growth was characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Hierarchical and high growth density of the nanowires led to exceptional mechanical properties of the composites. Compared with bare WKF/PES, the tensile strength and absorbed impact energy were enhanced by 96.2% and 92.3%, respectively, for WKF/NiCo2S4/rGO (1.5%)/PES. The synergistic effect of NiCo2S4 nanowires and rGO in the fabricated composites improved the electrical conductivity of insulating WKF/PES composites, reducing the resistance to ∼103 Ω. Joule heating performance depended strongly on the precursor concentration of the nanowires and the presence of rGO in the composite. A maximum surface temperature of 163 °C was obtained under low-voltage (5 V) application. The Joule heating performance of the composites was demonstrated in a surface deicing experiment; we observed that 17 g of ice melted from the surface of the composite in 14 min under an applied voltage of 5 V at -28 °C. The excellent performance of WKF/NiCo2S4/rGO/PES composites shows great potential for aerospace structural applications requiring outstanding mechanical properties and Joule heating capability for deicing of surfaces.

  17. Self-powered heat-resistant polymeric 1D nanowires and 3D micro/nanowire assemblies in a pressure-crystallized size-distributed graphene oxide/poly (vinylidene fluoride) composite

    Science.gov (United States)

    Tian, Pengfei; Lyu, Jun; Huang, Rui; Zhang, Chaoliang

    2017-12-01

    Piezoelectric one- (1D) and three-dimensional (3D) hybrid micro/nanostructured materials have received intense research interest because of their ability in capturing trace amounts of energy and transforming it into electrical energy. In this work, a size-distributed graphene oxide (GO) was utilized for the concurrent growth of both the 1D nanowires and 3D micro/nanowire architectures of poly (vinylidene fluoride) (PVDF) with piezoelectricity. The in situ formation of the polymeric micro/nanostructures, with crystalline beta phase, was achieved by the high-pressure crystallization of a well dispersed GO/PVDF composite, fabricated by an environmentally friendly physical approach. Particularly, by controlling the crystallization conditions of the binary composite at high pressure, the melting point of the polymeric micro/nanowires, which further constructed the 3D micro/nanoarchitectures, was nearly 30°C higher than that of the original PVDF. The large scale simultaneous formation of the 1D and 3D micro/nanostructures was attributed to a size-dependent catalysis of the GOs in the pressure-treated composite system. The as-fabricated heat-resistant hybrid micro/nanoarchitectures, consisting of GOs and piezoelectric PVDF micro/nanowires, may permit niche applications in self-powered micro/nanodevices for energy scavenging from their working environments.

  18. Structural and electronic properties of Ti-nanowires/C-single wall nanotubes composites by density functional theory calculations

    Energy Technology Data Exchange (ETDEWEB)

    Gialampouki, M.A.; Balerba, A.V. [Department of Materials Science and Engineering, University of Ioannina, Ioannina, 45110 (Greece); Lekka, Ch.E., E-mail: chlekka@cc.uoi.gr [Department of Materials Science and Engineering, University of Ioannina, Ioannina, 45110 (Greece)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer The nanowires (NWs) transform the cylindrical SWNTs' shape to ellipsoid. Black-Right-Pointing-Pointer Ti NWs contribute in the SWNTs' EDOSs with new states at the Fermi level. Black-Right-Pointing-Pointer The deposited bcc NW on the SWNT induce magnetization and electric dipole moment. Black-Right-Pointing-Pointer These composites appear promising for applications in electronic devices. - Abstract: Structural and electronic properties of composite Ti-nanowires/single wall carbon nanotubes ((6,0) and (10,0)) (SWNT) were evaluated by means of density functional theory computations. We considered the cases of monoatomic (MNW), BCC ({beta}-NW) and HCP ({alpha}-NW) nanowires that were either inserted or deposited in/on the SWNTs. In all cases the NWs turn the cylindrical SWNTs' shape to ellipsoid, an effect that is closely related to charge transfer from Ti toward C neighboring atoms. We found that the wires inside the SWNT appear to be more stable compared to the outside cases, while all NWs contribute with new energy states at the Fermi level, transforming the semiconducting (10,0) to a conducting composite. In addition, we found spin up-down differences in the {beta}-NW{sub on} case and electronic charge redistributions e.g. in {alpha}-NW{sub in} (charge accumulation internally along the tube's axis) or in {alpha}-NW{sub on} (superficial charge accumulation in the vicinity of the NW), accompanied by manifestation of electric dipole moment that reaches the value of 10 Debye in a-NW{sub on}. These results may be of use in the design of new C-based nanocomposite systems suitable for applications in microelectronics, sensors and catalysis.

  19. Urchin-like artificial gallium oxide nanowires grown by a novel MOCVD/CVD-based route for random laser application

    Energy Technology Data Exchange (ETDEWEB)

    Melo, Ronaldo P. de [Programa de Pós-Graduação em Ciências de Materiais, Universidade Federal de Pernambuco, Recife (Brazil); Colégio Militar do Recife, Exército Brasileiro, Recife PE 50730-120 (Brazil); Oliveira, Nathalia Talita C. [Programa de Pós-Graduação em Ciências de Materiais, Universidade Federal de Pernambuco, Recife (Brazil); Dominguez, Christian Tolentino; Gomes, Anderson S. L.; Araújo, Cid B. de [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife (Brazil); Falcão, Eduardo H. L.; Alves, Severino; Luz, Leonis L. da [Departamento de Química Fundamental, Universidade Federal de Pernambuco, 50670-901 Recife (Brazil); Chassagnon, Remi [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, 9 Av. A. Savary, BP 47870, 21078 Dijon Cedex (France); Sacilotti, Marco [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife (Brazil); Nanoform Group, Laboratoire Interdisciplinaire Carnot de Bourgogne, Université de Bourgogne, Dijon (France)

    2016-04-28

    A novel procedure based on a two-step method was developed to obtain β-Ga{sub 2}O{sub 3} nanowires by the chemical vapor deposition (CVD) method. The first step consists in the gallium micro-spheres growth inside a metal-organic chemical vapor deposition environment, using an organometallic precursor. Nanoscale spheres covering the microspheres were obtained. The second step involves the CVD oxidization of the gallium micro-spheres, which allow the formation of β-Ga{sub 2}O{sub 3} nanowires on the micro-sphere surface, with the final result being a nanostructure mimicking nature's sea urchin morphology. The grown nanomaterial is characterized by several techniques, including X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, transmission electron microscopy, and photoluminescence. A discussion about the growth mechanism and the optical properties of the β-Ga{sub 2}O{sub 3} material is presented considering its unknown true bandgap value (extending from 4.4 to 5.68 eV). As an application, the scattering properties of the nanomaterial are exploited to demonstrate random laser emission (around 570 nm) when it is permeated with a laser dye liquid solution.

  20. Urchin-like artificial gallium oxide nanowires grown by a novel MOCVD/CVD-based route for random laser application

    Science.gov (United States)

    de Melo, Ronaldo P.; Oliveira, Nathalia Talita C.; Dominguez, Christian Tolentino; Gomes, Anderson S. L.; Falcão, Eduardo H. L.; Alves, Severino; da Luz, Leonis L.; Chassagnon, Remi; de Araújo, Cid B.; Sacilotti, Marco

    2016-04-01

    A novel procedure based on a two-step method was developed to obtain β-Ga2O3 nanowires by the chemical vapor deposition (CVD) method. The first step consists in the gallium micro-spheres growth inside a metal-organic chemical vapor deposition environment, using an organometallic precursor. Nanoscale spheres covering the microspheres were obtained. The second step involves the CVD oxidization of the gallium micro-spheres, which allow the formation of β-Ga2O3 nanowires on the micro-sphere surface, with the final result being a nanostructure mimicking nature's sea urchin morphology. The grown nanomaterial is characterized by several techniques, including X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, transmission electron microscopy, and photoluminescence. A discussion about the growth mechanism and the optical properties of the β-Ga2O3 material is presented considering its unknown true bandgap value (extending from 4.4 to 5.68 eV). As an application, the scattering properties of the nanomaterial are exploited to demonstrate random laser emission (around 570 nm) when it is permeated with a laser dye liquid solution.

  1. Weak antilocalization effect of topological crystalline insulator Pb(1-x)Sn(x)Te nanowires with tunable composition and distinct {100} facets.

    Science.gov (United States)

    Safdar, Muhammad; Wang, Qisheng; Wang, Zhenxing; Zhan, Xueying; Xu, Kai; Wang, Fengmei; Mirza, Misbah; He, Jun

    2015-04-08

    Pb(1-x)Sn(x)Te is a unique topological crystalline insulator (TCI) that undergoes a topological phase transition from topological trivial insulator to TCI with the change of Sn content and temperature. Meanwhile, the surface states properties of Pb(1-x)Sn(x)Te are strongly dependent on crystallographic plane orientation. In this work, we first reported controllable synthesis of rectangular prismatic Pb(x)Sn(1-x)Te nanowires by vapor deposition method. Rectangular prismatic Pb(x)Sn(1-x)Te nanowires exhibits distinct {100} surfaces. Furthermore, The Sn composition of Pb(1-x)Sn(x)Te nanowires can be continuously controlled from 0 to 1. Low temperature magnetotransport shows that PbTe nanowire exhibits weak localization (WL) effect, whereas Pb0.5Sn0.5Te and Pb0.2Sn0.8Te nanowires display pronounced weak antilocalization (WAL) effect. This transition is explained by the topological phase transform of Pb(1-x)Sn(x)Te from trivial to nontrivial insulator with Sn content (x) exceeding 0.38. Pb(x)Sn(1-x)Te nanowires synthesized in this work lay a foundation for probing spin-correlated electron transport and show great potentials for future applications of tunable spintronic devices.

  2. Preparation and Characterization of Thin-Film Composite Membrane with Nanowire-Modified Support for Forward Osmosis Process

    Science.gov (United States)

    Low, Ze-Xian; Liu, Qi; Shamsaei, Ezzatollah; Zhang, Xiwang; Wang, Huanting

    2015-01-01

    Internal concentration polarization (ICP) in forward osmosis (FO) process is a characteristic problem for asymmetric thin-film composite (TFC) FO membrane which leads to lower water flux. To mitigate the ICP effect, modification of the substrates’ properties has been one of the most effective methods. A new polyethersulfone-based ultrafiltration membrane with increased surface porosity and high water flux was recently produced by incorporating Zn2GeO4 nanowires. The composite membrane was used as a substrate for the fabrication of TFC FO membrane, by coating a thin layer of polyamide on top of the substrate. The substrate and the nanowires were characterized by a range of techniques such as SEM, XRD, and contact angle goniometry. The water permeability and molecular weight cut-offs (MWCO) of the substrate; and the FO performance of the TFC membrane were also determined. The Zn2GeO4-modified membrane showed ~45% increase in water permeability and NaCl salt rejection of 80% under RO mode. In FO mode, the ratio of water flux to reverse solute flux was also improved. However, lower FO flux was obtained which could be due to ICP. The result shows that Zn2GO4 nanowire may be used as a modifier to the substrate to improve the quality of the polyamide layer on the substrate to improve the flux and selectivity, but not as effective in reducing ICP. This work demonstrates that the incorporation of nanomaterials to the membrane substrate may be an alternative approach to improve the formation of polyamide skin layer to achieve better FO performance. PMID:25803239

  3. Preparation and Characterization of Thin-Film Composite Membrane with Nanowire-Modified Support for Forward Osmosis Process

    Directory of Open Access Journals (Sweden)

    Ze-Xian Low

    2015-03-01

    Full Text Available Internal concentration polarization (ICP in forward osmosis (FO process is a characteristic problem for asymmetric thin-film composite (TFC FO membrane which leads to lower water flux. To mitigate the ICP effect, modification of the substrates’ properties has been one of the most effective methods. A new polyethersulfone-based ultrafiltration membrane with increased surface porosity and high water flux was recently produced by incorporating Zn2GeO4 nanowires. The composite membrane was used as a substrate for the fabrication of TFC FO membrane, by coating a thin layer of polyamide on top of the substrate. The substrate and the nanowires were characterized by a range of techniques such as SEM, XRD, and contact angle goniometry. The water permeability and molecular weight cut-offs (MWCO of the substrate; and the FO performance of the TFC membrane were also determined. The Zn2GeO4-modified membrane showed ~45% increase in water permeability and NaCl salt rejection of 80% under RO mode. In FO mode, the ratio of water flux to reverse solute flux was also improved. However, lower FO flux was obtained which could be due to ICP. The result shows that Zn2GO4 nanowire may be used as a modifier to the substrate to improve the quality of the polyamide layer on the substrate to improve the flux and selectivity, but not as effective in reducing ICP. This work demonstrates that the incorporation of nanomaterials to the membrane substrate may be an alternative approach to improve the formation of polyamide skin layer to achieve better FO performance.

  4. Healable capacitive touch screen sensors based on transparent composite electrodes comprising silver nanowires and a furan/maleimide diels-alder cycloaddition polymer.

    Science.gov (United States)

    Li, Junpeng; Liang, Jiajie; Li, Lu; Ren, Fengbo; Hu, Wei; Li, Juan; Qi, Shuhua; Pei, Qibing

    2014-12-23

    A healable transparent capacitive touch screen sensor has been fabricated based on a healable silver nanowire-polymer composite electrode. The composite electrode features a layer of silver nanowire percolation network embedded into the surface layer of a polymer substrate comprising an ultrathin soldering polymer layer to confine the nanowires to the surface of a healable Diels-Alder cycloaddition copolymer and to attain low contact resistance between the nanowires. The composite electrode has a figure-of-merit sheet resistance of 18 Ω/sq with 80% transmittance at 550 nm. A surface crack cut on the conductive surface with 18 Ω is healed by heating at 100 °C, and the sheet resistance recovers to 21 Ω in 6 min. A healable touch screen sensor with an array of 8×8 capacitive sensing points is prepared by stacking two composite films patterned with 8 rows and 8 columns of coupling electrodes at 90° angle. After deliberate damage, the coupling electrodes recover touch sensing function upon heating at 80 °C for 30 s. A capacitive touch screen based on Arduino is demonstrated capable of performing quick recovery from malfunction caused by a razor blade cutting. After four cycles of cutting and healing, the sensor array remains functional.

  5. Composition and diameter modulation of magnetic nanowire arrays fabricated by a novel approach

    Science.gov (United States)

    Shaker Salem, Mohamed; Tejo, Felipe; Zierold, Robert; Sergelius, Philip; Montero Moreno, Josep M.; Goerlitz, Detlef; Nielsch, Kornelius; Escrig, Juan

    2018-02-01

    Straight magnetic nanowires composed of nickel and permalloy segments having different diameters are synthesized using a promising approach. This approach involves the controlled electrodeposition of each magnetic material into specially designed diameter-modulated porous alumina templates. Standard alumina templates are exposed to pore widening followed by a protective coating of the pore wall with ultrathin silica and further anodization. Micromagnetic simulations are employed to investigate the process of magnetization reversal in the fabricated nanowires when the magnetic materials exchange their places in the thick and thin segments. It is found that the magnetization reversal occurs by the propagation of transverse domain wall (DW) when the thick segment is composed of permalloy. However, the reversal process proceeds by the propagation of vortex DW when permalloy is located at the thin segment.

  6. The effect of nanowire length and diameter on the properties of transparent, conducting nanowire films

    Science.gov (United States)

    Bergin, Stephen M.; Chen, Yu-Hui; Rathmell, Aaron R.; Charbonneau, Patrick; Li, Zhi-Yuan; Wiley, Benjamin J.

    2012-03-01

    This article describes how the dimensions of nanowires affect the transmittance and sheet resistance of a random nanowire network. Silver nanowires with independently controlled lengths and diameters were synthesized with a gram-scale polyol synthesis by controlling the reaction temperature and time. Characterization of films composed of nanowires of different lengths but the same diameter enabled the quantification of the effect of length on the conductance and transmittance of silver nanowire films. Finite-difference time-domain calculations were used to determine the effect of nanowire diameter, overlap, and hole size on the transmittance of a nanowire network. For individual nanowires with diameters greater than 50 nm, increasing diameter increases the electrical conductance to optical extinction ratio, but the opposite is true for nanowires with diameters less than this size. Calculations and experimental data show that for a random network of nanowires, decreasing nanowire diameter increases the number density of nanowires at a given transmittance, leading to improved connectivity and conductivity at high transmittance (>90%). This information will facilitate the design of transparent, conducting nanowire films for flexible displays, organic light emitting diodes and thin-film solar cells.This article describes how the dimensions of nanowires affect the transmittance and sheet resistance of a random nanowire network. Silver nanowires with independently controlled lengths and diameters were synthesized with a gram-scale polyol synthesis by controlling the reaction temperature and time. Characterization of films composed of nanowires of different lengths but the same diameter enabled the quantification of the effect of length on the conductance and transmittance of silver nanowire films. Finite-difference time-domain calculations were used to determine the effect of nanowire diameter, overlap, and hole size on the transmittance of a nanowire network. For

  7. Random Network Coding over Composite Fields

    DEFF Research Database (Denmark)

    Geil, Olav; Lucani Rötter, Daniel Enrique

    2017-01-01

    Random network coding is a method that achieves multicast capacity asymptotically for general networks [1, 7]. In this approach, vertices in the network randomly and linearly combine incoming information in a distributed manner before forwarding it through their outgoing edges. To ensure success...

  8. Insights into the Controllable Chemical Composition of Metal Oxide Nanowires and Graphene Aerogels

    Science.gov (United States)

    Goldstein, Anna Patrice

    The design and synthesis of materials that absorb visible light and create fuel to store solar energy is a pursuit that has captivated chemists for decades. In order to take part in solar water splitting, i.e. the production of hydrogen and oxygen gas from water and sunlight, electrode materials must fit specific requirements in terms of their electronic structure. Zinc oxide (ZnO) and titanium dioxide (TiO2) are both of interest for their ability to produce oxygen from photogenerated holes, but their band gaps are too large to capture a significant portion of the solar spectrum. We address this challenge by modifying the crystal structures of ZnO and TiO 2 to make lower band gap materials. Furthermore, we use nanowires as the synthetic template for these materials because they provide a large semiconductor-liquid interfacial area. ZnO nanowires can be alloyed with In3+, Fe3+ and other trivalent metal ions to form a unique structure with the formula M2O3(ZnO)n, also known as MZO. We synthesize indium zinc oxide (IZO) and indium iron zinc oxide (IFZO) nanowires and study their crystal structure using atomically-resolved transmission electron microscopy (TEM), among other methods. We elucidate a structural model for MZO that resolves inconsistencies in the existing literature, based on the identification of the zigzag layer as an inversion domain boundary. These nanowires are shown to have a lower band gap than ZnO and produce photocurrent under visible light illumination. The solid-state diffusion reaction to form ternary titanates is also studied by TEM. TiO2 nanowires are coated with metal oxides by a variety of deposition methods, and then converted to MTiO3 at high temperatures, where M is a divalent transition metal ion such as Mn 2+, CO2+, or Ni2+. When Co3O 4 particles attached to TiO2 nanowires are annealed for a short time, we observe the formation of a CoO(111)/TiO2 (010) interface. If the nanowires are instead coated with Co(NO3)2 salt and then annealed

  9. Composite films of highly ordered Si nanowires embedded in SiGe0.3 for thermoelectric applications

    Science.gov (United States)

    Kikuchi, Akiou; Yao, Akifumi; Mori, Isamu; Ono, Takahito; Samukawa, Seiji

    2017-10-01

    We fabricated a high-density array of silicon nanowires (SiNWs) with a diameter of 10 nm embedded in silicon germanium (SiGe0.3) to give a composite thin film for thermoelectric device applications. The SiNW array was first fabricated by bio-template mask and neutral beam etching techniques. The SiNW array was then embedded in SiGe0.3 by thermal chemical vapor deposition. The cross-plane thermal conductivity of the SiNW-SiGe0.3 composite film with a thickness of 100 nm was 3.5 ± 0.3 W/mK in the temperature range of 300-350 K. Moreover, the temperature dependences of the in-plane electrical conductivity and in-plane Seebeck coefficient of the SiNW-SiGe0.3 composite were evaluated. The fabricated SiNW-SiGe0.3 composite film displayed a maximum power factor of 1 × 103 W/m K2 (a Seebeck coefficient of 4.8 × 103 μV/K and an electrical conductivity of 4.4 × 103 S/m) at 873 K. The present high-density SiNW array structure represents a new route to realize practical thermoelectric devices using mature Si processes without any rare metals.

  10. UV-Assisted Photochemical Synthesis of Reduced Graphene Oxide/ZnO Nanowires Composite for Photoresponse Enhancement in UV Photodetectors

    Directory of Open Access Journals (Sweden)

    Changsong Chen

    2018-01-01

    Full Text Available The weak photon absorption and high recombination rate of electron-hole pairs in disordered zinc oxide nanowires (ZNWs limit its application in UV photodetection. This limitation can be overcome by introducing graphene sheets to the ZNWs. Herein we report a high-performance photodetector based on one-dimensional (1D wide band-gap semiconductor disordered ZNWs composited with reduced graphene oxide (RGO for ultraviolet (UV photoresponse enhancement. The RGO/ZNWs composites have been successfully synthetized through UV-assisted photochemical reduction of GO in ZNWs suspension. The material characterizations in morphology, Raman scattering, and Ultraviolet-visible light absorption verified the formation of graphene sheets attached in ZNWs network and the enhancement of UV absorption due to the introduction of graphene. In comparison with photodetectors based on pure ZNWs, the photodetectors based on RGO/ZNWs composite exhibit enhanced photoresponse with photocurrent density of 5.87 mA·cm−2, on/off current ratio of 3.01 × 104, and responsivity of 1.83 A·W−1 when a UV irradiation of 3.26 mW·cm−2 and 1.0 V bias were used. Theory analysis is also presented to get insight into the inherent mechanisms of separation and transportation of photo-excited carriers in RGO/ZNWs composite.

  11. Nanowire Growth for Photovoltaics

    DEFF Research Database (Denmark)

    Holm, Jeppe Vilstrup

    cells. Resonance effects between the light and nanowire causes an inherent concentration of the sunlight into the nanowires, and means that a sparse array of nanowires (less than 5% of the area) can absorb all the incoming light. The resonance effects, as well as a graded index of refraction, also traps...... of the percentage of P in the flux, while for planar growth it was a convex function. We have demonstrated GaAs0.8P0.2 nanowires and further grown a shell surrounding the core with the same composition. The lattice matched GaAsP core-shell nanowire were doped to produce radial p-i-n junctions in each...... of the nanowires, some of which were removed from their growth substrate and turned into single nanowire solar cells (SNWSC). The best device showed a conversion efficiency of 6.8% under 1.5AMG 1-sun illumination. In order to improve the efficiency a surface passivating shell consisting of highly doped, wide...

  12. A silicon nanowire-reduced graphene oxide composite as a high-performance lithium ion battery anode material.

    Science.gov (United States)

    Ren, Jian-Guo; Wang, Chundong; Wu, Qi-Hui; Liu, Xiang; Yang, Yang; He, Lifang; Zhang, Wenjun

    2014-03-21

    Toward the increasing demands of portable energy storage and electric vehicle applications, silicon has been emerging as a promising anode material for lithium-ion batteries (LIBs) owing to its high specific capacity. However, serious pulverization of bulk silicon during cycling limits its cycle life. Herein, we report a novel hierarchical Si nanowire (Si NW)-reduced graphene oxide (rGO) composite fabricated using a solvothermal method followed by a chemical vapor deposition process. In the composite, the uniform-sized [111]-oriented Si NWs are well dispersed on the rGO surface and in between rGO sheets. The flexible rGO enables us to maintain the structural integrity and to provide a continuous conductive network of the electrode, which results in over 100 cycles serving as an anode in half cells at a high lithium storage capacity of 2300 mA h g(-1). Due to its [111] growth direction and the large contact area with rGO, the Si NWs in the composite show substantially enhanced reaction kinetics compared with other Si NWs or Si particles.

  13. Tribological properties of self-lubricating NiAl/Mo-based composites containing AgVO{sub 3} nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Eryong, E-mail: ley401@163.com [State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Gao, Yimin, E-mail: ymgao@mail.xjtu.edu.cn [State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Bai, Yaping, E-mail: jingpingxue2004@163.com [State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Yi, Gewen, E-mail: gwyi@licp.cas.cn [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Wang, Wenzhen, E-mail: Wzwang@licp.cas.cn [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Zeng, Zhixiang, E-mail: zengzhx@nimte.ac.cn [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Jia, Junhong, E-mail: jhjia@licp.cas.cn [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

    2014-11-15

    Silver vanadate (AgVO{sub 3}) nanowires were synthesized by hydrothermal method and self-lubricating NiAl/Mo-AgVO{sub 3} composites were fabricated by powder metallurgy technique. The composition and microstructure of NiAl/Mo-based composites were characterized and the tribological properties were investigated from room temperature to 900 °C. The results showed that NiAl/Mo-based composites were consisted of nanocrystalline B2 ordered NiAl matrix, Al{sub 2}O{sub 3}, Mo{sub 2}C, metallic Ag and vanadium oxide phase. The appearance of metallic Ag and vanadium oxide phase can be attributed to the decomposition of AgVO{sub 3} during sintering. Wear testing results confirmed that NiAl/Mo-based composites have excellent tribological properties over a wide temperature range. For example, the friction coefficient and wear rate of NiAl/Mo-based composites containing AgVO{sub 3} were significantly lower than the composites containing only metallic Mo or AgVO{sub 3} lubricant when the temperature is above 300 °C, which can be attributed to the synergistic lubricating action of metallic Mo and AgVO{sub 3} lubricants. Furthermore, Raman results indicated that the composition on the worn surface of NiAl-based composites was self-adjusted after wear testing at different temperatures. For example, Ag{sub 3}VO{sub 4} and Fe{sub 3}O{sub 4} lubricants were responsible for the improvement of tribological properties at 500 °C, AgVO{sub 3}, Ag{sub 3}VO{sub 4} and molybdate for 700 °C, and AgVO{sub 3} and molybdate for 900 °C of NiAl-based composites with the addition of metallic Mo and AgVO{sub 3}. - Highlights: • NiAl/Mo-AgVO{sub 3} nanocomposites were prepared by mechanical alloying and sintering. • AgVO{sub 3} decomposed to metallic Ag and vanadium oxide during the sintering process. • NiAl/Mo-AgVO{sub 3} exhibited superior tribological properties at a board temperature range. • Phase composition on the worn surface was varied with temperatures. • Self-adjusted action

  14. Preparation and characterization of graphene-based vanadium oxide composite semiconducting films with horizontally aligned nanowire arrays

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Hye-Mi; Um, Sukkee, E-mail: sukkeeum@hanyang.ac.kr

    2016-05-01

    Highly oriented crystalline hybrid thin films primarily consisting of Magnéli-phase VO{sub 2} and conductive graphene nanoplatelets are fabricated by a sol–gel process via dipping pyrolysis. A combination of chemical, microstructural, and electrical analyses reveals that graphene oxide (GO)-templated vanadium oxide (VO{sub x}) nanocomposite films exhibit a vertically stacked multi-lamellar nanostructure consisting of horizontally aligned vanadium oxide nanowire (VNW) arrays along the (hk0) set of planes on a GO template, with an average crystallite size of 41.4 Å and a crystallographic tensile strain of 0.83%. In addition, GO-derived VO{sub x} composite semiconducting films, which have an sp{sup 3}/sp{sup 2} bonding ratio of 0.862, display thermally induced electrical switching properties in the temperature range of − 20 °C to 140 °C, with a transition temperature of approximately 65 °C. We ascribe these results to the use of GO sheets, which serve as a morphological growth template as well as an electrochemically tunable platform for enhancing the charge-carrier mobility. Moreover, the experimental studies demonstrate that graphene-based Magnéli-phase VO{sub x} composite semiconducting films can be used in advanced thermo-sensitive smart sensing/switching applications because of their outstanding thermo-electrodynamic properties and high surface charge density induced by the planar-type VNWs. - Highlights: • VO{sub x}-graphene oxide composite (G/VO{sub x}) films were fabricated by sol–gel process. • The G/VO{sub x} films mainly consisted of Magnéli-phase VO{sub 2} and reduced graphene sheets. • The G/VO{sub x} films exhibited multi-lamellar textures with planar VO{sub x} nanowire arrays. • The G/VO{sub x} films showed the thermo-sensitive electrical switching properties. • Effects of GOs on the electrical characteristics of the G/VO{sub x} films were discussed.

  15. Direct observation of interface and nanoscale compositional modulation in ternary III-As heterostructure nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Venkatesan, Sriram; Scheu, Christina [Department of Chemistry and Center for NanoScience, Ludwig-Maximilians-Universität München, Butenandstr 5-13(E), 81377 München (Germany); Madsen, Morten H.; Krogstrup, Peter; Johnson, Erik [Nano-Science Center and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen (Denmark); Schmid, Herbert [INM-Leibniz Institute for New Materials, 66123 Saarbrücken (Germany)

    2013-08-05

    Straight, axial InAs nanowire with multiple segments of Ga{sub x}In{sub 1−x}As was grown. High resolution X-ray energy-dispersive spectroscopy (EDS) mapping reveals the distribution of group III atoms at the axial interfaces and at the sidewalls. Significant Ga enrichment, accompanied by a structural change is observed at the Ga{sub x}In{sub 1−x}As/InAs interfaces and a higher Ga concentration for the early grown Ga{sub x}In{sub 1−x}As segments. The elemental map and EDS line profile infer Ga enrichment at the facet junctions between the sidewalls. The relative chemical potentials of ternary alloys and the thermodynamic driving force for liquid to solid transition explains the growth mechanisms behind the enrichment.

  16. Organic Nanowires

    DEFF Research Database (Denmark)

    Balzer, Frank; Schiek, Manuela; Al-Shamery, Katharina

    Single crystalline nanowires from fluorescing organic molecules like para-phenylenes or thiophenes are supposed to become key elements in future integrated optoelectronic devices [1]. For a sophisticated design of devices based on nanowires the basic principles of the nanowire formation have...

  17. Random nanowires of nickel doped TiO2 with high surface area and electron mobility for high efficiency dye-sensitized solar cells.

    Science.gov (United States)

    Archana, P S; Naveen Kumar, E; Vijila, C; Ramakrishna, S; Yusoff, M M; Jose, R

    2013-01-28

    Mesoporous TiO(2) with a large specific surface area (~150 m(2) g(-1)) is the most successful material in dye-sensitized solar cells so far; however, its inferior charge mobility is a major efficiency limiter. This paper demonstrates that random nanowires of Ni-doped TiO(2) (Ni:TiO(2)) have a dramatic influence on the particulate and charge transport properties. Nanowires (dia ~60 nm) of Ni:TiO(2) with a specific surface area of ~80 m(2) g(-1) were developed by an electrospinning technique. The band gap of the Ni:TiO(2) shifted to the visible region upon doping of 5 at% Ni atoms. The Mott-Schottky analysis shows that the flat band potential of Ni:TiO(2) shifts to a more negative value than the undoped samples. The electrochemical impedance spectroscopic measurements showed that the Ni:TiO(2) offer lower charge transport resistance, higher charge recombination resistance, and enhanced electron lifetime compared to the undoped samples. The dye-sensitized solar cells fabricated using the Ni:TiO(2) nanowires showed an enhanced photoconversion efficiency and short-circuit current density compared to the undoped analogue. The transient photocurrent measurements showed that the Ni:TiO(2) has improved charge mobility compared with TiO(2) and is several orders of magnitude higher compared to the P25 particles.

  18. Origin of high strength, low modulus superelasticity in nanowire-shape memory alloy composites

    Science.gov (United States)

    Zhang, Xudong; Zong, Hongxiang; Cui, Lishan; Fan, Xueling; Ding, Xiangdong; Sun, Jun

    2017-04-01

    An open question is the underlying mechanisms for a recent discovered nanocomposite, which composed of shape memory alloy (SMA) matrix with embedded metallic nanowires (NWs), demonstrating novel mechanical properties, such as large quasi-linear elastic strain, low Young’s modulus and high yield strength. We use finite element simulations to investigate the interplay between the superelasticity of SMA matrix and the elastic-plastic deformation of embedded NWs. Our results show that stress transfer plays a dominated role in determining the quasi-linear behavior of the nanocomposite. The corresponding microstructure evolution indicate that the transfer is due to the coupling between plastic deformation within the NWs and martensitic transformation in the matrix, i.e., the martensitic transformation of the SMA matrix promotes local plastic deformation nearby, and the high plastic strain region of NWs retains considerable martensite in the surrounding SMA matrix, thus facilitating continues martensitic transformation in subsequent loading. Based on these findings, we propose a general criterion for achieving quasi-linear elasticity.

  19. Direct monolithic integration of vertical single crystalline octahedral molecular sieve nanowires on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Carretero-Genevrier, Adrian [Institut des Nanotechnologies de Lyon (INL), UMR-CNRS 5270, Ecole Central de Lyon, Ecully (France); Institut de Ciencia de Materials de Barcelona ICMAB, Catalonia (Spain); Sorbonne Univ., UPMC Univ. Paris 06, CNRS, College de France, Paris (France); Oro-Sole, Judith [Institut de Ciencia de Materials de Barcelona ICMAB, Catalonia (Spain); Gazquez, Jaume [Institut de Ciencia de Materials de Barcelona ICMAB, Catalonia (Spain); Magen, Cesar [Univ. de Zaragoza, Zaragoza (Spain); Miranda, Laura [Sorbonne Univ., UPMC Univ. Paris 06, CNRS, College de France, Paris (France); Puig, Teresa [Institut de Ciencia de Materials de Barcelona ICMAB, Catalonia (Spain); Obradors, Xavier [Institut de Ciencia de Materials de Barcelona ICMAB, Catalonia (Spain); Ferain, Etienne [Univ. Catholique de Louvain, Louvain-la-Neuve (Belgium); Sanchez, Clement [Sorbonne Univ., UPMC Univ. Paris 06, CNRS, College de France, Paris (France); Rodriguez-Carvajal, Juan [Institut Laue-Langevin, Grenoble Cedex (France); Mestres, Narcis [Institut de Ciencia de Materials de Barcelona ICMAB, Catalonia (Spain)

    2013-12-13

    We developed an original strategy to produce vertical epitaxial single crystalline manganese oxide octahedral molecular sieve (OMS) nanowires with tunable pore sizes and compositions on silicon substrates by using a chemical solution deposition approach. The nanowire growth mechanism involves the use of track-etched nanoporous polymer templates combined with the controlled growth of quartz thin films at the silicon surface, which allowed OMS nanowires to stabilize and crystallize. α-quartz thin films were obtained after thermal activated crystallization of the native amorphous silica surface layer assisted by Sr2+- or Ba2+-mediated heterogeneous catalysis in the air at 800 °C. These α-quartz thin films work as a selective template for the epitaxial growth of randomly oriented vertical OMS nanowires. Furthermore, the combination of soft chemistry and epitaxial growth opens new opportunities for the effective integration of novel technological functional tunneled complex oxides nanomaterials on Si substrates.

  20. Continuously Producible Ultrasensitive Wearable Strain Sensor Assembled with Three-Dimensional Interpenetrating Ag Nanowires/Polyolefin Elastomer Nanofibrous Composite Yarn.

    Science.gov (United States)

    Zhong, Weibing; Liu, Cui; Xiang, Chenxue; Jin, Yuxia; Li, Mufang; Liu, Ke; Liu, Qiongzhen; Wang, Yuedan; Sun, Gang; Wang, Dong

    2017-12-06

    Fiber-shaped strain sensors with great flexibility and knittability have been tremendously concerned due to the wide applications in health manager devices, especially in human motion detection and physiological signal monitoring. Herein, a novel fiber-shaped strain sensor has been designed and prepared by interpenetrating Ag nanowires (NWs) into polyolefin elastomer nanofibrous yarn. The easy-to-obtain structure and simple roll-to-roll process make the continuous large-scale production of nanofibrous composite yarn possible. The continuous and alternating stretching and releasing reversibly change the contact probability between AgNWs in this interpenetrating network, leading to the variations of electrical resistance of the sensor. The gauge factors of strain sensors are calculated to be as high as 13920 and the minimum detection limit is only 0.065%. In addition, the strain sensor shows excellent durability during 4500 cycles with the strain of 10%. The response times of stretching and releasing strains are 10 and 15 ms, respectively. Furthermore, the strain sensor has been successfully applied in human motion detections both in single yarn and knitted fabrics. The result shows the practicability in applications of monitoring limbs movements, eye motion changes, artificial vocal cords, human pulse, and complex motions, which shows great potential in wearable sensors and electronic skin.

  1. In situ-growth of silica nanowires in ceramic carbon composites

    OpenAIRE

    Rahul Kumar; Parag Bhargava

    2017-01-01

    An understanding of the processing and microstructure of ceramic–carbon composites is critical to development of these composites for applications needing electrically conducting, thermal shock resistant ceramic materials. In the present study green compacts of carbon ceramic composites were prepared either by slurry processing or dry powder blending of one or more of the three — clay, glass, alumina and carbon black or graphite. The dried green compacts were sintered at 1400 °C in flowing ar...

  2. Atomistic theory of excitonic fine structure in InAs/InP nanowire quantum dot molecules

    Science.gov (United States)

    Świderski, M.; Zieliński, M.

    2017-03-01

    Nanowire quantum dots have peculiar electronic and optical properties. In this work we use atomistic tight binding to study excitonic spectra of artificial molecules formed by a double nanowire quantum dot. We demonstrate a key role of atomistic symmetry and nanowire substrate orientation rather than cylindrical shape symmetry of a nanowire and a molecule. In particular for [001 ] nanowire orientation we observe a nonvanishing bright exciton splitting for a quasimolecule formed by two cylindrical quantum dots of different heights. This effect is due to interdot coupling that effectively reduces the overall symmetry, whereas single uncoupled [001 ] quantum dots have zero fine structure splitting. We found that the same double quantum dot system grown on [111 ] nanowire reveals no excitonic fine structure for all considered quantum dot distances and individual quantum dot heights. Further we demonstrate a pronounced, by several orders of magnitude, increase of the dark exciton optical activity in a quantum dot molecule as compared to a single quantum dot. For [111 ] systems we also show spontaneous localization of single particle states in one of nominally identical quantum dots forming a molecule, which is mediated by strain and origins from the lack of the vertical inversion symmetry in [111 ] nanostructures of overall C3 v symmetry. Finally, we study lowering of symmetry due to alloy randomness that triggers nonzero excitonic fine structure and the dark exciton optical activity in realistic nanowire quantum dot molecules of intermixed composition.

  3. Protein immobilization onto electrochemically synthesized CoFe nanowires

    National Research Council Canada - National Science Library

    Torati, Sri Ramulu; Reddy, Venu; Yoon, Seok Soo; Kim, CheolGi

    2015-01-01

    CoFe nanowires have been synthesized by the electrodeposition technique into the pores of a polycarbonate membrane with a nominal pore diameter of 50 nm, and the composition of CoFe nanowires varying...

  4. Largely enhanced near band edge emission of ultrathin zinc oxide nanowire/gold nanoparticles composites by surface plasmon resonance

    Science.gov (United States)

    Li, Lei; Wang, Chenying; Han, Feng; Yang, Shuming; Jing, Weixuan; Jiang, Zhuangde

    2018-03-01

    Ultrathin zinc oxide nanowires with diameter less than 50 nm were synthesized by polyethyleneimine assisted solution method. Zinc oxide nanowire near band edge emission was enhanced obviously by gold nanoparticles coating, and a max 26 times enhancement was realized. The defects caused visible light emission was also quenched to noise level when gold was deposited more than 10 s. The large near band edge emission enhancement was caused by surface plasmon resonance mediated luminescent energy transfer, which absorbed the visible light energy and transferred to the near band edge emission. The large surface to volume ratio enhanced the coupling strength between gold nanoparticles and ultrathin zinc oxide nanowires. This research provide a method to improve the luminescent efficiency of zinc oxide nanowires.

  5. Template-Assisted Synthesis of Nickel Sulfide Nanowires: Tuning the Compositions for Supercapacitors with Improved Electrochemical Stability.

    Science.gov (United States)

    Zang, Xiaoxian; Dai, Ziyang; Yang, Jun; Zhang, Yizhou; Huang, Wei; Dong, Xiaochen

    2016-09-21

    Ni nanowires were first synthesized via a chemical method without surfactants or a magnetic field. A series of nickel sulfide nanowires (Ni3S2-Ni, Ni3S2-NiS-Ni, and Ni3S2-NiS) have been successfully prepared by a controlled sacrificial template route based on the conductive Ni nanowire template. Electrochemical characterizations indicate that Ni3S2-NiS nanowires present superior redox reactivity with a high specific capacitance of 1077.3 F g(-1) at 5 A g(-1). Besides, its specific capacitance can remain about 76.3% after 10 000 cycles at 20 A g(-1). On the contrary, the nickel-preserving sulfide nanowires (Ni3S2-Ni and Ni3S2-NiS-Ni) deliver enhanced cycling stability as 100% of the initial specific capacitance of Ni3S2-Ni is retained after 10 000 cycles. The outstanding electrochemical stability can be attributed to the interaction between nickel sulfides and the conductive nickel nanowires.

  6. Manganese oxide nanowires, films, and membranes and methods of making

    Science.gov (United States)

    Suib, Steven Lawrence [Storrs, CT; Yuan, Jikang [Storrs, CT

    2011-02-15

    Nanowires, films, and membranes comprising ordered porous manganese oxide-based octahedral molecular sieves and methods of making the same are disclosed. A method for forming nanowires includes hydrothermally treating a chemical precursor composition in a hydrothermal treating solvent to form the nanowires, wherein the chemical precursor composition comprises a source of manganese cations and a source of counter cations, and wherein the nanowires comprise ordered porous manganese oxide-based octahedral molecular sieves.

  7. Hierarchical Carbon Fibers with ZnO Nanowires for Volatile Sensing in Composite Curing (Postprint)

    Science.gov (United States)

    2014-07-01

    for a titanium replacement. While polyimides are commercially available in large quantities and polyimide composites have been used for a number...solution of Zinc Acetate dihydride (ZnAc2·H2O) in EtOH. Preparation of the seeding solution started with making a 0.02M solution of Sodium Hydroxide ... manufacture can be directly traced to volatile management. A more reliable method to sense volatile concentration would improve polyimide curing and

  8. Morphology and composition of oxidized InAs nanowires studied by combined Raman spectroscopy and transmission electron microscopy.

    Science.gov (United States)

    Tanta, Rawa; Kanne, Thomas; Amaduzzi, Francesca; Liao, Zhiyu; Madsen, Morten H; Alarcón-Lladó, Esther; Krogstrup, Peter; Johnson, Erik; Morral, Anna Fontcuberta I; Vosch, Tom; Nygård, Jesper; Jespersen, Thomas S

    2016-06-20

    Any device exposed to ambient conditions will be prone to oxidation. This may be of particular importance for semiconductor nanowires because of the high surface-to-volume ratio and only little is known about the consequences of oxidation for these systems. Here, we study the properties of indium arsenide nanowires which were locally oxidized using a focused laser beam. Polarization dependent micro-Raman measurements confirmed the presence of crystalline arsenic, and transmission electron microscopy diffraction showed the presence of indium oxide. The surface dependence of the oxidation was investigated in branched nanowires grown along the [Formula: see text] and [Formula: see text] wurtzite crystal directions exhibiting different surface facets. The oxidation did not occur at the [Formula: see text] direction. The origin of this selectivity is discussed in terms transition state kinetics of the free surfaces of the different crystal families of the facets and numerical simulations of the laser induced heating.

  9. Magnetic hysteresis in small-grained Co{sub x}Pd{sub 1−x} nanowire arrays

    Energy Technology Data Exchange (ETDEWEB)

    Viqueira, M.S. [Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba. Ciudad Universitaria, 5000 Córdoba (Argentina); Instituto de Física Enrique Gaviola – CONICET (Argentina); Pozo-López, G. [Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba. Ciudad Universitaria, 5000 Córdoba (Argentina); Instituto de Física Enrique Gaviola – CONICET (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina); Urreta, S.E., E-mail: urreta@famaf.unc.edu.ar [Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba. Ciudad Universitaria, 5000 Córdoba (Argentina); Condó, A.M. [Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina); Centro Atómico Bariloche, Comisión Nacional de Energía Atómica – Instituto Balseiro, Universidad Nacional de Cuyo. Av. Bustillo 9500, 8400, San Carlos de Bariloche (Argentina); Cornejo, D.R. [Instituto de Física, Universidade de São Paulo, 05508-900 São Paulo, SP (Brazil); and others

    2015-11-15

    Co–Pd nanowires with small grain size are fabricated by AC electrodeposition into hexagonally ordered alumina pores, 20–35 nm in diameter and about 1 µm long. The effects of the alloy composition, the nanowire diameter and the grain size on the hysteresis properties are considered. X-ray diffraction indicates that the nanowires are single phase, a fcc Co–Pd solid solution; electron microscopy results show that they are polycrystalline, with randomly oriented grains (7–12 nm), smaller than the wire diameter. Nanowire arrays are ferromagnetic, with an easy magnetization axis parallel to the nanowire long axis. Both, the coercive field and the loop squareness monotonously increase with the Co content and with the grain size, but no clear correlation with the wire diameter is found. The Co and Co-rich nanowire arrays exhibit coercive fields and reduced remanence values quite insensitive to temperature in the range 4 K–300 K; on the contrary, in Pd-rich nanowires both magnitudes are smaller and they largely increase during cooling below 100 K. These behaviors are systematized by considering the strong dependences displayed by the magneto-crystalline anisotropy and the saturation magnetostriction on composition and temperature. At low temperatures the effective anisotropy value and the domain-wall width to grain size ratio drastically change, promoting less cooperative and harder nucleation modes. - Highlights: • Polycrystalline Co–Pd nanowires, 20–35 nm diameter, 5–12 nm grain size are synthesized. • Coercivity (14–80 mT) and squareness mainly depend on composition and grain size. • Different contributions to the effective anisotropy are considered. • Strong temperature and composition dependence of the nucleation localization is found.

  10. Facile Synthesis of MnPO4·H2O Nanowire/Graphene Oxide Composite Material and Its Application as Electrode Material for High Performance Supercapacitors

    Directory of Open Access Journals (Sweden)

    Bo Yan

    2016-12-01

    Full Text Available In this work, we reported a facile one-pot hydrothermal method to synthesize MnPO4·H2O nanowire/graphene oxide composite material with coated graphene oxide. Transmission electron microscopy and scanning electron microscope were employed to study its morphology information, and X-ray diffraction was used to study the phase and structure of the material. Additionally, X-ray photoelectron spectroscopy was used to study the elements information. To measure electrochemical performances of electrode materials and the symmetry cell, cyclic voltammetry, chronopotentiometry and electrochemical impedance spectrometry were conducted on electrochemical workstation using 3 M KOH electrolytes. Importantly, electrochemical results showed that the as-prepared MnPO4·H2O nanowire/graphene oxide composite material exhibited high specific capacitance (287.9 F·g−1 at 0.625 A·g−1 and specific power (1.5 × 105 W·kg−1 at 2.271 Wh·kg−1, which is expected to have promising applications as supercapacitor electrode material.

  11. Polarization-induced pn diodes in wide-band-gap nanowires with ultraviolet electroluminescence.

    Science.gov (United States)

    Carnevale, Santino D; Kent, Thomas F; Phillips, Patrick J; Mills, Michael J; Rajan, Siddharth; Myers, Roberto C

    2012-02-08

    Almost all electronic devices utilize a pn junction formed by random doping of donor and acceptor impurity atoms. We developed a fundamentally new type of pn junction not formed by impurity-doping, but rather by grading the composition of a semiconductor nanowire resulting in alternating p and n conducting regions due to polarization charge. By linearly grading AlGaN nanowires from 0% to 100% and back to 0% Al, we show the formation of a polarization-induced pn junction even in the absence of any impurity doping. Since electrons and holes are injected from AlN barriers into quantum disk active regions, graded nanowires allow deep ultraviolet LEDs across the AlGaN band-gap range with electroluminescence observed from 3.4 to 5 eV. Polarization-induced p-type conductivity in nanowires is shown to be possible even without supplemental acceptor doping, demonstrating the advantage of polarization engineering in nanowires compared with planar films and providing a strategy for improving conductivity in wide-band-gap semiconductors. As polarization charge is uniform within each unit cell, polarization-induced conductivity without impurity doping provides a solution to the problem of conductivity uniformity in nanowires and nanoelectronics and opens a new field of polarization engineering in nanostructures that may be applied to other polar semiconductors. © 2012 American Chemical Society

  12. Semiconductor nanowires and templates for electronic applications

    Energy Technology Data Exchange (ETDEWEB)

    Ying, Xiang

    2009-07-15

    catalyzed germanium nanowires, a small process window has been determined where high aspect-ratio nanowires show single crystalline structure. Compositional analysis has been performed via electron energy loss spectroscopy (EELS) to monitor the presence of indium and bismuth in the nanowires. Both catalysts could be identified, validating their role as catalysts. A combined atomic force microscopy (AFM) and Raman spectroscopy characterization on single core-shell nanowires gives clear evidence of finite-size effects on the electron-phonon coupling, as well as the presence of strain. Field effect transistors were fabricated using gold, bismuth and indium catalyzed germanium nanowires. Initial room-temperature and temperature dependent transport measurements on gold and bismuth catalyzed nanowires show field effects. Indium catalyzed germanium nanowires show insulating behavior. (orig.)

  13. Germanium nanowires grown using different catalyst metals

    Energy Technology Data Exchange (ETDEWEB)

    Gouveia, R.C., E-mail: riama@ifsp.edu.br [Departamento de Física – NanO Lab, Universidade Federal de São Carlos, Rod. Washington Luís, Km 235 – SP 310, São Carlos, CEP 13565-905 (Brazil); Área de Ciências, Instituto Federal de Educação Ciência e Tecnologia de São Paulo, Rua Américo Ambrósio, 269, Jd. Canaã, Sertãozinho, CEP 14169-263 (Brazil); Kamimura, H.; Munhoz, R.; Rodrigues, A.D. [Departamento de Física – NanO Lab, Universidade Federal de São Carlos, Rod. Washington Luís, Km 235 – SP 310, São Carlos, CEP 13565-905 (Brazil); Leite, E.R. [Departamento de Química – LIEC, Universidade Federal de São Carlos, São Carlos, CEP 13565-905 (Brazil); Chiquito, A.J. [Departamento de Física – NanO Lab, Universidade Federal de São Carlos, Rod. Washington Luís, Km 235 – SP 310, São Carlos, CEP 13565-905 (Brazil)

    2016-11-01

    Germanium nanowires have been synthesized by the well known vapor-liquid-solid growth mechanism using gold, silver, cooper, indium and nickel as catalyst metals. The influence of metal seeds on nanowires structural and electronic transport properties was also investigated. Electron microscopy images demonstrated that, despite differences in diameters, all nanowires obtained presented single crystalline structures. X-ray patterns showed that all nanowires were composed by germanium with a small amount of germanium oxide, and the catalyst metal was restricted at the nanowires' tips. Raman spectroscopy evidenced the long range order in the crystalline structure of each sample. Electrical measurements indicated that variable range hopping was the dominant mechanism in carrier transport for all devices, with similar hopping distance, regardless the material used as catalyst. Then, in spite of the differences in synthesis temperatures and nanowires diameters, the catalyst metals have not affected the composition and crystalline quality of the germanium nanowires nor the carrier transport in the germanium nanowire network devices. - Highlights: • Ge nanowires were grown by VLS method using Au, Ag, Cu, In and Ni as catalysts. • All nanowires presented high single crystalline quality and long range order. • Devices showed semiconducting behavior having VRH as dominant transport mechanism. • The metal catalyst did not influence structural properties or the transport mechanism.

  14. Nanowire Lasers

    Directory of Open Access Journals (Sweden)

    Couteau C.

    2015-05-01

    Full Text Available We review principles and trends in the use of semiconductor nanowires as gain media for stimulated emission and lasing. Semiconductor nanowires have recently been widely studied for use in integrated optoelectronic devices, such as light-emitting diodes (LEDs, solar cells, and transistors. Intensive research has also been conducted in the use of nanowires for subwavelength laser systems that take advantage of their quasione- dimensional (1D nature, flexibility in material choice and combination, and intrinsic optoelectronic properties. First, we provide an overview on using quasi-1D nanowire systems to realize subwavelength lasers with efficient, directional, and low-threshold emission. We then describe the state of the art for nanowire lasers in terms of materials, geometry, andwavelength tunability.Next,we present the basics of lasing in semiconductor nanowires, define the key parameters for stimulated emission, and introduce the properties of nanowires. We then review advanced nanowire laser designs from the literature. Finally, we present interesting perspectives for low-threshold nanoscale light sources and optical interconnects. We intend to illustrate the potential of nanolasers inmany applications, such as nanophotonic devices that integrate electronics and photonics for next-generation optoelectronic devices. For instance, these building blocks for nanoscale photonics can be used for data storage and biomedical applications when coupled to on-chip characterization tools. These nanoscale monochromatic laser light sources promise breakthroughs in nanophotonics, as they can operate at room temperature, can potentially be electrically driven, and can yield a better understanding of intrinsic nanomaterial properties and surface-state effects in lowdimensional semiconductor systems.

  15. Mapping the local structure of nanowires

    DEFF Research Database (Denmark)

    Persson, Johan Mikael; Wagner, Jakob Birkedal

    2013-01-01

    The crystallographic and compositional structure of heterostructured semiconductor nanowires has been studied by means of transmission electron microscopy. The native geometry of the studied InP-GaAs nanowires (80-100 nm in diameter) is in general too thick for reliable high-resolution TEM imaging...

  16. Shape Evolution of Highly Lattice-Mismatched InN/InGaN Nanowire Heterostructures

    Science.gov (United States)

    Yan, Lifan; Hazari, Arnab; Bhattacharya, Pallab; Millunchick, Joanna M.

    2018-02-01

    We have investigated the structure and shape of GaN-based nanowires grown on (001) Si substrates for optoelectronic device applications. The nanowire heterostructures contained InN disks and In0.4Ga0.6N barrier layers in the active region. The resulting nanowire array comprised two differently shaped nanowires: shorter pencil-like nanowires and longer bead-like nanowires. The two different nanowire shapes evolve due to a variation in the In incorporation rate, which was faster for the bead-like nanowires. Both types of nanowires exhibited evidence of significant migration of both Ga and In during growth. Ga tended to diffuse away and down along the sidewalls, resulting in a Ga-rich shell for all nanowires. Despite the complex structure and great variability in the In composition, the optical properties of the nanowire arrays were very good, with strong luminescence peaking at ˜ 1.63 μm.

  17. Semiconductor nanowires: Controlled growth and thermal properties

    Science.gov (United States)

    Wu, Yiying

    This dissertation presents an experimental study of the controlled growth of semiconductor nanowires and their thermophysical properties. The synthesis of nanowires was based on the well-known Vapor-Liquid-Solid (VLS) mechanism in which the growth of nanowire is initiated by a nanosized liquid droplet. The prepared nanowires are single-crystalline with certain preferred growth direction. Nanowires with different compositions have been synthesized, including Si, Ge, boron and MgB2. The control of nanowire composition, diameter and orientation has also been achieved. In addition, a Pulsed Laser Ablation-Chemical Vapor Deposition (PLA-CVD) hybrid process was developed to synthesize Si/SiGe longitudinally superlattice nanowires. The thermal conductivity of individual pure Si nanowire and Si/SiGe nanowire was measured using a microfabricated suspended device over a temperature range of 20--320 K. The thermal conductivities of individual 22, 37, 56, and 115 nm diameter single crystalline intrinsic Si nanowires were much lower than the bulk value due to the strong phonon boundary scattering. Except for the 22 nm diameter nanowire, theoretical predictions using a modified Callaway model fit the experimental data very well. The data for the 22 nm diameter wire suggest that changes in phonon dispersion due to confinement can cause additional thermal conductivity reduction. The Si/SiGe superlattice nanowires with diameters of 83 run and 58 nm were also measured. Their thermal conductivities are smaller than pure Si nanowire with similar diameter, as well as Si/SiGe superlattice thin film with comparable period. Both the alloying scattering and the boundary scattering are believed to contribute to this reduction. Size dependent melting-recrystallization study of the carbon-sheathed semiconductor Ge nanowires was carried out in in-situ high temperature transmission electron microscope (TEM). Significant depression in melting temperature with decreasing size of the nanowires as

  18. Resistance Fluctuations in GaAs Nanowire Grids

    Directory of Open Access Journals (Sweden)

    Ivan Marasović

    2014-01-01

    Full Text Available We present a numerical study on resistance fluctuations in a series of nanowire-based grids. Each grid is made of GaAs nanowires arranged in parallel with metallic contacts crossing all nanowires perpendicularly. Electrical properties of GaAs nanowires known from previous experimental research are used as input parameters in the simulation procedure. Due to the nonhomogeneous doping, the resistivity changes along nanowire. Allowing two possible nanowire orientations (“upwards” or “downwards”, the resulting grid is partially disordered in vertical direction which causes resistance fluctuations. The system is modeled using a two-dimensional random resistor network. Transfer-matrix computation algorithm is used to calculate the total network resistance. It is found that probability density function (PDF of resistance fluctuations for a series of nanowire grids changes from Gaussian behavior towards the Bramwell-Holdsworth-Pinton distribution when both nanowire orientations are equally represented in the grid.

  19. CoFeCu electroplated nanowire arrays: Role of composition and annealing on structure and magnetic properties

    OpenAIRE

    Bran, Cristina; Palmero, Ester M.; Real, Rafael P. del; Vázquez Villalabeitia, Manuel

    2014-01-01

    CoxFe100-x and CoxFe95-xCu 5, with 30 < x < 90, arrays of nanowire, around 20 nm in diameter and about 5 μm long, have been prepared by electrodeposition filling the self-assembled nanopores of anodic alumina templates. These samples were later thermally annealed for 2 h in the range of temperatures up to 600 °C. Crystalline anisotropy was confirmed to exhibit bcc cubic structure with [110] texture in as-prepared state. First structural changes are observed after annealing at 450 °C when a re...

  20. Multifunctional Nanowire/film Composites based Bi-modular Sensors for In-situ and Real-time High Temperature Gas Detection

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Pu-Xian; Lei, Yu

    2013-06-01

    This final report to the Department of Energy/National Energy Technology Laboratory for DE-FE0000870 covers the period from 2009 to June, 2013 and summarizes the main research accomplishments, which can be divided in sensing materials innovation, bimodular sensor demonstration, and new understanding and discoveries. As a matter of fact, we have successfully completed all the project tasks in June 1, 2013, and presented the final project review presentation on the 9th of July, 2013. Specifically, the major accomplishments achieved in this project include: 1) Successful development of a new class of high temperature stable gas sensor nanomaterials based on composite nano-array strategy in a 3D or 2D fashion using metal oxides and perovskite nanostructures. 2) Successful demonstration of bimodular nanosensors using 2D nanofibrous film and 3D composite nanowire arrays using electrical resistance mode and electrochemical electromotive force mode. 3) Series of new discoveries and understandings based on the new composite nanostructure platform toward enhancing nanosensor performance in terms of stability, selectivity, sensitivity and mass flux sensing. In this report, we highlight some results toward these accomplishments.

  1. Preparation and Characterization of Tin Oxide Nanowires

    Directory of Open Access Journals (Sweden)

    A. Kabiri

    2013-12-01

    Full Text Available The aim of this research is preparation of SnO2 nanowires by means of Thermal chemical reaction vapor transport deposition (TCRVTD method from SnO powders. The morphology, chemical composition and microstructure properties of the nanowires are characterized using field emission scanning electron microscope (FE-SEM, EDS, and XRD. The XRD diffraction patterns reveal that the SnO2 nanowires have been grown in the form of tetragonal crystal structures with the lattice parameter of a=b=0.440 nm, and c=0.370 nm. The SEM images reveal that SnO2 nanowires have successfully been grown on the Si substrate. The EDS patterns show that only elements of Sn, O and Au are detected. Prior to the VLS process the substrate is coated by a thin layer of Au. The diameter of nanowires is measured to be something between 20-100 nm.

  2. Modulation of surface trap induced resistive switching by electrode annealing in individual PbS micro/nanowire-based devices for resistance random access memory.

    Science.gov (United States)

    Zheng, Jianping; Cheng, Baochang; Wu, Fuzhang; Su, Xiaohui; Xiao, Yanhe; Guo, Rui; Lei, Shuijin

    2014-12-10

    Bipolar resistive switching (RS) devices are commonly believed as a promising candidate for next generation nonvolatile resistance random access memory (RRAM). Here, two-terminal devices based on individual PbS micro/nanowires with Ag electrodes are constructed, whose electrical transport depends strongly on the abundant surface and bulk trap states in micro/nanostructures. The surface trap states can be filled/emptied effectively at negative/positive bias voltage, respectively, and the corresponding rise/fall of the Fermi level induces a variation in a degenerate/nondegenerate state, resulting in low/high resistance. Moreover, the filling/emptying of trap states can be utilized as RRAM. After annealing, the surface trap state can almost be eliminated completely; while most of the bulk trap states can still remain. In the devices unannealed and annealed at both ends, therefore, the symmetrical back-to-back Fowler-Nordheim tunneling with large ON/OFF resistance ratio and Poole-Frenkel emission with poor hysteresis can be observed under cyclic sweep voltage, respectively. However, a typical bipolar RS behavior can be observed effectively in the devices annealed at one end. The acquirement of bipolar RS and nonvolatile RRAM by the modulation of electrode annealing demonstrates the abundant trap states in micro/nanomaterials will be advantageous to the development of new type electronic components.

  3. Synthesis of nanostructures in nanowires using sequential catalyst reactions

    Science.gov (United States)

    Panciera, F.; Chou, Y.-C.; Reuter, M.C.; Zakharov, D.; Stach, E.A.; Hofmann, S.; Ross, F.M.

    2016-01-01

    Nanowire growth by the vapor-liquid-solid process enables a high level of control over nanowire composition, diameter, growth direction, branching and kinking, periodic twinning, and crystal structure. The tremendous impact of VLS-grown nanowires is due to this structural versatility, generating applications ranging from solid state lighting and single photon sources to thermoelectric devices. Here we show that the morphology of these nanostructures can be further tailored by using the liquid droplets that catalyze nanowire growth as a “mixing bowl”, in which growth materials are sequentially supplied to nucleate new phases. Growing within the liquid, these phases adopt the shape of faceted nanocrystals that are then incorporated into the nanowires by further growth. We demonstrate this concept by epitaxially incorporating metal silicide nanocrystals into Si nanowires with defect-free interfaces, and discuss how this process can be generalized to create complex nanowire-based heterostructures. PMID:26168344

  4. Mechanical Behavior of Homogeneous and Composite Random Fiber Networks

    Science.gov (United States)

    Shahsavari, Ali

    systems with large multiscale heterogeneity, which controls their mechanical behavior. This pronounced heterogeneity leads to a pronounced size and boundary condition effects on their mechanical behavior. To emphasize the source of the size effect, the network heterogeneity is characterized by analyzing the geometry of the network (density distribution), the strain field and the strain energy distribution. It is shown that the heterogeneity of the mechanical fields depends not only on the network topology, but also on the ratio between the bending and axial stiffness of fibers. In this study, the size effect is quantified and the minimum model size needed to eliminate the size effect for a given set of system parameters, is determined. The results are also used for the selection of the size of representative volume elements useful for multiscale models of fiber networks such as the sequential approach. The elastic response of composite random fiber networks in which two types of fibers are used, is studied. This analysis is performed by adding stiff fibers to a relatively softer base while considering two cases: cross-linked and non-cross-linked added fibers. The linear elastic modulus of the network is determined in terms of the system parameters, including the density of added fibers. The results are compared to the case of adding stiff fibers to a homogeneous continuum base. It is shown that there is a threshold of added fiber density, above which the axial stiffens of the base filaments controls the mechanics. In this regime, the elastic response of the composites that have network bases mimics the behavior of those with continuum bases. The results presented in this thesis are relevant for many biological and engineering fibrous materials, including connective tissue, the cellular cytoskeleton, special clothing, consumer products, filters, and dampers. It is shown that the overall behavior of the material is very sensitive to several system parameters (power law

  5. Ni/Mo2C nanowires and their carbon-coated composites as efficient catalysts for nitroarenes hydrogenation

    Science.gov (United States)

    Shu, Yijin; He, Sina; Xie, Lifang; Chan, Hang Cheong; Yu, Xiang; Yang, Lichun; Gao, Qingsheng

    2017-02-01

    The hydrogenation of nitroarenes to value-added aromatic amines requires active and selective catalysts. Due to the good efficiency, economic cost and high earth-abundance, Ni-based nanostructures emerge as the promising catalysts, which are however limited by the poor dispersion and unsatisfied durability. Herein, Mo2C nanowires was introduced as a versatile support towards the highly dispersive Ni owing to the strong metal-support interactions on carbide surface, accomplishing the high activity in the hydrogenation of 3-nitrobenzoic acid, 4-nitrobenzoic acid and nitrobenzene. However, the presence of water that promoted the selective hydrogenation unfortunately deactivated Ni species. An effective carbon coating was further introduced to remarkably enhance the stability, protecting active Ni from corrosive H+ and H2O. This work elucidates a feasible way towards efficient and stable catalysts by the introduction of both carbide supports and carbon coating, shedding some light on the development of high-performance catalysts.

  6. Superstable transparent conductive Cu@Cu4Ni nanowire elastomer composites against oxidation, bending, stretching, and twisting for flexible and stretchable optoelectronics.

    Science.gov (United States)

    Song, Jizhong; Li, Jianhai; Xu, Jiayue; Zeng, Haibo

    2014-11-12

    Low cost and high conductivity make copper (Cu) nanowire (NW) electrodes an attractive material to construct flexible and stretchable electronic skins, displays, organic light-emitting diodes (OLEDs), solar cells, and electrochromic windows. However, the vulnerabilities that Cu NW electrodes have to oxidation, bending, and stretching still present great challenges. This work demonstrates a new Cu@Cu4Ni NW conductive elastomer composite with ultrahigh stability for the first time. Cu@Cu4Ni NWs, facilely synthesized through a one-pot method, have highly crystalline alloyed shells, clear and abrupt interfaces, lengths more than 50 μm, and smooth surfaces. These virtues provide the NW-elastomer composites with a low resistance of 62.4 ohm/sq at 80% transparency, which is even better than the commercial ITO/PET flexible electrodes. In addition, the fluctuation amplitude of resistance is within 2 ohm/sq within 30 days, meaning that at ΔR/R0 = 1, the actual lifetime is estimated to be more than 1200 days. Neither the conductivity nor the performances of OLED with elastomers as conductive circuits show evident degradation during 600 cycles of bending, stretching, and twisting tests. These high-performance and extremely stable NW elastomeric electrodes could endow great chances for transparent, flexible, stretchable, and wearable electronic and optoelectronic devices.

  7. Extremely flexible, transparent, and strain-sensitive electroluminescent device based on ZnS:Cu-polyvinyl butyral composite and silver nanowires

    Science.gov (United States)

    Jun, Sungwoo; Kim, Youngmin; Ju, Byeong-Kwon; Kim, Jong-Woong

    2018-01-01

    A multifunctional alternate current electroluminescent device (ACEL) was achieved by compositing ZnS:Cu particles in polyvinyl butyral (PVB) with two layers of percolated silver nanowire (AgNW) electrodes. The strong hydrogen bonding interactions and entanglement of PVB chains considerably strengthened the PVB, and thus, the cured mixture of ZnS:Cu particles and freestanding PVB required no additional support. The device was fabricated by embedding AgNWs on both sides of the ZnS:Cu-PVB composite film using an inverted layer process and intense-pulsed-light treatment. The strong affinity of PVB to the polyvinyl pyrrolidone (PVP) layer, which capped the AgNWs, mechanically stabilized the device to such an extent that it could resist 10,000 bending cycles under a curvature radius of 500 μm. Using AgNW networks in both the top and bottom electrodes made a double-sided light-emitting device that could be applied to wearable lightings or flexible digital signage. The capacitance formed in the device sensitively varied with the applied bending and unfolding, thus demonstrating that the device can also be used as a deformation sensor.

  8. Plasmonic Properties of Vertically Aligned Nanowire Arrays

    Directory of Open Access Journals (Sweden)

    Hua Qi

    2012-01-01

    Full Text Available Nanowires (NWs/Ag sheath composites were produced to investigate plasmonic coupling between vertically aligned NWs for surface-enhanced Raman scattering (SERS applications. In this investigation, two types of vertical NW arrays were studied; those of ZnO NWs grown on nanosphere lithography patterned sapphire substrate via vapor-liquid-solid (VLS mechanism and Si NW arrays produced by wet chemical etching. Both types of vertical NW arrays were coated with a thin layer of silver by electroless silver plating for SERS enhancement studies. The experimental results show extremely strong SERS signals due to plasmonic coupling between the NWs, which was verified by COMSOL electric field simulations. We also compared the SERS enhancement intensity of aligned and random ZnO NWs, indicating that the aligned NWs show much stronger and repeatable SERS signal than those grown in nonaligned geometries.

  9. Metal-dielectric-CNT nanowires for surface-enhanced Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bond, Tiziana C.; Altun, Ali; Park, Hyung Gyu

    2017-10-03

    A sensor with a substrate includes nanowires extending vertically from the substrate, a hafnia coating on the nanowires that provides hafnia coated nanowires, and a noble metal coating on the hafnia coated nanowires. The top of the hafnia and noble metal coated nanowires bent onto one another to create a canopy forest structure. There are numerous randomly arranged holes that let through scattered light. The many points of contact, hot spots, amplify signals. The methods include the steps of providing a Raman spectroscopy substrate, introducing nano crystals to the Raman spectroscopy substrate, growing a forest of nanowires from the nano crystals on the Raman spectroscopy substrate, coating the nanowires with hafnia providing hafnia coated nanowires, and coating the hafnia coated nanowires with a noble metal or other metal.

  10. Step-flow kinetics in nanowire growth.

    Science.gov (United States)

    Wen, C-Y; Tersoff, J; Reuter, M C; Stach, E A; Ross, F M

    2010-11-05

    Nanowire growth occurs by step flow at the wire-catalyst interface, with strikingly different step-flow kinetics for solid versus liquid catalysts. Here we report quantitative in situ measurements of step flow together with a kinetic model that reproduces the behavior. This allows us to identify the key parameters controlling step-flow growth, evaluate changes in the catalyst composition during growth, and identify the most favorable conditions for growing abrupt heterojunctions in nanowires.

  11. Tunneling and Transport in Nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Goldman, Allen M. [Univ. of Minnesota, Minneapolis, MN (United States)

    2016-08-16

    The goal of this program was to study new physical phenomena that might be relevant to the performance of conductive devices and circuits of the smallest realizable feature sizes possible using physical rather than biological techniques. Although the initial scientific work supported involved the use of scanning tunneling microscopy and spectroscopy to ascertain the statistics of the energy level distribution of randomly sized and randomly shaped quantum dots, or nano-crystals, the main focus was on the investigation of selected properties, including superconductivity, of conducting and superconducting nanowires prepared using electron-beam-lithography. We discovered a magnetic-field-restoration of superconductivity in out-of-equilibrium nanowires driven resistive by current. This phenomenon was explained by the existence of a state in which dissipation coexisted with nonvanishing superconducting order. We also produced ultra-small superconducting loops to study a predicted anomalous fluxoid quantization, but instead, found a magnetic-field-dependent, high-resistance state, rather than superconductivity. Finally, we developed a simple and controllable nanowire in an induced charged layer near the surface of a masked single-crystal insulator, SrTiO3. The layer was induced using an electric double layer transistor employing an ionic liquid (IL). The transport properties of the induced nanowire resembled those of collective electronic transport through an array of quantum dots.

  12. Magnetic-composite-modified polycrystalline silicon nanowire field-effect transistor for vascular endothelial growth factor detection and cancer diagnosis.

    Science.gov (United States)

    Chen, Hsiao-Chien; Qiu, Jian-Tai; Yang, Fu-Liang; Liu, Yin-Chih; Chen, Min-Cheng; Tsai, Rung-Ywan; Yang, Hung-Wei; Lin, Chia-Yi; Lin, Chu-Chi; Wu, Tzong-Shoon; Tu, Yi-Ming; Xiao, Min-Cong; Ho, Chia-Hua; Huang, Chien-Chao; Lai, Chao-Sung; Hua, Mu-Yi

    2014-10-07

    This study proposes a vascular endothelial growth factor (VEGF) biosensor for diagnosing various stages of cervical carcinoma. In addition, VEGF concentrations at various stages of cancer therapy are determined and compared to data obtained by computed tomography (CT) and cancer antigen 125 (CA-125). The increase in VEGF concentrations during operations offers useful insight into dosage timing during cancer therapy. This biosensor uses Avastin as the biorecognition element for the potential cancer biomarker VEGF and is based on a n-type polycrystalline silicon nanowire field-effect transistor (poly-SiNW-FET). Magnetic nanoparticles with poly[aniline-co-N-(1-one-butyric acid) aniline]-Fe3O4 (SPAnH-Fe3O4) shell-core structures are used as carriers for Avastin loading and provide rapid purification due to their magnetic properties, which prevent the loss of bioactivity; furthermore, the high surface area of these structures increases the quantity of Avastin immobilized. Average concentrations in human blood for species that interfere with detection specificity are also evaluated. The detection range of the biosensor for serum samples covers the results expected from both healthy individuals and cancer patients.

  13. Composite Transparent Electrode of Graphene Nanowalls and Silver Nanowires on Micropyramidal Si for High-Efficiency Schottky Junction Solar Cells.

    Science.gov (United States)

    Jiao, Tianpeng; Liu, Jian; Wei, Dapeng; Feng, Yanhui; Song, Xuefen; Shi, Haofei; Jia, Shuming; Sun, Wentao; Du, Chunlei

    2015-09-16

    The conventional graphene-silicon Schottky junction solar cell inevitably involves the graphene growth and transfer process, which results in complicated technology, loss of quality of the graphene, extra cost, and environmental unfriendliness. Moreover, the conventional transfer method is not well suited to conformationally coat graphene on a three-dimensional (3D) silicon surface. Thus, worse interfacial conditions are inevitable. In this work, we directly grow graphene nanowalls (GNWs) onto the micropyramidal silicon (MP) by the plasma-enhanced chemical vapor deposition method. By controlling growth time, the cell exhibits optimal pristine photovoltaic performance of 3.8%. Furthermore, we improve the conductivity of the GNW electrode by introducing the silver nanowire (AgNW) network, which could achieve lower sheet resistance. An efficiency of 6.6% has been obtained for the AgNWs-GNWs-MP solar cell without any chemical doping. Meanwhile, the cell exhibits excellent stability exposed to air. Our studies show a promising way to develop simple-technology, low-cost, high-efficiency, and stable Schottky junction solar cells.

  14. Composite of macroporous carbon with honeycomb-like structure from mollusc shell and NiCo(2)O(4) nanowires for high-performance supercapacitor.

    Science.gov (United States)

    Xiong, Wei; Gao, Yongsheng; Wu, Xu; Hu, Xuan; Lan, Danni; Chen, Yangyang; Pu, Xuli; Zeng, Yan; Su, Jun; Zhu, Zhihong

    2014-01-01

    Novel biological carbon materials with highly ordered microstructure and large pore volume have caused great interest due to their multifunctional properties. Herein, we report the preparation of an interconnected porous carbon material by carbonizing the organic matrix of mollusc shell. The obtained three-dimensional carbon skeleton consists of hexangular and tightly arranged channels, which endow it with efficient electrolyte penetration and fast electron transfer, enable the mollusc shell based macroporous carbon material (MSBPC) to be an excellent conductive scaffold for supercapacitor electrodes. By growing NiCo2O4 nanowires on the obtained MSBPC, NiCo2O4/MSBPC composites were synthesized. When used on supercapacitor electrode, it exhibited anomalously high specific capacitance (∼1696 F/g), excellent rate performance (with the capacity retention of 58.6% at 15 A/g) and outstanding cycling stability (88% retention after 2000 cycles). Furthermore, an all-solid-state symmetric supercapacitor was also assembled based on this NiCo2O4/MSBPC electrode and showed good electrochemical performance with an energy density of 8.47 Wh/kg at 1 A/g, good stability over 10000 cycles. And we believe that more potential applications beyond energy storage can be developed based on this MSBPC.

  15. Nanowire Optoelectronics

    Directory of Open Access Journals (Sweden)

    Wang Zhihuan

    2015-12-01

    Full Text Available Semiconductor nanowires have been used in a variety of passive and active optoelectronic devices including waveguides, photodetectors, solar cells, light-emitting diodes (LEDs, lasers, sensors, and optical antennas. We review the optical properties of these nanowires in terms of absorption, guiding, and radiation of light, which may be termed light management. Analysis of the interaction of light with long cylindrical/hexagonal structures with subwavelength diameters identifies radial resonant modes, such as Leaky Mode Resonances, or Whispering Gallery modes. The two-dimensional treatment should incorporate axial variations in “volumetric modes,”which have so far been presented in terms of Fabry–Perot (FP, and helical resonance modes. We report on finite-difference timedomain (FDTD simulations with the aim of identifying the dependence of these modes on geometry (length, width, tapering, shape (cylindrical, hexagonal, core–shell versus core-only, and dielectric cores with semiconductor shells. This demonstrates how nanowires (NWs form excellent optical cavities without the need for top and bottommirrors. However, optically equivalent structures such as hexagonal and cylindrical wires can have very different optoelectronic properties meaning that light management alone does not sufficiently describe the observed enhancement in upward (absorption and downward transitions (emission of light inNWs; rather, the electronic transition rates should be considered. We discuss this “rate management” scheme showing its strong dimensional dependence, making a case for photonic integrated circuits (PICs that can take advantage of the confluence of the desirable optical and electronic properties of these nanostructures.

  16. Nanotubes, nanorods and nanowires having piezoelectric and/or pyroelectric properties and devices manufactured therefrom

    Science.gov (United States)

    Russell, Thomas P [Amherst, MA; Lutkenhaus, Jodie [Wethersfield, CT

    2012-05-15

    Disclosed herein is a device comprising a pair of electrodes; and a nanotube, a nanorod and/or a nanowire; the nanotube, nanorod and/or nanowire comprising a piezoelectric and/or pyroelectric polymeric composition; the pair of electrodes being in electrical communication with opposing surfaces of the nanotube, nanorod and/or a nanowire; the pair of electrodes being perpendicular to a longitudinal axis of the nanotube, nanorod and/or a nanowire.

  17. Arrays of indefinitely long uniform nanowires and nanotubes

    Science.gov (United States)

    Yaman, Mecit; Khudiyev, Tural; Ozgur, Erol; Kanik, Mehmet; Aktas, Ozan; Ozgur, Ekin O.; Deniz, Hakan; Korkut, Enes; Bayindir, Mehmet

    2011-07-01

    Nanowires are arguably the most studied nanomaterial model to make functional devices and arrays. Although there is remarkable maturity in the chemical synthesis of complex nanowire structures, their integration and interfacing to macro systems with high yields and repeatability still require elaborate aligning, positioning and interfacing and post-synthesis techniques. Top-down fabrication methods for nanowire production, such as lithography and electrospinning, have not enjoyed comparable growth. Here we report a new thermal size-reduction process to produce well-ordered, globally oriented, indefinitely long nanowire and nanotube arrays with different materials. The new technique involves iterative co-drawing of hermetically sealed multimaterials in compatible polymer matrices similar to fibre drawing. Globally oriented, endlessly parallel, axially and radially uniform semiconducting and piezoelectric nanowire and nanotube arrays hundreds of metres long, with nanowire diameters less than 15 nm, are obtained. The resulting nanostructures are sealed inside a flexible substrate, facilitating the handling of and electrical contacting to the nanowires. Inexpensive, high-throughput, multimaterial nanowire arrays pave the way for applications including nanowire-based large-area flexible sensor platforms, phase-changememory, nanostructure-enhanced photovoltaics, semiconductor nanophotonics, dielectric metamaterials,linear and nonlinear photonics and nanowire-enabled high-performance composites.

  18. Recommended Minimum Test Requirements and Test Methods for Assessing Durability of Random-Glass-Fiber Composites

    Energy Technology Data Exchange (ETDEWEB)

    Battiste, R.L.; Corum, J.M.; Ren, W.; Ruggles, M.B.

    1999-06-01

    This report provides recommended minimum test requirements are suggested test methods for establishing the durability properties and characteristics of candidate random-glass-fiber polymeric composites for automotive structural applications. The recommendations and suggestions are based on experience and results developed at Oak Ridge National Laboratory (ORNL) under a US Department of Energy Advanced Automotive Materials project entitled ''Durability of Lightweight Composite Structures,'' which is closely coordinated with the Automotive Composites Consortium. The report is intended as an aid to suppliers offering new structural composites for automotive applications and to testing organizations that are called on to characterize the composites.

  19. Electrochemical synthesis of CORE-shell magnetic nanowires

    KAUST Repository

    Ovejero, Jesús G.

    2015-04-16

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

  20. Spray-assisted alignment of Layer-by-Layer assembled silver nanowires: a general approach for the preparation of highly anisotropic nano-composite films.

    Science.gov (United States)

    Hu, H; Pauly, M; Felix, O; Decher, G

    2017-01-19

    The present article focuses on the build-up and the properties of oriented silver nanowire monolayer films and Layer-by-Layer assembled multilayer films. We describe the template-free oriented spray-assisted assembly of silver nanowires at solid/air-interfaces using Grazing Incidence Spraying, a simple and versatile approach that allows the formation of highly oriented thin films with a tunable density and in-plane orientation. Depending on the spraying conditions the nematic order parameter, which describes the angular spread of misaligned nanowires, can be as high as 0.98 (a value of 1.00 corresponding to a perfectly parallel alignment). The combination with the Layer-by-Layer assembly allows building multilayer thin films possessing in-plane anisotropy. In order to demonstrate that the local alignment does not cancel out on the macroscopic scale but leads to direction-dependent properties, we use linearly polarized UV-Vis-NIR spectroscopy to probe the selective excitation of the transverse and longitudinal localized plasmon resonances of the nanowires. The polarization efficiency of the thin films increases strongly with the in-plane density, the degree of orientation, and the number of silver nanowire layers. Multilayer films containing 4 layers of nanowires oriented in the same direction reach a polarization efficiency of up to 97% in the near-infrared region.

  1. Vertical nanowire architectures

    DEFF Research Database (Denmark)

    Vlad, A.; Mátéfl-Tempfli, M.; Piraux, L.

    2010-01-01

    Nanowires and statistics: A statistical process for reading ultradense arrays of nanostructured materials is presented (see image). The experimental realization is achieved through selective nanowire growth using porous alumina templates. The statistical patterning approach is found to provide ri...

  2. Nanowire-based detector

    Science.gov (United States)

    Berggren, Karl K; Hu, Xiaolong; Masciarelli, Daniele

    2014-06-24

    Systems, articles, and methods are provided related to nanowire-based detectors, which can be used for light detection in, for example, single-photon detectors. In one aspect, a variety of detectors are provided, for example one including an electrically superconductive nanowire or nanowires constructed and arranged to interact with photons to produce a detectable signal. In another aspect, fabrication methods are provided, including techniques to precisely reproduce patterns in subsequently formed layers of material using a relatively small number of fabrication steps. By precisely reproducing patterns in multiple material layers, one can form electrically insulating materials and electrically conductive materials in shapes such that incoming photons are redirected toward a nearby electrically superconductive materials (e.g., electrically superconductive nanowire(s)). For example, one or more resonance structures (e.g., comprising an electrically insulating material), which can trap electromagnetic radiation within its boundaries, can be positioned proximate the nanowire(s). The resonance structure can include, at its boundaries, electrically conductive material positioned proximate the electrically superconductive nanowire such that light that would otherwise be transmitted through the sensor is redirected toward the nanowire(s) and detected. In addition, electrically conductive material can be positioned proximate the electrically superconductive nanowire (e.g. at the aperture of the resonant structure), such that light is directed by scattering from this structure into the nanowire.

  3. Methods of fabricating nanostructures and nanowires and devices fabricated therefrom

    Science.gov (United States)

    Majumdar,; Arun, [Orinda, CA; Shakouri, Ali [Santa Cruz, CA; Sands, Timothy D [Moraga, CA; Yang, Peidong [Berkeley, CA; Mao, Samuel S [Berkeley, CA; Russo, Richard E [Walnut Creek, CA; Feick, Henning [Kensington, CA; Weber, Eicke R [Oakland, CA; Kind, Hannes [Schaffhausen, CH; Huang, Michael [Los Angeles, CA; Yan, Haoquan [Albany, CA; Wu, Yiying [Albany, CA; Fan, Rong [El Cerrito, CA

    2009-08-04

    One-dimensional nanostructures having uniform diameters of less than approximately 200 nm. These inventive nanostructures, which we refer to as "nanowires", include single-crystalline homostructures as well as heterostructures of at least two single-crystalline materials having different chemical compositions. Because single-crystalline materials are used to form the heterostructure, the resultant heterostructure will be single-crystalline as well. The nanowire heterostructures are generally based on a semiconducting wire wherein the doping and composition are controlled in either the longitudinal or radial directions, or in both directions, to yield a wire that comprises different materials. Examples of resulting nanowire heterostructures include a longitudinal heterostructure nanowire (LOHN) and a coaxial heterostructure nanowire (COHN).

  4. Methods of fabricating nanostructures and nanowires and devices fabricated therefrom

    Energy Technology Data Exchange (ETDEWEB)

    Majumdar, Arun; Shakouri, Ali; Sands, Timothy D.; Yang, Peidong; Mao, Samuel S.; Russo, Richard E.; Feick, Henning; Weber, Eicke R.; Kind, Hannes; Huang, Michael; Yan, Haoquan; Wu, Yiying; Fan, Rong

    2018-01-30

    One-dimensional nanostructures having uniform diameters of less than approximately 200 nm. These inventive nanostructures, which we refer to as "nanowires", include single-crystalline homostructures as well as heterostructures of at least two single-crystalline materials having different chemical compositions. Because single-crystalline materials are used to form the heterostructure, the resultant heterostructure will be single-crystalline as well. The nanowire heterostructures are generally based on a semiconducting wire wherein the doping and composition are controlled in either the longitudinal or radial directions, or in both directions, to yield a wire that comprises different materials. Examples of resulting nanowire heterostructures include a longitudinal heterostructure nanowire (LOHN) and a coaxial heterostructure nanowire (COHN).

  5. Stable and metastable nanowires displaying locally controllable properties

    Science.gov (United States)

    Sutter, Eli Anguelova; Sutter, Peter Werner

    2014-11-18

    Vapor-liquid-solid growth of nanowires is tailored to achieve complex one-dimensional material geometries using phase diagrams determined for nanoscale materials. Segmented one-dimensional nanowires having constant composition display locally variable electronic band structures that are determined by the diameter of the nanowires. The unique electrical and optical properties of the segmented nanowires are exploited to form electronic and optoelectronic devices. Using gold-germanium as a model system, in situ transmission electron microscopy establishes, for nanometer-sized Au--Ge alloy drops at the tips of Ge nanowires (NWs), the parts of the phase diagram that determine their temperature-dependent equilibrium composition. The nanoscale phase diagram is then used to determine the exchange of material between the NW and the drop. The phase diagram for the nanoscale drop deviates significantly from that of the bulk alloy.

  6. Stability of Organic Nanowires

    DEFF Research Database (Denmark)

    Balzer, F.; Schiek, M.; Wallmann, I.

    2011-01-01

    The morphological stability of organic nanowires over time and under thermal load is of major importance for their use in any device. In this study the growth and stability of organic nanowires from a naphthyl end-capped thiophene grown by organic molecular beam deposition is investigated via...... atomic force microscopy (AFM). Aging experiments under ambient conditions already show substantial morphological changes. Nanoscopic organic clusters, which initially coexist with the nanowires, vanish within hours. Thermal annealing of nanowire samples leads to even more pronounced morphology changes......, such as a strong decrease in nanowire number density, a strong increase in nanowire height, and the formation of new types of crystallites. This happens even before sublimation of organic material starts. These experiments also shine new light on the formation process of the nanowires....

  7. Growth and characterization of bismuth telluride nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Picht, Oliver

    2010-05-26

    Polycrystalline Bi{sub 2}Te{sub 3} nanowires are electrochemically grown in ion track-etched polycarbonate membranes. Potentiostatic growth is demonstrated in templates of various thicknesses ranging from 10 to 100 {mu}m. The smallest observed nanowire diameters are 20 nm in thin membranes and approx. 140-180 nm in thicker membranes. The influence of the various deposition parameters on the nanowire growth rate is presented. Slower growth rates are attained by selective change of deposition potentials and lower temperatures. Nanowires synthesized at slower growth rates have shown to possess a higher degree of crystalline order and smoother surface contours. With respect to structural properties, X-ray diffraction and transmission electron microscopy verified the growth of Bi{sub 2}Te{sub 3} and evidenced the stability of specific properties, e.g. grain size or preferential orientation, with regard to variations in the deposition conditions. The interdependency of the fabrication parameters, i.e. temperature, deposition potential and nanochannel diameters, is demonstrated for wires grown in 30 {mu}m thick membranes. It is visible from diffraction analysis that texture is tunable by the growth conditions but depends also on the size of the nanochannels in the template. Both (015) and (110) reflexes are observed for the nanowire arrays. Energy dispersive X-ray analysis further points out that variation of nanochannel size could lead to a change in elemental composition of the nanowires. (orig.)

  8. Posterior bulk-filled resin composite restorations. A 5-year randomized controlled clinical study

    DEFF Research Database (Denmark)

    van Dijken, Jan WV; Pallesen, Ulla

    2016-01-01

    Objective: To evaluate in a randomized controlled study the 5-year clinical durability of a flowable resin composite bulk-fill technique in Class I and Class II restorations. Material and methods: 38 pairs Class I and 62 pairs Class II restorations were placed in 44 male and 42 female (mean age 52.......4 years). Each patient received at least two, as similar as possible, extended Class I or Class II restorations. In all cavities, a 1-step self-etch adhesive (Xeno V+) was applied. Randomized, one of the cavities of each pair received the flowable bulk-filled resin composite (SDR), in increments up to 4...... mm as needed to fill the cavity 2 mm short of the occlusal cavosurface. The occlusal part was completed with the nano-hybrid resin composite (Ceram X mono+). In the other cavity, the resin composite-only (Ceram X mono+) was placed in 2 mm increments. The restorations were evaluated using slightly...

  9. Fatigue Damage Accumulation Under Quasi-Random Loading of Composite Airframe Elements

    Science.gov (United States)

    Strizhius, V.

    2016-09-01

    To perform engineering estimations of the fatigue life of quasi-randomly loaded layered composites, with geometric concentrators, representing the longitudinal elements of composite wing of a transport airplane, a special rule of fatigue damage accumulation is suggested. The main propositions of the method for calculating the fatigue life of these elements by using this rule are formulated. The examples of estimations presented show a good agreement between analytical results and experimental data. A number of important conclusions about the effect of different levels of cyclic loading and "GAG" cycles of different flight types of the quasi-random "TWIST" program on the total fatigue life are made.

  10. Misfit stresses in a composite core-shell nanowire with an eccentric parallelepipedal core subjected to one-dimensional cross dilatation eigenstrain

    Science.gov (United States)

    Krasnitckii, S. A.; Kolomoetc, D. R.; Smirnov, A. M.; Gutkin, M. Yu

    2017-05-01

    The boundary-value problem in the classical theory of elasticity for a core-shell nanowire with an eccentric parallelepipedal core of an arbitrary rectangular cross section is solved. The core is subjected to one-dimensional cross dilatation eigenstrain. The misfit stresses are given in a closed analytical form suitable for theoretical modeling of misfit accommodation in relevant heterostructures.

  11. Vertical group III-V nanowires on si, heterostructures, flexible arrays and fabrication

    Science.gov (United States)

    Wang, Deli; Soci, Cesare; Bao, Xinyu; Wei, Wei; Jing, Yi; Sun, Ke

    2015-01-13

    Embodiments of the invention provide a method for direct heteroepitaxial growth of vertical III-V semiconductor nanowires on a silicon substrate. The silicon substrate is etched to substantially completely remove native oxide. It is promptly placed in a reaction chamber. The substrate is heated and maintained at a growth temperature. Group III-V precursors are flowed for a growth time. Preferred embodiment vertical Group III-V nanowires on silicon have a core-shell structure, which provides a radial homojunction or heterojunction. A doped nanowire core is surrounded by a shell with complementary doping. Such can provide high optical absorption due to the long optical path in the axial direction of the vertical nanowires, while reducing considerably the distance over which carriers must diffuse before being collected in the radial direction. Alloy composition can also be varied. Radial and axial homojunctions and heterojunctions can be realized. Embodiments provide for flexible Group III-V nanowire structures. An array of Group III-V nanowire structures is embedded in polymer. A fabrication method forms the vertical nanowires on a substrate, e.g., a silicon substrate. Preferably, the nanowires are formed by the preferred methods for fabrication of Group III-V nanowires on silicon. Devices can be formed with core/shell and core/multi-shell nanowires and the devices are released from the substrate upon which the nanowires were formed to create a flexible structure that includes an array of vertical nanowires embedded in polymer.

  12. Study of the magnetization behavior of ferromagnetic nanowire array: Existence of growth defects revealed by micromagnetic simulations

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen Vien, G., E-mail: gilles.nguyen@univ-brest.fr [Laboratoire de Magnétisme de Bretagne, EA 4522, Université de Bretagne Occidentale, CS 93837, 29238 Brest-Cedex 3 (France); Rioual, S. [Laboratoire de Magnétisme de Bretagne, EA 4522, Université de Bretagne Occidentale, CS 93837, 29238 Brest-Cedex 3 (France); Gloaguen, F. [Chimie, Electrochimie Moléculaires et Chimie Analytique, UMR CNRS 6521, Université de Bretagne Occidentale, CS 93837, 29238 Brest-Cedex 3 (France); Rouvellou, B.; Lescop, B. [Laboratoire de Magnétisme de Bretagne, EA 4522, Université de Bretagne Occidentale, CS 93837, 29238 Brest-Cedex 3 (France)

    2016-03-01

    High aspect ratio nanowires were electrodeposited in nanoporous anodic alumina template by a potentiostatic method. The angular dependence of the coercive field and remanence magnetization extracted from magnetometry measurements are compared with micromagnetic simulations. Inclusion of magnetostatic interactions between Ni nanowires in simulations is required to explain some of the properties of the magnetization reversal. However, it is not sufficient to reproduce fully the angular dependence of the coercive field. Due to the polycrystalline nature of nanowires and thus to the presence of grain boundaries, defects are included in simulations. A good agreement between theory and experiment is then clearly highlighted, in particular in the nanowire easy axis direction. The achieved results allow a description of several experimental data published in the literature and consequently to get a better understanding of reversal mechanisms that operate in such nanowire arrays. A complementary study of composite nanowire array is successfully performed to prove the adequacy of the simulations method to describe the magnetic properties of nanowire array. - Highlights: • High axial squareness nanowire array are synthetized by a potentiostatic method. • Nanowires are modeled as non-ideal magnetic particles. • Segmentation of nanowire is required to describe the angular dependence of coercivity. • Respective role of magnetostatic coupling and nanowire segmentation in nanowire array are studied. • Micromagnetic simulations lead to quantitative agreement for well-defined composite nanowire array.

  13. Crown vs. composite for post-retained restorations: A randomized clinical trial

    NARCIS (Netherlands)

    Skupien, J.A.; Cenci, M.S.; Opdam, N.J.; Kreulen, C.M.; Huysmans, M.C.; Pereira-Cenci, T.

    2016-01-01

    OBJECTIVES: This randomized clinical trial compared the survival of composite resin restorations and metal-ceramic crowns on endodontically treated teeth that received a glass fiber post using 2 different cementation methods. METHODS: Forty-seven patients (age 42.5+/-11.5) with fifty-seven

  14. Advances in nanowire bioelectronics

    Science.gov (United States)

    Zhou, Wei; Dai, Xiaochuan; Lieber, Charles M.

    2017-01-01

    Semiconductor nanowires represent powerful building blocks for next generation bioelectronics given their attractive properties, including nanometer-scale footprint comparable to subcellular structures and bio-molecules, configurable in nonstandard device geometries readily interfaced with biological systems, high surface-to-volume ratios, fast signal responses, and minimum consumption of energy. In this review article, we summarize recent progress in the field of nanowire bioelectronics with a focus primarily on silicon nanowire field-effect transistor biosensors. First, the synthesis and assembly of semiconductor nanowires will be described, including the basics of nanowire FETs crucial to their configuration as biosensors. Second, we will introduce and review recent results in nanowire bioelectronics for biomedical applications ranging from label-free sensing of biomolecules, to extracellular and intracellular electrophysiological recording.

  15. Abrupt Schottky Junctions in Al/Ge Nanowire Heterostructures.

    Science.gov (United States)

    Kral, S; Zeiner, C; Stöger-Pollach, M; Bertagnolli, E; den Hertog, M I; Lopez-Haro, M; Robin, E; El Hajraoui, K; Lugstein, A

    2015-07-08

    In this Letter we report on the exploration of axial metal/semiconductor (Al/Ge) nanowire heterostructures with abrupt interfaces. The formation process is enabled by a thermal induced exchange reaction between the vapor-liquid-solid grown Ge nanowire and Al contact pads due to the substantially different diffusion behavior of Ge in Al and vice versa. Temperature-dependent I-V measurements revealed the metallic properties of the crystalline Al nanowire segments with a maximum current carrying capacity of about 0.8 MA/cm(2). Transmission electron microscopy (TEM) characterization has confirmed both the composition and crystalline nature of the pure Al nanowire segments. A very sharp interface between the ⟨111⟩ oriented Ge nanowire and the reacted Al part was observed with a Schottky barrier height of 361 meV. To demonstrate the potential of this approach, a monolithic Al/Ge/Al heterostructure was used to fabricate a novel impact ionization device.

  16. Core-shell magnetic nanowires fabrication and characterization

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-02-28

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

  17. Crown vs. composite for post-retained restorations: A randomized clinical trial.

    Science.gov (United States)

    Skupien, Jovito Adiel; Cenci, Maximiliano Sérgio; Opdam, Niek Johannes; Kreulen, C M; Huysmans, Marie-Charlotte; Pereira-Cenci, Tatiana

    2016-05-01

    This randomized clinical trial compared the survival of composite resin restorations and metal-ceramic crowns on endodontically treated teeth that received a glass fiber post using 2 different cementation methods. Forty-seven patients (age 42.5 ± 11.5) with fifty-seven endodontically treated teeth with extensive coronal damage but always with one intact surface were randomly allocated according to the type of coronal restoration: metal-ceramic crown or composite resin. In case of crown restoration, a core buildup was performed with microhybrid composite resin. The dentin bonding agent and composite resin used were the same for both direct and indirect restorations. Descriptive analysis was performed using FDI clinical criteria and survival of restorations/teeth analyzed using Kaplan-Meier statistics and log-rank tests. 57 restorations (30 composite resin and 27 crowns) were made in 47 patients. The recall rate was 100% and follow up time ranged between 1 and 5 years. One tooth was extracted 11 months post-restoration due to root fracture (composite group). Eight composite restorations and one crown had reparable failures, all due to secondary caries or restoration fracture. The overall annual failure rate (AFR) was 0.92% after 50 months for success of the restorations, with 1.83% for the composite group and 0.26% for the metal-ceramic crown group. The log-rank test showed no difference for survival according to the type of restoration (p=0.344). However, for success rates, metal-ceramic crowns demonstrated better performance (p=0.022). Indirect restorations provided higher acceptable clinical performance and lower need for re-intervention, but both types of restorations presented good survival rates. (NCT01461239). When endodontically treated teeth with at least one intact surface must be restored, composite resin restorations and metal-ceramic crows are acceptable alternatives to achieve good survival and success rates. Copyright © 2016 Elsevier Ltd. All rights

  18. Integration, gap formation, and sharpening of III-V heterostructure nanowires by selective etching

    DEFF Research Database (Denmark)

    Kallesoe, C.; Mølhave, Kristian; Larsen, K. F.

    2010-01-01

    Epitaxial growth of heterostructure nanowires allows for the definition of narrow sections with specific semiconductor composition. The authors demonstrate how postgrowth engineering of III-V heterostructure nanowires using selective etching can form gaps, sharpening of tips, and thin sections...... simultaneously on multiple nanowires. They investigate the potential of combining nanostencil deposition of catalyst, epitaxial III-V heterostructure nanowire growth, and selective etching, as a road toward wafer scale integration and engineering of nanowires with existing silicon technology. Nanostencil...... lithography is used for deposition of catalyst particles on trench sidewalls and the lateral growth of III-V nanowires is achieved from such catalysts. The selectivity of a bromine-based etch on gallium arsenide segments in gallium phosphide nanowires is examined, using a hydrochloride etch to remove the III...

  19. Molecular precursor derived silicon boron carbonitride/carbon nanotube and silicon oxycarbide/carbon nanotube composite nanowires for energy based applications

    Science.gov (United States)

    Bhandavat, Romil

    Molecular precursor derived ceramics (also known as polymer-derived ceramics or PDCs) are high temperature glasses that have been studied for applications involving operation at elevated temperatures. Prepared from controlled thermal degradation of liquid-phase organosilicon precursors, these ceramics offer remarkable engineering properties such as resistance to crystallization up to 1400 °C, semiconductor behavior at high temperatures and intense photoluminescence. These properties are a direct result of their covalent bonded amorphous network and free (-sp2) carbon along with mixed Si/B/C/N/O bonds, which otherwise can not be obtained through conventional ceramic processing techniques. This thesis demonstrates synthesis of a unique core/shell type nanowire structure involving either siliconboroncarbonitride (SiBCN) or siliconoxycarbide (SiOC) as the shell with carbon nanotube (CNT) acting as the core. This was made possible by liquid phase functionalization of CNT surfaces with respective polymeric precursor (e.g., home-made boron-modified polyureamethylvinylsilazane for SiBCN/CNT and commercially obtained polysiloxane for SiOC/CNT), followed by controlled pyrolysis in inert conditions. This unique architecture has several benefits such as high temperature oxidation resistance (provided by the ceramic shell), improved electrical conductivity and mechanical toughness (attributed to the CNT core) that allowed us to explore its use in energy conversion and storage devices. The first application involved use of SiBCN/CNT composite as a high temperature radiation absorbant material for laser thermal calorimeter. SiBCN/CNT spray coatings on copper substrate were exposed to high energy laser beams (continuous wave at 10.6 mum 2.5 kW CO2 laser, 10 seconds) and resulting change in its microstructure was studied ex-situ. With the aid of multiple techniques we ascertained the thermal damage resistance to be 15 kW/cm -2 with optical absorbance exceeding 97%. This represents

  20. High-performance laterally-arranged multiple-bandgap solar cells using spatially composition-graded CdxPb1-xS nanowires on a single substrate: a design study.

    Science.gov (United States)

    Caselli, D A; Ning, C Z

    2011-07-04

    In this paper, laterally arranged multiple bandgap (LAMB) solar cells based on CdxPb1-xS alloy nanowires of varying composition on a single substrate are designed to be used together with a dispersive concentrator. Simulation results for a design with six subcells in series connection are presented. The design is based on a unique materials capability achieved in our recent research. An efficiency of 34.9% was obtained for operation without solar concentration, which increased to 40.5%, 41.7%, and 42.7% for concentration ratios of 25, 100, and 240 respectively. The device was also simulated with decreased carrier mobilities to model the possible reduction in absorber conductivity, depending on the nanowire geometry and configuration. For a concentration ratio of unity, decreasing the mobilities to 25% of their original values caused less than a 2.5% absolute drop in efficiency. The LAMB design offers the advantages of an integrated cell platform and the potential for low-cost, high efficiency photovoltaic systems.

  1. Micromechanical Modeling of Fiber-Reinforced Composites with Statistically Equivalent Random Fiber Distribution

    Directory of Open Access Journals (Sweden)

    Wenzhi Wang

    2016-07-01

    Full Text Available Modeling the random fiber distribution of a fiber-reinforced composite is of great importance for studying the progressive failure behavior of the material on the micro scale. In this paper, we develop a new algorithm for generating random representative volume elements (RVEs with statistical equivalent fiber distribution against the actual material microstructure. The realistic statistical data is utilized as inputs of the new method, which is archived through implementation of the probability equations. Extensive statistical analysis is conducted to examine the capability of the proposed method and to compare it with existing methods. It is found that the proposed method presents a good match with experimental results in all aspects including the nearest neighbor distance, nearest neighbor orientation, Ripley’s K function, and the radial distribution function. Finite element analysis is presented to predict the effective elastic properties of a carbon/epoxy composite, to validate the generated random representative volume elements, and to provide insights of the effect of fiber distribution on the elastic properties. The present algorithm is shown to be highly accurate and can be used to generate statistically equivalent RVEs for not only fiber-reinforced composites but also other materials such as foam materials and particle-reinforced composites.

  2. Semiconductor Nanowire Light-Emitting Diodes Grown on Metal: A Direction Toward Large-Scale Fabrication of Nanowire Devices.

    Science.gov (United States)

    Sarwar, A T M Golam; Carnevale, Santino D; Yang, Fan; Kent, Thomas F; Jamison, John J; McComb, David W; Myers, Roberto C

    2015-10-28

    Bottom-up nanowires are attractive for realizing semiconductor devices with extreme heterostructures because strain relaxation through the nanowire sidewalls allows the combination of highly lattice mismatched materials without creating dislocations. The resulting nanowires are used to fabricate light-emitting diodes (LEDs), lasers, solar cells, and sensors. However, expensive single crystalline substrates are commonly used as substrates for nanowire heterostructures as well as for epitaxial devices, which limits the manufacturability of nanowire devices. Here, nanowire LEDs directly grown and electrically integrated on metal are demonstrated. Optical and structural measurements reveal high-quality, vertically aligned GaN nanowires on molybdenum and titanium films. Transmission electron microscopy confirms the composition variation in the polarization-graded AlGaN nanowire LEDs. Blue to green electroluminescence is observed from InGaN quantum well active regions, while GaN active regions exhibit ultraviolet emission. These results demonstrate a pathway for large-scale fabrication of solid state lighting and optoelectronics on metal foils or sheets. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Pseudodirect to Direct Compositional Crossover in Wurtzite GaP/InxGa1–xP Core–Shell Nanowires

    KAUST Repository

    Gagliano, L.

    2016-11-29

    Thanks to their uniqueness, nanowires allow the realization of novel semiconductor crystal structures with yet unexplored properties, which can be key to overcome current technological limits. Here we develop the growth of wurtzite GaP/InGaP core-shell nanowires with tunable indium concentration and optical emission in the visible region from 590 nm (2.1 eV) to 760 nm (1.6 eV). We demonstrate a pseudodirect (δ-δ) to direct (δ-δ) transition crossover through experimental and theoretical approach. Time resolved and temperature dependent photoluminescence measurements were used, which led to the observation of a steep change in carrier lifetime and temperature dependence by respectively one and 3 orders of magnitude in the range 0.28 ± 0.04 ≤ x ≤ 0.41 ± 0.04. Our work reveals the electronic properties of wurtzite InGaP.

  4. Nanowire Photovoltaic Devices

    Science.gov (United States)

    Forbes, David

    2015-01-01

    Firefly Technologies, in collaboration with the Rochester Institute of Technology and the University of Wisconsin-Madison, developed synthesis methods for highly strained nanowires. Two synthesis routes resulted in successful nanowire epitaxy: direct nucleation and growth on the substrate and a novel selective-epitaxy route based on nanolithography using diblock copolymers. The indium-arsenide (InAs) nanowires are implemented in situ within the epitaxy environment-a significant innovation relative to conventional semiconductor nanowire generation using ex situ gold nanoparticles. The introduction of these nanoscale features may enable an intermediate band solar cell while simultaneously increasing the effective absorption volume that can otherwise limit short-circuit current generated by thin quantized layers. The use of nanowires for photovoltaics decouples the absorption process from the current extraction process by virtue of the high aspect ratio. While no functional solar cells resulted from this effort, considerable fundamental understanding of the nanowire epitaxy kinetics and nanopatterning process was developed. This approach could, in principle, be an enabling technology for heterointegration of dissimilar materials. The technology also is applicable to virtual substrates. Incorporating nanowires onto a recrystallized germanium/metal foil substrate would potentially solve the problem of grain boundary shunting of generated carriers by restricting the cross-sectional area of the nanowire (tens of nanometers in diameter) to sizes smaller than the recrystallized grains (0.5 to 1 micron(exp 2).

  5. Metallic nanowire networks

    Science.gov (United States)

    Song, Yujiang; Shelnutt, John A.

    2012-11-06

    A metallic nanowire network synthesized using chemical reduction of a metal ion source by a reducing agent in the presence of a soft template comprising a tubular inverse micellar network. The network of interconnected polycrystalline nanowires has a very high surface-area/volume ratio, which makes it highly suitable for use in catalytic applications.

  6. Guided Growth of Horizontal p-Type ZnTe Nanowires.

    Science.gov (United States)

    Reut, Gilad; Oksenberg, Eitan; Popovitz-Biro, Ronit; Rechav, Katya; Joselevich, Ernesto

    2016-08-04

    A major challenge toward large-scale integration of nanowires is the control over their alignment and position. A possible solution to this challenge is the guided growth process, which enables the synthesis of well-aligned horizontal nanowires that grow according to specific epitaxial or graphoepitaxial relations with the substrate. However, the guided growth of horizontal nanowires was demonstrated for a limited number of materials, most of which exhibit unintentional n-type behavior. Here we demonstrate the vapor-liquid-solid growth of guided horizontal ZnTe nanowires and nanowalls displaying p-type behavior on four different planes of sapphire. The growth directions of the nanowires are determined by epitaxial relations between the nanowires and the substrate or by a graphoepitaxial effect that guides their growth along nanogrooves or nanosteps along the surface. We characterized the crystallographic orientations and elemental composition of the nanowires using transmission electron microscopy and photoluminescence. The optoelectronic and electronic properties of the nanowires were studied by fabricating photodetectors and top-gate thin film transistors. These measurements showed that the guided ZnTe nanowires are p-type semiconductors and are photoconductive in the visible range. The guided growth of horizontal p-type nanowires opens up the possibility of parallel nanowire integration into functional systems with a variety of potential applications not available by other means.

  7. Randomized controlled split-mouth clinical trial of direct laminate veneers with two micro-hybrid resin composites

    NARCIS (Netherlands)

    Gresnigt, Marco M. M.; Kalk, Warner; Ozcan, M.; Ozcan, Mutlu

    Objectives: This randomized, split-mouth clinical study evaluated the survival rate of direct laminate veneers made of two resin-composite materials. Methods: A total of 23 patients (mean age: 52.4 years old) received 96 direct composite laminate veneers using two micro-hybrid composites in

  8. Nanowire Growth for Photovoltaics

    DEFF Research Database (Denmark)

    Holm, Jeppe Vilstrup

    the small footprint of grown nanowires relaxes the crystal matching constraint. 1.7eV is the ideal bandgap for a top junction in a dual junction solar cell, where silicon is the bottom junction. This can be obtained with GaAs0.8P0.2. We have demonstrated how to incorporate phosphorous(P) into Ga......-catalyzed nanowire growth, and grown GaAs1−xPx nanowires with different inclusions of P(x) directly on silicon. The incorporation of P was generally higher in nanowires than for planar growth at identical P flux percentage. More interestingly, the percentage of P in the nanowire was found to be a concave function...

  9. Random-network simulation of an ultracapacitor based on metal-solid-electrolyte composite

    Science.gov (United States)

    Abel, J.; Kornyshev, A. A.

    1996-09-01

    A random-network model of a dense (pore-free) metal-solid-electrolyte composite is developed. Real and imaginary parts of admittance are simulated as a function of frequency and composition by means of the transfer matrix algorithm on a cubic lattice. For a composite without a solid-electrolyte membrane in the middle (insulating with respect to electronic current) the results predict the capacity maximum at the percolation threshold in three dimensions and two maxima in two dimensions as a function of composition; they are compared with the predictions of the effective medium theory. For a composite with an insulating membrane in the middle, typical for ultracapacitors, the maximum of capacitance in three dimensions is at equal portion of metal and solid-electrolyte particles. In contrast to metal dielectric mixtures there are no giant enhancement effects in static capacitance as a function of composition: the upper estimates of the enhancement factor are proportional to the ratio of the size of the sample to the size of the grains.

  10. Stochastic finite element method for random harmonic analysis of composite plates with uncertain modal damping parameters

    Science.gov (United States)

    Sepahvand, K.

    2017-07-01

    Damping parameters of fiber-reinforced composite possess significant uncertainty due to the structural complexity of such materials. Considering the parameters as random variables, this paper uses the generalized polynomial chaos (gPC) expansion to capture the uncertainty in the damping and frequency response function of composite plate structures. A spectral stochastic finite element formulation for damped vibration analysis of laminate plates is employed. Experimental modal data for samples of plates is used to identify and realize the range and probability distributions of uncertain damping parameters. The constructed gPC expansions for the uncertain parameters are used as inputs to a deterministic finite element model to realize random frequency responses on a few numbers of collocation points generated in random space. The realizations then are employed to estimate the unknown deterministic functions of the gPC expansion approximating the responses. Employing modal superposition method to solve harmonic analysis problem yields an efficient sparse gPC expansion representing the responses. The results show while the responses are influenced by the damping uncertainties at the mid and high frequency ranges, the impact in low frequency modes can be safely ignored. Utilizing a few random collocation points, the method indicates also a very good agreement compared to the sampling-based Monte Carlo simulations with large number of realizations. As the deterministic finite element model serves as black-box solver, the procedure can be efficiently adopted to complex structural systems with uncertain parameters in terms of computational time.

  11. Semiconductor Nanowires from Materials Science and Device Physics Perspectives

    Science.gov (United States)

    Samuelson, Lars

    2005-03-01

    Realization of extremely down-scaled devices gives tough challenges related to technology and materials science. One reason for the concern is that top-down fabricated nano-devices tend to have their properties dominated by process-induced damage, rendering ultra-small devices not so useful. Alternatively, bottom-up fabrication methods may allow dimensions on the scale even below 10 nm, still with superb device properties. I will in this talk describe our research on catalytically induced growth of semiconductor nanowires. Our method uses catalytic gold nanoparticles, allowing tight control of diameter as well as position of where the nanowire grows, with our work completely focused on epitaxially nucleated nanowires in which the nanowire structure can be seen as a coherent, monolithic extension of the crystalline substrate material. One of the most important achievements in this field of research is the realization of atomically abrupt heterostructures within nanowires, in which the material composition can be altered within only one or a few monolayers, thus allowing 1D heterostructure devices to be realized. This has allowed a variety of quantum devices to be realized, such as single-electron transistors, resonant tunneling devices as well as memory storage devices. A related recent field of progress has been the realization of ideally nucleated III-V nanowires on Si substrates, cases where we have also reported functioning III-V heterostructure device structures on Si. All of these device related challenges evolve from an improved understanding of the materials science involved in nucleation of nanowires, in altering of composition of the growing nanowire, in control of the growth direction etc. I will give examples of these materials science issues and will especially dwell on the opportunities to form new kinds of materials, e.g. as 3D complex nanowire structures, resembling nanotrees or nanoforests.

  12. Tunneling Conductivity and Piezoresistivity of Composites Containing Randomly Dispersed Conductive Nano-Platelets

    Directory of Open Access Journals (Sweden)

    Amirhossein Biabangard Oskouyi

    2014-03-01

    Full Text Available In this study, a three-dimensional continuum percolation model was developed based on a Monte Carlo simulation approach to investigate the percolation behavior of an electrically insulating matrix reinforced with conductive nano-platelet fillers. The conductivity behavior of composites rendered conductive by randomly dispersed conductive platelets was modeled by developing a three-dimensional finite element resistor network. Parameters related to the percolation threshold and a power-low describing the conductivity behavior were determined. The piezoresistivity behavior of conductive composites was studied employing a reoriented resistor network emulating a conductive composite subjected to mechanical strain. The effects of the governing parameters, i.e., electron tunneling distance, conductive particle aspect ratio and size effects on conductivity behavior were examined.

  13. Effect of SiC Nano powder on Multiaxial Woven and Chopped Randomly Oriented Flax/Sisal Fiber Reinforced composites

    Directory of Open Access Journals (Sweden)

    Kalagi Ganesh R.

    2018-01-01

    Full Text Available A study has been carried out to investigate effect of SiC Nano powder on tensile and impact properties of Multiaxial layers of Flax and Sisal fiber reinforced composites and randomly oriented chopped Flax and Sisal fiber reinforced composites. It has been observed that tensile strength and impact strength were improved using 6% of SiC Nanopowder into Multiaxial layer (+45º/-45º, 0º/90º of Flax and Sisal where as randomly oriented chopped Flax and Sisal fiber reinforced composites are improved in its stiffnes for the same composition of fiber, epoxy and SiC Nano powder. SEM Analysis are done to analyse the distribution of SiC in both Multiaxial layers of Flax and Sisal fiber reinforced composites and randomly oriented chopped Flax and Sisal fiber reinforced composites.

  14. Nanowire-based thermoelectrics

    Science.gov (United States)

    Ali, Azhar; Chen, Yixi; Vasiraju, Venkata; Vaddiraju, Sreeram

    2017-07-01

    Research on thermoelectrics has seen a huge resurgence since the early 1990s. The ability of tuning a material’s electrical and thermal transport behavior upon nanostructuring has led to this revival. Nevertheless, thermoelectric performances of nanowires and related materials lag far behind those achieved with thin-film superlattices and quantum dot-based materials. This is despite the fact that nanowires offer many distinct advantages in enhancing the thermoelectric performances of materials. The simplicity of the strategy is the first and foremost advantage. For example, control of the nanowire diameters and their surface roughnesses will aid in enhancing their thermoelectric performances. Another major advantage is the possibility of obtaining high thermoelectric performances using simpler nanowire chemistries (e.g., elemental and binary compound semiconductors), paving the way for the fabrication of thermoelectric modules inexpensively from non-toxic elements. In this context, the topical review provides an overview of the current state of nanowire-based thermoelectrics. It concludes with a discussion of the future vision of nanowire-based thermoelectrics, including the need for developing strategies aimed at the mass production of nanowires and their interface-engineered assembly into devices. This eliminates the need for trial-and-error strategies and complex chemistries for enhancing the thermoelectric performances of materials.

  15. Silicon nanowire hybrid photovoltaics

    KAUST Repository

    Garnett, Erik C.

    2010-06-01

    Silicon nanowire Schottky junction solar cells have been fabricated using n-type silicon nanowire arrays and a spin-coated conductive polymer (PEDOT). The polymer Schottky junction cells show superior surface passivation and open-circuit voltages compared to standard diffused junction cells with native oxide surfaces. External quantum efficiencies up to 88% were measured for these silicon nanowire/PEDOT solar cells further demonstrating excellent surface passivation. This process avoids high temperature processes which allows for low-cost substrates to be used. © 2010 IEEE.

  16. Excitonic photoluminescence and photoresponse of ZnS nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Jun, E-mail: daijun@just.edu.cn [Department of Physics, Jiangsu University of Science and Technology, Zhenjiang 212003 (China); Song, Xing [School of Material Science and Engineering, Jiangsu University, Zhenjiang 212003 (China); Zheng, Hongge [Department of Physics, Jiangsu University of Science and Technology, Zhenjiang 212003 (China); Wu, Chunxia, E-mail: chxwu7771@yahoo.com.cn [School of Material Science and Engineering, Jiangsu University, Zhenjiang 212003 (China)

    2016-05-01

    Single crystal ZnS nanowires are fabricated by vapor phase transport method on sapphire substrate in the presence of Au catalyst. The morphology, composition, and crystal structure are characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM). XRD and HRTEM reveal that the ZnS nanowires have perfect single crystal wurtzite structure. The temperature-dependent photoluminescence spectra show that the ZnS nanowires present pure near-bandgap ultraviolet exciton recombination emission at 347 nm. The exciton-related optical properties, including exciton activation energy, temperature-dependent exciton energy and Varshni coefficients describing exciton energy variation, are systematically discussed. In addition, an individual ZnS nanowire-based ultraviolet photodetector is fabricated, which shows good photoresponse ability and fast response rate. The result shows that the ZnS nanowires are particularly suitable for UV photodetectors. - Highlights: • Single crystal ultrathin ZnS nanowires with diameter of 20–100 nm were fabricated by vapor phase transport method. • Exciton-related optical properties were fitted by temperature-dependent photoluminescence spectra. • Single ZnS nanowire ultraviolet photodetector with good photoswitch ability and high photocurrent was demonstrated.

  17. Titanium mesh supported TiO2 nanowire arrays/upconversion luminescence Er3+-Yb3+ codoped TiO2 nanoparticles novel composites for flexible dye-sensitized solar cells

    Science.gov (United States)

    Liu, Wenwu; Zhang, Huanyu; Wang, Hui-gang; Zhang, Mei; Guo, Min

    2017-11-01

    Ti-mesh supported TiO2 nanowire arrays (NWAs)/upconversion luminescence Er3+-Yb3+ codoped TiO2 nanoparticles (UC-EY-TiO2 NPs) composite structured photoanodes for fully flexible dye sensitized solar cells (DSSCs) were firstly constructed via a hydrothermal and spin coating process. UV-vis-NIR absorption spectra of the TiO2 NWAs/UC-EY-TiO2 NPs composites exhibited strong absorption around near infrared (NIR) 980 nm. The composites excited by 980 nm NIR laser could emit upconversion fluorescence at 489, 526, 549 and 658 nm, which expanded the spectral response range and sunlight capturing capability of formed flexible DSSCs. Moreover, the TiO2 NWAs/UC-EY-TiO2 NPs was coated with an Nb2O5 thin layer to further suppress electron recombination losses. The complete flexible DSSCs based on Nb2O5 coated TiO2 NWAs/2.0 mol% Er3+-1.0 mol% Yb3+ codoped TiO2 NPs photoanode and Pt/ITO-PEN counter electrode exhibited an enhanced photon to current conversion efficiency of 8.10%, a 68% improvement compared to TiO2 NWAs/undoped TiO2 NPs based DSSCs (4.82%).

  18. Controlling the Coupling of a Single Nitrogen Vacancy Center to a Silver Nanowire

    DEFF Research Database (Denmark)

    Huck, Alexander; Kumar, Shailesh; Shakoor, Abdul

    2011-01-01

    -linear interaction at the level of a few photons. In our contribution we demonstrate the controlled coupling of a single nitrogen vacancy (NV) center in a diamond nano crystal to a nanowire made of silver. This is in contrast to previous realizations, where the nanowire dipole system was assembled randomly. Ultimate...

  19. Porous Silicon Nanowires

    Science.gov (United States)

    Qu, Yongquan; Zhou, Hailong; Duan, Xiangfeng

    2011-01-01

    In this minreview, we summarize recent progress in the synthesis, properties and applications of a new type of one-dimensional nanostructures — single crystalline porous silicon nanowires. The growth of porous silicon nanowires starting from both p- and n-type Si wafers with a variety of dopant concentrations can be achieved through either one-step or two-step reactions. The mechanistic studies indicate the dopant concentration of Si wafers, oxidizer concentration, etching time and temperature can affect the morphology of the as-etched silicon nanowires. The porous silicon nanowires are both optically and electronically active and have been explored for potential applications in diverse areas including photocatalysis, lithium ion battery, gas sensor and drug delivery. PMID:21869999

  20. Ballistic Majorana nanowire devices

    NARCIS (Netherlands)

    Gül, Önder

    2017-01-01

    The dissertation reports a series of electron transport experiments on semiconductor nanowires towards realizing the hypothesized topological quantum computation. A topological quantum computer manipulates information that is stored nonlocally in the topology of a physical system. Such an operation

  1. Biofunctionalized Magnetic Nanowires

    KAUST Repository

    Kosel, Jurgen

    2013-12-19

    Magnetic nanowires can be used as an alternative method overcoming the limitations of current cancer treatments that lack specificity and are highly cytotoxic. Nanowires are developed so that they selectively attach to cancer cells via antibodies, potentially destroying them when a magnetic field induces their vibration. This will transmit a mechanical force to the targeted cells, which is expected to induce apoptosis on the cancer cells.

  2. Controlling nanowire growth through electric field-induced deformation of the catalyst droplet

    DEFF Research Database (Denmark)

    Panciera, Federico; Norton, Michael M.; Alam, Sardar Bilal

    2016-01-01

    Semiconductor nanowires with precisely controlled structure, and hence well-defined electronic and optical properties, can be grown by self-assembly using the vapour-liquid-solid process. The structure and chemical composition of the growing nanowire is typically determined by global parameters s...

  3. Atomic-Resolution Spectrum Imaging of Semiconductor Nanowires.

    Science.gov (United States)

    Zamani, Reza R; Hage, Fredrik S; Lehmann, Sebastian; Ramasse, Quentin M; Dick, Kimberly A

    2017-11-13

    Over the past decade, III-V heterostructure nanowires have attracted a surge of attention for their application in novel semiconductor devices such as tunneling field-effect transistors (TFETs). The functionality of such devices critically depends on the specific atomic arrangement at the semiconductor heterointerfaces. However, most of the currently available characterization techniques lack sufficient spatial resolution to provide local information on the atomic structure and composition of these interfaces. Atomic-resolution spectrum imaging by means of electron energy-loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) is a powerful technique with the potential to resolve structure and chemical composition with sub-angstrom spatial resolution and to provide localized information about the physical properties of the material at the atomic scale. Here, we demonstrate the use of atomic-resolution EELS to understand the interface atomic arrangement in three-dimensional heterostructures in semiconductor nanowires. We observed that the radial interfaces of GaSb-InAs heterostructure nanowires are atomically abrupt, while the axial interface in contrast consists of an interfacial region where intermixing of the two compounds occurs over an extended spatial region. The local atomic configuration affects the band alignment at the interface and, hence, the charge transport properties of devices such as GaSb-InAs nanowire TFETs. STEM-EELS thus represents a very promising technique for understanding nanowire physical properties, such as differing electrical behavior across the radial and axial heterointerfaces of GaSb-InAs nanowires for TFET applications.

  4. Nonlinear optics in nonlocal nanowire metamaterials (Conference Presentation)

    Science.gov (United States)

    Podolskiy, Viktor A.; Wells, Brian; Marino, Giuseppe; Zayats, Anatoly V.

    2016-09-01

    Plasmonic nanowire metamaterials, arrays of aligned plasmonic nanowires grown inside an insulating substrate, have recently emerged as a flexible platform for engineering refraction, diffraction, and density of photonic states, as well as for applications in bio- and acoustic sensing. Majority of unique optical phenomena associated with nanowire metamaterials have been linked to the collective excitation of cylindrical surface plasmons propagating on individual nanowires. From the effective medium standpoint, this collective excitation can be described as an additional electromagnetic wave, emanating from nonlocal effective permittivity of metamaterial. The electromagnetic fields associated with such mode can are strongly inhomogeneous on the scale of the unit cell. In this work we analyze the effect of the strong field variation inside nanowire metamaterial on second harmonic generation (SHG). We show that second harmonic generation is strongly enhanced in the frequency region where metamaterial is nonlocal. Overall, the composite is predicted to outperform its homogeneous metal counterparts by several orders of magnitude. Quantitative description of SHG in nanowire medium is developed. The results suggest that bulk second harmonic polarizability emerges as result of collective surface-enhanced SHG by individual components of the composite.

  5. Solvothermal Synthesis of Indium Telluride Nanowires and Its Photoelectrical Property.

    Science.gov (United States)

    Yan, Shancheng; Zhou, Liyan; Shi, Yi; Wang, Bojun; Wang, Junzhuan; Xu, Xin

    2015-05-01

    In this paper, 1D In2Te3 nanowires were synthesizes through a simple solvothermal approach. The morphology was first studied by scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). From the results, the nanowires have a diameter from 100 to 200 nm and a length of dozens of microns. X-ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectrum were used to study the composition, crystal structures, and optical property. Based on the typical nanowire sample, experiment factors were changed to synthsize other samples in order to study the influence factors. A possible growth mechanism of the nanowires was proposed based on a series of experimental results. This material has a broad light detection range covering the UV-visible-NIR region from the photoelectrical test, which makes it potential for applications in photodetectors and solar cells.

  6. A Grazing-Incidence Small-Angle X-Ray Scattering View of Vertically Aligned ZnO Nanowires

    Directory of Open Access Journals (Sweden)

    M. Lučić Lavčević

    2013-01-01

    Full Text Available We report a grazing-incidence small-angle X-ray scattering study of ZnO films with vertically aligned and randomly distributed nanowires, grown through a hydrothermal growth process on nanostructured ZnO seeding coatings and deposited by electron beam evaporation on silicon and glass, respectively. The comparison of the scattering patterns of seeding coatings and nanowires showed that the scattering of vertically aligned nanowires exhibited a specific feature: the dominant characteristic of their scattering patterns is the appearance of fine structure effects around the specular peak. These effects were clarified by the combined reflection and scattering phenomena, suggested for the aligned nanowires-substrate system. Furthermore, they enabled the calculation of the average gyration radius of nanowires in horizontal direction. The calculated value was in good agreement with the radii of nanowires estimated by surface electron microscopy. Therefore, the observed feature in the scattering pattern can serve as evidence of the aligned growth of nanowires.

  7. Randomized Clinical Trial of Indirect Resin Composite and Ceramic Veneers : Up to 3-year Follow-up

    NARCIS (Netherlands)

    Gresnigt, Marco M. M.; Kalk, Warner; Ozcan, Mutlu

    2013-01-01

    Purpose: This randomized controlled split-mouth clinical trial evaluated the short-term survival rate of indirect resin composite and ceramic laminate veneers. Materials and Methods: A total of 10 patients (mean age: 48.6 years) received 46 indirect resin composite (Estenia; n = 23) and ceramic

  8. Cleaved-Coupled Nanowire Lasers

    Science.gov (United States)

    2013-01-15

    fabricated with micrometer -scale gaps (26, 27). This Fig. 1. Single-frequency lasing in 9-μm (4:3) cleaved-coupled nanowires. (A) SEM images showing the...modulation of modes observed in cleaved-coupled nanowire lasers can be predicted using transfer matrix methods. Although the Vernier effect provides an...Following the Vernier effect, coupled nanowires with integer ratios would produce the free spectral range of the shorter nanowire. The lasing spectra

  9. Perspectives: Nanofibers and nanowires for disordered photonics

    Directory of Open Access Journals (Sweden)

    Dario Pisignano

    2017-03-01

    Full Text Available As building blocks of microscopically non-homogeneous materials, semiconductor nanowires and polymer nanofibers are emerging component materials for disordered photonics, with unique properties of light emission and scattering. Effects found in assemblies of nanowires and nanofibers include broadband reflection, significant localization of light, strong and collective multiple scattering, enhanced absorption of incident photons, synergistic effects with plasmonic particles, and random lasing. We highlight recent related discoveries, with a focus on material aspects. The control of spatial correlations in complex assemblies during deposition, the coupling of modes with efficient transmission channels provided by nanofiber waveguides, and the embedment of random architectures into individually coded nanowires will allow the potential of these photonic materials to be fully exploited, unconventional physics to be highlighted, and next-generation optical devices to be achieved. The prospects opened by this technology include enhanced random lasing and mode-locking, multi-directionally guided coupling to sensors and receivers, and low-cost encrypting miniatures for encoders and labels.

  10. Perspectives: Nanofibers and nanowires for disordered photonics

    Science.gov (United States)

    Pisignano, Dario; Persano, Luana; Camposeo, Andrea

    2017-03-01

    As building blocks of microscopically non-homogeneous materials, semiconductor nanowires and polymer nanofibers are emerging component materials for disordered photonics, with unique properties of light emission and scattering. Effects found in assemblies of nanowires and nanofibers include broadband reflection, significant localization of light, strong and collective multiple scattering, enhanced absorption of incident photons, synergistic effects with plasmonic particles, and random lasing. We highlight recent related discoveries, with a focus on material aspects. The control of spatial correlations in complex assemblies during deposition, the coupling of modes with efficient transmission channels provided by nanofiber waveguides, and the embedment of random architectures into individually coded nanowires will allow the potential of these photonic materials to be fully exploited, unconventional physics to be highlighted, and next-generation optical devices to be achieved. The prospects opened by this technology include enhanced random lasing and mode-locking, multi-directionally guided coupling to sensors and receivers, and low-cost encrypting miniatures for encoders and labels.

  11. The Self- and Directed Assembly of Nanowires

    Science.gov (United States)

    Smith, Benjamin David

    This thesis explores the self- and directed assembly of nanowires. Specifically, we examine the driving forces behind nanowire self-assembly and the macro-structures that are formed. Particle-dense, oriented nanowire structures show promise in the fields of photonics, energy, sensing, catalysis, and electronics. Arrays of spherical particles have already found uses in electronic inks, sensing arrays, and many other commercial applications; but, it is a challenge to create specific arrays of morphologically and/or compositionally anisotropic particles. The following chapters illuminate the interactions that drive the assembly of anisotropic particles in high density solutions in the absence of applied fields or solution drying. Special emphasis is placed on the structures that are formed. The properties of micro- and nanoparticles and their assembly are introduced in Chapter 1. In particular, the properties of shape and material anisotropic particles are highlighted, while challenges in producing desired arrays are discussed. In this thesis, metallic nanowires of increasing complexity were used to examine the self-assembly behavior of both shape and material anisotropic particles. Nanowires were synthesized through templated electrodeposition. In this process, porous alumina membranes served as a template in which metal salts were reduced to form particles. Upon template dissolution, billions of nominally identical particles were released. We specifically focused on segmented, metallic nanowires 2-13 mum in length and 180 to 350 nm in diameter. Since these particles have strong van der Waals (VDWs) attractions, an electrostatically repulsive coating was necessary to prevent aggregation; we used small molecule, DNA, or amorphous silica coatings. Nanowires and their coatings were characterized by electron microscopy. In order to study self-assembly behavior, particle-dense aqueous suspensions were placed within an assembly chamber defined by a silicone spacer. The

  12. Off-axis electron holography of ferromagnetic multilayer nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Akhtari-Zavareh, Azadeh; Kavanagh, K. L. [Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A1S6 (Canada); Carignan, L. P. [Apollo Microwaves, 1650 Trans-Canada Highway, Dorval, Quebec H9P 1H7 (Canada); Department of Engineering Physics, École Polytechnique de Montréal, Montréal, Quebec, H3C 3A7 Canada (Canada); Department of Electrical Engineering, École Polytechnique de Montréal, Montréal, Quebec, H3C 3A7 Canada (Canada); Yelon, A.; Ménard, D. [Department of Engineering Physics, École Polytechnique de Montréal, Montréal, Quebec, H3C 3A7 Canada (Canada); Kasama, T. [Center for Electron Nanoscopy, Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark); Herring, R. [Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia V8W 3P6 (Canada); Dunin-Borkowski, R. E. [Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Institute for Microstructure Research, D-52425 Jülich (Germany); McCartney, M. R. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States)

    2014-07-14

    We have used electron holography to investigate the local magnetic behavior of isolated ferromagnetic nanowires (NWs) in their remanent states. The NWs consisted of periodic magnetic layers of soft, high-saturation magnetization CoFeB alloys, and non-magnetic layers of Cu. All NWs were fabricated by pulsed-potential electrodeposition in nanoporous alumina membranes. The NW composition and layer thicknesses were measured using scanning transmission electron microscopy and energy dispersive spectroscopy. The magnetization of individual NWs depended upon the thicknesses of the layers and the direction of an external magnetic field, which had been applied in situ. When the CoFeB was thicker than the diameter (50 nm), magnetization was axial for all external field directions, while thinner layers could be randomized via a perpendicular field. In some cases, magnetization inside the wire was detected at an angle with respect to the axis of the wires. In thinner Cu/CoFeB (<10 nm each) multilayer, magnetic field vortices were detected, associated with opposing magnetization in neighbouring layers. The measured crystallinity, compositions, and layer thicknesses of individual NWs were found to be significantly different from those predicted from calibration growths based on uniform composition NWs. In particular, a significant fraction of Cu (up to 50 at. %) was present in the CoFeB layers such that the measured magnetic induction was lower than expected. These results will be used to better understand previously measured effective anisotropy fields of similar NW arrays.

  13. In situ growth of SiC nanowires on RS-SiC substrate(s)

    Science.gov (United States)

    Yang, Wen; Araki, Hiroshi; Hu, Quanli; Ishikawa, Nobuhiro; Suzuki, Hiroshi; Noda, Tetsuji

    2004-03-01

    SiC nanowires over 10 μm in length and 20-100 nm in diameter have been synthesized by a novel in situ chemical vapor growth process on RS-SiC plates. The SiC nanowires were identified as single crystal β-SiC with Si-C chemistry. The growth direction of the nanowires is . The growth mechanism is discussed and a kinetic vapor-solid growth mechanism is proposed. The process demonstrates the possibility to fabricate SiC nanowires in ceramic matrix composites, such as continuous SiC fibers reinforced SiC matrix composites, with the SiC nanowires uniformly dispersed in the matrix.

  14. Nanowire mesh solar fuels generator

    Science.gov (United States)

    Yang, Peidong; Chan, Candace; Sun, Jianwei; Liu, Bin

    2016-05-24

    This disclosure provides systems, methods, and apparatus related to a nanowire mesh solar fuels generator. In one aspect, a nanowire mesh solar fuels generator includes (1) a photoanode configured to perform water oxidation and (2) a photocathode configured to perform water reduction. The photocathode is in electrical contact with the photoanode. The photoanode may include a high surface area network of photoanode nanowires. The photocathode may include a high surface area network of photocathode nanowires. In some embodiments, the nanowire mesh solar fuels generator may include an ion conductive polymer infiltrating the photoanode and the photocathode in the region where the photocathode is in electrical contact with the photoanode.

  15. The Mechanical Properties of Nanowires

    Science.gov (United States)

    Wang, Shiliang; Shan, Zhiwei

    2017-01-01

    Applications of nanowires into future generation nanodevices require a complete understanding of the mechanical properties of the nanowires. A great research effort has been made in the past two decades to understand the deformation physics and mechanical behaviors of nanowires, and to interpret the discrepancies between experimental measurements and theoretical predictions. This review focused on the characterization and understanding of the mechanical properties of nanowires, including elasticity, plasticity, anelasticity and strength. As the results from the previous literature in this area appear inconsistent, a critical evaluation of the characterization techniques and methodologies were presented. In particular, the size effects of nanowires on the mechanical properties and their deformation mechanisms were discussed. PMID:28435775

  16. A Randomized 10-year Prospective Follow-up of Class II Nanohybrid and Conventional Hybrid Resin Composite Restorations

    DEFF Research Database (Denmark)

    van Dijken, Jan Wv; Pallesen, Ulla

    2014-01-01

    Purpose: To evaluate the 10-year durability of a nanohybrid resin composite in Class II restorations in a randomized controlled intraindividual comparison with its conventional hybrid resin composite predecessor. Materials and Methods: Each of 52 participants received at least two Class II...... restorations that were as similar as possible. The cavities were chosen at random to be restored with a nanohybrid resin composite (Excite/Tetric EvoCeram (TEC); n = 61) and a conventional hybrid (Excite/Tetric Ceram (TC); n = 61). The restorations were evaluated with slightly modified USPHS criteria...... investigated resin composites. Conclusion: The nanohybrid and the conventional hybrid resin composite showed good clinical effectiveness in extensive Class II restorations during the 10-year study....

  17. Selective formation of tungsten nanowires

    Directory of Open Access Journals (Sweden)

    Bien Daniel

    2011-01-01

    Full Text Available Abstract We report on a process for fabricating self-aligned tungsten (W nanowires with polycrystalline silicon core. Tungsten nanowires as thin as 10 nm were formed by utilizing polysilicon sidewall transfer technology followed by selective deposition of tungsten by chemical vapor deposition (CVD using WF6 as the precursor. With selective CVD, the process is self-limiting whereby the tungsten formation is confined to the polysilicon regions; hence, the nanowires are formed without the need for lithography or for additional processing. The fabricated tungsten nanowires were observed to be perfectly aligned, showing 100% selectivity to polysilicon and can be made to be electrically isolated from one another. The electrical conductivity of the nanowires was characterized to determine the effect of its physical dimensions. The conductivity for the tungsten nanowires were found to be 40% higher when compared to doped polysilicon nanowires of similar dimensions.

  18. Piezoresistive boron doped diamond nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Sumant, Anirudha V.; Wang, Xinpeng

    2017-07-04

    A UNCD nanowire comprises a first end electrically coupled to a first contact pad which is disposed on a substrate. A second end is electrically coupled to a second contact pad also disposed on the substrate. The UNCD nanowire is doped with a dopant and disposed over the substrate. The UNCD nanowire is movable between a first configuration in which no force is exerted on the UNCD nanowire and a second configuration in which the UNCD nanowire bends about the first end and the second end in response to a force. The UNCD nanowire has a first resistance in the first configuration and a second resistance in the second configuration which is different from the first resistance. The UNCD nanowire is structured to have a gauge factor of at least about 70, for example, in the range of about 70 to about 1,800.

  19. Control and understanding of kink formation in InAs-InP heterostructure nanowires.

    Science.gov (United States)

    Fahlvik Svensson, S; Jeppesen, S; Thelander, C; Samuelson, L; Linke, H; Dick, K A

    2013-08-30

    Nanowire heterostructures are of special interest for band structure engineering due to an expanded range of defect-free material combinations. However, the higher degree of freedom in nanowire heterostructure growth comes at the expense of challenges related to nanowire-seed particle interactions, such as undesired composition, grading and kink formation. To better understand the mechanisms of kink formation in nanowires, we here present a detailed study of the dependence of heterostructure nanowire morphology on indium pressure, nanowire diameter, and nanowire density. We investigate InAs-InP-InAs heterostructure nanowires grown with chemical beam epitaxy, which is a material system that allows for very abrupt heterointerfaces. Our observations indicate that the critical parameter for kink formation is the availability of indium, and that the resulting morphology is also highly dependent on the length of the InP segment. It is shown that kinking is associated with the formation of an inclined facet at the interface between InP and InAs, which destabilizes the growth and leads to a change in growth direction. By careful tuning of the growth parameters, it is possible to entirely suppress the formation of this inclined facet and thereby kinking at the heterointerface. Our results also indicate the possibility of producing controllably kinked nanowires with a high yield.

  20. Effects of Nanowire Length and Surface Roughness on the Electrochemical Sensor Properties of Nafion-Free, Vertically Aligned Pt Nanowire Array Electrodes

    Directory of Open Access Journals (Sweden)

    Zhiyang Li

    2015-09-01

    Full Text Available In this paper, vertically aligned Pt nanowire arrays (PtNWA with different lengths and surface roughnesses were fabricated and their electrochemical performance toward hydrogen peroxide (H2O2 detection was studied. The nanowire arrays were synthesized by electroplating Pt in nanopores of anodic aluminum oxide (AAO template. Different parameters, such as current density and deposition time, were precisely controlled to synthesize nanowires with different surface roughnesses and various lengths from 3 μm to 12 μm. The PtNWA electrodes showed better performance than the conventional electrodes modified by Pt nanowires randomly dispersed on the electrode surface. The results indicate that both the length and surface roughness can affect the sensing performance of vertically aligned Pt nanowire array electrodes. Generally, longer nanowires with rougher surfaces showed better electrochemical sensing performance. The 12 μm rough surface PtNWA presented the largest sensitivity (654 μA·mM−1·cm−2 among all the nanowires studied, and showed a limit of detection of 2.4 μM. The 12 μm rough surface PtNWA electrode also showed good anti-interference property from chemicals that are typically present in the biological samples such as ascorbic, uric acid, citric acid, and glucose. The sensing performance in real samples (river water was tested and good recovery was observed. These Nafion-free, vertically aligned Pt nanowires with surface roughness control show great promise as versatile electrochemical sensors and biosensors.

  1. Characterization of composites fabricated from discontinuous random carbon fiber thermoplastic matrix sheets produced by a paper making process

    Science.gov (United States)

    Ducote, Martin Paul, Jr.

    In this thesis, a papermaking process was used to create two randomly oriented, high performance composite material systems. The primary objective of this was to discover the flexural properties of both composite systems and compare those to reported results from other studies. In addition, the process was evaluated for producing quality, randomly oriented composite panels. Thermoplastic polymers have the toughness and necessary strength to be alternatives to thermosets, but with the promise of lower cycle times and increased recyclability. The wet-lay papermaking process used in this study produces a quality, randomly oriented thermoplastic composite at low cycle times and simple production. The materials chosen represent high performance thermoplastics and carbon fibers. Short chopped carbon fiber filled Nylon 6,6 and PEEK composites were created at varying fiber volume fractions. Ten nylon based panels and five PEEK based panels were subjected to 4-point flexural testing. In several of the nylon-based panels, flexural testing was done in multiple direction to verify the in-plane isotropy of the final composite. The flexural strength performance of both systems showed promise when compared to equivalent products currently available. The flexural modulus results were less than expected and further research should be done into possibly causes. Overall, this research gives good insight into two high performance engineering composites and should aid in continued work.

  2. A sensitive and selective magnetic graphene composite-modified polycrystalline-silicon nanowire field-effect transistor for bladder cancer diagnosis.

    Science.gov (United States)

    Chen, Hsiao-Chien; Chen, Yi-Ting; Tsai, Rung-Ywan; Chen, Min-Cheng; Chen, Shi-Liang; Xiao, Min-Cong; Chen, Chien-Lun; Hua, Mu-Yi

    2015-04-15

    In this study, we describe the urinary quantification of apolipoprotein A II protein (APOA2 protein), a biomarker for the diagnosis of bladder cancer, using an n-type polycrystalline silicon nanowire field-effect transistor (poly-SiNW-FET). The modification of poly-SiNW-FET by magnetic graphene with long-chain acid groups (MGLA) synthesized via Friedel-Crafts acylation was compared with that obtained using short-chain acid groups (MGSA). Compared with MGSA, the MGLA showed a higher immobilization degree and bioactivity to the anti-APOA2 antibody (Ab) due to its lower steric hindrance. In addition, the magnetic properties enabled rapid separation and purification during Ab immobilization, ultimately preserving its bioactivity. The Ab-MGLA/poly-SiNW-FET exhibited a linear dependence of relative response to the logarithmical concentration in a range between 19.5pgmL(-1) and 1.95µgmL(-1), with a limit of detection (LOD) of 6.7pgmL(-1). An additional washing step before measurement aimed at excluding the interfering biocomponents ensured the reliability of the assay. We conclude that our biosensor efficiently distinguishes mean values of urinary APOA2 protein concentrations between patients with bladder cancer (29-344ngmL(-1)) and those with hernia (0.425-9.47ngmL(-1)). Copyright © 2014 Elsevier B.V. All rights reserved.

  3. Hydrothermal Fabrication of Silver Nanowires-Silver Nanoparticles-Graphene Nanosheets Composites in Enhancing Electrical Conductive Performance of Electrically Conductive Adhesives

    Directory of Open Access Journals (Sweden)

    Hongru Ma

    2016-06-01

    Full Text Available Silver nanowires-silver nanoparticles-graphene nanosheets (AgNWs-AgNPs-GN hybrid nanomaterials were fabricated through a hydrothermal method by using glucose as a green reducing agent. The charge carriers of AgNWs-AgNPs-GN passed through defect regions in the GNs rapidly with the aid of the AgNW and AgNP building blocks, leading to high electrical conductivity of electrically conductive adhesives (ECA filled with AgNWs-AgNPs-GN. The morphologies of synthesized AgNWs-AgNPs-GN hybrid nanomaterials were characterized by field emission scanning electron microscope (FESEM, and high resolution transmission electron microscopy (HRTEM. X-ray diffraction (XRD and laser confocal micro-Raman spectroscopy were used to investigate the structure of AgNWs-AgNPs-GN. The resistance of cured ECAs was investigated by the four-probe method. The results indicated AgNWs-AgNPs-GN hybrid nanomaterials exhibited excellent electrical properties for decreasing the resistivity of electrically conductive adhesives (ECA. The resistivity of ECA was 3.01 × 10−4 Ω·cm when the content of the AgNWs-AgNPs-GN hybrid nanomaterial was 0.8 wt %.

  4. A randomized controlled 30 years follow up of three conventional resin composites in Class II restorations

    DEFF Research Database (Denmark)

    Pallesen, Ulla; van Dijken, Jan WV

    2015-01-01

    three (one set) as similar as possible Class II restorations of moderate size.After cavity preparation, the three cavities were chosen at random to be restored with twochemical-cured (P10, Miradapt) and one light-cured resin composite (P30). A chemical-curedenamel bonding agent was applied after etching...... of the enamel. The chemical-cured resincomposites were placed in bulk and the light-cured in increments. One operator placed 99restorations (33 sets). The restorations were evaluated with slightly modified USPHS crite-ria at baseline, 2, 3, 5, 10, 15, 20 and 30 years. Statistical analyses were performed by the......Kaplan–Meier, log-rank test and Cox regression analyses. Results. After 30 years, 5 participants with 15 restorations (15%) could not be evaluated duringthe whole evaluation. Seven participants were considered as caries risk and eight partici-pants as having active parafunctional habits. Postoperative sensitivity...

  5. Structural investigation of GaInP nanowires using X-ray diffraction

    DEFF Research Database (Denmark)

    Kriegner, D.; Persson, Johan Mikael; Etzelstorfer, T.

    2013-01-01

    In this work the structure of ternary GaxIn1−xP nanowires is investigated with respect to the chemical composition and homogeneity. The nanowires were grown by metal–organic vapor-phase epitaxy. For the investigation of ensemble fluctuations on several lateral length scales, X-ray diffraction...... gradients along the sample by recording diffraction patterns at different positions. In addition, compositional variations were found also within single nanowires in X-ray energy dispersive spectroscopy measurements....... reciprocal space maps have been analyzed. The data reveal a complicated varying materials composition across the sample and in the nanowires on the order of 20%. The use of modern synchrotron sources, where beam-sizes in the order of several 10μm are available, enables us to investigate compositional...

  6. The influence of thermal annealing on structure and oxidation of iron nanowires

    Directory of Open Access Journals (Sweden)

    Krajewski Marcin

    2015-03-01

    Full Text Available Raman spectroscopy as well as Mössbauer spectroscopy were applied in order to study the phase composition of iron nanowires and its changes, caused by annealing in a neutral atmosphere at several temperatures ranging from 200°C to 800°C. As-prepared nanowires were manufactured via a simple chemical reduction in an external magnetic field. Both experimental techniques proved formation of the surface layer covered by crystalline iron oxides, with phase composition dependent on the annealing temperature (Ta. At higher Ta, hematite was the dominant phase in the nanowires.

  7. Randomized clinical trial comparing a polypropylene with a poliglecaprone and polypropylene composite mesh for inguinal hernioplasty.

    Science.gov (United States)

    śmietański, M

    2008-12-01

    : The aim was to assess whether a partially absorbable monofilament mesh could influence postoperative pain and time to return to normal activity after Lichtenstein hernioplasty. : The study randomized patients undergoing inguinal hernia repair in 15 centres into two groups according to mesh type: lightweight (poliglecaprone-polypropylene composite) and heavyweight (polypropylene). A modified suture technique was used in the lightweight group. Follow-up on day 7 and at 3, 6 and 12 months evaluated the incidence of early and late complications, recurrence rate, quality of life, postoperative pain and return to physical activity. : A total of 600 patients were randomized and, after monitoring visits (leading to the exclusion of seven hospitals), 392 qualified for assessment. At 12 months, the recurrence rate did not differ (1.9 versus 0.6 per cent; P = 0.493). The lightweight group reported less pain on day 7 (55.2 versus 36.2 per cent; P health and physical activity according to Short Form 36 scores increased in both groups. : Use of partially absorbable mesh reduced postoperative pain in the short term. No difference in pain or recurrence rates were observed at 12 months. CCT-NAPN-17412 (http://www.controlled-trials.com) Published by John Wiley & Sons, Ltd. Copyright (c) 2008 British Journal of Surgery Society Ltd.

  8. Effects of protein intake and gender on body composition changes: a randomized clinical weight loss trial

    Directory of Open Access Journals (Sweden)

    Evans Ellen M

    2012-06-01

    Full Text Available Abstract Limited data on sex differences in body composition changes in response to higher protein diets (PRO compared to higher carbohydrate diets (CARB suggest that a PRO diet helps preserve lean mass (LM in women more so than in men. Objective To compare male and female body composition responses to weight loss diets differing in macronutrient content. Design Twelve month randomized clinical trial with 4mo of weight loss and 8mo weight maintenance. Subjects Overweight (N = 130; 58 male (M, 72 female (F; BMI = 32.5 ± 0.5 kg/m2 middle-aged subjects were randomized to energy-restricted (deficit ~500 kcal/d diets providing protein at 1.6 g.kg-1.d-1 (PRO or 0.8 g.kg-1.d-1 (CARB. LM and fat mass (FM were measured using dual X-ray absorptiometry. Body composition outcomes were tested in a repeated measures ANOVA controlling for sex, diet, time and their two- and three-way interactions at 0, 4, 8 and 12mo. Results When expressed as percent change from baseline, males and females lost similar amounts of weight at 12mo (M:-11.2 ± 7.1 %, F:-9.9 ± 6.0 %, as did diet groups (PRO:-10.7 ± 6.8 %, CARB:-10.1 ± 6.2 %, with no interaction of gender and diet. A similar pattern emerged for fat mass and lean mass, however percent body fat was significantly influenced by both gender (M:-18.0 ± 12.8 %, F:-7.3 ± 8.1 %, p  Conclusion PRO was more effective in reducing percent body fat vs. CARB over 12mo weight loss and maintenance. Men lost percent total body fat and trunk fat more effectively than women. No interactive effects of protein intake and gender are evident.

  9. Effects of active video games on body composition: a randomized controlled trial.

    Science.gov (United States)

    Maddison, Ralph; Foley, Louise; Ni Mhurchu, Cliona; Jiang, Yannan; Jull, Andrew; Prapavessis, Harry; Hohepa, Maea; Rodgers, Anthony

    2011-07-01

    Sedentary activities such as video gaming are independently associated with obesity. Active video games, in which players physically interact with images on screen, may help increase physical activity and improve body composition. The aim of this study was to evaluate the effect of active video games over a 6-mo period on weight, body composition, physical activity, and physical fitness. We conducted a 2-arm, parallel, randomized controlled trial in Auckland, New Zealand. A total of 322 overweight and obese children aged 10-14 y, who were current users of sedentary video games, were randomly assigned at a 1:1 ratio to receive either an active video game upgrade package (intervention, n = 160) or to have no change (control group, n = 162). The primary outcome was the change from baseline in body mass index (BMI; in kg/m(2)). Secondary outcomes were changes in percentage body fat, physical activity, cardiorespiratory fitness, video game play, and food snacking. At 24 wk, the treatment effect on BMI (-0.24; 95% CI: -0.44, -0.05; P = 0.02) favored the intervention group. The change (±SE) in BMI from baseline increased in the control group (0.34 ± 0.08) but remained the same in the intervention group (0.09 ± 0.08). There was also evidence of a reduction in body fat in the intervention group (-0.83%; 95% CI: -1.54%, -0.12%; P = 0.02). The change in daily time spent playing active video games at 24 wk increased (10.03 min; 95% CI: 6.26, 13.81 min; P time spent playing nonactive video games (-9.39 min; 95% CI: -19.38, 0.59 min; P = 0.06). An active video game intervention has a small but definite effect on BMI and body composition in overweight and obese children. This trial was registered in the Australian New Zealand Clinical Trials Registry at http://www.anzctr.org.au/ as ACTRN12607000632493.

  10. Field emission properties of single crystal chromium disilicide nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Valentin, L. A.; Carpena-Nunez, J.; Yang, D.; Fonseca, L. F. [Department of Physics, University of Puerto Rico, Rio Piedras Campus, P.O. Box 70377, San Juan, 00931 (Puerto Rico)

    2013-01-07

    The composition, crystal structure, and field emission properties of high-crystallinity chromium disilicide (CrSi{sub 2}) nanowires synthesized by a vapor deposition method have been studied. High resolution transmission electron microscopy, energy dispersive spectroscopy, and selected area electron diffraction studies confirm the single-crystalline structure and composition of the CrSi{sub 2} nanowires. Field emission measurements show that an emission current density of 0.1 {mu}A/cm{sup 2} was obtained at a turn-on electric field intensity of 2.80 V/{mu}m. The maximum emission current measured was 1.86 mA/cm{sup 2} at 3.6 V/{mu}m. The relation between the emission current density and the electric field obtained follows the Fowler-Nordheim equation, with an enhancement coefficient of 1140. The electrical conductivity of single nanowires was measured by using four-point-probe specialized microdevices at different temperatures, and the calculated values are close to those reported in previous studies for highly conductive single crystal bulk CrSi{sub 2}. The thermal tolerance of the nanowires was studied up to a temperature of 1100 Degree-Sign C. The stability of the field emission current, the I-E values, their thermal tolerance, and high electrical conductivity make CrSi{sub 2} nanowires a promising material for field emission applications.

  11. Field emission properties of single crystal chromium disilicide nanowires

    Science.gov (United States)

    Valentín, L. A.; Carpena-Nuñez, J.; Yang, D.; Fonseca, L. F.

    2013-01-01

    The composition, crystal structure, and field emission properties of high-crystallinity chromium disilicide (CrSi2) nanowires synthesized by a vapor deposition method have been studied. High resolution transmission electron microscopy, energy dispersive spectroscopy, and selected area electron diffraction studies confirm the single-crystalline structure and composition of the CrSi2 nanowires. Field emission measurements show that an emission current density of 0.1 μA/cm2 was obtained at a turn-on electric field intensity of 2.80 V/μm. The maximum emission current measured was 1.86 mA/cm2 at 3.6 V/μm. The relation between the emission current density and the electric field obtained follows the Fowler-Nordheim equation, with an enhancement coefficient of 1140. The electrical conductivity of single nanowires was measured by using four-point-probe specialized microdevices at different temperatures, and the calculated values are close to those reported in previous studies for highly conductive single crystal bulk CrSi2. The thermal tolerance of the nanowires was studied up to a temperature of 1100 °C. The stability of the field emission current, the I-E values, their thermal tolerance, and high electrical conductivity make CrSi2 nanowires a promising material for field emission applications.

  12. Aging of Organic Nanowires

    DEFF Research Database (Denmark)

    Balzer, Frank; Schiek, Manuela; Osadnik, Andreas

    2012-01-01

    conditions already expose substantial changes in sample morphology within hours. Clusters show Ostwald ripening, whereas nanowires reveal strong faceting and even fragmentation. All these aging effects are ascribed to the influence of water vapor. Decay curves (cluster number vs. time) for clusters...

  13. Magnetic and superconducting nanowires

    DEFF Research Database (Denmark)

    Piraux, L.; Encinas, A.; Vila, L.

    2005-01-01

    This article is focused on the use of electrodeposition and of various nanoporous templates for the fabrication of metallic nanowires made from single metals (Ni, Co, Pb, Sn), alloys (NiFe, CoFe, CoPt), and multilayers (Co/Cu, NiFe/Cu). An overview is given of our recent studies performed on both...... discussed....

  14. Wrapping Aligned Carbon Nanotube Composite Sheets around Vanadium Nitride Nanowire Arrays for Asymmetric Coaxial Fiber-Shaped Supercapacitors with Ultrahigh Energy Density.

    Science.gov (United States)

    Zhang, Qichong; Wang, Xiaona; Pan, Zhenghui; Sun, Juan; Zhao, Jingxin; Zhang, Jun; Zhang, Cuixia; Tang, Lei; Luo, Jie; Song, Bin; Zhang, Zengxing; Lu, Weibang; Li, Qingwen; Zhang, Yuegang; Yao, Yagang

    2017-04-12

    The emergence of fiber-shaped supercapacitors (FSSs) has led to a revolution in portable and wearable electronic devices. However, obtaining high energy density FSSs for practical applications is still a key challenge. This article exhibits a facile and effective approach to directly grow well-aligned three-dimensional vanadium nitride (VN) nanowire arrays (NWAs) on carbon nanotube (CNT) fiber with an ultrahigh specific capacitance of 715 mF/cm(2) in a three-electrode system. Benefiting from their intriguing structural features, we successfully fabricated a prototype asymmetric coaxial FSS (ACFSS) with a maximum operating voltage of 1.8 V. From core to shell, this ACFSS consists of a CNT fiber core coated with VN@C NWAs as the negative electrode, Na2SO4 poly(vinyl alcohol) (PVA) as the solid electrolyte, and MnO2/conducting polymer/CNT sheets as the positive electrode. The novel coaxial architecture not only fully enables utilization of the effective surface area and decreases the contact resistance between the two electrodes but also, more importantly, provides a short pathway for the ultrafast transport of axial electrons and ions. The electrochemical results show that the optimized ACFSS exhibits a remarkable specific capacitance of 213.5 mF/cm(2) and an exceptional energy density of 96.07 μWh/cm(2), the highest areal capacitance and areal energy density yet reported in FSSs. Furthermore, the device possesses excellent flexibility in that its capacitance retention reaches 96.8% after bending 5000 times, which further allows it to be woven into flexible electronic clothes with conventional weaving techniques. Therefore, the asymmetric coaxial architectural design allows new opportunities to fabricate high-performance flexible FSSs for future portable and wearable electronic devices.

  15. Flexible transparent conducting hybrid film using a surface-embedded copper nanowire network: a highly oxidation-resistant copper nanowire electrode for flexible optoelectronics.

    Science.gov (United States)

    Im, Hyeon-Gyun; Jung, Soo-Ho; Jin, Jungho; Lee, Dasom; Lee, Jaemin; Lee, Daewon; Lee, Jung-Yong; Kim, Il-Doo; Bae, Byeong-Soo

    2014-10-28

    We report a flexible high-performance conducting film using an embedded copper nanowire transparent conducting electrode; this material can be used as a transparent electrode platform for typical flexible optoelectronic devices. The monolithic composite structure of our transparent conducting film enables simultaneously an outstanding oxidation stability of the copper nanowire network (14 d at 80 °C), an exceptionally smooth surface topography (R(rms) < 2 nm), and an excellent opto-electrical performances (Rsh = 25 Ω sq(-1) and T = 82%). A flexible organic light emitting diode device is fabricated on the transparent conducting film to demonstrate its potential as a flexible copper nanowire electrode platform.

  16. Endface reflectivities of optical nanowires.

    Science.gov (United States)

    Wang, Shanshan; Hu, Zhifang; Yu, Huakang; Fang, Wei; Qiu, Min; Tong, Limin

    2009-06-22

    Endface reflectivities (ERs) of optical nanowires are investigated using three-dimensional finite-difference time-domain simulations. Typical ERs of both free-standing and substrate-supported silica, tellurite, PMMA and semiconductor nanowires or nanofibers are obtained. Unlike in conventional waveguides such as optical fibers, ERs of nanowires are usually considerably lower when operated in single mode. Dependences of ER on the diameter and the refractive index of the nanowire, and the wavelength of the guided light are also investigated. These results are helpful for estimating and understanding ERs in optical nanowires with diameters close to or smaller than the wavelengths of the light, and may offer valuable references for practical applications such as nanowire or nanofiber-based resonators and lasers.

  17. Preparation, formation mechanism and photoelectric properties of well-aligned CuSbS{sub 2} nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Liang, E-mail: sliang@ustc.edu.cn; Li, Yanan; Wu, Chunyan; Dai, Yumei

    2015-11-05

    Well-aligned CuSbS{sub 2} single crystalline nanowires array has been prepared via a solvothermal synthetic route. The as-prepared CuSbS{sub 2} nanowires are uniform with a growth direction perpendicular to the (101) planes. Porous anodic aluminum oxide was used as a morphology directing template and was found to play a significant role for the formation of single crystalline CuSbS{sub 2} nanowires. Thin film prepared from CuSbS{sub 2} nanowires displayed an obvious photoelectric response, suggesting its potential application as a low cost solar absorber material. A possible formation mechanism for the single crystalline CuSbS{sub 2} nanowires array is proposed. The structure, morphology, composition and optical absorption properties of the as-prepared CuSbS{sub 2} nanowires were characterized using X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectrometry and UV–Vis spectrophotometry. - Highlights: • Uniform CuSbS{sub 2} single crystalline nanowires array has been synthesized. • The bandgap of the as-prepared CuSbS{sub 2} nanowires is 1.45 eV. • CuSbS{sub 2} nanowires displayed an obvious photoelectric response. • The growth direction of CuSbS{sub 2} nanowires is perpendicular to (101) planes.

  18. Magnetic and structural properties of Fe-Co nanowires fabricated by matrix synthesis in the pores of track membranes

    Science.gov (United States)

    Frolov, K. V.; Zagorskii, D. L.; Lyubutin, I. S.; Chuev, M. A.; Perunov, I. V.; Bedin, S. A.; Lomov, A. A.; Artemov, V. V.; Sulyanov, S. N.

    2017-03-01

    Fe1- x Co x nanowires are obtained by electrochemical deposition into the pores of track-etched membranes. The characteristics of the growth process that allow controlling the length and aspect ratio of the nanowires are established. The elemental composition and magnetic properties of the nanowires depend on the diameter of the track-etched pores, which varies from 30 to 200 nm, and the electrochemical potential U (650-850 mV), which determines the nanowire growth rate. According to the results of elemental analysis and the Mössbauer spectroscopy data, the Co content in Fe1- x Co x lies in the range of x=0.20-0.25. It is found that the orientation of the magnetic moment of Fe-Co nanoparticles in the wires depends both on the track pore size d and on the nanowire growth rate. Thus, the magnetic moments in nanowires grown in 50-nm-diameter pores are oriented within 0°-40° with respect to the nanowire axis. The magnetic properties of the nanowires are explained in the framework of a theoretical model describing the magnetic dynamics of nanocomposites, which was extended to include the relaxation of the magnetization vector and to take into account interaction between the particles. The key physical parameters important for the technological applications of the nanowires are determined, their dependence on the nanowire growth conditions is traced, and the possibility of controlling them is established.

  19. Influence of substrate orientation on the structural quality of GaAs nanowires in molecular beam epitaxy

    Science.gov (United States)

    Zhang, Zhi; Shi, Sui-Xing; Chen, Ping-Ping; Lu, Wei; Zou, Jin

    2015-01-01

    In this study, the effect of substrate orientation on the structural quality of Au-catalyzed epitaxial GaAs nanowires grown by a molecular beam epitaxy reactor has been investigated. It was found that the substrate orientations can be used to manipulate the nanowire catalyst composition and the catalyst surface energy and, therefore, to alter the structural quality of GaAs nanowires grown on different substrates. Defect-free wurtzite-structured GaAs nanowires grown on the GaAs (110) substrate have been achieved under our growth conditions.

  20. Synthesis, fabrication and characterization of Ge/Si axial nanowire heterostructure tunnel FETs

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-01-01

    Axial Ge/Si heterostructure nanowires allow energy band-edge engineering along the axis of the nanowire, which is the charge transport direction, and the realization of asymmetric devices for novel device architectures. This work reports on two advances in the area of heterostructure nanowires and tunnel FETs: (i) the realization of 100% compositionally modulated Si/Ge axial heterostructure nanowires with lengths suitable for device fabrication and (ii) the design and implementation of Schottky barrier tunnel FETs on these nanowires for high-on currents and suppressed ambipolar behavior. Initial prototype devices resulted in a current drive in excess of 100 {micro}A/{micro}m (I/{pi}D) and 10{sup 5} I{sub on}/I{sub off} ratios. These results demonstrate the potential of such asymmetric heterostructures (both in the semiconductor channel and metal-semiconductor barrier heights) for low-power and high performance electronics.

  1. Fabrication of Conjugated Polymer Nanowires by Edge Lithography

    NARCIS (Netherlands)

    Lipomi, Darren J.; Chiechi, Ryan C.; Dickey, Michael D.; Whitesides, George M.

    2008-01-01

    This paper describes the fabrication of conjugated polymer nanowires by a three stage process: (i) spin-coating a composite film comprising alternating layers of a conjugated polymer and a sacrificial material, (ii) embedding the film in an epoxy matrix and sectioning it with an ultramicrotome

  2. Raloxifene and body composition and muscle strength in postmenopausal women: a randomized, double-blind, placebo-controlled trial.

    NARCIS (Netherlands)

    Jacobsen, D.E.; Samson, M.M.; Emmelot-Vonk, M.H.; Verhaar, H.J.

    2010-01-01

    OBJECTIVE: To compare the effects of raloxifene and placebo on body composition and muscle strength. DESIGN: Randomized, double-blind, placebo-controlled trial involving 198 healthy women aged 70 years or older conducted between July 2003 and January 2008 at the University Medical Centre, Utrecht,

  3. Optical Spectroscopy of Single Nanowires

    OpenAIRE

    Trägårdh, Johanna

    2008-01-01

    This thesis describes optical spectroscopy on III-V semiconductor nanowires. The nanowires were grown by metal-organic vapor phase epitaxy (MOVPE) and chemical beam epitaxy (CBE). Photoluminescence and photocurrent spectroscopy are used as tools to investigate issues such as the size of the band gap, the effects of surface states, and the charge carrier transport in core-shell nanowires. The band gap of InAs1-xPx nanowires with wurtzite crystal structure is measured as a function of ...

  4. Fabrication of single-crystal tin nanowires by hydraulic pressure injection

    Science.gov (United States)

    Chen, Chien-Chon; Bisrat, Y.; Luo, Z. P.; Schaak, R. E.; Chao, C.-G.; Lagoudas, D. C.

    2006-01-01

    Tin (Sn) nanowires, with 15 and 60 nm average diameter and up to 10 µm in length, were fabricated by an injection process using a hydraulic pressure method. The Sn melt was injected into an anodic aluminium oxide (AAO) template and solidified to form nanowires. By back etching the aluminium substrate and barrier layer, the nanowire array ends were partially exposed from the bottom face of the AAO template. The filling ratio of nanowires inside and through the thickness of the AAO template was found to be close to 100%. The nanowires were also found to be dense and continuous with uniform diameter throughout their length. Transmission electron microscope (TEM) and x-ray diffraction (XRD) studies on the 60 nm diameter nanowires revealed that the nanowires were single crystals with body-centred-tetragonal (bct) structure predominantly growing along the [100] direction. The current method of synthesizing nanowires is straightforward, low-cost and suitable for low-melting point (<650 °C) metals including low-melting point alloys with stoichiometric composition.

  5. Nanowire Field-Effect Transistors : Sensing Simplicity?

    NARCIS (Netherlands)

    Mescher, M.

    2014-01-01

    Silicon nanowires are structures made from silicon with at least one spatial dimension in the nanometer regime (1-100 nm). From these nanowires, silicon nanowire field-effect transistors can be constructed. Since their introduction in 2001 silicon nanowire field-effect transistors have been studied

  6. Conductive Au nanowires regulated by silk fibroin nanofibers

    Science.gov (United States)

    Dong, Bo-Ju; Lu, Qiang

    2014-03-01

    Conductive Au-biopolymer composites have promising applications in tissue engineering such as nerve tissue regeneration. In this study, silk fibroin nanofibers were formed in aqueous solution by regulating silk self-assembly process and then used as template for Au nanowire fabrication. We performed the synthesis of Au seeds by repeating the seeding cycles for several times in order to increase the density of Au seeds on the nanofibers. After electroless plating, densely decorated Au seeds grew into irregularly shaped particles following silk nanofiber to fill the gaps between particles and finally form uniform continuous nanowires. The conductive property of the Au-silk fibroin nanowires was studied with current-voltage ( I-V) measurement. A typical ohmic behavior was observed, which highlighted their potential applications in nerve tissue regeneration.

  7. Silicon nanowire transistors

    CERN Document Server

    Bindal, Ahmet

    2016-01-01

    This book describes the n and p-channel Silicon Nanowire Transistor (SNT) designs with single and dual-work functions, emphasizing low static and dynamic power consumption. The authors describe a process flow for fabrication and generate SPICE models for building various digital and analog circuits. These include an SRAM, a baseband spread spectrum transmitter, a neuron cell and a Field Programmable Gate Array (FPGA) platform in the digital domain, as well as high bandwidth single-stage and operational amplifiers, RF communication circuits in the analog domain, in order to show this technology’s true potential for the next generation VLSI. Describes Silicon Nanowire (SNW) Transistors, as vertically constructed MOS n and p-channel transistors, with low static and dynamic power consumption and small layout footprint; Targets System-on-Chip (SoC) design, supporting very high transistor count (ULSI), minimal power consumption requiring inexpensive substrates for packaging; Enables fabrication of different types...

  8. Effect of Silicon Nanowire on Crystalline Silicon Solar Cell Characteristics

    Directory of Open Access Journals (Sweden)

    Zahra Ostadmahmoodi Do

    2016-06-01

    Full Text Available Nanowires (NWs are recently used in several sensor or actuator devices to improve their ordered characteristics. Silicon nanowire (Si NW is one of the most attractive one-dimensional nanostructures semiconductors because of its unique electrical and optical properties. In this paper, silicon nanowire (Si NW, is synthesized and characterized for application in photovoltaic device. Si NWs are prepared using wet chemical etching method which is commonly used as a simple and low cost method for producing nanowires of the same substrate material. The process conditions are adjusted to find the best quality of Si NWs. Morphology of Si NWs is studied using a field emission scanning electron microscopic technique. An energy dispersive X-Ray analyzer is also used to provide elemental identification and quantitative compositional information. Subsequently, Schottky type solar cell samples are fabricated on Si and Si NWs using ITO and Ag contacts. The junction properties are calculated using I-V curves in dark condition and the solar cell I-V characteristics are obtained under incident of the standardized light of AM1.5. The results for the two mentioned Schottky solar cell samples are compared and discussed. An improvement in short circuit current and efficiency of Schottky solar cell is found when Si nanowires are employed.

  9. Three-dimensional nanoelectrode by metal nanowire nonwoven clothes.

    Science.gov (United States)

    Kawamori, Makoto; Asai, Takahiro; Shirai, Yoshimasa; Yagi, Shunsuke; Oishi, Masatsugu; Ichitsubo, Tetsu; Matsubara, Eiichiro

    2014-01-01

    Metal nanowire nonwoven cloth (MNNC) is a metal sheet that has resulted from intertwined metal nanowires 100 nm in diameter with several dozen micrometers of length. Thus, it is a new metallic material having both a flexibility of the metal sheet and a large specific surface area of the nanowires. As an application that utilizes these properties, we propose a high-cyclability electrode for Li storage batteries, in which an active material is deposited or coated on MNNC. The proposed electrode can work without any binders, conductive additives, and current collectors, which might largely improve a practical gravimetric energy density. Huge electrode surfaces provide efficient ion/electron transports, and sufficient interspaces between the respective nanowires accommodate large volume expansions of the active material. To demonstrate these advantages, we have fabricated a NiO-covered nickel nanowire nonwoven cloth (NNNC) by electroless deposition under a magnetic field and annealing in air. The adequately annealed NNNC was shown to be an excellent conversion-type electrode that exhibits a quite high cyclability, 500 mAh/g at 1 C after 300 cycles, compared to that of a composite electrode consisting of NiO nanoparticles. Thus, the present design concept will contribute to a game-changing technology in future lithium ion battery (LIB) electrodes.

  10. Optical and morphological properties of graphene sheets decorated with ZnO nanowires via polyol enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Vinay, E-mail: winn201@gmail.com; Rajaura, Rajveer Singh, E-mail: winn201@gmail.com [Centre for Converging Technologies, University of Rajasthan, Jaipur - 302004 (India); Sharma, Preetam K.; Srivastava, Subodh; Vijay, Y. K. [Department of Physics, Thin Film and Membrane Science Lab., University of Rajasthan, Jaipur - 302004 (India); Sharma, S. S. [Department of Physics, Govt. Women Engineering College, Ajmer- 305002 (India)

    2014-04-24

    Graphene-ZnO nanocomposites have proven to be very useful materials for photovoltaic and sensor applications. Here, we report a facile, one-step in situ polymerization method for synthesis of graphene sheets randomly decorated with zinc oxide nanowires using ethylene glycol as solvent. We have used hydrothermal treatment for growth of ZnO nanowires. UV-visible spectra peak shifting around 288nm and 307 nm shows the presence of ZnO on graphene structure. Photoluminiscence spectra (PL) in 400nm-500nm region exhibits the luminescence quenching effect. Scanning electron microscopy (SEM) image confirms the growth of ZnO nanowires on graphene sheets.

  11. Junctions in Axial III-V Heterostructure Nanowires Obtained via an Interchange of Group III Elements

    DEFF Research Database (Denmark)

    Krogstrup, Peter; Yamasaki, Jun; Sørensen, Claus B.

    2009-01-01

    We present an investigation of the morphology and composition of novel types of axial nanowire heterostructures where GaxIn1-xAs is used as barrier material in InAs nanowires. Using aberration-corrected scanning transmission electron microscopy and energy dispersive X-ray analysis we demonstrate...... that it is possible to grow junctions by changing the group III elements, and we find that a substantial fraction of Ga can be incorporated in axial InAs/GaxIn1-xAs/InAs, retaining straight nanowire configurations. We explain how the adatoms are transferred to the incorporation site at the growth interface via two...

  12. Realization of single and double axial InSb-GaSb heterostructure nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Ghalamestani, Sepideh Gorji [Solid State Physics, Lund University, Lund (Sweden); Ek, Martin [Center for Analysis and Synthesis, Lund University, Lund (Sweden); Dick, Kimberly A. [Solid State Physics, Lund University, Lund (Sweden); Center for Analysis and Synthesis, Lund University, Lund (Sweden)

    2014-03-15

    Heteroepitaxial growth of III-Sb nanowires allows for the formation of various interesting complex structures and enables the combination of their remarkable properties. In this Letter, we investigate the heteroepitaxial growth of Au-seeded InSb and GaSb nanowires using metalorganic vapor phase epitaxy. We demonstrate successful single and double axial InSb-GaSb heterostructures in both directions. The formation properties of the grown nanowires including the compositional change of the particle and the interface sharpness are further discussed. In addition, the decomposition of InSb and GaSb segments and their side facet evolution are explained. XEDS compositional line scans overlaid on STEM HAADF image along the InSb-GaSb-InSb nanowire indicating sharp interface from GaSb to InSb segment and graded interface in the opposite direction. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Sleep quality and body composition variations in obese male adults after 14 weeks of yoga intervention: A randomized controlled trial

    OpenAIRE

    P B Rshikesan; Pailoor Subramanya; Deepeshwar Singh

    2017-01-01

    Background: Obesity is a big challenge all over the world. It is associated with many noncommunicable diseases. Yoga known to be add-on treatment may be effective for obesity control. Aim: To assess the effect of integrated approach of yoga therapy (IAYT) for body composition and quality of sleep in adult obese male. Subjects and Methods: A randomized controlled trial was conducted for 14 weeks on obese male of urban setting. Eighty individuals were randomly divided into two groups, i.e., yog...

  14. The bismuth triiodide-assisted horizontal growth of CdS nanowires and CdO-CdS necklace-like nanowires.

    Science.gov (United States)

    Li, Haiyan; Chen, Yanxue; Jiao, Jun

    2009-06-03

    Bismuth triiodide, a compound with a layered structure, is utilized to confine the growth of nanowires along the substrate surface in a low-temperature solution-phase reaction. The confinement is attributed to the electrostatic force between the bismuth triiodide sheet and the deposited Cd2+ cations that caused the CdS nanowires to grow within the surface of the bismuth triiodide sheet. As the nanowires grew longer, they began to form a high-yield woven network. Additionally, use of the same reaction system but with a minimized amount of sulfur led to the growth of CdO-CdS necklace-like nanowires. The optical and electric measurements suggest that the photoluminescence and electron field emission properties of these nanostructures are highly affected by their morphologies and chemical compositions.

  15. A micromechanical model of tension-softening and bridging toughening of short random fiber reinforced brittle matrix composites

    Science.gov (United States)

    Li, Victor C.; Wang, Youjiang; Backer, Stanley

    A MICROMECHANICAL model has been formulated for the post-cracking behavior of a brittle matrix composite reinforced with randomly distributed short fibers. This model incorporates the mechanics of pull-out of fibers which are inclined at an angle to the matrix crack plane and which undergo slip-weakening or slip-hardening during the pull-out process. In addition, the random location and orientation of fibers are accounted for. Comparisons of model predictions of post-cracking tension-softening behavior with experimental data appear to support the validity of the model. The model is used to examine the effects of fiber length, snubbing friction coefficient and interfacial bond behavior on composite post-cracking tensile properties. The scaling of the bridging fracture toughening with material parameters is discussed.

  16. Numerical study of electrical transport in co-percolative metal nanowire-graphene thin-films

    Science.gov (United States)

    Gupta, Man Prakash; Kumar, Satish

    2016-11-01

    Nanowires-dispersed polycrystalline graphene has been recently explored as a transparent conducting material for applications such as solar cells, displays, and touch-screens. Metal nanowires and polycrystalline graphene play synergetic roles during the charge transport in the material by compensating for each other's limitations. In the present work, we develop and employ an extensive computational framework to study the essential characteristics of the charge transport not only on an aggregate basis but also on individual constituents' levels in these types of composite thin-films. The method allows the detailed visualization of the percolative current pathways in the material and provides the direct evidence of current crowding in the 1-D nanowires and 2-D polygraphene sheet. The framework is used to study the effects of several important governing parameters such as length, density and orientation of the nanowires, grain density in polygraphene, grain boundary resistance, and the contact resistance between nanowires and graphene. We also present and validate an effective medium theory based generalized analytical model for the composite. The analytical model is in agreement with the simulations, and it successfully predicts the overall conductance as a function of several parameters including the nanowire network density and orientation and graphene grain boundaries. Our findings suggest that the longer nanowires (compared to grain size) with low angle orientation (60 × intra-grain resistance), the overall conductance becomes nearly independent of grain boundary resistance due to nanowires. The developed model can be applied to study other emerging transparent conducting materials such as nanowires, nanotubes, polygraphene, graphene oxide, and their hybrid nanostructures.

  17. Silicon Nanoparticle/Nanowire and Graphite Composite Anode with Increased Binder for Lithium-Ion Coin Cells Aimed at High Energy Density Battery Applications

    Science.gov (United States)

    Qureshi, Muhammad Ali

    Silicon and graphite composite anode materials were prepared for a lithium ion half-cell with lithium metal as the reference electrode. All silicon/graphite composite anodes were prepared in the lab with mixing of slurry using ball milling technique. Battery grade copper foil was used as the current collector for the anode. The anode was coated using the doctor blade technique with thickness of 100μm and further calendared to provide higher energy densities for active material per cubic volume. The ratio of binder used was significantly higher than previously tested to show silicon material takes longer to detach from current collector with increased cycle life. Galvanostatic cycling show lithiation and de-lithiation of silicon anode with respect to lithium metal. Impedance measurements were taken for coin cells prior to cycle life tests. Silicon anode half-cell was charged/discharged for many cycles showing improved cycle life with great capacity retention. Charts show silicon expansion of material after cycle life however due to increased amount of binder material less silicon separates from the copper current collector initially. The coin cells made provide reproducible results which can be used for practical applications and have the ability for large volume production of high energy Li-ion batteries.

  18. Randomized clinical trial of indirect resin composite and ceramic veneers: up to 3-year follow-up.

    Science.gov (United States)

    Gresnigt, Marco M; Kalk, Warner; Ozcan, Mutlu

    2013-04-01

    This randomized controlled split-mouth clinical trial evaluated the short-term survival rate of indirect resin composite and ceramic laminate veneers. A total of 10 patients (mean age: 48.6 years) received 46 indirect resin composite (Estenia; n = 23) and ceramic laminate veneers (IPS Empress Esthetic; n = 23) on the maxillary anterior teeth. Veneer preparations with incisal overlap were performed and existing resin composite restorations of good quality were not removed but conditioned using silica coating (CoJet) and silanization (ESPE-Sil). Enamel and dentin were etched and rinsed; adhesive resin (ExciTE) was then applied. After cementation (Variolink Veneer), restorations were evaluated at baseline and thereafter every 6 months for up to 3 years using modified USPHS criteria. Seventeen laminate veneers were bonded onto intact teeth and 29 on teeth having existing resin composite restorations. In total, 3 failures were observed in the form of debonding (n = 1) and fracture (n = 2) in the group of resin composite laminate veneers. No significant difference was observed between the survival rates of composite and ceramic laminate veneers (Estenia: 87%, IPS Empress Esthetic: 100%; p > 0.05). The overall survival rate was 93.5% (Kaplan-Meier). Of the 43 laminate veneers, minor voids and defects were observed in 6 of the composite and 3 of the ceramic veneers. Slight staining at the margins (n = 3) and slightly rough surfaces were more frequently observed for the resin composite laminate veneers (n = 18) up to the final recall. Early findings of this clinical trial on two veneer materials showed statistically similar survival rates. Surface quality changes were more frequent in the composite veneer material.

  19. Multi-surface composite vs stainless steel crown restorations after mineral trioxide aggregate pulpotomy: a randomized controlled trial.

    Science.gov (United States)

    Hutcheson, Candice; Seale, N Sue; McWhorter, Alton; Kerins, Carolyn; Wright, John

    2012-01-01

    Parents increasingly request esthetic restorations for their children's teeth. This split mouth, randomized controlled trial compared primary molars treated with white MTA pulpotomies and restored with either multi-surface composites (MSC) or stainless steel crowns (SSC). Forty matched, contra-lateral pairs of molars received MTA pulpotomies and were randomly assigned to MSC or SSC restorations and evaluated clinically and radiographically at 6 and 12 months. Two calibrated, blinded examiners evaluated and scored radiographs. Thirty-seven matched pairs were evaluated at 6 months, and 31 were available at 12 months. All teeth in both groups were radiographically and clinically successful at 6 and 12 months. Dentin bridge formation was noted in 20% of the primary molars by 12 months. Although not significant, the composite group exhibited fewer intact clinical margins than the SSC group. The vast majority (94%) of teeth restored with composite displayed gray discoloration at follow-up exams, which did not appear to affect the quality of the restoration and is believed to be associated with the white MTA. The white MTA pulpotomies succeeded over 12 months regardless of the restoration; however, the teeth restored with composite were not as durable nor considered an esthetic alternative to the SSC.

  20. One Year Clinical Evaluation of a Low Shrinkage Composite Compared with a Packable Composite Resin: A Randomized Clinical Trial

    Directory of Open Access Journals (Sweden)

    Razieh Hoseinifar

    2017-08-01

    Full Text Available Objectives: The aim of this study was to evaluate the clinical performance of a packable and a low shrinkage methacrylate-based composite after one year.Materials and Methods: In this clinical trial, 50 class I or II restorations were placed in 25 patients. Each patient received two restorations. The tested materials were: (I Filtek P60 + Single Bond 2 and (II Kalore GC + Single Bond 2. The restorations were evaluated by two independent examiners after one week (baseline, six months and one year according to the modified United States Public Health Service (USPHS criteria. The evaluated parameters included color match, marginal adaptation, anatomical form, retention, surface texture, postoperative sensitivity, marginal staining and secondary caries. Data were then analyzed using Friedman and conditional (matched logistic regression tests at P<0.05 level of significance. Results: P60 and Kalore performed similarly at six months and one year (P>0.05. When each composite resin was evaluated independently at baseline and after one year, no statistically significant differences were found except for marginal adaptation (P60 where four restorations were rated Bravo (clinically acceptable. In 8% of restorations, patients expressed postoperative sensitivity.Conclusions: Kalore GC and Filtek P60 showed acceptance clinical performance after one year of service.Keywords: Composite Resins; Dental Marginal Adaptation; Patients

  1. Superconductivity in nanowires

    CERN Document Server

    Bezryadin, Alexey

    2012-01-01

    The importance and actuality of nanotechnology is unabated and will be for years to come. A main challenge is to understand the various properties of certain nanostructures, and how to generate structures with specific properties for use in actual applications in Electrical Engineering and Medicine.One of the most important structures are nanowires, in particular superconducting ones. They are highly promising for future electronics, transporting current without resistance and at scales of a few nanometers. To fabricate wires to certain defined standards however, is a major challenge, and so i

  2. Radiation Stability of Metal Nanowires

    Science.gov (United States)

    Bedin, S. A.; Makhin'ko, F. F.; Ovchinnikov, V. V.; Gerasimenko, N. N.; Zagorskiy, D. L.

    2017-01-01

    The aim of this work is to investigate the radiation stability of pure nickel and iron- nickel Fe0.56Ni0.44 alloy nanowires fabricated by matrix synthesis using polymer track membranes and Ar+ and Xe+ (E = 20 keV, j = 300 μA/cm2) beam irradiation. The dependence of the stability of nanowires on their diameter, fluence, and type of implanted ions is investigated. The assumption that the thermalized regions of dense cascades of atomic displacements (thermal spikes) play an important role in the nanowire structure change is made. These regions are nanosized zones of explosive energy release and heated to several thousands of degrees.

  3. InSb heterostructure nanowires: MOVPE growth under extreme lattice mismatch.

    Science.gov (United States)

    Caroff, Philippe; Messing, Maria E; Mattias Borg, B; Dick, Kimberly A; Deppert, Knut; Wernersson, Lars-Erik

    2009-12-09

    We demonstrate the growth of InSb-based nanowire heterostructures by metalorganic vapour phase epitaxy and use it to integrate InSb on extremely lattice-mismatched III-V nanowire templates made of InAs, InP, and GaAs. Influence of temperature, V/III ratio, and diameter are investigated in order to investigate the growth rate and morphology. The range of growth temperatures used for InSb nanowire growth is very similar to that used for planar growth due to the nature of the precursor decomposition. This makes optimization of growth parameters very important, and more difficult than for most other nanowire III-V materials. Analysis of the InSb nanowire epitaxial quality when grown on InAs, InP, and GaAs, along with InSb segment and particle compositions are reported. This successful direct integration of InSb nanowires, on nanowire templates with unprecedented strain levels show great promise for fabrication of vertical InSb devices.

  4. Quantitative magnetometry analysis and structural characterization of multisegmented cobalt–nickel nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Cantu-Valle, Jesus [Department of Physics and Astronomy, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 (United States); Díaz Barriga-Castro, Enrique [Centro de Investigación de Ciencias Físico Matemáticas/Facultad de Ciencias Físico Matemáticas, Universidad Autónoma de Nuevo León, Pedro de Alba s/n, San Nicolás de Los Garza, Nuevo León 66450 (Mexico); Vega, Víctor; García, Javier [Departamento de Física, Universidad de Oviedo, Calvo Sotelo s/n, Oviedo 33007 (Spain); Mendoza-Reséndez, Raquel [Facultad de Ingeniería Mecánica y Eléctrica. Universidad Autónoma de Nuevo León, Pedro de Alba s/n, San Nicolás de Los Garza, Nuevo León 66450 (Mexico); Luna, Carlos [Centro de Investigación de Ciencias Físico Matemáticas/Facultad de Ciencias Físico Matemáticas, Universidad Autónoma de Nuevo León, Pedro de Alba s/n, San Nicolás de Los Garza, Nuevo León 66450 (Mexico); Manuel Prida, Víctor [Departamento de Física, Universidad de Oviedo, Calvo Sotelo s/n, Oviedo 33007 (Spain); and others

    2015-04-01

    Understanding and measuring the magnetic properties of an individual nanowire and their relationship with crystalline structure and geometry are of scientific and technological great interest. In this work, we report the localized study of the magnetic flux distribution and the undisturbed magnetization of a single ferromagnetic nanowire that poses a bar-code like structure using off-axis electron holography (EH) under Lorentz conditions. The nanowires were grown by template-assisted electrodeposition, using AAO templates. Electron holography allows the visualization of the magnetic flux distribution within and surroundings as well as its quantification. The magnetic analysis performed at individual nanowires was correlated with the chemical composition and crystalline orientation of the nanowires. - Highlights: • The structure-magnetic property relationship of CoNi nanowires is determined. • Off axis electron holography for the magnetic nanowires is used for the analysis. • The magnetization is quantitatively obtained from the retrieved phase images. • These results lead to a better comprehension of the magneto-crystalline phenomena.

  5. Synthesis and Characterization of ZnO/ZnS Core/Shell Nanowires

    Directory of Open Access Journals (Sweden)

    Taher Ghrib

    2014-01-01

    Full Text Available ZnO nanowires of approximately 3 µm length and 200 nm diameter are prepared and implanted vertically on substrate glass which is coated with thin layer of ITO which is too covered with bulk ZnO thin layer via electrodeposition process by cyclic voltammetry-chronoamperometry and with a chemical process that is described later; we have synthesized a ZnS nanolayer. ZnO/ZnS core/shell nanowires are formed by ZnO nanowires core surrounded by a very thin layer of porous ZnS shell principally constituted with a crystal which is about 15–20 nm in diameter. In the method, ZnS nanoparticles were prepared by reaction of ZnO nanowires with Na2S in aqueous solution at low temperature and also we have discussed the growth mechanism of ZnO/ZnS nanowires. The morphology, structure, and composition of the obtained nanostructures were obtained by using X-ray diffraction (XRD, scanning electron microscopy (SEM, transmission electron microscopy (TEM, and X-ray photoelectron spectroscopy (XPS. For the structure, SEM and XRD measurements indicated that the as-grown ZnO nanowires microscale was of hexagonal wurtzite phase with a high crystalline quality, and TEM shows that the ZnS is uniformly distributed on the surface of the ZnO nanowires.

  6. Structural characterization of Fe−Pd nanowires grown by electrodeposition using an acid electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Domenichini, P. [Instituto Balseiro, Universidad Nacional de Cuyo, Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina); Condó, A.M. [Instituto Balseiro, Universidad Nacional de Cuyo, Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina); Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina); Haberkorn, N., E-mail: nhaberk@cab.cnea.gov.ar [Instituto Balseiro, Universidad Nacional de Cuyo, Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina); Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina)

    2016-07-01

    Fe{sub 70}Pd{sub 30} nanostructures have potential application in actuators due to their conventional and magnetic shape memory. Here, we report the microstructure of electrodeposition grown Fe−Pd nanowires in which the process was confined to polycarbonate membranes with a nominal pore diameter of 200 nm. We used an acid electrolyte (pH ≈ 5) in which the solution was stabilized with sulfosalicylic acid. The average chemical concentration of the nanowires can be systematically shifted from rich palladium to rich iron by changing the growth potential. The study of the microstructure by transmission electron microscopy indicates high chemical inhomogeneities due to phase coexistence between rich palladium regions (with FCC structure) and rich iron regions. The latter present a combination of BCC and amorphous phases. The average chemical composition of the nanowires can be better adjusted by using a low frequency square wave voltage excitation (alternating rich Pd and rich Fe regions). However, independently of the growth process, the nanowires morphology collapses after thermal annealing. This could be ascribed to fragile grain boundaries due to the presence of amorphous hydroxides and chemical impurities produced during the electrochemical process. - Highlights: • Synthesis of Fe−Pd nanowires by electrodeposition is reported. • Structural characterization of the nanowires by transmission electron microscopy. • The synthesis of nanowires with austenitic phase is limited by fragile grain boundaries.

  7. Fracture resistance of short, randomly oriented, glass fiber-reinforced composite premolar crowns.

    Science.gov (United States)

    Garoushi, Sufyan; Vallittu, Pekka K; Lassila, Lippo V J

    2007-09-01

    The aim of this work was to determine the static load-bearing capacity of posterior composite crowns made of experimental composite resin (FC) with short fiber fillers and a semi-interpenetrating polymer network (IPN) matrix. In addition, we wanted to investigate how load-bearing capacity of surface composite resins was affected by substructures of fiber-reinforced composite (FRC) and FC, and by different curing systems. Five groups of crowns were fabricated (n=6). The crowns were either polymerized with a hand-light curing unit (LCU) or cured in a vacuum curing device (VLC) before they were statically loaded at a speed of 1mm min(-1) until fracture. Failure modes were visually examined. Data were analyzed using ANOVA. ANOVA revealed that crowns made from the FC had a statistically significant higher load-bearing capacity than the control PFC composite. Crowns with FRC substructure and PFC covering gave force values of 348N (LCU) and 1199N (VLC), respectively, which were lower than the values of FC composite. No statistically significant difference was found between crowns made from plain FC composite and those made from FC composite with a surface layer of PFC (P=0.892 and 1.00). Restorations made from short glass fiber-containing composite resin with IPN-polymer matrix showed better load bearing capacity than those made with either plain PFC or PFC reinforced with FRC substructure.

  8. Semiconductor nanowires and nanowire heterostructures: Nanoscience from the bottom up

    Science.gov (United States)

    Zhong, Zhaohui

    2005-07-01

    Nanoscale science and technology involves interdisciplinary research at the interface of chemistry, physics, biology, and engineering sciences. By developing and following a unique intellectual path---the bottom-up paradigm of nanoscale science and technology---it is possible to assemble integrated nanoscale systems with novel functionalities beyond the conventional lithography limit. In this thesis, I present research efforts focused on fundamental aspects of this bottom-up paradigm using semiconductor nanowires (NWs) and nanowire heterostructures as nanoscale building blocks. We first present studies conducted on one of the most important semiconductor materials, silicon nanowires (SiNWs). SiNWs are rationally synthesized via a metal cluster-catalyzed vapor-liquid-solid (VLS) growth mechanism. Room temperature electrical transport studies carried out on SiNW field effect transistors (FETs) show exceptional device performance; estimated hole mobilities in p-SiNWs are significantly higher than bulk silicon at similar doping levels. Furthermore, low temperature transport studies on molecular scale SiNWs reveal phase coherent single charge transport through discrete single particle quantum levels with length scales up to several hundred nanometers. Finally, we show that SiNWs can be assembled into functional nanoelectronic devices. We then discuss two types of nanowire heterostructures: modulation doped silicon nanowires, and branched and hyper-branched nanowire structures. All key properties of modulation doped nanowires can be controlled during the synthesis, including the number, size and periodicity of the differentially doped regions. Their potential applications are also discussed. Moreover, branched and hyper-branched nanowire structures are synthesized via a multi-step nanocluster-catalyzed VLS approach, with branch density controlled by the nanocluster catalyst concentration. Lastly, we describe the realization of complementary doping in gallium nitride

  9. Interactions between semiconductor nanowires and living cells.

    Science.gov (United States)

    Prinz, Christelle N

    2015-06-17

    Semiconductor nanowires are increasingly used for biological applications and their small dimensions make them a promising tool for sensing and manipulating cells with minimal perturbation. In order to interface cells with nanowires in a controlled fashion, it is essential to understand the interactions between nanowires and living cells. The present paper reviews current progress in the understanding of these interactions, with knowledge gathered from studies where living cells were interfaced with vertical nanowire arrays. The effect of nanowires on cells is reported in terms of viability, cell-nanowire interface morphology, cell behavior, changes in gene expression as well as cellular stress markers. Unexplored issues and unanswered questions are discussed.

  10. Extreme Band Engineering of III-Nitride Nanowire Heterostructures for Electronic and Photonic Application

    Science.gov (United States)

    Sarwar, ATM Golam

    Bottom-up nanowires are attractive for realizing semiconductor devices with extreme heterostructures because strain relaxation through the nanowire sidewalls allows the combination of highly lattice mismatched materials without creating dislocations. The resulting nanowires are used to fabricate light-emitting diodes (LEDs), lasers, solar cells, and sensors. The aim of this work is to investigate extreme heterostructures, which are impossible or very hard to realize in conventional planar films, exploiting the strain accommodation property of nanowires and engineer their band structure for novel electronic and photonic applications. To this end, in this thesis, III-Nitride semiconductor nanowires are investigated. In the first part of this work, a complete growth phase diagram of InN nanowires on silicon using plasma assisted molecular beam epitaxy is developed, and structural and optical characteristics are mapped as a function of growth parameters. Next, a novel up-side down pendeoepitaxial growth of InN forming mushroom-like microstructures is demonstrated and detail structural and optical characterizations are performed. Based on this, a method to grow strain-free large area single crystalline InN or thin film is proposed and the growth of InN on patterned GaN is investigated. The optimized growth conditions developed for InN are further used to grow InGaN nanowires graded over the whole composition range. Numerical energy band simulation is performed to better understand the effect of polarization charge on photo-carrier transport in these extremely graded nanowires. A novel photodetector device with negative differential photocurrent is demonstrated using the graded InGaN nanowires. In the second part of this thesis, polarization-induced nanowire light emitting diodes (PINLEDs) are investigated. The electrical and optical properties of the nanowire heterostructure are engineered and optimized for ultraviolet and deep ultraviolet applications. The electrical

  11. Oxidation of copper nanowire based transparent electrodes in ambient conditions and their stabilization by encapsulation: application to transparent film heaters

    Science.gov (United States)

    Celle, Caroline; Cabos, Anthony; Fontecave, Thomas; Laguitton, Bruno; Benayad, Anass; Guettaz, Laure; Pélissier, Nathalie; Huong Nguyen, Viet; Bellet, Daniel; Muñoz-Rojas, David; Simonato, Jean-Pierre

    2018-02-01

    Whereas the integration of silver nanowires in functional devices has reached a fair level of maturity, the integration of copper nanowires still remains difficult, mainly due to the intrinsic instability of copper nanowires in ambient conditions. In this paper, copper nanowire based transparent electrodes with good performances (33 Ω sq‑1 associated with 88% transparency) were obtained, and their degradation in different conditions was monitored, in particular by electrical measurements, transmission electron microscopy, x-ray photoelectron spectrometry and Auger electron spectroscopy. Several routes to stabilize the random networks of copper nanowires were evaluated. Encapsulation through laminated barrier film with optical clear adhesive and atmospheric pressure spatial atomic layer deposition were found to be efficient and were used for the fabrication of transparent film heaters.

  12. Surface Passivation of Germanium Nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Adhikari, Hemant; Sun, Shiyu; Pianetta, Piero; Chidsey, Chirstopher E.D.; McIntyre, Paul C.; /SLAC, SSRL

    2005-05-13

    The surface of single crystal, cold-wall CVD-grown germanium nanowires was studied by synchrotron radiation photoemission spectroscopy (SR-PES) and also by conventional XPS. The as-grown germanium nanowires seem to be hydrogen terminated. Exposure to laboratory atmosphere leads to germanium oxide growth with oxidation states of Ge{sup 1+}, Ge{sup 2+}, Ge{sup 3+}, while exposure to UV light leads to a predominance of the Ge{sup 4+} oxidation state. Most of the surface oxide could be removed readily by aqueous HF treatment which putatively leaves the nanowire surface hydrogen terminated with limited stability in air. Alternatively, chlorine termination could be achieved by aq. HCl treatment of the native oxide-coated nanowires. Chlorine termination was found to be relatively more stable than the HF-last hydrogen termination.

  13. Ballistic superconductivity in semiconductor nanowires

    NARCIS (Netherlands)

    Zhang, H.; Gül, Ö.; Conesa-Boj, S.; Nowak, M.P.; Wimmer, M.; Zuo, K.; Mourik, V.; Vries, F.K. de; Veen, J. van; Moor, M.W.A. de; Bommer, J.D.S.; Woerkom, D.J. van; Car, D.; Plissard, S.R.; Bakkers, E.P.A.M.; Quintero Pérez, M.; Cassidy, M.C.; Koelling, S.; Goswami, S.; Watanabe, K.; Taniguchi, T.; Kouwenhoven, L.P.

    2017-01-01

    Semiconductor nanowires have opened new research avenues in quantum transport owing to their confined geometry and electrostatic tunability. They have offered an exceptional testbed for superconductivity, leading to the realization of hybrid systems combining the macroscopic quantum properties of

  14. Hard template synthesis of metal nanowires

    Directory of Open Access Journals (Sweden)

    Go eKawamura

    2014-11-01

    Full Text Available Metal nanowires (NWs have attracted much attention because of their high electron conductivity, optical transmittance and tunable magnetic properties. Metal NWs have been synthesized using soft templates such as surface stabilizing molecules and polymers, and hard templates such as anodic aluminum oxide, mesoporous oxide, carbon nanotubes. NWs prepared from hard templates are composites of metals and the oxide/carbon matrix. Thus, selecting appropriate elements can simplify the production of composite devices. The resulting NWs are immobilized and spatially arranged, as dictated by the ordered porous structure of the template. This avoids the NWs from aggregating, which is common for NWs prepared with soft templates in solution. Herein, the hard template synthesis of metal NWs is reviewed, and the resulting structures, properties and potential applications are discussed.

  15. Nonlinear optics in photonic nanowires.

    Science.gov (United States)

    Foster, Mark A; Turner, Amy C; Lipson, Michal; Gaeta, Alexander L

    2008-01-21

    We review recent research on nonlinear optical interactions in waveguides with sub-micron transverse dimensions, which are termed photonic nanowires. Such nanowaveguides, fabricated from glasses or semiconductors, provide the maximal confinement of light for index guiding structures enabling large enhancement of nonlinear interactions and group-velocity dispersion engineering. The combination of these two properties make photonic nanowires ideally suited for many nonlinear optical applications including the generation of single-cycle pulses and optical processing with sub-mW powers.

  16. Randomized controlled split-mouth clinical trial of direct laminate veneers with two micro-hybrid resin composites.

    Science.gov (United States)

    Gresnigt, Marco M M; Kalk, Warner; Ozcan, Mutlu

    2012-09-01

    This randomized, split-mouth clinical study evaluated the survival rate of direct laminate veneers made of two resin-composite materials. A total of 23 patients (mean age: 52.4 years old) received 96 direct composite laminate veneers using two micro-hybrid composites in combination with two adhesive resins (Ena-Bond-Enamel HFO: n=48, Clearfil SE Bond-Miris2: n=48). Enamel was selectively etched with 38% H(3)PO(4) for 30s, rinsed 30s and the corresponding adhesive resin was applied accordingly. Existing resin composite restorations in good conditions (small or big) were not removed but conditioned using silica coating (CoJet) and silanized (ESPE-Sil). Restorations were evaluated at baseline and thereafter every 6 months. Additional qualitative analysis was performed using modified USPHS criteria. Mean observation period was 41.3 months. Altogether, 12 absolute failures were observed [survival rate: 87.5%] (Kaplan-Meier). The survival rates with the two resin composites did not show significant differences [Enamel HFO: 81.2%, Miris2: 93.8%] (p>0.05). The presence of existing composite restorations on the prepared teeth did not affect the survival rate significantly (intact teeth: 100%, small restorations: 90.6%, big restorations: 82.7%) (p>0.05). Surface roughness and marginal discolouration were the main qualitative deteriorations observed until the final recall. Secondary caries and endodontic complications did not occur in any of the teeth. Early findings of this clinical study with the two micro-hybrid composite laminate veneers showed similar survival rate and their clinical performance was not significantly influenced when bonded onto intact teeth or onto teeth with existing restorations with the protocol applied. Copyright © 2012 Elsevier Ltd. All rights reserved.

  17. Characterization of superconducting nanowire single-photon detector with artificial constrictions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Ling; Liu, Dengkuan; Wu, Junjie; He, Yuhao; Lv, Chaolin [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050 (China); Graduate University of the Chinese Academy of Sciences, Beijing 100049 (China); You, Lixing, E-mail: lxyou@mail.sim.ac.cn; Zhang, Weijun; Zhang, Lu; Liu, Xiaoyu; Wang, Zhen, E-mail: zwang@mail.sim.ac.cn; Xie, Xiaoming [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050 (China)

    2014-06-15

    Statistical studies on the performance of different superconducting nanowire single-photon detectors (SNSPDs) on one chip suggested that random constrictions existed in the nanowire that were barely registered by scanning electron microscopy. With the aid of advanced e-beam lithography, artificial geometric constrictions were fabricated on SNSPDs as well as single nanowires. In this way, we studied the influence of artificial constrictions on SNSPDs in a straight forward manner. By introducing artificial constrictions with different wire widths in single nanowires, we concluded that the dark counts of SNSPDs originate from a single constriction. Further introducing artificial constrictions in SNSPDs, we studied the relationship between detection efficiency and kinetic inductance and the bias current, confirming the hypothesis that constrictions exist in SNSPDs.

  18. Dairy Intake Enhances Body Weight and Composition Changes during Energy Restriction in 18-50-Year-Old Adults-A Meta-Analysis of Randomized Controlled Trials

    National Research Council Canada - National Science Library

    Stonehouse, Welma; Wycherley, Thomas; Luscombe-Marsh, Natalie; Taylor, Pennie; Brinkworth, Grant; Riley, Malcolm

    2016-01-01

    A meta-analysis of randomized controlled trials (RCTs) was performed to investigate the effects of dairy food or supplements during energy restriction on body weight and composition in 18-50-year-old. RCTs...

  19. Magnetic behavior of as-deposited and annealed CoFe and CoFeCu nanowire arrays by ac-pulse electrodeposition

    Science.gov (United States)

    Ramazani, A.; Almasi-Kashi, M.; Golafshan, E.; Arefpour, M.

    2014-09-01

    CoFe and CoFeCu self-organized alloy nanowires were grown into anodic aluminum oxide template by potentiostatic mode of ac-pulse electrodeposition technique and subsequently annealed at 580 °C. The influence of bath composition, off-time between pulses and annealing treatment on the Cu content, microstructure and magnetic properties of CoFeCu nanowire arrays have been discussed. Increasing the off-time between pulses decreased the coercivity and saturation magnetization of the CoFeCu nanowires due to substitution of Co and Fe with Cu atoms which resulted in electroless process. Coercivity and squareness of the annealed samples increased due to improvement of samples crystallinity. Magnetic measurements showed high perpendicular magnetic anisotropy of the nanowires with easy axis parallel to nanowires axis. X-ray diffraction results indicated that annealed CoFeCu nanowires were polycrystalline with two distinct CoFe and Cu phases.

  20. Dislocation-free axial InAs-on-GaAs nanowires on silicon

    Science.gov (United States)

    Beznasyuk, Daria V.; Robin, Eric; Den Hertog, Martien; Claudon, Julien; Hocevar, Moïra

    2017-09-01

    We report on the growth of axial InAs-on-GaAs nanowire heterostructures on silicon by molecular beam epitaxy using 20 nm diameter Au catalysts. First, the growth parameters of the GaAs nanowire segment were optimized to achieve a pure wurtzite crystal structure. Then, we developed a two-step growth procedure to enhance the yield of vertical InAs-on-GaAs nanowires. We achieved 90% of straight InAs-on-GaAs nanowires by further optimizing the growth parameters. We investigated the composition change at the interface by energy dispersive x-ray spectroscopy and the nanowire crystal structure by transmission electron microscopy. The composition of the nominal InAs segment is found to be In x Ga1-x As with x = 0.85 and corresponds to 6% of lattice mismatch with GaAs. Strain mapping performed by the geometrical phase analysis of high-resolution images revealed a dislocation-free GaAs/In0.85Ga0.15As interface. In conclusion, we successfully fabricated highly mismatched heterostructures, confirming the prediction that axial GaAs/In0.85Ga0.15As interfaces are pseudomorphic in nanowires with a diameter smaller than 40 nm.

  1. Fabrication and magnetic investigations of highly uniform CoNiGa alloy nanowires

    Science.gov (United States)

    Li, Wen-Jing; Khan, U.; Irfan, Muhammad; Javed, K.; Liu, P.; Ban, S. L.; Han, X. F.

    2017-06-01

    CoNiGa ternary alloy nanowire arrays were successfully fabricated by simple DC electrodeposition into the anodized aluminum oxide (AAO) templates. A systematic study of the potential and components of the electrolyte were conducted to obtain different components of CoNiGa nanowires. The largest Ga content in the prepared alloy nanowires was about 17%, while for Co and Ni contents which can be controlled in a wide range by adjusting the composition and pH value of the electrolyte appropriately. X-ray diffraction analysis confirmed that the as-grown CoNiGa nanowire arrays were polycrystal with fcc phase of Co where Co atoms partially substituted by Ni and Ga. Magnetization curves of samples with different composition were measured at room temperature as well as low temperature. The results showed that the components of the alloy nanowires have a great impact on its magnetic properties. For Co55Ni28Ga17 nanowires, the magnetization reversal mode changes from curling mode to coherent rotation as the angle increases, and the temperature dependence of coercivity can be well described by the thermal activation effect.

  2. ZrTiO4 nanowire growth using membrane-assisted Pechini route

    Directory of Open Access Journals (Sweden)

    P. R. de Lucena

    2014-11-01

    Full Text Available The high surface-to-volume ratio of nanowires makes them natural competitors as new device components. In this regard, a current major challenge is to produce quasi-one-dimensional nanostructures composed of well established oxide-based materials. This article reports the synthesis of ZrTiO4 nanowires on a silicon (100 wafer in a single-step deposition/thermal treatment. The template-directed membrane synthesis strategy was associated with the Pechini route and spin-coating deposition technique. ZrTiO4 nanowires were obtained at 700 ˚C with diameters in the range of 80-100 nm. FEG- SEM images were obtained to investigate ZrTiO4 nanowire formation on the silicon surface and energy dispersive x-ray detection (EDS and x-ray diffraction (XRD analyses were performed to confirm the oxide composition and structure.

  3. Integrated chemical and biological systems in nanowire structures towards nano-scale sensors

    Science.gov (United States)

    Hernandez, Rose M.

    Nanowires composed of metal and conducting polymers with integrated proteins and chemical systems have been investigated as building blocks for next-generation nano-scale sensors and assemblies. These nanowires were fabricated by combining chemical and electrochemical methods of synthesis of gold and conducting polymers in nanopores of anodized alumina membranes. Polymer nanowires were synthesized from buffer solutions as a mean to promote a biocompatible environment for the incorporation of proteins. A variety of proteins were incorporated into the polymer matrix by entrapment during polymerization that imparted the polymer material with biological functionality. Another class of composite nanowires containing electro-active conducting polymer junctions was developed for applications in chemical sensor arrays. The methodologies described in this thesis provide an inexpensive and straightforward approach to the synthesis of anisotropic nanoparticles incorporating a variety of biological and inorganic species that can be integrated to current microelectronic technologies for the development of nano-scale sensor arrays.

  4. A novel method for massive synthesis of SnO2 nanowires

    Indian Academy of Sciences (India)

    concrete experimental operating steps, is shown in figure 1. Table 1. Compositions of three reaction systems for synthesizing SnO2 nanowires by thermite reaction. ... infrared spectroscopy (FTIR) spectrometer equipped with an. Continuum IR microscope. 3. Results and discussion. The phase composition and structure ...

  5. Electrochemically grown rough-textured nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Tyagi, Pawan; Postetter, David; Saragnese, Daniel [Johns Hopkins University, Department of Chemical and Biomolecular Engineering (United States); Papadakis, Stergios J. [Johns Hopkins University, Applied Physics Laboratory (United States); Gracias, David H., E-mail: dgracias@jhu.ed [Johns Hopkins University, Department of Chemical and Biomolecular Engineering (United States)

    2010-03-15

    Nanowires with a rough surface texture show unusual electronic, optical, and chemical properties; however, there are only a few existing methods for producing these nanowires. Here, we describe two methods for growing both free standing and lithographically patterned gold (Au) nanowires with a rough surface texture. The first strategy is based on the deposition of nanowires from a silver (Ag)-Au plating solution mixture that precipitates an Ag-Au cyanide complex during electrodeposition at low current densities. This complex disperses in the plating solution, thereby altering the nanowire growth to yield a rough surface texture. These nanowires are mass produced in alumina membranes. The second strategy produces long and rough Au nanowires on lithographically patternable nickel edge templates with corrugations formed by partial etching. These rough nanowires can be easily arrayed and integrated with microscale devices.

  6. Optical second harmonic generation from Pt nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, N.; Aratake, K.; Okushio, R.; Iwai, T. [Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); Sugawara, A. [Hitachi Advanced Research Laboratory, Akanuma 2520, Hatoyama, Saitama 350-0395 (Japan); Sano, H. [Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); Mizutani, G. [Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan)], E-mail: mizutani@jaist.ac.jp

    2007-09-15

    We have measured optical second harmonic intensity from arrays of Pt nanowires of 20 nm and 9 nm average widths, as a function of the incident and output light polarizations, the azimuthal angle, and the excitation photon energy. The nanowires were fabricated through shadow deposition on self-organized NaCl(1 1 0) faceted templates. The anisotropy of the SH intensity from the Pt nanowires was found to be stronger than that from the Au nanowires reported previously. The effective nonlinear susceptibility element {chi}{sub 222}{sup (2)}, with the suffix 2 indicating the direction [11-bar0], was observed for Pt nanowires, although it was not observed for Au nanowires. This difference is suggested to be due to the weaker suppression of the incident fundamental fields by the depolarization field in the Pt nanowires and the larger anisotropy in the nonlinearity of Pt nanowires due to the thinner widths.

  7. A silicon nanowire heater and thermometer

    Science.gov (United States)

    Zhao, Xingyan; Dan, Yaping

    2017-07-01

    In the thermal conductivity measurements of thermoelectric materials, heaters and thermometers made of the same semiconducting materials under test, forming a homogeneous system, will significantly simplify fabrication and integration. In this work, we demonstrate a high-performance heater and thermometer made of single silicon nanowires (SiNWs). The SiNWs are patterned out of a silicon-on-insulator wafer by CMOS-compatible fabrication processes. The electronic properties of the nanowires are characterized by four-probe and low temperature Hall effect measurements. The I-V curves of the nanowires are linear at small voltage bias. The temperature dependence of the nanowire resistance allows the nanowire to be used as a highly sensitive thermometer. At high voltage bias, the I-V curves of the nanowire become nonlinear due to the effect of Joule heating. The temperature of the nanowire heater can be accurately monitored by the nanowire itself as a thermometer.

  8. Structural and tunneling properties of Si nanowires

    KAUST Repository

    Montes Muñoz, Enrique

    2013-12-06

    We investigate the electronic structure and electron transport properties of Si nanowires attached to Au electrodes from first principles using density functional theory and the nonequilibrium Green\\'s function method. We systematically study the dependence of the transport properties on the diameter of the nanowires, on the growth direction, and on the length. At the equilibrium Au-nanowire distance we find strong electronic coupling between the electrodes and nanowires, which results in a low contact resistance. With increasing nanowire length we study the transition from metallic to tunneling conductance for small applied bias. For the tunneling regime we investigate the decay of the conductance with the nanowire length and rationalize the results using the complex band structure of the pristine nanowires. The conductance is found to depend strongly on the growth direction, with nanowires grown along the ⟨110⟩ direction showing the smallest decay with length and the largest conductance and current.

  9. Epitaxy-enabled vapor-liquid-solid growth of tin-doped indium oxide nanowires with controlled orientations

    KAUST Repository

    Shen, Youde

    2014-08-13

    Controlling the morphology of nanowires in bottom-up synthesis and assembling them on planar substrates is of tremendous importance for device applications in electronics, photonics, sensing and energy conversion. To date, however, there remain challenges in reliably achieving these goals of orientation-controlled nanowire synthesis and assembly. Here we report that growth of planar, vertical and randomly oriented tin-doped indium oxide (ITO) nanowires can be realized on yttria-stabilized zirconia (YSZ) substrates via the epitaxy-assisted vapor-liquid-solid (VLS) mechanism, by simply regulating the growth conditions, in particular the growth temperature. This robust control on nanowire orientation is facilitated by the small lattice mismatch of 1.6% between ITO and YSZ. Further control of the orientation, symmetry and shape of the nanowires can be achieved by using YSZ substrates with (110) and (111), in addition to (100) surfaces. Based on these insights, we succeed in growing regular arrays of planar ITO nanowires from patterned catalyst nanoparticles. Overall, our discovery of unprecedented orientation control in ITO nanowires advances the general VLS synthesis, providing a robust epitaxy-based approach toward rational synthesis of nanowires. © 2014 American Chemical Society.

  10. Foreign-catalyst-free growth of InAs/InSb axial heterostructure nanowires on Si (111) by molecular-beam epitaxy

    Science.gov (United States)

    So, Hyok; Pan, Dong; Li, Lixia; Zhao, Jianhua

    2017-03-01

    Epitaxial high-quality InAs/InSb axial heterostructure nanowires are of great interest due to their distinct advantages in fundamental research as well as applications in semiconductor electronic and quantum devices. Currently, nearly all the growth of InAs/InSb axial heterostructure nanowires is assisted with foreign catalysts such as Au, and work on foreign-catalyst-free growth of InAs/InSb axial heterostructure nanowires is lacking. Here we report on the growth of InAs/InSb axial heterostructure nanowires on Si (111) substrates by molecular-beam epitaxy without using any foreign catalysts. The Sb/In beam equivalent pressure (BEP) ratio is found to have important influence on the heterostructure nanowire morphology, and InSb nanowires can be epitaxially grown on InAs nanowire stems with a hexagonal prism and nanosheet-like shapes when the Sb/In BEP ratio varies from 10 to 20. Transmission electron microscopy studies reveal that the InAs nanowire stems have a mixture of zincblende (ZB) and wurtzite (WZ) crystal structures, while InSb nanowire parts have a pure ZB crystal structure free of stacking faults. Composition analysis of axial heterostructure nanowires provides clear evidence that the InSb nanowires are epitaxially grown on InAs nanowires in an In self-assisted vapor-liquid-solid manner. This study paves a new route for growing narrow-gap semiconductor heterostructures with strong spin-orbit interaction for the study of topological states, and the growth manner presented here is expected to be used to grow other In-based axial heterostructure nanowires.

  11. H2 sensing properties of modified silicon nanowires

    Directory of Open Access Journals (Sweden)

    Latefa Baba Ahmed

    2015-04-01

    Full Text Available It has been found that the silicon nanowires modified with noble metals can be used to fabricate an effective H2 gas sensor in the present study. The preparation and surface modification of silicon nanowires (SiNWs were carried out by chemical methods. The morphology of the silicon nanowires unmodified and modified with nanoparticles of platinum, palladium, silver and gold was investigated using scanning electron microscopy (SEM. The chemical composition of the silicon nanowire layers was studied by secondary ion mass spectroscopy (SIMS and energy dispersive X-ray analysis (EDX. The structures of type metal/SiNWs/p-Si/Al were fabricated. The electrical characterization (I–V was performed in primary vacuum and H2 at different concentrations. It was found that the metal type used to modify the SiNWs strongly influenced the I–V characteristics. The response of these structures toward H2 gas was studied as a function of the metal type. Finally, the sensing characteristics and performance of the sensors were investigated.

  12. Influence of boric acid (H3BO3) concentration on the physical properties of electrochemical deposited nickel (Ni) nanowires

    Science.gov (United States)

    Kananathan, J.; Sofiah, A. G. N.; Samykano, M.; Ulakanathan, S.; Lah, N. A. C.; Harun, W. S. W.; Sudhakar, K.; Kadirgama, K.; Ngui, W. K.; Siregar, J. P.

    2017-10-01

    Authors have investigated the influence of the stabilizer (Boric Acid) concentration during the template-assisted electrochemical deposition of Nickel (Ni) nanowires in Anodic Alumina Oxide (AAO) templates. The synthesis was performed using Ni Sulfate Hexahydrate (NiSO4.6H2O) as metal salts and Boric Acid (H3BO3) as a stabilizer. The mixture of both solutions creates electrolyte and utilized for the electrochemical deposition of Ni nanowires. During the experiment, the boric acid concentration varied between 5 g/L, 37.5 g/L and 60 g/L with a deposition temperature of 80 °C (constant). After the electrochemical deposition process, AAO templates were cleaned with distilled water before dissolution in Sodium Hydroxide (NaOH) solution to obtain the freestanding Ni nanowires. Physical properties of the synthesized Ni nanowires were analyzed using Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDX) and X-ray Diffraction (XRD). The physical properties of obtained Ni nanowires has eloborated by taking into account the effect of boric acid concentration on the surface morphology, growth length, elemental composition and crystal orientation crystal of the synthesized nickel nanowires. The finding exposes that the boric acid concentration does not influence all aspects in the physicals properties of the synthesized Ni nanowires. The boric acid concentration did not affect the surface texture and crystal orientation. However, shorter Ni nanowires obtained as the concentration of boric acid increased.

  13. Single-crystal vanadium pentoxide nanowires.

    Science.gov (United States)

    Gao, Shaokang; Chen, Yuzhen; Luo, Haiyan; Jiang, Lilong; Ye, Binghuo; Wei, Mingdeng; Wei, Kemei

    2008-07-01

    Single-crystal V2O5 nanowires were successfully synthesized from the starting materials V6O13 powder and water. The experimental results indicate that high purity nanowires can be obtained using this simple synthetic route in absence of templates or catalysts. The diameter of the nanowires was found to be ca. 20 approximately 60 nm and the length up to several tens of micrometers, and the phases of nanowires were determined by XRD and TEM measurements.

  14. Semiconducting silicon nanowires for biomedical applications

    CERN Document Server

    Coffer, JL

    2014-01-01

    Biomedical applications have benefited greatly from the increasing interest and research into semiconducting silicon nanowires. Semiconducting Silicon Nanowires for Biomedical Applications reviews the fabrication, properties, and applications of this emerging material. The book begins by reviewing the basics, as well as the growth, characterization, biocompatibility, and surface modification, of semiconducting silicon nanowires. It goes on to focus on silicon nanowires for tissue engineering and delivery applications, including cellular binding and internalization, orthopedic tissue scaffol

  15. Fabry Perot phenomena in nanowire cavities

    Science.gov (United States)

    Tomczyk, Michelle; Cheng, Guanglei; Lu, Shicheng; Veazey, Joshua; Huang, Mengchen; Irvin, Patrick; Lee, Hyungwoo; Ryu, Sangwoo; Eom, Chang-Beom; Levy, Jeremy

    2015-03-01

    A solid-state geometry analogous to an optical Fabry-Perot cavity gives evidence for coherent transport on the order of microns through nanowires at the LaAlO3/SrTiO3 (LAO/STO) interface. Conductive AFM lithography is used to create both the nanowires and the two confining barriers which define the cavity. These two barriers act as the primary scattering centers so that as the chemical potential is tuned through the conducting state of the device, partial reflections from the barriers interfere in the cavity, resulting in quasi-periodic oscillations of the conductance at low temperatures. Full and extended single-mode periodicity is not observed in all devices; however, the conductance oscillations are only observed in cavity structures, suggesting that the effects of the two manufactured barriers dominate over any random scattering sites from disorder. The conductance oscillations from interference of coherently scattered electrons give evidence for ballistic transport on much longer length scales than implied by mobility measurements in two-dimensional LAO/STO. We gratefully acknowledge financial support from ARO (W911NF-08-1-0317), AFOSR (FA9550-10-1-0524 and FA9550-12-1-0342), and NSF (DMR-1104191, DMR-1124131, and DMR-1234096).

  16. Nanowire resonant tunneling diodes

    Science.gov (United States)

    Björk, M. T.; Ohlsson, B. J.; Thelander, C.; Persson, A. I.; Deppert, K.; Wallenberg, L. R.; Samuelson, L.

    2002-12-01

    Semiconductor heterostructures and their implementation into electronic and photonic devices have had tremendous impact on science and technology. In the development of quantum nanoelectronics, one-dimensional (1D) heterostructure devices are receiving a lot of interest. We report here functional 1D resonant tunneling diodes obtained via bottom-up assembly of designed segments of different semiconductor materials in III/V nanowires. The emitter, collector, and the central quantum dot are made from InAs and the barrier material from InP. Ideal resonant tunneling behavior, with peak-to-valley ratios of up to 50:1 and current densities of 1 nA/μm2 was observed at low temperatures.

  17. Chemical composition separation of a propylene-ethylene random copolymer by high temperature solvent gradient interaction chromatography.

    Science.gov (United States)

    Liu, Yonggang; Phiri, Mohau Justice; Ndiripo, Anthony; Pasch, Harald

    2017-11-03

    A propylene-ethylene random copolymer was fractionated by preparative temperature rising elution fractionation (TREF). The structural heterogeneity of the bulk sample and its TREF fractions was studied by high temperature liquid chromatography with a solvent gradient elution from 1-decanol to 1,2,4-trichlorobenzene. HPLC alone cannot resolve those propylene-ethylene copolymers with high ethylene content in the bulk sample, due to their low weight fractions in the bulk sample and a small response factor of these components in the ELSD detector, as well as their broad chemical composition distribution. These components can only be detected after being separated and enriched by TREF followed by HPLC analysis. Chemical composition separations were achieved for TREF fractions with average ethylene contents between 2.1 and 22.0mol%, showing that copolymers with higher ethylene contents were adsorbed stronger in the Hypercarb column and eluted later. All TREF fractions, except the 40°C fraction, were relatively homogeneous in both molar mass and chemical composition. The 40°C fraction was rather broad in both molar mass and chemical composition distributions. 2D HPLC showed that the molar masses of the components containing more ethylene units were getting lower for the 40°C fraction. HPLC revealed and confirmed that co-crystallization influences the separation in TREF of the studied propylene-ethylene copolymer. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Corrosion detection of nanowires by magnetic sensors

    KAUST Repository

    Kosel, Jürgen

    2017-10-05

    Disclosed are various embodiments related to a corrosion detection device for detecting corrosive environments. A corrosion detection device comprises a magnetic sensor and at least one magnetic nanowire disposed on the magnetic sensor. The magnetic sensor is configured to detect corrosion of the one or more magnetic nanowires based at least in part on a magnetic field of the one or more magnetic nanowires.

  19. Stationary and nonstationary random vibrations of laminated composite plates via a higher order theory

    Science.gov (United States)

    Elishakoff, Isaac; Librescu, Liviu; Cederbaum, Gabriel

    1990-01-01

    Higher order shear deformation theory is utilized to study he weakly stationary and nonstationary random vibrations of cross-ply laminated plates. Normal mode method, in conjunction with the biorthogonality condition, for the nonsymmetric differential equations is applied. Detailed derivation is given for the governing equations, biorthogonality condition, the generalized mass and the generalized forces. Results are listed for a plate which is simply supported at all the edges, and subjected to a point load which is either timewise stationary or nonstationary random process.

  20. Growth and properties of In(Ga)As nanowires on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Hertenberger, Simon

    2012-10-15

    nanowire properties and homogeneous array-like characteristics. High vertical growth yields of 90 % are achieved on substrates patterned either by e-beam lithography (for small scale arrays) or nanoimprint lithography (NIL, for large scale arrays > 5 x 5 mm{sup 2}). In addition, X-ray rocking curve measurements evidence very low crystal tilt and perfect vertical alignment along the (111) direction with full widths at half maximum (FWHM) as low as 0.6 . Furthermore, systematic investigations of the size scaling behavior as a function of the pitch (interwire distance) highlight the existence of two growth regimes: (i) a competitive growth regime for narrow pitches and (ii) a diffusion-limited regime for wider pitches, where growth is limited by the diffusion length of In adatoms on the SiO{sub 2} surface (∝750 nm at T=480 C). Furthermore, the growth of ternary InGaAs nanowires on sputter-deposited SiO{sub x}/Si(111) and NIL-patterned SiO{sub 2}/Si(111) substrates is investigated. Here, composition tuning with Ga contents ranging from 0-60 % was achieved as confirmed by X-ray diffraction and energy dispersive X-ray spectroscopy. Furthermore, the two different growth strategies are compared yielding a significantly lower FWHM of the 2θ-XRD-peak in the case of NIL-patterned substrates (0.031 ) as compared to self-assembled grown nanowires (0.084 ). This finding is further supported by Raman spectroscopy showing lower longitudinal optical to transversal optical (LO/TO) intensity ratios and lower LO-FWHM for both the InAs-like and GaAs-like LO modes in the case of NIL-patterned nanowire growth. These observations indicate superior composition homogeneity for positioned nanowire growth on patterned substrates. In addition, low-T photoluminescence (PL) measurements are presented showing band gap tuning over a wavelength range of ∝1800-2850 nm where PL peak linewidths are as narrow as ∝30 meV, independent of the Ga content. Finally, the effect of growth parameters on the

  1. Particle-assisted GaxIn1xP nanowire growth for designed bandgap structures

    DEFF Research Database (Denmark)

    Jacobsson, D.; Persson, Johan Mikael; Kriegner, D.

    2012-01-01

    Non-tapered vertically straight GaxIn1−xP nanowires were grown in a compositional range from Ga0.2In0.8P to pure GaP in particle-assisted mode by controlling the trimethylindium, trimethylgallium and hydrogen chloride flows in metal–organic vapor phase epitaxy. X-ray energy dispersive spectroscop...... sample area, i.e., including edge effects during growth. The non-capped nanowires emit room temperature photoluminescence strongly in the energy range of 1.43–2.16 eV, correlated with the bandgap expected from the material composition....... in transmission electron microscopy revealed homogeneous radial material composition in single nanowires, whereas variations in the material composition were found along the nanowires. High-resolution x-ray diffraction indicates a variation of the material composition on the order of about 19% measuring an entire...

  2. Development of Novel Composite and Random Materials for Nonlinear Optics and Lasers

    Science.gov (United States)

    Noginov, Mikhail

    2002-01-01

    A qualitative model explaining sharp spectral peaks in emission of solid-state random laser materials with broad-band gain is proposed. The suggested mechanism of coherent emission relies on synchronization of phases in an ensemble of emitting centers, via time delays provided by a network of random scatterers, and amplification of spontaneous emission that supports the spontaneously organized coherent state. Laser-like emission from powders of solid-state luminophosphors, characterized by dramatic narrowing of the emission spectrum and shortening of emission pulses above the threshold, was first observed by Markushev et al. and further studied by a number of research groups. In particular, it has been shown that when the pumping energy significantly exceeds the threshold, one or several narrow emission lines can be observed in broad-band gain media with scatterers, such as films of ZnO nanoparticles, films of pi-conjugated polymers or infiltrated opals. The experimental features, commonly observed in various solid-state random laser materials characterized by different particle sizes, different values of the photon mean free path l*, different indexes of refraction, etc.. can be described as follows. (Liquid dye random lasers are not discussed here.)

  3. Optical and thermal properties of PTh-co-PANI-Ti random copolymer composite for photovoltaic application

    Directory of Open Access Journals (Sweden)

    Sanjay R. Takpire

    2015-12-01

    Full Text Available In thе present work, a polythiophene (PTh-co-polyaniline (PANI-titanium (Ti copolymer has been synthesized as a novel copolymeric composite material for photovoltaic (PV application. The focus of the study was to evaluate optical and thermal properties of the PTh-co-PANI-Ti copolymer containing different types of monomers. The optical conductivity was determined from the UV–VIS spectra that were used to calculate the extinction coefficients. The structure and morphology of composite was analyzed through field emission-electron microscopy (FESEM. The PTh-co-PANI-Ti copolymer composite exhibited significant photovoltaic (PV response to light intensity. J–V analysis showed an increase in conversion efficiency from 0.21 to 1.5 of PTh-co-PANi-Ti with illumination light intensity. PV properties demonstrated that the PTh-co-PANI-Ti exhibited the highest power conversion efficiency ɳ=1.5, with a short circuit current Isc=0.72mA, an open circuit voltage Voc=0.9V and a fill factor FF=0.51. Thermo-gravimetric (TG and differential thermal (DTA analyses were carried out for the thermal stability of the PTh-co-PANI-Ti copolymer composite. The results obtained from the characterization of PTh-co-PANI-Ti showed that many properties of PV action are present in as-synthesized material.

  4. Micromagnetic simulations of cylindrical magnetic nanowires

    KAUST Repository

    Ivanov, Yurii P.

    2015-05-27

    This chapter reviews micromagnetic simulations of cylindrical magnetic nanowires and their ordered arrays. It starts with a description of the theoretical background of micromagnetism. The chapter discusses main magnetization reversal modes, domain wall types, and state diagrams in cylindrical nanowires of different types and sizes. The results of the hysteresis process in individual nanowires and nanowire arrays also are presented. Modeling results are compared with experimental ones. The chapter also discusses future trends in nanowire applications in relation to simulations, such as current-driven dynamics, spintronics, and spincaloritronics. The main micromagnetic programs are presented and discussed, together with the corresponding links.

  5. Controllable High-Speed Rotation of Nanowires

    Science.gov (United States)

    Fan, D. L.; Zhu, F. Q.; Cammarata, R. C.; Chien, C. L.

    2005-06-01

    We report a versatile method for executing controllable high-speed rotation of nanowires by ac voltages applied to multiple electrodes. The rotation of the nanowires can be instantly switched on or off with precisely controlled rotation speed (to at least 1800 rpm), definite chirality, and total angle of rotation. We have determined the torque due to the fluidic drag force on nanowire of different lengths. We also demonstrate a micromotor using a rotating nanowire driving a dust particle into circular motion. This method has been used to rotate magnetic and nonmagnetic nanowires as well as carbon nanotubes.

  6. Gold nanowires and the effect of impurities

    Directory of Open Access Journals (Sweden)

    Novaes Frederico

    2006-01-01

    Full Text Available AbstractMetal nanowires and in particular gold nanowires have received a great deal of attention in the past few years. Experiments on gold nanowires have prompted theory and simulation to help answer questions posed by these studies. Here we present results of computer simulations for the formation, evolution and breaking of very thin Au nanowires. We also discuss the influence of contaminants, such as atoms and small molecules, and their effect on the structural and mechanical properties of these nanowires.

  7. Self-Catalyzed Growth of Axial GaAs/GaAsSb Nanowires by Molecular Beam Epitaxy for Photodetectors

    Science.gov (United States)

    2015-06-01

    Compositional variation of Sb in Ga Assisted Axial GaAs/GaAsSb/GaAs Heterostructure Nanowires on Chemically Etched Si Substrate...reported which is claimed to be the longest cutoff wavelength for any nanowire device so far[69]. Hence these heterostructured NWs are suited in the MWIR...of Sb in Ga Assisted Axial GaAs/GaAsSb/GaAs Heterostructure Nanowires on Chemically Etched Si Substrate 8.1 Introduction GaAs/GaAsSb NWs have been

  8. Nitrogen and Fluorine-Codoped Carbon Nanowire Aerogels as Metal-Free Electrocatalysts for Oxygen Reduction Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Shaofang [School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164 USA; Zhu, Chengzhou [School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164 USA; Song, Junhua [School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164 USA; Engelhard, Mark H. [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland WA 99352 USA; Xiao, Biwei [Energy and Environmental Directory, Pacific Northwest National Laboratory, Richland WA 99352 USA; Du, Dan [School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164 USA; Lin, Yuehe [School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164 USA

    2017-07-11

    The development of active, durable, and low-cost catalysts to replace noble metal-based materials is highly desirable to promote the sluggish oxygen reduction reaction in fuel cells. Herein, nitrogen and fluorine-codoped three-dimensional carbon nanowire aerogels, composed of interconnected carbon nanowires, were synthesized for the first time by a hydrothermal carbonization process. Owing to their porous nanostructures and heteroatom-doping, the as-prepared carbon nanowire aerogels, with optimized composition, present excellent electrocatalytic activity that is comparable to commercial Pt/C. Remarkably, the aerogels also exhibit superior stability and methanol tolerance. This synthesis procedure paves a new way to design novel heteroatomdoped catalysts.

  9. Ballistic superconductivity in semiconductor nanowires.

    Science.gov (United States)

    Zhang, Hao; Gül, Önder; Conesa-Boj, Sonia; Nowak, Michał P; Wimmer, Michael; Zuo, Kun; Mourik, Vincent; de Vries, Folkert K; van Veen, Jasper; de Moor, Michiel W A; Bommer, Jouri D S; van Woerkom, David J; Car, Diana; Plissard, Sébastien R; Bakkers, Erik P A M; Quintero-Pérez, Marina; Cassidy, Maja C; Koelling, Sebastian; Goswami, Srijit; Watanabe, Kenji; Taniguchi, Takashi; Kouwenhoven, Leo P

    2017-07-06

    Semiconductor nanowires have opened new research avenues in quantum transport owing to their confined geometry and electrostatic tunability. They have offered an exceptional testbed for superconductivity, leading to the realization of hybrid systems combining the macroscopic quantum properties of superconductors with the possibility to control charges down to a single electron. These advances brought semiconductor nanowires to the forefront of efforts to realize topological superconductivity and Majorana modes. A prime challenge to benefit from the topological properties of Majoranas is to reduce the disorder in hybrid nanowire devices. Here we show ballistic superconductivity in InSb semiconductor nanowires. Our structural and chemical analyses demonstrate a high-quality interface between the nanowire and a NbTiN superconductor that enables ballistic transport. This is manifested by a quantized conductance for normal carriers, a strongly enhanced conductance for Andreev-reflecting carriers, and an induced hard gap with a significantly reduced density of states. These results pave the way for disorder-free Majorana devices.

  10. Alloying InAs and InP nanowires for optoelectronic applications: A first principles study

    Energy Technology Data Exchange (ETDEWEB)

    Toniolo, Giuliano R.; Anversa, Jonas [Departamento de Fisica, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS (Brazil); Santos, Cláudia L. dos [Área de Ciências Tecnológicas, Centro Universitário Franciscano, 97010-032, Santa Maria, RS (Brazil); Piquini, Paulo, E-mail: paulo.piquini@ufsm.br [Departamento de Fisica, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS (Brazil)

    2014-08-01

    The capability of nanowires to relieve the stress introduced by lattice mismatching through radial relaxation opens the possibility to search for devices for optoelectronic applications. However, there are difficulties to fabricate, and therefore to explore the properties of nanowires with narrow diameters. Here we apply first principles calculations to study the electronic and optical properties of narrow InAs{sub 1−x}P{sub x} nanowires. Our results show that the absorption threshold can be pushed to near-ultraviolet region, and suggests that arrays of these nanowires with different diameters and compositions could be used as devices acting from the mid-infrared to the near-ultraviolet region. - Highlights: • The optical properties of InAsP alloy nanowires were studied using DFT calculations. • The variation of band edges and band offsets with composition were determined. • The dependence of the optical absorption with alloy composition was settled. • The onset for optical absorption is suggested to be pushed to the UV region.

  11. Composition

    DEFF Research Database (Denmark)

    Bergstrøm-Nielsen, Carl

    2014-01-01

    Cue Rondo is an open composition to be realised by improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound/video files will in some cases only provide a few minutes' sample, or the visuals will not appear at all...

  12. Composition

    DEFF Research Database (Denmark)

    Bergstrøm-Nielsen, Carl

    2011-01-01

    Strategies are open compositions to be realised by improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound files will in some cases only provide a few minutes' sample. Please DOWNLOAD them to hear them in full...

  13. Composition

    DEFF Research Database (Denmark)

    Bergstrøm-Nielsen, Carl

    2010-01-01

    New Year is an open composition to be realised by improvising musicians. It is included in "From the Danish Seasons" (see under this title). See more about my composition practise in the entry "Composition - General Introduction". This work is licensed under a Creative Commons "by-nc" License. You...

  14. Composition

    DEFF Research Database (Denmark)

    2014-01-01

    Memory Pieces are open compositions to be realised solo by an improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound files will in some cases only provide a few minutes' sample. Please DOWNLOAD them to hear them...

  15. Sub-Poissonian Narrowing of Length Distributions Realized in Ga-Catalyzed GaAs Nanowires.

    Science.gov (United States)

    Koivusalo, Eero S; Hakkarainen, Teemu V; Guina, Mircea D; Dubrovskii, Vladimir G

    2017-09-13

    Herein, we present experimental data on the record length uniformity within the ensembles of semiconductor nanowires. The length distributions of Ga-catalyzed GaAs nanowires obtained by cost-effective lithography-free technique on silicon substrates systematically feature a pronounced sub-Poissonian character. For example, nanowires with the mean length ⟨L⟩ of 2480 nm show a length distribution variance of only 367 nm(2), which is more than twice smaller than the Poisson variance h⟨L⟩ of 808 nm(2) for this mean length (with h = 0.326 nm as the height of GaAs monolayer). For 5125 nm mean length, the measured variance is 1200 nm(2) against 1671 nm(2) for Poisson distribution. A supporting model to explain the experimental findings is proposed. We speculate that the fluctuation-induced broadening of the length distribution is suppressed by nucleation antibunching, the effect which is commonly observed in individual vapor-liquid-solid nanowires but has never been seen for their ensembles. Without kinetic fluctuations, the two remaining effects contributing to the length distribution width are the nucleation randomness for nanowires emerging from the substrate and the shadowing effect on long enough nanowires. This explains an interesting time evolution of the variance that saturates after a short incubation stage but then starts increasing again due to shadowing, remaining, however, smaller than the Poisson value for a sufficiently long time.

  16. Sleep quality and body composition variations in obese male adults after 14 weeks of yoga intervention: A randomized controlled trial

    Directory of Open Access Journals (Sweden)

    P B Rshikesan

    2017-01-01

    Full Text Available Background: Obesity is a big challenge all over the world. It is associated with many noncommunicable diseases. Yoga known to be add-on treatment may be effective for obesity control. Aim: To assess the effect of integrated approach of yoga therapy (IAYT for body composition and quality of sleep in adult obese male. Subjects and Methods: A randomized controlled trial was conducted for 14 weeks on obese male of urban setting. Eighty individuals were randomly divided into two groups, i.e., yoga group (n = 40; age; 40.03 ± 8.74 years, body mass index [BMI] 28.7 ± 2.35 kg/m2 and control group (age; 42.20 ± 12.06 years, BMI 27.70 ± 2.05 kg/m2. The IAYT was imparted to yoga group for 1½ hour for 5 days in a week for 14 weeks. The control group continued their regular activities. The body composition by InBody R20 and sleep quality by Pittsburgh Sleep Quality Index (PSQI were assessed. Statistical analysis was done for within and between groups using SPSS version 21. The correlation analysis was done on the difference in pre-post values. Results: The results showed that weight (P = 0.004, BMI (P = 0.008, bone mass (P = 0.017, obesity degree (P = 0.005, and mineral mass (P = 0.046 were improved in yoga group and no change in control group (P > 0.05. The global score of PSQI improved (P = 0.017 in yoga group alone. Conclusion: The results indicate the beneficial effects of IAYT on body composition and sleep quality in obese males. The yoga practice may reduce obesity with the improvement in quality of life.

  17. Electrically Injected UV-Visible Nanowire Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Wang, George T.; Li, Changyi; Li, Qiming; Liu, Sheng; Wright, Jeremy Benjamin; Brener, Igal; Luk, Ting -Shan; Chow, Weng W.; Leung, Benjamin; Figiel, Jeffrey J.; Koleske, Daniel D.; Lu, Tzu-Ming

    2015-09-01

    There is strong interest in minimizing the volume of lasers to enable ultracompact, low-power, coherent light sources. Nanowires represent an ideal candidate for such nanolasers as stand-alone optical cavities and gain media, and optically pumped nanowire lasing has been demonstrated in several semiconductor systems. Electrically injected nanowire lasers are needed to realize actual working devices but have been elusive due to limitations of current methods to address the requirement for nanowire device heterostructures with high material quality, controlled doping and geometry, low optical loss, and efficient carrier injection. In this project we proposed to demonstrate electrically injected single nanowire lasers emitting in the important UV to visible wavelengths. Our approach to simultaneously address these challenges is based on high quality III-nitride nanowire device heterostructures with precisely controlled geometries and strong gain and mode confinement to minimize lasing thresholds, enabled by a unique top-down nanowire fabrication technique.

  18. Near field heat transfer between random composite materials. Applications and limitations

    Energy Technology Data Exchange (ETDEWEB)

    Santiago, Eva Yazmin; Esquivel-Sirvent, Raul [Univ. Nacional Autonoma de Mexico (Mexico). Inst. de Fisica

    2017-05-01

    We present a theoretical study of the limits and bounds of using effective medium approximations in the calculation of the near field radiative heat transfer between a composite system made of Au nanoparticles in a SiC host and an homogeneous SiC slab. The effective dielectric function of the composite slab is calculated using three different approximations: Maxwell-Garnett, Bruggeman, and Looyenga's. In addition, we considered an empirical fit to the effective dielectric function by Grundquist and Hunderi. We show that the calculated value of the heat flux in the near field is dependent on the model, and the difference in the effective dielectric function is larger around the plasmonic response of the Au nanoparticles. This, in turn, accounts for the difference in the near field radiative heat flux. For all values of filling fractions, the Looyenga approximation gives a lower bound for the heat flux.

  19. Impact of exercise changes on body composition during the college years--a five year randomized controlled study.

    Science.gov (United States)

    Kemmler, Wolfgang; von Stengel, Simon; Kohl, Matthias; Bauer, Julia

    2016-01-19

    Observational studies have consistently reported severe weight gains during the college years; information about the effect on body composition is scarce, however. Thus, the aim of the study was to determine the effect of exercise changes on body composition during 5 years at university. Sixty-one randomly selected male and female dental (DES; 21 ± 3 years., 22 ± 2 kg/m(2)) and 53 sport (physical education) students (SPS; 20 ± 2 years., 22 ± 3 kg/m(2)) were accompanied over their 5-year study program. Body mass and body composition as determined via Dual-Energy x-ray-absorptiometry (DXA) at baseline and follow-up were selected as primary study endpoints. Confounding parameters (i.e., nutritional intake, diseases, medication) that may affect study endpoints were determined every two years. Endpoints were log-transformed to stabilize variance and achieve normal distributed values. Paired t-tests and unpaired Welch-t-tests were used to check intra and inter-group differences. Exercise volume decreased significantly by 33% (p effect on fatness and fitness in young college students was the pronounced decreases in exercise volume and particularly exercise intensity. NCT00521235; "Effect of Different Working Conditions on Risk Factors in Dentists Versus Trainers. A Combined Cross sectional and Longitudinal Trial with Student and Senior Employees."; August 24, 2007.

  20. Different growth regimes in InP nanowire growth mediated by Ag nanoparticles

    Science.gov (United States)

    Oliveira, D. S.; Zavarize, M.; Tizei, L. H. G.; Walls, M.; Ospina, C. A.; Iikawa, F.; Ugarte, D.; Cotta, M. A.

    2017-12-01

    We report on the existence of two different regimes in one-step Ag-seeded InP nanowire growth. The vapor–liquid–solid-mechanism is present at larger In precursor flows and temperatures, ∼500 °C, yielding high aspect ratio and pure wurtzite InP nanowires with a semi-spherical metal particle at the thin apex. Periodic diameter oscillations can be achieved under extreme In supersaturations at this temperature range, showing the presence of a liquid catalyst. However, under lower temperatures and In precursor flows, large diameter InP nanowires with mixed wurtzite/zincblende segments are obtained, similarly to In-assisted growth. Chemical composition analysis suggest that In-rich droplet formation is catalyzed at the substrate surface via Ag nanoparticles; this process might be facilitated by the sulfur contamination detected in these nanoparticles. Furthermore, part of the original Ag nanoparticle remains solid and is embedded inside the actual catalyst, providing an in situ method to switch growth mechanisms upon changing In precursor flow. Nevertheless, our Ag-seeded InP nanowires exhibit overall optical emission spectra consistent with the observed structural properties and similar to Au-catalyzed InP nanowires. We thus show that Ag nanoparticles may be a suitable replacement for Au in InP nanowire growth.

  1. Manganese Dioxide Nanowires of Tunable Dimensions Synthesized via a Facile Hydrothermal Route

    Directory of Open Access Journals (Sweden)

    Ying Ying Kong

    2015-01-01

    Full Text Available Manganese dioxide (MnO2 nanowires of tunable dimensions were successfully synthesized via the facile water-bathing hydrothermal route. Homogeneous solution mixtures of KMnO4 and MnSO4 of varying compositions were being aged in a thermostated water bath under controlled conditions. The dimensional aspect ratios of MnO2 nanowires formed were readily modulated by varying synthesis parameters such as the initial concentration of chemical precursors, reaction temperature, and aging duration. At fixed initial precursor concentrations, the mean diameter of MnO2 nanowires decreased slightly from 57 nm to 53 nm with increased reaction temperature from 60°C to 90°C. The mean diameter of MnO2 nanowires decreased linearly within the range of 104 nm and 35 nm as the initial concentration of both precursors was increased in turn within the range of 10 mmol and 40 mmol at fixed aging temperature and duration. Upon aging for 2 to 24 hours at 80°C, the mean diameter and length of MnO2 nanowires were observed to vary within the range of 33–55 nm and 0.69–2.68 μm, respectively, which corresponded to the dimensional aspect ratio range of 21 to 49. Henceforth, MnO2 nanowires of tunable dimensions could be synthesized through optimally controlled synthesis parameters.

  2. Room-Temperature Surface Modification of Cu Nanowires and Their Applications in Transparent Electrodes, SERS-Based Sensors, and Organic Solar Cells.

    Science.gov (United States)

    Wang, Xiao; Wang, Ranran; Zhai, Haitao; Shen, Xi; Wang, Tao; Shi, Liangjing; Yu, Richeng; Sun, Jing

    2016-10-26

    Cu nanowires (Copper nanowires) have attracted lots of attention recently due to their potential applications in transparent electrodes, surface enhanced Raman scattering (SERS) based sensors, and solar cells. However, as the surface composition and morphology of Cu nanowires severely influence the performance of the devices based on them, facile surface modification methods need to be developed. Herein, we propose a room-temperature, time-saving aqueous solution method, through which clean Cu nanowires with small Ag nanoparticles decorating around them could be achieved. The unique "sesame candy bar" structure of Cu nanowires brought about significant enhancement on the electrical, optical, and mechanical performances of Cu nanowire networks. Transparent electrodes with ideal opto-electrical performance (47 Ω sq(-1) @ 89.1% T) and high antioxidation, antithermal, and electrical stability were fabricated. Stretchable electrodes based on the modified Cu nanowire networks showed superior stretch-ability and cyclic stability. SERS sensors and organic solar cells based on Cu nanowire networks exhibited high performance due to the enhanced surface plasmonic coupling and light scattering effect. We believe that the method will shed light on the large-scale fabrication and application of Cu nanowire based devices.

  3. Tunneling magnetoresistance in Si nanowires

    KAUST Repository

    Montes Muñoz, Enrique

    2016-11-09

    We investigate the tunneling magnetoresistance of small diameter semiconducting Si nanowires attached to ferromagnetic Fe electrodes, using first principles density functional theory combined with the non-equilibrium Green\\'s functions method for quantum transport. Silicon nanowires represent an interesting platform for spin devices. They are compatible with mature silicon technology and their intrinsic electronic properties can be controlled by modifying the diameter and length. Here we systematically study the spin transport properties for neutral nanowires and both n and p doping conditions. We find a substantial low bias magnetoresistance for the neutral case, which halves for an applied voltage of about 0.35 V and persists up to 1 V. Doping in general decreases the magnetoresistance, as soon as the conductance is no longer dominated by tunneling.

  4. III-Nitride nanowire optoelectronics

    Science.gov (United States)

    Zhao, Songrui; Nguyen, Hieu P. T.; Kibria, Md. G.; Mi, Zetian

    2015-11-01

    Group-III nitride nanowire structures, including GaN, InN, AlN and their alloys, have been intensively studied in the past decade. Unique to this material system is that its energy bandgap can be tuned from the deep ultraviolet (~6.2 eV for AlN) to the near infrared (~0.65 eV for InN). In this article, we provide an overview on the recent progress made in III-nitride nanowire optoelectronic devices, including light emitting diodes, lasers, photodetectors, single photon sources, intraband devices, solar cells, and artificial photosynthesis. The present challenges and future prospects of III-nitride nanowire optoelectronic devices are also discussed.

  5. Electrochemical synthesis of multisegmented nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Kok, Kuan-Ying; Ng, Inn-Khuan; Saidin, Nur Ubaidah [Malaysian Nuclear Agency, Bangi, 43000 Kajang (Malaysia)

    2012-11-27

    Electrochemical deposition has emerged as a promising route for nanostructure fabrication in recent years due to the many inherent advantages it possesses. This study focuses on the synthesis of high-aspect-ratio multisegmented Au/Ni nanowires using template-directed sequential electrochemical deposition techniques. By selectively removing the Ni segments in the nanowires, high-yield of pure gold nanorods of predetermined lengths was obtained. Alternatively, the sacrificial Ni segments in the nanowires can be galvanically displaced with Bi and Te to form barbells structures with Bi{sub x}Te{sub y} nanotubes attached to neighbouring gold segments. Detailed studies on the nanostructures obtained were carried out using various microscopy, diffraction and probebased techniques for structural, morphological and chemical characterizations.

  6. Fabrication of nanowires and nanostructures

    DEFF Research Database (Denmark)

    Mátéfi-Tempfli, Stefan; Mátéfi-Tempfli, M.; Piraux, L.

    2009-01-01

    We report on different approaches that we have adopted and developed for the fabrication of nanowires and nanostructures. Methods based on template synthesis and on self organization seem to be the most promising for the fabrication of nanomaterials and nanostructures due to their easiness and low...... cost. The development of a supported nanoporous alumina template and the possibility of using this template to combine electrochemical synthesis with lithographic methods open new ways for the fabrication of complex nanostructures. The numerous advantages of the supported template and its compatibility...... with microelectronic processes make it an ideal candidate for further integration into large-scale fabrication of various nanowire-based devices....

  7. A randomized trial of functional electrical stimulation for walking in incomplete spinal cord injury: effects on body composition.

    Science.gov (United States)

    Giangregorio, Lora; Craven, Catharine; Richards, Kieva; Kapadia, Naaz; Hitzig, Sander L; Masani, Kei; Popovic, Milos R

    2012-09-01

    To evaluate the effects of functional electrical stimulation (FES)-assisted walking on body composition, compared to a non-FES exercise program in individuals with a spinal cord injury (SCI). Parallel-group randomized controlled trial. Individuals with chronic (≥ 18 months) incomplete SCI (level C2 to T12, AIS C or D) were recruited and randomized to FES-assisted walking (intervention), or aerobic and resistance training (control) sessions thrice-weekly for 16 weeks. Whole body and leg lean mass and whole body fat mass, measured with dual-energy X-ray absorptiometry, and lower-limb muscle cross-sectional area (CSA) and fat CSA, measured with peripheral computed tomography were assessed at baseline, 4 months, and 12 months. Intention-to-treat analyses using repeated measures general linear models were used to assess between-group differences. Thirty-four individuals were randomized (17 per group); 27 remained at 12 months. There were no significant main effects of FES-assisted walking on body composition variables in intention-to-treat analyses with group means. There was a significant group-by-time interaction for muscle area from baseline to 12 months (P = 0.04). Intention-to-treat analysis of muscle area change scores between baseline and 12 months revealed a significant difference between groups (mean (SD) muscle area change score 212 (517) mm(s) for FES, -136 (268) mm(s) for control, P = 0.026). There were 13 side effects or adverse events deemed related to study participation (7 intervention, 5 control); most were resolved with modifications to the protocol. One fainting episode resulted in a hospital visit and study withdrawal. Thrice-weekly FES-assisted walking exercise over 4 months did not result in a change in body composition in individuals with chronic, motor incomplete C2 to T12 SCI (AIS classification C and D). However, longer-term follow-up revealed that it might maintain muscle area.

  8. Epitaxial nanowire formation in metamorphic GaAs/GaPAs short-period superlattices

    Science.gov (United States)

    Zheng, Nan; Ahrenkiel, S. Phillip

    2017-07-01

    Metamorphic growth presents routes to novel nanomaterials with unique properties that may be suitable for a range of applications. We discuss self-assembled, epitaxial nanowires formed during metalorganic chemical vapor deposition of metamorphic GaAs/GaPAs short-period superlattices. The heterostructures incorporate strain-engineered GaPAs compositional grades on 6°-B miscut GaAs substrates. Lateral diffusion within the SPS into vertically aligned, three-dimensional columns results in nanowires extending along A directions with a lateral period of 70-90 nm. The microstructure is probed by transmission electron microscopy to confirm the presence of coherent GaAs nanowires within GaPAs barriers. The compositional profile is inferred from analysis of {200} dark-field image contrast and lattice images.

  9. Overweight and obesity in Slovak high school students and body composition indicators: a non-randomized cross-sectional study

    Directory of Open Access Journals (Sweden)

    Bibiana Vadasova

    2016-08-01

    Full Text Available Abstract Background Physical development can be considered as an indicator of the overall health status of the youth population. Currently, it appears that the increasing trend of the prevalence of obesity among children and youths has stopped in a number of countries worldwide. Studies point to the fact that adolescence is a critical period for the development of obesity. Body mass index (BMI seems to be an orientation parameter in the assessment of prevalence of obesity which is not sufficient for more accurate identification of at risk individuals. The purpose of this study was to evaluate association between BMI percentile zones as health-risk for being overweight and obese and body composition indicators in high-school students from the Prešov (Slovakia region. Methods A non-randomized cross-sectional study in high school students from the Prešov (Slovakia region was conducted. The research sample consisted of 1014 participants (boys n = 466, girls n = 549. Body composition was measured using direct segmental multi-frequency bioelectrical impedance analysis (DSM-BIA. To examine the association between obesity and selected body composition indicators, Kruskal-Wallis ANOVA and Eta2 were used. The relationship between selected body composition indicators and percentile BMI zones was determined using the Kendall tau correlation. Results In groups with different BMI percentile zones (normal weight, overweight, obese, ANOVA showed significant differences for girls and boys (p ˂.05 with high effect size (η2 ˂.26 in body weight, body fat mass index, body fat percentage, fat free mass index, fat-free mass percentage, visceral fat area, waist-to-hip ratio, waist circumference, protein mass and mineral mass. The highest degree of correlation among boys was between BMI values indicating overweight and obesity and fat free mass index and waist circumference, respectively (τ = .71, τ = .70, respectively. In girls, the highest

  10. Void formation induced electrical switching in phase-change nanowires.

    Science.gov (United States)

    Meister, Stefan; Schoen, David T; Topinka, Mark A; Minor, Andrew M; Cui, Yi

    2008-12-01

    Solid-state structural transformation coupled with an electronic property change is an important mechanism for nonvolatile information storage technologies, such as phase-change memories. Here we exploit phase-change GeTe single-nanowire devices combined with ex situ and in situ transmission electron microscopy to correlate directly nanoscale structural transformations with electrical switching and discover surprising results. Instead of crystalline-amorphous transformation, the dominant switching mechanism during multiple cycling appears to be the opening and closing of voids in the nanowires due to material migration, which offers a new mechanism for memory. During switching, composition change and the formation of banded structural defects are observed in addition to the expected crystal-amorphous transformation. Our method and results are important to phase-change memories specifically, but also to any device whose operation relies on a small scale structural transformation.

  11. Synthesis, microstructure, and physical properties of metallic barcode nanowires

    Science.gov (United States)

    Park, Bum Chul; Kim, Young Keun

    2017-05-01

    With rapid progress in nanotechnology, nanostructured materials have come closer to our life. Single-component nanowires are actively investigated because of their novel properties, attributed to their nanoscale dimensions and adjustable aspect ratio, but their technical limitations cannot be resolved easily. Heterostructured nanomaterials gained attention as alternatives because they can improve the existing single-component structure or add new functions to it. Among them, barcode nanowires (BNWs), comprising at least two different functional segments, can perform multiple functions for use in biomedical sensors, information encoding and security, and catalysts. BNW applications require reliable response to the external field. Hence, researchers have been attempting to improve the reliability of synthesis and regulate the properties precisely. This article highlights the recent progress and prospects for the synthesis, properties, and applications of metallic BNWs with focus on the dependence of the magnetic, optical, and mechanical properties on material, composition, shape, and microstructure.

  12. Randomized Clinical Trial of Composite Restorations in Primary Teeth: Effect of Adhesive System after Three Years

    Directory of Open Access Journals (Sweden)

    Secil Bektaş Donmez

    2016-01-01

    Full Text Available The purpose of this study was to assess the clinical performance of composite restorations placed with different adhesive systems in primary teeth. In 32 patients, 128 composite restorations were placed using a split-mouth design as follows (4 groups/patient: three-step etch-and-rinse (Group 1, two-step etch-and-rinse (Group 2, two-step self-etch (Group 3, and one-step self-etch (Group 4. The restorations were clinically evaluated at baseline and at 6, 18, and 36 months according to the FDI criteria. There was no significant difference between the adhesive systems in retention of the restorations (p>0.05. Over time, there was a statistically significant decrease in marginal adaptation in all groups, whereas surface and marginal staining significantly increased in Groups 3 and 4 (p<0.05. The etch-and-rinse adhesive systems resulted in better marginal adaptation than the self-etch adhesive systems (p<0.05. It was concluded that preetching of the primary enamel might help improve the clinical performance of the self-etch adhesive systems in primary teeth.

  13. Vapor-liquid-solid growth of silicon and silicon germanium nanowires

    Science.gov (United States)

    Nimmatoori, Pramod

    2009-12-01

    time, temperature, SiH4 partial pressure and wire diameter and discussed in the context of the literature. The wire growth rate was found to increase with wire diameter in agreement with a size-related effect known as the Gibbs-Thomson effect. Subsequently, the effect of P and Sb doping on the growth rate and structural properties of Si nanowires was investigated. A reduction in wire growth rate was observed upon doping, which was pronounced in case of Sb doping, ascribable to P/Sb segregation at the vapor-liquid interface (catalyst surface) and the liquid-solid interface (growth front) that in turn reduces Si incorporation at these interfaces. The second part of thesis was focused on the Si1-xGe x alloy nanowires. The effect of wire diameter and growth conditions on the interfacial abruptness of Si/Si1-xGex heterostructure nanowires was examined. Abrupt interfaces were obtained at smaller wire diameters. However, the growth temperature wasn't found to have much impact on the interfacial abruptness. These results were explained in terms of catalyst effects on the interfacial abruptness. The remaining part of the study was focused on the effect of growth conditions on the growth rate of Si1-x Gex nanowires. It was found that the Si incorporation mechanism was different between Si and Si1-xGex nanowire growth which was ascribed to changes in the gas phase or catalyst composition that can impact the SiH4 decomposition kinetics at the catalyst surface (vapor-liquid interface) and/or Si incorporation at the growth front (liquid-solid interface).

  14. Axial shear modulus of a fiber-reinforced composite with random fiber cross-sections

    Directory of Open Access Journals (Sweden)

    S. K. Bose

    1982-01-01

    Full Text Available A study is made of the effective axial shear modulus of a fiber reinforced material with random fiber cross-sections so that the micromechanics is governed by stochastic differential equations. A coarse-graining procedure is adopted to investigate the macroscopic behavior of the material. This analysis leads to the formula for the effective axial shear modulus μ∗=μ1/{1−2c(μ2−μ1/(μ2+μ1},where μ1 and μ2 are the shear modulus of the matrix and fibers respectively and c is the concentration of the fibers less that 0.5. For c>0.5, the fiber and matrix moduli are to be interchanged and c is to be replaced by 1−c. The results of this study are compared with those of the theory of fibre reinforced materials. Finally, a numerical example is presented with graphical representation.

  15. Influence of melt structure on the crystallization behavior and polymorphic composition of polypropylene random copolymer

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Bin [State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065 (China); Ecole Normale Supérieure, CNRS-ENS-UPMC UMR 8640, 24 Rue Lhomond, Paris 75005 (France); Chen, Zhengfang [State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065 (China); Kang, Jian, E-mail: jiankang@scu.edu.cn [State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065 (China); Yang, Feng; Chen, Jinyao; Cao, Ya; Xiang, Ming [State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065 (China)

    2015-03-20

    Highlights: • We prepared β-PPR and studied its crystallization behavior with different melt structures. • We observed surprising synergetic effect between β-NA and the ordered structures. • We explored the nature of ordered structures by calculating the equilibrium temperature. - Abstract: Polypropylene random copolymer (PPR) is one of important polypropylene types for the application fields. However, due to the random copolymer chain configuration, it is difficult to obtain high proportion of β-phase even under the influence of β-nucleating agent (β-NA). In this study, the melt structure (namely, the content of ordered structures in the melt) of β-nucleated ethylene-copolymerized PPR (β-PPR) was controlled by tuning the fusion temperature (T{sub f}), and its impact on the crystallization and polymorphic behavior of β-PPR was investigated by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), polarized optical microscopy (PLM) and scanning electronic microscopy (SEM). The result revealed that compared with the β-nucleated iPP homo-polymer, it is more difficult for β-PPR to form β-crystals; interestingly, when T{sub f} is in the temperature range of 162–173 °C, the ordered structures survived in melt exhibit high β-nucleation efficiency under the influence of β-NA, resulting in significant increase of β-phase proportion and evident variation of crystalline morphology, which is called the Ordered Structure Effect (OSE). Moreover, through investigating the self-nucleation behavior and equilibrium melting temperature of pure PPR (non-nucleated PPR), the physical nature of the lower and upper limiting T{sub f} temperatures for the occurrence of OSE in β-PPR was explored; the role of ethylene co-monomer in the occurrence of OSE was discussed.

  16. Variability of Fiber Elastic Moduli in Composite Random Fiber Networks Makes the Network Softer

    Science.gov (United States)

    Ban, Ehsan; Picu, Catalin

    2015-03-01

    Athermal fiber networks are assemblies of beams or trusses. They have been used to model mechanics of fibrous materials such as biopolymer gels and synthetic nonwovens. Elasticity of these networks has been studied in terms of various microstructural parameters such as the stiffness of their constituent fibers. In this work we investigate the elasticity of composite fiber networks made from fibers with moduli sampled from a distribution function. We use finite elements simulations to study networks made by 3D Voronoi and Delaunay tessellations. The resulting data collapse to power laws showing that variability in fiber stiffness makes fiber networks softer. We also support the findings by analytical arguments. Finally, we apply these results to a network with curved fibers to explain the dependence of the network's modulus on the variation of its structural parameters.

  17. Carbon doping of InSb nanowires for high-performance p-channel field-effect-transistors.

    Science.gov (United States)

    Yang, Zai-xing; Han, Ning; Wang, Fengyun; Cheung, Ho-Yuen; Shi, Xiaoling; Yip, SenPo; Hung, TakFu; Lee, Min Hyung; Wong, Chun-Yuen; Ho, Johnny C

    2013-10-21

    Due to the unique physical properties, small bandgap III-V semiconductor nanowires such as InAs and InSb have been extensively studied for the next-generation high-speed and high-frequency electronics. However, further CMOS applications are still limited by the lack of efficient p-doping in these nanowire materials for high-performance p-channel devices. Here, we demonstrate a simple and effective in situ doping technique in the solid-source chemical vapor deposition of InSb nanowires on amorphous substrates employing carbon dopants. The grown nanowires exhibit excellent crystallinity and uniform stoichiometric composition along the entire length of the nanowires. More importantly, the versatility of this doping scheme is illustrated by the fabrication of high-performance p-channel nanowire field-effect-transistors. High electrically active carbon concentrations of ~7.5 × 10(17) cm(-3) and field-effect hole mobility of ~140 cm(2) V(-1) s(-1) are achieved which are essential for compensating the electron-rich surface layers of InSb to enable heavily p-doped and high-performance device structures. All these further indicate the technological potency of this in situ doping technique as well as p-InSb nanowires for the fabrication of future CMOS electronics.

  18. Facile synthesis of core-shell CuO/Ag nanowires with enhanced photocatalytic and enhancement in photocurrent.

    Science.gov (United States)

    Liu, Xueqin; Li, Zhen; Zhao, CaiXin; Zhao, Wen; Yang, Jianbo; Wang, Yang; Li, Fei

    2014-04-01

    CuO nanowires were grown on Cu foil via a simple cost-effective wet-chemical route in large scales and used as templates for making silver-coated CuO (CuO/Ag) core-shell nanowires. The coverage of Ag shells on CuO nanowires was controlled by varying the concentration of Ag precursor. The structure, composition, morphology and optical properties of the synthesized core-shell CuO/Ag nanowires (CACs) were considered. The discussion on the growth process of CACs revealed the important role of Sn(2+). And, the novel structure enlarged the range of absorbed light and enhanced the absorption intensity of light. The CACs were evaluated for their ability to degrade methyl orange (MeO) solution under visible-light irradiation. The rate of degradation of the as-prepared CACs was more than 7 times faster than that of using pure CuO nanowires under solar light irradiation. Moreover, the incorporation of Ag shells at the surface causes a quenching of PL emissions and enhanced photocurrent of CuO nanowires. The mechanisms of enhanced photocatalytic activity, luminescence emission quenching, and photocurrent multiplication of the core-shell nanowires have been discussed. Copyright © 2014 Elsevier Inc. All rights reserved.

  19. COMPOSITE

    African Journals Online (AJOL)

    An effective medium theory of ferroelectric ceramic-polymer composite materials which treats both components symmetrically has been investigated to demonstrate the role played by the microgeometry of inclusions on dielectric, mechanical and piezoelectric properties of 0-3 composites. The limits of the various theoretical ...

  20. Photonic nanowires for quantum optics

    DEFF Research Database (Denmark)

    Munsch, M.; Claudon, J.; Bleuse, J.

    Photonic nanowires (PWs) are simple dielectric structures for which a very efficient and broadband spontaneous emission (SE) control has been predicted [1]. Recently, a single photon source featuring a record high efficiency was demonstrated using this geometry [2]. Using time-resolved micro-phot...

  1. Nanowire-based gas sensors

    NARCIS (Netherlands)

    Chen, X.; Wong, C.K.Y.; Yuan, C.A.; Zhang, G.

    2013-01-01

    Gas sensors fabricated with nanowires as the detecting elements are powerful due to their many improved characteristics such as high surface-to-volume ratios, ultrasensitivity, higher selectivity, low power consumption, and fast response. This paper gives an overview on the recent process of the

  2. Majorana fermions in semiconductor nanowires

    Science.gov (United States)

    Stanescu, Tudor D.; Lutchyn, Roman M.; Das Sarma, S.

    2011-10-01

    We study multiband semiconducting nanowires proximity coupled with an s-wave superconductor and calculate the topological phase diagram as a function of the chemical potential and magnetic field. The nontrivial topological state corresponds to a superconducting phase supporting an odd number of pairs of Majorana modes localized at the ends of the wire, whereas the nontopological state corresponds to a superconducting phase with no Majoranas or with an even number of pairs of Majorana modes. Our key finding is that multiband occupancy not only lifts the stringent constraint of one-dimensionality, but also allows having higher carrier density in the nanowire. Consequently, multiband nanowires are better suited for stabilizing the topological superconducting phase and for observing the Majorana physics. We present a detailed study of the parameter space for multiband semiconductor nanowires focusing on understanding the key experimental conditions required for the realization and detection of Majorana fermions in solid-state systems. We include various sources of disorder and characterize their effects on the stability of the topological phase. Finally, we calculate the local density of states as well as the differential tunneling conductance as functions of external parameters and predict the experimental signatures that would establish the existence of emergent Majorana zero-energy modes in solid-state systems.

  3. Nanowire-based Quantum Photonics

    NARCIS (Netherlands)

    Bulgarini, G.

    2014-01-01

    In this thesis work, I studied individual quantum dots embedded in one-dimensional nanostructures called nanowires. Amongst the effects given by the nanometric dimensions, quantum dots enable the generation of single light particles: photons. Single photon emitters and detectors are central building

  4. Alterations in fecal microbiota composition by probiotic supplementation in healthy adults: a systematic review of randomized controlled trials.

    Science.gov (United States)

    Kristensen, Nadja B; Bryrup, Thomas; Allin, Kristine H; Nielsen, Trine; Hansen, Tue H; Pedersen, Oluf

    2016-05-10

    The effects of probiotic supplementation on fecal microbiota composition in healthy adults have not been well established. We aimed to provide a systematic review of the potential evidence for an effect of probiotic supplementation on the composition of human fecal microbiota as assessed by high-throughput molecular approaches in randomized controlled trials (RCTs) of healthy adults. The survey of peer-reviewed papers was performed on 17 August 2015 by a literature search through PubMed, SCOPUS, and ISI Web of Science. Additional papers were identified by checking references of relevant papers. Search terms included healthy adult, probiotic, bifidobacterium, lactobacillus, gut microbiota, fecal microbiota, intestinal microbiota, intervention, and (clinical) trial. RCTs of solely probiotic supplementation and placebo in healthy adults that examined alteration in composition of overall fecal microbiota structure assessed by shotgun metagenomic sequencing, 16S ribosomal RNA sequencing, or phylogenetic microarray methods were included. Independent collection and quality assessment of studies were performed by two authors using predefined criteria including methodological quality assessment of reports of the clinical trials based on revised tools from PRISMA/Cochrane and by the Jadad score. Seven RCTs investigating the effect of probiotic supplementation on fecal microbiota in healthy adults were identified and included in the present systematic review. The quality of the studies was assessed as medium to high. Still, no effects were observed on the fecal microbiota composition in terms of α-diversity, richness, or evenness in any of the included studies when compared to placebo. Only one study found that probiotic supplementation significantly modified the overall structure of the fecal bacterial community in terms of β-diversity when compared to placebo. This systematic review of the pertinent literature demonstrates a lack of evidence for an impact of probiotics on

  5. Randomized trial reveals that physical activity and energy expenditure are associated with weight and body composition after RYGB.

    Science.gov (United States)

    Carnero, Elvis Alvarez; Dubis, Gabriel S; Hames, Kazanna C; Jakicic, John M; Houmard, Joseph A; Coen, Paul M; Goodpaster, Bret H

    2017-07-01

    This study investigated the associations of both physical activity time (PA) and energy expenditure (EE) with weight and fat mass (FM) loss in patients following Roux-en-Y gastric bypass (RYGB) surgery. Ninety-six nondiabetic patients were included in this analysis. Post-RYGB patients were randomized in one of two treatments: A 6-month exercise training program (RYBG+EX) or lifestyle educational classes (RYGB). Body composition was assessed by dual-energy X-ray absorptiometry and computed tomography. Components of PA and EE were quantified by a multisensory device. Dose-response relationships of both PA and EE with weight loss and body composition were explored according to quartiles of change in steps per day. Patients in the highest quartiles of steps per day change lost more FM (3rd = -19.5 kg and 4th = -22.7 kg, P muscle mass (3rd = -3.1 cm2 and 4th = -4.5 cm2 , P weight and FM, while maintaining higher skeletal muscle mass. © 2017 The Obesity Society.

  6. Six-month bracket failure rate with a flowable composite: A split-mouth randomized controlled trial

    Directory of Open Access Journals (Sweden)

    Sindhuja Krishnan

    Full Text Available ABSTRACT INTRODUCTION: The use of flowable composites as an orthodontic bonding adhesive merits great attention because of their adequate bond strength, ease of clinical handling and reduced number of steps in bonding. OBJECTIVE: The aim of this Randomized Controlled Trial was to comparatively evaluate over a 6-month period the bond failure rate of a flowable composite (Heliosit Orthodontic, Ivoclar Vivadent AG, Schaan and a conventional orthodontic bonding adhesive (Transbond XT, 3M Unitek. METHODS: 53 consecutive patients (23 males and 30 females who fulfilled the inclusion and exclusion criteria were included in the study. A total of 891 brackets were analyzed, where 444 brackets were bonded using Heliosit Orthodontic and 447 brackets were bonded using Transbond XT. The survival rates of brackets were estimated with the Kaplan-Meier analysis. Bracket survival distributions for bonding adhesives, tooth location and dental arch were compared with the log-rank test. RESULTS: The failure rates of the Transbond XT and the Heliosit Orthodontic groups were 8.1% and 6% respectively. No significant differences in the survival rates were observed between them (p= 0.242. There was no statistically significant difference in the bond failure rates when the clinical performance of the maxillary versus the mandibular arches and the anterior versus the posterior segments were compared. CONCLUSIONS: Both systems had clinically acceptable bond failure rates and are adequate for orthodontic bonding needs.

  7. Randomized Clinical Trial of a Self-Adhering Flowable Composite for Class I Restorations: 2-Year Results.

    Science.gov (United States)

    Sabbagh, J; Dagher, S; El Osta, N; Souhaid, P

    2017-01-01

    Objectives. To compare the clinical performances of a self-adhering resin composite and a conventional flowable composite with a self-etch bonding system on permanent molars. The influence of using rubber dam versus cotton roll isolation was also investigated. Materials and Methods. Patients aged between 6 and 12 years and presenting at least two permanent molars in need of small class I restorations were selected. Thirty-four pairs of restorations were randomly placed by the same operator. Fifteen patients were treated under rubber dam and nineteen using cotton rolls isolation and saliva ejector. They were evaluated according to the modified USPHS criteria at baseline, 6 months, and 1 and 2 years by two independent evaluators. Results. All patients attended the two-year recall. For all measured variables, there was no significant difference between rubber dam and cotton after 2 years of restoration with Premise Flowable or Vertise Flow (p value > 0.05). The percentage of restorations scored alpha decreased significantly over time with Premise Flowable and Vertise Flow for marginal adaptation and surface texture as well as marginal discoloration while it did not vary significantly for color matching. After 2 years, Vertise Flow showed a similar behaviour to the Premise Flowable used with a self-adhesive resin system.

  8. Randomized Clinical Trial of a Self-Adhering Flowable Composite for Class I Restorations: 2-Year Results

    Directory of Open Access Journals (Sweden)

    J. Sabbagh

    2017-01-01

    Full Text Available Objectives. To compare the clinical performances of a self-adhering resin composite and a conventional flowable composite with a self-etch bonding system on permanent molars. The influence of using rubber dam versus cotton roll isolation was also investigated. Materials and Methods. Patients aged between 6 and 12 years and presenting at least two permanent molars in need of small class I restorations were selected. Thirty-four pairs of restorations were randomly placed by the same operator. Fifteen patients were treated under rubber dam and nineteen using cotton rolls isolation and saliva ejector. They were evaluated according to the modified USPHS criteria at baseline, 6 months, and 1 and 2 years by two independent evaluators. Results. All patients attended the two-year recall. For all measured variables, there was no significant difference between rubber dam and cotton after 2 years of restoration with Premise Flowable or Vertise Flow (p value > 0.05. The percentage of restorations scored alpha decreased significantly over time with Premise Flowable and Vertise Flow for marginal adaptation and surface texture as well as marginal discoloration while it did not vary significantly for color matching. After 2 years, Vertise Flow showed a similar behaviour to the Premise Flowable used with a self-adhesive resin system.

  9. A six-year prospective randomized study of a nano-hybrid and a conventional hybrid resin composite in Class II restorations

    DEFF Research Database (Denmark)

    van Dijken, Jan W V; Pallesen, Ulla

    2013-01-01

    The objective of this 6 year prospective randomized equivalence trial was to evaluate the long-term clinical performance of a new nano-hybrid resin composite (RC) in Class II restorations in an intraindividual comparison with its well-established conventional hybrid RC predecessor.......The objective of this 6 year prospective randomized equivalence trial was to evaluate the long-term clinical performance of a new nano-hybrid resin composite (RC) in Class II restorations in an intraindividual comparison with its well-established conventional hybrid RC predecessor....

  10. Suppression of alloy fluctuations in GaAs-AlGaAs core-shell nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Loitsch, Bernhard; Winnerl, Julia; Parzinger, Eric; Matich, Sonja; Wurstbauer, Ursula; Riedl, Hubert; Abstreiter, Gerhard; Finley, Jonathan J.; Koblmüller, Gregor [Walter Schottky Institut and Physik Department, Technische Universität München, 85748 Garching (Germany); Jeon, Nari; Lauhon, Lincoln J. [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Döblinger, Markus [Department of Chemistry, Ludwig-Maximilians-Universität Munich, 81377 München (Germany)

    2016-08-29

    Probing localized alloy fluctuations and controlling them by growth kinetics have been relatively limited so far in nanoscale structures such as semiconductor nanowires (NWs). Here, we demonstrate the tuning of alloy fluctuations in molecular beam epitaxially grown GaAs-AlGaAs core-shell NWs by modifications of shell growth temperature, as investigated by correlated micro-photoluminescence, scanning transmission electron microscopy, and atom probe tomography. By reducing the shell growth temperature from T > 600 °C to below 400 °C, we find a strong reduction in alloy fluctuation mediated sharp-line luminescence, concurrent with a decrease in the non-randomness of the alloy distribution in the AlGaAs shell. This trend is further characterized by a change in the alloy compositional structure from unintentional quasi-superlattices of Ga- and Al-rich AlGaAs layers at high T to a nearly homogeneous random alloy distribution at low T.

  11. Effects of medium-chain triglycerides on weight loss and body composition: a meta-analysis of randomized controlled trials.

    Science.gov (United States)

    Mumme, Karen; Stonehouse, Welma

    2015-02-01

    Medium-chain triglycerides (MCTs) may result in negative energy balance and weight loss through increased energy expenditure and lipid oxidation. However, results from human intervention studies investigating the weight reducing potential of MCTs, have been mixed. To conduct a systematic review and meta-analysis of randomized controlled trials comparing the effects of MCTs, specifically C8:0 and C10:0, to long-chain triglycerides (LCTs) on weight loss and body composition in adults. Changes in blood lipid levels were secondary outcomes. Randomized controlled trials >3 weeks' duration conducted in healthy adults were identified searching Web of Knowledge, Discover, PubMed, Scopus, New Zealand Science, and Cochrane CENTRAL until March 2014 with no language restriction. Identified trials were assessed for bias. Mean differences were pooled and analyzed using inverse variance models with fixed effects. Heterogeneity between studies was calculated using I(2) statistic. An I(2)>50% or P<0.10 indicated heterogeneity. Thirteen trials (n=749) were identified. Compared with LCTs, MCTs decreased body weight (-0.51 kg [95% CI-0.80 to -0.23 kg]; P<0.001; I(2)=35%); waist circumference (-1.46 cm [95% CI -2.04 to -0.87 cm]; P<0.001; I(2)=0%), hip circumference (-0.79 cm [95% CI -1.27 to -0.30 cm]; P=0.002; I(2)=0%), total body fat (standard mean difference -0.39 [95% CI -0.57 to -0.22]; P<0.001; I(2)=0%), total subcutaneous fat (standard mean difference -0.46 [95% CI -0.64 to -0.27]; P<0.001; I(2)=20%), and visceral fat (standard mean difference -0.55 [95% CI -0.75 to -0.34]; P<0.001; I(2)=0%). No differences were seen in blood lipid levels. Many trials lacked sufficient information for a complete quality assessment, and commercial bias was detected. Although heterogeneity was absent, study designs varied with regard to duration, dose, and control of energy intake. Replacement of LCTs with MCTs in the diet could potentially induce modest reductions in body weight and composition

  12. Magnetostatic Interaction in Fe-Co Nanowires

    Directory of Open Access Journals (Sweden)

    Laura Elbaile

    2012-01-01

    Full Text Available Arrays of Fe-Co alloy nanowires with diameter around 35 nm and several micrometers in length have been synthesized by codepositing Fe and Co into porous anodic alumina. The morphology, structure, and magnetic properties of the nanowires (hysteresis loops and remanence curves were characterized by SEM, TEM, X-ray diffraction (XRD, and VSM, respectively. The XRD patterns indicate that the Fe-Co nanowires present a body-centered cubic (bcc structure and a preferred (110 orientation perpendicular to the template surface. From the hysteresis loops obtained with the magnetic field applied in the axis direction of the nanowires, we can observe that the coercive field slightly decreases when the nanowire length increases. This magnetic behaviour is analyzed considering the shape anisotropy and the dipolar interactions among nanowires.

  13. Magnetic crossover effect in Nickel nanowire arrays

    Energy Technology Data Exchange (ETDEWEB)

    Ghaddar, A. [Laboratoire de Magnetisme de Bretagne, CNRS-FRE 3117, C.S. 93837, 29238 Brest, Cedex (France); Gloaguen, F. [Laboratoire de Chimie, Electrochimie Moleculaire et Chimie Analytique, CNRS-UMR 6521, C. S. 93837 Brest Cedex 3 (France); Gieraltowski, J. [Laboratoire de Magnetisme de Bretagne, CNRS-FRE 3117, C.S. 93837, 29238 Brest, Cedex (France); Tannous, C., E-mail: tannous@univ-brest.f [Laboratoire de Magnetisme de Bretagne, CNRS-FRE 3117, C.S. 93837, 29238 Brest, Cedex (France)

    2011-05-01

    A crossover effect in the magnetic reversal mechanism within arrays of Nickel nanowires whose diameter varies from 15 to 100 nm is observed around 50 nm. Hysteresis loops and FMR measurements confirm that nanowire diameter controls effectively the nanowire easy axis as well as the magnetization reversal mechanism. This might be very interesting for spintronic devices based on current-induced domain motion such as non-volatile magnetic memory elements (MRAM) and low Ohmic loss devices.

  14. Redox exchange induced MnO2 nanoparticle enrichment in poly(3,4-ethylenedioxythiophene) nanowires for electrochemical energy storage.

    Science.gov (United States)

    Liu, Ran; Duay, Jonathon; Lee, Sang Bok

    2010-07-27

    MnO2 nanoparticle enriched poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires are fabricated by simply soaking the PEDOT nanowires in potassium permanganate (KMnO4) solution. The structures of these MnO2 nanoparticle enriched PEDOT nanowires are characterized by SEM and TEM, which show that the MnO2 nanoparticles have uniform sizes and are finely dispersed in the PEDOT matrix. The chemical constituents and bonding of these composite nanowires are characterized by energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, and infrared spectroscopy, which indicate that the formation and dispersion of these MnO2 nanoparticles into the nanoscale pores of the PEDOT nanowires are most likely triggered by the reduction of KMnO4 via the redox exchange of permanganate ions with the functional group on PEDOT. Varying the concentrations of KMnO4 and the reaction time controls the loading amount and size of the MnO2 nanoparticles. Cyclic voltammetry and galvanostatic charge-discharge are used to characterize the electrochemical properties of these MnO2 nanoparticle loaded PEDOT nanowires. Due to their extremely high exposed surface area with nanosizes, the pristine MnO2 nanoparticles in these MnO2 nanoparticle enriched PEDOT nanowires show very high specific capacitance (410 F/g) as the supercapacitor electrode materials as well as high Li+ storage capacity (300 mAh/g) as cathode materials of Li ion battery, which boost the energy storage capacity of PEDOT nanowires to 4 times without causing excessive volume expansion in the polymer. The highly conductive and porous PEDOT matrix facilitates fast charge/discharge of the MnO2 nanoparticles and prevents them from agglomerating. These synergic properties enable the MnO2 nanoparticle enriched PEDOT nanowires to be promising electrode materials for supercapacitors and lithium ion batteries.

  15. Growth and Physical Property Study of Single Nanowire (Diameter ~45 nm of Half Doped Manganite

    Directory of Open Access Journals (Sweden)

    Subarna Datta

    2013-01-01

    Full Text Available We report here the growth and characterization of functional oxide nanowire of hole doped manganite of La0.5Sr0.5MnO3 (LSMO. We also report four-probe electrical resistance measurement of a single nanowire of LSMO (diameter ~45 nm using focused ion beam (FIB fabricated electrodes. The wires are fabricated by hydrothermal method using autoclave at a temperature of 270 °C. The elemental analysis and physical property like electrical resistivity are studied at an individual nanowire level. The quantitative determination of Mn valency and elemental mapping of constituent elements are done by using Electron Energy Loss Spectroscopy (EELS in the Transmission Electron Microscopy (TEM mode. We address the important issue of whether as a result of size reduction the nanowires can retain the desired composition, structure, and physical properties. The nanowires used are found to have a ferromagnetic transition (TC at around 325 K which is very close to the bulk value of around 330 K found in single crystal of the same composition. It is confirmed that the functional behavior is likely to be retained even after size reduction of the nanowires to a diameter of 45 nm. The electrical resistivity shows insulating behavior within the measured temperature range which is similar to the bulk system.

  16. ZnO Hemisphere Pits Nanowire/CdS Photoelectrode for High-Efficiency Photoelectrochemical Water Splitting

    Science.gov (United States)

    Chen, Peiyang; Liu, Zhifeng; Geng, Xuemin; Wang, Jialu; Zhang, Min; Liu, Junqi; Yan, Lu

    2017-03-01

    In this paper, a ZnO hemisphere pits nanowire (HPW) photoelectrode is fabricated by using polystyrene (PS) nanospheres as templates, and CdS is deposited on ZnO nanowires to improve further its photoelectrochemical performance. Firstly, PS nanospheres are deposited on ZnO seed layers by air-liquid interface self-assembling method. Subsequently, ZnO HPWs are grown which effected by PS nanospheres. Finally, CdS nanoparticles were deposited on the ZnO HPWs to construct ZnO/CdS heterojunction photoanodes by successive ionic layer adsorption and reaction method. This hemisphere pits nanowires composite structure demonstrated a highly efficient photoelectrocatalytic performance with a remarkable photocurrent density of 2.27 mA cm-2 determined at 0.8 V versus Ag/AgCl. The enhanced performance of ZnO hemisphere pits nanowires/CdS nanoparticles (ZnO/CdS) composite photoanodes originated from the enhanced light absorption in the visible region and reduced photogenerated charges recombination rate. Furthermore, compared with ordinary nanowire arrays, hemisphere pits nanowire structure can reflect light more times to facilitate light harvesting. This work exhibits the important significance in constructing photoelectrodes for photoelectrochemical water splitting and other photoelectric devices.

  17. InGaN/GaN disk-in-nanowire white light emitting diodes on (001) silicon

    KAUST Repository

    Guo, Wei

    2011-01-01

    High density (? 1011 cm-2) GaN nanowires and InGaN/GaN disk-in-nanowire heterostructures have been grown on (001) silicon substrates by plasma-assisted molecular beam epitaxy. The nanowires exhibit excellent uniformity in length and diameter and a broad emission is obtained by incorporating InGaN disks of varying composition along the length of the nanowires. Monolithic lighting emitting diodes were fabricated with appropriate n- and p-doping of contact layers. White light emission with chromaticity coordinates of x=0.29 and y=0.37 and a correlated color temperature of 5500-6500 K at an injection current of 50 A/ cm2 is measured. The measured external quantum efficiency of the devices do not exhibit any rollover (droop) up to an injection current density of 400 A/ cm2. © 2011 American Institute of Physics.

  18. Preparation and characterization of haematite nanowire arrays

    CERN Document Server

    Xue, D S; Liu, Q F; Zhang, L Y

    2003-01-01

    Arrays of alpha-Fe sub 2 O sub 3 nanowires embedded in anodic alumina membranes were obtained after heat-treating beta-FeOOH nanowire arrays fabricated by electrochemical deposition. Haematite polycrystalline nanowires with maximum length of about 7 mu m and average diameter of about 120 nm were characterized by means of x-ray diffraction and transmission electron microscopy. The Morin temperature below 80 K and Neel temperature of about 350 K for the alpha-Fe sub 2 O sub 3 nanowire arrays, far lower than those of bulk material, were measured by Moessbauer spectroscopy and using a Magnetic Property Measurement System.

  19. Diluted magnetic semiconductor nanowires exhibiting magnetoresistance

    Science.gov (United States)

    Yang, Peidong [El Cerrito, CA; Choi, Heonjin [Seoul, KR; Lee, Sangkwon [Daejeon, KR; He, Rongrui [Albany, CA; Zhang, Yanfeng [El Cerrito, CA; Kuykendal, Tevye [Berkeley, CA; Pauzauskie, Peter [Berkeley, CA

    2011-08-23

    A method for is disclosed for fabricating diluted magnetic semiconductor (DMS) nanowires by providing a catalyst-coated substrate and subjecting at least a portion of the substrate to a semiconductor, and dopant via chloride-based vapor transport to synthesize the nanowires. Using this novel chloride-based chemical vapor transport process, single crystalline diluted magnetic semiconductor nanowires Ga.sub.1-xMn.sub.xN (x=0.07) were synthesized. The nanowires, which have diameters of .about.10 nm to 100 nm and lengths of up to tens of micrometers, show ferromagnetism with Curie temperature above room temperature, and magnetoresistance up to 250 Kelvin.

  20. A generic approach for vertical integration of nanowires.

    Science.gov (United States)

    Latu-Romain, E; Gilet, P; Noel, P; Garcia, J; Ferret, P; Rosina, M; Feuillet, G; Lévy, F; Chelnokov, A

    2008-08-27

    We report on the collective integration technology of vertically aligned nanowires (NWs). Si and ZnO NWs have been used in order to develop a generic technological process. Both mineral and organic planarizations of the as-grown nanowires have been achieved. Chemical vapour deposition (CVD) oxides, spin on glass (SOG), and polymer have been investigated as filling materials. Polishing and/or etching of the composite structures have been set up so as to obtain a suitable morphology for the top and bottom electrical contacts. Electrical and optical characterizations of the integrated NWs have been performed. Contacts ohmicity has been demonstrated and specific contact resistances have been reported. The photoconducting properties of polymer-integrated ZnO NWs have also been investigated in the UV-visible range through collective electrical contacts. A small increase of the resistivity in the ZnO NWs under sub-bandgap illumination has been observed and discussed. A comparison of the photoluminescence (PL) spectra at 300 K of the as-grown and SOG-integrated ZnO nanowires has shown no significant impact of the integration process on the crystal quality of the NWs.

  1. Easy growth of undoped and doped tungsten oxide nanowires with high purity and orientation

    Science.gov (United States)

    Liu, Kun; Foord, David T.; Scipioni, Lawrence

    2005-01-01

    An economic method is presented to grow undoped/doped tungsten oxide nanowires with high purity and erect orientation, simply by heating a tungsten filament in a vacuum chamber with some room air leakage. Tungsten oxide nanowires were studied using scanning electron microscopy (SEM), energy dispersion x-ray spectroscopy (EDS) and transmission electron microscopy (TEM). Wires are found standing straight and clean on the filament, {\\sim }30 nm in diameter and up to a few tens of micrometres long. The composition along the wire is uniform for all elements including dopants.

  2. Solution-Grown Silicon Nanowires for Lithium-Ion Battery Anodes

    KAUST Repository

    Chan, Candace K.

    2010-03-23

    Composite electrodes composed of silicon nanowires synthesized using the supercritical fluid-liquid-solid (SFLS) method mixed with amorphous carbon or carbon nanotubes were evaluated as Li-ion battery anodes. Carbon coating of the silicon nanowires using the pyrolysis of sugar was found to be crucial for making good electronic contact to the material. Using multiwalled carbon nanotubes as the conducting additive was found to be more effective for obtaining good cycling behavior than using amorphous carbon. Reversible capacities of 1500 mAh/g were observed for 30 cycles. © 2010 American Chemical Society.

  3. Investigation of the electronic transport in polarization-induced nanowires using conductive atomic force microscopy (AFM)

    Science.gov (United States)

    Selcu, Camelia; Carnevale, Santino C.; Kent, Thomas F.; Akyol, Fatih; Phillips, Patrick J.; Mills, Michael J.; Rajan, Siddharth; Pelz, Jonathan P.; Myers, Roberto C.

    2013-03-01

    In the search to improve short wavelength light emitting diodes (LED's), where the dislocations limit their performance and hole doping (Mg) is a fundamental challenge, the III-Nitride polarization-induced nanowire LED provides a promising system to address these problems. The new type of pn diode, polarization-induced nanowire LED (PINLED), was developed by linearly grading AlGaN composition of the nanowires (from GaN to AlN and back to GaN) from 0% to 100% and back to 0% Al (Carnevale et al, Nano Lett., 12, 915 (2012)). In III-Nitrides (Ga,Al/N), the effects of polarization are commonly observed at the surfaces and interfaces. Thus, in the case of the polarization-induced nanowire LEDs, taking advantage of the bound polarization charge, due to the grading of the AlGaN, the pn diodes are formed. The polarity of the nanowires determines the carrier type in each graded region, and therefore the diode orientation (n/p vs p/n). We used conductive AFM to investigate polarity of the PINLED's as well as hole conductivity in PINLED's made of AlGaN with and without acceptor doping. The results reveal that most of the wires are n-top/p-bottom (N-face), but some are p-top/n-bottom (Ga-face). Also, we found that the current density is 3 orders of magnitude larger in the case of the doped nanowires than the nanowires with no impurity doping.

  4. Self-Seeded Axio-Radial InAs-InAs1-xPxNanowire Heterostructures beyond "Common" VLS Growth.

    Science.gov (United States)

    Mandl, Bernhard; Keplinger, Mario; Messing, Maria E; Kriegner, Dominik; Wallenberg, Reine; Samuelson, Lars; Bauer, Günther; Stangl, Julian; Holý, Václav; Deppert, Knut

    2018-01-10

    Semiconductors are essential for modern electronic and optoelectronic devices. To further advance the functionality of such devices, the ability to fabricate increasingly complex semiconductor nanostructures is of utmost importance. Nanowires offer excellent opportunities for new device concepts; heterostructures have been grown in either the radial or axial direction of the core nanowire but never along both directions at the same time. This is a consequence of the common use of a foreign metal seed particle with fixed size for nanowire heterostructure growth. In this work, we present for the first time a growth method to control heterostructure growth in both the axial and the radial directions simultaneously while maintaining an untapered self-seeded growth. This is demonstrated for the InAs/InAs 1-x P x material system. We show how the dimensions and composition of such axio-radial nanowire heterostructures can be designed including the formation of a "pseudo-superlattice" consisting of five separate InAs 1-x P x segments with varying length. The growth of axio-radial nanowire heterostructures offers an exciting platform for novel nanowire structures applicable for fundamental studies as well as nanowire devices. The growth concept for axio-radial nanowire heterostructures is expected to be fully compatible with Si substrates.

  5. Effect of Thermal Annealing in Ammonia on the Properties of InGaN Nanowires with Different Indium Concentrations

    Energy Technology Data Exchange (ETDEWEB)

    Hahn, Cristopher; Cordones, Amy; Andrews, Sean; Gao, Hanwei; Fu, Anthony; Leone, Stephen; Yang, Peidong

    2012-10-02

    The utility of an annealing procedure in ammonia ambient is investigated for improving the optical characteristics of InxGa1?xN nanowires (0.07 ≤ x ≤ 0.42) grown on c-Al2O3 using a halide chemical vapor deposition method. Morphological studies using scanning electron microscopy confirm that the nanowire morphology is retained after annealing in ammonia at temperatures up to 800 ?C. However, significant indium etching and composition inhomogeneities are observed for higher indium composition nanowires (x = 0.28, 0.42), as measured by energy-dispersive X-ray spectroscopy and Z-contrast scanning transmission electron microscopy. Structural analyses, using X-ray diffraction and high-resolution transmission electron microscopy, indicate that this is a result of the greater thermal instability of higher indium composition nanowires. The effect of these structural changes on the optical quality of InGaN nanowires is examined using steady-state and time-resolved photoluminescence measurements. Annealing in ammonia enhances the integrated photoluminescence intensity of InxGa1?xN nanowires by up to a factor of 4.11 ? 0.03 (for x = 0.42) by increasing the rate of radiative recombination. Fitting of photoluminescence decay curves to a Kohlrausch stretched exponential indicates that this increase is directly related to a larger distribution of recombination rates from composition inhomogeneities caused by annealing. The results demonstrate the role of thermal instability on the improved optical properties of InGaN nanowires annealed in ammonia.

  6. Randomized controlled clinical trial of the 24-months survival of composite resin restorations after one-step incomplete and complete excavation on primary teeth

    NARCIS (Netherlands)

    Franzon, R.; Opdam, N.J.; Guimaraes, L.F.; Demarco, F.F.; Casagrande, L.; Haas, A.N de; Araujo, F.B.

    2015-01-01

    OBJECTIVE: This randomized clinical trial aimed to compare the 24-months survival of composite restorations in primary molars after partial caries removal (PCR) and total caries removal (TCR). METHODS: Forty-eight children aged 3-8 years with at least one molar with a deep carious lesion were

  7. A prospective randomized clinical trial of one bis-GMA-based and two ormocer-based composite restorative systems in class II cavities: five-year results

    NARCIS (Netherlands)

    Bottenberg, P.; Jacquet, W.; Alaerts, M.; Keulemans, F.

    2009-01-01

    Objectives: Ormocer composites, consisting of a silicon-based polymer, have been developed recently as a tooth-colored restorative material. The purpose of this prospective randomized clinical trial was to evaluate the performance of two small-particle hybrid ormocer-based restorative systems (AD,

  8. Single crystalline PtSi nanowires, PtSi/Si/PtSi nanowire heterostructures, and nanodevices.

    Science.gov (United States)

    Lin, Yung-Chen; Lu, Kuo-Chang; Wu, Wen-Wei; Bai, Jingwei; Chen, Lih J; Tu, K N; Huang, Yu

    2008-03-01

    We report the formation of PtSi nanowires, PtSi/Si/PtSi nanowire heterostructures, and nanodevices from such heterostructures. Scanning electron microscopy studies show that silicon nanowires can be converted into PtSi nanowires through controlled reactions between lithographically defined platinum pads and silicon nanowires. High-resolution transmission electron microscopy studies show that PtSi/Si/PtSi heterostructure has an atomically sharp interface with epitaxial relationships of Si[110]//PtSi[010] and Si(111)//PtSi(101). Electrical measurements show that the pure PtSi nanowires have low resistivities approximately 28.6 microOmega.cm and high breakdown current densities>1x10(8) A/cm2. Furthermore, using single crystal PtSi/Si/PtSi nanowire heterostructures with atomically sharp interfaces, we have fabricated high-performance nanoscale field-effect transistors from intrinsic silicon nanowires, in which the source and drain contacts are defined by the metallic PtSi nanowire regions, and the gate length is defined by the Si nanowire region. Electrical measurements show nearly perfect p-channel enhancement mode transistor behavior with a normalized transconductance of 0.3 mS/microm, field-effect hole mobility of 168 cm2/V.s, and on/off ratio>10(7), demonstrating the best performing device from intrinsic silicon nanowires.

  9. Indium Tin Oxide@Carbon Core–Shell Nanowire and Jagged Indium Tin Oxide Nanowire

    Directory of Open Access Journals (Sweden)

    Wang Yong

    2010-01-01

    Full Text Available Abstract This paper reports two new indium tin oxide (ITO-based nanostructures, namely ITO@carbon core–shell nanowire and jagged ITO nanowire. The ITO@carbon core–shell nanowires (~50 nm in diameter, 1–5 μm in length, were prepared by a chemical vapor deposition process from commercial ITO nanoparticles. A carbon overlayer (~5–10 in thickness was observed around ITO nanowire core, which was in situ formed by the catalytic decomposition of acetylene gas. This carbon overlayer could be easily removed after calcination in air at an elevated temperature of 700°C, thus forming jagged ITO nanowires (~40–45 nm in diameter. The growth mechanisms of ITO@carbon core–shell nanowire and jagged ITO nanowire were also suggested.

  10. Magnetic features of a mixed ferro-ferrimagnetic ternary alloy cylindrical nanowire

    Science.gov (United States)

    Vatansever, Z. D.

    2017-10-01

    In the present study, we have investigated the finite temperature magnetic phase transition properties of a mixed ferro-ferrimagnetic ternary alloy cylindrical nanowire of the type ABpC1-p by Monte Carlo simulation technique. The nanowire system consists of two interpenetrating sublattices, one of which contains type-A magnetic components with spin-3/2 and the other one is randomly occupied type-B and type-C magnetic components with spin-1 and spin-5/2, respectively. We have examined the effect of exchange interaction ratio, R, and the concentration value of type-B magnetic ions, p, on the transition temperature of the system. It has been found that one can modify the transition temperature and saturation magnetization of the system by varying concentration value and interaction ratio. Moreover, our numerical results show that the ternary alloy nanowire system exhibits compensation behavior for particular values of the system parameters.

  11. Atomically abrupt silicon-germanium axial heterostructure nanowires synthesized in a solvent vapor growth system.

    Science.gov (United States)

    Geaney, Hugh; Mullane, Emma; Ramasse, Quentin M; Ryan, Kevin M

    2013-04-10

    The growth of Si/Ge axial heterostructure nanowires in high yield using a versatile wet chemical approach is reported. Heterostructure growth is achieved using the vapor zone of a high boiling point solvent as a reaction medium with an evaporated tin layer as the catalyst. The low solubility of Si and Ge within the Sn catalyst allows the formation of extremely abrupt heterojunctions of the order of just 1-2 atomic planes between the Si and Ge nanowire segments. The compositional abruptness was confirmed using aberration corrected scanning transmission electron microscopy and atomic level electron energy loss spectroscopy. Additional analysis focused on the role of crystallographic defects in determining interfacial abruptness and the preferential incorporation of metal catalyst atoms near twin defects in the nanowires.

  12. Junctions in axial III-V heterostructure nanowires obtained via an interchange of group III elements.

    Science.gov (United States)

    Krogstrup, Peter; Yamasaki, Jun; Sørensen, Claus B; Johnson, Erik; Wagner, Jakob B; Pennington, Robert; Aagesen, Martin; Tanaka, Nobuo; Nygård, Jesper

    2009-11-01

    We present an investigation of the morphology and composition of novel types of axial nanowire heterostructures where Ga(x)In(1-x)As is used as barrier material in InAs nanowires. Using aberration-corrected scanning transmission electron microscopy and energy dispersive X-ray analysis we demonstrate that it is possible to grow junctions by changing the group III elements, and we find that a substantial fraction of Ga can be incorporated in axial InAs/Ga(x)In(1-x)As/InAs, retaining straight nanowire configurations. We explain how the adatoms are transferred to the incorporation site at the growth interface via two different routes, (1) interface diffusion and (2) volume diffusion through the catalyst particle.

  13. Growth of axial SiGe heterostructures in nanowires using pulsed laser deposition

    Science.gov (United States)

    Eisenhawer, Björn; Sivakov, Vladimir; Berger, Andreas; Christiansen, Silke

    2011-07-01

    Axial heterojunctions between pure silicon and pure germanium in nanowires have been realized combining pulsed laser deposition, chemical vapor deposition and electron beam evaporation in a vapor-liquid-solid nanowire growth experiment using gold nanoparticles as catalyst for the 1D wire growth. Energy dispersive x-ray mappings and line scans show a compositional transition from pure silicon to pure germanium and vice versa with exponential and thus comparably sharp transition slopes. Based on these results not only Si-Ge heterojunctions seem to be possible using the vapor-liquid-solid growth process but also heterojunctions in optoelectronic III-V compounds such as InGaAs/GaAs or group III nitride compounds such as InGaN/GaN as well as axial p-n junctions in Si nanowires.

  14. Growth of axial SiGe heterostructures in nanowires using pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Eisenhawer, Bjoern; Sivakov, Vladimir; Berger, Andreas; Christiansen, Silke, E-mail: bjoern.eisenhawer@ipht-jena.de [Institute of Photonic Technology, Albert-Einstein-Strasse 9, D-07745 Jena (Germany)

    2011-07-29

    Axial heterojunctions between pure silicon and pure germanium in nanowires have been realized combining pulsed laser deposition, chemical vapor deposition and electron beam evaporation in a vapor-liquid-solid nanowire growth experiment using gold nanoparticles as catalyst for the 1D wire growth. Energy dispersive x-ray mappings and line scans show a compositional transition from pure silicon to pure germanium and vice versa with exponential and thus comparably sharp transition slopes. Based on these results not only Si-Ge heterojunctions seem to be possible using the vapor-liquid-solid growth process but also heterojunctions in optoelectronic III-V compounds such as InGaAs/GaAs or group III nitride compounds such as InGaN/GaN as well as axial p-n junctions in Si nanowires.

  15. Hydrothermal Synthesis of Nanoclusters of ZnS Comprised on Nanowires

    Directory of Open Access Journals (Sweden)

    Magnus Willander

    2013-09-01

    Full Text Available Cetyltrimethyl ammonium bromide cationic (CTAB surfactant was used as template for the synthesis of nanoclusters of ZnS composed of nanowires, by hydrothermal method. The structural and morphological studies were performed by using X-ray diffraction (XRD, scanning electron microscopy (SEM and high resolution transmission electron microscopy (HRTEM techniques. The synthesized ZnS nanoclusters are composed of nanowires and high yield on the substrate was observed. The ZnS nanocrystalline consists of hexagonal phase and polycrystalline in nature. The chemical composition of ZnS nanoclusters composed of nanowires was studied by X-ray photo electron microscopy (XPS. This investigation has shown that the ZnS nanoclusters are composed of Zn and S atoms.

  16. Growth of axial SiGe heterostructures in nanowires using pulsed laser deposition.

    Science.gov (United States)

    Eisenhawer, Björn; Sivakov, Vladimir; Berger, Andreas; Christiansen, Silke

    2011-07-29

    Axial heterojunctions between pure silicon and pure germanium in nanowires have been realized combining pulsed laser deposition, chemical vapor deposition and electron beam evaporation in a vapor-liquid-solid nanowire growth experiment using gold nanoparticles as catalyst for the 1D wire growth. Energy dispersive x-ray mappings and line scans show a compositional transition from pure silicon to pure germanium and vice versa with exponential and thus comparably sharp transition slopes. Based on these results not only Si-Ge heterojunctions seem to be possible using the vapor-liquid-solid growth process but also heterojunctions in optoelectronic III-V compounds such as InGaAs/GaAs or group III nitride compounds such as InGaN/GaN as well as axial p-n junctions in Si nanowires.

  17. Fabrication of free-standing copper foils covered with highly-ordered copper nanowire arrays

    Science.gov (United States)

    Zaraska, Leszek; Sulka, Grzegorz D.; Jaskuła, Marian

    2012-07-01

    The through-hole nanoporous anodic aluminum oxide (AAO) membranes with relatively large surface area (ca. 2 cm2) were employed for fabrication of free-standing and mechanically stable copper foils covered with close-packed and highly-ordered copper nanowire arrays. The home-made AAO membranes with different pore diameters and interpore distances were fabricated via a two-step self-organized anodization of aluminum performed in sulfuric acid, oxalic acid and phosphoric acid followed by the pore opening/widening procedure. The direct current (DC) electrodeposition of copper was performed efficiently on both sides of AAO templates. The bottom side of the AAO templates was not insulated and consequently Cu nanowire arrays on thick Cu layers were obtained. The proposed template-assisted fabrication of free-standing copper nanowire array electrodes is a promising method for synthesis of nanostructured current collectors. The composition of Cu nanowires was confirmed by energy dispersive X-Ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses. The structural features of nanowires were evaluated from field emission scanning electron microscopy (FE-SEM) images and compared with the characteristic parameters of anodic alumina membranes.

  18. Magnetic Properties of Ni0.3Fe0.7 Alloy Nanowires

    Directory of Open Access Journals (Sweden)

    M. Almasi Kashi

    2013-03-01

    Full Text Available The effect of length variation on the magnetic properties of NiFe alloy nanowires electrodeposited into the alumina template was investigated. The diameter (45±2.5 nm and length (~ 1.9, 7.12, 8.3, 9.5 and 13.3 µm of the nanowires were estimated from scanning electron microscopy images. Energy dispersive spectroscopy results showed Ni3Fe7 composition of the alloy nanowires.  The magnetic properties of the samples were investigated by vibrating sample magnetometer. It showed that with increasing the length of the nanowires from 1.9±0.1µm to 13.3±0.66 µm, coercivity reduced from 1050 Oe to 705 Oe and squareness reduced from 0.64 to 0.46. The results proved increasing the magnetostatic interaction between the nanowires with length. Progress toward the multi-domain behavior was predicted caused to drastically reduce in the coercivity.

  19. Step-flow kinetics model for the vapor-solid-solid Si nanowires growth.

    Science.gov (United States)

    Cui, H; Lü, Y Y; Yang, G W; Chen, Y M; Wang, C X

    2015-05-13

    Vapor-solid-solid (VSS) process has recently received continued attention as an alternative to grow Si nanowire. In comparison with common vapor-liquid-solid (VLS) growth with liquid catalyst, VSS growth can prevent the catalyst species from incorporating into nanowires with deep-level impurity, and achieve the compositionally abrupt interfaces by restraining the so-called "reservoir effect". However, despite the huge advances in experimental observations with in situ electron microscopy, VSS growth still remains much less understood in theory. Here, we developed a general mass-transport-limited kinetic model to describe the VSS growth process of Si nanowires by considering three surface diffusion processes and a slow interface diffusion process, where the former determines the atoms supplies way, while the latter dominates the growth of nanowires. The present model is not only well consistent with the available experimental data of Si nanowire, but also gives a clear physical image for the successive side-to-side ledge flow VSS growth.

  20. Composition.

    Science.gov (United States)

    Communication: Journalism Education Today, 2002

    2002-01-01

    Considers how photography is more than just pointing a camera in the right direction. Explains that good pictures use elements of composition such as the Rule of Thirds, leading lines, framing and repetition of shapes. Presents 16 photographs from college and secondary school publications, and describes the techniques that makes them effective.…

  1. Growth and properties of low-dimensional III-V semiconductor nanowire heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Heiss, Martin

    2010-08-25

    symmetry from cubic zinc-blende to hexagonal wurtzite structure, while the chemical composition of the material remains constant. The GaAs nanowires synthesized with the Au-free technique can be grown under conditions where a statistical wurtzite/zinc-blende polytypism occurs. A novel method for the direct correlation at the nanoscale of structural and optical properties of single GaAs nanowires is developed in order to characterize the resulting statistically distributed quantum heterostructures. Nanowires consisting of {approx}100% wurtzite and nanowires presenting zinc-blende/wurtzite polytypism are studied by photoluminescence spectroscopy and Transmission Electron Microscopy. The photoluminescence of wurtzite GaAs is found to be consistent with a bulk wurtzite band gap of 1.50 eV, slightly smaller compared to the zinc-blende GaAs band gap. In the polytypic nanowires, it is shown that the regions that are predominantly composed of either zinc-blende or wurtzite phase show photoluminescence emission close to the according bulk band gaps, while regions composed of a non periodic superlattice of wurtzite and zinc-blende phases exhibit a redshift of the photoluminescence spectra as low as 1.455 eV. The dimensions of the quantum heterostructures are correlated with the light emission, allowing us to estimate the band offsets of {delta}E{sub CB}=53{+-}20 meV and {delta}E{sub VB}=76{+-}12 meV between the two crystalline phases. These results are in excellent agreement with recent theoretical band structure calculations. (orig.)

  2. Benefits of different intensity of aerobic exercise in modulating body composition among obese young adults: a pilot randomized controlled trial.

    Science.gov (United States)

    Chiu, Chih-Hui; Ko, Ming-Chen; Wu, Long-Shan; Yeh, Ding-Peng; Kan, Nai-Wen; Lee, Po-Fu; Hsieh, Jenn-Woei; Tseng, Ching-Yu; Ho, Chien-Chang

    2017-08-24

    The aim of present study was to compare the effects of different aerobic exercise intensities and energy expenditures on the body composition of sedentary obese college students in Taiwan. Forty-eight obese participants [body mass index (BMI) ≥ 27 kg/m2, age 18-26 years] were randomized into four equal groups (n = 12): light-intensity training group (LITG), 40%-50% heart rate reserve (HRR); middle-intensity training group (MITG), 50%-70% HRR; high-intensity training group (HITG), 70%-80% HRR; and control group (CG). The aerobic exercise training program was conducted for 60 min per day on a treadmill 3 days per week for 12 weeks. All participant anthropometric data, blood biochemical parameters, and health-related physical fitness components were measured at baseline and after 12 weeks. At baseline, the anthropometric indices did not differ significantly among the four groups (p > 0.05). After 12-week exercise intervention, the HITG and MITG had significantly more changes in body weight, waist circumference (WC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR) than the LITG. The changes in BMI and body fat percentage differed among all four groups (p exercise intervention with high energy expenditure can considerably reduce body weight, body fat, WC, WHR, and WHtR, whereas a light-intensity exercise intervention can significantly reduce body weight and body fat. Current Controlled Trials TPECTR09831410900 , registered on 24th Dec 2009.

  3. Angular Magnetoresistance of Nanowires with Alternating Cobalt and Nickel Segments

    KAUST Repository

    Mohammed, Hanan

    2017-06-22

    Magnetization reversal in segmented Co/Ni nanowires with varying number of segments was studied using angular Magnetoresistance (MR) measurements on isolated nanowires. The MR measurements offer an insight into the pinning of domain walls within the nanowires. Angular MR measurements were performed on nanowires with two and multiple segments by varying the angle between the applied magnetic field and nanowire (−90° ≤θ≤90°). The angular MR measurements reveal that at lower values of θ the switching fields are nearly identical for the multisegmented and two-segmented nanowires, whereas at higher values of θ, a decrease in the switching field is observed in the case of two segmented nanowires. The two segmented nanowires generally exhibit a single domain wall pinning event, whereas an increased number of pinning events are characteristic of the multisegmented nanowires at higher values of θ. In-situ magnetic force microscopy substantiates reversal by domain wall nucleation and propagation in multisegmented nanowires.

  4. High-Performance Single Nanowire Tunnel Diodes

    DEFF Research Database (Denmark)

    Wallentin, Jesper; Persson, Johan Mikael; Wagner, Jakob Birkedal

    2010-01-01

    We demonstrate single nanowire tunnel diodes with room temperature peak current densities of up to 329 A/cm(2). Despite the large surface to volume ratio of the type-II InP-GaAs axial heterostructure nanowires, we measure peak to valley current ratios (PVCR) of up to 8.2 at room temperature and 27...

  5. Epitaxy of advanced nanowire quantum devices

    NARCIS (Netherlands)

    Gazibegovic, S.; Car, D.; Zhang, H.; Balk, S.C.; Logan, J.A.; Moor, M.W.A. de; Cassidy, M.C.; Schmits, R.; Xu, D.; Wang, G.; Krogstrup, P.; Veld, R.L.M. op het; Zuo, K.; Vos, Y.; Shen, J.; Bouman, D.; Shojaei, B.; Pennachio, D.; Lee, J.S.; Veldhoven, P.J. van; Koelling, S.; Verheijen, M.A.; Kouwenhoven, L.P.; Palmstrøm, C.J.; Bakkers, E.P.A.M.

    2017-01-01

    Semiconductor nanowires are ideal for realizing various low-dimensional quantum devices. In particular, topological phases of matter hosting non-Abelian quasiparticles (such as anyons) can emerge when a semiconductor nanowire with strong spin-orbit coupling is brought into contact with a

  6. Functionalization of magnetic nanowires by charged biopolymers

    DEFF Research Database (Denmark)

    Magnin, D.; Callegari, V.; Mátéfi-Tempfli, Stefan

    2008-01-01

    We report on a facile method for the preparation of biocompatible and bioactive magnetic nanowires. The method consists of the direct deposition of polysaccharides by layer-by-layer (LbL) assembly onto a brush of metallic nanowires; obtained by electrodeposition of the metal within the nanopores ...

  7. Growth and structural characterization of III-V semiconductor nanowires

    OpenAIRE

    Rieger, Torsten

    2015-01-01

    In this thesis, the growth and structural properties of III-V semiconductor nanowires and nanowire heterostructures are studied. These nanowires represent structures suitable for both fundamental physics and applications in electronic devices such as (tunnel) field effect transistors. The III-V nanowires are grown with molecular beam epitaxy, high κ dielectric layers are deposited conformally around the nanowires by atomic layer deposition. The morphological and structural characteristics of ...

  8. Synthesis of silicon and germanium nanowires.

    Energy Technology Data Exchange (ETDEWEB)

    Clement, Teresa J. (Arizona State University); Hsu, Julia W. P.

    2007-11-01

    The vapor-liquid-solid growth process for synthesis of group-IV semiconducting nanowires using silane, germane, disilane and digermane precursor gases has been investigated. The nanowire growth process combines in situ gold seed formation by vapor deposition on atomically clean silicon (111) surfaces, in situ growth from the gaseous precursor(s), and real-time monitoring of nanowire growth as a function of temperature and pressure by a novel optical reflectometry technique. A significant dependence on precursor pressure and growth temperature for the synthesis of silicon and germanium nanowires is observed, depending on the stability of the specific precursor used. Also, the presence of a nucleation time for the onset of nanowire growth has been found using our new in situ optical reflectometry technique.

  9. Nanowires for thermal energy conversion and management

    Science.gov (United States)

    Chen, Renkun

    This dissertation presents the application of nanowires in two aspects of thermal energy conversion and management: (i) silicon (Si) nanowires as efficient and scalable thermoelectric materials due to the reduced thermal conductivity (k), and (ii) Si and copper (Cu) nanowire arrays for enhanced phase change heat transfer including boiling and evaporation and their applications in thermal management of microelectronics. In the first half of the thesis (chapter 2 and 3), we describe thermal and thermoelectric measurements of individual Si nanowires for studying phonon transport properties and their potential application in thermoelectrics. A theoretical model based on coherent phonon scattering was developed to explain the experiemental data, which suggests that phonon-boundary scattering is highly frequency dependent. For low frequency (long wavelength) phonons, the transport is nearly ballistic, whereas high frequency or short wavelength phonons scatter diffusively at nanowire boundary. The competition between the two phonon transmission regimes results in the unusual linear behavior of the thermal conductance of thin VLS Si nanowires at low temperature. Next, the thermal conductivity of EE Si nanowires, which have much rougher surface compared to VLS nanowires, was measured and found to be five-eight times lower than that of VLS counterparts with similar diameters. The substantial reduction in k is presumably due to the higher surface roughness, since both types of nanowires have single crystalline cores. In particular, for ˜ 50 nm EE Si nanowires etched from 0.1 O-cm B-doped p-Si (˜2 x 1017 cm-3 dopant concentration), the k is around 1.6 Wm-1K-1 and the kL is ˜1.2 Wm-1 K-1 at room temperature, approaching that of amorphous Si. The single nanowire measurements show the great promise of using Si nanowire arrays as high-performance, scalable thermoelectric materials. As the second focus of the thesis (chapter 4 and 5), nanowire arrays were used for enhanced phase

  10. Core-shell silicon nanowire solar cells.

    Science.gov (United States)

    Adachi, M M; Anantram, M P; Karim, K S

    2013-01-01

    Silicon nanowires can enhance broadband optical absorption and reduce radial carrier collection distances in solar cell devices. Arrays of disordered nanowires grown by vapor-liquid-solid method are attractive because they can be grown on low-cost substrates such as glass, and are large area compatible. Here, we experimentally demonstrate that an array of disordered silicon nanowires surrounded by a thin transparent conductive oxide has both low diffuse and specular reflection with total values as low as nanowire facilitates enhancement in external quantum efficiency using two different active shell materials: amorphous silicon and nanocrystalline silicon. As a result, the core-shell nanowire device exhibits a short-circuit current enhancement of 15% with an amorphous Si shell and 26% with a nanocrystalline Si shell compared to their corresponding planar devices.

  11. Superconductive silicon nanowires using gallium beam lithography.

    Energy Technology Data Exchange (ETDEWEB)

    Henry, Michael David; Jarecki, Robert Leo,

    2014-01-01

    This work was an early career LDRD investigating the idea of using a focused ion beam (FIB) to implant Ga into silicon to create embedded nanowires and/or fully suspended nanowires. The embedded Ga nanowires demonstrated electrical resistivity of 5 m-cm, conductivity down to 4 K, and acts as an Ohmic silicon contact. The suspended nanowires achieved dimensions down to 20 nm x 30 nm x 10 m with large sensitivity to pressure. These structures then performed well as Pirani gauges. Sputtered niobium was also developed in this research for use as a superconductive coating on the nanowire. Oxidation characteristics of Nb were detailed and a technique to place the Nb under tensile stress resulted in the Nb resisting bulk atmospheric oxidation for up to years.

  12. Thiolated Gold Nanowires: Metallic versus Semiconducting

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Deen [ORNL; Luo, Weidong [ORNL; Nobusada, Katsuyuki [Institute for Molecular Science, Japan; Whetten, Robert L [Georgia Institute of Technology

    2009-01-01

    Tremendous research efforts have been spent on thiolated gold nanoparticles and self-assembled monolayers of thiolate (RS-) on gold, but thiolated gold nanowires have received almost no attention. Here we computationally design two such one-dimensional nanosystems by creating a linear chain of Au icosahedra, fused together by either vertex sharing or face sharing. Then neighboring Au icosahedra are bridged by five thiolate groups for the vertex-sharing model and three RS?Au?SR motifs for the face-sharing model. We show that the vertex-sharing thiolated gold nanowire can be made either semiconducting or metallic by tuning the charge, while the face-sharing one is always metallic. We explain this difference between the two nanowires by examining their band structures and invoking a previously proposed electron-count rule. Implications of our findings for previous experimentation of gold nanowires are discussed, and a potential way to make thiolated gold nanowires is proposed.

  13. Thiolated gold nanowires: metallic versus semiconducting.

    Science.gov (United States)

    Jiang, De-en; Nobusada, Katsuyuki; Luo, Weidong; Whetten, Robert L

    2009-08-25

    Tremendous research efforts have been spent on thiolated gold nanoparticles and self-assembled monolayers of thiolate (RS-) on gold, but thiolated gold nanowires have received almost no attention. Here we computationally design two such one-dimensional nanosystems by creating a linear chain of Au icosahedra, fused together by either vertex sharing or face sharing. Then neighboring Au icosahedra are bridged by five thiolate groups for the vertex-sharing model and three RS-Au-SR motifs for the face-sharing model. We show that the vertex-sharing thiolated gold nanowire can be made either semiconducting or metallic by tuning the charge, while the face-sharing one is always metallic. We explain this difference between the two nanowires by examining their band structures and invoking a previously proposed electron-count rule. Implications of our findings for previous experimentation of gold nanowires are discussed, and a potential way to make thiolated gold nanowires is proposed.

  14. Precise Placement of Metallic Nanowires on a Substrate by Localized Electric Fields and Inter-Nanowire Electrostatic Interaction

    Directory of Open Access Journals (Sweden)

    U Hyeok Choi

    2017-10-01

    Full Text Available Placing nanowires at the predetermined locations on a substrate represents one of the significant hurdles to be tackled for realization of heterogeneous nanowire systems. Here, we demonstrate spatially-controlled assembly of a single nanowire at the photolithographically recessed region at the electrode gap with high integration yield (~90%. Two popular routes, such as protruding electrode tips and recessed wells, for spatially-controlled nanowire alignment, are compared to investigate long-range dielectrophoretic nanowire attraction and short-range nanowire-nanowire electrostatic interaction for determining the final alignment of attracted nanowires. Furthermore, the post-assembly process has been developed and tested to make a robust electrical contact to the assembled nanowires, which removes any misaligned ones and connects the nanowires to the underlying electrodes of circuit.

  15. Carrier Dynamics and Band Structure in InGaAs and InGaAs/InP Nanowires

    Science.gov (United States)

    Linser, Samuel; Shojaei, Iraj; Jnawali, Giriraj; Wickramasuriya, Nadeeka; Jackson, Howard; Smith, Leigh; Ameruddin, Amira; Caroff, Philippe; Tan, Hoe; Jagadish, Chennupati

    We use transient Rayleigh scattering (TRS) measurements to explore the electronic energy structure of wurtzite InGaAs nanowires. We studied single core-only InGaAs nanowires as well as strained core-shell InGaAs-InP heterostructures at 300 K and 10 K, with probe photon energies in the near-infrared from 0.79 to 1.16 eV. We report a factor of four enhancement of the typical lifetime of excited states in the core-shell nanowires (500 ps) when compared to the core-only nanowires (125 ps). We observe a clear band-edge-like structure in the core-shell wires at energies of 0.98 eV at 10 K and 0.88 eV at 300 K. In both cases, this structure is at a significantly higher energy than the reported bandgap of bulk zincblende InGaAs of the same nominal composition as our nanowires. We also present a phenomenological fitting model of our TRS spectra which provides insight into the cooling dynamics of the electron-hole plasma within a single photo-excited nanowire. We acknowledge the financial support of the NSF through Grants DMR 1507844, DMR 1531373 and ECCS 1509706, and the financial support of the Australian Research Council.

  16. Properties of Fe{sub 8−N}Co{sub N} nanoribbons and nanowires: A DFT approach

    Energy Technology Data Exchange (ETDEWEB)

    Muñoz, Francisco [Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Germany); Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago 7800024 (Chile); Centro para el Desarrollo de la Nanociencia y la Nanotecnología, CEDENNA, Avda. Ecuador 3493, Santiago 9170124 (Chile); Altbir, D. [Centro para el Desarrollo de la Nanociencia y la Nanotecnología, CEDENNA, Avda. Ecuador 3493, Santiago 9170124 (Chile); Departamento de Física, Universidad de Santiago (Chile); Kiwi, Miguel, E-mail: m.kiwi.t@gmail.com [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago 7800024 (Chile); Centro para el Desarrollo de la Nanociencia y la Nanotecnología, CEDENNA, Avda. Ecuador 3493, Santiago 9170124 (Chile); Morán-López, J.L. [Departamento de Física, Laboratorio Interdisciplinario, Facultad de Ciencias, Universidad Nacional Autónoma de México, México, D.F. (Mexico)

    2013-08-15

    The structural configurations and magnetic properties of zig-zag nanoribbons and nanowires of Fe{sub 8−N}Co{sub N}, for 0≤N≤8, are calculated within the density functional theory. Both, for the zig-zag nanoribbons and the nanowires, there is a tendency towards forming Fe–Co bonds, while segregation of the Fe and Co is energetically unfavorable. For the nanowire structures a transition from bcc Fe to hcp Co spatial arrangements is observed when N is increased from 4 to 6, in spite of the small size of the systems under investigation. The energy minimization was performed taking into consideration the electronic and magnetic structures, since for each crystalline structure, chemical composition, and short range order, particular magnetic properties of these systems do correspond. The magnetocrystalline anisotropy energy is calculated, and it is found that the easy axis changes from a transverse direction in Fe-rich systems, to the axial direction as the Co concentration increases. It is also found that although there are important variations of the local magnetic moment of the components, and their particular location in the system, the average magnetic moment is an almost linear function of N. - Highlights: ► Properties of Fe{sub 8−N}Co{sub N} nanoribbons and nanowires are calculated ab initio. ► Structural and magnetic properties of nanoribbons and nanowires are calculated. ► Shape and crystalline anisotropies of nanoribbons and nanowires are contrasted.

  17. New transparent conductive metal based on polymer composite

    Energy Technology Data Exchange (ETDEWEB)

    Keshavarz Hedayati, Mehdi; Jamali, Mohammad [Nanochemistry and Nanoengineering, Institute for Materials Science, Faculty of Engineering, Christian-Albrechts-University, Kiel (Germany); Strunkus, Thomas; Zaporochentko, Vladimir; Faupel, Franz [Multicomponent Materials, Institute for Materials Science, Faculty of Engineering, Christian-Albrechts-University, Kiel (Germany); Elbahri, Mady [Nanochemistry and Nanoengineering, Institute for Materials Science, Faculty of Engineering, Christian-Albrechts-University, Kiel (Germany); Helmholtz-Zentrum Geesthacht GmbH, Institute of Polymer Research, Nanochemistry and Nanoengineering (Germany)

    2011-07-01

    Currently great efforts are made to develop new kind of transparent conductors (TCs) to replace ITO. In this regard different materials and composites have been proposed and studied including conductive polymers, carbon nanotubes (CNTs), metal grids, and random networks of metallic nanowires. But so far none of them could be used as a replacing material, since either they are either fragile and brittle or their electrical conductivity is below the typical ITO. Thin metallic films due to their high electrical conductivity could be one of the best replacing materials for ITO, however their poor transparency makes their application as TCs limited. Here we design and fabricate a new polymeric composite coating which enhances the transparency of the thin metal film up to 100% relative to the initial value while having a high electrical conductivity of typical metals. Therefore our proposed device has a great potential to be used as new transparent conductor.

  18. Green urea synthesis catalyzed by hematite nanowires in magnetic field

    Science.gov (United States)

    Yahya, Noorhana; Qureshi, Saima; Rehman, Zia ur; Alqasem, Bilal; Fai Kait, Chong

    2017-04-01

    The catalytic activity of hematite (α-Fe2O3) nanowires under the influence of magnetic field on urea synthesis is considered green. The adsorption and subsequent dissociative reaction of hydrogen, nitrogen and carbon dioxide gases on the α-Fe2O3 (111) nanowires were investigated using the density functional theory (DFT) method. The average adsorption energy is -4.12 kcal/mole at different sites. The adsorption of gases resulted in a difference in density and net spin of electrons from 68 to 120 and 0-21 respectively. In addition, it induces magnetic moment value of 36.33 μB, which confirms the enhanced magnetic behaviour of hematite. α-Fe2O3 nanowires (NWs) synthesized by heating iron wire in a box furnace at (750-800) °C and as synthesized α-Fe2O3 nanoparticles (NPs) were received to use as a catalyst in the magnetic reaction of urea synthesis. X-ray Diffractometer (XRD) confirms the peaks of rhombohedral structure of α-Fe2O3 and Raman spectrum analyses confirms the α-Fe2O3 peaks at 410 cm-1, 500 cm-1 and 616 cm-1. The needle-like shape of hematite nanowires with length ranging from 16-25) μm and diameter from 74 to 145 nm confirmed by Field emission scanning electron microscopy (FESEM). The magnetic properties of the nanowires exhibited different levels of saturation magnetization, for α-Fe2O3 perpendicularly aligned direction (13.18 emu/g) and random direction (10.73 emu/g). Urea synthesis was done under magnetic field ranges from 0.0 to 2.5 T. The activation energy of α-Fe2O3 NWs for urea production is lower than NPs in the range of 0-1 T, whereas it is reversed for higher magnetic induction values. Fourier transform infrared spectroscopy (FTIR) confirmed the formation of urea at the peaks of 1690-1600 cm-1. This green urea employing magnetically induced method could be a contender to the Haber-Bosch process currently used by the current industry which utilizes high temperature and high pressure.

  19. Analysis of the vapor-liquid-solid mechanism for nanowire growth and a model for this mechanism.

    Science.gov (United States)

    Mohammad, S Noor

    2008-05-01

    The vapor-liquid-solid (VLS) mechanism is most widely employed to grow nanowires (NWs). The mechanism uses foreign element catalytic agent (FECA) to mediate the growth. Because of this, it is believed to be very stable with the FECA-mediated droplets not consumed even when reaction conditions change. Recent experiments however differ, which suggest that even under cleanest growth conditions, VLS mechanism may not produce long, thin, uniform, single-crystal nanowires of high purity. The present investigation has addressed various issues involving fundamentals of VLS growth. While addressing these issues, it has taken into consideration the influence of the electrical, hydrodynamic, thermodynamic, and surface tension effects on NW growth. It has found that parameters such as mesoscopic effects on nanoparticle seeds, charge distribution in FECA-induced droplets, electronegativity of the droplet with respect to those of reactive nanowire vapor species, growth temperature, and chamber pressure play important role in the VLS growth. On the basis of an in-depth analysis of various issues, a simple, novel, malleable (SNM) model has been presented for the VLS mechanism. The model appears to explain the formation and observed characteristics of a wide variety of nanowires, including elemental and compound semiconductor nanowires. Also it provides an understanding of the influence of the dynamic behavior of the droplets on the NW growth. This study finds that increase in diameter with time of the droplet of tapered nanowires results primarily from gradual incorporation of oversupplied nanowire species into the FECA-mediated droplet, which is supported by experiments. It finds also that optimum compositions of the droplet constituents are crucial for VLS nanowire growth. An approximate model presented to exemplify the parametric dependency of VLS growth provides good description of NW growth rate as a function of temperature.

  20. Effects of Whole-Body Electromyostimulation versus High-Intensity Resistance Exercise on Body Composition and Strength: A Randomized Controlled Study

    OpenAIRE

    Wolfgang Kemmler; Marc Teschler; Anja Weißenfels; Michael Bebenek; Michael Fröhlich; Matthias Kohl; Simon von Stengel

    2016-01-01

    High-intensity (resistance) exercise (HIT) and whole-body electromyostimulation (WB-EMS) are both approaches to realize time-efficient favorable changes of body composition and strength. The purpose of this study was to determine the effectiveness of WB-EMS compared with the gold standard reference HIT, for improving body composition and muscle strength in middle-aged men. Forty-eight healthy untrained men, 30?50 years old, were randomly allocated to either HIT (2 sessions/week) or a WB-EMS g...

  1. Children with autism spectrum disorder and social skills groups at school: a randomized trial comparing intervention approach and peer composition.

    Science.gov (United States)

    Kasari, Connie; Dean, Michelle; Kretzmann, Mark; Shih, Wendy; Orlich, Felice; Whitney, Rondalyn; Landa, Rebecca; Lord, Catherine; King, Bryan

    2016-02-01

    Peer relationships improve for children with autism spectrum disorder (ASD) in clinic-based social skills groups but rarely generalize to real world contexts. This study compares child outcomes of two social skills interventions conducted in schools with children in Kindergarten through fifth grade. Children with ASD were randomized to one of two interventions that varied on group composition (mixed typical and ASD vs. all ASD or social difficulties) and intervention approach (didactic SKILLS based vs. activity-based ENGAGE groups). Interventions were implemented at school for 8 weeks (16 sessions) with an 8-week follow-up. Innovative measures of peer nomination and playground peer engagement, as well as teacher reports of child behavior problems and teacher-child relationship were analyzed for 137 children with ASD across four sites. On the primary outcome of social network connections from the peer nomination measure, there was no main effect of treatment, but there were moderator effects. Children with low teacher-child closeness or high conflict improved more in their social connections if they received the SKILLS intervention, whereas children with higher teacher-child closeness improved more if they received the ENGAGE intervention. Only two secondary outcome measures yielded significant effects of treatment. Children in the SKILLS groups increased peer engagement and decreased isolation during recess. Child behavior problems and teacher-child closeness moderated peer engagement such that children with higher behavior problems and lower closeness benefitted more from SKILLS groups. These findings suggest that social skills groups conducted at school can affect both peer engagement during recess as well as peer acceptability. Child characteristics and teacher-child relationship prior to intervention yield important information on who might benefit from a specific social skills intervention. © 2015 Association for Child and Adolescent Mental Health.

  2. Homoepitaxial n-core: p-shell gallium nitride nanowires: HVPE overgrowth on MBE nanowires.

    Science.gov (United States)

    Sanders, Aric; Blanchard, Paul; Bertness, Kris; Brubaker, Matthew; Dodson, Christopher; Harvey, Todd; Herrero, Andrew; Rourke, Devin; Schlager, John; Sanford, Norman; Chiaramonti, Ann N; Davydov, Albert; Motayed, Abhishek; Tsvetkov, Denis

    2011-11-18

    We present the homoepitaxial growth of p-type, magnesium doped gallium nitride shells by use of halide vapor phase epitaxy (HVPE) on n-type gallium nitride nanowires grown by plasma-assisted molecular beam epitaxy (MBE). Scanning electron microscopy shows clear dopant contrast between the core and shell of the nanowire. The growth of magnesium doped nanowire shells shows little or no effect on the lattice parameters of the underlying nanowires, as measured by x-ray diffraction (XRD). Photoluminescence measurements of the nanowires show the appearance of sub-bandgap features in the blue and the ultraviolet, indicating the presence of acceptors. Finally, electrical measurements confirm the presence of electrically active holes in the nanowires.

  3. Examination Of Si-Ge Heterostructure Nanowire Growth Using Monte Carlo Simulation

    Science.gov (United States)

    Nastovjak, A. G.; Neizvestny, I. G.; Shwartz, N. L.

    2011-12-01

    The process of Si-Ge heterostructures formation in nanowires (NWs) grown by vapor-liquid-solid mechanism was investigated using Monte Carlo simulation. Dependences of catalyst drop composition on temperature, flux intensity and nanowire diameter were obtained. Periodical oscillations of drop composition near mean value were observed. Oscillation results from layer-by-layer growth at the drop-whisker interface and necessity of supersaturation onset to start new layer formation. It was demonstrated that it is impossible to grow atomically abrupt axial heterojunctions via classical vapor-liquid-solid mechanism due to gradual change of catalyst drop composition when switching the fluxes. This phenomenon is the main reason of heterojunction blurriness. Junction abruptness was found to be dependent on nanowhisker diameter: in adsorption-induced growth mode abruptness of heterojunction decreases with diameter and in diffusion-induced mode it increases.

  4. Synthesis and characterization of germanium nanowires and germanium/silicon radially heterostructured nanowires

    Science.gov (United States)

    Goldthorpe, Irene Anne

    Semiconductor nanowires offer new opportunities to study physical phenomena in low-dimensional nanostructures. They also possess technologically useful properties for applications in electronics, optics, sensing, and thermoelectrics. Germanium nanowires are of particular interest, because of germanium's compatibility with standard silicon integrated circuit fabrication processes, its high electronic carrier mobilities, and the low temperature required for germanium nanowire growth. In this work, epitaxially-aligned germanium nanowires are grown on silicon substrates by chemical vapor deposition through the vapor-liquid-solid mechanism. Uniform nanowire diameters between 5 and 50 nm are obtained through the use of monodisperse gold colloids as catalysts. The crystallographic orientation of the nanowires, their strain, and their heteroepitaxial relationship with the substrate are characterized with transmission electron microscopy (TEM) and x-ray diffraction (XRD). A process for removing the gold catalysts from the tips of the germanium nanowires is demonstrated. Silicon shells are then heteroepitaxially deposited around the wires to fabricate radial heterostructures. These shells passivate the germanium nanowire surface, create electronic band offsets to confine holes away the surface where they can scatter or recombine, and induce strain which could allow for the engineering of properties such as band gap and carrier mobilities. However, analogous to planar heteroepitaxy, surface roughening and misfit dislocations can relax this strain. The effects of coaxial dimensions on strain relaxation in these structures are analyzed quantitatively by TEM and synchrotron XRD, and these results are related to continuum elasticity models. Lessons learned generated two successful strategies for synthesizing coherent core-shell nanowires with large misfit strain: chlorine surface passivation and growth of nanowires with low-energy sidewall facets. Both approaches avoid the strain

  5. Oxide nanowires for solar cell applications.

    Science.gov (United States)

    Zhang, Qifeng; Yodyingyong, Supan; Xi, Junting; Myers, Daniel; Cao, Guozhong

    2012-03-07

    Oxide nanowire arrays were studied for their applications to solar cells. It was demonstrated that the nanowires could provide direct pathways for electron transport in dye-sensitized solar cells and therefore, while forming photoelectrode films, they offered better suppression of charge recombination than nanoparticles. However, the photoelectron films consisting of nanowires suffered a disadvantage in giving large surface area for dye adsorption. Such a shortcoming of nanowires had been exemplified in this paper illustrating that it could be well compensated by incorporating with nanoparticles to form a nanoparticle-nanowire array hybrid photoelectrode film. The oxide nanowires were also demonstrated to be able to enhance the performance of inverted structure polymer solar cells as a cathode buffer layer by establishing a large interface with the polymers so as to facilitate the transport of photogenerated electrons from the polymer to the electron collecting electrode. Such an enhancement effect could be further boosted while the nanowires were replaced with nanotubes; the latter may build up larger interface with the polymers than the former and therefore facilitates the electron transport more efficiently.

  6. Three-year randomized controlled clinical study of a one step universal adhesive and a 2-step self-etch adhesive in Class II resin composite restorations

    DEFF Research Database (Denmark)

    van Dijken, Jan WV; Pallesen, Ulla

    2017-01-01

    Purpose: To evaluate in a randomized clinical evaluation the 3-year clinical durability of a one-step universal adhesive bonding system and compare it intraindividually with a 2-step self-etch adhesive in Class II restorations. Materials and Methods: Each of 57 participants (mean age 58.3 yr......) received at least two, as similar as possible, extended Class II restorations. The cavities in each of the 60 individual pairs of cavities were randomly distributed to the 1-step universal adhesive (All Bond Universal: AU) and the control 2-step self-etch adhesive (Optibond XTR: OX). A low shrinkage resin......) success rates (p>0.05). Annual failure rates were 1.8% and 2.6%, respectively.The main reason for failure was resin composite fracture. Conclusion: Class II resin composite restorations placed with a one-step universal adhesive showed good short time effectiveness....

  7. Review on photonic properties of nanowires for photovoltaics.

    Science.gov (United States)

    Mokkapati, S; Jagadish, C

    2016-07-25

    III-V semiconductor nanowires behave as optical antennae because of their shape anisotropy and high refractive index. The antennae like behavior modifies the absorption and emission properties of nanowires compared to planar materials. Nanowires absorb light more efficiently compared to an equivalent volume planar material, leading to higher short circuit current densities. The modified emission from the nanowires has the potential to increase the open circuit voltage from nanowire solar cells compared to planar solar cells. In order to achieve high efficiency nanowire solar cells it is essential to control the surface state density and doping in nanowires. We review the physics of nanowire solar cells and progress made in addressing the surface recombination and doping of nanowires, with emphasis on GaAs and InP materials.

  8. ZnO-nanowire as a nanogenerator?

    Energy Technology Data Exchange (ETDEWEB)

    Schubert, Markus Andreas; Senz, Stephan; Alexe, Marin; Goesele, Ulrich [Max Planck Institut fuer Mikrostrukturphysik, Halle (Germany)

    2008-07-01

    Recently nanogenerators for powering nanodevices were reported in which ZnO-nanowire arrays convert mechanical energy in electrical energy by bending the ZnO-nanowires. We simulate the experiments in which the ZnO nanowires were bent by AFM tip by FEM-calculations for an ideal nonconducting piezoelectric ZnO-nanowire with a length of 600 nm and a diameter of 50 nm fixed perpendicular to a substrate. The top part of this nanowire was bent about 140 nm by a force applied at the top of the nanowire. At the point of the applied force the electrical potential has a maximum of +1.3 V. In the rest of the nanowire the electrical potential is +0.3 V for the stretched side and -0.3 V for the compressed. The piezoelectric charge generate the signal on the capacitance between the two sides, which is about 10{sup -5} pF for the whole wire. A lower value of 10{sup -7} pF is estimated for the AFM point contact. However, most ZnO-nanowires are n-doped semiconductors with a typically resistivity of 1 {omega}cm. One consequence is a very fast discharging of the piezoelectric generate charge in the order of magnitude of 1 ps. Even, in the case of an ideal nonconducting nanowire, the voltage at the input capacity of any preamplifier ({proportional_to}1-5 pF) would be of the order of 10{sup -7} V, which corresponds to a charge of about one electron.

  9. TiO2 nanowire-templated hierarchical nanowire network as water-repelling coating

    Science.gov (United States)

    Hang, Tian; Chen, Hui-Jiuan; Xiao, Shuai; Yang, Chengduan; Chen, Meiwan; Tao, Jun; Shieh, Han-ping; Yang, Bo-ru; Liu, Chuan; Xie, Xi

    2017-12-01

    Extraordinary water-repelling properties of superhydrophobic surfaces make them novel candidates for a great variety of potential applications. A general approach to achieve superhydrophobicity requires low-energy coating on the surface and roughness on nano- and micrometre scale. However, typical construction of superhydrophobic surfaces with micro-nano structure through top-down fabrication is restricted by sophisticated fabrication techniques and limited choices of substrate materials. Micro-nanoscale topographies templated by conventional microparticles through surface coating may produce large variations in roughness and uncontrollable defects, resulting in poorly controlled surface morphology and wettability. In this work, micro-nanoscale hierarchical nanowire network was fabricated to construct self-cleaning coating using one-dimensional TiO2 nanowires as microscale templates. Hierarchical structure with homogeneous morphology was achieved by branching ZnO nanowires on the TiO2 nanowire backbones through hydrothermal reaction. The hierarchical nanowire network displayed homogeneous micro/nano-topography, in contrast to hierarchical structure templated by traditional microparticles. This hierarchical nanowire network film exhibited high repellency to both water and cell culture medium after functionalization with fluorinated organic molecules. The hierarchical structure templated by TiO2 nanowire coating significantly increased the surface superhydrophobicity compared to vertical ZnO nanowires with nanotopography alone. Our results demonstrated a promising strategy of using nanowires as microscale templates for the rational design of hierarchical coatings with desired superhydrophobicity that can also be applied to various substrate materials.

  10. Optical properties of heavily doped GaAs nanowires and electroluminescent nanowire structures

    Energy Technology Data Exchange (ETDEWEB)

    Lysov, A; Offer, M; Gutsche, C; Regolin, I; Geller, M; Prost, W; Tegude, F-J [Center for Nanointegration Duisburg-Essen, University of Duisburg-Essen, D-47048 Duisburg (Germany); Topaloglu, S, E-mail: andrey.lysov@uni-due.de [Department of Electronics Engineering, Maltepe University, Marmara Egitim Koeyue, 34857, Maltepe, Istanbul (Turkey)

    2011-02-25

    We present GaAs electroluminescent nanowire structures fabricated by metal organic vapor phase epitaxy. Electroluminescent structures were realized in both axial pn-junctions in single GaAs nanowires and free-standing nanowire arrays with a pn-junction formed between nanowires and substrate, respectively. The electroluminescence emission peak from single nanowire pn-junctions at 10 K was registered at an energy of around 1.32 eV and shifted to 1.4 eV with an increasing current. The line is attributed to the recombination in the compensated region present in the nanowire due to the memory effect of the vapor-liquid-solid growth mechanism. Arrayed nanowire electroluminescent structures with a pn-junction formed between nanowires and substrate demonstrated at 5 K a strong electroluminescence peak at 1.488 eV and two shoulder peaks at 1.455 and 1.519 eV. The main emission line was attributed to the recombination in the p-doped GaAs. The other two lines correspond to the tunneling-assisted photon emission and band-edge recombination in the abrupt junction, respectively. Electroluminescence spectra are compared with the micro-photoluminescence spectra taken along the single p-, n- and single nanowire pn-junctions to find the origin of the electroluminescence peaks, the distribution of doping species and the sharpness of the junctions.

  11. Optical properties of heavily doped GaAs nanowires and electroluminescent nanowire structures

    Science.gov (United States)

    Lysov, A.; Offer, M.; Gutsche, C.; Regolin, I.; Topaloglu, S.; Geller, M.; Prost, W.; Tegude, F.-J.

    2011-02-01

    We present GaAs electroluminescent nanowire structures fabricated by metal organic vapor phase epitaxy. Electroluminescent structures were realized in both axial pn-junctions in single GaAs nanowires and free-standing nanowire arrays with a pn-junction formed between nanowires and substrate, respectively. The electroluminescence emission peak from single nanowire pn-junctions at 10 K was registered at an energy of around 1.32 eV and shifted to 1.4 eV with an increasing current. The line is attributed to the recombination in the compensated region present in the nanowire due to the memory effect of the vapor-liquid-solid growth mechanism. Arrayed nanowire electroluminescent structures with a pn-junction formed between nanowires and substrate demonstrated at 5 K a strong electroluminescence peak at 1.488 eV and two shoulder peaks at 1.455 and 1.519 eV. The main emission line was attributed to the recombination in the p-doped GaAs. The other two lines correspond to the tunneling-assisted photon emission and band-edge recombination in the abrupt junction, respectively. Electroluminescence spectra are compared with the micro-photoluminescence spectra taken along the single p-, n- and single nanowire pn-junctions to find the origin of the electroluminescence peaks, the distribution of doping species and the sharpness of the junctions.

  12. Optical properties of heavily doped GaAs nanowires and electroluminescent nanowire structures.

    Science.gov (United States)

    Lysov, A; Offer, M; Gutsche, C; Regolin, I; Topaloglu, S; Geller, M; Prost, W; Tegude, F-J

    2011-02-25

    We present GaAs electroluminescent nanowire structures fabricated by metal organic vapor phase epitaxy. Electroluminescent structures were realized in both axial pn-junctions in single GaAs nanowires and free-standing nanowire arrays with a pn-junction formed between nanowires and substrate, respectively. The electroluminescence emission peak from single nanowire pn-junctions at 10 K was registered at an energy of around 1.32 eV and shifted to 1.4 eV with an increasing current. The line is attributed to the recombination in the compensated region present in the nanowire due to the memory effect of the vapor-liquid-solid growth mechanism. Arrayed nanowire electroluminescent structures with a pn-junction formed between nanowires and substrate demonstrated at 5 K a strong electroluminescence peak at 1.488 eV and two shoulder peaks at 1.455 and 1.519 eV. The main emission line was attributed to the recombination in the p-doped GaAs. The other two lines correspond to the tunneling-assisted photon emission and band-edge recombination in the abrupt junction, respectively. Electroluminescence spectra are compared with the micro-photoluminescence spectra taken along the single p-, n- and single nanowire pn-junctions to find the origin of the electroluminescence peaks, the distribution of doping species and the sharpness of the junctions.

  13. Quantum plasmonic waveguides: Au nanowires

    Science.gov (United States)

    Cordaro, C. E. A.; Piccitto, G.; Priolo, F.

    2017-11-01

    Combining miniaturization and good operating speed is a compelling yet crucial task for our society. Plasmonic waveguides enable the possibility of carrying information at optical operating speed while maintaining the dimension of the device in the nanometer range. Here we present a theoretical study of plasmonic waveguides extending our investigation to structures so small that Quantum Size Effects (QSE) become non-negligible, namely quantum plasmonic waveguides. Specifically, we demonstrate and evaluate a blue-shift in Surface Plasmon (SP) resonance energy for an ultra-thin gold nanowire.

  14. Angular dependence of switching behaviour in template released isolated NiFe nanowires

    Science.gov (United States)

    Sultan, Musaab Salman

    2017-12-01

    In this article, the magnetisation behaviour and magnetisation reversal process of both single and bundles of 3 and 7 closely-packed template released Ni60Fe40 nanowires were investigated using high-sensitivity Magneto-Optical Kerr Effect (MOKE) magnetometry. The nanowires were deposited from a dilute suspension onto gold pre-patterned silicon substrates. They were typically 9 μm in length with a diameter of approximately 200 nm. By increasing the number of clumped wires a reduction in the switching field was observed, suggesting that overall the bundle behaves like a single system and decreasing the effective external field required to switch the magnetisation. Square hysteresis loops with a sharp jump in the Kerr signal were seen for all MOKE measurement angles. This result may reflect the surface magnetisation of the nanowire, compared to their bulk behaviour as compared with the literature that adopted the same and different investigative techniques on comparable compositions and dimensions of wires. The influence of applying the magnetic field at different angles with respect to the long axis of the nanowire on the switching behaviour was analysed and compared with the theoretical calculations of non-uniform rotation of the curling model of domain reversal. An agreement and disagreement with this model was seen, respectively, for low and high angles, indicating the complexity of the magnetic state of such isolated nanowires. To confirm the results presented here, further studies are recommended using a combination of techniques sensitive to surface and bulk magnetisation on similar isolated ferromagnetic nanowires.

  15. Green urea synthesis catalyzed by hematite nanowires in magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Yahya, Noorhana, E-mail: noorhana_yahya@petronas.com.my; Qureshi, Saima; Rehman, Zia ur; Alqasem, Bilal; Fai Kait, Chong

    2017-04-15

    The catalytic activity of hematite (α-Fe{sub 2}O{sub 3}) nanowires under the influence of magnetic field on urea synthesis is considered green. The adsorption and subsequent dissociative reaction of hydrogen, nitrogen and carbon dioxide gases on the α-Fe{sub 2}O{sub 3} (111) nanowires were investigated using the density functional theory (DFT) method. The average adsorption energy is −4.12 kcal/mole at different sites. The adsorption of gases resulted in a difference in density and net spin of electrons from 68 to 120 and 0–21 respectively. In addition, it induces magnetic moment value of 36.33 µB, which confirms the enhanced magnetic behaviour of hematite. α-Fe{sub 2}O{sub 3} nanowires (NWs) synthesized by heating iron wire in a box furnace at (750−800) °C and as synthesized α-Fe{sub 2}O{sub 3} nanoparticles (NPs) were received to use as a catalyst in the magnetic reaction of urea synthesis. X-ray Diffractometer (XRD) confirms the peaks of rhombohedral structure of α-Fe{sub 2}O{sub 3} and Raman spectrum analyses confirms the α-Fe{sub 2}O{sub 3} peaks at 410 cm{sup −1}, 500 cm{sup −1} and 616 cm{sup −1}. The needle-like shape of hematite nanowires with length ranging from 16–25) μm and diameter from 74 to 145 nm confirmed by Field emission scanning electron microscopy (FESEM). The magnetic properties of the nanowires exhibited different levels of saturation magnetization, for α-Fe{sub 2}O{sub 3} perpendicularly aligned direction (13.18 emu/g) and random direction (10.73 emu/g). Urea synthesis was done under magnetic field ranges from 0.0 to 2.5 T. The activation energy of α-Fe{sub 2}O{sub 3} NWs for urea production is lower than NPs in the range of 0–1 T, whereas it is reversed for higher magnetic induction values. Fourier transform infrared spectroscopy (FTIR) confirmed the formation of urea at the peaks of 1690–1600 cm{sup −1}. This green urea employing magnetically induced method could be a contender to the Haber-Bosch process

  16. Optical Properties of Rotationally Twinned Nanowire Superlattices

    DEFF Research Database (Denmark)

    Bao, Jiming; Bell, David C.; Capasso, Federico

    2008-01-01

    blende InP nanowires. We have constructed the energy band diagram of the resulting multiquantum well heterostructure and have performed detailed quantum mechanical calculations of the electron and hole wave functions. The excitation power dependent blue-shift of the photoluminescence can be explained...... a heterostructure in a chemically homogeneous nanowire material and alter in a major way its optical properties opens new possibilities for band-structure engineering.......We have developed a technique so that both transmission electron microscopy and microphotoluminescence can be performed on the same semiconductor nanowire over a large range of optical power, thus allowing us to directly correlate structural and optical properties of rotationally twinned zinc...

  17. Antimonide Heterostructure Nanowires - Growth, Physics and Devices

    OpenAIRE

    Borg, Mattias

    2012-01-01

    This thesis investigates the growth and application of antimonide heterostructure nanowires for low-power electronics. In the first part of the thesis, GaSb, InSb and InAsSb nanowire growth is presented, and the distinguishing features of the growth are described. It is found that the presence of Sb results in more than 50 at. % group-III concentration in the Au seed particle on top of the nanowires. It is further concluded that the effective V/III ratio inside the seed particle is reduced co...

  18. Semiconductor Nanowires: What's Next?

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Peidong; Yan, Ruoxue; Fardy, Melissa

    2010-04-28

    In this perspective, we take a critical look at the research progress within the nanowire community for the past decade. We discuss issues on the discovery of fundamentally new phenomena versus performance benchmarking for many of the nanowire applications. We also notice that both the bottom-up and top-down approaches have played important roles in advancing our fundamental understanding of this new class of nanostructures. Finally we attempt to look into the future and offer our personal opinions on what the future trends will be in nanowire research.

  19. Electrodeposited L10 CoPt nanowires

    DEFF Research Database (Denmark)

    Mallet, J.; Yu-Zhang, K.; Mátéfi-Tempfli, Stefan

    2005-01-01

    Arrays of face-centred cubic (fee) CoPt (0.45 nanowires were electrodeposited into thin film nanoporous alumina supported on a Si substrate. The heat treatment under specific conditions was then carried out in order to transform the fee phase into the face-centred tetragonal or L1 ordered...... phase. The influence of both the phase transition and the temperature on the magnetic properties of Co Pt nanowires has been studied. Coercive fields higher than 1 T (10kOe) have been obtained at room temperature with ordered nanowires, 80 nm in diameter....

  20. Silicon carbide nanowires: synthesis and cathodoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Huczko, Andrzej; Dabrowska, Agnieszka [Department of Chemistry, Warsaw University (Poland); Savchyn, Volodymyr; Karbovnyk, Ivan [Department of Electronics, Ivan Franko National University of Lviv (Ukraine); Popov, Anatoli I. [Institut Laue-Langevin, Grenoble (France); Institute of Solid State Physics, University of Latvia, Riga (Latvia)

    2009-12-15

    Silicon carbide nanowires have been synthesized via a combustion synthesis route. Structural studies showed that obtained SiC nanowires belong dominantly to 3C polytype with zincblend structure. Cathodoluminescence spectra from these nanostructures within the temperature range of 77..300 K, show obvious differences with respect to the bulk materials. The exciton band of the bulk 3C-SiC is significantly damped and the prevailing line is found to be at 1.99 eV (77 K), proving the key role of defect centers in optical properties of the investigated nanomaterial. Purified SiC nanowires. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  1. Biofunctionalization of zinc oxide nanowires for DNA sensory applications

    Directory of Open Access Journals (Sweden)

    Rudolph Bettina

    2011-01-01

    Full Text Available Abstract We report on the biofunctionalization of zinc oxide nanowires for the attachment of DNA target molecules on the nanowire surface. With the organosilane glycidyloxypropyltrimethoxysilane acting as a bifunctional linker, amino-modified capture molecule oligonucleotides have been immobilized on the nanowire surface. The dye-marked DNA molecules were detected via fluorescence microscopy, and our results reveal a successful attachment of DNA capture molecules onto the nanowire surface. The electrical field effect induced by the negatively charged attached DNA molecules should be able to control the electrical properties of the nanowires and gives way to a ZnO nanowire-based biosensing device.

  2. Survey of Synergistic Effect of L-carnitine with Glutamine on Body Composition and Dietary Intake in Soccer Players: A Double-blind, Randomized Clinical Trial

    Directory of Open Access Journals (Sweden)

    Mohammad Hozoori

    2016-10-01

    Full Text Available Background: The present study was conducted to investigate the possible effects of L-carnitine and glutamine and their synergistic effects on male soccer athletes. Methods: 28 male soccer players (21.1 ± 0.7 y were enrolled in a randomized pre and post intervention, double-blind design. Before the intervention, their performances were assessed by Bruce protocol, and their body composition was measured with the body composition analyzer. Then, athletes were randomly allocated into four groups: 2 g L-glutamine, 2 g L-carnitine, 2 g L-carnitine + 2 g L-glutamine and placebo. Supplements were prescribed for 21 days and after three weeks, athletes' performances and body composition were re-evaluated. Results: The results showed that body weight, body fat percentage, lean muscle mass, and dietary intake made no significant changes in different groups of athletes. In between groups comparison, results did not significantly change in any performance indices. However, in L-carnitine supplement group, the results of pre and post intervention showed that the running distance and maximal oxygen uptake (VO2max increased significantly while the subjective sense of fatigue decreased significantly. Conclusions: Based on our findings, a three-week prescription of separateor combined glutamine and L-carnitine, had no effects on body composition or dietary intake in soccer players. But, the athletes' energy intake was more than the one reported in other studies. Although further studies are required to assess these effects on athletic performance.

  3. Electrically pumped waveguide lasing from ZnO nanowires.

    Science.gov (United States)

    Chu, Sheng; Wang, Guoping; Zhou, Weihang; Lin, Yuqing; Chernyak, Leonid; Zhao, Jianze; Kong, Jieying; Li, Lin; Ren, Jingjian; Liu, Jianlin

    2011-07-03

    Ultraviolet semiconductor lasers are widely used for applications in photonics, information storage, biology and medical therapeutics. Although the performance of gallium nitride ultraviolet lasers has improved significantly over the past decade, demand for lower costs, higher powers and shorter wavelengths has motivated interest in zinc oxide (ZnO), which has a wide direct bandgap and a large exciton binding energy. ZnO-based random lasing has been demonstrated with both optical and electrical pumping, but random lasers suffer from reduced output powers, unstable emission spectra and beam divergence. Here, we demonstrate electrically pumped Fabry-Perot type waveguide lasing from laser diodes that consist of Sb-doped p-type ZnO nanowires and n-type ZnO thin films. The diodes exhibit highly stable lasing at room temperature, and can be modelled with finite-difference time-domain methods.

  4. Topological Insulator Nanowires and Nanoribbons

    KAUST Repository

    Kong, Desheng

    2010-01-13

    Recent theoretical calculations and photoemission spectroscopy measurements on the bulk Bi2Se3 material show that it is a three-dimensional topological insulator possessing conductive surface states with nondegenerate spins, attractive for dissipationless electronics and spintronics applications. Nanoscale topological insulator materials have a large surface-to-volume ratio that can manifest the conductive surface states and are promising candidates for devices. Here we report the synthesis and characterization of high quality single crystalline Bi2Se5 nanomaterials with a variety of morphologies. The synthesis of Bi 2Se5 nanowires and nanoribbons employs Au-catalyzed vapor-liquid-solid (VLS) mechanism. Nanowires, which exhibit rough surfaces, are formed by stacking nanoplatelets along the axial direction of the wires. Nanoribbons are grown along [1120] direction with a rectangular cross-section and have diverse morphologies, including quasi-one-dimensional, sheetlike, zigzag and sawtooth shapes. Scanning tunneling microscopy (STM) studies on nanoribbons show atomically smooth surfaces with ∼ 1 nm step edges, indicating single Se-Bi-Se-Bi-Se quintuple layers. STM measurements reveal a honeycomb atomic lattice, suggesting that the STM tip couples not only to the top Se atomic layer, but also to the Bi atomic layer underneath, which opens up the possibility to investigate the contribution of different atomic orbitais to the topological surface states. Transport measurements of a single nanoribbon device (four terminal resistance and Hall resistance) show great promise for nanoribbons as candidates to study topological surface states. © 2010 American Chemical Society.

  5. Nanopatterning of ultrananocrystalline diamond nanowires.

    Science.gov (United States)

    Wang, Xinpeng; Ocola, Leonidas E; Divan, Ralu S; Sumant, Anirudha V

    2012-02-24

    We report the fabrication of horizontally aligned ultrananocrystalline diamond (UNCD) nanowires (NWs) via two different approaches. First, with the top-down approach by using electron beam lithography (EBL) and reactive ion etching (RIE) with a photo resist layer as an etch mask. Using this approach, we demonstrate fabrication of 50 µm long UNCD NWs with widths as narrow as 40 nm. We further present an alternative approach to grow UNCD NWs at pre-defined positions through a selective seeding process. No RIE was needed either to etch the NWs or to remove the mask. In this case, we achieved UNCD NWs with lengths of 50 µm and smallest width of 90 nm respectively. Characterization of these nanowires by using scanning electron microscopy (SEM) and atomic force microscopy (AFM) shows that the UNCD NWs are well defined and fully released, with no indication of residual stress. Characterization using visible and ultraviolet (UV) Raman spectroscopy indicates that in both fabrication approaches, UNCD NWs maintain their intrinsic diamond structure.

  6. Nanopatterning of ultrananocrystalline diamond nanowires

    Science.gov (United States)

    Wang, Xinpeng; Ocola, Leonidas E.; Divan, Ralu S.; Sumant, Anirudha V.

    2012-02-01

    We report the fabrication of horizontally aligned ultrananocrystalline diamond (UNCD) nanowires (NWs) via two different approaches. First, with the top-down approach by using electron beam lithography (EBL) and reactive ion etching (RIE) with a photo resist layer as an etch mask. Using this approach, we demonstrate fabrication of 50 µm long UNCD NWs with widths as narrow as 40 nm. We further present an alternative approach to grow UNCD NWs at pre-defined positions through a selective seeding process. No RIE was needed either to etch the NWs or to remove the mask. In this case, we achieved UNCD NWs with lengths of 50 µm and smallest width of 90 nm respectively. Characterization of these nanowires by using scanning electron microscopy (SEM) and atomic force microscopy (AFM) shows that the UNCD NWs are well defined and fully released, with no indication of residual stress. Characterization using visible and ultraviolet (UV) Raman spectroscopy indicates that in both fabrication approaches, UNCD NWs maintain their intrinsic diamond structure.

  7. Plasmonic Waveguide-Integrated Nanowire Laser

    DEFF Research Database (Denmark)

    Bermudez-Urena, Esteban; Tutuncuoglu, Gozde; Cuerda, Javier

    2017-01-01

    Next-generation optoelectronic devices and photonic circuitry will have to incorporate on-chip compatible nanolaser sources. Semiconductor nanowire lasers have emerged as strong candidates for integrated systems with applications ranging from ultrasensitive sensing to data communication technolog...

  8. Optical properties of nanowire metamaterials with gain

    DEFF Research Database (Denmark)

    Isidio de Lima, Joaquim Junior; Adam, Jost; Rego, Davi

    2016-01-01

    The transmittance, reflectance and absorption of a nanowire metamaterial with optical gain are numerically simulated and investigated. It is assumed that the metamaterial is represented by aligned silver nanowires embedded into a semiconductor matrix, made of either silicon or gallium phosphide....... The gain in the matrix is modeled by adding a negative imaginary part to the dielectric function of the semiconductor. It is found that the optical coefficients of the metamaterial depend on the gain magnitude in a non-trivial way: they can both increase and decrease with gain depending on the lattice...... constant of the metamaterial. This peculiar behavior is explained by the field redistribution between the lossy metal nanowires and the amplifying matrix material. These findings are significant for a proper design of nanowire metamaterials with low optical losses for diverse applications....

  9. Oleylamine Assisted Synthesis of Ultralong Copper Nanowires

    Directory of Open Access Journals (Sweden)

    Tan Michael

    2015-01-01

    Full Text Available This paper reports the hydrothermal synthesis of smooth and ultralong copper nanowires (Cu NW prepared using oleylamine (OM, oleic acid (OA, and Cl- ion as coordinating and etching agents respectively. Cu nanowires with mean diameters around 82.3 nm and lengths exceeding 300 μm were synthesized using 2 % vol. OM and 1.8 mM OA at 120ºC after 12 h. The Cu NWs exhibit five-fold twinning and growth along the [110] direction. The morphological evolution of the products were also observed and discussed. Without Cl-, octahedral crystals instead of nanowires were formed. The addition of oleic acid as coordinating agent resulted to fewer particles and smoother nanowires which exhibit excellent mechanical stability. This method provides a simple, low-cost and high yield synthesis of Cu NWs for applications such as gas sensors and transparent conducting electrodes.

  10. Nonradiative Step Facets in Semiconductor Nanowires.

    Science.gov (United States)

    Sanchez, Ana M; Zhang, Yunyan; Tait, Edward W; Hine, Nicholas D M; Liu, Huiyun; Beanland, Richard

    2017-04-12

    One of the main advantages of nanowires for functional applications is their high perfection, which results from surface image forces that act on line defects such as dislocations, rendering them unstable and driving them out of the crystal. Here we show that there is a class of step facets that are stable in nanowires, with no long-range strain field or dislocation character. In zinc-blende semiconductors, they take the form of Σ3 (112) facets with heights constrained to be a multiple of three {111} monolayers. Density functional theory calculations show that they act as nonradiative recombination centers and have deleterious effects on nanowire properties. We present experimental observations of these defects on twin boundaries and twins that terminate inside GaAsP nanowires and find that they are indeed always multiples of three monolayers in height. Strategies to use the three-monolayer rule during growth to prevent their formation are discussed.

  11. Axial Ge/Si nanowire heterostructure tunnel FETs

    Energy Technology Data Exchange (ETDEWEB)

    Picraux, Sanuel T [Los Alamos National Laboratory; Daych, Shadi A [Los Alamos National Laboratory

    2010-01-01

    The vapor-liquid-solid (VLS) growth of semiconductor nanowires allows doping and composition modulation along their axis and the realization of axial 1 D heterostructures. This provides additional flexibility in energy band-edge engineering along the transport direction which is difficult to attain by planar materials growth and processing techniques. We report here on the design, growth, fabrication, and characterization of asymmetric heterostructure tunnel field-effect transistors (HTFETs) based on 100% compositionally modulated Si/Ge axial NWs for high on-current operation and low ambipolar transport behavior. We discuss the optimization of band-offsets and Schottky barrier heights for high performance HTFETs and issues surrounding their experimental realization. Our HTFET devices with 10 nm PECVD SiN{sub x} gate dielectric resulted in a measured current drive exceeding 100 {mu}A/{mu}m (I/{pi}D) and 10{sup 5} I{sub on}/I{sub off} ratios.

  12. High-performance single nanowire tunnel diodes.

    Science.gov (United States)

    Wallentin, Jesper; Persson, Johan M; Wagner, Jakob B; Samuelson, Lars; Deppert, Knut; Borgström, Magnus T

    2010-03-10

    We demonstrate single nanowire tunnel diodes with room temperature peak current densities of up to 329 A/cm(2). Despite the large surface to volume ratio of the type-II InP-GaAs axial heterostructure nanowires, we measure peak to valley current ratios (PVCR) of up to 8.2 at room temperature and 27.6 at liquid helium temperature. These sub-100-nm-diameter structures are promising components for solar cells as well as electronic applications.

  13. Plasmon resonant cavities in vertical nanowire arrays

    Energy Technology Data Exchange (ETDEWEB)

    Bora, M; Bond, T; Behymer, E; Chang, A

    2010-02-23

    We investigate tunable plasmon resonant cavity arrays in paired parallel nanowire waveguides. Resonances are observed when the waveguide length is an odd multiple of quarter plasmon wavelengths, consistent with boundary conditions of node and antinode at the ends. Two nanowire waveguides satisfy the dispersion relation of a planar metal-dielectric-metal waveguide of equivalent width equal to the square field average weighted gap. Confinement factors over 103 are possible due to plasmon focusing in the inter-wire space.

  14. Structure and Thermoelectric Properties of Bi2−xSbxTe3 Nanowires Grown in Flexible Nanoporous Polycarbonate Templates

    Directory of Open Access Journals (Sweden)

    Anuja Datta

    2017-05-01

    Full Text Available We report the room-temperature growth of vertically aligned ternary Bi2−xSbxTe3 nanowires of diameter ~200 nm and length ~12 µm, within flexible track-etched nanoporous polycarbonate (PC templates via a one-step electrodeposition process. Bi2−xSbxTe3 nanowires with compositions spanning the entire range from pure Bi2Te3 (x = 0 to pure Sb2Te3 (x = 2 were systematically grown within the nanoporous channels of PC templates from a tartaric–nitric acid based electrolyte, at the end of which highly crystalline nanowires of uniform composition were obtained. Compositional analysis showed that the Sb concentration could be tuned by simply varying the electrolyte composition without any need for further annealing of the samples. Thermoelectric properties of the Bi2−xSbxTe3 nanowires were measured using a standardized bespoke setup while they were still embedded within the flexible PC templates.

  15. Indium antimonide nanowires arrays for promising thermoelectric converters

    Directory of Open Access Journals (Sweden)

    Gorokh G. G.

    2015-02-01

    Full Text Available The authors have theoretically substantiated the possibility to create promising thermoelectric converters based on quantum wires. The calculations have shown that the use of quantum wires with lateral dimensions smaller than quantum confinement values and high concentration and mobility of electrons, can lead to a substantial cooling of one of the contacts up to tens of degrees and to the heating of the other. The technological methods of manufacturing of indium antimonide nanowires arrays with high aspect ratio of the nanowire diameters to their length in the modified nanoporous anodic alumina matrixes were developed and tested. The microstructure and composition of the formed nanostructures were investigated. The electron microscopy allowed establishing that within each pore nanowires are formed with diameters of 35 nm and a length of 35 microns (equal to the matrix thickness. The electron probe x-ray microanalysis has shown that the atomic ratio of indium and antimony in the semiconductor nanostructures amounted to 38,26% and 61,74%, respectively. The current-voltage measurement between the upper and lower contacts of Cu/InSb/Cu structure (1 mm2 has shown that at 2.82 V negative voltage at the emitter contact, current density is 129,8 A/cм2, and the collector contact is heated up to 75 degrees during 150 sec. Thus, the experimental results confirmed the theoretical findings that the quantum wire systems can be used to create thermoelectric devices, which can be widely applied in electronics, in particular, for cooling integrated circuits (processors, thermal controlling of the electrical circuits by changing voltage value.

  16. Five-year evaluation of a low-shrinkage Silorane resin composite material: A randomized clinical trial

    DEFF Research Database (Denmark)

    Schmidt, Malene; Dige, Irene; Kirkevang, Lise-Lotte

    2015-01-01

    Objectives The aim of the present study was to investigate the clinical performance of a low-shrinkage silorane-based composite material (Filtek™ Silorane, 3 M-Espe) by comparing it with a methacrylate-based composite material (Ceram•X™, Dentsply DeTrey). Material and methods A number of 72patien...

  17. Silicon nanowires in polymer nanocomposites for photovoltaic hybrid thin films

    Energy Technology Data Exchange (ETDEWEB)

    Ben Dkhil, S., E-mail: sadok.bendekhil@gmail.com [Laboratoire Physique des Materiaux, Structures et Proprietes Groupe Physique des Composants et Dispositifs Nanometriques, 7021 Jarzouna, Bizerte (Tunisia); Ingenierie des Materiaux Polymeres, IMP, UMR CNRS 5223, Universite Claude Bernard - Lyon 1, 15, boulevard Latarjet, 69622 Villeurbanne (France); Bourguiga, R. [Laboratoire Physique des Materiaux, Structures et Proprietes Groupe Physique des Composants et Dispositifs Nanometriques, 7021 Jarzouna, Bizerte (Tunisia); Davenas, J. [Ingenierie des Materiaux Polymeres, IMP, UMR CNRS 5223, Universite Claude Bernard - Lyon 1, 15, boulevard Latarjet, 69622 Villeurbanne (France); Cornu, D. [Institut Europeen des Membranes, UMR CNRS 5635, Ecole Nationale superieure de Chimie, Universite de Montpellier, 1919 route de Mende, F34000 Montpellier (France)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Hybrid solar cells based on blends of poly(N-vinylcarbazole) and silicon nanowires have been fabricated. Black-Right-Pointing-Pointer We have investigated the charge transfer between PVK and SiNWs by the way of the quenching of the PVK photoluminescence. Black-Right-Pointing-Pointer The relation between the morphology of the composite thin films and the charge transfer between SiNWs and PVK has been examined. Black-Right-Pointing-Pointer We have investigated the effects of SiNWs concentration on the photovoltaic characteristics leading to the optimization of a critical SiNWs concentration. - Abstract: Hybrid thin films combining the high optical absorption of a semiconducting polymer film and the electronic properties of silicon fillers have been investigated in the perspective of the development of low cost solar cells. Bulk heterojunction photovoltaic materials based on blends of a semiconductor polymer poly(N-vinylcarbazole) (PVK) as electron donor and silicon nanowires (SiNWs) as electron acceptor have been studied. Composite PVK/SiNWs films were cast from a common solvent mixture. UV-visible spectrometry and photoluminescence of the composites have been studied as a function of the SiNWs concentration. Photoluminescence spectroscopy (PL) shows the existence of a critical SiNWs concentration of about 10 wt % for PL quenching corresponding to the most efficient charge pair separation. The photovoltaic (PV) effect has been studied under illumination. The optimum open-circuit voltage V{sub oc} and short-circuit current density J{sub sc} are obtained for 10 wt % SiNWs whereas a degradation of these parameters is observed at higher SiNWs concentrations. These results are correlated to the formation of aggregates in the composite leading to recombination of the photogenerated charge pairs competing with the dissociation mechanism.

  18. Periodic nanowire array at the crystal interface.

    Science.gov (United States)

    Nakamura, Atsutomo; Mizoguchi, Teruyasu; Matsunaga, Katsuyuki; Yamamoto, Takahisa; Shibata, Naoya; Ikuhara, Yuichi

    2013-07-23

    A dislocation in a crystalline material has dangling bonds at its core and a strong strain field in its vicinity. Consequently, the dislocation attracts solute atoms and forms a so-called Cottrell atmosphere along the dislocation. A crystalline dislocation can be used as a template to produce nanowires by selectively doping foreign atoms along the dislocation. However, control of the configuration, spacing, and density of the formed periodic nanowire array has heretofore been extremely difficult. Here we show a method for fabricating ordered, electrically conductive nanowire arrays using periodic dislocations at crystal interfaces. As a demonstration, we fabricated arrays of titanium nanowires arranged at intervals of either 13 or 90 nm and then confirmed by scanning probe microscopy that they exhibit electrical conductivity inside an insulating aluminum oxide. Significantly, we were able to precisely control nanowire periodicity by the choice of crystal orientation and/or crystal planes at the crystal interface. This simple method for the fabrication of periodic nanowire arrays of highly controlled density should be widely applicable to electrical, magnetic, and optical devices.

  19. Nanowire assembly, e.g. for optical probes, comprises optically trapping high aspect ratio semiconductor nanowire with infrared single-beam optical trap and attaching nanowire to organic or inorganic structure

    OpenAIRE

    Pauzauskie, P.; Radenovic, A.; Trepagnier, E.; Liphardt, J.; Yang, P.

    2007-01-01

    NOVELTY - A nanowire assembly method comprises optically trapping a semiconductor nanowire with an infrared single-beam optical trap and attaching the nanowire to an organic or inorganic structure by laser fusing. The nanowire is further trapped in a fluid environment. The optical trap has a beam wavelength of 1064 nm. The nanowire has an aspect ratio greater than 100 and a diameter less than 100 (preferably less than 80) nm. The nanowire and the organic or inorganic structure form a heterost...

  20. Nanoscale manipulation of Ge nanowires by ion hammering

    Energy Technology Data Exchange (ETDEWEB)

    Picraux, Samuel T [Los Alamos National Laboratory; Romano, Lucia [UNIV OF FLORIDA; Rudawski, Nicholas G [UNIV OF FLORIDA; Holzworth, Monta R [UNIV OF FLORIDA; Jones, Kevin S [UNIV OF FLORIDA; Choi, S G [NREL

    2009-01-01

    Nanowires generated considerable interest as nanoscale interconnects and as active components of both electronic and electromechanical devices. However, in many cases, manipulation and modification of nanowires are required to realize their full potential. It is essential, for instance, to control the orientation and positioning of nanowires in some specific applications. This work demonstrates a simple method to reversibly control the shape and the orientation of Ge nanowires by using ion beams. Initially, crystalline nanowires were partially amorphized by 30 keY Ga+-implantation. After amorphization, viscous flow and plastic deformation occurred due to the ion hammering effect, causing the nanowires to bend toward the beam direction. The bending was reversed multiple times by ion-implanting the opposite side of the nanowires, resulting in straightening of the nanowires and subsequent bending in the opposite direction. This ion hammering effect demonstrates the detailed manipulation of nanoscale structures is possible through the use of ion irradiation.

  1. Memristive properties of hexagonal WO3 nanowires induced by oxygen vacancy migration

    Science.gov (United States)

    2013-01-01

    Tungsten trioxide (WO3) is always oxygen-deficient or non-stoichiometric under atmospheric conditions. Positively charged oxygen vacancies prefer to drift as well as electrons when the electric field is strong enough, which will alter the distribution of oxygen vacancies and then endow WO3 with memristive properties. In Au/WO3 nanowire/Au sandwich structures with two ohmic contacts, the axial distribution of oxygen vacancies and then the electrical transport properties can be more easily modulated by bias voltage. The threshold electric field for oxygen vacancy drifting in single-crystal hexagonal WO3 nanowire is about 106 V/m, one order of magnitude less than that in its granular film. At elevated temperatures, the oxygen vacancy drifts and then the memristive effect can be enhanced remarkably. When the two metallic contacts are asymmetric, the WO3 nanowire devices even demonstrate good rectifying characteristic at elevated temperatures. Based on the drift of oxygen vacancies, nanoelectronic devices such as memristor, rectifier, and two-terminal resistive random access memory can be fabricated on individual WO3 nanowires. PMID:23347429

  2. Zinc oxide nanowire-poly(methyl methacrylate) dielectric layers for polymer capacitive pressure sensors.

    Science.gov (United States)

    Chen, Yan-Sheng; Hsieh, Gen-Wen; Chen, Shih-Ping; Tseng, Pin-Yen; Wang, Cheng-Wei

    2015-01-14

    Polymer capacitive pressure sensors based on a dielectric composite layer of zinc oxide nanowire and poly(methyl methacrylate) show pressure sensitivity in the range of 2.63 × 10(-3) to 9.95 × 10(-3) cm(2) gf(-1). This represents an increase of capacitance change by as much as a factor of 23 over pristine polymer devices. An ultralight load of only 10 mg (corresponding to an applied pressure of ∼0.01 gf cm(-2)) can be clearly recognized, demonstrating remarkable characteristics of these nanowire-polymer capacitive pressure sensors. In addition, optical transmittance of the dielectric composite layer is approximately 90% in the visible wavelength region. Their low processing temperature, transparency, and flexible dielectric film makes them a highly promising means for flexible touching and pressure-sensing applications.

  3. Zero-bias photocurrents in highly-disordered networks of Ge and Si nanowires

    OpenAIRE

    Rabbani, M. Golam; Patil, Sunil R.; Verma, Amit; Villarreal, Julian E.; Korgel, Brian A.; Nekovei, Reza; Khader, Mahmoud M.; Darling, R. B.; Anantram, M. P.

    2017-01-01

    Semiconducting nanowire (NW) devices have garnered attention in self-powered electronic and optoelectronic applications. This work explores and exhibits, for the first time for visible light, a clear evidence of the zero-biased optoelectronic switching in randomly dispersed Ge and Si NW networks. The test bench, on which the NWs were dispersed for optoelectronic characterization, was fabricated using standard CMOS fabrication process, and utilized metal contacts with dissimilar work functions...

  4. Synthesis and Characterization of CdS/CdSxSe1-x Nanowires

    Science.gov (United States)

    Agueda Lopez, Kleyser; Wu, Marvin

    Semiconductor nanowire heterostructures are of interest for potential applications in solar cells and other advanced optoelectronic devices. We report here on synthesis of CdS/CdSxSe1-x nanowires (NWs) using a dual source vapor = liquid - solid technique, and characterization of these NWs with scanning electron microscopy and optical microscopy. We determine the effect of growth parameters, including source / substrate temperatures and time of exposure, on NW size, shape, and composition. The crystal structure and optical properties individual NWs from selected substrates has been mapped using transmission Kikuchi diffraction and photoluminescence (PL) microscopy. NWs consistently exhibit a hexagonal structure, with growth along the c-axis. Strong PL peaks are observed between the expected bandgap emission from CdS and CdSe, confirming formation of CdSxSe1-x. PL peaks vary significantly with intensity along the long axis of the nanowire, suggesting that the NW surface is not uniformly passivated. These nanowires show promise for future investigation and manipulation of energy band gaps contain in CdS/CdSe. CREST.

  5. Solution-Based Epitaxial Growth of Magnetically Responsive Cu@Ni Nanowires

    KAUST Repository

    Zhang, Shengmao

    2010-02-23

    An experiment was conducted to show the solution-based epitaxial growth of magnetically responsive Cu@Ni nanowires. The Ni-sheathed Cu nanowires were synthesized with a one-pot approach. 30 mL of high concentration NaOH, Cu(NO3)2. 3H2O, Cu(NO3)2. 3H2O and 0.07-0.30 mL of Ni(NO3)2. 6H 2O aqueous solutions were added into a plastic reactor with a capacity of 50.0 mL. A varying amount of ethylenediamine (EDA) and hydrazine were also added sequentially, followed by thorough mixing of all reagents. The dimension, morphology, and chemical composition of the products were examined with scanning electron microscopy with energy dispersive X-ray spectroscopy. The XPS analysis on the as formed Cu nanowires confirms that there is indeed no nickel inclusion in the nanowires prior to the formation of nickel overcoat, which rules out the possibility of Cu-Ni alloy formation.

  6. Broad spectral response photodetector based on individual tin-doped CdS nanowire

    Directory of Open Access Journals (Sweden)

    Weichang Zhou

    2014-12-01

    Full Text Available High purity and tin-doped 1D CdS micro/nano-structures were synthesized by a convenient thermal evaporation method. SEM, EDS, XRD and TEM were used to examine the morphology, composition, phase structure and crystallinity of as-prepared samples. Raman spectrum was used to confirm tin doped into CdS effectively. The effect of impurity on the photoresponse properties of photodetectors made from these as-prepared pure and tin-doped CdS micro/nano-structures under excitation of light with different wavelength was investigated. Various photoconductive parameters such as responsivity, external quantum efficiency, response time and stability were analyzed to evaluate the advantage of doped nanowires and the feasibility for photodetector application. Comparison with pure CdS nanobelt, the tin-doped CdS nanowires response to broader spectral range while keep the excellect photoconductive parameters. Both trapped state induced by tin impurity and optical whispering gallery mode microcavity effect in the doped CdS nanowires contribute to the broader spectral response. The micro-photoluminescence was used to confirm the whispering gallery mode effect and deep trapped state in the doped CdS nanowires.

  7. Suspended tungsten-based nanowires with enhanced mechanical properties grown by focused ion beam induced deposition

    Science.gov (United States)

    Córdoba, Rosa; Lorenzoni, Matteo; Pablo-Navarro, Javier; Magén, César; Pérez-Murano, Francesc; María De Teresa, José

    2017-11-01

    The implementation of three-dimensional (3D) nano-objects as building blocks for the next generation of electro-mechanical, memory and sensing nano-devices is at the forefront of technology. The direct writing of functional 3D nanostructures is made feasible by using a method based on focused ion beam induced deposition (FIBID). We use this technique to grow horizontally suspended tungsten nanowires and then study their nano-mechanical properties by three-point bending method with atomic force microscopy. These measurements reveal that these nanowires exhibit a yield strength up to 12 times higher than that of the bulk tungsten, and near the theoretical value of 0.1 times the Young’s modulus (E). We find a size dependence of E that is adequately described by a core-shell model, which has been confirmed by transmission electron microscopy and compositional analysis at the nanoscale. Additionally, we show that experimental resonance frequencies of suspended nanowires (in the MHz range) are in good agreement with theoretical values. These extraordinary mechanical properties are key to designing electro-mechanically robust nanodevices based on FIBID tungsten nanowires.

  8. Flexible Photodiodes Based on Nitride Core/Shell p-n Junction Nanowires.

    Science.gov (United States)

    Zhang, Hezhi; Dai, Xing; Guan, Nan; Messanvi, Agnes; Neplokh, Vladimir; Piazza, Valerio; Vallo, Martin; Bougerol, Catherine; Julien, François H; Babichev, Andrey; Cavassilas, Nicolas; Bescond, Marc; Michelini, Fabienne; Foldyna, Martin; Gautier, Eric; Durand, Christophe; Eymery, Joël; Tchernycheva, Maria

    2016-10-05

    A flexible nitride p-n photodiode is demonstrated. The device consists of a composite nanowire/polymer membrane transferred onto a flexible substrate. The active element for light sensing is a vertical array of core/shell p-n junction nanowires containing InGaN/GaN quantum wells grown by MOVPE. Electron/hole generation and transport in core/shell nanowires are modeled within nonequilibrium Green function formalism showing a good agreement with experimental results. Fully flexible transparent contacts based on a silver nanowire network are used for device fabrication, which allows bending the detector to a few millimeter curvature radius without damage. The detector shows a photoresponse at wavelengths shorter than 430 nm with a peak responsivity of 0.096 A/W at 370 nm under zero bias. The operation speed for a 0.3 × 0.3 cm(2) detector patch was tested between 4 Hz and 2 kHz. The -3 dB cutoff was found to be ∼35 Hz, which is faster than the operation speed for typical photoconductive detectors and which is compatible with UV monitoring applications.

  9. Light-induced antifungal activity of TiO{sub 2} nanoparticles/ZnO nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Haghighi, N. [Nano-Physics Research Lab., Department of Physics, University of Tehran, Tehran (Iran, Islamic Republic of); Abdi, Y., E-mail: y.abdi@ut.ac.ir [Nano-Physics Research Lab., Department of Physics, University of Tehran, Tehran (Iran, Islamic Republic of); Haghighi, F. [Department of Medical Mycology, School of Medical sciences, Tarbiat Modares University, Tehran (Iran, Islamic Republic of)

    2011-09-15

    Antifungal activity of TiO{sub 2}/ZnO nanostructures under visible light irradiation was investigated. A simple chemical method was used to synthesize ZnO nanowires. Zinc acetate dihydrate, Polyvinyl Pyrrolidone and deionized water were used as precursor, capping and solvent, respectively. TiO{sub 2} nanoparticles were deposited on ZnO nanowires using an atmospheric pressure chemical vapor deposition system. X-ray diffraction pattern of TiO{sub 2}/ZnO nano-composite has represented the diffraction peaks relating to the crystal planes of the TiO{sub 2} (anatase and rutile) and ZnO. TiO{sub 2}/ZnO nanostructure antifungal effect on Candida albicans biofilms was studied and compared with the activity of TiO{sub 2} nanoparticles and ZnO nanowires. The high efficiency photocatalytic activity of TiO{sub 2} nanoparticles leads to increased antifungal activity of ZnO nanowires. Scanning electron microscope was utilized to study the morphology of the as prepared nanostructures and the degradation of the yeast.

  10. Suspended tungsten-based nanowires with enhanced mechanical properties grown by focused ion beam induced deposition.

    Science.gov (United States)

    Córdoba, Rosa; Lorenzoni, Matteo; Pablo-Navarro, Javier; Magén, César; Pérez-Murano, Francesc; De Teresa, José María

    2017-11-03

    The implementation of three-dimensional (3D) nano-objects as building blocks for the next generation of electro-mechanical, memory and sensing nano-devices is at the forefront of technology. The direct writing of functional 3D nanostructures is made feasible by using a method based on focused ion beam induced deposition (FIBID). We use this technique to grow horizontally suspended tungsten nanowires and then study their nano-mechanical properties by three-point bending method with atomic force microscopy. These measurements reveal that these nanowires exhibit a yield strength up to 12 times higher than that of the bulk tungsten, and near the theoretical value of 0.1 times the Young's modulus (E). We find a size dependence of E that is adequately described by a core-shell model, which has been confirmed by transmission electron microscopy and compositional analysis at the nanoscale. Additionally, we show that experimental resonance frequencies of suspended nanowires (in the MHz range) are in good agreement with theoretical values. These extraordinary mechanical properties are key to designing electro-mechanically robust nanodevices based on FIBID tungsten nanowires.

  11. Morphology controlling method for amorphous silica nanoparticles and jellyfish-like nanowires and their luminescence properties

    Science.gov (United States)

    Liu, Haitao; Huang, Zhaohui; Huang, Juntong; Xu, Song; Fang, Minghao; Liu, Yan-Gai; Wu, Xiaowen; Zhang, Shaowei

    2016-03-01

    Uniform silica nanoparticles and jellyfish-like nanowires were synthesized by a chemical vapour deposition method on Si substrates treated without and with Ni(NO3)2, using silicon powder as the source material. Composition and structural characterization using field emission scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and fourier-transform infrared spectroscopy showed that the as-prepared products were silica nanoparticles and nanowires which have amorphous structures. The form of nanoparticles should be related to gas-phase nucleation procedure. The growth of the nanowires was in accordance with vapour-liquid-solid mechanism, followed by Ostwald ripening to form the jellyfish-like morphology. Photoluminescence and cathodoluminescence measurements showed that the silica products excited by different light sources show different luminescence properties. The emission spectra of both silica nanoparticles and nanowires are due to the neutral oxygen vacancies (≡Si-Si≡). The as-synthesized silica with controlled morphology can find potential applications in future nanodevices with tailorable photoelectric properties.

  12. Manganese oxide nanowires wrapped with nitrogen doped carbon layers for high performance supercapacitors.

    Science.gov (United States)

    Li, Ying; Mei, Yuan; Zhang, Lin-Qun; Wang, Jian-Hai; Liu, An-Ran; Zhang, Yuan-Jian; Liu, Song-Qin

    2015-10-01

    In this study, manganese oxide nanowires wrapped by nitrogen-doped carbon layers (MnO(x)@NCs) were prepared by carbonization of poly(o-phenylenediamine) layer coated onto MnO2 nanowires for high performance supercapacitors. The component and structure of the MnO(x)@NCs were controlled through carbonization procedure under different temperatures. Results demonstrated that this composite combined the high conductivity and high specific surface area of nitrogen-doped carbon layers with the high pseudo-capacitance of manganese oxide nanowires. The as-prepared MnO(x)@NCs exhibited superior capacitive properties in 1 M Na2SO4 aqueous solution, such as high conductivity (4.167×10(-3) S cm(-1)), high specific capacitance (269 F g(-1) at 10 mV s(-1)) and long cycle life (134 F g(-1) after 1200 cycles at a scan rate of 50 mV s(-1)). It is reckoned that the present novel hybrid nanowires can serve as a promising electrode material for supercapacitors and other electrochemical devices. Copyright © 2015 Elsevier Inc. All rights reserved.

  13. Conductivity of ZnO nanowires, nanoparticles, and thin films using time-resolved terahertz spectroscopy.

    Science.gov (United States)

    Baxter, Jason B; Schmuttenmaer, Charles A

    2006-12-21

    The terahertz absorption coefficient, index of refraction, and conductivity of nanostructured ZnO have been determined using time-resolved terahertz spectroscopy, a noncontact optical probe. ZnO properties were measured directly for thin films and were extracted from measurements of nanowire arrays and mesoporous nanoparticle films by applying Bruggeman effective medium theory to the composite samples. Annealing significantly reduces the intrinsic carrier concentration in the ZnO films and nanowires, which were grown by chemical bath deposition. The complex-valued, frequency-dependent photoconductivities for all morphologies were found to be similar at short pump-probe delay times. Fits using the Drude-Smith model show that films have the highest mobility, followed by nanowires and then nanoparticles, and that annealing the ZnO increases its mobility. Time constants for decay of photoinjected electron density in films are twice as long as those in nanowires and more than 5 times those for nanoparticles due to increased electron interaction with interfaces and grain boundaries in the smaller-grained materials. Implications for electron transport in dye-sensitized solar cells are discussed.

  14. Conductive Cellulose Composites with Low Percolation Threshold for 3D Printed Electronics

    OpenAIRE

    Park, Jae Sung; Kim, Taeil; Kim, Woo Soo

    2017-01-01

    We are reporting a 3D printable composite paste having strong thixotropic rheology. The composite has been designed and investigated with highly conductive silver nanowires. The optimized electrical percolation threshold from both simulation and experiment is shown from 0.7 vol. % of silver nanowires which is significantly lower than other composites using conductive nano-materials. Reliable conductivity of 1.19 × 102 S/cm has been achieved from the demonstrated 3D...

  15. A Six-Month Randomized Controlled Trial of Whole Soy and Isoflavones Daidzein on Body Composition in Equol-Producing Postmenopausal Women with Prehypertension

    Directory of Open Access Journals (Sweden)

    Zhao-min Liu

    2013-01-01

    Full Text Available Objectives. This paper reported the effects of commonly used whole soy foods (soy flour and purified daidzein (one of the major isoflavones and the precursor of equol on changes in anthropometric measurements and body composition in a 6-month double-blind, randomized, placebo-controlled trial among prehypertensive postmenopausal women who are also equol producers. Methods. 270 eligible women were randomized to either one of the three treatments: 40 g soy flour (whole soy group, 40 g low-fat milk powder + 63 mg daidzein (daidzein group, or 40 g low-fat milk powder (placebo group daily each for 6 months. Anthropometric indicators and body composition were measured before and after intervention. Results. 253 subjects completed the study with good compliance. Urinary isoflavones levels suggested good compliance of subjects with supplementation. Whole soy and purified daidzein had no significant effect on body weight, body mass index (BMI, waist and hip circumferences, waist to hip ratio (WHR, body fat percentage, fat mass, and free fat mass. Conclusion. Six-month consumption of whole soy and purified daidzein at provided dosage had no improvement on body weight and composition compared with isocaloric milk placebo among prehypertensive equol-producing postmenopausal women. This trial is registered with ClinicalTrials.gov NCT01270737.

  16. Clinical Effectiveness of Different Polishing Systems and Self-Etch Adhesives in Class V Composite Resin Restorations: Two-Year Randomized Controlled Clinical Trial.

    Science.gov (United States)

    Jang, J-H; Kim, H-Y; Shin, S-M; Lee, C-O; Kim, D S; Choi, K-K; Kim, S-Y

    The aim of this randomized controlled clinical trial was to compare the clinical effectiveness of different polishing systems and self-etch adhesives in class V composite resin restorations. A total of 164 noncarious cervical lesions (NCCLs) from 35 patients were randomly allocated to one of four experimental groups, each of which used a combination of polishing systems and adhesives. The two polishing systems used were Sof-Lex XT (Sof), a multistep abrasive disc, and Enhance/Pogo (EP), a simplified abrasive-impregnated rubber instrument. The adhesive systems were Clearfil SE bond (CS), a two-step self-etch adhesive, and Xeno V (XE), a one-step self-etch adhesive. All NCCLs were restored with light-cured microhybrid resin composites (Z250). Restorations were evaluated at baseline and at 6, 12, 18, and 24 months by two blinded independent examiners using modified FDI criteria. The Fisher exact test and generalized estimating equation analysis considering repeated measurements were performed to compare the outcomes between the polishing systems and adhesives. Three restorations were dislodged: two in CS/Sof and one in CS/EP. None of the restorations required any repair or retreatment except those showing retention loss. Sof was superior to EP with regard to surface luster, staining, and marginal adaptation (p0.05). Sof is clinically superior to EP for polishing performance in class V composite resin restoration. XE demonstrates clinically equivalent bonding performance to CS.

  17. Three-year Randomized Clinical Study of a One-step Universal Adhesive and a Two-step Self-etch Adhesive in Class II Composite Restorations.

    Science.gov (United States)

    van Dijken, Jan Wv; Pallesen, Ulla

    2017-01-01

    To evaluate in a randomized clinical evaluation the 3-year clinical durability of a one-step universal adhesive and compare it intraindividually with a 2-step self-etch adhesive in Class II restorations. Each of 57 participants (mean age 58.3 years) received at least two extended Class II restorations that were as similar as possible. The cavities in each of the 60 individual pairs of cavities were randomly distributed to the 1-step universal adhesive (All-Bond Universal: AU) and the control 2-step self-etch adhesive (Optibond XTR: OX). A low shrinkage composite (Aelite LS) was used for all restorations, which were evaluated using slightly modified USPHS criteria at baseline and 1, 2, and 3 years. 114 Class II restorations were evaluated at three years. Eight restorations, 3 AU and 5 OX, failed during the follow-up, resulting in 94.7% (AU) and 91.2% (OX) success rates (p > 0.05). Annual failure rates were 1.8% and 2.9%, respectively.The main reason for failure was composite fracture. Class II composite restorations placed with a 1-step universal adhesive showed good short-term efficacy.

  18. Long-range magnetostatic interactions in arrays of nanowires

    CERN Document Server

    Raposo, V; González, J M; Vázquez, M

    2000-01-01

    Experimental measurements and micromagnetic simulations of the hysteresis loops of arrays of cobalt nanowires are compared here. Arrays of cobalt nanowires (200 nm in diameter) were electrodeposited into the pores of alumina membranes (thickness 60 mu m). Their hysteresis loops along the axial direction of nanowires were measured using vibrating sample magnetometry. Micromagnetic simulations were performed considering dipolar interaction between nanowires leading to similar hysteresis loops as those obtained experimentally.

  19. Vertical nanowire probes for intracellular signaling of living cells

    OpenAIRE

    Lee, Ki-Young; Kim, Ilsoo; Kim, So-Eun; Jeong, Du-Won; Kim, Ju-Jin; Rhim, Hyewhon; Ahn, Jae-Pyeong; Park, Seung-Han; Choi, Heon-Jin

    2014-01-01

    The single living cell action potential was measured in an intracellular mode by using a vertical nanoelectrode. For intracellular interfacing, Si nanowires were vertically grown in a controlled manner, and optimum conditions, such as diameter, length, and nanowire density, were determined by culturing cells on the nanowires. Vertical nanowire probes were then fabricated with a complimentary metal-oxide-semiconductor (CMOS) process including sequential deposition of the passivation and electr...

  20. Lactobacillus casei Shirota Supplementation Does Not Restore Gut Microbiota Composition and Gut Barrier in Metabolic Syndrome: A Randomized Pilot Study

    National Research Council Canada - National Science Library

    Stadlbauer, Vanessa; Leber, Bettina; Lemesch, Sandra; Trajanoski, Slave; Bashir, Mina; Horvath, Angela; Tawdrous, Monika; Stojakovic, Tatjana; Fauler, Günter; Fickert, Peter; Högenauer, Christoph; Klymiuk, Ingeborg; Stiegler, Philipp; Lamprecht, Manfred; Pieber, Thomas R; Tripolt, Norbert J; Sourij, Harald

    2015-01-01

    .... We aimed to investigate the effect of Lactobacillus casei Shirota (LcS) on gut microbiota composition, gut barrier integrity, intestinal inflammation and serum bile acid profile in metabolic syndrome...

  1. Benefits of different intensity of aerobic exercise in modulating body composition among obese young adults: a pilot randomized controlled trial

    National Research Council Canada - National Science Library

    Chih-Hui Chiu; Ming-Chen Ko; Long-Shan Wu; Ding-Peng Yeh; Nai-Wen Kan; Po-Fu Lee; Jenn-Woei Hsieh; Ching-Yu Tseng; Chien-Chang Ho

    2017-01-01

    Background The aim of present study was to compare the effects of different aerobic exercise intensities and energy expenditures on the body composition of sedentary obese college students in Taiwan...

  2. Nanowires: properties, applications and synthesis via porous anodic ...

    Indian Academy of Sciences (India)

    Quasi one-dimensional nanowires possess unique electrical, electronic, thermoelectrical, optical, magnetic and chemical properties, which are different from that of their parent counterpart. The physical properties of nanowires are influenced by the morphology of the nanowires, diameter dependent band gap, carrier ...

  3. Failure mechanisms and electromechanical coupling in semiconducting nanowires

    Directory of Open Access Journals (Sweden)

    Peng B.

    2010-06-01

    Full Text Available One dimensional nanostructures, like nanowires and nanotubes, are increasingly being researched for the development of next generation devices like logic gates, transistors, and solar cells. In particular, semiconducting nanowires with a nonsymmetric wurtzitic crystal structure, such as zinc oxide (ZnO and gallium nitride (GaN, have drawn immense research interests due to their electromechanical coupling. The designing of the future nanowire-based devices requires component-level characterization of individual nanowires. In this paper, we present a unique experimental set-up to characterize the mechanical and electromechanical behaviour of individual nanowires. Using this set-up and complementary atomistic simulations, mechanical properties of ZnO nanowires and electromechanical properties of GaN nanowires were investigated. In ZnO nanowires, elastic modulus was found to depend on nanowire diameter decreasing from 190 GPa to 140 GPa as the wire diameter increased from 5 nm to 80 nm. Inconsistent failure mechanisms were observed in ZnO nanowires. Experiments revealed a brittle fracture, whereas simulations using a pairwise potential predicted a phase transformation prior to failure. This inconsistency is addressed in detail from an experimental as well as computational perspective. Lastly, in addition to mechanical properties, preliminary results on the electromechanical properties of gallium nitride nanowires are also reported. Initial investigations reveal that the piezoresistive and piezoelectric behaviour of nanowires is different from bulk gallium nitride.

  4. Theory of surface second-harmonic generation in silica nanowires

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper

    2010-01-01

    -based nanowires is critically discussed, based on simulations of second-harmonic generation in nanowires with a fluctuating phase-matching wavelength. It is concluded that efficient wavelength conversion will require strong improvements in the nanowire uniformity, peak powers well in excess of 10 KW, increase...

  5. Understanding quantum confinement in nanowires: basics, applications and possible laws.

    Science.gov (United States)

    Mohammad, S Noor

    2014-10-22

    A comprehensive investigation of quantum confinement in nanowires has been carried out. Though applied to silicon nanowires (SiNWs), it is general and applicable to all nanowires. Fundamentals and applications of quantum confinement in nanowires and possible laws obeyed by these nanowires, have been investigated. These laws may serve as backbones of nanowire science and technology. The relationship between energy band gap and nanowire diameter has been studied. This relationship appears to be universal. A thorough review indicates that the first principles results for quantum confinement vary widely. The possible cause of this variation has been examined. Surface passivation and surface reconstruction of nanowires have been elucidated. It has been found that quantum confinement owes its origin to surface strain resulting from surface passivation and surface reconstruction and hence thin nanowires may actually be crystalline-core/amorphous-shell (c-Si/a-Si) nanowires. Experimental data available in the literature corroborate with the suggestion. The study also reveals an intrinsic relationship between quantum confinement and the surface amorphicity of nanowires. It demonstrates that surface amorphicity may be an important tool to investigate the electronic, optoelectronic and sensorial properties of quantum-confined nanowires.

  6. Controlled growth of single nanowires within a supported alumina template

    DEFF Research Database (Denmark)

    Vlad, A.; Mátéfi-Tempfli, M.; Faniel, S.

    2006-01-01

    A simple technique for fabricating single nanowires with well-defined position is presented. The process implies the use of a silicon nitride mask for selective electrochemical growth of the nanowires in a porous alumina template. We show that this method allows the realization of complex nanowire...

  7. Measurement of light diffusion in ZnO nanowire forests

    NARCIS (Netherlands)

    Versteegh, M.A.M.; van der Wel, R.E.C.; Dijkhuis, J.I.

    2012-01-01

    Optimum design of efficient nanowire solar cells requires better understanding of light diffusion in a nanowire array. Here we demonstrate that our recently developed ultrafast all-optical shutter can be used to directly measure the dwell time of light in a nanowire array. Our measurements on

  8. Microbial nanowires and methods of making and using

    Energy Technology Data Exchange (ETDEWEB)

    Reguera, Gemma; Cologgi, Dena; Worden, Robert Mark; Castro-Forero, Angelines A.; Steidl, Rebecca

    2017-03-21

    Electrically conductive nanowires, and genetically or chemically modified production and use of such nanowires with altered conductive, adhesive, coupling or other properties are described. The disclosed nanowires are used as device or device components or may be adapted for soluble metal remediation.

  9. Topological Insulator Nanowires and Nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Kong, D.S.

    2010-06-02

    Recent theoretical calculations and photoemission spectroscopy measurements on the bulk Bi{sub 2}Se{sub 3} material show that it is a three-dimensional topological insulator possessing conductive surface states with nondegenerate spins, attractive for dissipationless electronics and spintronics applications. Nanoscale topological insulator materials have a large surface-to-volume ratio that can manifest the conductive surface states and are promising candidates for devices. Here we report the synthesis and characterization of high quality single crystalline Bi{sub 2}Se{sub 3} nanomaterials with a variety of morphologies. The synthesis of Bi{sub 2}Se{sub 3} nanowires and nanoribbons employs Au-catalyzed vapor-liquid-solid (VLS) mechanism. Nanowires, which exhibit rough surfaces, are formed by stacking nanoplatelets along the axial direction of the wires. Nanoribbons are grown along [11-20] direction with a rectangular crosssection and have diverse morphologies, including quasi-one-dimensional, sheetlike, zigzag and sawtooth shapes. Scanning tunneling microscopy (STM) studies on nanoribbons show atomically smooth surfaces with {approx}1 nm step edges, indicating single Se-Bi-Se-Bi-Se quintuple layers. STM measurements reveal a honeycomb atomic lattice, suggesting that the STM tip couples not only to the top Se atomic layer, but also to the Bi atomic layer underneath, which opens up the possibility to investigate the contribution of different atomic orbitals to the topological surface states. Transport measurements of a single nanoribbon device (four terminal resistance and Hall resistance) show great promise for nanoribbons as candidates to study topological surface states.

  10. Effect of the Thermal Conductivity on Resistive Switching in GeTe and Ge2Sb2Te5 Nanowires.

    Science.gov (United States)

    Park, Sungjin; Park, Dambi; Jeong, Kwangsik; Kim, Taeok; Park, SeungJong; Ahn, Min; Yang, Won Jun; Han, Jeong Hwa; Jeong, Hong Sik; Jeon, Seong Gi; Song, Jae Yong; Cho, Mann-Ho

    2015-10-07

    The thermal conduction characteristics of GeTe and Ge2Sb2Te5(GST) nanowires were investigated using an optical method to determine the local temperature by Raman spectroscopy. Since the localization of surface charge in a single-crystalline nanostructure can enhance charge-phonon scattering, the thermal conductivity value (κ) of single crystalline GeTe and GST nanowires was decreased significantly to 1.44 Wm(-1) K(-1) for GeTe and 1.13 Wm(-1) K(-1) for GST, compared to reported values for polycrystalline structures. The SET-to-RESET state in single-crystalline GeTe and GST nanowires are characteristic of a memory device. Unlike previous reports using GeTe and GST nanowires, the SET-to-RESET characteristics showed a bipolar switching shape and no unipolar switching. In addition, after multiple cycles of operation, a significant change in morphology and composition was observed without any structural phase transition, indicating that atoms migrate toward the cathode or anode, depending on their electronegativities. This change caused by a field effect indicates that the structural phase transition does not occur in the case of GeTe and GST nanowires with a significantly lowered thermal conductivity and stable crystalline structure. Finally, the formation of voids and hillocks as the result of the electromigration critically degrades device reliability.

  11. Broad Band Light Absorption and High Photocurrent of (In,Ga)N Nanowire Photoanodes Resulting from a Radial Stark Effect.

    Science.gov (United States)

    Kamimura, Jumpei; Bogdanoff, Peter; Corfdir, Pierre; Brandt, Oliver; Riechert, Henning; Geelhaar, Lutz

    2016-12-21

    The photoelectrochemical properties of (In,Ga)N nanowire photoanodes are investigated using H2O2 as a hole scavenger to prevent photocorrosion. Under simulated solar illumination, In0.16Ga0.84N nanowires grown by plasma-assisted molecular beam epitaxy show a high photocurrent of 2.7 mA/cm2 at 1.2 V vs reversible hydrogen electrode. This value is almost the theoretical maximum expected from the corresponding band gap (2.8 eV) for homogeneous bulk material without taking into account surface effects. These nanowires exhibit a higher incident photon-to-current conversion efficiency over a broader wavelength range and a higher photocurrent than a compact layer with higher In content of 28%. These results are explained by the combination of built-in electric fields at the nanowire sidewall surfaces and compositional fluctuations in (In,Ga)N, which gives rise to a radial Stark effect. This effect enables spatially indirect transitions at energies much lower than the band gap. The resulting broad band light absorption leads to high photocurrents. This benefit of the radial Stark effect in (In,Ga)N nanowires for solar harvesting applications opens up the perspective to break the theoretical limit for photocurrents.

  12. Fabrication of Supramolecular n/p-Nanowires via Coassembly of Oppositely Charged Peptide-Chromophore Systems in Aqueous Media.

    Science.gov (United States)

    Khalily, Mohammad Aref; Bakan, Gokhan; Kucukoz, Betul; Topal, Ahmet Emin; Karatay, Ahmet; Yaglioglu, H Gul; Dana, Aykutlu; Guler, Mustafa O

    2017-07-25

    Fabrication of supramolecular electroactive materials at the nanoscale with well-defined size, shape, composition, and organization in aqueous medium is a current challenge. Herein we report construction of supramolecular charge-transfer complex one-dimensional (1D) nanowires consisting of highly ordered mixed-stack π-electron donor-acceptor (D-A) domains. We synthesized n-type and p-type β-sheet forming short peptide-chromophore conjugates, which assemble separately into well-ordered nanofibers in aqueous media. These complementary p-type and n-type nanofibers coassemble via hydrogen bonding, charge-transfer complex, and electrostatic interactions to generate highly uniform supramolecular n/p-coassembled 1D nanowires. This molecular design ensures highly ordered arrangement of D-A stacks within n/p-coassembled supramolecular nanowires. The supramolecular n/p-coassembled nanowires were found to be formed by A-D-A unit cells having an association constant (KA) of 5.18 × 105 M-1. In addition, electrical measurements revealed that supramolecular n/p-coassembled nanowires are approximately 2400 and 10 times more conductive than individual n-type and p-type nanofibers, respectively. This facile strategy allows fabrication of well-defined supramolecular electroactive nanomaterials in aqueous media, which can find a variety of applications in optoelectronics, photovoltaics, organic chromophore arrays, and bioelectronics.

  13. Shewanella oneidensis MR-1 Nanowires are Outer Membrane and Periplasmic Extensions of the Extracellular Electron Transport Components

    Energy Technology Data Exchange (ETDEWEB)

    Pirbadian, S.; Barchinger, S. E.; Leung, K. M.; Byun, H. S.; Jangir, Y.; Bouhenni, Rachida; Reed, Samantha B.; Romine, Margaret F.; Saffarini, Daad; Shi, Liang; Gorby, Yuri A.; Golbeck, J. H.; El-Naggar, Mohamed Y.

    2014-08-20

    Bacterial nanowires offer an extracellular electron transport (EET) pathway for linking the respiratory chain of bacteria to external surfaces, including oxidized metals in the environment and engineered electrodes in renewable energy devices. Despite the global, environmental, and technological consequences of this biotic-abiotic interaction, the composition, physiological relevance, and electron transport mechanisms of bacterial nanowires remain unclear. We report the first in vivo observations of the formation and respiratory impact of nanowires in the model metal-reducing microbe Shewanella neidensis MR-1. Using live fluorescence measurements, immunolabeling, and quantitative gene expression analysis, we report that S. oneidensis MR-1 nanowires are extensions of the outer membrane and periplasm that include the multiheme cytochromes responsible for EET, rather than pilin-based structures, as previously thought. These bacterial nanowires were also associated with outer membrane vesicles and vesicle chains, structures ubiquitous in gram-negative bacteria. Redoxfunctionalized membrane and vesicular extensions may represent a general microbial strategy for electron transport and energy distribution.

  14. Electroluminescent, polycrystalline cadmium selenide nanowire arrays.

    Science.gov (United States)

    Ayvazian, Talin; van der Veer, Wytze E; Xing, Wendong; Yan, Wenbo; Penner, Reginald M

    2013-10-22

    Electroluminescence (EL) from nanocrystalline CdSe (nc-CdSe) nanowire arrays is reported. The n-type, nc-CdSe nanowires, 400-450 nm in width and 60 nm in thickness, were synthesized using lithographically patterned nanowire electrodeposition, and metal-semiconductor-metal (M-S-M) devices were prepared by the evaporation of two gold contacts spaced by either 0.6 or 5 μm. These M-S-M devices showed symmetrical current voltage curves characterized by currents that increased exponentially with applied voltage bias. As the applied biased was increased, an increasing number of nanowires within the array "turned on", culminating in EL emission from 30 to 50% of these nanowires at applied voltages of 25-30 V. The spectrum of the emitted light was broad and centered at 770 nm, close to the 1.74 eV (712 nm) band gap of CdSe. EL light emission occurred with an external quantum efficiency of 4 × 10(-6) for devices with a 0.60 μm gap between the gold contacts and 0.5 × 10(-6) for a 5 μm gap-values similar to those reported for M-S-M devices constructed from single-crystalline CdSe nanowires. Kelvin probe force microscopy of 5 μm nc-CdSe nanowire arrays showed pronounced electric fields at the gold electrical contacts, coinciding with the location of strongest EL light emission in these devices. This electric field is implicated in the Poole-Frenkel minority carrier emission and recombination mechanism proposed to account for EL light emission in most of the devices that were investigated.

  15. Quantification of nanowire uptake by live cells

    KAUST Repository

    Margineanu, Michael B.

    2015-05-01

    Nanostructures fabricated by different methods have become increasingly important for various applications at the cellular level. In order to understand how these nanostructures “behave” and for studying their internalization kinetics, several attempts have been made at tagging and investigating their interaction with living cells. In this study, magnetic iron nanowires with an iron oxide layer are coated with (3-Aminopropyl)triethoxysilane (APTES), and subsequently labeled with a fluorogenic pH-dependent dye pHrodo™ Red, covalently bound to the aminosilane surface. Time-lapse live imaging of human colon carcinoma HCT 116 cells interacting with the labeled iron nanowires is performed for 24 hours. As the pHrodo™ Red conjugated nanowires are non-fluorescent outside the cells but fluoresce brightly inside, internalized nanowires are distinguished from non-internalized ones and their behavior inside the cells can be tracked for the respective time length. A machine learning-based computational framework dedicated to automatic analysis of live cell imaging data, Cell Cognition, is adapted and used to classify cells with internalized and non-internalized nanowires and subsequently determine the uptake percentage by cells at different time points. An uptake of 85 % by HCT 116 cells is observed after 24 hours incubation at NW-to-cell ratios of 200. While the approach of using pHrodo™ Red for internalization studies is not novel in the literature, this study reports for the first time the utilization of a machine-learning based time-resolved automatic analysis pipeline for quantification of nanowire uptake by cells. This pipeline has also been used for comparison studies with nickel nanowires coated with APTES and labeled with pHrodo™ Red, and another cell line derived from the cervix carcinoma, HeLa. It has thus the potential to be used for studying the interaction of different types of nanostructures with potentially any live cell types.

  16. Shear induced alignment of short nanofibers in 3D printed polymer composites

    Science.gov (United States)

    Erdem Yunus, Doruk; Shi, Wentao; Sohrabi, Salman; Liu, Yaling

    2016-12-01

    3D printing of composite materials offers an opportunity to combine the desired properties of composite materials with the flexibility of additive manufacturing in geometric shape and complexity. In this paper, the shear-induced alignment of aluminum oxide nanowires during stereolithography printing was utilized to fabricate a nanowire reinforced polymer composite. To align the fibers, a lateral oscillation mechanism was implemented and combined with wall pattern printing technique to generate shear flow in both vertical and horizontal directions. A series of specimens were fabricated for testing the composite material’s tensile strength. The results showed that mechanical properties of the composite were improved by reinforcement of nanofibers through shear induced alignment. The improvement of tensile strength was approximately ∼28% by aligning the nanowires at 5 wt% (∼1.5% volume fraction) loading of aluminum oxide nanowires.

  17. Fivefold Enhanced Photoelectrochemical Properties of ZnO Nanowire Arrays Modified with C3N4 Quantum Dots

    Directory of Open Access Journals (Sweden)

    Hao Yang

    2017-03-01

    Full Text Available A facile and effective growing strategy of graphite-like carbon nitride quantum dots (CNQDs modified on ZnO nanowire array composite electrodes has been successfully designed and prepared for the first time. The remarkable quantum enhanced properties were carefully studied by means of scanning electron microscope (SEM, transmission electron microscopy (TEM, X-ray photoelectron spectroscope (XPS, UV-vis diffuse reflectance, PEC performance, and photocatalytic hydrogen production, and the results were in good agreement. Fivefold enhanced photoelectrochemical performances of this novel hierarchical hetero-array prepared in this paper compared with pure ZnO nanowire arrays were obtained under UV-light. The effect was attributed to the remarkable charge separation between CNQDs and ZnO nanowire arrays. Additional investigations revealed that the particular structure of CNQDs/ZnO composites contributed to the separation of a photon-generation carrier and an enhanced photoelectric current. Moreover, the absorption edge of CNQD-modified ZnO nanowire arrays was slightly broadened, and the diameter was reduced as well. The photoelectrochemistry hydrogen evolution splitting water using simulated solar irradiation exhibited the foreground of a possible application of a mechanism of photoelectrochemistry hydrogen evolution over CNQDs/ZnO composite electrodes.

  18. A randomized trial of high-dairy-protein, variable-carbohydrate diets and exercise on body composition in adults with obesity.

    Science.gov (United States)

    Parr, Evelyn B; Coffey, Vernon G; Cato, Louise E; Phillips, Stuart M; Burke, Louise M; Hawley, John A

    2016-05-01

    This study determined the effects of 16-week high-dairy-protein, variable-carbohydrate (CHO) diets and exercise training (EXT) on body composition in men and women with overweight/obesity. One hundred and eleven participants (age 47 ± 6 years, body mass 90.9 ± 11.7 kg, BMI 33 ± 4 kg/m(2) , values mean ± SD) were randomly stratified to diets with either: high dairy protein, moderate CHO (40% CHO: 30% protein: 30% fat; ∼4 dairy servings); high dairy protein, high CHO (55%: 30%: 15%; ∼4 dairy servings); or control (55%: 15%: 30%; ∼1 dairy serving). Energy restriction (500 kcal/day) was achieved through diet (∼250 kcal/day) and EXT (∼250 kcal/day). Body composition was measured using dual-energy X-ray absorptiometry before, midway, and upon completion of the intervention. Eighty-nine (25 M/64 F) of 115 participants completed the 16-week intervention, losing 7.7 ± 3.2 kg fat mass (P composition (fat mass or lean mass) between groups. Compared to a healthy control diet, energy-restricted high-protein diets containing different proportions of fat and CHO confer no advantage to weight loss or change in body composition in the presence of an appropriate exercise stimulus. © 2016 The Obesity Society.

  19. Vibrational spectra of nanowires measured using laser doppler vibrometry and STM studies of epitaxial graphene : an LDRD fellowship report.

    Energy Technology Data Exchange (ETDEWEB)

    Biedermann, Laura Butler

    2009-09-01

    MWNTs, their vibration spectra was more extensively studied. The thermal vibration spectra of Ag{sub 2}Ga nanoneedles was measured under both ambient and low-vacuum conditions. The operational deflection shapes of the vibrating Ag{sub 2}Ga nanoneedles was also measured, allowing confirmation of the eigenmodes of vibration. The modulus of the crystalline nanoneedles was 84.3 {+-} 1.0 GPa. Gas damping is the dominate mechanism of energy loss for nanowires oscillating under ambient conditions. The measured quality factors, Q, of oscillation are in line with theoretical predictions of air damping in the free molecular gas damping regime. In the free molecular regime, Q{sub gas} is linearly proportional to the density and diameter of the nanowire and inversely proportional to the air pressure. Since the density of the Ag{sub 2}Ga nanoneedles is three times that of the MWNTs, the Ag{sub 2}Ga nanoneedles have greater Q at atmospheric pressures. Our initial measurements of Q for Ag{sub 2}Ga nanoneedles in low-vacuum (10 Torr) suggest that the intrinsic Q of these nanoneedles may be on the order of 1000. The epitaxial carbon that grows after heating (000{bar 1}) silicon carbide (SiC) to high temperatures (1450-1600) in vacuum was also studied. At these high temperatures, the surface Si atoms sublime and the remaining C atoms reconstruct to form graphene. X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) were used to characterize the quality of the few-layer graphene (FLG) surface. The XPS studies were useful in confirming the graphitic composition and measuring the thickness of the FLG samples. STM studies revealed a wide variety of nanometer-scale features that include sharp carbon-rich ridges, moire superlattices, one-dimensional line defects, and grain boundaries. By imaging these features with atomic scale resolution, considerable insight into the growth mechanisms of FLG on the carbon-face of SiC is obtained.

  20. Electrodeposition of textured Bi{sub 27}Sb{sub 28}Te{sub 45} nanowires with enhanced electrical conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Hasan, Maksudul, E-mail: maksudul.hasan@tyndall.ie [Tyndall National Institute, University College Cork, Lee Maltings, Cork (Ireland); Gautam, Devendraprakash [Tyndall National Institute, University College Cork, Lee Maltings, Cork (Ireland); Enright, Ryan [Thermal Management Research Group, Efficient Energy Transfer Department, Bell Labs Ireland, Alcatel-Lucent Ireland Ltd., Dublin (Ireland)

    2016-04-15

    This work presents the template based pulsed potential electrodeposition technique of highly textured single crystalline bismuth antimony telluride (Bi{sub 1-x}Sb{sub x}){sub 2}Te{sub 3} nanowires from a single aqueous electrolyte. Cyclic voltammetry was used as an electroanalytical tool to assess the effect of the precursor concentrations on the composition of the deposits and to determine the deposition potential for each element. Pulsed potential electrodeposition was then applied on a gold-coated anodised alumina template to examine the effect of the pulse parameters on the composition and texture of Bi{sub 27}Sb{sub 28}Te{sub 45} nanowires. The nanowires are cylindrical in shape formed during the deposition inside the porous template and highly textured as they are decorated with sparse distribution of small crystal domains. The electrical conductivity (24.1 × 10{sup 4} S m{sup −1}) of a single nanowire was measured using a four-point probe technique implemented on a custom fabricated test chip. In this work, we demonstrated that crystal orientation with respect to the transport direction controlled by tuning the pulsed electrodeposition parameters. This allowed us to realise electrical conductivities ∼2.5 times larger than Sb doped bismuth-tellurium based ternary material systems and similar to what is typically seen in binary systems. - Highlights: • Pulsed electrodeposition is described towards fabrication of (Bi{sub 1-x}Sb{sub x}){sub 2}Te{sub 3} nanowires. • The adopted method is compatible with existing CMOS process. • The nanowires were fabricated as highly textured to enhance phonon scattering. • The electrical conductivity is ∼2.5 times larger than the current ternary materials.

  1. Silicon nanowire properties from theory and experiment

    Energy Technology Data Exchange (ETDEWEB)

    Scheel, H.M.

    2007-09-10

    Silicon has played an outstanding role at the end of the 20th century and is still one of the most important components for micro computing. In recent years the ability to miniaturize semiconductor structures and devices to nanometer length scales has opened an all new field of physics, i.e. nanoscience. Simply by miniaturizing the size of semiconducting structures the physics describing electronic or vibronic properties has to be altered fundamentally leading to new phenomena and interesting effects. For silicon the two major mile-stones where the fabrication of porous silicon and later the fabrication of free-standing silicon nanowires. The intense research concerning the fabrication of silicon nanowires has led to single crystalline nanowires with diameters of only a few nanometers. The hope that drove these intense research efforts where to find efficient photonic properties in these quantized systems. In the first part of this work detailed theoretical investigations are presented for the commonly observed ([111] and [11 anti 2]) representatives of free-standing and for the most frequently discussed ([001]) silicon nanowires not (so far) observed as free standing wires. Using density functional theory in the local density approximation the electronic properties as well as the structural changes due to the reduced dimensionality of silicon nanowires are calculated and discussed. The comparison to recent experimental, scanning tunneling experiments reveal a fundamental discrepancy between the calculated band structures and experimental findings. With our results we are able to explain these differences. Raman investigations on silicon nanowires where in a state of controversial discussion about the origin of observed red shifted spectra. Various contributions like quantum confinement, photo excitation and thermal effects where discussed. The second part of this thesis contributes to this discussion, with detailed laser power dependent Raman spectroscopic

  2. Sensors and devices containing ultra-small nanowire arrays

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Zhili

    2017-04-11

    A network of nanowires may be used for a sensor. The nanowires are metallic, each nanowire has a thickness of at most 20 nm, and each nanowire has a width of at most 20 nm. The sensor may include nanowires comprising Pd, and the sensor may sense a change in hydrogen concentration from 0 to 100%. A device may include the hydrogen sensor, such as a vehicle, a fuel cell, a hydrogen storage tank, a facility for manufacturing steel, or a facility for refining petroleum products.

  3. Light-trapping properties of the Si inclined nanowire arrays

    Science.gov (United States)

    Xu, Zhaopeng; Huangfu, Huichao; He, Long; Wang, Jiazhuang; Yang, Dong; Guo, Jingwei; Wang, Haiyan

    2017-01-01

    The light trapping performance of Si nanowire with different inclination angles were systematically studied by COMSOL Multiphysics. The inclined nanowires with inclination angles smaller than 60° show greater light trapping ability than their counterparts of the vertical nanowires. The Si solar cell with the inclined nanowires of the optimal parameters, whose θ=30°, P=400 nm, D=140 nm, can achieve a 32.395 mA/cm2 short circuit photocurrent density and a 35.655% conversion efficiency. The study of the inclined nanowire provides an effective way for further utilization of the incoming light.

  4. Effect of almond and pistachio consumption on gut microbiota composition in a randomized cross-over human feeding study

    DEFF Research Database (Denmark)

    Ukhanova, M; Wang, X; Baer, D J

    2014-01-01

    The modification of microbiota composition to a ‘beneficial’ one is a promising approach for improving intestinal as well as overall health. Natural fibres and phytochemicals that reach the proximal colon, such as those present in various nuts, provide substrates for the maintenance of healthy...... for 18 d. Gut microbiota composition was analysed using a 16S rRNA-based approach for bacteria and an internal transcribed spacer region sequencing approach for fungi. The 16S rRNA sequence analysis of 528 028 sequence reads, retained after removing low-quality and short-length reads, revealed various...

  5. Identification and characterization of icosahedral metallic nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Pelaez, Samuel; Serena, Pedro A. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, c/Sor Juana Ines de la Cruz 3, Cantoblanco, 28049-Madrid (Spain); Guerrero, Carlo [Departamento de Fisica, Facultad Experimental de Ciencias, La Universidad del Zulia, Maracaibo (Venezuela); Paredes, Ricardo [Centro de Fisica, Instituto Venezolano de Investigaciones Cientificas, Apto. 20632, Caracas 1020A (Venezuela); Garcia-Mochales, Pedro [Departamento de Fisica de la Materia Condensada, Facultad de Ciencias, Universidad Autonoma de Madrid, c/Tomas y Valiente 7, Cantoblanco, 28049-Madrid (Spain)

    2009-10-15

    We present and discuss an algorithm to identify ans characterize the long icosahedral structures (staggered pentagonal nanowires with 1-5-1-5 atomic structure) that appear in Molecular Dynamics simulations of metallic nanowires of different species subjected to stretching. The use of the algorithm allows the identification of pentagonal rings forming the icosahedral structure as well as the determination of its number n{sub p}, and the maximum length of the pentagonal nanowire L{sub p}{sup m}. The algorithm is tested with some ideal structures to show its ability to discriminate between pentagonal rings and other ring structures. We applied the algorithm to Ni nanowires with temperatures ranging between 4 K and 865 K, stretched along the[100] direction. We studied statistically the formation of pentagonal nanowires obtaining the distributions of length L{sub p}{sup m} and number of rings n{sub p} as function of the temperature. The L{sub p}{sup m} distribution presents a peaked shape, with peaks locate at fixes distances whose separation corresponds to the distance between two consecutive pentagonal rings. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Thermoelectric Properties of Semiconducting Silicide Nanowires

    Science.gov (United States)

    Jin, Song; Sczech, Jeannine; Higgins, Jeremy; Zhou, Feng; Shi, Li

    2008-03-01

    Semiconducting silicides are promising thermoelectric materials. In addition to their respectable thermoelectric figure-of-merit (ZT up to 0.8), silicides have the advantages of low cost, excellent thermal stability and mechanical strength, and outstanding oxidation resistance, making them suitable for high temperature applications. We have developed general synthetic approaches to single crystal nanowires of silicides to investigate the enhancement of thermoelectric properties due to the reduced nanoscale dimension and to explore their applications in thermoelectrics. We will discuss the synthesis and structural characterization of nanowires of chromium disilicide (CrSi2) prepared via a chemical vapor transport (CVT) method and chemical vapor deposition (CVD) of organometallic precursors to synthesize the Novontony Chimney ladder phase MnSi1.75. The Seebeck coefficient, electrical conductivity, and thermal conductivity of individual CrSi2 nanowires were characterized using a suspended microdevice and correlated with the structural information obtained by microscopy on the same nanowires. This combined Seebeck coefficient and electrical conductivity measurements also provide an effective approach to probing the Fermi level, carrier concentration and mobility in nanowires. We will also discuss our progress in using individual nanostructures combined well-defined structural characterization to conclusively investigate the complex thermoelectric behaviors of silicide materials.

  7. Nanomechanics of Single Crystalline Tungsten Nanowires

    Directory of Open Access Journals (Sweden)

    Volker Cimalla

    2008-01-01

    Full Text Available Single crystalline tungsten nanowires were prepared from directionally solidified NiAl-W alloys by a chemical release from the resulting binary phase material. Electron back scatter diffraction (EBSD proves that they are single crystals having identical crystallographic orientation. Mechanical investigations such as bending tests, lateral force measurements, and mechanical resonance measurements were performed on 100–300 nm diameter wires. The wires could be either directly employed using micro tweezers, as a singly clamped nanowire or in a doubly clamped nanobridge. The mechanical tests exhibit a surprisingly high flexibility for such a brittle material resulting from the small dimensions. Force displacement measurements on singly clamped W nanowires by an AFM measurement allowed the determination of a Young's modulus of 332 GPa very close to the bulk value of 355 GPa. Doubly clamped W nanowires were employed as resonant oscillating nanowires in a magnetomotively driven resonator running at 117 kHz. The Young's modulus determined from this setup was found to be higher 450 GPa which is likely to be an artefact resulting from the shift of the resonance frequency by an additional mass loading.

  8. Growth Mechanism of Nanowires: Ternary Chalcogenides

    Science.gov (United States)

    Singh, N. B.; Coriell, S. R.; Hopkins, R. H.; Su, Ching Hua; Arnold, B.; Choa, Fow-Sen; Cullum, Brian

    2016-01-01

    In the past two decades there has been a large rise in the investment and expectations for nanotechnology use. Almost every area of research has projected improvements in sensors, or even a promise for the emergence of some novel device technologies. For these applications major focuses of research are in the areas of nanoparticles and graphene. Although there are some near term applications with nanowires in photodetectors and other low light detectors, there are few papers on the growth mechanism and fabrication of nanowire-based devices. Semiconductor nanowires exhibit very favorable and promising optical properties, including high transparency and a several order of magnitude better photocurrent than thin film and bulk materials. We present here an overview of the mechanism of nanowire growth from the melt, and some preliminary results for the thallium arsenic selenide material system. Thallium arsenic selenide (TAS) is a multifunctional material combining excellent acousto-optical, nonlinear and radiation detection properties. We observed that small units of (TAS) nanocubes arrange and rearrange at moderate melt undercooling to form the building block of a nanowire. In some cases very long wires (less than mm) are formed. Since we avoided the catalyst, we observed self-nucleation and uncontrolled growth of wires from different places.

  9. Nanowire Electrodes for Advanced Lithium Batteries

    Directory of Open Access Journals (Sweden)

    Lei eHuang

    2014-10-01

    Full Text Available Since the commercialization of lithium ion batteries (LIBs in the past two decades, rechargeable LIBs have become widespread power sources for portable devices used in daily life. However, current demands require higher energy density and power density of batteries. The electrochemical energy storage performance of LIBs could be improved by applying nanomaterial electrodes, but their fast capacity fading is still one of the key limitations and the mechanism needs to be clearly understood. Single nanowire electrode devices are considered as a versatile platform for in situ probing the direct relationship between electrical transport, structure change, and other properties of the single nanowire electrode along with the charge/discharge process. The results indicate the conductivity decrease of the nanowire electrode and the structural disorder/destruction during electrochemical reactions which limit the cycling performance of LIBs. Based on the in situ observations, some feasible structure architecture strategies, including prelithiation, coaxial structure, nanowire arrays and hierarchical structure architecture, are proposed and utilized to restrain the conductivity decrease and structural disorder/destruction. Further, the applications of nanowire electrodes in some beyond Li-ion batteries, such as Li-S and Li-air battery, are also described.

  10. Directed Assembly of Cells with Magnetic Nanowires

    Science.gov (United States)

    Tanase, M.; Hultgren, A.; Chen, C. S.; Reich, D. H.

    2003-03-01

    We demonstrate the use of magnetic nanowires for assembly and manipulation of mammalian cells. Currently, superparamagnetic beads are used for manipulations of cells, but large field strengths and gradients are required for these to be effective. Unlike the beads, the large remnant magnetization of the nanowires offers the prospect of a variety of low-field manipulation techniques. Ferromagnetic nanowires suspended in fluids can be easily manipulated and assembled using small magnetic field [1]. The wires can be bound to cells, and the dipolar interaction between the nanowires can be used to create self-assembled cell chains. Microfabricated arrays of Py magnets were used to trap single cells or chains of cells bound to Ni nanowires. Possible applications of these techniques include controlled initiation of cell cultures, as well as isolation of individual cells. This work was supported by DARPA/AFOSR Grant No. F49620-02-1-0307 and by the David and Lucile Packard Foundation Grant No. 2001-17715. [1] M. Tanase et.al., Nanoletters 1, 155 (2001), J. Appl. Phys. 91, 8549 (2002).

  11. Metastable magnetic domain walls in cylindrical nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Ferguson, C.A.; MacLaren, D.A.; McVitie, S., E-mail: Stephen.McVitie@glasgow.ac.uk

    2015-05-01

    The stability of the asymmetric domain wall (ATDW) in soft magnetic cylindrical nanowires and nanotubes is investigated using micromagnetic simulations. Our calculated phase diagram shows that for cylindrical permalloy nanowires, the transverse domain wall (TDW) is the ground state for radii below 20 nm whilst the Bloch point wall (BPW) is favoured in thicker wires. The ATDW stabilises only as a metastable state but with energy close to that of the BPW. Characterisation of the DW spin structures reveals that the ATDW has a vortex-like surface spin state, in contrast to the divergent surface spins of the TDW. This results in lowering of surface charge above the critical radius. For both cylindrical nanotubes and nanowires we find that ATDWs only appear to exist as metastable static states and are particularly suppressed in nanotubes due to an increase in magnetostatic energy. - Highlights: • We simulate the micromagnetic structures of domain walls in cylindrical nanowires. • A phase diagram identifies ground and metastable states. • Asymmetric transverse walls are metastable in nanowires but suppressed in tubes. • Unrolling surface magnetisation aids visualisation of asymmetry and chirality. • We predict experimental discrimination based on magnetic charge distribution.

  12. Controlling Axial p-n Heterojunction Abruptness Through Catalyst Alloying in Vapor-Liquid-Solid Grown Semiconductor Nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Perea, Daniel E.; Schreiber, Daniel K.; Devaraj, Arun; Thevuthasan, Suntharampillai; Yoo, Jinkyoung; Dayeh, Shadi A.; Picraux, Samuel T.

    2012-07-30

    The p-n junction can be regarded as the most important electronic structure that is responsible for the ubiquity of semiconductor microelectronics today. Efforts to continually scale down the size of electronic components is guiding research to explore the use of nanomaterials synthesized from a bottom-up approach - group-IV semiconductor nanowires being one such material. However, Au-catalyzed synthesis of Si/Si1-x-Gex semiconductor nanowire heterojunctions using the commonly-used vapor-liquid-solid (VLS) growth technique results in diffuse heterojunction interfaces [1], leading to doubts of producing compositionally-sharp p-n junctions using this approach. However, we have recently reported the ability to increase Ge-Si nanowire heterojunction abruptness by VLS synthesis from a Au(1-x)Ga(x) catalyst alloy as shown by EDX analysis in an SEM [2]. In this work, we have extended the use of a AuGa catalyst alloy to produce more compositionally abrupt p-n junction interfaces compared to using pure Au as directly measured by atom probe tomography. As shown in Figure 1(a-b), individual Ge-Si heterostructured nanowires were grown vertically atop Ge(111) microposts. Direct growth on the microposts provides a facile approach to nanowire analysis which circumvents the need to use FIB-based sample preparation techniques. Both nanowires grown from pure Au and a AuGa catalyst alloy were analyzed. The corresponding 3D APT reconstruction of an individual heterostructured nanowire is shown in Figure 1(c) with the corresponding materials labeled. A 1-dimensional composition profile along the analysis direction in Figure 1(d) confirms an increase in heterojunction abruptness for nanowires grown from AuGa (~10nm) compared to nanowires grown from pure Au (~65nm). Analysis of the P distribution within the Si region (Figure 1(e)) indicates that P reaches a constant distribution over approximately 10nm when incorporated through the AuGa catalyst, whereas it continually increases over 100

  13. Impact of exercise changes on body composition during the college years--a five year randomized controlled study

    National Research Council Canada - National Science Library

    Kemmler, Wolfgang; von Stengel, Simon; Kohl, Matthias; Bauer, Julia

    2016-01-01

    .... Sixty-one randomly selected male and female dental (DES; 21 ± 3 years., 22 ± 2 kg/m(2)) and 53 sport (physical education) students (SPS; 20 ± 2 years., 22 ± 3 kg/m(2)) were accompanied over their 5-year study program...

  14. Growth and morphological analysis of segmented AuAg alloy nanowires created by pulsed electrodeposition in ion-track etched membranes

    Directory of Open Access Journals (Sweden)

    Ina Schubert

    2015-06-01

    Full Text Available Background: Multicomponent heterostructure nanowires and nanogaps are of great interest for applications in sensorics. Pulsed electrodeposition in ion-track etched polymer templates is a suitable method to synthesise segmented nanowires with segments consisting of two different types of materials. For a well-controlled synthesis process, detailed analysis of the deposition parameters and the size-distribution of the segmented wires is crucial.Results: The fabrication of electrodeposited AuAg alloy nanowires and segmented Au-rich/Ag-rich/Au-rich nanowires with controlled composition and segment length in ion-track etched polymer templates was developed. Detailed analysis by cyclic voltammetry in ion-track membranes, energy-dispersive X-ray spectroscopy and scanning electron microscopy was performed to determine the dependency between the chosen potential and the segment composition. Additionally, we have dissolved the middle Ag-rich segments in order to create small nanogaps with controlled gap sizes. Annealing of the created structures allows us to influence their morphology.Conclusion: AuAg alloy nanowires, segmented wires and nanogaps with controlled composition and size can be synthesised by electrodeposition in membranes, and are ideal model systems for investigation of surface plasmons.

  15. Detection of charge dynamics of a tetraphenylporphyrin particle using GaAs-based nanowire enhanced by particle-metal tip capacitive coupling

    Science.gov (United States)

    Okamoto, Shoma; Sato, Masaki; Sasaki, Kentaro; Kasai, Seiya

    2017-06-01

    We investigate a detection technique of charge dynamics of a molecular particle using a GaAs-based nanowire where the charge sensitivity is locally enhanced by particle-metal tip capacitive coupling. By equivalent circuit analysis, it was clarified that the nanowire channel potential becomes sensitive to the molecular particle on the nanowire when the particle is capacitively coupled with a metal tip. The concept was demonstrated using a GaAs-based nanowire with tetraphenylporphyrin (TPP) particles on its surface and a measurement system integrating an atomic force microscope (AFM) and a dynamic current measurement monitor/spectrum analyzer. When the metal tip was in contact with a TPP particle on the nanowire under an appropriate tip bias condition, random telegraph signal (RTS) noise was imposed on the nanowire current, suggesting the increase in sensitivity to the charge state of the particle by the metal tip contact. We discussed the origin of the RTS noise through analysis of the time constant of RTS noise, RTS amplitude, and noise spectrum.

  16. A randomized clinical trial of cusp-replacing resin composite restorations: efficiency and short-term effectiveness.

    NARCIS (Netherlands)

    Kuijs, R.H.; Fennis, W.M.M.; Kreulen, C.M.; Roeters, F.J.M.; Creugers, N.H.J.; Burgersdijk, R.C.W.

    2006-01-01

    PURPOSE: This study aimed to assess the efficacy and short-term effectiveness of the morphology and function of direct and indirect cusp-replacing resin composite restorations. MATERIALS AND METHODS: In 94 patients, 106 cusp-replacing restorations for maxillary premolars were fabricated to restore

  17. Large-scale organic nanowire lithography and electronics.

    Science.gov (United States)

    Min, Sung-Yong; Kim, Tae-Sik; Kim, Beom Joon; Cho, Himchan; Noh, Yong-Young; Yang, Hoichang; Cho, Jeong Ho; Lee, Tae-Woo

    2013-01-01

    Controlled alignment and patterning of individual semiconducting nanowires at a desired position in a large area is a key requirement for electronic device applications. High-speed, large-area printing of highly aligned individual nanowires that allows control of the exact numbers of wires, and their orientations and dimensions is a significant challenge for practical electronics applications. Here we use a high-speed electrohydrodynamic organic nanowire printer to print large-area organic semiconducting nanowire arrays directly on device substrates in a precisely, individually controlled manner; this method also enables sophisticated large-area nanowire lithography for nano-electronics. We achieve a maximum field-effect mobility up to 9.7 cm(2) V(-1) s(-1) with extremely low contact resistance (organic semiconducting nanowires. Extremely fast nanolithography using printed semiconducting nanowire arrays provide a simple, reliable method of fabricating large-area and flexible nano-electronics.

  18. Optical properties of indium phosphide nanowire ensembles at various temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Lohn, Andrew J; Onishi, Takehiro; Kobayashi, Nobuhiko P [Baskin School of Engineering, University of California Santa Cruz, Santa Cruz, CA 95064 (United States); Nanostructured Energy Conversion Technology and Research (NECTAR), Advanced Studies Laboratories, University of California Santa Cruz-NASA Ames Research Center, Moffett Field, CA 94035 (United States)

    2010-09-03

    Ensembles that contain two types (zincblende and wurtzite) of indium phosphide nanowires grown on non-single crystalline surfaces were studied by micro-photoluminescence and micro-Raman spectroscopy at various low temperatures. The obtained spectra are discussed with the emphasis on the effects of differing lattice types, geometries, and crystallographic orientations present within an ensemble of nanowires grown on non-single crystalline surfaces. In the photoluminescence spectra, a typical Varshni dependence of band gap energy on temperature was observed for emissions from zincblende nanowires and in the high temperature regime energy transfer from excitonic transitions and band-edge transitions was identified. In contrast, the photoluminescence emissions associated with wurtzite nanowires were rather insensitive to temperature. Raman spectra were collected simultaneously from zincblende and wurtzite nanowires coexisting in an ensemble. Raman peaks of the wurtzite nanowires are interpreted as those related to the zincblende nanowires by a folding of the phonon dispersion.

  19. Tunable magnetic nanowires for biomedical and harsh environment applications

    KAUST Repository

    Ivanov, Yurii P.

    2016-04-13

    We have synthesized nanowires with an iron core and an iron oxide (magnetite) shell by a facile low-cost fabrication process. The magnetic properties of the nanowires can be tuned by changing shell thicknesses to yield remarkable new properties and multi-functionality. A multi-domain state at remanence can be obtained, which is an attractive feature for biomedical applications, where a low remanence is desirable. The nanowires can also be encoded with different remanence values. Notably, the oxidation process of single-crystal iron nanowires halts at a shell thickness of 10 nm. The oxide shell of these nanowires acts as a passivation layer, retaining the magnetic properties of the iron core even during high-temperature operations. This property renders these core-shell nanowires attractive materials for application to harsh environments. A cell viability study reveals a high degree of biocompatibility of the core-shell nanowires.

  20. A detailed study of magnetization reversal in individual Ni nanowires

    KAUST Repository

    Vidal, Enrique Vilanova

    2015-01-19

    Magnetic nanowires have emerged as essential components for a broad range of applications. In many cases, a key property of these components is the switching field, which is studied as a function of the angle between the field and the nanowire. We found remarkable differences of up to 100% between the switching fields of different nanowires from the same fabrication batch. Our experimental results and micromagnetic simulations indicate that the nanowires exhibit a single domain behavior and that the switching mechanism includes vortex domain wall motion across the nanowire. The differences between the switching fields are attributed to different cross-sections of the nanowires, as found by electron microscopy. While a circular cross-section yields the smallest switching field values, any deviation from this shape results in an increase of the switching field. The shape of the nanowires\\' cross-sections is thus a critical parameter that has not been previously taken into account.

  1. Microfiber coupled superconducting nanowire single-photon detectors

    Science.gov (United States)

    Xu, Yingxin; Wu, Junjie; Fang, Wei; You, Lixing; Tong, Limin

    2017-12-01

    Superconducting nanowires single-photon detectors (SNSPDs or SSPDs) have emerged as an attractive single-photon detection technology with high performance. Two types of SNSPDs have been developed so far. One is the standard-fiber-coupled SNSPD with the light normally incident on the meandered nanowires, the other is waveguide-coupled SNSPD with the nanowires fabricated on the surface of the waveguide which guides photons while the fiber is coupled to the waveguide. Here we propose a new type of SNSPD integrated with microfiber. The photons are guided by a microfiber and evanescently absorbed by the nanowire of SNSPD when the nanowire is parallel and very close to the microfiber. The numerical simulation results show that the fiber to detector coupling efficiency can be close to unity with optimized device structure/parameters. With a minimal total NbN nanowire length of about 300 μm, the absorption of the nanowire can reach 90%.

  2. Solution-processed metal nanowire mesh transparent electrodes.

    Science.gov (United States)

    Lee, Jung-Yong; Connor, Stephen T; Cui, Yi; Peumans, Peter

    2008-02-01

    Transparent conductive electrodes are important components of thin-film solar cells, light-emitting diodes, and many display technologies. Doped metal oxides are commonly used, but their optical transparency is limited for films with a low sheet resistance. Furthermore, they are prone to cracking when deposited on flexible substrates, are costly, and require a high-temperature step for the best performance. We demonstrate solution-processed transparent electrodes consisting of random meshes of metal nanowires that exhibit an optical transparency equivalent to or better than that of metal-oxide thin films for the same sheet resistance. Organic solar cells deposited on these electrodes show a performance equivalent to that of devices based on a conventional metal-oxide transparent electrode.

  3. A randomized clinical trial of the effect of low-level laser therapy before composite placement on postoperative sensitivity in class V restorations.

    Science.gov (United States)

    Moosavi, Horieh; Maleknejad, Fatemeh; Sharifi, Mahsa; Ahrari, Farzaneh

    2015-05-01

    This study aimed to investigate the efficacy of low-level laser irradiation when applied just before placement of resin composite on reducing postoperative sensitivity of class V lesions. In this randomized clinical trial, 31 patients with 62 class V cavities were included (two teeth in each participant). The teeth were randomly assigned into laser and placebo groups. After cavity preparation, the teeth in the experimental group were subjected to irradiation from a low-power red laser (630 nm, 28 mW, continuous wave, 60 s, 1.68 J), which was applied for 1 min on the axial wall of the cavity. In the control group, the same procedure was performed but with laser simulation. Then, a self-etch adhesive was applied and the cavities were restored with a microhybrid resin composite. Before treatment and on days 1, 14, and 30 after treatment, tooth sensitivity to a cold stimulus was recorded using a visual analogue scale. Data were analyzed by Friedman and Wilcoxon signed-rank tests (p class V restorations.

  4. 1.55 µm emission from a single III-nitride top-down and site-controlled nanowire quantum disk

    Science.gov (United States)

    Chen, Qiming; Yan, Changling; Qu, Yi

    2017-07-01

    InN/InGaN single quantum well (SQW) was fabricated on 100 nm GaN buffer layer which was deposited on GaN template by plasma assisted molecular beam epitaxy (PA-MBE). The In composition and the surface morphology were measured by x-ray diffusion (XRD) and atom force microscope (AFM), respectively. Afterwards, the sample was fabricated into site-controlled nanowires arrays by hot-embossing nano-imprint lithography (HE-NIL) and ultraviolet nanoimprint lithography (UV-NIL). The nanowires were uniform along the c-axis and aligned periodically as presented by scanning electron microscope (SEM). The single nanowire showed disk-in-a-wire structure by high angle annular dark field (HAADF) and an In-rich or Ga deficient region was observed by energy dispersive x-ray spectrum (EDXS). The optical properties of the SQW film and single nanowire were measured using micro photoluminescence (µ-PL) spectroscopy. The stimulating light wavelength was 632.8 nm which was emitted from a He-Ne laser and the detector was a liquid nitrogen cooled InGaAs detector. A blue peak shift from the film material to the nanowire was observed. This was due to the quantum confinement Stark Effect. More importantly, the 1.55 µm emission was given from the single disk-in-a-wire structure at room temperature. We believe the arrays of such nanowires may be useful for quantum communication in the future.

  5. Superconductivity in Centimeter Length Indium-Gallium Nanowires

    Science.gov (United States)

    Zhao, Weiwei; Bischof, Jesse; Singh, Meenakshi; Fitzgibbons, Thomas; Liu, Xin; Liu, Chaoxing; Wang, Lin; Cai, Zhonghou; Chen, Si; Hayes, John; Sazio, Pier; Badding, John; Chan, Moses

    2013-03-01

    In-doped Ga nanowires 150 nm in diameter and 6mm in length have been formed in silica nanocapillaries. X-ray fluorescence and diffraction measurements performed at the Advanced Photon Source have been used to characterize their chemical composition and crystal structure. Investigation of the low temperature transport properties of these wires reveals a two stage superconducting transition. Magnetoresistance measurements are suggestive of vortex trapping in the wire. The X-ray fluorescence measurements suggest phase separation in the capillaries into Ga nanodroplets and In-Ga eutectic wires. A model to explain the vortex trapping consistent with this observation is being developed. This work is supported by the Penn State Materials Research Science and Engineering Center, funded by the National Science Foundation (DMR 0820404). TF and LW are supported by the Energy Frontier Research Center (DE-0001057), DOE.

  6. Silicon nanowires for biosensing, energy storage, and conversion.

    Science.gov (United States)

    Wang, Yanli; Wang, Tianyu; Da, Peimei; Xu, Ming; Wu, Hao; Zheng, Gengfeng

    2013-10-04

    Semiconducting silicon nanowires (SiNWs) represent one of the most interesting research directions in nanoscience and nanotechnology, with capabilities of realizing structural and functional complexity through rational design and synthesis. The exquisite control of chemical composition, structure, morphology, doping, and assembly of SiNWs, in both individual and array format, as well as incorporation with other materials, offers a nanoscale building block with unique electronic, optoelectronic, and catalytic properties, thus allowing for a variety of exciting opportunities in the fields of life sciences and renewable energy. This review provides a brief summary of SiNW research in the past decade, from the SiNW synthesis by both the top-down approaches and the bottom-up approaches, to several important biological and energy applications including biomolecule sensing, interfacing with cells and tissues, lithium-ion batteries, solar cells, and photoelectrochemical conversion. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Vertically Integrated Multiple Nanowire Field Effect Transistor.

    Science.gov (United States)

    Lee, Byung-Hyun; Kang, Min-Ho; Ahn, Dae-Chul; Park, Jun-Young; Bang, Tewook; Jeon, Seung-Bae; Hur, Jae; Lee, Dongil; Choi, Yang-Kyu

    2015-12-09

    A vertically integrated multiple channel-based field-effect transistor (FET) with the highest number of nanowires reported ever is demonstrated on a bulk silicon substrate without use of wet etching. The driving current is increased by 5-fold due to the inherent vertically stacked five-level nanowires, thus showing good feasibility of three-dimensional integration-based high performance transistor. The developed fabrication process, which is simple and reproducible, is used to create multiple stiction-free and uniformly sized nanowires with the aid of the one-route all-dry etching process (ORADEP). Furthermore, the proposed FET is revamped to create nonvolatile memory with the adoption of a charge trapping layer for enhanced practicality. Thus, this research suggests an ultimate design for the end-of-the-roadmap devices to overcome the limits of scaling.

  8. Rare earth silicide nanowires on silicon surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Wanke, Martina

    2008-11-10

    The growth, structure and electronic properties of rare earth silicide nanowires are investigated on planar and vicinal Si(001) und Si(111) surfaces with scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and angle-resolved photoelectron spectroscopy (ARPES). On all surfaces investigated within this work hexagonal disilicides are grown epitaxially with a lattice mismatch of -2.55% up to +0.83% along the hexagonal a-axis. Along the hexagonal c-axis the lattice mismatch is essentially larger with 6.5%. On the Si(001)2 x 1 surface two types of nanowires are grown epitaxially. The socalled broad wires show a one-dimensional metallic valence band structure with states crossing the Fermi level. Along the nanowires two strongly dispersing states at the anti J point and a strongly dispersing state at the anti {gamma} point can be observed. Along the thin nanowires dispersing states could not be observed. Merely in the direction perpendicular to the wires an intensity variation could be observed, which corresponds to the observed spacial structure of the thin nanowires. The electronic properties of the broad erbium silicide nanowires are very similar to the broad dysprosium silicide nanowires. The electronic properties of the DySi{sub 2}-monolayer and the Dy{sub 3}Si{sub 5}-multilayer on the Si(111) surface are investigated in comparison to the known ErSi{sub 2}/Si(111) and Er{sub 3}Si{sub 5}/Si(111) system. The positions and the energetic locations of the observed band in the surface Brillouin zone will be confirmed for dysprosium. The shape of the electron pockets in the (vector)k {sub parallel} space is elliptical at the anti M points, while the hole pocket at the anti {gamma} point is showing a hexagonal symmetry. On the Si(557) surface the structural and electronic properties depend strongly on the different preparation conditions likewise, in particular on the rare earth coverage. At submonolayer coverage the thin nanowires grow in wide areas

  9. Electrowetting on ZnO nanowires

    Science.gov (United States)

    Wu, Jun; Xia, Jun; Lei, Wei; Wang, Bao-Ping

    2010-06-01

    In this paper, we study the electrowetting character on ZnO nanowires. We grow the ZnO nanowires on indium tin oxide (ITO) by a hydrothermal method, and the ZnO nanowires surface is further hydrophobized by spin-coating Teflon. Such a prepared surface shows superhydrophobic properties with an initial contact angle 165°. When the applied external voltage between the ITO and the sessile droplet is less than 50 V, the contact angle continuously changed from 165° to 120°, and exhibits instant reversibility. For a slightly higher voltage, a mutation of the contact angle changing to 100° was observed and the contact angle was not reversible after removing the applied voltage, which indicates a transition from non-wetting state to wetting state. Further increasing of the applied voltage, the apparent contact angle decreased to an invariable value 70°, and electrical breakdown emerged synchronously.

  10. Roll up nanowire battery from silicon chips.

    Science.gov (United States)

    Vlad, Alexandru; Reddy, Arava Leela Mohana; Ajayan, Anakha; Singh, Neelam; Gohy, Jean-François; Melinte, Sorin; Ajayan, Pulickel M

    2012-09-18

    Here we report an approach to roll out Li-ion battery components from silicon chips by a continuous and repeatable etch-infiltrate-peel cycle. Vertically aligned silicon nanowires etched from recycled silicon wafers are captured in a polymer matrix that operates as Li(+) gel-electrolyte and electrode separator and peeled off to make multiple battery devices out of a single wafer. Porous, electrically interconnected copper nanoshells are conformally deposited around the silicon nanowires to stabilize the electrodes over extended cycles and provide efficient current collection. Using the above developed process we demonstrate an operational full cell 3.4 V lithium-polymer silicon nanowire (LIPOSIL) battery which is mechanically flexible and scalable to large dimensions.

  11. How Copper Nanowires Grow and How To Control Their Properties.

    Science.gov (United States)

    Ye, Shengrong; Stewart, Ian E; Chen, Zuofeng; Li, Bo; Rathmell, Aaron R; Wiley, Benjamin J

    2016-03-15

    Scalable, solution-phase nanostructure synthesis has the promise to produce a wide variety of nanomaterials with novel properties at a cost that is low enough for these materials to be used to solve problems. For example, solution-synthesized metal nanowires are now being used to make low cost, flexible transparent electrodes in touch screens, organic light-emitting diodes (OLEDs), and solar cells. There has been a tremendous increase in the number of solution-phase syntheses that enable control over the assembly of atoms into nanowires in the last 15 years, but proposed mechanisms for nanowire formation are usually qualitative, and for many syntheses there is little consensus as to how nanowires form. It is often not clear what species is adding to a nanowire growing in solution or what mechanistic step limits its rate of growth. A deeper understanding of nanowire growth is important for efficiently directing the development of nanowire synthesis toward producing a wide variety of nanostructure morphologies for structure-property studies or producing precisely defined nanostructures for a specific application. This Account reviews our progress over the last five years toward understanding how copper nanowires form in solution, how to direct their growth into nanowires with dimensions ideally suited for use in transparent conducting films, and how to use copper nanowires as a template to grow core-shell nanowires. The key advance enabling a better understanding of copper nanowire growth is the first real-time visualization of nanowire growth in solution, enabling the acquisition of nanowire growth kinetics. By measuring the growth rate of individual nanowires as a function of concentration of the reactants and temperature, we show that a growing copper nanowire can be thought of as a microelectrode that is charged with electrons by hydrazine and grows through the diffusion-limited addition of Cu(OH)2(-). This deeper mechanistic understanding, coupled to an

  12. Impedance Analysis of Silicon Nanowire Lithium Ion Battery Anodes

    KAUST Repository

    Ruffo, Riccardo

    2009-07-02

    The impedance behavior of silicon nanowire electrodes has been investigated to understand the electrochemical process kinetics that influences the performance when used as a high-capacity anode in a lithium ion battery. The ac response was measured by using impedance spectroscopy in equilibrium conditions at different lithium compositions and during several cycles of charge and discharge in a half cell vs. metallic lithium. The impedance analysis shows the contribution of both surface resistance and solid state diffusion through the bulk of the nanowires. The surface process is dominated by a solid electrolyte layer (SEI) consisting of an inner, inorganic insoluble part and several organic compounds at the outer interface, as seen by XPS analysis. The surface resistivity, which seems to be correlated with the Coulombic efficiency of the electrode, grows at very high lithium contents due to an increase in the inorganic SEI thickness. We estimate the diffusion coefficient of about 2 × 10 -10 cm 2/s for lithium diffusion in silicon. A large increase in the electrode impedance was observed at very low lithium compositions, probably due to a different mechanism for lithium diffusion inside the wires. Restricting the discharge voltage to 0.7 V prevents this large impedance and improves the electrode lifetime. Cells cycled between 0.07 and 0.70 V vs. metallic lithium at a current density of 0.84 A/g (C/5) showed good Coulombic efficiency (about 99%) and maintained a capacity of about 2000 mAh/g after 80 cycles. © 2009 American Chemical Society.

  13. Thermodynamic assessment and binary nucleation modeling of Sn-seeded InGaAs nanowires

    Science.gov (United States)

    Ghasemi, Masoomeh; Selleby, Malin; Johansson, Jonas

    2017-11-01

    We have performed a thermodynamic assessment of the As-Ga-In-Sn system based on the CALculation of PHAse Diagram (CALPHAD) method. This system is part of a comprehensive thermodynamic database that we are developing for nanowire materials. Specifically, the As-Ga-In-Sn can be used in modeling the growth of GaAs, InAs, and InxGa1-xAs nanowires assisted by Sn liquid seeds. In this work, the As-Sn binary, the As-Ga-Sn, As-In-Sn, and Ga-In-Sn ternary systems have been thermodynamically assessed using the CALPHAD method. We show the relevant phase diagrams and property diagrams. They all show good agreement with experimental data. Using our optimized description we have modeled the nucleation of InxGa1-xAs in the zinc blende phase from a Sn-based quaternary liquid alloy using binary nucleation modeling. We have linked the composition of the solid nucleus to the composition of the liquid phase. Eventually, we have predicted the critical size of the nucleus that forms from InAs and GaAs pairs under various conditions. We believe that our modeling can guide future experimental realization of Sn-seeded InxGa1-xAs nanowires.

  14. A comparison of regular consumption of fresh lean pork, beef and chicken on body composition: a randomized cross-over trial.

    Science.gov (United States)

    Murphy, Karen J; Parker, Barbara; Dyer, Kathryn A; Davis, Courtney R; Coates, Alison M; Buckley, Jonathan D; Howe, Peter R C

    2014-02-14

    Pork is the most widely eaten meat in the world and recent evidence shows that diets high in pork protein, with and without energy restriction, may have favourable effects on body composition. However, it is unclear whether these effects on body composition are specific to pork or whether consumption of other high protein meat diets may have the same benefit. Therefore we aimed to compare regular consumption of pork, beef and chicken on indices of adiposity. In a nine month randomised open-labelled cross-over intervention trial, 49 overweight or obese adults were randomly assigned to consume up to 1 kg/week of pork, chicken or beef, in an otherwise unrestricted diet for three months, followed by two further three month periods consuming each of the alternative meat options. BMI and waist/hip circumference were measured and body composition was determined using dual energy x-ray absorptiometry. Dietary intake was assessed using three day weighed food diaries. Energy expenditure was estimated from activity diaries. There was no difference in BMI or any other marker of adiposity between consumption of pork, beef and chicken diets. Similarly there were no differences in energy or nutrient intakes between diets. After three months, regular consumption of lean pork meat as compared to that of beef and chicken results in similar changes in markers of adiposity of overweight and obese Australian middle-aged men and women.

  15. A Comparison of Regular Consumption of Fresh Lean Pork, Beef and Chicken on Body Composition: A Randomized Cross-Over Trial

    Directory of Open Access Journals (Sweden)

    Karen J. Murphy

    2014-02-01

    Full Text Available Pork is the most widely eaten meat in the world and recent evidence shows that diets high in pork protein, with and without energy restriction, may have favourable effects on body composition. However, it is unclear whether these effects on body composition are specific to pork or whether consumption of other high protein meat diets may have the same benefit. Therefore we aimed to compare regular consumption of pork, beef and chicken on indices of adiposity. In a nine month randomised open-labelled cross-over intervention trial, 49 overweight or obese adults were randomly assigned to consume up to 1 kg/week of pork, chicken or beef, in an otherwise unrestricted diet for three months, followed by two further three month periods consuming each of the alternative meat options. BMI and waist/hip circumference were measured and body composition was determined using dual energy x-ray absorptiometry. Dietary intake was assessed using three day weighed food diaries. Energy expenditure was estimated from activity diaries. There was no difference in BMI or any other marker of adiposity between consumption of pork, beef and chicken diets. Similarly there were no differences in energy or nutrient intakes between diets. After three months, regular consumption of lean pork meat as compared to that of beef and chicken results in similar changes in markers of adiposity of overweight and obese Australian middle-aged men and women.

  16. Effects of cognitive speed of processing training on a composite neuropsychological outcome: results at one-year from the IHAMS randomized controlled trial.

    Science.gov (United States)

    Wolinsky, Fredric D; Vander Weg, Mark W; Howren, M Bryant; Jones, Michael P; Dotson, Megan M

    2016-02-01

    Age-related cognitive decline is common and well-documented. Cognitive speed of processing training (SOPT) has been shown to improve trained abilities (Useful Field of View; UFOV), but transfer to individual non-trained cognitive outcomes or neuropsychological composites is sparse. We examine the effects of SOPT on a composite of six equally weighted tests--UFOV, Trail-making A and B, Symbol Digit Modality, Controlled Oral Word Association, Stroop Color and Word, and Digit Vigilance. 681 patients were randomized separately within two age-bands (50-64, ≥ 65) to three SOPT groups (10 initial hours on-site, 10 initial hours on-site plus 4 hours of boosters, or 10 initial hours at-home) or an attention-control group (10 initial hours on-site of crossword puzzles). At one-year, 587 patients (86.2%) had complete data. A repeated measures linear mixed model was used. Factor analysis revealed a simple unidimensional structure with Cronbach's α of 0.82. The time effect was statistically significant (p age-band (p = 0.463), and time by treatment group by age-band (p = 0.564) effects were not. Compared to the attention-control group who played a computerized crossword puzzle game, assignment to 10-14 hours of SOPT did not significantly improve a composite measure of cognitive abilities.

  17. Imaging Electrons in Ultra-thin Nanowires

    Science.gov (United States)

    Boyd, Erin E.

    2011-12-01

    Ultra-thin semiconductor nanowires are promising systems in which to explore novel low-dimensional physics and are attractive candidates for future nanoelectronics. Ultra-thin nanowires with diameters of 20 to 30 nm are essentially one-dimensional (ID) for moderate electron number, because only one radial subband is occupied. Low-temperature scanning gate microscopy is especially well suited for improving our understanding of nanowires in order to optimize the construction of nanowire systems. We use a home-built liquid-He cooled scanning gate microscope (SGM) to probe and manipulate electrons beneath the surface of devices. The SGM's conductance images are obtained by scanning the charged SGM tip above the sample and recording the change in conductance through the device as a function of tip position. We present simulations of extracting the amplitude of the 1D electron wavefunction along the length of the quantum dot in an ultra-thin InAs/InP heterostructure nanowire (diameter = 30 nm) using a SGM. A weakly perturbing SGM tip slightly dents the electron wavefunction inside the quantum dot, and we propose measuring the change in energy of the dot due to the perturbation as a function of tip position. By measuring the change in energy of the dot and by knowing the form of the tip potential, the amplitude of the wavefunction can be found. This extraction technique could serve as a powerful tool to improve our understanding of electron behavior in quasi-1 D systems. We have used our SGM to image the conductance through an ultra-thin (diameter ˜ 30 nm) 1nAs nanowire with two InP barriers. Our imaging technique provides detailed information regarding the position and flow of electrons in the nanowire. We demonstrate that the charged SPM tip's position or voltage can be used to control the number of electrons on the quantum dots. We spatially locate three quantum dots in series along the length of the ultra-thin nanowire. Using energy level spectroscopy and the

  18. Synthesis and Characterization of Glassy Carbon Nanowires

    Directory of Open Access Journals (Sweden)

    C. M. Lentz

    2011-01-01

    Full Text Available The advent of carbon-based micro- and nanoelectromechanical systems has revived the interest in glassy carbon, whose properties are relatively unknown at lower dimensions. In this paper, electrical conductivity of individual glassy carbon nanowires was measured as a function of microstructure (controlled by heat treatment temperature and ambient temperature. The semiconducting nanowires with average diameter of 150 nm were synthesized from polyfurfuryl alcohol precursors and characterized using transmission electron and Raman microscopy. DC electrical measurements made at 90 K to 450 K show very strong dependence of temperature, following mixed modes of activation energy and hopping-based conduction.

  19. Magnetic logic using nanowires with perpendicular anisotropy.

    Science.gov (United States)

    Jaworowicz, J; Vernier, N; Ferré, J; Maziewski, A; Stanescu, D; Ravelosona, D; Jacqueline, A S; Chappert, C; Rodmacq, B; Diény, B

    2009-05-27

    In addition to a storage function through the magnetization of nanowires, domain wall propagation can be used to trigger magnetic logic functions. Here, we present a new way to realize a pure magnetic logic operation by using magnetic nanowires with perpendicular anisotropy. Emphasis is given on the generation of the logic function 'NOT' that is based on the dipolar interaction between two neighbouring magnetic wires, which favours the creation of a domain wall. This concept has been validated on several prototypes and the results fit well with the expectations.

  20. Titanium catalyzed silicon nanowires and nanoplatelets

    Directory of Open Access Journals (Sweden)

    Mohammad A. U. Usman

    2013-03-01

    Full Text Available Silicon nanowires, nanoplatelets, and other morphologies resulted from silicon growth catalyzed by thin titanium layers. The nanowires have diameters down to 5 nm and lengths to tens of micrometers. The two-dimensional platelets, in some instances with filigreed, snow flake-like shapes, had thicknesses down to the 10 nm scale and spans to several micrometers. These platelets grew in a narrow temperature range around 900 celsius, apparently representing a new silicon crystallite morphology at this length scale. We surmise that the platelets grow with a faceted dendritic mechanism known for larger crystals nucleated by titanium silicide catalyst islands.

  1. Nanowires and nanostructures fabrication using template methods

    DEFF Research Database (Denmark)

    Mátéfi-Tempfli, Stefan; Mátéfi-Tempfli, M.; Vlad, A.

    2009-01-01

    One of the great challenges of today is to find reliable techniques for the fabrication of nanomaterials and nanostructures. Methods based on template synthesis and on self organization are the most promising due to their easiness and low cost. This paper focuses on the electrochemical synthesis ...... of nanowires and nanostructures using nanoporous host materials such as supported anodic aluminum considering it as a key template for nanowires based devices. New ways are opened for applications by combining such template synthesis methods with nanolithographic techniques....

  2. Silicon nanowires for photovoltaic solar energy conversion.

    Science.gov (United States)

    Peng, Kui-Qing; Lee, Shuit-Tong

    2011-01-11

    Semiconductor nanowires are attracting intense interest as a promising material for solar energy conversion for the new-generation photovoltaic (PV) technology. In particular, silicon nanowires (SiNWs) are under active investigation for PV applications because they offer novel approaches for solar-to-electric energy conversion leading to high-efficiency devices via simple manufacturing. This article reviews the recent developments in the utilization of SiNWs for PV applications, the relationship between SiNW-based PV device structure and performance, and the challenges to obtaining high-performance cost-effective solar cells.

  3. An optically guided microdevice comprising a nanowire

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention relates to a microdevice (100) for emitting electromagnetic radiation onto an associated object. Simultaneous non-contact spatial control over the microdevice in terms of translational movement in three dimensions, and rotational movement around at least two axes, preferably...... three axes, is possible. The microdevice further comprises a nanowire (150) being arranged for emitting electromagnetic radiation onto said associated object. This is advantageous for obtaining better spatial control of the microdevice comprising the nanowire, and this enables that light could more...

  4. Enhanced magnetotransport in nanopatterned manganite nanowires.

    Science.gov (United States)

    Marín, Lorena; Morellón, Luis; Algarabel, Pedro A; Rodríguez, Luis A; Magén, César; De Teresa, José M; Ibarra, Manuel R

    2014-02-12

    We have combined optical and focused ion beam lithographies to produce large aspect-ratio (length-to-width >300) single-crystal nanowires of La2/3Ca1/3MnO3 that preserve their functional properties. Remarkably, an enhanced magnetoresistance value of 34% in an applied magnetic field of 0.1 T in the narrowest 150 nm nanowire is obtained. The strain release at the edges together with a destabilization of the insulating regions is proposed to account for this behavior. This opens new strategies to implement these structures in functional spintronic devices.

  5. Synchrotron characterization of functional tin dioxide nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Domashevskaya, E. P., E-mail: ftt@phys.vsu.ru; Chuvenkova, O. A.; Turishchev, S. Yu. [Voronezh State University, Voronezh (Russian Federation)

    2015-12-31

    Wire-like crystals of tin dioxide were synthesized by a gas-transport technique. The wires, of mainly nanometric diameters, were characterized by spectroscopy and microscopy techniques with the use of highly brilliant and intense synchrotron radiation. We studied the influence of the surface chemical state and the oxygen vacancies on the atomic and electronic structure of the nanowires. The surface of the nanowires is covered by a few nanometers of tin suboxides. The lack of oxygen over the surface layers leads to specific sub-zone formation in a gap, as shown by synchrotron studies.

  6. Lactobacillus casei Shirota Supplementation Does Not Restore Gut Microbiota Composition and Gut Barrier in Metabolic Syndrome: A Randomized Pilot Study.

    Science.gov (United States)

    Stadlbauer, Vanessa; Leber, Bettina; Lemesch, Sandra; Trajanoski, Slave; Bashir, Mina; Horvath, Angela; Tawdrous, Monika; Stojakovic, Tatjana; Fauler, Günter; Fickert, Peter; Högenauer, Christoph; Klymiuk, Ingeborg; Stiegler, Philipp; Lamprecht, Manfred; Pieber, Thomas R; Tripolt, Norbert J; Sourij, Harald

    2015-01-01

    Metabolic syndrome is associated with disturbances in gut microbiota composition. We aimed to investigate the effect of Lactobacillus casei Shirota (LcS) on gut microbiota composition, gut barrier integrity, intestinal inflammation and serum bile acid profile in metabolic syndrome. In a single-centre, prospective, randomised controlled pilot study, 28 subjects with metabolic syndrome received either LcS for 12 weeks (n = 13) or no LcS (n = 15). Data were compared to healthy controls (n = 16). Gut microbiota composition was characterised from stool using 454 pyrosequencing of 16S rRNA genes. Serum bile acids were quantified by tandem mass spectrometry. Zonulin and calprotectin were measured in serum and stool by ELISA. Bacteroidetes/Firmicutes ratio was significantly higher in healthy controls compared to metabolic syndrome but was not influenced by LcS. LcS supplementation led to enrichment of Parabacteroides. Zonulin and calprotectin were increased in metabolic syndrome stool samples but not influenced by LcS supplementation. Serum bile acids were similar to controls and not influenced by LcS supplementation. Metabolic syndrome is associated with a higher Bacteroidetes/Firmicutes ratio and gut barrier dysfunction but LcS was not able to change this. LcS administration was associated with subtle microbiota changes at genus level. ClinicalTrials.gov NCT01182844.

  7. A morphological and structural approach to evaluate the electromagnetic performances of composites based on random networks of carbon nanotubes

    Science.gov (United States)

    De Vivo, B.; Lamberti, P.; Spinelli, G.; Tucci, V.

    2014-04-01

    Small quantities of carbon nanotubes (CNTs) in polymer resins allow to obtain new lightweight nanocomposites suitable for microwave applications, such as efficient electromagnetic shielding or radar absorbing materials. The availability of appropriate simulation models taking into account the morphological and physical features of such very interesting composites is very important for design and performance optimization of devices and systems. In this study, a 3-dimensional (3D) numerical structure modeling the morphology of a CNT-based composite is considered in order to carry out a computational analysis of their electromagnetic performances. The main innovative features of the proposed model consists in the identification of a resistance and capacitance network whose values depend on the filler geometry and loading and whose complexity is associated with the percolation paths. Tunneling effect and capacitive interactions between the individual conductive particles are properly taken into account. The obtained network allows an easy calculation in a wide frequency range of the complex permittivity and others electromagnetic parameters. Moreover, a reliable sensitivity analysis concerning the impact of some crucial parameters, such as the CNTs properties and the dielectric permittivity of the neat resin, on the electromagnetic features of the resulting composites can be carried out. The model predictions are in good agreement with existing experimental data, suggesting that the proposed model can be a useful tool for their design and performance optimization in the microwave range.

  8. Photon-triggered nanowire transistors

    Science.gov (United States)

    Kim, Jungkil; Lee, Hoo-Cheol; Kim, Kyoung-Ho; Hwang, Min-Soo; Park, Jin-Sung; Lee, Jung Min; So, Jae-Pil; Choi, Jae-Hyuck; Kwon, Soon-Hong; Barrelet, Carl J.; Park, Hong-Gyu

    2017-10-01

    Photon-triggered electronic circuits have been a long-standing goal of photonics. Recent demonstrations include either all-optical transistors in which photons control other photons or phototransistors with the gate response tuned or enhanced by photons. However, only a few studies report on devices in which electronic currents are optically switched and amplified without an electrical gate. Here we show photon-triggered nanowire (NW) transistors, photon-triggered NW logic gates and a single NW photodetection system. NWs are synthesized with long crystalline silicon (CSi) segments connected by short porous silicon (PSi) segments. In a fabricated device, the electrical contacts on both ends of the NW are connected to a single PSi segment in the middle. Exposing the PSi segment to light triggers a current in the NW with a high on/off ratio of >8 × 106. A device that contains two PSi segments along the NW can be triggered using two independent optical input signals. Using localized pump lasers, we demonstrate photon-triggered logic gates including AND, OR and NAND gates. A photon-triggered NW transistor of diameter 25 nm with a single 100 nm PSi segment requires less than 300 pW of power. Furthermore, we take advantage of the high photosensitivity and fabricate a submicrometre-resolution photodetection system. Photon-triggered transistors offer a new venue towards multifunctional device applications such as programmable logic elements and ultrasensitive photodetectors.

  9. Axial InGaAs/GaAs nanowire separate absorption-multiplication avalanche photodetectors (Conference Presentation)

    Science.gov (United States)

    Huffaker, Diana L.

    2017-05-01

    In0.53Ga0.47As/InP single photon avalanche detectors (SPADs) have a high photon detection efficiency in the near-IR, however the dark count rate is prohibitively high at room temperature. A nanowire-based In0.3Ga0.7As/GaAs SPAD can significantly reduce the DCR through a nearly three order of magnitude reduction in bulk InGaAs volume, as well as by reducing the indium composition for operation at 1064 nm. As a first step, we have successfully grown axial InGaAs/GaAs heterostructures using catalyst-free selective-area epitaxy. We will present the electrical characterization of a vertically oriented nanowire array InGaAs/GaAs SPADs operating at 1064 nm and use 3-dimensional modeling to aid in the analysis.

  10. Improvement of efficiency in graphene/gallium nitride nanowire on Silicon photoelectrode for overall water splitting

    Science.gov (United States)

    Bae, Hyojung; Rho, Hokyun; Min, Jung-Wook; Lee, Yong-Tak; Lee, Sang Hyun; Fujii, Katsushi; Lee, Hyo-Jong; Ha, Jun-Seok

    2017-11-01

    Gallium nitride (GaN) nanowires are one of the most promising photoelectrode materials due to their high stability in acidic and basic electrolytes, and tunable band edge potentials. In this study, GaN nanowire arrays (GaN NWs) were prepared by molecular beam epitaxy (MBE); their large surface area enhanced the solar to hydrogen conversion efficiency. More significantly, graphene was grown by chemical vapor deposition (CVD), which enhanced the electron transfer between NWs for water splitting and protected the GaN NW surface. Structural characterizations of the prepared composite were performed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The photocurrent density of Gr/GaN NWs exhibited a two-fold increase over pristine GaN NWs and sustained water splitting up to 70 min. These improvements may accelerate possible applications for hydrogen generation with high solar to hydrogen conversion efficiency.

  11. Monolithic electrically injected nanowire array edge-emitting laser on (001) silicon

    KAUST Repository

    Frost, Thomas

    2014-08-13

    A silicon-based laser, preferably electrically pumped, has long been a scientific and engineering goal. We demonstrate here, for the first time, an edge-emitting InGaN/GaN disk-in-nanowire array electrically pumped laser emitting in the green (λ = 533 nm) on (001) silicon substrate. The devices display excellent dc and dynamic characteristics with values of threshold current density, differential gain, T0 and small signal modulation bandwidth equal to 1.76 kA/cm2, 3 × 10-17 cm2, 232 K, and 5.8 GHz respectively under continuous wave operation. Preliminary reliability measurements indicate a lifetime of 7000 h. The emission wavelength can be tuned by varying the alloy composition in the quantum disks. The monolithic nanowire laser on (001)Si can therefore address wide-ranging applications such as solid state lighting, displays, plastic fiber communication, medical diagnostics, and silicon photonics. © 2014 American Chemical Society.

  12. Formation of aligned silicon nanowire on silicon by electroless etching in HF solution

    Energy Technology Data Exchange (ETDEWEB)

    Megouda, N.; Douani, R. [Faculte des Sciences, Universite Mouloud Mammeri, Tizi-Ouzou (Algeria); Hadjersi, T., E-mail: hadjersi@yahoo.co [Unite de Developpement de la Technologie du Silicium (UDTS), 2, Bd. Frantz Fanon, B.P. 140 Alger-7 merveilles, Alger (Algeria); Boukherroub, R. [Institut de Recherche Interdisciplinaire (IRI, FRE 2963), Institut d' Electronique, de Microelectronique et de Nanotechnologie (IEMN, CNRS-8520), Cite Scientifique, Avenue Poincare-B.P. 60069, 59652 Villeneuve d' Ascq (France)

    2009-12-15

    It was demonstrated that the etching in HF-based aqueous solution containing AgNO{sub 3} and Na{sub 2}S{sub 2}O{sub 8} as oxidizing agents or by Au-assisted electroless etching in HF/H{sub 2}O{sub 2} solution at 50 deg. C yields films composed of aligned Si nanowire (SiNW). SiNW of diameters {approx}10 nm were formed. The morphology and the photoluminescence (PL) of the etched layer as a function of etching solution composition were studied. The SiNW layers formed on silicon were investigated by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and photoluminescence. It was demonstrated that the morphology and the photoluminescence of the etched layers strongly depends on the type of etching solution. Finally, a discussion on the formation process of the silicon nanowires is presented.

  13. Recyclable patterning of silver nanowire percolated network for fabrication of flexible transparent electrode

    Science.gov (United States)

    Yoo, Byungwook; Kim, Youngmin; Han, Chul Jong; Oh, Min Suk; Kim, Jong-Woong

    2018-01-01

    Recent studies have revealed that silver nanowires (AgNWs) are a promising material for highly flexible transparent electrodes. Here we introduce a novel photoinduced recyclable approach to AgNW patterning to overcome the issue of loss of material during fabrication of AgNW patterns, which is a leading factor in the high fabrication costs of AgNW-based electrodes. Our patterning scheme involves the selective irradiation of an AgNW/polymer composite with high-intensity pulsed light, followed by immersion of the sample in a liquid and an ultrasonication treatment. The nanowires that detach during sonication could be recycled, and the recycled AgNWs achieved comparable performance to that of pristine AgNWs. The recycled AgNWs were also superior to commercial indium tin oxide films and other competing materials. We successfully demonstrated a high performance transparent heater by employing the recyclable patterning method and recycled AgNWs.

  14. Strong light absorption capability directed by structured profile of vertical Si nanowires

    Science.gov (United States)

    Chaliyawala, Harsh A.; Ray, Abhijit; Pati, Ranjan K.; Mukhopadhyay, Indrajit

    2017-11-01

    Si nanowire arrays (SiNWAs) with random fractal geometry was fabricated using fast, mask-less, non-lithographic and facile approach by incorporating metal assisted electroless etching of n-type Si (111) substrates. The FESEM images demonstrate the formation of nano-porous surfaces that provide effective path for the incoming light to get trapped into the cavity of nanowires. The length of NWs increases from ∼1 to 10 μm with increase in the etching time having a diameter in the range of ∼25-82 nm. A transformation from zero to first order kinetics after a prolonged etching has been determined. The synthesized SiNWAs show high light trapping properties, including a maximum photon absorption across the entire visible and near IR range below the band gap of Si. The SiNWAs etched for 15 min exhibit extremely low specular and total reflectance of ∼0.2% and 4.5%, respectively over a broadband of wavelength. The reduction in the reflection loss is accompanied with the gradient of refractive index from air to Si substrate as well as due to the sub-wavelength structures, which manifests the light scattering effect. The COMSOL multiphysics simulation has been performed to study the high broadband light absorption capability in terms of the strong localized light field confinement by varying the length of the nanowire. Moreover, the SiNWs induces the dewetting ability at the solid/liquid interface and enhances the superhydrophobicity. Furthermore, a maximum length scale of 100-200 nm manifests a strong heterogeneity along the planar section of the surface of SiNWs. The study thus provides an insight on the light propagation into the random fractal geometries of Si nanowires. These outstanding properties should contribute to the structural optimization of various optoelectronic and photonic devices.

  15. Plasmonic engineering of metal-oxide nanowire heterojunctions in integrated nanowire rectification units

    Science.gov (United States)

    Lin, Luchan; Zou, Guisheng; Liu, Lei; Duley, Walt W.; Zhou, Y. Norman

    2016-05-01

    We show that irradiation with femtosecond laser pulses can produce robust nanowire heterojunctions in coupled non-wetting metal-oxide Ag-TiO2 structures. Simulations indicate that joining arises from the effect of strong plasmonic localization in the region of the junction. Strong electric field effects occur in both Ag and TiO2 resulting in the modification of both surfaces and an increase in wettability of TiO2, facilitating the interconnection of Ag and TiO2 nanowires. Irradiation leads to the creation of a thin layer of highly defected TiO2 in the contact region between the Ag and TiO2 nanowires. The presence of this layer allows the formation of a heterojunction and offers the possibility of engineering the electronic characteristics of interfacial structures. Rectifying junctions with single and bipolar properties have been generated in Ag-TiO2 nanowire circuits incorporating asymmetrical and symmetrical interfacial structures, respectively. This fabrication technique should be applicable for the interconnection of other heterogeneous metal-oxide nanowire components and demonstrates that femtosecond laser irradiation enables interfacial engineering for electronic applications of integrated nanowire structures.

  16. Study of spin dynamics and damping on the magnetic nanowire arrays with various nanowire widths

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Jaehun [Department of Physics, Inha University, Incheon, 402-751 (Korea, Republic of); Fujii, Yuya; Konioshi, Katsunori [Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Yoon, Jungbum [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); Kim, Nam-Hui; Jung, Jinyong [Department of Physics, Inha University, Incheon, 402-751 (Korea, Republic of); Miwa, Shinji [Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Jung, Myung-Hwa [Department of Physics, Sogang University, Seoul, 121-742 (Korea, Republic of); Suzuki, Yoshishige [Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); You, Chun-Yeol, E-mail: cyyou@inha.ac.kr [Department of Physics, Inha University, Incheon, 402-751 (Korea, Republic of)

    2016-07-01

    We investigate the spin dynamics including Gilbert damping in the ferromagnetic nanowire arrays. We have measured the ferromagnetic resonance of ferromagnetic nanowire arrays using vector-network analyzer ferromagnetic resonance (VNA-FMR) and analyzed the results with the micromagnetic simulations. We find excellent agreement between the experimental VNA-FMR spectra and micromagnetic simulations result for various applied magnetic fields. We find that the same tendency of the demagnetization factor for longitudinal and transverse conditions, N{sub z} (N{sub y}) increases (decreases) as increasing the nanowire width in the micromagnetic simulations while N{sub x} is almost zero value in transverse case. We also find that the Gilbert damping constant increases from 0.018 to 0.051 as the increasing nanowire width for the transverse case, while it is almost constant as 0.021 for the longitudinal case. - Highlights: • We investigate the spin dynamic properties in the ferromagnetic nanowire arrays. • The demagnetization factors have similar tendency with the prism geometry results. • The Gilbert damping constant is increased from 0.018 to 0.051 as the increasing nanowire width for the transverse. • The Gilbert damping constant is almost constant as 0.021 for the longitudinal case.

  17. Plasmonic engineering of metal-oxide nanowire heterojunctions in integrated nanowire rectification units

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Luchan; Zhou, Y. Norman, E-mail: liulei@tsinghua.edu.cn, E-mail: nzhou@uwaterloo.ca [Department of Mechanical Engineering, State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China); Centre for Advanced Materials Joining, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Zou, Guisheng; Liu, Lei, E-mail: liulei@tsinghua.edu.cn, E-mail: nzhou@uwaterloo.ca [Department of Mechanical Engineering, State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China); Duley, Walt W. [Centre for Advanced Materials Joining, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)

    2016-05-16

    We show that irradiation with femtosecond laser pulses can produce robust nanowire heterojunctions in coupled non-wetting metal-oxide Ag-TiO{sub 2} structures. Simulations indicate that joining arises from the effect of strong plasmonic localization in the region of the junction. Strong electric field effects occur in both Ag and TiO{sub 2} resulting in the modification of both surfaces and an increase in wettability of TiO{sub 2}, facilitating the interconnection of Ag and TiO{sub 2} nanowires. Irradiation leads to the creation of a thin layer of highly defected TiO{sub 2} in the contact region between the Ag and TiO{sub 2} nanowires. The presence of this layer allows the formation of a heterojunction and offers the possibility of engineering the electronic characteristics of interfacial structures. Rectifying junctions with single and bipolar properties have been generated in Ag-TiO{sub 2} nanowire circuits incorporating asymmetrical and symmetrical interfacial structures, respectively. This fabrication technique should be applicable for the interconnection of other heterogeneous metal-oxide nanowire components and demonstrates that femtosecond laser irradiation enables interfacial engineering for electronic applications of integrated nanowire structures.

  18. Effects of short-term oral corticosteroid intake on dietary intake, body weight and body composition in adults with asthma - a randomized controlled trial.

    Science.gov (United States)

    Berthon, B S; Gibson, P G; McElduff, P; MacDonald-Wicks, L K; Wood, L G

    2015-05-01

    Oral corticosteroids (OCS) are an efficacious treatment for asthma exacerbations, yet risk of adverse effects may decrease patient adherence to therapy. In particular, changes in appetite and dietary intake, which lead to weight gain and changes in body composition, are considered undesirable. To determine whether 10-day OCS therapy in adults with asthma causes changes in leptin, appetite, dietary intake, body weight and body composition. Double-blinded, placebo-controlled randomized cross-over trial of 10 days prednisolone (50 mg) in adults with stable asthma (n = 55) (ACTRN12611000562976). Pre- and post-assessment included spirometry, body weight, body composition measured by dual-energy X-ray absorptiometry and bioelectrical impedance analysis, appetite measured using a validated visual analogue scale (VAS) and dietary intake assessed using 4-day food records. Leptin was measured as a biomarker of appetite and eosinophils as an adherence biomarker. Outcomes were analysed by generalized linear mixed models. Subject adherence was confirmed by a significant decrease in blood eosinophils (× 10(9) /L) following prednisolone compared to placebo [Coef. -0.29, 95% CI: (-0.39, -0.19) P body weight (kg) [Coef. -0.38, 95% CI: (-0.81, 0.05) P = 0.083] or body fat (%) [Coef. -0.31, 95% CI: (-0.81, 0.20) P = 0.230]. Symptoms including sleep and gastrointestinal disturbance were reported significantly more often during prednisolone vs. placebo. Short-term OCS in stable asthma did not induce significant changes in appetite, dietary intake, body weight or composition, although other adverse effects may require medical management. This evidence may assist in increasing medication adherence of asthmatics prescribed OCS for exacerbations. © 2015 John Wiley & Sons Ltd.

  19. Clinical and radiographic evaluation of citric acid-based nano hydroxyapatite composite graft in the regeneration of intrabony defects - A randomized controlled trial

    Directory of Open Access Journals (Sweden)

    Chaurasia Priya Dayashankar

    2017-01-01

    Full Text Available Background: Conventional periodontal therapy with various bone grafts has limited scope and the results are not predictable. To improve their utility, the hybridization of bioceramics and biodegradable polymers has been widely adopted to reform the mechanical properties of bone grafts. One such biodegradable polymer is POC (Poly 1,8 octanediol. Secondly, citric acid is considered as the key material in bone mineralization, which is related to the overall stability, strength and fracture resistance of bone. Hence citric acid is incorporated in a polymer and Nano hydroxyapatite to form a composite graft, for periodontal bone regeneration. This study attempts to evaluate the efficacy of citric acid based Nano-hydroxyapatite composite graft for the treatment of intrabony defects in chronic periodontitis patients over 12 months. Methods: A split mouth study, which consists of 10 systemically healthy patients, were randomly treated with Citric acid based Nano hydroxyapatite composite graft (test sites, n=18 or with Nano hydroxyapatite alone (control sites, n=15. Plaque index, gingival index, gingival bleeding index, probing pocket depth (PPD, clinical attachment level (CAL, bone probing depth (BPD and hard tissue parameters such as amount of defect fill, percentage of defect fill, and changes in alveolar crest were assessed over a period of 12 months. Statistical analysis used was student's t-test and One-Way ANOVA. Results: Both test and control sites demonstrated statistically significant reduction of PD, BPD, gain in CAL and radiographic bone fill. Nevertheless the test sites showed Statistically significant improvements in all the parameters as compared to control sites at 12 months. Conclusion: Citric acid based Nano hydroxyapatite composite graft can be considered as a newer material for periodontal regeneration.

  20. Size Effect and Deformation Mechanism in Twinned Copper Nanowires

    Directory of Open Access Journals (Sweden)

    Jiapeng Sun

    2017-10-01

    Full Text Available Molecular dynamics simulations were performed to demonstrate the synergistic effects of the extrinsic size (nanowire length and intrinsic size (twin boundary spacing on the failure manner, yield strength, ductility and deformation mechanism of the twinned nanowires containing high density coherent twin boundaries CTBs paralleled to the nanowires’ axis. The twinned nanowires show an intense extrinsic size effect, i.e., shorter is stronger and more ductile, and an intense intrinsic size effect, i.e., thinner is stronger. Notably, the strengthening effect degradation of CTBs in the twinned nanowires is observed with an increase in nanowire length: remarkable strengthening effect can be obtained for the short nanowires, but the strengthening effect becomes less pronounced for the long nanowires. The twinned nanowires fail via a ductile manner or via a brittle manner depending on the synergistic effect of the nanowire length and twin boundary spacing. By atomic-level observation of the plastic deformation, we found that the emission of a trailing 30° partial from the free surface controls the yield behavior of the twinned nanowires. We also found that the special zigzag extended dislocations are formed by the dislocation–CTBs interactions, and propagate to sustain the plastic deformation.