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Sample records for atomic carbon nanowires

  1. Single-Atom Scale Structural Selectivity in Te Nanowires Encapsulated Inside Ultranarrow, Single-Walled Carbon Nanotubes.

    PubMed

    Medeiros, Paulo V C; Marks, Samuel; Wynn, Jamie M; Vasylenko, Andrij; Ramasse, Quentin M; Quigley, David; Sloan, Jeremy; Morris, Andrew J

    2017-06-27

    Extreme nanowires (ENs) represent the ultimate class of crystals: They are the smallest possible periodic materials. With atom-wide motifs repeated in one dimension (1D), they offer a privileged perspective into the physics and chemistry of low-dimensional systems. Single-walled carbon nanotubes (SWCNTs) provide ideal environments for the creation of such materials. Here we present a comprehensive study of Te ENs encapsulated inside ultranarrow SWCNTs with diameters between 0.7 nm and 1.1 nm. We combine state-of-the-art imaging techniques and 1D-adapted ab initio structure prediction to treat both confinement and periodicity effects. The studied Te ENs adopt a variety of structures, exhibiting a true 1D realization of a Peierls structural distortion and transition from metallic to insulating behavior as a function of encapsulating diameter. We analyze the mechanical stability of the encapsulated ENs and show that nanoconfinement is not only a useful means to produce ENs but also may actually be necessary, in some cases, to prevent them from disintegrating. The ability to control functional properties of these ENs with confinement has numerous applications in future device technologies, and we anticipate that our study will set the basic paradigm to be adopted in the characterization and understanding of such systems.

  2. Quantum galvanometer by interfacing a vibrating nanowire and cold atoms.

    PubMed

    Kálmán, O; Kiss, T; Fortágh, J; Domokos, P

    2012-01-11

    We evaluate the coupling of a Bose-Einstein condensate (BEC) of ultracold, paramagnetic atoms to the magnetic field of the current in a mechanically vibrating carbon nanotube within the frame of a full quantum theory. We find that the interaction is strong enough to sense quantum features of the nanowire current noise spectrum by means of hyperfine-state-selective atom counting. Such a nondestructive measurement of the electric current via its magnetic field corresponds to the classical galvanometer scheme, extended to the quantum regime of charge transport. The calculated high sensitivity of the interaction in the nanowire-BEC hybrid systems opens up the possibility of quantum control, which may be further extended to include other relevant degrees of freedom. © 2011 American Chemical Society

  3. Preparation of Metal Nanowire Decorated Carbon Allotropes

    NASA Technical Reports Server (NTRS)

    Southward, Robin E. (Inventor); Delozier, Donavon Mark (Inventor); Watson, Kent A. (Inventor); Smith, Jr., Joseph G. (Inventor); Ghose, Sayata (Inventor); Connell, John W. (Inventor)

    2016-01-01

    In the method of embodiments of the invention, the metal seeded carbon allotropes are reacted in solution forming zero valent metallic nanowires at the seeded sites. A polymeric passivating reagent, which selects for anisotropic growth is also used in the reaction to facilitate nanowire formation. The resulting structure resembles a porcupine, where carbon allotropes have metallic wires of nanometer dimensions that emanate from the seed sites on the carbon allotrope. These sites are populated by nanowires having approximately the same diameter as the starting nanoparticle diameter.

  4. Preparation of Metal Nanowire Decorated Carbon Allotropes

    NASA Technical Reports Server (NTRS)

    Southward, Robin E. (Inventor); Delozier, Donavon Mark (Inventor); Watson, Kent A. (Inventor); Smith, Joseph G. (Inventor); Ghose, Sayata (Inventor); Connell, John W. (Inventor)

    2014-01-01

    In the method of embodiments of the invention, the metal seeded carbon allotropes are reacted in solution forming zero valent metallic nanowires at the seeded sites. A polymeric passivating reagent, which selects for anisotropic growth is also used in the reaction to facilitate nanowire formation. The resulting structure resembles a porcupine, where carbon allotropes have metallic wires of nanometer dimensions that emanate from the seed sites on the carbon allotrope. These sites are populated by nanowires having approximately the same diameter as the starting nanoparticle diameter.

  5. Colossal injection of catalyst atoms into silicon nanowires.

    PubMed

    Moutanabbir, Oussama; Isheim, Dieter; Blumtritt, Horst; Senz, Stephan; Pippel, Eckhard; Seidman, David N

    2013-04-04

    The incorporation of impurities during the growth of nanowires from the vapour phase alters their basic properties substantially, and this process is critical in an extended range of emerging nanometre-scale technologies. In particular, achieving precise control of the behaviour of group III and group V dopants has been a crucial step in the development of silicon (Si) nanowire-based devices. Recently it has been demonstrated that the use of aluminium (Al) as a growth catalyst, instead of the usual gold, also yields an effective p-type doping, thereby enabling a novel and efficient route to functionalizing Si nanowires. Besides the technological implications, this self-doping implies the detachment of Al from the catalyst and its injection into the growing nanowire, involving atomic-scale processes that are crucial for the fundamental understanding of the catalytic assembly of nanowires. Here we present an atomic-level, quantitative study of this phenomenon of catalyst dissolution by three-dimensional atom-by-atom mapping of individual Al-catalysed Si nanowires using highly focused ultraviolet-laser-assisted atom-probe tomography. Although the observed incorporation of the catalyst atoms into nanowires exceeds by orders of magnitude the equilibrium solid solubility and solid-solution concentrations in known non-equilibrium processes, the Al impurities are found to be homogeneously distributed in the nanowire and do not form precipitates or clusters. As well as the anticipated effect on the electrical properties, this kinetics-driven colossal injection also has direct implications for nanowire morphology. We discuss the observed strong deviation from equilibrium using a model of solute trapping at step edges, and identify the key growth parameters behind this phenomenon on the basis of a kinetic model of step-flow growth of nanowires. The control of this phenomenon provides opportunities to create a new class of nanoscale devices by precisely tailoring the shape and

  6. Atomic Structure of Ultrathin Gold Nanowires.

    PubMed

    Yu, Yi; Cui, Fan; Sun, Jianwei; Yang, Peidong

    2016-05-11

    Understanding of the atomic structure and stability of nanowires (NWs) is critical for their applications in nanotechnology, especially when the diameter of NWs reduces to ultrathin scale (1-2 nm). Here, using aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM), we report a detailed atomic structure study of the ultrathin Au NWs, which are synthesized using a silane-mediated approach. The NWs contain large amounts of generalized stacking fault defects. These defects evolve upon sustained electron exposure, and simultaneously the NWs undergo necking and breaking. Quantitative strain analysis reveals the key role of strain in the breakdown process. Besides, ligand-like morphology is observed at the surface of the NWs, indicating the possibility of using AC-HRTEM for surface ligand imaging. Moreover, the coalescence dynamic of ultrathin Au NWs is demonstrated by in situ observations. This work provides a comprehensive understanding of the structure of ultrathin metal NWs at atomic-scale and could have important implications for their applications.

  7. Formation of pentagonal atomic chains in BCC Fe nanowires

    NASA Astrophysics Data System (ADS)

    Sainath, G.; Choudhary, B. K.

    2016-12-01

    For the first time, we report the formation of pentagonal atomic chains during tensile deformation of ultra thin BCC Fe nanowires. Extensive molecular dynamics simulations have been performed on <100>/{110} BCC Fe nanowires with different cross section width varying from 0.404 to 3.634 nm at temperatures ranging from 10 to 900 K. The results indicate that above certain temperature, long and stable pentagonal atomic chains form in BCC Fe nanowires with cross section width less than 2.83 nm. The temperature, above which the pentagonal chains form, increases with increase in nanowire size. The pentagonal chains have been observed to be highly stable over large plastic strains and contribute to high ductility in Fe nanowires.

  8. The torsional mechanical properties of copper nanowires supported by carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Huan, Hao; Fu, Bing; Ye, Xiang

    2017-02-01

    The torsional mechanical properties of hollow Cu nanowires supported by carbon nanotubes (CNTs) are studied by all atoms molecular dynamic simulation. It is found that the critical angles of Cu nanowires almost do not decrease when the temperature increases to a limit value, and this invariant feature also has been found as the torsional loading rate is lower than 4.5 ×1012 °s-1. Due to the support of CNTs, Cu nanowires can bear larger torsional angle at low torsional rates and high temperatures compared with those without CNTs, which means the CNTs will increase the torsion-tolerance of Cu nanowires.

  9. Carbon nanowires fabrications via top down approach.

    PubMed

    Tan, Chong Wei; Tay, Beng Kang

    2012-01-01

    Carbon nanowires are fabricated by the Langmuir Blodgett (LB) method via the top down approach on amorphous carbon. Thick a-C films (500 nm to 1 microm) have been successfully deposited after the treatment on silicon. The anisotropic etching of carbon using reactive ion etching (RIE) has been verified giving near vertical sidewalls. The LB method for depositing monolayer requires a hydrophilic surface. Plasma treatment is being performed on the silicon oxide hard mask to reduce the surface energy thereby making the surface from hydrophobic to hydrophilic. PS balls which are being deposited by LB method have one disadvantage which is the low adhesion of the PS ball to the silicon oxide surface. This adhesion is being improved by subjecting the PS ball to annealing which changes the shape and increase the contact area between the PS balls and the silicon oxide surface. As carbon and PS ball is vulnerable to oxygen plasma, a modified recipe of CF4:Ar was being used to etch the silicon oxide hard mask. There is almost little chemical reaction of the CF4 on carbon and PS ball. Carbon nanowires were successfully fabricated using polystyrene (PS) balls of diameter 450 nm. Through a series of steps, carbon nanowire of 500 nm in length and diameter approximately 250 nm can be produced.

  10. Pseudo-topotactic conversion of carbon nanotubes to T-carbon nanowires under picosecond laser irradiation in methanol.

    PubMed

    Zhang, Jinying; Wang, Rui; Zhu, Xi; Pan, Aifei; Han, Chenxiao; Li, Xin; Dan Zhao; Ma, Chuansheng; Wang, Wenjun; Su, Haibin; Niu, Chunming

    2017-09-25

    Pseudo-topotactic conversion of carbon nanotubes into one-dimensional carbon nanowires is a challenging but feasible path to obtain desired diameters and morphologies. Here, a previously predicted but experimentally unobserved carbon allotrope, T-carbon, has been produced from pseudo-topotactic conversion of a multi-walled carbon nanotube suspension in methanol by picosecond pulsed-laser irradiation. The as-grown T-carbon nanowires have the same diameter distribution as pristine carbon nanotubes, and have been characterized by high-resolution transmission electron microscopy, fast Fourier transform, electron energy loss, ultraviolet-visible, and photoluminescence spectroscopies to possess a diamond-like lattice, where each carbon is replaced by a carbon tetrahedron, and a lattice constant of 7.80 Å. The change in entropy from carbon nanotubes to T-carbon reveals the phase transformation to be first order in nature. The computed electronic band structures and projected density of states are in good agreement with the optical absorption and photoluminescence spectra of the T-carbon nanowires.T-carbon is a previously predicted but so far unobserved allotrope of carbon, with a crystal structure similar to diamond, but with each atomic lattice position replaced by a carbon tetrahedron. Here, the authors produce T-carbon nanowires via laser-irradiating a suspension of carbon nanotubes in methanol.

  11. Atomic scale investigation of silicon nanowires and nanoclusters

    PubMed Central

    2011-01-01

    In this study, we have performed nanoscale characterization of Si-clusters and Si-nanowires with a laser-assisted tomographic atom probe. Intrinsic and p-type silicon nanowires (SiNWs) are elaborated by chemical vapor deposition method using gold as catalyst, silane as silicon precursor, and diborane as dopant reactant. The concentration and distribution of impurity (gold) and dopant (boron) in SiNW are investigated and discussed. Silicon nanoclusters are produced by thermal annealing of silicon-rich silicon oxide and silica multilayers. In this process, atom probe tomography (APT) provides accurate information on the silicon nanoparticles and the chemistry of the nanolayers. PMID:21711788

  12. Carbon Slurry Secondary Atomization.

    DTIC Science & Technology

    1986-09-01

    ELEMENT NO. NO. N ACCESSION NO. 1 62203F 3048 I 05 I 34 11 TITLE (Include Securty Clasification ) Carbon Slurry Secondary Atomization 12. PERSONAL AUTHOR(S...density, size, and induction time. Any continuing program in this area should attempt to keep these criteria in mind . IV. VOLATILE ADDITIVE STUDIES 1

  13. Sprout-like growth of carbon nanowires on a carbon-doped Ni(1 1 1) surface

    NASA Astrophysics Data System (ADS)

    Fujita, D.; Kumakura, T.; Onishi, K.; Sagisaka, K.; Ohgi, T.; Harada, M.

    2004-09-01

    Sprout-like growth of carbon nanowires on single-crystal graphite (0 0 0 1) terraces on a carbon-doped Ni(1 1 1) substrate has been observed for the first time using only a heat treatment in ultrahigh vacuum. Nanometer-scale morphology and chemistry have been clarified by low-energy electron diffraction, Auger electron spectroscopy and scanning tunneling microscopy (STM). The growth mechanism is based on a bulk-to-surface precipitation process of internal carbon atoms that were doped in a high-purity Ni(1 1 1) substrate in advance. The observed carbon nanowires are single wires and their bundles, which have a metallic conductivity. The structures have some similarity to those of single-wall and multi-wall carbon nanotubes. Simple manipulation of a single carbon nanowire is demonstrated by STM.

  14. Steering epitaxial alignment of Au, Pd, and AuPd nanowire arrays by atom flux change.

    PubMed

    Yoo, Youngdong; Seo, Kwanyong; Han, Sol; Varadwaj, Kumar S K; Kim, Hyun You; Ryu, Ji Hoon; Lee, Hyuck Mo; Ahn, Jae Pyoung; Ihee, Hyotcherl; Kim, Bongsoo

    2010-02-10

    We have synthesized epitaxial Au, Pd, and AuPd nanowire arrays in vertical or horizontal alignment on a c-cut sapphire substrate. We show that the vertical and horizontal nanowire arrays grow from half-octahedral seeds by the correlations of the geometry and orientation of seed crystals with those of as-grown nanowires. The alignment of nanowires can be steered by changing the atom flux. At low atom deposition flux vertical nanowires grow, while at high atom flux horizontal nanowires grow. Similar vertical/horizontal epitaxial growth is also demonstrated on SrTiO(3) substrates. This orientation-steering mechanism is visualized by molecular dynamics simulations.

  15. Atomic-Scale Spectroscopy of Polydiacetylene Nanowires

    NASA Astrophysics Data System (ADS)

    Giridharagopal, Rajiv; Kelly, K. F.

    2006-03-01

    In recent years, the appeal of organic electronic devices has spurred interest in conducting polymers, such as polydiacetylene. Polydiacetylene nanowires offer numerous possibilities for application in molecular electronics, and they are a model system for understanding conduction mechanisms in polymers. We have used scanning tunneling microscopy to investigate monolayer films of pentacosadiynoic acid formed on highly ordered pyrolytic graphite using the Langmuir-Blodgett and Langmuir-Schaeffer deposition techniques and subsequently polymerized to form polydiacetylene nanowires. By applying a novel method of microwave frequency mixing at the STM tip junction, we have obtained capacitance-voltage spectroscopic data to characterize the wires across a range of bias voltages, tunneling gap resistances, and microwave mixing frequencies.

  16. A first-principle study of one-dimensional carbon atomic chain inserted single-wall carbon nanotubes.

    PubMed

    Mao, Yuliang; Zhong, JianXin; Yuan, JianMei; Zhao, Xinluo; Ando, Yoshinori

    2006-05-01

    Using first principles calculations, we investigate the atomic and electronic structure of carbon nanowires (CNWs) as the carbon chain inserted into single wall carbon nanotubes (SWCNTs). It indicates that the (5,5) CNW system exhibits metallic character, however, the insertion of carbon chain can transit a semi-conducting (9,0) SWCNT into a metallic.

  17. Temperature effects on electrical transport in semiconducting nanoporous carbon nanowires

    NASA Astrophysics Data System (ADS)

    Samuel, B. A.; Rajagopalan, R.; Foley, H. C.; Haque, M. A.

    2008-07-01

    In this paper we report on the effect of temperature on the electrical conductivity of amorphous and nanoporous (pores size around 0.5 nm) carbon nanowires. Poly(furfuryl alcohol) nanowires with diameter varying from 150 to 250 nm were synthesized by a template-based technique and upon pyrolysis yielded amorphous carbon nanowires with nanosized pores in them. We observed significant (as high as 700%) decrease in electrical resistance when the nanowire surface temperature was increased from room temperature to 160 °C. On the basis of the experimental and microscopy evidence, we infer a thermally activated carrier transport mechanism to be the primary electrical transport mechanism, at elevated temperatures, in these semiconducting, amorphous, and nanoporous carbon nanowires.

  18. Novel Carbon Nitride Nanowire (CNW) Conjugates for Breast Cancer Treatment

    DTIC Science & Technology

    2008-09-01

    2004, "Optical limiting and enhanced optical nonlinearity in boron -doped carbon nanotubes ", Chemical Physics Letters, vol. 389, no. 4-6, pp. 247-250...AD_________________ (Leave blank) Award Number: W81XWH-06-1-0681 TITLE: Novel Carbon Nitride Nanowire (CNW...Annual 3. DATES COVERED (From - To) 15 Aug 2007-14 Aug 2008 4. TITLE AND SUBTITLE Novel Carbon Nitride Nanowire (CNW) Conjugates for Breast Cancer

  19. From carbon nanotubes to carbon atomic chains

    NASA Astrophysics Data System (ADS)

    Casillas García, Gilberto; Zhang, Weijia; José-Yacamán, Miguel

    2010-10-01

    Carbyne is a linear allotrope of carbon. It is formed by a linear arrangement of carbon atoms with sp-hybridization. We present a reliable and reproducible experiment to obtain these carbon atomic chains using few-layer-graphene (FLG) sheets and a HRTEM. First the FLG sheets were synthesized from worm-like exfoliated graphite and then drop-casted on a lacey-carbon copper grid. Once in the TEM, two holes are opened near each other in a FLG sheet by focusing the electron beam into a small spot. Due to the radiation, the carbon atoms rearrange themselves between the two holes and form carbon fibers. The beam is concentrated on the carbon fibers in order excite the atoms and induce a tension until multi wall carbon nanotube (MWCNT) is formed. As the radiation continues the MWCNT breaks down until there is only a single wall carbon nanotube (SWCNT). Then, when the SWCNT breaks, an atomic carbon chain is formed, lasts for several seconds under the radiation and finally breaks. This demonstrates the stability of this carbon structure.

  20. Carbon nanotubes and nanowires for biological sensing

    NASA Technical Reports Server (NTRS)

    Li, Jun; Ng, Hou Tee; Chen, Hua

    2005-01-01

    This chapter reviews the recent development in biological sensing using nanotechnologies based on carbon nanotubes and various nanowires. These 1D materials have shown unique properties that are efficient in interacting with biomolecules of similar dimensions, i.e., on a nanometer scale. Various aspects including synthesis, materials properties, device fabrication, biofunctionalization, and biological sensing applications of such materials are reviewed. The potential of such integrated nanobiosensors in providing ultrahigh sensitivity, fast response, and high-degree multiplex detection, yet with minimum sample requirements is demonstrated. This chapter is intended to provide comprehensive updated information for people from a variety of backgrounds but with common interests in the fast-moving interdisciplinary field of nanobiotechnology.

  1. Carbon nanotubes and nanowires for biological sensing

    NASA Technical Reports Server (NTRS)

    Li, Jun; Ng, Hou Tee; Chen, Hua

    2005-01-01

    This chapter reviews the recent development in biological sensing using nanotechnologies based on carbon nanotubes and various nanowires. These 1D materials have shown unique properties that are efficient in interacting with biomolecules of similar dimensions, i.e., on a nanometer scale. Various aspects including synthesis, materials properties, device fabrication, biofunctionalization, and biological sensing applications of such materials are reviewed. The potential of such integrated nanobiosensors in providing ultrahigh sensitivity, fast response, and high-degree multiplex detection, yet with minimum sample requirements is demonstrated. This chapter is intended to provide comprehensive updated information for people from a variety of backgrounds but with common interests in the fast-moving interdisciplinary field of nanobiotechnology.

  2. Atom-by-Atom Analysis of Semiconductor Nanowires with Parts Per Million Sensitivity.

    PubMed

    Koelling, S; Li, A; Cavalli, A; Assali, S; Car, D; Gazibegovic, S; Bakkers, E P A M; Koenraad, P M

    2017-02-08

    The functionality of semiconductor devices is determined by the incorporation of dopants at concentrations down to the parts per million (ppm) level and below. Optimization of intentional and unintentional impurity doping relies on methods to detect and map the level of impurities. Detecting such low concentrations of impurities in nanostructures is however challenging to date as on the one hand methods used for macroscopic samples cannot be applied due to the inherent small volumes or faceted surfaces and on the other hand conventional microscopic analysis techniques are not sufficiently sensitive. Here, we show that we can detect and map impurities at the ppm level in semiconductor nanowires using atom probe tomography. We develop a method applicable to a wide variety of nanowires relevant for electronic and optical devices. We expect that it will contribute significantly to the further optimization of the synthesis of nanowires, nanostructures and devices based on these structures.

  3. Atomic Layer Deposition Enabled Interconnect Technology for Vertical Nanowire Arrays

    DTIC Science & Technology

    2009-06-01

    nanowire light emitting diodes (LEDs), nanowire-based field effect transistors (FETs), resonators, batteries or biomedical applications. Keywords...various vertical nanowire-based devices, such as nanowire light emitting diodes (LEDs), nanowire-based field effect transistors (FETs), resonators...Silvija Gradecˇak, Yat Li, Cheng-Yen Wen, and Charles M. Lieber, “Core/Multishell Nanowire Heterostructures as Multicolor, High-Efficiency Light- Emitting

  4. Atomic transportation via carbon nanotubes.

    PubMed

    Wang, Quan

    2009-01-01

    The transportation of helium atoms in a single-walled carbon nanotube is reported via molecular dynamics simulations. The efficiency of the atomic transportation is found to be dependent on the type of the applied loading and the loading rate as well as the temperature in the process. Simulations show the transportation is a result of the van der Waals force between the nanotube and the helium atoms through a kink propagation initiated in the nanotube.

  5. Mechanical Resonances of Helically Coiled Carbon Nanowires

    PubMed Central

    Saini, D.; Behlow, H.; Podila, R.; Dickel, D.; Pillai, B.; Skove, M. J.; Serkiz, S. M.; Rao, A. M.

    2014-01-01

    Despite their wide spread applications, the mechanical behavior of helically coiled structures has evaded an accurate understanding at any length scale (nano to macro) mainly due to their geometrical complexity. The advent of helically coiled micro/nanoscale structures in nano-robotics, nano-inductors, and impact protection coatings has necessitated the development of new methodologies for determining their shear and tensile properties. Accordingly, we developed a synergistic protocol which (i) integrates analytical, numerical (i.e., finite element using COMSOL®) and experimental (harmonic detection of resonance; HDR) methods to obtain an empirically validated closed form expression for the shear modulus and resonance frequency of a singly clamped helically coiled carbon nanowire (HCNW), and (ii) circumvents the need for solving 12th order differential equations. From the experimental standpoint, a visual detection of resonances (using in situ scanning electron microscopy) combined with HDR revealed intriguing non-planar resonance modes at much lower driving forces relative to those needed for linear carbon nanotube cantilevers. Interestingly, despite the presence of mechanical and geometrical nonlinearities in the HCNW resonance behavior the ratio of the first two transverse modes f2/f1 was found to be similar to the ratio predicted by the Euler-Bernoulli theorem for linear cantilevers. PMID:24986377

  6. Mechanical resonances of helically coiled carbon nanowires.

    PubMed

    Saini, D; Behlow, H; Podila, R; Dickel, D; Pillai, B; Skove, M J; Serkiz, S M; Rao, A M

    2014-07-02

    Despite their wide spread applications, the mechanical behavior of helically coiled structures has evaded an accurate understanding at any length scale (nano to macro) mainly due to their geometrical complexity. The advent of helically coiled micro/nanoscale structures in nano-robotics, nano-inductors, and impact protection coatings has necessitated the development of new methodologies for determining their shear and tensile properties. Accordingly, we developed a synergistic protocol which (i) integrates analytical, numerical (i.e., finite element using COMSOL) and experimental (harmonic detection of resonance; HDR) methods to obtain an empirically validated closed form expression for the shear modulus and resonance frequency of a singly clamped helically coiled carbon nanowire (HCNW), and (ii) circumvents the need for solving 12th order differential equations. From the experimental standpoint, a visual detection of resonances (using in situ scanning electron microscopy) combined with HDR revealed intriguing non-planar resonance modes at much lower driving forces relative to those needed for linear carbon nanotube cantilevers. Interestingly, despite the presence of mechanical and geometrical nonlinearities in the HCNW resonance behavior the ratio of the first two transverse modes f₂/f₁ was found to be similar to the ratio predicted by the Euler-Bernoulli theorem for linear cantilevers.

  7. Mechanical Resonances of Helically Coiled Carbon Nanowires

    NASA Astrophysics Data System (ADS)

    Saini, D.; Behlow, H.; Podila, R.; Dickel, D.; Pillai, B.; Skove, M. J.; Serkiz, S. M.; Rao, A. M.

    2014-07-01

    Despite their wide spread applications, the mechanical behavior of helically coiled structures has evaded an accurate understanding at any length scale (nano to macro) mainly due to their geometrical complexity. The advent of helically coiled micro/nanoscale structures in nano-robotics, nano-inductors, and impact protection coatings has necessitated the development of new methodologies for determining their shear and tensile properties. Accordingly, we developed a synergistic protocol which (i) integrates analytical, numerical (i.e., finite element using COMSOL®) and experimental (harmonic detection of resonance; HDR) methods to obtain an empirically validated closed form expression for the shear modulus and resonance frequency of a singly clamped helically coiled carbon nanowire (HCNW), and (ii) circumvents the need for solving 12th order differential equations. From the experimental standpoint, a visual detection of resonances (using in situ scanning electron microscopy) combined with HDR revealed intriguing non-planar resonance modes at much lower driving forces relative to those needed for linear carbon nanotube cantilevers. Interestingly, despite the presence of mechanical and geometrical nonlinearities in the HCNW resonance behavior the ratio of the first two transverse modes f2/f1 was found to be similar to the ratio predicted by the Euler-Bernoulli theorem for linear cantilevers.

  8. Atomic characterization of Au clusters in vapor-liquid-solid grown silicon nanowires

    SciTech Connect

    Chen, Wanghua; Roca i Cabarrocas, Pere; Pareige, Philippe; Castro, Celia; Xu, Tao; Grandidier, Bruno; Stiévenard, Didier

    2015-09-14

    By correlating atom probe tomography with other conventional microscope techniques (scanning electron microscope, scanning transmission electron microscope, and scanning tunneling microscopy), the distribution and composition of Au clusters in individual vapor-liquid-solid grown Si nanowires is investigated. Taking advantage of the characteristics of atom probe tomography, we have developed a sample preparation method by inclining the sample at certain angle to characterize the nanowire sidewall without using focused ion beam. With three-dimensional atomic scale reconstruction, we provide direct evidence of Au clusters tending to remain on the nanowire sidewall rather than being incorporated into the Si nanowires. Based on the composition measurement of Au clusters (28% ± 1%), we have demonstrated the supersaturation of Si atoms in Au clusters, which supports the hypothesis that Au clusters are formed simultaneously during nanowire growth rather than during the cooling process.

  9. Atomic structure of self-organizing iridium induced nanowires on Ge(001)

    NASA Astrophysics Data System (ADS)

    Kabanov, N. S.; Heimbuch, R.; Zandvliet, H. J. W.; Saletsky, A. M.; Klavsyuk, A. L.

    2017-05-01

    The atomic structure of self-organizing iridium (Ir) induced nanowires on Ge(001) is studied by density functional theory (DFT) calculations and variable-temperature scanning tunneling microscopy. The Ir induced nanowires are aligned in a direction perpendicular to the Ge(001) substrate dimer rows, have a width of two atoms and are completely kink-less. Density functional theory calculations show that the Ir atoms prefer to dive into the Ge(001) substrate and push up the neighboring Ge substrate atoms. The nanowires are composed of Ge atoms and not Ir atoms as previously assumed. The regions in the vicinity of the nanowires are very dynamic, even at temperatures as low as 77 K. Time-resolved scanning tunneling microscopy measurements reveal that this dynamics is caused by buckled Ge substrate dimers that flip back and forth between their two buckled configurations.

  10. Electric field-assisted deposition of nanowires on carbon nanotubes for nanoelectronics and sensor applications.

    PubMed

    Sivakumar, Kousik; Panchapakesan, Balaji

    2005-02-01

    Manipulation and control of matter at the nanoscale and atomic scale levels are crucial for the success of nanoscale sensors and actuators. The ability to control and synthesize multilayer structures using carbon nanotubes that will enable the building of electronic devices within a nanotube is still in its infancy. In this paper, we present results on selective electric field-assisted deposition of metals on carbon nanotubes realizing metallic nanowire structures. Silver and platinum nanowires have been fabricated using this approach for their applications in chemical sensing as catalytic materials to sniff toxic agents and in the area of biomedical nanotechnology for construction of artificial muscles. Electric field-assisted deposition allows the deposition of metals with a high degree of selectivity on carbon nanotubes by manipulating the charges on the surface of the nanotubes and forming electrostatic double-layer supercapacitors. Deposition of metals primarily occurred due to electrochemical reduction, electrophoresis, and electro-osmosis inside the walls of the nanotube. SEM and TEM investigations revealed silver and platinum nanowires between 10 nm and 100 nm in diameter. The present technique is versatile and enables the fabrication of a host of different types of metallic and semiconducting nanowires using carbon nanotube templates for nanoelectronics and a myriad of sensor applications.

  11. Indium phosphide nanowires integrated directly on carbon fibers

    NASA Astrophysics Data System (ADS)

    Lohn, Andrew J.; Longson, Timothy J.; Kobayashi, Nobuhiko P.

    2011-10-01

    We have demonstrated the growth of a group III-V semiconductor binary alloy, indium phosphide (InP), directly on carbon fibers thereby enabling a union of semiconductor and structural materials. Carbon fibers were prepared by electrospinning solutions of polyacrilonitrile (PAN) and dimethylformamide (DMF) followed by carbonization at 750 °C in inert atmosphere. Gold nanoparticles dispersed on the fibers catalyzed nanowire growth by metal organic chemical vapor deposition. X-ray diffraction suggests that the nanowires appear to be epitaxially grown along the (110) direction. Geometrical parameters have been determined by scanning electron microscopy and transmission electron microscopy and elemental analysis has been carried out using energy dispersive spectroscopy. The nanowires grown from carbon fibers are composed of an amorphous shell and crystalline core which alternates at high spatial frequency.mountai

  12. Lithium Ion Battery Performance of Silicon Nanowires With Carbon Skin

    SciTech Connect

    Bogart, Timothy D.; Oka, Daichi; Lu, Xiaotang; Gu, Meng; Wang, Chong M.; Korgel, Brian A.

    2013-12-06

    Silicon (Si) nanomaterials have emerged as a leading candidate for next generation lithium-ion battery anodes. However, the low electrical conductivity of Si requires the use of conductive additives in the anode film. Here we report a solution-based synthesis of Si nanowires with a conductive carbon skin. Without any conductive additive, the Si nanowire electrodes exhibited capacities of over 2000 mA h g-1 for 100 cycles when cycled at C/10 and over 1200 mA h g-1 when cycled more rapidly at 1C against Li metal.. In situ transmission electron microscopy (TEM) observation reveals that the carbon skin performs dual roles: it speeds lithiation of the Si nanowires significantly, while also constraining the final volume expansion. The present work sheds light on ways to optimize lithium battery performance by smartly tailoring the nanostructure of composition of materials based on silicon and carbon.

  13. Lithium ion battery peformance of silicon nanowires with carbon skin.

    PubMed

    Bogart, Timothy D; Oka, Daichi; Lu, Xiaotang; Gu, Meng; Wang, Chongmin; Korgel, Brian A

    2014-01-28

    Silicon (Si) nanomaterials have emerged as a leading candidate for next generation lithium-ion battery anodes. However, the low electrical conductivity of Si requires the use of conductive additives in the anode film. Here we report a solution-based synthesis of Si nanowires with a conductive carbon skin. Without any conductive additive, the Si nanowire electrodes exhibited capacities of over 2000 mA h g(-1) for 100 cycles when cycled at C/10 and over 1200 mA h g(-1) when cycled more rapidly at 1C against Li metal. In situ transmission electron microscopy (TEM) observation reveals that the carbon skin performs dual roles: it speeds lithiation of the Si nanowires significantly, while also constraining the final volume expansion. The present work sheds light on ways to optimize lithium battery performance by smartly tailoring the nanostructure of composition of materials based on silicon and carbon.

  14. GaN nanowire tips for nanoscale atomic force microscopy.

    PubMed

    Behzadirad, Mahmoud; Nami, Mohsen; Rishinaramagalam, Ashwin; Feezell, Daniel; Busani, Tito

    2017-04-07

    Imaging of high-aspect-ratio nanostructures with sharp edges and straight walls in nanoscale metrology by Atomic Force Microscopy (AFM) has been challenging due to the mechanical properties and conical geometry of the majority of available commercial tips. Here we report on the fabrication of GaN probes for nanoscale metrology of high-aspect-ratio structures to enhance the resolution of AFM imaging and improve the durability of AFM tips. GaN nanowires (NWs) were fabricated using bottom-up and top-down techniques and bonded to Si cantilevers to scan vertical trenches on Si substrates. Over several scans, the GaN probes demonstrated excellent durability while scanning uneven structures and showed resolution enhancements in topography images, independent of scan direction, compared to commercial Si tips.

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

    DTIC Science & Technology

    2014-07-01

    AFRL-RX-WP-JA-2014-0171 HIERARCHICAL CARBON FIBERS WITH ZnO NANOWIRES FOR VOLATILE SENSING IN COMPOSITE CURING (POSTPRINT) Gregory...REPORT TYPE Interim 3. DATES COVERED (From – To) 16 April 2012 – 02 June 2014 4. TITLE AND SUBTITLE HIERARCHICAL CARBON FIBERS WITH ZnO NANOWIRES ...needed to demonstrate the use of Zinc Oxide (ZnO) nanowire coated carbon fibers as a volatile sensor. ZnO nanowires are demonstrated to function as

  16. Nanowire modified carbon fibers for enhanced electrical energy storage

    NASA Astrophysics Data System (ADS)

    Shuvo, Mohammad Arif Ishtiaque; (Bill) Tseng, Tzu-Liang; Ashiqur Rahaman Khan, Md.; Karim, Hasanul; Morton, Philip; Delfin, Diego; Lin, Yirong

    2013-09-01

    The study of electrochemical super-capacitors has become one of the most attractive topics in both academia and industry as energy storage devices because of their high power density, long life cycles, and high charge/discharge efficiency. Recently, there has been increasing interest in the development of multifunctional structural energy storage devices such as structural super-capacitors for applications in aerospace, automobiles, and portable electronics. These multifunctional structural super-capacitors provide structures combining energy storage and load bearing functionalities, leading to material systems with reduced volume and/or weight. Due to their superior materials properties, carbon fiber composites have been widely used in structural applications for aerospace and automotive industries. Besides, carbon fiber has good electrical conductivity which will provide lower equivalent series resistance; therefore, it can be an excellent candidate for structural energy storage applications. Hence, this paper is focused on performing a pilot study for using nanowire/carbon fiber hybrids as building materials for structural energy storage materials; aiming at enhancing the charge/discharge rate and energy density. This hybrid material combines the high specific surface area of carbon fiber and pseudo-capacitive effect of metal oxide nanowires, which were grown hydrothermally in an aligned fashion on carbon fibers. The aligned nanowire array could provide a higher specific surface area that leads to high electrode-electrolyte contact area thus fast ion diffusion rates. Scanning Electron Microscopy and X-Ray Diffraction measurements are used for the initial characterization of this nanowire/carbon fiber hybrid material system. Electrochemical testing is performed using a potentio-galvanostat. The results show that gold sputtered nanowire carbon fiber hybrid provides 65.9% higher energy density than bare carbon fiber cloth as super-capacitor.

  17. Structural, electronic and magnetic properties of carbon doped boron nitride nanowire: Ab initio study

    NASA Astrophysics Data System (ADS)

    Jalilian, Jaafar; Kanjouri, Faramarz

    2016-11-01

    Using spin-polarized density functional theory calculations, we demonstrated that carbon doped boron nitride nanowire (C-doped BNNW) has diverse electronic and magnetic properties depending on position of carbon atoms and their percentages. Our results show that only when one carbon atom is situated on the edge of the nanowire, C-doped BNNW is transformed into half-metal. The calculated electronic structure of the C-doped BNNW suggests that doping carbon can induce localized edge states around the Fermi level, and the interaction among localized edge states leads to semiconductor to half-metal transition. Overall, the bond reconstruction causes of appearance of different electronic behavior such as semiconducting, half-metallicity, nonmagnetic metallic, and ferromagnetic metallic characters. The formation energy of the system shows that when a C atom is doped on surface boron site, system is more stable than the other positions of carbon impurity. Our calculations show that C-doped BNNW may offer unique opportunities for developing nanoscale spintronic materials.

  18. Wafer scale tilt-compensated silicon nanowire atomic force microscopy probes for high aspect ratio geometries

    NASA Astrophysics Data System (ADS)

    Bryce, Brian A.; Ilic, B. Robert; Reuter, Mark C.; Tiwari, Sandip

    2014-09-01

    Using site controlled growth of single vapor-liquid-solid silicon nanowires, high aspect ratio tilt-compensated atomic force microscope probes are fabricated on a wafer scale. Methods are developed to sculpt the tips of these probes for desirable performance attributes. Probe performance is explored by imaging high aspect ratio structures using an atomic force microscope. Wafer scale tilt-compensated silicon nanowire probes are an excellent mass producible platform for non-destructive topographic imaging of high aspect ratio features.

  19. Electrodeposition of Pd Nanowires and Nanorods on Carbon Nanoparticles

    SciTech Connect

    Bliznakov, S.; Vukmirovic, M.; Sutter, E.; Adzic, R.

    2011-06-01

    We report on the method for synthesizing palladium nanowires and nanorods involving the electrodeposition on oxidized amorphous carbon nanoparticles from chloride containing solutions. The effect of the deposition overpotential and the concentration of palladium ions on the morphology of the Pd electrodeposits have been established. Palladium grows predominately in the shape of nanowires if electrodeposited at potentials in the H underpotential deposition potential (UPD) range, where chloride ions are adsorbed only at the edges of nucleated monolayer-thick clusters on the carbon surface. The effect of the concentration of palladium ions on deposits morphology is also discussed. The mechanism of electrodeposition of Pd nanowires and nanorods in the H UPD potential range has been proposed.

  20. Preparation of nanowire specimens for laser-assisted atom probe tomography.

    PubMed

    Blumtritt, H; Isheim, D; Senz, S; Seidman, D N; Moutanabbir, O

    2014-10-31

    The availability of reliable and well-engineered commercial instruments and data analysis software has led to development in recent years of robust and ergonomic atom-probe tomographs. Indeed, atom-probe tomography (APT) is now being applied to a broader range of materials classes that involve highly important scientific and technological problems in materials science and engineering. Dual-beam focused-ion beam microscopy and its application to the fabrication of APT microtip specimens have dramatically improved the ability to probe a variety of systems. However, the sample preparation is still challenging especially for emerging nanomaterials such as epitaxial nanowires which typically grow vertically on a substrate through metal-catalyzed vapor phase epitaxy. The size, morphology, density, and sensitivity to radiation damage are the most influential parameters in the preparation of nanowire specimens for APT. In this paper, we describe a step-by-step process methodology to allow a precisely controlled, damage-free transfer of individual, short silicon nanowires onto atom probe microposts. Starting with a dense array of tiny nanowires and using focused ion beam, we employed a sequence of protective layers and markers to identify the nanowire to be transferred and probed while protecting it against Ga ions during lift-off processing and tip sharpening. Based on this approach, high-quality three-dimensional atom-by-atom maps of single aluminum-catalyzed silicon nanowires are obtained using a highly focused ultraviolet laser-assisted local electrode atom probe tomograph.

  1. Preparation of nanowire specimens for laser-assisted atom probe tomography

    NASA Astrophysics Data System (ADS)

    Blumtritt, H.; Isheim, D.; Senz, S.; Seidman, D. N.; Moutanabbir, O.

    2014-10-01

    The availability of reliable and well-engineered commercial instruments and data analysis software has led to development in recent years of robust and ergonomic atom-probe tomographs. Indeed, atom-probe tomography (APT) is now being applied to a broader range of materials classes that involve highly important scientific and technological problems in materials science and engineering. Dual-beam focused-ion beam microscopy and its application to the fabrication of APT microtip specimens have dramatically improved the ability to probe a variety of systems. However, the sample preparation is still challenging especially for emerging nanomaterials such as epitaxial nanowires which typically grow vertically on a substrate through metal-catalyzed vapor phase epitaxy. The size, morphology, density, and sensitivity to radiation damage are the most influential parameters in the preparation of nanowire specimens for APT. In this paper, we describe a step-by-step process methodology to allow a precisely controlled, damage-free transfer of individual, short silicon nanowires onto atom probe microposts. Starting with a dense array of tiny nanowires and using focused ion beam, we employed a sequence of protective layers and markers to identify the nanowire to be transferred and probed while protecting it against Ga ions during lift-off processing and tip sharpening. Based on this approach, high-quality three-dimensional atom-by-atom maps of single aluminum-catalyzed silicon nanowires are obtained using a highly focused ultraviolet laser-assisted local electrode atom probe tomograph.

  2. Fabrication of carbon nanowires by pyrolysis of aqueous solution of sugar within asbestos nanofibers

    NASA Astrophysics Data System (ADS)

    Butko, V. Yu.; Fokin, A. V.; Nevedomskii, V. N.; Kumzerov, Yu. A.

    2015-05-01

    Carbon nanowires have been fabricated by pyrolysis of an aqueous solution of sugar in nanochannels of asbestos fibers. Electron microscopy demonstrates that the diameter of these nanochannels corresponds to the diameter of the thinnest of the carbon nanowires obtained. Some of these nanowires have a graphite crystal lattice and internal pores. After asbestos is etched out, the carbon nanowires can retain the original shape of the asbestos fibers. Heating in an inert atmosphere reduces the electrical resistivity of the carbon nanowires to ˜0.035 Ω cm.

  3. Electrical and Surface Properties of InAs/InSb Nanowires Cleaned by Atomic Hydrogen.

    PubMed

    Webb, James L; Knutsson, Johan; Hjort, Martin; Gorji Ghalamestani, Sepideh; Dick, Kimberly A; Timm, Rainer; Mikkelsen, Anders

    2015-08-12

    We present a study of InAs/InSb heterostructured nanowires by X-ray photoemission spectroscopy (XPS), scanning tunneling microscopy (STM), and in-vacuum electrical measurements. Starting with pristine nanowires covered only by the native oxide formed through exposure to ambient air, we investigate the effect of atomic hydrogen cleaning on the surface chemistry and electrical performance. We find that clean and unreconstructed nanowire surfaces can be obtained simultaneously for both InSb and InAs by heating to 380 ± 20 °C under an H2 pressure 2 × 10(-6) mbar. Through electrical measurement of individual nanowires, we observe an increase in conductivity of 2 orders of magnitude by atomic hydrogen cleaning, which we relate through theoretical simulation to the contact-nanowire junction and nanowire surface Fermi level pinning. Our study demonstrates the significant potential of atomic hydrogen cleaning regarding device fabrication when high quality contacts or complete control of the surface structure is required. As hydrogen cleaning has recently been shown to work for many different types of III-V nanowires, our findings should be applicable far beyond the present materials system.

  4. 3-D Atomic-Scale Mapping of Manganese Dopants in Lead Sulfide Nanowires

    SciTech Connect

    Isheim, Dieter; Kaszpurenko, Jason; Yu, Dong; Mao, Zugang; Seidman, David N.; Arslan, Ilke

    2012-03-22

    Dopants in nanowires, whether intentional or unintentional, can ultimately control the material's properties and therefore need to be understood on the atomic scale. We study vapor-liquid-solid grown manganese-doped lead sulfide nanowires by atom-probe tomography for the first time for lead salt materials. The three-dimensional chemical concentration maps at the atomic scale demonstrate a radial distribution profile of Mn ions, with a concentration of only 0.18 at.% and 0.01 at.% for MnCl2 and Mn-acetate precursors, respectively. The ability to characterize these small concentrations of dopant atoms in Pb1-xMnxS nanowires (x = 0.0036 and 0.0002), important for spintronic and thermoelectric devices, sets a platform for similar analyses for all nanostructures. First-principles calculations confirm that Mn atoms substitute for Pb in the PbS structure.

  5. Strong gold atom strands formed by incorporation of carbon atoms

    NASA Astrophysics Data System (ADS)

    Oshima, Yoshifumi; Kurui, Yoshihiko; Nguyen, Huy Duy; Ono, Tomoya; Takayanagi, Kunio

    2011-07-01

    Single metal atom strands have attracted significant interest because of their unique properties, such as quantization effects and a high degree of strength. Recently it was suggested that the strength of a gold atom strand can be enhanced by the insertion of an impurity atom, but it has not been experimentally investigated. Using a transmission electron microscope under ultrahigh vacuum conditions, we observed that gold atoms were pulled out one by one from a carbon-contaminated gold (111) surface to form a long atom strand. The strand was so strong that it did not break even upon bending. Supported by first-principles calculations, the strand was found to have two carbon atoms at each gold atom interval. Our observations suggest that the carbon atoms act as a glue to form a long gold atom strand.

  6. Silicon nanowire transistors with a channel width of 4 nm fabricated by atomic force microscope nanolithography.

    PubMed

    Martinez, J; Martínez, R V; Garcia, R

    2008-11-01

    The emergence of an ultrasensitive sensor technology based on silicon nanowires requires both the fabrication of nanoscale diameter wires and the integration with microelectronic processes. Here we demonstrate an atomic force microscopy lithography that enables the reproducible fabrication of complex single-crystalline silicon nanowire field-effect transistors with a high electrical performance. The nanowires have been carved from a silicon-on-insulator wafer by a combination of local oxidation processes with a force microscope and etching steps. We have fabricated and measured the electrical properties of a silicon nanowire transistor with a channel width of 4 nm. The flexibility of the nanofabrication process is illustrated by showing the electrical performance of two nanowire circuits with different geometries. The fabrication method is compatible with standard Si CMOS processing technologies and, therefore, can be used to develop a wide range of architectures and new microelectronic devices.

  7. Conductive-probe atomic force microscopy characterization of silicon nanowire

    PubMed Central

    2011-01-01

    The electrical conduction properties of lateral and vertical silicon nanowires (SiNWs) were investigated using a conductive-probe atomic force microscopy (AFM). Horizontal SiNWs, which were synthesized by the in-plane solid-liquid-solid technique, are randomly deployed into an undoped hydrogenated amorphous silicon layer. Local current mapping shows that the wires have internal microstructures. The local current-voltage measurements on these horizontal wires reveal a power law behavior indicating several transport regimes based on space-charge limited conduction which can be assisted by traps in the high-bias regime (> 1 V). Vertical phosphorus-doped SiNWs were grown by chemical vapor deposition using a gold catalyst-driving vapor-liquid-solid process on higly n-type silicon substrates. The effect of phosphorus doping on the local contact resistance between the AFM tip and the SiNW was put in evidence, and the SiNWs resistivity was estimated. PMID:21711623

  8. Atomic Entanglement in Carbon Nanotubes.

    NASA Astrophysics Data System (ADS)

    Bondarev, Igor; Vlahovic, Branislav

    2006-03-01

    The development of materials that may host quantum coherent states is a critical research problem for the nearest future. Recent progress in the growth of centimeter-long small-diameter single-walled carbon nanotubes (CNs)[1] and successful experiments on the encapsulation of single atoms into CNs[2], stimulate the study of dynamical quantum processes in atomically doped CN systems. We have recently shown[3] that atomic states may be strongly coupled to vacuum surface photonic modes in the CN, thus forming quasi-1D cavity polaritons similar to those observed for quantum dots in semiconductor nanocavities[4], which were recently suggested to be a possible way to produce the excitonic qubit entanglement[5]. Here, we show that, being strongly coupled to the (resonator-like) cylindrical nanotube environment, the two atomic quasi-1D polaritons can be easily entangled as well, thus challenging a novel alternative approach towards quantum information transfer over centimeter-long distances. [1]L.X.Zheng et al, Proc. Nanotech 2005 (May 8-12, 2005, Anaheim, CA, USA), vol.3, p.126. [2]G.-H.Jeong et al, Phys. Rev. B68,075410(2003). [3]I.V.Bondarev and Ph.Lambin, in: Trends in Nanotubes Reasearch (NovaScience, NY, 2005); Phys. Rev. B70,035407(2004); Phys. Rev. B72,035451(2005). [4]T.Yoshie et al, Nature 432,200(2004). [5]S.Hughes, Phys. Rev. Lett.94,227402(2005).

  9. Detection and quantized conductance of neutral atoms near a charged carbon nanotube.

    PubMed

    Ristroph, Trygve; Goodsell, Anne; Golovchenko, J A; Hau, Lene Vestergaard

    2005-02-18

    We describe a novel single atom detector that uses the high electric field surrounding a charged single-walled carbon nanotube to attract and subsequently field-ionize neutral atoms. A theoretical study of the field-ionization tunneling rates for atomic trajectories in the attractive potential near a nanowire shows that a broadly applicable, high spatial resolution, low-power, neutral-atom detector with nearly 100% efficiency is realizable with present-day technology. Calculations also show that the system can provide the first opportunity to study quantized conductance phenomena when detecting cold neutral atoms with mean velocities less than 15 m/s.

  10. Fabrication of Cu nanowires along atomic step edge lines on Si(1 1 1) substrates

    NASA Astrophysics Data System (ADS)

    Tokuda, Norio; Watanabe, Hidenobu; Hojo, Daisuke; Yamasaki, Satoshi; Miki, Kazushi; Yamabe, Kikuo

    2004-10-01

    We have succeeded in the fabrication of high-aspect-ratio (length to width) Cu nanowires along atomic step edge lines on Si(1 1 1) substrates. The fabrication procedure consisted of two wet process steps: (1) flattening of the surface roughness to an atomic level by immersing Si(1 1 1) wafers in ultralow-dissolved-oxygen water (LOW), and (2) Cu nanowire formation by immersion in LOW containing 10 ppm Cu ions for 1 s at room temperature. On the other hand, no Cu nanowires were formed on the Si(1 1 1) surfaces when the dissolved oxygen content was 8 ppm in alkaline solution during the Cu deposition stage, even though the Si etching with OH - was enhanced. We consider that it is due to the decrease in reduced Cu atom density by the existence of the dissolved oxygen as superoxide anion radicals.

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

    PubMed

    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. Synthesis of SiC nanowires with in-situ deposition of carbon coating.

    PubMed

    Yang, Wen; Araki, Hiroshi; Tang, Chengchun; Hu, Quanli; Suzuki, Hiroshi; Noda, Tetsuji

    2005-02-01

    SiC nanowires are effective reinforcement materials in ceramic matrix composites. A compliant coating such as carbon on nanowires is necessary in order to moderate the nanowire/matrix interfacial bounding for taking the most advantages of SiC nanowires. SiC nanowires with an in-situ deposition of carbon shell coating were fabricated by a novel chemical vapor growth process. Highresolution transmission electron microscopy examinations showed that the nanowires consisted of a single crystal beta-SiC core with an amorphous carbon shell 2-5 nm in thickness. The nanowires were straight with a length generally over 10 microm and a diameter 15-150 nm. The growth direction of the core SiC nanowires is (111). A simple three-step growth model for SiC nanowires was proposed based on a vapor-solid growth mechanism. Because the carbon-coated nanowires were grown directly on continuous Tyranno-SA SiC fibers, in-situ application of the present technique on the fabrication of SiC nanowire-reinforced SiC/SiC composites is expected.

  13. Tensile manipulation of ultrathin gold nanowires at different sizes and atomic vacancies

    NASA Astrophysics Data System (ADS)

    Wang, Fenying; Fu, Yingqiang; Chi, Baozhu; Dai, Yanfeng; Zhao, Jianwei

    2016-09-01

    The fractures of ultrathin metallic nanowires usually exhibit their uncertainties at small scales. Here, statistics was used to study the uniaxial tension-induced deformation of ultrathin gold nanowires. With the same cross section of gold nanowires (5a × 5a × Ha), different sizes show various deformation mechanisms due to the moving styles of slipped crystalline planes. However, the deformations at different sizes (5a × 5a × 5a) and (5a × 5a × 25a) both show the sensitivity to one atomic vacancy, attributed to the dominant role of the same cross section. The statistical broken position distributions further provide that the deformation fracture is size dependent and sensitive to atomic vacancies, which is explained with the relationship between broken bonds and tensile wave propagation. For the size dependence of mechanical property, the nanowire height (H) of 10a is observed to be a transitional point, when the height is less than 10a, the mechanical strength is unstable, while above this transitional point, mechanical strengths decrease with the nanowire size increasing. Our work provides mechanistic insights into enhancing the reliability of metallic nanostructures by engineering the internal atomic imperfection and structural dimensions.

  14. From single atoms to self-assembled quantum single-atomic nanowires: noble metal atoms on black phosphorene monolayers.

    PubMed

    Zhao, X J; Shan, Wen-Wen; He, Hao; Xue, Xinlian; Guo, Z X; Li, S F

    2017-03-15

    Transition metal (TM) nanostructures, such as one dimensional (1D) nanowires with/without substrates, usually possess drastically different properties from their bulk counterparts, due to their distinct stacking and electronic confinement. Correspondingly, it is of great importance to establish the dominant driving force in forming 1D single-metal-atom-wires (SMAWs). Here, with first-principles calculations, taking the black phosphorene (BP) monolayer as a prototype 2D substrate, we investigate the energetic and kinetic properties of all the 5d-TM atoms on the 2D substrate to reveal the mechanism of formation of SMAWs. In contrast to other 5d- and 4d-TMs, noble metal elements Pd and Pt are found to prefer to grow along the trough in an atom-by-atom manner, self-assembling into SMAWs with a significant magic growth behavior. This is due to distinct binding energies and diffusion barriers along the trough, i.e., zig-zag direction, as compared to other directions of the BP. The present findings are valuable in the fabrication and modulation of 1D nanostructures which can be anticipated to possess desirable functionalities for potential applications such as in nanocatalysis, nanosensors, and related areas.

  15. Bending properties of carbon nanotubes encapsulating solid nanowires.

    PubMed

    Danailov, D; Keblinski, P; Nayak, S; Ajayan, P M

    2002-10-01

    Using empirical potentials and atomistic simulations, we model three-point bend tests of single-walled carbon nanotubes encapsulating metal nanowires. The presence of a metal nanowire inside the nanotube greatly suppresses the tube-buckling instability. Increasing tube diameter leads to an increase in the bending strength; however, in contrast to hollow tubes, there is no decrease in the maximum deflection before buckling. Analysis of the principal bending vibrational mode shows a lowering of the frequency, associated with increased tube inertia. Remarkably, metal-filled tubes exhibit strong damping of oscillations whereas unfilled single-walled and multiwalled tubes show no damping. Our studies demonstrate the benefits of filling tubes with solids to modify bending strength and flexibility, suggesting applications for nanotube-based elements in micromechanical devices or nanoprobes.

  16. Electrical characterization of HgTe nanowires using conductive atomic force microscopy

    SciTech Connect

    Gundersen, P.; Kongshaug, K. O.; Selvig, E.; Haakenaasen, R.

    2010-12-01

    Self-organized HgTe nanowires grown by molecular beam epitaxy (MBE) have been characterized using conductive atomic force microscopy. As HgTe will degrade or evaporate at normal baking temperatures for electron beam lithography (EBL) resists, an alternative method was developed. Using low temperature optical lithography processes, large Au contacts were deposited on a sample covered with randomly oriented, lateral HgTe nanowires. Nanowires partly covered by the large electrodes were identified with a scanning electron microscope and then localized in the atomic force microscope (AFM). The conductive tip of the AFM was then used as a movable electrode to measure current-voltage curves at several locations on HgTe nanowires. The measurements revealed that polycrystalline nanowires had diffusive electron transport, with resistivities two orders of magnitude larger than that of an MBE-grown HgTe film. The difference can be explained by scattering at the rough surface walls and at the grain boundaries in the wires. The method can be a solution when EBL is not available or requires too high temperature, or when measurements at several positions along a wire are required.

  17. Local Atomic Density of Microporous Carbons

    SciTech Connect

    Dmowski, Wojtek; Contescu, Cristian I.; Llobet, Anna; Gallego, Nidia C.; Egami, Takeskhi

    2012-07-12

    We investigated the structure of two disordered carbons: activated carbon fibers (ACF) and ultramicroporous carbon (UMC). These carbons have highly porous structure with large surface areas and consequently low macroscopic density that should enhance adsorption of hydrogen. We used the atomic pair distribution function to probe the local atomic arrangements. The results show that the carbons maintain an in-plane local atomic structure similar to regular graphite, but the stacking of graphitic layers is strongly disordered. Although the local atomic density of these carbons is lower than graphite, it is only {approx}20% lower and is much higher than the macroscopic density due to the porosity of the structure. For this reason, the density of graphene sheets that have optimum separation for hydrogen adsorption is lower than anticipated.

  18. Carbon nanowires generated by ion irradiation of hydrocarbon ices

    NASA Astrophysics Data System (ADS)

    Puglisi, O.; Compagnini, G.; D'Urso, L.; Baratta, G. A.; Palumbo, M. E.; Strazzulla, G.

    2014-05-01

    In this paper we present the formation of carbon nanowires (polyynes and polycumulenes) in the solid state by ion irradiation of frozen hydrocarbons (C6H6 and C2H2). Irradiations have been performed using H+ ions in the 100's keV energy regime using fluences up to 5 × 1014 ions/cm2. Beyond the intrinsic significance of these results in the field of material science, this work has been motivated by the fact that ion beam irradiation of hydrocarbon ices is one of the most important process thought to happen in several extraterrestrial environments where many spectroscopic features of polyyne molecules have been identified.

  19. Catalyst-particle configurations: From nanowires to carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Zhang, Qian; Davis, Stephen H.; Voorhees, Peter W.

    2017-08-01

    Surface-energy minimization is used to study capillary effects that determine the stable configurations of (liquid or solid) particles atop tubes or wires. The results give allowable ranges for the volume (Vc) of the particles as a function of the inner and outer radii of the tubes, RI and Ro, respectively. When RI/Ro=0 , the object is a nanowire. When RI/Ro=1 , it is a single-wall carbon nanotube. When 0 carbon nanotube. Moreover, the transition paths among different configurations are studied. These results suggest possible mechanisms for the reshaping of the "pear-like" catalyst particles in carbon nanotubes that oscillate across local energy-maximum points with respect to the position of the lower interface in the inner wall.

  20. Growth of Si nanowires in porous carbon with enhanced cycling stability for Li-ion storage

    NASA Astrophysics Data System (ADS)

    Zhao, Xiaoxu; Rui, Xianhong; Zhou, WenWen; Tan, Liping; Yan, Qingyu; Lu, Ziyang; Hng, Huey Hoon

    2014-03-01

    Si nanowires are successfully grown in porous carbon by supercritical fluid-liquid-solid (SFLS) process, which show high specific capacities and charge-discharge cycling stability as anode materials for Li-ion storage. The enhancement capacity and cycling stability of the Si nanowires/porous carbon composite nanostructures is attributed to the porous carbon serving as a highly conductive framework and absorption of volume changes of Si nanowires during the lithiation/delithiation process. At optimized condition, the Si nanowires/porous carbon electrodes maintain reversible capacities of 1678 mAh g-1 for the 100th cycle at a current density of 420 mA g-1, which is much better as compared to that of pure Si nanowires.

  1. Growth of gallium nitride and indium nitride nanowires on conductive and flexible carbon cloth substrates.

    PubMed

    Yang, Yi; Ling, Yichuan; Wang, Gongming; Lu, Xihong; Tong, Yexiang; Li, Yat

    2013-03-07

    We report a general strategy for synthesis of gallium nitride (GaN) and indium nitride (InN) nanowires on conductive and flexible carbon cloth substrates. GaN and InN nanowires were prepared via a nanocluster-mediated growth method using a home built chemical vapor deposition (CVD) system with Ga and In metals as group III precursors and ammonia as a group V precursor. Electron microscopy studies reveal that the group III-nitride nanowires are single crystalline wurtzite structures. The morphology, density and growth mechanism of these nanowires are determined by the growth temperature. Importantly, a photoelectrode fabricated by contacting the GaN nanowires through a carbon cloth substrate shows pronounced photoactivity for photoelectrochemical water oxidation. The ability to synthesize group III-nitride nanowires on conductive and flexible substrates should open up new opportunities for nanoscale photonic, electronic and electrochemical devices.

  2. Ionized Carbon Atoms in Orion

    NASA Image and Video Library

    2016-10-12

    The dusty side of the Sword of Orion is illuminated in this striking infrared image from the European Space Agency's Hershel Space Observatory. This immense nebula is the closest large region of star formation, situated about 1,500 light years away in the constellation of Orion. The parts that are easily observed in visible light, known alternatively as the Orion Nebula or Messier 42, correspond to the light blue regions. This is the glow from the warmest dust, illuminated by clusters of hot stars that have only recently been born in this chaotic region. The red spine of material running from corner to corner reveals colder, denser filaments of dust and gas that are scattered throughout the Orion nebula. In visible light this would be a dark, opaque feature, hiding the reservoir of material from which stars have recently formed and will continue to form in the future. Herschel data from the PACS instrument observations, at wavelengths of 100 and 160 microns, is displayed in blue and green, respectively, while SPIRE 250-micron data is shown in red. Within the inset image, the emission from ionized carbon atoms (C+), overlaid in yellow, was isolated and mapped out from spectrographic data obtained by the HIFI instrument. http://photojournal.jpl.nasa.gov/catalog/PIA21073

  3. Nonlinear input-output feature of the atom-nanowires coupling system

    NASA Astrophysics Data System (ADS)

    Xia, Xiuwen; Zhang, Xinqin; Xu, Jingping; Cheng, Mutian; Yang, Yaping

    2017-07-01

    We consider in this paper the input-output properties of an atom-nanowire coupling system which is composed of two individual terminated metal nanowaveguides and a two-level optical emitter. In detail, four aspects of the input-output properties are studied. First, we discuss in particular the coherent perfect absorber in the linear excitation regime and give the condition to realize it. Second, the transmittivity of the atom-nanowire system in the nonlinear regime is calculated, and a Rabi-like splitting associated with optical nonlinearity is found. Such a result is much different from the Rabi splitting in the atom-cavity system in the low excitation limit. Third, we find that the cooperation of optical nonlinearity and spatial asymmetry can generate optical nonreciprocity. Finally, a negative differential transmittivity is achieved with appropriate parameters. Our findings show promising applications in the full-optical device.

  4. Electrowetting properties of atomic layer deposited Al2O3 decorated silicon nanowires

    NASA Astrophysics Data System (ADS)

    Rajkumar, K.; Rajavel, K.; Cameron, D. C.; Mangalaraj, D.; Rajendrakumar, R. T.

    2015-06-01

    This paper reports the electrowetting properties of liquid droplet on superhydrophobic silicon nanowires with Atomic layer deposited (ALD) Al2O3 as dielectric layer. Silicon wafer were etched by metal assisted wet chemical etching with silver as catalyst. ALD Al2O3 films of 10nm thickness were conformally deposited over silicon nanowires. Al2O3 dielectric film coated silicon nanowires was chemically modified with Trichloro (1H, 1H, 2H, 2H-perfluorooctyl) silane to make it superhydrophobic(SHP). The contact angle was measured and all the samples exhibited superhydrophobic nature with maximum contact angles of 163° and a minimum contact angle hysteresis of 6°. Electrowetting induced a maximum reversible decrease of the contact angle of 20°at 150V in air.

  5. Atomic-level cotrol of the thermoelectric properties in polytypoid nanowires

    SciTech Connect

    Andrews, Sean C.; Fardy, Melissa A.; Moore, Michael C.; Aloni, Shaoul; Zhang, Minjuan; Radmilovic, Velimir; Yang, Peidong

    2010-10-23

    Thermoelectric materials have generated interest as a means of increasing the efficiency of power generation through the scavenging of waste heat. Materials containing nanometer-sized structural and compositional features can exhibit enhanced thermoelectric performance due to the decoupling of certain electrical and thermal properties, but the extent to which these features can be controlled is often limited. Here we report a simple synthesis of M{sub 2}O{sub 3}(ZnO){sub n} (M = In, Ga, Fe) nanowires with controllable polytypoid structures, where the nanostructured features are tuned by adjusting the amount of metal precursor. After the introduction of nanometer-scale features (individual atomic layers and alloying), thermal and electrical measurements on single In{sub 2-x}Ga{sub x}O3(ZnO){sub n} nanowires reveal a simultaneous improvement in all contributing factors to the thermoelectric figure of merit, indicating successful modification of the nanowire transport properties.

  6. Sodium ion insertion in hollow carbon nanowires for battery applications.

    PubMed

    Cao, Yuliang; Xiao, Lifen; Sushko, Maria L; Wang, Wei; Schwenzer, Birgit; Xiao, Jie; Nie, Zimin; Saraf, Laxmikant V; Yang, Zhengguo; Liu, Jun

    2012-07-11

    Hollow carbon nanowires (HCNWs) were prepared through pyrolyzation of a hollow polyaniline nanowire precursor. The HCNWs used as anode material for Na-ion batteries deliver a high reversible capacity of 251 mAh g(-1) and 82.2% capacity retention over 400 charge-discharge cycles between 1.2 and 0.01 V (vs Na(+)/Na) at a constant current of 50 mA g(-1) (0.2 C). Excellent cycling stability is also observed at an even higher charge-discharge rate. A high reversible capacity of 149 mAh g(-1) also can be obtained at a current rate of 500 mA g(-1) (2C). The good Na-ion insertion property is attributed to the short diffusion distance in the HCNWs and the large interlayer distance (0.37 nm) between the graphitic sheets, which agrees with the interlayered distance predicted by theoretical calculations to enable Na-ion insertion in carbon materials.

  7. Mechanical Behavior of Carbon Nanotubes Filled With Metal Nanowires By Atomistic Simulations

    NASA Astrophysics Data System (ADS)

    Danailov, Daniel; Keblinski, Pawel; Pulickel, Ajayan; Nayak, Saroj

    2002-03-01

    Using molecular dynamics simulations we studied mechanical behavior of (10,10) carbon nanotubes filled with a crystalline fcc metal wires. The interatomic interactions were described by a combination of Terfoff’s bond-order potential for carbon, embedded atom method (EAM) potential for metal and pair potential for carbon-metal interactions. The elastic properties, as well as failure mechanism were determined by simulating three point bending test, by pressing the center and the ends of relatively long tube in determined relatively small ring areas. We observed that following elastic response, at larger deformation, the metal wire yields well before the carbon bonding is affected. The behavior of filled tubes was compared with that of hollow tubes. Interesting is thet the hollow carbon (10,10) nanotube is more strong elastically than the same tube filled with Au-metal nanowire. We also simulated indentation of filled tubes residing on a hard flat surface. Similarly as in the bending test, metal wire yields first, is cut in between hard cylinder and hard plane and pushed away from under the indenter. Upon further increase of the indentation force, carbon tube is broken and forms two open ends that are rapidly zipped around the cut metal wire. Remarkably, the shape of the zipped tube ends strong depend of the speed of the punching of the tube. This result imply a possibility of designing tubes with various closed end shapes with applicationusing in the nanoscale manipulation procedures used for production.

  8. Zinc oxide nanowires on carbon microfiber as flexible gas sensor

    NASA Astrophysics Data System (ADS)

    Tonezzer, M.; Lacerda, R. G.

    2012-03-01

    In the past years, zinc oxide nanowires (ZnO NWs) have been proven to be an excellent material for gas sensors. In this work, we used ZnO nanowires in a novel architecture integrated on a carbon microfiber (μC) textile. This innovative design permits us to obtain mechanical flexibility, while the absence of any lithographic technique allows a large-area and low-cost fabrication of gas sensors. The performances of the devices are investigated for both oxidizing and reducing gases. The nano-on-micro structure of the sensor provides a high surface-to-volume ratio, leading to a fast and intense response for both oxygen (O2) and hydrogen (H2) gases. The sensor response has an optimum temperature condition at 280 °C with a response value of 10 for oxygen and 11 for hydrogen. The limit of detection (LoD) has been found to be 2 and 4 ppm for oxygen and hydrogen, respectively. Additionally, the sensor response and recovery time is small being less than 10 s for both O2 and H2.

  9. Generalized Redox-Responsive Assembly of Carbon-Sheathed Metallic and Semiconducting Nanowire Heterostructures.

    PubMed

    Choi, Sinho; Kim, Jieun; Hwang, Dae Yeon; Park, Hyungmin; Ryu, Jaegeon; Kwak, Sang Kyu; Park, Soojin

    2016-02-10

    One-dimensional metallic/semiconducting materials have demonstrated as building blocks for various potential applications. Here, we report on a unique synthesis technique for redox-responsive assembled carbon-sheathed metal/semiconducting nanowire heterostructures that does not require a metal catalyst. In our approach, germanium nanowires are grown by the reduction of germanium oxide particles and subsequent self-catalytic growth during the thermal decomposition of natural gas, and simultaneously, carbon sheath layers are uniformly coated on the nanowire surface. This process is a simple, reproducible, size-controllable, and cost-effective process whereby most metal oxides can be transformed into metallic/semiconducting nanowires. Furthermore, the germanium nanowires exhibit stable chemical/thermal stability and outstanding electrochemical performance including a capacity retention of ∼96% after 1200 cycles at the 0.5-1C rate as lithium-ion battery anode.

  10. Characterization of SiC nanowires obtained from carbon black powder

    NASA Astrophysics Data System (ADS)

    Wieligor, Monika; Zerda, T. W.

    2009-03-01

    SiC nanowires were obtained by a reaction between vapor silicon and carbon black powder in vacuum at 1200oC. Their structures and properties were studied using X-ray diffraction, high resolution transmission microscopy, HRTEM, and Raman scattering techniques. We show that diameter of sintered nanowires depends on carbon black grade and its history of thermal treatment. SiC nanowires of diameter as small as 10 nm were obtained from graphitized furnace carbon blacks. Chemical composition of nanowires was similar for all samples, but concentration of structural defects varied and depended on carbon black surface properties and surface morphology. Stacking faults and twins dislocations were observed in all specimens and characterized by HRTEM, X-ray diffraction, and Raman spectroscopy.

  11. Sub-5 nm nanostructures fabricated by atomic layer deposition using a carbon nanotube template

    NASA Astrophysics Data System (ADS)

    Woo, Ju Yeon; Han, Hyo; Kim, Ji Weon; Lee, Seung-Mo; Ha, Jeong Sook; Shim, Joon Hyung; Han, Chang-Soo

    2016-07-01

    The fabrication of nanostructures having diameters of sub-5 nm is very a important issue for bottom-up nanofabrication of nanoscale devices. In this work, we report a highly controllable method to create sub-5 nm nano-trenches and nanowires by combining area-selective atomic layer deposition (ALD) with single-walled carbon nanotubes (SWNTs) as templates. Alumina nano-trenches having a depth of 2.6 ∼ 3.0 nm and SiO2 nano-trenches having a depth of 1.9 ∼ 2.2 nm fully guided by the SWNTs have been formed on SiO2/Si substrate. Through infilling ZnO material by ALD in alumina nano-trenches, well-defined ZnO nanowires having a thickness of 3.1 ∼ 3.3 nm have been fabricated. In order to improve the electrical properties of ZnO nanowires, as-fabricated ZnO nanowires by ALD were annealed at 350 °C in air for 60 min. As a result, we successfully demonstrated that as-synthesized ZnO nanowire using a specific template can be made for various high-density resistive components in the nanoelectronics industry.

  12. Current imaging and electromigration-induced splitting of GaN nanowires as revealed by conductive atomic force microscopy.

    PubMed

    Li, Chun; Bando, Yoshio; Golberg, Dmitri

    2010-04-27

    Current images of electromigration-induced common vapor-liquid-solid-grown GaN nanowires were obtained using a conductive atomic force microscope. Structural characterization indicated that these wurtzite (ZW) [0110] nanowires contained longitudinal zinc blende (ZB) defects as stacking faults. The current was attributed to tunneling current through the Schottky barrier between the AFM tip and a nanowire, which was dominated by the local nanowire surface work function. Due to the electromigration induced by large current densities around the defects, the axial splitting process of the nanowires was directly observed under continuous current scanning. The electromigration was likely enhanced by non-uniformly distributed electrostatic pressure around the axial ZW/ZB domain interfaces.

  13. Atomic mechanisms governing the elastic limit and the incipient plasticity of bending Si nanowires.

    PubMed

    Zheng, Kun; Han, Xiaodong; Wang, Lihua; Zhang, Yuefei; Yue, Yonghai; Qin, Yan; Zhang, Xiaona; Zhang, Ze

    2009-06-01

    Individual single-crystalline Si nanowires (NWs) were bent by forming loops or arcs with different radius. Positional-resolved atomic level strain distribution (PRALSD) along both of the radial and axial directions were calculated and mapped directly from the atomic-resolution strained high-resolution electron microscopy (HREM) images of the bent Si NWs. For the first time, the neutral-strain axis shifted from the compressive zone to the tensile region was directly demonstrated from the PRALSD along the radial direction. Bending-induced ripple-buckling of the bent Si NW was observed and a significant strain variation along the bending axial direction in the compressive region was revealed. The tensile surface atomic steps and the compressive buckling are the physical origin of the asymmetric tensile-compressive properties of postelastic instabilities and the incipient plasticity. Both of the tensile surface atomic-steps and the compressive buckling initiated versatile ductile plastic dislocation events.

  14. Atomic layer deposition of lead sulfide quantum dots on nanowire surfaces.

    PubMed

    Dasgupta, Neil P; Jung, Hee Joon; Trejo, Orlando; McDowell, Matthew T; Hryciw, Aaron; Brongersma, Mark; Sinclair, Robert; Prinz, Fritz B

    2011-03-09

    Quantum dots provide unique advantages in the design of novel optoelectronic devices owing to the ability to tune their properties as a function of size. Here we demonstrate a new technique for fabrication of quantum dots during the nucleation stage of atomic layer deposition (ALD) of PbS. Islands with sub-10 nm diameters were observed during the initial ALD cycles by transmission electron microscopy, and in situ observations of the coalescence and sublimation behavior of these islands show the possibility of further modifying the size and density of dots by annealing. The ALD process can be used to cover high-aspect-ratio nanostructures, as demonstrated by the uniform coating of a Si nanowire array with a single layer of PbS quantum dots. Photoluminescence measurements on the quantum dot/nanowire composites show a blue shift when the number of ALD cycles is decreased, suggesting a route to fabricate unique three-dimensional nanostructured devices such as solar cells.

  15. Atomic and electronic structure of Mo6S9-xIx nanowires

    NASA Astrophysics Data System (ADS)

    Meden, A.; Kodre, A.; Padeznik Gomilsek, J.; Arcon, I.; Vilfan, I.; Vrbanic, D.; Mrzel, A.; Mihailovic, D.

    2005-09-01

    Moybdenum-based subnanometre diameter nanowires are easy to synthesize and disperse, and they exhibit a variety of functional properties in which they are superior to other one-dimensional materials. However, further progress in the understanding of physical properties and the development of new and specific applications have so far been impeded by the fact that their structure was not accurately known. Here we report on a combination of systematic x-ray diffraction and extended x-ray absorption fine structure experiments, and first-principles theoretical structure calculations, which are used to determine the atomic skeletal structure of individual Mo6S9-xIx (MoSIx) nanowires, their packing arrangement within bundles and their electronic band structure. From this work we conclude that the variations in functional properties appear to arise from different stoichiometry, not skeletal structure. A supplementary data file is available from http://stacks.iop.org/0957-4484/16/1578

  16. Synthesis and photocatalytic property of porous metal oxides nanowires based on carbon nanofiber template

    NASA Astrophysics Data System (ADS)

    Fan, Weiqiang; Li, Meng; Xu, Jinfu; Bai, Hongye; Zhang, Rongxian; Chen, Chao

    2015-11-01

    A series of porous metal oxides nanowires (Fe2O3, Co3O4, NiO and CuO) have been successfully synthesized, where commercial carbon nanofibers were used as the template. The obtained samples were systematically characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-Vis diffuse reflectance (UV-Vis DR) spectra and transmission electron microscope (TEM). According to the photodegradation data, the porous metal oxides nanowires exhibit significantly photocatalytic activity for degrading tetracycline (TC). Furthermore, the porous Fe2O3 nanowires show the best photocatalytic performance among all the samples.

  17. Capillarity creates single-crystal calcite nanowires from amorphous calcium carbonate.

    PubMed

    Kim, Yi-Yeoun; Hetherington, Nicola B J; Noel, Elizabeth H; Kröger, Roland; Charnock, John M; Christenson, Hugo K; Meldrum, Fiona C

    2011-12-23

    Single-crystal calcite nanowires are formed by crystallization of morphologically equivalent amorphous calcium carbonate (ACC) particles within the pores of track etch membranes. The polyaspartic acid stabilized ACC is drawn into the membrane pores by capillary action, and the single-crystal nature of the nanowires is attributed to the limited contact of the intramembrane ACC particle with the bulk solution. The reaction environment then supports transformation to a single-crystal product.

  18. Imaging Atomic Scale Dynamics on III-V Nanowire Surfaces During Electrical Operation.

    PubMed

    Webb, J L; Knutsson, J; Hjort, M; McKibbin, S R; Lehmann, S; Thelander, C; Dick, K A; Timm, R; Mikkelsen, A

    2017-10-06

    As semiconductor electronics keep shrinking, functionality depends on individual atomic scale surface and interface features that may change as voltages are applied. In this work we demonstrate a novel device platform that allows scanning tunneling microscopy (STM) imaging with atomic scale resolution across a device simultaneously with full electrical operation. The platform presents a significant step forward as it allows STM to be performed everywhere on the device surface and high temperature processing in reactive gases of the complete device. We demonstrate the new method through proof of principle measurements on both InAs and GaAs nanowire devices with variable biases up to 4 V. On InAs nanowires we observe a surprising removal of atomic defects and smoothing of the surface morphology under applied bias, in contrast to the expected increase in defects and electromigration-related failure. As we use only standard fabrication and scanning instrumentation our concept is widely applicable and opens up the possibility of fundamental investigations of device surface reliability as well as new electronic functionality based on restructuring during operation.

  19. Detection of gas atoms with carbon nanotubes

    PubMed Central

    Arash, B.; Wang, Q.

    2013-01-01

    Owning to their unparalleled sensitivity resolution, nanomechanical resonators have excellent capabilities in design of nano-sensors for gas detection. The current challenge is to develop new designs of the resonators for differentiating distinct gas atoms with a recognizably high sensitivity. In this work, the characteristics of impulse wave propagation in carbon nanotube-based sensors are investigated using molecular dynamics simulations to provide a new method for detection of noble gases. A sensitivity index based on wave velocity shifts in a single-walled carbon nanotube, induced by surrounding gas atoms, is defined to explore the efficiency of the nano-sensor. The simulation results indicate that the nano-sensor is able to differentiate distinct noble gases at the same environmental temperature and pressure. The inertia and the strengthening effects by the gases on wave characteristics of carbon nanotubes are particularly discussed, and a continuum mechanics shell model is developed to interpret the effects.

  20. Fabrication of carbon-coated silicon nanowires and their application in dye-sensitized solar cells.

    PubMed

    Kim, Junhee; Lim, Jeongmin; Kim, Minsoo; Lee, Hae-Seok; Jun, Yongseok; Kim, Donghwan

    2014-11-12

    We report the fabrication of silicon/carbon core/shell nanowire arrays using a two-step process, involving electroless metal deposition and chemical vapor deposition. In general, foreign shell materials that sheath core materials change the inherent characteristics of the core materials. The carbon coating functionalized the silicon nanowire arrays, which subsequently showed electrocatalytic activities for the reduction of iodide/triiodide. This was verified by cyclic voltammetry and electrochemical impedance spectroscopy. We employed the carbon-coated silicon nanowire arrays in dye-sensitized solar cells as counter electrodes. We optimized the carbon shells to maximize the photovoltaic performance of the resulting devices, and subsequently, a peak power conversion efficiency of 9.22% was achieved.

  1. The Synergic Effect of Atomic Hydrogen Adsorption and Catalyst Spreading on Ge Nanowire Growth Orientation and Kinking.

    PubMed

    Kolíbal, Miroslav; Pejchal, Tomáš; Vystavěl, Tomáš; Šikola, Tomáš

    2016-08-10

    Hydride precursors are commonly used for semiconductor nanowire growth from the vapor phase and hydrogen is quite often used as a carrier gas. Here, we used in situ scanning electron microscopy and spatially resolved Auger spectroscopy to reveal the essential role of atomic hydrogen in determining the growth direction of Ge nanowires with an Au catalyst. With hydrogen passivating nanowire sidewalls the formation of inclined facets is suppressed, which stabilizes the growth in the ⟨111⟩ direction. By contrast, without hydrogen gold diffuses out of the catalyst and decorates the nanowire sidewalls, which strongly affects the surface free energy of the system and results in the ⟨110⟩ oriented growth. The experiments with intentional nanowire kinking reveal the existence of an energetic barrier, which originates from the kinetic force needed to drive the droplet out of its optimum configuration on top of a nanowire. Our results stress the role of the catalyst material and surface chemistry in determining the nanowire growth direction and provide additional insights into a kinking mechanism, thus allowing to inhibit or to intentionally initiate spontaneous kinking.

  2. Self-aligned process for forming microlenses at the tips of vertical silicon nanowires by atomic layer deposition

    SciTech Connect

    Dan, Yaping Chen, Kaixiang; Crozier, Kenneth B.

    2015-01-01

    The microlens is a key enabling technology in optoelectronics, permitting light to be efficiently coupled to and from devices such as image sensors and light-emitting diodes. Their ubiquitous nature motivates the development of new fabrication techniques, since existing methods face challenges as microlenses are scaled to smaller dimensions. Here, the authors demonstrate the formation of microlenses at the tips of vertically oriented silicon nanowires via a rapid atomic layer deposition process. The nature of the process is such that the microlenses are centered on the nanowires, and there is a self-limiting effect on the final sizes of the microlenses arising from the nanowire spacing. Finite difference time domain electromagnetic simulations are performed of microlens focusing properties, including showing their ability to enhance visible-wavelength absorption in silicon nanowires.

  3. Atomic Ordering in InGaN Alloys within Nanowire Heterostructures.

    PubMed

    Woo, Steffi Y; Bugnet, Matthieu; Nguyen, Hieu P T; Mi, Zetian; Botton, Gianluigi A

    2015-10-14

    Ternary III-nitride based nanowires (NWs) are promising for optoelectronic applications by offering advantageous design and control over composition, structure, and strain. Atomic-level chemical ordering in wurtzite InGaN alloys along the c-plane direction with a 1:1 periodicity within InGaN/GaN NW heterostructures was investigated by scanning transmission electron microscopy. Atomic-number-sensitive imaging contrast was used to simultaneously assign the In-rich and Ga-rich planes and determine the crystal polarity to differentiate unique sublattice sites. The nonrandom occupation of the c-planes in the InGaN alloys is confirmed by the occurrence of additional superlattice spots in the diffraction pattern within the ternary alloy. Compositional modulations in the ordered InGaN was further studied using atomic-resolution elemental mapping, outlining the substantial In-enrichment. Confirming the preferential site occupation of In-atoms provides experimental validation for the previous theoretical model of ordered InGaN alloys in bulk epilayers based on differences in surface site energy. Therefore, this study strongly suggests that atomic ordering in InGaN has a surface energetics-induced origin. Optimization of atomic ordering, in particular in III-nitride NW heterostructures, could be an alternative design tool toward desirable structural and compositional properties for various device applications operating at longer visible wavelengths.

  4. A controllable interface performance through varying ZnO nanowires dimensions on the carbon fibers

    NASA Astrophysics Data System (ADS)

    Wang, Ben; Duan, Yugang; Zhang, Jingjing

    2016-12-01

    The fiber/matrix interface was reinforced by introducing nanostructure on the fiber surface, which enlarged the interphase area for stress transfer across the interface. To study the relationship between the interphase area and the interface performance, a low-temperature method for varying the dimensions of ZnO nanowires grown on the carbon fiber surface was proposed. The surface area with ZnO nanowires introduced was controlled by the conditions for growth: ultrasonic dispersion time, reaction time and Polyethylene glycol concentration. The effects of that varying ZnO the nanowires dimensions on interface performance was evaluated using wettability test and interfacial shear strength (IFSS). ZnO nanowires affect the liquid-motion on the fiber surface, and a shift to hydrophobicity was observed with decreasing the surface coverage of ZnO nanowires. A nonlinear relationship between IFSS and the ratio of the area of the introduced ZnO nanowires suggested unfavorable wettability impeded resin infiltration into ZnO nanowires.

  5. Atomistic simulations on the axial nanowelding configuration and contact behavior between Ag nanowire and single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Cui, Jianlei; Zhang, Jianwei; He, Xiaoqiao; Yang, Xinjun; Mei, Xuesong; Wang, Wenjun; Jiang, Gedong; Wang, Kedian; Yang, Lijun; Xie, Hui

    2017-03-01

    As for the interesting new building blocks, the Ag nanowires (AgNWs) and single-walled carbon nanotubes (SWNTs) as the interesting new building blocks are viewed as the promising candidates for the next-generation interconnects due to their most remarkable electrical, thermal, optical, mechanical, and other properties. The axial nanowelding of head-to-head style and side-to-side style is relatively simulated with the molecular dynamics method. As for the head-to-head structural style, SWNTs will move toward the AgNWs and contact with the head of AgNWs. And, the part of the Ag nanowire may be subsequently encapsulated in SWNT with the core-filling Ag atom chain as the final atomic contact configuration during nanowelding, which is related to the nanowelding temperature. When the SWNTs and AgNWs are arranged by the side-to-side contact style, the SWNTs will move along the SWNT surface and may eventually catch up with the AgNW being neck and neck. Aiming at the final axial atomic configurations and the contact behavior during nanowelding process, the related dominant mechanism is revealed in this paper.

  6. Monolithic carbon structures including suspended single nanowires and nanomeshes as a sensor platform

    PubMed Central

    2013-01-01

    With the development of nanomaterial-based nanodevices, it became inevitable to develop cost-effective and simple nanofabrication technologies enabling the formation of nanomaterial assembly in a controllable manner. Herein, we present suspended monolithic carbon single nanowires and nanomeshes bridging two bulk carbon posts, fabricated in a designed manner using two successive UV exposure steps and a single pyrolysis step. The pyrolysis step is accompanied with a significant volume reduction, resulting in the shrinkage of micro-sized photoresist structures into nanoscale carbon structures. Even with the significant elongation of the suspended carbon nanowire induced by the volume reduction of the bulk carbon posts, the resultant tensional stress along the nanowire is not significant but grows along the wire thickness; this tensional stress gradient and the bent supports of the bridge-like carbon nanowire enhance structural robustness and alleviate the stiction problem that suspended nanostructures frequently experience. The feasibility of the suspended carbon nanostructures as a sensor platform was demonstrated by testing its electrochemical behavior, conductivity-temperature relationship, and hydrogen gas sensing capability. PMID:24256942

  7. The synthesis of a copper/multi-walled carbon nanotube hybrid nanowire in a microfluidic reactor

    NASA Astrophysics Data System (ADS)

    Peng, Yitian; Chen, Quanfang

    2009-06-01

    Metallic nanowires are promising as components in nanoscale systems including nanoelectronics. However, the application of nanowires made of a single material is limited by the properties of the material used. We report here an effort to fabricate a hybrid copper-coated carbon nanotube (CNT)—Cu/CNT nanowire, using a microfluidic reactor. The fabrication of copper/multi-walled carbon nanotube (MWCNT) hybrid nanowires was realized by an electroless copper deposition technique in which MWCNT templates and an electrolyte were introduced separately into the microfluidic reactor. The morphology and structure of the Cu/MWCNT hybrid nanowire were studied by means of transmission electron microscopy (TEM), selected-area electron diffraction (SAED), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX), as well as XRD. Results reveal that the fabricated Cu/MWCNT hybrid nanowires are continuously covered by crystallized copper with a preferred crystal orientation along the (111) planes in the radial direction of the MWCNTs. These structural properties are attributed to the unique reaction environment including laminar flow and diffusion-controlled reaction.

  8. The synthesis of a copper/multi-walled carbon nanotube hybrid nanowire in a microfluidic reactor.

    PubMed

    Peng, Yitian; Chen, Quanfang

    2009-06-10

    Metallic nanowires are promising as components in nanoscale systems including nanoelectronics. However, the application of nanowires made of a single material is limited by the properties of the material used. We report here an effort to fabricate a hybrid copper-coated carbon nanotube (CNT)-Cu/CNT nanowire, using a microfluidic reactor. The fabrication of copper/multi-walled carbon nanotube (MWCNT) hybrid nanowires was realized by an electroless copper deposition technique in which MWCNT templates and an electrolyte were introduced separately into the microfluidic reactor. The morphology and structure of the Cu/MWCNT hybrid nanowire were studied by means of transmission electron microscopy (TEM), selected-area electron diffraction (SAED), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX), as well as XRD. Results reveal that the fabricated Cu/MWCNT hybrid nanowires are continuously covered by crystallized copper with a preferred crystal orientation along the (111) planes in the radial direction of the MWCNTs. These structural properties are attributed to the unique reaction environment including laminar flow and diffusion-controlled reaction.

  9. Carbon Nanotube Sheet as Top Contact Electrode for Nanowires: Highly Versatile and Simple Process.

    PubMed

    Ternon, Céline; Dupas, Florence; Stein, Sergio; Aguirre, Carla; Dhalluin, Florian; Baron, Thierry

    2015-02-01

    In the past years, lots of research works were dedicated to nanowires and their integration into functional devices. However, despite the great potential of such materials, no device based on nanowires has been transferred in all-day-life. In fact, the vertical device integration is slowed down by the difficulty to contact easily the top electrode. With this work, we present a simple, elegant and versatile process for creating a top electrode contact on nanowires: a carbon nanotube sheet is suspended at the top of the nanowire field. The proof of concept is made through the realization of photovoltaic devices composed of an assembly of vertical PN-junctions based on silicon nanowires. For an illumination density of 100 mW . cm-2, our devices exhibit short circuit current density as high as 15 mA . cm-2. Due to the numerous advantages of the carbon nanotube sheets as top electrode, such as transparency, porosity, good mechanical performance and no need to embed nanowires, such simple and elegant technology should definitely find developments in every field of nanotechnology.

  10. Copper nanowire coated carbon fibers as efficient substrates for detecting designer drugs using SERS.

    PubMed

    Halouzka, Vladimir; Halouzkova, Barbora; Jirovsky, David; Hemzal, Dusan; Ondra, Peter; Siranidi, Eirini; Kontos, Athanassios G; Falaras, Polycarpos; Hrbac, Jan

    2017-04-01

    Miniature Surface Enhanced Raman Scattering (SERS) sensors were fabricated by coating the carbon fiber microelectrodes with copper nanowires. The coating procedure, based on anodizing the copper wire in ultrapure water followed by cathodic deposition of the anode-derived material onto carbon fiber electrodes, provides a "clean" copper nanowire network. The developed miniature (10µm in diameter and 2mm in length) and nanoscopically rough SERS substrates are applicable in drug sensing, as shown by the detection and resolving of a range of seized designer drugs in trace amounts (microliter volumes of 10(-10)-10(-12)M solutions). The copper nanowire modified carbon microfiber substrates could also find further applications in biomedical and environmental sensing.

  11. Manipulation and Joule heat welding of Ag nanowires prepared by atomic migration

    NASA Astrophysics Data System (ADS)

    Tohmyoh, Hironori; Fukui, Satoru

    2012-09-01

    Ag nanowires (NWs) with diameters of about 200 nm and length of 2-7 μm are prepared on a substrate by an atomic migration called stress-induced migration and are picked up from the substrate with electrostatic forces. The Ag NWs are then offered for the welding experiment in a scanning electron microscope and successfully welded together using Joule heating introduced into the NWs by supplying the constant direct current. It is discovered that the welding of Ag NWs is achieved under the current supply in a self-completed manner. The conditions for successful Joule heat welding are analyzed by the parameter that governs the melting phenomenon at the nanocontacts of two NWs. From the experiment and the analysis, electromigration, i.e., another type of atomic migration due to higher electron flow, is found to be occurred during the welding and this is considered to enhance the welding performance of two NWs with Joule heat.

  12. Atomic resolution studies of carbonic anhydrase II

    PubMed Central

    Behnke, Craig A.; Le Trong, Isolde; Godden, Jeff W.; Merritt, Ethan A.; Teller, David C.; Bajorath, Jürgen; Stenkamp, Ronald E.

    2010-01-01

    Carbonic anhydrase has been well studied structurally and functionally owing to its importance in respiration. A large number of X-ray crystallographic structures of carbonic anhydrase and its inhibitor complexes have been determined, some at atomic resolution. Structure determination of a sulfonamide-containing inhibitor complex has been carried out and the structure was refined at 0.9 Å resolution with anisotropic atomic displacement parameters to an R value of 0.141. The structure is similar to those of other carbonic anhydrase complexes, with the inhibitor providing a fourth nonprotein ligand to the active-site zinc. Comparison of this structure with 13 other atomic resolution (higher than 1.25 Å) isomorphous carbonic anhydrase structures provides a view of the structural similarity and variability in a series of crystal structures. At the center of the protein the structures superpose very well. The metal complexes superpose (with only two exceptions) with standard deviations of 0.01 Å in some zinc–protein and zinc–ligand bond lengths. In contrast, regions of structural variability are found on the protein surface, possibly owing to flexibility and disorder in the individual structures, differences in the chemical and crystalline environments or the different approaches used by different investigators to model weak or complicated electron-density maps. These findings suggest that care must be taken in interpreting structural details on protein surfaces on the basis of individual X-ray structures, even if atomic resolution data are available. PMID:20445237

  13. Enhancement of the electrical properties of silver nanowire transparent conductive electrodes by atomic layer deposition coating with zinc oxide

    NASA Astrophysics Data System (ADS)

    Pham, Anh-Tuan; Nguyen, Xuan-Quang; Tran, Duc-Huy; Phan, Vu Ngoc; Duong, Thanh-Tung; Nguyen, Duy-Cuong

    2016-08-01

    Transparent conductive electrodes for applications in optoelectronic devices such as solar cells and light-emitting diodes are important components and require low sheet resistance and high transmittance. Herein, we report an enhancement of the electrical properties of silver (Ag) nanowire networks by coating with zinc oxide using the atomic layer deposition technique. A strong decrease in the sheet resistance of Ag nanowires, namely from 20-40 Ω/□ to 7-15 Ω/□, was observed after coating with ZnO. Ag nanowire electrodes coated with 200-cycle ZnO by atomic layer deposition show the best quality, with a sheet resistance of 11 Ω/□ and transmittance of 75%.

  14. Enhancement of the electrical properties of silver nanowire transparent conductive electrodes by atomic layer deposition coating with zinc oxide.

    PubMed

    Pham, Anh-Tuan; Nguyen, Xuan-Quang; Tran, Duc-Huy; Ngoc Phan, Vu; Duong, Thanh-Tung; Nguyen, Duy-Cuong

    2016-08-19

    Transparent conductive electrodes for applications in optoelectronic devices such as solar cells and light-emitting diodes are important components and require low sheet resistance and high transmittance. Herein, we report an enhancement of the electrical properties of silver (Ag) nanowire networks by coating with zinc oxide using the atomic layer deposition technique. A strong decrease in the sheet resistance of Ag nanowires, namely from 20-40 Ω/□ to 7-15 Ω/□, was observed after coating with ZnO. Ag nanowire electrodes coated with 200-cycle ZnO by atomic layer deposition show the best quality, with a sheet resistance of 11 Ω/□ and transmittance of 75%.

  15. Encapsulated nanowires: Boosting electronic transport in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Vasylenko, Andrij; Wynn, Jamie; Medeiros, Paulo V. C.; Morris, Andrew J.; Sloan, Jeremy; Quigley, David

    2017-03-01

    The electrical conductivity of metallic carbon nanotubes (CNTs) quickly saturates with respect to bias voltage due to scattering from a large population of optical phonons. The decay of these dominant scatterers in pristine CNTs is too slow to offset an increased generation rate at high voltage bias. We demonstrate from first principles that encapsulation of one-dimensional atomic chains within a single-walled CNT can enhance the decay of "hot" phonons by providing additional channels for thermalization. Pacification of the phonon population growth reduces the electrical resistivity of metallic CNTs by 51% for an example system with encapsulated beryllium.

  16. Silver-filled single-walled carbon nanotubes: Atomic and electronic structures from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Li, Weifeng; Zhao, Mingwen; Xia, Yueyuan; He, Tao; Song, Chen; Lin, Xiaohang; Liu, Xiangdong; Mei, Liangmo

    2006-11-01

    We have studied the atomic and electronic structures of silver-filled (n,0) single-walled carbon nanotubes (Ag@SWCNTs) for n=6 , 7, 8, and 10 by using first-principles calculations. We find that silver atoms encapsulated in SWCNTs self-aggregate to form ultrathin nanowires, of which the atomic arrangement depends on the diameter of the SWCNTs as well as the silver content. The electronic structures of the Ag@SWCNTs can be tuned from semiconducting to metallic by controlling the silver content. The hybridization of electronic states and the charge transfer between the encapsulated silver nanowires (AgNWs) and the SWCNTs are also addressed by performing Milliken population analysis combined with the projected density of states.

  17. Texturing Carbon-carbon Composite Radiator Surfaces Utilizing Atomic Oxygen

    NASA Technical Reports Server (NTRS)

    Raack, Taylor

    2004-01-01

    Future space nuclear power systems will require radiator technology to dissipate excess heat created by a nuclear reactor. Large radiator fins with circulating coolant are in development for this purpose and an investigation of how to make them most efficient is underway. Maximizing the surface area while minimizing the mass of such radiator fins is critical for obtaining the highest efficiency in dissipating heat. Processes to develop surface roughness are under investigation to maximize the effective surface area of a radiator fin. Surface roughness is created through several methods including oxidation and texturing. The effects of atomic oxygen impingement on carbon-carbon surfaces are currently being investigated for texturing a radiator surface. Early studies of atomic oxygen impingement in low Earth orbit indicate significant texturing due to ram atomic oxygen. The surface morphology of the affected surfaces shows many microscopic cones and valleys which have been experimentally shown to increase radiation emittance. Further study of this morphology proceeded in the Long Duration Exposure Facility (LDEF). Atomic oxygen experiments on the LDEF successfully duplicated the results obtained from materials in spaceflight by subjecting samples to 4.5 eV atomic oxygen from a fixed ram angle. These experiments replicated the conical valley morphology that was seen on samples subjected to low Earth orbit.

  18. Template-directed atomically precise self-organization of perfectly ordered parallel cerium silicide nanowire arrays on Si(110)-16 × 2 surfaces

    PubMed Central

    2013-01-01

    The perfectly ordered parallel arrays of periodic Ce silicide nanowires can self-organize with atomic precision on single-domain Si(110)-16 × 2 surfaces. The growth evolution of self-ordered parallel Ce silicide nanowire arrays is investigated over a broad range of Ce coverages on single-domain Si(110)-16 × 2 surfaces by scanning tunneling microscopy (STM). Three different types of well-ordered parallel arrays, consisting of uniformly spaced and atomically identical Ce silicide nanowires, are self-organized through the heteroepitaxial growth of Ce silicides on a long-range grating-like 16 × 2 reconstruction at the deposition of various Ce coverages. Each atomically precise Ce silicide nanowire consists of a bundle of chains and rows with different atomic structures. The atomic-resolution dual-polarity STM images reveal that the interchain coupling leads to the formation of the registry-aligned chain bundles within individual Ce silicide nanowire. The nanowire width and the interchain coupling can be adjusted systematically by varying the Ce coverage on a Si(110) surface. This natural template-directed self-organization of perfectly regular parallel nanowire arrays allows for the precise control of the feature size and positions within ±0.2 nm over a large area. Thus, it is a promising route to produce parallel nanowire arrays in a straightforward, low-cost, high-throughput process. PMID:24188092

  19. "Drawing with nanotubes": creating nanowires with complex geometries by pulsed electrodeposition on self-organized carbon nanotube patterns.

    PubMed

    Yarden, Tohar S; Joselevich, Ernesto

    2010-11-10

    We present a new approach for the creation of nanowires with well-defined complex geometries by electrodeposition onto self-organized single-walled carbon nanotubes. The concept is demonstrated by generation of continuous Au nanowires with various geometries, including parallel arrays, serpentines, and coils. The generality of this approach is further illustrated by synthesizing Bi(2)Te(3) nanowires. Our concept of "drawing with nanotubes" offers to combine different material properties with complex geometries on the route to new functional nanosystems.

  20. Silver nanowire catalysts on carbon nanotubes-incorporated bacterial cellulose membrane electrodes for oxygen reduction reaction.

    PubMed

    Kim, Bona; Choi, Youngeun; Cho, Se Youn; Yun, Young Soo; Jin, Hyoung-Joon

    2013-11-01

    Silver nanowires have unique electrical, thermal and optical properties, which support their potential application in numerous fields including catalysis, electronics, optoelectronics, sensing, and surface-enhanced spectroscopy. Especially, their application such as catalysts for alkaline fuel cells (AFCs) have attracted much interest because of their superior electrical conductivity over that of any metal and their lower cost compared to Pt. In this study, multiwalled carbon nanotubes (MWCNTs)-incorporated bacterial cellulose (BC) membrane electrode with silver nanowire catalyst was prepared. First, acid-treated MWCNTs were incorporated into BC membranes and then freeze-dried after solvent exchange to tert-butanol in order to maintain the 3D-network macroporous structure. Second, silver nanowires synthesized by polyol process were introduced onto the surface of the MWCNTs-incorporated BC membrane through easy vacuum filtration. Finally, thermal treatment was carried out to confirm the effect of the PVP on the silver nanowire catalysts toward oxygen reduction reaction. The electrode with thermally treated silver nanowire had great electrocatalytic activity compared with non-treated one. These results suggest that the MWCNTs-incorporated BC electrode with silver nanowire catalysts after thermal treatment could be potentially used in cathodes of AFCs.

  1. Carbon-assisted growth and high visible-light optical reflectivity of amorphous silicon oxynitride nanowires

    PubMed Central

    2011-01-01

    Large amounts of amorphous silicon oxynitride nanowires have been synthesized on silicon wafer through carbon-assisted vapor-solid growth avoiding the contamination from metallic catalysts. These nanowires have the length of up to 100 μm, with a diameter ranging from 50 to 150 nm. Around 3-nm-sized nanostructures are observed to be homogeneously distributed within a nanowire cross-section matrix. The unique configuration might determine the growth of ternary amorphous structure and its special splitting behavior. Optical properties of the nanowires have also been investigated. The obtained nanowires were attractive for their exceptional whiteness, perceived brightness, and optical brilliance. These nanowires display greatly enhanced reflection over the whole visible wavelength, with more than 80% of light reflected on most of the wavelength ranging from 400 to 700 nm and the lowest reflectivity exceeding 70%, exhibiting performance superior to that of the reported white beetle. Intense visible photoluminescence is also observed over a broad spectrum ranging from 320 to 500 nm with two shoulders centered at around 444 and 468 nm, respectively. PMID:21787429

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

    PubMed

    Rana, Sravendra; Cho, Jae Whan

    2011-07-08

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

  3. Growth of InN Nanowires with Uniform Diameter on Si(111) Substrates: Competition Between Migration and Desorption of In Atoms.

    PubMed

    Gao, Fangliang; Wen, Lei; Xu, Zhenzhu; Han, Jinglei; Yu, Yuefeng; Zhang, Shuguang; Li, Guoqiang

    2017-04-06

    The effects of the growth parameters on the uniformity and the aspect ratio of InN nanowires grown on Si(111) substrates have been studied systematically, and a modified quasi-equilibrium model is proposed. The growth temperature is of great importance for both the nucleation of the nanowires and the migration of In and N atoms, thus affecting the uniformity of the InN nanowires. In order to improve the uniformity of the InN nanowires, both traditional substrate nitridation and pre-In-droplet deposition have been implemented. It is found that the substrate nitridation is favorable for the nucleation of InN nanowires. However, the initial In atoms adhered to the substrate are insufficient to sustain the uniform growth of the InN nanowires. We have found that the initial In droplet on the substrate is not only advantageous for the nucleation of the InN nanowire, but also favorable for the In atom equilibrium between the initial In droplets and the direct In flux. Therefore, InN nanowires with a uniform aspect ratio and optimal diameter can be achieved. The results reported herein provide meaningful insights to understanding the growth kinetics during the InN nanowires growth, and open up great possibilities of developing high-performance group III-nitride-based devices.

  4. Atomic Layer Deposited Coatings on Nanowires for High Temperature Water Corrosion Protection.

    PubMed

    Yersak, Alexander S; Lewis, Ryan J; Liew, Li-Anne; Wen, Rongfu; Yang, Ronggui; Lee, Yung-Cheng

    2016-11-30

    Two-phase liquid-cooling technologies incorporating micro/nanostructured copper or silicon surfaces have been established as a promising thermal management solution to keep up with the increasing power demands of high power electronics. However, the reliability of nanometer-scale features of copper and silicon in these devices has not been well investigated. In this work, accelerated corrosion testing reveals that copper nanowires are not immune to corrosion in deaerated pure hot water. To solve this problem, we investigate atomic layer deposition (ALD) TiO2 coatings grown at 150 and 175 °C. We measured no difference in coating thickness for a duration of 12 days. Using a core/shell approach, we grow ALD TiO2/Al2O3 protective coatings on copper nanowires and demonstrate a preservation of nanoengineered copper features. These studies have identified a critical reliability problem of nanoscale copper and silicon surfaces in deaerated, pure, hot water and have successfully demonstrated a reliable solution using ALD TiO2/Al2O3 protective coatings.

  5. Functionalization of Carbon Nanotubes using Atomic Hydrogen

    NASA Technical Reports Server (NTRS)

    Khare, Bishun N.; Cassell, Alan M.; Nguyen, Cattien V.; Meyyappan, M.; Han, Jie; Arnold, Jim (Technical Monitor)

    2001-01-01

    We have investigated the irradiation of multi walled and single walled carbon nanotubes (SWNTs) with atomic hydrogen. After irradiating the SWNT sample, a band at 2940/cm (3.4 microns) that is characteristic of the C-H stretching mode is observed using Fourier transform infrared (FTIR) spectroscopy. Additional confirmation of SWNT functionalization is tested by irradiating with atomic deuterium. A weak band in the region 1940/cm (5.2 micron) to 2450/cm (4.1 micron) corresponding to C-D stretching mode is also observed in the FTIR spectrum. This technique provides a clean gas phase process for the functionalization of SWNTs, which could lead to further chemical manipulation and/or the tuning of the electronic properties of SWNTs for nanodevice applications.

  6. Complementary response of In2O3 nanowires and carbon nanotubes to low-density lipoprotein chemical gating

    NASA Astrophysics Data System (ADS)

    Tang, Tao; Liu, Xiaolei; Li, Chao; Lei, Bo; Zhang, Daihua; Rouhanizadeh, Mahsa; Hsiai, Tzung; Zhou, Chongwu

    2005-03-01

    In2O3 nanowire and carbon nanotube transistors were used to study the chemical gating effect of low-density lipoproteins (LDL). The adsorption of LDL on these two different surfaces was investigated, which revealed a tenfold more LDL particle adsorption on carbon nanotubes than on In2O3 nanowires because of hydrophobic/hydrophilic interactions. The conductance of field-effect transistors based on nanowires and nanotubes showed complementary response after the adsorption of LDL: while In2O3 nanowire transistors exhibited higher conductance accompanied by a negative shift of the threshold voltage, the nanotube transistors showed lower conductance after the exposure. This is attributed to the complementary doping type of In2O3 nanowires (n type) and carbon nanotubes (p type).

  7. Manganese oxide nanowires wrapped with nitrogen doped carbon layers for high performance supercapacitors.

    PubMed

    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.

  8. Atomic layer deposition of platinum catalysts on nanowire surfaces for photoelectrochemical water reduction.

    PubMed

    Dasgupta, Neil P; Liu, Chong; Andrews, Sean; Prinz, Fritz B; Yang, Peidong

    2013-09-04

    The photocathodic hydrogen evolution reaction (HER) from p-type Si nanowire (NW) arrays was evaluated using platinum deposited by atomic layer deposition (ALD) as a HER cocatalyst. ALD of Pt on the NW surface led to a highly conformal coating of nanoparticles with sizes ranging from 0.5 to 3 nm, allowing for precise control of the Pt loading in deep submonolayer quantities. The catalytic performance was measured using as little as 1 cycle of Pt ALD, which corresponded to a surface mass loading of ∼10 ng/cm(2). The quantitative exploration of the lower limits of Pt cocatalyst loading reported here, and its application to high-surface-area NW photoelectrodes, establish a general approach for minimizing the cost of precious-metal cocatalysts for efficient and affordable solar-to-fuel applications.

  9. Electric-field-dependent charge delocalization from dopant atoms in silicon junctionless nanowire transistor

    NASA Astrophysics Data System (ADS)

    Wang, Hao; Han, Wei-Hua; Zhao, Xiao-Song; Zhang, Wang; Lyu, Qi-Feng; Ma, Liu-Hong; Yang, Fu-Hua

    2016-10-01

    We study electric-field-dependent charge delocalization from dopant atoms in a silicon junctionless nanowire transistor by low-temperature electron transport measurement. The Arrhenius plot of the temperature-dependent conductance demonstrates the transport behaviors of variable-range hopping (below 30 K) and nearest-neighbor hopping (above 30 K). The activation energy for the charge delocalization gradually decreases due to the confinement potential of the conduction channel decreasing from the threshold voltage to the flatband voltage. With the increase of the source-drain bias, the activation energy increases in a temperature range from 30 K to 100 K at a fixed gate voltage, but decreases above the temperature of 100 K. Project supported partly by the National Key R & D Program of China (Grant No. 2016YFA02005003) and the National Natural Science Foundation of China (Grant Nos. 61376096 and 61327813).

  10. Sulfur Nanowires

    NASA Astrophysics Data System (ADS)

    Carvajal, Eliel; Santiago, Patricia; Escudero, Roberto; Mendoza, Doroteo

    2000-03-01

    We have synthetized sulfur nanowires by a template approach using nanoporous anodic alumina. High resolution electron microscopy shows that isolated sulfur nanowires (15 nanometers of diameter) present crystalline structure different to that observed in the stable bulk allotrope (orthorhombic alfa-sulfur). Melting behavior of the sulfur nanowires embedded into the nanoporous alumina matrix was studied by differential scanning calorimetry, showing again very different behavior of the nanowires compared to that of the bulk sulfur. On the other hand, in order to study the bonding configuration of the sulfur atoms in the nanowires, we will present infrared spectroscopy characterization of the nanowires confined into the nanoporous alumina. Finally, on the base of the experimental observations, we will present a structural model for the sulfur nanowires.

  11. Electrowetting properties of atomic layer deposited Al{sub 2}O{sub 3} decorated silicon nanowires

    SciTech Connect

    Rajkumar, K.; Rajavel, K.; Cameron, D. C.; Mangalaraj, D.; Rajendrakumar, R. T.

    2015-06-24

    This paper reports the electrowetting properties of liquid droplet on superhydrophobic silicon nanowires with Atomic layer deposited (ALD) Al{sub 2}O{sub 3} as dielectric layer. Silicon wafer were etched by metal assisted wet chemical etching with silver as catalyst. ALD Al{sub 2}O{sub 3} films of 10nm thickness were conformally deposited over silicon nanowires. Al{sub 2}O{sub 3} dielectric film coated silicon nanowires was chemically modified with Trichloro (1H, 1H, 2H, 2H-perfluorooctyl) silane to make it superhydrophobic(SHP). The contact angle was measured and all the samples exhibited superhydrophobic nature with maximum contact angles of 163° and a minimum contact angle hysteresis of 6°. Electrowetting induced a maximum reversible decrease of the contact angle of 20°at 150V in air.

  12. Single nanowire electrode electrochemistry of silicon anode by in situ atomic force microscopy: solid electrolyte interphase growth and mechanical properties.

    PubMed

    Liu, Xing-Rui; Deng, Xin; Liu, Ran-Ran; Yan, Hui-Juan; Guo, Yu-Guo; Wang, Dong; Wan, Li-Jun

    2014-11-26

    Silicon nanowires (SiNWs) have attracted great attention as promising anode materials for lithium ion batteries (LIBs) on account of their high capacity and improved cyclability compared with bulk silicon. The interface behavior, especially the solid electrolyte interphase (SEI), plays a significant role in the performance and stability of the electrodes. We report herein an in situ single nanowire atomic force microscopy (AFM) method to investigate the interface electrochemistry of silicon nanowire (SiNW) electrode. The morphology and Young's modulus of the individual SiNW anode surface during the SEI growth were quantitatively tracked. Three distinct stages of the SEI formation on the SiNW anode were observed. On the basis of the potential-dependent morphology and Young's modulus evolution of SEI, a mixture-packing structural model was proposed for the SEI film on SiNW anode.

  13. Controlled synthesis of cadmium carbonate nanowires, nanoribbons, nanorings and sphere like architectures via hydrothermal method

    SciTech Connect

    Ashoka, S.; Nagaraju, G.; Thipperudraiah, K.V.; Chandrappa, G.T.

    2010-11-15

    Crystalline nanowires, nanoribbons, nanorings and sphere like architectures of cadmium carbonate have been synthesized with the spontaneous self-assembly of nanocrystals in aqueous solution under hydrothermal condition. The powder X-ray diffraction (PXRD) patterns of these materials exhibit phase pure hexagonal structure. The perfect circular nanorings with radius 375-437 nm, as a new member of nanostructured cadmium carbonate family are being reported for the first time. The width of the cadmium carbonate nanowires/nanoribbons and nanorings, respectively are found to be in the range 11-30 and 26-50 nm as observed by transmission electron microscope (TEM). The effect of temperature and concentration of urea on the cadmium carbonate morphology is discussed. The plausible growth mechanism for the formation of nanorings is also proposed.

  14. Thermal and quantum phase slips in niobium-nitride nanowires based on suspended carbon nanotubes

    SciTech Connect

    Masuda, Kohei; Takagi, Tasuku; Hashimoto, Takayuki; Moriyama, Satoshi Komatsu, Katsuyoshi; Morita, Yoshifumi; Miki, Norihisa; Tanabe, Takasumi; Maki, Hideyuki

    2016-05-30

    Superconducting nanowires have attracted considerable attention due to their unique quantum-mechanical properties, as well as their potential as next-generation quantum nanodevices, such as single-photon detectors, phase-slip (PS) qubits, and other hybrid structures. In this study, we present the results of one-dimensional (1D) superconductivity in nanowires fabricated by coating suspended carbon nanotubes with a superconducting thin niobium nitride (NbN) film. In the resistance-temperature characteristic curves, hallmarks of 1D superconductivity with PS events are observed with unconventional negative magnetoresistance. We also confirm that a crossover occurs between thermal and quantum PSs as the temperature is lowered.

  15. Comparison of effects on crustaceans: carbon nanoparticles and molybdenum compounds nanowires

    NASA Astrophysics Data System (ADS)

    Baumerte, A.; Sakale, G.; Zavickis, J.; Putna, I.; Balode, M.; Mrzel, A.; Knite, M.

    2013-04-01

    Carbon nanomaterials (CNM) and molybdenum compound nanostructures are materials with various applications yet little is known regarding the toxicity of these nanoparticles in pristine form in aquatic environment. Daphnia magna standard acute toxicity test (EN ISO 6341:1996; freshwater) and Artemia salina standard acute toxicity test (ArtoxKit standard method; 15 ppt saltwater) were applied to assess the toxicity of non-modified CNM and molybdenum compound nanowires in water. It has been observed that CNM are more toxic in freshwater suspensions and somewhat more toxic than the tested molybdenum compound nanowires.

  16. Hierarchical ZnO Nanowire Growth with Tunable Orientations on Versatile Substrates Using Atomic Layer Deposition Seeding

    SciTech Connect

    Bielinski, Ashley R.; Kazyak, Eric; Schleputz, Christian M.; Jung, Hee Joon; Wood, Kevin N.; Dasgupta, Neil P.

    2015-07-14

    The ability to synthesize semiconductor nanowires with deterministic and tunable control of orientation and morphology on a wide range of substrates, while high precision and repeatability are maintained, is a challenge currently faced for the development of many nanoscale material systems. Here we show that atomic layer deposition (ALD) presents a reliable method of surface and interfacial modification to guide nanowire orientation on a variety of substrate materials and geometries, including high-aspect-ratio, three-dimensional templates. We demonstrate control of the orientation and geometric properties of hydrothermally grown single crystalline ZnO nanowires via the deposition of a ZnO seed layer by ALD. The crystallographic texture and roughness of the seed layer result in tunable preferred nanowire orientations and densities for identical hydrothermal growth conditions. The structural and chemical relationship between the ALD layers and nanowires was investigated with synchrotron X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy to elucidate the underlying mechanisms of orientation and morphology control. The resulting control parameters were utilized to produce hierarchical nanostructures with tunable properties on a wide range of substrates, including vertical micropillars, paper fibers, porous polymer membranes, and biological substrates. This illustrates the power of ALD for interfacial engineering of heterogeneous material systems at the nanoscale, to provide a highly controlled and scalable seeding method for bottom-up synthesis of integrated nanosystems.

  17. Dissolution-Induced Nanowire Synthesis on Hot-Dip Galvanized Surface in Supercritical Carbon Dioxide.

    PubMed

    Kaleva, Aaretti; Saarimaa, Ville; Heinonen, Saara; Nikkanen, Juha-Pekka; Markkula, Antti; Väisänen, Pasi; Levänen, Erkki

    2017-07-11

    In this study, we demonstrate a rapid treatment method for producing a needle-like nanowire structure on a hot-dip galvanized sheet at a temperature of 50 °C. The processing method involved only supercritical carbon dioxide and water to induce a reaction on the zinc surface, which resulted in growth of zinc hydroxycarbonate nanowires into flower-like shapes. This artificial patina nanostructure predicts high surface area and offers interesting opportunities for its use in industrial high-end applications. The nanowires can significantly improve paint adhesion and promote electrochemical stability for organic coatings, or be converted to ZnO nanostructures by calcining to be used in various semiconductor applications.

  18. Dissolution-Induced Nanowire Synthesis on Hot-Dip Galvanized Surface in Supercritical Carbon Dioxide

    PubMed Central

    Saarimaa, Ville; Heinonen, Saara; Nikkanen, Juha-Pekka; Markkula, Antti; Väisänen, Pasi; Levänen, Erkki

    2017-01-01

    In this study, we demonstrate a rapid treatment method for producing a needle-like nanowire structure on a hot-dip galvanized sheet at a temperature of 50 °C. The processing method involved only supercritical carbon dioxide and water to induce a reaction on the zinc surface, which resulted in growth of zinc hydroxycarbonate nanowires into flower-like shapes. This artificial patina nanostructure predicts high surface area and offers interesting opportunities for its use in industrial high-end applications. The nanowires can significantly improve paint adhesion and promote electrochemical stability for organic coatings, or be converted to ZnO nanostructures by calcining to be used in various semiconductor applications. PMID:28696374

  19. The peeling behavior of nanowires and carbon nanotubes from a substrate using continuum modeling

    NASA Astrophysics Data System (ADS)

    Li, Yue; Xiong, Yan; Zhou, Zhikang; Tang, Bingxian; Yang, Zhaoyao; Zhao, Junhua

    2017-02-01

    The peeling behavior of different nanowires or single-walled/multi-walled carbon nanotubes (CNTs) from a substrate is studied by using the Kendall model of the continuum mechanics, where a basic assumption is that the deformation of the part of the nanowire/nanotube attached to the substrate under peeling force is ignored. The cohesive energy between a nanowire (or a CNT) and a substrate is obtained through continuum modeling of the van der Waals interaction, which has high accuracy by comparison of our molecular dynamics simulations. Our analytical results show that the peeling behavior strongly depends on the peeling angle, the pre-tension, the separation distance toward the substrate, the radius, and the Young's modulus of the nanowire (or the CNT). In particular, the peeling forces with a generalized peeling model in the steady-state stage are compared with those of the classical Kendall model. In the generalized peeling model, the effect of the bending stiffness and cohesive energy between the bending nanowire and the substrate on peeling forces is considered. The obtained analytical solution should be of great help for understanding the interaction between the nanostructures and the substrates, and designing nanoelectromechanical systems.

  20. Effect of Elastic Strain Fluctuation on Atomic Layer Growth of Epitaxial Silicide in Si Nanowires by Point Contact Reactions.

    PubMed

    Chou, Yi-Chia; Tang, Wei; Chiou, Chien-Jyun; Chen, Kai; Minor, Andrew M; Tu, K N

    2015-06-10

    Effects of strain impact a range of applications involving mobility change in field-effect-transistors. We report the effect of strain fluctuation on epitaxial growth of NiSi2 in a Si nanowire via point contact and atomic layer reactions, and we discuss the thermodynamic, kinetic, and mechanical implications. The generation and relaxation of strain shown by in situ TEM is periodic and in synchronization with the atomic layer reaction. The Si lattice at the epitaxial interface is under tensile strain, which enables a high solubility of supersaturated interstitial Ni atoms for homogeneous nucleation of an epitaxial atomic layer of the disilicide phase. The tensile strain is reduced locally during the incubation period of nucleation by the dissolution of supersaturated Ni atoms in the Si lattice but the strained-Si state returns once the atomic layer epitaxial growth of NiSi2 occurs by consuming the supersaturated Ni.

  1. High throughput nanofabrication of silicon nanowire and carbon nanotube tips on AFM probes by stencil-deposited catalysts.

    PubMed

    Engstrom, Daniel S; Savu, Veronica; Zhu, Xueni; Bu, Ian Y Y; Milne, William I; Brugger, Juergen; Boggild, Peter

    2011-04-13

    A new and versatile technique for the wafer scale nanofabrication of silicon nanowire (SiNW) and multiwalled carbon nanotube (MWNT) tips on atomic force microscope (AFM) probes is presented. Catalyst material for the SiNW and MWNT growth was deposited on prefabricated AFM probes using aligned wafer scale nanostencil lithography. Individual vertical SiNWs were grown epitaxially by a catalytic vapor-liquid-solid (VLS) process and MWNTs were grown by a plasma-enhanced chemical vapor (PECVD) process on the AFM probes. The AFM probes were tested for imaging micrometers-deep trenches, where they demonstrated a significantly better performance than commercial high aspect ratio tips. Our method demonstrates a reliable and cost-efficient route toward wafer scale manufacturing of SiNW and MWNT AFM probes.

  2. Nanowire-templated formation of SnO2/carbon nanotubes with enhanced lithium storage properties.

    PubMed

    Zhou, Xiaosi; Yu, Le; Lou, Xiong Wen David

    2016-04-21

    In this work, we have designed and synthesized SnO2 nanotubes wrapped by a porous carbon layer via a multistep method. Single-crystalline MnO(x) nanowires are employed as the template. SnO2 is grown on MnO(x) nanowires by a simple hydrothermal method to generate MnO(x)/SnO2 core-shell nanocables, followed by further coating with a layer of polydopamine. After carbonization of polydopamine and selective removal of MnO(x) nanowires, carbon coated SnO2 nanotubes are obtained. This structure combines several advantages. First, the internal empty space of the tubular structure can buffer the huge volume variation during lithium insertion-extraction processes properly, leading to improved cycling performance. Second, the nanosized SnO2 subunits and porous carbon coating not only shorten the distance for lithium ion diffusion but also offer large electrode-electrolyte contact area for fast Li(+) crossing the interface, thus enabling improved rate capability. Third, the flexible carbon coating is closely covered onto the SnO2 nanocrystals, which could facilitate the electronic transport and also significantly mitigate the pulverization. As a result, the as-synthesized SnO2/C-NT nanocomposites exhibit a high reversible capacity of 596 mA h g(-1) after 200 cycles, as well as an outstanding rate capability.

  3. Atomic Carbon in the Southern Milky Way

    NASA Astrophysics Data System (ADS)

    Oka, Tomoharu; Kamegai, Kazuhisa; Hayashida, Masaaki; Nagai, Makoto; Ikeda, Masafumi; Kuboi, Nobuyuki; Tanaka, Kunihiko; Bronfman, Leonardo; Yamamoto, Satoshi

    2005-04-01

    We present a coarsely sampled longitude-velocity (l-V) map of the region l=300deg-354°, b=0deg in the 492 GHz fine-structure transition of neutral atomic carbon (C0 3P1-3P0 [C I]), observed with the Portable 18 cm Submillimeter-wave Telescope (POST18). The l-V distribution of the [C I] emission resembles closely that of the CO J=1-0 emission, showing a widespread distribution of atomic carbon on the Galactic scale. The ratio of the antenna temperatures, RCI/CO, concentrates on the narrow range from 0.05 to 0.3. A large velocity gradient (LVG) analysis shows that the [C I] emission from the Galactic disk is dominated by a population of neutral gas with high C0/CO abundance ratios and moderate column densities, which can be categorized as diffuse translucent clouds. The ratio of bulk emissivity, JCI/JCO, shows a systematic trend, suggesting the bulk C0/CO abundance ratio increasing with the Galactic radius. A mechanism related to kiloparsec-scale structure of the Galaxy may control the bulk C0/CO abundance ratio in the Galactic disk. Two groups of high-ratio (RCI/CO>0.3) areas reside in the l-V loci several degrees inside of tangential points of the Galactic spiral arms. These could be gas condensations just accumulated in the potential well of spiral arms and be in the early stages of molecular cloud formation.

  4. The influence of covering a germanium nanowire with a single wall carbon nanotube on mechanical properties: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Abdollahi, M.; Davoodi, J.

    2017-07-01

    Semiconductor nanowires are potential candidates for applications in quantum information processing, Josephson junctions, and field-effect transistors. Therefore, this study focused on the effects of covering a germanium nanowire (GeNW) with a single wall carbon nanotube (CNT) on the stress-strain diagram, failure points, and Young's modulus using molecular dynamics simulations. To describe the interactions between atoms in the system, we used Tersoff potential. Also, a Nose-Hoover thermostat was employed to control temperature of the system. The stress-strain curves of GeNW and GeNW inside CNT (CNT-GeNW) were obtained at various temperatures, radii, and strain velocities. It was found that coverage of GeNW with CNT led to 2-6 fold improved Young's modulus. It was also determined that a significant part of the Young's modulus in CNT-GeNW is due to the presence of CNT. Moreover, we defined the behavior of Young's modulus of GeNW as well as CNT-GeNW in the [100], [110], and [111] crystallography direction and found that Young's modulus decreased with increasing temperature. In addition, by increasing strain velocity, Young's modulus decreased for GeNW but increased for CNT-GeNW. Finally, we observed that when a GeNW is covered by a CNT, its failure point increased as compared with GeNW.

  5. Atomic-scale observation of parallel development of super elasticity and reversible plasticity in GaAs nanowires

    SciTech Connect

    Bao, Peite; Du, Sichao; Zheng, Rongkun; Wang, Yanbo; Liao, Xiaozhou; Cui, Xiangyuan; Yen, Hung-Wei; Kong Yeoh, Wai; Ringer, Simon P.; Gao, Qiang; Hoe Tan, H.; Jagadish, Chennupati; Liu, Hongwei; Zou, Jin

    2014-01-13

    We report the atomic-scale observation of parallel development of super elasticity and reversible dislocation-based plasticity from an early stage of bending deformation until fracture in GaAs nanowires. While this phenomenon is in sharp contrast to the textbook knowledge, it is expected to occur widely in nanostructures. This work indicates that the super recoverable deformation in nanomaterials is not simple elastic or reversible plastic deformation in nature, but the coupling of both.

  6. Chains of carbon atoms: A vision or a new nanomaterial?

    PubMed

    Banhart, Florian

    2015-01-01

    Linear strings of sp(1)-hybridized carbon atoms are considered as a possible phase of carbon since decades. Whereas the debate about the stability of the corresponding bulk phase carbyne continues until today, the existence of isolated chains of carbon atoms has meanwhile been corroborated experimentally. Since graphene, as the two-dimensional sp(2)-bonded allotrope of carbon, has become a vast field, the question about the importance of one-dimensional carbon became of renewed interest. The present article gives an overview of the work that has been carried out on chains of carbon atoms in the past one or two decades. The review concentrates on isolated chains of carbon atoms and summarizes the experimental observations to date. While the experimental information is still very limited, many calculations of the physical and chemical properties have been published in the past years. Some of the most important theoretical studies and their importance in the present experimental situation are reviewed.

  7. Chains of carbon atoms: A vision or a new nanomaterial?

    PubMed Central

    2015-01-01

    Summary Linear strings of sp1-hybridized carbon atoms are considered as a possible phase of carbon since decades. Whereas the debate about the stability of the corresponding bulk phase carbyne continues until today, the existence of isolated chains of carbon atoms has meanwhile been corroborated experimentally. Since graphene, as the two-dimensional sp2-bonded allotrope of carbon, has become a vast field, the question about the importance of one-dimensional carbon became of renewed interest. The present article gives an overview of the work that has been carried out on chains of carbon atoms in the past one or two decades. The review concentrates on isolated chains of carbon atoms and summarizes the experimental observations to date. While the experimental information is still very limited, many calculations of the physical and chemical properties have been published in the past years. Some of the most important theoretical studies and their importance in the present experimental situation are reviewed. PMID:25821697

  8. Structurally uniform and atomically precise carbon nanostructures

    NASA Astrophysics Data System (ADS)

    Segawa, Yasutomo; Ito, Hideto; Itami, Kenichiro

    2016-01-01

    Nanometre-sized carbon materials consisting of benzene units oriented in unique geometric patterns, hereafter named nanocarbons, conduct electricity, absorb and emit light, and exhibit interesting magnetic properties. Spherical fullerene C60, cylindrical carbon nanotubes and sheet-like graphene are representative forms of nanocarbons, and theoretical simulations have predicted several exotic 3D nanocarbon structures. At present, synthetic routes to nanocarbons mainly lead to mixtures of molecules with a range of different structures and properties, which cannot be easily separated or refined into pure forms. Some researchers believe that it is impossible to synthesize these materials in a precise manner. Obtaining ‘pure’ nanocarbons is a great challenge in the field of nanocarbon science, and the construction of structurally uniform nanocarbons, ideally as single molecules, is crucial for the development of functional materials in nanotechnology, electronics, optics and biomedical applications. This Review highlights the organic chemistry approach — more specifically, bottom-up construction with atomic precision — that is currently the most promising strategy towards this end.

  9. Carbon based thirty six atom spheres

    DOEpatents

    Piskoti, Charles R.; Zettl, Alex K.; Cohen, Marvin L.; Cote, Michel; Grossman, Jeffrey C.; Louie, Steven G.

    2005-09-06

    A solid phase or form of carbon is based on fullerenes with thirty six carbon atoms (C.sub.36). The C.sub.36 structure with D.sub.6h symmetry is one of the two most energetically favorable, and is conducive to forming a periodic system. The lowest energy crystal is a highly bonded network of hexagonal planes of C.sub.36 subunits with AB stacking. The C.sub.36 solid is not a purely van der Waals solid, but has covalent-like bonding, leading to a solid with enhanced structural rigidity. The solid C.sub.36 material is made by synthesizing and selecting out C.sub.36 fullerenes in relatively large quantities. A C.sub.36 rich fullerene soot is produced in a helium environment arc discharge chamber by operating at an optimum helium pressure (400 torr). The C.sub.36 is separated from the soot by a two step process. The soot is first treated with a first solvent, e.g. toluene, to remove the higher order fullerenes but leave the C.sub.36. The soot is then treated with a second solvent, e.g. pyridine, which is more polarizable than the first solvent used for the larger fullerenes. The second solvent extracts the C.sub.36 from the soot. Thin films and powders can then be produced from the extracted C.sub.36. Other materials are based on C.sub.36 fullerenes, providing for different properties.

  10. Carbon nanotube-clamped metal atomic chain

    PubMed Central

    Tang, Dai-Ming; Yin, Li-Chang; Li, Feng; Liu, Chang; Yu, Wan-Jing; Hou, Peng-Xiang; Wu, Bo; Lee, Young-Hee; Ma, Xiu-Liang; Cheng, Hui-Ming

    2010-01-01

    Metal atomic chain (MAC) is an ultimate one-dimensional structure with unique physical properties, such as quantized conductance, colossal magnetic anisotropy, and quantized magnetoresistance. Therefore, MACs show great potential as possible components of nanoscale electronic and spintronic devices. However, MACs are usually suspended between two macroscale metallic electrodes; hence obvious technical barriers exist in the interconnection and integration of MACs. Here we report a carbon nanotube (CNT)-clamped MAC, where CNTs play the roles of both nanoconnector and electrodes. This nanostructure is prepared by in situ machining a metal-filled CNT, including peeling off carbon shells by spatially and elementally selective electron beam irradiation and further elongating the exposed metal nanorod. The microstructure and formation process of this CNT-clamped MAC are explored by both transmission electron microscopy observations and theoretical simulations. First-principles calculations indicate that strong covalent bonds are formed between the CNT and MAC. The electrical transport property of the CNT-clamped MAC was experimentally measured, and quantized conductance was observed. PMID:20427743

  11. Atomic Migration Induced Crystal Structure Transformation and Core-Centered Phase Transition in Single Crystal Ge2Sb2Te5 Nanowires.

    PubMed

    Lee, Jun-Young; Kim, Jeong-Hyeon; Jeon, Deok-Jin; Han, Jaehyun; Yeo, Jong-Souk

    2016-10-12

    A phase change nanowire holds a promise for nonvolatile memory applications, but its transition mechanism has remained unclear due to the analytical difficulties at atomic resolution. Here we obtain a deeper understanding on the phase transition of a single crystalline Ge2Sb2Te5 nanowire (GST NW) using atomic scale imaging, diffraction, and chemical analysis. Our cross-sectional analysis has shown that the as-grown hexagonal close-packed structure of the single crystal GST NW transforms to a metastable face-centered cubic structure due to the atomic migration to the pre-existing vacancy layers in the hcp structure going through iterative electrical switching. We call this crystal structure transformation "metastabilization", which is also confirmed by the increase of set-resistance during the switching operation. For the set to reset transition between crystalline and amorphous phases, high-resolution imaging indicates that the longitudinal center of the nanowire mainly undergoes phase transition. According to the atomic scale analysis of the GST NW after repeated electrical switching, partial crystallites are distributed around the core-centered amorphous region of the nanowire where atomic migration is mainly induced, thus potentially leading to low power electrical switching. These results provide a novel understanding of phase change nanowires, and can be applied to enhance the design of nanowire phase change memory devices for improved electrical performance.

  12. Carbon Nanotubes, Semiconductor Nanowires and Graphene for Thin Film Transistor and Circuit Applications

    NASA Astrophysics Data System (ADS)

    Pribat, Didier; Cojocaru, Costel-Sorin

    2011-03-01

    In this paper, we briefly review the use of carbon nanotubes and semiconductor nanowires, which represent a new class of nanomaterials actively studied for thin film transistors and electronics applications. Although these nanomaterials are usually synthesised at moderate to high temperatures, they can be transferred to any kind of substrate after growth, paving the way for the fabrication of flexible displays and large area electronics systems on plastic. Over the past few years, the field has progressed well beyond the realisation of elementary devices, since active matrix displays driven by nanowire thin film transistors have been demonstrated, as well as the fabrication of medium scale integrated circuits based on random arrays of carbon nanotubes. Also, graphene, a new nanomaterial has appeared in the landscape; although it is a zero gap semiconductor, it can still be used to make transistors, provided narrow ribbons or bilayers are used. Graphene is also a serious contender for the replacement of oxide-based transparent conducting films.

  13. High-performance two-ply yarn supercapacitors based on carbon nanotubes and polyaniline nanowire arrays.

    PubMed

    Wang, Kai; Meng, Qinghai; Zhang, Yajie; Wei, Zhixiang; Miao, Menghe

    2013-03-13

    Fine count two-ply yarn supercapacitors are constructed from carbon nanotube yarns and polyaniline nanowires. The thread-like supercapacitor possess excellent electrochemical capacity and are very strong and flexible. When being woven or knitted into wearable electronic devices, alone or in combination with conventional textile yarns, the two-ply yarn supercapacitors can be flexed and stretched repeatedly without significant loss of capacitance.

  14. Charge transport in DNA nanowires connected to carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Tan, Bikan; Hodak, Miroslav; Lu, Wenchang; Bernholc, J.

    2015-08-01

    DNA is perhaps the worlds most controllable nanowire, with potential applications in nanoelectronics and sensing. However, understanding of its charge transport (CT) properties remains elusive, with experiments reporting a wide range of behaviors from insulating to superconductive. We report extensive first-principle simulations that account for DNA's high flexibility and its native solvent environment. The results show that the CT along the DNA's long axis is strongly dependent on DNA's instantaneous conformation varying over many orders of magnitude. In high CT conformations, delocalized conductive states extending over up to 10 base pairs are found. Their low exponential decay constants further indicate that coherent CT, which is assumed to be active only over 2-3 base pairs in the commonly accepted DNA CT models, can act over much longer length scales. We also identify a simple geometrical rule that predicts CT properties of a given conformation with high accuracy. The effect of mismatched base pairs is also considered: while they decrease conductivities of specific DNA conformations, thermally induced conformational fluctuations wash out this effect. Overall, our results indicate that an immobilized partially dried poly(G)-poly(C) B-DNA is preferable for nanowire applications.

  15. Alignment control and atomically-scaled heteroepitaxial interface study of GaN nanowires.

    PubMed

    Liu, Qingyun; Liu, Baodan; Yang, Wenjin; Yang, Bing; Zhang, Xinglai; Labbé, Christophe; Portier, Xavier; An, Vladimir; Jiang, Xin

    2017-04-11

    Well-aligned GaN nanowires are promising candidates for building high-performance optoelectronic nanodevices. In this work, we demonstrate the epitaxial growth of well-aligned GaN nanowires on a [0001]-oriented sapphire substrate in a simple catalyst-assisted chemical vapor deposition process and their alignment control. It is found that the ammonia flux plays a key role in dominating the initial nucleation of GaN nanocrystals and their orientation. Typically, significant improvement of the GaN nanowire alignment can be realized at a low NH3 flow rate. X-ray diffraction and cross-sectional scanning electron microscopy studies further verified the preferential orientation of GaN nanowires along the [0001] direction. The growth mechanism of GaN nanowire arrays is also well studied based on cross-sectional high-resolution transmission electron microscopy (HRTEM) characterization and it is observed that GaN nanowires have good epitaxial growth on the sapphire substrate following the crystallographic relationship between (0001)GaN∥(0001)sapphire and (101[combining macron]0)GaN∥(112[combining macron]0)sapphire. Most importantly, periodic misfit dislocations are also experimentally observed in the interface region due to the large lattice mismatch between the GaN nanowire and the sapphire substrate, and the formation of such dislocations will favor the release of structural strain in GaN nanowires. HRTEM analysis also finds the existence of "type I" stacking faults and voids inside the GaN nanowires. Optical investigation suggests that the GaN nanowire arrays have strong emission in the UV range, suggesting their crystalline nature and chemical purity. The achievement of aligned GaN nanowires will further promote the wide applications of GaN nanostructures toward diverse high-performance optoelectronic nanodevices including nano-LEDs, photovoltaic cells, photodetectors etc.

  16. Improvement of carrier diffusion length in silicon nanowire arrays using atomic layer deposition.

    PubMed

    Kato, Shinya; Kurokawa, Yasuyoshi; Miyajima, Shinsuke; Watanabe, Yuya; Yamada, Akira; Ohta, Yoshimi; Niwa, Yusuke; Hirota, Masaki

    2013-08-23

    To achieve a high-efficiency silicon nanowire (SiNW) solar cell, surface passivation technique is very important because a SiNW array has a large surface area. We successfully prepared by atomic layer deposition (ALD) high-quality aluminum oxide (Al2O3) film for passivation on the whole surface of the SiNW arrays. The minority carrier lifetime of the Al2O3-depositedSiNW arrays with bulk silicon substrate was improved to 27 μs at the optimum annealing condition. To remove the effect of bulk silicon, the effective diffusion length of minority carriers in the SiNW array was estimated by simple equations and a device simulator. As a result, it was revealed that the effective diffusion length in the SiNW arrays increased from 3.25 to 13.5 μm by depositing Al2O3 and post-annealing at 400°C. This improvement of the diffusion length is very important for application to solar cells, and Al2O3 deposited by ALD is a promising passivation material for a structure with high aspect ratio such as SiNW arrays.

  17. Technique for measurement of magnetostriction in an individual nanowire using atomic force microscopy

    SciTech Connect

    Jin Park, Jung Flatau, Alison B.; Estrine, Eliot C.; Madhukar Reddy, Sai; Stadler, Bethanie J. H.

    2014-05-07

    We have investigated a method for measuring the dimensions of an individual multilayered Fe-Ga/Cu nanowire (NW) as it changes with induced magnetization. In this study, we demonstrate the proposed approach and establish this as a viable method for measuring the magnetostrictive behavior of an individual Fe-Ga/Cu NW using atomic force microscopy (AFM). When an external magnetic field (∼300 Oe) was applied perpendicular to the NW axis, the NW length appeared minimized. When a field (∼1000 Oe) was applied parallel to the NW axis, the height profile of the NW was found to be higher than in the case with no parallel external field. Since both ends of the NW were welded to the substrate, the magnetic field induced dimensional change of the NW caused deflection of the NW in the upward direction, which was significant enough to be detected by AFM. An average height difference of 15 nm was measured with and without an applied field which was then used to calculate the magnetostriction of the multilayered NW.

  18. Atomic Scale Surface Structure and Morphology of InAs Nanowire Crystal Superlattices: The Effect of Epitaxial Overgrowth

    PubMed Central

    2015-01-01

    While shell growth engineering to the atomic scale is important for tailoring semiconductor nanowires with superior properties, a precise knowledge of the surface structure and morphology at different stages of this type of overgrowth has been lacking. We present a systematic scanning tunneling microscopy (STM) study of homoepitaxial shell growth of twinned superlattices in zinc blende InAs nanowires that transforms {111}A/B-type facets to the nonpolar {110}-type. STM imaging along the nanowires provides information on different stages of the shell growth revealing distinct differences in growth dynamics of the crystal facets and surface structures not found in the bulk. While growth of a new surface layer is initiated simultaneously (at the twin plane interface) on the {111}A and {111}B nanofacets, the step flow growth proceeds much faster on {111}A compared to {111}B leading to significant differences in roughness. Further, we observe that the atomic scale structures on the {111}B facet is different from its bulk counterpart and that shell growth on this facet occurs via steps perpendicular to the ⟨112⟩B-type directions. PMID:25710727

  19. ATOMIC CARBON IN THE UPPER ATMOSPHERE OF TITAN

    SciTech Connect

    Zhang, X.; Yung, Y. L.; Ajello, J. M.

    2010-01-01

    The atomic carbon emission C I line feature at 1657 A ({sup 3} P {sup 0} {sub J}-{sup 3} P{sub J} ) in the upper atmosphere of Titan is first identified from the airglow spectra obtained by the Cassini Ultra-violet Imaging Spectrograph. A one-dimensional photochemical model of Titan is used to study the photochemistry of atomic carbon on Titan. Reaction between CH and atomic hydrogen is the major source of atomic carbon, and reactions with hydrocarbons (C{sub 2}H{sub 2} and C{sub 2}H{sub 4}) are the most important loss processes. Resonance scattering of sunlight by atomic carbon is the dominant emission mechanism. The emission intensity calculations based on model results show good agreement with the observations.

  20. High-performance solid-state on-chip supercapacitors based on Si nanowires coated with ruthenium oxide via atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Zheng, Wen; Cheng, Qingmei; Wang, Dunwei; Thompson, Carl V.

    2017-02-01

    Solid-state on-chip supercapacitors based on ruthenium oxide coated silicon nanowires were fabricated using a process that is compatible with silicon integrated circuit processing. Ordered arrays of silicon nanowires were fabricated using metal-assisted anodic etching (MAAE). Atomic layer deposition (ALD) was used to form a uniform coating of ruthenium oxide on high-aspect-ratio silicon nanowires at a moderate temperature of 290 °C. Coated nanowire electrodes were studied using cyclic voltammetry and charge-discharge tests in a neutral Na2SO4 electrolyte, and a specific capacitance of 19 mFcm-2 was achieved at 5 mVs-1. Solid state nanowire capacitors were then fabricated with symmetric face to face nanowire arrays separated by a polymer-based electrolyte. This device exhibited a specific capacitance as high as 6.5 mFcm-2 at 2 mVs-1. The full device was tested over 10000 cycles under galvanostatic charge-discharge at 0.4 mAcm-2, and showed a retention of 92% of the specific capacitance. The specific capacitance was found to scale with the total nanowire surface area, as controlled by controlling the aspect ratios of the wires. The solid state nanowire-based device also achieved high specific energies without sacrificing power performance.

  1. N-doped carbon-coated tungsten oxynitride nanowire arrays for highly efficient electrochemical hydrogen evolution.

    PubMed

    Li, Qun; Cui, Wei; Tian, Jingqi; Xing, Zhicai; Liu, Qian; Xing, Wei; Asiri, Abdullah M; Sun, Xuping

    2015-08-10

    It is highly desired but still challenging to develop active nonprecious metal hydrogen evolution reaction (HER) electrocatalysts operating under all pH conditions. Herein, the development of three-dimensional N-doped carbon-coated tungsten oxynitride nanowire arrays on carbon cloth as a highly efficient and durable HER cathode was explored. The material delivers current densities of 10 and 100 mA cm(-2) at overpotentials of 106 and 172 mV, respectively, in acidic medium, and it also performs well in neutral and basic electrolytes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Catalyst-induced growth of carbon nanotubes on tips of cantilevers and nanowires

    DOEpatents

    Lee, James Weifu; Lowndes, Douglas H.; Merkulov, Vladimir I.; Eres, Gyula; Wei, Yayi; Greenbaum, Elias; Lee, Ida

    2004-06-29

    A method is described for catalyst-induced growth of carbon nanotubes, nanofibers, and other nanostructures on the tips of nanowires, cantilevers, conductive micro/nanometer structures, wafers and the like. The method can be used for production of carbon nanotube-anchored cantilevers that can significantly improve the performance of scaning probe microscopy (AFM, EFM etc). The invention can also be used in many other processes of micro and/or nanofabrication with carbon nanotubes/fibers. Key elements of this invention include: (1) Proper selection of a metal catalyst and programmable pulsed electrolytic deposition of the desired specific catalyst precisely at the tip of a substrate, (2) Catalyst-induced growth of carbon nanotubes/fibers at the catalyst-deposited tips, (3) Control of carbon nanotube/fiber growth pattern by manipulation of tip shape and growth conditions, and (4) Automation for mass production.

  3. Nanowire-templated formation of SnO2/carbon nanotubes with enhanced lithium storage properties

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaosi; Yu, Le; Lou, Xiong Wen (David)

    2016-04-01

    In this work, we have designed and synthesized SnO2 nanotubes wrapped by a porous carbon layer via a multistep method. Single-crystalline MnOx nanowires are employed as the template. SnO2 is grown on MnOx nanowires by a simple hydrothermal method to generate MnOx/SnO2 core-shell nanocables, followed by further coating with a layer of polydopamine. After carbonization of polydopamine and selective removal of MnOx nanowires, carbon coated SnO2 nanotubes are obtained. This structure combines several advantages. First, the internal empty space of the tubular structure can buffer the huge volume variation during lithium insertion-extraction processes properly, leading to improved cycling performance. Second, the nanosized SnO2 subunits and porous carbon coating not only shorten the distance for lithium ion diffusion but also offer large electrode-electrolyte contact area for fast Li+ crossing the interface, thus enabling improved rate capability. Third, the flexible carbon coating is closely covered onto the SnO2 nanocrystals, which could facilitate the electronic transport and also significantly mitigate the pulverization. As a result, the as-synthesized SnO2/C-NT nanocomposites exhibit a high reversible capacity of 596 mA h g-1 after 200 cycles, as well as an outstanding rate capability.In this work, we have designed and synthesized SnO2 nanotubes wrapped by a porous carbon layer via a multistep method. Single-crystalline MnOx nanowires are employed as the template. SnO2 is grown on MnOx nanowires by a simple hydrothermal method to generate MnOx/SnO2 core-shell nanocables, followed by further coating with a layer of polydopamine. After carbonization of polydopamine and selective removal of MnOx nanowires, carbon coated SnO2 nanotubes are obtained. This structure combines several advantages. First, the internal empty space of the tubular structure can buffer the huge volume variation during lithium insertion-extraction processes properly, leading to improved cycling

  4. Carbon-in-Al4C3 nanowire superstructures for field emitters.

    PubMed

    Sun, Yong; Cui, Hao; Gong, Li; Chen, Jian; She, Juncong; Ma, Yanming; Shen, Peikang; Wang, Chengxin

    2011-02-22

    As a kind of ionic (or salt-like) carbide, for Al(4)C(3), hardly any active functions have been found except for structure material purposes. However, considering the unique characteristic features of its crystal structure, we think Al(4)C(3) in fact might have huge potential for exhibiting active functionality on field-emission applications. Herein, we report the feasibility to approach such emitters by creating Al(4)C(3)-based nanowire superstructures. The conductive amorphous carbon (a-C) nanolayers are embedded quasi-periodically in Al(4)C(3) nanowire and generate essential electrical contact to the insulating Al(4)C(3). The superstructures acting as cold electron emitters display excellent field emission performance with the turn-on field as low as 0.65-1.3 V/μm and the threshold field down to 2.1-2.6 V/μm. We speculate that the emission characteristics, which are ever better than carbon nanotubes, are attributed to the unique crystal structure of Al(4)C(3) and the enhanced electrons transport in the nanowires due to the existence of a-C nanolayers. Such emitters are technologically useful, because they can be easily fabricated on large substrates, and the synthesis process is simple and broadly applicable. The findings conceptually provide new opportunities for the application of Al(4)C(3) ceramic material in vacuum microelectronic devices.

  5. Polyaniline nanowire arrays aligned on nitrogen-doped carbon fabric for high-performance flexible supercapacitors.

    PubMed

    Yu, Pingping; Li, Yingzhi; Yu, Xinyi; Zhao, Xin; Wu, Lihao; Zhang, Qinghua

    2013-09-24

    A combination of vertical polyaniline (PANI) nanowire arrays and nitrogen plasma etched carbon fiber cloths (eCFC) was fabricated to create 3D nanostructured PANI/eCFC composites. The small size of the highly ordered PANI nanowires can greatly reduce the scale of the diffusion length, allowing for the improved utilization of electrode materials. A two-electrode flexible supercapacitor based on PANI/eCFC demonstrates a high specific capacitance (1035 F g(-1) at a current density of 1 A g(-1)), good rate capability (88% capacity retention at 8 A g(-1)), and long-term cycle life (10% capacity loss after 5000 cycles). The lightweight, low-cost, flexible composites are promising candidates for use in energy storage device applications.

  6. Carbon nanoscrolls fabricated from graphene nanoribbons using Ni nanowire templates: A molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Huang, Senpeng; Wang, Bin; Feng, Min; Xu, Xiaoxuan; Cao, Xuewei; Wang, Yufang

    2015-04-01

    Carbon nanoscroll (CNS) has aroused the great interest of research in many fields, due to its unique properties and potential industrial applications. However, there exists a number of challenges in the fabrication of CNSs. A molecular dynamics simulation on the fabrication of a CNS from a graphene nanoribbon (GNR) initiated by a nickel nanowire (Ni NW) has been carried out. The GNR twines around the Ni NW and spontaneously scrolls into a CNS with an interlayer distance of 3.417 Å, forming a stable multi-layer core-shell construction. The Ni NW plays a role of activator in the process, resulting in the structural transition of the GNR from 2D to 3D phase. An irreversible deformation of the Ni NW occurs during the self-scrolling process, which induces the nanowire to be more stable.

  7. Patterned growth of carbon nanotubes over vertically aligned silicon nanowire bundles for achieving uniform field emission.

    PubMed

    Hung, Yung-Jr; Huang, Yung-Jui; Chang, Hsuan-Chen; Lee, Kuei-Yi; Lee, San-Liang

    2014-01-01

    A fabrication strategy is proposed to enable precise coverage of as-grown carbon nanotube (CNT) mats atop vertically aligned silicon nanowire (VA-SiNW) bundles in order to realize a uniform bundle array of CNT-SiNW heterojunctions over a large sample area. No obvious electrical degradation of as-fabricated SiNWs is observed according to the measured current-voltage characteristic of a two-terminal single-nanowire device. Bundle arrangement of CNT-SiNW heterojunctions is optimized to relax the electrostatic screening effect and to maximize the field enhancement factor. As a result, superior field emission performance and relatively stable emission current over 12 h is obtained. A bright and uniform fluorescent radiation is observed from CNT-SiNW-based field emitters regardless of its bundle periodicity, verifying the existence of high-density and efficient field emitters on the proposed CNT-SiNW bundle arrays.

  8. Green synthesis of carbon quantum dots embedded onto titanium dioxide nanowires for enhancing photocurrent

    NASA Astrophysics Data System (ADS)

    Yen, Yin-Cheng; Lin, Chia-Chi; Chen, Ping-Yu; Ko, Wen-Yin; Tien, Tzu-Rung; Lin, Kuan-Jiuh

    2017-05-01

    The green synthesis of nanowired photocatalyst composed of carbon quantum dots-titanium hybrid-semiconductors, CQDs/TiO2, are reported. Where graphite-based CQDs with a size less than 5 nm are directly synthesized in pure water electrolyte by a one-step electrochemistry approach and subsequently electrodeposited onto as-prepared TiO2 nanowires through a voltage-driven reduction process. Electron paramagnetic resonance studies show that the CQDs can generate singlet oxygen and/or oxygen radicals to decompose the kinetic H2O2 intermediate species upon UV light illumination. With the effect of peroxidase-like CQDs, photocurrent density of CQDs/TiO2 is remarkably enhanced by a 6.4 factor when compared with that of as-prepared TiO2.

  9. Protective capping and surface passivation of III-V nanowires by atomic layer deposition

    SciTech Connect

    Dhaka, Veer Perros, Alexander; Kakko, Joona-Pekko; Haggren, Tuomas; Lipsanen, Harri; Naureen, Shagufta; Shahid, Naeem; Jiang, Hua; Kauppinen, Esko; Srinivasan, Anand

    2016-01-15

    Low temperature (∼200 °C) grown atomic layer deposition (ALD) films of AlN, TiN, Al{sub 2}O{sub 3}, GaN, and TiO{sub 2} were tested for protective capping and surface passivation of bottom-up grown III-V (GaAs and InP) nanowires (NWs), and top-down fabricated InP nanopillars. For as-grown GaAs NWs, only the AlN material passivated the GaAs surface as measured by photoluminescence (PL) at low temperatures (15K), and the best passivation was achieved with a few monolayer thick (2Å) film. For InP NWs, the best passivation (∼2x enhancement in room-temperature PL) was achieved with a capping of 2nm thick Al{sub 2}O{sub 3}. All other ALD capping layers resulted in a de-passivation effect and possible damage to the InP surface. Top-down fabricated InP nanopillars show similar passivation effects as InP NWs. In particular, capping with a 2 nm thick Al{sub 2}O{sub 3} layer increased the carrier decay time from 251 ps (as-etched nanopillars) to about 525 ps. Tests after six months ageing reveal that the capped nanostructures retain their optical properties. Overall, capping of GaAs and InP NWs with high-k dielectrics AlN and Al{sub 2}O{sub 3} provides moderate surface passivation as well as long term protection from oxidation and environmental attack.

  10. Modeling and optimization of atomic layer deposition processes on vertically aligned carbon nanotubes.

    PubMed

    Yazdani, Nuri; Chawla, Vipin; Edwards, Eve; Wood, Vanessa; Park, Hyung Gyu; Utke, Ivo

    2014-01-01

    Many energy conversion and storage devices exploit structured ceramics with large interfacial surface areas. Vertically aligned carbon nanotube (VACNT) arrays have emerged as possible scaffolds to support large surface area ceramic layers. However, obtaining conformal and uniform coatings of ceramics on structures with high aspect ratio morphologies is non-trivial, even with atomic layer deposition (ALD). Here we implement a diffusion model to investigate the effect of the ALD parameters on coating kinetics and use it to develop a guideline for achieving conformal and uniform thickness coatings throughout the depth of ultra-high aspect ratio structures. We validate the model predictions with experimental data from ALD coatings of VACNT arrays. However, the approach can be applied to predict film conformality as a function of depth for any porous topology, including nanopores and nanowire arrays.

  11. Modeling and optimization of atomic layer deposition processes on vertically aligned carbon nanotubes

    PubMed Central

    Yazdani, Nuri; Chawla, Vipin; Edwards, Eve; Wood, Vanessa

    2014-01-01

    Summary Many energy conversion and storage devices exploit structured ceramics with large interfacial surface areas. Vertically aligned carbon nanotube (VACNT) arrays have emerged as possible scaffolds to support large surface area ceramic layers. However, obtaining conformal and uniform coatings of ceramics on structures with high aspect ratio morphologies is non-trivial, even with atomic layer deposition (ALD). Here we implement a diffusion model to investigate the effect of the ALD parameters on coating kinetics and use it to develop a guideline for achieving conformal and uniform thickness coatings throughout the depth of ultra-high aspect ratio structures. We validate the model predictions with experimental data from ALD coatings of VACNT arrays. However, the approach can be applied to predict film conformality as a function of depth for any porous topology, including nanopores and nanowire arrays. PMID:24778944

  12. Synthesizing boron nitride nanotubes filled with SiC nanowires by using carbon nanotubes as templates

    NASA Astrophysics Data System (ADS)

    Han, Weiqiang; Redlich, Philipp; Ernst, Frank; Rühle, Manfred

    1999-09-01

    A method is described to synthesize silicon carbide (SiC)-filled boron nitride (BN) nanotubes (NT) simultaneously in high yield by using carbon nanotubes (CNTs) as templates. This method combines both carbon nanotube-substitution reaction and confined reaction. Through the CNT-substitution reaction, CNTs react with boron oxide vapor in the presence of nitrogen gas to form BN NTs, whose diameters and lengths are similar to those of the starting CNTs. The formation of the SiC filling is proceeded by the penetration of SiO vapor into the cavity of the nanotubes and subsequent reaction of SiO vapor with the inner carbon layers or volatile carbon mono-oxide in the interior to form SiC nanowires. The filled length can be up to the entire length of the nanotubes. SiC-filled (BN)xCy nanotubes also form in the product.

  13. Enhanced electrochemical performance of polyaniline/carbon/titanium nitride nanowire array for flexible supercapacitor

    NASA Astrophysics Data System (ADS)

    Xie, Yibing; Xia, Chi; Du, Hongxiu; Wang, Wei

    2015-07-01

    The ternary nanocomposite of polyaniline/carbon/titanium nitride (PANI/C/TiN) nanowire array (NWA) is fabricated as electroactive electrode material for flexible supercapacitor application. Firstly, TiN NWA is formed through ammonia nitridation treatment of TiO2 NWA, which is synthesized via seed-assisted hydrothermal reaction. PANI/C/TiN NWA is then formed through sequentially coating carbon and PANI on the surface of TiN NWA. PANI/C/TiN NWA has unique shell/shell/core architecture, including a core layer of TiN NWA with a diameter of 40-160 nm and a length of 1.5 μm, a middle shell layer of carbon with a thickness of about 6.0 nm and an external surface layer of PANI with a thickness of 20-50 nm. PANI/C/TiN NWA provides ion diffusion channel at interspaces between the neighboring nanowires and electron transfer route along independent nanowires. The carbon shell layer is able to protect TiN NWA from electrochemical corrosion during charge/discharge process. PANI/C/TiN NWA displays high specific capacitance of 1093 F g-1 at 1.0 Ag-1, and good cycling stability with a capacity retention of 98% after 2000 cycles, presenting better supercapacitive performance than other integrated nanocomposites of C/PANI/TiN, PANI/TiN and PANI/C/TiO2 NWA. Such a ternary nanocomposite of PANI/C/TiN NWA can be used as an electrode material of flexible supercapacitors.

  14. Angular distribution of photoelectrons from atomic oxygen, nitrogen, and carbon

    NASA Technical Reports Server (NTRS)

    Manson, S. T.; Kennedy, D. J.; Starace, A. F.; Dill, D.

    1974-01-01

    The angular distribution of photoelectrons from atomic oxygen is investigated using Hartree-Fock (HF) wave functions. The correct formulation is used to compare HS and HF results. Agreement between these results is good and the HS calculations have been extended to atomic nitrogen and carbon as well.

  15. Effect of atomic layer deposition temperature on the performance of top-down ZnO nanowire transistors

    PubMed Central

    2014-01-01

    This paper studies the effect of atomic layer deposition (ALD) temperature on the performance of top-down ZnO nanowire transistors. Electrical characteristics are presented for 10-μm ZnO nanowire field-effect transistors (FETs) and for deposition temperatures in the range 120°C to 210°C. Well-behaved transistor output characteristics are obtained for all deposition temperatures. It is shown that the maximum field-effect mobility occurs for an ALD temperature of 190°C. This maximum field-effect mobility corresponds with a maximum Hall effect bulk mobility and with a ZnO film that is stoichiometric. The optimized transistors have a field-effect mobility of 10 cm2/V.s, which is approximately ten times higher than can typically be achieved in thin-film amorphous silicon transistors. Furthermore, simulations indicate that the drain current and field-effect mobility extraction are limited by the contact resistance. When the effects of contact resistance are de-embedded, a field-effect mobility of 129 cm2/V.s is obtained. This excellent result demonstrates the promise of top-down ZnO nanowire technology for a wide variety of applications such as high-performance thin-film electronics, flexible electronics, and biosensing. PMID:25276107

  16. Focused ion beam-assisted fabrication of soft high-aspect ratio silicon nanowire atomic force microscopy probes.

    PubMed

    Knittel, Peter; Hibst, Nicolas; Mizaikoff, Boris; Strehle, Steffen; Kranz, Christine

    2017-03-28

    In this study, high-aspect ratio silicon nanowire (SiNW) - modified atomic force microscopy (AFM) probes are fabricated using focused ion beam (FIB) microfabrication technology and vapor-solid-solid synthesis. Commercially available soft silicon nitride probes are used for localized nanowire growth yielding soft high-aspect ratio AFM probes. The SiNW-modified cantilevers are used here for imaging in PeakForce Tappingۛ (PFT) mode, which offers high force control along with valuable information about tip-sample adhesion. A platinum catalyst, deposited accurately at a truncated AFM tip by ion beam-induced deposition (IBID), was used for localized nanowire synthesis. It could be shown that the deposition of a thin silicon dioxide layer prior to the catalyst deposition resulted in controlled SiNW growth on silicon as well as silicon nitride probes. In addition, a FIB-based method for post-growth alignment of the fabricated SiNW tips is presented, which allows tilt-compensation specifically tailored to the specifications of the used AFM instrumentation. To demonstrate the capability of such soft, high-aspect ratio AFM probes, optical gratings fabricated in GaAs and silver halide fibers were imaged in PFT mode. Additionally, the mechanical stability of these high-aspect AFM probes was evaluated on a sapphire substrate.

  17. Nano-structured composite of Si/(S-doped-carbon nanowire network) as anode material for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Shao, Dan; Tang, Daoping; Yang, Jianwen; Li, Yanwei; Zhang, Lingzhi

    2015-11-01

    Novel nanostructured silicon composites, Si/Poly(3,4-ethylenedioxythiophene) nanowire network (Si/PNW) and Si/(S-doped-carbon nanowire network) (Si/S-CNW), are prepared by a soft-template polymerization of 3,4-ethylenedioxythiophene (EDOT) using sodium dodecyl sulfate (SDS) as surfactant with the presence of Si nanoparticles and a subsequent carbonization of Si/PNW, respectively. The presence of Si nanoparticles in the soft-template polymerization of EDOT plays a critical role in the formation of PEDOT nanowire network instead of 1D nanowire. After the carbonization of PEDOT, the S-doped-carbon nanowire network matrix shows higher electrical conductivity than PNW counterpart, which facilitates to construct robust conductive bridges between Si nanoparticles and provide large electrode/electrolyte interfaces for rapid charge transfer reactions. Thus, Si/S-CNW composite exhibits excellent cycling stability and rate capability as anode material, retaining a specific capacity of 820 mAh g-1 after 400 cycles with a very small capacity fade of 0.09% per cycle.

  18. Preparation and dielectric properties of SiC nanowires self-sacrificially templated by carbonated bacterial cellulose

    SciTech Connect

    Wen, Lixia; Ma, Yongjun; Dai, Bo; Zhou, Yong; Liu, Jinsong; Pei, Chonghua

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► A new material – CBC is introduced as a template to prepare SiC nanowires. ► SiC nanowires are synthesized by the infiltration process of reactive vapor Si. ► The highest ε″ of β-SiC nanowires is obtained at 1400 °C. -- Abstract: SiC nanowires were synthesized by the infiltration process of reactive vapor Si in Ar atmosphere at 1350–1450 °C, using carbonated bacterial cellulose (CBC) as carbon template and a reactant. Scanning electron microscopy (SEM), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and vector network analyzer were employed to characterize the samples. The diameter of the resulting β-SiC nanowires changes with calcination temperatures, specifically, 35–60 nm for 1350 °C, 40–80 nm for 1400 °C, and 30–60 nm for 1450 °C. The β-SiC nanowires obtained at 1400 °C possess the highest ε″ of complex permittivity.

  19. A novel investigation on carbon nanotube/ZnO, Ag/ZnO and Ag/carbon nanotube/ZnO nanowires junctions for harvesting piezoelectric potential on textile

    SciTech Connect

    Khan, Azam Edberg, Jesper; Nur, Omer; Willander, Magnus

    2014-07-21

    In the present work, three junctions were fabricated on textile fabric as an alternative substrate for harvesting piezoelectric potential. First junction was formed on ordinary textile as (textile/multi-walled carbon nanotube film/zinc oxide nanowires (S1: T/CNTs/ZnO NWs)) and the other two were formed on conductive textile with the following layer sequence: conductive textile/zinc oxide nanowires (S2: CT/ZnO NWs) and conductive textile/multi-walled carbon nanotubes film/zinc oxide nanowires (S3: CT/CNTs/ZnO NWs). Piezoelectric potential was harvested by using atomic force microscopy in contact mode for the comparative analysis of the generated piezoelectric potential. ZnO NWs were synthesized by using the aqueous chemical growth method. Surface analysis of the grown nanostructures was performed by using scanning electron microscopy and transmission electron microscopy. The growth orientation and crystalline size were studied by using X-ray diffraction technique. This study reveals that textile as an alternative substrate have many features like cost effective, highly flexible, nontoxic, light weight, soft, recyclable, reproducible, portable, wearable, and washable for nanogenerators fabrication with acceptable performance and with a wide choice of modification for obtaining large amount of piezoelectric potential.

  20. A novel investigation on carbon nanotube/ZnO, Ag/ZnO and Ag/carbon nanotube/ZnO nanowires junctions for harvesting piezoelectric potential on textile

    NASA Astrophysics Data System (ADS)

    Khan, Azam; Edberg, Jesper; Nur, Omer; Willander, Magnus

    2014-07-01

    In the present work, three junctions were fabricated on textile fabric as an alternative substrate for harvesting piezoelectric potential. First junction was formed on ordinary textile as (textile/multi-walled carbon nanotube film/zinc oxide nanowires (S1: T/CNTs/ZnO NWs)) and the other two were formed on conductive textile with the following layer sequence: conductive textile/zinc oxide nanowires (S2: CT/ZnO NWs) and conductive textile/multi-walled carbon nanotubes film/zinc oxide nanowires (S3: CT/CNTs/ZnO NWs). Piezoelectric potential was harvested by using atomic force microscopy in contact mode for the comparative analysis of the generated piezoelectric potential. ZnO NWs were synthesized by using the aqueous chemical growth method. Surface analysis of the grown nanostructures was performed by using scanning electron microscopy and transmission electron microscopy. The growth orientation and crystalline size were studied by using X-ray diffraction technique. This study reveals that textile as an alternative substrate have many features like cost effective, highly flexible, nontoxic, light weight, soft, recyclable, reproducible, portable, wearable, and washable for nanogenerators fabrication with acceptable performance and with a wide choice of modification for obtaining large amount of piezoelectric potential.

  1. Silicon carbide nanowires and composites obtained from carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Wang, Yuejian

    In this dissertation a simple route has been developed to synthesize Silicon Carbide (beta-SiC) nanothreads and C-SiC coaxial nanotubes by solid/liquid-state reaction between multiwall carbon nanotubes and silicon conducted at 1473 K and 1723 K, respectively. Through the kinetics study of SiC formation from carbon nanotubes and Si, our results demonstrated that carbon nanotubes may have higher chemical reactivity than other forms of elemental Carbon. Based on the above investigation, CNT/SiC and diamond/CNT/SiC were manufactured. Key factors influencing the mechanical properties of final products, such as phase composition, grain size, stress-strain, sintering time, and sintering temperature were thoroughly studied with Raman spectroscopy, x-ray diffraction, SEM and TEM techniques. Taking advantage of high elasticity of Carbon nanotube and its ability to block the microcrack propagation and dislocation movement, both composites showed enhanced fracture toughness. Carbon nanotubes composites trigger a new field in fundamental science and manifest potential application in multiple industries.

  2. Investigating the performance limits of silicon-nanowire and carbon-nanotube FETs

    NASA Astrophysics Data System (ADS)

    Marchi, A.; Gnani, E.; Reggiani, S.; Rudan, M.; Baccarani, G.

    2006-01-01

    In this work we investigate and compare the electrostatics of fully depleted cylindrical silicon-nanowire (SiCNW) FETs, four-gate rectangular nanowire (4G RNW) FETs, tri-gate rectangular nanowire (3G RNW) FETs and gate-all-around carbon-nanotube (GAA-CNT) FETs at advanced miniaturization limits. In doing so, we rigorously solve the coupled Schrödinger-Poisson equations within the device cross-sections and fully account for quantum-mechanical effects. The investigation, carried out for the 65 and 45 nm technology nodes, leads to the unexpected conclusion that, for an assigned threshold voltage, the gate-all-around CNT-FET offers only a slightly better performance with respect to the SiCNW and the 4G RNW-FETs. This is due to the compensation of two different mechanisms, namely a higher gate effectiveness and a lower density of states. The 3G RNW yields instead an electron density within the channel which is about 25% lower than the SiCNW and 4G RNW-FETs at a given gate voltage. Such a reduced performance is due to its inherent asymmetry, which negatively affects the gate control on the channel charge.

  3. Automated manipulation of carbon nanotubes using atomic force microscopy.

    PubMed

    Zhang, Chao; Wu, Sen; Fu, Xing

    2013-01-01

    The manipulation of carbon nanotubes is an important and essential step for carbon-based nanodevice or nanocircuit assembly. However, the conventional push-and-image approach of manipulating carbon nanotubes using atomic force microscopy has low efficiency on account of the reduplicated scanning process during manipulation. In this article, an automated manipulation system is designed and tested. This automated manipulation system, which includes an atomic force microscope platform and a self-developed computer program for one-dimensional manipulation, is capable of automatically moving any assigned individual carbon nanotube to a defined target location without any intermediate scanning procedure. To demonstrate the high-efficiency of this automated manipulation system and its potential applications in nanoassembly, two experiments were conducted. The first experiment used this system to manipulate a carbon nanotube to a defined target location. In the second experiment, this system was used to automatically manipulate several carbon nanotubes for generating and translating a defined pattern of nanotubes.

  4. Hybrid heterojunction and photoelectrochemistry solar cell based on silicon nanowires and double-walled carbon nanotubes.

    PubMed

    Shu, Qinke; Wei, Jinquan; Wang, Kunlin; Zhu, Hongwei; Li, Zhen; Jia, Yi; Gui, Xuchun; Guo, Ning; Li, Xinming; Ma, Chaoran; Wu, Dehai

    2009-12-01

    A hybrid solar cell model composed of a heterojunction cell and a photoelectrochemical (PEC) cell has been proposed and characterized. In the hybrid cell, a thin film of double-walled carbon nanotubes forms a heterojunction with the silicon nanowire (SiNW) array and also functions as the transparent counter electrode of the PEC cell. The cell performance can be readily tuned by controlling the SiNW density. Under AM 1.5G illumination, a power conversion efficiency of 1.29%, higher than those reported for SiNW array-based PEC cells, has been obtained.

  5. Novel Carbon Nitride Nanowire (CNW) Conjugates for Breast Cancer Treatment

    DTIC Science & Technology

    2007-09-01

    100( 4 3 { CC CCM waterwater NTNT o o ρ π . RZONK is the “zone of nanotube killing” (ZONK), the radius from the surface of the nanotube that...Forro, L. 2000, "Multiwall carbon nanotubes", Physics World, vol. 13, no. 6, pp. 37-41. Webster, S., Reyes-Reyes, M., Pedron, X., Lopez- Sandoval

  6. Carbon-Coated Silicon Nanowires on Carbon Fabric as Self-Supported Electrodes for Flexible Lithium-Ion Batteries.

    PubMed

    Wang, Xiaolei; Li, Ge; Seo, Min Ho; Lui, Gregory; Hassan, Fathy M; Feng, Kun; Xiao, Xingcheng; Chen, Zhongwei

    2017-03-22

    A novel self-supported electrode with long cycling life and high mass loading was developed based on carbon-coated Si nanowires grown in situ on highly conductive and flexible carbon fabric substrates through a nickel-catalyzed one-pot atmospheric pressure chemical vapor deposition. The high-quality carbon coated Si nanowires resulted in high reversible specific capacity (∼3500 mA h g(-1) at 100 mA g(-1)), while the three-dimensional electrode's unique architecture leads to a significantly improved robustness and a high degree of electrode stability. An exceptionally long cyclability with a capacity retention of ∼66% over 500 cycles at 1.0 A g(-1) was achieved. The controllable high mass loading enables an electrode with extremely high areal capacity of ∼5.0 mA h cm(-2). Such a scalable electrode fabrication technology and the high-performance electrodes hold great promise in future practical applications in high energy density lithium-ion batteries.

  7. Atomic scale simulation of carbon nanotube nucleation from hydrocarbon precursors

    PubMed Central

    Khalilov, Umedjon; Bogaerts, Annemie; Neyts, Erik C.

    2015-01-01

    Atomic scale simulations of the nucleation and growth of carbon nanotubes is essential for understanding their growth mechanism. In spite of over twenty years of simulation efforts in this area, limited progress has so far been made on addressing the role of the hydrocarbon growth precursor. Here we report on atomic scale simulations of cap nucleation of single-walled carbon nanotubes from hydrocarbon precursors. The presented mechanism emphasizes the important role of hydrogen in the nucleation process, and is discussed in relation to previously presented mechanisms. In particular, the role of hydrogen in the appearance of unstable carbon structures during in situ experimental observations as well as the initial stage of multi-walled carbon nanotube growth is discussed. The results are in good agreement with available experimental and quantum-mechanical results, and provide a basic understanding of the incubation and nucleation stages of hydrocarbon-based CNT growth at the atomic level. PMID:26691537

  8. One step biofunctionalized electrospun multiwalled carbon nanotubes embedded zinc oxide nanowire interface for highly sensitive detection of carcinoma antigen-125.

    PubMed

    Paul, K Brince; Singh, Vikrant; Vanjari, Siva Rama Krishna; Singh, Shiv Govind

    2017-02-15

    Ovarian cancer is the most leading cause of cancer-related death in women . The carcinoma antigen-125, which is found on the surface of many ovarian cancer cells is known to be a gold standard clinical biomarker associated with life-threatening gynecological malignancy. In this work, we demonstrate a novel biosensor platform based on multiwalled carbon nanotubes embedded zinc oxide nanowire for the ultrasensitive detection of carcinoma antigen-125. Label free detection of the carcinoma antigen-125 was accomplished by differential voltammetry technique that demonstrated excellent sensitivity (90.14µA/(U/mL)/cm(2)) with a detection limit of 0.00113UmL(-1) concentration. The fabricated immunosensor exhibits good performance with wider detection range (0.001UmL(-1)-1kUmL(-1)), reproducibility, selectivity, acceptable stability, and thus is a potential cost-effective methodology for point-of-care diagnosis. The multiwalled carbon nanotubes (MWCNTs) embedded highly oriented zinc oxide (ZnO) nanowires were synthesized by simple, low cost electrospinning technique. Compared to pure ZnO nanowires, electrochemical activity of MWCNTs embedded ZnO nanowires was found to be much higher. The calcination temperature was optimized to avoid any decomposition of the CNTs and to obtain multiwalled carbon nanotubes embedded highly crystalline ZnO nanowires. The salient feature of this biosensing platform is that one step calcination process is enough to create the functional groups on MWCNT-ZnO nanowire surface that are effective for the covalent conjugation of antibody without further surface modification. To the best of our knowledge, this is the first report on MWCNT-ZnO nanowire based immunosensor explored for the detection of cancer biomarker.

  9. Photoelectrochemical properties of TiO2 nanowire arrays: a study of the dependence on length and atomic layer deposition coating.

    PubMed

    Hwang, Yun Jeong; Hahn, Chris; Liu, Bin; Yang, Peidong

    2012-06-26

    We report that the length and surface properties of TiO(2) nanowires can have a dramatic effect on their photoelectrochemical properties. To study the length dependence, rutile TiO(2) nanowires (0.28-1.8 μm) were grown on FTO substrates with different reaction times (50-180 min) using a hydrothermal method. Nanowires show an increase in photocurrent with length, and a maximum photocurrent of 0.73 mA/cm(2) was measured (1.5 V vs RHE) for 1.8 μm long nanowires under AM 1.5G simulated sunlight illumination. While the incident photon to current conversion efficiency (IPCE) increases linearly with photon absorptance (1-10(-α×length)) with near band gap illumination (λ = 410 nm), it decreases severely at shorter wavelengths of light for longer nanowires due to poor electron mobility. Atomic layer deposition (ALD) was used to deposit an epitaxial rutile TiO(2) shell on nanowire electrodes which enhanced the photocatalytic activity by 1.5 times (1.5 V vs RHE) with 1.8 μm long nanowires, reaching a current density of 1.1 mA/cm(2) (61% of the maximum photocurrent for rutile TiO(2)). Additionally, by fixing the epitaxial rutile shell thickness and studying photoelectrochemical (PEC) properties of different nanowire lengths (0.28-1.8 μm), we found that the enhancement of current increases with length. These results demonstrate that ALD coating improves the charge collection efficiency from TiO(2) nanowires due to the passivation of surface states and an increase in surface area. Therefore, we propose that epitaxial coating on materials is a viable approach to improving their energy conversion efficiency.

  10. Inquisition of Microcystis aeruginosa and Synechocystis nanowires: characterization and modelling.

    PubMed

    Sure, Sandeep; Torriero, Angel A J; Gaur, Aditya; Li, Lu Hua; Chen, Ying; Tripathi, Chandrakant; Adholeya, Alok; Ackland, M Leigh; Kochar, Mandira

    2015-11-01

    Identification of extracellular conductive pilus-like structures (PLS) i.e. microbial nanowires has spurred great interest among scientists due to their potential applications in the fields of biogeochemistry, bioelectronics, bioremediation etc. Using conductive atomic force microscopy, we identified microbial nanowires in Microcystis aeruginosa PCC 7806 which is an aerobic, photosynthetic microorganism. We also confirmed the earlier finding that Synechocystis sp. PCC 6803 produces microbial nanowires. In contrast to the use of highly instrumented continuous flow reactors for Synechocystis reported earlier, we identified simple and optimum culture conditions which allow increased production of nanowires in both test cyanobacteria. Production of these nanowires in Synechocystis and Microcystis were found to be sensitive to the availability of carbon source and light intensity. These structures seem to be proteinaceous in nature and their diameter was found to be 4.5-7 and 8.5-11 nm in Synechocystis and M. aeruginosa, respectively. Characterization of Synechocystis nanowires by transmission electron microscopy and biochemical techniques confirmed that they are type IV pili (TFP) while nanowires in M. aeruginosa were found to be similar to an unnamed protein (GenBank : CAO90693.1). Modelling studies of the Synechocystis TFP subunit i.e. PilA1 indicated that strategically placed aromatic amino acids may be involved in electron transfer through these nanowires. This study identifies PLS from Microcystis which can act as nanowires and supports the earlier hypothesis that microbial nanowires are widespread in nature and play diverse roles.

  11. An advanced fabrication method of highly ordered ZnO nanowire arrays on silicon substrates by atomic layer deposition.

    PubMed

    Subannajui, Kittitat; Güder, Firat; Danhof, Julia; Menzel, Andreas; Yang, Yang; Kirste, Lutz; Wang, Chunyu; Cimalla, Volker; Schwarz, Ulrich; Zacharias, Margit

    2012-06-15

    In this work, the controlled fabrication of highly ordered ZnO nanowire (NW) arrays on silicon substrates is reported. Si NWs fabricated by a combination of phase shift lithography and etching are used as a template and are subsequently substituted by ZnO NWs with a dry-etching technique and atomic layer deposition. This fabrication technique allows the vertical ZnO NWs to be fabricated on 4 in Si wafers. Room temperature photoluminescence and micro-photoluminescence are used to observe the optical properties of the atomic layer deposition (ALD) based ZnO NWs. The sharp UV luminescence observed from the ALD ZnO NWs is unexpected for the polycrystalline nanostructure. Surprisingly, the defect related luminescence is much decreased compared to an ALD ZnO film deposited at the same time ona plane substrate. Electrical characterization was carried out by using nanomanipulators. With the p-type Si substrate and the n-type ZnO NWs the nanodevices represent p–n NW diodes.The nanowire diodes show a very high breakthrough potential which implies that the ALD ZnO NWs can be used for future electronic applications.

  12. Structural, electronic, optical and vibrational properties of nanoscale carbons and nanowires: a colloquial review

    NASA Astrophysics Data System (ADS)

    Cole, Milton W.; Crespi, Vincent H.; Dresselhaus, Mildred S.; Dresselhaus, Gene; Fischer, John E.; Gutierrez, Humberto R.; Kojima, K.; Mahan, Gerald D.; Rao, Apparao M.; Sofo, Jorge O.; Tachibana, M.; Wako, K.; Xiong, Qihua

    2010-08-01

    This review addresses the field of nanoscience as viewed through the lens of the scientific career of Peter Eklund, thus with a special focus on nanocarbons and nanowires. Peter brought to his research an intense focus, imagination, tenacity, breadth and ingenuity rarely seen in modern science. His goal was to capture the essential physics of natural phenomena. This attitude also guides our writing: we focus on basic principles, without sacrificing accuracy, while hoping to convey an enthusiasm for the science commensurate with Peter's. The term 'colloquial review' is intended to capture this style of presentation. The diverse phenomena of condensed matter physics involve electrons, phonons and the structures within which excitations reside. The 'nano' regime presents particularly interesting and challenging science. Finite size effects play a key role, exemplified by the discrete electronic and phonon spectra of C60 and other fullerenes. The beauty of such molecules (as well as nanotubes and graphene) is reflected by the theoretical principles that govern their behavior. As to the challenge, 'nano' requires special care in materials preparation and treatment, since the surface-to-volume ratio is so high; they also often present difficulties of acquiring an experimental signal, since the samples can be quite small. All of the atoms participate in the various phenomena, without any genuinely 'bulk' properties. Peter was a master of overcoming such challenges. The primary activity of Eklund's research was to measure and understand the vibrations of atoms in carbon materials. Raman spectroscopy was very dear to Peter. He published several papers on the theory of phonons (Eklund et al 1995a Carbon 33 959-72, Eklund et al 1995b Thin Solid Films 257 211-32, Eklund et al 1992 J. Phys. Chem. Solids 53 1391-413, Dresselhaus and Eklund 2000 Adv. Phys. 49 705-814) and many more papers on measuring phonons (Pimenta et al 1998b Phys. Rev. B 58 16016-9, Rao et al 1997a Nature

  13. GaN nanowire functionalized with atomic layer deposition techniques for enhanced immobilization of biomolecules.

    PubMed

    Guo, D J; Abdulagatov, A I; Rourke, D M; Bertness, K A; George, S M; Lee, Y C; Tan, W

    2010-12-07

    We report the use of atomic layer deposition (ALD) coating as a nanobiosensor functionalization strategy for enhanced surface immobilization that may enable higher detection sensitivity. Three kinds of ALD coating films, Al(2)O(3), TiO(2), and SiO(2), were grown on the gallium nitride nanowire (GaN NW) surfaces and characterized with high-resolution transmission electron microscopy (HRTEM) and vacuum Fourier transform infrared spectroscopy (FTIR). Results from HRTEM showed that the thicknesses of ALD-Al(2)O(3), ALD-TiO(2) and ALD-SiO(2) coatings were 4-5 nm, 5-6 nm, and 12-14 nm, respectively. Results from FTIR showed that the OH contents of these coatings were, respectively, ∼6.9, ∼7.4, and ∼9.3 times that of piranha-treated GaN NW. Furthermore, to compare protein attachments on the different surfaces, poly(ethylene glycol) (PEG)-biotin was grafted on the OH-functionalized GaN NW surfaces through active Si-Cl functional groups. Streptavidin protein molecules were then attached to the biotin ends via specific binding. The immobilized streptavidin molecules were examined with scanning electron microscopy, HRTEM, and fluorescent imaging. Results from HRTEM and energy-dispersive X-ray revealed that the nitrogen concentrations on the three ALD coatings were significantly higher than that on the piranha-treated surface. Results from fluorescent imaging further showed that the protein attachments on the Al(2)O(3), TiO(2), and SiO(2) ALD coatings were, respectively, 6.4, 7.8, and 9.8 times that of piranha-treated surface. This study demonstrates that ALD coating can be used as a functionalization strategy for nanobiosensors because it is capable of creating functional groups with much higher density compared to widely used acid modifications, and among the three ALD coatings, ALD-SiO(2) yielded the most promising results in OH content and protein attachment.

  14. Renormalization plus convolution method for atomic-scale modeling of electrical and thermal transport in nanowires.

    PubMed

    Wang, Chumin; Salazar, Fernando; Sánchez, Vicenta

    2008-12-01

    Based on the Kubo-Greenwood formula, the transport of electrons and phonons in nanowires is studied by means of a real-space renormalization plus convolution method. This method has the advantage of being efficient, without introducing additional approximations and capable to analyze nanowires of a wide range of lengths even with defects. The Born and tight-binding models are used to investigate the lattice thermal and electrical conductivities, respectively. The results show a quantized electrical dc conductance, which is attenuated when an oscillating electric field is applied. Effects of single and multiple planar defects, such as a quasi-periodic modulation, on the conductance of nanowires are also investigated. For the low temperature region, the lattice thermal conductance reveals a power-law temperature dependence, in agreement with experimental data.

  15. Growth Of Graphitic Polyhedra, SiC Platelets, And Carbon Nanotubes Filled With SiC Nanowires By Laser Ablation

    SciTech Connect

    Kokai, Fumio; Uchiyama, Kunihiro; Chigusa, Hajime; Nozaki, Iori; Noguchi, Eriko; Kameda, Yuto; Koshio, Akira

    2010-10-08

    Three characteristic silicon/carbon nanostructures, i.e., graphitic polyhedral (GP) particles, silicon carbide (SiC) platelets, and carbon nanotubes (CNTs) filled with SiC nanowires, were synthesized by the laser ablation of Si-C targets in the presence of high-pressure Ar gas up to 0.9 MPa. The growth of nanostructures was controlled merely by adjusting the Si content in graphite and the ambient Ar gas pressure. Deposits containing GP particles were purified by heat treatment at 550 deg. C in a pure oxygen atmosphere for 1 h. CNTs filled with SiC nanowires were grown without a catalyst. Unlike previous studies of CNTs filled with metals or compounds, all the CNTs checked by transmission electron microscopy contained SiC nanowires and no unfilled CNTs were produced. We discuss the growth mechanisms of the three nanostructures.

  16. Dispersion forces between ultracold atoms and a carbon nanotube.

    PubMed

    Schneeweiss, P; Gierling, M; Visanescu, G; Kern, D P; Judd, T E; Günther, A; Fortágh, J

    2012-08-01

    Dispersion forces are long-range interactions between polarizable objects that arise from fluctuations in the electromagnetic field between them. Dispersion forces have been observed between microscopic objects such as atoms and molecules (the van der Waals interaction), between macroscopic objects (the Casimir interaction) and between an atom and a macroscopic object (the Casimir-Polder interaction). Dispersion forces are known to increase the attractive forces between the components in nanomechanical devices, to influence adsorption rates onto nanostructures, and to influence the interactions between biomolecules in biological systems. In recent years, there has been growing interest in studying dispersion forces in nanoscale systems and in exploring the interactions between carbon nanotubes and cold atoms. However, there are considerable difficulties in developing dispersion force theories for general, finite geometries such as nanostructures. Thus, there is a need for new experimental methods that are able to go beyond measurements of planar surfaces and nanoscale gratings and make measurements on isolated nanostructures. Here, we measure the dispersion force between a rubidium atom and a multiwalled carbon nanotube by inserting the nanotube into a cloud of ultracold rubidium atoms and monitoring the loss of atoms from the cloud as a function of time. We perform these experiments with both thermal clouds of ultracold atoms and with Bose-Einstein condensates. The results obtained with this approach will aid the development of theories describing quantum fields near nanostructures, and hybrid cold-atom/solid-state devices may also prove useful for applications in quantum sensing and quantum information.

  17. Carbon fiber-ZnO nanowire hybrid structures for flexible and adaptable strain sensors

    NASA Astrophysics Data System (ADS)

    Liao, Qingliang; Mohr, Markus; Zhang, Xiaohui; Zhang, Zheng; Zhang, Yue; Fecht, Hans-Jörg

    2013-11-01

    We report the flexible piezotronic strain sensors fabricated using carbon fiber-ZnO nanowire hybrid structures by a novel and reliable method. The I-V characteristic of the sensor shows high sensitivity to external strain due to the change in Schottky barrier height (SBH), which has a linear relationship with strain. This fabricated strain sensor has a quick, real-time current response under both static and dynamic mechanical loads. The change in SBH resulted from the strain-induced piezoelectric potential is investigated by band gap theory. In this work we develop a new feasible method to fabricate a flexible strain sensor within the fabric adapted to textile structures, able to measure their strain.We report the flexible piezotronic strain sensors fabricated using carbon fiber-ZnO nanowire hybrid structures by a novel and reliable method. The I-V characteristic of the sensor shows high sensitivity to external strain due to the change in Schottky barrier height (SBH), which has a linear relationship with strain. This fabricated strain sensor has a quick, real-time current response under both static and dynamic mechanical loads. The change in SBH resulted from the strain-induced piezoelectric potential is investigated by band gap theory. In this work we develop a new feasible method to fabricate a flexible strain sensor within the fabric adapted to textile structures, able to measure their strain. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03536k

  18. Protein biosensors based on polymer nanowires, carbon nanotubes and zinc oxide nanorods.

    PubMed

    Anish Kumar, M; Jung, Soyoun; Ji, Taeksoo

    2011-01-01

    The development of biosensors using electrochemical methods is a promising application in the field of biotechnology. High sensitivity sensors for the bio-detection of proteins have been developed using several kinds of nanomaterials. The performance of the sensors depends on the type of nanostructures with which the biomaterials interact. One dimensional (1-D) structures such as nanowires, nanotubes and nanorods are proven to have high potential for bio-applications. In this paper we review these three different kinds of nanostructures that have attracted much attention at recent times with their great performance as biosensors. Materials such as polymers, carbon and zinc oxide have been widely used for the fabrication of nanostructures because of their enhanced performance in terms of sensitivity, biocompatibility, and ease of preparation. Thus we consider polymer nanowires, carbon nanotubes and zinc oxide nanorods for discussion in this paper. We consider three stages in the development of biosensors: (a) fabrication of biomaterials into nanostructures, (b) alignment of the nanostructures and (c) immobilization of proteins. Two different methods by which the biosensors can be developed at each stage for all the three nanostructures are examined. Finally, we conclude by mentioning some of the major challenges faced by many researchers who seek to fabricate biosensors for real time applications.

  19. Protein Biosensors Based on Polymer Nanowires, Carbon Nanotubes and Zinc Oxide Nanorods

    PubMed Central

    M., Anish Kumar; Jung, Soyoun; Ji, Taeksoo

    2011-01-01

    The development of biosensors using electrochemical methods is a promising application in the field of biotechnology. High sensitivity sensors for the bio-detection of proteins have been developed using several kinds of nanomaterials. The performance of the sensors depends on the type of nanostructures with which the biomaterials interact. One dimensional (1-D) structures such as nanowires, nanotubes and nanorods are proven to have high potential for bio-applications. In this paper we review these three different kinds of nanostructures that have attracted much attention at recent times with their great performance as biosensors. Materials such as polymers, carbon and zinc oxide have been widely used for the fabrication of nanostructures because of their enhanced performance in terms of sensitivity, biocompatibility, and ease of preparation. Thus we consider polymer nanowires, carbon nanotubes and zinc oxide nanorods for discussion in this paper. We consider three stages in the development of biosensors: (a) fabrication of biomaterials into nanostructures, (b) alignment of the nanostructures and (c) immobilization of proteins. Two different methods by which the biosensors can be developed at each stage for all the three nanostructures are examined. Finally, we conclude by mentioning some of the major challenges faced by many researchers who seek to fabricate biosensors for real time applications. PMID:22163892

  20. Tellurium-nanowire-coated glassy carbon electrodes for selective and sensitive detection of dopamine.

    PubMed

    Tsai, Hsiang-Yu; Lin, Zong-Hong; Chang, Huan-Tsung

    2012-05-15

    Tellurium-nanowire-coated glassy carbon electrodes (TNGCEs) have been fabricated and employed for selective and sensitive detection of dopamine (DA). TNGCEs were prepared by direct deposition of tellurium nanowires, 600 ± 150 nm in length and 16 ± 3 nm in diameter, onto glassy carbon electrodes, which were further coated with Nafion to improve their selectivity and stability. Compared to the GCE, the TNGCE is more electroactive (by approximately 1.9-fold) for DA, and its selectivity toward DA over ascorbic acid (AA) and uric acid (UA) is also greater. By applying differential pulse voltammetry, at a signal-to-noise ratio of 3, the TNGCE provides a limit of detection of 1 nM for DA in the presence of 0.5mM AA and UA. Linearity (R(2)=0.9955) of the oxidation current at 0.19 V against the concentration of DA is found over the range 5 nM-1 μM. TNGCEs have been applied to determine the concentration of dopamine to be 0.59 ± 0.07 μM in PC12 cells.

  1. Relative stopping powers for atomic and molecular ions in carbon

    NASA Astrophysics Data System (ADS)

    Steuer, Malcolm F.

    1986-03-01

    Electronic stopping powers of carbon for atomic and molecular nitrogen ions have been calculated using semi-classical free electron scattering from Herman-Skillman potentials, parametrized to include an adjustable exponential screening factor F( tv, Z), representing atomic ions. For molecular ions, aligned along the beam direction and having velocity 1.2 a.u., the stopping powers for individual atomic components were calculated as a function of internuclear separation. Screening factors for the two centers of force were assumed to decrease linearly from the value at zero internuclear separation, equivalent to that of a silicon ion, to that for nitrogen ions at large separations. Results are consistent with the diminishment of average stopping power per atomic ion which has been observed for beam-aligned nitrogen molecular ions. Similar calculations for molecular hydrogen in carbon agree with the enhancement of stopping power which has been observed. Evidence of nonlinear effects is indicated.

  2. Fabrication of Te and Te-Au Nanowires-Based Carbon Fiber Fabrics for Antibacterial Applications

    PubMed Central

    Chou, Ting-Mao; Ke, Yi-Yun; Tsao, Yu-Hsiang; Li, Ying-Chun; Lin, Zong-Hong

    2016-01-01

    Pathogenic bacteria that give rise to diseases every year remain a major health concern. In recent years, tellurium-based nanomaterials have been approved as new and efficient antibacterial agents. In this paper, we developed the approach to directly grow tellurium nanowires (Te NWs) onto commercial carbon fiber fabrics and demonstrated their antibacterial activity. Those Te NWs can serve as templates and reducing agents for gold nanoparticles (Au NPs) to deposit. Three different Te-Au NWs with varied concentration of Au NPs were synthesized and showed superior antibacterial activity and biocompability. These results indicate that the as-prepared carbon fiber fabrics with Te and Te-Au NWs can become antimicrobial clothing products in the near future. PMID:26861380

  3. Ultrathin gold nanowire-functionalized carbon nanotubes for hybrid molecular sensing.

    PubMed

    Cui, Huizhong; Hong, Chenglin; Ying, Andrew; Yang, Xinmai; Ren, Shenqiang

    2013-09-24

    Carbon nanotubes (CNTs) have shown great potential as sensing component in the electrochemical field effect transistor and optical sensors, because of their extraordinary one-dimensional electronic structure, thermal conductivity, and tunable and stable near-infrared emission. However, the insolubility of CNTs due to strong van der Waals interactions limits their use in the field of nanotechnology. In this study, we demonstrate that noncovalent ultrathin gold nanowires functionalized multiwalled carbon nanotube (GNW-CNT) hybrid sensing agents show highly efficient and selective immune molecular sensing in electrochemical and near-infrared photoacoustic imaging methods. A detection limit of 0.01 ng/mL for the alpha-fetoprotein (AFP) antigen with high selectivity is shown. The extraordinary optical absorption, thermal, and electric conductivity of hybrid GNW-CNTs presented in this study could be an effective tactic to integrate imaging, sensing, and treatment functionalities.

  4. Facile electrosynthesis of silicon carbide nanowires from silica/carbon precursors in molten salt.

    PubMed

    Zou, Xingli; Ji, Li; Lu, Xionggang; Zhou, Zhongfu

    2017-08-30

    Silicon carbide nanowires (SiC NWs) have attracted intensive attention in recent years due to their outstanding performances in many applications. A large-scale and facile production of SiC NWs is critical to its successful application. Here, we report a simple method for the production of SiC NWs from inexpensive and abundantly available silica/carbon (SiO2/C) precursors in molten calcium chloride. The solid-to-solid electroreduction and dissolution-electrodeposition mechanisms can easily lead to the formation of homogenous SiC NWs. This template/catalyst-free approach greatly simplifies the synthesis procedure compared to conventional methods. This general strategy opens a direct electrochemical route for the conversion of SiO2/C into SiC NWs, and may also have implications for the electrosynthesis of other micro/nanostructured metal carbides/composites from metal oxides/carbon precursors.

  5. Hierarchical carbon nanowire microarchitectures made by plasma-assisted pyrolysis of photoresist.

    PubMed

    De Volder, Michaël F L; Vansweevelt, Rob; Wagner, Patrick; Reynaerts, Dominiek; Van Hoof, Chris; Hart, A John

    2011-08-23

    We present a new approach for the fabrication and integration of vertically aligned forests of amorphous carbon nanowires (CNWs), using only standard lithography, oxygen plasma treatment, and thermal processing. The simplicity and scalability of this process, as well as the hierarchical organization of CNWs, provides a potential alternative to the use of carbon nanotubes and graphene for applications in microsystems and high surface area materials. The CNWs are highly branched at the nanoscale, and novel hierarchical microstructures with CNWs connected to a solid amorphous core are made by controlling the plasma treatment time. By multilayer processing we demonstrate deterministic joining of CNW micropillars into 3D sensing networks. Finally we show that these networks can be chemically functionalized and used for measurement of DNA binding with increased sensitivity.

  6. Fabrication of Te and Te-Au Nanowires-Based Carbon Fiber Fabrics for Antibacterial Applications.

    PubMed

    Chou, Ting-Mao; Ke, Yi-Yun; Tsao, Yu-Hsiang; Li, Ying-Chun; Lin, Zong-Hong

    2016-02-06

    Pathogenic bacteria that give rise to diseases every year remain a major health concern. In recent years, tellurium-based nanomaterials have been approved as new and efficient antibacterial agents. In this paper, we developed the approach to directly grow tellurium nanowires (Te NWs) onto commercial carbon fiber fabrics and demonstrated their antibacterial activity. Those Te NWs can serve as templates and reducing agents for gold nanoparticles (Au NPs) to deposit. Three different Te-Au NWs with varied concentration of Au NPs were synthesized and showed superior antibacterial activity and biocompability. These results indicate that the as-prepared carbon fiber fabrics with Te and Te-Au NWs can become antimicrobial clothing products in the near future.

  7. Thermally induced local failures in quasi-one-dimensional systems: collapse in carbon nanotubes, neckling in nanowires, bubbles in DNA

    SciTech Connect

    Nisoli, Cristiano; Lookman, Turab; Saxena, Avadh; Abraham, Douglas

    2009-01-01

    Quasi one dimensional systems can suffer local structural failures-broadly defined-along their length: for instance, carbon nanotubes can collapse, nanowires can show bottlenecks below which conductance drops, bubbles open in DNA. We present a formalism to explore the occurrence of those thermally activated failures in complete generality, to calculate the average length between them as a function of the thermodynamic observables.

  8. Reactions of carbon atoms in pulsed molecular beams

    SciTech Connect

    Reisler, H.

    1993-12-01

    This research program consists of a broad scope of experiments designed to unravel the chemistry of atomic carbon in its two spin states, P and D, by using well-controlled initial conditions and state-resolved detection of products. Prerequisite to the proposed studies (and the reason why so little is known about carbon atom reactions), is the development of clean sources of carbon atoms. Therefore, in parallel with the studies of its chemistry and reaction dynamics, the authors continuously explore new, state-specific and efficient ways of producing atomic carbon. In the current program, C({sup 3}P) is produced via laser ablation of graphite, and three areas of study are being pursued: (i) exothermic reactions with small inorganic molecules (e.g., O{sub 2}, N{sub 2}O, NO{sub 2}) that can proceed via multiple pathways; (ii) the influence of vibrational and translational energy on endothermic reactions involving H-containing reactants that yield CH products (e.g., H{sub 2}O H{sub 2}CO); (iii) reactions of C({sup 3}P) with free radicals (e.g., HCO, CH{sub 3}O). In addition, the authors plan to develop a source of C({sup 1}D) atoms by exploiting the pyrolysis of diazotetrazole and its salts in the ablation source. Another important goal involves collaboration with theoreticians in order to obtain relevant potential energy surfaces, rationalize the experimental results and predict the roles of translational and vibrational energies.

  9. Carbon atomic wires: charge transfer induced electron conduction

    NASA Astrophysics Data System (ADS)

    Larade, Brian; Taylor, Jeremy; Mehrez, Hatem; Guo, Hong

    2001-03-01

    We report a first principles theoretical analysis of quantum transport properties of carbon atomic wires. Our theory is based on density functional theory within the LDA approximation, with standard norm conserving pseudopotentials defining the atomic core, and a localized orbital basis set to model the valence states. The charge density for the open atomic wire system is calculated using the non-equilibrium Green's functions. This theory is implemented in our molecular electronics modeling package McDCAL. For carbon atomic chains with different lengths in contact with metallic electrodes, we calculated linear DC conductance as a function of the chain-electrode distance and the current-voltage characteristics. Our results show that charge transfer from the electrodes to the atomic wire plays a most important role in aligning the Fermi level of the electrodes to the LUMO state of the atomic wire, inducing a substantial conductance variation due to this effect. Our results also show that the eigenstates of the carbon chain and band structure of the electrodes are of particular importance to the transport properties. We will compare our results to those obtained previously.

  10. A Monolithically Integrated Gallium Nitride Nanowire/Silicon Solar Cell Photocathode for Selective Carbon Dioxide Reduction to Methane.

    PubMed

    Wang, Yichen; Fan, Shizhao; AlOtaibi, Bandar; Wang, Yongjie; Li, Lu; Mi, Zetian

    2016-06-20

    A gallium nitride nanowire/silicon solar cell photocathode for the photoreduction of carbon dioxide (CO2 ) is demonstrated. Such a monolithically integrated nanowire/solar cell photocathode offers several unique advantages, including the absorption of a large part of the solar spectrum and highly efficient carrier extraction. With the incorporation of copper as the co-catalyst, the devices exhibit a Faradaic efficiency of about 19 % for the 8e(-) photoreduction to CH4 at -1.4 V vs Ag/AgCl, a value that is more than thirty times higher than that for the 2e(-) reduced CO (ca. 0.6 %).

  11. A nanoelectronic nose: a hybrid nanowire/carbon nanotube sensor array with integrated micromachined hotplates for sensitive gas discrimination.

    PubMed

    Chen, Po-Chiang; Ishikawa, Fumiaki N; Chang, Hsiao-Kang; Ryu, Koungmin; Zhou, Chongwu

    2009-03-25

    A novel hybrid chemical sensor array composed of individual In(2)O(3) nanowires, SnO(2) nanowires, ZnO nanowires, and single-walled carbon nanotubes with integrated micromachined hotplates for sensitive gas discrimination was demonstrated. Key features of our approach include the integration of nanowire and carbon nanotube sensors, precise control of the sensor temperature using the micromachined hotplates, and the use of principal component analysis for pattern recognition. This sensor array was exposed to important industrial gases such as hydrogen, ethanol and nitrogen dioxide at different concentrations and sensing temperatures, and an excellent selectivity was obtained to build up an interesting 'smell-print' library of these gases. Principal component analysis of the sensing results showed great discrimination of those three tested chemicals, and in-depth analysis revealed clear improvement of selectivity by the integration of carbon nanotube sensors. This nanoelectronic nose approach has great potential for detecting and discriminating between a wide variety of gases, including explosive ones and nerve agents.

  12. A nanoelectronic nose: a hybrid nanowire/carbon nanotube sensor array with integrated micromachined hotplates for sensitive gas discrimination

    NASA Astrophysics Data System (ADS)

    Chen, Po-Chiang; Ishikawa, Fumiaki N.; Chang, Hsiao-Kang; Ryu, Koungmin; Zhou, Chongwu

    2009-03-01

    A novel hybrid chemical sensor array composed of individual In2O3 nanowires, SnO2 nanowires, ZnO nanowires, and single-walled carbon nanotubes with integrated micromachined hotplates for sensitive gas discrimination was demonstrated. Key features of our approach include the integration of nanowire and carbon nanotube sensors, precise control of the sensor temperature using the micromachined hotplates, and the use of principal component analysis for pattern recognition. This sensor array was exposed to important industrial gases such as hydrogen, ethanol and nitrogen dioxide at different concentrations and sensing temperatures, and an excellent selectivity was obtained to build up an interesting 'smell-print' library of these gases. Principal component analysis of the sensing results showed great discrimination of those three tested chemicals, and in-depth analysis revealed clear improvement of selectivity by the integration of carbon nanotube sensors. This nanoelectronic nose approach has great potential for detecting and discriminating between a wide variety of gases, including explosive ones and nerve agents.

  13. Neutral atomic carbon in dense molecular clouds

    NASA Technical Reports Server (NTRS)

    Zmuidzinas, J.; Betz, A. L.; Boreiko, R. T.; Goldhaber, D. M.

    1988-01-01

    The 370 micron 3P2-3P1 fine-structure line of neutral carbon was detected in seven sources: OMC 1, NGC 2024, S140, W3, DR 21, M17, and W51. Simultaneous analysis of J = 2-1 data and available observations of the J = 1-0 line make it possible to deduce optical depths and excitation temperatures for these lines. These data indicate that both C I lines are likely to be optically thin, and that the ratio of C I to CO column densities in these clouds is typically about 0.1.

  14. Nanowires of Fe/multi-walled carbon nanotubes and nanometric thin films of Fe/MgO

    SciTech Connect

    Newman, Alexander; Khatiwada, Suman; Neupane, Suman; Seifu, Dereje

    2015-04-14

    We observed that nanowires of Fe grown in the lumens of multi-walled carbon nanotubes required four times higher magnetic field strength to reach saturation compared to planar nanometric thin films of Fe on MgO(100). Nanowires of Fe and nanometric thin films of Fe both exhibited two fold magnetic symmetries. Structural and magnetic properties of 1-dimensional nanowires and 2-dimensional nanometric films were studied by several magnetometery techniques. The θ-2θ x-ray diffraction measurements showed that a (200) peak of Fe appeared on thin film samples deposited at higher substrate temperatures. In these samples prepared at higher temperatures, lower coercive field and highly pronounced two-fold magnetic symmetry were observed. Our results show that maximum magnetocrystalline anisotropy occurred for sample deposited at 100 °C and it decreased at higher deposition temperatures.

  15. Hierarchically mesoporous CuO/carbon nanofiber coaxial shell-core nanowires for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Park, Seok-Hwan; Lee, Wan-Jin

    2015-05-01

    Hierarchically mesoporous CuO/carbon nanofiber coaxial shell-core nanowires (CuO/CNF) as anodes for lithium ion batteries were prepared by coating the Cu2(NO3)(OH)3 on the surface of conductive and elastic CNF via electrophoretic deposition (EPD), followed by thermal treatment in air. The CuO shell stacked with nanoparticles grows radially toward the CNF core, which forms hierarchically mesoporous three-dimensional (3D) coaxial shell-core structure with abundant inner spaces in nanoparticle-stacked CuO shell. The CuO shells with abundant inner spaces on the surface of CNF and high conductivity of 1D CNF increase mainly electrochemical rate capability. The CNF core with elasticity plays an important role in strongly suppressing radial volume expansion by inelastic CuO shell by offering the buffering effect. The CuO/CNF nanowires deliver an initial capacity of 1150 mAh g-1 at 100 mA g-1 and maintain a high reversible capacity of 772 mAh g-1 without showing obvious decay after 50 cycles.

  16. Hierarchically mesoporous CuO/carbon nanofiber coaxial shell-core nanowires for lithium ion batteries

    PubMed Central

    Park, Seok-Hwan; Lee, Wan-Jin

    2015-01-01

    Hierarchically mesoporous CuO/carbon nanofiber coaxial shell-core nanowires (CuO/CNF) as anodes for lithium ion batteries were prepared by coating the Cu2(NO3)(OH)3 on the surface of conductive and elastic CNF via electrophoretic deposition (EPD), followed by thermal treatment in air. The CuO shell stacked with nanoparticles grows radially toward the CNF core, which forms hierarchically mesoporous three-dimensional (3D) coaxial shell-core structure with abundant inner spaces in nanoparticle-stacked CuO shell. The CuO shells with abundant inner spaces on the surface of CNF and high conductivity of 1D CNF increase mainly electrochemical rate capability. The CNF core with elasticity plays an important role in strongly suppressing radial volume expansion by inelastic CuO shell by offering the buffering effect. The CuO/CNF nanowires deliver an initial capacity of 1150 mAh g−1 at 100 mA g−1 and maintain a high reversible capacity of 772 mAh g−1 without showing obvious decay after 50 cycles. PMID:25944615

  17. Plasmon-assisted local temperature control to pattern individual semiconductor nanowires and carbon nanotubes.

    PubMed

    Cao, Linyou; Barsic, David N; Guichard, Alex R; Brongersma, Mark L

    2007-11-01

    We demonstrate a new versatile strategy to rapidly heat and cool subdiffraction-limited volumes of material with a focused light beam. The local temperature rise is obtained by exploiting the unique optical properties of metallic nanostructures that facilitate efficient light-to-heat conversion through the excitation of surface plasmons (collective electron oscillations). By locally heating nanoscale metallic catalysts, growth of semiconductor nanowires and carbon nanotubes can be initiated and controlled at arbitrarily prespecified locations and down to the single nanostructure level in a room-temperature chamber. This local heating strategy can be orders of magnitude (>10(5)) more energy efficient than conventional chemical vapor deposition (CVD) tools in which an entire chamber/substrate is heated. For these reasons, it has great potential for use in process- and energy-efficient assembly of nanowires into complementary metal-oxide-semiconductor (CMOS) compatible device architectures. In general, the high degree of spatial and temporal control over nanoscale thermal environments afforded by this method inspires new pathways for manipulating a range of important thermally stimulated processes and the development of novel photothermal devices.

  18. Silicon nanowires, carbon nanotubes, and magnetic nanocrystals: Synthesis, properties, and applications

    NASA Astrophysics Data System (ADS)

    Lee, Doh Chang

    Central to the practical use of nanoscale materials is the controlled growth in technologically meaningful quantities. Many of the proposed applications of the nanomaterials potentially require inexpensive production of the building blocks. Solution-based synthetic approach offers controllability, high throughput, and scalability, which make the process attractive for the potential scale-up. Growth kinetics could be readily influenced by chemical interactions between the precursor and the solvent. In order to fully utilize its benefits, it is therefore pivotal to understand the decomposition chemistry of the precursors used in the reactions. Supercritical fluids were used as solvent in which high temperature reactions could take place. Silicon nanowires with diameters of 20˜30 nm was synthesized in supercritical fluids with metal nanocrystals as seeds for the nanowire growth. To unravel the effect of silicon precursors, several silicon precursors were reacted and the resulting products were investigated. The scalability of the system is discussed based on the experimental data. The nanowires were characterized with various characterization tools, including high-resolution transmission electron microscopy and electron energy loss spectroscopy. The crystallographic signatures were analyzed through the transmission electron microscopic study, and fundamental electrical and optical properties were probed by electron energy loss spectroscopy. Carbon nanotubes were prepared by reacting carbon-containing chemicals in supercritical fluids with organometallic compounds that form metal seed particles in-situ. A batch reaction, in which the temperature control was relatively poor, yielded a mixture of multiwall nanotubes and amorphous carbon nanofilaments with a low selectivity of nanotubes in the product. When reaction parameters were translated into a continuous flow-through reaction, nanotube selectivity as well as the throughput of the total product significantly

  19. Atomic-scale imaging of cation ordering in inverse spinel Zn2SnO4 nanowires.

    PubMed

    Bao, Lihong; Zang, Jianfeng; Wang, Guofeng; Li, Xiaodong

    2014-11-12

    By using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) coupled with density functional theory (DFT) calculations, we demonstrate the atomic-level imaging of cation ordering in inverse spinel Zn2SnO4 nanowires. This cation ordering was identified as 1:1 ordering of Zn(2+) and Sn(4+) at the octahedral sites of the inverse spinel crystal with microscopic symmetry transition from original cubic Fd3̅m to orthorhombic Imma group. This ordering generated a 67.8% increase in the elastic modulus and 1-2 order of magnitude lower in the electric conductivity and electron mobility compared to their bulk counterpart.

  20. Fluorescence modulation of single CdSe nanowires by charge injection through the tip of an atomic-force microscope.

    PubMed

    Schäfer, Sebastian; Wang, Zhe; Kipp, Tobias; Mews, Alf

    2011-09-23

    We demonstrate a direct correlation between the charge state and photoluminescence (PL) intensity of individual CdSe nanowires by actively charging them and performing electrostatic force microscopy and PL measurements simultaneously. While the injection of positive charges leads to an immediate PL quenching, a small amount of injected electrons can lead to an increase of the PL intensity. We directly observed the migration of excess charges into the substrate, which leads to a recovery of the PL. Further, we show that the PL of individual NWs can be actively switched between on and off states by charging with the atomic-force microscope tip. We propose a model based on charge trapping and migration into the substrate to explain our results.

  1. One-dimensional metallic surface states of Pt-induced atomic nanowires on Ge(0 0 1)

    NASA Astrophysics Data System (ADS)

    Yaji, Koichiro; Kim, Sunghun; Mochizuki, Izumi; Takeichi, Yasuo; Ohtsubo, Yoshiyuki; Le Fèvre, Patrick; Bertran, François; Taleb-Ibrahimi, Amina; Shin, Shik; Komori, Fumio

    2016-07-01

    Surface states of platinum-induced atomic nanowires on a germanium (0 0 1) surface, which shows a structural phase transition at 80 K, were studied by angle-resolved photoelectron spectroscopy (ARPES). We observed four one-dimensional metallic surface states, among which, two bands were reported in our previous study (Yaji et al 2013 Phys. Rev. B 87 241413). One of the newly-found two bands is a quasi-one-dimensional state and is split into two due to the Rashba effect. Photoelectron intensity from one of the spin-polarized branches is reduced at a boundary of the surface Brillouin zone below the phase transition temperature. The reduction of the photoelectron intensity in the low temperature phase is interpreted as the interference of photoelectrons, not as the Peierls instability. We also discuss the low energy properties of the metallic surface states and their spin splitting using high-resolution ARPES with a vacuum ultraviolet laser.

  2. Atomic-scale observation of pressure-dependent reduction dynamics of W18O49 nanowires using environmental TEM.

    PubMed

    Zhang, Zhengfei; Sheng, Liping; Chen, Lu; Zhang, Ze; Wang, Yong

    2017-06-28

    The real-time observation of structural evolution of materials can provide critical information for understanding their reduction mechanisms under different environments. Herein, we report the atomic-scale observation of the reduction dynamics of W18O49 nanowires (NWs) using environmental transmission electron microscopy. Intriguingly, the reduction pathway is found to be affected by oxygen pressure. Under high oxygen pressure (∼0.095 Pa), a W18O49 NW epitaxially transforms into a WO2 NW via mass transport across the interface between (010)W18O49 and (101)WO2. While under low oxygen pressure (∼0.0004 Pa), the transformation follows the sequence of W18O49(NW) → WO2(NW) → β-W(nanoparticles), which is identified as a new reduction pathway. These findings reveal the pressure-dependent reduction and a new transformation pathway, and extend our current understanding of the reduction dynamics of metal oxides.

  3. Atomic Layer Deposition Alumina-Passivated Silicon Nanowires: Probing the Transition from Electrochemical Double-Layer Capacitor to Electrolytic Capacitor.

    PubMed

    Gaboriau, Dorian; Boniface, Maxime; Valero, Anthony; Aldakov, Dmitry; Brousse, Thierry; Gentile, Pascal; Sadki, Said

    2017-04-10

    Silicon nanowires were coated by a 1-5 nm thin alumina layer by atomic layer deposition (ALD) in order to replace poorly reproducible and unstable native silicon oxide by a highly conformal passivating alumina layer. The surface coating enabled probing the behavior of symmetric devices using such electrodes in the EMI-TFSI electrolyte, allowing us to attain a large cell voltage up to 6 V in ionic liquid, together with very high cyclability with less than 4% capacitance fade after 10(6) charge/discharge cycles. These results yielded fruitful insights into the transition between an electrochemical double-layer capacitor behavior and an electrolytic capacitor behavior. Ultimately, thin ALD dielectric coatings can be used to obtain hybrid devices exhibiting large cell voltage and excellent cycle life of dielectric capacitors, while retaining energy and power densities close to the ones displayed by supercapacitors.

  4. Dielectric barrier discharge carbon atomic emission spectrometer: universal GC detector for volatile carbon-containing compounds.

    PubMed

    Han, Bingjun; Jiang, Xiaoming; Hou, Xiandeng; Zheng, Chengbin

    2014-01-07

    It was found that carbon atomic emission can be excited in low temperature dielectric barrier discharge (DBD), and an atmospheric pressure, low power consumption, and compact microplasma carbon atomic emission spectrometer (AES) was constructed and used as a universal and sensitive gas chromatographic (GC) detector for detection of volatile carbon-containing compounds. A concentric DBD device was housed in a heating box to increase the plasma operation temperature to 300 °C to intensify carbon atomic emission at 193.0 nm. Carbon-containing compounds directly injected or eluted from GC can be decomposed, atomized, and excited in this heated DBD for carbon atomic emission. The performance of this new optical detector was first evaluated by determination of a series of volatile carbon-containing compounds including formaldehyde, ethyl acetate, methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol, and absolute limits of detection (LODs) were found at a range of 0.12-0.28 ng under the optimized conditions. Preliminary experimental results showed that it provided slightly higher LODs than those obtained by GC with a flame ionization detector (FID). Furthermore, it is a new universal GC detector for volatile carbon-containing compounds that even includes those compounds which are difficult to detect by FID, such as HCHO, CO, and CO2. Meanwhile, hydrogen gas used in conventional techniques was eliminated; and molecular optical emission detection can also be performed with this GC detector for multichannel analysis to improve resolution of overlapped chromatographic peaks of complex mixtures.

  5. Discrete distribution of implanted and annealed arsenic atoms in silicon nanowires and its effect on device performance

    PubMed Central

    2012-01-01

    We have theoretically investigated the effects of random discrete distribution of implanted and annealed arsenic (As) atoms on device characteristics of silicon nanowire (Si NW) transistors. Kinetic Monte Carlo simulation is used for generating realistic random distribution of active As atoms in Si NWs. The active As distributions obtained through the kinetic Monte Carlo simulation are introduced into the source and drain extensions of n-type gate-all-around NW transistors. The current–voltage characteristics are calculated using the non-equilibrium Green's function method. The calculated results show significant fluctuation of the drain current. We examine the correlation between the drain current fluctuation and the factors related to random As distributions. We found that the fluctuation of the number of dopants in the source and drain extensions has little effect on the on-current fluctuation. We also found that the on-current fluctuation mainly originated from the randomness of interatomic distances of As atoms and hence is inherent in ultra-small NW transistors. PMID:23259464

  6. Investigation of Ag-TiO2 Interfacial Reaction of Highly Stable Ag Nanowire Transparent Conductive Film with Conformal TiO2 Coating by Atomic Layer Deposition.

    PubMed

    Yeh, Ming-Hua; Chen, Po-Hsun; Yang, Yi-Ching; Chen, Guan-Hong; Chen, Hsueh-Shih

    2017-03-29

    The atomic layer deposition (ALD) technique is applied to coat Ag nanowires (NWs) with a highly uniform and conformal TiO2 layer to improve the stability and sustainability of Ag NW transparent conductive films (TCFs) at high temperatures. The TiO2 layer can be directly deposited on Ag NWs with a surface polyvinylpyrrolidone (PVP) coat that acts a bed for TiO2 seeding in the ALD process. The ALD TiO2 layer significantly enhances the thermal stability at least 100 fold when aged between 200-400 °C and also provides an extra function of violet-blue light filtration for Ag NW TCFs. Investigation into the interaction between TiO2 and Ag reveals that the conformal TiO2 shell could effectively prevent Ag from 1D-to-3D ripening. However, Ag could penetrate the conformal TiO2 shell and form nanocrystals on the TiO2 shell surface when it is aged at 400 °C. According to experimental data and thermodynamic evaluation, the Ag penetration leads to an interlayer composed of mixed Ag-Ag2O-amorphous carbon phases and TiO2-x at the Ag-TiO2 interface, which is thought to be caused by extremely high vapor pressure of Ag at the Ag-TiO2 interface at a higher temperature (e.g., 400 °C).

  7. Abundance of atomic carbon /C I/ in dense interstellar clouds

    NASA Technical Reports Server (NTRS)

    Phillips, T. G.; Huggins, P. J.

    1981-01-01

    The abundance of interstellar neutral atomic carbon is investigated by means of its ground state fine-structure line emission at 492 GHz using the 91.5 cm telescope of NASAs Kuiper Airborne Observatory. Atomic carbon is found to be very abundant in dense interstellar molecular clouds with column densities of about 10 to the 19th per sq cm. Because the observations have considerably greater column densities than current theories of carbon chemistry, it is suggested that the physical conditions of these clouds are not as simple as assumed in the models. Various situations are discussed which would lead to large C I abundances, including the possibility that the chemical lifetimes of the clouds are relatively short.

  8. Fiber and fabric solar cells by directly weaving carbon nanotube yarns with CdSe nanowire-based electrodes.

    PubMed

    Zhang, Luhui; Shi, Enzheng; Ji, Chunyan; Li, Zhen; Li, Peixu; Shang, Yuanyuan; Li, Yibin; Wei, Jinquan; Wang, Kunlin; Zhu, Hongwei; Wu, Dehai; Cao, Anyuan

    2012-08-21

    Electrode materials are key components for fiber solar cells, and when combined with active layers (for light absorption and charge generation) in appropriate ways, they enable design and fabrication of efficient and innovative device structures. Here, we apply carbon nanotube yarns as counter electrodes in combination with CdSe nanowire-grafted primary electrodes (Ti wire) for making fiber and fabric-shaped photoelectrochemical cells with power conversion efficiencies in the range 1% to 2.9%. The spun-twist long nanotube yarns possess both good electrical conductivity and mechanical flexibility compared to conventional metal wires or carbon fibers, which facilitate fabrication of solar cells with versatile configurations. A unique feature of our process is that instead of making individual fiber cells, we directly weave single or multiple nanotube yarns with primary electrodes into a functional fabric. Our results demonstrate promising applications of semiconducting nanowires and carbon nanotubes in woven photovoltaics.

  9. Planar silver nanowire, carbon nanotube and PEDOT:PSS nanocomposite transparent electrodes

    PubMed Central

    Stapleton, Andrew J; Yambem, Soniya D; Johns, Ashley H; Afre, Rakesh A; Ellis, Amanda V; Shapter, Joe G; Andersson, Gunther G; Quinton, Jamie S; Burn, Paul L; Meredith, Paul

    2015-01-01

    Highly conductive, transparent and flexible planar electrodes were fabricated using interwoven silver nanowires and single-walled carbon nanotubes (AgNW:SWCNT) in a PEDOT:PSS matrix via an epoxy transfer method from a silicon template. The planar electrodes achieved a sheet resistance of 6.6 ± 0.0 Ω/□ and an average transmission of 86% between 400 and 800 nm. A high figure of merit of 367 Ω−1 is reported for the electrodes, which is much higher than that measured for indium tin oxide and reported for other AgNW composites. The AgNW:SWCNT:PEDOT:PSS electrode was used to fabricate low temperature (annealing free) devices demonstrating their potential to function with a range of organic semiconducting polymer:fullerene bulk heterojunction blend systems. PMID:27877771

  10. Hybrid transparent electrodes of silver nanowires and carbon nanotubes: a low-temperature solution process.

    PubMed

    Tokuno, Takehiro; Nogi, Masaya; Jiu, Jinting; Suganuma, Katsuaki

    2012-05-31

    Hybrid transparent electrodes with silver nanowires (AgNWs) and single-walled carbon nanotubes (SWCNTs) were fabricated on plastic films by a low-temperature solution process. The hybrid transparent electrodes exhibited a sheet resistance of 29.2 Ω/sq with a transparency of 80% when 6 wt.% of SWCNTs was mixed with AgNWs. This sheet resistance was less than one-fourth that of the AgNW transparent electrodes that were prepared using the same method. This reduction in sheet resistance is because the SWCNTs formed bridges between the AgNWs, thus, resulting in high conductivity of the hybrid transparent electrodes. The hybrid electrodes formed on plastic films exhibited high conductivity as well as excellent stability in sheet resistance when tested using a repeated bending test.PACS: 62.23.Hj; 61.48.De; 81.15.-z.

  11. Different roles of carbon and silicon vacancies in silicon carbide bulks and nanowires

    NASA Astrophysics Data System (ADS)

    Li, Shu-Long; Li, Ya-Lin; Li, Yan-Jing; Gong, Pei; Fang, Xiao-Yong

    2017-09-01

    We investigated the effects of carbon and silicon vacancies on the electronic structure and optical properties of pure silicon carbide (SiC) bulks and nanowires (NWs) based on density functional theory in CASTEP module. Calculation results showed that vacancies only slightly influenced structure and stability, particularly those of NWs. By contrast, effects on electronic function and optical properties were more notable. We found that the energy gaps of SiC bulks and NWs decreased with increased vacancies redistributing the electron density, which critically contributed to the formation of C-C and Si-Si bonds. The dielectric loss of SiC bulks and NWs in the ultraviolet region was primarily attributed to conductivity, whereas the loss in this region was due to the polarization of dangling bonds.

  12. Joining and interconnect formation of nanowires and carbon nanotubes for nanoelectronics and nanosystems.

    PubMed

    Cui, Qingzhou; Gao, Fan; Mukherjee, Subhadeep; Gu, Zhiyong

    2009-06-01

    Interconnect formation is critical for the assembly and integration of nanocomponents to enable nanoelectronics- and nanosystems-related applications. Recent progress on joining and interconnect formation of key nanomaterials, especially nanowires and carbon nanotubes, into functional circuits and/or prototype devices is reviewed. The nanosoldering technique through nanoscale lead-free solders is discussed in more detail in this Review. Various strategies of fabricating lead-free nanosolders and the utilization of the nanosoldering technique to form functional solder joints are reviewed, and related challenges facing the nanosoldering technique are discussed. A perspective is given for using lead-free nanosolders and the nanosoldering technique for the construction of complex and/or hybrid nanoelectronics and nanosystems.

  13. Planar silver nanowire, carbon nanotube and PEDOT:PSS nanocomposite transparent electrodes.

    PubMed

    Stapleton, Andrew J; Yambem, Soniya D; Johns, Ashley H; Afre, Rakesh A; Ellis, Amanda V; Shapter, Joe G; Andersson, Gunther G; Quinton, Jamie S; Burn, Paul L; Meredith, Paul; Lewis, David A

    2015-04-01

    Highly conductive, transparent and flexible planar electrodes were fabricated using interwoven silver nanowires and single-walled carbon nanotubes (AgNW:SWCNT) in a PEDOT:PSS matrix via an epoxy transfer method from a silicon template. The planar electrodes achieved a sheet resistance of 6.6 ± 0.0 Ω/□ and an average transmission of 86% between 400 and 800 nm. A high figure of merit of 367 Ω(-1) is reported for the electrodes, which is much higher than that measured for indium tin oxide and reported for other AgNW composites. The AgNW:SWCNT:PEDOT:PSS electrode was used to fabricate low temperature (annealing free) devices demonstrating their potential to function with a range of organic semiconducting polymer:fullerene bulk heterojunction blend systems.

  14. Planar silver nanowire, carbon nanotube and PEDOT:PSS nanocomposite transparent electrodes

    NASA Astrophysics Data System (ADS)

    Stapleton, Andrew J.; Yambem, Soniya D.; Johns, Ashley H.; Afre, Rakesh A.; Ellis, Amanda V.; Shapter, Joe G.; Andersson, Gunther G.; Quinton, Jamie S.; Burn, Paul L.; Meredith, Paul; Lewis, David A.

    2015-04-01

    Highly conductive, transparent and flexible planar electrodes were fabricated using interwoven silver nanowires and single-walled carbon nanotubes (AgNW:SWCNT) in a PEDOT:PSS matrix via an epoxy transfer method from a silicon template. The planar electrodes achieved a sheet resistance of 6.6 ± 0.0 Ω/□ and an average transmission of 86% between 400 and 800 nm. A high figure of merit of 367 Ω-1 is reported for the electrodes, which is much higher than that measured for indium tin oxide and reported for other AgNW composites. The AgNW:SWCNT:PEDOT:PSS electrode was used to fabricate low temperature (annealing free) devices demonstrating their potential to function with a range of organic semiconducting polymer:fullerene bulk heterojunction blend systems.

  15. Highly flexible and transparent dielectric elastomer actuators using silver nanowire and carbon nanotube hybrid electrodes.

    PubMed

    Lee, Ye Rim; Kwon, Hyungho; Lee, Do Hoon; Lee, Byung Yang

    2017-09-27

    We demonstrate a dielectric elastomer actuator (DEA) with a high areal strain value of 146% using hybrid electrodes of silver nanowires (AgNWs) and single-walled carbon nanotubes (SWCNTs). The addition of a very small amount of SWCNTs (∼35 ng mm(-2)) to a highly resistive AgNW network resulted in a remarkable reduction of the electrode sheet resistance by three orders, increasing the breakdown field by 183% and maximum strain, while maintaining the reduction of optical transmittance within 11%. The DEA based on our transparent and stretchable hybrid electrodes can be easily fabricated by a simple vacuum filtration and transfer process of the electrode film on a pre-strained dielectric elastomer membrane. We expect that our approach will be useful in the future for fabricating stretchable and transparent electrodes in various soft electronic devices.

  16. Silicon nanowire and carbon nanotube hybrid for room temperature multiwavelength light source

    PubMed Central

    Lo Faro, Maria Josè; D’Andrea, Cristiano; Messina, Elena; Fazio, Barbara; Musumeci, Paolo; Reitano, Riccardo; Franzò, Giorgia; Gucciardi, Pietro Giuseppe; Vasi, Cirino; Priolo, Francesco; Iacona, Fabio; Irrera, Alessia

    2015-01-01

    The realization of an innovative hybrid light source operating at room temperature, obtained by embedding a carbon nanotube (CNT) dispersion inside a Si nanowire (NW) array is reported. The NW/CNT system exhibits a peculiar photoluminescence spectrum, consisting of a wide peak, mainly observed in the visible range, due to quantum confined Si NWs, and of several narrower IR peaks, due to the different CNT chiralities present in the dispersion. The detailed study of the optical properties of the hybrid system evidences that the ratio between the intensity of the visible and the IR emissions can be varied within a wide range by changing the excitation wavelength or the CNT concentration; the conditions leading to the prevalence of one signal with respect to the other are identified. The multiplicity of emission spectra obtainable from this composite material opens new perspectives for Si nanostructures as active medium in light sources for Si photonics applications. PMID:26592198

  17. Highly conductive and stretchable Ag nanowire/carbon nanotube hybrid conductors

    NASA Astrophysics Data System (ADS)

    Woo, Ju Yeon; Kim, Kyun Kyu; Lee, Jongsoo; Kim, Ju Tae; Han, Chang-Soo

    2014-07-01

    Fabricating stretchable conductors through simple, cost-effective and scalable methods is a challenge. Here, we report on an approach used to develop nanowelded Ag nanowire/single-walled carbon nanotube (AgNW/SWCNT) hybrid films to be used as high-performance stretchable conductors. Plasmonic welding, which was done at the junctions of AgNWs in order to form hybrid AgNW/SWCNT conductors on an Ecoflex substrate, enabled excellent electrical and mechanical stability under large tensile strains of over 480% without the need to pre-strain. Furthermore, we demonstrate highly stretchable circuits that are used to power LED arrays. The LED arrays are formed using the plasmonic-welded AgNW/SWCNT/Ecoflex hybrid material, which demonstrates suitability for interconnector applications in flexible electronics.

  18. Carbon fiber-ZnO nanowire hybrid structures for flexible and adaptable strain sensors.

    PubMed

    Liao, Qingliang; Mohr, Markus; Zhang, Xiaohui; Zhang, Zheng; Zhang, Yue; Fecht, Hans-Jörg

    2013-12-21

    We report the flexible piezotronic strain sensors fabricated using carbon fiber-ZnO nanowire hybrid structures by a novel and reliable method. The I-V characteristic of the sensor shows high sensitivity to external strain due to the change in Schottky barrier height (SBH), which has a linear relationship with strain. This fabricated strain sensor has a quick, real-time current response under both static and dynamic mechanical loads. The change in SBH resulted from the strain-induced piezoelectric potential is investigated by band gap theory. In this work we develop a new feasible method to fabricate a flexible strain sensor within the fabric adapted to textile structures, able to measure their strain.

  19. Surface-initiated atom transfer radical polymerization-induced transformation of selenium nanowires into copper selenide@polystyrene core-shell nanowires.

    PubMed

    Wang, Michael C P; Gates, Byron D

    2013-10-09

    This Article reports the first preparation of cuprous and cupric selenide nanowires coated with a ∼5 nm thick sheath of polystyrene (copper selenide@polystyrene). These hybrid nanostructures are prepared by the transformation of selenium nanowires in a one-pot reaction, which is performed under ambient conditions. The composition, purity, and crystallinity of the copper selenide@polystyrene products were assessed by scanning transmission electron microscopy, electron energy-loss spectroscopy, X-ray powder diffraction, and X-ray photoelectron spectroscopy techniques. We determined that the single crystalline selenium nanowires are converted into polycrystalline copper selenide@polystyrene nanowires containing both cuprous selenide and cupric selenide. The product is purified through the selective removal of residual, non-transformed selenium nanowires by performing thermal evaporation below the decomposition temperature of these copper selenides. Powder X-ray diffraction of the purified copper selenide nanowires@polystyrene identified the presence of hexagonal, cubic, and orthorhombic phases of copper selenide. These purified cuprous and cupric selenide@polystyrene nanowires have an indirect bandgap of 1.44 eV, as determined by UV-vis absorption spectroscopy. This new synthesis of polymer-encapsulated nanoscale materials may provide a method for preparing other complex hybrid nanostructures.

  20. Fiber and fabric solar cells by directly weaving carbon nanotube yarns with CdSe nanowire-based electrodes

    NASA Astrophysics Data System (ADS)

    Zhang, Luhui; Shi, Enzheng; Ji, Chunyan; Li, Zhen; Li, Peixu; Shang, Yuanyuan; Li, Yibin; Wei, Jinquan; Wang, Kunlin; Zhu, Hongwei; Wu, Dehai; Cao, Anyuan

    2012-07-01

    Electrode materials are key components for fiber solar cells, and when combined with active layers (for light absorption and charge generation) in appropriate ways, they enable design and fabrication of efficient and innovative device structures. Here, we apply carbon nanotube yarns as counter electrodes in combination with CdSe nanowire-grafted primary electrodes (Ti wire) for making fiber and fabric-shaped photoelectrochemical cells with power conversion efficiencies in the range 1% to 2.9%. The spun-twist long nanotube yarns possess both good electrical conductivity and mechanical flexibility compared to conventional metal wires or carbon fibers, which facilitate fabrication of solar cells with versatile configurations. A unique feature of our process is that instead of making individual fiber cells, we directly weave single or multiple nanotube yarns with primary electrodes into a functional fabric. Our results demonstrate promising applications of semiconducting nanowires and carbon nanotubes in woven photovoltaics.Electrode materials are key components for fiber solar cells, and when combined with active layers (for light absorption and charge generation) in appropriate ways, they enable design and fabrication of efficient and innovative device structures. Here, we apply carbon nanotube yarns as counter electrodes in combination with CdSe nanowire-grafted primary electrodes (Ti wire) for making fiber and fabric-shaped photoelectrochemical cells with power conversion efficiencies in the range 1% to 2.9%. The spun-twist long nanotube yarns possess both good electrical conductivity and mechanical flexibility compared to conventional metal wires or carbon fibers, which facilitate fabrication of solar cells with versatile configurations. A unique feature of our process is that instead of making individual fiber cells, we directly weave single or multiple nanotube yarns with primary electrodes into a functional fabric. Our results demonstrate promising applications

  1. Facile preparation of carbon wrapped copper telluride nanowires as high performance anodes for sodium and lithium ion batteries.

    PubMed

    Yu, Hong; Yang, Jun; Geng, Hongbo; Li, Cheng Chao

    2017-04-07

    Uniform carbon wrapped copper telluride nanowires were successfully prepared by using an in situ conversion reaction. The length of these nanowires is up to several micrometers and the width is around 30-40 nm. The unique one dimensional structure and the presence of conformal carbon coating of copper telluride greatly accommodate the large volumetric changes during cycling, significantly increase the electrical conductivity and reduce charge transfer resistance. The copper telluride nanowires show promising performance in a lithium ion battery with a discharge capacity of 130.2 mA h g(-1) at a high current density of 6.0 A g(-1) (26.74 C) and a stable cycling performance of 673.3 mA h g(-1) during the 60th cycle at 100 mA g(-1). When evaluated as anode material for a sodium ion battery, the copper telluride nanowires deliver a reversible capacity of 68.1 mA h g(-1) at 1.0 A g(-1) (∼4.46 C) and have a high capacity retention of 177.5 mA h g(-1) during the 500th cycle at 100 mA g(-1).

  2. Facile preparation of carbon wrapped copper telluride nanowires as high performance anodes for sodium and lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Yu, Hong; Yang, Jun; Geng, Hongbo; Chao Li, Cheng

    2017-04-01

    Uniform carbon wrapped copper telluride nanowires were successfully prepared by using an in situ conversion reaction. The length of these nanowires is up to several micrometers and the width is around 30–40 nm. The unique one dimensional structure and the presence of conformal carbon coating of copper telluride greatly accommodate the large volumetric changes during cycling, significantly increase the electrical conductivity and reduce charge transfer resistance. The copper telluride nanowires show promising performance in a lithium ion battery with a discharge capacity of 130.2 mA h g‑1 at a high current density of 6.0 A g‑1 (26.74 C) and a stable cycling performance of 673.3 mA h g‑1 during the 60th cycle at 100 mA g‑1. When evaluated as anode material for a sodium ion battery, the copper telluride nanowires deliver a reversible capacity of 68.1 mA h g‑1 at 1.0 A g‑1 (∼4.46 C) and have a high capacity retention of 177.5 mA h g‑1 during the 500th cycle at 100 mA g‑1.

  3. Integrated atom detector based on field ionization near carbon nanotubes

    SciTech Connect

    Gruener, B.; Jag, M.; Stibor, A.; Visanescu, G.; Haeffner, M.; Kern, D.; Guenther, A.; Fortagh, J.

    2009-12-15

    We demonstrate an atom detector based on field ionization and subsequent ion counting. We make use of field enhancement near tips of carbon nanotubes to reach extreme electrostatic field values of up to 9x10{sup 9} V/m, which ionize ground-state rubidium atoms. The detector is based on a carpet of multiwall carbon nanotubes grown on a substrate and used for field ionization, and a channel electron multiplier used for ion counting. We measure the field enhancement at the tips of carbon nanotubes by field emission of electrons. We demonstrate the operation of the field ionization detector by counting atoms from a thermal beam of a rubidium dispenser source. By measuring the ionization rate of rubidium as a function of the applied detector voltage we identify the field ionization distance, which is below a few tens of nanometers in front of nanotube tips. We deduce from the experimental data that field ionization of rubidium near nanotube tips takes place on a time scale faster than 10{sup -10} s. This property is particularly interesting for the development of fast atom detectors suitable for measuring correlations in ultracold quantum gases. We also describe an application of the detector as partial pressure gauge.

  4. GaN Nanowire Functionalized with Atomic Layer Deposition Techniques for Enhanced Immobilization of Biomolecules

    DTIC Science & Technology

    2010-01-01

    GaN NW chips were fabricated using the molecular beam epitaxy technique under the condition of a high substrate temperature (∼800 C) and a high N2...18382 DOI: 10.1021/la103337a Langmuir 2010, 26(23), 18382–18391Published on Web 11/01/2010 pubs.acs.org/Langmuir © 2010 American Chemical Society...detection sensitivity. Three kinds of ALD coating films, Al2O3, TiO2, and SiO2, were grown on the gallium nitride nanowire (GaNNW) surfaces and

  5. Single-shell carbon nanotubes imaged by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Höper, Ralf; Workman, Richard K.; Chen, Dong; Sarid, Dror; Yadav, Tapesh; Withers, James C.; Loutfy, Raouf O.

    1994-05-01

    Single-shell carbon nanotubes, approximately 1 nm in diameter, have been imaged for the first time by atomic force microscopy operating in both the contact and tapping modes. For the contact mode, the height of the imaged nanotubes has been calibrated using the atomic steps of the silicon substrate on which the nanotubes were deposited. For the tapping mode, the calibration was performed using an industry-standard grating. The paper discusses substrate and sample preparation methods for the characterization by scanning probe microscopy of nanotubes deposited on a substrate.

  6. Atomic-scale deformation in N-doped carbon nanotubes.

    PubMed

    Sun, Chia-Liang; Wang, Houng-Wei; Hayashi, Michitoshi; Chen, Li-Chyong; Chen, Kuei-Hsien

    2006-07-05

    We present the N-doping induced atomic-scale structural deformation in N-doped carbon nanotubes by using density functional theory calculations. For substitutional N-doped nanotube clusters, the N dopant with an excess electron lone pair exhibits the high negative charge, and the homogeneously distributed dopants enlarge the tube diameter in both zigzag and armchair cases. On the other hand, in pyridine-like N-doped ones, the concentrated N atoms result in a positively curved graphene layer and, thus, can be responsible for tube wall roughness and the formation of interlinked structures.

  7. Atomic hydrogen maser measurements with wall surfaces of carbon tetrafluoride

    NASA Technical Reports Server (NTRS)

    Vessot, R. F. C.; Mattison, E. M.; Imbier, E. A.; Zhai, Z. C.

    1984-01-01

    The principal objectives of the Smithsonian Astrophysical Observatory cold maser research programs are given. This work is aimed principally at understanding more about the interaction of hydrogen atoms with wall coatings of fluorinated ethylene propylene (Dupont Teflon FEP-120 co-polymer) and of carbon tetrafluoride (CE4). The principal measured quantity in these experiments is the wall shift of the maser's output frequency. The wall shift per atomic collision was calculated from the measured wall frequency shift. This assumes that the wall surface area is smooth on a molecular scale.

  8. Carbon Quantum Dot Surface-Engineered VO2 Interwoven Nanowires: A Flexible Cathode Material for Lithium and Sodium Ion Batteries.

    PubMed

    Balogun, Muhammad-Sadeeq; Luo, Yang; Lyu, Feiyi; Wang, Fuxin; Yang, Hao; Li, Haibo; Liang, Chaolun; Huang, Miao; Huang, Yongchao; Tong, Yexiang

    2016-04-20

    The use of electrode materials in their powdery form requires binders and conductive additives for the fabrication of the cells, which leads to unsatisfactory energy storage performance. Recently, a new strategy to design flexible, binder-, and additive-free three-dimensional electrodes with nanoscale surface engineering has been exploited in boosting the storage performance of electrode materials. In this paper, we design a new type of free-standing carbon quantum dot coated VO2 interwoven nanowires through a simple fabrication process and demonstrate its potential to be used as cathode material for lithium and sodium ion batteries. The versatile carbon quantum dots that are vastly flexible for surface engineering serve the function of protecting the nanowire surface and play an important role in the diffusion of electrons. Also, the three-dimensional carbon cloth coated with VO2 interwoven nanowires assisted in the diffusion of ions through the inner and the outer surface. With this unique architecture, the carbon quantum dot nanosurface engineered VO2 electrode exhibited capacities of 420 and 328 mAh g(-1) at current density rate of 0.3 C for lithium and sodium storage, respectively. This work serves as a milestone for the potential replacement of lithium ion batteries and next generation postbatteries.

  9. Ab initio quantum transport in atomic carbon chains

    NASA Astrophysics Data System (ADS)

    Botello-Méndez, Andrés R.; Charlier, Jean-Christophe; Banhart, Florian; NAPS Team; Carbyne Collaboration

    2015-03-01

    Carbyne, the sp-hybridized phase of carbon, is still a missing link in the family of carbon allotropes. Recently, detailed electrical measurements and first-principles electronic transport calculations have been performed on monoatomic carbon chains. When the 1D system is under strain, the current-voltage curves exhibit a semiconducting behavior, which corresponds to the polyyne structure of the atomic chain with alternating single and triple bonds. Conversely, when the chain is unstrained, the ohmic behavior is observed in agreement with the metallic cumulene structure with double bonds, confirming recent theoretical predictions, namely that a metal-insulator transition can be induced by adjusting the strain. The key role of the contacting leads is also scrutinized by ab initio quantum conductance calculations, explaining the rectifying behavior measured in monoatomic carbon chains in a non-symmetric contact configuration.

  10. Glucose-Derived Porous Carbon-Coated Silicon Nanowires as Efficient Electrodes for Aqueous Micro-Supercapacitors.

    PubMed

    Devarapalli, Rami Reddy; Szunerits, Sabine; Coffinier, Yannick; Shelke, Manjusha V; Boukherroub, Rabah

    2016-02-01

    In this study, we report on carbon coating of vertically aligned silicon nanowire (SiNWs) arrays via a simple hydrothermal process using glucose as carbon precursor. Using this process, a thin carbon layer is uniformly deposited on the SiNWs. Under optimized conditions, the coated SiNWs electrode showed better electrochemical energy storage capacity as well as exceptional stability in aqueous system as compared to uncoated SiNWs. The as-measured capacitance reached 25.64 mF/cm(2) with a good stability up to 25000 charging/discharging cycles in 1 M Na2SO4 aqueous solution.

  11. Electroanalytical performance of carbon films with near-atomic flatness.

    PubMed

    Ranganathan, S; McCreery, R L

    2001-03-01

    Physicochemical and electrochemical characterization of carbon films obtained by pyrolyzing a commercially available photoresist has been performed. Photoresist spin-coated on to a silicon wafer was pyrolyzed at 1,000 degrees C in a reducing atmosphere (95% nitrogen and 5% hydrogen) to produce conducting carbon films. The pyrolyzed photoresist films (PPF) show unusual surface properties compared to other carbon electrodes. The surfaces are nearly atomically smooth with a root-mean-square roughness of <0.5 nm. PPF have a very low background current and oxygen/carbon atomic ratio compared to conventional glassy carbon and show relatively weak adsorption of methylene blue and anthraquinone-2,6-disulfonate. The low oxygen/carbon ratio and the relative stability of PPF indicate that surfaces may be partially hydrogen terminated. The pyrolyzed films were compared to glassy carbon (GC) heat treated under the same conditions as pyrolysis to evaluate the electroanalytical utility of PPF. Heterogeneous electron-transfer kinetics of various redox systems were evaluated. For Ru(NH3)6(3+/2+), Fe(CN)6(3-/4-), and chlorpromazine, fresh PPF surfaces show electron-transfer rates similar to those on GC, but for redox systems such as Fe3+/2+, ascorbic acid, dopamine, and oxygen, the kinetics on PPF are slower. Very weak interactions between the PPF surface and these redox systems lead to their slow electron-transfer kinetics. Electrochemical anodization results in a simultaneous increase in background current, adsorption, and electron-transfer kinetics. The PPF surfaces can be chemically modified via diazonium ion reduction to yield a covalently attached monolayer. Such a modification could help in the preparation of low-cost, high-volume analyte-specific electrodes for diverse electroanalytical applications. Overall, pyrolysis of the photoresist yields an electrode surface with properties similar to a very smooth version of glassy carbon, with some important differences in surface

  12. Effective Surface Passivation of InP Nanowires by Atomic-Layer-Deposited Al2O3 with POx Interlayer.

    PubMed

    Black, L E; Cavalli, A; Verheijen, M A; Haverkort, J E M; Bakkers, E P A M; Kessels, W M M

    2017-10-11

    III/V semiconductor nanostructures have significant potential in device applications, but effective surface passivation is critical due to their large surface-to-volume ratio. For InP such passivation has proven particularly difficult, with substantial depassivation generally observed following dielectric deposition on InP surfaces. We present a novel approach based on passivation with a phosphorus-rich interfacial oxide deposited using a low-temperature process, which is critical to avoid P-desorption. For this purpose we have chosen a POx layer deposited in a plasma-assisted atomic layer deposition (ALD) system at room temperature. Since POx is known to be hygroscopic and therefore unstable in atmosphere, we encapsulate this layer with a thin ALD Al2O3 capping layer to form a POx/Al2O3 stack. This passivation scheme is capable of improving the photoluminescence (PL) efficiency of our state-of-the-art wurtzite (WZ) InP nanowires by a factor of ∼20 at low excitation. If we apply the rate equation analysis advocated by some authors, we derive a PL internal quantum efficiency (IQE) of 75% for our passivated wires at high excitation. Our results indicate that it is more reliable to calculate the IQE as the ratio of the integrated PL intensity at room temperature to that at 10 K. By this means we derive an IQE of 27% for the passivated wires at high excitation (>10 kW cm(-2)), which constitutes an unprecedented level of performance for undoped InP nanowires. This conclusion is supported by time-resolved PL decay lifetimes, which are also shown to be significantly higher than previously reported for similar wires. The passivation scheme displays excellent long-term stability (>7 months) and is additionally shown to substantially improve the thermal stability of InP surfaces (>300 °C), significantly expanding the temperature window for device processing. Such effective surface passivation is a key enabling technology for InP nanowire devices such as nanolasers and

  13. Atom probe tomography evaporation behavior of C-axis GaN nanowires: Crystallographic, stoichiometric, and detection efficiency aspects

    SciTech Connect

    Diercks, David R. Gorman, Brian P.; Kirchhofer, Rita; Sanford, Norman; Bertness, Kris; Brubaker, Matt

    2013-11-14

    The field evaporation behavior of c-axis GaN nanowires was explored in two different laser-pulsed atom probe tomography (APT) instruments. Transmission electron microscopy imaging before and after atom probe tomography analysis was used to assist in reconstructing the data and assess the observed evaporation behavior. It was found that the ionic species exhibited preferential locations for evaporation related to the underlying crystal structure of the GaN and that the species which evaporated from these locations was dependent on the pulsed laser energy. Additionally, the overall stoichiometry measured by APT was significantly correlated with the energy of the laser pulses. At the lowest laser energies, the apparent composition was nitrogen-rich, while higher laser energies resulted in measurements of predominantly gallium compositions. The percent of ions detected (detection efficiency) for these specimens was found to be considerably below that shown for other materials, even for laser energies which produced the expected Ga:N ratio. The apparent stoichiometry variation and low detection efficiency appear to be a result of evaporation of Ga ions between laser pulses at the lowest laser energies and evaporation of neutral N{sub 2} species at higher laser energies. All of these behaviors are tied to the formation of nitrogen-nitrogen bonds on the tip surface, which occurred under all analysis conditions. Similar field evaporation behaviors are therefore expected for other materials where the anionic species readily form a strong diatomic bond.

  14. Atom probe tomography evaporation behavior of C-axis GaN nanowires: Crystallographic, stoichiometric, and detection efficiency aspects

    NASA Astrophysics Data System (ADS)

    Diercks, David R.; Gorman, Brian P.; Kirchhofer, Rita; Sanford, Norman; Bertness, Kris; Brubaker, Matt

    2013-11-01

    The field evaporation behavior of c-axis GaN nanowires was explored in two different laser-pulsed atom probe tomography (APT) instruments. Transmission electron microscopy imaging before and after atom probe tomography analysis was used to assist in reconstructing the data and assess the observed evaporation behavior. It was found that the ionic species exhibited preferential locations for evaporation related to the underlying crystal structure of the GaN and that the species which evaporated from these locations was dependent on the pulsed laser energy. Additionally, the overall stoichiometry measured by APT was significantly correlated with the energy of the laser pulses. At the lowest laser energies, the apparent composition was nitrogen-rich, while higher laser energies resulted in measurements of predominantly gallium compositions. The percent of ions detected (detection efficiency) for these specimens was found to be considerably below that shown for other materials, even for laser energies which produced the expected Ga:N ratio. The apparent stoichiometry variation and low detection efficiency appear to be a result of evaporation of Ga ions between laser pulses at the lowest laser energies and evaporation of neutral N2 species at higher laser energies. All of these behaviors are tied to the formation of nitrogen-nitrogen bonds on the tip surface, which occurred under all analysis conditions. Similar field evaporation behaviors are therefore expected for other materials where the anionic species readily form a strong diatomic bond.

  15. Diamond-modified AFM probes: from diamond nanowires to atomic force microscopy-integrated boron-doped diamond electrodes.

    PubMed

    Smirnov, Waldemar; Kriele, Armin; Hoffmann, René; Sillero, Eugenio; Hees, Jakob; Williams, Oliver A; Yang, Nianjun; Kranz, Christine; Nebel, Christoph E

    2011-06-15

    In atomic force microscopy (AFM), sharp and wear-resistant tips are a critical issue. Regarding scanning electrochemical microscopy (SECM), electrodes are required to be mechanically and chemically stable. Diamond is the perfect candidate for both AFM probes as well as for electrode materials if doped, due to diamond's unrivaled mechanical, chemical, and electrochemical properties. In this study, standard AFM tips were overgrown with typically 300 nm thick nanocrystalline diamond (NCD) layers and modified to obtain ultra sharp diamond nanowire-based AFM probes and probes that were used for combined AFM-SECM measurements based on integrated boron-doped conductive diamond electrodes. Analysis of the resonance properties of the diamond overgrown AFM cantilevers showed increasing resonance frequencies with increasing diamond coating thicknesses (i.e., from 160 to 260 kHz). The measured data were compared to performed simulations and show excellent correlation. A strong enhancement of the quality factor upon overgrowth was also observed (120 to 710). AFM tips with integrated diamond nanowires are shown to have apex radii as small as 5 nm and where fabricated by selectively etching diamond in a plasma etching process using self-organized metal nanomasks. These scanning tips showed superior imaging performance as compared to standard Si-tips or commercially available diamond-coated tips. The high imaging resolution and low tip wear are demonstrated using tapping and contact mode AFM measurements by imaging ultra hard substrates and DNA. Furthermore, AFM probes were coated with conductive boron-doped and insulating diamond layers to achieve bifunctional AFM-SECM probes. For this, focused ion beam (FIB) technology was used to expose the boron-doped diamond as a recessed electrode near the apex of the scanning tip. Such a modified probe was used to perform proof-of-concept AFM-SECM measurements. The results show that high-quality diamond probes can be fabricated, which are

  16. Carbon nanotube forests growth using catalysts from atomic layer deposition

    SciTech Connect

    Chen, Bingan; Zhang, Can; Esconjauregui, Santiago; Xie, Rongsi; Zhong, Guofang; Robertson, John; Bhardwaj, Sunil; Cepek, Cinzia

    2014-04-14

    We have grown carbon nanotubes using Fe and Ni catalyst films deposited by atomic layer deposition. Both metals lead to catalytically active nanoparticles for growing vertically aligned nanotube forests or carbon fibres, depending on the growth conditions and whether the substrate is alumina or silica. The resulting nanotubes have narrow diameter and wall number distributions that are as narrow as those grown from sputtered catalysts. The state of the catalyst is studied by in-situ and ex-situ X-ray photoemission spectroscopy. We demonstrate multi-directional nanotube growth on a porous alumina foam coated with Fe prepared by atomic layer deposition. This deposition technique can be useful for nanotube applications in microelectronics, filter technology, and energy storage.

  17. Heat conduction in double-walled carbon nanotubes with intertube additional carbon atoms.

    PubMed

    Cui, Liu; Feng, Yanhui; Tan, Peng; Zhang, Xinxin

    2015-07-07

    Heat conduction of double-walled carbon nanotubes (DWCNTs) with intertube additional carbon atoms was investigated for the first time using a molecular dynamics method. By analyzing the phonon vibrational density of states (VDOS), we revealed that the intertube additional atoms weak the heat conduction along the tube axis. Moreover, the phonon participation ratio (PR) demonstrates that the heat transfer in DWCNTs is dominated by low frequency modes. The added atoms cause the mode weight factor (MWF) of the outer tube to decrease and that of the inner tube to increase, which implies a lower thermal conductivity. The effects of temperature, tube length, and the number and distribution of added atoms were studied. Furthermore, an orthogonal array testing strategy was designed to identify the most important structural factor. It is indicated that the tendencies of thermal conductivity of DWCNTs with added atoms change with temperature and length are similar to bare ones. In addition, thermal conductivity decreases with the increasing number of added atoms, more evidently for atom addition concentrated at some cross-sections rather than uniform addition along the tube length. Simultaneously, the number of added atoms at each cross-section has a considerably more remarkable impact, compared to the tube length and the density of chosen cross-sections to add atoms.

  18. Probing the improbable: imaging carbon atoms in alumina

    SciTech Connect

    Marquis, E A; Yahia, Noor; Larson, David J.; Miller, Michael K; Todd, Richard

    2010-01-01

    Atom-probe tomography has proven very powerful to analyze the detailed structure and chemistry of metallic alloys and semiconductor structures while ceramic materials have remained outside its standard purview. In the current work, we demonstrate that bulk alumina can be quantitatively analyzed and microstructural features observed. The analysis of grain boundary carbon segregation - barely achievable by electron microscopy - opens the possibility of understanding the mechanistic effects of dopants on mechanical properties, fracture and wear properties of bulk oxides.

  19. Stability of conductance oscillations in carbon atomic chains

    NASA Astrophysics Data System (ADS)

    Yu, Jing-Xin; Hou, Zhi-Wei; Liu, Xiu-Ying

    2015-06-01

    The conductance stabilities of carbon atomic chains (CACs) with different lengths are investigated by performing theoretical calculations using the nonequilibrium Green’s function method combined with density functional theory. Regular even-odd conductance oscillation is observed as a function of the wire length. This oscillation is influenced delicately by changes in the end carbon or sulfur atoms as well as variations in coupling strength between the chain and leads. The lowest unoccupied molecular orbital in odd-numbered chains is the main transmission channel, whereas the conductance remains relatively small for even-numbered chains and a significant drift in the highest occupied molecular orbital resonance toward higher energies is observed as the number of carbon atoms increases. The amplitude of the conductance oscillation is predicted to be relatively stable based on a thiol joint between the chain and leads. Results show that the current-voltage evolution of CACs can be affected by the chain length. The differential and second derivatives of the conductance are also provided. Project supported by the National Natural Science Foundation of China (Grant Nos. 11304079, 11404094, and 51201059), the Priority Scientific and Technological Project of Henan Province, China (Grant No. 14A140027), the School Fund (Grant No. 2012BS055), and the Plan of Natural Science Fundamental Research of Henan University of Technology, China (Grant No. 2014JCYJ15).

  20. Selective ultrathin carbon sheath on porous silicon nanowires: materials for extremely high energy density planar micro-supercapacitors.

    PubMed

    Alper, John P; Wang, Shuang; Rossi, Francesca; Salviati, Giancarlo; Yiu, Nicholas; Carraro, Carlo; Maboudian, Roya

    2014-01-01

    Microsupercapacitors are attractive energy storage devices for integration with autonomous microsensor networks due to their high-power capabilities and robust cycle lifetimes. Here, we demonstrate porous silicon nanowires synthesized via a lithography compatible low-temperature wet etch and encapsulated in an ultrathin graphitic carbon sheath, as electrochemical double layer capacitor electrodes. Specific capacitance values reaching 325 mF cm(-2) are achieved, representing the highest specific ECDL capacitance for planar microsupercapacitor electrode materials to date.

  1. An interwoven network of MnO₂ nanowires and carbon nanotubes as the anode for bendable lithium-ion batteries.

    PubMed

    Ee, Shu Jing; Pang, Hongchang; Mani, Ulaganathan; Yan, Qingyu; Ting, Siong Luong; Chen, Peng

    2014-08-25

    A porous interwoven network is synthesized, consisting of ultralong MnO2 nanowires and multi-walled carbon nanotubes (MWCNTs). Serving as the anode for a lithium-ion battery, this nanocomposite demonstrates excellent performance due to the synergistic integration of these two 1D materials. Taking advantage of the excellent flexibility and strength of this MnO2-MWCNT network, a full, bendable battery is made that offers high capacity, cycling stability, and low cost.

  2. A palladium-doped ceria@carbon core-sheath nanowire network: a promising catalyst support for alcohol electrooxidation reactions

    NASA Astrophysics Data System (ADS)

    Tan, Qiang; Du, Chunyu; Sun, Yongrong; Du, Lei; Yin, Geping; Gao, Yunzhi

    2015-08-01

    A novel palladium-doped ceria and carbon core-sheath nanowire network (Pd-CeO2@C CSNWN) is synthesized by a template-free and surfactant-free solvothermal process, followed by high temperature carbonization. This hierarchical network serves as a new class of catalyst support to enhance the activity and durability of noble metal catalysts for alcohol oxidation reactions. Its supported Pd nanoparticles, Pd/(Pd-CeO2@C CSNWN), exhibit >9 fold increase in activity toward the ethanol oxidation over the state-of-the-art Pd/C catalyst, which is the highest among the reported Pd systems. Moreover, stability tests show a virtually unchanged activity after 1000 cycles. The high activity is mainly attributed to the superior oxygen-species releasing capability of Pd-doped CeO2 nanowires by accelerating the removal of the poisoning intermediate. The unique interconnected one-dimensional core-sheath structure is revealed to facilitate immobilization of the metal catalysts, leading to the improved durability. This core-sheath nanowire network opens up a new strategy for catalyst performance optimization for next-generation fuel cells.A novel palladium-doped ceria and carbon core-sheath nanowire network (Pd-CeO2@C CSNWN) is synthesized by a template-free and surfactant-free solvothermal process, followed by high temperature carbonization. This hierarchical network serves as a new class of catalyst support to enhance the activity and durability of noble metal catalysts for alcohol oxidation reactions. Its supported Pd nanoparticles, Pd/(Pd-CeO2@C CSNWN), exhibit >9 fold increase in activity toward the ethanol oxidation over the state-of-the-art Pd/C catalyst, which is the highest among the reported Pd systems. Moreover, stability tests show a virtually unchanged activity after 1000 cycles. The high activity is mainly attributed to the superior oxygen-species releasing capability of Pd-doped CeO2 nanowires by accelerating the removal of the poisoning intermediate. The unique

  3. Atomic scale characterization and surface chemistry of metal modified titanate nanotubes and nanowires

    NASA Astrophysics Data System (ADS)

    Kukovecz, Ákos; Kordás, Krisztián; Kiss, János; Kónya, Zoltán

    2016-10-01

    Titanates are salts of polytitanic acid that can be synthesized as nanostructures in a great variety concerning crystallinity, morphology, size, metal content and surface chemistry. Titanate nanotubes (open-ended hollow cylinders measuring up to 200 nm in length and 15 nm in outer diameter) and nanowires (solid, elongated rectangular blocks with length up to 1500 nm and 30-60 nm diameter) are the most widespread representatives of the titanate nanomaterial family. This review covers the properties and applications of these two materials from the surface science point of view. Dielectric, vibrational, electron and X-ray spectroscopic results are comprehensively discussed first, then surface modification methods including covalent functionalization, ion exchange and metal loading are covered. The versatile surface chemistry of one-dimensional titanates renders them excellent candidates for heterogeneous catalytic, photocatalytic, photovoltaic and energy storage applications, therefore, these fields are also reviewed.

  4. Phonons in Ge nanowires

    NASA Astrophysics Data System (ADS)

    Peelaers, H.; Partoens, B.; Peeters, F. M.

    2009-09-01

    The phonon spectra of thin freestanding, hydrogen passivated, Ge nanowires are calculated by ab initio techniques. The effect of confinement on the phonon modes as caused by the small diameters of the wires is investigated. Confinement causes a hardening of the optical modes and a softening of the longitudinal acoustic modes. The stability of the nanowires, undoped or doped with B or P atoms, is investigated using the obtained phonon spectra. All considered wires were stable, except for highly doped, very thin nanowires.

  5. Controllable Synthesis of Copper Oxide/Carbon Core/Shell Nanowire Arrays and Their Application for Electrochemical Energy Storage.

    PubMed

    Zhan, Jiye; Chen, Minghua; Xia, Xinhui

    2015-10-09

    Rational design/fabrication of integrated porous metal oxide arrays is critical for the construction of advanced electrochemical devices. Herein, we report self-supported CuO/C core/shell nanowire arrays prepared by the combination of electro-deposition and chemical vapor deposition methods. CuO/C nanowires with diameters of ~400 nm grow quasi-vertically to the substrates forming three-dimensional arrays architecture. A thin carbon shell is uniformly coated on the CuO nanowire cores. As an anode of lithium ion batteries, the resultant CuO/C nanowire arrays are demonstrated to have high specific capacity (672 mAh·g(-1) at 0.2 C) and good cycle stability (425 mAh·g(-1) at 1 C up to 150 cycles). The core/shell arrays structure plays positive roles in the enhancement of Li ion storage due to fast ion/electron transfer path, good strain accommodation and sufficient contact between electrolyte and active materials.

  6. Controllable Synthesis of Copper Oxide/Carbon Core/Shell Nanowire Arrays and Their Application for Electrochemical Energy Storage

    PubMed Central

    Zhan, Jiye; Chen, Minghua; Xia, Xinhui

    2015-01-01

    Rational design/fabrication of integrated porous metal oxide arrays is critical for the construction of advanced electrochemical devices. Herein, we report self-supported CuO/C core/shell nanowire arrays prepared by the combination of electro-deposition and chemical vapor deposition methods. CuO/C nanowires with diameters of ~400 nm grow quasi-vertically to the substrates forming three-dimensional arrays architecture. A thin carbon shell is uniformly coated on the CuO nanowire cores. As an anode of lithium ion batteries, the resultant CuO/C nanowire arrays are demonstrated to have high specific capacity (672 mAh·g−1 at 0.2 C) and good cycle stability (425 mAh·g−1 at 1 C up to 150 cycles). The core/shell arrays structure plays positive roles in the enhancement of Li ion storage due to fast ion/electron transfer path, good strain accommodation and sufficient contact between electrolyte and active materials. PMID:28347084

  7. Novel approach for observing the asymmetrical evolution and the compositional nonuniformity of laser pulsed atom probe tomography of a single ZnO nanowire

    NASA Astrophysics Data System (ADS)

    Seol, Jae-Bok; Kim, Young-Tae; Kim, Bo-Hwa; Park, Chan-Gyung

    2016-01-01

    The characterization of ZnO nanowires is crucial for developing nanostructured devices together with related compounds and alloys with an atomic-scale regime. This study describes the effects of laser energy on the atom probe tomography analysis of a single ZnO nanowire with a high aspect ratio, diameters of 80?100 nm and lengths of 10 µm. We observed both an asymmetrical evolution in the apex morphology and the compositional nonuniformities of Zn and O ions with respect to the laser energies ranging from 5 to 40 nJ. When the higher laser illumination exposed to the ZnO nanowires, non-uniform field strength becomes noticeable especially at the laser incident side of the samples. Moreover, we measured the charge state ratios of Zn+ and Zn2+ ions as a function of the applied laser energies. Our results proved important for accurate quantitative characterization and better interpretation for the laser-pulsed atom probe tomography of ZnO-based devices.

  8. Metallic WO2-Carbon Mesoporous Nanowires as Highly Efficient Electrocatalysts for Hydrogen Evolution Reaction.

    PubMed

    Wu, Rui; Zhang, Jingfang; Shi, Yanmei; Liu, Dali; Zhang, Bin

    2015-06-10

    The development of electrocatalysts to generate hydrogen, with good activity and stability, is a great challenge in the fields of chemistry and energy. Here we demonstrate a "hitting three birds with one stone" method to synthesize less toxic metallic WO2-carbon mesoporous nanowires with high concentration of oxygen vacancies (OVs) via calcination of inorganic/organic WO3-ethylenediamine hybrid precursors. The products exhibit excellent performance for H2 generation: the onset overpotential is only 35 mV, the required overpotentials for 10 and 20 mA/cm(2) are 58 and 78 mV, the Tafel slope is 46 mV/decade, the exchange current density is 0.64 mA/cm(2), and the stability is over 10 h. Further studies, in combination with density functional theory, demonstrate that the unusual electronic structure and the large amount of active sites, generated by the high concentration of OVs, as well as the closely attached carbon materials, were key factors for excellent performance. Our results experimentally and theoretically establish metallic transition metal oxides (TMOs) as intriguing novel electrocatalysts for H2 generation. Such TMOs with OVs might be promising candidates for other energy storage and conversion applications.

  9. Aligned carbon nanotube/zinc oxide nanowire hybrids as high performance electrodes for supercapacitor applications

    NASA Astrophysics Data System (ADS)

    Al-Asadi, Ahmed S.; Henley, Luke Alexander; Wasala, Milinda; Muchharla, Baleeswaraiah; Perea-Lopez, Nestor; Carozo, Victor; Lin, Zhong; Terrones, Mauricio; Mondal, Kanchan; Kordas, Krisztian; Talapatra, Saikat

    2017-03-01

    Carbon nanotube/metal oxide based hybrids are envisioned as high performance electrochemical energy storage electrodes since these systems can provide improved performances utilizing an electric double layer coupled with fast faradaic pseudocapacitive charge storage mechanisms. In this work, we show that high performance supercapacitor electrodes with a specific capacitance of ˜192 F/g along with a maximum energy density of ˜3.8 W h/kg and a power density of ˜ 28 kW/kg can be achieved by synthesizing zinc oxide nanowires (ZnO NWs) directly on top of aligned multi-walled carbon nanotubes (MWCNTs). In comparison to pristine MWCNTs, these constitute a 12-fold of increase in specific capacitance as well as corresponding power and energy density values. These electrodes also possess high cycling stability and were able to retain ˜99% of their specific capacitance value over 2000 charging discharging cycles. These findings indicate potential use of a MWCNT/ZnO NW hybrid material for future electrochemical energy storage applications.

  10. Carbon related donor bound exciton transitions in ZnO nanowires

    SciTech Connect

    Mohammadbeigi, F.; Kumar, E. Senthil; Alagha, S.; Anderson, I.; Watkins, S. P.

    2014-08-07

    Several shallow donor bound exciton photoluminescence (PL) transitions are reported in ZnO nanowires doped with carbon. The emission energies are in the range of 3360.8–3361.9 meV, close to previously reported emission lines due to excitons bound to donor point defects, such as Ga, Al, In, and H. The addition of small amounts of hydrogen during growth results in a strong enhancement of the PL of these carbon related emission lines, yet PL and annealing measurements indicate no appreciable bulk hydrogen. The observation of two electron satellites for these emission lines enables the determination of the donor binding energies. The dependence of exciton localization energy on donor binding energy departs somewhat from the usual linear relationship observed for group III donors, indicating a qualitatively different central cell potential, as one would expect for a complex. Emission lines due to excitons bound to ionized donors associated with these defects are also observed. The dependence of the PL emission intensities on temperature and growth conditions demonstrates that the lines are due to distinct complexes and not merely excited states of each other.

  11. Novel mechanical behaviors of wurtzite CdSe nanowires

    NASA Astrophysics Data System (ADS)

    Fu, Bing; Chen, Li; Xie, Yiqun; Feng, Jie; Ye, Xiang

    2015-09-01

    As an important semiconducting nanomaterial, CdSe nanowires have attracted much attention. Although many studies have been conducted in the electronic and optical properties of CdSe NWs, the mechanical properties of Wurtzite (WZ) CdSe nanowires remain unclear. Using molecular dynamics simulations, we have studied the tensile mechanical properties and behaviors of [0001]-oriented Wurtzite CdSe nanowires. By monitoring the stretching processes of CdSe nanowires, three distinct structures are found: the WZ wire, a body-centered tetragonal structure with four-atom rings (denoted as BCT-4), and a structure that consists of ten-atom rings with two four-atom rings (denoted as TAR-4) which is observed for the first time. Not only the elastic tensile characteristics are highly reversible under unloading, but a reverse transition between TAR-4 and BCT-4 is also observed. The stretching processes also have a strong dependence on temperature. A tubular structure similar to carbon nanotubes is observed at 150 K, a single-atom chain is formed at 300, 350 and 450 K, and a double-atom chain is found at 600 K. Our findings on tensile mechanical properties of WZ CdSe nanowires does not only provide inspiration to future study on other properties of CdSe nanomaterials but also help design and build efficient nanoscale devices.

  12. Voronoi analysis of the short–range atomic structure in iron and iron–carbon melts

    SciTech Connect

    Sobolev, Andrey; Mirzoev, Alexander

    2015-08-17

    In this work, we simulated the atomic structure of liquid iron and iron–carbon alloys by means of ab initio molecular dynamics. Voronoi analysis was used to highlight changes in the close environments of Fe atoms as carbon concentration in the melt increases. We have found, that even high concentrations of carbon do not affect short–range atomic order of iron atoms — it remains effectively the same as in pure iron melts.

  13. AAO-assisted synthesis of highly ordered, large-scale TiO2 nanowire arrays via sputtering and atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Yao, Zhao; Wang, Cong; Li, Yang; Kim, Nam-Young

    2015-04-01

    Highly ordered nanoporous anodic aluminum oxide (AAO) thin films were fabricated in oxalic acid under a constant voltage via a two-step anodization process. To investigate the high-aspect-ratio (7.5:1) filling process, both sputtering and atomic layer deposition (ALD) were used to form TiO2 nanowires. Field emission scanning electron microscopy and high-resolution transmission electron microscopy images indicated that mushroom-like TiO2 structures were sputtered onto the AAO template surface, and the ALD-coated TiO2 exhibited fine filling results and clear crystal grain boundaries. Large-scale and free-standing TiO2 nanowire arrays were liberated by selectively removing the aluminum substrate and AAO template via a wet etching process with no collapsing or agglomeration after the drying process. ALD-deposited TiO2 nanowire arrays that were 67 nm in diameter and 400 nm high were transferred from the AAO template. The ALD process enabled the rapid, simple synthesis of highly ordered TiO2 nanowire arrays with desired parameters such as diameter, density, and thickness determined using diverse AAO templates.

  14. Carbon quantum dots decorated Cu2S nanowire arrays for enhanced photoelectrochemical performance

    NASA Astrophysics Data System (ADS)

    Li, Ming; Zhao, Renjie; Su, Yanjie; Yang, Zhi; Zhang, Yafei

    2016-04-01

    The photoelectrochemical (PEC) performance of Cu2S nanowire arrays (NWAs) has been demonstrated to be greatly enhanced by dipping-assembly of carbon quantum dots (CQDs) on the surfaces of Cu2S NWAs. Experimental results show that the pristine Cu2S NWAs with higher aspect ratios exhibit better PEC performance due to the longer length scale for light absorption and the shorter length scale for minority carrier diffusion. Importantly, the CQDs decorated Cu2S NWAs exhibit remarkably enhanced photocurrent density, giving a photocurrent density of 1.05 mA cm-2 at 0 V vs. NHE and an optimal photocathode efficiency of 0.148% under illumination of AM 1.5G (100 mW cm-2), which is 4 times higher than that of the pristine Cu2S NWAs. This can be attributed to the improved electron transfer and the energy-down-shift effect of CQDs. We believe that this inexpensive Cu2S/CQD photocathode with increased photocurrent density opens up new opportunities in PEC water splitting.The photoelectrochemical (PEC) performance of Cu2S nanowire arrays (NWAs) has been demonstrated to be greatly enhanced by dipping-assembly of carbon quantum dots (CQDs) on the surfaces of Cu2S NWAs. Experimental results show that the pristine Cu2S NWAs with higher aspect ratios exhibit better PEC performance due to the longer length scale for light absorption and the shorter length scale for minority carrier diffusion. Importantly, the CQDs decorated Cu2S NWAs exhibit remarkably enhanced photocurrent density, giving a photocurrent density of 1.05 mA cm-2 at 0 V vs. NHE and an optimal photocathode efficiency of 0.148% under illumination of AM 1.5G (100 mW cm-2), which is 4 times higher than that of the pristine Cu2S NWAs. This can be attributed to the improved electron transfer and the energy-down-shift effect of CQDs. We believe that this inexpensive Cu2S/CQD photocathode with increased photocurrent density opens up new opportunities in PEC water splitting. Electronic supplementary information (ESI) available

  15. A hierarchical three-dimensional NiCo2O4 nanowire array/carbon cloth as an air electrode for nonaqueous Li-air batteries.

    PubMed

    Liu, Wei-Ming; Gao, Ting-Ting; Yang, Yin; Sun, Qian; Fu, Zheng-Wen

    2013-10-14

    A 3D NiCo2O4 nanowire array/carbon cloth (NCONW/CC) was employed as the cathode for Li-air batteries with a non-aqueous electrolyte. After its discharge, novel porous ball-like Li2O2 was found to be deposited on the tip of NiCo2O4 nanowires. The special structure of Li2O2 and active sites of catalysts are also discussed.

  16. Nanoscale current spreading analysis in solution-processed graphene oxide/silver nanowire transparent electrodes via conductive atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Shaw, Joseph E.; Perumal, Ajay; Bradley, Donal D. C.; Stavrinou, Paul N.; Anthopoulos, Thomas D.

    2016-05-01

    We use conductive atomic force microscopy (CAFM) to study the origin of long-range conductivity in model transparent conductive electrodes composed of networks of reduced graphene oxide (rGOX) and silver nanowires (AgNWs), with nanoscale spatial resolution. Pristine networks of rGOX (1-3 monolayers-thick) and AgNWs exhibit sheet resistances of ˜100-1000 kΩ/□ and 100-900 Ω/□, respectively. When the materials are deposited sequentially to form bilayer rGOX/AgNW electrodes and thermally annealed at 200 °C, the sheet resistance reduces by up to 36% as compared to pristine AgNW networks. CAFM was used to analyze the current spreading in both systems in order to identify the nanoscale phenomena responsible for this effect. For rGOX networks, the low intra-flake conductivity and the inter-flake contact resistance is found to dominate the macroscopic sheet resistance, while for AgNW networks the latter is determined by the density of the inter-AgNW junctions and their associated resistance. In the case of the bilayer rGOX/AgNWs' networks, rGOX flakes are found to form conductive "bridges" between AgNWs. We show that these additional nanoscopic electrical connections are responsible for the enhanced macroscopic conductivity of the bilayer rGOX/AgNW electrodes. Finally, the critical role of thermal annealing on the formation of these nanoscopic connections is discussed.

  17. Direct Synthesis of Carbon-Doped TiO2-Bronze Nanowires as Anode Materials for High Performance Lithium-Ion Batteries.

    PubMed

    Goriparti, Subrahmanyam; Miele, Ermanno; Prato, Mirko; Scarpellini, Alice; Marras, Sergio; Monaco, Simone; Toma, Andrea; Messina, Gabriele C; Alabastri, Alessandro; De Angelis, Francesco; Manna, Liberato; Capiglia, Claudio; Zaccaria, Remo Proietti

    2015-11-18

    Carbon-doped TiO2-bronze nanowires were synthesized via a facile doping mechanism and were exploited as active material for Li-ion batteries. We demonstrate that both the wire geometry and the presence of carbon doping contribute to the high electrochemical performance of these materials. Direct carbon doping for example reduces the Li-ion diffusion length and improves the electrical conductivity of the wires, as demonstrated by cycling experiments, which evidenced remarkably higher capacities and superior rate capability over the undoped nanowires. The as-prepared carbon-doped nanowires, evaluated in lithium half-cells, exhibited lithium storage capacity of ∼306 mA h g(-1) (91% of the theoretical capacity) at the current rate of 0.1C as well as excellent discharge capacity of ∼160 mAh g(-1) even at the current rate of 10 C after 1000 charge/discharge cycles.

  18. Enhancement of field emission and hydrophobic properties of silicon nanowires by chemical vapor deposited carbon nanoflakes coating

    NASA Astrophysics Data System (ADS)

    Banerjee, D.; Das, N. S.; Chattopadhyay, K. K.

    2012-11-01

    Vertically aligned silicon nanowires (SiNWs) have been synthesized by chemical etching process on commercially available p-type silicon wafer substrates. The surfaces of the as-synthesized nanowires have been modified with plasma enhanced chemical vapor deposited carbon nanoflakes. All the pure and coated SiNWs have been characterized by field emission scanning electron microscope, high resolution transmission electron microscope, Raman spectrometer and photoluminescence spectrometer. Surface wettability of the pure and carbon coated SiNWs has been studied and calculation of porosity has been done by using Cassie's equation. It has been found that hydrophobicity of the coated SiNWs varied with deposition time of carbon and for deposition time of 3 min the surface showed super hydrophobicity. For showing versatility of applications of the carbon coated SiNWs we have also investigated its electron field emission characteristics. Our results showed significant improvement of emission characteristics after carbon flakes with turn-on field downshifted from 9.30 to 2.77 V/μm. The results were explained due to enhanced surface roughness leading to higher enhancement factor, favorable band bending for electron emission and overall reduction of potential barrier on application of external electric field.

  19. Electronic structure and charge transport properties of atomic carbon wires.

    PubMed

    Lambropoulos, K; Simserides, C

    2017-10-11

    Atomic carbon wires represent the ultimate one-atom-thick one-dimensional structure. We use a Tight-binding (TB) approach to determine the electronic structure of polyynic and cumulenic carbynes, in terms of their dispersion relations (for cyclic boundaries), eigenspectra (for fixed boundaries) and density of states (DOS). We further derive the transmission coefficient at zero-bias by attaching the carbynes to semi-infinite metallic leads, and demonstrate the effect of the coupling strength and asymmetry to the transparency of the system to incident carriers. Finally, we determine the current-voltage (I-V) characteristics of carbynes and study the effect of factors such as the weakening of the coupling of the system to one of the leads, the relative position of the Fermi levels of the carbyne and the leads, the leads' bandwidth and, finally, the difference in the energy structure between the leads. Our results confirm and reproduce some of the most recent experimental findings.

  20. Metal-organic framework derived hybrid Co3O4-carbon porous nanowire arrays as reversible oxygen evolution electrodes.

    PubMed

    Ma, Tian Yi; Dai, Sheng; Jaroniec, Mietek; Qiao, Shi Zhang

    2014-10-01

    Hybrid porous nanowire arrays composed of strongly interacting Co3O4 and carbon were prepared by a facile carbonization of the metal-organic framework grown on Cu foil. The resulting material, possessing a high surface area of 251 m(2) g(-1) and a large carbon content of 52.1 wt %, can be directly used as the working electrode for oxygen evolution reaction without employing extra substrates or binders. This novel oxygen evolution electrode can smoothly operate in alkaline solutions (e.g., 0.1 and 1.0 M KOH), affording a low onset potential of 1.47 V (vs reversible hydrogen electrode) and a stable current density of 10.0 mA cm(-2) at 1.52 V in 0.1 M KOH solution for at least 30 h, associated with a high Faradaic efficiency of 99.3%. The achieved ultrahigh oxygen evolution activity and strong durability, with superior performance in comparison to the state-of-the-art noble-metal/transition-metal and nonmetal catalysts, originate from the unique nanowire array electrode configuration and in situ carbon incorporation, which lead to the large active surface area, enhanced mass/charge transport capability, easy release of oxygen gas bubbles, and strong structural stability. Furthermore, the hybrid Co3O4-carbon porous nanowire arrays can also efficiently catalyze oxygen reduction reaction, featuring a desirable four-electron pathway for reversible oxygen evolution and reduction, which is potentially useful for rechargeable metal-air batteries, regenerative fuel cells, and other important clean energy devices.

  1. Atomic-Thick PtNi Nanowires Assembled on Graphene for High-Sensitivity Extracellular Hydrogen Peroxide Sensors.

    PubMed

    Sun, Yingjun; Luo, Mingchuan; Qin, Yingnan; Zhu, Sihao; Li, Yingjie; Xu, Nuoyan; Meng, Xiangxi; Ren, Qiushi; Wang, Lei; Guo, Shaojun

    2017-10-11

    H2O2 sensors with high sensitivity and selectivity are essential for monitoring the normal activities of cells. Inorganic catalytic nanomaterials show the obvious advantage in boosting the sensitivity of H2O2 sensors; however, the H2O2 detection limit of reported inorganic catalysts is still limited, which is not suitable for high-sensitivity detection of H2O2 in real cells. Herein, novel atomic-thick PtNi nanowires (NWs) were synthesized and assembled on reduced graphene oxide (rGO) via an ultrasonic self-assembly method to attain PtNi NWs/rGO composite for boosting the electroanalysis of H2O2. In 0.05 M phosphate-buffered saline (pH 7.4) solution, the as-prepared PtNi NWs/rGO shows an extraordinary performance in quantifying H2O2 in a wide range of concentrations from 1 nM to 5.3 mM. Significantly, the detection limit of PtNi NWs/rGO reaches unprecedented 0.3 nM at an applied potential of -0.6 V (vs Ag/AgCl), which enables the detection of traced amounts of H2O2 released from Raw 264.7 cells. The excellent performance of H2O2 detection on PtNi NWs/rGO is ascribed to the high-density active sites of atomic-thick PtNi NWs.

  2. Surface effects on the mechanical elongation of AuCu nanowires: De-alloying and the formation of mixed suspended atomic chains

    SciTech Connect

    Lagos, M. J.; Autreto, P. A. S.; Galvao, D. S. Ugarte, D.; Bettini, J.; Sato, F.; Dantas, S. O.

    2015-03-07

    We report here an atomistic study of the mechanical deformation of Au{sub x}Cu{sub (1−x)} atomic-size wires (nanowires (NWs)) by means of high resolution transmission electron microscopy experiments. Molecular dynamics simulations were also carried out in order to obtain deeper insights on the dynamical properties of stretched NWs. The mechanical properties are significantly dependent on the chemical composition that evolves in time at the junction; some structures exhibit a remarkable de-alloying behavior. Also, our results represent the first experimental realization of mixed linear atomic chains (LACs) among transition and noble metals; in particular, surface energies induce chemical gradients on NW surfaces that can be exploited to control the relative LAC compositions (different number of gold and copper atoms). The implications of these results for nanocatalysis and spin transport of one-atom-thick metal wires are addressed.

  3. Carbon-supported Pt nanowire as novel cathode catalysts for proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Li, Bing; Yan, Zeyu; Higgins, Drew C.; Yang, Daijun; Chen, Zhongwei; Ma, Jianxin

    2014-09-01

    Carbon-supported platinum nanowires (PtNW/C) are successfully synthesized by a simple and inexpensive template-free methodology and demonstrated as novel, suitable cathode electrode materials for proton exchange membrane fuel cell (PEMFC) applications. The synthesis conditions, such as the amount of reducing agent and reaction time, were investigated to investigate the effect on the nanostructures and activities of the PtNW/C catalysts. High-resolution transmission electron microscopy (TEM) results show that the formic acid facilitated reduction is capable of producing uniformly distributed 1-dimensional PtNW with an average cross-sectional diameter of 4.0 ± 0.2 nm and length of 20-40 nm. Investigation of the electrocatalytic activity by half-cell electrochemical testing reveals that PtNW/C catalyst demonstrates significant oxygen reduction reaction (ORR) activity, superior to that of commercially available Pt/C. Using a loading of 0.4 mgPt cm-2 PtNW/C as the cathode catalyst, a maximum power density of 748.8 mW cm-2 in a 50 cm2 single cell of commercial Pt/C. In addition, accelerated degradation testing (ADT) showed that the PtNW/C catalyst exhibits better durability than commercial Pt/C, rendering PtNW/C as a promising replacement to conventional Pt/C as cathode electrocatalysts for PEMFCs applications.

  4. Carbon Nanotube Networks Reinforced by Silver Nanowires with Improved Optical Transparency and Conductivity

    NASA Astrophysics Data System (ADS)

    Martine, Patricia; Fakhimi, Azin; Lin, Ling; Jurewicz, Izabela; Dalton, Alan; Zakhidov, Anvar A.; Baughman, Ray H.

    2015-03-01

    We have fabricated highly transparent and conductive free-standing nanocomposite thin film electrodes by adding silver nanowires (AgNWs) to dry-spun Multiwall Carbon Nanotube (MWNT) aerogels. This nanocomposite exhibits desirable properties such as high optical transmittance, excellent flexibility and enhanced electrical conductivity. The incorporation of the AgNWs to the MWNT aerogels was accomplished by using a spray coating method. The optical transparency and sheet resistance of the nanocomposite was tuned by adjusting the concentration of AgNWs, back pressure and nozzle distance of the spray gun to the MWNT aerogel during deposition. As the solvent evaporated, the aerogel MWNT bundles densified via surface tension which caused the MWNT bundles to collapse. This adjustable process was responsible in forming well defined apertures that increased the nanocomposite's transmittance up to 90 percent. Via AgNWs percolation and random interconnections between separate MWNT bundles in the aerogel matrix, the sheet resistance decreased from 1 K ohm/sq to less than 100 ohm/sq. Alan G. MacDiarmid NanoTech Institute

  5. Atomic-focuser imaging in electron nanodiffraction from carbon nanoshells

    PubMed

    Cowley

    2000-03-01

    When nanodiffraction patterns are obtained by transmission through the top and bottom walls of near-spherical, hollow carbon nano-shells, using the focused probe of a STEM instrument, a graphitic crystal in one wall may act as an atomic focuser to produce high-resolution images of small regions of the other wall within the central beam and the diffraction disks of the nanodiffraction pattern. A theoretical analysis of the imaging process is given. Images showing one- and two-dimensional periodicities, with fringe spacings as small as 0.124 nm, and also images showing non-periodic features have been obtained from carbon nanoshells having diameters of the order of 100 nm.

  6. Atom Diffusion and Evaporation of Free-Ended Amorphous SiOx Nanowires: Nanocurvature Effect and Beam-Induced Athermal Activation Effect

    NASA Astrophysics Data System (ADS)

    Su, Jiangbin; Zhu, Xianfang

    2016-11-01

    Arresting effects of nanocurvature and electron beam-induced athermal activation on the structure changes at nanoscale of free-ended amorphous SiOx nanowire were demonstrated. It was observed that under in situ uniform electron beam irradiation in transmission electron microscope, the near surface atoms at the most curved free end of the nanowire preferentially vaporized or diffused to the less curved wire sidewall. The processing resulted in an intriguing axial shrinkage and an abnormal radial expansion of the wire. It was also observed that with the beam energy deposition rate being lowered, although both the diffusion and the evaporation slowed down, the processing transferred from an evaporation-dominated status to a diffusion-dominated status. These results are crucial not only to the fundamental understanding but also to the technical controlling of the electron beam-induced structure change at nanoscale or nanoprocessing of low dimensional nanostructures.

  7. An important atomic process in the CVD growth of graphene: Sinking and up-floating of carbon atom on copper surface

    NASA Astrophysics Data System (ADS)

    Li, Yingfeng; Li, Meicheng; Gu, TianSheng; Bai, Fan; Yu, Yue; Trevor, Mwenya; Yu, Yangxin

    2013-11-01

    By density functional theory (DFT) calculations, the early stages of the growth of graphene on copper (1 1 1) surface are investigated. At the very first time of graphene growth, the carbon atom sinks into subsurface. As more carbon atoms are adsorbed nearby the site, the sunken carbon atom will spontaneously form a dimer with one of the newly adsorbed carbon atoms, and the formed dimer will up-float on the top of the surface. We emphasize the role of the co-operative relaxation of the co-adsorbed carbon atoms in facilitating the sinking and up-floating of carbon atoms. In detail: when two carbon atoms are co-adsorbed, their co-operative relaxation will result in different carbon-copper interactions for the co-adsorbed carbon atoms. This difference facilitates the sinking of a single carbon atom into the subsurface. As a third carbon atom is co-adsorbed nearby, it draws the sunken carbon atom on top of the surface, forming a dimer. Co-operative relaxations of the surface involving all adsorbed carbon atoms and their copper neighbors facilitate these sinking and up-floating processes. This investigation is helpful for the deeper understanding of graphene synthesis and the choosing of optimal carbon sources or process.

  8. Carbon atom-initiated degradation of carbon tetrachloride in the presence of molecular oxygen: A product and mechanistic study

    SciTech Connect

    Nicoll, G.; Francisco, J.S.

    1998-10-15

    This paper reports an investigation of the gas-phase reaction of atomic carbon with carbon tetrachloride in the presence of molecular oxygen. It is demonstrated that carbon tetrachloride can be oxidatively degraded by this method. Results from FT-IR and GC/MS studies suggest that the major products from the reaction are phosgene and carbon dioxide. The initial step involves breaking the carbon-chlorine bond as a result of the reaction of atomic carbon with carbon tetrachloride. Laser-induced fluorescence studies have shown the presence of CCl as an intermediate produced from this reaction. A tentative mechanism is proposed to describe the details of the chemistry.

  9. Carbon Nanotube/Cu Nanowires/Epoxy Composite Mats with Improved Thermal and Electrical Conductivity.

    PubMed

    Xing, Yajuan; Cao, Wei; Li, Wei; Chen, Hongyuan; Wang, Miao; Wei, Hanxing; Hu, Dongmei; Chen, Minghai; Li, Qingwen

    2015-04-01

    Polymer composites with carbon nanofillers have been regarded as a promising candidate for electronic package materials. The challenge for such materials is to increase the electrical and thermal conductivity of the composites. Herein, we reported an epoxy composite film with high thermal and electrical conductivity that were prepared by loading high volume fraction of well-dispersed multi-walled carbon nanotubes (MWCNTs, around 50 nm in diameter, 1-10 µm in length) and copper nanowires (Cu NWs, 60-70 nm in diameter, 1-5 µm in length) in epoxy matrix. The MWCNT-Cu NW hybrid mats were prepared by a vacuum filtration method with an optimum Cu NW content of 50 wt%. The hybrid mats was then impregnated by epoxy solution to prepare epoxy composite films. The epoxy was modified by the toughening agent to make the composite films tough and flexible. The loading fraction of MWCNTs and Cu NWs was tuned by controlling the viscosity of epoxy solution. A remarkable synergetic effect between the MWCNTs and Cu NWs in improving the electrical and thermal conductivity of epoxy composites was demonstrated. The results showed that the electrical conductivity of nanocomposites with 42.5 wt% epoxy was 1500 S/m, and the thermal conductivity was 2.83 W/m K, which was 10.1 times of the neat epoxy. Its thermal resistance was as low as 1% of the pure epoxy. And the mechanical properties of composites were also investigated. These robust and flexible nanocomposites showed prospective applications as thermal interface materials (TIMs) in the electronic industry.

  10. Catalyst patterning for nanowire devices

    NASA Technical Reports Server (NTRS)

    Li, Jun (Inventor); Cassell, Alan M. (Inventor); Han, Jie (Inventor)

    2004-01-01

    Nanowire devices may be provided that are based on carbon nanotubes or single-crystal semiconductor nanowires. The nanowire devices may be formed on a substrate. Catalyst sites may be formed on the substrate. The catalyst sites may be formed using lithography, thin metal layers that form individual catalyst sites when heated, collapsible porous catalyst-filled microscopic spheres, microscopic spheres that serve as masks for catalyst deposition, electrochemical deposition techniques, and catalyst inks. Nanowires may be grown from the catalyst sites.

  11. Carbon atom adsorption on and diffusion into Fe(110) and Fe(100) from first principles

    NASA Astrophysics Data System (ADS)

    Jiang, D. E.; Carter, Emily A.

    2005-01-01

    We employ spin-polarized periodic density functional theory (DFT) to examine carbon atom adsorption on, absorption in, and diffusion into Fe(110) and Fe(100). We find that carbon atoms bind strongly with Fe surfaces and prefer high coordination sites. The carbon atom is predicted to adsorb on the long-bridge site on Fe(110) and the fourfold hollow site on Fe(100). Due to the very short distance between the carbon atom and the subsurface Fe atom of Fe(100), the carbon atom binds more strongly with Fe(100) than with Fe(110). In the subsurface region, the carbon atom prefers the octahedral site, as in bulk Fe. We find that the carbon atom is more stable in the subsurface octahedral site of Fe(110) than that of Fe(100), since the strain caused by the interstitial carbon atom is released by pushing one surface Fe atom towards vacuum by 0.5 Å in Fe(110), while the distortion in Fe(100) propagates far into the lattice. Diffusion of carbon atoms into Fe(110) and Fe(100) subsurfaces goes through transition states where the carbon atom is coordinated to four Fe atoms. The barriers to diffusion into Fe(110) and Fe(100) are 1.18 eV and 1.47 eV, respectively. The larger diffusion barrier into Fe(100) is mainly due to the stronger bonding between carbon and the Fe(100) surface. We predict that the rate-limiting step for C incorporation into bulk Fe is the initial diffusion to subsurface sites, while the rate-limiting step for absorbed carbon segregation to the surface is bulk diffusion, with no expected difference between rates to segregate to different surfaces. Lastly, we predict that graphite formation will be more favorable on C -covered Fe(110) than C -covered Fe(100).

  12. Polycrystalline nanowires of gadolinium-doped ceria via random alignment mediated by supercritical carbon dioxide

    NASA Astrophysics Data System (ADS)

    Kim, Sang Woo; Ahn, Jae-Pyoung

    2013-04-01

    This study proposes a seed/template-free method that affords high-purity semiconducting nanowires from nanoclusters, which act as basic building blocks for nanomaterials, under supercritical CO2 fluid. Polycrystalline nanowires of Gd-doped ceria (Gd-CeO2) were formed by CO2-mediated non-oriented attachment of the nanoclusters resulting from the dissociation of single-crystalline aggregates. The unique formation mechanism underlying this morphological transition may be exploited for the facile growth of high-purity polycrystalline nanowires.

  13. Polycrystalline nanowires of gadolinium-doped ceria via random alignment mediated by supercritical carbon dioxide.

    PubMed

    Kim, Sang Woo; Ahn, Jae-Pyoung

    2013-01-01

    This study proposes a seed/template-free method that affords high-purity semiconducting nanowires from nanoclusters, which act as basic building blocks for nanomaterials, under supercritical CO2 fluid. Polycrystalline nanowires of Gd-doped ceria (Gd-CeO2) were formed by CO2-mediated non-oriented attachment of the nanoclusters resulting from the dissociation of single-crystalline aggregates. The unique formation mechanism underlying this morphological transition may be exploited for the facile growth of high-purity polycrystalline nanowires.

  14. Polycrystalline nanowires of gadolinium-doped ceria via random alignment mediated by supercritical carbon dioxide

    PubMed Central

    Kim, Sang Woo; Ahn, Jae-Pyoung

    2013-01-01

    This study proposes a seed/template-free method that affords high-purity semiconducting nanowires from nanoclusters, which act as basic building blocks for nanomaterials, under supercritical CO2 fluid. Polycrystalline nanowires of Gd-doped ceria (Gd-CeO2) were formed by CO2-mediated non-oriented attachment of the nanoclusters resulting from the dissociation of single-crystalline aggregates. The unique formation mechanism underlying this morphological transition may be exploited for the facile growth of high-purity polycrystalline nanowires. PMID:23572061

  15. Atomic-scale imaging correlation on the deformation and sensing mechanisms of SnO{sub 2} nanowires

    SciTech Connect

    Sun, Yong; Liu, Jie; Koley, Goutam; Blom, Douglas; Duan, Zhiyao; Wang, Guofeng E-mail: xl3p@virginia.edu; Li, Xiaodong E-mail: xl3p@virginia.edu

    2014-12-15

    We demonstrate direct evidence that the strain variation induced by local lattice distortion exists in the surface layers of SnO{sub 2} nanowires by coupled scanning transmission electron microscopy and digital image correlation techniques. First-principles calculations suggest that surface reduction and subsurface oxygen vacancies account for such vigorous wavelike strain. Our study revealed that the localized change of surface atomistic configuration was responsible for the observed reduction of elastic modulus and hardness of SnO{sub 2} nanowires, as well as the superior sensing properties of SnO{sub 2} nanowire network.

  16. Effect of hydrogen plasma irradiation of catalyst films on growth of carbon nanotubes filled with iron nanowires

    SciTech Connect

    Sato, Hideki Kubonaka, Nobuo; Nagata, Atsushi; Fujiwara, Yuji

    2014-03-15

    Carbon nanotubes filled with iron (Fe-filled CNTs) show shape anisotropy on account of the high aspect ratio of magnetic nanowires, and are promising candidates for various applications, such as magnetic recording media, probes for scanning force microscopy, and medical treatment for cancer. The ability to appropriately control the magnetic properties of CNTs for those applications is desirable. In this study, the authors investigated magnetic properties of Fe-filled CNTs synthesized by thermal chemical vapor deposition for the purpose of tuning their coercivity. Here, the authors implemented hydrogen plasma irradiation of catalyst film that was previously deposited on a substrate as a catalyst layer. This treatment activates the catalyst film and thus enhances the growth of the Fe-filled CNTs. It was confirmed that the H{sub 2} plasma irradiation enhances the growth of the CNTs in terms of increasing their length and diameter compared to CNTs without irradiation. On the other hand, the coercivity of Fe-filled CNTs dropped to approximately half of those without H{sub 2} plasma irradiation. This is probably due to a decrease in the aspect ratio of the Fe nanowires, which results from the increase in their diameter. Furthermore, the crystal structure of the Fe nanowires may affect the coercivity.

  17. Atomic layer confined vacancies for atomic-level insights into carbon dioxide electroreduction

    PubMed Central

    Gao, Shan; Sun, Zhongti; Liu, Wei; Jiao, Xingchen; Zu, Xiaolong; Hu, Qitao; Sun, Yongfu; Yao, Tao; Zhang, Wenhua; Wei, Shiqiang; Xie, Yi

    2017-01-01

    The role of oxygen vacancies in carbon dioxide electroreduction remains somewhat unclear. Here we construct a model of oxygen vacancies confined in atomic layer, taking the synthetic oxygen-deficient cobalt oxide single-unit-cell layers as an example. Density functional theory calculations demonstrate the main defect is the oxygen(II) vacancy, while X-ray absorption fine structure spectroscopy reveals their distinct oxygen vacancy concentrations. Proton transfer is theoretically/experimentally demonstrated to be a rate-limiting step, while energy calculations unveil that the presence of oxygen(II) vacancies lower the rate-limiting activation barrier from 0.51 to 0.40 eV via stabilizing the formate anion radical intermediate, confirmed by the lowered onset potential from 0.81 to 0.78 V and decreased Tafel slope from 48 to 37 mV dec−1. Hence, vacancy-rich cobalt oxide single-unit-cell layers exhibit current densities of 2.7 mA cm−2 with ca. 85% formate selectivity during 40-h tests. This work establishes a clear atomic-level correlation between oxygen vacancies and carbon dioxide electroreduction. PMID:28220847

  18. Atomic layer confined vacancies for atomic-level insights into carbon dioxide electroreduction

    NASA Astrophysics Data System (ADS)

    Gao, Shan; Sun, Zhongti; Liu, Wei; Jiao, Xingchen; Zu, Xiaolong; Hu, Qitao; Sun, Yongfu; Yao, Tao; Zhang, Wenhua; Wei, Shiqiang; Xie, Yi

    2017-02-01

    The role of oxygen vacancies in carbon dioxide electroreduction remains somewhat unclear. Here we construct a model of oxygen vacancies confined in atomic layer, taking the synthetic oxygen-deficient cobalt oxide single-unit-cell layers as an example. Density functional theory calculations demonstrate the main defect is the oxygen(II) vacancy, while X-ray absorption fine structure spectroscopy reveals their distinct oxygen vacancy concentrations. Proton transfer is theoretically/experimentally demonstrated to be a rate-limiting step, while energy calculations unveil that the presence of oxygen(II) vacancies lower the rate-limiting activation barrier from 0.51 to 0.40 eV via stabilizing the formate anion radical intermediate, confirmed by the lowered onset potential from 0.81 to 0.78 V and decreased Tafel slope from 48 to 37 mV dec-1. Hence, vacancy-rich cobalt oxide single-unit-cell layers exhibit current densities of 2.7 mA cm-2 with ca. 85% formate selectivity during 40-h tests. This work establishes a clear atomic-level correlation between oxygen vacancies and carbon dioxide electroreduction.

  19. Engineering the electronic properties of nanowires for device applications

    NASA Astrophysics Data System (ADS)

    Thelander, Claes

    2007-03-01

    Semiconductor nanowires have recently been recognized as a possible add-on technology to silicon CMOS. Successful integration of nanowires may push the miniaturization of components further and could also bring improved, and completely new, device functions to a chip. In particular, nanowires composed of III-V materials are of interest for applications as they benefit from a small and/or direct bandgap. We will present results from electrical measurements on InAs/InP nanowires grown by chemical beam epitaxy. Changes in the precursors fed to the growth chamber can be made to control the electronic properties of the grown material. In this way it is possible to create atomically sharp heterostructure interfaces, as well as to change the carrier concentration along the wire. The latter can be achieved by controlling the carbon incorporation from the In precursor. It will be shown that heterostructure nanowires can be used in memory cells, and also as single-electron transistors for electrostatic read-out of such cells. Finally, we will discuss the design and application of InAs nanowire-based field-effect transistors, where issues related to lateral and vertical processing of nanowires will be addressed.

  20. Nanoscale current spreading analysis in solution-processed graphene oxide/silver nanowire transparent electrodes via conductive atomic force microscopy

    SciTech Connect

    Shaw, Joseph E.; Perumal, Ajay; Bradley, Donal D. C.; Stavrinou, Paul N.; Anthopoulos, Thomas D.

    2016-05-21

    We use conductive atomic force microscopy (CAFM) to study the origin of long-range conductivity in model transparent conductive electrodes composed of networks of reduced graphene oxide (rGO{sub X}) and silver nanowires (AgNWs), with nanoscale spatial resolution. Pristine networks of rGO{sub X} (1–3 monolayers-thick) and AgNWs exhibit sheet resistances of ∼100–1000 kΩ/□ and 100–900 Ω/□, respectively. When the materials are deposited sequentially to form bilayer rGO{sub X}/AgNW electrodes and thermally annealed at 200 °C, the sheet resistance reduces by up to 36% as compared to pristine AgNW networks. CAFM was used to analyze the current spreading in both systems in order to identify the nanoscale phenomena responsible for this effect. For rGO{sub X} networks, the low intra-flake conductivity and the inter-flake contact resistance is found to dominate the macroscopic sheet resistance, while for AgNW networks the latter is determined by the density of the inter-AgNW junctions and their associated resistance. In the case of the bilayer rGO{sub X}/AgNWs' networks, rGO{sub X} flakes are found to form conductive “bridges” between AgNWs. We show that these additional nanoscopic electrical connections are responsible for the enhanced macroscopic conductivity of the bilayer rGO{sub X}/AgNW electrodes. Finally, the critical role of thermal annealing on the formation of these nanoscopic connections is discussed.

  1. Carbon Nanotube Devices Engineered by Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Prisbrey, Landon

    This dissertation explores the engineering of carbon nanotube electronic devices using atomic force microscopy (AFM) based techniques. A possible application for such devices is an electronic interface with individual biological molecules. This single molecule biosensing application is explored both experimentally and with computational modeling. Scanning probe microscopy techniques, such as AFM, are ideal to study nanoscale electronics. These techniques employ a probe which is raster scanned above a sample while measuring probe-surface interactions as a function of position. In addition to topographical and electrostatic/magnetic surface characterization, the probe may also be used as a tool to manipulate and engineer at the nanoscale. Nanoelectronic devices built from carbon nanotubes exhibit many exciting properties including one-dimensional electron transport. A natural consequence of onedimensional transport is that a single perturbation along the conduction channel can have extremely large effects on the device's transport characteristics. This property may be exploited to produce electronic sensors with single-molecule resolution. Here we use AFM-based engineering to fabricate atomic-sized transistors from carbon nanotube network devices. This is done through the incorporation of point defects into the carbon nanotube sidewall using voltage pulses from an AFM probe. We find that the incorporation of an oxidative defect leads to a variety of possible electrical signatures including sudden switching events, resonant scattering, and breaking of the symmetry between electron and hole transport. We discuss the relationship between these different electronic signatures and the chemical structure/charge state of the defect. Tunneling through a defect-induced Coulomb barrier is modeled with numerical Verlet integration of Schrodinger's equation and compared with experimental results. Atomic-sized transistors are ideal for single-molecule applications due to their

  2. Carbon-Free CoO Mesoporous Nanowire Array Cathode for High-Performance Aprotic Li-O2 Batteries.

    PubMed

    Wu, Baoshan; Zhang, Hongzhang; Zhou, Wei; Wang, Meiri; Li, Xianfeng; Zhang, Huamin

    2015-10-21

    Although various kinds of catalysts have been developed for aprotic Li-O2 battery application, the carbon-based cathodes are still vulnerable to attacks from the discharge intermediates or products, as well as the accompanying electrolyte decomposition. To ameliorate this problem, the free-standing and carbon-free CoO nanowire array cathode was purposely designed for Li-O2 batteries. The single CoO nanowire formed as a special mesoporous structure, owing even comparable specific surface area and pore volume to the typical Super-P carbon particles. In addition to the highly selective oxygen reduction/evolution reactions catalytic activity of CoO cathodes, both excellent discharge specific capacity and cycling efficiency of Li-O2 batteries were obtained, with 4888 mAh gCoO(-1) and 50 cycles during 500 h period. Owing to the synergistic effect between elaborate porous structure and selective intermediate absorption on CoO crystal, a unique bimodal growth phenomenon of discharge products was occasionally observed, which further offers a novel mechanism to control the formation/decomposition morphology of discharge products in nanoscale. This research work is believed to shed light on the future development of high-performance aprotic Li-O2 batteries.

  3. Porous CoFe{sub 2}O{sub 4} nanowire arrays on carbon cloth as binder-free anodes for flexible lithium-ion batteries

    SciTech Connect

    Zhao, Saihua; Guo, Jinxin; Jiang, Fei; Su, Qingmei; Du, Gaohui

    2016-07-15

    Highlights: • Hierarchal CoFe{sub 2}O{sub 4} nanowire arrays are directly grown on flexible carbon cloth. • Porous CoFe{sub 2}O{sub 4} nanowires are composed of many nanocrystals of 20–40 nm. • CoFe{sub 2}O{sub 4} nanowire arrays exhibit excellent rate capability and cycling stability. • Integrated CoFe{sub 2}O{sub 4}/carbon cloth electrodes show high flexibility and areal capacity. - Abstract: A three-dimensional CoFe{sub 2}O{sub 4} nanowire array on carbon cloth was fabricated with a hydrothermal method together with a post-annealing treatment. As a binder-free and flexible anode material for LIBs, it showed an improved electrochemical performance with high cycling stability and excellent rate capability. It exhibited an initial discharge capacity of 1615 mAh g{sup −1} and retained a reversible capacity of about 1204 mAh g{sup −1} after 200 cycles at a specific current of 500 mA g{sup −1}. The high capacity, outstanding rate performance and cycling stability can be attributed to the special configuration of hierarchal porous CoFe{sub 2}O{sub 4} nanowires on carbon cloth, which possess many advantages like short diffusion length, easy strain relaxation and fast electron transport. Moreover, the integrated CoFe{sub 2}O{sub 4} nanowires/carbon cloth electrode shows high flexibility and high areal capacity (2.41 mAh cm{sup −2}), which makes it suitable for use as a binder-free anode to build flexible LIBs.

  4. Atomic nanotube welders: boron interstitials triggering connections in double-walled carbon nanotubes.

    PubMed

    Endo, Morinobu; Muramatsu, Hiroyuki; Hayashi, Takuya; Kim, Yoong-Ahm; Van Lier, Gregory; Charlier, Jean-Christophe; Terrones, Humberto; Terrones, Mauricio; Dresselhaus, Mildred S

    2005-06-01

    Here we demonstrate that the incorporation of boron (B) atoms between double-walled carbon nanotubes (DWNTs) during thermal annealing (1400-1600 degrees C) results in covalent nanotube "Y" junctions, DWNT coalescence, and the formation of flattened multiwalled carbon nanotubes (MWNTs). These processes occur via the merging of adjacent tubes, which is triggered by B interstitial atoms. We observe that B atom interstitials between DWNTs are responsible for the rapid establishment of covalent connections between neighboring tubes (polymerization), thereby resulting in the fast annealing of the carbon cylinders with B atoms embedded in the newly created carbon nanotube network. Once B is in the lattice, tube faceting (polygonization) starts to occur, and the electronic properties are expected to change dramatically. Therefore, B atoms indeed act as atomic nanotube fusers (or welders), and this process could now be used in assembling novel electronic nanotube devices, nanotube networks, carbon nanofoams and heterojunctions exhibiting p-type electronic properties.

  5. Dual-template ordered mesoporous carbon/Fe2O3 nanowires as lithium-ion battery anodes

    NASA Astrophysics Data System (ADS)

    Hu, Junkai; Sun, Chuan-Fu; Gillette, Eleanor; Gui, Zhe; Wang, Yuhuang; Lee, Sang Bok

    2016-06-01

    Ordered mesoporous carbons (OMCs) are ideal host materials that can provide the desirable electrical conductivity and ion accessibility for high-capacity oxide electrode materials in lithium-ion batteries (LIBs). To this end, however, it is imperative to establish the correlations among material morphology, pore structure and electrochemical performance. Here, we fabricate an ordered mesoporous carbon nanowire (OMCNW)/Fe2O3 composite utilizing a novel soft-hard dual-template approach. The structure and electrochemical performance of OMCNW/Fe2O3 were systematically compared with single-templated OMC/Fe2O3 and carbon nanowire/Fe2O3 composites. This dual-template strategy presents synergetic effects combining the advantages of both soft and hard single-template methods. The resulting OMCNW/Fe2O3 composite enables a high pore volume, high structural stability, enhanced electrical conductivity and Li+ accessibility. These features collectively enable excellent electrochemical cyclability (1200 cycles) and a reversible Li+ storage capacity as high as 819 mA h g-1 at a current density of 0.5 A g-1. Our findings highlight the synergistic benefits of the dual-template approach to heterogeneous composites for high performance electrochemical energy storage materials.Ordered mesoporous carbons (OMCs) are ideal host materials that can provide the desirable electrical conductivity and ion accessibility for high-capacity oxide electrode materials in lithium-ion batteries (LIBs). To this end, however, it is imperative to establish the correlations among material morphology, pore structure and electrochemical performance. Here, we fabricate an ordered mesoporous carbon nanowire (OMCNW)/Fe2O3 composite utilizing a novel soft-hard dual-template approach. The structure and electrochemical performance of OMCNW/Fe2O3 were systematically compared with single-templated OMC/Fe2O3 and carbon nanowire/Fe2O3 composites. This dual-template strategy presents synergetic effects combining the

  6. Atomic-Scale Investigations of Multiwall Carbon Nanotube Growth

    NASA Astrophysics Data System (ADS)

    Behr, Michael John

    The combination of unique mechanical, thermal, optical, and electronic properties of carbon nanotubes (CNTs) make them a desirable material for use in a wide range of applications. Many of these unique properties are highly sensitive to how carbon atoms are arranged within the graphene nanotube wall. Precise structural control of this arrangement remains the key challenge of CNT growth to realizing their technological potential. Plasma-enhanced chemical vapor deposition (PECVD) from methane-hydrogen gas mixtures using catalytic nanoparticles enables large-scale growth of CNT films and controlled spatial placement of CNTs on a substrate, however, much is still unknown about what happens to the catalyst particle during growth, the atomistic mechanisms involved, and how these dictate the final nanotube structure. To investigate the fundamental processes of CNT growth by PECVD, a suite of characterization techniques were implemented, including attenuated total-reflection Fourier transform infrared spectroscopy (ATR-FTIR), optical emission spectroscopy (OES), Raman spectroscopy, convergent-beam electron diffraction (CBED), high-resolution transmission and scanning-transmission electron microscopy (TEM, STEM), energy dispersive x-ray spectroscopy, and electron energy-loss spectroscopy (EELS). It is found that hydrogen plays a critical role in determining the final CNT structure through controlling catalyst crystal phase and morphology. At low hydrogen concentrations in the plasma iron catalysts are converted to Fe3C, from which high-quality CNTs grow; however, catalyst particles remain as pure iron when hydrogen is in abundance, and produce highly defective CNTs with large diameters. The initially faceted and equiaxed catalyst nanocrystals become deformed and are elongated into a teardrop morphology once a tubular CNT structure is formed around the catalyst particles. Although catalyst particles are single crystalline, they exhibit combinations of small-angle (˜1°-3

  7. The Relativistic Effects on the Carbon-Carbon Coupling Constants Mediated by a Heavy Atom.

    PubMed

    Wodyński, Artur; Malkina, Olga L; Pecul, Magdalena

    2016-07-21

    The (2)JCC, (3)JCC, and (4)JCC spin-spin coupling constants in the systems with a heavy atom (Cd, In, Sn, Sb, Te, Hg, Tl, Pb, Bi, and Po) in the coupling path have been calculated by means of density functional theory. The main goal was to estimate the relativistic effects on spin-spin coupling constants and to explore the factors which may influence them, including the nature of the heavy atom and carbon hybridization. The methods applied range, in order of reduced complexity, from the Dirac-Kohn-Sham (DKS) method (density functional theory with four-component Dirac-Coulomb Hamiltonian), through DFT with two- and one-component zeroth-order regular approximation (ZORA) Hamiltonians, to scalar effective core potentials (ECPs) with the nonrelativistic Hamiltonian. The use of DKS and ZORA methods leads to very similar results, and small-core ECPs of the MDF and MWB variety reproduce correctly the scalar relativistic effects. Scalar relativistic effects usually are larger than the spin-orbit coupling effects. The latter tend to influence the most the coupling constants of the sp(3)-hybridized carbon atoms and in compounds of the p-block heavy atoms. Large spin-orbit coupling contributions for the Po compounds are probably connected with the inverse of the lowest triplet excitation energy.

  8. Study on the electronic properties and molecule adsorption of W18O49 nanowires as a catalyst support in the cathodes of direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Karim, N. A.; Kamarudin, S. K.; Shyuan, L. K.; Yaakob, Z.; Daud, W. R. W.; Kadhum, A. A. H.

    2015-08-01

    Catalyst supports have been used to increase the catalytic activity of reactions in the cathode of Direct Methanol Fuel Cells (DMFCs). The properties of tungsten oxide (W18O49) nanowires were studied, and their adsorption capability was evaluated using density functional theory. The electronic properties of the bulk material and two different diameter nanowires were calculated. Moreover, the molecules involved in adsorption were carbon monoxide, methanol, oxygen and hydrogen peroxide. The results showed that the high adsorption energy produced is primarily the result of the adsorption of methanol, followed by that of hydrogen peroxide, carbon monoxide and oxygen. The negative adsorption energies obtained showed that the adsorption reactions were exothermic, and only oxygen was stable. Therefore, a new surface model was described where cobalt atoms were adsorbed on tungsten atoms on the surface of a 12 Å nanowire. In this new nanowire doped with cobalt atoms, the adsorption energy was reduced.

  9. Facile synthesis of carbon doped TiO2 nanowires without an external carbon source and their opto-electronic properties.

    PubMed

    Kiran, Vankayala; Sampath, Srinivasan

    2013-11-07

    The present study demonstrates a simple protocol for the preparation of one dimensional (1D) oxidized titanium carbide nanowires and their opto-electronic properties. The oxidized titanium carbide nanowires (Ox-TiC-NW) are prepared from TiC nanowires (TiC-NW) that are in turn synthesized from micron sized TiC particles using the solvothermal technique. The Ox-TiC-NW is characterized by X-ray diffraction, UV-Vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Raman spectroscopy. Thermal oxidation of TiC-NW yields carbon doped TiO2-NW (C-TiO2-NW), a simple methodology to obtain 1D C-TiO2-NW. Temperature dependent Raman spectra reveal characteristic bands for TiO2-NW. Electrical characterization of individual C-TiO2-NW is performed by fabricating a device structure using the focused ion beam deposition technique. The opto-electronic properties of individual C-TiO2-NW demonstrate visible light activity and the parameters obtained from photoconductivity measurements reveal very good sensitivity. This methodology opens up the possibility of using C-TiO2-NW in electronic and opto-electronic device applications.

  10. Rotational Spectrum and Carbon Atom Structure of Dihydroartemisinic Acid

    NASA Astrophysics Data System (ADS)

    Evangelisti, Luca; Seifert, Nathan A.; Spada, Lorenzo; Pate, Brooks

    2016-06-01

    Dihydroartemisinic acid (DHAA, C15H24O2, five chiral centers) is a precursor in proposed low-cost synthetic routes to the antimalarial drug artemisinin. In one reaction process being considered in pharmaceutical production, DHAA is formed from an enantiopure sample of artemisinic acid through hydrogenation of the alkene. This reaction needs to properly set the stereochemistry of the asymmetric carbon for the synthesis to produce artemisinin. A recrystallization process can purify the diastereomer mixture of the hydrogenation reaction if the unwanted epimer is produced in less than 10% abundance. There is a need in the process analytical chemistry to rapidly (less than 1 min) measure the diastereomer excess and current solutions, such a HPLC, lack the needed measurement speed. The rotational spectrum of DHAA has been measured at 300:1 signal-to-noise ratio in a chirped-pulsed Fourier transform microwave spectrometer operating from 2-8 GHz using simple heating of the compound. The 13C isotope analysis provides a carbon atom structure that confirms the diastereomer. This structure is in excellent agreement with quantum chemistry calculations at the B2PLYPD3/ 6-311++G** level of theory. The DHAA spectrum is expected to be fully resolved from the unwanted diastereomer raising the potential for fast diastereomer excess measurement by rotational spectroscopy in the pharmaceutical production process.

  11. In situ nucleation of carbon nanotubes by the injection of carbon atoms into metal particles

    NASA Astrophysics Data System (ADS)

    Rodríguez-Manzo, Julio A.; Terrones, Mauricio; Terrones, Humberto; Kroto, Harold W.; Sun, Litao; Banhart, Florian

    2007-05-01

    The synthesis of carbon nanotubes (CNTs) of desired chiralities and diameters is one of the most important challenges in nanotube science and achieving such selectivity may require a detailed understanding of their growth mechanism. We report the formation of CNTs in an entirely condensed phase process that allows us, for the first time, to monitor the nucleation of a nanotube on the spherical surface of a metal particle. When multiwalled CNTs containing metal particle cores are irradiated with an electron beam, carbon from graphitic shells surrounding the metal particles is ingested into the body of the particle and subsequently emerges as single-walled nanotubes (SWNTs) or multiwalled nanotubes (MWNTs) inside the host nanotubes. These observations, at atomic resolution in an electron microscope, show that there is direct bonding between the tubes and the metal surface from which the tubes sprout and can be readily explained by bulk diffusion of carbon through the body of catalytic particles, with no evidence of surface diffusion.

  12. High efficiency n-Si/ p-Cu2O core-shell nanowires photodiode prepared by atomic layer deposition of Cu2O on well-ordered Si nanowires array

    NASA Astrophysics Data System (ADS)

    Kim, Hangil; Kim, Soo-Hyun; Ko, Kyung Yong; Kim, Hyungjun; Kim, Jaehoon; Oh, Jihun; Lee, Han-Bo-Ram

    2016-05-01

    A highly efficient n-Si/ p-Cu2O core-shell (C-S) nanowire (NW) photodiode was fabricated using Cu2O grown by atomic layer deposition (ALD) on a well-ordered Si NW array. Ordered Si nanowires arrays were fabricated by nano-sphere lithography to pattern metal catalysts for the metal-assisted etching of silicon, resulting in a Si NW arrays with a good arrangement, smooth surface and small diameter distribution. The ALD-Cu2O thin films were grown using a new non-fluorinated Cu precursor, bis(1-dimethylamino-2-methyl-2-butoxy)copper (C14H32N2O2Cu), and water vapor (H2O) at 140°C. Transmission electron microscopy equipped with an energy dispersive spectrometer confirmed that p-Cu2O thin films had been coated over arrayed Si NWs with a diameter of 150 nm (aspect ratio of ˜7.6). The C-S NW photodiode exhibited more sensitive photodetection performance under ultraviolet illumination as well as an enhanced photocurrent density in the forward biasing region than the planar structure diode. The superior performance of C-S NWs photodiode was explained by the lower reflectance of light and the effective carrier separation and collection originating from the C-S NWs structure. [Figure not available: see fulltext.

  13. Application Of Metal Coated Carbon Nanotubes To Direct Methanol Fuel Cells And For The Formation Of Nanowires

    NASA Astrophysics Data System (ADS)

    Frackowiak, E.; Lota, G.; Lota, K.; Béguin, F.

    2004-09-01

    Homogeneously distributed particles of Pt, Ru or their alloys were electrochemically deposited on catalytic and template multiwalled carbon nanotubes (CNTs). The catalysts supported on the entangled or straight CNTs network with open mesopores have been tested for the reaction of methanol oxidation (1M) in acidic medium (1M H2SO4) by potentiodynamic and galvanostatic methods. The high current densities (500 mA/g) for methanol oxidation proved that such a composite enables a good accessibility of the reagent molecules to the electrode interface. Contrarily, continuous layers of such metals as nickel, copper and silver were chemically and/or electrochemically deposited on carbon nanotubes. These novel materials of nanometer size can be adapted for some electronic application, e.g. nanowires.

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

    NASA Astrophysics Data System (ADS)

    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.

  15. High performance of carbon nanotubes/silver nanowires-PET hybrid flexible transparent conductive films via facile pressing-transfer technique.

    PubMed

    Jing, Mao-Xiang; Han, Chong; Li, Min; Shen, Xiang-Qian

    2014-01-01

    To obtain low sheet resistance, high optical transmittance, small open spaces in conductive networks, and enhanced adhesion of flexible transparent conductive films, a carbon nanotube (CNT)/silver nanowire (AgNW)-PET hybrid film was fabricated by mechanical pressing-transfer process at room temperature. The morphology and structure were characterized by scanning electron microscope (SEM) and atomic force microscope (AFM), the optical transmittance and sheet resistance were tested by ultraviolet-visible spectroscopy (UV-vis) spectrophotometer and four-point probe technique, and the adhesion was also measured by 3M sticky tape. The results indicate that in this hybrid nanostructure, AgNWs form the main conductive networks and CNTs as assistant conductive networks are filled in the open spaces of AgNWs networks. The sheet resistance of the hybrid films can reach approximately 20.9 to 53.9 Ω/□ with the optical transmittance of approximately 84% to 91%. The second mechanical pressing step can greatly reduce the surface roughness of the hybrid film and enhance the adhesion force between CNTs, AgNWs, and PET substrate. This process is hopeful for large-scale production of high-end flexible transparent conductive films.

  16. Low-temperature study of array of dopant atoms on transport behaviors in silicon junctionless nanowire transistor

    SciTech Connect

    Wang, Hao; Han, Weihua Li, Xiaoming; Zhang, Yanbo; Yang, Fuhua

    2014-09-28

    We demonstrate temperature-dependent quantum transport characteristics in silicon junctionless nanowire transistor fabricated on Silicon-on-Insulator substrate by the femtosecond laser lithography. Clear drain-current oscillations originated from dopant-induced quantum dots are observed in the initial stage of the conduction for the silicon nanowire channel at low temperatures. Arrhenius plot of the conductance indicates the transition temperature of 30 K from variable-range hopping to nearest-neighbor hopping, which can be well explained under Mott formalism. The transition of electron hopping behavior is the interplay result between the thermal activation and the Coulomb interaction.

  17. Trapping of metal atoms in vacancies of carbon nanotubes and graphene.

    PubMed

    Rodríguez-Manzo, Julio A; Cretu, Ovidiu; Banhart, Florian

    2010-06-22

    Lattice defects in carbon nanotubes and graphene are created by focusing an electron beam in a scanning transmission electron microscope onto a 0.1 nm spot on the objects. Metal atoms migrating on the graphenic surfaces are observed to be trapped by these defects. Depending on the size of the defect, single metal atoms or clusters of several atoms can be localized in or on nanotubes or graphene layers. Subsequent escape of the metal atoms from the trapping centers gives information about the bonding between the metal atom and the defect. The process of trapping and detrapping is studied in a temperature range of 20-670 degrees C. The technique allows one to place metal atoms with almost atomic precision in graphenic structures and to create a predefined pattern of foreign atoms in graphene or carbon nanotubes.

  18. Three-dimensional cross-linked carbon network wrapped with ordered polyaniline nanowires for high-performance pseudo-supercapacitors

    NASA Astrophysics Data System (ADS)

    Hu, Huan; Liu, Shuwu; Hanif, Muddasir; Chen, Shuiliang; Hou, Haoqing

    2014-12-01

    The polyaniline (PANI)-based pseudo-supercapacitor has been extensively studied due to its good conductivity, ease of synthesis, low-cost monomer, tunable properties and remarkable specific capacitance. In this work, a three-dimensional cross-linked carbon network (3D-CCN) was used as a contact-resistance-free substrate for PANI-based pseudo-supercapacitors. The ordered PANI nanowires (PaNWs) were grown on the 3D-CCN to form PaNWs/3D-CCN composites by in-situ polymerization. The PaNWs/3D-CCN composites exhibited a specific capacitance (Cs) of 1191.8 F g-1 at a current density of 0.5 A g-1 and a superior rate capability with 66.4% capacitance retention at 100.0 A g-1. The high specific capacitance is attributed to the thin PaNW coating and the spaced PANI nanowire array, which ensure a higher utilization of PANI due to the ease of diffusion of protons through/on the PANI nanowires. In addition, the unique 3D-CCN was used as a high-conductivity platform (or skeleton) with no contact resistance for fast electron transfer and facile charge transport within the composites. Therefore, the binder-free composites can process rapid gains or losses of electrons and ions, even at a high current density. As a result, the specific capacitance and rate capability of our composites are remarkably higher than those of other PANI composites.

  19. The effect of annealing on the photoconductivity of carbon nanofiber/TiO2 core-shell nanowires for use in dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Rochford, Caitlin; Li, Zhuang-Zhi; Baca, Javier; Liu, Jianwei; Li, Jun; Wu, Judy

    2010-07-01

    Electrical transport properties and photoresponse of individual TiO2-coated carbon nanofibers were studied in an attempt to elucidate the limiting factors of core-shell nanowire-based dye-sensitized solar cells (DSSC). The role of the semiconductor shell microstructure was investigated by comparing as grown and thermally annealed samples. Steady state I-V and transient photoconductivity measurements suggest that improving the microstructure leads to reduced resistivity and contact resistance, a decrease in charge traps, improved surface stoichiometry for dye adsorption, and reduced absorption of visible light by the semiconductor, all of which may improve nanowire-based DSSC performance.

  20. Beam-deposited platinum as versatile catalyst for bottom-up silicon nanowire synthesis

    SciTech Connect

    Hibst, N.; Strehle, S.; Knittel, P.; Kranz, C.; Mizaikoff, B.

    2014-10-13

    The controlled localized bottom-up synthesis of silicon nanowires on arbitrarily shaped surfaces is still a persisting challenge for functional device assembly. In order to address this issue, electron beam and focused ion beam-assisted catalyst deposition have been investigated with respect to platinum expected to form a PtSi alloy catalyst for a subsequent bottom-up nanowire synthesis. The effective implementation of pure platinum nanoparticles or thin films for silicon nanowire growth has been demonstrated recently. Beam-deposited platinum contains significant quantities of amorphous carbon due to the organic precursor and gallium ions for a focused ion beam-based deposition process. Nevertheless, silicon nanowires could be grown on various substrates regardless of the platinum purity. Additionally, p-type doping could be realized with diborane whereas n-type doping suppressed a nanowire growth. The rational utilization of this beam-assisted approach enables us to control the localized synthesis of single silicon nanowires at planar surfaces but succeeded also in single nanowire growth at the three-dimensional apex of an atomic force microscopy tip. Therefore, this catalyst deposition method appears to be a unique extension of current technologies to assemble complex nanowire-based devices.

  1. Atomic-scale understanding of dichlorobenzene-assisted poly 3-hexylthiophene-2,5-diyl nanowire formation mechanism

    NASA Astrophysics Data System (ADS)

    Yagmurcukardes, M.; Kiymaz, D.; Zafer, C.; Senger, R. T.; Sahin, H.

    2017-04-01

    Low-dimensional Poly 3-hexylthiophene-2,5-diyl (P3HT) structures that serve efficient exciton dissociation in organic solar cells, play a major role in increasing the charge collection, and hence, the efficiency of organic devices. In this study, we theoretically and experimentally investigate the Dichlorobenzene (DCB)-assisted formation of P3HT nanowires. Our experiments show that the solution of DCB molecules drive randomly oriented P3HT polymers to form well-stacked nanowires by stabilizing tail-tail and π-π interactions. Here the question is how DCB molecules migrate into the P3HT layers while forming the nanowire structure. Our density functional theory-based calculations reveal that the vertical migration of the DCB molecules between P3HT layers is forbidden due to a high energy barrier that stems from strong alkyl chain-DCB interaction. In contrast to vertical diffusion, lateral diffusion of DCB molecules in between P3HT layers is much more likely. Our results show that migration of a DCB molecule occurs through the alkyl groups with a low energy barrier. Therefore, laterally diffused DCB molecules assist nucleation of top-to-top stacking of P3HT polymers and formation of well-ordered nanowires.

  2. Site specific atomic polarizabilities in endohedral fullerenes and carbon onions.

    PubMed

    Zope, Rajendra R; Bhusal, Shusil; Basurto, Luis; Baruah, Tunna; Jackson, Koblar

    2015-08-28

    We investigate the polarizability of trimetallic nitride endohedral fullerenes by partitioning the total polarizability into site specific components. This analysis indicates that the polarizability of the endohedral fullerene is essentially due to the outer fullerene cage and has insignificant contribution from the encapsulated unit. Thus, the outer fullerene cages effectively shield the encapsulated clusters and behave like Faraday cages. The polarizability of endohedral fullerenes is slightly smaller than the polarizability of the corresponding bare carbon fullerenes. The application of the site specific polarizabilities to C60@C240 and C60@C180 onions shows that, compared to the polarizability of isolated C60 fullerene, the encapsulation of the C60 in C240 and C180 fullerenes reduces its polarizability by 75% and 83%, respectively. The differences in the polarizability of C60 in the two onions is a result of differences in the bonding (intershell electron transfer), fullerene shell relaxations, and intershell separations. The site specific analysis further shows that the outer atoms in a fullerene shell contribute most to the fullerene polarizability.

  3. Site specific atomic polarizabilities in endohedral fullerenes and carbon onions

    NASA Astrophysics Data System (ADS)

    Zope, Rajendra R.; Bhusal, Shusil; Basurto, Luis; Baruah, Tunna; Jackson, Koblar

    2015-08-01

    We investigate the polarizability of trimetallic nitride endohedral fullerenes by partitioning the total polarizability into site specific components. This analysis indicates that the polarizability of the endohedral fullerene is essentially due to the outer fullerene cage and has insignificant contribution from the encapsulated unit. Thus, the outer fullerene cages effectively shield the encapsulated clusters and behave like Faraday cages. The polarizability of endohedral fullerenes is slightly smaller than the polarizability of the corresponding bare carbon fullerenes. The application of the site specific polarizabilities to C60@C240 and C60@C180 onions shows that, compared to the polarizability of isolated C60 fullerene, the encapsulation of the C60 in C240 and C180 fullerenes reduces its polarizability by 75% and 83%, respectively. The differences in the polarizability of C60 in the two onions is a result of differences in the bonding (intershell electron transfer), fullerene shell relaxations, and intershell separations. The site specific analysis further shows that the outer atoms in a fullerene shell contribute most to the fullerene polarizability.

  4. Site specific atomic polarizabilities in endohedral fullerenes and carbon onions

    SciTech Connect

    Zope, Rajendra R. Baruah, Tunna; Bhusal, Shusil; Basurto, Luis; Jackson, Koblar

    2015-08-28

    We investigate the polarizability of trimetallic nitride endohedral fullerenes by partitioning the total polarizability into site specific components. This analysis indicates that the polarizability of the endohedral fullerene is essentially due to the outer fullerene cage and has insignificant contribution from the encapsulated unit. Thus, the outer fullerene cages effectively shield the encapsulated clusters and behave like Faraday cages. The polarizability of endohedral fullerenes is slightly smaller than the polarizability of the corresponding bare carbon fullerenes. The application of the site specific polarizabilities to C{sub 60}@C{sub 240} and C{sub 60}@C{sub 180} onions shows that, compared to the polarizability of isolated C{sub 60} fullerene, the encapsulation of the C{sub 60} in C{sub 240} and C{sub 180} fullerenes reduces its polarizability by 75% and 83%, respectively. The differences in the polarizability of C{sub 60} in the two onions is a result of differences in the bonding (intershell electron transfer), fullerene shell relaxations, and intershell separations. The site specific analysis further shows that the outer atoms in a fullerene shell contribute most to the fullerene polarizability.

  5. Reactions of Atomic Carbon with Butene Isomers: Implications for Molecular Growth in Carbon-Rich Environments

    DOE PAGES

    Bourgalais, J.; Spencer, Michael; Osborn, David L.; ...

    2016-10-31

    We carried out the product detection studies of C(3P) atom reactions with butene (C4H8) isomers (but-1-ene, cis-but-2-ene, trans-but-2-ene) in a flow tube reactor at 353 K and 4 Torr under multiple collision conditions. Ground state carbon atoms are generated by 248 nm laser photolysis of tetrabromomethane, CBr4, in a buffer of helium. Thermalized reaction products are detected using synchrotron tunable VUV photoionization and time-of-flight mass spectrometry. The temporal profiles of the detected ions are used to discriminate products from side or secondary reactions. Furthermore, for the C(3P) + trans-but-2-ene and C(3P) + cis-but-2-ene reactions, various isomers of C4H5 and C5H7more » are identified as reaction products formed via CH3 and H elimination. Assuming equal ionization cross sections for all C4H5 and C5H7 isomers, C4H5:C5H7 branching ratios of 0.63:1 and 0.60:1 are derived for the C(3P) + trans-but-2-ene and the C(3P) + cis-but-2-ene reactions, respectively. For the C(3P) + but-1-ene reaction, two reaction channels are observed: the H-elimination channel, leading to the formation of the ethylpropargyl isomer, and the C3H3 + C2H5 channel. Assuming equal ionization cross sections for ethylpropargyl and C3H3 radicals, a branching ratio of 1:0.95 for the C3H3 + C2H5 and H + ethylpropargyl channels is derived. Finally, the experimental results are compared to previous H atom branching ratios and used to propose the most likely mechanisms for the reaction of ground state carbon atoms with butene isomers.« less

  6. Reactions of Atomic Carbon with Butene Isomers: Implications for Molecular Growth in Carbon-Rich Environments

    NASA Astrophysics Data System (ADS)

    Bourgalais, J.; Spencer, Michael; Osborn, David L.; Goulay, F.; Le Picard, S. D.

    2016-10-01

    Product detection studies of C(3P) atom reactions with butene (C4H8) isomers (but-1-ene, cis-but-2-ene, trans-but-2-ene) are carried out in a flow tube reactor at 353 K and 4 Torr under multiple collision conditions. Ground state carbon atoms are generated by 248 nm laser photolysis of tetrabromomethane, CBr4, in a buffer of helium. Thermalized reaction products are detected using synchrotron tunable VUV photoionization and time-of-flight mass spectrometry. The temporal profiles of the detected ions are used to discriminate products from side or secondary reactions. For the C(3P) + trans-but-2-ene and C(3P) + cis-but-2-ene reactions, various isomers of C4H5 and C5H7 are identified as reaction products formed via CH3 and H elimination. Assuming equal ionization cross sections for all C4H5 and C5H7 isomers, C4H5:C5H7 branching ratios of 0.63:1 and 0.60:1 are derived for the C(3P) + trans-but-2-ene and the C(3P) + cis-but-2-ene reactions, respectively. For the C(3P) + but-1ene reaction, two reaction channels are observed: the H-elimination channel, leading to the formation of the ethylpropargyl isomer, and the C3H3 + C2H5 channel. Assuming equal ionization cross sections for ethylpropargyl and C3H3 radicals, a branching ratio of 1:0.95 for the C3H3 + C2H5 and H + ethylpropargyl channels is derived. The experimental results are compared to previous H atom branching ratios and used to propose the most likely mechanisms for the reaction of ground state carbon atoms with butene isomers.

  7. Electrically Robust Metal Nanowire Network Formation by In-Situ Interconnection with Single-Walled Carbon Nanotubes

    PubMed Central

    Woo, Jong Seok; Han, Joong Tark; Jung, Sunshin; Jang, Jeong In; Kim, Ho Young; Jeong, Hee Jin; Jeong, Seung Yol; Baeg, Kang-Jun; Lee, Geon-Woong

    2014-01-01

    Modulation of the junction resistance between metallic nanowires is a crucial factor for high performance of the network-structured conducting film. Here, we show that under current flow, silver nanowire (AgNW) network films can be stabilised by minimizing the Joule heating at the NW-NW junction assisted by in-situ interconnection with a small amount (less than 3 wt%) of single-walled carbon nanotubes (SWCNTs). This was achieved by direct deposition of AgNW suspension containing SWCNTs functionalised with quadruple hydrogen bonding moieties excluding dispersant molecules. The electrical stabilisation mechanism of AgNW networks involves the modulation of the electrical transportation pathway by the SWCNTs through the SWCNT-AgNW junctions, which results in a relatively lower junction resistance than the NW-NW junction in the network film. In addition, we propose that good contact and Fermi level matching between AgNWs and modified SWCNTs lead to the modulation of the current pathway. The SWCNT-induced stabilisation of the AgNW networks was also demonstrated by irradiating the film with microwaves. The development of the high-throughput fabrication technology provides a robust and scalable strategy for realizing high-performance flexible transparent conductor films. PMID:24763208

  8. Effect of added silicon carbide nanowires and carbon nanotubes on mechanical properties of 0-3 natural rubber composites

    NASA Astrophysics Data System (ADS)

    Janyakunmongkol, Khantichai; Nhuapeng, Wim; Thamjaree, Wandee

    2016-01-01

    In this work, the mechanical properties of 0-3 nanocomposite materials containing silicon carbide nanowires (SiCNWs), carbon nanotubes (CNTs), and natural rubber were studied. The SiCNWs and CNTs were used as reinforcement fiber whereas natural rubber was used as the matrix phase. The chemical vapor depositions (CVD) was used for synthesizing the nanowire and nanotube phases. The volume fraction of reinforcement was varied from 0 to 10%. The nanophases were mixed in the natural rubber matrix and molded by the hand lay-up technique. The mechanical properties of the samples were examined and compared with those of neat natural rubber. From the results, it was found that the hardness and density of the samples increased with the quantities of nanophases. The nanocomposites with a volume fraction of 10% exhibited maximum hardness (50.5 SHORE A). The maximum tensile strength and extent of elongation at break of the samples were obtained from the 4% volume fraction sample, which were 16.13 MPa and 1,540%, respectively.

  9. Exchange of carbon-bound hydrogen atoms ortho to the hydroxyl group in tyrosine.

    PubMed

    Martin, R B; Morlino, V J

    1965-10-22

    The carbon-bound hydrogen atoms of tyrosine that exchange with solvent protons in strongly acid solutions at about 100 degrees C are not the methylene hydrogen atoms but a pair on the aromatic ring. Of the two pairs of protons on the aromatic ring, observed in the proton magnetic resonance spectra, the pair at higher field undergoes exchange in 2.4N DCI at 100 degrees C. Other hydrogen atoms, attached either to aliphatic or aromatic carbon atoms, exhibit no noticeable exchange under the same conditions. From a chemicalshift analysis the exchanging protons are assigned as those ortho to the hydroxyl group on the aromatic ring.

  10. Facile synthesis of carbon doped TiO2 nanowires without an external carbon source and their opto-electronic properties

    NASA Astrophysics Data System (ADS)

    Kiran, Vankayala; Sampath, Srinivasan

    2013-10-01

    The present study demonstrates a simple protocol for the preparation of one dimensional (1D) oxidized titanium carbide nanowires and their opto-electronic properties. The oxidized titanium carbide nanowires (Ox-TiC-NW) are prepared from TiC nanowires (TiC-NW) that are in turn synthesized from micron sized TiC particles using the solvothermal technique. The Ox-TiC-NW is characterized by X-ray diffraction, UV-Vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Raman spectroscopy. Thermal oxidation of TiC-NW yields carbon doped TiO2-NW (C-TiO2-NW), a simple methodology to obtain 1D C-TiO2-NW. Temperature dependent Raman spectra reveal characteristic bands for TiO2-NW. Electrical characterization of individual C-TiO2-NW is performed by fabricating a device structure using the focused ion beam deposition technique. The opto-electronic properties of individual C-TiO2-NW demonstrate visible light activity and the parameters obtained from photoconductivity measurements reveal very good sensitivity. This methodology opens up the possibility of using C-TiO2-NW in electronic and opto-electronic device applications.The present study demonstrates a simple protocol for the preparation of one dimensional (1D) oxidized titanium carbide nanowires and their opto-electronic properties. The oxidized titanium carbide nanowires (Ox-TiC-NW) are prepared from TiC nanowires (TiC-NW) that are in turn synthesized from micron sized TiC particles using the solvothermal technique. The Ox-TiC-NW is characterized by X-ray diffraction, UV-Vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Raman spectroscopy. Thermal oxidation of TiC-NW yields carbon doped TiO2-NW (C-TiO2-NW), a simple methodology to obtain 1D C-TiO2-NW. Temperature dependent Raman spectra reveal characteristic bands for TiO2-NW. Electrical characterization of individual C-TiO2-NW is performed by fabricating a device structure using the

  11. Characterization of individual straight and kinked boron carbide nanowires

    NASA Astrophysics Data System (ADS)

    Cui, Zhiguang

    axes where stacking faults are invisible. In collaboration with the experts in the field of thermal property characterization of one dimensional nanostructures, thermal conductivities of over 60 nanowires including both straight and kinked ones have been measured in the temperature range of 20 - 420 K and the parameters (i.e., carbon contents, diameters, stacking faults densities/orientations and kinks) affecting the phonon transport were explored. The results disclose strong carbon content and diameter dependence of thermal conductivities of boron carbide nanowires, which decreases as lowering the carbon content and diameter. Stacking fault orientations do modulate the phonon transport (kappaTF < kappa AF), while stacking fault densities seems to only have obvious effects on phonon transport when meeting certain threshold ( 39%). The most interesting discovery is significant reduction of thermal conductivity (15% - 40%) in kinked boron carbide nanowires due to phonon mode conversions and scattering at the kink site. Last but not least, micro-Raman spectroscopy study on individual boron carbide nanowires has been performed for the first time, to the best of our knowledge. Based on the preliminary data, it is found that the stacking fault orientations have no apparent effect on the Raman scattering, but the stacking fault densities do. In addition, up as the size going down to nanoscale, some Raman modes are inactive while some new ones show up, which is largely ascribed to the quantum confinement effects. One more important finding is that the carbon content also plays important role in the Raman scattering of boron carbide nanowires in the low frequency region (< 600 cm-1), which mainly comes from the 3-atom chains (C-B-C or C-B-B).

  12. Investigating the energy harvesting capabilities of a hybrid ZnO nanowires/carbon fiber polymer composite beam.

    PubMed

    Masghouni, N; Burton, J; Philen, M K; Al-Haik, M

    2015-03-06

    Hybrid piezoelectric composite structures that are able to convert mechanical energy into electricity have gained growing attention in the past few years. In this work, an energy harvesting composite beam is developed by growing piezoelectric zinc oxide nanowires on the surface of carbon fiber prior to forming structural composites. The piezoelectric behavior of the composite beam was demonstrated under different vibration sources such as water bath sonicator and permanent magnet vibration shaker. The beam was excited at its fundamental natural frequency (43.2 Hz) and the open circuit voltage and the short circuit current were measured to be 3.1 mV and 23 nA, respectively. Upon connecting an optimal resistor (1.2 kΩ) in series with the beam a maximum power output 2.5 nW was achieved.

  13. Carbon Nanotube Atomic Force Microscopy for Proteomics and Biological Forensics

    SciTech Connect

    Noy, A; De Yoreo, J J; Malkin, A J

    2002-01-01

    The Human Genome Project was focused on mapping the complete genome. Yet, understanding the structure and function of the proteins expressed by the genome is the real end game. But there are approximately 100,000 proteins in the human body and the atomic structure has been determined for less than 1% of them. Given the current rate at which structures are being solved, it will take more than one hundred years to complete this task. The rate-limiting step in protein structure determination is the growth of high-quality single crystals for X-ray diffraction. Synthesis of the protein stock solution as well as X-ray diffraction and analysis can now often be done in a matter of weeks, but developing a recipe for crystallization can take years and, especially in the case of membrane proteins, is often completely unsuccessful. Consequently, techniques that can either help to elucidate the factors controlling macromolecular crystallization, increase the amount of structural information obtained from crystallized macromolecules or eliminate the need for crystallization altogether are of enormous importance. In addition, potential applications for those techniques extend well beyond the challenges of proteomics. The global spread of modern technology has brought with it an increasing threat from biological agents such as viruses. As a result, developing techniques for identifying and understanding the operation of such agents is becoming a major area of forensic research for DOE. Previous to this project, we have shown that we can use in situ atomic force microscopy (AFM) to image the surfaces of growing macromolecular crystals with molecular resolution (1-5) In addition to providing unprecedented information about macromolecular nucleation, growth and defect structure, these results allowed us to obtain low-resolution phase information for a number of macromolecules, providing structural information that was not obtainable from X-ray diffraction(3). For some virus systems

  14. Carbon fiber CVD coating by carbon nanostructured for space materials protection against atomic oxygen

    NASA Astrophysics Data System (ADS)

    Pastore, Roberto; Bueno Morles, Ramon; Micheli, Davide

    2016-07-01

    , by the purpose to integrate the carbon nanostructures in the carbon fibers by means of chemical vapor deposition (CVD) method, in order to develop the basic substrate of advanced carbon-based nanocomposite for atomic oxygen protection. The nanostructures grown onto the carbon fibers can be used to create multiscale hybrid carbon nanotube/carbon fiber composites where individual carbon fibers, which are several microns in diameter, are surrounded by nanotubes. The present objective is the setting-up of the CVD parameters for a reliable growth of carbon nanostructures on carbon fiber surface; after that, the results of a preliminary characterization related to atomic oxygen effects testing by means of a ground LEO simulation facility are reported and discussed.

  15. Determination of Diclofenac on a Dysprosium Nanowire- Modified Carbon Paste Electrode Accomplished in a Flow Injection System by Advanced Filtering

    PubMed Central

    Daneshgar, Parandis; Norouzi, Parviz; Ganjali, Mohammad Reza; Dinarvand, Rasoul; Moosavi-Movahedi, Ali Akbar

    2009-01-01

    A new detection technique called Fast Fourier Transform Square-Wave Voltammetry (FFT SWV) is based on measurements of electrode admittance as a function of potential. The response of the detector (microelectrode), which is generated by a redox processes, is fast, which makes the method suitable for most applications involving flowing electrolytes. The carbon paste electrode was modified by nanostructures to improve sensitivity. Synthesized dysprosium nanowires provide a more effective nanotube-like surface [1-4] so they are good candidates for use as a modifier for electrochemical reactions. The redox properties of diclofenac were used for its determination in human serum and urine samples. The support electrolyte that provided a more defined and intense peak current for diclofenac determination was a 0.05 mol L−1 acetate buffer pH = 4.0. The drug presented an irreversible oxidation peak at 850 mV vs. Ag/AgCl on a modified nanowire carbon paste electrode which produced high current and reduced the oxidation potential by about 100 mV. Furthermore, the signal-to-noise ratio was significantly increased by application of a discrete Fast Fourier Transform (FFT) method, background subtraction and two-dimensional integration of the electrode response over a selected potential range and time window. To obtain the much sensivity the effective parameters such as frequency, amplitude and pH was optimized. As a result, CDL of 2.0 × 10−9 M and an LOQ of 5.0 × 10−9 M were found for the determination for diclofenac. A good recovery was obtained for assay spiked urine samples and a good quantification of diclofenac was achieved in a commercial formulation. PMID:22408485

  16. Atomic Resolution in Situ Imaging of a Double-Bilayer Multistep Growth Mode in Gallium Nitride Nanowires

    DOE PAGES

    Gamalski, A. D.; Tersoff, J.; Stach, E. A.

    2016-04-13

    We study the growth of GaN nanowires from liquid Au–Ga catalysts using environmental transmission electron microscopy. GaN wires grow in either (11¯20) or (11¯00) directions, by the addition of {11¯00} double bilayers via step flow with multiple steps. Step-train growth is not typically seen with liquid catalysts, and we suggest that it results from low step mobility related to the unusual double-height step structure. Finally, the results here illustrate the surprising dynamics of catalytic GaN wire growth at the nanoscale and highlight striking differences between the growth of GaN and other III–V semiconductor nanowires.

  17. Atomic Resolution in Situ Imaging of a Double-Bilayer Multistep Growth Mode in Gallium Nitride Nanowires

    SciTech Connect

    Gamalski, A. D.; Tersoff, J.; Stach, E. A.

    2016-04-13

    We study the growth of GaN nanowires from liquid Au–Ga catalysts using environmental transmission electron microscopy. GaN wires grow in either (11¯20) or (11¯00) directions, by the addition of {11¯00} double bilayers via step flow with multiple steps. Step-train growth is not typically seen with liquid catalysts, and we suggest that it results from low step mobility related to the unusual double-height step structure. Finally, the results here illustrate the surprising dynamics of catalytic GaN wire growth at the nanoscale and highlight striking differences between the growth of GaN and other III–V semiconductor nanowires.

  18. Atomic Resolution in Situ Imaging of a Double-Bilayer Multistep Growth Mode in Gallium Nitride Nanowires.

    PubMed

    Gamalski, A D; Tersoff, J; Stach, E A

    2016-04-13

    We study the growth of GaN nanowires from liquid Au-Ga catalysts using environmental transmission electron microscopy. GaN wires grow in either ⟨112̅0⟩ or ⟨11̅00⟩ directions, by the addition of {11̅00} double bilayers via step flow with multiple steps. Step-train growth is not typically seen with liquid catalysts, and we suggest that it results from low step mobility related to the unusual double-height step structure. The results here illustrate the surprising dynamics of catalytic GaN wire growth at the nanoscale and highlight striking differences between the growth of GaN and other III-V semiconductor nanowires.

  19. Ab initio study of semiconductor atoms impurities in zigzag edge (10,0) carbon nanotubes

    SciTech Connect

    Muttaqien, Fahdzi Suprijadi

    2015-04-16

    The substitutional impurities in zigzag edge (10,0) carbon nanotubes have been studied by using first principles calculations. Silicon (Si), gallium (Ga), and arsenic (As) atom have been chosen as semiconductor based-atom for replacing carbon atoms in CNT’s surface. The silicon atom changes the energy gap of pristine zigzag (10,0) CNT, it is 0.19 eV more narrow than that of pristine CNT. Geometrically, the silicon atom creates sp{sup 3} bond with three adjacent carbon atoms, where the tetrahedral form of its sp{sup 3} bond is consisted of free unoccupied state. The silicon atom does not induce magnetism to zigzag CNT. Due to gallium (Ga) and arsenic (As) atom substitution, the zigzag CNT becomes metallic and has magnetic moment of 1 µ{sub B}. The valance and conduction band are crossed each other, then the energy gap is vanished. The electronic properties of GaAs-doped CNT are dominantly affected by gallium atom and its magnetic properties are dominantly affected by arsenic atom. These results prove that the CNT with desired properties can be obtained with substitutional impurities without any giving structural defect.

  20. Atomic Scale Dynamics of Contact Formation in the Cross-Section of InGaAs Nanowire Channels.

    PubMed

    Chen, Renjie; Jungjohann, Katherine L; Mook, William M; Nogan, John; Dayeh, Shadi A

    2017-04-12

    Alloyed and compound contacts between metal and semiconductor transistor channels enable self-aligned gate processes which play a significant role in transistor scaling. At nanoscale dimensions and for nanowire channels, prior experiments focused on reactions along the channel length, but the early stage of reaction in their cross sections remains unknown. Here, we report on the dynamics of the solid-state reaction between metal (Ni) and semiconductor (In0.53Ga0.47As), along the cross-section of nanowires that are 15 nm in width. Unlike planar structures where crystalline nickelide readily forms at conventional, low alloying temperatures, nanowires exhibit a solid-state amorphization step that can undergo a crystal regrowth step at elevated temperatures. In this study, we capture the layer-by-layer reaction mechanism and growth rate anisotropy using in situ transmission electron microscopy (TEM). Our kinetic model depicts this new, in-plane contact formation which could pave the way for engineered nanoscale transistors.

  1. Atomic Scale Dynamics of Contact Formation in the Cross-Section of InGaAs Nanowire Channels

    DOE PAGES

    Chen, Renjie; Jungjohann, Katherine L.; Mook, William M.; ...

    2017-03-23

    In the alloyed and compound contacts between metal and semiconductor transistor channels we see that they enable self-aligned gate processes which play a significant role in transistor scaling. At nanoscale dimensions and for nanowire channels, prior experiments focused on reactions along the channel length, but the early stage of reaction in their cross sections remains unknown. We report on the dynamics of the solid-state reaction between metal (Ni) and semiconductor (In0.53Ga0.47As), along the cross-section of nanowires that are 15 nm in width. Unlike planar structures where crystalline nickelide readily forms at conventional, low alloying temperatures, nanowires exhibit a solid-state amorphizationmore » step that can undergo a crystal regrowth step at elevated temperatures. Here, we capture the layer-by-layer reaction mechanism and growth rate anisotropy using in situ transmission electron microscopy (TEM). Our kinetic model depicts this new, in-plane contact formation which could pave the way for engineered nanoscale transistors.« less

  2. Characterization of electrical properties in axial Si-Ge nanowire heterojunctions using off-axis electron holography and atom-probe tomography

    SciTech Connect

    Gan, Zhaofeng; Perea, Daniel E.; Yoo, Jinkyoung; He, Yang; Colby, Robert J.; Barker, Josh E.; Gu, Meng; Mao, Scott X.; Wang, Chongmin; Picraux, S. T.; Smith, David J.; McCartney, Martha R.

    2016-09-13

    Doped Si-Ge nanowire (NW) heterojunctions were grown using the vapor-liquid-solid method with AuGa and Au catalyst particles. Transmission electron microscopy and off-axis electron holography (EH) were used to characterize the nanostructure and to measure the electrostatic potential profile across the junction resulting from electrically active dopants, while atom-probe tomography (APT) was used to determine the Si, Ge and total (active and inactive) dopant concentration profiles. A comparison of the measured potential profile with simulations indicated that Ga dopants unintentionally introduced during AuGa catalyst growth were electronically inactive despite APT results that showed considerable amounts of Ga in the Si region. 10% P in Ge and 100% B in Si were estimated to be activated, which was corroborated by in situ electron-holography biasing experiments. This combination of EH, APT, in situ biasing and simulations allows a better knowledge and understanding of the electrically active dopant distributions in NWs.

  3. A simple and clean source of low-energy atomic carbon

    SciTech Connect

    Krasnokutski, S. A.; Huisken, F.

    2014-09-15

    A carbon source emitting low-energy carbon atoms from a thin-walled, sealed tantalum tube via thermal evaporation has been constructed. The tube is made from a 0.05 mm thick tantalum foil and filled with {sup 12}C or {sup 13}C carbon powder. After being sealed, it is heated by direct electric current. The solvated carbon atoms diffuse to the outer surface of the tube and, when the temperature rises over 2200 K, the evaporation of atomic carbon from the surface of the tantalum tube is observed. As the evaporated species have low energy they are well-suited for the incorporation into liquid helium droplets by the pick-up technique. Mass analysis of the incorporated species reveals the dominant presence of atomic carbon and very low abundances of C{sub 2} and C{sub 3} molecules (<1%). This is in striking contrast to the thermal evaporation of pure carbon, where C{sub 3} molecules are found to be the dominant species in the gas phase. Due to the thermal evaporation and the absence of high-energy application required for the dissociation of C{sub 2} and C{sub 3} molecules, the present source provides carbon atoms with rather low energy.

  4. Dynamics of carbon-hydrogen and carbon-methyl exchanges in the collision of 3P atomic carbon with propene

    NASA Astrophysics Data System (ADS)

    Lee, Shih-Huang; Chen, Wei-Kan; Chin, Chih-Hao; Huang, Wen-Jian

    2013-11-01

    We investigated the dynamics of the reaction of 3P atomic carbon with propene (C3H6) at reactant collision energy 3.8 kcal mol-1 in a crossed molecular-beam apparatus using synchrotron vacuum-ultraviolet ionization. Products C4H5, C4H4, C3H3, and CH3 were observed and attributed to exit channels C4H5 + H, C4H4 + 2H, and C3H3 + CH3; their translational-energy distributions and angular distributions were derived from the measurements of product time-of-flight spectra. Following the addition of a 3P carbon atom to the C=C bond of propene, cyclic complex c-H2C(C)CHCH3 undergoes two separate stereoisomerization mechanisms to form intermediates E- and Z-H2CCCHCH3. Both the isomers of H2CCCHCH3 in turns decompose to C4H5 + H and C3H3 + CH3. A portion of C4H5 that has enough internal energy further decomposes to C4H4 + H. The three exit channels C4H5 + H, C4H4 + 2H, and C3H3 + CH3 have average translational energy releases 13.5, 3.2, and 15.2 kcal mol-1, respectively, corresponding to fractions 0.26, 0.41, and 0.26 of available energy deposited to the translational degrees of freedom. The H-loss and 2H-loss channels have nearly isotropic angular distributions with a slight preference at the forward direction particularly for the 2H-loss channel. In contrast, the CH3-loss channel has a forward and backward peaked angular distribution with an enhancement at the forward direction. Comparisons with reactions of 3P carbon atoms with ethene, vinyl fluoride, and vinyl chloride are stated.

  5. Atomic Scale Analysis of the Enhanced Electro- and Photo-Catalytic Activity in High-Index Faceted Porous NiO Nanowires

    PubMed Central

    Shen, Meng; Han, Ali; Wang, Xijun; Ro, Yun Goo; Kargar, Alireza; Lin, Yue; Guo, Hua; Du, Pingwu; Jiang, Jun; Zhang, Jingyu; Dayeh, Shadi A.; Xiang, Bin

    2015-01-01

    Catalysts play a significant role in clean renewable hydrogen fuel generation through water splitting reaction as the surface of most semiconductors proper for water splitting has poor performance for hydrogen gas evolution. The catalytic performance strongly depends on the atomic arrangement at the surface, which necessitates the correlation of the surface structure to the catalytic activity in well-controlled catalyst surfaces. Herein, we report a novel catalytic performance of simple-synthesized porous NiO nanowires (NWs) as catalyst/co-catalyst for the hydrogen evolution reaction (HER). The correlation of catalytic activity and atomic/surface structure is investigated by detailed high resolution transmission electron microscopy (HRTEM) exhibiting a strong dependence of NiO NW photo- and electrocatalytic HER performance on the density of exposed high-index-facet (HIF) atoms, which corroborates with theoretical calculations. Significantly, the optimized porous NiO NWs offer long-term electrocatalytic stability of over one day and 45 times higher photocatalytic hydrogen production compared to commercial NiO nanoparticles. Our results open new perspectives in the search for the development of structurally stable and chemically active semiconductor-based catalysts for cost-effective and efficient hydrogen fuel production at large scale. PMID:25707903

  6. Reactions of Atomic Carbon with Butene Isomers: Implications for Molecular Growth in Carbon-Rich Environments

    SciTech Connect

    Bourgalais, J.; Spencer, Michael; Osborn, David L.; Goulay, F.; Le Picard, S. D.

    2016-10-31

    We carried out the product detection studies of C(3P) atom reactions with butene (C4H8) isomers (but-1-ene, cis-but-2-ene, trans-but-2-ene) in a flow tube reactor at 353 K and 4 Torr under multiple collision conditions. Ground state carbon atoms are generated by 248 nm laser photolysis of tetrabromomethane, CBr4, in a buffer of helium. Thermalized reaction products are detected using synchrotron tunable VUV photoionization and time-of-flight mass spectrometry. The temporal profiles of the detected ions are used to discriminate products from side or secondary reactions. Furthermore, for the C(3P) + trans-but-2-ene and C(3P) + cis-but-2-ene reactions, various isomers of C4H5 and C5H7 are identified as reaction products formed via CH3 and H elimination. Assuming equal ionization cross sections for all C4H5 and C5H7 isomers, C4H5:C5H7 branching ratios of 0.63:1 and 0.60:1 are derived for the C(3P) + trans-but-2-ene and the C(3P) + cis-but-2-ene reactions, respectively. For the C(3P) + but-1-ene reaction, two reaction channels are observed: the H-elimination channel, leading to the formation of the ethylpropargyl isomer, and the C3H3 + C2H5 channel. Assuming equal ionization cross sections for ethylpropargyl and C3H3 radicals, a branching ratio of 1:0.95 for the C3H3 + C2H5 and H + ethylpropargyl channels is derived. Finally, the experimental results are compared to previous H atom branching ratios and used to propose the most likely mechanisms for the reaction of ground state carbon atoms with butene isomers.

  7. Plasmon enhanced Raman scattering effect for an atom near a carbon nanotube

    SciTech Connect

    Bondarev, I. V.

    2015-01-01

    Quantum electrodynamics theory of the resonance Raman scattering is developed for an atom in a close proximity to a carbon nanotube. The theory predicts a dramatic enhancement of the Raman intensity in the strong atomic coupling regime to nanotube plasmon near-fields. This resonance scattering is a manifestation of the general electromagnetic surface enhanced Raman scattering effect, and can be used in designing efficient nanotube based optical sensing substrates for single atom detection, precision spontaneous emission control, and manipulation.

  8. Tailoring Thermal Conductivity of Single-stranded Carbon-chain Polymers through Atomic Mass Modification

    NASA Astrophysics Data System (ADS)

    Liao, Quanwen; Zeng, Lingping; Liu, Zhichun; Liu, Wei

    2016-10-01

    Tailoring the thermal conductivity of polymers is central to enlarge their applications in the thermal management of flexible integrated circuits. Progress has been made over the past decade by fabricating materials with various nanostructures, but a clear relationship between various functional groups and thermal properties of polymers remains to be established. Here, we numerically study the thermal conductivity of single-stranded carbon-chain polymers with multiple substituents of hydrogen atoms through atomic mass modification. We find that their thermal conductivity can be tuned by atomic mass modifications as revealed through molecular dynamics simulations. The simulation results suggest that heavy homogeneous substituents do not assist heat transport and trace amounts of heavy substituents can in fact hinder heat transport substantially. Our analysis indicates that carbon chain has the biggest contribution (over 80%) to the thermal conduction in single-stranded carbon-chain polymers. We further demonstrate that atomic mass modifications influence the phonon bands of bonding carbon atoms, and the discrepancies of phonon bands between carbon atoms are responsible for the remarkable drops in thermal conductivity and large thermal resistances in carbon chains. Our study provides fundamental insight into how to tailor the thermal conductivity of polymers through variable substituents.

  9. Tailoring Thermal Conductivity of Single-stranded Carbon-chain Polymers through Atomic Mass Modification.

    PubMed

    Liao, Quanwen; Zeng, Lingping; Liu, Zhichun; Liu, Wei

    2016-10-07

    Tailoring the thermal conductivity of polymers is central to enlarge their applications in the thermal management of flexible integrated circuits. Progress has been made over the past decade by fabricating materials with various nanostructures, but a clear relationship between various functional groups and thermal properties of polymers remains to be established. Here, we numerically study the thermal conductivity of single-stranded carbon-chain polymers with multiple substituents of hydrogen atoms through atomic mass modification. We find that their thermal conductivity can be tuned by atomic mass modifications as revealed through molecular dynamics simulations. The simulation results suggest that heavy homogeneous substituents do not assist heat transport and trace amounts of heavy substituents can in fact hinder heat transport substantially. Our analysis indicates that carbon chain has the biggest contribution (over 80%) to the thermal conduction in single-stranded carbon-chain polymers. We further demonstrate that atomic mass modifications influence the phonon bands of bonding carbon atoms, and the discrepancies of phonon bands between carbon atoms are responsible for the remarkable drops in thermal conductivity and large thermal resistances in carbon chains. Our study provides fundamental insight into how to tailor the thermal conductivity of polymers through variable substituents.

  10. Tailoring Thermal Conductivity of Single-stranded Carbon-chain Polymers through Atomic Mass Modification

    PubMed Central

    Liao, Quanwen; Zeng, Lingping; Liu, Zhichun; Liu, Wei

    2016-01-01

    Tailoring the thermal conductivity of polymers is central to enlarge their applications in the thermal management of flexible integrated circuits. Progress has been made over the past decade by fabricating materials with various nanostructures, but a clear relationship between various functional groups and thermal properties of polymers remains to be established. Here, we numerically study the thermal conductivity of single-stranded carbon-chain polymers with multiple substituents of hydrogen atoms through atomic mass modification. We find that their thermal conductivity can be tuned by atomic mass modifications as revealed through molecular dynamics simulations. The simulation results suggest that heavy homogeneous substituents do not assist heat transport and trace amounts of heavy substituents can in fact hinder heat transport substantially. Our analysis indicates that carbon chain has the biggest contribution (over 80%) to the thermal conduction in single-stranded carbon-chain polymers. We further demonstrate that atomic mass modifications influence the phonon bands of bonding carbon atoms, and the discrepancies of phonon bands between carbon atoms are responsible for the remarkable drops in thermal conductivity and large thermal resistances in carbon chains. Our study provides fundamental insight into how to tailor the thermal conductivity of polymers through variable substituents. PMID:27713563

  11. Structure and stability of a silicon cluster on sequential doping with carbon atoms

    NASA Astrophysics Data System (ADS)

    AzeezullaNazrulla, Mohammed; Joshi, Krati; Israel, S.; Krishnamurty, Sailaja

    2016-02-01

    SiC is a highly stable material in bulk. On the other hand, alloys of silicon and carbon at nanoscale length are interesting from both technological as well fundamental view point and are being currently synthesized by various experimental groups (Truong et. al., 2015 [26]). In the present work, we identify a well-known silicon cluster viz., Si10 and dope it sequentially with carbon atoms. The evolution of electronic structure (spin state and the structural properties) on doping, the charge redistribution and structural properties are analyzed. It is interesting to note that the ground state SiC clusters prefer to be in the lowest spin state. Further, it is seen that carbon atoms are the electron rich centres while silicon atoms are electron deficient in every SiC alloy cluster. The carbon-carbon bond lengths in alloy clusters are equivalent to those seen in fullerene molecules. Interestingly, the carbon atoms tend to aggregate together with silicon atoms surrounding them by donating the charge. As a consequence, very few Si-Si bonds are noted with increasing concentrations of C atoms in a SiC alloy. Physical and chemical stability of doped clusters is studied by carrying out finite temperature behaviour and adsorbing O2 molecule on Si9C and Si8C2 clusters, respectively.

  12. Effects of Atomic-Scale Structure on the Fracture Properties of Amorphous Carbon - Carbon Nanotube Composites

    NASA Technical Reports Server (NTRS)

    Jensen, Benjamin D.; Wise, Kristopher E.; Odegard, Gregory M.

    2015-01-01

    The fracture of carbon materials is a complex process, the understanding of which is critical to the development of next generation high performance materials. While quantum mechanical (QM) calculations are the most accurate way to model fracture, the fracture behavior of many carbon-based composite engineering materials, such as carbon nanotube (CNT) composites, is a multi-scale process that occurs on time and length scales beyond the practical limitations of QM methods. The Reax Force Field (ReaxFF) is capable of predicting mechanical properties involving strong deformation, bond breaking and bond formation in the classical molecular dynamics framework. This has been achieved by adding to the potential energy function a bond-order term that varies continuously with distance. The use of an empirical bond order potential, such as ReaxFF, enables the simulation of failure in molecular systems that are several orders of magnitude larger than would be possible in QM techniques. In this work, the fracture behavior of an amorphous carbon (AC) matrix reinforced with CNTs was modeled using molecular dynamics with the ReaxFF reactive forcefield. Care was taken to select the appropriate simulation parameters, which can be different from those required when using traditional fixed-bond force fields. The effect of CNT arrangement was investigated with three systems: a single-wall nanotube (SWNT) array, a multi-wall nanotube (MWNT) array, and a SWNT bundle system. For each arrangement, covalent bonds are added between the CNTs and AC, with crosslink fractions ranging from 0-25% of the interfacial CNT atoms. The SWNT and MWNT array systems represent ideal cases with evenly spaced CNTs; the SWNT bundle system represents a more realistic case because, in practice, van der Waals interactions lead to the agglomeration of CNTs into bundles. The simulation results will serve as guidance in setting experimental processing conditions to optimize the mechanical properties of CNT

  13. Nanowire-bacteria hybrids for unassisted solar carbon dioxide fixation to value-added chemicals.

    PubMed

    Liu, Chong; Gallagher, Joseph J; Sakimoto, Kelsey K; Nichols, Eva M; Chang, Christopher J; Chang, Michelle C Y; Yang, Peidong

    2015-05-13

    Direct solar-powered production of value-added chemicals from CO2 and H2O, a process that mimics natural photosynthesis, is of fundamental and practical interest. In natural photosynthesis, CO2 is first reduced to common biochemical building blocks using solar energy, which are subsequently used for the synthesis of the complex mixture of molecular products that form biomass. Here we report an artificial photosynthetic scheme that functions via a similar two-step process by developing a biocompatible light-capturing nanowire array that enables a direct interface with microbial systems. As a proof of principle, we demonstrate that a hybrid semiconductor nanowire-bacteria system can reduce CO2 at neutral pH to a wide array of chemical targets, such as fuels, polymers, and complex pharmaceutical precursors, using only solar energy input. The high-surface-area silicon nanowire array harvests light energy to provide reducing equivalents to the anaerobic bacterium, Sporomusa ovata, for the photoelectrochemical production of acetic acid under aerobic conditions (21% O2) with low overpotential (η < 200 mV), high Faradaic efficiency (up to 90%), and long-term stability (up to 200 h). The resulting acetate (∼6 g/L) can be activated to acetyl coenzyme A (acetyl-CoA) by genetically engineered Escherichia coli and used as a building block for a variety of value-added chemicals, such as n-butanol, polyhydroxybutyrate (PHB) polymer, and three different isoprenoid natural products. As such, interfacing biocompatible solid-state nanodevices with living systems provides a starting point for developing a programmable system of chemical synthesis entirely powered by sunlight.

  14. Carbon nanotube-ZnO nanowire hybrid architectures as multifunctional devices

    NASA Astrophysics Data System (ADS)

    Singh, L. T.; Sugavaneshwar, R. P.; Nanda, K. K.

    2013-08-01

    We report on multifunctional devices based on CNT arrays-ZnO nanowires hybrid architectures. The hybrid structure exhibit excellent high current Schottky like behavior with ZnO as p-type and an ideality factor close to the ideal value. Further the CNT-ZnO hybrid structures can be used as high current p-type field effect transistors that can deliver currents of the order of milliamperes and also can be used as ultraviolet detectors with controllable current on-off ratio and response time. The p-type nature of ZnO and possible mechanism for the rectifying characteristics of CNT-ZnO has been presented.

  15. Graphene-based nanowire supercapacitors.

    PubMed

    Chen, Zhi; Yu, Dingshan; Xiong, Wei; Liu, Peipei; Liu, Yong; Dai, Liming

    2014-04-01

    We present a new type of electrochemical supercapacitors based on graphene nanowires. Graphene oxide (GO)/polypyrrole (PPy) nanowires are prepared via electrodepostion of GO/PPy composite into a micoroporous Al2O3 template, followed by the removal of template. PPy is electrochemically doped by oxygen-containing functional groups of the GO to enhance the charging/discharging rates of the supercapacitor. A high capacitance 960 F g(-1) of the GO/PPy nanowires is obtained due to the large surface area of the vertically aligned nanowires and the intimate contact between the nanowires and the substrate electrode. The capacitive performance remains stable after charging and discharging for 300 cycles. To improve the thermal stability and long-term charge storage, GO is further electrochemically reduced into graphene and PPy is subsequently thermally carbonized, leading to a high capacitance of 200 F g(-1) for the resultant pure reduced graphene oxide/carbon based nanowire supercapacitor. This value of capacitance (200 F g(-1)) is higher than that of conventional porous carbon materials while the reduced graphene oxide/carbon nanowires show a lower Faraday resistance and higher thermal stability than the GO/PPy nanowires.

  16. Atomic carbon emission from photodissociation of CO2. [planetary atmospheric chemistry

    NASA Technical Reports Server (NTRS)

    Wu, C. Y. R.; Phillips, E.; Lee, L. C.; Judge, D. L.

    1978-01-01

    Atomic carbon fluorescence, C I 1561, 1657, and 1931 A, has been observed from photodissociation of CO2, and the production cross sections have been measured. A line emission source provided the primary photons at wavelengths from threshold to 420 A. The present results suggest that the excited carbon atoms are produced by total dissociation of CO2 into three atoms. The cross sections for producing the O I 1304-A fluorescence through photodissociation of CO2 are found to be less than 0.01 Mb in the wavelength region from 420 to 835 A. The present data have implications with respect to photochemical processes in the atmospheres of Mars and Venus.

  17. Diastereospecific nazarov cyclization of fully substituted dienones: generation of vicinal all-carbon-atom quaternary stereocenters.

    PubMed

    Jolit, Anais; Vazquez-Rodriguez, Saleta; Yap, Glenn P A; Tius, Marcus A

    2013-10-11

    No vacancy: Fully substituted dienones that are highly polarized by a vinylogous carbonate group were found to undergo a remarkably rapid and diastereospecific Nazarov cyclization that led to cyclopentenones with vicinal all-carbon-atom quaternary centers (see example; SEM=2-(trimethylsilyl)ethoxymethyl, Tf=trifluoromethanesulfonyl). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Electrocatalytic activity of NiO on silicon nanowires with a carbon shell and its application in dye-sensitized solar cell counter electrodes

    NASA Astrophysics Data System (ADS)

    Kim, Junhee; Jung, Cho-Long; Kim, Minsoo; Kim, Soomin; Kang, Yoonmook; Lee, Hae-Seok; Park, Jeounghee; Jun, Yongseok; Kim, Donghwan

    2016-03-01

    To improve the catalytic activity of a material, it is critical to maximize the effective surface area by directly contacting the electrolyte. Nanowires are a promising building block for catalysts in electrochemical applications because of their large surface area. Nickel oxide (NiO) decoration was achieved by drop-casting a nickel-dissolved solution onto vertically aligned silicon nanowire arrays with a carbon shell (SiNW/C). Based on the hybridization of the NiO and silicon nanowire arrays with a carbon shell this study aimed to achieve a synergic effect for the catalytic activity performance. This study demonstrated that the resulting nanomaterial exhibits excellent electrocatalytic activity and performs well as a counter electrode for dye-sensitized solar cells (DSSCs). The compositions of the materials were examined using X-ray diffraction, X-ray photoelectron spectroscopy, and energy dispersive spectroscopy. Their micro- and nano-structures were investigated using scanning electron microscopy and transmission electron microscopy. The electrochemical activity toward I-/I3- was examined using cyclic voltammetry and electrochemical impedance spectroscopy. The obtained peak power conversion efficiency of the DSSC based on the NiO@SiNW/C counter electrode was 9.49%, which was greater than that of the DSSC based on the Pt counter electrode.To improve the catalytic activity of a material, it is critical to maximize the effective surface area by directly contacting the electrolyte. Nanowires are a promising building block for catalysts in electrochemical applications because of their large surface area. Nickel oxide (NiO) decoration was achieved by drop-casting a nickel-dissolved solution onto vertically aligned silicon nanowire arrays with a carbon shell (SiNW/C). Based on the hybridization of the NiO and silicon nanowire arrays with a carbon shell this study aimed to achieve a synergic effect for the catalytic activity performance. This study demonstrated that the

  19. Unexpected Huge Dimerization Ratio in One-Dimensional Carbon Atomic Chains.

    PubMed

    Lin, Yung-Chang; Morishita, Shigeyuki; Koshino, Masanori; Yeh, Chao-Hui; Teng, Po-Yuan; Chiu, Po-Wen; Sawada, Hidetaka; Suenaga, Kazutomo

    2017-01-11

    Peierls theory predicted atomic distortion in one-dimensional (1D) crystal due to its intrinsic instability in 1930. Free-standing carbon atomic chains created in situ in transmission electron microscope (TEM)1-3 are an ideal example to experimentally observe the dimerization behavior of carbon atomic chain within a finite length. We report here a surprisingly huge distortion found in the free-standing carbon atomic chains at 773 K, which is 10 times larger than the value expected in the system. Such an abnormally distorted phase only dominates at the elevated temperatures, while two distinct phases, distorted and undistorted, coexist at lower or ambient temperatures. Atom-by-atom spectroscopy indeed shows considerable variations in the carbon 1s spectra at each atomic site but commonly observes a slightly downshifted π* peak, which proves its sp(1) bonding feature. These results suggest that the simple model, relaxed and straight, is not fully adequate to describe the realistic 1D structure, which is extremely sensitive to perturbations such as external force or boundary conditions.

  20. Peapod-like Li3 VO4 /N-Doped Carbon Nanowires with Pseudocapacitive Properties as Advanced Materials for High-Energy Lithium-Ion Capacitors.

    PubMed

    Shen, Laifa; Lv, Haifeng; Chen, Shuangqiang; Kopold, Peter; van Aken, Peter A; Wu, Xiaojun; Maier, Joachim; Yu, Yan

    2017-07-01

    Lithium ion capacitors are new energy storage devices combining the complementary features of both electric double-layer capacitors and lithium ion batteries. A key limitation to this technology is the kinetic imbalance between the Faradaic insertion electrode and capacitive electrode. Here, we demonstrate that the Li3 VO4 with low Li-ion insertion voltage and fast kinetics can be favorably used for lithium ion capacitors. N-doped carbon-encapsulated Li3 VO4 nanowires are synthesized through a morphology-inheritance route, displaying a low insertion voltage between 0.2 and 1.0 V, a high reversible capacity of ≈400 mAh g(-1) at 0.1 A g(-1) , excellent rate capability, and long-term cycling stability. Benefiting from the small nanoparticles, low energy diffusion barrier and highly localized charge-transfer, the Li3 VO4 /N-doped carbon nanowires exhibit a high-rate pseudocapacitive behavior. A lithium ion capacitor device based on these Li3 VO4 /N-doped carbon nanowires delivers a high energy density of 136.4 Wh kg(-1) at a power density of 532 W kg(-1) , revealing the potential for application in high-performance and long life energy storage devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Synthetic Strategies toward Natural Products Containing Contiguous Stereogenic Quaternary Carbon Atoms.

    PubMed

    Büschleb, Martin; Dorich, Stéphane; Hanessian, Stephen; Tao, Daniel; Schenthal, Kyle B; Overman, Larry E

    2016-03-18

    Strategies for the total synthesis of complex natural products that contain two or more contiguous stereogenic quaternary carbon atoms in their intricate structures are reviewed with 12 representative examples. Emphasis has been put on methods to create quaternary carbon stereocenters, including syntheses of the same natural product by different groups, thereby showcasing the diversity of thought and individual creativity. A compendium of selected natural products containing two or more contiguous stereogenic quaternary carbon atoms and key reactions in their total or partial syntheses is provided in the Supporting Information. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. A nine-atom rhodium–aluminum oxide cluster oxidizes five carbon monoxide molecules

    PubMed Central

    Li, Xiao-Na; Zhang, Hua-Min; Yuan, Zhen; He, Sheng-Gui

    2016-01-01

    Noble metals can promote the direct participation of lattice oxygen of very stable oxide materials such as aluminum oxide, to oxidize reactant molecules, while the fundamental mechanism of noble metal catalysis is elusive. Here we report that a single atom of rhodium, a powerful noble metal catalyst, can promote the transfer of five oxygen atoms to oxidize carbon monoxide from a nine-atom rhodium–aluminum oxide cluster. This is a sharp improvement in the field of cluster science where the transfer of at most two oxygen atoms from a doped cluster is more commonly observed. Rhodium functions not only as the preferred trapping site to anchor and oxidize carbon monoxide by the oxygen atoms in direct connection with rhodium but also the primarily oxidative centre to accumulate the large amounts of electrons and the polarity of rhodium is ultimately transformed from positive to negative. PMID:27094921

  3. Optically promoted bipartite atomic entanglement in hybrid metallic carbon nanotube systems

    SciTech Connect

    Gelin, M. F.; Bondarev, I. V.; Meliksetyan, A. V.

    2014-02-14

    We study theoretically a pair of spatially separated extrinsic atomic type species (extrinsic atoms, ions, molecules, or semiconductor quantum dots) near a metallic carbon nanotube, that are coupled both directly via the inter-atomic dipole-dipole interactions and indirectly by means of the virtual exchange by resonance plasmon excitations on the nanotube surface. We analyze how the optical preparation of the system by using strong laser pulses affects the formation and evolution of the bipartite atomic entanglement. Despite a large number of possible excitation regimes and evolution pathways, we find a few generic scenarios for the bipartite entanglement evolution and formulate practical recommendations on how to optimize and control the robust bipartite atomic entanglement in hybrid carbon nanotube systems.

  4. Study on nitrogen doped carbon atom chains with negative differential resistance effect

    NASA Astrophysics Data System (ADS)

    Shen, Ji-Mei; Liu, Jing; Min, Yi; Zhou, Li-Ping

    2016-05-01

    Recent calculations (Mahmoud and Lugli, 2013, [21]) of gold leads sandwiching carbon chains which are separated by diphenyl-dimethyl demonstrated that the negative differential resistance (NDR) effect appears only for ;odd; numbers of carbon atoms. In this paper, according to a first-principles study based on non-equilibrium Green's function combining density functional theory, we find that the NDR effect appears both for ;odd; and for ;even; numbers of carbon atoms when the chains are doped by nitrogen atom. Our calculations remove the restriction of ;odd/even; chains for the NDR effect, which may promise the potential applications of carbon chains in the nano-scale or molecular devices in the future.

  5. Atomic Layer Deposition on Carbon Nanotubes and their Assemblies

    NASA Astrophysics Data System (ADS)

    Stano, Kelly Lynn

    Global issues related to energy and the environment have motivated development of advanced material solutions outside of traditional metals ceramics, and polymers. Taking inspiration from composites, where the combination of two or more materials often yields superior properties, the field of organic-inorganic hybrids has recently emerged. Carbon nanotube (CNT)-inorganic hybrids have drawn widespread and increasing interest in recent years due to their multifunctionality and potential impact across several technologically important application areas. Before the impacts of CNT-inorganic hybrids can be realized however, processing techniques must be developed for their scalable production. Optimization in chemical vapor deposition (CVD) methods for synthesis of CNTs and vertically aligned CNT arrays has created production routes both high throughput and economically feasible. Additionally, control of CVD parameters has allowed for growth of CNT arrays that are able to be drawn into aligned sheets and further processed to form a variety of aligned 1, 2, and 3-dimensional bulk assemblies including ribbons, yarns, and foams. To date, there have only been a few studies on utilizing these bulk assemblies for the production of CNT-inorganic hybrids. Wet chemical methods traditionally used for fabricating CNT-inorganic hybrids are largely incompatible with CNT assemblies, since wetting and drying the delicate structures with solvents can destroy their structure. It is therefore necessary to investigate alternative processing strategies in order to advance the field of CNT-inorganic hybrids. In this dissertation, atomic layer deposition (ALD) is evaluated as a synthetic route for the production of large-scale CNT-metal oxide hybrids as well as pure metal oxide architectures utilizing CNT arrays, ribbons, and ultralow density foams as deposition templates. Nucleation and growth behavior of alumina was evaluated as a function of CNT surface chemistry. While highly graphitic

  6. Characterization of electrical properties in axial Si-Ge nanowire heterojunctions using off-axis electron holography and atom-probe tomography

    NASA Astrophysics Data System (ADS)

    Gan, Zhaofeng; Perea, Daniel E.; Yoo, Jinkyoung; He, Yang; Colby, Robert J.; Barker, Josh E.; Gu, Meng; Mao, Scott X.; Wang, Chongmin; Picraux, S. T.; Smith, David J.; McCartney, Martha R.

    2016-09-01

    Nanowires (NWs) consisting of P-doped Si/B-doped Ge axial heterojunctions were grown via vapor-liquid-solid synthesis using a combination of Au and AuGa catalyst particles. Off-axis electron holography (EH) was used to measure the electrostatic potential profile across the junction resulting from electrically active dopants, and atom-probe tomography (APT) was used to map total dopant concentration profiles. A comparison of the electrostatic potential profile measured from EH with simulations that were based on the APT results indicates that Ga atoms unintentionally introduced during AuGa catalyst growth were mostly electronically inactive. This finding was also corroborated by in situ electron-holography biasing experiments. Electronic band structure simulations guided by the experimental results helped to provide a much better explanation of the NW electrical behavior. Overall, this work demonstrates that the combination of EH, APT, in situ biasing, and simulations allows a more complete understanding of NW electrical properties to be developed.

  7. Conductive Nanowires Templated by Molecular Brushes.

    PubMed

    Raguzin, Ivan; Stamm, Manfred; Ionov, Leonid

    2015-10-21

    In this paper, we report the fabrication of conductive nanowires using polymer bottle brushes as templates. In our approach, we synthesized poly(2-dimethylamino)ethyl methacrylate methyl iodide quaternary salt brushes by two-step atom transfer radical polymerization, loaded them with palladium salt, and reduced them in order to form metallic nanowires with average lengths and widths of 300 and 20 nm, respectively. The obtained nanowires were deposited between conductive gold pads and were connected to them by sputtering of additional pads to form an electric circuit. We connected the nanowires in an electric circuit and demonstrated that the conductivity of these nanowires is around 100 S·m(-1).

  8. Migration Mechanism for Atomic Hydrogen in Porous Carbon Materials

    SciTech Connect

    Narayanan, B.; Zhao, Y. F.; Ciobanu, C. V.

    2012-05-14

    To explain the fast kinetics of H in porous carbon, we propose that the migration relies on H hopping from a carbon nanotube (CNT) to another. Using density functional theory, we have found that the barrier for H hopping becomes smaller than that for diffusion along a tube for certain CNT separations, decreasting to less than 0.5 eV for separations of -3.1 {angstrom}. Such significant reduction occurs irrespective of radius, chirality, registry, and orientation of the two CNTs: the diffusion is thus facilitated by the porous nature of the material itself. The mechanism proposed is applicable for any porous carbon-based nanomaterials.

  9. Diamond like carbon coatings: Categorization by atomic number density

    NASA Technical Reports Server (NTRS)

    Angus, John C.

    1986-01-01

    Dense diamond-like hydrocarbon films grown at the NASA Lewis Research Center by radio frequency self bias discharge and by direct ion beam deposition were studied. A new method for categorizing hydrocarbons based on their atomic number density and elemental composition was developed and applied to the diamond-like hydrocarbon films. It was shown that the diamond-like hydrocarbon films are an entirely new class of hydrocarbons with atomic number densities lying between those of single crystal diamond and adamantanes. In addition, a major review article on these new materials was completed in cooperation with NASA Lewis Research Center personnel.

  10. A dysprosium nanowire modified carbon paste electrode for determination of levodopa using fast Fourier transformation square-wave voltammetry method.

    PubMed

    Daneshgar, Parandis; Norouzi, Parviz; Ganjali, Mohammad Reza; Ordikhani-Seyedlar, Amin; Eshraghi, Hasan

    2009-01-01

    A new detection technique called the fast Fourier transform square-wave voltammetry (FFT-SWV) is based on the measurements of electrode admittance as a function of potential. The response of the detector (microelectrode) is fast, which makes the method suitable for most applications involving flowing electrolytes. The carbon paste electrode was modified by nanostructures to improve better sensitivity. The response is generated by a redox processes. The redox property of L-dopa was used for determination of it in human serum and urine samples. The support electrolyte that provided a more defined and intense peak current for L-dopa determination was at 0.05 mol l(-1) acetate buffer pH 7.0. Synthesized dysprosium nanowires make more effective surface like nanotubes [P.M. Ajayan, S. Iijima, Nature 361 (1993) 333; I.A. Merkoc, Microchim. Acta 152 (2006) 157; F.H. Wu, G.C. Zhao, X.W. Wei, Z.S. Yang, Microchim. Acta 144 (2004) 243; L. Liu, J. Song, Anal. Biochem. 354 (2006) 22] so they are good candidates for using as a modifier for electrochemical reactions. The drug presented one irreversible oxidation peaks at 360 mV versus Ag/AgCl by modified nanowire carbon paste electrode which produced high current and reduced the oxidation potential about 80 mV. Furthermore, signal-to-noise ratio has significantly increased by application of discrete fast Fourier transform (FFT) method, background subtraction and two-dimensional integration of the electrode response over a selected potential range and time window. To obtain the much sensitivity the effective parameters such as frequency, amplitude and pH was optimized. As a result, C(DL) of 4.0 x 10(-9)M and an LOQ of 7.0 x 10(-9) M were found for determination for L-dopa. A good recovery was obtained for assay spiked urine samples and a good quantification of L-dopa was achieved in a commercial formulation.

  11. Insights into hydrogen atom adsorption on and the electrochemical properties of nitrogen-substituted carbon materials.

    PubMed

    Zhu, Z H; Hatori, H; Wang, S B; Lu, G Q

    2005-09-08

    The nitrogen substitution in carbon materials is investigated theoretically using the density functional theory method. Our calculations show that nitrogen substitution decreases the hydrogen adsorption energy if hydrogen atoms are adsorbed on both nitrogen atoms and the neighboring carbon atoms. On the contrary, the hydrogen adsorption energy can be increased if hydrogen atoms are adsorbed only on the neighboring carbon atoms. The reason can be explained by the electronic structures analysis of N-substituted graphene sheets. Nitrogen substitution reduces the pi electron conjugation and increases the HOMO energy of a graphene sheet, and the nitrogen atom is not stable due to its 3-valent character. This raises an interesting research topic on the optimization of the N-substitution degree, and is important to many applications such as hydrogen storage and the tokamaks device. The electronic structure studies also explain well why nitrogen substitution increases the capacitance but decreases the electron conductivity of carbon electrodes as was experimentally observed in our experiments on the supercapacitor.

  12. Growth and Destruction of PAH Molecules in Reactions with Carbon Atoms

    NASA Astrophysics Data System (ADS)

    Krasnokutski, Serge A.; Huisken, Friedrich; Jäger, Cornelia; Henning, Thomas

    2017-02-01

    A very high abundance of atomic carbon in the interstellar medium (ISM), and the high reactivity of these species toward different hydrocarbon molecules including benzene, raise questions regarding the stability of polycyclic aromatic hydrocarbon (PAH) molecules in space. To test the efficiency of destruction of PAH molecules via reactions with atomic carbon, we performed a set of laboratory and computational studies of the reactions of naphthalene, anthracene, and coronene molecules with carbon atoms in the ground state. The reactions were investigated in liquid helium droplets at T = 0.37 K and by quantum chemical computations. Our studies suggest that all small and all large catacondensed PAHs react barrierlessly with atomic carbon, and therefore should be efficiently destroyed by such reactions in a broad temperature range. At the same time, large compact pericondensed PAHs should be more inert toward such a reaction. In addition, taking into account their higher photostability, much higher abundances of pericondensed PAHs should be expected in various astrophysical environments. The barrierless reactions between carbon atoms and small PAHs also suggest that, in the ISM, these reactions could lead to the bottom-up formation of PAH molecules.

  13. Molecular dynamics simulation for arrangement of nickel atoms filled in carbon nanotubes

    SciTech Connect

    Bai, Liu Zhenyu, Zhao; Lirui, Liu

    2014-08-28

    Carbon Nanotubes (CNTs) filled with metals can be used in capacitors, sensors, rechargeable batteries, and so on. Atomic arrangement of the metals has an important role in the function of the composites. The tips of CNTs were opened, and then nickel was filled by means of hydrothermal oxidation/ultrasonic vibration method. The tests of TEM, HREM, and EDX (energy-dispersive X-ray spectroscopy) analysis showed that Ni was filled in CNTs successfully. The atomic arrangement of nickel filled into single wall carbon nanotubes was investigated by molecular dynamics simulation. The radial distribution function and bond orientation order were established to analyze the atomic arrangement of nickel filled in carbon nanotubes during the cooling process. The results show that nickel atoms became in order gradually and preferably crystallized on the inner wall of carbon nanotubes when the temperature decreased from 1600 K. After it cooled to 100 K, the arrangement of nickel atoms in outermost circle was regular and dense, but there were many defects far from the wall of CNTs. According to the calculation of bond orientation order parameters Q{sub 6} and its visualization, the structure of nickel is Face-centered cube (f.c.c). (1,1,1){sub Ni} was close on the inner surface of carbon nanotubes. Radial direction of CNTs was [1,1,1] crystal orientation. Axial direction of CNTs, namely, filling direction, was [1{sup ¯}, 1{sup ¯},2] crystal orientation.

  14. Molecular dynamics simulation for arrangement of nickel atoms filled in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Bai, Liu; Lirui, Liu; Zhenyu, Zhao

    2014-08-01

    Carbon Nanotubes (CNTs) filled with metals can be used in capacitors, sensors, rechargeable batteries, and so on. Atomic arrangement of the metals has an important role in the function of the composites. The tips of CNTs were opened, and then nickel was filled by means of hydrothermal oxidation/ultrasonic vibration method. The tests of TEM, HREM, and EDX (energy-dispersive X-ray spectroscopy) analysis showed that Ni was filled in CNTs successfully. The atomic arrangement of nickel filled into single wall carbon nanotubes was investigated by molecular dynamics simulation. The radial distribution function and bond orientation order were established to analyze the atomic arrangement of nickel filled in carbon nanotubes during the cooling process. The results show that nickel atoms became in order gradually and preferably crystallized on the inner wall of carbon nanotubes when the temperature decreased from 1600 K. After it cooled to 100 K, the arrangement of nickel atoms in outermost circle was regular and dense, but there were many defects far from the wall of CNTs. According to the calculation of bond orientation order parameters Q6 and its visualization, the structure of nickel is Face-centered cube (f.c.c). (1,1,1)Ni was close on the inner surface of carbon nanotubes. Radial direction of CNTs was [1,1,1] crystal orientation. Axial direction of CNTs, namely, filling direction, was [1¯, 1¯,2] crystal orientation.

  15. Strain-induced metal-semiconductor transition observed in atomic carbon chains

    NASA Astrophysics Data System (ADS)

    La Torre, A.; Botello-Mendez, A.; Baaziz, W.; Charlier, J.-C.; Banhart, F.

    2015-03-01

    Carbyne, the sp1-hybridized phase of carbon, is still a missing link in the family of carbon allotropes. While the bulk phases of carbyne remain elusive, the elementary constituents, that is, linear chains of carbon atoms, have already been observed using the electron microscope. Isolated atomic chains are highly interesting one-dimensional conductors that have stimulated considerable theoretical work. Experimental information, however, is still very limited. Here we show electrical measurements and first-principles transport calculations on monoatomic carbon chains. When the 1D system is under strain, the chains are semiconducting corresponding to the polyyne structure with alternating bond lengths. Conversely, when the chain is unstrained, the ohmic behaviour of metallic cumulene with uniform bond lengths is observed. This confirms the recent prediction of a metal-insulator transition that is induced by strain. The key role of the contacting leads explains the rectifying behaviour measured in monoatomic carbon chains in a nonsymmetric contact configuration.

  16. Strain-induced metal–semiconductor transition observed in atomic carbon chains

    PubMed Central

    La Torre, A.; Botello-Mendez, A.; Baaziz, W.; Charlier, J. -C.; Banhart, F.

    2015-01-01

    Carbyne, the sp1-hybridized phase of carbon, is still a missing link in the family of carbon allotropes. While the bulk phases of carbyne remain elusive, the elementary constituents, that is, linear chains of carbon atoms, have already been observed using the electron microscope. Isolated atomic chains are highly interesting one-dimensional conductors that have stimulated considerable theoretical work. Experimental information, however, is still very limited. Here we show electrical measurements and first-principles transport calculations on monoatomic carbon chains. When the 1D system is under strain, the chains are semiconducting corresponding to the polyyne structure with alternating bond lengths. Conversely, when the chain is unstrained, the ohmic behaviour of metallic cumulene with uniform bond lengths is observed. This confirms the recent prediction of a metal–insulator transition that is induced by strain. The key role of the contacting leads explains the rectifying behaviour measured in monoatomic carbon chains in a nonsymmetric contact configuration. PMID:25818506

  17. Carbon concentration measurements by atom probe tomography in the ferritic phase of high-silicon steels

    SciTech Connect

    Rementeria, Rosalia; Poplawsky, Jonathan D.; Aranda, Maria M.; Guo, Wei; Jimenez, Jose A.; Garcia-Mateo, Carlos; Caballero, Francisca G.

    2016-12-19

    Current studies using atom probe tomography (APT) show that bainitic ferrite formed at low temperature contains more carbon than what is consistent with the paraequilibrium phase diagram. However, nanocrystalline bainitic ferrite exhibits a non-homogeneous distribution of carbon atoms in arrangements with specific compositions, i.e. Cottrell atmospheres, carbon clusters, and carbides, in most cases with a size of a few nanometers. The ferrite volume within a single platelet that is free of these carbon-enriched regions is extremely small. Proximity histograms can be compromised on the ferrite side, and a great deal of care should be taken to estimate the carbon content in regions of bainitic ferrite free from carbon agglomeration. For this purpose, APT measurements were first validated for the ferritic phase in a pearlitic sample and further performed for the bainitic ferrite matrix in high-silicon steels isothermally transformed between 200 °C and 350 °C. Additionally, results were compared with the carbon concentration values derived from X-ray diffraction (XRD) analyses considering a tetragonal lattice and previous APT studies. In conclusion, the present results reveal a strong disagreement between the carbon content values in the bainitic ferrite matrix as obtained by APT and those derived from XRD measurements. Those differences have been attributed to the development of carbon-clustered regions with an increased tetragonality in a carbon-depleted matrix.

  18. Carbon concentration measurements by atom probe tomography in the ferritic phase of high-silicon steels

    DOE PAGES

    Rementeria, Rosalia; Poplawsky, Jonathan D.; Aranda, Maria M.; ...

    2016-12-19

    Current studies using atom probe tomography (APT) show that bainitic ferrite formed at low temperature contains more carbon than what is consistent with the paraequilibrium phase diagram. However, nanocrystalline bainitic ferrite exhibits a non-homogeneous distribution of carbon atoms in arrangements with specific compositions, i.e. Cottrell atmospheres, carbon clusters, and carbides, in most cases with a size of a few nanometers. The ferrite volume within a single platelet that is free of these carbon-enriched regions is extremely small. Proximity histograms can be compromised on the ferrite side, and a great deal of care should be taken to estimate the carbon contentmore » in regions of bainitic ferrite free from carbon agglomeration. For this purpose, APT measurements were first validated for the ferritic phase in a pearlitic sample and further performed for the bainitic ferrite matrix in high-silicon steels isothermally transformed between 200 °C and 350 °C. Additionally, results were compared with the carbon concentration values derived from X-ray diffraction (XRD) analyses considering a tetragonal lattice and previous APT studies. In conclusion, the present results reveal a strong disagreement between the carbon content values in the bainitic ferrite matrix as obtained by APT and those derived from XRD measurements. Those differences have been attributed to the development of carbon-clustered regions with an increased tetragonality in a carbon-depleted matrix.« less

  19. Layer-by-layer assembly of TiO2 nanowire/carbon nanotube films and characterization of their photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Darányi, Mária; Csesznok, Tamás; Kukovecz, Ákos; Kónya, Zoltán; Kiricsi, Imre; Ajayan, Pulickel M.; Vajtai, Robert

    2011-05-01

    We report on the layer-by-layer (LbL) formation of TiO2-MWNT-TiO2 coatings on quartz with either trititanate derived TiO2 nanowires or Degussa P25 as the photocatalytically active material. The optimized deposition sequence is discussed in detail and the morphology of the prepared coatings is analyzed by SEM and XRD. The heterogeneous photocatalytic performance of the coatings was tested in the methyl orange oxidation reaction. The apparent first order rate constant fell in the 0.01-0.20 h - 1 range over a 2.5 × 2.5 cm2 film depending on the type and the thickness of the titanate coating. Building a multiwall carbon nanotube layer into the middle of the layer improved the photocatalytic activity for each material for all of the studied thicknesses. P25 based films performed 2-5 times better than TiO2 nanowire films; however, the pores in the P25 based films were largely blocked because the isotropic P25 nanoparticles form closely packed layers by themselves and even more so with the comparably sized multiwall carbon nanotubes. Therefore, films derived from titanate nanowires appear to be more suitable for use as multifunctional, photocatalytically active filtration media.

  20. Layer-by-layer assembly of TiO2 nanowire/carbon nanotube films and characterization of their photocatalytic activity.

    PubMed

    Darányi, Mária; Csesznok, Tamás; Kukovecz, Akos; Kónya, Zoltán; Kiricsi, Imre; Ajayan, Pulickel M; Vajtai, Robert

    2011-05-13

    We report on the layer-by-layer (LbL) formation of TiO(2)-MWNT-TiO(2) coatings on quartz with either trititanate derived TiO(2) nanowires or Degussa P25 as the photocatalytically active material. The optimized deposition sequence is discussed in detail and the morphology of the prepared coatings is analyzed by SEM and XRD. The heterogeneous photocatalytic performance of the coatings was tested in the methyl orange oxidation reaction. The apparent first order rate constant fell in the 0.01-0.20 h(-1) range over a 2.5 × 2.5 cm(2) film depending on the type and the thickness of the titanate coating. Building a multiwall carbon nanotube layer into the middle of the layer improved the photocatalytic activity for each material for all of the studied thicknesses. P25 based films performed 2-5 times better than TiO(2) nanowire films; however, the pores in the P25 based films were largely blocked because the isotropic P25 nanoparticles form closely packed layers by themselves and even more so with the comparably sized multiwall carbon nanotubes. Therefore, films derived from titanate nanowires appear to be more suitable for use as multifunctional, photocatalytically active filtration media.

  1. From cobalt nitrate carbonate hydroxide hydrate nanowires to porous Co(3)O(4) nanorods for high performance lithium-ion battery electrodes.

    PubMed

    Zhang, Hui; Wu, Jianbo; Zhai, Chuanxin; Ma, Xiangyang; Du, Ning; Tu, Jiangping; Yang, Deren

    2008-01-23

    We have developed a simple approach for the large-scale synthesis of cobalt nitrate carbonate hydroxide hydrate (Co(CO(3))(0.35)(NO(3))(0.2)(OH)(1.1)·1.74H(2)O) nanowires via the hydrothermal process using sodium hydroxide and formaldehyde as mineralizers at 120 °C. The porous Co(3)O(4) nanorods 10-30 nm in diameter and hundreds of nanometres in length have been fabricated from the above-mentioned multicomponent nanowires by calcination at 400 °C. The morphology and structure of cobalt nitrate carbonate hydroxide hydrate nanowires and Co(3)O(4) nanorods have been characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and x-ray powder diffraction (XRD). Moreover, the porous Co(3)O(4) nanorods have been applied in the negative electrode materials for lithium ion batteries, which exhibit high electrochemical performance.

  2. Monte Carlo simulation of nanowires of different metals and two-metal alloys.

    PubMed

    Giménez, M C; Schmicker, Wolfgang

    2011-02-14

    Nanowires of different metals and two-metal alloys have been studied by means of canonical Monte Carlo simulations and the embedded atom method for the interatomic potentials. For nanowires of gold, a relatively stable three-atom-wide chain was observed. The presence of one-atom-wide linear atomic chains is not stable in any case. For two-metal alloy nanowires, the metal with a higher surface energy tends to locate in the inner region of the nanowire.

  3. Tensile and compressive mechanical behavior of twinned silicon carbide nanowires

    SciTech Connect

    Wang, Zhiguo; Li, Jingbo; Gao, Fei; Weber, William J.

    2010-04-01

    Molecular dynamics simulations with the Tersoff potential were used to study the response of twinned SiC nanowires under tensile and compressive strains. The critical strain of the twinned nanowires can be enhanced by twin-stacking faults, and their critical strains are larger than those of perfect nanowires with the same diameters. Under axial tensile strain, the bonds of the nanowires are just stretched before failure. The failure behavior is found to depend on the twin segment thickness and the diameter of the nanowires. An atomic chain is observed for the thin nanowires with small twin segment thickness under tension strain. Under axial compressive strain, the collapse of the twinned SiC nanowires exhibits two differently failure modes, depending on the length and diameter of the nanowires, i.e. shell buckling for short length nanowires and columnar buckling for longer length nanowires.

  4. Carbon nanotubes under electron irradiation: Stability of the tubes and their action as pipes for atom transport

    SciTech Connect

    Banhart, F.; Li, J.X.; Krasheninnikov, A.V.

    2005-06-15

    The production and migration of carbon interstitials in carbon nanotubes under electron irradiation is studied experimentally and theoretically. It is shown that the threshold for displacing carbon atoms and the defect production rate strongly depend on the diameter of the nanotubes. Multiwalled nanotubes shrink by a loss of atoms and by diffusion of interstitials through the inner hollow in the axial direction. Thus, experimental evidence is given that nanotubes can act as nanoscale pipes for the transport of atoms.

  5. Computational studies of gas phase reactions of carbon chain anions with N and O atoms.

    PubMed

    Yang, Zhibo; Snow, Theodore P; Bierbaum, Veronica M

    2010-10-28

    Experimental studies of gas phase reactions of carbanions with N and O atoms have been reported previously to understand ion chemistry relevant to the interstellar medium. In all cases reactions of anions with O atoms exhibit larger reaction rate constants compared to the corresponding N atom reactions. In addition, the open-shell carbon chain anions exhibit higher reactivities than the corresponding closed-shell species in N atom reactions, whereas similar reactivities were observed for both open and closed-shell anions in O atom reactions. These trends are investigated by the current theoretical study of the reactions of HC(n)(-)(n = 2, 4, and 6) and C(n)(-) (n = 2, 4-7) with N and O atoms. Our results indicate that spin-forbidden processes are the probable pathways in reactions of closed-shell anions HC(n)(-) with N atoms, and spin conversion limits the reaction efficiency. In reactions of open-shell anions C(n)(-) with N atoms, about 50% of the collisions may proceed through spin-allowed barrierless pathways, which results in relatively higher reaction efficiencies than for the closed-shell reactions. For reactions of all anions with O atoms, the spin-allowed barrierless pathways are the only channels, such that all reactions occur with very high efficiencies. This work provides a greater understanding of the influence of spin effects on the reactivities of anion reactions involving N and O atoms that may be important in the interstellar medium.

  6. Surface modification of carbon post arrays by atomic layer deposition of ZnO film.

    PubMed

    Lee, Hyun Ae; Byun, Young-Chul; Singh, Umesh; Cho, Hyoung J; Kim, Hyoungsub

    2011-08-01

    The applicability of atomic layer deposition (ALD) process to the carbon microelectromechanical system technology was studied for a surface modification method of the carbon post electrodes. A conformal coating of the ALD-ZnO film was successfully demonstrated on the carbon post arrays which were fabricated by the traditional photolithography and subsequent two-step pyrolysis. A significant Zn diffusion into the underlying carbon posts was observed during the ALD process. The addition of a sputter-deposited ZnO interfacial layer efficiently blocked the Zn diffusion without altering the microstructure and surface morphology of the ALD-ZnO film.

  7. Atomic migration of carbon in hard turned layers of carburized bearing steel

    SciTech Connect

    Bedekar, Vikram; Poplawsky, Jonathan D.; Guo, Wei; Shivpuri, Rajiv; Scott Hyde, R.

    2016-01-01

    In grain finement and non-equilibrium there is carbon segregation within grain boundaries alters the mechanical performance of hard turning layers in carburized bearing steel. Moreover, an atom probe tomography (APT) study on the nanostructured hard turning layers reveals carbon migration to grain boundaries as a result of carbide decomposition during severe plastic deformation. In addition, samples exposed to different cutting speeds show that the carbon migration rate increases with the cutting speed. For these two effects lead to an ultrafine carbon network structure resulting in increased hardness and thermal stability in the severely deformed surface layer.

  8. Atomic migration of carbon in hard turned layers of carburized bearing steel

    DOE PAGES

    Bedekar, Vikram; Poplawsky, Jonathan D.; Guo, Wei; ...

    2016-01-01

    In grain finement and non-equilibrium there is carbon segregation within grain boundaries alters the mechanical performance of hard turning layers in carburized bearing steel. Moreover, an atom probe tomography (APT) study on the nanostructured hard turning layers reveals carbon migration to grain boundaries as a result of carbide decomposition during severe plastic deformation. In addition, samples exposed to different cutting speeds show that the carbon migration rate increases with the cutting speed. For these two effects lead to an ultrafine carbon network structure resulting in increased hardness and thermal stability in the severely deformed surface layer.

  9. Racing Carbon Atoms. Atomic Motion Reaction Coordinates and Structural Effects on Newtonian Kinetic Isotope Effects

    PubMed Central

    Andujar-De Sanctis, Ivonne L.

    2012-01-01

    Intramolecular 13C kinetic isotope effects were determined for the dimerization of methacrolein. Trajectory studies accurately predict the isotope effects and support an origin in Newton’s second law of motion, with no involvement of zero-point energy or transition state recrossing. Atomic motion reaction coordinate diagrams are introduced as a way to qualitatively understand the selectivity. PMID:23025278

  10. Racing carbon atoms. Atomic motion reaction coordinates and structural effects on Newtonian kinetic isotope effects.

    PubMed

    Andujar-De Sanctis, Ivonne L; Singleton, Daniel A

    2012-10-19

    Intramolecular (13)C kinetic isotope effects were determined for the dimerization of methacrolein. Trajectory studies accurately predict the isotope effects and support an origin in Newton's second law of motion, with no involvement of zero-point energy or transition state recrossing. Atomic motion reaction coordinate diagrams are introduced as a way to qualitatively understand the selectivity.

  11. High performance current and spin diode of atomic carbon chain between transversely symmetric ribbon electrodes

    PubMed Central

    Dong, Yao-Jun; Wang, Xue-Feng; Yang, Shuo-Wang; Wu, Xue-Mei

    2014-01-01

    We demonstrate that giant current and high spin rectification ratios can be achieved in atomic carbon chain devices connected between two symmetric ferromagnetic zigzag-graphene-nanoribbon electrodes. The spin dependent transport simulation is carried out by density functional theory combined with the non-equilibrium Green's function method. It is found that the transverse symmetries of the electronic wave functions in the nanoribbons and the carbon chain are critical to the spin transport modes. In the parallel magnetization configuration of two electrodes, pure spin current is observed in both linear and nonlinear regions. However, in the antiparallel configuration, the spin-up (down) current is prohibited under the positive (negative) voltage bias, which results in a spin rectification ratio of order 104. When edge carbon atoms are substituted with boron atoms to suppress the edge magnetization in one of the electrodes, we obtain a diode with current rectification ratio over 106. PMID:25142376

  12. Synthesis of novel amorphous calcium carbonate by sono atomization for reactive mixing.

    PubMed

    Kojima, Yoshiyuki; Kanai, Makoto; Nishimiya, Nobuyuki

    2012-03-01

    Droplets of several micrometers in size can be formed in aqueous solution by atomization under ultrasonic irradiation at 2 MHz. This phenomenon, known as atomization, is capable of forming fine droplets for use as a reaction field. This synthetic method is called SARM (sono atomization for reactive mixing). This paper reports on the synthesis of a novel amorphous calcium carbonate formed by SARM. The amorphous calcium carbonate, obtained at a solution concentration of 0.8 mol/dm(3), had a specific surface area of 65 m(2)/g and a composition of CaCO(3)•0.5H(2)O as determined using thermogravimetric/differential thermal analysis (TG-DTA). Because the ACC had a lower hydrate composition than conventional amorphous calcium carbonate (ACC), the ACC synthesized in this paper was very stable at room temperature. Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.

  13. Integrating Carbon Nanotubes For Atomic Force Microscopy Imaging Applications

    NASA Technical Reports Server (NTRS)

    Ye, Qi; Cassell, Alan M.; Liu, Hongbing; Han, Jie; Meyyappan, Meyya

    2004-01-01

    Carbon nanotube (CNT) related nanostructures possess remarkable electrical, mechanical, and thermal properties. To produce these nanostructures for real world applications, a large-scale controlled growth of carbon nanotubes is crucial for the integration and fabrication of nanodevices and nanosensors. We have taken the approach of integrating nanopatterning and nanomaterials synthesis with traditional silicon micro fabrication techniques. This integration requires a catalyst or nanomaterial protection scheme. In this paper, we report our recent work on fabricating wafer-scale carbon nanotube AFM cantilever probe tips. We will address the design and fabrication considerations in detail, and present the preliminary scanning probe test results. This work may serve as an example of rational design, fabrication, and integration of nanomaterials for advanced nanodevice and nanosensor applications.

  14. 4.4.4 R1 and R2: Leading atom other than carbon; R3: Leading atom carbon

    NASA Astrophysics Data System (ADS)

    Beckwith, A. L. J.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  15. A general strategy to construct uniform carbon-coated spinel LiMn2O4 nanowires for ultrafast rechargeable lithium-ion batteries with a long cycle life

    NASA Astrophysics Data System (ADS)

    Sun, Weiwei; Liu, Huiqin; Liu, Yumin; Bai, Gongxun; Liu, Wei; Guo, Shishang; Zhao, Xing-Zhong

    2015-07-01

    Control over one-dimensional growth of spinel-type LiMn2O4 nanowires is challenging in the area of materials science due to their cubic crystal structure. The current strategy is to use a self-support template to fabricate LiMn2O4 nanowires, which is time-consuming and limits their large-scale commercial production. In this paper, we propose a general strategy to construct well-defined LiMn2O4 nanowires terminated with amorphous carbon at the edges by an ingenious method without using any template. Benefited from its unique carbon-coated nanowire structure, the electrode exhibits a capacitor-like rate performance and battery-like high capacity for long-time cycling. Even after 1500 cycles at an extremely high current density of 30 C, approximately 82% of its initial capacity can still be retained. Significantly, the strategy reported here will be beneficial and revelatory to manufacture other extensive one-dimensional robust carbon-decorated nanowires, paving new ways for future developments of ultrafast rechargeable lithium-ion batteries.Control over one-dimensional growth of spinel-type LiMn2O4 nanowires is challenging in the area of materials science due to their cubic crystal structure. The current strategy is to use a self-support template to fabricate LiMn2O4 nanowires, which is time-consuming and limits their large-scale commercial production. In this paper, we propose a general strategy to construct well-defined LiMn2O4 nanowires terminated with amorphous carbon at the edges by an ingenious method without using any template. Benefited from its unique carbon-coated nanowire structure, the electrode exhibits a capacitor-like rate performance and battery-like high capacity for long-time cycling. Even after 1500 cycles at an extremely high current density of 30 C, approximately 82% of its initial capacity can still be retained. Significantly, the strategy reported here will be beneficial and revelatory to manufacture other extensive one-dimensional robust

  16. Totally embedded hybrid thin films of carbon nanotubes and silver nanowires as flat homogenous flexible transparent conductors

    PubMed Central

    Pillai, Suresh Kumar Raman; Wang, Jing; Wang, Yilei; Sk, Md Moniruzzaman; Prakoso, Ari Bimo; Rusli; Chan-Park, Mary B.

    2016-01-01

    There is a great need for viable alternatives to today’s transparent conductive film using largely indium tin oxide. We report the fabrication of a new type of flexible transparent conductive film using silver nanowires (AgNW) and single-walled carbon nanotube (SWCNT) networks which are fully embedded in a UV curable resin substrate. The hybrid SWCNTs-AgNWs film is relatively flat so that the RMS roughness of the top surface of the film is 3 nm. Addition of SWCNTs networks make the film resistance uniform; without SWCNTs, sheet resistance of the surface composed of just AgNWs in resin varies from 20 Ω/sq to 107 Ω/sq. With addition of SWCNTs embedded in the resin, sheet resistance of the hybrid film is 29 ± 5 Ω/sq and uniform across the 47 mm diameter film discs; further, the optimized film has 85% transparency. Our lamination-transfer UV process doesn’t need solvent for sacrificial substrate removal and leads to good mechanical interlocking of the nano-material networks. Additionally, electrochemical study of the film for supercapacitors application showed an impressive 10 times higher current in cyclic voltammograms compared to the control without SWCNTs. Our fabrication method is simple, cost effective and enables the large-scale fabrication of flat and flexible transparent conductive films. PMID:27929125

  17. Electrochemistry at nanoscale electrodes: individual single-walled carbon nanotubes (SWNTs) and SWNT-templated metal nanowires.

    PubMed

    Dudin, Petr V; Snowden, Michael E; Macpherson, Julie V; Unwin, Patrick R

    2011-12-27

    Individual nanowires (NWs) and native single-walled carbon nanotubes (SWNTs) can be readily used as well-defined nanoscale electrodes (NSEs) for voltammetric analysis. Here, the simple photolithography-free fabrication of submillimeter long Au, Pt, and Pd NWs, with sub-100 nm heights, by templated electrodeposition onto ultralong flow-aligned SWNTs is demonstrated. Both individual Au NWs and SWNTs are employed as NSEs for electron-transfer (ET) kinetic quantification, using cyclic voltammetry (CV), in conjunction with a microcapillary-based electrochemical method. A small capillary with internal diameter in the range 30-70 μm, filled with solution containing a redox-active mediator (FcTMA(+) ((trimethylammonium)methylferrocene), Fe(CN)(6)(4-), or hydrazine) is positioned above the NSE, so that the solution meniscus completes an electrochemical cell. A 3D finite-element model, faithfully reproducing the experimental geometry, is used to both analyze the experimental CVs and derive the rate of heterogeneous ET, using Butler-Volmer kinetics. For a 70 nm height Au NW, intrinsic rate constants, k(0), up to ca. 1 cm s(-1) can be resolved. Using the same experimental configuration the electrochemistry of individual SWNTs can also be accessed. For FcTMA(+/2+) electrolysis the simulated ET kinetic parameters yield very fast ET kinetics (k(0) > 2 ± 1 cm s(-1)). Some deviation between the experimental voltammetry and the idealized model is noted, suggesting that double-layer effects may influence ET at the nanoscale.

  18. High-performance all-solid state asymmetric supercapacitor based on Co3O4 nanowires and carbon aerogel

    NASA Astrophysics Data System (ADS)

    Liu, Weiwei; Li, Xin; Zhu, Menghua; He, Xiong

    2015-05-01

    An all-solid state asymmetric supercapacitor has been fabricated using carbon aerogel (CA) microspheres as the negative electrode and Co3O4 nanowires on nickel foam (Co3O4-NF) as the positive electrode separated by PVA-KOH membrane as the electrolyte. For the desirable porous structure, high specific capacitance and rate capability of CA and Co3O4-NF, broader potential window of the two electrodes, no binder and conductive agent added, the asymmetric supercapacitor can be cycled reversibly in a wide potential window of 0-1.5 V with an energy density of 17.9 Wh kg-1 at a power density of 750 W kg-1. The energy density of the asymmetric supercapacitor is significantly improved in comparison with those of the symmetric supercapacitors based on CA (6.28 Wh kg-1) and Co3O4-NF (2.42 Wh kg-1). The asymmetric supercapacitor can also deliver a high energy density of 10.44 Wh kg-1, even at a high power density of 7.5 kW kg-1. In addition, the asymmetric device shows good stability with approximately 85% of its initial capacitance after 1000 cycles.

  19. Core-shell heterojunction of silicon nanowire arrays and carbon quantum dots for photovoltaic devices and self-driven photodetectors.

    PubMed

    Xie, Chao; Nie, Biao; Zeng, Longhui; Liang, Feng-Xia; Wang, Ming-Zheng; Luo, Linbao; Feng, Mei; Yu, Yongqiang; Wu, Chun-Yan; Wu, Yucheng; Yu, Shu-Hong

    2014-04-22

    Silicon nanostructure-based solar cells have lately intrigued intensive interest because of their promising potential in next-generation solar energy conversion devices. Herein, we report a silicon nanowire (SiNW) array/carbon quantum dot (CQD) core-shell heterojunction photovoltaic device by directly coating Ag-assisted chemical-etched SiNW arrays with CQDs. The heterojunction with a barrier height of 0.75 eV exhibited excellent rectifying behavior with a rectification ratio of 10(3) at ±0.8 V in the dark and power conversion efficiency (PCE) as high as 9.10% under AM 1.5G irradiation. It is believed that such a high PCE comes from the improved optical absorption as well as the optimized carrier transfer and collection capability. Furthermore, the heterojunction could function as a high-performance self-driven visible light photodetector operating in a wide switching wavelength with good stability, high sensitivity, and fast response speed. It is expected that the present SiNW array/CQD core-shell heterojunction device could find potential applications in future high-performance optoelectronic devices.

  20. Totally embedded hybrid thin films of carbon nanotubes and silver nanowires as flat homogenous flexible transparent conductors.

    PubMed

    Pillai, Suresh Kumar Raman; Wang, Jing; Wang, Yilei; Sk, Md Moniruzzaman; Prakoso, Ari Bimo; Rusli; Chan-Park, Mary B

    2016-12-08

    There is a great need for viable alternatives to today's transparent conductive film using largely indium tin oxide. We report the fabrication of a new type of flexible transparent conductive film using silver nanowires (AgNW) and single-walled carbon nanotube (SWCNT) networks which are fully embedded in a UV curable resin substrate. The hybrid SWCNTs-AgNWs film is relatively flat so that the RMS roughness of the top surface of the film is 3 nm. Addition of SWCNTs networks make the film resistance uniform; without SWCNTs, sheet resistance of the surface composed of just AgNWs in resin varies from 20 Ω/sq to 10(7 )Ω/sq. With addition of SWCNTs embedded in the resin, sheet resistance of the hybrid film is 29 ± 5 Ω/sq and uniform across the 47 mm diameter film discs; further, the optimized film has 85% transparency. Our lamination-transfer UV process doesn't need solvent for sacrificial substrate removal and leads to good mechanical interlocking of the nano-material networks. Additionally, electrochemical study of the film for supercapacitors application showed an impressive 10 times higher current in cyclic voltammograms compared to the control without SWCNTs. Our fabrication method is simple, cost effective and enables the large-scale fabrication of flat and flexible transparent conductive films.

  1. Totally embedded hybrid thin films of carbon nanotubes and silver nanowires as flat homogenous flexible transparent conductors

    NASA Astrophysics Data System (ADS)

    Pillai, Suresh Kumar Raman; Wang, Jing; Wang, Yilei; Sk, Md Moniruzzaman; Prakoso, Ari Bimo; Rusli; Chan-Park, Mary B.

    2016-12-01

    There is a great need for viable alternatives to today’s transparent conductive film using largely indium tin oxide. We report the fabrication of a new type of flexible transparent conductive film using silver nanowires (AgNW) and single-walled carbon nanotube (SWCNT) networks which are fully embedded in a UV curable resin substrate. The hybrid SWCNTs-AgNWs film is relatively flat so that the RMS roughness of the top surface of the film is 3 nm. Addition of SWCNTs networks make the film resistance uniform; without SWCNTs, sheet resistance of the surface composed of just AgNWs in resin varies from 20 Ω/sq to 107 Ω/sq. With addition of SWCNTs embedded in the resin, sheet resistance of the hybrid film is 29 ± 5 Ω/sq and uniform across the 47 mm diameter film discs; further, the optimized film has 85% transparency. Our lamination-transfer UV process doesn’t need solvent for sacrificial substrate removal and leads to good mechanical interlocking of the nano-material networks. Additionally, electrochemical study of the film for supercapacitors application showed an impressive 10 times higher current in cyclic voltammograms compared to the control without SWCNTs. Our fabrication method is simple, cost effective and enables the large-scale fabrication of flat and flexible transparent conductive films.

  2. SiC@Si core-shell nanowires on carbon paper as a hybrid anode for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Wang, Yewu; Gu, Lin; Lu, Ren; Qian, Haolei; Peng, Xinsheng; Sha, Jian

    2015-10-01

    Silicon has been considered as one of the most promising anode materials for the next generation lithium-ion battery due to its high theoretical capacity, but large volume changes during the electrochemical cycling limit its commercial application. In this study, we report the synthesis of silicon carbide @ silicon core-shell nanowires on carbon paper and their application in lithium-ion batteries. The hybrid nano-structures are fabricated via a two-step chemical vapor deposition method and directly used as the working electrode without any additional binder, exhibiting high specific capacity, high coulombic efficiency and good cycling stability. After 50 cycles, the discharge capacities still remain 2837 and 1809 mAh g-1 at the rates of 0.1C and 0.5C, respectively. Furthermore, we also study the influence of the growth time of SiC NWs and the thickness of Si film on the lithium-ion batteries' performance, and propose the possible method to further improve the battery performance.

  3. Dye-sensitized solar cells with vertically aligned TiO2 nanowire arrays grown on carbon fibers.

    PubMed

    Cai, Xin; Wu, Hongwei; Hou, Shaocong; Peng, Ming; Yu, Xiao; Zou, Dechun

    2014-02-01

    One-dimensional semiconductor TiO2 nanowires (TNWs) have received widespread attention from solar cell and related optoelectronics scientists. The controllable synthesis of ordered TNW arrays on arbitrary substrates would benefit both fundamental research and practical applications. Herein, vertically aligned TNW arrays in situ grown on carbon fiber (CF) substrates through a facile, controllable, and seed-assisted thermal process is presented. Also, hierarchical TiO2 -nanoparticle/TNW arrays were prepared that favor both the dye loading and depressed charge recombination of the CF/TNW photoanode. An impressive conversion efficiency of 2.48 % (under air mass 1.5 global illumination) and an apparent efficiency of 4.18 % (with a diffuse board) due to the 3D light harvesting of the wire solar cell were achieved. Moreover, efficient and inexpensive wire solar cells made from all-CF electrodes and completely flexible CF-based wire solar cells were demonstrated, taking into account actual application requirements. This work may provide an intriguing avenue for the pursuit of lightweight, cost-effective, and high-performance flexible/wearable solar cells.

  4. An ultrasensitive electrochemical DNA biosensor based on a copper oxide nanowires/single-walled carbon nanotubes nanocomposite

    NASA Astrophysics Data System (ADS)

    Chen, Mei; Hou, Changjun; Huo, Danqun; Yang, Mei; Fa, Huanbao

    2016-02-01

    Here, we developed a novel and sensitive electrochemical biosensor to detect specific-sequence target DNA. The biosensor was based on a hybrid nanocomposite consisting of copper oxide nanowires (CuO NWs) and carboxyl-functionalized single-walled carbon nanotubes (SWCNTs-COOH). The resulting CuO NWs/SWCNTs layers exhibited a good differential pulse voltammetry (DPV) current response for the target DNA sequences, which we attributed to the properties of CuO NWs and SWCNTs. CuO NWs and SWCNTs hybrid composites with highly conductive and biocompatible nanostructure were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and cyclic voltammetry (CV). Immobilization of the probe DNA on the electrode surface was largely improved due to the unique synergetic effect of CuO NWs and SWCNTs. DPV was applied to monitor the DNA hybridization event, using adriamycin as an electrochemical indicator. Under optimal conditions, the peak currents of adriamycin were linear with the logarithm of target DNA concentrations (ranging from 1.0 × 10-14 to 1.0 × 10-8 M), with a detection limit of 3.5 × 10-15 M (signal/noise ratio of 3). The biosensor also showed high selectivity to single-base mismatched target DNA. Compared with other electrochemical DNA biosensors, we showed that the proposed biosensor is simple to implement, with good stability and high sensitivity.

  5. Silver nanowire-carbon fiber cloth nanocomposites synthesized by UV curing adhesive for electrochemical point-of-use water disinfection.

    PubMed

    Hong, Xuesen; Wen, Junjie; Xiong, Xuhua; Hu, Yongyou

    2016-07-01

    Novel silver nanowire (AgNW) - carbon fiber cloth (CC) nanocomposites were synthesized by a rapid and facile method. Acting as filter in an electrical gravity filtration device, the AgNW-CC nanocomposites were applied to electrochemical point-of-use water disinfection. AgNW-CC nanocomposites were characterized by FESEM, XRD, and FTIR. Their disinfection performance toward Escherichia coli and bacteriophage MS2 was evaluated by inhibition zone tests, optical density growth curve tests, and flow tests. The results showed that complex 3D AgNW networks with controllable silver release (<100 ppb) were fabricated on CC by using UV curing adhesive. AgNW-CC nanocomposites exhibited excellent intrinsic antibacterial activities against E. coli. The concentration of AgNWs and UV adhesive controlled the released silver and hence led to the change in antibacterial activity. The external electric field significantly enhanced the disinfection efficiency of AgNW-CC nanocomposites. Over 99.999% removal of E. coli and MS2 could be achieved. More complex AgNW networks contributed to higher disinfection efficiency under 10 V and 10(6) CFU (PFU) mL(-1) of microorganism. UV adhesive could keep the disinfection performance from being affected by flow rate. The convenient synthesis and outstanding disinfection performance offer AgNW-CC nanocomposites opportunities in the application of electrochemical point-of-use drinking water disinfection.

  6. A novel asymmetric supercapacitors based on binder-free carbon fiber paper@ nickel cobaltite nanowires and graphene foam electrodes

    NASA Astrophysics Data System (ADS)

    Tang, Qianqiu; Chen, Mingming; Wang, Le; Wang, Gengchao

    2015-01-01

    Aqueous-based asymmetric supercapacitors (AASCs) provide an effective way to improve the energy density of the device by broadening the operating voltage window. In this work, nickel cobaltite (NiCo2O4) nanowires are grown homogenously on carbon fiber paper (CFP) to obtain a binder-free CFP@NiCo2O4 positive electrode through a simple hydrothermal method followed by calcination. The highly porous graphene foam (GF) as negative electrode which also exhibits self-supporting structure is prepared by a facile mild reduction process. Taking advantages of the complementary voltage window of CFP@NiCo2O4 and GF, the as-fabricated CFP@NiCo2O4//GF AASC obtains a stable working voltage window of 1.6 V, and a high energy density of 34.5 Wh kg-1 at the power density of 547 W kg-1, which still maintains 17.1 Wh kg-1 at 9.68 kW kg-1. Furthermore, it exhibits superior cycling performance with 92.2% capacitance retention rate after 10000 cycles.

  7. Carbon nanotube synthesis: from large-scale production to atom-by-atom growth

    NASA Astrophysics Data System (ADS)

    Journet, Catherine; Picher, Matthieu; Jourdain, Vincent

    2012-04-01

    The extraordinary electronic, thermal and mechanical properties of carbon nanotubes (CNTs) closely relate to their structure. They can be seen as rolled-up graphene sheets with their electronic properties depending on how this rolling up is achieved. However, this is not the way they actually grow. Various methods are used to produce carbon nanotubes. They all have in common three ingredients: (i) a carbon source, (ii) catalyst nanoparticles and (iii) an energy input. In the case where the carbon source is provided in solid form, one speaks about ‘high temperature methods’ because they involve the sublimation of graphite which does not occur below 3200 °C. The first CNTs were synthesized by these techniques. For liquid or gaseous phases, the generic term of ‘medium or low temperature methods’ is used. CNTs are now commonly produced by these latter techniques at temperatures ranging between 350 and 1000 °C, using metal nanoparticles that catalyze the decomposition of the gaseous carbon precursor and make the growth of nanotubes possible. The aim of this review article is to give a general overview of all these methods and an understanding of the CNT growth process.

  8. Catalytic conversion of alcohols having at least three carbon atoms to hydrocarbon blendstock

    DOEpatents

    Narula, Chaitanya K.; Davison, Brian H.

    2015-11-13

    A method for producing a hydrocarbon blendstock, the method comprising contacting at least one saturated acyclic alcohol having at least three and up to ten carbon atoms with a metal-loaded zeolite catalyst at a temperature of at least 100°C and up to 550°C, wherein the metal is a positively-charged metal ion, and the metal-loaded zeolite catalyst is catalytically active for converting the alcohol to the hydrocarbon blendstock, wherein the method directly produces a hydrocarbon blendstock having less than 1 vol % ethylene and at least 35 vol % of hydrocarbon compounds containing at least eight carbon atoms.

  9. The influence of the atomic structure of basal planes on interplanar distance in pyrolytic carbon materials

    NASA Astrophysics Data System (ADS)

    Borgardt, N. I.; Prihodko, A. S.; Seibt, M.

    2016-12-01

    The atomic structure of carbon materials is studied using the example of pyrocarbon and boronrich pyrocarbon by means of the method of reconstruction of the wave function in transmission electron microscopy. It is shown that the digital processing of the phase distributions of these functions allows us to find the average distance between the basal planes. Using the method of molecular dynamics for the formation of the test structures and obtaining for them the calculated phase distributions, the effect of depletion of the basal planes of the carbon atoms on the interplanar distance in the pyrocarbon materials is quantified.

  10. Coke formation and carbon atom economy of methanol-to-olefins reaction.

    PubMed

    Wei, Yingxu; Yuan, Cuiyu; Li, Jinzhe; Xu, Shutao; Zhou, You; Chen, Jingrun; Wang, Quanyi; Xu, Lei; Qi, Yue; Zhang, Qing; Liu, Zhongmin

    2012-05-01

    The methanol-to-olefins (MTO) process is becoming the most important non-petrochemical route for the production of light olefins from coal or natural gas. Maximizing the generation of the target products, ethene and propene, and minimizing the production of byproducts and coke, are major considerations in the efficient utilization of the carbon resource of methanol. In the present work, the heterogeneous catalytic conversion of methanol was evaluated by performing simultaneous measurements of the volatile products generated in the gas phase and the confined coke deposition in the catalyst phase. Real-time and complete reaction profiles were plotted to allow the comparison of carbon atom economy of methanol conversion over the catalyst SAPO-34 at varied reaction temperatures. The difference in carbon atom economy was closely related with the coke formation in the SAPO-34 catalyst. The confined coke compounds were determined. A new type of confined organics was found, and these accounted for the quick deactivation and low carbon atom economy under low-reaction-temperature conditions. Based on the carbon atom economy evaluation and coke species determination, optimized operating conditions for the MTO process are suggested; these conditions guarantee high conversion efficiency of methanol.

  11. Atomically isolated nickel species anchored on graphitized carbon for efficient hydrogen evolution electrocatalysis

    PubMed Central

    Fan, Lili; Liu, Peng Fei; Yan, Xuecheng; Gu, Lin; Yang, Zhen Zhong; Yang, Hua Gui; Qiu, Shilun; Yao, Xiangdong

    2016-01-01

    Hydrogen production through electrochemical process is at the heart of key renewable energy technologies including water splitting and hydrogen fuel cells. Despite tremendous efforts, exploring cheap, efficient and durable electrocatalysts for hydrogen evolution still remains as a great challenge. Here we synthesize a nickel–carbon-based catalyst, from carbonization of metal-organic frameworks, to replace currently best-known platinum-based materials for electrocatalytic hydrogen evolution. This nickel-carbon-based catalyst can be activated to obtain isolated nickel atoms on the graphitic carbon support when applying electrochemical potential, exhibiting highly efficient hydrogen evolution performance with high exchange current density of 1.2 mA cm−2 and impressive durability. This work may enable new opportunities for designing and tuning properties of electrocatalysts at atomic scale for large-scale water electrolysis. PMID:26861684

  12. Atomically isolated nickel species anchored on graphitized carbon for efficient hydrogen evolution electrocatalysis

    NASA Astrophysics Data System (ADS)

    Fan, Lili; Liu, Peng Fei; Yan, Xuecheng; Gu, Lin; Yang, Zhen Zhong; Yang, Hua Gui; Qiu, Shilun; Yao, Xiangdong

    2016-02-01

    Hydrogen production through electrochemical process is at the heart of key renewable energy technologies including water splitting and hydrogen fuel cells. Despite tremendous efforts, exploring cheap, efficient and durable electrocatalysts for hydrogen evolution still remains as a great challenge. Here we synthesize a nickel-carbon-based catalyst, from carbonization of metal-organic frameworks, to replace currently best-known platinum-based materials for electrocatalytic hydrogen evolution. This nickel-carbon-based catalyst can be activated to obtain isolated nickel atoms on the graphitic carbon support when applying electrochemical potential, exhibiting highly efficient hydrogen evolution performance with high exchange current density of 1.2 mA cm-2 and impressive durability. This work may enable new opportunities for designing and tuning properties of electrocatalysts at atomic scale for large-scale water electrolysis.

  13. Low-temperature in situ large strain plasticity of ceramic SiC nanowires and its atomic-scale mechanism.

    PubMed

    Han, X D; Zhang, Y F; Zheng, K; Zhang, X N; Zhang, Z; Hao, Y J; Guo, X Y; Yuan, J; Wang, Z L

    2007-02-01

    Large strain plasticity is phenomenologically defined as the ability of a material to exhibit an exceptionally large deformation rate during mechanical deformation. It is a property that is well established for metals and alloys but is rarely observed for ceramic materials especially at low temperature ( approximately 300 K). With the reduction in dimensionality, however, unusual mechanical properties are shown by ceramic nanomaterials. In this Letter, we demonstrated unusually large strain plasticity of ceramic SiC nanowires (NWs) at temperatures close to room temperature that was directly observed in situ by a novel high-resolution transmission electron microscopy technique. The continuous plasticity of the SiC NWs is accompanied by a process of increased dislocation density at an early stage, followed by an obvious lattice distortion, and finally reaches an entire structure amorphization at the most strained region of the NW. These unusual phenomena for the SiC NWs are fundamentally important for understanding the nanoscale fracture and strain-induced band structure variation for high-temperature semiconductors. Our result may also provide useful information for further studying of nanoscale elastic-plastic and brittle-ductile transitions of ceramic materials with superplasticity.

  14. Single Pd atoms in activated carbon fibers and their contribution to hydrogen storage

    SciTech Connect

    Contescu, Cristian I; van Benthem, Klaus; Li, Sa; Bonifacio, Cecile S; Pennycook, Stephen J; Jena, Puru; Gallego, Nidia C

    2011-01-01

    Palladium-modified activated carbon fibers (Pd-ACF) were synthesized by meltspinning, carbonization and activation of an isotropic pitch carbon precursor premixed with an organometallic Pd compound. The hydrogen uptake at 25 oC and 20 bar on Pd- ACF exceeded the expected capacity based solely on Pd hydride formation and hydrogen physisorption on the microporous carbon support. Aberration-corrected scanning transmission electron microscopy (STEM) with sub- ngstrom spatial resolution provided unambiguous identification of isolated Pd atoms occurring in the carbon matrix that coexist with larger Pd particles. First principles calculations revealed that each single Pd atom can form Kubas-type complexes by binding up to three H2 molecules in the pressure range of adsorption measurements. Based on Pd atom concentration determined from STEM images, the contribution of various mechanisms to the excess hydrogen uptake measured experimentally was evaluated. With consideration of Kubas binding as a viable mechanism (along with hydride formation and physisorption to carbon support) the role of hydrogen spillover in this system may be smaller than previously thought.

  15. Evaluation of a carbon-rod atomizer for routine determination of trace metals by atomic-absorption spectroscopy applications to analysis of lubricating oil and crude oil.

    PubMed

    Hall, G; Bratzel, M P; Chakrabarti, C L

    1973-08-01

    A carbon-rod atomizer (CRA) fitted with a 'mini-Massmann' carbon rod was evaluated for routine analysis of petroleum and petroleum products for trace metal content by atomic-absorption spectroscopy. Aspects investigated included sensitivity, detection limit, effect of solvent type, and interferences. The results of analysis of oil samples with this technique were compared with those obtained by other techniques. Metals studied were silver, copper, iron, nickel, and lead. Sensitivity and detection limit values obtained with the CRA were similar to those obtained with the carbon-filament atomizer. Strong 'solvent effects' were observed as well as interference by cations. On the basis of this study, design changes for the CRA are suggested, with the object of minimizing 'solvent effects' and interferences, increasing the atomization efficiency, and increasing the residence time of the atomic vapour in the optical path of the instrumental system.

  16. Radiation Stability of Metal Nanowires

    NASA Astrophysics Data System (ADS)

    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.

  17. In Situ Growth of Core-Sheath Heterostructural SiC Nanowire Arrays on Carbon Fibers and Enhanced Electromagnetic Wave Absorption Performance.

    PubMed

    Yan, Liwen; Hong, Changqing; Sun, Boqian; Zhao, Guangdong; Cheng, Yehong; Dong, Shun; Zhang, Dongyang; Zhang, Xinghong

    2017-02-22

    Large-scale core-sheath heterostructural SiC nanowires were facilely grown on the surface of carbon fibers using a one-step chemical vapor infiltration process. The as-synthesized SiC nanowires consist of single crystalline SiC cores with a diameter of ∼30 nm and polycrystalline SiC sheaths with an average thickness of ∼60 nm. The formation mechanisms of core-sheath heterostructural SiC nanowires (SiCnws) were discussed in detail. The SiCnws-CF shows strong electromagnetic (EM) wave absorption performance with a maximum reflection loss value of -45.98 dB at 4.4 GHz. Moreover, being coated with conductive polymer polypyrrole (PPy) by a simple chemical polymerization method, the SiCnws-CF/PPy nanocomposites exhibited superior EM absorption abilities with maximum RL value of -50.19 dB at 14.2 GHz and the effective bandwidth of 6.2 GHz. The SiCnws-CF/PPy nanocomposites in this study are very promising as absorber materials with strong electromagnetic wave absorption performance.

  18. Characteristics of carbon monoxide sensors made by polar and nonpolar zinc oxide nanowires gated AlGaN/GaN high electron mobility transistor

    NASA Astrophysics Data System (ADS)

    Hung, S. C.; Woon, W. Y.; Lan, S. M.; Ren, F.; Pearton, S. J.

    2013-08-01

    AlGaN/GaN high electron mobility transistors (HEMTs) with polar and nonpolar ZnO nanowires modified gate exhibit significant changes in channel conductance upon exposure to different concentration of carbon monoxide (CO) at room temperature. The ZnO nanowires, grown by chemical vapor deposition, with perfect crystal quality will attach CO molecules and release electrons, which will lead to a change of surface charge in the gate region of the HEMTs, inducing a higher positive charge on the AlGaN surface, and increasing the piezo-induced charge density in the HEMTs channel. These electrons create an image positive charge on the gate region for the required neutrality, thus increasing the drain current of the HEMTs. The HEMTs source-drain current was highly dependent on the CO concentration. The limit of detection achieved was 400 ppm and 3200 ppm in the open cavity with continuous gas flow using a 50 × 50 μm2 gate sensing area for polar and nonpolar ZnO nanowire gated HEMTs sensor, respectively.

  19. Ni-Co bimetal nanowires filled multiwalled carbon nanotubes for the highly sensitive and selective non-enzymatic glucose sensor applications

    NASA Astrophysics Data System (ADS)

    Ramachandran, K.; Raj Kumar, T.; Babu, K. Justice; Gnana Kumar, G.

    2016-11-01

    The facile, time and cost efficient and environmental benign approach has been developed for the preparation of Nickel (Ni)-Cobalt (Co) alloy nanowires filled multiwalled carbon nanotubes (MWCNTs) with the aid of mesoporous silica nanoparticles (MSN)/Ni-Co catalyst. The controlled incorporation of Ni-Co nanostructures in the three dimensional (3D) pore structures of MSN yielded the catalytically active system for the MWCNT growth. The inner surface of MWCNTs was quasi-continuously filled with face-centered cubic (fcc) structured Ni-Co nanowires. The as-prepared nanostructures were exploited as non-enzymatic electrochemical sensor probes for the reliable detection of glucose. The electrochemical measurements illustrated that the fabricated sensor exhibited an excellent electrochemical performance toward glucose oxidation with a high sensitivity of 0.695 mA mM-1 cm-2, low detection limit of 1.2 μM, a wide linear range from 5 μM-10 mM and good selectivity. The unprecedented electrochemical performances obtained for the prepared nanocomposite are purely attributed to the synergistic effects of Ni-Co nanowires and MWCNTs. The constructed facile, selective and sensitive glucose sensor has also endowed its reliability in analyzing the human serum samples, which wide opened the new findings for exploring the novel nanostructures based glucose sensor devices with affordable cost and good stability.

  20. Ni-Co bimetal nanowires filled multiwalled carbon nanotubes for the highly sensitive and selective non-enzymatic glucose sensor applications

    PubMed Central

    Ramachandran, K.; Raj kumar, T.; Babu, K. Justice; Gnana kumar, G.

    2016-01-01

    The facile, time and cost efficient and environmental benign approach has been developed for the preparation of Nickel (Ni)-Cobalt (Co) alloy nanowires filled multiwalled carbon nanotubes (MWCNTs) with the aid of mesoporous silica nanoparticles (MSN)/Ni-Co catalyst. The controlled incorporation of Ni-Co nanostructures in the three dimensional (3D) pore structures of MSN yielded the catalytically active system for the MWCNT growth. The inner surface of MWCNTs was quasi-continuously filled with face-centered cubic (fcc) structured Ni-Co nanowires. The as-prepared nanostructures were exploited as non-enzymatic electrochemical sensor probes for the reliable detection of glucose. The electrochemical measurements illustrated that the fabricated sensor exhibited an excellent electrochemical performance toward glucose oxidation with a high sensitivity of 0.695 mA mM−1 cm−2, low detection limit of 1.2 μM, a wide linear range from 5 μM–10 mM and good selectivity. The unprecedented electrochemical performances obtained for the prepared nanocomposite are purely attributed to the synergistic effects of Ni-Co nanowires and MWCNTs. The constructed facile, selective and sensitive glucose sensor has also endowed its reliability in analyzing the human serum samples, which wide opened the new findings for exploring the novel nanostructures based glucose sensor devices with affordable cost and good stability. PMID:27833123

  1. The Reception of J. H. van't Hoff's Theory of the Asymmetric Carbon Atom

    ERIC Educational Resources Information Center

    Snelders, H. A. M.

    1974-01-01

    Discusses Jacobus Henricus van't Hoff's revolutionary theory of the asymmetric carbon atom and its early reception among his contemporaries in the Netherlands. Indicates that the extension of the new idea to practical problems gives the impetus to the development of stereochemistry. (CC)

  2. Atomic scale observation of oxygen delivery during silver-oxygen nanoparticle catalysed oxidation of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Yue, Yonghai; Yuchi, Datong; Guan, Pengfei; Xu, Jia; Guo, Lin; Liu, Jingyue

    2016-07-01

    To probe the nature of metal-catalysed processes and to design better metal-based catalysts, atomic scale understanding of catalytic processes is highly desirable. Here we use aberration-corrected environmental transmission electron microscopy to investigate the atomic scale processes of silver-based nanoparticles, which catalyse the oxidation of multi-wall carbon nanotubes. A direct semi-quantitative estimate of the oxidized carbon atoms by silver-based nanoparticles is achieved. A mechanism similar to the Mars-van Krevelen process is invoked to explain the catalytic oxidation process. Theoretical calculations, together with the experimental data, suggest that the oxygen molecules dissociate on the surface of silver nanoparticles and diffuse through the silver nanoparticles to reach the silver/carbon interfaces and subsequently oxidize the carbon. The lattice distortion caused by oxygen concentration gradient within the silver nanoparticles provides the direct evidence for oxygen diffusion. Such direct observation of atomic scale dynamics provides an important general methodology for investigations of catalytic processes.

  3. Atomic scale observation of oxygen delivery during silver–oxygen nanoparticle catalysed oxidation of carbon nanotubes

    PubMed Central

    Yue, Yonghai; Yuchi, Datong; Guan, Pengfei; Xu, Jia; Guo, Lin; Liu, Jingyue

    2016-01-01

    To probe the nature of metal-catalysed processes and to design better metal-based catalysts, atomic scale understanding of catalytic processes is highly desirable. Here we use aberration-corrected environmental transmission electron microscopy to investigate the atomic scale processes of silver-based nanoparticles, which catalyse the oxidation of multi-wall carbon nanotubes. A direct semi-quantitative estimate of the oxidized carbon atoms by silver-based nanoparticles is achieved. A mechanism similar to the Mars–van Krevelen process is invoked to explain the catalytic oxidation process. Theoretical calculations, together with the experimental data, suggest that the oxygen molecules dissociate on the surface of silver nanoparticles and diffuse through the silver nanoparticles to reach the silver/carbon interfaces and subsequently oxidize the carbon. The lattice distortion caused by oxygen concentration gradient within the silver nanoparticles provides the direct evidence for oxygen diffusion. Such direct observation of atomic scale dynamics provides an important general methodology for investigations of catalytic processes. PMID:27406595

  4. The Reception of J. H. van't Hoff's Theory of the Asymmetric Carbon Atom

    ERIC Educational Resources Information Center

    Snelders, H. A. M.

    1974-01-01

    Discusses Jacobus Henricus van't Hoff's revolutionary theory of the asymmetric carbon atom and its early reception among his contemporaries in the Netherlands. Indicates that the extension of the new idea to practical problems gives the impetus to the development of stereochemistry. (CC)

  5. Atom Vacancies on a Carbon Nanotube: To What Extent Can We Simulate their Effects?

    PubMed

    Kroes, Jaap M H; Pietrucci, Fabio; van Duin, Adri C T; Andreoni, Wanda

    2015-07-14

    Atom vacancies are intrinsic defects of carbon nanotubes. Using a zigzag nanotube as reference, this paper focuses on the comparison of calculations performed within density functional theory and a number of classical force fields widely used for carbon systems. The results refer to single and double vacancies and, in particular, to the induced structural changes, the formation energies, and the energy barriers relative to elementary processes such as reconstruction, migration, and coalescence. Characterization of these processes is remarkably different in the different approaches. These findings are meant to contribute to the construction of DFT-based classical schemes for carbon nanostructures.

  6. Direct laser fabrication of nanowires on semiconductor surfaces

    NASA Astrophysics Data System (ADS)

    Haghizadeh, Anahita; Yang, Haeyeon

    2016-03-01

    Periodic nanowires are observed from (001) orientation of Si and GaAs when the surfaces are irradiated interferentially by high power laser pulses. These nanowires are self-assembled and can be strain-free while their period is consistent with interference period. The nanowire morphologies are studied by atomic force microscopy. The observed period between nanowires depends on the wavelengths used and interference angle. The nanowire width increases with laser intensity. The narrowest nanowires observed have the width smaller than 20 nm, which is more than 10 times smaller than the interference period.

  7. Facile synthesis of Ag@Au core-sheath nanowires with greatly improved stability against oxidation.

    PubMed

    Yang, Miaoxin; Hood, Zachary D; Yang, Xuan; Chi, Miaofang; Xia, Younan

    2017-02-07

    We report a facile synthesis of Ag@Au core-sheath nanowires through the conformal deposition of Au atoms onto the surface of pre-synthesized Ag nanowires. The resulting Ag@Au nanowires showed morphology and optical properties almost identical to the pristine Ag nanowires, but with greatly improved stability under different corrosive environments.

  8. Phase transitions of adsorbed atoms on the surface of a carbon nanotube.

    PubMed

    Wang, Zenghui; Wei, Jiang; Morse, Peter; Dash, J Gregory; Vilches, Oscar E; Cobden, David H

    2010-01-29

    Phase transitions of adsorbed atoms and molecules on two-dimensional substrates are well explored, but similar transitions in the one-dimensional limit have been more difficult to study experimentally. Suspended carbon nanotubes can act as nanoscale resonators with remarkable electromechanical properties and the ability to detect adsorption at the level of single atoms. We used single-walled carbon nanotube resonators to study the phase behavior of adsorbed argon and krypton atoms as well as their coupling to the substrate electrons. By monitoring the resonance frequency in the presence of gases, we observed the formation of monolayers on the cylindrical surface, phase transitions within them, and simultaneous modification of the electrical conductance.

  9. Interaction of Si atoms and Si-based radicals with carbon nanotubes and graphene monolayers

    NASA Astrophysics Data System (ADS)

    Chang, Kiseok; Berber, Savas; Tománek, David

    2008-03-01

    We use ab initio density functional calculations to study the interaction of Si atoms and Si-based radicals, such as SiH3, with single-wall carbon nanotubes and graphene monolayers. We find that both Si atoms and radicals form a strong chemisorption bond, accompanied by a small relaxation and a locally increased sp^3 bond character of the graphitic nanostructure. We identify the optimum adsorption geometries at different adsorbate coverages and adsorbate-related changes in the electronic structure and vibration spectra of the systems. We propose that successful functionalization of carbon nanotubes or graphene by Si atoms or Si-based radicals can be verified by studying changes in the radial breathing mode of nanotubes and the G-band of graphitic nanocarbons using Raman spectroscopy.

  10. ATOMIC-LEVEL IMAGING OF CO2 DISPOSAL AS A CARBONATE MINERAL: OPTIMIZING REACTION PROCESS DESIGN

    SciTech Connect

    M.J. McKelvy; R. Sharma; A.V.G. Chizmeshya; H. Bearat; R.W. Carpenter

    2000-08-01

    Fossil fuels, especially coal, can support the energy demands of the world for centuries to come, if the environmental problems associated with CO{sub 2} emissions can be overcome. Permanent and safe methods for CO{sub 2} capture and disposal/storage need to be developed. Mineralization of stationary-source CO{sub 2} emissions as carbonates can provide such safe capture and long-term sequestration. Mg-rich lamellar-hydroxide based minerals (e.g., brucite and serpentine) offer a class of widely available, low-cost materials, with intriguing mineral carbonation potential. Carbonation of such materials inherently involves dehydroxylation, which can disrupt the material down to the atomic level. As such, controlled dehydroxylation before and/or during carbonation may provide an important parameter for enhancing carbonation reaction processes. Mg(OH){sub 2} was chosen as the model material for investigating lamellar hydroxide mineral dehydroxylation/carbonation mechanisms due to (i) its structural and chemical simplicity, (ii) interest in Mg(OH){sub 2} gas-solid carbonation as a potentially cost-effective CO{sub 2} mineral sequestration process component, and (iii) its structural and chemical similarity to other lamellar-hydroxide-based minerals (e.g., serpentine-based minerals) whose carbonation reaction processes are being explored due to their low-cost CO{sub 2} sequestration potential. Fundamental understanding of the mechanisms that govern dehydroxylation/carbonation processes is essential for cost optimization of any lamellar-hydroxide-based mineral carbonation sequestration process.

  11. Engineered nanowires, carbon nanotubes and graphene for sensors, actuators and electronics

    NASA Astrophysics Data System (ADS)

    Yang, E. H.

    2010-02-01

    We are exploring nanoelectronic engineering areas based on low dimensional materials, including carbon nanotubes and graphene. Our primary research focus is investigating carbon nanotube and graphene architectures for field emission applications, energy harvesting and sensing. In a second effort, we are developing a high-throughput desktop nanolithography process. Lastly, we are studying nanomechanical actuators and associated nanoscale measurement techniques for re-configurable arrayed nanostructures with applications in antennas, remote detectors and biomedical nanorobots. The devices we fabricate, assemble, manipulate and characterize potentially have a wide range of applications including sensors, detectors, system-on-a-chip, system-in-a-package, programmable logic controls, energy storage systems and allelectronic systems.

  12. Carbon-coated ZnO mat passivation by atomic-layer-deposited HfO2 as an anode material for lithium-ion batteries.

    PubMed

    Jung, Mi-Hee

    2017-11-01

    ZnO has had little consideration as an anode material in lithium-ion batteries compared with other transition-metal oxides due to its inherent poor electrical conductivity and large volume expansion upon cycling and pulverization of ZnO-based electrodes. A logical design and facile synthesis of ZnO with well-controlled particle sizes and a specific morphology is essential to improving the performance of ZnO in lithium-ion batteries. In this paper, a simple approach is reported that uses a cation surfactant and a chelating agent to synthesize three-dimensional hierarchical nanostructured carbon-coated ZnO mats, in which the ZnO mats are composed of stacked individual ZnO nanowires and form well-defined nanoporous structures with high surface areas. In order to improve the performance of lithium-ion batteries, HfO2 is deposited on the carbon-coated ZnO mat electrode via atomic layer deposition. Lithium-ion battery devices based on the carbon-coated ZnO mat passivation by atomic layer deposited HfO2 exhibit an excellent initial discharge and charge capacities of 2684.01 and 963.21mAhg(-1), respectively, at a current density of 100mAg(-1) in the voltage range of 0.01-3V. They also exhibit cycle stability after 125 cycles with a capacity of 740mAhg(-1) and a remarkable rate capability. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Hierarchical three-dimensional ZnCo₂O₄ nanowire arrays/carbon cloth anodes for a novel class of high-performance flexible lithium-ion batteries.

    PubMed

    Liu, Bin; Zhang, Jun; Wang, Xianfu; Chen, Gui; Chen, Di; Zhou, Chongwu; Shen, Guozhen

    2012-06-13

    Flexible electronics is an emerging and promising technology for next generation of optoelectronic devices. Herein, hierarchical three-dimensional ZnCo(2)O(4) nanowire arrays/carbon cloth composites were synthesized as high performance binder-free anodes for Li-ion battery with the features of high reversible capacity of 1300-1400 mAh g(-1) and excellent cycling ability even after 160 cycles with a capacity of 1200 mAh g(-1). Highly flexible full batteries were also fabricated, exhibiting high flexibility, excellent electrical stability, and superior electrochemical performances.

  14. Spatial Distributions of Metal Atoms During Carbon SWNTs Formation: Measurements and Modelling

    NASA Technical Reports Server (NTRS)

    Cau, M.; Dorval, N.; Attal-Tretout, B.; Cochon, J. L.; Loiseau, A.; Farhat, S.; Hinkov, I.; Scott, C. D.

    2004-01-01

    Experiments and modelling have been undertaken to clarify the role of metal catalysts during single-wall carbon nanotube formation. For instance, we wonder whether the metal catalyst is active as an atom, a cluster, a liquid or solid nanoparticle [1]. A reactor has been developed for synthesis by continuous CO2-laser vaporisation of a carbon-nickel-cobalt target in laminar helium flow. The laser induced fluorescence technique [2] is applied for local probing of gaseous Ni, Co and CZ species throughout the hot carbon flow of the target heated up to 3500 K. A rapid depletion of C2 in contrast to the spatial extent of metal atoms is observed in the plume (Fig. 1). This asserts that C2 condenses earlier than Ni and Co atoms.[3, 4]. The depletion is even faster when catalysts are present. It may indicate that an interaction between metal atoms and carbon dimers takes place in the gas as soon as they are expelled from the target surface. Two methods of modelling are used: a spatially I-D calculation developed originally for the arc process [5], and a zero-D time dependent calculation, solving the chemical kinetics along the streamlines [6]. The latter includes Ni cluster formation. The peak of C2 density is calculated close to the target surface where the temperature is the highest. In the hot region, C; is dominant. As the carbon products move away from the target and mix with the ambient helium, they recombine into larger clusters, as demonstrated by the peak of C5 density around 1 mm. The profile of Ni-atom density compares fairly well with the measured one (Fig. 2). The early increase is due to the drop of temperature, and the final decrease beyond 6 mm results from Ni cluster formation at the eutectic temperature (approx.1600 K).

  15. Spatial Distributions of Metal Atoms During Carbon SWNTs Formation: Measurements and Modelling

    NASA Technical Reports Server (NTRS)

    Cau, M.; Dorval, N.; Attal-Tretout, B.; Cochon, J. L.; Loiseau, A.; Farhat, S.; Hinkov, I.; Scott, C. D.

    2004-01-01

    Experiments and modelling have been undertaken to clarify the role of metal catalysts during single-wall carbon nanotube formation. For instance, we wonder whether the metal catalyst is active as an atom, a cluster, a liquid or solid nanoparticle [1]. A reactor has been developed for synthesis by continuous CO2-laser vaporisation of a carbon-nickel-cobalt target in laminar helium flow. The laser induced fluorescence technique [2] is applied for local probing of gaseous Ni, Co and CZ species throughout the hot carbon flow of the target heated up to 3500 K. A rapid depletion of C2 in contrast to the spatial extent of metal atoms is observed in the plume (Fig. 1). This asserts that C2 condenses earlier than Ni and Co atoms.[3, 4]. The depletion is even faster when catalysts are present. It may indicate that an interaction between metal atoms and carbon dimers takes place in the gas as soon as they are expelled from the target surface. Two methods of modelling are used: a spatially I-D calculation developed originally for the arc process [5], and a zero-D time dependent calculation, solving the chemical kinetics along the streamlines [6]. The latter includes Ni cluster formation. The peak of C2 density is calculated close to the target surface where the temperature is the highest. In the hot region, C; is dominant. As the carbon products move away from the target and mix with the ambient helium, they recombine into larger clusters, as demonstrated by the peak of C5 density around 1 mm. The profile of Ni-atom density compares fairly well with the measured one (Fig. 2). The early increase is due to the drop of temperature, and the final decrease beyond 6 mm results from Ni cluster formation at the eutectic temperature (approx.1600 K).

  16. Multiphoton inner-shell ionization of the carbon atom

    NASA Astrophysics Data System (ADS)

    Rey, H. F.; van der Hart, H. W.

    2015-07-01

    We apply time-dependent R -matrix theory to study inner-shell ionization of C atoms in ultrashort high-frequency light fields with a photon energy between 170 and 245 eV. At an intensity of 1017 W /cm2, ionization is dominated by single-photon emission of a 2 ℓ electron, with two-photon emission of a 1 s electron accounting for about 2-3% of all emission processes, and two-photon emission of 2 ℓ contributing about 0.5-1%. Three-photon emission of a 1 s electron is estimated to contribute about 0.01-0.03%. Around a photon energy of 225 eV, two-photon emission of a 1 s electron, leaving C+ in either 1 s 2 s 2 p3 or 1 s 2 p4 , is resonantly enhanced by intermediate 1 s 2 s22 p3 states. The results demonstrate the capability of time-dependent R -matrix theory to describe inner-shell ionization processes including rearrangement of the outer electrons.

  17. A new material with atomized cobalt-multiwalled carbon nanotubes: a possible substitute for human implants.

    PubMed

    Joshi, Bharat; Gupta, Sachin; Kalra, Nitin; Gudyka, Russell; Santhanam, K S V

    2010-06-01

    A new material composed of atomized cobalt-multiwalled carbon nanotube has been produced and characterized by thermogravimetric analysis and polarization studies to estimate its lifetime. This does not show cobalt thermal oxidation suggesting that it is confined inside the carbon nanotube matrix. The density functional calculations in the literature predict a strong interaction leading to higher hybridization of cobalt atom and carbon nanotubes. A detailed investigation of the corrosion measurements shows that the new material of thickness 0.8 mm, 1 mm, 1.5 mm and 2 mm would last for 31, 39, 60 and 79 years and it would substitute with cobalt-chromium alloy that is used as a load bearing implant for patients with knee pain or partial denture implant.

  18. Bias in bonding behavior among boron, carbon, and nitrogen atoms in ion implanted a-BN, a-BC, and diamond like carbon films

    SciTech Connect

    Genisel, Mustafa Fatih; Uddin, Md. Nizam; Say, Zafer; Bengu, Erman; Kulakci, Mustafa; Turan, Rasit; Gulseren, Oguz

    2011-10-01

    In this study, we implanted N{sup +} and N{sub 2}{sup +} ions into sputter deposited amorphous boron carbide (a-BC) and diamond like carbon (DLC) thin films in an effort to understand the chemical bonding involved and investigate possible phase separation routes in boron carbon nitride (BCN) films. In addition, we investigated the effect of implanted C{sup +} ions in sputter deposited amorphous boron nitride (a-BN) films. Implanted ion energies for all ion species were set at 40 KeV. Implanted films were then analyzed using x-ray photoelectron spectroscopy (XPS). The changes in the chemical composition and bonding chemistry due to ion-implantation were examined at different depths of the films using sequential ion-beam etching and high resolution XPS analysis cycles. A comparative analysis has been made with the results from sputter deposited BCN films suggesting that implanted nitrogen and carbon atoms behaved very similar to nitrogen and carbon atoms in sputter deposited BCN films. We found that implanted nitrogen atoms would prefer bonding to carbon atoms in the films only if there is no boron atom in the vicinity or after all available boron atoms have been saturated with nitrogen. Implanted carbon atoms also preferred to either bond with available boron atoms or, more likely bonded with other implanted carbon atoms. These results were also supported by ab-initio density functional theory calculations which indicated that carbon-carbon bonds were energetically preferable to carbon-boron and carbon-nitrogen bonds.

  19. Copper@carbon coaxial nanowires synthesized by hydrothermal carbonization process from electroplating wastewater and their use as an enzyme-free glucose sensor.

    PubMed

    Zhao, Yuxin; He, Zhaoyang; Yan, Zifeng

    2013-01-21

    In the pursuit of electrocatalysts with great economic and ecological values for non-enzymatic glucose sensors, one-dimensional copper@carbon (Cu@C) core-shell coaxial nanowires (NWs) have been successfully prepared via a simple continuous flow wet-chemistry approach from electroplating wastewater. The as-obtained products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, energy dispersive X-ray spectroscopy and Raman spectroscopy. The electrocatalytic activity of the modified electrodes by Cu@C NWs towards glucose oxidation was investigated by cyclic voltammetry and chronoamperometry. It was found that the as-obtained Cu@C NWs showed good electrochemical properties and could be used as an electrochemical sensor for the detection of glucose molecules. Compared to the other electrodes including the bare Nafion/glassy carbon electrode (GCE) and several hot hybrid nanostructures modified GCE, a substantial decrease in the overvoltage of the glucose oxidation was observed at the Cu@C NWs electrodes with oxidation starting at ca. 0.20 V vs. Ag/AgCl (3 M KCl). At an applied potential of 0.65 V, Cu@C NWs electrodes had a high and reproducible sensitivity of 437.8 µA cm(-2) mM(-1) to glucose. Linear responses were obtained with a detection limit of 50 nM. More importantly, the proposed electrode also had good stability, high resistance against poisoning by chloride ion and commonly interfering species. These good analytical performances make Cu@C NWs promising for the future development of enzyme-free glucose sensors.

  20. First principles study of foreign interstitial atom (carbon, nitrogen) interactions with intrinsic defects in tungsten

    NASA Astrophysics Data System (ADS)

    Kong, Xiang-Shan; You, Yu-Wei; Song, Chi; Fang, Q. F.; Chen, Jun-Ling; Luo, G.-N.; Liu, C. S.

    2012-11-01

    We performed a series of first-principles calculations to investigate the foreign interstitial atom (FIA) interactions with intrinsic defects in tungsten. We found the following: (i) The introduction of the FIA reduces the vacancy formation energy, resulting in the increase of the equilibrium concentration of vacancies. (ii) The positive binding energy between two FIAs suggests that the FIA can attract other FIAs. (iii) The FIA is easily trapped by the vacancy, and a single vacancy can accommodate up to 4 and 6 atoms in a stable manner for carbon and nitrogen, respectively. (iv) There is an attraction interaction between the FIA and the self-interstitial atom (SIA), and the FIA can reduce the SIA jump frequency and enhance the formation of SIA clusters in tungsten. Moreover, the difference between carbon and nitrogen are also discussed with respect to the formation of FIA-FIA covalent bond and the accumulation around the saturated -, where d is the ith nearest-neighbor (inn) solute-tungsten distance before relaxation and ▵di=(di-d) is the change in distance due to relaxation. The calculated relaxations are presented in Table 3. The relaxations of 1nn of octahedral interstitial carbon and nitrogen atoms are 23.30% and 22.42%, respectively, which are greatly larger than the relaxations of other nearest-neighbor atoms (0.1-2%). These results indicate that the influence range of FIA is very local. The lattice distortions introduced by the octahedral interstitial carbon or nitrogen atom can be characterized by determining the dipolar tensor from Kanzaki forces. Here, to obtain the dipolar tensor, we adopt a similar calculation procedure as used in Ref. [14], where the dipolar tensor P is calculated from the Kanzaki forces on all the tungsten atoms. The detailed procedure could be found in Ref. [14]. Due to the symmetry of the configuration, the dipolar tensor has two independent values: P11 and P33, which are listed in Table 3. Similarly with Ref. [14], approximate

  1. ATOMIC-LEVEL IMAGING OF CO2 DISPOSAL AS A CARBONATE MINERAL: OPTIMIZING REACTION PROCESS DESIGN

    SciTech Connect

    M.J. McKelvy; R. Sharma; A.V.G. Chizmeshya; H. Bearat; R.W. Carpenter; K. Streib

    1999-09-01

    Fossil fuels, especially coal, can support the energy demands of the world for centuries to come, if the environmental problems associated with CO{sub 2} emissions can be overcome. Permanent and safe methods for CO{sub 2} capture and disposal/storage need to be developed. Mineralization of stationary-source CO{sub 2} emissions as carbonates can provide such safe capture and long-term sequestration. Mg(OH){sub 2} carbonation is a leading process candidate, which generates the stable naturally occurring mineral magnesite (MgCO{sub 3}) and water. Key to process cost and viability are the carbonation reaction rate and its degree of completion. This process, which involves simultaneous dehydroxylation and carbonation is very promising, but far from optimized. In order to optimize the dehydroxylation/carbonation process, an atomic-level understanding of the mechanisms involved is needed. Since Mg(OH){sub 2} dehydroxylation is intimately associated with the carbonation process, its mechanisms are also of direct interest in understanding and optimizing the process. In the first project year, our investigations have focused on developing an atomic-level understanding of the dehydroxylation/carbonation reaction mechanisms that govern the overall carbonation reaction process in well crystallized material. In years two and three, we will also explore the roles of crystalline defects and impurities. Environmental-cell, dynamic high-resolution transmission electron microscopy has been used to directly observe the dehydroxylation process at the atomic-level for the first time. These observations were combined with advanced computational modeling studies to better elucidate the atomic-level process. These studies were combined with direct carbonation studies to better elucidate dehydroxylation/carbonation reaction mechanisms. Dehydroxylation follows a lamellar nucleation and growth process involving oxide layer formation. These layers form lamellar oxyhydroxide regions, which can

  2. Atomic-layer-deposition-assisted formation of carbon nanoflakes on metal oxides and energy storage application.

    PubMed

    Guan, Cao; Zeng, Zhiyuan; Li, Xianglin; Cao, Xiehong; Fan, Yu; Xia, Xinhui; Pan, Guoxiang; Zhang, Hua; Fan, Hong Jin

    2014-01-29

    Nanostructured carbon is widely used in energy storage devices (e.g., Li-ion and Li-air batteries and supercapacitors). A new method is developed for the generation of carbon nanoflakes on various metal oxide nanostructures by combining atomic layer deposition (ALD) and glucose carbonization. Various metal oxide@nanoflake carbon (MO@f-C) core-branch nanostructures are obtained. For the mechanism, it is proposed that the ALD Al2 O3 and glucose form a composite layer. Upon thermal annealing, the composite layer becomes fragmented and moves outward, accompanied by carbon deposition on the alumina skeleton. When tested as electrochemical supercapacitor electrode, the hierarchical MO@f-C nanostructures exhibit better properties compared with the pristine metal oxides or the carbon coating without ALD. The enhancement can be ascribed to increased specific surface areas and electric conductivity due to the carbon flake coating. This peculiar carbon coating method with the unique hierarchical nanostructure may provide a new insight into the preparation of 'oxides + carbon' hybrid electrode materials for energy storage applications.

  3. Application of Nanoparticles/Nanowires and Carbon Nanotubes for Breast Cancer Research

    DTIC Science & Technology

    2005-09-01

    stage can be a priceless gift to patients suffering from this disease . With progress in the area of nanotechnology, it is now possible to synthesize...applications of mAb-SWCNT to detect a wide variety of surface markers on diseased cells, which could lead to sensitive nanotube-based biosensors for detecting...various disease diagnoses. Significant progress in interfacing carbon nanotubes with biological materials has been made in key areas such as aqueous

  4. Silicon solar cell performance deposited by diamond like carbon thin film ;Atomic oxygen effects;

    NASA Astrophysics Data System (ADS)

    Aghaei, Abbas Ail; Eshaghi, Akbar; Karami, Esmaeil

    2017-09-01

    In this research, a diamond-like carbon thin film was deposited on p-type polycrystalline silicon solar cell via plasma-enhanced chemical vapor deposition method by using methane and hydrogen gases. The effect of atomic oxygen on the functioning of silicon coated DLC thin film and silicon was investigated. Raman spectroscopy, field emission scanning electron microscopy, atomic force microscopy and attenuated total reflection-Fourier transform infrared spectroscopy were used to characterize the structure and morphology of the DLC thin film. Photocurrent-voltage characteristics of the silicon solar cell were carried out using a solar simulator. The results showed that atomic oxygen exposure induced the including oxidation, structural changes, cross-linking reactions and bond breaking of the DLC film; thus reducing the optical properties. The photocurrent-voltage characteristics showed that although the properties of the fabricated thin film were decreased after being exposed to destructive rays, when compared with solar cell without any coating, it could protect it in atomic oxygen condition enhancing solar cell efficiency up to 12%. Thus, it can be said that diamond-like carbon thin layer protect the solar cell against atomic oxygen exposure.

  5. Theoretical realization of cluster-assembled hydrogen storage materials based on terminated carbon atomic chains.

    PubMed

    Liu, Chun-Sheng; An, Hui; Guo, Ling-Ju; Zeng, Zhi; Ju, Xin

    2011-01-14

    The capacity of carbon atomic chains with different terminations for hydrogen storage is studied using first-principles density functional theory calculations. Unlike the physisorption of H(2) on the H-terminated chain, we show that two Li (Na) atoms each capping one end of the odd- or even-numbered carbon chain can hold ten H(2) molecules with optimal binding energies for room temperature storage. The hybridization of the Li 2p states with the H(2)σ orbitals contributes to the H(2) adsorption. However, the binding mechanism of the H(2) molecules on Na arises only from the polarization interaction between the charged Na atom and the H(2). Interestingly, additional H(2) molecules can be bound to the carbon atoms at the chain ends due to the charge transfer between Li 2s2p (Na 3s) and C 2p states. More importantly, dimerization of these isolated metal-capped chains does not affect the hydrogen binding energy significantly. In addition, a single chain can be stabilized effectively by the C(60) fullerenes termination. With a hydrogen uptake of ∼10 wt.% on Li-coated C(60)-C(n)-C(60) (n = 5, 8), the Li(12)C(60)-C(n)-Li(12)C(60) complex, keeping the number of adsorbed H(2) molecules per Li and stabilizing the dispersion of individual Li atoms, can serve as better building blocks of polymers than the (Li(12)C(60))(2) dimer. These findings suggest a new route to design cluster-assembled hydrogen storage materials based on terminated sp carbon chains.

  6. Recent Advances in Atomic Metal Doping of Carbon-based Nanomaterials for Energy Conversion.

    PubMed

    Bayatsarmadi, Bita; Zheng, Yao; Vasileff, Anthony; Qiao, Shi-Zhang

    2017-04-12

    Nanostructured metal-contained catalysts are one of the most widely used types of catalysts applied to facilitate some of sluggish electrochemical reactions. However, the high activity of these catalysts cannot be sustained over a variety of pH ranges. In an effort to develop highly active and stable metal-contained catalysts, various approaches have been pursued with an emphasis on metal particle size reduction and doping on carbon-based supports. These techniques enhances the metal-support interactions, originating from the chemical bonding effect between the metal dopants and carbon support and the associated interface, as well as the charge transfer between the atomic metal species and carbon framework. This provides an opportunity to tune the well-defined metal active centers and optimize their activity, selectivity and stability of this type of (electro)catalyst. Herein, recent advances in synthesis strategies, characterization and catalytic performance of single atom metal dopants on carbon-based nanomaterials are highlighted with attempts to understand the electronic structure and spatial arrangement of individual atoms as well as their interaction with the supports. Applications of these new materials in a wide range of potential electrocatalytic processes in renewable energy conversion systems are also discussed with emphasis on future directions in this active field of research.

  7. Diamond Nanowire for UV Detection

    DTIC Science & Technology

    2010-02-28

    ten top physics stories of 2007” by the American Institute of Physics. Diamond, nanowire, ultraviolet, detector, nanotechnology, carbon, optics, nano ...material has been made, and resulted in a surprising discovery – bismuth when nano -patterned could undergo a phase transition from metallic to insulating...Sylvain Cloutier, Steven Palefsky, Jimmy Xu. Synthesis of Diamond Nanowires using Atmospheric-Pressure Chemical Vapor Deposition. (In review, at Nano

  8. Enhanced ionized impurity scattering in nanowires

    NASA Astrophysics Data System (ADS)

    Oh, Jung Hyun; Lee, Seok-Hee; Shin, Mincheol

    2013-06-01

    The electronic resistivity in silicon nanowires is investigated by taking into account scattering as well as the donor deactivation from the dielectric mismatch. The effects of poorly screened dopant atoms from the dielectric mismatch and variable carrier density in nanowires are found to play a crucial role in determining the nanowire resistivity. Using Green's function method within the self-consistent Born approximation, it is shown that donor deactivation and ionized impurity scattering combined with the charged interface traps successfully to explain the increase in the resistivity of Si nanowires while reducing the radius, measured by Björk et al. [Nature Nanotech. 4, 103 (2009)].

  9. Reactions of atomic carbon with oxygenated compounds and the investigation of fullerene chemistry

    SciTech Connect

    Chang, Tsongming.

    1993-01-01

    The reaction of atomic carbon with oxygenated organics produces CO and an energetic fragment. Reactions involving deoxygenation of carbonyl compounds to carbenes, epoxides to alkenes, and ethers to a pair of radicals have been investigated. Carbon atom deoxygenation of cyclopentanone and cylcopentene oxide give the cleavage products, ethylene and allene, along with cyclopentene. The use of 2,2,5,5-d[sub 4]-cyclopentanone as the substrate reveals the direct cleavage of cyclopentanylidene carbene is occurring. A calculation of the energetics of this reaction at the MP4/6-31G[sup *]//6-31G[sup *] level suggests a nonconcerted cleavage via a biradical intermediate. Carbon atoms deoxygenate cyclohexene. Inert gas deactivated energetic cyclohexene. The deoxygenation of other oxygenated compounds by atomic carbon, such as 7-oxabicyclo[2.2.1]heptane to cyclohexane-1,4-diyl biradical, 1,2-epoxy-5-hexane to energetic 1,S-hexadiene, allyl ether to allyl radicals, and [gamma]-butyrolactone to trimethylene-1,3-diyl biradical have also been carried out. Methylketene was deoxygenated to vinylidene carbene which rearranges to propyne via a 1,2-H shift. Dimethylketene was deoxygenated to dimethylethylidene carbene which gives 2-butyne via a 1,2-methyl shift and 1,3-butadiene via a vicinal C-H bond insertion. The addition of hydrogen donors to systems in which C[sub 60] is generated results in the formation of polycyclic aromatic hydrocarbons whose carbon skeleton might represent intermediates in fullerene formation. Based on this result, the author proposed a mechanism of fullerene formation. The use of various amounts of propene as a trap showed that the yield of fullerenes decreases as the amount of the trapped product increases. Attempts to trap intermediates in fullerene formation using halides and metals have been studied. The author has attempted metal encapsulation reactions and investigated some possible chemical reactions of fullerenes.

  10. Confinement induced binding in noble gas atoms within a BN-doped carbon nanotube

    NASA Astrophysics Data System (ADS)

    Chakraborty, Debdutta; Chattaraj, Pratim Kumar

    2015-02-01

    Confinement induced binding interaction patterns for noble gas atoms (Hen/m, Arn, Krn; n = 2, m = 3) atoms inside pristine and -BN doped (3, 3) single walled carbon nanotube (SWCNT) have been studied through density functional theory calculations. The kinetic stability for He dimer and trimer has been investigated at 100 K and 300 K through an ab initio molecular dynamics simulation. The positive role of doping in SWCNT in enhancing the nature of interaction as well as the kinetic stability of the said systems has been found.

  11. Formation and stability of crystalline and amorphous Al2O3 layers deposited on Ga2O3 nanowires by atomic layer epitaxy

    NASA Astrophysics Data System (ADS)

    Katz, M. B.; Twigg, M. E.; Prokes, S. M.

    2016-09-01

    Although the crystalline α and γ phases are the most stable forms of alumina, small-diameter (<6 nm) nanoparticles are known to be completely amorphous, due to the surface energy being correspondingly lower for the less stable non-crystalline phase. Al2O3 films with a thickness of 5 nm grown by low temperature (200 °C) atomic layer deposition (ALD) on small-diameter (<20 nm) Ga2O3 nanowires (NWs), however, are identified by transmission electron microscopy as belonging to the α, γ, and possibly θ crystalline phases of Al2O3, while films deposited on larger diameter (>20 nm) NWs are found to be amorphous. Indeed, until recently, all Al2O3, films deposited by low-temperature ALD using trimethylaluminum and water have been reported to be amorphous, regardless of film thickness or substrate. The formation of a crystalline ALD film can be understood in terms of the energetics of misfit dislocations that maintain the registry between the ALD film and the NW substrate, as well as the influence of strain and surface energy. The decreasing energy of co-axial misfit dislocations with NW diameter results in a corresponding decrease in the contribution of the Al2O3/Ga2O3 interface to the free energy, while the interfacial energy for an amorphous film is independent of the NW diameter. Therefore, for NW cores of sufficiently small diameter, the free energy contribution of the Al2O3/Ga2O3 interface is smaller for crystalline films than for amorphous films, thereby favoring the formation of crystalline films for small-diameter NWs. For ALD Al2O3 films of 10 nm thickness deposited on small-diameter Ga2O3 NWs, however, only the first 5 nm of the ALD film is found to be crystalline, possibly due to well-established kinetic limitations to low temperature epitaxial growth.

  12. Vibrational spectra of nanowires measured using laser doppler vibrometry and STM studies of epitaxial graphene : an LDRD fellowship report.

    SciTech Connect

    Biedermann, Laura Butler

    2009-09-01

    A few of the many applications for nanowires are high-aspect ratio conductive atomic force microscope (AFM) cantilever tips, force and mass sensors, and high-frequency resonators. Reliable estimates for the elastic modulus of nanowires and the quality factor of their oscillations are of interest to help enable these applications. Furthermore, a real-time, non-destructive technique to measure the vibrational spectra of nanowires will help enable sensor applications based on nanowires and the use of nanowires as AFM cantilevers (rather than as tips for AFM cantilevers). Laser Doppler vibrometry is used to measure the vibration spectra of individual cantilevered nanowires, specifically multiwalled carbon nanotubes (MWNTs) and silver gallium nanoneedles. Since the entire vibration spectrum is measured with high frequency resolution (100 Hz for a 10 MHz frequency scan), the resonant frequencies and quality factors of the nanowires are accurately determined. Using Euler-Bernoulli beam theory, the elastic modulus and spring constant can be calculated from the resonance frequencies of the oscillation spectrum and the dimensions of the nanowires, which are obtained from parallel SEM studies. Because the diameters of the nanowires studied are smaller than the wavelength of the vibrometer's laser, Mie scattering is used to estimate the lower diameter limit for nanowires whose vibration can be measured in this way. The techniques developed in this thesis can be used to measure the vibrational spectra of any suspended nanowire with high frequency resolution Two different nanowires were measured - MWNTs and Ag{sub 2}Ga nanoneedles. Measurements of the thermal vibration spectra of MWNTs under ambient conditions showed that the elastic modulus, E, of plasma-enhanced chemical vapor deposition (PECVD) MWNTs is 37 {+-} 26 GPa, well within the range of E previously reported for CVD-grown MWNTs. Since the Ag{sub 2}Ga nanoneedles have a greater optical scattering efficiency than MWNTs

  13. Octagraphene as a versatile carbon atomic sheet for novel nanotubes, unconventional fullerenes, and hydrogen storage

    NASA Astrophysics Data System (ADS)

    Sheng, Xian-Lei; Cui, Hui-Juan; Ye, Fei; Yan, Qing-Bo; Zheng, Qing-Rong; Su, Gang

    2012-10-01

    We study a versatile structurally favorable periodic sp2-bonded carbon atomic planar sheet with C4v symmetry by means of the first-principles calculations. This carbon allotrope is composed of carbon octagons and squares with two bond lengths and is thus dubbed as octagraphene. It is a semimetal with the Fermi surface consisting of one hole and one electron pocket, whose low-energy physics can be well described by a tight-binding model of π-electrons. Its Young's modulus, breaking strength, and Poisson's ratio are obtained to be 306 N/m, 34.4 N/m, and 0.13, respectively, which are close to those of graphene. The novel sawtooth and armchair carbon nanotubes as well as unconventional fullerenes can also be constructed from octagraphene. It is found that the Ti-absorbed octagraphene can be allowed for hydrogen storage with capacity around 7.76 wt. %.

  14. Three-Dimensional NiCo2O4@Polypyrrole Coaxial Nanowire Arrays on Carbon Textiles for High-Performance Flexible Asymmetric Solid-State Supercapacitor.

    PubMed

    Kong, Dezhi; Ren, Weina; Cheng, Chuanwei; Wang, Ye; Huang, Zhixiang; Yang, Hui Ying

    2015-09-30

    In this article, we report a novel electrode of NiCo2O4 nanowire arrays (NWAs) on carbon textiles with a polypyrrole (PPy) nanosphere shell layer to enhance the pseudocapacitive performance. The merits of highly conductive PPy and short ion transport channels in ordered NiCo2O4 mesoporous nanowire arrays together with the synergistic effect between NiCo2O4 and PPy result in a high specific capacitance of 2244 F g(-1), excellent rate capability, and cycling stability in NiCo2O4/PPy electrode. Moreover, a lightweight and flexible asymmetric supercapacitor (ASC) device is successfully assembled using the hybrid NiCo2O4@PPy NWAs and activated carbon (AC) as electrodes, achieving high energy density (58.8 W h kg(-1) at 365 W kg(-1)), outstanding power density (10.2 kW kg(-1) at 28.4 W h kg(-1)) and excellent cycling stability (∼89.2% retention after 5000 cycles), as well as high flexibility. The three-dimensional coaxial architecture design opens up new opportunities to fabricate a high-performance flexible supercapacitor for future portable and wearable electronic devices.

  15. Studies of hydrogen diffusion, hydrocarbon adsorption and palladium nanowires on silicon(001) with scanning tunneling microscopy and atom tracking

    NASA Astrophysics Data System (ADS)

    Freelon, Byron Kendall

    The design and preliminary microfabrication of a scanning tunneling microscope (STM) has been undertaken. A three-dimensional suspended microelectromechanical system (MEMS) was started to master preliminary micro-processing techniques. The design of an STM weighing 2 x 10-10 kg, consisting of single crystal silicon beams is based on capacitive comb and torsional drives as a means of actuation. The mechanical resonant frequencies of the x, y and z drives are 100 kHz, 100 kHz, and 1MHz, respectively. The microfabrication was performed using single crystal silicon, reactive ion etching, and metallization (SCREAM). In addition, studies on the silicon (001) surface were performed in three areas: hydrogen diffusion, hydrocarbon adsorption, and selective palladium deposition. The diffusion of hydrogen was measured and compared to deuterium using STM atom tracking. Attempt frequencies and activation energies for diffusion along the dimer row (intrarow) and between the atoms of a single Si dimer (intradimer) are extracted. For intrarow H diffusion, an activation energy of 1.75 +/- 0.10 eV and an attempt frequency of 1014.5+/-0.8 Hz are found. For intradimer H diffusion, an activation energy of 1.01 +/- 0.05 eV and a low attempt frequency of 1010.3+/-0.5 diffusion are also determined. Alkane and Alkene hydrocarbons were deposited on Si(001). The alkanes were observed to have low sticking coefficients in addition to no regularized adsorption morphology. Alkenes had high sticking probabilities. Anthracene and thiophene (C4H4S) were found to have high sticking coefficients in addition to adsorbing along dimer rows. STM images support the theoretical prediction that thiophene adsorbs atop, to one side of the dimer rows. We find that the diffusion of thiophene rules out Si-Si dimer bonds breaking upon C4H4S adsorption. The annealing of naphthalene induces a c(4 x 4) phase of Si(001) at 1000K, and SiC cluster formation near BOOK. We demonstrate selective physical vapor deposition

  16. One-Pot Synthesis of Penta-twinned Palladium Nanowires and Their Enhanced Electrocatalytic Properties.

    PubMed

    Huang, Hongwen; Ruditskiy, Aleksey; Choi, Sang-Il; Zhang, Lei; Liu, Jingyue; Ye, Zhizhen; Xia, Younan

    2017-09-13

    This article reports the design and successful implementation of a one-pot, polyol method for the synthesis of penta-twinned Pd nanowires with diameters below 8 nm and aspect ratios up to 100. The key to the success of this protocol is the controlled reduction of Na2PdCl4 by diethylene glycol and ascorbic acid through the introduction of NaI and HCl. The I(-) and H(+) ions can slow the reduction kinetics by forming PdI4(2-) and inhibiting the dissociation of ascorbic acid, respectively. When the initial reduction rate is tuned into the proper regime, Pd decahedral seeds with a penta-twinned structure appear during nucleation. In the presence of I(-) ions as a selective capping agent toward the Pd(100) surface, the decahedral seeds can be directed to grow axially into penta-twinned nanorods and then nanowires. The Pd nanowires are found to evolve into multiply twinned particles if the reaction time is extended beyond 1.5 h, owing to the involvement of oxidative etching. When supported on carbon, the Pd nanowires show greatly enhanced specific electrocatalytic activities, more than five times the value for commercial Pd/C toward formic acid oxidation and three times the value for Pt/C toward oxygen reduction under an alkaline condition. In addition, the carbon-supported Pd nanowires exhibit greatly enhanced electrocatalytic durability toward both reactions. Furthermore, we demonstrate that the Pd nanowires can serve as sacrificial templates for the conformal deposition of Pt atoms to generate Pd@Pt core-sheath nanowires and then Pd-Pt nanotubes with a well-defined surface structure.

  17. Microwave absorption properties of carbon nanocoils coated with highly controlled magnetic materials by atomic layer deposition.

    PubMed

    Wang, Guizhen; Gao, Zhe; Tang, Shiwei; Chen, Chaoqiu; Duan, Feifei; Zhao, Shichao; Lin, Shiwei; Feng, Yuhong; Zhou, Lei; Qin, Yong

    2012-12-21

    In this work, atomic layer deposition is applied to coat carbon nanocoils with magnetic Fe(3)O(4) or Ni. The coatings have a uniform and highly controlled thickness. The coated nanocoils with coaxial multilayer nanostructures exhibit remarkably improved microwave absorption properties compared to the pristine carbon nanocoils. The enhanced absorption ability arises from the efficient complementarity between complex permittivity and permeability, chiral morphology, and multilayer structure of the products. This method can be extended to exploit other composite materials benefiting from its convenient control of the impedance matching and combination of dielectric-magnetic multiple loss mechanisms for microwave absorption applications.

  18. Fabrication and Characterization of Oriented Carbon Atom Wires Assembled on Gold

    SciTech Connect

    Xue,K.H.; Wu,L.; Chen, S.-P.; Wanga, L.X.; Wei, R.-B.; Xu, S.-M.; Cui, L.; Mao, B.-W.; Tian, Z.-Q.; Zen, C.-H.; Sun, S.-G.; Zhu, Y.-M.

    2009-02-17

    Carbon atom wires (CAWs) are of the sp-hybridized allotrope of carbon. To augment the extraordinary features based on sp-hybridization, we developed an approach to make CAWs be self-assembled and orderly organized on Au substrate. The self-assembling process was investigated in situ by using scanning tunneling microscopy (STM) and electrochemical quartz crystal microbalance (EQCM). The properties of the assembled film were characterized by voltammetry, Raman spectroscopy, electron energy loss spectroscopy (EELS), and the contact angle measurements. Experimental results indicated that the assembled CAW film was of the good structural integrity and well organized, with the sp-hybridized features enhanced.

  19. Angular distribution of photoelectrons from atomic oxygen, nitrogen and carbon. [in upper atmosphere

    NASA Technical Reports Server (NTRS)

    Manson, S. J.; Kennedy, D. J.; Starace, A. F.; Dill, D.

    1974-01-01

    The angular distributions of photoelectrons from atomic oxygen, nitrogen, and carbon are calculated. Both Hartree-Fock and Hartree-Slater (Herman-Skillman) wave functions are used for oxygen, and the agreement is excellent; thus only Hartree-Slater functions are used for carbon and nitrogen. The pitch-angle distribution of photoelectrons is discussed, and it is shown that previous approximations of energy-independent isotropic or sin squared theta distributions are at odds with the authors' results, which vary with energy. This variation with energy is discussed, as is the reliability of these calculations.

  20. A Molecular Dynamics of Cold Neutral Atoms Captured by Carbon Nanotube Under Electric Field and Thermal Effect as a Selective Atoms Sensor.

    PubMed

    Santos, Elson C; Neto, Abel F G; Maneschy, Carlos E; Chen, James; Ramalho, Teodorico C; Neto, A M J C

    2015-05-01

    Here we analyzed several physical behaviors through computational simulation of systems consisting of a zig-zag type carbon nanotube and relaxed cold atoms (Rb, Au, Si and Ar). These atoms were chosen due to their different chemical properties. The atoms individually were relaxed on the outside of the nanotube during the simulations. Each system was found under the influence of a uniform electric field parallel to the carbon nanotube and under the thermal effect of the initial temperature at the simulations. Because of the electric field, the cold atoms orbited the carbon nanotube while increasing the initial temperature allowed the variation of the radius of the orbiting atoms. We calculated the following quantities: kinetic energy, potential energy and total energy and in situ temperature, molar entropy variation and average radius of the orbit of the atoms. Our data suggest that only the action of electric field is enough to generate the attractive potential and this system could be used as a selected atoms sensor.

  1. An upper limit to the atomic carbon abundance in the Orion plateau

    NASA Technical Reports Server (NTRS)

    Beichman, C. A.; Phillips, T. G.; Wootten, H. A.; Frerking, M.

    1982-01-01

    Observations made of the atomic carbon line at 492 GHz toward OMC-1 show no evidence for the high velocity dispersion wings observed for many molecular rotational lines. The 3sigma upper limit to the CI column density, NCI, is 6.9 x 10 to the 17th per sq cm for velocities greater than or equal to 4 km per sec from the line center. This upper limit corresponds to a ratio of CI to CO abundances as low as less than 0.13, depending on the assumed CO column density. Atomic carbon is apparently depleted by a factor as large as five in the hot plateau gas, relative to its abundance in other molecular clouds. The lack of CI in the plateau source may mean that the shocks thought to be present in the region are not dissociative in nature and thus do not produce the UV radiation required to convert CO into CI.

  2. The abundance of atomic carbon near the ionization fronts in M17 and S140

    NASA Technical Reports Server (NTRS)

    Keene, J.; Blake, G. A.; Phillips, T. G.; Huggins, P. J.; Beichman, C. A.

    1985-01-01

    The 492 GHz ground-state line of atomic carbon in the edge-on ionization fronts in M17 and S140 were observed. It was found that, contrary to expectation, the C I emission peaks farther into the molecular cloud from the ionization front than does the CO. In fact the peak C I abundance in M17 occurs more than 60 mag of visual extinction into the cloud from the ionization front. Calculations of the ratio of C I to CO column densities yield values of 0.1-0.2. These observations do not support chemical models which predict that neutral atomic carbon should be found only near the edges of molelcular clouds. Other models are discussed which may explain the observations.

  3. Small angle neutron and X-ray studies of carbon structures with metal atoms

    NASA Astrophysics Data System (ADS)

    Lebedev, V. T.; Szhogina, A. A.; Bairamukov, V. Yu

    2017-05-01

    Encapsulation of metal atoms inside carbon single-wall cages or within multi-layer cells has been realized using molecular precursors and high temperature processes transforming them into desirable structures. Endohedral fullerenols Fe@C60(OH)X with 3d-metal (iron) have been studied by SANS in aqueous solutions where they form stable globular clusters with radii R C ∼ 10-12 nm and aggregation numbers N C ∼ 104. This self-assembly is a crucial feature of paramagnetic fullerenols as perspective contrast agents for Magneto-Resonance Imaging in medicine. Cellular carbon-metal structures have been created by the pyrolysis of diphthalocyanines of lanthanides and actinides. It was established that these ultra porous matrices consist of globular cells of molecular precursor size (∼ 1 nm) which are aggregated into superstructures. This provides retain of metal atoms inside matrices which may serve for safety storage of spent fuel of nuclear power plants.

  4. Capture and ionization detection of laser-cooled rubidium atoms with a charged suspended carbon nanotube

    NASA Astrophysics Data System (ADS)

    Ristroph, Trygve Gibbens

    The capture and ionization of neutral rubidium atoms with a positively charged suspended carbon nanotube is realized. The electric field surrounding the nanotube polarizes and pulls atoms into the highly singular attractive inverse square potential. Atoms are ionized by the nanotube, and Rb+ ions are ejected radially and subsequently detected individually. The entire process of capture, ionization, and ion-detection reveals a rich set of behavior, probing the dynamics of laser-cooled atoms as well as nanotube and ionization physics. When the device is used as an atom detector, the cold-atom ionization signal replicates time-dependent features in the instantaneous atom beam density on sub-millisecond time scales. This time resolution allows a time-of-flight measurement of atom velocity, corroborated with a laser absorption measurement. Position sensitivity on the 200 micron scale is demonstrated, as the detector is scanned to map out the atom beam transverse mode profile, a capability otherwise forbidden by the system's optical access. A measurement of the nanotube ionization cross-section as a function of atomic velocity and charging voltage shows the capture process is dominated by an inverse square potential energy. The cross-section reveals an inverse velocity scaling, consistent with the prediction. The analogous charging voltage measurement shows a linear scaling in voltage with measured and predicted slopes in agreement. Sending current through the nanotube changes the voltage offset of the cross-section versus voltage curve. This suggests that the ionization occurs in close proximity to the nanotube surface and is therefore sensitive to its electronic and mechanical properties. Theoretical foundations are developed to describe the capture and ionization physics involved in observing the quantization of atomic orbital angular momentum with the detector. For experimentally accessible parameters, the observation of the quantized conductance of neutral atoms is

  5. Doping of carbon nanotubes with aluminum atom to improve Pt adsorption

    NASA Astrophysics Data System (ADS)

    Ganji, M. D.; Ahangari, M. Ghorbanzadeh; Khosravi, A.

    2014-01-01

    We implement the ab initio van der Waals (vdW) calculations at the density functional level of theory (vdW-DF) for the investigation of Pt adsorption ability of Al-doped carbon nanotubes (Al-CNTs). We present and discuss the energetically favorable sites for a single Pt atom adsorbed on the surface of Al-CNTs. Our results show significantly increment in the binding energy of Pt on the Al-CNT compared with pristine CNTs. We also find that Pt adsorption ability of Al-CNTs is more stronger than that of B- and N-doped CNTs. This is explained by the negative charges introduced in the neighboring C atoms by dopant atom. Our results verify that Al-doped CNTs seems to be more suitable materials for Pt adsorption than pure and also B- and N-doped CNTs.

  6. Reactive pathways of hydrogen and carbon removal from organosilicate glass low- κ films by F atoms

    NASA Astrophysics Data System (ADS)

    Voronina, Ekaterina N.; Mankelevich, Yuri A.; Rakhimova, Tatyana V.

    2017-07-01

    Direct molecular dynamic simulation on the base of the density functional theory (DFT) method is used to study some critical reactions of F atoms with organosilicate glass (OSG) low-κ films. Here static and dynamic DFT-based approaches are applied for a variety of reactive pathways of hydrogen and carbon removal in the form of volatile products (HF, CF2 and CF3 molecules) from initial SiCH3 surface groups. These reactions constitute an important part of the proposed multi-step mechanism of OSG films damage and etching by thermal F atoms. Two models (POSS and TMCTS macromolecules and their modifications) are used to illustrate the peculiarities and dynamics of the successive reactions of F atoms with the initial SiCH3 and appeared SiCHxFy (x + y ≤ 3) surface groups. Contribution to the Topical Issue "Dynamics of Molecular Systems (MOLEC 2016)", edited by Alberto Garcia-Vela, Luis Banares and Maria Luisa Senent.

  7. Detection of the 610 micron /492 GHz/ line of interstellar atomic carbon

    NASA Technical Reports Server (NTRS)

    Phillips, T. G.; Huggins, P. J.; Kuiper, T. B. H.; Miller, R. E.

    1980-01-01

    The ground-state transition of neutral atomic carbon, 3P1-3P0, has been detected in the interstellar medium at the frequency of 492.162 GHz determined in the laboratory by Saykally and Evenson (1980). The observations were made from the NASA Kuiper Airborne Observatory using an InSb heterodyne bolometer receiver. The line was detected as strong emission from eight molecular clouds and apparently provides a widely useful probe of the interstellar medium.

  8. Evidence for sp3 carbon atoms in the RbC60 dimer phase

    NASA Astrophysics Data System (ADS)

    Thier, K.-F.; Mehring, M.; Rachdi, F.

    1997-01-01

    High resolution 13C NMR experiments prove the existence of sp3 carbon atoms which are assigned to the dimer bonds in the quenched phase of RbC60. The relative intensities of the sp3 lines support a model where the C60 monomers are connected via a single bond. Spin-lattice relaxation measurements and 13C spectral changes reveal the transition to the polymer phase above 200 K.

  9. Catalytic enantioselective Nazarov cyclization: construction of vicinal all-carbon-atom quaternary stereocenters.

    PubMed

    Jolit, Anais; Walleser, Patrick M; Yap, Glenn P A; Tius, Marcus A

    2014-06-10

    The diastereoselective asymmetric synthesis of vicinal all-carbon-atom quaternary stereocenters is a challenging problem in organic synthesis for which only few solutions have been described. A catalytic asymmetric Nazarov cyclization of fully substituted dienones that provides cyclopentenone derivatives with vicinal quaternary stereocenters in high optical purity and as single diastereoisomers is now reported. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Direct observation of Sn crystal growth during the lithiation and delithiation processes of SnO(2) nanowires.

    PubMed

    Zhang, Li Qiang; Liu, Xiao Hua; Perng, Ya-Chuan; Cho, Jea; Chang, Jane P; Mao, Scott X; Ye, Zhi Zhen; Huang, Jian Yu

    2012-11-01

    Tin (Sn) crystal growth on Sn-based anodes in lithium ion batteries is hazardous for reasons such as possible short-circuit failure by Sn whiskers and Sn-catalyzed electrolyte decomposition, but the growth mechanism of Sn crystals during battery cycling is not clear. Here we report different growth mechanisms of Sn crystal during the lithiation and delithiation processes of SnO(2) nanowires revealed by in situ transmission electron microscopy (TEM). Large spherical Sn nanoparticles with sizes of 20-200nm grew instantaneously upon lithiation of a single-crystalline SnO(2) nanowire at large current density (j>20A/cm(2)), which suppressed formation of the Li(x)Sn alloy but promoted agglomeration of Sn atoms. Control experiments of Joule-heating (j≈2400A/cm(2)) the pristine SnO(2) nanowires resulted in melting of the SnO(2) nanowires but not Sn particle growth, indicating that the abnormal Sn particle growth was induced by both chemical reduction (i.e., breaking the SnO(2) lattice to produce Sn atoms) and agglomeration of the Sn atoms assisted by Joule heating. Intriguingly, Sn crystals grew out of the nanowire surface via a different "squeeze-out" mechanism during delithiation of the lithiated SnO(2) nanowires coated with an ultra-thin solid electrolyte LiAlSiO(x) layer. It is attributed to the negative stress gradient generated by the fast Li extraction in the surface region through the Li(+)-conducting LiAlSiO(x) layer. Our previous studies showed that Sn precipitation does not occur in the carbon-coated SnO(2) nanowires, highlighting the effect of nanoengineering on tailoring the electrochemical reaction kinetics to suppress the hazardous Sn whiskers or nanoparticles formation in a lithium ion battery.

  11. Controlled fabrication of theophylline imprinted polymers on multiwalled carbon nanotubes via atom transfer radical polymerization.

    PubMed

    Xu, Jianxiong; Gao, Yong; Li, Huaming

    2011-02-01

    Theophylline imprinted polymers were synthesized on the surface of multiwalled carbon nanotubes via atom transfer radical polymerization using brominated multiwalled carbon nanotubes as an initiator. The nanotube-based initiator was prepared by directly reacting acyl chloride-modified multiwalled carbon nanotubes with 2-hydroxylethyl-2'-bromoisobutyrate. The grafting copolymerization of 2-hydroxyethyl-2-methyl-2-propenoate and ethylene glycol dimethacrylate in the presence of template theophylline led to thin molecularly imprinted polymer films coating multiwalled carbon nanotubes. The thickness of molecularly imprinted polymer films prepared in this study was about 5 nm as determined by transmission electron microscopy. Fourier-transform infrared spectroscopy was utilized to follow the introduction of initiator groups as well as polymers on the carbon nanotube surfaces. Thermogravimetric analysis indicated that the molecularly imprinted polymers were successfully grown from the carbon nanotube surfaces, with the final products having a polymer weight percentage of ca. 50 wt%. The adsorption properties, such as adsorption dynamics, special binding and selective recognition capacity, of the as-prepared molecularly imprinted polymer films were evaluated. The results demonstrated that the composite of molecularly imprinted polymers and multiwalled carbon nanotubes not only possessed a rapid dynamics but also exhibited a good selectivity toward theophylline, compared to caffeine.

  12. Characteristics of Al-doped ZnO films grown by atomic layer deposition for silicon nanowire photovoltaic device.

    PubMed

    Oh, Byeong-Yun; Han, Jin-Woo; Seo, Dae-Shik; Kim, Kwang-Young; Baek, Seong-Ho; Jang, Hwan Soo; Kim, Jae Hyun

    2012-07-01

    We report the structural, electrical, and optical characteristics of Al-doped ZnO (ZnO:Al) films deposited on glass by atomic layer deposition (ALD) with various Al2O3 film contents for use as transparent electrodes. Unlike films fabricated by a sputtering method, the diffraction peak position of the films deposited by ALD progressively moved to a higher angle with increasing Al2O3 film content. This indicates that Zn sites were effectively replaced by Al, due to layer-by-layer growth mechanism of ALD process which is based on alternate self-limiting surface chemical reactions. By adjusting the Al2O3 film content, a ZnO:Al film with low electrical resistivity (9.84 x 10(-4) Omega cm) was obtained at an Al2O3 film content of 3.17%, where the Al concentration, carrier mobility, optical transmittance, and bandgap energy were 2.8 wt%, 11.20 cm2 V(-1) s(-1), 94.23%, and 3.6 eV, respectively. Moreover, the estimated figure of merit value of our best sample was 8.2 m7Omega(-1). These results suggest that ZnO:Al films deposited by ALD could be useful for electronic devices in which especially require 3-dimensional conformal deposition of the transparent electrode and surface passivation.

  13. ATOMIC-LEVEL IMAGING OF CO2 DISPOSAL AS A CARBONATE MINERAL: OPTIMIZING REACTION PROCESS DESIGN

    SciTech Connect

    M.J. McKelvy; R. Sharma; A.V.G. Chizmeshya; H. Bearat; R.W. Carpenter

    2001-10-01

    Fossil fuels, especially coal, can support the energy demands of the world for centuries to come, if the environmental problems associated with CO{sub 2} emissions can be overcome. Permanent and safe methods for CO{sub 2} capture and disposal/storage need to be developed. Mineralization of stationary-source CO{sub 2} emissions as carbonates can provide such safe capture and long-term sequestration. Mg-rich lamellar-hydroxide based minerals (e.g., brucite and serpentine) offer a class of widely available, low-cost materials, with intriguing mineral carbonation potential. Carbonation of such materials inherently involves dehydroxylation, which can disrupt the material down to the atomic level. As such, controlled dehydroxylation, before and/or during carbonation, may provide an important parameter for enhancing carbonation reaction processes. Mg(OH){sub 2} was chosen as the model material for investigating lamellar hydroxide mineral dehydroxylation/carbonation mechanisms due to (i) its structural and chemical simplicity, (ii) interest in Mg(OH){sub 2} gas-solid carbonation as a potentially cost-effective CO{sub 2} mineral sequestration process component, and (iii) its structural and chemical similarity to other lamellar-hydroxide-based minerals (e.g., serpentine-based minerals) whose carbonation reaction processes are being explored due to their low-cost CO{sub 2} sequestration potential. Fundamental understanding of the mechanisms that govern dehydroxylation/carbonation processes is essential for minimizing the cost of any lamellar-hydroxide-based mineral carbonation sequestration process. This report covers the third year progress of this grant, as well as providing an integrated overview of the progress in years 1-3, as we have been granted a one-year no-cost extension to wrap up a few studies and publications to optimize project impact.

  14. ATOMIC-LEVEL IMAGING OF CO2 DISPOSAL AS A CARBONATE MINERAL: OPTIMIZING REACTION PROCESS DESIGN

    SciTech Connect

    M.J. McKelvy; R. Sharma; A.V.G. Chizmeshya; H. Bearat; R.W. Carpenter

    2002-11-01

    Fossil fuels, especially coal, can support the energy demands of the world for centuries to come, if the environmental problems associated with CO{sub 2} emissions can be overcome. Permanent and safe methods for CO{sub 2} capture and disposal/storage need to be developed. Mineralization of stationary-source CO{sub 2} emissions as carbonates can provide such safe capture and long-term sequestration. Mg-rich lamellar-hydroxide based minerals (e.g., brucite and serpentine) offer a class of widely available, low-cost materials, with intriguing mineral carbonation potential. Carbonation of such materials inherently involves dehydroxylation, which can disrupt the material down to the atomic level. As such, controlled dehydroxylation, before and/or during carbonation, may provide an important parameter for enhancing carbonation reaction processes. Mg(OH){sub 2} was chosen as the model material for investigating lamellar hydroxide mineral dehydroxylation/carbonation mechanisms due to (1) its structural and chemical simplicity, (2) interest in Mg(OH){sub 2} gas-solid carbonation as a potentially cost-effective CO{sub 2} mineral sequestration process component, and (3) its structural and chemical similarity to other lamellar-hydroxide-based minerals (e.g., serpentine-based minerals) whose carbonation reaction processes are being explored due to their low-cost CO{sub 2} sequestration potential. Fundamental understanding of the mechanisms that govern dehydroxylation/carbonation processes is essential for minimizing the cost of any lamellar-hydroxide-based mineral carbonation sequestration process. This final report covers the overall progress of this grant.

  15. Development of carbon electrodes for electrochemistry, solid-state electronics and multimodal atomic force microscopy imaging

    NASA Astrophysics Data System (ADS)

    Morton, Kirstin Claire

    Carbon is one of the most remarkable elements due to its wide abundance on Earth and its many allotropes, which include diamond and graphite. Many carbon allotropes are conductive and in recent decades scientists have discovered and synthesized many new forms of carbon, including graphene and carbon nanotubes. The work in this thesis specifically focuses on the fabrication and characterization of pyrolyzed parylene C (PPC), a conductive pyrocarbon, as an electrode material for diodes, as a conductive coating for atomic force microscopy (AFM) probes and as an ultramicroelectrode (UME) for the electrochemical interrogation of cellular systems in vitro. Herein, planar and three-dimensional (3D) PPC electrodes were microscopically, spectroscopically and electrochemically characterized. First, planar PPC films and PPC-coated nanopipettes were utilized to detect a model redox species, Ru(NH3) 6Cl3. Then, free-standing PPC thin films were chemically doped, with hydrazine and concentrated nitric acid, to yield p- and n-type carbon films. Doped PPC thin films were positioned in conjunction with doped silicon to create Schottky and p-n junction diodes for use in an alternating current half-wave rectifier circuit. Pyrolyzed parylene C has found particular merit as a 3D electrode coating of AFM probes. Current sensing-atomic force microscopy imaging in air of nanoscale metallic features was undertaken to demonstrate the electronic imaging applicability of PPC AFM probes. Upon further insulation with parylene C and modification with a focused ion beam, a PPC UME was microfabricated near the AFM probe apex and utilized for electrochemical imaging. Subsequently, scanning electrochemical microscopy-atomic force microscopy imaging was undertaken to electrochemically quantify and image the spatial location of dopamine exocytotic release, elicited mechanically via the AFM probe itself, from differentiated pheochromocytoma 12 cells in vitro.

  16. Highly aligned vertical GaN nanowires using submonolayer metal catalysts

    DOEpatents

    Wang, George T [Albuquerque, NM; Li, Qiming [Albuquerque, NM; Creighton, J Randall [Albuquerque, NM

    2010-06-29

    A method for forming vertically oriented, crystallographically aligned nanowires (nanocolumns) using monolayer or submonolayer quantities of metal atoms to form uniformly sized metal islands that serve as catalysts for MOCVD growth of Group III nitride nanowires.

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

    PubMed

    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.

  18. Investigation of the Interactions and Bonding between Carbon and Group VIII Metals at the Atomic Scale.

    PubMed

    Zoberbier, Thilo; Chamberlain, Thomas W; Biskupek, Johannes; Suyetin, Mikhail; Majouga, Alexander G; Besley, Elena; Kaiser, Ute; Khlobystov, Andrei N

    2016-03-23

    The nature and dynamics of bonding between Fe, Ru, Os, and single-walled carbon nanotubes (SWNTs) is studied by aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM). The metals catalyze a wide variety of different transformations ranging from ejection of carbon atoms from the nanotube sidewall to the formation of hollow carbon shells or metal carbide within the SWNT, depending on the nature of the metal. The electron beam of AC-HRTEM serves the dual purpose of providing energy to the specimen and simultaneously enabling imaging of chemical transformations. Careful control of the electron beam parameters, energy, flux, and dose allowed direct comparison between the metals, demonstrating that their chemical reactions with SWNTs are determined by a balance between the cohesive energy of the metal particles and the strength of the metal-carbon σ- or π-bonds. The pathways of transformations of a given metal can be drastically changed by applying different electron energies (80, 40, or 20 keV), thus demonstrating AC-HRTEM as a new tool to direct and study chemical reactions. The understanding of interactions and bonding between SWNT and metals revealed by AC-HRTEM at the atomic level has important implications for nanotube-based electronic devices and catalysis.

  19. Size dependence of melting of GaN nanowires with triangular cross sections

    SciTech Connect

    Wang, Zhiguo; Zu, Xiaotao; Gao, Fei; Weber, William J.

    2007-02-15

    Molecular dynamics simulations have been used to study the melting of GaN nanowires with triangular cross-sections. The curve of the potential energy, along with the atomic configuration is used to monitor the phase transition. The thermal stability of GaN nanowires is dependent on the size of the nanowires. The melting temperature of the GaN nanowires increases with the increasing of area cross-section of the nanowires to a saturation value. An interesting result is that of the nanowires start to melt from the edges, then the surface, and extends to the inner regions of nanowires as temperature increases.

  20. Practical use of a carbon nanotube attached to a blunt apex in an atomic force microscope

    SciTech Connect

    Kuwahara, Masashi; Abe, Hidekazu; Tokumoto, Hiroshi; Shima, Takayuki; Tominaga, Junji; Fukuda, Hajime

    2004-03-15

    A carbon nanotube (CNT) was successfully attached to a base probe with a blunt apex and subsequently used as a probe for an atomic force microscope (AFM). This setup demonstrates high spatial resolution properties, plus an advantage: we were able to readily identify the loss of the CNT from the end of the probe by the resultant sudden drop in resolution. This design of probe is expected to feature yet another advantage: that of relative immunity to accidental collision compared to a CNT attached to a commercially available sharp tip. We also discuss the problems specific to CNT-attached probes, which are carbon contamination of the sample surface and artifact images formed at the edge of pit structures. We demonstrate that carbon contamination can be suppressed by a rubbing procedure before the scanning use, and that pit artifacts can be eliminated by optimizing the CNT length.

  1. Cross section database for carbon atoms and ions: Electron-impact ionization, excitation, and charge exchange in collisions with hydrogen atoms

    SciTech Connect

    Suno, Hiroya . E-mail: suno@jamstec.go.jp; Kato, Takako

    2006-07-15

    A database has been constructed consisting of the recommended cross sections for electron-impact excitation and ionization of carbon atoms and ions C, C{sup +}-C{sup 5+}, asl as for charge exchange processes between carbon ions C{sup +}-C{sup 6+} and hydrogen atoms. We have collected a large amount of theoretical and experimental cross section data from the literature, and have critically assessed their accuracy. The recommended cross sections, the best values for use, are expressed in the form of simple analytical functions. These are also presented in graphical form.

  2. In Situ Integration of Ultrathin PtCu Nanowires with Reduced Graphene Oxide Nanosheets for Efficient Electrocatalytic Oxygen Reduction.

    PubMed

    Yan, Xiaoxiao; Chen, Yifan; Deng, Sihui; Yang, Yifan; Huang, Zhenna; Ge, Cunwang; Xu, Lin; Sun, Dongmei; Fu, Gengtao; Tang, Yawen

    2017-09-20

    Ultrathin Pt-based nanowires are considered as promising electrocatalysts due to their high atomic utilization efficiency and structural robustness. Moreover, integration of Pt-based nanowires with graphene oxide (GO) could further increase the electrocatalytic performance, yet remains challenging to date. Herein, we for the first time demonstrate the in situ synthesis of ultrathin PtCu nanowires grown over reduced GO (PtCu-NWs/rGO) via a one-pot hydrothermal approach with the aid of amine-terminated poly (N-isopropyl acrylamide) (PNIPAM-NH2). The judicious selection of PNIPAM-NH2 facilitates the in situ nucleation and anisotropic growth of nanowires on rGO surface and oriented attachment mechanism accounts for the formation of PtCu ultrathin nanowires. Due to the synergy between PtCu NWs and rGO support, the PtCu-NWs/rGO outperforms the rGO supported PtCu nanoparticles (PtCu-NPs/rGO), PtCu-NWs and commercial Pt/C toward the oxygen reduction reaction (ORR) with higher activity and better stability, making it a promising cathodic electrocatalyst for both fuel cells and metal-air cells. Moreover, the present synthetic strategy could inspire the future design of other metal alloy nanowires/carbon hybrid catalysts. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Atom Probe Tomography Examination of Carbon Redistribution in Quenched and Tempered 4340 Steel

    SciTech Connect

    Clarke, Amy J.; Miller, Michael K.; Alexander, David J.; Field, Robert D.; Clarke, Kester D.

    2012-08-07

    Quenching and tempering produces a wide range of mechanical properties in medium carbon, low alloyed steels - Study fragmentation behavior as a function of heat-treatment. Subtle microstructural changes accompany the mechanical property changes that result from quenching and tempering - Characterize the location and distribution of carbon and alloying elements in the microstructure using atom probe tomography (APT). Perform complementary transmission electron microscopy (TEM). Tempering influences the mechanical properties and fragmentation of quenched 4340 (hemi-shaped samples). APT revealed carbon-enriched features that contain a maximum of {approx}12-14 at.% carbon after quenching to RT (the level of carbon is perhaps associated with the extent of autotempering). TEM confirmed the presence of twinned martensite and indicates {var_epsilon} ({eta}) transition carbides after oil quenching to RT. Tempering at 325 C resulted in carbon-enriched plates (> 25 at.% C) with no significant element partitioning (transition carbides?). Tempering at 450 C and 575 C resulted in cementite ({approx} 25 at.% C) during late stage tempering; Cr, Mn, Mo partitioned to cementite and Si partitioned to ferrite. Tempering at 575 C resulted in P segregation at cementite interfaces and the formation of Cottrell atmospheres.

  4. Detection of nickel atom by laser induced fluorescence during carbon nanotube formation in a laser produced plume

    NASA Astrophysics Data System (ADS)

    De Boer, G.; Arepalli, S.; Holmes, W.; Nikolaev, P.; Range, C.; Scott, C.

    2001-05-01

    In situ monitoring of catalyst nickel atoms by laser induced fluorescence during carbon nanotube formation in a laser-produced plume was performed at the Johnson Space Center nanotube production laboratory. The results indicate that ablation of nickel and plume dynamics are strongly related to the oven temperature. Nickel atoms have a long lifetime of several milliseconds and have an electronic temperature of at least 1500 K during carbon nanotube formation.

  5. Electrical conductivity measurements of bacterial nanowires from Pseudomonas aeruginosa

    NASA Astrophysics Data System (ADS)

    Maruthupandy, Muthusamy; Anand, Muthusamy; Maduraiveeran, Govindhan; Sait Hameedha Beevi, Akbar; Jeeva Priya, Radhakrishnan

    2015-12-01

    The extracellular appendages of bacteria (flagella) that transfer electrons to electrodes are called bacterial nanowires. This study focuses on the isolation and separation of nanowires that are attached via Pseudomonas aeruginosa bacterial culture. The size and roughness of separated nanowires were measured using transmission electron microscopy (TEM) and atomic force microscopy (AFM), respectively. The obtained bacterial nanowires indicated a clear image of bacterial nanowires measuring 16 nm in diameter. The formation of bacterial nanowires was confirmed by microscopic studies (AFM and TEM) and the conductivity nature of bacterial nanowire was investigated by electrochemical techniques. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which are nondestructive voltammetry techniques, suggest that bacterial nanowires could be the source of electrons—which may be used in various applications, for example, microbial fuel cells, biosensors, organic solar cells, and bioelectronic devices. Routine analysis of electron transfer between bacterial nanowires and the electrode was performed, providing insight into the extracellular electron transfer (EET) to the electrode. CV revealed the catalytic electron transferability of bacterial nanowires and electrodes and showed excellent redox activities. CV and EIS studies showed that bacterial nanowires can charge the surface by producing and storing sufficient electrons, behave as a capacitor, and have features consistent with EET. Finally, electrochemical studies confirmed the development of bacterial nanowires with EET. This study suggests that bacterial nanowires can be used to fabricate biomolecular sensors and nanoelectronic devices.

  6. First principles study of electronic and mechanical properties of molybdenum selenide type nanowires

    NASA Astrophysics Data System (ADS)

    Çakır, D.; Durgun, E.; Gülseren, O.; Ciraci, S.

    2006-12-01

    Using the first-principles plane-wave pseudopotential method within density functional theory, we have systematically investigated structural, electronic, and mechanical properties of M2Y6X6 , Y6X6 ( X=Se,Te,S ; Y=Mo,Cr,W ; and M=Li,Na ) nanowires and bulk phase of M2Y6X6 . We found that not only Mo6X6 , but also transition metal and chalcogen atoms lying in the same columns of Mo and Se can form stable nanowires consisting of staggered triangles of Y3X3 . We have shown that all wires have nonmagnetic ground states in their equilibrium geometry. Furthermore, these structures can be either a metal or semiconductor depending on the type of chalcogen element. All Y6X6 wires with X=Te atom are semiconductors. Mechanical stability, elastic stiffness constants, breaking point, and breaking force of these wires have been calculated in order to investigate the strength of these wires. Ab initio molecular dynamic simulations performed at 500K suggest that overall structure remains unchanged at high temperature. Adsorption of H, O, and transition metal atoms like Cr and Ti on Mo6Se6 have been investigated for possible functionalization. All these elements interact with Mo6Se6 wire forming strong chemisorption bonds, and a permanent magnetic moment is induced upon the adsorption of Cr or Ti atoms. Molybdenum selenide-type nanowires can be alternative for carbon nanotubes, since the crystalline ropes consisting of one type of (M2)Y6X6 structures can be decomposed into individual nanowires by using solvents, and an individual nanowire by itself is either a metal or semiconductor and can be functionalized.

  7. Bridged single-walled carbon nanotube-based atomic-scale mass sensors

    NASA Astrophysics Data System (ADS)

    Ali-Akbari, H. R.; Shaat, M.; Abdelkefi, A.

    2016-08-01

    The potentials of carbon nanotubes (CNTs) as mechanical resonators for atomic-scale mass sensing are presented. To this aim, a nonlocal continuum-based model is proposed to study the dynamic behavior of bridged single-walled carbon nanotube-based mass nanosensors. The carbon nanotube (CNT) is considered as an elastic Euler-Bernoulli beam with von Kármán type geometric nonlinearity. Eringen's nonlocal elastic field theory is utilized to model the interatomic long-range interactions within the structure of the CNT. This developed model accounts for the arbitrary position of the deposited atomic-mass. The natural frequencies and associated mode shapes are determined based on an eigenvalue problem analysis. An atom of xenon (Xe) is first considered as a specific case where the results show that the natural frequencies and mode shapes of the CNT are strongly dependent on the location of the deposited Xe and the nonlocal parameter of the CNT. It is also indicated that the first vibrational mode is the most sensitive when the mass is deposited at the middle of a single-walled carbon nanotube. However, when deposited in other locations, it is demonstrated that the second or third vibrational modes may be more sensitive. To investigate the sensitivity of bridged single-walled CNTs as mass sensors, different noble gases are considered, namely Xe, argon (Ar), and helium (He). It is shown that the sensitivity of the single-walled CNT to the Ar and He gases is much lower than the Xe gas due to the significant decrease in their masses. The derived model and performed analysis are so needed for mass sensing applications and particularly when the detected mass is randomly deposited.

  8. Energy of the Isolated Metastable Iron-Nickel FCC Nanocluster with a Carbon Atom in the Tetragonal Interstice

    NASA Astrophysics Data System (ADS)

    Bondarenko, Natalya V.; Nedolya, Anatoliy V.

    2017-02-01

    The energy of the isolated iron-nickel nanocluster was calculated by molecular mechanics method using Lennard-Jones potential. The cluster included a carbon atom that drifted from an inside octahedral interstice to a tetrahedral interstice in direction and after that in <222> direction to the surface. In addition, one of 14 iron atoms was replaced by a nickel atom, the position of which was changing during simulation.

  9. Resonance Raman Spectroscopy of Extreme Nanowires and Other 1D Systems

    PubMed Central

    Smith, David C.; Spencer, Joseph H.; Sloan, Jeremy; McDonnell, Liam P.; Trewhitt, Harrison; Kashtiban, Reza J.; Faulques, Eric

    2016-01-01

    This paper briefly describes how nanowires with diameters corresponding to 1 to 5 atoms can be produced by melting a range of inorganic solids in the presence of carbon nanotubes. These nanowires are extreme in the sense that they are the limit of miniaturization of nanowires and their behavior is not always a simple extrapolation of the behavior of larger nanowires as their diameter decreases. The paper then describes the methods required to obtain Raman spectra from extreme nanowires and the fact that due to the van Hove singularities that 1D systems exhibit in their optical density of states, that determining the correct choice of photon excitation energy is critical. It describes the techniques required to determine the photon energy dependence of the resonances observed in Raman spectroscopy of 1D systems and in particular how to obtain measurements of Raman cross-sections with better than 8% noise and measure the variation in the resonance as a function of sample temperature. The paper describes the importance of ensuring that the Raman scattering is linearly proportional to the intensity of the laser excitation intensity. It also describes how to use the polarization dependence of the Raman scattering to separate Raman scattering of the encapsulated 1D systems from those of other extraneous components in any sample. PMID:27168195

  10. Influence of atomic vacancies on the dynamic characteristics of nanoresonators based on double walled carbon nanotube

    NASA Astrophysics Data System (ADS)

    Patel, Ajay M.; Joshi, Anand Y.

    2015-06-01

    The dynamic analysis of double walled carbon nanotubes (DWCNTs) with different boundary conditions has been performed using atomistic finite element method. The double walled carbon nanotube is modeled considering it as a space frame structure similar to a three dimensional beam. The elastic properties of beam element are calculated by considering mechanical characteristics of covalent bonds between the carbon atoms in the hexagonal lattice. Spring elements are used to describe the interlayer interactions between the inner and outer tubes caused due to the van der Waals forces. The mass of each beam element is assumed as point mass at nodes coinciding with carbon atoms at inner and outer wall of DWCNT. It has been reported that atomic vacancies are formed during the manufacturing process in DWCNT which tend to migrate leading to a change in the mechanical characteristics of the same. Simulations have been carried out to visualize the behavior of such defective DWCNTs subjected to different boundary conditions and when used as mass sensing devices. The variation of such atomic vacancies in outer wall of Zigzag and Armchair DWCNT is performed along the length and the change in response is noted. Moreover, as CNTs have been used as mass sensors extensively, the present approach is focused to explore the use of zigzag and armchair DWCNT as sensing device with a mono-atomic vacancy in it. The results clearly state that the dynamic characteristics are greatly influenced by defects like vacancies in it. A higher frequency shift is observed when the vacancy is located away from the fixed end for both Armchair as well as zigzag type of CNTs. A higher frequency shift is reported for armchair CNT for a mass of 10-22 g which remains constant for 10-21 g and then decreases gradually. Comparison with the other experimental and theoretical studies exhibits good association which suggests that defective DWCNTs can further be explored for mass sensing. This investigation is helpful

  11. An atomistic study of growth mode and microstructure evolution of amorphous carbon films by different incident carbon atoms

    NASA Astrophysics Data System (ADS)

    Xue, Chen; Zhou, Jianqiu

    2014-09-01

    In this paper, molecular dynamics (MD) simulation has been performed to describe the growth and interfacial microstructure of amorphous carbon films. We focus on the film growth mode and surface morphology for diverse deposition process parameters mainly including incident energy and incident angle. To explore the relationship between the motion of deposition atoms and amorphous films growth, a series of snapshots for each deposition process has been taken for comparison. The snapshots show that the films growth modes are diverse at different incident parameters. In the next step, surface morphology, atom distribution along film growth direction and internal structure including vacancy defects evolution during deposition process are analyzed. The results reveal that incident energy on the horizontal plane dominates the surface roughness, and incident energy on the vertical plane dominates the compactness of the film. We conclude that a suitable incident parameter is not only beneficial to prepare amorphous films with compact and smooth or bump-like surface which will meet different needs, but also can avoid formation of defects during deposition. The simulation results are expected to provide useful guidance for improving amorphous carbon films quality.

  12. A first principle study for the adsorption and absorption of carbon atom and the CO dissociation on Ir(100) surface

    SciTech Connect

    Erikat, I. A.; Hamad, B. A.

    2013-11-07

    We employ density functional theory to examine the adsorption and absorption of carbon atom as well as the dissociation of carbon monoxide on Ir(100) surface. We find that carbon atoms bind strongly with Ir(100) surface and prefer the high coordination hollow site for all coverages. In the case of 0.75 ML coverage of carbon, we obtain a bridging metal structure due to the balance between Ir–C and Ir–Ir interactions. In the subsurface region, the carbon atom prefers the octahedral site of Ir(100) surface. We find large diffusion barrier for carbon atom into Ir(100) surface (2.70 eV) due to the strong bonding between carbon atom and Ir(100) surface, whereas we find a very small segregation barrier (0.22 eV) from subsurface to the surface. The minimum energy path and energy barrier for the dissociation of CO on Ir(100) surface are obtained by using climbing image nudge elastic band. The energy barrier of CO dissociation on Ir(100) surface is found to be 3.01 eV, which is appreciably larger than the association energy (1.61 eV) of this molecule.

  13. Nanowire Lasers

    NASA Astrophysics Data System (ADS)

    Couteau, C.; Larrue, A.; Wilhelm, C.; Soci, C.

    2015-05-01

    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.

  14. Tetragonality and the distribution of carbon atoms in the Fe-C martensite: Molecular-dynamics simulation

    NASA Astrophysics Data System (ADS)

    Chirkov, P. V.; Mirzoev, A. A.; Mirzaev, D. A.

    2016-01-01

    In the statistical theory of the ordering of carbon atoms in the z sublattice of martensite, the most important role is played by the parameter of the strain interaction of carbon atoms λ0, which determines the critical temperature of the bcc-bct transition. The values of this parameter (6-11 eV/atom) obtained in recent years by the methods of computer simulation differ significantly from the value λ0 = 2.73 eV/atom obtained by A. G. Khachaturyan. In this article, we calculated the value of λ0 by two methods based on the molecular-dynamics simulation of the ordering of carbon atoms in the lattice of martensite at temperatures of 500, 750, 900, and 1000 K in a wide range of carbon concentrations, which includes c crit. No tails of ordering below c crit have been revealed. It has been shown analytically that there is an inaccuracy in the Khachaturyan theory of ordering for the crystal in an elastic environment. After eliminating this inaccuracy, no tails of the order parameter appear; the tetragonality changes jumpwise from η = 0 to ηcrit = 0.75 at c crit = 2.9 kT/λ0 instead of ηcrit = 0.5 and c crit= 2.77 kT/λ0 for an isolated crystal. Upon the simulation, clustering of carbon atoms was revealed in the form of platelike pileups along {102} planes separated by flat regions where no carbon atoms were present. The influence of short-range order in the arrangement of neighboring carbon atoms on the thermodynamics of ordering is discussed.

  15. Atomic-scaled cobalt encapsulated in P,N-doped carbon sheaths over carbon nanotubes for enhanced oxygen reduction electrocatalysis under acidic and alkaline media.

    PubMed

    Guo, Shiyu; Yuan, Pengfei; Zhang, Jianan; Jin, Pengbo; Sun, Hongming; Lei, Kaixiang; Pang, Xinchang; Xu, Qun; Cheng, Fangyi

    2017-08-31

    A one-step in situ nanoconfined pyrolysis strategy was developed to anchor highly active single Co atoms on the P,N-doped porous carbon@carbon nanotube coaxial nanocables (Co-P,N-CNT), which exhibit remarkable enhanced ORR electrocatalytic activity in both acidic and alkaline media.

  16. Atomic scale enhancement of the adhesion of beryllium films to carbon substrates

    SciTech Connect

    Musket, R.G.; Wirtenson, G.R.

    1995-12-01

    We have used 200 keV carbon ions to enhance the adhesion of 240-nm thick Be films to polished, vitreous carbon substrates. Adhesion of the as-deposited films was below that necessary to pass the scotch-tape test. Carbon ion fluences less than 1.6x10{sup 14} C/cm{sup 2} were sufficient to ensure the passage of the tape test without affecting the optical properties of the films. Adhesion failure of the as-deposited film was attributed to an inner oxide layer between the Be and the carbon. Because this oxide ({approximately}5 nm of BeO) was not measurably changed by the irradiation process, these results are consistent with adhesion enhancement occurring on the atomic scale at the interface between the inner oxide and the carbon substrate. This conclusion was supported by Rutherford backscattering (RBS) data, and potential adhesion mechanisms are discussed with consideration of relative contributions from electronic and nuclear stopping.

  17. Carbon-hydrogen defects with a neighboring oxygen atom in n-type Si

    NASA Astrophysics Data System (ADS)

    Gwozdz, K.; Stübner, R.; Kolkovsky, Vl.; Weber, J.

    2017-07-01

    We report on the electrical activation of neutral carbon-oxygen complexes in Si by wet-chemical etching at room temperature. Two deep levels, E65 and E75, are observed by deep level transient spectroscopy in n-type Czochralski Si. The activation enthalpies of E65 and E75 are obtained as EC-0.11 eV (E65) and EC-0.13 eV (E75). The electric field dependence of their emission rates relates both levels to single acceptor states. From the analysis of the depth profiles, we conclude that the levels belong to two different defects, which contain only one hydrogen atom. A configuration is proposed, where the CH1BC defect, with hydrogen in the bond-centered position between neighboring C and Si atoms, is disturbed by interstitial oxygen in the second nearest neighbor position to substitutional carbon. The significant reduction of the CH1BC concentration in samples with high oxygen concentrations limits the use of this defect for the determination of low concentrations of substitutional carbon in Si samples.

  18. Inelastic and reactive scattering of hyperthermal atomic oxygen from amorphous carbon

    NASA Technical Reports Server (NTRS)

    Minton, Timothy K.; Nelson, Christine M.; Brinza, David E.; Liang, Ranty H.

    1991-01-01

    The reaction of hyperthermal oxygen atoms with an amorphous carbon-13 surface was studied using a modified universal crossed molecular beams apparatus. Time-of-flight distributions of inelastically scattered O-atoms and reactively scattered CO-13 and CO2-13 were measured with a rotatable mass spectrometer detector. Two inelastic scattering channels were observed, corresponding to a direct inelastic process in which the scattered O-atoms retain 20 to 30 percent of their initial kinetic energy and to a trapping desorption process whereby O-atoms emerge from the surface at thermal velocities. Reactive scattering data imply the formation of two kinds of CO products, slow products whose translational energies are determined by the surface temperature and hyperthermal (Approx. 3 eV) products with translational energies comprising roughly 30 percent of the total available energy (E sub avl), where E sub avl is the sum of the collision energy and the reaction exothermicity. Angular data show that the hyperthermal CO is scattered preferentially in the specular direction. CO2 product was also observed, but at much lower intensities than CO and with only thermal velocities.

  19. Characterization of carbon nanotube yarn after exposure to hyperthermal atomic oxygen and thermal fatigue

    NASA Astrophysics Data System (ADS)

    Misak, H. E.; Mall, S.

    2016-12-01

    Carbon nanotube (CNT)-yarn was evaluated for the survivability under hazardous space environmental conditions which were thermal fatigue, atomic oxygen and additive effect of these two exposures. Its tensile strength, tenacity, stiffness, strain to failure and electrical conductivity were characterized at the two extreme space temperatures of -150 and 120 °C before and after exposure to these environmental conditions. Tensile strength, stiffness and electrical conductivity of unexposed CNT yarn increased at the cryogenic temperature relative to at the elevated temperature. There was no change in the tensile properties after exposure to the space environmental conditions when measured at the elevated and cryogenic temperatures. Electrical conductivity decreased after exposure to three hazardous environments involving thermal fatigue, but it had no or small decrease when exposed to atomic oxygen only. No additive effect of thermal fatigue followed by atomic oxygen or by atomic oxygen followed by thermal fatigue environments on the CNTs' tensile properties and electrical conductivity was observed. Considering the low density 0.59 g/cc and good resistant to the extreme hazardous space environment, CNT-yarns have potential for applications in spacecraft and satellites.

  20. Interaction between a single Pt atom and a carbon nanotube studied by density functional theory

    NASA Astrophysics Data System (ADS)

    Chen, G.; Kawazoe, Y.

    2006-03-01

    Using density functional theory with the generalized gradient approximation, we have studied the interaction between a single Pt atom and a carbon nanotube. The bridge adsorption site on the outer wall of nanotube is favorable. The curvature affects the binding strength. Compared to the larger nanotube, Pt could bind stronger to the outer wall of a small radius nanotube. For zigzag nanotube, the most stable site on the outer wall is the bridge site with the underlying C-C bond being parallel to the axis of the nanotube, while for the armchair nanotube it is the bridge site with the underlying C-C bond being tilted to the axis of the nanotube. The energy in average differs by ˜1.5eV for adsorbing on both sidewalls of small radius nanotube, while it decreases much for the larger nanotube. Either by penetrating the wall or by substituting one C atom on the wall, the Pt atom is found to be hard to diffuse from the outside to the inside. The studied charge density suggests the weak covalentlike bonding between Pt and C atoms.

  1. Highly doped silicon nanowires by monolayer doping.

    PubMed

    Veerbeek, Janneke; Ye, Liang; Vijselaar, Wouter; Kudernac, Tibor; van der Wiel, Wilfred G; Huskens, Jurriaan

    2017-02-23

    Controlling the doping concentration of silicon nanostructures is challenging. Here, we investigated three different monolayer doping techniques to obtain silicon nanowires with a high doping dose. These routes were based on conventional monolayer doping, starting from covalently bound dopant-containing molecules, or on monolayer contact doping, in which a source substrate coated with a monolayer of a carborane silane was the dopant source. As a third route, both techniques were combined to retain the benefits of conformal monolayer formation and the use of an external capping layer. These routes were used for doping fragile porous nanowires fabricated by metal-assisted chemical etching. Differences in porosity were used to tune the total doping dose inside the nanowires, as measured by X-ray photoelectron spectroscopy and secondary ion mass spectrometry measurements. The higher the porosity, the higher was the surface available for dopant-containing molecules, which in turn led to a higher doping dose. Slightly porous nanowires could be doped via all three routes, which resulted in highly doped nanowires with (projected areal) doping doses of 10(14)-10(15) boron atoms per cm(2) compared to 10(12) atoms per cm(2) for a non-porous planar sample. Highly porous nanowires were not compatible with the conventional monolayer doping technique, but monolayer contact doping and the combined route resulted for these highly porous nanowires in tremendously high doping doses up to 10(17) boron atoms per cm(2).

  2. Self-supported Zn3P2 nanowire arrays grafted on carbon fabrics as an advanced integrated anode for flexible lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Li, Wenwu; Gan, Lin; Guo, Kai; Ke, Linbo; Wei, Yaqing; Li, Huiqiao; Shen, Guozhen; Zhai, Tianyou

    2016-04-01

    We, for the first time, successfully grafted well-aligned binary lithium-reactive zinc phosphide (Zn3P2) nanowire arrays on carbon fabric cloth by a facile CVD method. When applied as a novel self-supported binder-free anode for lithium ion batteries (LIBs), the hierarchical three-dimensional (3D) integrated anode shows excellent electrochemical performances: a highly reversible initial lithium storage capacity of ca. 1200 mA h g-1 with a coulombic efficiency of up to 88%, a long lifespan of over 200 cycles without obvious decay, and a high rate capability of ca. 400 mA h g-1 capacity retention at an ultrahigh rate of 15 A g-1. More interestingly, a flexible LIB full cell is assembled based on the as-synthesized integrated anode and the commercial LiFePO4 cathode, and shows striking lithium storage performances very close to the half cells: a large reversible capacity over 1000 mA h g-1, a long cycle life of over 200 cycles without obvious decay, and an ultrahigh rate performance of ca. 300 mA h g-1 even at 20 A g-1. Considering the excellent lithium storage performances of coin-type half cells as well as flexible full cells, the as-prepared carbon cloth grafted well-aligned Zn3P2 nanowire arrays would be a promising integrated anode for flexible LIB full cell devices.We, for the first time, successfully grafted well-aligned binary lithium-reactive zinc phosphide (Zn3P2) nanowire arrays on carbon fabric cloth by a facile CVD method. When applied as a novel self-supported binder-free anode for lithium ion batteries (LIBs), the hierarchical three-dimensional (3D) integrated anode shows excellent electrochemical performances: a highly reversible initial lithium storage capacity of ca. 1200 mA h g-1 with a coulombic efficiency of up to 88%, a long lifespan of over 200 cycles without obvious decay, and a high rate capability of ca. 400 mA h g-1 capacity retention at an ultrahigh rate of 15 A g-1. More interestingly, a flexible LIB full cell is assembled based on the as

  3. Hierarchical core-shell NiCo2O4@NiMoO4 nanowires grown on carbon cloth as integrated electrode for high-performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Huang, Liang; Zhang, Wei; Xiang, Jinwei; Xu, Henghui; Li, Guolong; Huang, Yunhui

    2016-08-01

    Hierarchical core-shell NiCo2O4@NiMoO4 nanowires were grown on carbon cloth (CC@NiCo2O4@NiMoO4) by a two-step hydrothermal route to fabricate a flexible binder-free electrode. The prepared CC@NiCo2O4@NiMoO4 integrated electrode was directly used as an electrode for faradaic supercapacitor. It shows a high areal capacitance of 2.917 F cm‑2 at 2 mA cm‑2 and excellent cycling stability with 90.6% retention over 2000 cycles at a high current density of 20 mA cm‑2. The superior specific capacitance, rate and cycling performance can be ascribed to the fast transferring path for electrons and ions, synergic effect and the stability of the hierarchical core-shell structure.

  4. Hierarchical core-shell NiCo2O4@NiMoO4 nanowires grown on carbon cloth as integrated electrode for high-performance supercapacitors.

    PubMed

    Huang, Liang; Zhang, Wei; Xiang, Jinwei; Xu, Henghui; Li, Guolong; Huang, Yunhui

    2016-08-12

    Hierarchical core-shell NiCo2O4@NiMoO4 nanowires were grown on carbon cloth (CC@NiCo2O4@NiMoO4) by a two-step hydrothermal route to fabricate a flexible binder-free electrode. The prepared CC@NiCo2O4@NiMoO4 integrated electrode was directly used as an electrode for faradaic supercapacitor. It shows a high areal capacitance of 2.917 F cm(-2) at 2 mA cm(-2) and excellent cycling stability with 90.6% retention over 2000 cycles at a high current density of 20 mA cm(-2). The superior specific capacitance, rate and cycling performance can be ascribed to the fast transferring path for electrons and ions, synergic effect and the stability of the hierarchical core-shell structure.

  5. Hierarchical core-shell NiCo2O4@NiMoO4 nanowires grown on carbon cloth as integrated electrode for high-performance supercapacitors

    PubMed Central

    Huang, Liang; Zhang, Wei; Xiang, Jinwei; Xu, Henghui; Li, Guolong; Huang, Yunhui

    2016-01-01

    Hierarchical core-shell NiCo2O4@NiMoO4 nanowires were grown on carbon cloth (CC@NiCo2O4@NiMoO4) by a two-step hydrothermal route to fabricate a flexible binder-free electrode. The prepared CC@NiCo2O4@NiMoO4 integrated electrode was directly used as an electrode for faradaic supercapacitor. It shows a high areal capacitance of 2.917 F cm−2 at 2 mA cm−2 and excellent cycling stability with 90.6% retention over 2000 cycles at a high current density of 20 mA cm−2. The superior specific capacitance, rate and cycling performance can be ascribed to the fast transferring path for electrons and ions, synergic effect and the stability of the hierarchical core-shell structure. PMID:27515274

  6. Carbon Nanotube-Silicon Nanowire Heterojunction Solar Cells with Gas-Dependent Photovoltaic Performances and Their Application in Self-Powered NO2 Detecting

    NASA Astrophysics Data System (ADS)

    Jia, Yi; Zhang, Zexia; Xiao, Lin; Lv, Ruitao

    2016-06-01

    A multifunctional device combining photovoltaic conversion and toxic gas sensitivity is reported. In this device, carbon nanotube (CNT) membranes are used to cover onto silicon nanowire (SiNW) arrays to form heterojunction. The porous structure and large specific surface area in the heterojunction structure are both benefits for gas adsorption. In virtue of these merits, gas doping is a feasible method to improve cell's performance and the device can also work as a self-powered gas sensor beyond a solar cell. It shows a significant improvement in cell efficiency (more than 200 times) after NO2 molecules doping (device working as a solar cell) and a fast, reversible response property for NO2 detection (device working as a gas sensor). Such multifunctional CNT-SiNW structure can be expected to open a new avenue for developing self-powered, efficient toxic gas-sensing devices in the future.

  7. Carbon Nanotube-Silicon Nanowire Heterojunction Solar Cells with Gas-Dependent Photovoltaic Performances and Their Application in Self-Powered NO2 Detecting.

    PubMed

    Jia, Yi; Zhang, Zexia; Xiao, Lin; Lv, Ruitao

    2016-12-01

    A multifunctional device combining photovoltaic conversion and toxic gas sensitivity is reported. In this device, carbon nanotube (CNT) membranes are used to cover onto silicon nanowire (SiNW) arrays to form heterojunction. The porous structure and large specific surface area in the heterojunction structure are both benefits for gas adsorption. In virtue of these merits, gas doping is a feasible method to improve cell's performance and the device can also work as a self-powered gas sensor beyond a solar cell. It shows a significant improvement in cell efficiency (more than 200 times) after NO2 molecules doping (device working as a solar cell) and a fast, reversible response property for NO2 detection (device working as a gas sensor). Such multifunctional CNT-SiNW structure can be expected to open a new avenue for developing self-powered, efficient toxic gas-sensing devices in the future.

  8. Hierarchical silicon nanowires-carbon textiles matrix as a binder-free anode for high-performance advanced lithium-ion batteries

    PubMed Central

    Liu, Bin; Wang, Xianfu; Chen, Haitian; Wang, Zhuoran; Chen, Di; Cheng, Yi-Bing; Zhou, Chongwu; Shen, Guozhen

    2013-01-01

    Toward the increasing demands of portable energy storage and electric vehicle applications, the widely used graphite anodes with significant drawbacks become more and more unsuitable. Herein, we report a novel scaffold of hierarchical silicon nanowires-carbon textiles anodes fabricated via a facile method. Further, complete lithium-ion batteries based on Si and commercial LiCoO2 materials were assembled to investigate their corresponding across-the-aboard performances, demonstrating their enhanced specific capacity (2950 mAh g−1 at 0.2 C), good repeatability/rate capability (even >900 mAh g−1 at high rate of 5 C), long cycling life, and excellent stability in various external conditions (curvature, temperature, and humidity). Above results light the way to principally replacing graphite anodes with silicon-based electrodes which was confirmed to have better comprehensive performances. PMID:23572030

  9. Probing spin-orbit-interaction-induced electron dynamics in the carbon atom by multiphoton ionization

    NASA Astrophysics Data System (ADS)

    Rey, H. F.; van der Hart, H. W.

    2014-09-01

    We use R-matrix theory with time dependence (RMT) to investigate multiphoton ionization of ground-state atomic carbon with initial orbital magnetic quantum number ML=0 and ML=1 at a laser wavelength of 390 nm and peak intensity of 1014W/cm2. Significant differences in ionization yield and ejected-electron momentum distribution are observed between the two values for ML. We use our theoretical results to model how the spin-orbit interaction affects electron emission along the laser polarization axis. Under the assumption that an initial C atom is prepared at zero time delay with ML=0, the dynamics with respect to time delay of an ionizing probe pulse modeled by using RMT theory is found to be in good agreement with available experimental data.

  10. Ultrafine Mn3O4 Nanowires/Three-Dimensional Graphene/Single-Walled Carbon Nanotube Composites: Superior Electrocatalysts for Oxygen Reduction and Enhanced Mg/Air Batteries.

    PubMed

    Li, Chun-Sheng; Sun, Yan; Lai, Wei-Hong; Wang, Jia-Zhao; Chou, Shu-Lei

    2016-10-07

    The exploration of highly efficient catalysts for the oxygen reduction reaction to improve sluggish kinetics still remains a great challenge for advanced energy conversion and storage in metal/air batteries. In this work, ultrafine Mn3O4 nanowires/three-dimensional graphene/single-walled carbon nanotube catalysts with an electron transfer number of 3.95 (at 0.60 V vs Ag/AgCl) and kinetic current density of 21.7-28.8 mA cm(-2) were developed via a microwave-irradiation-assisted hexadecyl trimethylammonium bromide (CTAB) surfactant procedure to greatly enhance the overall catalytic performance in Mg/air batteries. To match the electrochemical activity of the cathode catalysts, a large-scale Mg anode prepared with micropersimmon-like particles via a mechanical disintegrator and Mg(NO3)2-NaNO2-based electrolyte containing 1.0 wt % trihexyl(tetradecyl)phosphonium chloride ionic liquid were applied. Combining the ultrafine Mn3O4 nanowires/three-dimensional graphene/single-walled carbon nanotube as an efficient electrocatalyst for the oxygen reduction reaction and an Mg micro-/nanoscale anode in the novel electrolyte, the advanced Mg/air batteries demonstrated a high cell open circuit voltage (1.49 V), a high plateau voltage (1.34 V), and a long discharge time (4177 min) at 0.2 mA cm(-1), showing a high energy density. Therefore, it is believed that this device configuration has great potential for application in new energy storage technologies.

  11. Reconstruction of carbon atoms around a point defect of a graphene: a hybrid quantum/classical molecular-dynamics simulation.

    PubMed

    Kowaki, Y; Harada, A; Shimojo, F; Hoshino, K

    2009-02-11

    We have investigated the rearrangement of carbon atoms around a point defect of a graphene using a hybrid ab initio/classical molecular-dynamics (MD) simulation method, in which 36 carbon atoms surrounding a point defect are treated by the ab initio MD method and the other 475 carbon atoms relatively far from the point defect are treated by the classical MD method. We have confirmed a formation of a 5-1DB defect (a pentagon and a dangling bond) from the time dependence of atomic configurations and electron density distributions obtained by our simulation. We have found that the pentagon is formed in two different positions around the point defect, and that the two positions appear alternately during the simulation, the frequency of which increases with increasing temperature.

  12. Synthesis and characterization of carbon fibers functionalized with poly (glycidyl methacrylate) via atom transfer radical polymerization

    NASA Astrophysics Data System (ADS)

    Wu, Yongwei; Xiong, Lei; Qin, Xiaokang; Wang, Zhengyue; Ding, Bei; Ren, Huan; Pi, Xiaolong

    2015-07-01

    In this work, polyacrylonitrile (PAN)-based carbon fibers (CF) were chemically modified with poly (glycidyl methacrylate) (PGMA) via atom transfer radical polymerization (ATRP) to improve the interaction between the CF and polymer matrix. The FT-IR, TGA, and XPS were used to determine the chemical structure of the resulting products and the quantities of PGMA chains grafted from the CF surface. The experimental results confirm that the CF surface was functionalized and glycidyl methacrylate was graft-polymerized onto the CF, and the grafting content of polymer could reach 10.2%.

  13. STM Images of Atomic-Scale Carbon Nanotube Defects Produced by Ar+ Irradiation

    NASA Astrophysics Data System (ADS)

    Osváth, Z.; Vértesy, G.; Tapasztó, L.; Wéber, F.; Horváth, Z. E.; Gyulai, J.; Biró, L. P.

    2005-09-01

    Multi-wall carbon nanotubes (MWCNTs) dispersed on graphite (HOPG) substrate were irradiated with Ar+ ions of 30 keV, using a low-dose of D = 5×1011 ions/cm2. The irradiated samples were investigated by scanning tunneling microscopy (STM) under ambient conditions. Atomic resolution STM images reveal individual nanotube defects, which appear as hillocks of 1-2 angstroms in height, due to the locally changed electronic structure. After annealing at 450 °C in nitrogen atmosphere, the irradiated MWCNTs were investigated again by STM. The effect of the heat treatment on the irradiation-induced nanotube defects is also discussed.

  14. Carbon nanotubes as solid-phase extraction sorbents prior to atomic spectrometric determination of metal species: a review.

    PubMed

    Herrero Latorre, C; Álvarez Méndez, J; Barciela García, J; García Martín, S; Peña Crecente, R M

    2012-10-24

    New materials have significant impact on the development of new methods and instrumentation for chemical analysis. From the discovery of carbon nanotubes in 1991, single and multi-walled carbon nanotubes--due to their high adsorption and desorption capacities--have been employed as sorption substrates in solid-phase extraction for the preconcentration of metal species from diverse matrices. Looking for successive improvements in sensitivity and selectivity, in the past few years, carbon nanotubes have been utilized as sorbents for solid phase extraction in three different ways: like as-grown, oxidized and functionalized nanotubes. In the present paper, an overview of the recent trends in the use of carbon nanotubes for solid phase extraction of metal species in environmental, biological and food samples is presented. The determination procedures involved the adsorption of metals on the nanotube surface, their quantitative desorption and subsequent measurement by means of atomic spectrometric techniques such as flame atomic absorption spectrometry, electrothermal atomic absorption spectrometry or inductively coupled plasma atomic emission spectrometry/mass spectrometry, among others. Synthesis, purification and types of carbon nanotubes, as well as the diverse chemical and physical strategies for their functionalization are described. Based on 140 references, the performance and general properties of the applications of solid phase extraction based on carbon nanotubes for metal species atomic spectrometric determination are discussed.

  15. Effect of atomic interconnects on percolation in single-walled carbon nanotube thin film networks.

    PubMed

    Tian, Xiaojuan; Moser, Matthew L; Pekker, Aron; Sarkar, Santanu; Ramirez, Jason; Bekyarova, Elena; Itkis, Mikhail E; Haddon, Robert C

    2014-07-09

    The formation of covalent bonds to single-walled carbon nanotube (SWNT) or graphene surfaces usually leads to a decrease in the electrical conductivity and mobility as a result of the structural rehybridization of the functionalized carbon atoms from sp(2) to sp(3). In the present study, we explore the effect of metal deposition on semiconducting (SC-) and metallic (MT-) SWNT thin films in the vicinity of the percolation threshold and we are able to clearly delineate the effects of weak physisorption, ionic chemisorption with charge transfer, and covalent hexahapto (η(6)) chemisorption on these percolating networks. The results support the idea that for those metals capable of forming bis-hexahapto-bonds, the generation of covalent (η(6)-SWNT)M(η(6)-SWNT) interconnects provides a conducting pathway in the SWNT films and establishes the transition metal bis-hexahapto organometallic bond as an electronically conjugating linkage between graphene surfaces.

  16. Branched aliphatic alkanes with quaternary substituted carbon atoms in modern and ancient geologic samples.

    SciTech Connect

    Kenig, F.; Simons, D.-J. H.; Crich, D.; Cowen, J. P.; Ventura, G. T.; Rehbein-Khalily, T.; Brown, T. C.; Anderson, K. B.; Chemistry; Univ. of Illinois at Chicago; Univ. of Hawaii

    2003-01-01

    A pseudohomologous series of branched aliphatic alkanes with a quaternary substituted carbon atom (BAQCs, specifically 2,2-di-methylalkanes and 3,3- and 5,5-diethylalkanes) were identified in warm (65{sup o}C) deep-sea hydrothermal waters and Late Cretaceous black shales. 5,5-Diethylalkanes were also observed in modern and Holocene marine shelf sediments and in shales spanning the last 800 million years of the geological record. The carbon number distribution of BAQCs indicates a biological origin. These compounds were observed but not identified in previous studies of 2.0 billion- to 2.2 billion-year-old metasediments and were commonly misidentified in other sediment samples, indicating that BAQCs are widespread in the geological record. The source organisms of BAQCs are unknown, but their paleobiogeographic distribution suggests that they have an affinity for sulfides and might be nonphotosynthetic sulfide oxidizers.

  17. Raman spectroscopy as a tool to investigate the structure and electronic properties of carbon-atom wires

    PubMed Central

    Milani, Alberto; Tommasini, Matteo; Russo, Valeria; Li Bassi, Andrea; Lucotti, Andrea; Cataldo, Franco

    2015-01-01

    Summary Graphene, nanotubes and other carbon nanostructures have shown potential as candidates for advanced technological applications due to the different coordination of carbon atoms and to the possibility of π-conjugation. In this context, atomic-scale wires comprised of sp-hybridized carbon atoms represent ideal 1D systems to potentially downscale devices to the atomic level. Carbon-atom wires (CAWs) can be arranged in two possible structures: a sequence of double bonds (cumulenes), resulting in a 1D metal, or an alternating sequence of single–triple bonds (polyynes), expected to show semiconducting properties. The electronic and optical properties of CAWs can be finely tuned by controlling the wire length (i.e., the number of carbon atoms) and the type of termination (e.g., atom, molecular group or nanostructure). Although linear, sp-hybridized carbon systems are still considered elusive and unstable materials, a number of nanostructures consisting of sp-carbon wires have been produced and characterized to date. In this short review, we present the main CAW synthesis techniques and stabilization strategies and we discuss the current status of the understanding of their structural, electronic and vibrational properties with particular attention to how these properties are related to one another. We focus on the use of vibrational spectroscopy to provide information on the structural and electronic properties of the system (e.g., determination of wire length). Moreover, by employing Raman spectroscopy and surface enhanced Raman scattering in combination with the support of first principles calculations, we show that a detailed understanding of the charge transfer between CAWs and metal nanoparticles may open the possibility to tune the electronic structure from alternating to equalized bonds. PMID:25821689

  18. Semiconductor nanowires: Controlled growth and thermal properties

    NASA Astrophysics Data System (ADS)

    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

  19. Chemical vapor deposition of aluminum nanowires on metal substrates for electrical energy storage applications.

    PubMed

    Benson, James; Boukhalfa, Sofiane; Magasinski, Alexandre; Kvit, Alexander; Yushin, Gleb

    2012-01-24

    Metal nanowires show promise in a broad range of applications, but many synthesis techniques require complex methodologies. We have developed a method for depositing patterned aluminum nanowires (Al NWs) onto Cu, Ni, and stainless steel substrates using low-pressure decomposition of trimethylamine alane complex. The NWs exhibited an average diameter in the range from 45 to 85 nm, were crystalline, and did not contain a detectable amount of carbon impurities. Atomic layer deposition of 50 nm of vanadium oxide on the surface of Al NW allows fabrication of supercapacitor electrodes with volumetric capacitance in excess of 1400 F·cc(-3), which exceeds the capacitance of traditional activated carbon supercapacitor electrodes by more than an order of magnitude. © 2011 American Chemical Society

  20. Determination of mercury in carbon black by cold vapor atomic absorption spectrometry.

    PubMed

    Hepp, Nancy M

    2006-01-01

    Recently, a new color additive, D&C Black No. 2, a high-purity furnace black in the general category of carbon blacks, was listed as a color subject to batch certification by the U.S. Food and Drug Administration. A simple procedure was developed to determine mercury (Hg) in D&C Black No. 2, which is limited by specification to not more than 1 ppm Hg. The method uses partial acid digestion followed by cold vapor atomic absorption and was developed by modifying a method used for other color additives. The carbon black samples are treated with a mixture of nitric and hydrochloric acids and heated by microwave in sealed Teflon vessels. The resulting solutions, which are stable to Hg loss for at least 1 week, are diluted and analyzed for Hg using cold vapor atomic absorption spectrometry. Validation was performed by spiking carbon black samples with inorganic Hg (HgNO3) at levels from 0.1 to 1.5 microg/g, and by analyzing 2 standard reference materials. At the specification level of 1 ppm Hg (1 microg Hg/g), the 95% confidence interval was +/-0.01 ppm Hg (0.01 microg Hg/g). The method developed in this study gave good results for very difficult-to-analyze materials, such as coal standard reference materials and carbon black. By eliminating volatility and adsorption factors through the formation of HgCl4(-2) complexes, one can avoid using extremely hazardous acids such as HF and HClO4.