WorldWideScience

Sample records for atomic carbon nanowires

  1. Strong ionisation in carbon nanowires

    Science.gov (United States)

    Kaymak, V.; Pukhov, A.; Shlyaptsev, V. N.; Rocca, J. J.

    2016-04-01

    Surfaces covered with nanostructures, such as nanowire arrays, are shown to facilitate a significantly higher absorption of laser energy as compared to flat surfaces. Due to the efficient coupling of the laser energy, highly energetic electrons are produced, which in turn can emit intense ultrafast X-ray pulses. Full three dimensional PIC simulations are used to analyse the behaviour of arrays of carbon nanowires 400 nm in diameter, irradiated by a 400-nm laser pulse of 60-fs duration at FWHM and a vector potential of α0 = 18. We analyse the ionisation dynamics of the nanowires. The difference of the ionisation strength and structure between linearly and circularly polarised laser beam is investigated. The nanowires are found to be fully ionised after about 30 laser cycles. Circularly polarised light reveals a slightly stronger ionisation effect.

  2. Strong Ionization in carbon Nanowires

    CERN Document Server

    Kaymak, Vural; Shlyaptsev, Vyacheslav N; Rocca, Jorge J

    2015-01-01

    Surfaces covered with nanostructures, such as nanowire arrays, have shown to facilitate a significantly higher absorption of laser energy as compared to flat surfaces. Due to the efficient coupling of the laser energy, highly energetic electrons are produced, which in turn can emit intense ultrafast X-ray pulses. In the present work we use full three dimensional PIC simulations to analyze the behavior of arrays of carbon nanowires $400 nm$ in diameter, irradiated by a $\\lambda_0 = 400 nm$ laser pulse of $60 fs$ duration at FWHM and a vector potential of $a_0 = 18$. We analyze the ionization dynamics of the nanowires. We investigate the difference of the ionization strength and structure between linearly and circularly polarized laser beam. The nanowires are found to be fully ionized after about 30 laser cycles. Circularly polarized light reveals a slightly stronger ionization effect.

  3. Contacting nanowires and nanotubes with atomic precision for electronic transport

    KAUST Repository

    Qin, Shengyong

    2012-01-01

    Making contacts to nanostructures with atomic precision is an important process in the bottom-up fabrication and characterization of electronic nanodevices. Existing contacting techniques use top-down lithography and chemical etching, but lack atomic precision and introduce the possibility of contamination. Here, we report that a field-induced emission process can be used to make local contacts onto individual nanowires and nanotubes with atomic spatial precision. The gold nano-islands are deposited onto nanostructures precisely by using a scanning tunneling microscope tip, which provides a clean and controllable method to ensure both electrically conductive and mechanically reliable contacts. To demonstrate the wide applicability of the technique, nano-contacts are fabricated on silicide atomic wires, carbon nanotubes, and copper nanowires. The electrical transport measurements are performed in situ by utilizing the nanocontacts to bridge the nanostructures to the transport probes. © 2012 American Institute of Physics.

  4. Conducting carbon nanopatterns (nanowire) by energetic ion irradiation

    International Nuclear Information System (INIS)

    This work reports the formation of conducting carbon nanopatterns (nano-wires) in a semi-inorganic polymer by irradiation with energetic ions. The conducting nano-patterns/wires are evidenced by conducting atomic force microscopy. The typical diameter of the conducting wires is observed to be about ∼50-200 nm. The density (spacing), growth direction and length of these carbon nanowires can be changed simply by ion fluence, angle of irradiation and the film thickness, respectively. The formation of conducting nanopatterns in an insulating matrix (polymers/gels) is correlated with the structural transformation of films, investigated by means of Raman spectroscopy

  5. Preparation of Metal Nanowire Decorated Carbon Allotropes

    Science.gov (United States)

    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.

  6. Synthesis and Characterization of Glassy Carbon Nanowires

    Directory of Open Access Journals (Sweden)

    C. M. Lentz

    2011-01-01

    Full Text Available The advent of carbon-based micro- and nanoelectromechanical systems has revived the interest in glassy carbon, whose properties are relatively unknown at lower dimensions. In this paper, electrical conductivity of individual glassy carbon nanowires was measured as a function of microstructure (controlled by heat treatment temperature and ambient temperature. The semiconducting nanowires with average diameter of 150 nm were synthesized from polyfurfuryl alcohol precursors and characterized using transmission electron and Raman microscopy. DC electrical measurements made at 90 K to 450 K show very strong dependence of temperature, following mixed modes of activation energy and hopping-based conduction.

  7. Atomic Structure of Ultrathin Gold Nanowires.

    Science.gov (United States)

    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. PMID:27071038

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

    Directory of Open Access Journals (Sweden)

    Wang Yong

    2010-01-01

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

  9. Looking into meta-atoms of plasmonic nanowire metamaterial

    KAUST Repository

    Tsai, Kuntong

    2014-09-10

    Nanowire-based plasmonic metamaterials exhibit many intriguing properties related to the hyperbolic dispersion, negative refraction, epsilon-near-zero behavior, strong Purcell effect, and nonlinearities. We have experimentally and numerically studied the electromagnetic modes of individual nanowires (meta-atoms) forming the metamaterial. High-resolution, scattering-type near-field optical microscopy has been used to visualize the intensity and phase of the modes. Numerical and analytical modeling of the mode structure is in agreement with the experimental observations and indicates the presence of the nonlocal response associated with cylindrical surface plasmons of nanowires.

  10. Atomic-scale nanowires: physical and electronic structure

    International Nuclear Information System (INIS)

    The technology to build and study nanowires with sizes ranging from individual atoms to tens of nanometres has been developing rapidly over the last few years. We survey the motivation behind these developments, and summarize the basics behind quantized conduction. Several of the different experimental techniques and materials systems used in the creation of nanowires are examined, and the range of theoretical methods developed both for examining open systems (especially their conduction properties) and for modelling large systems are considered. We present various noteworthy example results from the field, before concluding with a look at future directions. (topical review)

  11. Local electrode atom probe analysis of silicon nanowires grown with an aluminum catalyst

    International Nuclear Information System (INIS)

    Local electrode atom probe (LEAP) tomography of Al-catalyzed silicon nanowires synthesized by the vapor–liquid–solid method is presented. The concentration of Al within the Al-catalyzed nanowire was found to be 2 × 1020 cm−3, which is higher than the expected solubility limit for Al in Si at the nanowire growth temperature of 550 °C. Reconstructions of the Al contained within the nanowire indicate a denuded region adjacent to the Al catalyst/Si nanowire interface, while Al clusters are distributed throughout the rest of the silicon nanowire. (paper)

  12. Mechanical Resonances of Helically Coiled Carbon Nanowires

    Science.gov (United States)

    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.

  13. Structural, electronic and magnetic properties of hcp Fe, Co and Ni nanowires encapsulated in zigzag carbon nanotubes

    Science.gov (United States)

    Xie, Y.; Zhang, J. M.; Huo, Y. P.

    2011-06-01

    The structural, electronic and magnetic properties of hcp transition metal (TM = Fe, Co or Ni) nanowires TM4 encapsulated inside zigzag nanotubes C( m, 0) ( m = 7, 8, 9, 10, 11 or 12), along with TM n ( n = 4, 10 or 13) encapsulated inside C(12, 0), have been systematically investigated using the first-principle calculations. The results show that the TM nanowires can be inserted inside a variety of zigzag carbon nanotubes (CNTs) exothermically, except from the systems TM4@(7, 0) and TM13@(12, 0) which are endothermic. The charge is transferred from TM nanowires to CNTs, and the transferred charge increases with decreasing CNT diameter or increasing nanowire thickness. The magnetic moments of hybrid systems are smaller than those of the freestanding TM nanowires, especially for the atoms on the outermost shell of the nanowires. The magnetic moment per TM atom of TM/CNT system increases with increasing CNT diameter or decreasing nanowire thickness. Both the density of states and spin charge density analysis show that the spin polarization and the magnetic moments of all hybrid systems mainly originate from the TM nanowires, implying these systems can be applied in magnetic data storage devices.

  14. Charge transport in a single superconducting tin nanowire encapsulated in a multiwalled carbon nanotube

    NARCIS (Netherlands)

    Tombros, Nikolaos; Buit, Luuk; Arfaoui, Imad; Tsoufis, Theodoros; Gournis, Dimitrios; Trikalitis, Pantelis N.; van der Molen, Sense Jan; Rudolf, Petra; van Wees, Bart J.

    2008-01-01

    The charge transport properties of single superconducting tin nanowires encapsulated by multiwalled carbon nanotubes have been investigated by multiprobe measurements. The multiwalled carbon nanotube protects the tin nanowire from oxidation and shape fragmentation and therefore allows us to investig

  15. The mechanism of transforming diamond nanowires to carbon nanostructures

    International Nuclear Information System (INIS)

    The transformation of diamond nanowires (DNWs) with different diameters and geometries upon heating is investigated with density-functional-based tight-binding molecular dynamics. DNWs of 〈100〉 and 〈111〉 oriented cross-section with projected average line density between 7 and 20 atoms Å−1 transform into carbon nanotubes (CNTs) under gradual heating up to 3500–4000 K. DNWs with projected average line density larger than 25 atoms Å−1 transform into double-wall CNTs. The route of transformation into CNTs clearly exhibits three stages, with the intriguing intermediate structural motif of a carbon nanoscroll (CNS). Moreover, the morphology plays an important role in the transformation involving the CNS as one important intermediate motif to form CNTs. When starting with 〈 2-bar 11〉 oriented DNWs with a square cross-section consisting of two {111} facets facing each other, one interesting structure with ‘nano-bookshelf’ shape emerges: a number of graphene ‘shelves’ located inside the CNT, bonding to the CNT walls with sp3 hybridized atoms. The nano-bookshelf structures exist in a wide range of temperatures up to 3000 K. The further transformation from nano-bookshelf structures depends on the strength of the joints connecting shelves with CNT walls. Notably, the nano-bookshelf structure can evolve into two end products: one is CNT via the CNS pathway, the other is graphene transformed directly from the nano-bookshelf structure at high temperature. This work sheds light on the microscopic insight of carbon nanostructure formation mechanisms with the featured motifs highlighted in the pathways. (paper)

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

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wanghua; Roca i Cabarrocas, Pere [Laboratoire de Physique des Interfaces et Couches Minces (LPICM), UMR 7647, CNRS, Ecole Polytechnique, 91128 Palaiseau (France); Pareige, Philippe; Castro, Celia [Groupe de Physique des Matériaux (GPM), Université et INSA de Rouen, UMR 6634, CNRS, Av. de l' Université, BP 12, 76801 Saint Etienne du Rouvray (France); Xu, Tao; Grandidier, Bruno; Stiévenard, Didier [Institut d' Electronique et de Microélectronique et de Nanotechnologies (IEMN), UMR 8520, CNRS, Département ISEN, 41 bd Vauban, 59046 Lille Cedex (France)

    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.

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

    International Nuclear Information System (INIS)

    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

  18. Intermittent contact interaction between an atomic force microscope cantilever and a nanowire

    Science.gov (United States)

    Knittel, I.; Ungewitter, L.; Hartmann, U.

    2012-05-01

    We investigate in theory and experiment the intermittent contact interaction between an atomic force microscope (AFM) cantilever and a nanowire under ambient conditions. The nanowire is modeled as a spring reacting instantaneously to any change of the force between the wire and the cantilever. This implies that the cantilever is subject to an "effective" force-distance relation, containing not only the surface forces but also the deflection of the nanowire. Experimentally, CVD-grown tin oxide nanowires and lithographically structured silicon nanowire arrays were investigated by intermittent contact AFM. By comparison of experimental and simulated distance-dependent resonance curves it is found that the nanowires behave like "fast nanosprings" and that the adhesion force is one of the key factors determining distance-dependent resonance curves. The results are fully applicable to a scenario in which a cantilever equipped by a nanowire interacts with a surface.

  19. Investigation on the effect of atomic defects on the breaking behaviors of gold nanowires

    International Nuclear Information System (INIS)

    The mechanical properties and breaking behaviors of the [100]-oriented single-crystal gold nanowires containing a set of defect ratios have been studied at different temperatures using molecular dynamics simulations. The size of the nanowire is 10a × 10a × 30a (a stands for lattice constant, 0.408 nm for gold). The mechanical strengths of the nanowires decrease with the increasing temperature. However, the defects that enhance the local thermal energy have improved the nanowire mechanical strength under a wide range of temperature. Comparing to the single-crystal nanowire, the existence of the atomic defects extends the elastic deformation showing a larger yield strain. By summarizing 300 samples at each temperature, the statistical breaking position distribution shows that the nanowire breaking behavior is sensitive to the atomic defects when the defect ratio is 5 % at 100 K, whereas the ratio is 1 % when temperatures are 300 and 500 K.

  20. Enhanced synthesis of Sn nanowires with aid of Se atom via physical vapor transport

    Science.gov (United States)

    Cai, Huacheng; Wang, Wendong; Liu, Peiwen; Wang, Guangming; Liu, Ankang; He, Zhe; Cheng, Zhaofang; Zhang, Shengli; Xia, Minggang

    2015-06-01

    We demonstrate tin (Sn) nanowires growth enhanced by Selenium (Se) atoms via physical vapor transport (PVT) method. The Raman spectroscopy, X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy show that Sn nanowires are synthesized with a large quantity, good quality and high purity of Sn. The growth of Sn nanowires is attributed to Solid-Vapor-Liquid mechanism. The effects of gold nanoparticles catalyst, Si substrate, and Se atoms on Sn nanowires growth are discussed in detail. We find that Se atom plays a key role in the growth of Sn nanowires. The gaseous Sn atoms are absorbed by the eutectic alloy droplets of Se-Au at first. Then Sn atoms precipitate at the liquid-solid phase interface due to a supersaturated solution and form a one-dimensional nanostructure. In all, this PVT method could provide a simple and quick way to synthesize monocrystalline Sn nanowires with an advantage in both quality and quantity. The optical transmittance of Sn nanowires thin film with 2 μm2 density approaches 85-90% in visible wavelength. Therefore, the Sn nanowires thin film can be applied to transparent electrode along with their metallic property.

  1. Nanowire modified carbon fibers for enhanced electrical energy storage

    Science.gov (United States)

    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.

  2. Atomic size effects studied by transport in single silicide nanowires

    Science.gov (United States)

    Miccoli, I.; Edler, F.; Pfnür, H.; Appelfeller, S.; Dähne, M.; Holtgrewe, K.; Sanna, S.; Schmidt, W. G.; Tegenkamp, C.

    2016-03-01

    Ultrathin metallic silicide nanowires with extremely high aspect ratios can be easily grown, e.g., by deposition of rare earth elements on semiconducting surfaces. These wires play a pivotal role in fundamental research and open intriguing perspectives for CMOS applications. However, the electronic properties of these one-dimensional systems are extremely sensitive to atomic-sized defects, which easily alter the transport characteristics. In this study, we characterized comprehensively TbSi2 wires grown on Si(100) and correlated details of the atomic structure with their electrical resistivities. Scanning tunneling microscopy (STM) as well as all transport experiments were performed in situ using a four-tip STM system. The measurements are complemented by local spectroscopy and density functional theory revealing that the silicide wires are electronically decoupled from the Si template. On the basis of a quasiclassical transport model, the size effect found for the resistivity is quantitatively explained in terms of bulk and surface transport channels considering details of atomic-scale roughness. Regarding future applications the full wealth of these robust nanostructures will emerge only if wires with truly atomically sharp interfaces can be reliably grown.

  3. Electrical transport measurements of individual bismuth nanowires and carbon nanotubes

    Science.gov (United States)

    Jang, Wan Young

    Nanostructures are defined by reducing dimensions. When the reduced size of materials is comparable to the Fermi wavelength, quantum size effect occurs. Dimensionality plays a critical role in determining the electronic properties of materials, because the density of states of materials is quite different. Nanowires have attracted much attention recently due to their fundamental interest and potential applications. A number of materials have been tried. Among them, bismuth has unique properties. Bismuth has the smallest effective mass as small as 0.001me. This small effective mass of Bi nanowires allows one to observe the quantum confinement effect easily. Also Bi nanowires are good candidates for a low-dimensional transport study due to long mean free path. Because of these remarkable properties of Bi nanowires, many efforts have been made to study Bi nanowires. However, because bismuth is extremely sensitive to the oxide, it is very difficult to make a reliable device. So far, array measurements of Bi nanowires have been reported. The study is focused on the synthesis and electric transport measurements of individual Bi nanowires. Bi nanowires are synthesized by electrodeposition using either anodic aluminum oxide (AAO) templates or commercially available track etched polycarbonate membranes (PCTE). The desired nanowire has a heterostructure of Au - Bi - Au. Au wires on both sides serve as contact electrodes with Bi. To extract nanowires from PCTE or AAO, several attempts have been made. Devices consisting of single Bi nanowires grown by hydrothermal method are fabricated and electrical measurements have been carried out after in-situ deposition of Pt electrodes. The temperature dependence of resistance of majority of nanowires increases with decreasing temperature, showing polycrystalline nature of nanowires. However, some nanowires show resistance peaks at low temperature, suggesting quantum size effect (QSE). Magnetoresistance (MR) has also been measured. We

  4. Detection and Quantized Conductance of Neutral Atoms Near a Charged Carbon Nanotube

    OpenAIRE

    Ristroph, Trygve; Goodsell, Anne; Golovchenko, Jene Andrew; Hau, Lene V.

    2005-01-01

    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 t...

  5. Morphology of Platinum Nanowire Array Electrodeposited Within Anodic Aluminium Oxide Template Characterized by Atomic Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    孔令斌; 陆梅; 李梦轲; 郭新勇; 力虎林

    2003-01-01

    Uniform platinum nanowires were synthesized by electrodepositing the platinum under a very low altering current frequency (20Hz) and increasing voltage (5-15 V) in the pores of anodic aluminium oxide (AAO) template.Atomic force microscopy observation indicates that the template membranes we obtained have hexagonally closepacked nanochannels. The platinum nanowires have highly ordered arrays after partially dissolving the aluminium oxide membrane. With the increasing dissolving time, the platinum nanowire array collapsed. A concave topography of the aluminium substrate was observed after the aluminium oxide membrane was dissolved completely and the platinum nanowires were released from the template. Platinum nanowires were also characterized by transmission electron microscopy and the phase structure of the Al/AAO/Pt composite was proven by x-ray diffraction.

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

    Directory of Open Access Journals (Sweden)

    Yu Linwei

    2011-01-01

    Full Text Available Abstract 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.

  7. Scattering cross section of metal catalyst atoms in silicon nanowires

    DEFF Research Database (Denmark)

    Markussen, Troels; Rurali, R.; Cartoixa, X.;

    2010-01-01

    A common technique to fabricate silicon nanowires is to use metal particles (e.g., Au, Ag, Cu, Al) to catalyze the growth reaction. As a consequence, the fabricated nanowires contain small concentrations of these metals as impurities. In this work we investigate the effect of the metallic impurit...

  8. Semiconductor nanowires and carbon nanotubes and their process technology for quantum information devices

    International Nuclear Information System (INIS)

    This paper shows an example of the concept of quantum information processor, and describes the possibility of semiconductor nanowires and carbon nanotubes (CNT) as the materials for spin form quantum bits and external interface. Required physical effects are the Coulomb blockade effect of double-bond quantum dots, technology for controlling spins in electric field using spin-orbit interaction and its physics, and quantum interaction between quantum bits as artificial atoms and microwave circuit resonator. This paper describes the merits to use InSb and Ge/Si nanowires and process technology for realizing the above targets. Finally, it introduces the preparation of high-order structure using the heterojunction of molecules and nanotubes for the purpose of utilizing monolayer CNT. (A.O.)

  9. Carbon-doped SiO x nanowires with a large yield of white emission

    International Nuclear Information System (INIS)

    The growth of SiO x nanowires (NWs) with intense white emission is reported. Due to carbon monoxide gas being used as a dopant precursor, carbon-doped under-stoichiometric silicon dioxide NWs are obtained. The doping of the NWs is studied by means of x-ray photoelectron spectroscopy, which allows to assess the presence of carbon atoms in the silicon oxide amorphous structure. The light emission properties are studied by means of cathodoluminescence spectroscopy, which shows three main emission bands set at 2.7 eV (blue), 2.3 eV (green) and 1.9 eV (red), resulting in the white emission. (papers)

  10. Carbon-doped SiO(x) nanowires with a large yield of white emission.

    Science.gov (United States)

    Fabbri, Filippo; Rossi, Francesca; Negri, Marco; Tatti, Roberta; Aversa, Lucrezia; Dhanabalan, Sathish Chander; Verucchi, Roberto; Attolini, Giovanni; Salviati, Giancarlo

    2014-05-01

    The growth of SiOx nanowires (NWs) with intense white emission is reported. Due to carbon monoxide gas being used as a dopant precursor, carbon-doped under-stoichiometric silicon dioxide NWs are obtained. The doping of the NWs is studied by means of x-ray photoelectron spectroscopy, which allows to assess the presence of carbon atoms in the silicon oxide amorphous structure. The light emission properties are studied by means of cathodoluminescence spectroscopy, which shows three main emission bands set at 2.7 eV (blue), 2.3 eV (green) and 1.9 eV (red), resulting in the white emission. PMID:24736107

  11. High Throughput Nanofabrication of Silicon Nanowire and Carbon Nanotube Tips on AFM Probes by Stencil-Deposited Catalysts

    DEFF Research Database (Denmark)

    Engstrøm, Daniel Southcott; Savu, Veronica; Zhu, Xueni;

    2011-01-01

    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...... 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....

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

    Science.gov (United States)

    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.

  13. Carbon-assisted nucleation and vertical growth of high-quality ZnO nanowire arrays

    Directory of Open Access Journals (Sweden)

    Chun Cheng

    2011-09-01

    Full Text Available We developed a carbon-assisted physical-vapor-deposition method for the growth of highly aligned ZnO nanowire arrays on any flat substrates in large area. Amorphous carbon (a-C films acted as the preferential nucleation sites to facilitate the growth of high-quality ZnO nanowire array patterns. The ultrathin a-C films can effectively retard the inclined growth of ZnO nanowires at the edge of the a-C patterns. The investigations of the nanowire structures, photoluminescence and electrical transport properties have shown that the ZnO nanowires were well crystallized and the formation of defects in the nanowires was largely suppressed.

  14. Tribological characteristics of ZnO nanowires investigated by atomic force microscope

    Science.gov (United States)

    Chung, Koo-Hyun; Kim, Hyun-Joon; Lin, Li-Yu; Kim, Dae-Eun

    2008-08-01

    Zinc oxide (ZnO) nanowires have attracted great interest in nanodevices. In this work, the tribological characteristics of vertically grown ZnO nanowires obtained by metalorganic chemical vapor deposition were investigated by using an atomic force microscope (AFM). The ZnO nanowires were slid against flattened silicon and diamond-coated AFM probes under 50 150 nN normal force while monitoring the frictional force. The wear of the ZnO nanowires was observed by a scanning electron microscope and quantified based on Archard’s wear law. Also, the wear debris accumulated on the silicon probe was analyzed by using a transmission electron microscope (TEM). The results showed that the wear of ZnO nanowires slid against the silicon probe was extremely small. However, when the ZnO nanowires were slid against the diamond-coated probe, the wear coefficients ranged from 0.006 to 0.162, which correspond to the range of severe wear at the macroscale. It was also shown that the friction coefficient decreased from 0.30 to 0.25 as the sliding cycles increased. From TEM observation, it was found that the ZnO wear debris was mainly amorphous in structure. Also, crystalline ZnO nanoparticles were observed among the wear debris.

  15. Carbon-supported SnO2 nanowire arrays with enhanced lithium storage properties

    International Nuclear Information System (INIS)

    Graphical abstract: Carbon-supported SnO2 nanowire arrays were synthesized facilely using self-assembled mesoporous carbon as template followed by partial removal of the carbon. The obtained materials exhibit improved lithium storage capabilities with high capacity retention due to the presence of the carbon buffering layer. - Highlights: • Carbon-supported SnO2 nanowire arrays were synthesized. • No extra carbon coating step is needed. • The materials exhibit enhanced lithium storage capacity. - Abstract: Carbon-supported SnO2 nanowire arrays were synthesized by a facile strategy using self-assembled mesoporous carbon as template followed by partial removal of the carbon. The as-obtained materials were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and nitrogen adsorption. The resulting products possess a large specific surface area due to the free interspaces between the nanowires. When evaluated as anode materials for lithium-ion batteries, the carbon-supported SnO2 nanowires can deliver large reversible capabilities with excellent cycling performance on account of the mesoporous carbon matrix, which can be served as a buffering layer to relax the stress, reduce the volume variation, and protect the SnO2 nanowires from severe structural degradation during the insertion-deinsertion process of lithium ions

  16. On-chip microplasma reactors using carbon nanofibres and tungsten oxide nanowires as electrodes

    NARCIS (Netherlands)

    Agiral, Anil; Groenland, Alforns W.; Kumar Chinthaginjala, J.; Seshan, K.; Lefferts, Leon; Gardeniers, J.G.E. (Han)

    2008-01-01

    Carbon nanofibres (CNFs) and tungsten oxide (W18O49) nanowires have been incorporated into a continuous flow type microplasma reactor to increase the reactivity and efficiency of the barrier discharge at atmospheric pressure. CNFs and tungsten oxide nanowires were characterized by high-resolution sc

  17. Filling double-walled carbon nanotubes with AgCl nanowires

    International Nuclear Information System (INIS)

    Double-walled carbon nanotubes (DWCNTs) filled with AgCl crystal nanowires were synthesized and characterized by X-ray diffraction, transmission electron microscopy and Raman spectroscopy. It has been found that there exists charge transfer between the AgCl nanowires and the DWCNT inner tubes

  18. Photoluminescence Properties of Silicon Nanowires and Carbon Nanotube-Silicon Nanowire Composite Arrays

    Institute of Scientific and Technical Information of China (English)

    李梦轲; 陆梅; 孔令斌; 王成伟; 郭新勇; 力虎林

    2002-01-01

    Composite arrays of multi-wall carbon nanotubes (MWNTs) and silicon nanowires (SiNWs) are fabricated by means of the chemical vapour deposition method in porous anodic aluminium oxide (AAO) templates. The results of the scanning electron microscopy, high-resolution transmission electron microscopy, and transmission electron microscopy have shown that SiNWs are successful nested or filled in the hollow cavities of synthesized MWNT arrays in AAO templates to form MWNT-SiNW composite arrays. The photoluminescence (PL) intensity degradation and a blueshift of PL peak position, usually created from the chemical instability of the SiNW surfaces, are decreased and eliminated clearly in the composite arrays. The composite arrays of MWNTs-SiNWs exhibit more enhanced intensity and stability of PL performance than the SiNW arrays deposited in AAO templates.

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

    International Nuclear Information System (INIS)

    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

  20. Preparation and characterization of carbon/SiC nanowire/Na-doped carbonated hydroxyapatite multilayer coating for carbon/carbon composites

    Energy Technology Data Exchange (ETDEWEB)

    Leilei, Zhang, E-mail: zhangleilei1121@aliyun.com; Hejun, Li; Kezhi, Li; Shouyang, Zhang; Qiangang, Fu; Yulei, Zhang; Jinhua, Lu; Wei, Li

    2014-09-15

    Highlights: • CSH coatings were prepared by combination of magnetron sputter ion plating, CVD and UECD. • Na{sup +} and CO{sub 3}{sup 2−} were developed to co-substitute hydroxyapatite. • SiC nanowires were introduced into Na-doped carbonated hydroxyapatite. • CSH coatings showed excellent cell activity and cell proliferation behavior. - Abstract: A carbon/SiC nanowire/Na-doped carbonated hydroxyapatite multilayer coating (CSH coating) was prepared on carbon/carbon composites using a combination method of magnetron sputter ion plating, chemical vapor deposition and ultrasound-assisted electrochemical deposition procedure. The morphology, microstructure and chemical composition of the coating were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results showed that the CSH coating was consisted of three components: carbon layer, SiC nanowires and Na-doped carbonated hydroxyapatite. The carbon layer provided a dense and uniform surface structure for the growth of SiC nanowires. The SiC nanowires exhibited a porous structure, favoring the infiltration of Na-doped carbonated hydroxyapatite crystals. The Na-doped carbonated hydroxyapatite could infiltrate into the pores of SiC nanowires and finally cover the SiC nanowires entirely with a needle shape. The osteoblast-like MG63 cells were employed to assess the in vitro biocompatibility of the CSH coating. The MG63 cells favorably spread and grew well across the CSH coating surface with plenty of filopods and microvilli, exhibiting excellent cell activity. Moreover, the CSH coating elicited higher cell proliferation as compared to bare carbon/carbon composites. In conclusion, the CSH offers great potential as a coating material for future medical application in hard tissue replacement.

  1. Preparation and characterization of carbon/SiC nanowire/Na-doped carbonated hydroxyapatite multilayer coating for carbon/carbon composites

    International Nuclear Information System (INIS)

    Highlights: • CSH coatings were prepared by combination of magnetron sputter ion plating, CVD and UECD. • Na+ and CO32− were developed to co-substitute hydroxyapatite. • SiC nanowires were introduced into Na-doped carbonated hydroxyapatite. • CSH coatings showed excellent cell activity and cell proliferation behavior. - Abstract: A carbon/SiC nanowire/Na-doped carbonated hydroxyapatite multilayer coating (CSH coating) was prepared on carbon/carbon composites using a combination method of magnetron sputter ion plating, chemical vapor deposition and ultrasound-assisted electrochemical deposition procedure. The morphology, microstructure and chemical composition of the coating were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results showed that the CSH coating was consisted of three components: carbon layer, SiC nanowires and Na-doped carbonated hydroxyapatite. The carbon layer provided a dense and uniform surface structure for the growth of SiC nanowires. The SiC nanowires exhibited a porous structure, favoring the infiltration of Na-doped carbonated hydroxyapatite crystals. The Na-doped carbonated hydroxyapatite could infiltrate into the pores of SiC nanowires and finally cover the SiC nanowires entirely with a needle shape. The osteoblast-like MG63 cells were employed to assess the in vitro biocompatibility of the CSH coating. The MG63 cells favorably spread and grew well across the CSH coating surface with plenty of filopods and microvilli, exhibiting excellent cell activity. Moreover, the CSH coating elicited higher cell proliferation as compared to bare carbon/carbon composites. In conclusion, the CSH offers great potential as a coating material for future medical application in hard tissue replacement

  2. Quantitative dopant distributions in GaAs nanowires using atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Du, Sichao [School of Physics, The University of Sydney, NSW 2006 (Australia); Burgess, Timothy [Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Gault, Baptiste [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Department of Materials Science and Engineering, McMaster University, 1280 Main St W, Hamilton, Ontario L8S4L8 (Canada); Gao, Qiang [Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Bao, Peite; Li, Li [School of Physics, The University of Sydney, NSW 2006 (Australia); Cui, Xiangyuan; Kong Yeoh, Wai; Liu, Hongwei; Yao, Lan [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Ceguerra, Anna V. [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Hoe Tan, Hark; Jagadish, Chennupati [Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Ringer, Simon P. [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Zheng, Rongkun, E-mail: rongkun.zheng@sydney.edu.au [School of Physics, The University of Sydney, NSW 2006 (Australia)

    2013-09-15

    Controllable doping of semiconductor nanowires is critical to realize their proposed applications, however precise and reliable characterization of dopant distributions remains challenging. In this article, we demonstrate an atomic-resolution three-dimensional elemental mapping of pristine semiconductor nanowires on growth substrates by using atom probe tomography to tackle this major challenge. This highly transferrable method is able to analyze the full diameter of a nanowire, with a depth resolution better than 0.17 nm thanks to an advanced reconstruction method exploiting the specimen's crystallography, and an enhanced chemical sensitivity of better than 8-fold increase in the signal-to-noise ratio. - Highlights: ► Probing pristine semiconductor NWs from growth substrate has been demonstrated. ► Analyzing the full diameter of a nanowire has been achieved. ► A spatial resolution better than 0.17 nm in depth has been obtained for GaAs. ► An enhanced SNR 100:2 has been achieved.

  3. Quantitative dopant distributions in GaAs nanowires using atom probe tomography

    International Nuclear Information System (INIS)

    Controllable doping of semiconductor nanowires is critical to realize their proposed applications, however precise and reliable characterization of dopant distributions remains challenging. In this article, we demonstrate an atomic-resolution three-dimensional elemental mapping of pristine semiconductor nanowires on growth substrates by using atom probe tomography to tackle this major challenge. This highly transferrable method is able to analyze the full diameter of a nanowire, with a depth resolution better than 0.17 nm thanks to an advanced reconstruction method exploiting the specimen's crystallography, and an enhanced chemical sensitivity of better than 8-fold increase in the signal-to-noise ratio. - Highlights: ► Probing pristine semiconductor NWs from growth substrate has been demonstrated. ► Analyzing the full diameter of a nanowire has been achieved. ► A spatial resolution better than 0.17 nm in depth has been obtained for GaAs. ► An enhanced SNR 100:2 has been achieved

  4. Highly conductive interwoven carbon nanotube and silver nanowire transparent electrodes

    Directory of Open Access Journals (Sweden)

    Andrew J Stapleton, Rakesh A Afre, Amanda V Ellis, Joe G Shapter, Gunther G Andersson, Jamie S Quinton and David A Lewis

    2013-01-01

    Full Text Available Electrodes fabricated using commercially available silver nanowires (AgNWs and single walled carbon nanotubes (SWCNTs produced sheet resistances in the range 4–24 Ω squ−1 with specular transparencies up to 82 %. Increasing the aqueous dispersibility of SWCNTs decreased the bundle size present in the film resulting in improved SWCNT surface dispersion in the films without compromising transparency or sheet resistance. In addition to providing conduction pathways between the AgNW network, the SWCNTs also provide structural support, creating stable self-supporting films. Entanglement of the AgNWs and SWCNTs was demonstrated to occur in solution prior to deposition by monitoring the transverse plasmon resonance mode of the AgNWs during processing. The interwoven AgNW/SWCNT structures show potential for use in optoelectronic applications as transparent electrodes and as an ITO replacement.

  5. Effects of catalyst precursors on carbon nanowires by using ethanol catalytic combustion technique

    Institute of Scientific and Technical Information of China (English)

    CHENG Jin; ZOU Xiao-ping; LI Fei; ZHANG Hong-dan; REN Peng-fei

    2006-01-01

    Iron nitrate,nickel nitrate and cobalt nitrate were used as catalyst precursors to study their effects on carbon nanowires synthesized by ethanol catalytic combustion (ECC) process. The as-grown carbon nanowires were characterized by means of scanning electron microscopy,transmission electron microscopy and Raman spectroscopy. The results show that relatively uniform nanowires will be formed when the catalyst precursor is iron nitrate:while helical structure or disordered structure will be formed when the catalyst precursor is nickel nitrate or cobalt nitrate.

  6. A supercritical carbon dioxide plasma process for preparing tungsten oxide nanowires.

    Science.gov (United States)

    Kawashima, Ayato; Nomura, Shinfuku; Toyota, Hiromichi; Takemori, Toshihiko; Mukasa, Shinobu; Maehara, Tsunehiro

    2007-12-12

    A supercritical carbon dioxide (CO(2)) plasma process for fabricating one-dimensional tungsten oxide nanowires coated with amorphous carbon is presented. High-frequency plasma was generated in supercritical carbon dioxide at 20 MPa by using tungsten electrodes mounted in a supercritical cell, and subsequently an organic solvent was introduced with supercritical carbon dioxide into the plasma. Electron microscopy and Raman spectroscopy investigations of the deposited materials showed the production of tungsten oxide nanowires with or without an outer layer. The nanowires with an outer layer exhibited a coaxial structure with an outer concentric layer of amorphous carbon and an inner layer of tungsten oxide with a thickness and diameter of 20-30 and 10-20 nm, respectively. PMID:20442477

  7. A supercritical carbon dioxide plasma process for preparing tungsten oxide nanowires

    International Nuclear Information System (INIS)

    A supercritical carbon dioxide (CO2) plasma process for fabricating one-dimensional tungsten oxide nanowires coated with amorphous carbon is presented. High-frequency plasma was generated in supercritical carbon dioxide at 20 MPa by using tungsten electrodes mounted in a supercritical cell, and subsequently an organic solvent was introduced with supercritical carbon dioxide into the plasma. Electron microscopy and Raman spectroscopy investigations of the deposited materials showed the production of tungsten oxide nanowires with or without an outer layer. The nanowires with an outer layer exhibited a coaxial structure with an outer concentric layer of amorphous carbon and an inner layer of tungsten oxide with a thickness and diameter of 20-30 and 10-20 nm, respectively

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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. PMID:27188268

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

    Science.gov (United States)

    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. PMID:25319204

  12. Plasma enhanced atomic layer deposition of magnesium oxide as a passivation layer for enhanced photoluminescence of ZnO nanowires

    International Nuclear Information System (INIS)

    The growth characteristics and film properties of magnesium oxide (MgO) thin films fabricated by plasma enhanced atomic layer deposition (PE-ALD) and thermal ALD (Th-ALD) were comparatively investigated for passivation layer applications. For both processes, well-saturated growth characteristics were observed, with a higher saturated growth rate for Th-ALD. X-ray photoemission analysis showed that very high purity MgO film with virtually no carbon contamination was deposited by PE-ALD. X-ray diffraction and transmission electron microscopy analysis showed that the PE-ALD MgO thin films had a larger grain size than the Th-ALD MgO thin films and were predominantly (1 1 1) crystal orientation. The photoluminescence analysis showed enhanced luminescence properties of the ALD MgO shell/ZnO nanowires. In particular, PE-ALD MgO showed greater enhancement of the luminescence properties than Th-ALD MgO. -- Highlights: • Atomic layer deposition of Magnesium oxide (MgO) thin films were studied using Magnesium bis(cyclopentadienyl) (MgCp2) with H2O and O2 plasma. • PE-ALD MgO thin films show (1 1 1) orientation and have larger grain size than Th-ALD MgO thin films. • Enhanced luminescence properties of the ALD MgO shell/ZnO nanowires are observed. • PE-ALD MgO showed greater enhancement of the luminescence properties than Th-ALD MgO

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

    Directory of Open Access Journals (Sweden)

    Jung Han Kim

    2016-01-01

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

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

    Science.gov (United States)

    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. PMID:27458789

  15. Solid source growth of Si oxide nanowires promoted by carbon nanotubes

    International Nuclear Information System (INIS)

    Highlights: • An array of well aligned and uniform CNTs is successfully fabricated by PECVD. • SiONW growth utilizes Si substrate as the source, ruling out the usage of silane. • With CNT array on the substrate, SiONW growth is improved significantly. • CNTs help dispersion of the catalysts and diffusion of the Si atoms. - Abstract: We report a method to promote solid source growth of Si oxide nanowires (SiONWs) by using an array of vertically aligned carbon nanotubes (CNTs). It starts with the fabrication of CNT array by plasma enhanced chemical vapor deposition (PECVD) on Si wafers, followed by growth of SiONWs. Herein, CNTs serve as a scaffold, which helps the dispersion of catalysts for SiONWs and also provides space for hydrogen which boosts the diffusion of Si atoms and hence formation of SiONWs. As the result, a three dimensional (3D) hybrid network of densely packed SiONWs and CNTs can be produced rapidly

  16. Highly porous CdO nanowires: preparation based on hydroxy- and carbonate-containing cadmium compound precursor nanowires, gas sensing and optical properties

    International Nuclear Information System (INIS)

    Highly porous cadmium oxide (CdO) nanowires have been prepared by calcining the hydroxy- and carbonate-containing cadmium compound precursor nanowires. The large-scale precursor nanowires were synthesized through a hydrothermal method. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to characterize and analyze the as-synthesized precursor nanowires as well as the calcined products. It was revealed that the wire-like morphology of the precursor was fundamentally retained during the process of calcination and the CdO nanowires obtained were polycrystalline with highly porous structures. In order to illustrate the formation mechanism of the porous structures, the morphology and composition evolutions of the precursor nanowires under different stages of the calcining process were further investigated via SEM, x-ray diffraction (XRD) and infrared (IR) absorbance spectroscopy. Gas sensing has been explored for the sensor device fabricated with highly porous CdO nanowires, which demonstrates that it has good response owing to its special structures and great selectivity to NOx. Furthermore, the UV-visible and photoluminescence spectra of highly porous CdO nanowires have also been investigated

  17. Growth of crystalline silicon nanowires on nickel-coated silicon wafer beneath sputtered amorphous carbon

    International Nuclear Information System (INIS)

    Growth of crystalline silicon nanowire of controllable diameter directly from Si wafer opens up another avenue for its application in solar cells and optical sensing. Crystalline Si nanowire can be directly grown from Si wafer upon rapid thermal annealing in the presence of the catalyst such as nickel (Ni). However, the accompanying oxidation immediately changes the crystalline Si nanowire to amorphous SiOx. In this study, amorphous carbon layer was sputtered to on top of the catalyst Ni layer to retard the oxidation. Scanning electron microscope, transmission electron microscope, Raman spectroscopy and X-ray photoelectron spectroscopy were employed to characterize the wires and oxidation process. A model was developed to explain the growth and oxidation process of the crystalline Si nanowire. - Highlights: ► Carbon was sputtered on nickel to retard the oxidation of silicon nanowires. ► Silicon core was controlled by carbon layer thickness and annealing duration. ► An oxidation-accompanying solid–liquid–solid growth mechanism was developed

  18. Oxygen atom loss coefficient of carbon nanowalls

    Energy Technology Data Exchange (ETDEWEB)

    Mozetic, Miran, E-mail: miran.mozetic@guest.arnes.si [Jozef Stefan Institute, Jamova cesta 39, 1000 Ljubljana (Slovenia); Vesel, Alenka [Jozef Stefan Institute, Jamova cesta 39, 1000 Ljubljana (Slovenia); Stoica, Silviu Daniel; Vizireanu, Sorin; Dinescu, Gheorghe [National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilo Street, PO Box MG-36, Magurele, Bucharest 077125 (Romania); Zaplotnik, Rok [Jozef Stefan Institute, Jamova cesta 39, 1000 Ljubljana (Slovenia)

    2015-04-01

    Highlights: • Atomic oxygen loss coefficient on carbon nanowalls (CNWs) was evaluated. • Atomic oxygen loss coefficient of CNW is the largest among any known materials. • Surface atom loss is a major loss mechanism at room temperatures. - Abstract: Extremely high values of atomic oxygen loss coefficient on carbon nanowall (CNW) surface are reported. CNW layers consisting of interconnected individual nanostructures with average length of 1.1 μm, average thickness of 66 nm and surface density of 3 CNW/μm{sup 2} were prepared by plasma jet enhanced chemical-vapor deposition using C{sub 2}H{sub 2}/H{sub 2}/Ar gas mixtures. The samples were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), Raman spectrometry (RS) as well as X-ray photoelectron spectroscopy (XPS). The surface loss coefficient was measured at room temperature in a flowing afterglow at different densities of oxygen atoms supplied from inductively coupled radiofrequency O{sub 2} plasma. The RF generator operated at 13.56 MHz and different nominal powers up to 900 W corresponding to different O-atom density in the afterglow up to 1.3 × 10{sup 21} m{sup −3}. CNW and several different samples of known coefficients for heterogeneous surface recombination of neutral oxygen atoms have been placed separately in the afterglow chamber and the O-atom density in their vicinity was measured with calibrated catalytic probes. Comparison of measured results allowed for determination of the loss coefficient for CNWs and the obtained value of 0.59 ± 0.03 makes this material an extremely effective sink for O-atoms.

  19. Atomic resolution studies of carbonic anhydrase II

    International Nuclear Information System (INIS)

    The structure of human carbonic anhydrase II has been solved with a sulfonamide inhibitor at 0.9 Å resolution. Structural variation and flexibility is seen on the surface of the protein and is consistent with the anisotropic ADPs obtained from refinement. Comparison with 13 other atomic resolution carbonic anhydrase structures shows that surface variation exists even in these highly ordered isomorphous crystals. 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

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

    Directory of Open Access Journals (Sweden)

    Tang Zirong

    2011-01-01

    Full Text Available Abstract 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.

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

    Science.gov (United States)

    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%.

  2. Detection of gas atoms with carbon nanotubes

    Science.gov (United States)

    Arash, B.; Wang, Q.

    2013-05-01

    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.

  3. Synthesis of β-SiC nanowires by ball milled nanoparticles of silicon and carbon

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Pengchao, E-mail: kangpc@hit.edu.cn [Materials Science and Engineering School, Harbin Institute of Technology, P.O.B. 433, Harbin 150001 (China); Zhang, Bin; Wu, Gaohui; Gou, Huasong; Chen, Guoqin; Jiang, Longtao [Materials Science and Engineering School, Harbin Institute of Technology, P.O.B. 433, Harbin 150001 (China); Mula, Suhrit [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Roorkee 247667 (India)

    2014-08-01

    Highlights: • The β-SiC nanowires were synthesized only use milled Si and C nanoparticles. • No catalyst was used in this process. • The grown mechanism of β-SiC nanowires is nanoparticles self-assembly and solid–solid reaction. • This notion, together with the nanowires synthesis are expected to apply opens up other semiconductor nanomaterials. - Abstract: In the present investigation, we report a simple and new technique to synthesize silicon carbide nanowires by high energy ball milling of silicon and carbon powders followed by annealing at elevated temperatures. The detailed structural analysis was carried out by X-ray diffraction, scanning and transmission electron microscopy, and FT-IR analysis. Nanocrystalline silicon particles were detected to be covered by amorphous carbon after milling. This typical structure was transformed to β-SiC nanowires during annealing by new growth mechanism. The β-SiC nanoparticles were found to be self-assembled one by one and formed a curly chain, and then rotated gradually in accordance to the same crystal orientation along the β-SiC [1 1 1] direction.

  4. SiC nanowires reinforced MAS joint of SiC coated carbon/carbon composites to LAS glass ceramics

    International Nuclear Information System (INIS)

    Graphical abstract: Schematic cross-section images of the samples with SiC nanowires and assembly sequence for the raw materials through the process of the hot-pressing method. Highlights: ► The SiC nanowires were firstly used as porous layer in the middle of the joint. ► The shear strength of the joint with SiC nanowires was largely improved. ► A new mode of fracture was proposed. - Abstract: In order to improve the shear strength of the joints of carbon/carbon (C/C) composites to lithium aluminum silicate (LAS) glass ceramics, SiC coating and magnesium aluminum silicate (MAS) glass ceramics were used as transition layer and middle layer, respectively, and high quality SiC nanowires were applied as the reinforcement materials in MAS. The SiC nanowires reinforced MAS joint of SiC coated C/C composites to LAS glass ceramics was prepared by a three-step technique of pack cementation, CVD and hot-pressing. The microstructures of the as-prepared joints were characterized by SEM and EDS, and the shear strength of the joints was also examined. The shear strength of the SiC–MAS joint increased from 24.0 ± 2.0 MPa to 35.5 ± 5.5 MPa after adding SiC nanowires in MAS. The load decreases in step-style but not perpendicularly after the maximum value, which demonstrates good toughness of the joint with SiC nanowire porous layer.

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

    International Nuclear Information System (INIS)

    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.

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

    Science.gov (United States)

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

    2016-05-01

    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.

  7. Photoelectrochemical reduction of carbon dioxide using Ge doped GaN nanowire photoanodes

    Directory of Open Access Journals (Sweden)

    Yichen Wang

    2015-11-01

    Full Text Available We report on the direct conversion of carbon dioxide (CO2 in a photoelectrochemical cell consisting of germanium doped gallium nitride nanowire anode and copper (Cu cathode. Various products including methane (CH4, carbon monoxide (CO, and formic acid (HCOOH were observed under light illumination. A Faradaic efficiency of ∼10% was measured for HCOOH. Furthermore, this photoelectrochemical system showed enhanced stability for 6 h CO2 reduction reaction on low cost, large area Si substrates.

  8. Hybrid Carbon Fiber/ZnO Nanowires Polymeric Composite for Stuctural and Energy Harvesting Applications

    OpenAIRE

    Masghouni, Nejib

    2014-01-01

    Despite the many attractive features of carbon fiber reinforced polymers (FRPs) composites, they are prone to failure due to delamination. The ability to tailor the fiber/matrix interface FRPs is crucial to the development of composite materials with enhanced structural performance. In this dissertation, ZnO nanowires (NWs) were grown on the surface of carbon fibers utilizing low temperature hydrothermal synthesis technique prior to the hybrid composite fabrication. The scanning electron micr...

  9. Carbon-layer-protected cuprous oxide nanowire arrays for efficient water reduction

    KAUST Repository

    Zhang, Zhonghai

    2013-02-26

    In this work, we propose a solution-based carbon precursor coating and subsequent carbonization strategy to form a thin protective carbon layer on unstable semiconductor nanostructures as a solution to the commonly occurring photocorrosion problem of many semiconductors. A proof-of-concept is provided by using glucose as the carbon precursor to form a protective carbon coating onto cuprous oxide (Cu2O) nanowire arrays which were synthesized from copper mesh. The carbon-layer-protected Cu2O nanowire arrays exhibited remarkably improved photostability as well as considerably enhanced photocurrent density. The Cu2O nanowire arrays coated with a carbon layer of 20 nm thickness were found to give an optimal water splitting performance, producing a photocurrent density of -3.95 mA cm-2 and an optimal photocathode efficiency of 0.56% under illumination of AM 1.5G (100 mW cm-2). This is the highest value ever reported for a Cu 2O-based electrode coated with a metal/co-catalyst-free protective layer. The photostability, measured as the percentage of the photocurrent density at the end of 20 min measurement period relative to that at the beginning of the measurement, improved from 12.6% on the bare, nonprotected Cu2O nanowire arrays to 80.7% on the continuous carbon coating protected ones, more than a 6-fold increase. We believe that the facile strategy presented in this work is a general approach that can address the stability issue of many nonstable photoelectrodes and thus has the potential to make a meaningful contribution in the general field of energy conversion. © 2013 American Chemical Society.

  10. Detection of gas atoms with carbon nanotubes

    OpenAIRE

    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....

  11. Atom probe tomography (APT) of carbonate minerals.

    Science.gov (United States)

    Pérez-Huerta, Alberto; Laiginhas, Fernando; Reinhard, David A; Prosa, Ty J; Martens, Rich L

    2016-01-01

    Atom probe tomography (APT) combines the highest spatial resolution with chemical data at atomic scale for the analysis of materials. For geological specimens, the process of field evaporation and molecular ion formation and interpretation is not yet entirely understood. The objective of this study is to determine the best conditions for the preparation and analysis by APT of carbonate minerals, of great importance in the interpretation of geological processes, focusing on the bulk chemical composition. Results show that the complexity of the mass spectrum is different for calcite and dolomite and relates to dissimilarities in crystalochemical parameters. In addition, APT bulk chemistry of calcite closely matches the expected stoichiometry but fails to provide accurate atomic percentages for elements in dolomite under the experimental conditions evaluated in this work. For both calcite and dolomite, APT underestimates the amount of oxygen based on their chemical formula, whereas it is able to detect small percentages of elemental substitutions in crystal lattices. Overall, our results demonstrate that APT of carbonate minerals is possible, but further optimization of the experimental parameters are required to improve the use of atom probe tomography for the correct interpretation of mineral geochemistry. PMID:26519815

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

    Energy Technology Data Exchange (ETDEWEB)

    Rajkumar, K.; Rajavel, K. [Department of Physics, Bharathiar University, Coimbatore, Tamil Nadu (India); Cameron, D. C. [ASTRaL, Lappeenranta University of Technology, Mikkeli (Finland); current address Miktech Oy, Mikkeli (Finland); Mangalaraj, D. [Department of NanoScience and Technology, Bharathiar University, Coimbatore, Tamil Nadu (India); Rajendrakumar, R. T., E-mail: buc@edu.in [Department of Physics, Bharathiar University, Coimbatore, Tamil Nadu (India); Department of NanoScience and Technology, Bharathiar University, Coimbatore, Tamil Nadu (India)

    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.

  13. Carbon nanotube atomic force microscopy probes

    Science.gov (United States)

    Yamanaka, Shigenobu; Okawa, Takashi; Akita, Seiji; Nakayama, Yoshikazu

    2005-05-01

    We have developed a carbon nanotube atomic force microscope probe. Because the carbon nanotube are well known to have high aspect ratios, small tip radii and high stiffness, carbon nanotube probes have a long lifetime and can be applied for the observation deep trenches. Carbon nanotubes were synthesized by a well-controlled DC arc discharge method, because this method can make nanotubes to have straight shape and high crystalline. The nanotubes were aligned on the knife-edge using an alternating current electrophoresis technique. A commercially available Si probe was used for the base of the nanotube probe. The nanotube probe was fabricated by the SEM manipulation method. The nanotube was then attached tightly to the Si probe by deposition of amorphous carbon. We demonstrate the measurement of a fine pith grating that has vertical walls. However, a carbon nanotube has a problem that is called "Sticking". The sticking is a chatter image on vertical like region in a sample. We solved this problem by applying 2 methods, 1. a large cantilever vibration amplitude in tapping mode, 2. an attractive mode measurement. We demonstrate the non-sticking images by these methods.

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

    Science.gov (United States)

    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.

  15. The Effect of Atomic Vacancies and Grain Boundaries on Mechanical Properties of GaN Nanowires

    Institute of Scientific and Technical Information of China (English)

    XIE Shi-Feng; CHEN Shang-Da; SOS Ai-Kah

    2011-01-01

    @@ Molecular dynamics simulations are carried out to investigate the influences of various defects on mechanical properties of wurtzite GaN nanowires by adopting the empirical Stillinger-Weber potential.Different types of vacancies and grain boundaries are considered and the uniaxial loading condition is implemented along the [001] direction.It is found that surface defects have less impact on Voung's moduli and critical stresses of GaN nanowires compared with random defects.The grain boundary normal to the axial direction of a nanowire would not significantly affect Young's moduli of nanowires.However, the inversion domain grain boundaries with and without wrong bonds would significantly lower Young's moduli of GaN nanowires.In addition, the inversion domain grain boundary affects the critical stress of GaN nanowires more than the grain boundary with interface normal to the axial direction of the nanowire.%Molecular dynamics simulations are carried out to investigate the influences of various defects on mechanical properties of wurtzite GaN nanowires by adopting the empirical Stillinger-Weber potential. Different types of vacancies and grain boundaries are considered and the uniaxial loading condition is implemented along the [001] direction. It is found that surface defects have less impact on Young's moduli and critical stresses of GaN nanowires compared with random defects. The grain boundary normal to the axial direction of a nanowire would not significantly affect Young's moduli of nanowires. However, the inversion domain grain boundaries with and without wrong bonds would significantly lower Young's moduli of GaN nanowires. In addition, the inversion domain grain boundary affects the critical stress of GaN nanowires more than the grain boundary with interface normal to the axial direction of the nanowire.

  16. Growth rate model and doping metrology by atom probe tomography in silicon nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Chen, W.H.; Larde, R.; Cadel, E.; Pareige, P. [Groupe de Physique des Materiaux, Universite et INSA de Rouen, UMR CNRS 6634, Av. de l' Universite, BP 12, 76801 Saint Etienne du Rouvray (France); Xu, T.; Grandidier, B.; Nys, J.P.; Stievenard, D. [Institut d' Electronique, de Microelectronique et de Nanotechnologie, UMR CNRS 8520, Departement ISEN, 41 bd Vauban, 59046 Lille Cedex (France)

    2011-03-15

    Silicon nanowires (SiNWs) with different surface number density are fabricated using Chemical Vapor Deposition (CVD) method by controlling the catalyst droplet number density with in-situ evaporation. For comparison, another type of SiNWs is fabricated by Molecular Beam Epitaxy (MBE) method. To study these two types of SiNWs a general growth rate model is presented. The fit curves from this model are consistent with our experimental data. In both growing conditions the SiNW growth rate as a function of their diameter are compared and discussed. The p-type SiNWs have also been prepared by adding diborane into precursor. The doping metrology in an individual SiNW is realized by laser assisted Atom Probe Tomography (APT). We have shown that the doping atoms (e.g. B) can incorporate into SiNW and an accurate quantification can be given (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Charge transport in DNA nanowires connected to carbon nanotubes

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Bao, Peite; Du, Sichao; Zheng, Rongkun, E-mail: rongkun.zheng@sydney.edu.au [School of Physics, The University of Sydney, Sydney, NSW 2006 (Australia); Wang, Yanbo; Liao, Xiaozhou, E-mail: xiaozhou.liao@sydney.edu.au [School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, NSW 2006 (Australia); Cui, Xiangyuan; Yen, Hung-Wei; Kong Yeoh, Wai; Ringer, Simon P. [School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, NSW 2006 (Australia); Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006 (Australia); Gao, Qiang; Hoe Tan, H.; Jagadish, Chennupati [Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Liu, Hongwei [Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006 (Australia); Zou, Jin [Materials Engineering and Centre for Microscopy and Microanalysis, The University of Queensland, Brisbane, QLD 4072 (Australia)

    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.

  19. Recombination of atomic oxygen and hydrogen on amorphous carbon

    International Nuclear Information System (INIS)

    Deposit buildup and fuel entrapment due to amorphous carbon are relevant issues in fusion devices with carbon based plasma facing components. Neutral atomic species play a significant role – atomic hydrogen facilitates the formation of amorphous carbon while atomic oxygen could be used to remove carbon deposits. The kinetics of either reaction depends on the density of neutral species, which in turn is influenced by recombination on the vessel walls. In this work, we measured the probability of heterogeneous recombination of atomic hydrogen and oxygen on amorphous carbon deposits. The recombination coefficients were determined by observing density profiles of atomic species in a closed side-arm of a plasma vessel with amorphous carbon deposit-lined walls. Density profiles were measured with fiber optics catalytic probes. The source of atomic species was inductively coupled radiofrequency plasma. The measured recombination coefficient values were of the order of 10−3 for both species

  20. Special structures and properties of hydrogen nanowire confined in a single walled carbon nanotube at extreme high pressure

    Directory of Open Access Journals (Sweden)

    Yueyuan Xia

    2012-06-01

    Full Text Available Extensive ab initio molecular dynamics simulations indicate that hydrogen can be confined in single walled carbon nanotubes to form high density and high pressure H2 molecular lattice, which has peculiar shell and axial structures depending on the density or pressure. The band gap of the confined H2 lattice is sensitive to the pressure. Heating the system at 2000K, the H2 lattice is firstly melted to form H2 molecular liquid, and then some of the H2 molecules dissociate accompanied by drastic molecular and atomic reactions, which have essential effect on the electronic structure of the hydrogen system. The liquid hydrogen system at 2000K is found to be a particular mixed liquid, which consists of H2 molecules, H atoms, and H-H-H trimers. The dissociated H atoms and the trimers in the liquid contribute resonance electron states at the Fermi energy to change the material properties substantially. Rapidly cooling the system from 2000K to 0.01 K, the mixed liquid is frozen to form a mixed solid melt with a clear trend of band gap closure. It indicates that this solid melt may become a superconducting nanowire when it is further compressed.

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

    Science.gov (United States)

    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

  2. An enzymatic glucose biosensor based on a glassy carbon electrode modified with manganese dioxide nanowires

    International Nuclear Information System (INIS)

    A glassy carbon electrode was modified with β-manganese dioxide (β-MnO2), and glucose oxidase (GOx) was immobilized on its surface. The β-MnO2 nanowires were prepared by a hydrothermal method and characterized by scanning electron microscopy and powder X-ray diffraction. They were then dispersed in Nafion solution and cast on the glassy carbon electrode (GCE) to form an electrode modified with β-MnO2 nanowires that exhibits improved sensitivity toward hydrogen peroxide. If GOx is immobilized in the surface, the β-MnO2 acts as a mediator, and Nafion as a polymer backbone. The fabrication process was characterized by electrochemical impedance spectroscopy, and the sensor and its materials were characterized by cyclic voltammetry and amperometry. The biosensor enables amperometric detection of glucose with a sensitivity of 38.2 μA · mM−1 · cm−2, and a response time of 2 nanowires. (author)

  3. Synthesis of Nanoscale Heterostructures Comprised of Metal Nanowires, Carbon Nanotubes, and Metal Nanoparticles: Investigation of Their Structure and Electrochemical Properties

    Directory of Open Access Journals (Sweden)

    Nitin Chopra

    2015-01-01

    Full Text Available One-dimensional nanoscale heterostructures comprised of multisegment gold-nickel nanowires, carbon nanotube, and nickel nanoparticles were fabricated in a unique approach combining top-down and bottom-up assembly methods. Porous alumina template was utilized for sequential electrodeposition of gold and nickel nanowire segments. This was followed by chemical vapor deposition growth of carbon nanotubes on multisegment gold-nickel nanowires, where nickel segment also acted as a carbon nanotube growth catalyst. The aligned arrays of these gold-nickel-carbon nanotube heterostructures were released from porous alumina template and then subjected to wet-chemical process to be decorated with nickel/nickel oxide core/shell nanoparticles. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy were utilized for morphology, interface, defect, and structure characterization. The electrochemical performance of these heterostructures was studied using cyclic voltammetry method and the specific capacitance of various heterostructures was estimated and compared.

  4. Template synthesis, characterization and magnetic property of Fe nanowires-filled amorphous carbon nanotubes array

    International Nuclear Information System (INIS)

    A Fe nanowires-filled amorphous carbon nanotubes (FeNW-filled a-CNTs) array was synthesized by sequential growth of electrodeposited Fe nanowires and subsequent chemical vapour deposition of amorphous CNTs in the nanochannels of alumina template. Structural characterizations of as-prepared FeNW-filled a-CNTs were carried out via field emission scanning electron microscope (FE-SEM), x-ray diffraction (XRD), elemental mapping, high-resolution transmission electron microscope (HRTEM) and Raman scattering. The formation mechanism of such Fe/C nanoheterostructure was proposed according to the detailed HRTEM analyses. Furthermore, the room temperature magnetic property of the as-prepared FeNW-filled a-CNTs array was also investigated, and obvious anisotropic behaviour in magnetization was observed

  5. Investigation on single carbon atom transporting through the single-walled carbon nanotube by MD simulation

    International Nuclear Information System (INIS)

    The single carbon atom transporting through the single-walled carbon nanotube has been studied by molecular-dynamics (MD) simulation. We got different trajectories of the carbon atom by changing the input parameters. The simulation results indicate that the single carbon atom with low energy can transport through the carbon nanotube under some input conditions and result in different trajectories being straight line or 'rosette' or circular. (authors)

  6. Carbon based thirty six atom spheres

    Science.gov (United States)

    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.

  7. Structurally uniform and atomically precise carbon nanostructures

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    Florian Banhart

    2015-02-01

    Full Text Available 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.

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

    International Nuclear Information System (INIS)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Lixia; Ma, Yongjun; Dai, Bo [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); Zhou, Yong [Eco-materials and Renewable Energy Research Center (ERERC), School of Physics, National Lab of Solid State Microstructure, ERERC, Nanjing University, Nanjing 210093 (China); Liu, Jinsong [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); Pei, Chonghua, E-mail: peichonghua@swust.edu.cn [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China)

    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.

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

    Science.gov (United States)

    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.

  12. Oxidation behaviour of carbon monoxide at the photostimulated surface of ZnO nanowires

    International Nuclear Information System (INIS)

    Normally carbon monoxide is considered to be a reducing agent, which can be used for CO detection. However, oxidizing behaviour of CO, to the best of our knowledge, has not been reported. In this work, we find that CO can also act as oxidizing gas at room temperature on photostimulated ZnO nanowires. For photostimulation, the low intensity of light emitting diodes is used to induce a very low photocurrent, which, however, leads to a large resistance change due to the ultraviolet light interaction with the nanowire surface. During CO detection, the oxygen vacancies enhance the CO adsorption on the nanowire surface even at room temperature. CO molecules adsorbing on the surface are presumably bound to a zinc-oxygen vacancy complex, causing a reduction in free electron concentration, which leads to an oxidizing effect of CO gas. An adsorption model for CO is proposed to explain the experimental observations. These results shed light on developing room-temperature CO sensor using oxide nanostructures with the help of high energetic photon replacing the high-temperature process normally used in traditional gas sensors.

  13. Fabrication of carbon nanostructures (nanodots, nanowires) by energetic ion irradiation

    International Nuclear Information System (INIS)

    Carbon nanostructures were synthesized by energetic ion irradiation of Si-based gel films. These polymer-like films with different side groups and C concentrations were prepared by sol-gel chemistry and irradiated with Si or Au ions of different energies in the range 3 MeV-2 GeV. The shape and size of the formed carbon nanostructures was studied by energy filtered transmission electron microscopy. They exhibited a visible photoluminescence emission, due to their semiconducting nature and the confinement of excitons. The changes in the optical properties were correlated with the structural transformation of films, investigated by means of Fourier transformed infrared (FTIR) and Raman spectroscopies. The role of carbon concentration, structure and energy transferred by ions on the luminescence properties are discussed

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

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Azam, E-mail: azam.khan@liu.se; Edberg, Jesper; Nur, Omer; Willander, Magnus [Department of Science and Technology (ITN), Campus Norrköping, Linköping University, SE-601 74 Norrköping (Sweden)

    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.

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

    Science.gov (United States)

    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.

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

    International Nuclear Information System (INIS)

    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.

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

    International Nuclear Information System (INIS)

    Low temperature (∼200 °C) grown atomic layer deposition (ALD) films of AlN, TiN, Al2O3, GaN, and TiO2 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 Al2O3. 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 Al2O3 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 Al2O3 provides moderate surface passivation as well as long term protection from oxidation and environmental attack

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

    Directory of Open Access Journals (Sweden)

    Veer Dhaka

    2016-01-01

    Full Text Available Low temperature (∼200 °C grown atomic layer deposition (ALD films of AlN, TiN, Al2O3, GaN, and TiO2 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 Al2O3. 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 Al2O3 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 Al2O3 provides moderate surface passivation as well as long term protection from oxidation and environmental attack.

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

    Energy Technology Data Exchange (ETDEWEB)

    Dhaka, Veer, E-mail: veer.dhaka@aalto.fi; Perros, Alexander; Kakko, Joona-Pekko; Haggren, Tuomas; Lipsanen, Harri [Department of Micro- and Nanosciences, Micronova, Aalto University, P.O. Box 13500, FI-00076 (Finland); Naureen, Shagufta; Shahid, Naeem [Research School of Physics & Engineering, Department of Electronic Materials Engineering, Australian National University, Canberra ACT 2601 (Australia); Jiang, Hua; Kauppinen, Esko [Department of Applied Physics and Nanomicroscopy Center, Aalto University, P.O. Box 15100, FI-00076 (Finland); Srinivasan, Anand [School of Information and Communication Technology, KTH Royal Institute of Technology, Electrum 229, S-164 40 Kista (Sweden)

    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.

  20. Fabrication of β-Silicon Carbide Nanowires from Carbon Powder and Silicon Wafer

    Directory of Open Access Journals (Sweden)

    Majid S. Al-Ruqeishi

    2016-06-01

    Full Text Available β-SiCNWs were synthesized by simple carbo-thermal process using silicon wafer and carbon powder only. The obtained β-SiCNWs were short and thick with random distribution over Si wafer surface when rapid heating rate is applied. While β-SiCNWs fabricated under low heating rate are 57.0±3.0 nm in average diameter and few millimeters in length. An ambient Ar gas flow rates were found to be critical in the growth yield of resultant β-SiC nanowires. XRD diffraction patterns and FTIR spectrum reveals the composition structure of theses wires.

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

    OpenAIRE

    Seok-Hwan Park; Wan-Jin Lee

    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-s...

  2. Nitrogenases-A Tale of Carbon Atom(s).

    Science.gov (United States)

    Hu, Yilin; Ribbe, Markus W

    2016-07-11

    Named after its ability to catalyze the reduction of nitrogen to ammonia, nitrogenase has a surprising rapport with carbon-both through the interstitial carbide that resides in the central cavity of its cofactor and through its ability to catalyze the reductive carbon-carbon coupling of small carbon compounds into hydrocarbon products. Recently, a radical-SAM-dependent pathway was revealed for the insertion of carbide, which signifies a novel biosynthetic route to complex bridged metalloclusters. Moreover, a sulfur-displacement mechanism was proposed for the activation of carbon monoxide by nitrogenase, which suggests an essential role of the interstitial carbide in maintaining the stability while permitting a certain flexibility of the cofactor structure during substrate turnover. PMID:27206025

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

    Science.gov (United States)

    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. PMID:26319534

  4. Fabrication of silicon carbide nanowires/carbon nanotubes heterojunction arrays by high-flux Si ion implantation.

    Science.gov (United States)

    Liu, Huaping; Cheng, Guo-An; Liang, Changlin; Zheng, Ruiting

    2008-06-18

    An array of silicon carbide nanowire (SiCNW)-carbon nanotube (CNT) heterojunctions was fabricated by high-flux Si ion implantation into a multi-walled carbon nanotube (MWCNT) array with a metal vapor vacuum arc (MEVVA) ion source. Under Si irradiation, the top part of a CNT array was gradually transformed into an amorphous nanowire array with increasing Si dose while the bottom part still remained a CNT structure. X-ray photoelectron spectroscopy (XPS) analysis shows that the SiC compound was produced in the nanowire part even at the lower Si dose of 5 × 10(16) ions cm(-2), and the SiC amount increased with increasing the Si dose. Therefore, the fabrication of a SiCNW-CNT heterojunction array with the MEVVA technique has been successfully demonstrated. The corresponding formation mechanism of SiCNWs was proposed. PMID:21825818

  5. Study of removal of Direct Yellow 12 by cadmium oxide nanowires loaded on activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    Ghaedi, Mehrorang, E-mail: m_ghaedi@mail.yu.ac.ir [Chemistry Department, Yasouj University Yasouj 75914-35 (Iran, Islamic Republic of); Sadeghian, Batuol [Chemistry Department, Yasouj University Yasouj 75914-35 (Iran, Islamic Republic of); Kokhdan, Syamak Nasiri, E-mail: syamak.nasiri@yahoo.com [Chemistry Department, Yasouj University Yasouj 75914-35 (Iran, Islamic Republic of); Pebdani, Arezou Amiri [Chemistry Department, Yasouj University Yasouj 75914-35 (Iran, Islamic Republic of); Sahraei, Reza; Daneshfar, Ali; Mihandoost, Asma [Department of Chemistry, University of Ilam, P.O. Box: 65315-516, Ilam (Iran, Islamic Republic of)

    2013-05-01

    In this research, cadmium oxide nanowires loaded on activated carbon (CdO-NW-AC) has been synthesized by a simple procedure and characterized by different techniques such as XRD, SEM and UV–vis spectrometry. This new adsorbent has been efficiently utilized for the removal of the Direct Yellow 12 (DY-12) from wastewater. To obtain maximum DY-12 removal efficiency, the influences of variables such as pH, DY-12 concentration, amount of CdO-NW-AC, contact time, and temperature have been examined and optimized in a batch method. Following the variable optimization, the experimental equilibrium data (at different concentration of DY-12) was fitted to conventional isotherm models such as Langmuir, Freundlich and Tempkin. The applicability of each method is based on the R{sup 2} and error analysis for each model. It was found that the experimental equilibrium data well fitted to the Langmuir isotherm model. The dependency of removal process to time and the experimental data follow second order kinetic model with involvement of intraparticle diffusion model. The negative value of Gibbs's free energy and positive value of adsorption enthalpy show the spontaneous and endothermic nature of adsorption process. - Graphical abstract: Typical FE-SEM image of the CdO nanowires. Highlights: ► Cadmium oxide nanowires loaded on activated carbon was utilized as an adsorbent. ► It was used for the removal of Direct Yellow 12 from aqueous solutions. ► The adsorption of Direct Yellow 12 on this adsorbent is endothermic in nature. ► The adsorption equilibrium data was well described by the Langmuir isotherm model.

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

    International Nuclear Information System (INIS)

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Cole, Milton W [Department of Physics, Penn State University, 104 Davey Lab MB123, University Park, PA 16802-6300 (United States); Crespi, Vincent H [Department of Physics and Department of Material Science and Engineering, 104 Davey Lab MB193, University Park, PA 16802-6300 (United States); Dresselhaus, Mildred S [Department of Electrical Engineering and Computer Science and Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02138 (United States); Dresselhaus, Gene [Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02138 (United States); Fischer, John E [Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut St, Philadelphia, PA 19104-6272 (United States); Gutierrez, Humberto R [Department of Physics, Penn State University, 104 Davey Lab MB060, University Park, PA 16802-6300 (United States); Kojima, K; Wako, K [Department of Information Science, Yokohama Soei Junior College, Miho-cho 1, Midori-ku, Yokohama 226-0015 (Japan); Mahan, Gerald D [Department of Physics, Penn State University, 104 Davey Lab MB169, University Park, PA 16802-6300 (United States); Rao, Apparao M [Department of Physics and Astronomy and Center for Optical Materials Science and Engineering Technologies, Clemson University, Clemson, SC 29634 (United States); Sofo, Jorge O [Department of Physics, Penn State University, 104 Davey Lab MB172, University Park, PA 16802-6300 (United States); Tachibana, M [Graduate School of Integrated Science, Yokohama City University, Seto 22-2, Kanazawa-ku, Yokohama 236-0027 (Japan); Xiong Qihua, E-mail: mwc@psu.ed, E-mail: millie@mgm.mit.ed, E-mail: gene@mgm.mit.ed, E-mail: fischer@seas.upenn.ed, E-mail: hur3@psu.ed, E-mail: gdm12@psu.ed, E-mail: arao@clemson.ed [School of Physical and Mathematical Sciences, Division of Physics and Applied Physics, Nanyang Technological University, 21 Nanyang Link, SPMS-PAP-04-14 (Singapore)

    2010-08-25

    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 C{sub 60} 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

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

    Directory of Open Access Journals (Sweden)

    Taeksoo Ji

    2011-05-01

    Full Text Available 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.

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

    Directory of Open Access Journals (Sweden)

    Ting-Mao Chou

    2016-02-01

    Full Text Available 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.

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

    OpenAIRE

    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 nucleat...

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

    Science.gov (United States)

    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 %). PMID:27128407

  12. Study of the reaction of carbon with atomic oxygen

    International Nuclear Information System (INIS)

    This research thesis reports the study of reactions of carbon when in contact with atomic oxygen in order to have a better understanding of the combustion mechanism. It appears that, at room temperature, oxygen atoms impacting the carbon surface do not all react with this surface (the reaction shock efficiency is very low). At temperatures higher than 200 C, all atoms which reach the surface react with it and the efficiency is much higher. The study of the reaction rate with respect to temperature allows three domains of reaction conditions to be distinguished according to the stability of formed surface oxides. The initial degassing of carbon results in a temporary excitation of the reaction rate, even with atomic oxygen. Whatever is the temperature, reaction is localised at the vicinity of the sample outer surface (this means that the regime is constantly diffusion). The BET surface of carbons does not vary with the reaction. As texture, the structure of the different carbons does not seem to have an influence on the reaction with atomic oxygen. Even though results are obtained in very different temperature ranges (600 C with O2, less than 200 C with atomic oxygen), there is an analogy between some phenomena noticed with atomic oxygen and molecular oxygen: surface oxides play a prevailing role

  13. Theoretical study of adsorption of lithium atom on carbon nanotube

    OpenAIRE

    Senami, Masato; Ikeda, Yuji; Fukushima, Akinori; Tachibana, Akitomo

    2011-01-01

    We investigate the adsorption of lithium atoms on the surface of the (12,0) single wall carbon nanotube (SWCNT) by using ab initio quantum chemical calculations. The adsorption of one lithium atom on the inside of this SWCNT is favored compared to the outside. We check this feature by charge transfer and regional chemical potential density. The adsorption of multiple lithium atoms on the interior of the SWCNT is studied in terms of adsorption energy and charge transfer. We show that repulsive...

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

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • We prepared a self-supported porous Co3O4/C core/shell nanowire array. • Core/shell nanowire array showed high pseudo-capacitive properties. • Core/shell array structure was favorable for fast ion and electron transfer. - Abstract: High-reactivity electrode materials are indispensible for developing high-performance electrochemical energy storage devices. Herein, we report self-supported core/shell Co3O4/C nanowire arrays by using hydrothermal synthesis and chemical vapor deposition methods. A uniform and thin carbon shell is coated on the surface of Co3O4 nanowire forming core/shell nanowires with diameters of ∼100 nm. Asymmetric supercapacitors have been assembled with the core/shell Co3O4/C nanowire arrays as the positive electrode and activated carbon (AC) as the negative electrode. The core/shell Co3O4/C nanowire arrays exhibit a specific capacity of 116 mAh g−1 at the working current of 100 mA (4 A g−1), and a long cycle life along with ∼ 92% retention after 8000 cycles at 4 A g−1, higher than the unmodified Co3O4 nanowire arrays (81 mAh g−1 at 4 A g−1). The introduction of uniform carbon layer into the core/shell structure is favorable for the enhancement of supercapacitor due to the improved electrical conductivity and reaction kinetics

  15. p-type doping of GaAs nanowires using carbon

    Science.gov (United States)

    Salehzadeh, O.; Zhang, X.; Gates, B. D.; Kavanagh, K. L.; Watkins, S. P.

    2012-11-01

    We report on the electrical properties of Au-catalyzed C-doped GaAs nanowires (NWs) grown by metal organic vapor phase epitaxy. Transport measurements were carried out using a tungsten nanoprobe inside a scanning electron microscope by contacting to the Au catalyst particle of individual nanowires. The doping level could be varied from approximately (4 ± 1) × 1016 cm-3 to (1.0 ± 0.3) × 1019 cm-3 by varying the molar flow of the gas phase carbon precursor, as well as the group V to group III precursor ratio. It was found that the current transport mechanism switches from generation-recombination to tunnelling field emission by increasing the doping level to 1 × 1019 cm-3. Based on a diameter-dependent analysis of the apparent resistivity of the C-doped NWs, we propose that C incorporates into GaAs NWs through the triple boundary at the Au/NW interface. The p-type conductivity of the C-doped NWs was inferred by observing a rectification at negative bias (applied to the Au electrode) and confirmed by back-gating measurements performed on field effect transistor devices.

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

    Science.gov (United States)

    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.

  17. Growth Mechanism of Cubic-Silicon Carbide Nanowires

    Directory of Open Access Journals (Sweden)

    K. Y. Cheong

    2009-01-01

    Full Text Available Cubic-SiC nanowires were synthesized using activated carbon powder and Si substrate in vacuum at 1200–1350°C for 1–4 hours. The nanowires were grown according to the following proposed mechanisms: (1 diffusion of C/CO into Si substrate, (2 weakening of Si bond and atomic kick-out, (3 formation of Si-C in vapor phase, (4 formation of saturated SiC layer, (5 formation of pyramid-like SiC nanostructure, and (6 formation of SiC nanowires.

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

    Science.gov (United States)

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

    2015-12-01

    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.

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

    Science.gov (United States)

    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

  20. Silicon nanowire array/polymer hybrid solar cell incorporating carbon nanotubes

    International Nuclear Information System (INIS)

    Here we present a simple and novel approach of fabricating three dimensional (3D) n-Si nanowires (NWs) and poly(3-octylthiophene) hybrid solar cells incorporating carbon nanotubes (CNTs). Vertically aligned n-Si NWs arrays were fabricated by electroless chemical etching of a n-Si [1 1 1] wafer. n-Si NWs/poly(3-octylthiophene) hybrid solar cells were fabricated with and without functionalized CNTs incorporation. Fabricated solar cells incorporating CNTs show open circuit voltage (Voc), short circuit current density (Jsc) fill factor (FF) and conversion efficiency as 0.353, 7.85 mA cm-2, 22% and 0.61%, respectively. In fabricated devices n-Si NWs arrays form multiple heterojunctions with the polymer and provide efficient electron collection and transportation, whereas CNTs provide efficient hole transportation.

  1. Enhanced electroactive properties of polyurethane films loaded with carbon-coated SiC nanowires

    International Nuclear Information System (INIS)

    Polyurethane-based nanocomposite films were prepared by incorporating carbon-coated SiC nanowires (SiC-C) into the polymer matrix. Electric field-induced strain measurements revealed that a loading of 0.5 wt% SiC-C increased the strain level by a factor of 1.7 at a moderate field strength (6.5 V μm-1). Current-electric field characteristics and the film thickness dependence of strain demonstrated that the improvement of the electromechanical response was linked to a more pronounced space charge effect in the nanocomposite than in the polymer host. DSC measurements revealed that the level of phase mixing in the PU matrix remained unchanged after SiC-C filling; hence, the nano-objects themselves acted as charge traps.

  2. Enhanced electroactive properties of polyurethane films loaded with carbon-coated SiC nanowires

    Science.gov (United States)

    Guiffard, B.; Guyomar, D.; Seveyrat, L.; Chowanek, Y.; Bechelany, M.; Cornu, D.; Miele, P.

    2009-03-01

    Polyurethane-based nanocomposite films were prepared by incorporating carbon-coated SiC nanowires (SiC@C) into the polymer matrix. Electric field-induced strain measurements revealed that a loading of 0.5 wt% SiC@C increased the strain level by a factor of 1.7 at a moderate field strength (6.5 V µm-1). Current-electric field characteristics and the film thickness dependence of strain demonstrated that the improvement of the electromechanical response was linked to a more pronounced space charge effect in the nanocomposite than in the polymer host. DSC measurements revealed that the level of phase mixing in the PU matrix remained unchanged after SiC@C filling; hence, the nano-objects themselves acted as charge traps.

  3. Atomic and electronic properties of quasi-one-dimensional MoS2 nanowires

    OpenAIRE

    Fernandez Seivane, Lucas; Barron, Hector; Botti, Silvana; Lopes Marques, Miguel Alexandre; Rubio Secades, Ángel; López-Lozano, Xóchitl

    2013-01-01

    The structural, electronic, and magnetic properties of quasi-one-dimensional MoS2nanowires (NWs), passivated by extra sulfur, have been determined using ab initio density functional theory. The nanostructures were simulated using several different models based on experimental electron microscopy images and theoretical literature. It is found that independently of the geometrical details and the coverage of extra sulfur at the Mo edge, quasi-one-dimensional metallic states are predominant in a...

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

    Science.gov (United States)

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

    2016-07-20

    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. PMID:27228337

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

    Science.gov (United States)

    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. PMID:27028048

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

    Science.gov (United States)

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

    2016-02-24

    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. PMID:26866275

  7. Stability of Organic Nanowires

    DEFF Research Database (Denmark)

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

    2011-01-01

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

  8. XPS analysis by exclusion of a-carbon layer on silicon carbide nanowires by a gold catalyst-supported metal-organic chemical vapor deposition method.

    Science.gov (United States)

    Nam, Sang-Hun; Kim, Myoung-Hwa; Hyun, Jae-Sung; Kim, Young Dok; Boo, Jin-Hyo

    2010-04-01

    Silicon carbide (SiC) nano-structures would be favorable for application in high temperature, high power, and high frequency nanoelectronic devices. In this study, we have deposited cubic-SiC nanowires on Au-deposited Si(001) substrates using 1,3-disilabutane as a single molecular precursor through a metal-organic chemical vapor deposition (MOCVD) method. The general deposition pressure and temperature were 3.0 x 10(-6) Torr and 1000 degrees C respectively, with the deposition carried out for 1 h. Au played an important role as a catalyst in growing the SiC nanowires. SiC nanowires were grown using a gold catalyst, with amorphous carbon surrounding the final SiC nanowire. Thus, the first step involved removal of the remaining SiO2, followed by slicing of the amorphous carbon into thin layers using a heating method. Finally, the thinly sliced amorphous carbon is perfectly removed using an Ar sputtering method. As a result, this method may provide more field emission properties for the SiC nanowires that are normally inhibited by the amorphous carbon layer. Therefore, exclusion of the amorphous carbon layer is expected to improve the overall emission properties of SiC nanowires. PMID:20355494

  9. Reactions of carbon atoms in pulsed molecular beams

    Energy Technology Data Exchange (ETDEWEB)

    Reisler, H. [Univ. of Southern California, Los Angeles (United States)

    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.

  10. On the stability of carbon nanotube and titania nanowire based catalyst materials:from synthesis to applications

    OpenAIRE

    Rautio, A.-R. (Anne-Riikka)

    2016-01-01

    Abstract Degradation of the support and sintering of catalyst nanoparticles inherently leads to a loss of functionality of catalyst materials in converters and sensors. Malfunction in such devices may lead to serious economic and environmental damage. The quest for novel and sustainable catalyst materials with better durability is thus ongoing. In this thesis, one-dimensional nanomaterials such as carbon nanotubes and titanium dioxide nanowires are studied and compared to their convention...

  11. Gas sensing properties of zinc stannate (Zn{sub 2}SnO{sub 4}) nanowires prepared by carbon assisted thermal evaporation process

    Energy Technology Data Exchange (ETDEWEB)

    Tharsika, T., E-mail: tharsika@siswa.um.edu.my [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Haseeb, A.S.M.A., E-mail: haseeb@um.edu.my [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Akbar, S.A., E-mail: akbar.1@osu.edu [Center for Industrial Sensors and Measurements (CISM), Department of Materials Science and Engineering, Ohio State University, 2041 College Road, Columbus, OH 43210 (United States); Sabri, M.F.M., E-mail: faizul@um.edu.my [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Wong, Y.H., E-mail: yhwong@um.edu.my [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2015-01-05

    Highlights: • Zn{sub 2}SnO{sub 4} nanowires are grown on Au/alumina substrate by a carbon assisted thermal evaporation process. • Optimum growth conditions for Zn{sub 2}SnO{sub 4} nanowires are determined. • Ethanol gas is selectively sensed with high sensitivity. - Abstract: Zn{sub 2}SnO{sub 4} nanowires are successfully synthesized by a carbon assisted thermal evaporation process with the help of a gold catalyst under ambient pressure. The as-synthesized nanowires are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) equipped with an energy dispersive X-ray spectroscopy (EDS). The XRD patterns and elemental mapping via TEM–EDS clearly indicate that the nanowires are Zn{sub 2}SnO{sub 4} with face centered spinel structure. HRTEM image confirms that Zn{sub 2}SnO{sub 4} nanowires are single crystalline with an interplanar spacing of 0.26 nm, which is ascribed to the d-spacing of (3 1 1) planes of Zn{sub 2}SnO{sub 4}. The optimum processing condition and a possible formation mechanism of these Zn{sub 2}SnO{sub 4} nanowires are discussed. Additionally, sensor performance of Zn{sub 2}SnO{sub 4} nanowires based sensor is studied for various test gases such as ethanol, methane and hydrogen. The results reveal that Zn{sub 2}SnO{sub 4} nanowires exhibit excellent sensitivity and selectivity toward ethanol with quick response and recovery times. The response of the Zn{sub 2}SnO{sub 4} nanowires based sensors to 50 ppm ethanol at an optimum operating temperature of 500 °C is about 21.6 with response and recovery times of about 116 s and 182 s, respectively.

  12. Covalent bond orders for non-bonded atoms: The case for carbon-carbon interactions

    International Nuclear Information System (INIS)

    The Cioslowski-Mixon (CM) covalent bond order and the atoms-in-molecules (AIM) delocalization index can be used to study bonding characteristics between atoms not bonded in the conventional chemical sense. In particular, the bond orders between atoms (AIM basins) with one intervening atom evolve in a predictable manner and are related to the bond orders of conventionally bonded species. The CM approach shows that it is the tails of the incompletely localized orbitals that provide for such interactions. Single, multiple, and resonant bond effects are seen which are physically meaningful and useful as an additional characterization of molecular bonding. The important case of carbon-carbon interactions is studied here.

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

    Directory of Open Access Journals (Sweden)

    Jiye Zhan

    2015-10-01

    Full Text Available 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.

  14. Neutral Atomic Carbon in Centers of Galaxies

    OpenAIRE

    Israel, F.P.; Baas, F

    2001-01-01

    We present measurements of the emission from the centers of fifteen spiral galaxies in the 3P1-3P0 [CI] fine-structure transition at 492 GHz. Observed galaxy centers range from quiescent to starburst to active. The intensities of neutral carbon, the J=2-1 transition of 13CO and the J=4-3 transition of 12CO are compared in matched beams. Most galaxy centers emit more strongly in [CI] than in 13CO, completely unlike the situation pertaining to Galactic molecular cloud regions. [CI] intensities ...

  15. Neutral atomic carbon in dense molecular clouds

    Science.gov (United States)

    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.

  16. A sensitive DNA biosensor fabricated from gold nanoparticles, carbon nanotubes, and zinc oxide nanowires on a glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Wang Jie [College of Chemistry and Materials Science, Anhui Key Laboratory of Chemo-Biosensing, Anhui Normal University, Wuhu 241000 (China); Li Shuping [College of Environment Science, Anhui Normal University, Wuhu 241000 (China); Zhang Yuzhong, E-mail: zhyz65@mail.ahnu.edu.c [College of Chemistry and Materials Science, Anhui Key Laboratory of Chemo-Biosensing, Anhui Normal University, Wuhu 241000 (China)

    2010-06-01

    We outline here the fabrication of a sensitive electrochemical DNA biosensor for the detection of sequence-specific target DNA. Zinc oxide nanowires (ZnONWs) were first immobilized on the surface of a glassy carbon electrode. Multi-walled carbon nanotubes (MWCNTs) with carboxyl groups were then dropped onto the surface of the ZnONWs. Gold nanoparticles (AuNPs) were subsequently introduced to the surface of the MWNTs/ZnONWs by electrochemical deposition. A single-stranded DNA probe with a thiol group at the end (HS-ssDNA) was covalently immobilized on the surface of the AuNPs by forming an Au-S bond. Scanning electron microscopy (SEM) and cyclic voltammetry (CV) were used to investigate the film assembly process. Differential pulse voltammetry (DPV) was used to monitor DNA hybridization by measuring the electrochemical signals of [Ru(NH{sub 3}){sub 6}]{sup 3+} bounding to double-stranded DNA (dsDNA). The incorporation of ZnONWs and MWCNTs in this sensor design significantly enhances the sensitivity and the selectivity. This DNA biosensor can detect the target DNA quantitatively in the range of 1.0 x 10{sup -13} to 1.0 x 10{sup -7} M, with a detection limit of 3.5 x 10{sup -14} M (S/N = 3). In addition, the DNA biosensor exhibits excellent selectivity, even for single-mismatched DNA detection.

  17. Formation of Silicon/Carbon Core-Shell Nanowires Using Carbon Nitride Nanorods Template and Gold Catalyst

    Directory of Open Access Journals (Sweden)

    Ilyani Putri Jamal

    2013-01-01

    Full Text Available In this experiment, silicon/carbon (Si/C core-shell nanowires (NWs were synthesized using gold nanoparticles (Au NPs coated carbon nitride nanorods (CN NRs as a template. To begin with, the Au NPs coated CN NRs were prepared by using plasma-enhanced chemical vapor deposition assisted with hot-wire evaporation technique. Fourier transform infrared spectrum confirms the C–N bonding of the CN NRs, while X-ray diffraction pattern indicates the crystalline structure of the Au NPs and amorphous structure of the CN NRs. The Au NPs coated CN NRs were thermally annealed at temperature of 800°C in nitrogen ambient for one hour to induce the growth of Si/C core-shell NWs. The growth mechanism for the Si/C core-shell NWs is related to the nitrogen evolution and solid-liquid-solid growth process which is a result of the thermal annealing. The formation of Si/C core-shell NWs is confirmed by electron spectroscopic imaging analysis.

  18. Nanotubes and nanowires

    Indian Academy of Sciences (India)

    C N R Rao; A Govindaraj

    2001-10-01

    Synthesis and characterization of nanotubes and nanowires constitute an important part of nanoscience since these materials are essential bui lding units for several devices. We have prepared aligned carbon nanotube bundles and Y-junction nanotubes by the pyrolysis of appropriate organic precursors. The aligned bundles are useful for field emission display while the Y-junction nanotubes are likely to be useful as nanochips since they exhibit diode properties at the junction. By making use of carbon nanotubes, nanowires of metals, metal oxides and GaN have be en obt a ined. Both the oxide and GaN nanowires are single crystalline. Gold nanowires exhibit plasmon bands varying markedly with the aspect ratio. GaN nanowires show excellent photoluminescence characteristics. It has been possible to synthesise nanotubes and nanowires of metal chalcogenides by employing different strategies.

  19. First principles investigation of interaction between impurity atom (Si, Ge, Sn) and carbon atom in diamond-like carbon system

    International Nuclear Information System (INIS)

    The interaction between impurity atom (Si, Ge, and Sn) and carbon atom in diamond-like carbon (DLC) system was investigated by the first principles simulation method based on the density functional theory. The tetrahedral configuration was selected as the calculation model for simplicity. When the bond angle varied in a range of 90°–130° from the equivalent state of 109.471°, the distortion energy and the electronic structures including charge density of the highest occupied molecular orbital (HOMO) and partial density of state (PDOS) in the different systems were calculated. The results showed that the addition of Si, Ge and Sn atom into amorphous carbon matrix significantly decreased the distortion energy of the system as the bond angles deviated from the equilibrium one. Further studies of the HOMO and PDOS indicated that the weak covalent bond between Si(Ge, Sn) and C atoms was formed with the decreased strength and directionality, which were influenced by the electronegative difference. These results implied that the electron transfer behavior at the junction of carbon nano-devices could be tailored by the impurity element, and the compressive stress in DLC films could be reduced by the incorporation of Si, Ge and Sn because of the formation of weaker covalent bonds. - Highlights: ►Distortion energy after bond angle distortion was decreased comparing with C-C unit. ►The weak covalent bond was formed between impurity atoms and corner carbon atoms. ►Observed electron transfer behavior affected the strength and directionality of bond. ►Reduction of strength and directionality of bond contributed to small energy change.

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

    Science.gov (United States)

    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

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

    OpenAIRE

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

    2014-01-01

    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 ...

  2. Novel mechanical behaviors of wurtzite CdSe nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Bing [Shanghai Normal University, Department of Physics (China); Chen, Li [MCPHS University, School of Arts and Sciences (United States); Xie, Yiqun; Feng, Jie; Ye, Xiang, E-mail: yexiang@shnu.edu.cn [Shanghai Normal University, Department of Physics (China)

    2015-09-15

    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.

  3. Novel mechanical behaviors of wurtzite CdSe nanowires

    International Nuclear Information System (INIS)

    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

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

    Science.gov (United States)

    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. Gas-Phase Growth of Heterostructures of Carbon Nanotubes and Bimetallic Nanowires

    Directory of Open Access Journals (Sweden)

    Whi Dong Kim

    2011-01-01

    Full Text Available A simple, inexpensive, and viable method for growing multiple heterostructured carbon nanotubes (CNTs over the entire surface of Ni-Al bimetallic nanowires (NWs in the gas phase was developed. Polymer-templated bimetallic nitrate NWs were produced by electrospinning in the first step, and subsequent calcination resulted in the formation of bimetallic oxide NWs by thermal decomposition. In the second step, free-floating bimetallic NWs were produced by spray pyrolysis in an environment containing hydrogen gas as a reducing gas. These NWs were continuously introduced into a thermal CVD reactor in order to grow CNTs in the gas phase. Scanning electron microscopy (SEM, transmission electron microscopy (TEM, and Raman spectrometry analyses revealed that the catalytic Ni sites exposed in the non-catalytic Al matrix over the entire surface of the bimetallic NWs were seeded to radially grow highly graphitized CNTs, which resembled “foxtail” structures. The grown CNTs were found to have a relatively uniform diameter of approximately 10±2 nm and 10 to 15 walls with a hollow core. The average length of the gas-phase-grown CNTs can be controlled between 100 and 1000 nm by adjusting the residence time of the free-floating bimetallic NWs in the thermal CVD reactor.

  6. Atomic carbon in comet atmospheres. Origin and emission spectra

    International Nuclear Information System (INIS)

    A detailed study of neutral carbon emissions is made, to precise the excitation mechanism nature, to determine the production mechanisms and examine wether information on CO and CO2 molecule abundance could be deduced, or wether another source must be looked for. After an exhaustive study of excitation rates necessary for theoretical intensity calculation, a new effect has been discovered, and which acts on the atom excitation rates, via their distribution on the fundamental hyperfine levels. On the other hand, the strong dependency of the excitation rate ratio with heliocentric velocity and with the hypothesis which is made on the atom population initial distribution has been revealed. The carbon abundance in all the comets of the initial sample has been calculated, then compared to the water one revealing two groups of comets. Then an abundance criterium to remove the CO and CO2 molecules from the carbon potential-parents in the Bradfield comet has been used while CO is the best candicate for C(3P) and C(1D) atom production in the West, Kohoutek and Bennet comets (but to certain conditions). The important conclusion is that, while the relative abundance (C2/OH, CN/OH,...) of the minor carbon compounds were constant, the CO relative abundance varies from an object to the other, probably an effect due to repeated passage of some comets near the sun

  7. Atomic and electronic structure of divacancies in carbon nanotubes

    Science.gov (United States)

    Berber, Savas; Oshiyama, Atsushi

    2008-04-01

    We present atomic and electronic structure of divacancies in carbon nanotubes, which is calculated using the density functional theory. Divacancies in carbon nanotubes self-heal by spontaneous reconstructions, which consist of concerted bond formations. Divacancy formation energies EDV , which strongly depend on the divacancy orientation with respect to the tube axis, are in the range of 2.8 4.3 eV for favorable orientations in the nanotubes of 4 9Å diameter, making divacancies more probable than monovacancies in carbon nanotubes. Defect related states lead to a higher density of states around the Fermi level. Semiconducting nanotubes develop midgap levels that may adversely affect the functionality of carbon nanotube based devices. Our spin polarized density functional calculations show that the exchange splitting of defect-related bands in nonsemiconducting defective nanotubes leads to net spin polarizations of ρ↑-ρ↓≤0.5μB per divacancy for some divacancy orientations.

  8. Single-crystal γ-MnS nanowires conformally coated with carbon.

    Science.gov (United States)

    Beltran-Huarac, Juan; Resto, Oscar; Carpena-Nuñez, Jennifer; Jadwisienczak, Wojciech M; Fonseca, Luis F; Weiner, Brad R; Morell, Gerardo

    2014-01-22

    We report for the first time the fabrication of single-crystal metastable manganese sulfide nanowires (γ-MnS NWs) conformally coated with graphitic carbon via chemical vapor deposition technique using a single-step route. Advanced spectroscopy and electron microscopy techniques were applied to elucidate the composition and structure of these NWs at the nanoscale, including Raman, XRD, SEM, HRTEM, EELS, EDS, and SAED. No evidence of α-MnS and β-MnS allotropes was found. The γ-MnS/C NWs have hexagonal cross-section and high aspect ratio (∼1000) on a large scale. The mechanical properties of individual γ-MnS/C NWs were examined via in situ uniaxial compression tests in a TEM-AFM. The results show that γ-MnS/C NWs are brittle with a Young's modulus of 65 GPa. The growth mechanism proposed suggests that the bottom-up fabrication of γ-MnS/C NWs is governed by vapor-liquid-solid mechanism catalyzed by bimetallic Au-Ni nanoparticles. The electrochemical performance of γ-MnS/C NWs as an anode material in lithium-ion batteries indicates that they outperform the cycling stability of stable micro-sized α-MnS, with an initial capacity of 1036 mAh g(-1) and a reversible capacity exceeding 503 mAh g(-1) after 25 cycles. This research advances the integration of carbon materials and metal sulfide nanostructures, bringing forth new avenues for potential miniaturization strategies to fabricate 1D core/shell heterostructures with intriguing bifunctional properties that can be used as building blocks in nanodevices. PMID:24392737

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

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Bingan; Zhang, Can; Esconjauregui, Santiago; Xie, Rongsi; Zhong, Guofang; Robertson, John [Department of Engineering, University of Cambridge, Cambridge CB3 0FA (United Kingdom); Bhardwaj, Sunil [Istituto Officina dei Materiali-CNR Laboratorio TASC, s.s. 14, km 163.4, I-34012 Trieste (Italy); Sincrotone Trieste S.C.p.A., s.s. 14, km 163.4, I-34149 Trieste (Italy); Cepek, Cinzia [Istituto Officina dei Materiali-CNR Laboratorio TASC, s.s. 14, km 163.4, I-34012 Trieste (Italy)

    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.

  10. Interpretation of Hund's multiplicity rule for the carbon atom.

    Science.gov (United States)

    Hongo, Kenta; Maezono, Ryo; Kawazoe, Yoshiyuki; Yasuhara, Hiroshi; Towler, M D; Needs, R J

    2004-10-15

    Hund's multiplicity rule is investigated for the carbon atom using quantum Monte Carlo methods. Our calculations give an accurate account of electronic correlation and obey the virial theorem to high accuracy. This allows us to obtain accurate values for each of the energy terms and therefore to give a convincing explanation of the mechanism by which Hund's rule operates in carbon. We find that the energy gain in the triplet with respect to the singlet state is due to the greater electron-nucleus attraction in the higher spin state, in accordance with Hartree-Fock calculations and studies including correlation. The method used here can easily be extended to heavier atoms. PMID:15473780

  11. Observation of linear I-V curves on vertical GaAs nanowires with atomic force microscope

    Science.gov (United States)

    Geydt, P.; Alekseev, P. A.; Dunaevskiy, M.; Lähderanta, E.; Haggrén, T.; Kakko, J.-P.; Lipsanen, H.

    2015-12-01

    In this work we demonstrate the possibility of studying the current-voltage characteristics for single vertically standing semiconductor nanowires on standard AFM equipped by current measuring module in PeakForce Tapping mode. On the basis of research of eight different samples of p-doped GaAs nanowires grown on different GaAs substrates, peculiar electrical effects were revealed. It was found how covering of substrate surface by SiOx layer increases the current, as well as phosphorous passivation of the grown nanowires. Elimination of the Schottky barrier between golden cap and the top parts of nanowires was observed. It was additionally studied that charge accumulation on the shell of single nanowires affects its resistivity and causes the hysteresis loops on I-V curves.

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

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Hideki, E-mail: sato@elec.mie-u.ac.jp; Kubonaka, Nobuo; Nagata, Atsushi; Fujiwara, Yuji [Graduate School of Engineering, Mie University, 1577 Kurima-machiya-cho, Tsu 514-8507 (Japan)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Lagos, M. J. [Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, R. Sergio B. de Holanda 777, 13083-859 Campinas-SP (Brazil); Laboratório Nacional de Nanotecnologia-LNNANO, 13083-970 Campinas-SP (Brazil); Autreto, P. A. S.; Galvao, D. S., E-mail: galvao@ifi.unicamp.br; Ugarte, D. [Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, R. Sergio B. de Holanda 777, 13083-859 Campinas-SP (Brazil); Bettini, J. [Laboratório Nacional de Nanotecnologia-LNNANO, 13083-970 Campinas-SP (Brazil); Sato, F.; Dantas, S. O. [Departamento de Física, ICE, Universidade Federal de Juiz de Fora, 36036-330 Juiz de Fora-MG (Brazil)

    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.

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

    International Nuclear Information System (INIS)

    We report here an atomistic study of the mechanical deformation of AuxCu(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

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

    Science.gov (United States)

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

    2016-07-14

    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. PMID:27304986

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

    Science.gov (United States)

    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. PMID:26400109

  17. Atomic-scale imaging correlation on the deformation and sensing mechanisms of SnO2 nanowires

    International Nuclear Information System (INIS)

    We demonstrate direct evidence that the strain variation induced by local lattice distortion exists in the surface layers of SnO2 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 SnO2 nanowires, as well as the superior sensing properties of SnO2 nanowire network

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

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yong [Department of Mechanical Engineering, University of South Carolina, 300 Main Street, Columbia, South Carolina 29208 (United States); Liu, Jie; Koley, Goutam [Department of Electrical Engineering, University of South Carolina, 301 Main Street, Columbia, South Carolina 29208 (United States); Blom, Douglas [Electron Microscopy Center, University of South Carolina, 301 Main Street, Columbia, South Carolina 29205 (United States); Duan, Zhiyao; Wang, Guofeng, E-mail: guw8@pitt.edu, E-mail: xl3p@virginia.edu [Department of Mechanical Engineering and Materials Science, University of Pittsburgh, 3700 O' Hara Street, Pittsburgh, Pennsylvania 15261 (United States); Li, Xiaodong, E-mail: guw8@pitt.edu, E-mail: xl3p@virginia.edu [Department of Mechanical Engineering, University of South Carolina, 300 Main Street, Columbia, South Carolina 29208 (United States); Department of Mechanical and Aerospace Engineering, University of Virginia, 122 Engineer' s Way, Charlottesville, Virginia 22904 (United States)

    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.

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

    Science.gov (United States)

    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

  20. Carbon dust formation under heavy atomic hydrogen irradiation

    International Nuclear Information System (INIS)

    Dust formation mechanism in plasma-material surface interactions has been investigated by using high pressure inductively coupled plasmas (ICPs), which have a feature of high atomic particle flux (atomic hydrogen flux: ∼1024 m-2s-1, ion flux: ∼1021 m-2s-1). Experiments have been conducted in argon/hydrogen mixture plasma irradiation to graphite targets. In the present experiments, physical sputtering is not expected and the dominant erosion process of graphite target is chemical sputtering by atomic hydrogen irradiation. Carbon dust particles with various shapes have been observed on the graphite target irradiated by argon/hydrogen plasma. It is found that the shapes of the dust particles are strongly related to the target surface temperature, graphite spherical particle when the surface temperature is below ∼1100 K and polyhedral particle like diamond when above ∼1100 K. It is also shown that the carbon dust formation and growth does not choose the surface materials. The number density of dust formed decreases as the plasma input power decreases or the distance between the target and induction coil increases, while the weight loss remains almost the same even though the input power and distance between the target and induction coil are varied. The size of dust particles increases as increasing surface temperature. These experimental results indicate that the dust growth is strongly related to surface temperature. (author)

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

    International Nuclear Information System (INIS)

    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

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

    Science.gov (United States)

    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 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 chemistry. PMID:11289433

  3. Growth and composition-dependent optoelectronic properties of Al x Ga1‑x N alloy nanowires arrays across the entire composition range on carbon cloth

    Science.gov (United States)

    Chen, Fei; Ji, Xiaohong; Zhang, Qinyuan

    2016-07-01

    Composition-tunable ternary Al x Ga1‑x N (0 ≤ x ≤ 1) alloy nanowires have been grown on flexible carbon cloth in large scale through a one-step and catalyst-free chemical vapor deposition method. Field emission scanning electron microscopy, x-ray diffraction analysis, transmission electron microscopy and x-ray energy-dispersive spectroscopy were employed to characterize the morphology, crystal structure, composition properties. All Al x Ga1‑x N samples exhibit hexagonal wurtzite single-phase structure and a preferred orientation along [0001] direction. The progressively evolutions in structural, Raman and field emission properties of Al x Ga1‑x N nanowires demonstrate the continuous composition tunability across the entire composition range. The enhancement in the field emission characteristic of Al x Ga1‑x N nanowires on carbon cloth is ascribed to the combined effect of the nanostructures and the excellent electron transport path of the conductive carbon cloth. The successful synthesis of Al x Ga1‑x N nanowires on carbon cloth provides the new possibility for the further development of flexible nano- and opto-electronic devices.

  4. A Theoretical Simulation of Deformed Carbon Nanotubes with Adsorbed Metal Atoms: Enhanced Reactivity by Deformation

    OpenAIRE

    Hosoya, Naoki; Kusakabe, Koichi; Maheswari, S. Uma

    2010-01-01

    First-principles simulations were performed to investigate reaction of carbon nanotubes with adsorbed metal atoms. Mechanical modification of their structures enhances chemical reactivity of carbon nanotubes. Adsorption of a tungsten, tantalum, or niobium atom on a (5, 0) nanotube with a Stone-Wales defect was shown to have characteristically strong chemisorption. Bond-breaking in the carbon-carbon network and formation of a local metal-carbon complex were observed during the simulation. Adso...

  5. Preparation and electrochemical properties of the ternary nanocomposite of polyaniline/activated carbon/TiO2 nanowires for supercapacitors

    International Nuclear Information System (INIS)

    Highlights: ► Preparation of ternary nanocomposites (ACTB/PANI) consisting of polyaniline (PANI), activated carbon, and TiO2(B) nanowires. ► Structural and electrochemical characterizations of ternary ACTB/PANI nanocomposites. ► Excellent cycle stability of ACTB/PANI based electrode. ► Tailoring the electrochemical performance by means of a composite construction. -- Abstract: We herein report the synthesis of ternary nanocomposites consisting of polyaniline (PANI), activated carbon, and TiO2(B) components, which involves the preparation of activated carbon/TiO2(B) nanowires (ACTB) using sonochemical–hydrothermal method, and their subsequent composites with PANI via in situ polymerization. The morphology and structure of ACTB/PANI ternary nanocomposites are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR) and X-ray diffraction (XRD). Morphology analysis shows that the porous network layer of PANI homogeneously coated on the outer surface of ACTB support. The electrochemical properties of the ternary nanocomposite as the electrode material for electrochemical capacitors are examined by cyclic voltammetry and galvanostatic charge/discharge test in an organic electrolyte (1.0 M LiClO4 in propylene carbonate). The results show that the ternary nanocomposites have a specific capacitance as large as 286 F g−1 in the potential range from −3 to 3 V (vs. SCE) at a charge–discharge current density of 1.0 A g−1, which is a significant improvement compared to those of the three separate components, demonstrating that the ACTB/PANI nanocomposites are promising materials for supercapacitor electrode

  6. Elastic property characterization of oxidized Si nanowires by contact-resonance atomic force microscopy

    Science.gov (United States)

    Stan, Gheorghe; Cook, Robert

    2010-03-01

    The synthesis and processing of materials into nanostructures opens new avenues for advancement and diversification of current electronic, optoelectronic, and sensor applications. Among these structures, Si NWs are distinctly remarkable as they bring the previous decades knowledge of silicon technology into nanoscale applications. From this perspective, the characterization and understanding of the mechanical properties of nonplanar Si-SiO2 interfaces are of significant utility in developing Si nanostructures for Si-based integrated circuits. To investigate the elastic properties of as-grown and oxidized Si NWs we have extended and specifically tailored the applicability of contact-resonance atomic force microscopy (CR- AFM). From such CR-AFM measurements, the effect of the compressive stress at the Si-SiO2 interface was revealed in a diameter dependence of the elastic modulus of oxidized Si NWs. A modified core-shell model that includes the interface stress developed during oxidation captures the observed dependence. The values of strain and stress as well as the width of the stressed transition region at the Si-SiO2 interface agree with those reported from simulations and other experiments. This novel approach advances CR-AFM applicability in investigating structure-mechanical property relationships at the nanoscale.

  7. Novel MnOx@Carbon hybrid nanowires with core/shell architecture as highly reversible anode materials for lithium ion batteries

    International Nuclear Information System (INIS)

    Novel MnOx@Carbon hybrid nanowires were successfully synthesized by the combination of a hydrothermal process and a simple PVP (polyvinylpyrrolidone) – solution-soaking method followed by a subsequent carbonization treatment. The nanostructures exhibit the unique feature of having nanocrystalline manganese oxide particle encapsulated inside and an amorphous carbon layer coating the outside. The unique porous characteristics with many meso/micro-pores, and further the highly conductive carbon matrix would lead to the excellent electrochemical performance of the MnOx@Carbon nanowire electrode. The MnOx@Carbon hybrid nanowires exhibit a high initial reversible capacity of 824.4 mAhg−1, a reversible capacity of approximately 541 mAhg−1 after 54 cycles, and excellent cycling stability and rate capability with specific capacity of 298.24 mAhg−1 when cycled at the current density of 1000 mAg−1, which indicates that the composite is a promising anode candidate for Li-ion batteries. - Highlights: • MnOx@C composite were obtained by hydrothermal and PVP-solution-soaking method. • The structures is characteristic of MnOx nanocrystals coated into carbon matrix. • The electrode exhibits good Li+ capacities, cycling stability and rate capability

  8. SiC Nanowires Synthesized by Rapidly Heating a Mixture of SiO and Arc-Discharge Plasma Pretreated Carbon Black

    Directory of Open Access Journals (Sweden)

    Wang Feng-Lei

    2008-01-01

    Full Text Available Abstract SiC nanowires have been synthesized at 1,600 °C by using a simple and low-cost method in a high-frequency induction furnace. The commercial SiO powder and the arc-discharge plasma pretreated carbon black were mixed and used as the source materials. The heating-up and reaction time is less than half an hour. It was found that most of the nanowires have core-shell SiC/SiO2nanostructures. The nucleation, precipitation, and growth processes were discussed in terms of the oxide-assisted cluster-solid mechanism.

  9. Current-induced dynamics in carbon atomic contacts

    Directory of Open Access Journals (Sweden)

    Jing-Tao Lü

    2011-12-01

    Full Text Available Background: The effect of electric current on the motion of atoms still poses many questions, and several mechanisms are at play. Recently there has been focus on the importance of the current-induced nonconservative forces (NC and Berry-phase derived forces (BP with respect to the stability of molecular-scale contacts. Systems based on molecules bridging electrically gated graphene electrodes may offer an interesting test-bed for these effects.Results: We employ a semi-classical Langevin approach in combination with DFT calculations to study the current-induced vibrational dynamics of an atomic carbon chain connecting electrically gated graphene electrodes. This illustrates how the device stability can be predicted solely from the modes obtained from the Langevin equation, including the current-induced forces. We point out that the gate offers control of the current, independent of the bias voltage, which can be used to explore current-induced vibrational instabilities due the NC/BP forces. Furthermore, using tight-binding and the Brenner potential we illustrate how Langevin-type molecular-dynamics calculations including the Joule heating effect for the carbon-chain systems can be performed. Molecular dynamics including current-induced forces enables an energy redistribution mechanism among the modes, mediated by anharmonic interactions, which is found to be vital in the description of the electrical heating.Conclusion: We have developed a semiclassical Langevin equation approach that can be used to explore current-induced dynamics and instabilities. We find instabilities at experimentally relevant bias and gate voltages for the carbon-chain system.

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

    Science.gov (United States)

    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.

  11. Multishelled Gold Nanowires

    OpenAIRE

    Bilalbegovic, G.

    1999-01-01

    The current miniaturization of electronic devices raises many questions about the properties of various materials at nanometre-scales. Recent molecular dynamics computer simulations have shown that small finite nanowires of gold exist as multishelled structures of lasting stability. These classical simulations are based on a well-tested embedded atom potential. Molecular dynamics simulation studies of metallic nanowires should help in developing methods for their fabrication, such as electron...

  12. The Unique Hoyle State of the Carbon Atom

    Directory of Open Access Journals (Sweden)

    Thorvaldsen, Steinar

    2015-05-01

    Full Text Available The famous astronomer Fred Hoyle (1915-2001 started his research career as an atheist. Hoyle’s most important contribution to astrophysics is the theory of nucleosynthesis, i.e. the idea that chemical elements such as carbon can form in stars on the basis of hydrogen and helium. Essentially here was his prediction that the carbon core has a state with a specific energy which is precisely adapted to the basic fusion process. This result was one of the most important breakthroughs in modern astrophysics, and the so called Hoyle state has become a cornerstone for state-ofthe- art nuclear theory. The calculations he made, eventually revealed a fine-tuning of the universe. Hoyle’s work in this area supported the anthropic principle that the universe was fine-tuned so that intelligent life would be possible. It is said that what really made him conclude that creation demanded intelligence, were his calculations of the special properties of the carbon atom. This shook his atheism fundamentally [1, p. 57]. In this paper we describe this discovery.

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

    International Nuclear Information System (INIS)

    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.

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

    Science.gov (United States)

    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.

  15. Carbon-atom wires produced by nanosecond pulsed laser deposition in a background gas

    OpenAIRE

    Casari, C. S.; Giannuzzi, C. S.; V. Russo

    2016-01-01

    Wires of sp-hybridized carbon atoms are attracting interest for both fundamental aspects of carbon science and for their appealing functional properties. The synthesis by physical vapor deposition has been reported to provide sp-rich carbon films but still needs to be further developed and understood in detail. Here the synthesis of carbon-atom wires (CAWs) has been achieved by nanosecond pulsed laser deposition (PLD) expoliting the strong out-of-equilibrium conditions occurring when the abla...

  16. Determination of Diclofenac on a Dysprosium Nanowire- Modified Carbon Paste Electrode Accomplished in a Flow Injection System by Advanced Filtering

    Directory of Open Access Journals (Sweden)

    Ali Akbar Moosavi-Movahedi

    2009-09-01

    Full Text Available 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.

  17. Atomic Layer Deposition of Zirconium Oxide on Carbon Nanoparticles

    International Nuclear Information System (INIS)

    In this report we describe preparation of structures containing carbon nanoparticles for potential applications in nonvolatile memories. The carbon nanoparticles were synthesized from 5-methylresorcinol and formaldehyde via base catalysed polycondensation reaction, and were distributed over substrates by dip-coating the substrates into an organic solution. Before deposition of nanoparticles the substrates were covered with 2 nm thick Al2O3 layer grown by atomic layer deposition (ALD) from Al(CH3)3 and O3. After deposition of nanoparticles the samples were coated with ZrO2 films grown from C5H5Zr[N(CH3)2]3 and H2O. Both dielectrics were grown in two-temperature ALD processes starting deposition of Al2O3 at 25 °C and ZrO2 at 200 °C, thereafter completing both processes at a substrate temperature of 300 °C. Deposition of ZrO2 changed the structure of C-nanoparticles, which still remained in a Si/Al2O3/C/ZrO2 structure as a separate layer. Electrical characterization of nanostructures containing Al2O3 as tunnel oxide, C-nanoparticles as charge traps and ZrO2 as control oxide showed hysteretic flat-band voltage shift of about 1V

  18. The mechanical property and resistance ability to atomic oxygen corrosion of boron modified carbon/carbon composites

    International Nuclear Information System (INIS)

    Before being densified by chemical vapor deposition, carbon preform was modified by boron. The mechanical property and resistance to atomic oxygen corrosion of carbon/carbon composites were investigated. The results show that fiber surface modification induces the deposition of high texture pyrocarbon and a moderate interfacial transition layer between carbon fibers and matrix carbon. After being modified by boron, the flexural and compressive strength of carbon/carbon composite is significantly increased. The bending curve has been adjusted with obvious pseudo-ductility phenomenon. The resistance ability to atomic oxygen corrosion is improved significantly. The mass loss and corrosion degree of the modified composite are lower than that of pure carbon/carbon composite

  19. Behavior of pure and modified carbon/carbon composites in atomic oxygen environment

    Institute of Scientific and Technical Information of China (English)

    Xiao-chong Liu; Lai-fei Cheng; Li-tong Zhang; Xin-gang Luan; Hui Mei

    2014-01-01

    Atomic oxygen (AO) is considered the most erosive particle to spacecraft materials in low earth orbit (LEO). Carbon fiber, car-bon/carbon (C/C), and some modified C/C composites were exposed to a simulated AO environment to investigate their behaviors in LEO. Scanning electron microscopy (SEM), AO erosion rate calculation, and mechanical property testing were used to characterize the material properties. Results show that the carbon fiber and C/C specimens undergo significant degradation under the AO bombing. According to the effects of AO on C/C-SiC and CVD-SiC-coated C/C, a condensed CVD-SiC coat is a feasible approach to protect C/C composites from AO degradation.

  20. Study the Characteristic of P-Type Junction-Less Side Gate Silicon Nanowire Transistor Fabricated by Atomic Force Microscopy Lithography

    Directory of Open Access Journals (Sweden)

    Arash Dehzangi

    2011-01-01

    Full Text Available Problem statement: Nanotransistor now is one of the most promising fields in nanoelectronics in order to decrease the energy consuming and application to create developed programmable information processors. Most of Computing and communications companies invest hundreds of millions of dollars in research funds every year to develop smaller transistors. Approach: The Junction-less side gate silicon Nano-wire transistor has been fabricated by Atomic Force Microscopy (AFM and wet etching on p-type Silicon On Insulator (SOI wafer. Then, we checked the characteristic and conductance trend in this device regarding to semi-classical approach by Semiconductor Probe Analyser (SPA. Results: We observed in characteristic of the device directly proportionality of the negative gate voltage and Source-Drain current. In semi classical approach, negative Gate voltage decreased the energy States of the Nano-wire between the source and the drain. The graph for positive gate voltage plotted as well to check. In other hand, the conductance will be following characteristic due to varying the gate voltage under the different drain-source voltage. Conclusion: The channel energy states are supposed to locate between two electrochemical potentials of the contacts in order to transform the charge. For the p-type channel the transform of the carriers is located in valence band and changing the positive or negative gate voltage, making the valence band energy states out of or in the area between the electrochemical potentials of the contacts causing the current reduced or increased.

  1. Nanowire-bacteria hybrids for unassisted solar carbon dioxide fixation to value-added chemicals.

    Science.gov (United States)

    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. PMID:25848808

  2. Atomic Resolution in Situ Imaging of a Double-Bilayer Multistep Growth Mode in Gallium Nitride Nanowires.

    Science.gov (United States)

    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. PMID:26990711

  3. Electric Conductivity of Phosphorus Nanowires

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jing-Xiang; LI Hui; ZHANG Xue-Qing; LIEW Kim-Meow

    2009-01-01

    We present the structures and electrical transport properties of nanowires made from different strands of phosphorus chains encapsulated in carbon nanotubes. Optimized by density function theory, our results indicate that the conductance spectra reveal an oscillation dependence on the size of wires. It can be seen from the density of states and current-voltage curves that the structure of nanowires affects their properties greatly. Among them,the DNA-like double-helical phosphorus nanowire exhibits the distinct characteristic of an approximately linear I - V relationship and has a higher conductance than others. The transport properties of phosphorus nanowires are highly correlated with their microstructures.

  4. On the structural and mechanical properties of Fe-filled carbon nanotubes-a computer simulation approach

    International Nuclear Information System (INIS)

    The structural and mechanical properties of single-and multi-walled carbon nanotubes filled with iron nanowires are studied using a recent parameterization of the modified embedded atom model. We have analyzed the effect of different crystal structures of iron (bcc and fcc) inside carbon nanotubes of different topographies. We have computed strain energy versus strain curves for pure systems: Fe nanowires, carbon and Fe-filled carbon nanotubes. A noticeable difference is found when these monatomic systems are joined to form iron-capped nanowires and where multi-layers of graphite are added to the nanotubes.

  5. Hierarchical silicon nanowires-carbon textiles matrix as a binder-free anode for high-performance advanced lithium-ion batteries

    OpenAIRE

    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 enh...

  6. Enhanced Performance of Nanowire-Based All-TiO2 Solar Cells using Subnanometer-Thick Atomic Layer Deposited ZnO Embedded Layer

    International Nuclear Information System (INIS)

    In this paper, the effect of angstrom-thick atomic layer deposited (ALD) ZnO embedded layer on photovoltaic (PV) performance of Nanowire-Based All-TiO2 solar cells has been systematically investigated. Our results indicate that by varying the thickness of ZnO layer the efficiency of the solar cell can be significantly changed. It is shown that the efficiency has its maximum for optimal thickness of 1 ALD cycle in which this ultrathin ZnO layer improves device performance through passivation of surface traps without hampering injection efficiency of photogenerated electrons. The mechanisms contributing to this unprecedented change in PV performance of the cell have been scrutinized and discussed

  7. Electrocatalytic activity of NiO on silicon nanowires with a carbon shell and its application in dye-sensitized solar cell counter electrodes

    Science.gov (United States)

    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

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

    International Nuclear Information System (INIS)

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Zope, Rajendra R., E-mail: rzope@utep.edu; Baruah, Tunna [Department of Physics, The University of Texas at El Paso, El Paso, Texas 79958 (United States); Computational Science Program, The University of Texas at El Paso, El Paso, Texas 79958 (United States); Bhusal, Shusil; Basurto, Luis [Department of Physics, The University of Texas at El Paso, El Paso, Texas 79958 (United States); Jackson, Koblar [Physics Department and Science of Advanced Materials Ph.D. Program, Central Michigan University, Mt. Pleasant, Michigan 48859 (United States)

    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.

  10. Nickel-cobalt layered double hydroxide anchored zinc oxide nanowires grown on carbon fiber cloth for high-performance flexible pseudocapacitive energy storage devices

    KAUST Repository

    Shakir, Imran

    2014-05-01

    Nickel-cobalt layered double hydroxide (Ni-Co LDH) nanoflakes-ZnO nanowires hybrid array has been directly synthesized on a carbon cloth substrate by a facile cost-effective two-step hydrothermal route. As electrode materials for flexible pseudocapacitors, Ni-Co LDH nanoflakes-ZnO nanowires hybrid array exhibits a significantly enhanced specific capacitance of 1927 Fg-1, which is a ∼1.8 time greater than pristine Ni-Co LDH nanoflakes. The synthesized Ni-Co LDH nanoflakes-ZnO nanowires hybrid array shows a maximum energy density of 45.55 Whkg-1 at a power density of 46.15 kWkg -1, which is 35% higher than the pristine Ni-Co LDH nanoflakes electrode. Moreover, Ni-Co LDH nanoflakes-ZnO nanowires hybrid array exhibit excellent excellent rate capability (80.3% capacity retention at 30 Ag -1) and cycling stability (only 3.98% loss after 3000 cycles), due to the significantly improved faradaic redox reaction. © 2014 Elsevier Ltd.

  11. Dynamic and atomic-scale understanding of the twin thickness effect on dislocation nucleation and propagation activities by in situ bending of Ni nanowires

    International Nuclear Information System (INIS)

    Although their mechanical behavior has been extensively studied, the atomic-scale deformation mechanisms of metallic nanowires (NWs) with growth twins are not completely understood. Using our own atomic-scale and dynamic mechanical testing techniques, bending experiments were conducted on single-crystalline and twin-structural Ni NWs (D = ∼40 nm) using a high-resolution transmission electron microscope (HRTEM). Atomic-scale and time-resolved dislocation nucleation and propagation activities were captured in situ. A large number of in situ HRTEM observations indicated strong effects from the twin thickness (TT) on dislocation type and glide system. In thick twin lamella (TT > ∼12 nm) and single-crystalline NWs, the plasticity was controlled by full dislocation nucleation. For NWs with twin thicknesses of ∼9 nm < TT < ∼12 nm, full and partial dislocation nucleation occurred from the free surface, and the dislocations glided on multiple systems and interacted with each other during plastic deformation. For NWs with twin thicknesses of ∼6 nm < TT < ∼9 nm, partial dislocation nucleation from the free surface and the gliding of those dislocations on the plane that intersected the twin boundaries (TBs) were the dominant plasticity events. For the NWs with twin thicknesses of ∼1 nm < TT < ∼6 nm, the plasticity was accommodated by a partial dislocation nucleation process and glide parallel to the TBs. When TT < ∼1 nm, TB migration and detwinning processes resulting from partial dislocation nucleation and glide adjacent to the TBs were frequently observed

  12. Atomic Scale Analysis of the Enhanced Electro- and Photo-Catalytic Activity in High-Index Faceted Porous NiO Nanowires

    Science.gov (United States)

    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

    2015-02-01

    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.

  13. Process of Energetic Carbon Atom Deposition on Si (001) Substrate by Molecular Dynamics Simulation

    Institute of Scientific and Technical Information of China (English)

    于威; 滕晓云; 李晓苇; 傅广生

    2002-01-01

    The process of energetic C atom deposition on Si (001)-(2×1) is studied by the molecular dynamics method using the semi-empirical many-bond Tersoff potential. It is found that the incident energy of the carbon atom has an important effect on the collision process and its diffusion process on the substrate. Most of the incident energy of the carbon atom is transferred to the substrate atoms within the initial two vibration periods of substrate atoms and its value increases with the incident energy. The spreading distance and penetration depth of the incident atom increasing with the incident energy are also identified. The simulated results imply that an important effect of energy of incident carbon on the film growth at Iow substrate temperature provides activation energy for silicon carbide formation through the vibration enhancement of local substrate atoms. In addition, suppressing carbon atom inhomogeneous collection and dispensing with the silicon diffusion process may be effectively promoted by the spreading and penetration of the energetic carbon atom in the silicon substrate.

  14. Understanding the carbon-monoxide oxidation mechanism on ultrathin palladium nanowires: a density functional theory study.

    Science.gov (United States)

    Yang, Po-Yu; Ju, Shin-Pon; Lai, Zhu-Min; Lin, Jenn-Sen; Hsieh, Jin-Yuan

    2016-01-28

    The CO oxidation mechanism catalyzed by ultrathin helical palladium nanowires (PdNW) was investigated by density functional theory (DFT) calculation. The helical PdNW structure was constructed on the basis of the simulated annealing basin-hopping (SABH) method with the tight-binding potential and the penalty method in our previous studies (J. Mater. Chem., 2012, 22, 20319). The low-lying adsorption configurations as well as the adsorption energies for O2 and CO molecules on different PdNW adsorption sites were obtained by DFT calculation. The most stable adsorption configurations for the Langmuir-Hinshelwood (LH) mechanism processes were considered for investigating the CO oxidation mechanism. The nudged elastic band (NEB) method was adopted to obtain the transition state configuration and the minimum energy pathways (MEPs). PMID:26701650

  15. Understanding the carbon-monoxide oxidation mechanism on ultrathin palladium nanowires: a density functional theory study

    Science.gov (United States)

    Yang, Po-Yu; Ju, Shin-Pon; Lai, Zhu-Min; Lin, Jenn-Sen; Hsieh, Jin-Yuan

    2016-01-01

    The CO oxidation mechanism catalyzed by ultrathin helical palladium nanowires (PdNW) was investigated by density functional theory (DFT) calculation. The helical PdNW structure was constructed on the basis of the simulated annealing basin-hopping (SABH) method with the tight-binding potential and the penalty method in our previous studies (J. Mater. Chem., 2012, 22, 20319). The low-lying adsorption configurations as well as the adsorption energies for O2 and CO molecules on different PdNW adsorption sites were obtained by DFT calculation. The most stable adsorption configurations for the Langmuir-Hinshelwood (LH) mechanism processes were considered for investigating the CO oxidation mechanism. The nudged elastic band (NEB) method was adopted to obtain the transition state configuration and the minimum energy pathways (MEPs).

  16. Gold nanowires and the effect of impurities

    Directory of Open Access Journals (Sweden)

    Novaes Frederico

    2006-01-01

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

  17. Carbon fiber CVD coating by carbon nanostructured for space materials protection against atomic oxygen

    Science.gov (United States)

    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.

  18. Organic Nanowires

    DEFF Research Database (Denmark)

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

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

  19. Stacking faults in SiC nanowires.

    Science.gov (United States)

    Wallis, K L; Wieligor, M; Zerda, T W; Stelmakh, S; Gierlotka, S; Palosz, B

    2008-07-01

    SiC nanowires were obtained by a reaction between vapor silicon and multiwall carbon nanotubes, CNT, in vacuum at 1200 degrees C. Raman and IR spectrometry, X-ray diffraction and high resolution transmission electron microscopy, HRTEM, were used to characterize properties of SiC nanowires. Morphology and chemical composition of the nanowires was similar for all samples, but concentration of structural defects varied and depended on the origin of CNT. Stacking faults were characterized by HRTEM and Raman spectroscopy, and both techniques provided complementary results. Raman microscopy allowed studying structural defects inside individual nanowires. A thin layer of amorphous silicon carbide was detected on the surface of nanowires. PMID:19051903

  20. Carbon nanotubes as tips for atomic force microscopy

    Institute of Scientific and Technical Information of China (English)

    国立秋; 徐宗伟; 赵铁强; 赵清亮; 张飞虎; 董申

    2004-01-01

    Ordinary AFM probes' characters prevent the AFM' s application in various scopes. Carbon nanotubes represent ideal AFM probe materials for their higher aspect ratio, larger Young' s modulus, unique chemical structure, and well-defined electronic property. Carbon nanotube AFM probes are obtained by using a new method of attaching carbon nanotubes to the end of ordinary AFM probes, and are then used for doing AFM experiments. These experiments indicated that carbon nanotube probes have higher elastic deformation, higher resolution and higher durability. And it was also found that carbon nanotube probes can accurately reflect the morphology of deep narrow gaps, while ordinary probes can not reflect.

  1. Carbon nanofiber/cobalt oxide nanopyramid core-shell nanowires for high-performance lithium-ion batteries

    Science.gov (United States)

    An, Geon-Hyoung; Ahn, Hyo-Jin

    2014-12-01

    Carbon nanofiber (CNF)/Co3O4 nanopyramid core-shell nanowires (NWs) are synthesized using an electrospinning method followed by reduction and hydrothermal treatment in order to improve the capacity, cycle stability, and high-rate capability of the electrodes in Li ion batteries (LIBs). The morphology, crystal structure, and chemical states of all samples are investigated by means of field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and thermogravimetric analysis. For comparison, conventional CNFs, octahedral Co3O4, and Co3O4/CNF composite electrodes are prepared. LIB cells fabricate with the CNF/Co3O4 nanopyramid core-shell NWs exhibit superb discharge capacity (1173 mAh g-1 at the 1st cycle), cycle stability (795 mAh g-1 at 50 cycles), high initial Coulombic efficiency (84.8%), and high-rate capability (570 mAh g-1 at a current density of 700 mA g-1) as compared to the conventional CNF, octahedral Co3O4, and Co3O4/CNF composite electrodes. The performance improvement is owing to the introduction of one-dimensional CNFs relative to efficient electron transport in the core region, extensive utilization of Co3O4 nanopyramids with high capacity grown closely on the CNFs in the shell region, and the network structures of the electrode relative to the improvement of Li ion diffusion.

  2. Silver nanowire-carbon fiber cloth nanocomposites synthesized by UV curing adhesive for electrochemical point-of-use water disinfection.

    Science.gov (United States)

    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. PMID:27085313

  3. Effects of Atomic-Scale Structure on the Fracture Properties of Amorphous Carbon - Carbon Nanotube Composites

    Science.gov (United States)

    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

  4. The dynamics simulation of Ne atom injected into single-wall carbon nanotube

    International Nuclear Information System (INIS)

    The dynamical processes of Ne atom injected into single-wall carbon nanotube (SWCNT) are modeled with molecular dynamics simulations. The threshold energies to encapsulate rare-gas atoms in SWCNT are presented. The range of tube radius for stable oscillation is revealed, which is independent of the type of carbon nanotubes. And the oscillatory frequency is sensitive to the change in the diameter, the length and chirality of the tube

  5. Structure and stability of a silicon cluster on sequential doping with carbon atoms

    Science.gov (United States)

    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.

  6. Carbon fiber CVD coating by carbon nanostructured for space materials protection against atomic oxygen

    Science.gov (United States)

    Pastore, Roberto; Bueno Morles, Ramon; Micheli, Davide

    2016-07-01

    In recent years, the emphasis in space research has been shifting from space exploration to commercialization of space. In order to utilize space for commercial purposes it is necessary to understand the low earth orbit (LEO) space environment where most of the activities will be carried out. The studies on the LEO environment are mainly focused towards understanding the effect of atomic oxygen (AO) on spacecraft materials. In the first few shuttle flights, materials looked frosty because they were actually being eroded and textured: AO reacts with organic materials on spacecraft exteriors, gradually damaging them. When a spacecraft travel in LEO (where crewed vehicles and the International Space Station fly), the AO formed from the residual atmosphere can react with the spacecraft surfaces, causing damage to the vehicle. Polymers are widely used in space vehicles and systems as structural materials, thermal blankets, thermal control coatings, conformal coatings, adhesives, lubricants, etc. Exposure of polymers and composites to the space environment may result in different detrimental effects via modification of their chemical, electrical, thermal, optical and mechanical properties as well as surface erosion. The major degradation effects in polymers are due to their exposure to atomic oxygen, vacuum ultraviolet and synergistic effects, which result in different damaging effects by modification of the polymer's chemical properties. In hydrocarbon containing polymers the main AO effect is the surface erosion via chemical reactions and the release of volatile reaction products associated with the mass loss. The application of a thin protective coating to the base materials is one of the most commonly used methods of preventing AO degradation. The purpose is to provide a barrier between base material and AO environment or, in some cases, to alter AO reactions to inhibit its diffusion. The effectiveness of a coating depends on its continuity, porosity, degree of

  7. Computer simulation of rare-gas atoms injection into single-wall carbon nanotube

    International Nuclear Information System (INIS)

    The process of rare-gas atoms (He, Ne, Ar) injected into single-wall carbon nanotube (SWNT) was modeled with molecular-dynamics simulations. The site dependence of the threshold energy of rare-gas atoms forming endohedral complexes was investigated, and the formation mechanism of some defects was revealed. The hole on the sidewall of the SWNT induced by incident rare-gas atoms can be healed by annealing at a certain temperature

  8. Visualization of arrangements of carbon atoms in graphene layers by Raman mapping and atomic-resolution TEM

    KAUST Repository

    Cong, Chunxiao

    2013-02-01

    In-plane and out-of-plane arrangements of carbon atoms in graphene layers play critical roles in the fundamental physics and practical applications of these novel two-dimensional materials. Here, we report initial results on the edge/crystal orientations and stacking orders of bi-and tri-layer graphene (BLG and TLG) from Raman spectroscopy and transmission electron microscopy (TEM) experiments performed on the same sample. We introduce a new method of transferring graphene flakes onto a normal TEM grid. Using this novel method, we probed the BLG and TLG flakes that had been previously investigated by Raman scattering with high-resolution (atomic) TEM.

  9. Atomic scale mass delivery driven by bend kink in single walled carbon nanotube

    International Nuclear Information System (INIS)

    The possibility of atomic scale mass delivery by bend kink in single walled carbon nanotube was investigated with the aid of molecular dynamics simulation. By keeping the bending angle while moving the tube end, the encapsulated atomic scale mass such as atom, molecule and atom group were successfully delivered through the nanotube. The van der Waals interaction between the encapsulated mass and the tube wall provided the driving force for the delivery. There were no dramatic changes in the van der Waals interaction, and a smooth and steady delivery was achieved when constant loading rate was applied. The influence of temperature on the atom group delivery was also analyzed. It is found raising temperature is harmful to the smooth movement of the atom group. However, the delivery rate can be promoted under higher temperature when the atom group is situated before the kink during the delivery.

  10. Preparation of well-aligned carbon nanotubes/silicon nanowires core-sheath composite structure arrays in porous anodic aluminum oxide templates

    Institute of Scientific and Technical Information of China (English)

    李梦轲; 陆梅; 王成伟; 力虎林

    2002-01-01

    The well-aligned carbon nanotubes (CNTs) arrays with opened ends were prepared in ordered pores of anodic aluminum oxide (AAO) template by the chemical vapor deposition (CVD) method. After then, silicon nanowires (SiNWs) were deposited in the hollow cavities of CNTs. By using this method, CNTs/SiNWs core-sheath composite structure arrays were synthesized successfully. Growing structures and physical properties of the CNTs/SiNWs composite structure arrays were analyzed and researched by the scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction spectrum (XRD), respectively. The field emission (FE) behavior of the CNTs/SiNWs composite structure arrays was studied based on Fowler- Nordheim tunneling mechanism and current-voltage (I -V) curve. And the photoluminescence (PL) was also characterized. Significantly, the CNTs/SiNWs core-sheath composite structure nanowire fabricated by AAO template method is characteristic of a metal/semiconductor (M/S) behavior and can be utilized to synthesize nanoscale PN junction or Schottky diode device. This process also could be useful for the fabrication of SiNWs and other nanoscale core-sheath composite structure nanowires with chemically inert interfaces for nanoscale electronic and device applications where surface oxidation is undesirable. The diameters and lengths of nanoscale composite structure arrays can be dominated easily, and the experimental result shows that the curling and twisting structures are fewer than those prepared by other synthesized methods.

  11. Measurement of 5-eV atomic oxygen using carbon-based films: preliminary results

    OpenAIRE

    White, C de B; Roberts, G. T.; Chambers, A.R.

    2005-01-01

    Carbon-based sensors have been developed to measure the atmospheric neutral atomic oxygen (AO) flux experienced by spacecraft in low Earth orbit. Thin- and thick-film carbon sensor elements were deposited onto an alumina substrate between thick-film gold tracks and silver palladium solder pads. AO flux is deduced by measuring resistance changes as the carbon film erodes and applying a simple theory. A wide range of responses were observed that are dependent on the deposition process and post ...

  12. Atomic scale observations of bainite transformation in a high carbon high silicon steel

    OpenAIRE

    García Caballero, Francisca; Miller, M. K.; Babu, S. S.; García Mateo, Carlos

    2007-01-01

    A fine-scale bainitic microstructure with high strength and high toughness has been achieved by transforming austenite at 200 ºC. X-ray diffraction analysis showed the carbon concentration of these bainitic ferrite plates to be higher than expected from paraequilibrium. Atom probe tomography revealed that a substantial quantity of carbon was trapped at dislocations in the vicinity of the ferrite/austenite interface. These results suggest that the carbon trapping at dislocations...

  13. Early Stages of the Chemical Vapor Deposition of Pyrolytic Carbon Investigated by Atomic Force Microscopy

    OpenAIRE

    Pfrang, Andreas; WAN Yong-Zhong; Schimmel, Thomas

    2009-01-01

    The early stages of chemical vapor deposition of pyrolytic carbon on planar silicon substrates were studied by the atomic force microscopy-based technique of chemical contrast imaging. Short deposition times were chosen to focus on the early stages of the deposition process, and three different types of nucleation were found: random nucleation of single islands, nucleation of carbon islands along lines and secondary nucleation which corresponds to the nucleation of carbon islands at the edges...

  14. Study on nitrogen doped carbon atom chains with negative differential resistance effect

    Science.gov (United States)

    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.

  15. Atomic-scale study of the role of carbon on boron clustering

    International Nuclear Information System (INIS)

    Boron (BF2, 20 keV, 3.14/cm2) and carbon (13 keV, 1015/cm2) implanted silicon annealed at 800 oC during 30 min or at 1000 oC during 10 s has been investigated using a laser-assisted wide-angle tomographic atom probe (LaWaTAP) instrument. Boron-silicon clusters containing ∼ 1.3 at.% of boron atoms have been observed in boron implanted silicon with a concentration exceeding the solubility limit. Often identified as BICs, they are interpreted as a metastable phase. Furthermore, addition of carbon clearly reduced the clustering of boron. This was interpreted as a diminution of boron diffusion or as an increase of the solubility limit of boron. Carbon-silicon clusters containing ∼ 1.5 at.% of carbon atoms were observed, maybe the precursors of the SiC phase.

  16. Direct chemical conversion of graphene to boron- and nitrogen- and carbon-containing atomic layers

    Science.gov (United States)

    Gong, Yongji; Shi, Gang; Zhang, Zhuhua; Zhou, Wu; Jung, Jeil; Gao, Weilu; Ma, Lulu; Yang, Yang; Yang, Shubin; You, Ge; Vajtai, Robert; Xu, Qianfan; MacDonald, Allan H.; Yakobson, Boris I.; Lou, Jun; Liu, Zheng; Ajayan, Pulickel M.

    2014-01-01

    Graphene and hexagonal boron nitride are typical conductor and insulator, respectively, while their hybrids hexagonal boron carbonitride are promising as a semiconductor. Here we demonstrate a direct chemical conversion reaction, which systematically converts the hexagonal carbon lattice of graphene to boron nitride, making it possible to produce uniform boron nitride and boron carbonitride structures without disrupting the structural integrity of the original graphene templates. We synthesize high-quality atomic layer films with boron-, nitrogen- and carbon-containing atomic layers with full range of compositions. Using this approach, the electrical resistance, carrier mobilities and bandgaps of these atomic layers can be tuned from conductor to semiconductor to insulator. Combining this technique with lithography, local conversion could be realized at the nanometre scale, enabling the fabrication of in-plane atomic layer structures consisting of graphene, boron nitride and boron carbonitride. This is a step towards scalable synthesis of atomically thin two-dimensional integrated circuits.

  17. A nine-atom rhodium–aluminum oxide cluster oxidizes five carbon monoxide molecules

    Science.gov (United States)

    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

  18. A nine-atom rhodium-aluminum oxide cluster oxidizes five carbon monoxide molecules.

    Science.gov (United States)

    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

  19. Direct laser fabrication of nanowires on semiconductor surfaces

    Science.gov (United States)

    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.

  20. Study on the π-meson capture by carbon atoms in organic molecules

    International Nuclear Information System (INIS)

    It is established that the intensity of π--meson interception by carbon in organic molecules Csub(m)Hsub(n) differs in the hydrocarbon series from that in the gas mixtures H2+Csub(m)Hsub(n). It is suggested that this difference is due to the different excitation energies of the hydrogen mesic atoms produced on the free (H2) and on the chemically bound (Z-H) hydrogen. The grouping of the atoms Z into molecules, their surrounding by hydrogen atoms, and singularities in the chemical bonds of the Z atoms exert on noticeable influence on the interception

  1. Atomically resolved surface structures of vapor deposited amorphous silicon-carbon alloys: An atomic force microscopy and spectroscopic study

    International Nuclear Information System (INIS)

    Silicon carbide alloys are widely used in high-tech applications due to their interesting combination of chemical, mechanical and electronic properties. Growing thin films of this material in a simple and controlled way is a hot topic in modern material's science. In particular, the possibility to tailor the film properties just by tuning the deposition temperature would be an important progress. In the present work amorphous silicon-carbon alloys thin films have been deposited by electron beam sublimation of a poly-crystalline silicon carbide target in vacuum environment. The deposition temperature was varied from Room Temperature to about 1300 K. The resulting films were analyzed by means of Ultra High Vacuum-Atomic Force Microscopy (UHV-AFM) down to even atomic resolution. The observed features agree with literature data, e.g. interatomic bond lengths, as achieved by others methods, and the structural arrangements of silicon and carbon atoms as concluded from IR and Raman spectroscopy measurements carried out on the same samples. The results not only allow a correlation between film properties and deposition temperature but also support the notion of the UHV-AFM images of the amorphous surfaces being atomically resolved.

  2. High Area Capacity Lithium-Sulfur Full-cell Battery with Prelitiathed Silicon Nanowire-Carbon Anodes for Long Cycling Stability

    OpenAIRE

    Andreas Krause; Susanne Dörfler; Markus Piwko; Florian M. Wisser; Tony Jaumann; Eike Ahrens; Lars Giebeler; Holger Althues; Stefan Schädlich; Julia Grothe; Andrea Jeffery; Matthias Grube; Jan Brückner; Jan Martin; Jürgen Eckert

    2016-01-01

    We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm2. The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D su...

  3. High-performance flexible Ag nanowire electrode with low-temperature atomic-layer-deposition fabrication of conductive-bridging ZnO film

    Science.gov (United States)

    Duan, Ya-Hui; Duan, Yu; Chen, Ping; Tao, Ye; Yang, Yong-Qiang; Zhao, Yi

    2015-02-01

    As material for flexible transparent electrodes for organic photoelectric devices, the silver nanowires (AgNWs) have been widely studied. In this work, we propose a hybrid flexible anode with photopolymer substrate, which is composed of spin-coating-processed AgNW meshes and of zinc oxide (ZnO) prepared by low-temperature (60°C) atomic layer deposition. ZnO effectively fills in the voids of the AgNW mesh electrode, which is thus able to contact to the device all over the active area, to allow for efficient charge extraction/injection. Furthermore, ZnO grown by low temperature mainly relies on hole conduction to make the anode play a better role. Hole-only devices are fabricated to certify the functionality of the low-temperature ZnO film. Finally, we confirm that the ZnO film grown at a low temperature bring a significant contribution to the performance of the modified AgNW anode.

  4. Surface-plasmon mediated photoluminescence enhancement of Pt-coated ZnO nanowires by inserting an atomic-layer-deposited Al2O3 spacer layer

    Science.gov (United States)

    Ren, Qing-Hua; Zhang, Yan; Lu, Hong-Liang; Chen, Hong-Yan; Zhang, Yuan; Li, De-Hui; Liu, Wen-Jun; Ding, Shi-Jin; Jiang, An-Quan; Zhang, David Wei

    2016-04-01

    Surface-plasmon mediated photoluminescence emission enhancement has been investigated for ZnO nanowire (NW)/Pt nanoparticle (NP) nanostructures by inserting an Al2O3 spacer layer. The thickness of the Al2O3 spacer layer and of the Pt NPs capped on the ZnO NWs are well controlled by atomic layer deposition. It is found that the photoluminescence property of the ZnO NW/Al2O3/Pt hybrid structure is highly tunable with respect to the thickness of the inserted Al2O3 spacer layer. The highest enhancement (˜14 times) of the near band emission of ZnO NWs is obtained with an optimized Al2O3 spacer layer thickness of 10 nm leading to a ultraviolet-visible emission ratio of 271.2 compared to 18.8 for bare ZnO NWs. The enhancement of emission is influenced by a Förster-type non-radiative energy transfer process of the exciton energy from ZnO NWs to Pt NPs as well as the coupling effect between excitons of ZnO NWs and surface plasmons of Pt NPs. The highly versatile and tunable photoluminescence properties of Pt-coated ZnO NWs achieved by introducing an Al2O3 spacer layer demonstrate their potential application in highly efficient optoelectronic devices.

  5. Fivefold twinned boron carbide nanowires.

    Science.gov (United States)

    Fu, Xin; Jiang, Jun; Liu, Chao; Yuan, Jun

    2009-09-01

    Chemical composition and crystal structure of fivefold twinned boron carbide nanowires have been determined by electron energy-loss spectroscopy and electron diffraction. The fivefold cyclic twinning relationship is confirmed by systematic axial rotation electron diffraction. Detailed chemical analysis reveals a carbon-rich boron carbide phase. Such boron carbide nanowires are potentially interesting because of their intrinsic hardness and high temperature thermoelectric property. Together with other boron-rich compounds, they may form a set of multiply twinned nanowire systems where the misfit strain could be continuously tuned to influence their mechanical properties. PMID:19687534

  6. Current-induced dynamics in carbon atomic contacts

    DEFF Research Database (Denmark)

    Lu, Jing Tao; Gunst, Tue; Brandbyge, Mads;

    2011-01-01

    Background: The effect of electric current on the motion of atoms still poses many questions, and several mechanisms are at play. Recently there has been focus on the importance of the current-induced nonconservative forces (NC) and Berry-phase derived forces (BP) with respect to the stability of...

  7. Molecular dynamics simulation for arrangement of nickel atoms filled in carbon nanotubes

    International Nuclear Information System (INIS)

    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

  8. Blue Luminescence of CdS Nanowires Synthesized by Sulfurization

    Institute of Scientific and Technical Information of China (English)

    GAO Tao; MENG Guo-Wen; WANG Tai-Hong

    2004-01-01

    @@ Polycrystalline CdS nanowires have been synthesized by sulfurizing metal Cd nanowires deposited electrochemically within the nanochannels of porous anodic alumina (PAA) templates. Photoluminescence (PL) investigation shows that the CdS nanowires have an intensive and broad PL emission band peaked around 435nm. The investigation results suggest that localized defects and excess S atoms existing in the CdS nanowires are responsible for this blue luminescence.

  9. Ultra-Low-Temperature Reactions of Carbon Atoms with Hydrogen Molecules

    CERN Document Server

    Krasnokutski, S A; Renzler, M; Jäger, C; Henning, Th; Scheier, P

    2016-01-01

    The reactions of carbon atoms with dihydrogen have been investigated in liquid helium droplets at $T$ = 0.37 K. A calorimetric technique was applied to monitor the energy released in the reaction. The barrierless reaction between a single carbon atom and a single dihydrogen molecule was detected. Reactions between dihydrogen clusters and carbon atoms have been studied by high-resolution mass spectrometry. The formation of hydrocarbon cations of the type C$_m$H$_n^+$, with $m$ = 1-4 and $n$ = 1-15 was observed. With enhanced concentration of dihydrogen, the mass spectra demonstrated the main "magic" peak assigned to the CH$_5^+$ cation. A simple formation pathway and the high stability of this cation suggest its high abundance in the interstellar medium.

  10. Weighing a single atom using a coupled plasmon–carbon nanotube system

    Directory of Open Access Journals (Sweden)

    Jin-Jin Li and Ka-Di Zhu

    2012-01-01

    Full Text Available We propose an optical weighing technique with a sensitivity down to a single atom, using a surface plasmon and a doubly clamped carbon nanotube resonator. The mass of a single atom is determined via the vibrational frequency shift of the carbon nanotube while the atom attaches to the nanotube surface. Owing to the ultralight mass and high quality factor of the carbon nanotube, and the spectral enhancement by the use of surface plasmon, this method results in a narrow linewidth (kHz and high sensitivity (2.3×10−28 Hzcenterdot g−1, which is five orders of magnitude more sensitive than traditional electrical mass detection techniques.

  11. Enhanced ionized impurity scattering in nanowires

    Science.gov (United States)

    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)].

  12. Carbon nanotube synthesis: from large-scale production to atom-by-atom growth

    International Nuclear Information System (INIS)

    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. (topical review)

  13. The over-step coalescence of carbon atoms on copper surface in the CVD growth of graphene: density functional calculations

    Directory of Open Access Journals (Sweden)

    Yingfeng Li

    2013-05-01

    Full Text Available The ways in which carbon atoms coalesce over the steps on copper (111 surface are ascertained by density functional theory (DFT calculations in the context of chemical vapor deposition (CVD growth of graphene. Two strategies, (1 by putting carbon atoms on and under the steps separately and (2 by importing additional carbon atoms between the ones separated by the steps, have been attempted to investigate if an over-step coalescence of carbon atoms could take place. Based on analyses about the optimized configurations and adsorption energies of carbon atoms nearby the steps, as well as the energy evolution curve of the system throughout the geometry optimizations process, we determined the main way in which graphene grows over the steps continuously: the carbon atoms, adsorbed additionally on the locations between the already existing ones which are separated by the steps, link them (these carbon atoms separated by the steps together. The direct over-step coalescence of the carbon atoms separated by the steps is very difficult, although the energy barrier preventing their coalescence can be weakened by importing carbon atoms on and under the steps gradually. Our results imply potential applications in directing the fabrication of graphene with particular structure by controlling the surface topography of copper substrate.

  14. Catalytic conversion of alcohols having at least three carbon atoms to hydrocarbon blendstock

    Energy Technology Data Exchange (ETDEWEB)

    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.

  15. Numerical Investigation Of The Bombardment Of A Graphene Sheet By A Beam Of Carbon Atoms

    Directory of Open Access Journals (Sweden)

    O.V. Khomenko

    2009-01-01

    Full Text Available Classical molecular dynamics simulations of the bombardment of a graphene sheet by a beam of carbon atoms are carried out. Covalent bonds in the irradiated sample are described by the Brenner potential. The approximation of elastic balls interacting with graphene via the Lennard-Jones potential is used for particles in a beam. The influence of the energy and density of irradiating carbon atoms and of the presence of a thermostat on physical processes occurring during the collisions with the sample is investigated. Energy values of the particles in a beam, which are enough for the sample destruction, are defined.

  16. Atoms

    Institute of Scientific and Technical Information of China (English)

    刘洪毓

    2007-01-01

    Atoms(原子)are all around us.They are something like the bricks (砖块)of which everything is made. The size of an atom is very,very small.In just one grain of salt are held millions of atoms. Atoms are very important.The way one object acts depends on what

  17. Multiphoton inner-shell ionization of the carbon atom

    OpenAIRE

    Rey, H. F.; Hart, H W

    2015-01-01

    We apply time-dependent R-matrix theory to study inner-shell ionization of C atoms in ultra-short 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 2l electron, with two-photon emission of a 1s electron accounting for about 2-3% of all emission processes, and two-photon emission of 2l contributing about 0.5-1%. Three-photon emission of a 1s electron is estimated to contribute about 0.0...

  18. Atomically isolated nickel species anchored on graphitized carbon for efficient hydrogen evolution electrocatalysis

    Science.gov (United States)

    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.

  19. Semiconductor nanowires and templates for electronic applications

    Energy Technology Data Exchange (ETDEWEB)

    Ying, Xiang

    2009-07-15

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

  20. Quantification of tip-broadening in non-contact atomic force microscopy with carbon nanotube tips

    DEFF Research Database (Denmark)

    Meinander, Kristoffer; Jensen, Thomas N.; Simonsen, Soren B.;

    2012-01-01

    Carbon nanotube terminated atomic force microscopy (AFM) probes have been used for the imaging of 5 nm wide surface supported Pt nanoclusters by non-contact (dynamic mode) AFM in an ultra-high vacuum. The results are compared to AFM measurements done with conventional Si-tips, as well...... with geometrically limited conventional probes. Superior durability also stands out as a defining feature of carbon nanotube terminated probes, allowing them to give results with a greatly enhanced reproducibility....

  1. Vibrational spectra of nanowires measured using laser doppler vibrometry and STM studies of epitaxial graphene : an LDRD fellowship report.

    Energy Technology Data Exchange (ETDEWEB)

    Biedermann, Laura Butler

    2009-09-01

    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

  2. Atomic size-limited intercalation into single wall carbon nanotubes

    International Nuclear Information System (INIS)

    Intercalation of single wall carbon nanotubes (SWNTs) provides an important tool to modify their electronic band structure. Using multiple excitation wavelength Raman spectroscopy, we demonstrate that intercalation into SWNT interiors can be limited by intercalant size resulting in an unusual material comprising SWNTs with varying charge density. In the particular case of iodine intercalation, larger SWNTs with iodine-filled interiors were found to carry significantly higher charge density as compared to smaller empty ones. This difference was used to separate the intercalated SWNT material into fractions with homogeneous charge density

  3. Trapping of metal Atoms on nanoprotrusions of carbon nanotubes

    DEFF Research Database (Denmark)

    Shao, Lidong; Zhang, Wei; Kuhn, Luise Theil

    2013-01-01

    Nanoprotrusions on CNTs are engineered using conventional lab treatments at a low temperature. The experimental set-up of applying a mild acid treatment with sonication and base washing is based on the development of introduced defects and vacancies. Compared with previous reports realizing selec...... selective metal depositions on individual carbon nanostructures, our work achieve a selective deposition of Pd nanoparticles on nanoprotrusions of CNTs in a bulk-phase. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim....

  4. Atoms

    International Nuclear Information System (INIS)

    Completed by recent contributions on various topics (atoms and the Brownian motion, the career of Jean Perrin, the evolution of atomic physics since Jean Perrin, relationship between scientific atomism and philosophical atomism), this book is a reprint of a book published at the beginning of the twentieth century in which the author addressed the relationship between atomic theory and chemistry (molecules, atoms, the Avogadro hypothesis, molecule structures, solutes, upper limits of molecular quantities), molecular agitation (molecule velocity, molecule rotation or vibration, molecular free range), the Brownian motion and emulsions (history and general features, statistical equilibrium of emulsions), the laws of the Brownian motion (Einstein's theory, experimental control), fluctuations (the theory of Smoluchowski), light and quanta (black body, extension of quantum theory), the electricity atom, the atom genesis and destruction (transmutations, atom counting)

  5. Photoluminescence enhancement of ZnO nanowire arrays by atomic layer deposition of ZrO2 layers and thermal annealing.

    Science.gov (United States)

    Zhang, Yuan; Lu, Hong-Liang; Wang, Tao; Ren, Qing-Hua; Chen, Hong-Yan; Zhang, Hao; Ji, Xin-Ming; Liu, Wen-Jun; Ding, Shi-Jin; Zhang, David Wei

    2016-06-28

    The effects of shell thickness and rapid thermal annealing on photoluminescence properties of one-dimensional ZnO/ZrO2 core/shell nanowires (NWs) are studied in this work. The ZnO/ZrO2 core/shell structures were synthesized by coating thin ZrO2 layers on the surface of ZnO NWs using atomic layer deposition. The morphological and structural characterization studies reveal that the ZrO2 shells have a polycrystalline structure, which are uniformly and conformally coated on the high quality single-crystal ZnO NWs. As compared with bare ZnO NWs, the ZnO/ZrO2 core/shell structures show a remarkable and continuous enhancement of ultraviolet (UV) emission in intensity with increasing ZrO2 shell thickness up to 10 nm. The great improvement mechanism of the UV emission arises from the surface passivation and the efficient carrier confinement effect of the type-I core/shell system. Moreover, it is observed that the UV emission of ZnO/ZrO2 core/shell structures after thermal annealing increases with increasing annealing temperature. The dominant surface exciton (SX) emission in the bare ZnO NWs and the ZnO/ZrO2 core/shell nanostructures has been detected in the low temperature photoluminescence spectra. A blue shift of the NBE emission peak as well as the varied decay rate of the SX emission intensity are also found in the ZnO NWs after the growth of ZrO2 shells and further thermal treatment. Our results suggest that the ZnO/ZrO2 core/shell nanostructures could be widely implemented in the optical and electronic devices in the future. PMID:27263423

  6. Nanowire photonics

    Directory of Open Access Journals (Sweden)

    Peter J. Pauzauskie

    2006-10-01

    Full Text Available The development of integrated electronic circuitry ranks among the most disruptive and transformative technologies of the 20th century. Even though integrated circuits are ubiquitous in modern life, both fundamental and technical constraints will eventually test the limits of Moore's law. Nanowire photonic circuitry constructed from myriad one-dimensional building blocks offers numerous opportunities for the development of next-generation optical information processors and spectroscopy. However, several challenges remain before the potential of nanowire building blocks is fully realized. We cover recent advances in nanowire synthesis, characterization, lasing, integration, and the eventual application to relevant technical and scientific questions.

  7. Electric Conductivity of Phosphorus Nanowires

    International Nuclear Information System (INIS)

    We present the structures and electrical transport properties of nanowires made from different strands of phosphorus chains encapsulated in carbon nanotubes. Optimized by density function theory, our results indicate that the conductance spectra reveal an oscillation dependence on the size of wires. It can be seen from the density of states and current-voltage curves that the structure of nanowires affects their properties greatly. Among them, the DNA-like double-helical phosphorus nanowire exhibits the distinct characteristic of an approximately linear I – V relationship and has a higher conductance than others. The transport properties of phosphorus nanowires are highly correlated with their microstructures. (condensed matter: structure, mechanical and thermal properties)

  8. Migration behaviour of carbon atoms on clean diamond (0 0 1) surface: A first principle study

    Science.gov (United States)

    Liu, Xuejie; Xia, Qing; Li, Wenjuan; Luo, Hao; Ren, Yuan; Tan, Xin; Sun, Shiyang

    2016-01-01

    The adsorption and migration energies of a single carbon atom and the configuration evolution energies of two carbon atoms on a clean diamond (0 0 1) surface were calculated using the first principle method based on density functional theory to investigate the formation of ultra-nanocrystalline diamond (UNCD) film. The activation energy of a single atom diffusing along a dimer row is 1.96 eV, which is almost the same as that of a CH2 migrating along a dimer row under hydrogen-rich conditions. However, the activation energy of a single atom diffusing along a dimer chain is 2.66 eV, which is approximately 1.55 times greater than that of a CH2 migrating along a dimer chain in a hydrogen-rich environment. The configuration evolution of the two carbon atoms is almost impossible at common diamond film deposition temperatures (700-900 °C) because the activation energies reach 4.46 or 5.90 eV. Therefore, the high-energy barrier could result in insufficient migration of adatoms, leading to the formation of amorphous in UNCD films in hydrogen-poor CVD environment.

  9. Atomic scale observation of oxygen delivery during silver-oxygen nanoparticle catalysed oxidation of carbon nanotubes

    Science.gov (United States)

    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.

  10. Fragmentation of neutral carbon clusters formed by high velocity atomic collision

    International Nuclear Information System (INIS)

    The aim of this work is to understand the fragmentation of small neutral carbon clusters formed by high velocity atomic collision on atomic gas. In this experiment, the main way of deexcitation of neutral clusters formed by electron capture with ionic species is the fragmentation. To measure the channels of fragmentation, a new detection tool based on shape analysis of current pulse delivered by semiconductor detectors has been developed. For the first time, all branching ratios of neutral carbon clusters are measured in an unambiguous way for clusters size up to 10 atoms. The measurements have been compared to a statistical model in microcanonical ensemble (Microcanonical Metropolis Monte Carlo). In this model, various structural properties of carbon clusters are required. These data have been calculated with Density Functional Theory (DFT-B3LYP) to find the geometries of the clusters and then with Coupled Clusters (CCSD(T)) formalism to obtain dissociation energies and other quantities needed to compute fragmentation calculations. The experimental branching ratios have been compared to the fragmentation model which has allowed to find an energy distribution deposited in the collision. Finally, specific cluster effect has been found namely a large population of excited states. This behaviour is completely different of the atomic carbon case for which the electron capture in the ground states predominates. (author)

  11. Atomic carbon chains as spin-transmitters: An ab initio transport study

    DEFF Research Database (Denmark)

    Fürst, Joachim Alexander; Brandbyge, Mads; Jauho, Antti-Pekka

    2010-01-01

    An atomic carbon chain joining two graphene flakes was recently realized in a ground-breaking experiment by Jin et al. (Phys. Rev. Lett., 102 (2009) 205501). We present ab initio results for the electron transport properties of such chains and demonstrate complete spin-polarization of the transmi...

  12. The role of the atomic force function in molecular mechanics simulations for carbon nanostructures

    International Nuclear Information System (INIS)

    Molecular mechanics studies were performed on structures consisting of Y junctions of carbon nanotubes. Tensile simulations were run on the same structure, wherein atomic force functions of various shape were used. According to the numerical test results the behavior of the structure, the failure site and the failure process could be determined irrespective of the shape of the force function

  13. The Reception of J. H. van't Hoff's Theory of the Asymmetric Carbon Atom

    Science.gov (United States)

    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)

  14. Electrocatalytic activity of atomic layer deposited Pt–Ru catalysts onto N-doped carbon nanotubes

    DEFF Research Database (Denmark)

    Johansson, Anne-Charlotte Elisabeth Birgitta; Larsen, Jackie Vincent; Verheijen, Marcel A.;

    2014-01-01

    Pt–Ru catalysts of various compositions, between 0 and 100at.% of Ru, were deposited onto N-doped multi-walled carbon nanotubes (N-CNTs) by atomic layer deposition (ALD) at 250°C. The Pt and Ru precursors were trimethyl(methylcyclopentadienyl)platinum (MeCpPtMe3) and bis...

  15. Thermal stability of silicon nanowires:atomistic simulation study

    Institute of Scientific and Technical Information of China (English)

    Liu Wen-Liang; Zhang Kai-Wang; Zhong Jian-Xin

    2009-01-01

    Using the Stillinger-Weber (SW) potential model, we investigate the thermal stability of pristine silicon nanowires based on classical molecular dynamics (MD) simulations. We explore the structural evolutions and the Lindemann indices of silicon nanowires at different temperatures in order to unveil atomic-level melting behaviour of silicon nanowires.The simulation results show that silicon nanowires with surface reconstructions have higher thermal stability than those without surface reconstructions, and that silicon nanowires with perpendicular dimmer rows on the two (100) surfaces have somewhat higher thermal stability than nanowires with parallel dimmer rows on the two (100) surfaces. Furthermore, the melting temperature of silicon nanowires increases as their diameter increases and reaches a saturation value close to the melting temperature of bulk silicon. The value of the Lindemann index for melting silicon nanowires is 0.037.

  16. Reactions of the inner surface of carbon nanotubes and nanoprotrusion processes imaged at the atomic scale

    Science.gov (United States)

    Chamberlain, Thomas W.; Meyer, Jannik C.; Biskupek, Johannes; Leschner, Jens; Santana, Adriano; Besley, Nicholas A.; Bichoutskaia, Elena; Kaiser, Ute; Khlobystov, Andrei N.

    2011-09-01

    Although the outer surface of single-walled carbon nanotubes (atomically thin cylinders of carbon) can be involved in a wide range of chemical reactions, it is generally thought that the interior surface of nanotubes is unreactive. In this study, we show that in the presence of catalytically active atoms of rhenium inserted into nanotubes, the nanotube sidewall can be engaged in chemical reactions from the inside. Aberration-corrected high-resolution transmission electron microscopy operated at 80 keV allows visualization of the formation of nanometre-sized hollow protrusions on the nanotube sidewall at the atomic level in real time at ambient temperature. Our direct observations and theoretical modelling demonstrate that the nanoprotrusions are formed in three stages: (i) metal-assisted deformation and rupture of the nanotube sidewall, (ii) the fast formation of a metastable asymmetric nanoprotrusion with an open edge and (iii) a slow symmetrization process that leads to a stable closed nanoprotrusion.

  17. The fabrication and characterization of novel carbon doped TiO2 nanotubes, nanowires and nanorods with high visible light photocatalytic activity.

    Science.gov (United States)

    Wu, Zhongbiao; Dong, Fan; Zhao, Weirong; Wang, Haiqiang; Liu, Yue; Guan, Baohong

    2009-06-10

    Novel carbon doped TiO(2) nanotubes, nanowires and nanorods were fabricated by utilizing the nanoconfinement of hollow titanate nanotubes (TNTs). The fabrication process included adsorption of ethanol molecules in the inner space of TNTs and thermal treatment of the complex in inert N(2) atmosphere. The structural morphology of carbon doped TiO(2) nanostructures can be tuned using the calcination temperature. X-ray diffraction, Raman and Brunauer-Emmett-Teller studies proved that the doped carbon promoted the crystallization and phase transition by acting as nucleation seeds. X-ray photoelectron spectroscopy (XPS) showed that O-Ti-C and Ti-O-C bonds were formed in the nanostructures. Additional electronic states from the XPS valence band due to carbon doping were observed. This evidence indicated the electronic origin of the band gap narrowing and visible light absorption. The differences in chemical and electronic states between the surface and bulk of as-prepared samples confirmed that carbon was doped into the lattice of TiO(2) nanostructure through an inner doping process. The as-prepared catalysts exhibited enhanced photocatalytic activity for degradation of toluene in gas phase under both visible and simulated solar light irradiation compared with that of commercial Degussa P25. This novel fabrication approach can valuably contribute to designing nanostructured photocatalytic materials and modifying various nanotube materials. PMID:19451679

  18. Multiphoton inner-shell ionization of the carbon atom

    CERN Document Server

    Rey, H F

    2015-01-01

    We apply time-dependent R-matrix theory to study inner-shell ionization of C atoms in ultra-short high-frequency light fields with a photon energy between 170 and 245 eV. At an intensity of 10$^{17}$ W/cm$^2$, ionization is dominated by single-photon emission of a $2\\ell$ electron, with two-photon emission of a 1s electron accounting for about 2-3\\% of all emission processes, and two-photon emission of $2\\ell$ contributing about 0.5-1\\%. Three-photon emission of a 1s electron is estimated to contribute about 0.01-0.03\\%. Around a photon energy of 225 eV, two-photon emission of a 1s electron, leaving C$^+$ in either 1s2s2p$^3$ or 1s2p$^4$ is resonantly enhanced by intermediate 1s2s$^2$2p$^3$ states. The results demonstrate the capability of time-dependent R-matrix theory to describe inner-shell ionization processes including rearrangement of the outer electrons.

  19. Nanowire Lasers

    Science.gov (United States)

    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.

  20. Analysis of Carbon Nanotubes on the Mechanical Properties at Atomic Scale

    Directory of Open Access Journals (Sweden)

    Xiaowen Lei

    2011-01-01

    Full Text Available This paper aims at developing a mathematic model to characterize the mechanical properties of single-walled carbon nanotubes (SWCNTs. The carbon-carbon (C–C bonds between two adjacent atoms are modeled as Euler beams. According to the relationship of Tersoff-Brenner force theory and potential energy acting on C–C bonds, material constants of beam element are determined at the atomic scale. Based on the elastic deformation energy and mechanical equilibrium of a unit in graphite sheet, simply form ED equations of calculating Young's modulus of armchair and zigzag graphite sheets are derived. Following with the geometrical relationship of SWCNTs in cylindrical coordinates and the structure mechanics approach, Young's modulus and Poisson's ratio of armchair and zigzag SWCNTs are also investigated. The results show that the approach to research mechanical properties of SWCNTs is a concise and valid method. We consider that it will be useful technique to progress on this type of investigation.

  1. Electrical conductivity measurements of bacterial nanowires from Pseudomonas aeruginosa

    Science.gov (United States)

    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.

  2. Preparation of well-aligned carbon nanotubes/silicon nanowires core-sheath composite structure arrays in porous anodic aluminum oxide templates

    Institute of Scientific and Technical Information of China (English)

    李梦轲; 力虎林; 陆梅; 王成伟

    2002-01-01

    The well-aligned carbon nanotubes (CNTs) arrays with opened ends were prepared in ordered pores of anodic aluminum oxide (AAO) template by the chemical vapor deposition (CVD) method. After then, silicon nanowires (SiNWs) were deposited in the hollow cavities of CNTs. By using this method, CNTs/SiNWs core-sheath composite structure arrays were synthesized successfully. Growing structures and physical properties of the CNTs/SiNWs composite structure arrays were analyzed and researched by the scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction spectrum (XRD), respectively. The field emission (FE) behavior of the CNTs/SiNWs composite structure arrays was studied based on Fowler-Nordheim tunneling mechanism and current-voltage (/-V) curve. And the photoluminescence (PL) was also characterized. Significantly, the CNTs/SiNWs core-sheath composite structure nanowire fabricated by AAO template method is characteristic of a metal/semiconductor (M/S) behavior and can be

  3. Modeling the Mechanical Properties of Functionalized Carbon Nanotubes and Their Composites: Design at the Atomic Level

    Directory of Open Access Journals (Sweden)

    Qing-Sheng Yang

    2014-01-01

    Full Text Available This investigation focuses on the design of functionalization configuration at the atomic level to determine the influence of atomic structure on the mechanical properties of functionalized carbon nanotubes (F-CNTs and their composites. Tension and compressive buckling behaviors of different configurations of CNTs functionalized by H atoms are studied by a molecular dynamics (MD method. It is shown that H-atom functionalization reduces Young’s modulus of CNTs, but Young’s modulus is not sensitive to the functionalization configuration. The configuration does, however, affect the tensile strength and critical buckling stress of CNTs. Further, the stress-strain relations of composites reinforced by nonfunctionalized and various functionalized CNTs are analyzed.

  4. Low-temperature carbon monoxide oxidation catalysed by regenerable atomically dispersed palladium on alumina

    Science.gov (United States)

    Peterson, Eric J.; Delariva, Andrew T.; Lin, Sen; Johnson, Ryan S.; Guo, Hua; Miller, Jeffrey T.; Hun Kwak, Ja; Peden, Charles H. F.; Kiefer, Boris; Allard, Lawrence F.; Ribeiro, Fabio H.; Datye, Abhaya K.

    2014-09-01

    Catalysis by single isolated atoms of precious metals has attracted much recent interest, as it promises the ultimate in atom efficiency. Most previous reports are on reducible oxide supports. Here we show that isolated palladium atoms can be catalytically active on industrially relevant γ-alumina supports. The addition of lanthanum oxide to the alumina, long known for its ability to improve alumina stability, is found to also help in the stabilization of isolated palladium atoms. Aberration-corrected scanning transmission electron microscopy and operando X-ray absorption spectroscopy confirm the presence of intermingled palladium and lanthanum on the γ-alumina surface. Carbon monoxide oxidation reactivity measurements show onset of catalytic activity at 40 °C. The catalyst activity can be regenerated by oxidation at 700 °C in air. The high-temperature stability and regenerability of these ionic palladium species make this catalyst system of potential interest for low-temperature exhaust treatment catalysts.

  5. Electronic and Elastic Properties of Helical Nickel Nanowires

    Institute of Scientific and Technical Information of China (English)

    WANG Bao-Lin; ZHAO Ji-Jun; SHI Da-Ning; JIA Jian-Min; WANG Guang-Hou

    2005-01-01

    @@ The structural and elastic properties of ultrathin nickel nanovires are investigated by using molecular dynamics simulation with a Sutton-Chen potential. Helical multi-shell structures are obtained as the most stable structures for Ni nanowires with diameters of about 1 nm. The electronic states of these nanowires are computed and compared with that of Ni solid. The mechanical responses of the helical nanowires under tensile forces are simulated. We observe elastic deformation of nanowires characterized by periodic oscillations of the nanowire length under constant force. Within an elastic limit, both the atomic structures and the electronic structures remain stable under external tensile loading.

  6. Formation and atomic structure of tetrahedral carbon onion produced by electron-beam irradiation

    International Nuclear Information System (INIS)

    Full text: Various fullerene structures has been designed and produced after the discovery of C60. These fullerene materials are good candidates as nanoscale devises such as single-electron devices, nano-diode, nano-transistor, nano-ball bearing and insulator lubricant. The onion structures, which generally consist of some quasi-spherical fullerene group, are also discovered and studied in detail. The tetrahedral carbon onions had been calculated to be unstable compared to the spherical onions due to the rigidity. The purpose of the present work is to produce new carbon onion by high-energy electron-irradiation on amorphous carbon at 1250 kV, and to investigate atomic structures and stability of the new carbon onion cluster by high-resolution electron microscopy (HREM) and molecular orbital/mechanics calculations. To confirm the structure model from HREM data, HREM image simulation were carried out. The tetrahedral carbon onion was successfully produced by high-energy electron-irradiation. A HREM image of tetrahedral carbon onion would consist of pentagonal and hexagonal rings. The HREM result indicates that new fullerene structures formed into the carbon onion. Molecular mechanics calculations (MM2), semi-empirical molecular orbital calculations (PM3), and density functional theory (DFT) were used to get structure optimization about first and second internal shell. The energy levels and density of states were also calculated by the first principles method (DV-Xα). The smallest tetrahedral onion in the HREM image agreed well with the proposed structure model of C84atC276. Each vertex consists of a hexagonal ring, and three pentagonal rings exist around the vertex along the edge. In summary, the tetrahedral carbon cluster was produced by energy transfer of electron-irradiation, and the new atomic structure model of tetrahedral carbon onion was proposed. The electronic structures were also calculated theoretically. Copyright (2002) Australian Society for Electron

  7. Functionalization of terminal carbon atoms of hydroxyl terminated polybutadiene by polyazido nitrogen rich molecules

    Indian Academy of Sciences (India)

    Rajavelu Murali Sankar; Tapta Kanchan Roy; Tushar Jana

    2011-07-01

    We report a novel synthetic approach for the attachment of the polyazido nitrogen rich molecule on to the hydroxyl terminated polybutadiene (HTPB) backbone. The terminal carbon atoms of the HTPB are functionalized by attaching cyanuric chloride (CYC) covalently on the HTPB backbone. Further reaction of this modified HTPB with sodium azide yields polyazido nitrogen rich HTPB. The unique physico-chemical properties and the microstructure of the HTPB do not get affected upon modification. IR, gel permeable chromatography (GPC) and absorption spectroscopy studies prove that the polyazido nitrogen rich molecules are covalently attached at the terminal carbon atoms of the HTPB. The π electron delocalization owing to long butadiene chain, strong electron withdrawing effect of the triazine molecules are the major driving forces for the covalent attachment of the triazine at the terminal carbon atoms of the HTPB. The disruption of the intermolecular hydrogen bonding between the terminal hydroxyl groups of the HTPB chains and the presence of hydrogen bonding between the N atoms of the triazine ring with OH group of the HTPB are observed. Theoretical study also reveals the existence of the hydrogen bonding between the OH and N. Theoretical calculation shows that the detonation performance of the polyazido nitrogen rich HTPB are very promising.

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

    Science.gov (United States)

    Bhandavat, Romil

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

  9. Hierarchical silicon nanowires-carbon textiles matrix as a binder-free anode for high-performance advanced lithium-ion batteries

    Science.gov (United States)

    Liu, Bin; Wang, Xianfu; Chen, Haitian; Wang, Zhuoran; Chen, Di; Cheng, Yi-Bing; Zhou, Chongwu; Shen, Guozhen

    2013-04-01

    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.

  10. Carbon Nanotube-Silicon Nanowire Heterojunction Solar Cells with Gas-Dependent Photovoltaic Performances and Their Application in Self-Powered NO2 Detecting

    Science.gov (United States)

    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.

  11. Carbon Nanotube-Silicon Nanowire Heterojunction Solar Cells with Gas-Dependent Photovoltaic Performances and Their Application in Self-Powered NO2 Detecting.

    Science.gov (United States)

    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. PMID:27299654

  12. Self-supported Zn3P2 nanowire arrays grafted on carbon fabrics as an advanced integrated anode for flexible lithium ion batteries

    Science.gov (United States)

    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

  13. Three-Dimensional Bimetal-Graphene-Semiconductor Coaxial Nanowire Arrays to Harness Charge Flow for the Photochemical Reduction of Carbon Dioxide.

    Science.gov (United States)

    Hou, Jungang; Cheng, Huijie; Takeda, Osamu; Zhu, Hongmin

    2015-07-13

    The photochemical conversion of carbon dioxide provides a straightforward and effective strategy for the highly efficient production of solar fuels with high solar-light utilization efficiency. However, the high recombination rate of photoexcited electron-hole (e-h) pairs and the poor photostability have greatly limited their practical applications. Herein, a practical strategy is proposed to facilitate the separation of e-h pairs and enhance the photostability in a semiconductor by the use of a Schottky junction in a bimetal-graphene-semiconductor stack array. Importantly, Au-Cu nanoalloys (ca. 3 nm) supported on a 3D ultrathin graphene shell encapsulating a p-type Cu2O coaxial nanowire array promotes the stable photochemical reduction of CO2 to methanol by the synergetic catalytic effect of interfacial modulation and charge-transfer channel design. This work provides a promising lead for the development of practical catalysts for sustainable fuel synthesis. PMID:26068934

  14. Conductance of a single-atom carbon chain with graphene leads

    OpenAIRE

    Chen, Wei; Andreev, A. V.; Bertsch, G. F.

    2008-01-01

    We study the conductance of an interconnect between two graphene leads formed by a single-atom carbon chain. Its dependence on the chemical potential and the number of atoms in the chain is qualitatively different from that in the case of normal metal leads. Electron transport proceeds via narrow resonant states in the wire. The latter arise due to strong reflection at the junctions between the chain and the leads, which is caused by the small density of states in the leads at low energy. The...

  15. Facile one-step direct electrodeposition of bismuth nanowires on glassy carbon electrode for selective determination of folic acid

    International Nuclear Information System (INIS)

    Highlights: • BiNWs prepared through simple, fast one step electrochemical route. • BiNWs showed more catalytic activity and sensitivity than GC towards FA reduction. • Selective detection of FA was achieved with low limit of detection (9.53 × 10−9 mol L−1). • Real sample analysis was successfully demonstrated using FA pharmaceutical tablets. • BiNWs based sensor matrix is inexpensive, and more suitable for FA real application. - Abstract: In the present work, we have developed a facile one step route to electrodeposition of stabilizer-free bismuth nanowires (BiNWs) on glassy carbon (GC) substrates by using a simple potentiostatic method. Formation of BiNWs on GC substrate was confirmed by field emission scanning electron microscopy (FE-SEM). The growth of BiNWs on the GC substrate was monitored by cyclic voltammetry and found that continuous in-situ generation of hydrogen bubbles during electrodeposition provides a stagnant template for the formation of BiNWs on the GC substrate. Phase-purity of the deposited BiNWs on GC substrate studied by XRD indicates no other oxide formation. The electrodeposited BiNWs on GC substrate was used for electro-reduction of folic acid (FA) and its quantitative determination in Britton-Robinson buffer of pH 4.5 solutions. The observed cyclic voltammetric reduction current of FA on BiNWs/GC is almost 15 times higher with 0.015 V less negative overpotential compared to bare GC substrate alone. This result clearly reveals the electrocatalytic activity of the deposited BiNWs. In addition, square wave voltammetry (SWV) showed a perfectly linear response in the concentration range of 1 × 10−8–15 × 10−8 mol L−1 with a correlation coefficient of 0.9956. The limit of detection (LOD) and limit of quantitation (LOQ) are determined to be 9.53 × 10−9 and 31.68 × 10−9 mol L−1 respectively. The response of the BiNWs/GC sensor matrix is not affected by any usual interference from excess concentrations of metal ions

  16. Influence of supersaturated carbon on the diffusion of Ni in ferrite determined by atom probe tomography

    KAUST Repository

    Kresse, T.

    2013-09-01

    In patented and cold-drawn pearlitic steel wires dissociation of cementite occurs during mechanical deformation. In this study the influence of the carbon decomposition on the diffusion of nickel in ferrite is investigated by means of atom probe tomography. In the temperature range 423-523 K we observed a much smaller activation energy of Ni diffusion than for self-diffusion in body-centered cubic iron, indicating an increased vacancy density owing to enhanced formation of vacancy-carbon complexes. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  17. Synthesis of Nanowires by Spray Pyrolysis

    Directory of Open Access Journals (Sweden)

    Kalyana C. Pingali

    2009-01-01

    Full Text Available Nanowires of carbon as well as nickel-carbon (Ni-C were synthesized by spray-pyrolysis. The carbon nanowires were synthesized using methanol as a precursor while the Ni-C nanowires were obtained by using nickel chloride methanol solution as feed. It was found that low argon carrier gas flow rates (<100 cm3/min and suitable reaction temperatures (∼700∘C were found to be critical for the formation of wired structures. The formation of nanowires was quite sensitive to reaction temperature. Nanowires could not form at temperatures higher than 900∘C in the presence of hexane. Ruthenium chloride and nickel chloride dissolved in hexane and methanol resulted in carbon coated binary metallic nanoparticles. Morphological differences of carbon nanowires, Ni-C wires and carbon coated binary nanoparticles were characterized by scanning electron microscopy (SEM and energy-dispersive X-ray analysis (EDS. The formation mechanism for the wired structures is proposed to explain the structural results obtained.

  18. IMPROVED FABRICATION METHOD FOR CARBON NANOTUBE PROBE OF ATOMIC FORCE MICROSCOPY(AFM)

    Institute of Scientific and Technical Information of China (English)

    XU Zongwei; DONG Shen; GUO Liqiu; ZHAO Qingliang

    2006-01-01

    An improved arc discharge method is developed to fabricate carbon nanotube probe of atomic force microscopy (AFM) here. First, silicon probe and carbon nanotube are manipulated under an optical microscope by two high precision microtranslators. When silicon probe and carbon nanotube are very close, several tens voltage is applied between them. And carbon nanotube is divided and attached to the end of silicon probe, which mainly due to the arc welding function.Comparing with the arc discharge method before, the new method here needs no coat silicon probe with metal film in advance, which can greatly reduce the fabrication's difficulty. The fabricated carbon nanotube probe shows good property of higher aspect ratio and can more accurately reflect the true topography of silicon grating than silicon probe. Under the same image drive force, carbon nanotube probe had less indentation depth on soft triblock copolymer sample than silicon probe. This showed that carbon nanotube probe has lower spring constant and less damage to the scan sample than silicon probe.

  19. Synthesis of silicon and germanium nanowires.

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-11-01

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

  20. The atomic configuration of graphene/vanadium carbide interfaces in vanadium carbide-encapsulating carbon nanocapsules.

    Science.gov (United States)

    Yazaki, Gaku; Matsuura, Daisuke; Kizuka, Tokushi

    2014-03-01

    Carbon nanocapsules (CNCs) encapsulating vanadium carbide (VC) nanocrystals with a NaCI structure were synthesized by a gas-evaporation method using arc-discharge heating. The CNCs were observed by high-resolution transmission electron microscopy. The VC nanocrystals within the nanospaces of CNCs were truncated by low-index facets and were coated with several graphene layers, forming graphene/VC interfaces. The atomic configuration and interlayer spacings at the interfaces were found. PMID:24745251

  1. Localised quantum states of atomic and molecular particles physisorbed on carbon-based nanoparticles

    Czech Academy of Sciences Publication Activity Database

    Kaprálová-Žďánská, Petra Ruth; Trachta, Michal; Bludský, Ota; Špirko, Vladimír

    2014-01-01

    Roč. 141, č. 11 (2014), "114702-1"-"114702-10". ISSN 0021-9606 R&D Projects: GA ČR GAP205/11/0571; GA ČR GAP208/11/0436; GA ČR GAP208/10/0725 Institutional support: RVO:68378271 ; RVO:61388963 Keywords : periodic structure * carbon nanostructures * graphene * quantum mechanics * physisorbed Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 2.952, year: 2014

  2. MD investigation of the collective carbon atom behavior of a (17, 0) zigzag single wall carbon nanotube under axial tensile strain

    International Nuclear Information System (INIS)

    The collective dynamic behavior of carbon atoms of a (17, 0) zigzag single wall carbon nanotube is investigated under tensile strains by molecular dynamics (MD) simulations. The 'slip vector' parameter is used to study the collective motion of a group of atoms and the deformation behavior in three different directions (axial, radial, and tangential) of a (17, 0) carbon nanotube. The variations of radial slip vectors indicate almost all carbon atoms of the (17, 0) carbon nanotube will stay on the cylindrical surface before the yielding of the single wall carbon nanotube (SWNT). Furthermore, the tangential vectors show kinking deformation for the (17, 0) zigzag tube only rarely appears when the crack occurs. Non-symmetrical deformation around a carbon atom along the axial direction also can be found. The variations in the slip vector values of each atom display a symmetrical crack along the horizontal direction and normal to the tube axis. Chain-like structures with 3-4 atoms can be observed, with the number of chain-like structures decreasing before the breakage of the SWNT. The mechanical properties and dynamic behavior of a (17, 0) zigzag SWNT under tensile strain are also compared with that of a (10, 10) armchair tube in our previous study (Weng et al. 2009).

  3. Electronic transport in large systems through a QUAMBO-NEGF approach: Application to atomic carbon chains

    International Nuclear Information System (INIS)

    The conductance of single-atom carbon chain (SACC) between two zigzag graphene nanoribbons (GNR) is studied by an efficient scheme utilizing tight-binding (TB) parameters generated via quasi-atomic minimal basis set orbitals (QUAMBOs) and non-equilibrium Green's function (NEGF). Large systems (SACC contains more than 50 atoms) are investigated and the electronic transport properties are found to correlate with SACC's parity. The SACCs provide a stable off or on state in broad energy region (0.1-1 eV) around Fermi energy. The off state is not sensitive to the length of SACC while the corresponding energy region decreases with the increase of the width of GNR. -- Highlights: → Graphene has many superior electronic properties. → First-principles calculation are accurate but limited to system size. → QUAMBOs construct tight-binding parameters with spatial localization, and then use divide-and-conquer method. → SACC (single carbon atom chain): structure and transport show even-odd parity, and long chains are studied.

  4. Investigation of the Interactions and Bonding between Carbon and Group VIII Metals at the Atomic Scale.

    Science.gov (United States)

    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. PMID:26848826

  5. Adsorption and manipulation of carbon onions on highly oriented pyrolytic graphite studied with atomic force microscopy

    International Nuclear Information System (INIS)

    Carbon onions produced by DC arc discharge method were deposited on highly oriented pyrolytic graphite (HOPG) surface and their adsorption and manipulation was studied using an atomic force microscopy (AFM). Well-dispersed adsorption of carbon onions on HOPG surface was obtained and aggregations of onions were not observed. The van der Waals interaction between the onion and HOPG surface and that between two onions, were calculated and discussed using Hamaker's theory. The manipulation of adsorbed onions on HOPG surface was realized using the AFM in both the raster mode and the vector mode. The controllability and precision of two manipulation modes were compared and the vector mode manipulation was found superior, and is a useful technique for the construction of nano-scale devices based on carbon onions

  6. Atom Probe Tomography Examination of Carbon Redistribution in Quenched and Tempered 4340 Steel

    Energy Technology Data Exchange (ETDEWEB)

    Clarke, Amy J. [Los Alamos National Laboratory; Miller, Michael K. [ORNL; Alexander, David J. [Los Alamos National Laboratory; Field, Robert D. [Los Alamos National Laboratory; Clarke, Kester D. [Los Alamos National Laboratory

    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.

  7. Artificial neural network approach for atomic coordinate prediction of carbon nanotubes

    Science.gov (United States)

    Acı, Mehmet; Avcı, Mutlu

    2016-07-01

    In this paper, four artificial neural network (ANN) models [i.e., feed-forward neural network (FFNN), function fitting neural network (FITNET), cascade-forward neural network (CFNN) and generalized regression neural network] have been developed for atomic coordinate prediction of carbon nanotubes (CNTs). The research reported in this study has two primary objectives: (1) to develop ANN prediction models that calculate atomic coordinates of CNTs instead of using any simulation software and (2) to use results of the ANN models as an initial value of atomic coordinates for reducing number of iterations in calculation process. The dataset consisting of 10,721 data samples was created by combining the atomic coordinates of elements and chiral vectors using BIOVIA Materials Studio CASTEP (CASTEP) software. All prediction models yield very low mean squared normalized error and mean absolute error rates. Multiple correlation coefficient (R) results of FITNET, FFNN and CFNN models are close to 1. Compared with CASTEP, calculation times decrease from days to minutes. It would seem possible to predict CNTs' atomic coordinates using ANN models can be successfully used instead of mathematical calculations.

  8. Bridged single-walled carbon nanotube-based atomic-scale mass sensors

    Science.gov (United States)

    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.

  9. Formation of chiral branched nanowires by the Eshelby Twist.

    Science.gov (United States)

    Zhu, Jia; Peng, Hailin; Marshall, A F; Barnett, D M; Nix, W D; Cui, Yi

    2008-08-01

    Manipulating the morphology of inorganic nanostructures, such as their chirality and branching structure, has been actively pursued as a means of controlling their electrical, optical and mechanical properties. Notable examples of chiral inorganic nanostructures include carbon nanotubes, gold multishell nanowires, mesoporous nanowires and helical nanowires. Branched nanostructures have also been studied and been shown to have interesting properties for energy harvesting and nanoelectronics. Combining both chiral and branching motifs into nanostructures might provide new materials properties. Here we show a chiral branched PbSe nanowire structure, which is formed by a vapour-liquid-solid branching from a central nanowire with an axial screw dislocation. The chirality is caused by the elastic strain of the axial screw dislocation, which produces a corresponding Eshelby Twist in the nanowires. In addition to opening up new opportunities for tailoring the properties of nanomaterials, these chiral branched nanowires also provide a direct visualization of the Eshelby Twist. PMID:18685634

  10. Silicon carbide nanowires synthesized with phenolic resin and silicon powders

    Science.gov (United States)

    Zhao, Hongsheng; Shi, Limin; Li, Ziqiang; Tang, Chunhe

    2009-02-01

    Large-scale silicon carbide nanowires with the lengths up to several millimeters were synthesized by a coat-mix, moulding, carbonization, and high-temperature sintering process, using silicon powder and phenolic resin as the starting materials. Ordinary SiC nanowires, bamboo-like SiC nanowires, and spindle SiC nanochains are found in the fabricated samples. The ordinary SiC nanowire is a single-crystal SiC phase with a fringe spacing of 0.252 nm along the [1 1 1] growth direction. Both of the bamboo-like SiC nanowires and spindle SiC nanochains exhibit uniform periodic structures. The bamboo-like SiC nanowires consist of amorphous stem and single-crystal knots, while the spindle SiC nanochains consist of uniform spindles which grow uniformly on the entire nanowires.

  11. Influence of atomic vacancies on the dynamic characteristics of nanoresonators based on double walled carbon nanotube

    Science.gov (United States)

    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

  12. A first principle study for the adsorption and absorption of carbon atom and the CO dissociation on Ir(100) surface

    Energy Technology Data Exchange (ETDEWEB)

    Erikat, I. A., E-mail: ihsanas@yahoo.com [Department of Physics, Jerash University, Jerash-26150 (Jordan); Hamad, B. A. [Department of Physics, The University of Jordan, Amman-11942 (Jordan)

    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. A first principle study for the adsorption and absorption of carbon atom and the CO dissociation on Ir(100) surface

    International Nuclear Information System (INIS)

    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

  14. A first principle study for the adsorption and absorption of carbon atom and the CO dissociation on Ir(100) surface

    Science.gov (United States)

    Erikat, I. A.; Hamad, B. A.

    2013-11-01

    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.

  15. Energy loss of 10 MeV/amu atomic helium in carbon

    Energy Technology Data Exchange (ETDEWEB)

    Ogawa, H.; Sakamoto, N. [Nara Women`s Univ. (Japan). Dept. of Physics; Katayama, I. [Institute for Nuclear Study, University of Tokyo, Tanashi, Tokyo 188 (Japan); Haruyama, Y.; Saito, M. [Laboratory of Applied Physics, Kyoto Prefectural University, Kyoto 606 (Japan); Yoshida, K. [Department of Nuclear Engineering, Kyoto University, Kyoto 606-01 (Japan); Tosaki, M. [Radio Isotope Research Center, Kyoto University, Kyoto 606 (Japan); Susuki, Y.; Kimura, K. [Department of Engineering Physics and Mechanics, Kyoto University, Kyoto 606-01 (Japan)

    1997-10-01

    Mean energy losses of 31.8 MeV neutral {sup 3}He atoms penetrating through thin carbon foils of 1.6-7.2 {mu}g/cm{sup 2} were measured using a high-resolution magnetic spectrograph. The measured particles are those entered into the carbon foil as {sup 3}He{sup 0} and emerged from it as {sup 3}He{sup 0}. From the attenuation measurement of {sup 3}He{sup 0} in the foils, we can regard the measured energy losses as those of {sup 3}He{sup 0} in a frozen charge state. The measured stopping power of carbon for 31.8 MeV {sup 3}He{sup 0} is 58.2 {+-} 4.9 eV/{mu}g/cm{sup 2}. Including our previous data for other partially clothed ions of the same velocity, the projectile atomic number dependence of the screening effect due to the bound electrons is roughly reproduced by the theoretical predictions based on the Born approximation. (orig.). 14 refs.

  16. Is atomic carbon a good tracer of molecular gas in metal-poor galaxies?

    CERN Document Server

    Glover, Simon C O

    2015-01-01

    Carbon monoxide (CO) is widely used as a tracer of molecular hydrogen (H2) in metal-rich galaxies, but is known to become ineffective in low metallicity dwarf galaxies. Atomic carbon has been suggested as a superior tracer of H2 in these metal-poor systems, but its suitability remains unproven. To help us to assess how well atomic carbon traces H2 at low metallicity, we have performed a series of numerical simulations of turbulent molecular clouds that cover a wide range of different metallicities. Our simulations demonstrate that in star-forming clouds, the conversion factor between [CI] emission and H2 mass, $X_{\\rm CI}$, scales approximately as $X_{\\rm CI} \\propto Z^{-1}$. We recover a similar scaling for the CO-to-H2 conversion factor, $X_{\\rm CO}$, but find that at this point in the evolution of the clouds, $X_{\\rm CO}$ is consistently smaller than $X_{\\rm CI}$, by a factor of a few or more. We have also examined how $X_{\\rm CI}$ and $X_{\\rm CO}$ evolve with time. We find that $X_{\\rm CI}$ does not vary ...

  17. Inelastic and reactive scattering of hyperthermal atomic oxygen from amorphous carbon

    Science.gov (United States)

    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.

  18. C3 coefficients for the alkali atoms interacting with a graphene layer and carbon nanotube

    International Nuclear Information System (INIS)

    We evaluate separation dependent van der Waals dispersion (C3) coefficients for the interactions of the Li, Na, K and Rb atoms with a graphene layer and with a single walled carbon nanotube (CNT) using the hydrodynamic and Dirac models. The results from both the models are evaluated using accurate values of the dynamic polarizabilities of the above alkali atoms. Accountability of accurate dynamic polarizabilities of the alkali atoms to determine the C3 coefficients are accentuated by comparing the obtained coefficients using the precise values of the dynamic dipole polarizabilities against the values estimated from the single oscillator approximation that are generally used in the earlier calculations. For a practical description of the atom–surface interaction potentials, the C3 coefficients are given for a wide range of separation distances between the considered ground states of the atoms and the wall surfaces and also for different nanotube radii. The coefficients for the graphene layer are fitted to a logistic function of the separation distance. For CNT, we find a paraboloid kind of fit dependence both on the separation distances and radii of the CNT. (paper)

  19. Velocity distribution of carbon and oxygen atoms in front of a tokamak limiter

    International Nuclear Information System (INIS)

    From the Doppler-broadened emission profiles of a CI line (3P2→3P20, λ=909.5 nm) and of an OI line (3P2,1,0→3S10, λ=844.6 nm), the velocity distribution of carbon and oxygen atoms in front of a graphite limiter has been deduced. For the π-component of the CI line, the Zeeman splitting is negligible, but for the π-components of the OI line, the Paschen-Back effect has to be taken into account. The contribution of chemical and physical sputtering to the release of impurities under various experimental conditions has been investigated at the tip of the limiter. For C atoms, chemical sputtering dominates at low boundary temperatures, and physical sputtering at high temperature. For oxygen, chemical sputtering is always indicated to be the more efficient process. (orig.)

  20. Role of atomic transverse migration in growth of diamond-like carbon films

    Institute of Scientific and Technical Information of China (English)

    Ma Tian-Bao; Hu Yuan-Zhong; Wang Hui

    2007-01-01

    The growth of diamond-like carbon (DLC) films is studied using molecular dynamics simulations. The effect of impact angle on film structure is carefully studied, which shows that the transverse migration of the incident atoms is the main channel of film relaxation. A transverse-migration-induced film relaxation model is presented to elucidate the process of film relaxation which advances the original model of subplantation. The process of DLC film growth on a rough surface is also investigated, as well as the evolution of microstructure and surface morphology of the film. A preferential-to-homogeneous growth mode and a smoothing of the film are observed, which are due to the transverse migration of the incident atoms.

  1. Electron dynamics in the carbon atom induced by spin-orbit interaction

    CERN Document Server

    Rey, H F

    2014-01-01

    We use R-Matrix theory with Time dependence (RMT) to investigate multiphoton ionization of ground-state atomic carbon with initial orbital magnetic quantum number $M_L$=0 and $M_L$=1 at a laser wavelength of 390 nm and peak intensity of 10$^{14}$ W cm$^{-2}$. Significant differences in ionization yield and ejected-electron momentum distribution are observed between the two values for $M_L$. 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 $M_L=0$, the dynamics with respect to time delay of an ionizing probe pulse modelled using RMT theory is found to be in good agreement with available experimental data.

  2. Ferromagnetism in Cr-doped passivated AlN nanowires

    KAUST Repository

    Kanoun, Mohammed

    2014-01-01

    We apply first principles calculations to predict the effect of Cr doping on the electronic and magnetic properties of passivated AlN nanowires. We compare the energetics of the possible dopant sites and demonstrate the favorable configuration ferromagnetic ordering. The charge density of the pristine passivated AlN nanowires is used to elucidate the bonding character. Spin density maps demonstrate an induced spin polarization for N atoms next to dopant atoms, though most of the magnetism is carried by the Cr atoms. Cr-doped AlN nanowires turn out to be interesting for spintronic devices. © 2014 the Partner Organisations.

  3. Carbon nanotubes with atomic impurities on boron nitride sheets under applied electric fields

    OpenAIRE

    Kang, Seoung-Hun; Kim, Gunn; Kwon, Young-Kyun

    2013-01-01

    We perform first-principles calculations to investigate the structural and electronic properties of metal-doped (10, 0) carbon nanotubes (CNTs) on a single hexagonal boron nitride (hBN) sheet in the presence of an external electric field. We consider K, Cl and Ni atoms as dopants to study the dependence of the electronic properties of the CNT on doping polarity and concentration. The electric field strength is varied from -0.2 V/\\AA to +0.2 V/\\AA to explore the effects of an external electric...

  4. Artificial atom and quantum terahertz response in carbon nanotube quantum dots

    International Nuclear Information System (INIS)

    Artificial atom behaviours have been observed in single-wall carbon nanotube (SWCNT) quantum dots (QDs). Two-electron shell structures and the Zeeman splitting of single-particle states were revealed in single-electron transport measurements in low temperatures. To demonstrate that the charging energy of the dot lies in a terahertz (THz) range, the THz photon-assisted tunnelling was tested, and was really observed as a satellite Coulomb peak. Some satellite peaks moved as a frequency was changed, but other peaks did not move. We give possible models to explain the existence of two different satellite peaks.

  5. Robust operation and performance of integrated carbon nanotubes atomic force microscopy probes

    International Nuclear Information System (INIS)

    We present a complete characterization of carbon nanotubes-atomic force microscopy (CNT-AFM) probes to evaluate the cantilever operation and advanced properties originating from the CNTs. The fabrication consists of silicon probes tip-functionalized with multiwalled CNTs by microwave plasma enhanced chemical vapor deposition. A dedicated methodology has been defined to evaluate the effect of CNT integration into the Si cantilevers. The presence of the CNTs provides enhanced capability for sensing and durability, as demonstrated using dynamic and static modes, e.g. imaging, indentation and force/current characterization.

  6. NANOMECHANICAL MAPPING OF CARBON BLACK REINFORCED NATURAL RUBBER BY ATOMIC FORCE MICROSCOPY

    Institute of Scientific and Technical Information of China (English)

    Toshio Nishi; Hideyuki Nukaga; So Fujinami; Ken Nakajima

    2007-01-01

    Atomic force microscopy (AFM) has the advantage of obtaining mechanical properties as well as topographic information at the same time. By analyzing force-distance curves measured over two-dimensional area using Hertzian contact mechanics, Young's modulus mapping was obtained with nanometer-scale resolution. Furthermore, the sample deformation by the force exerted was also estimated from the force-distance curve analyses. We could thus reconstruct a real topographic image by incorporating apparent topographic image with deformation image. We applied this method to carbon black reinforced natural rubber to obtain Young's modulus distribution image together with reconstructed real topographic image.Then we were able to recognize three regions; rubber matrix, carbon black (or bound rubber) and intermediate regions.Though the existence of these regions had been investigated by pulsed nuclear magnetic resonance, this paper would be the first to report on the quantitative evaluation of the interfacial region in real space.

  7. The Synthesized of Carbon Nano tubes from Palm Oil by Topas Atomizer Chemical Vapor Deposition Method

    International Nuclear Information System (INIS)

    This paper focused on preparation of Carbon Nano tubes (CNTs) based on palm oil as a natural resource precursor. The Topas Atomizer was utilized to vapor up the carbon gas into the reaction chamber of Chemical Vapor Deposition (CVD) to yield the CNTs in powder form at the inner wall of the Quartz tube. The purpose of this work was to investigate the effects of deposition temperature from 650 - 850 degree Celsius. The samples characteristics were analyzed by Raman spectroscopy. The results revealed that the increasing of the deposition temperature, the ID/IG ratio decreased from 650 - 850 degree Celsius. The results of Field Emission Scanning Electron Microscopy (FESEM) are also presented. (author)

  8. Atomic oxygen resistant behaviors of Mo/diamond-like carbon nanocomposite lubricating films

    International Nuclear Information System (INIS)

    Mo doped diamond-like carbon (Mo/DLC) films were deposited on Si substrates via unbalanced magnetron sputtering of molybdenum combined with plasma chemical vapor deposition of CH4/Ar. The microstructure of the films, characterized by transmission electron microscopy and selected area electron diffraction, was considered as a nanocomposite with nano-sized MoC particles uniformly embedded in the amorphous carbon matrix. The structure, morphology, surface composition and tribological properties of the Mo/DLC films before and after the atomic oxygen (AO) irradiation were investigated and a comparison made with the DLC films. The Mo/DLC films exhibited more excellent degradation resistant behaviors in AO environment than the DLC films, and the MoC nanoparticles were proved to play a critical role of preventing the incursion of AO and maintaining the intrinsic structure and excellent tribological properties of DLC films.

  9. Sc3CH@C80: selective (13)C enrichment of the central carbon atom.

    Science.gov (United States)

    Junghans, Katrin; Rosenkranz, Marco; Popov, Alexey A

    2016-05-01

    Sc3CH@C80 is synthesized and characterized by (1)H, (13)C, and (45)Sc NMR. A large negative chemical shift of the proton, -11.73 ppm in the Ih and -8.79 ppm in the D5h C80 cage isomers, is found. (13)C satellites in the (1)H NMR spectrum enabled indirect determination of the (13)C chemical shift for the central carbon at 173 ± 1 ppm. Intensity of the satellites allowed determination of the (13)C content for the central carbon atom. This unique possibility is applied to analyze the cluster/cage (13)C distribution in mechanistic studies employing either (13)CH4 or (13)C powder to enrich Sc3CH@C80 with (13)C. PMID:27109443

  10. Redistribution of carbon atoms in Pt substrate for high quality monolayer graphene synthesis

    International Nuclear Information System (INIS)

    The two-dimensional material graphene shows its extraordinary potential in many application fields. As the most effective method to synthesize large-area monolayer graphene, chemical vapor deposition has been well developed; however, it still faces the challenge of a high occurrence of multilayer graphene, which causes the small effective area of monolayer graphene. This phenomenon limits its applications in which only a big size of monolayer graphene is needed. In this paper, by introducing a redistribution stage after the decomposition of carbon source gas to redistribute the carbon atoms dissolved in Pt foils, the number of multilayer flakes on the monolayer graphene decreases. The mean area of monolayer graphene can be extended to about 16 000 μm2, which is eight times larger than that of the graphene grown without the redistribution stage. A Raman spectrograph is used to demonstrate the high quality of the monolayer graphene grown by the improved process. (semiconductor materials)

  11. Nanowire photonics

    OpenAIRE

    Peter J. Pauzauskie; Peidong Yang

    2006-01-01

    The development of integrated electronic circuitry ranks among the most disruptive and transformative technologies of the 20th century. Even though integrated circuits are ubiquitous in modern life, both fundamental and technical constraints will eventually test the limits of Moore's law. Nanowire photonic circuitry constructed from myriad one-dimensional building blocks offers numerous opportunities for the development of next-generation optical information processors and spectroscopy. Howev...

  12. Nanowire Optoelectronics

    Science.gov (United States)

    Wang, Zhihuan; Nabet, Bahram

    2015-12-01

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

  13. Drawing conclusions from graphene[Graphene: A sheet of crystalline carbon just one atom thick

    Energy Technology Data Exchange (ETDEWEB)

    Neto, A.C. [Boston University (United States)]. E-mail: neto@bu.edu; Guinea, F. [ICMM-CSIC (Spain); Peres, N.M. [Minho University (Portugal)

    2006-11-15

    In a time when cutting-edge scientific research is expensive and complex, it seems absurd that a breakthrough in physics could be achieved with simple adhesive tape. But in 2004, Andre Geim, Kostya Novoselov and co-workers at the University of Manchester in the UK did just that. By delicately cleaving a sample of graphite with sticky tape, they produced something that was long considered impossible: a sheet of crystalline carbon just one atom thick, known as graphene. The single-layered honeycomb structure of graphene makes it the 'mother' of all carbon-based systems: the graphite we find in our pencils is simply a stack of graphene layers; carbon nanotubes are made or rolled up sheets of graphene; and buckminsterfullerene molecules, or 'buckyballs' are nanometre-size spheres of wrapped-up graphene. These forms of carbon were isolated long before graphene and have been used in many applications, but their electric, magnetic and elastic properties all originate in the properties of graphene. In the November issue of Physics World, Antonio Castro Neto, Francisco Guinea and Nuno Miguel Peres explore the fascinating structure of graphene, which is so unique that it could allow scientists to observe strange relativistic effects at speeds much slower than the speed of light. (U.K.)

  14. Raman spectroscopy as a tool to investigate the structure and electronic properties of carbon-atom wires

    Directory of Open Access Journals (Sweden)

    Alberto Milani

    2015-02-01

    Full Text Available 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.

  15. Ultrafine Metal-Organic Right Square Prism Shaped Nanowires.

    Science.gov (United States)

    Otake, Ken-Ichi; Otsubo, Kazuya; Sugimoto, Kunihisa; Fujiwara, Akihiko; Kitagawa, Hiroshi

    2016-05-23

    We report the structural design and control of electronic states of a new series of ultrafine metal-organic right square prism-shaped nanowires. These nanowires have a very small inner diameter of about 2.0 Å, which is larger than hydrogen and similar to xenon atomic diameters. The electronic states of nanowires can be widely controlled by substitution of structural components. Moreover, the platinum homometallic nanowire shows a 100 times higher proton conductivity than a palladium/platinum heterometallic one depending on the electronic states. PMID:27080935

  16. Heterojunction nanowires having high activity and stability for the reduction of oxygen: Formation by self-assembly of iron phthalocyanine with single walled carbon nanotubes (FePc/SWNTs)

    KAUST Repository

    Zhu, Jia

    2014-04-01

    A self-assembly approach to preparing iron phthalocyanine/single-walled carbon nanotube (FePc/SWNT) heterojunction nanowires as a new oxygen reduction reaction (ORR) electrocatalyst has been developed by virtue of water-adjusted dispersing in 1-cyclohexyl-pyrrolidone (CHP) of the two components. The FePc/SWNT nanowires have a higher Fermi level compared to pure FePc (d-band center, DFT. =. -0.69. eV versus -0.87. eV, respectively). Consequently, an efficient channel for transferring electron to the FePc surface is readily created, facilitating the interaction between FePc and oxygen, so enhancing the ORR kinetics. This heterojunction-determined activity in ORR illustrates a new stratagem to preparing non-noble ORR electrocatalysts of significant importance in constructing real-world fuel cells. © 2013 Elsevier Inc.

  17. Effective surface anisotropy in polycrystalline ferromagnetic nanowires

    International Nuclear Information System (INIS)

    Highlights: • Here we make a mixing of two models. A macroscopic and a microscopic model. • The principal idea in this paper is to write the free magnetic energy for a soft magnetic cylindrical nanowire and make the comparison with our previous models. • The model is tested to determine the effective constant in Ni nanowires. - Abstract: Here we express the effective surface anisotropy for soft ferromagnetic nanowires as the function of the micro-structural behaviors. Many papers about these systems determine the reversal modes for the magnetization to explain magnetic properties of the nanowires. Our previous works related morphological structure with magnetic properties. The principal idea in this paper is to write the free magnetic energy for a soft magnetic cylindrical nanowire and make the comparison with our previous models. In this way we include the macroscopic effective anisotropy due to the disordered atoms and ignoring other microstructure terms related in our previous works. From this idea and our last model to these systems, we made an association that permit to express the effective anisotropy in function of the principal morphological characteristics of nanowires. The model is tested to determine the numerical value of the mentioned constant in Ni nanowires obtained by electrodeposition in porous anodic aluminum oxide membranes using the Transmission Electron Microscopy

  18. Competition of elastic and adhesive properties of carbon nanotubes anchored to atomic force microscopy tips

    International Nuclear Information System (INIS)

    In this paper we address the mechanical properties of carbon nanotubes anchored to atomic force microscopy (AFM) tips in a detailed analysis of experimental results and exhaustive description of a simple model. We show that volume elastic and surface adhesive forces both contribute to the dynamical AFM experimental signals. Their respective weights depend on the nanotube properties and on an experimental parameter: the oscillation amplitude. To quantify the elastic and adhesive contributions, a simple analytical model is used. It enables analytical expressions of the resonance frequency shift and dissipation that can be measured in the atomic force microscopy dynamical frequency modulation mode. It includes the nanotube adhesive contribution to the frequency shift. Experimental data for single-wall and multi-wall carbon nanotubes compare well to the model predictions for different oscillation amplitudes. Three parameters can be extracted: the distance necessary to unstick the nanotube from the surface and two spring constants corresponding to tube compression and to the elastic force required to overcome the adhesion force

  19. High Area Capacity Lithium-Sulfur Full-cell Battery with Prelitiathed Silicon Nanowire-Carbon Anodes for Long Cycling Stability

    Science.gov (United States)

    Krause, Andreas; Dörfler, Susanne; Piwko, Markus; Wisser, Florian M.; Jaumann, Tony; Ahrens, Eike; Giebeler, Lars; Althues, Holger; Schädlich, Stefan; Grothe, Julia; Jeffery, Andrea; Grube, Matthias; Brückner, Jan; Martin, Jan; Eckert, Jürgen; Kaskel, Stefan; Mikolajick, Thomas; Weber, Walter M.

    2016-01-01

    We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm2. The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D substrates. In contrast to metallic Li, the presented system exhibits superior characteristics as an anode in Li/S batteries such as safe operation, long cycle life and easy handling. These anodes are combined with high area density S/C composite cathodes into a Li/S full-cell with an ether- and lithium triflate-based electrolyte for high ionic conductivity. The result is a highly cyclable full-cell with an areal capacity of 2.3 mAh/cm2, a cyclability surpassing 450 cycles and capacity retention of 80% after 150 cycles (capacity loss <0.4% per cycle). A detailed physical and electrochemical investigation of the SiNW Li/S full-cell including in-operando synchrotron X-ray diffraction measurements reveals that the lower degradation is due to a lower self-reduction of polysulfides after continuous charging/discharging. PMID:27319783

  20. Three-dimensional carbon- and binder-free nickel nanowire arrays as a high-performance and low-cost anode for direct hydrogen peroxide fuel cell

    Science.gov (United States)

    Ye, Ke; Guo, Fen; Gao, Yinyi; Zhang, Dongming; Cheng, Kui; Zhang, Wenping; Wang, Guiling; Cao, Dianxue

    2015-12-01

    A novel three-dimensional carbon- and binder-free nickel nanowire arrays (Ni NAs) electrode is successfully fabricated by a facile galvanostatic electrodeposition method using polycarbonate membrane as the template. The Ni NAs electrode achieves a oxidation current density (divided by the electroactive surface areas of Ni) of 25.1 mA cm-2 in 4 mol L-1 KOH and 0.9 mol L-1 H2O2 at 0.2 V (vs. Ag/AgCl) accompanied with a desirable stability, which is significantly higher than the catalytic activity of H2O2 electro-oxidation achieved previously with precious metals as catalysts. The impressive electrocatalytic performance is largely attributed to the superior 3D open structure and high electronic conductivity, which ensures the high utilization of Ni surfaces and makes the electrode have higher electrochemical activity. The apparent activation energy of H2O2 electro-oxidation on the Ni NAs catalyst is 13.59 kJ mol-1. A direct peroxide-peroxide fuel cell using the Ni NAs as anode exhibits a peak power density of 48.7 mW cm-2 at 20 °C. The electrode displays a great promise as the anode of direct peroxide-peroxide fuel cell due to its low cost, high activity and stability.

  1. High Area Capacity Lithium-Sulfur Full-cell Battery with Prelitiathed Silicon Nanowire-Carbon Anodes for Long Cycling Stability.

    Science.gov (United States)

    Krause, Andreas; Dörfler, Susanne; Piwko, Markus; Wisser, Florian M; Jaumann, Tony; Ahrens, Eike; Giebeler, Lars; Althues, Holger; Schädlich, Stefan; Grothe, Julia; Jeffery, Andrea; Grube, Matthias; Brückner, Jan; Martin, Jan; Eckert, Jürgen; Kaskel, Stefan; Mikolajick, Thomas; Weber, Walter M

    2016-01-01

    We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm(2). The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D substrates. In contrast to metallic Li, the presented system exhibits superior characteristics as an anode in Li/S batteries such as safe operation, long cycle life and easy handling. These anodes are combined with high area density S/C composite cathodes into a Li/S full-cell with an ether- and lithium triflate-based electrolyte for high ionic conductivity. The result is a highly cyclable full-cell with an areal capacity of 2.3 mAh/cm(2), a cyclability surpassing 450 cycles and capacity retention of 80% after 150 cycles (capacity loss <0.4% per cycle). A detailed physical and electrochemical investigation of the SiNW Li/S full-cell including in-operando synchrotron X-ray diffraction measurements reveals that the lower degradation is due to a lower self-reduction of polysulfides after continuous charging/discharging. PMID:27319783

  2. Electrochemical synthesis of elongated noble metal nanoparticles, such as nanowires and nanorods, on high-surface area carbon supports

    Energy Technology Data Exchange (ETDEWEB)

    Adzic, Radoslav; Blyznakov, Stoyan; Vukmirovic, Miomir

    2015-08-04

    Elongated noble-metal nanoparticles and methods for their manufacture are disclosed. The method involves the formation of a plurality of elongated noble-metal nanoparticles by electrochemical deposition of the noble metal on a high surface area carbon support, such as carbon nanoparticles. Prior to electrochemical deposition, the carbon support may be functionalized by oxidation, thus making the manufacturing process simple and cost-effective. The generated elongated nanoparticles are covalently bound to the carbon support and can be used directly in electrocatalysis. The process provides elongated noble-metal nanoparticles with high catalytic activities and improved durability in combination with high catalyst utilization since the nanoparticles are deposited and covalently bound to the carbon support in their final position and will not change in forming an electrode assembly.

  3. How Copper Nanowires Grow and How To Control Their Properties.

    Science.gov (United States)

    Ye, Shengrong; Stewart, Ian E; Chen, Zuofeng; Li, Bo; Rathmell, Aaron R; Wiley, Benjamin J

    2016-03-15

    Scalable, solution-phase nanostructure synthesis has the promise to produce a wide variety of nanomaterials with novel properties at a cost that is low enough for these materials to be used to solve problems. For example, solution-synthesized metal nanowires are now being used to make low cost, flexible transparent electrodes in touch screens, organic light-emitting diodes (OLEDs), and solar cells. There has been a tremendous increase in the number of solution-phase syntheses that enable control over the assembly of atoms into nanowires in the last 15 years, but proposed mechanisms for nanowire formation are usually qualitative, and for many syntheses there is little consensus as to how nanowires form. It is often not clear what species is adding to a nanowire growing in solution or what mechanistic step limits its rate of growth. A deeper understanding of nanowire growth is important for efficiently directing the development of nanowire synthesis toward producing a wide variety of nanostructure morphologies for structure-property studies or producing precisely defined nanostructures for a specific application. This Account reviews our progress over the last five years toward understanding how copper nanowires form in solution, how to direct their growth into nanowires with dimensions ideally suited for use in transparent conducting films, and how to use copper nanowires as a template to grow core-shell nanowires. The key advance enabling a better understanding of copper nanowire growth is the first real-time visualization of nanowire growth in solution, enabling the acquisition of nanowire growth kinetics. By measuring the growth rate of individual nanowires as a function of concentration of the reactants and temperature, we show that a growing copper nanowire can be thought of as a microelectrode that is charged with electrons by hydrazine and grows through the diffusion-limited addition of Cu(OH)2(-). This deeper mechanistic understanding, coupled to an

  4. Microspheres for the Growth of Silicon Nanowires via Vapor-Liquid-Solid Mechanism

    Directory of Open Access Journals (Sweden)

    Arancha Gómez-Martínez

    2014-01-01

    Full Text Available Silicon nanowires have been synthesized by a simple process using a suitable support containing silica and carbon microspheres. Nanowires were grown by thermal chemical vapor deposition via a vapor-liquid-solid mechanism with only the substrate as silicon source. The curved surface of the microsized spheres allows arranging the gold catalyst as nanoparticles with appropriate dimensions to catalyze the growth of nanowires. The resulting material is composed of the microspheres with the silicon nanowires attached on their surface.

  5. Carbon nanotubes as solid-phase extraction sorbents prior to atomic spectrometric determination of metal species: A review

    International Nuclear Information System (INIS)

    Highlights: ► The use of CNTs as sorbent for metal species in solid phase extraction has been described. ► Physical and chemical strategies for functionalization of carbon nanotubes have been discussed. ► Published analytical methods concerning solid phase extraction and atomic spectrometric determination have been reviewed. - Abstract: 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.

  6. Carbon nanotubes as solid-phase extraction sorbents prior to atomic spectrometric determination of metal species: A review

    Energy Technology Data Exchange (ETDEWEB)

    Herrero Latorre, C., E-mail: carlos.herrero@usc.es [Universidad de Santiago de Compostela, Dpto. Quimica Analitica, Nutricion y Bromatologia, Facultad de Ciencias, Alfonso X el Sabio s/n, 27002 Lugo (Spain); Alvarez Mendez, J.; Barciela Garcia, J.; Garcia Martin, S.; Pena Crecente, R.M. [Universidad de Santiago de Compostela, Dpto. Quimica Analitica, Nutricion y Bromatologia, Facultad de Ciencias, Alfonso X el Sabio s/n, 27002 Lugo (Spain)

    2012-10-24

    Highlights: Black-Right-Pointing-Pointer The use of CNTs as sorbent for metal species in solid phase extraction has been described. Black-Right-Pointing-Pointer Physical and chemical strategies for functionalization of carbon nanotubes have been discussed. Black-Right-Pointing-Pointer Published analytical methods concerning solid phase extraction and atomic spectrometric determination have been reviewed. - Abstract: 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.

  7. Nanowire Optoelectronics

    Directory of Open Access Journals (Sweden)

    Wang Zhihuan

    2015-12-01

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

  8. Mineral sequestration of carbon dioxide in San Carlos olivine: An atomic level reaction study

    Science.gov (United States)

    Nunez, Ryan

    Since the late 19th century, atmospheric carbon dioxide (CO2) levels have been steadily on the rise. Approximately one third of all human emissions come from fossil fuel power plants. As countries become more dependent on electrical energy and bring on line new power plants, these atmospheric CO2 levels will continue to rise, generating strong environmental concern. Potential avenues to address this problem convert the CO2 from the gaseous phase to a liquid, supercritical fluid, or solid state and store it. Oceans, subsurface reservoirs such as depleted oil fields, and terrestrial carbon pools have all been suggested. The essential problem with all of these possible solutions is the issue of permanency. Mineral sequestration of CO2 is a candidate technology for reducing the amount of anthropogenic CO2 that is being released into the atmosphere. Olivine (e.g. forsterite, Mg2SiO4) is a widely available mineral that reacts with CO2 to form magnesite (MgCO3) and silica (SiO2). Magnesite is capable of immobilizing CO2 over geological time periods. Thus the issue of permanency has been addressed. The most promising mineral sequestration process developed to date is aqueous solution mineral carbonation. The solid/aqueous solution reaction interface provides insight to the mechanisms that govern the carbonation reactivity of olivine. Study of these mechanisms at the atomic level is critically important to facilitate engineering new processes that will enhance the reactivity of olivine with CO2 bearing media and to lower process costs. The study of the olivine carbonation reaction herein can be divided into three separate areas of research. The first area is a comprehensive study of olivine under conditions of electron irradiation. Analyzing radiation damage is critical to the verification and reliability of data collected from the samples using electron beam techniques. The next area of research is the analysis of the reaction layer composition and structure using High

  9. Atomic Structures of Graphene, Benzene and Methane with Bond Lengths as Sums of the Single, Double and Resonance Bond Radii of Carbon

    OpenAIRE

    Heyrovska, Raji

    2008-01-01

    Two dimensional layers of graphene are currently drawing a great attention in fundamental and applied nanoscience. Graphene consists of interconnected hexagons of carbon atoms as in graphite. This article presents for the first time the structures of graphene at the atomic level and shows how it differs from that of benzene, due to the difference in the double bond and resonance bond based radii of carbon. The carbon atom of an aliphatic compound such as methane has a longer covalent single b...

  10. DFT study of Fe-Ni core-shell nanoparticles: Stability, catalytic activity, and interaction with carbon atom for single-walled carbon nanotube growth

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Zhimin; Wang, Qiang, E-mail: wangqiang@njtech.edu.cn; Shan, Xiaoye; Zhu, Hongjun, E-mail: zhuhj@njtech.edu.cn [Department of Applied Chemistry, College of Science, Nanjing Tech University, Nanjing 211816 (China); Li, Wei-qi [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); Chen, Guang-hui [Department of Chemistry, Shantou University, Shantou, Guangdong 515063 (China)

    2015-02-21

    Metal catalysts play an important role in the nucleation and growth of single-walled carbon nanotubes (SWCNTs). It is essential for probing the nucleation and growth mechanism of SWCNTs to fundamentally understand the properties of the metal catalysts and their interaction with carbon species. In this study, we systematically studied the stability of 13- and 55-atom Fe and Fe-Ni core-shell particles as well as these particles interaction with the carbon atoms using the density functional theory calculations. Icosahedral 13- and 55-atom Fe-Ni core-shell bimetallic particles have higher stability than the corresponding monometallic Fe and Ni particles. Opposite charge transfer (or distribution) in these particles leads to the Fe surface-shell displays a positive charge, while the Ni surface-shell exhibits a negative charge. The opposite charge transfer would induce different chemical activities. Compared with the monometallic Fe and Ni particles, the core-shell bimetallic particles have weaker interaction with C atoms. More importantly, C atoms only prefer staying on the surface of the bimetallic particles. In contrast, C atoms prefer locating into the subsurface of the monometallic particles, which is more likely to form stable metal carbides. The difference of the mono- and bimetallic particles on this issue may result in different nucleation and growth mechanism of SWCNTs. Our findings provide useful insights for the design of bimetallic catalysts and a better understanding nucleation and growth mechanism of SWCNTs.

  11. DFT study of Fe-Ni core-shell nanoparticles: Stability, catalytic activity, and interaction with carbon atom for single-walled carbon nanotube growth

    International Nuclear Information System (INIS)

    Metal catalysts play an important role in the nucleation and growth of single-walled carbon nanotubes (SWCNTs). It is essential for probing the nucleation and growth mechanism of SWCNTs to fundamentally understand the properties of the metal catalysts and their interaction with carbon species. In this study, we systematically studied the stability of 13- and 55-atom Fe and Fe-Ni core-shell particles as well as these particles interaction with the carbon atoms using the density functional theory calculations. Icosahedral 13- and 55-atom Fe-Ni core-shell bimetallic particles have higher stability than the corresponding monometallic Fe and Ni particles. Opposite charge transfer (or distribution) in these particles leads to the Fe surface-shell displays a positive charge, while the Ni surface-shell exhibits a negative charge. The opposite charge transfer would induce different chemical activities. Compared with the monometallic Fe and Ni particles, the core-shell bimetallic particles have weaker interaction with C atoms. More importantly, C atoms only prefer staying on the surface of the bimetallic particles. In contrast, C atoms prefer locating into the subsurface of the monometallic particles, which is more likely to form stable metal carbides. The difference of the mono- and bimetallic particles on this issue may result in different nucleation and growth mechanism of SWCNTs. Our findings provide useful insights for the design of bimetallic catalysts and a better understanding nucleation and growth mechanism of SWCNTs

  12. Intensive irradiation of carbon nanotubes by Si ion beam

    Institute of Scientific and Technical Information of China (English)

    NI Zhichun; LI Qintao; YAN Long; GONG Jinlong; ZHU Dezhang; ZHU Zhiyuan

    2007-01-01

    Multi-walled carbon nanotubes were irradiated with 40 keV Si ion beam to a dose of 1×1017 cm-2. The multiple-way carbon nanowire junctions and the Si doping in carbon nanowires were realized. Moreover, the formation processes of carbon nanowire junctions and the corresponding mechanism were studied.

  13. Growth of Few-Layer Graphene on Sapphire Substrates by Directly Depositing Carbon Atoms

    Institute of Scientific and Technical Information of China (English)

    KANG Chao-Yang; TANG Jun; LIU Zhong-Liang; LI Li-Min; YAN Wen-Sheng; WEI Shi-Qiang; XU Peng-Shou

    2011-01-01

    Few-layer graphene (FLG) is successfully grown on sapphire substrates by directly depositing carbon atoms at the substrate temperature of 1300℃ in a molecular beam epitaxy chamber.The reflection high energy diffraction,Raman spectroscopy and near-edge x-ray absorption fine structure are used to characterize the sample,which confirm the formation of graphene layers.The mean domain size of FLG is around 29.2 nm and the layer number is about 2-3.The results demonstrate that the grown FLG displays a turbostratic stacking structure similar to that of the FLG produced by annealing C-terminated a-SiC surface.Graphene,a monolayer of sp2-bonded carbon atoms,is a quasi two-dimensional (2D) material.It has attracted great interest because of its distinctive band structure and physical properties.[1] Graphene can now be obtained by several different approaches including micromechanical[1] and chemical[2] exfoliation of graphite,epitaxial growth on hexagonal SiC substrates by Si sublimation in vacuum,[3] and CVD growth on metal substrates.[4] However,these preparation methods need special substrates,otherwise,in order to design microelectronic devices,the prepared graphene should be transferred to other appropriate substrates.Thus the growth of graphene on the suitable substrates is motivated.%Few-layer graphene (FLG) is successfully grown on sapphire substrates by directly depositing carbon atoms at the substrate temperature of 1300℃ in a molecular beam epitaxy chamber. The reflection high energy diffraction, Raman spectroscopy and near-edge x-ray absorption fine structure are used to characterize the sample, which confirm the formation of graphene layers. The mean domain size of FLG is around 29.2nm and the layer number is about 2-3. The results demonstrate that the grown FLG displays a turbostratic stacking structure similar to that of the FLG produced by annealing C-terminated α-SiC surface.

  14. Experimental Investigation Of Segregation Of Carbon Atoms Due To Sub-Zero Cryogenic Treatment In Cold Work Tool Steel By Mechanical Spectroscopy And Atom Probe Tomography

    Directory of Open Access Journals (Sweden)

    Min N.

    2015-06-01

    Full Text Available In this work, we present mechanical spectroscopy of cold work tool steel subjected to sub-zero cryogenic soaking treatment to reveal the carbon segregation and the subsequent carbides refinement. The maximum of Snoek-Köster (SK peak height was obtained in the sample subjected to soaking 1h at −130°C cryogenic treatment. The SK peak height is reduced with prolonging the soaking time. The results indicate that an increase in the height of SK peak is connected with an increase in dislocation density and the number of segregated carbon atoms in the vicinity of dislocations or twin planes after martensite transformation at −130°C which is confirmed by corresponding TEM and atom probe tomography measurement. Hence, it is suggested that the isothermal martensite, formed during the cryogenic soaking treatment decreases (APT the height of SK peak.

  15. Selective determination of antimony(III) and antimony(V) with ammonium pyrrolidinedithiocarbamate, sodium diethyldithiocarbamate and dithizone by atomic-absorption spectrometry with a carbon-tube atomizer.

    Science.gov (United States)

    Kamada, T; Yamamoto, Y

    1977-05-01

    The extraction behaviour of antimony(III) and antimony(V) with ammonium pyrrolidinedithiocarbamate, sodium diethyldithiocarbamate and dithizone in organic solvents has been investigated by means of frameless atomic-absorption spectrophotometry with a carbon-tube atomizer. The selective extraction of antimony(III) and differential determination of antimony(III) and antimony(V) have been developed. With ammonium pyrrolidinedithiocarbamate and methyl isobutyl ketone, when the aqueous phase/solvent volume ratio is 50 ml/10 ml and the injection volume in the carbon tube is 20 mul, the sensitivity for antimony is 0.2 ng/ml for 1% absorption. The relative standard deviations are ca. 2%. Interferences by many metal ions can be prevented by masking with EDTA. The proposed methods have been applied satisfactorily to determination of antimony(III) and antimony(V) in various types of water. PMID:18962096

  16. Optical trapping of cold neutral atoms using a two-color evanescent light field around a carbon nanotube

    International Nuclear Information System (INIS)

    We suggest a new schema of trapping cold atoms using a two-color evanescent light field around a carbon nanotube. The two light fields circularly polarized sending through a carbon nanotube generates an evanescent wave around this nanotube. By evanescent effect, the wave decays away from the nanotube producing a set of trapping minima of the total potential in the transverse plane as a ring around the nanotube. This schema allows capture of atoms to a cylindrical shell around the nanotube. We consider some possible boundary conditions leading to the non-trivial bound state solution. Our result will be compared to some recent trapping models and our previous trapping models.

  17. Agglomeration defects on irradiated carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Steini Moura, Cassio [Faculty of Physics, Pontificia Universidade Catolica do Rio Grande do Sul, 90619-900, Porto Alegre, RS (Brazil); Balzaretti, Naira Maria; Amaral, Livio [Institute of Physics, Universidade Federal do Rio Grande do Sul, C.P.: 15051, 91501-070, Porto Alegre, RS (Brazil); Gribel Lacerda, Rodrigo; Pimenta, Marcos A. [Universidade Federal de Minas Gerais, C.P.: 702, 31270-901, Belo Horizonte, MG (Brazil)

    2012-03-15

    Aligned carbon nanotubes (CNT) were irradiated in the longitudinal and perpendicular directions, with low energy carbon and helium ions in order to observe the formation of defects in the atomic structure. Analysis through Raman spectroscopy and scanning electron microscopy indicated bundle rupture and ion track formation on nanotube bundles. Aligned CNT presented a kind of defect comprising ravine formation and tube agglomeration on top of the substrate. The latter structure is possibly caused by static charge accumulation induced by the incoming ions. Fluence plays a role on the short range order. Higher fluence irradiation transforms CNT into amorphous carbon nanowires.

  18. Agglomeration defects on irradiated carbon nanotubes

    International Nuclear Information System (INIS)

    Aligned carbon nanotubes (CNT) were irradiated in the longitudinal and perpendicular directions, with low energy carbon and helium ions in order to observe the formation of defects in the atomic structure. Analysis through Raman spectroscopy and scanning electron microscopy indicated bundle rupture and ion track formation on nanotube bundles. Aligned CNT presented a kind of defect comprising ravine formation and tube agglomeration on top of the substrate. The latter structure is possibly caused by static charge accumulation induced by the incoming ions. Fluence plays a role on the short range order. Higher fluence irradiation transforms CNT into amorphous carbon nanowires.

  19. Numerical investigation on the influence of atomic defects on the tensile and torsional behavior of hetero-junction carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Ghavamian, Ali, E-mail: alighavamian@yahoo.com [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603, Kuala Lumpur (Malaysia); Andriyana, Andri, E-mail: andri.andriyana@um.edu.my [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603, Kuala Lumpur (Malaysia); Chin, Ang Bee, E-mail: amelynang@um.edu.my [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603, Kuala Lumpur (Malaysia); Öchsner, Andreas, E-mail: andreas.oechsner@gmail.com [Griffith School of Engineering, Griffith University, Gold Coast Campus, Southport, 4222 (Australia)

    2015-08-15

    The finite element method was employed for the numerical simulation of hetero-junction carbon nanotubes with all possible connection types and their corresponding fundamental homogeneous tubes. Then, atomically defective hetero-junction carbon nanotubes were modeled by introducing silicon impurities and vacant sites into their structures. Finally, the elastic and shear moduli of all the models were evaluated under tensile and torsional loads, based on the assumption of linear-elastic deformation of these nanomaterials. The results showed that armchair and zigzag carbon nanotubes have the highest Young's and shear moduli respectively, among homogeneous carbon nanotubes. The mechanical tests on the hetero-junction carbon nanotubes revealed that these nanotube types have lower moduli when compared to their fundamental tubes. It was clearly observed that armchair–armchair and zigzag–zigzag hetero-junction carbon nanotubes have the highest Young's modulus among the hetero-junction carbon nanotubes while the shear modulus peaks were seen in zigzag-zigzag models. On the other hand, the lowest values for the Young's and shear moduli of hetero-junction carbon nanotubes were obtained for the models with armchair-zigzag kinks. It was also discovered that the atomic defects in the structure of hetero-junction carbon nanotubes lead to a decrease in their Young's and shear moduli which seems to follow a linear trend and could be expressed by a mathematical relation in terms of the amount of the atomic defect in their structures which could be used for the prediction of the tensile and torsional strength of the atomically defective hetero-junction carbon nanotubes for their proper selection and applications in nanoindustry. - Graphical abstract: Display Omitted - Highlights: • Hetero-junction and homogeneous carbon nanotubes are numerically simulated. • Two atomic defects i.e. Si-doping and carbon vacancy are introduced to the models. • Influence of

  20. 4D electron microscopy visualization of anisotropic atomic motions in carbon nanotubes.

    Science.gov (United States)

    Park, Sang Tae; Flannigan, David J; Zewail, Ahmed H

    2012-06-01

    We report the anisotropic atomic expansion dynamics of multi-walled carbon nanotubes, using 4D electron microscopy. From time-resolved diffraction on the picosecond to millisecond scale, following ultrafast heating at the rate of 10(13) K/s, it is shown that nanotubes expand only in the radial (intertubule) direction, whereas no significant change is observed in the intratubular axial or equatorial dimensions. The non-equilibrium heating occurs on an ultrafast time scale, indicating that the anisotropy is the result of an efficient electron-lattice coupling and is maintained up to equilibration. The recovery time, which measures the heat dissipation rate for equilibration, was found to be on the order of ∼100 μs. This recovery is reproduced theoretically by considering the composite specimen-substrate heat exchange. PMID:22591381

  1. Single ionization of helium atoms by energetic fully stripped carbon ions

    Institute of Scientific and Technical Information of China (English)

    Ebrahim Ghanbari-Adivi; Sadjad Eskandari

    2015-01-01

    A four-body distorted wave approximation is presented for theoretical investigations of the single ionization of ground-state helium atoms by fully stripped carbon ions at impact energies of 2 MeV/amu and 100 MeV/amu. The nine-dimensional integrals for the partial quantum-mechanical transition amplitudes of the specified reaction are reduced to some analytical expressions or one-dimensional integrals over real variables. Fully differential cross sections (FDCSs) are calculated and compared with their experimental values as well as the results obtained from other theories. Despite the simplicity and quickness of the proposed quadrature, the comparison shows that the obtained results are in reasonable agreement with the experiment and are compatible with those of other complicated theories.

  2. Determination of molybdenum in silicates through atomic absorption spectrometry using pre-concentration by active carbon

    International Nuclear Information System (INIS)

    An analytical procedure for molybdenum determination in geological materials through Atomic Absorption Spectrometry, after pre-concentration of the Mo-APDC complex in activated carbon, has been developed, which is needed in order to reduce the dilution effect in the sample decomposition. During the development of this method the influence of pH, the amount of APDC for complexation of Mo and the interference of Fe, Ca, Mn, Al, K, Na, Mg and Ti were tested. It was shown that none of these causes any significant effect on the Mo determination proposed. The results of the analysis at the international geochemical reference samples JB-1 (basalt) and GH (granite) were very accurate and showed that the detection limit in rocks (1,00g) is 0,6 ppm, when using sample dilution of 1 ml and microinjection techniques. (author)

  3. The ground state of the carbon atom in strong magnetic fields

    CERN Document Server

    Ivanov, M V

    1999-01-01

    The ground and a few excited states of the carbon atom in external uniform magnetic fields are calculated by means of our 2D mesh Hartree-Fock method for field strengths ranging from zero up to 2.35 10^9 T. With increasing field strength the ground state undergoes six transitions involving seven different electronic configurations which belong to three groups with different spin projections S_z=-1,-2,-3. For weak fields the ground state configuration arises from the field-free 1s^2 2s^2 2p_0 2p_{-1}, S_z=-1 configuration. With increasing field strength the ground state involves the four S_z=-2 configurations 1s^22s2p_0 2p_{-1}2p_{+1}, 1s^22s2p_0 2p_{-1}3d_{-2}, 1s^22p_0 2p_{-1}3d_{-2}4f_{-3} and 1s^22p_{-1}3d_{-2}4f_{-3}5g_{-4}, followed by the two fully spin polarized S_z=-3 configurations 1s2p_02p_{-1}3d_{-2}4f_{-3}5g_{-4} and 1s2p_{-1}3d_{-2}4f_{-3}5g_{-4}6h_{-5}. The last configuration forms the ground state of the carbon atom in the high field regime \\gamma>18.664. The above series of ground state config...

  4. Growth and characterization of semiconductor nanowires

    Science.gov (United States)

    Philipose, Usha

    This thesis describes a catalytic growth approach to synthesize semiconductor nanowires with good control over their physical dimensions, chemical composition, and optical/electronic properties. Using the Vapour-Liquid-Solid growth mechanism, gold nanoclusters serve as the catalytic sites directing the growth of crystalline Zinc Selenide (ZnSe), Zinc Oxide (ZnO) and Zinc Sulphide (ZnS) nanowires with length of several microns and diameters varying from 15 nm to 100 nm. The morphology and properties of the nanowires were found to be strongly dependent on growth conditions. Optical characterization by photoluminescence spectroscopy show that the spectra is dominated by near band edge emission for low defect density nanowires in contrast to the high level of defect related emission from high defect density nanowires. The growth parameters were optimized leading to the synthesis of nanowires with minimum defect concentration. Electrical transport studies on an array of ZnSe nanowires confirm that there exists a non-uniform carrier distribution along the nanowires leading to 'super-linear' current-voltage behaviour with carrier mobilities comparable to that of bulk material. Photoconductivity measurements on ZnSe nanoribbons show that they are of good quality, enabling realization of a nanoscale photodetector with a peak efficiency of 43%. Spectral response of photoconductivity had a threshold character with edge corresponding to the ZnSe bandgap, which makes it an ideal candidate for blue and ultraviolet light detection. The effect of doping of these nanowires with transition elements such as manganese (Mn) has been studied. In this effort, the first successful attempt at synthesizing room temperature ferromagnetic nanowires has been realized. Above room temperature ferromagnetism has been observed for the first time in dilute Mn-doped crystalline ZnO nanowires. From the observed saturation magnetization, the magnetic moment per Mn atom is estimated to be in the range

  5. Simulation study on radius dependence in rare-gas atoms injection into single-wall carbon nanotubes

    International Nuclear Information System (INIS)

    With molecular dynamics (MD) simulation, a model was established to investigate the radius dependence of rare-gas atoms (He, Ne, Ar) injection into the sidewall of the single-wall carbon nanotubes (SWNTs). The probabilities of the formation of endohedral X at SWNT complexes as a function of incident energies were carefully observed for the SWNTs with different radii. We have compared the maximal probabilities of different rare-gas atoms and different radii of SWNTs. It seems more difficult to form endohedral complexes for larger SWNTs, especially when the incident atom is bigger

  6. Topological Insulator Nanowires and Nanoribbons

    KAUST Repository

    Kong, Desheng

    2010-01-13

    Recent theoretical calculations and photoemission spectroscopy measurements on the bulk Bi2Se3 material show that it is a three-dimensional topological insulator possessing conductive surface states with nondegenerate spins, attractive for dissipationless electronics and spintronics applications. Nanoscale topological insulator materials have a large surface-to-volume ratio that can manifest the conductive surface states and are promising candidates for devices. Here we report the synthesis and characterization of high quality single crystalline Bi2Se5 nanomaterials with a variety of morphologies. The synthesis of Bi 2Se5 nanowires and nanoribbons employs Au-catalyzed vapor-liquid-solid (VLS) mechanism. Nanowires, which exhibit rough surfaces, are formed by stacking nanoplatelets along the axial direction of the wires. Nanoribbons are grown along [1120] direction with a rectangular cross-section and have diverse morphologies, including quasi-one-dimensional, sheetlike, zigzag and sawtooth shapes. Scanning tunneling microscopy (STM) studies on nanoribbons show atomically smooth surfaces with ∼ 1 nm step edges, indicating single Se-Bi-Se-Bi-Se quintuple layers. STM measurements reveal a honeycomb atomic lattice, suggesting that the STM tip couples not only to the top Se atomic layer, but also to the Bi atomic layer underneath, which opens up the possibility to investigate the contribution of different atomic orbitais to the topological surface states. Transport measurements of a single nanoribbon device (four terminal resistance and Hall resistance) show great promise for nanoribbons as candidates to study topological surface states. © 2010 American Chemical Society.

  7. Discovery of a Shell of Neutral Atomic Hydrogen Surrounding the Carbon Star IRC+10216

    CERN Document Server

    Matthews, L D; Bertre, T Le

    2015-01-01

    We have used the Robert C. Byrd Green Bank Telescope to perform the most sensitive search to date for neutral atomic hydrogen (HI) in the circumstellar envelope (CSE) of the carbon star IRC+10216. Our observations have uncovered a low surface brightness HI shell of diameter ~1300" (~0.8 pc), centered on IRC+10216. The HI shell has an angular extent comparable to the far ultraviolet-emitting astrosphere of IRC+10216 previously detected with the GALEX satellite, and its kinematics are consistent with circumstellar matter that has been decelerated by the local interstellar medium. The shell appears to completely surround the star, but the highest HI column densities are measured along the leading edge of the shell, near the location of a previously identified bow shock. We estimate a total mass of atomic hydrogen associated with IRC+10216 CSE of M_HI~3x10e-3 M_sun. This is only a small fraction of the expected total mass of the CSE (<1%) and is consistent with the bulk of the stellar wind originating in molec...

  8. Vertical nanowire architectures

    DEFF Research Database (Denmark)

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

    2010-01-01

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

  9. Magnetic and superconducting nanowires

    DEFF Research Database (Denmark)

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

    2005-01-01

    magnetic and superconducting nanowires. Using different approaches entailing measurements on both single wires and arrays, numerous interesting physical properties have been identified in relation to the nanoscopic dimensions of these materials. Finally, various novel applications of the nanowires are also...

  10. Fragmentation of neutral carbon clusters formed by high velocity atomic collision; Fragmentation d'agregats de carbone neutres formes par collision atomique a haute vitesse

    Energy Technology Data Exchange (ETDEWEB)

    Martinet, G

    2004-05-01

    The aim of this work is to understand the fragmentation of small neutral carbon clusters formed by high velocity atomic collision on atomic gas. In this experiment, the main way of deexcitation of neutral clusters formed by electron capture with ionic species is the fragmentation. To measure the channels of fragmentation, a new detection tool based on shape analysis of current pulse delivered by semiconductor detectors has been developed. For the first time, all branching ratios of neutral carbon clusters are measured in an unambiguous way for clusters size up to 10 atoms. The measurements have been compared to a statistical model in microcanonical ensemble (Microcanonical Metropolis Monte Carlo). In this model, various structural properties of carbon clusters are required. These data have been calculated with Density Functional Theory (DFT-B3LYP) to find the geometries of the clusters and then with Coupled Clusters (CCSD(T)) formalism to obtain dissociation energies and other quantities needed to compute fragmentation calculations. The experimental branching ratios have been compared to the fragmentation model which has allowed to find an energy distribution deposited in the collision. Finally, specific cluster effect has been found namely a large population of excited states. This behaviour is completely different of the atomic carbon case for which the electron capture in the ground states predominates. (author)

  11. Vertically-aligned sandwich nanowires enhance the photoelectrochemical reduction of hydrogen peroxide: hierarchical formation on carbon nanotubes of cadmium sulfide quantum dots and Prussian blue nanocoatings.

    Science.gov (United States)

    Gong, Kuanping

    2015-07-01

    We describe a vertically-aligned array of sandwiched nanowires comprising Prussian blue (PB) nanocoating-carbon nanotube (CNT) core-shell structures with CdS particles positioning at the core/shell interface, viz. PB/CdS/CNT. The PB/CdS/CNT electrode thus constructed are noticeable in synchronically harvesting photon-, ionic-, and chemical-energies, respectively, from visible light radiation, K(+) uptaking and releasing, and the reduction of H2O2. In 0.2 M K2SO4 aqueous solution, the photoelectrocatalytic reduction of 1.5 mM H2O2 at PB/CdS/CNT delivered the current density as high as 1.91 mA/cm(2) at reduced overpotential, that is, three times that at the Pt/C. This superb performance is causally linked to the judicious choice of materials and their assembly into defining sandwich nanostructures wherein the three components closely cooperate with each other in the photoelectrocatalytic reduction of H2O2, including photo-induced charge separation in CdS, spontaneous electron injection into PB due to its relatively low Fermi level, and the electrocatalytic reduction of H2O2 by PB via an electrochemical-chemical-electrochemical reaction mechanism. The structural alignment of PB/CdS/CNT ensures the simplest pathway for the mass diffusion and electron shuttle, and a high surface area accessible to the chemical and electrochemical reactions, so as to minimize the concentration- and electrochemical-polarization and thus ensure the fast overall kinetics of the electrode reaction. PMID:25458868

  12. Studies of single walled carbon nanotubes for biomedical, mechanical and electrical applications using atomic force microscopy

    Science.gov (United States)

    Lahiji, Roya Roientan

    The promise of carbon nanotubes to provide high-strength composites implies that carbon nanotubes might find widespread use throughout the world, implying that humans everywhere will be exposed to carbon nanotube-containing materials. In order to study what effects if any carbon nanotubes might have on the function of living cells, we have studied the association of single stranded DNA (ssDNA) with single wall carbon nanotubes (SWCNTs) as a first step toward understanding the interaction of SWCNTs with living matter. Studies have been performed on both as-received and chemically oxidized SWCNTs to better understand the preferential association of ssDNA with SWCNTs. Samples of T30 ssDNA:SWCNT were examined under ambient conditions using non-contact Atomic Force Microscopy (AFM)) techniques. AFM images of well-dispersed, as-received SWCNTs revealed isolated features on the SWCNT that are 1.4 to 2.8 nm higher than the bare SWCNT itself. X-ray Photoemission Spectroscopy (XPS) confirmed these features to be T30 ssDNA in nature. Chemically oxidizing SWCNTs before dispersion by sonication is found to be an effective way to increase the number of T30 ssDNA features. A series of experiments showed that free radical scavengers such as ascorbic acid and trolox can effectively prevent the conjugation of ssDNA to SWCNTs, suggesting a significant role of free radicals in this association. Also hybridization of the complimentary ssDNA sequences showed the covalent nature of this association. These results are important to understanding the precise mechanism of ssDNA:SWCNT association and provide valuable information for future use in electronics, biosensors and as a possible drug carrier into individual cells. If SWCNTs are used in biosensor or circuit design applications then it is important to note how much energy can be stored in a SWCNT based on its shape and configuration before a permanent damage is introduced to it. Therefore a study has been done on bending SWCNTs into

  13. Surface modification of nitrogen-doped carbon nanotubes by ozone via atomic layer deposition

    International Nuclear Information System (INIS)

    The use of ozone as an oxidizing agent for atomic layer deposition (ALD) processes is rapidly growing due to its strong oxidizing capabilities. However, the effect of ozone on nanostructured substrates such as nitrogen-doped multiwalled carbon nanotubes (NCNTs) and pristine multiwalled carbon nanotubes (PCNTs) are not very well understood and may provide an avenue toward functionalizing the carbon nanotube surface prior to deposition. The effects of ALD ozone treatment on NCNTs and PCNTs using 10 wt. % ozone at temperatures of 150, 250, and 300 °C are studied. The effect of ozone pulse time and ALD cycle number on NCNTs and PCNTs was also investigated. Morphological changes to the substrate were observed by scanning electron microscopy and high resolution transmission electron microscopy. Brunauer-Emmett-Teller measurements were also conducted to determine surface area, pore size, and pore size distribution following ozone treatment. The graphitic nature of both NCNTs and PCNTs was determined using Raman analysis while x-ray photoelectron spectroscopy (XPS) was employed to probe the chemical nature of NCNTs. It was found that O3 attack occurs preferentially to the outermost geometric surface of NCNTs. Our research also revealed that the deleterious effects of ozone are found only on NCNTs while little or no damage occurs on PCNTs. Furthermore, XPS analysis indicated that ALD ozone treatment on NCNTs, at elevated temperatures, results in loss of nitrogen content. Our studies demonstrate that ALD ozone treatment is an effective avenue toward creating low nitrogen content, defect rich substrates for use in electrochemical applications and ALD of various metal/metal oxides

  14. X-ray diffraction study of atomic structure features of amorphous carbon containing materials of nature and synthetic origin

    International Nuclear Information System (INIS)

    The atomic structure of amorphous carbon-containing materials such as carbon glass, spectroscopically pure carbon, schungite and anthracite is investigated using X ray diffraction analysis and computerized simulation. In computerized simulation of model gratings packing into packets an interlayer distance and a number of layer in a packet varied and a gratings turn is predetermined randomly. The quantity of gratings in a packet is shown to vary between four for anthracite and six for spectroscopically pure coal. The interlayer distance for all amorphous carbonaceous materials is above 3.35 A which is typical for graphite

  15. Direct Observation of Transient Surface Species during Ge Nanowire Growth and Their Influence on Growth Stability.

    Science.gov (United States)

    Sivaram, Saujan V; Shin, Naechul; Chou, Li-Wei; Filler, Michael A

    2015-08-12

    Surface adsorbates are well-established choreographers of material synthesis, but the presence and impact of these short-lived species on semiconductor nanowire growth are largely unknown. Here, we use infrared spectroscopy to directly observe surface adsorbates, hydrogen atoms and methyl groups, chemisorbed to the nanowire sidewall and show they are essential for the stable growth of Ge nanowires via the vapor-liquid-solid mechanism. We quantitatively determine the surface coverage of hydrogen atoms during nanowire growth by comparing ν(Ge-H) absorption bands from operando measurements (i.e., during growth) to those after saturating the nanowire sidewall with hydrogen atoms. This method provides sub-monolayer chemical information at relevant reaction conditions while accounting for the heterogeneity of sidewall surface sites and their evolution during elongation. Our findings demonstrate that changes to surface bonding are critical to understand Ge nanowire synthesis and provide new guidelines for rationally selecting catalysts, forming heterostructures, and controlling dopant profiles. PMID:26147949

  16. ATOMIC-LEVEL IMAGING OF CO2 DISPOSAL AS A CARBONATE MINERAL: OPTIMIZING REACTION PROCESS DESIGN; ANNUAL

    International Nuclear Information System (INIS)

    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

  17. The Atomic-scale Finite Element Method for Analyzing Mechanical Behavior of Carbon Nanotube and Quartz

    OpenAIRE

    Kim, Kyusang

    2006-01-01

    The mechanical behavior of discrete atoms has been studied with molecular dynamics whose computational time is proportional to the square of the number of atoms, O(N2). Recently, a faster algorithm, Atomic-scale Finite Element Method (AFEM) with computational time proportional to the number of atoms, O(N), had been developed. The main idea of AFEM, compared with conventional finite element method is to replace nodes with atoms and elements with electric forces between atoms. When interpreting...

  18. Selective visualization of point defects in carbon nanotubes at the atomic scale by an electron-donating molecular tip.

    Science.gov (United States)

    Nishino, Tomoaki; Kanata, Satoshi; Umezawa, Yoshio

    2011-07-14

    Electron-donating molecular tips were used for the observation of single-walled carbon nanotubes (SWNTs). Defects in SWNTs were selectively visualized at the atomic scale on the basis of charge-transfer interaction with the molecular tip. PMID:21629907

  19. Ab initio vibrations in nonequilibrium nanowires

    DEFF Research Database (Denmark)

    Jauho, Antti-Pekka; Engelund, Mads; Markussen, T;

    2010-01-01

    We review recent results on electronic and thermal transport in two different quasi one-dimensional systems: Silicon nanowires (SiNW) and atomic gold chains. For SiNW's we compute the ballistic electronic and thermal transport properties on equal footing, allowing us to make quantitative...

  20. TOPICAL REVIEW: DNA nanowire fabrication

    Science.gov (United States)

    Gu, Qun; Cheng, Chuanding; Gonela, Ravikanth; Suryanarayanan, Shivashankar; Anabathula, Sathish; Dai, Kun; Haynie, Donald T.

    2006-01-01

    Deoxyribonucleic acid (DNA) has been a key building block in nanotechnology since the earliest work on what is now called DNA-templated self-assembly (Alivisatos et al 1996 Nature 382 609; Mirkin et al 1996 Nature 382 607; Braun et al 1998 Nature 391 775). A range of different nanoparticles and nanoclusters have been assembled on single DNA molecules for a variety of purposes (Braun et al 1998 Nature 391 775; Richter et al 2001 Appl. Phys. Lett. 78 536; Park et al 2002 Science 295 1503; Mirkin 2000 Inorg. Chem. 39 2258; Keren et al 2003 Science 302 1380). Electrically conductive silver (Braun et al 1998 Nature 391 775) and palladium (Richter et al 2001 Appl. Phys. Lett. 78 536) nanowires, for example, have been fabricated by DNA templating for the development of interconnection of nanoelectric elements, and field effect transistors have been built by assembly of a single carbon nanotube and DNA-templated nanowires (Keren et al 2003 Science 302 1380). DNA is well suited for nanowire assembly because of its size, well organized structure, and exquisite molecular-recognition-ability-specific base pairing. This property has been used to detect nucleic acids (Park et al 2002 Science 295 1503) and anthrax (Mirkin 2000 Inorg. Chem. 39 2258) with high sensitivity and specificity. Molecular recognition can also be used to localize nanowires in electronics. Various methods, for example molecular combing, electrophoretic stretching, and hydrodynamic stretching, have been developed to orient DNA molecules on a solid support. This review focuses on methods used to manipulate and metallize DNA in nanowire fabrication. A novel approach based on a single-stranded DNA template and molecular recognition is also discussed.

  1. Activation of extended red emission photoluminescence in carbon solids by exposure to atomic hydrogen and UV radiation

    Science.gov (United States)

    Furton, Douglas G.; Witt, Adolf N.

    1993-01-01

    We report on new laboratory results which relate directly to the observation of strongly enhanced extended red emission (ERE) by interstellar dust in H2 photodissociation zones. The ERE has been attributed to photoluminescence by hydrogenated amorphous carbon (HAC). We are demonstrating that exposure to thermally dissociated atomic hydrogen will restore the photoluminescence efficiency of previously annealed HAC. Also, pure amorphous carbon (AC), not previously photoluminescent, can be induced to photoluminesce by exposure to atomic hydrogen. This conversion of AC into HAC is greatly enhanced by the presence of UV irradiation. The presence of dense, warm atomic hydrogen and a strong UV radiation field are characteristic environmental properties of H2 dissociation zones. Our results lend strong support to the HAC photoluminescence explanation for ERE.

  2. Atomic Structures of Graphene, Benzene and Methane with Bond Lengths as Sums of the Single, Double and Resonance Bond Radii of Carbon

    CERN Document Server

    Heyrovska, Raji

    2008-01-01

    Two dimensional layers of graphene are currently drawing a great attention in fundamental and applied nanoscience. Graphene consists of interconnected hexagons of carbon atoms as in graphite. This article presents for the first time the structures of graphene at the atomic level and shows how it differs from that of benzene, due to the difference in the double bond and resonance bond based radii of carbon. The carbon atom of an aliphatic compound such as methane has a longer covalent single bond radius as in diamond. All the atomic structures presented here have been drawn to scale.

  3. Analysis of mechanism of carbon removal from GaAs(1 0 0) surface by atomic hydrogen

    International Nuclear Information System (INIS)

    Etching of carbon contaminations from the GaAs(1 0 0) surface by irradiating with atomic hydrogen, which is one of the key reactions to promote high-quality thin films growth by molecular beam epitaxy (MBE), has been investigated by mass spectrometry (MS), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). It is shown that during the cleaning process at room temperature a total reduction of the Auger carbon signal, accompanied by desorption of methane as major reaction product, can be observed. The reaction pathways as well as the processes responsible for the observed carbon removal are discussed in detail to give a support for etching and growth quality enhancement not only in thin films epitaxy but in all atomic hydrogen promoted gas-phase III-V semiconductor processes

  4. The atomic scale structure of CXV carbon: wide-angle x-ray scattering and modeling studies

    Science.gov (United States)

    Hawelek, L.; Brodka, A.; Dore, J. C.; Honkimaki, V.; Burian, A.

    2013-11-01

    The disordered structure of commercially available CXV activated carbon produced from finely powdered wood-based carbon has been studied using the wide-angle x-ray scattering technique, molecular dynamics and density functional theory simulations. The x-ray scattering data has been converted to the real space representation in the form of the pair correlation function via the Fourier transform. Geometry optimizations using classical molecular dynamics based on the reactive empirical bond order potential and density functional theory at the B3LYP/6-31g* level have been performed to generate nanoscale models of CXV carbon consistent with the experimental data. The final model of the structure comprises four chain-like and buckled graphitic layers containing a small percentage of four-fold coordinated atoms (sp3 defects) in each layer. The presence of non-hexagonal rings in the atomic arrangement has been also considered.

  5. Initial evaluation and comparison of plasma damage to atomic layer carbon materials using conventional and low Te plasma sources

    International Nuclear Information System (INIS)

    The ability to achieve atomic layer precision is the utmost goal in the implementation of atomic layer etch technology. Carbon-based materials such as carbon nanotubes (CNTs) and graphene are single atomic layers of carbon with unique properties and, as such, represent the ultimate candidates to study the ability to process with atomic layer precision and assess impact of plasma damage to atomic layer materials. In this work, the authors use these materials to evaluate the atomic layer processing capabilities of electron beam generated plasmas. First, the authors evaluate damage to semiconducting CNTs when exposed to beam-generated plasmas and compare these results against the results using typical plasma used in semiconductor processing. The authors find that the beam generated plasma resulted in significantly lower current degradation in comparison to typical plasmas. Next, the authors evaluated the use of electron beam generated plasmas to process graphene-based devices by functionalizing graphene with fluorine, nitrogen, or oxygen to facilitate atomic layer deposition (ALD). The authors found that all adsorbed species resulted in successful ALD with varying impact on the transconductance of the graphene. Furthermore, the authors compare the ability of both beam generated plasma as well as a conventional low ion energy inductively coupled plasma (ICP) to remove silicon nitride (SiN) deposited on top of the graphene films. Our results indicate that, while both systems can remove SiN, an increase in the D/G ratio from 0.08 for unprocessed graphene to 0.22 to 0.26 for the beam generated plasma, while the ICP yielded values from 0.52 to 1.78. Generally, while some plasma-induced damage was seen for both plasma sources, a much wider process window as well as far less damage to CNTs and graphene was observed when using electron beam generated plasmas

  6. Core–shell photoanode developed by atomic layer deposition of Bi2O3 on Si nanowires for enhanced photoelectrochemical water splitting

    International Nuclear Information System (INIS)

    Core–shell nanowire (NW) arrays, which feature a vertically aligned n-type Si NW core and a p-type α-Bi2O3 shell, are developed as a highly efficient photoanode that is suitable for water splitting. The morphology and structure of the heterostructure were characterized by scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), x-ray photoelectron spectroscopy (XPS), and x-ray diffraction (XRD). The deposition of Bi2O3 nanolayers on the surface of the smooth Si NWs causes the surface of the NWs to become rough. The as-prepared core–shell NW photoelectrode has a relatively low reflectance in the visible light region, suggesting good light absorption. The core–shell NW arrays show greatly improved photoelectrochemical water-splitting performance. Photoelectrochemical stability for over 16 h under constant light illumination and fixed bias potential was achieved, illustrating the good stability of this core–shell NW photoanode. These Si/Bi2O3 core–shell NW arrays effectively combine the light absorption ability of the Si NWs and the wide energy gap and chemical stability of Bi2O3 for water splitting. This study furthers the attempts to design photoanodes from low-cost, abundant materials for applications in water splitting and photovoltaics. (paper)

  7. C-atom-induced bandgap modulation in two-dimensional (100) silicon carbon alloys

    Science.gov (United States)

    Mizuno, Tomohisa; Nagamine, Yoshiki; Omata, Yuhsuke; Suzuki, Yuhya; Urayama, Wako; Aoki, Takashi; Sameshima, Toshiyuki

    2016-04-01

    We experimentally studied the effects of the C atom on bandgap E G modulation in two-dimensional (2D) silicon carbon alloys, Si1- Y C Y , fabricated by hot C+ ion implantation into the (100) SOI substrate in a wide range of Y (4 × 10-5 ≤ Y ≤ 0.13), in comparison with the characteristics of 3D silicon carbide (SiC). X-ray photoelectron spectroscopy (XPS) and UV-Raman analysis confirm the Si-C, C-C, and Si-Si bonds in the 2D-Si1- Y C Y layer. The photoluminescence (PL) method shows that the E G and PL intensity I PL of 2D-Si1- Y C Y drastically increase with increasing Y for high Y (≥0.005), and thus we demonstrated a high E G of 2.5 eV and a visible wavelength λPL less than 500 nm. Even for low Y (<10-3), I PL of 2D-Si1- Y C Y also increases with increasing Y, owing to the compressive strain of the 2D-Si1- Y C Y layer caused by the C atoms, but the Y dependence of E G is very small. E G of 2D-Si1- Y C Y can be controlled by changing Y. Thus, the 2D-Si1- Y C Y technique is very promising for new E G engineering of future high-performance CMOS and Si photonics.

  8. Nanowire Growth for Photovoltaics

    DEFF Research Database (Denmark)

    Holm, Jeppe Vilstrup

    Solar cells commercial success is based on an efficiency/cost calculation. Nanowire solar cells is one of the foremost candidates to implement third generation photo voltaics, which are both very efficient and cheap to produce. This thesis is about our progress towards commercial nanowire solar...... cells. Resonance effects between the light and nanowire causes an inherent concentration of the sunlight into the nanowires, and means that a sparse array of nanowires (less than 5% of the area) can absorb all the incoming light. The resonance effects, as well as a graded index of refraction, also traps...... the light. The concentration and light trapping means that single junction nanowire solar cells have a higher theoretical maximum efficiency than equivalent planar solar cells. We have demonstrated the built-in light concentration of nanowires, by growing, contacting and characterizing a solar cell...

  9. Self-Assembled PbSe Nanowire:Perovskite Hybrids

    KAUST Repository

    Yang, Zhenyu

    2015-12-02

    © 2015 American Chemical Society. Inorganic semiconductor nanowires are of interest in nano- and microscale photonic and electronic applications. Here we report the formation of PbSe nanowires based on directional quantum dot alignment and fusion regulated by hybrid organic-inorganic perovskite surface ligands. All material synthesis is carried out at mild temperatures. Passivation of PbSe quantum dots was achieved via a new perovskite ligand exchange. Subsequent in situ ammonium/amine substitution by butylamine enables quantum dots to be capped by butylammonium lead iodide, and this further drives the formation of a PbSe nanowire superlattice in a two-dimensional (2D) perovskite matrix. The average spacing between two adjacent nanowires agrees well with the thickness of single atomic layer of 2D perovskite, consistent with the formation of a new self-assembled semiconductor nanowire:perovskite heterocrystal hybrid.

  10. Stability of core–shell nanowires in selected model solutions

    Energy Technology Data Exchange (ETDEWEB)

    Kalska-Szostko, B., E-mail: kalska@uwb.edu.pl; Wykowska, U.; Basa, A.; Zambrzycka, E.

    2015-03-30

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

  11. Stability of core–shell nanowires in selected model solutions

    International Nuclear Information System (INIS)

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

  12. Synchrotron characterization of functional tin dioxide nanowires

    International Nuclear Information System (INIS)

    Wire-like crystals of tin dioxide were synthesized by a gas-transport technique. The wires, of mainly nanometric diameters, were characterized by spectroscopy and microscopy techniques with the use of highly brilliant and intense synchrotron radiation. We studied the influence of the surface chemical state and the oxygen vacancies on the atomic and electronic structure of the nanowires. The surface of the nanowires is covered by a few nanometers of tin suboxides. The lack of oxygen over the surface layers leads to specific sub-zone formation in a gap, as shown by synchrotron studies

  13. Synchrotron characterization of functional tin dioxide nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Domashevskaya, E. P., E-mail: ftt@phys.vsu.ru; Chuvenkova, O. A.; Turishchev, S. Yu. [Voronezh State University, Voronezh (Russian Federation)

    2015-12-31

    Wire-like crystals of tin dioxide were synthesized by a gas-transport technique. The wires, of mainly nanometric diameters, were characterized by spectroscopy and microscopy techniques with the use of highly brilliant and intense synchrotron radiation. We studied the influence of the surface chemical state and the oxygen vacancies on the atomic and electronic structure of the nanowires. The surface of the nanowires is covered by a few nanometers of tin suboxides. The lack of oxygen over the surface layers leads to specific sub-zone formation in a gap, as shown by synchrotron studies.

  14. Merging Single-Atom-Dispersed Silver and Carbon Nitride to a Joint Electronic System via Copolymerization with Silver Tricyanomethanide.

    Science.gov (United States)

    Chen, Zupeng; Pronkin, Sergey; Fellinger, Tim-Patrick; Kailasam, Kamalakannan; Vilé, Gianvito; Albani, Davide; Krumeich, Frank; Leary, Rowan; Barnard, Jon; Thomas, John Meurig; Pérez-Ramírez, Javier; Antonietti, Markus; Dontsova, Dariya

    2016-03-22

    Herein, we present an approach to create a hybrid between single-atom-dispersed silver and a carbon nitride polymer. Silver tricyanomethanide (AgTCM) is used as a reactive comonomer during templated carbon nitride synthesis to introduce both negative charges and silver atoms/ions to the system. The successful introduction of the extra electron density under the formation of a delocalized joint electronic system is proven by photoluminescence measurements, X-ray photoelectron spectroscopy investigations, and measurements of surface ζ-potential. At the same time, the principal structure of the carbon nitride network is not disturbed, as shown by solid-state nuclear magnetic resonance spectroscopy and electrochemical impedance spectroscopy analysis. The synthesis also results in an improvement of the visible light absorption and the development of higher surface area in the final products. The atom-dispersed AgTCM-doped carbon nitride shows an enhanced performance in the selective hydrogenation of alkynes in comparison with the performance of other conventional Ag-based materials prepared by spray deposition and impregnation-reduction methods, here exemplified with 1-hexyne. PMID:26863408

  15. Study of adhesion of vertically aligned carbon nanotubes to a substrate by atomic-force microscopy

    Science.gov (United States)

    Ageev, O. A.; Blinov, Yu. F.; Il'ina, M. V.; Il'in, O. I.; Smirnov, V. A.; Tsukanova, O. G.

    2016-02-01

    The adhesion to a substrate of vertically aligned carbon nanotubes (VA CNT) produced by plasmaenhanced chemical vapor deposition has been experimentally studied by atomic-force microscopy in the current spectroscopy mode. The longitudinal deformation of VA CNT by applying an external electric field has been simulated. Based on the results, a technique of determining VA CNT adhesion to a substrate has been developed that is used to measure the adhesion strength of connecting VA CNT to a substrate. The adhesion to a substrate of VA CNT 70-120 nm in diameter varies from 0.55 to 1.19 mJ/m2, and the adhesion force from 92.5 to 226.1 nN. When applying a mechanical load, the adhesion strength of the connecting VA CNT to a substrate is 714.1 ± 138.4 MPa, and the corresponding detachment force increases from 1.93 to 10.33 μN with an increase in the VA CNT diameter. As an external electric field is applied, the adhesion strength is almost doubled and is 1.43 ± 0.29 GPa, and the corresponding detachment force is changed from 3.83 to 20.02 μN. The results can be used in the design of technological processes of formation of emission structures, VA CNT-based elements for vacuum microelectronics and micro- and nanosystem engineering, and also the methods of probe nanodiagnostics of VA CNT.

  16. Quantitative Conductive Atomic Force Microscopy on Single-Walled Carbon Nanotube-Based Polymer Composites.

    Science.gov (United States)

    Bârsan, Oana A; Hoffmann, Günter G; van der Ven, Leendert G J; de With, Gijsbertus

    2016-08-01

    Conductive atomic force microscopy (C-AFM) is a valuable technique for correlating the electrical properties of a material with its topographic features and for identifying and characterizing conductive pathways in polymer composites. However, aspects such as compatibility between tip material and sample, contact force and area between the tip and the sample, tip degradation and environmental conditions render quantifying the results quite challenging. This study aims at finding the suitable conditions for C-AFM to generate reliable, reproducible, and quantitative current maps that can be used to calculate the resistance in each point of a single-walled carbon nanotube (SWCNT) network, nonimpregnated as well as impregnated with a polymer. The results obtained emphasize the technique's limitation at the macroscale as the resistance of these highly conductive samples cannot be distinguished from the tip-sample contact resistance. Quantitative C-AFM measurements on thin composite sections of 150-350 nm enable the separation of sample and tip-sample contact resistance, but also indicate that these sections are not representative for the overall SWCNT network. Nevertheless, the technique was successfully used to characterize the local electrical properties of the composite material, such as sample homogeneity and resistance range of individual SWCNT clusters, at the nano- and microscale. PMID:27404764

  17. Atomic Force Microscopy of DNA-wrapped Single-walled Carbon Nanotubes in Aqueous Solution.

    Science.gov (United States)

    Hayashida, Takuya; Umemura, Kazuo

    2016-07-01

    We evaluated hybrids of DNA and single-walled carbon nanotubes (SWNTs) in aqueous solution and in air using atomic force microscopy (AFM). Although intensive AFM observations of these hybrids were previously carried out for samples in air, this is the first report on AFM observations of these hybrids in solution. As expected, diameters of DNA-SWNT hybrids dramatically increased in tris(hydroxymethyl)aminomethane-ethylenediaminetetraacetic acid (TE) buffer solution. The data suggest that DNA molecules maintain their structures even on the SWNT surfaces. Furthermore, we simultaneously observed single DNA-SWNT hybrids using three different AFM modes in air and in the TE buffer solution. Height value of the hybrids was largest in the solution, and lowest for the mode that repulsive force is expected in air. For the bare SWNT molecules, height differences among the three AFM modes were much lower than those of the DNA-SWNT hybrids. DNA molecules adsorbed on SWNT surfaces flexibly changed their morphology as well as DNA molecules on flat surfaces such as mica. This is hopeful results for biological applications of DNA-SWNT hybrids. In addition, our results revealed the importance of the single-molecule approach to evaluate DNA structures on SWNT surfaces. PMID:27045980

  18. The effect of carbon impurities on the distribution of implanted iron atoms in titanium

    International Nuclear Information System (INIS)

    Moessbauer Spectroscopy along with Rutherford Backscattering Analysis (R.B.S.) has been used to analyse the chemical phases formed during implantation of 40 keV 57Fe into titanium foils at a dose of 2 x 101757Fe ions cm-2. Two different substrate temperatures were used, nominal room temperature and 550 deg C. For the foil implanted at 550 deg C the components of the Moessbauer spectrum were identified as α-iron and iron carbide. The room temperature implant, however, resulted in the formation of a highly disordered iron carbide which was converted to a mixture of 'crystalline' Fe3C and α-iron after annealing at 600 deg C. The implantations were repeated under cleaner conditions when the Moessbauer spectra of the samples were completely different with no evidence for the previously observed disordered phase. The implantation profiles as determined from R.B.S. were also different. Estimates of the levels of oxygen and carbon were determined from a (d,p) analysis of the samples. The relationship between the presence of impurities and the distribution of implanted iron atoms is discussed. (author)

  19. Atomic carbon as a tracer of molecular gas in high-redshift galaxies: perspectives for ALMA

    CERN Document Server

    Tomassetti, Matteo; Romano-Diaz, Emilio; Ludlow, Aaron D; Papadopoulos, Padelis P

    2014-01-01

    We use a high-resolution simulation that tracks the non-equilibrium abundance of molecular hydrogen, H2, within a massive high-redshift galaxy to produce mock ALMA maps of the fine-structure lines of atomic carbon CI 1-0 and CI 2-1. Inspired by recent observational and theoretical work, we assume that CI is thoroughly mixed in giant molecular clouds and demonstrate that its emission is an excellent proxy for H2. The entire H2 mass of a galaxy at redshift z<4 can be detected using a compact interferometric configuration with a large synthesized beam (that does not resolve the target galaxy) in less than 1 hour of integration time. Low-resolution imaging of the CI lines (in which the target galaxy is resolved into 3-4 beams) will detect nearly 50-60 per cent of the molecular hydrogen in less than 12 hours. In this case, the data cube also provides valuable information regarding the dynamical state of the galaxy. We conclude that ALMA observations of the CI 1-0 and 2-1 emission will widely extend the interval...

  20. Multi-Directional Growth of Aligned Carbon Nanotubes Over Catalyst Film Prepared by Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Zhou Kai

    2010-01-01

    Full Text Available Abstract The structure of vertically aligned carbon nanotubes (CNTs severely depends on the properties of pre-prepared catalyst films. Aiming for the preparation of precisely controlled catalyst film, atomic layer deposition (ALD was employed to deposit uniform Fe2O3 film for the growth of CNT arrays on planar substrate surfaces as well as the curved ones. Iron acetylacetonate and ozone were introduced into the reactor alternately as precursors to realize the formation of catalyst films. By varying the deposition cycles, uniform and smooth Fe2O3 catalyst films with different thicknesses were obtained on Si/SiO2 substrate, which supported the growth of highly oriented few-walled CNT arrays. Utilizing the advantage of ALD process in coating non-planar surfaces, uniform catalyst films can also be successfully deposited onto quartz fibers. Aligned few-walled CNTs can be grafted on the quartz fibers, and they self-organized into a leaf-shaped structure due to the curved surface morphology. The growth of aligned CNTs on non-planar surfaces holds promise in constructing hierarchical CNT architectures in future.

  1. Geometric Characterization of Carbon Nanotubes by Atomic Force Microscopy in Conjunction with a Tip Characterizer

    Science.gov (United States)

    Wang, Chunmei; Itoh, Hiroshi; Homma, Yoshikazu; Sun, Jielin; Hu, Jun; Ichimura, Shingo

    2008-07-01

    An atomic force microscopy (AFM) probe tip characterizer with 14 line and space structures and two knife edges was fabricated by means of a superlattice technique. The shape of a probe tip both before and after AFM imaging was acquired by this tip characterizer with general variations <1.5 nm; depending on imaging conditions. The geometric structures of carbon nanotubes (CNTs) on a SiO2 substrate were studied by dynamic mode AFM in conjunction with this tip characterizer. Contact points between the tip and the CNTs were detected by observing changes in the AFM phase images. A modified CNT width correction model was established to calculate the estimated and upper-limit widths of two CNTs. The experimental results showed that imaging under a weak attractive force was suitable for obtaining accurate CNT height measurements, whereas a weak repulsive force provided the most accurate widths. Differing heights and widths between the two CNTs suggested that one CNT was double-walled, whereas the other had more than two walls; these results agree with transmission electron microscopy (TEM) measurements of the CNTs.

  2. Hydrogen atom injection into carbon surfaces by comparison between Monte-Carlo, molecular dynamics and ab-initio calculations

    International Nuclear Information System (INIS)

    Full text: To understand the plasma-wall interaction on divertor plates, we investigate the interaction of hydrogen atoms and carbon materials used in the high heat flux components by the use of the following simulations. Monte-Carlo (MC) method based on binary collision approximation can calculate the sputtering process of hydrogen atoms on the carbon material quickly. Classical molecular dynamics (MD) method employs multi-body potential models and can treat realistic structures of crystal and molecule. The ab-initio method can calculate electron energy in quantum mechanics, which is regarded as realistic potential for atoms. In the present paper, the interaction of the hydrogen and the carbon material is investigated using the multi-scale (MC, MD and ab-initio) methods. The bombardment of hydrogen atoms onto the carbon material is simulated by the ACAT-code of the MC method, which cannot represent the structure of crystal, and the MD method using modified reactive empirical bond order (REBO) potential, which treats single crystal graphite and amorphous carbon. Consequently, we clarify that the sputtering yield and the reflection rate calculated by the ACAT-code agree with those on the amorphous carbon calculated by the MD. Moreover, there are many kinds of REBO potential for the MD. Adsorption, reflection and penetration rates between a hydrogen atom and a graphene surface are calculated by the MD simulations using the two kinds of potential model. For the incident energy of less than 1 eV, the MD simulation using the modified REBO potential, which is based on Brenner's REBO potential in 2002, shows that reflection is dominant, while the most popular Brenner's REBO potential in 1990 shows that adsorption is dominant. This reflection of the low energy injection is caused by a small potential barrier for the hydrogen atom in the modified REBO potential. The small potential barrier is confirmed by the ab-initio calculations, which are hybrid DFT (B3LYP/cc-pVDZ), ab

  3. Atomic layer deposition of Co3O4 on carbon nanotubes/carbon cloth for high-capacitance and ultrastable supercapacitor electrode

    International Nuclear Information System (INIS)

    Co3O4 nanolayers have been successfully deposited on a flexible carbon nanotubes/carbon cloth (CC) substrate by atomic layer deposition. Much improved capacitance and ultra-long cycling life are achieved when the CNTs@Co3O4/CC is tested as a supercapacitor electrode. The improvement can be from the mechanically robust CC/CNTs substrate, the uniform coated high capacitance materials of Co3O4 nanoparticles, and the unique hierarchical structure. The flexible electrode of CNTs@Co3O4/CC with high areal capacitance and excellent cycling ability promises great potential for developing high-performance flexible supercapacitors. (paper)

  4. Bibliography of electron and photon cross sections with atoms and molecules published in the 20th century. Carbon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Makoto [Gaseous Electronics Institute, Nagoya, Aichi (Japan)

    2003-04-01

    A bibliography of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for carbon dioxide (CO{sub 2}). About 1,240 papers were compiled. A comprehensive author index is included. The bibliography covers the period 1901 through 2000 for CO{sub 2}. Finally, author's comments for CO{sub 2} electron collision cross sections are given. (author)

  5. Bibliography of electron and photon cross sections with atoms and molecules published in the 20th century. Carbon dioxide

    International Nuclear Information System (INIS)

    A bibliography of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for carbon dioxide (CO2). About 1,240 papers were compiled. A comprehensive author index is included. The bibliography covers the period 1901 through 2000 for CO2. Finally, author's comments for CO2 electron collision cross sections are given. (author)

  6. An examination of surface stress effects and deformation mechanisms in Al–Cu nanowires

    International Nuclear Information System (INIS)

    A molecular dynamics simulation was utilized to study AlCu and AlCu3 nanowires. The simulation results showed that surface stress can force AlCu nanowires into high-elastic states and induce slip and clusters in AlCu3 nanowires. Two distinct types of deformation mechanisms were observed. One is that the AlCu nanowires underwent the changes of elastic deformation, amorphous transition, necking and breaking. The other is because the {1 0 1} twinning and crystal region coexist, the calculated tensile curves of AlCu3 nanowires also show many yield points, and unloading can lead to elastic recovery of 4–9%. It implies that AlCu3 nanowires are usable even after external shock waves. This work indicates that changing atomic proportions in alloy nanowires can be utilized to control the deformation mechanism upon loading

  7. Zirconia (ZrO2) Embedded in Carbon Nanowires via Electrospinning for Efficient Arsenic Removal from Water Combined with DFT Studies.

    Science.gov (United States)

    Luo, Jinming; Luo, Xubiao; Hu, Chengzhi; Crittenden, John C; Qu, Jiuhui

    2016-07-27

    To use zirconia (ZrO2) as an efficient environmental adsorbent, it can be impregnated on a support to improve its physical properties and lower the overall cost. In this study, ZrO2 embedded in carbon nanowires (ZCNs) is fabricated via an electrospinning method to remove arsenic (As) from water. The maximum adsorption capacity values of As(III) and As(V) on the ZCNs are 28.61 and 106.57 mg/g, respectively, at 40 °C. These capacities are considerably higher than those of pure ZrO2 (2.56 and 3.65 mg/g for As(III) and As(V), respectively) created using the same procedure as for the ZCNs. Meanwhile, the adsorption behaviors of As(III) and As(V) on the ZCNs are endothermic and pH dependent and follow the Freundlich isotherm model and pseudo-first-order kinetic model. Both As(III) and As(V) are chemisorbed onto the ZCNs, which is confirmed by a partial density of state (PDOS) analysis and Dubinin-Radushkevich (D-R) model calculations. Furthermore, the ZCNs also possess the capability to enhance or catalyze the oxidation process of As(III) to As(V) using dissolved oxygen. This result is confirmed by a batch experiment, XPS analysis and Mulliken net charge analysis. Density functional theory (DFT) calculations indicate the different configurations of As(III) and As(V) complexes on the tetragonal ZrO2 (t-ZrO2)(111) and monoclinic ZrO2 (m-ZrO2)(111) planes, respectively. The adsorption energy (Ead) of As(V) is higher than that of As(III) on both the t-ZrO2(111) and m-ZrO2 (111) planes (3.38 and 1.90 eV, respectively, for As(V) and 0.37 and 0.12 eV, respectively, for As(III)). PMID:27381268

  8. Novel nanotubes and encapsulated nanowires

    Science.gov (United States)

    Terrones, M.; Hsu, W. K.; Schilder, A.; Terrones, H.; Grobert, N.; Hare, J. P.; Zhu, Y. Q.; Schwoerer, M.; Prassides, K.; Kroto, H. W.; Walton, D. R. M.

    Carbon nanotubes, with or without encapsulated material, generated by arc discharge and electrolytic techniques have been studied. Microcrystals of refractory carbides (i.e. NbC, TaC, MoC), contained in nanotubes and polyhedral particles, produced by arcing electrodes of graphite/metal mixtures, were analysed by high hesolution transmission electron microscopy (HRTEM) and X-ray powder diffraction. Encapsulation of MoC was found to give rise to an unusual stable form, namely face-centered-cubic MoC. SQUID measurements indicate that the encapsulated carbides exhibit superconducting transitions at about 10-12 K, thus they differ from carbon nanotubes/nanoparticles which do not superconduct. Four-probe and microwave (contactless) conductivity measurements indicate that most of the analysed samples behave as semiconductors. However, metallic transport was observed in specimens containing single conglomerated carbon nanotube bundles and boron-doped carbon nanotubes. Novel metallic βSn nanowires were produced by electrolysis of graphite electrodes immersed in molten LiCl/SnCl2 mixtures. Prolonged electron irradiation of these nanowires leads to axial growth and to dynamic transformations. These observations suggest ways in which materials may be modified by microencapsulation and irradiation.

  9. Neutral-atom scattering from random isolated adsorbate atoms on clean metal surfaces: Oxygen and carbon monoxide on nickel (001)

    International Nuclear Information System (INIS)

    The intensity I of the specular beam of a helium nozzle beam scattered from a Ni(001) surface has been measured as a function of adsorbate coverage CTHETA for both oxygen and CO exposures at 350 K for different angles of incidence. A linear relationship is found between ln (I/I0) (I0, the intensity of the specular beam from the clean surface) and CTHETA up to CTHETA = 0.15 monolayer of O on Ni and CTHETA = 0.1 monolayer of CO on Ni. A model is proposed in which the scattering is governed by the repulsive part of the gas-surface potential, the latter being described by a hard-wall corrugation. A constant attractive well depth and a temperature-dependent vibration amplitude of the atoms are also incorporated into the model. The adsorbate atoms are treated as a shot noise on a flat metal surface. By means of suitable averaging, a formula is found that explains the linear dependence indicated. From the best fit of the model to the experimental data, a set of parameters describing the corrugation of a single adsorbate is derived. Cross sections for the helium-adatom scattering are 65 and 26 A2 for CO and O, respectively. The corresponding corrugations have been fitted with Gaussians of height 0.62 A (for CO) and 0.32 A (for O)

  10. Synthesis of pyrite/carbon shells on cobalt nanowires forming core/branch arrays as high-performance cathode for lithium ion batteries

    Science.gov (United States)

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

    2016-01-01

    Construction of self-supported porous metal sulfide arrays is critical for the development of high-performance electrochemical energy storage devices. Herein we report hierarchical porous Co/FeS2-C core/branch nanowires arrays by the combination of facile solution-based methods. FeS2-C nanoflakes branch is uniformly coated on the Co nanowire core forming composite core/branch arrays. The as-prepared Co/FeS2-C core/branch nanowire arrays possess combined properties of highly porous structure and strong mechanical stability. As cathode of lithium ion batteries, the Co/FeS2-C core/branch nanowire arrays exhibit good electrochemical performances with initial discharge capacity of 850 mAh g-1 at 0.25 °C and stable high-rate cycling life (539 mAh g-1 after 70 cycles at 0.25 °C). The hierarchical core/branch architecture provides positive roles in the enhancement of electrochemical properties, including fast transportation path of electron, short diffusion of ions and high contact area between the active material and electrolyte.

  11. Flow injection sorbent extraction of metals with activated carbon and its application to flame atomic absorption spectrometry

    International Nuclear Information System (INIS)

    In the present study activated carbon was used as a sorbent material for the flow injection on-line sorbent extraction of metal ions combined with atomic absorption spectrometry. On-line chelation of zinc was performed with 8-Hydroxyquinoline and the resultant metal chelate was adsorbed on the activated carbon, then adsorbed with zinc acid and on-line detected with flame AAS. Various parameters affecting the zinc enrichment were optimized and the method was applied for the determination of zinc in tap water, natural water, boiled and tea samples. The results obtained with the present method were compared with those obtained by the ICP-AES. (author)

  12. Single Atom (Pd/Pt) Supported on Graphitic Carbon Nitride as an Efficient Photocatalyst for Visible-Light Reduction of Carbon Dioxide.

    Science.gov (United States)

    Gao, Guoping; Jiao, Yan; Waclawik, Eric R; Du, Aijun

    2016-05-18

    Reducing carbon dioxide to hydrocarbon fuel with solar energy is significant for high-density solar energy storage and carbon balance. In this work, single atoms of palladium and platinum supported on graphitic carbon nitride (g-C3N4), i.e., Pd/g-C3N4 and Pt/g-C3N4, respectively, acting as photocatalysts for CO2 reduction were investigated by density functional theory calculations for the first time. During CO2 reduction, the individual metal atoms function as the active sites, while g-C3N4 provides the source of hydrogen (H*) from the hydrogen evolution reaction. The complete, as-designed photocatalysts exhibit excellent activity in CO2 reduction. HCOOH is the preferred product of CO2 reduction on the Pd/g-C3N4 catalyst with a rate-determining barrier of 0.66 eV, while the Pt/g-C3N4 catalyst prefers to reduce CO2 to CH4 with a rate-determining barrier of 1.16 eV. In addition, deposition of atom catalysts on g-C3N4 significantly enhances the visible-light absorption, rendering them ideal for visible-light reduction of CO2. Our findings open a new avenue of CO2 reduction for renewable energy supply. PMID:27116595

  13. Individualization and Electrical Characterization of SiGe Nanowires

    OpenAIRE

    Monasterio, Manuel; Rodríguez Domínguez, Andrés; Rodríguez Rodríguez, Tomás; Ballesteros Pérez, Carmen Inés

    2011-01-01

    SiGe nanowires of different Ge atomic fractions up to 15% were grown and ex-situ n-type doped by diffusion from a solid source in contact with the sample. The phenomenon of dielectrophoresis was used to locate single nanowires between pairs of electrodes in order to carry out electrical measurements. The measured resistance of the as-grown nanowires is very high, but it decreases more than three orders of magnitude upon doping, indicating that the doping procedure used has been effective

  14. Growth of vertical InAs nanowires on heterostructured substrates

    International Nuclear Information System (INIS)

    We investigate the Au-assisted growth of InAs nanowires on two different kinds of heterostructured substrates: GaAs/AlGaAs structures capped by a 50 nm thick InAs layer grown by molecular beam epitaxy and a 2 μm thick InAs buffer layer on Si(111) obtained by vapor phase epitaxy. Morphological and structural properties of substrates and nanowires are analyzed by atomic force and transmission electron microscopy. Our results indicate a promising direction for the integration of III-V nanostructures on Si-based electronics as well as for the development of novel micromechanical structures incorporating nanowires as their active elements.

  15. Structural and electronic properties of lead nanowires: Ab-initio study

    International Nuclear Information System (INIS)

    Highlights: → In the present revised manuscript entitled 'Structural and Electronic Properties of Lead Nanowires: Ab-initio study', we have analyzed the stability, electronic properties as well as ground state properties of various atomic configurations of Lead nanowires. → The two-atom zigzag shaped lead nanowire with highest binding energy and lowest total energy has been confirmed as the most stable structure out of the six atomic configurations taken into consideration. → The electronic band structure and density of states have been described in detail with a remarkable observation in case of three-atom triangular lead nanowire having a very small band gap while other atomic configurations are found to be metallic. → The bulk modulus and pressure derivatives for all the stable geometries have also been computed and discussed in the manuscript. The mechanical strength of nanowires has also been discussed in terms of its bulk modulus. → The two-atom ladder shaped nanowire with highest bulk modulus, defends this structure as mechanically stronger than the other tested structure. - Abstract: Ab-initio self-consistent study has been performed to analyze the stability of lead nanowires in its six stable configurations like linear, zigzag, triangular, ladder, square and dumbbell. In the present study, the lowest energy structures have been analyzed under the revised Perdew-Burke-Ernzerhof (revPBE) parameterization of generalized gradient approximation (GGA) potential. The two-atom zigzag shaped atomic configuration with highest binding energy and lowest total energy has been confirmed as the most stable structure out of the six atomic configurations. The electronic band structure and density of states have been discussed in detail with a remarkable observation in case of three-atom triangular lead nanowire having a very small band gap while other configurations are found to be metallic. Bulk modulus, pressure derivatives and lattice parameters for different

  16. Atomic Scale Analysis of the Enhanced Electro- and Photo-Catalytic Activity in High-Index Faceted Porous NiO Nanowires

    OpenAIRE

    Meng Shen; Ali Han; Xijun Wang; Yun Goo Ro; Alireza Kargar; Yue Lin; Hua Guo; Pingwu Du; Jun Jiang; Jingyu Zhang; Dayeh, Shadi A.; Bin Xiang

    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-synth...

  17. Identification and characterization of icosahedral metallic nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Pelaez, Samuel; Serena, Pedro A. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, c/Sor Juana Ines de la Cruz 3, Cantoblanco, 28049-Madrid (Spain); Guerrero, Carlo [Departamento de Fisica, Facultad Experimental de Ciencias, La Universidad del Zulia, Maracaibo (Venezuela); Paredes, Ricardo [Centro de Fisica, Instituto Venezolano de Investigaciones Cientificas, Apto. 20632, Caracas 1020A (Venezuela); Garcia-Mochales, Pedro [Departamento de Fisica de la Materia Condensada, Facultad de Ciencias, Universidad Autonoma de Madrid, c/Tomas y Valiente 7, Cantoblanco, 28049-Madrid (Spain)

    2009-10-15

    We present and discuss an algorithm to identify ans characterize the long icosahedral structures (staggered pentagonal nanowires with 1-5-1-5 atomic structure) that appear in Molecular Dynamics simulations of metallic nanowires of different species subjected to stretching. The use of the algorithm allows the identification of pentagonal rings forming the icosahedral structure as well as the determination of its number n{sub p}, and the maximum length of the pentagonal nanowire L{sub p}{sup m}. The algorithm is tested with some ideal structures to show its ability to discriminate between pentagonal rings and other ring structures. We applied the algorithm to Ni nanowires with temperatures ranging between 4 K and 865 K, stretched along the[100] direction. We studied statistically the formation of pentagonal nanowires obtaining the distributions of length L{sub p}{sup m} and number of rings n{sub p} as function of the temperature. The L{sub p}{sup m} distribution presents a peaked shape, with peaks locate at fixes distances whose separation corresponds to the distance between two consecutive pentagonal rings. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Black-colored ZnO nanowires with enhanced photocatalytic hydrogen evolution

    Science.gov (United States)

    Zhang, Nan; Shan, Chong-Xin; Tan, Hua-Qiao; Zhao, Qi; Wang, Shuang-Peng; Sun, Zai-Cheng; Xia, Yong-de; Shen, De-Zhen

    2016-06-01

    Black-colored ZnO nanowires have been prepared in a metal–organic chemical vapor deposition system by employing a relatively low growth temperature and oxygen-deficient conditions. X-ray photoelectron spectroscopy reveals the incorporation of carbon into the nanowires. The photocatalytic hydrogen evolution activity of the black-colored ZnO nanowires is over 2.5 times larger than that of the pristine ZnO nanowires under simulated solar illumination conditions, and the enhanced photocatalytic activity can be attributed to the higher absorption of visible light by the black color and better carrier separation at the ZnO/carbon interface.

  19. Black-colored ZnO nanowires with enhanced photocatalytic hydrogen evolution.

    Science.gov (United States)

    Zhang, Nan; Shan, Chong-Xin; Tan, Hua-Qiao; Zhao, Qi; Wang, Shuang-Peng; Sun, Zai-Cheng; Xia, Yong-de; Shen, De-Zhen

    2016-06-01

    Black-colored ZnO nanowires have been prepared in a metal-organic chemical vapor deposition system by employing a relatively low growth temperature and oxygen-deficient conditions. X-ray photoelectron spectroscopy reveals the incorporation of carbon into the nanowires. The photocatalytic hydrogen evolution activity of the black-colored ZnO nanowires is over 2.5 times larger than that of the pristine ZnO nanowires under simulated solar illumination conditions, and the enhanced photocatalytic activity can be attributed to the higher absorption of visible light by the black color and better carrier separation at the ZnO/carbon interface. PMID:27109699

  20. Fibrous Containment for Improved Laboratory Handling and Uniform Nanocoating of Milligram Quantities of Carbon Nanotubes by Atomic Layer Deposition

    OpenAIRE

    Devine, Christina K.; Oldham, Christopher J.; Jur, Jesse S.; Gong, Bo; Parsons, Gregory N.

    2011-01-01

    The presence of nanostructured materials in the work place is bringing attention to the importance of safe practices for nanomaterial handling. We explored novel fiber containment methods to improve the handling of carbon nanotube (CNT) powders in the laboratory, while simultaneously allowing highly uniform and controlled atomic layer deposition (ALD) coatings on the nanotubes, down to less than 4 nm on some CNT materials. Moreover, the procedure yields uniform coatings on milligram quantitie...

  1. Synthesis of self-assembly BaTiO3 nanowire by sol-gel and microwave method

    International Nuclear Information System (INIS)

    Self-assembly ferroelectric BaTiO3 nanowires were fabricated using sol-gel and microwave method. The X-ray diffraction patterns show that BaTiO3 nanowires belong to the tetragonal perovskite structure. An increase in the intensity of (1 1 0) peak was observed as the annealing time increased. The shape of BaTiO3 nanowires microwave-annealed for different minutes was investigated using atomic force microscopy. It is found that nanowires of BaTiO3 annealed for 2.5 min are very clear-cut, orderly and almost uninterrupted. The height of nanowire is near to the film thickness. However, nanowires of BaTiO3 annealed for 5 min are lesser, shorter and lower, and the distances among these nanowires are wider and well-proportioned. The origin of the distinct differences due to the remotion of atoms obtained enough energy was discussed.

  2. Permeation of low-Z atoms through carbon sheets: Density functional theory study on energy barriers and deformation effects

    International Nuclear Information System (INIS)

    Energetic and geometric aspects of the permeation of the atoms hydrogen to neon neutral atoms through graphene sheets are investigated by investigating the associated energy barriers and sheet deformations. Density functional theory calculations on cluster models, where graphene is modeled by planar polycyclic aromatic hydrocarbons (PAHs), provide the energies and geometries. Particularities of our systems, such as convergence of both energy barriers and deformation curves with increasing size of the PAHs, are discussed. Three different interaction regimes, adiabatic, planar and vertical, are investigated by enforcing different geometrical constraints. The adiabatic energy barriers range from 5 eV for hydrogen to 20 eV for neon. We find that the permeation of oxygen and carbon into graphene is facilitated by temporary chemical bonding while for other, in principle reactive atoms, it is not. We discuss implications of our results for modeling chemical sputtering of graphite

  3. Computational insights into the effect of carbon structures at the atomic level for non-aqueous sodium-oxygen batteries

    Science.gov (United States)

    Jiang, H. R.; Wu, M. C.; Zhou, X. L.; Yan, X. H.; Zhao, T. S.

    2016-09-01

    Carbon materials have been widely used to form air cathodes for non-aqueous sodium-oxygen (Nasbnd O2) batteries due to their large specific surface area, high conductivity and low cost. However, the effect of carbon structures at the atomic level remains poorly understood. In this work, a first-principles study is conducted to investigate how representative carbon structures, including graphite (0001) surface, point defects and fractured edge, influence the discharge and charge processes of non-aqueous Nasbnd O2 batteries. It is found that the single vacancy (SV) defect has the largest adsorption energy (5.81 eV) to NaO2 molecule among the structures studied, even larger than that of the NaO2 molecule on NaO2 crystal (2.81 eV). Such high adsorption energy is attributed to two factors: the dangling atoms in SV defects decrease the distance from NaO2 molecules, and the attachment through oxygen atoms increases the electrons transfer. The findings suggest that SV defects can act as the nucleation sites for NaO2 in the discharge process, and increasing the number of SV defects can facilitate the uniform formation of small-sized particles. The uniformly distributed discharge products lower the possibility for pore clogging, leading to an increased discharge capacity and improved cyclability for non-aqueous Nasbnd O2 batteries.

  4. Reactions of Hot Cl38 Atoms in Mixtures of Carbon Tetrachloride with Aliphatic Alcohols

    International Nuclear Information System (INIS)

    Investigations of the chemical effects of nuclear reactions in binary systems are expected to yield much useful information. Study of the recoil processes of the halogen derivatives when the second component is suitably chosen and its concentration varied in a wide range might permit inferences to be made on the role and mechanism of the various stabilizing processes. Considering the results obtained with CCl4-Cl2, CCl4-SiCl4, CCl4-C6H6 and CCl4-c-hexane mixtures as well as the energy scavenger property of alcohol, it seemed of interest to study the contribution of the alcohols to the stabilization of hot Cl38. Chemical processes induced by hot Cl38 from the nuclear reaction Cl97 (n, γ)Cl38 were investigated in mixtures of CCl4-ROH (where R = CH3-, C2H5-, C3H7- and (CH3)2CH-). The irradiations were performed in the thermal column of the 2 MW VVRS reactor using rather short exposure times to keep the radiation chemical effects at negligible level. The organic fractions were separated from the inorganic ones by extraction and the former were analysed by gas chromatographic method. Total retention and the yield of the complete set of organic chlorine compounds were determined in terms of alcohol concentration. Some interesting results are that the yield of reaction products in which the OH radical of aliphatic alcohol has been replaced by Cl38 increases with increasing alcohol concentration with a simultaneous decrease in the labelled CCI4 yield and that, in addition to the monochlorine derivates with less carbon atoms than the alcohol molecule, a considerable amount of chloroform is formed with maximum yield at a given alcohol concentration. The relative contributions of the hot and the epithermal stabilization processes of energetic Cl38 and the mechanism of the various reactions are discussed. (author)

  5. Optical fibre nanowire devices

    OpenAIRE

    Xu, Fei

    2008-01-01

    The Optical Fibre Nanowire (OFN) is a potential building block in future micro- and nano-photonic device since it offers a number of unique optical and mechanical properties. In this thesis, the background and fundamental features of nanowires are introduced; the theory, design and demonstration of novel nanowire devices are discussed. At first, a short adiabatic taper tip is manufactured, and it is used as optical tweezers for trapping 1?m microspheres. Then, the most important devic...

  6. Preparation of SiC Nanowires Self-sacrificially Templated by Carbonated Bacterial Cellulose%以碳化细菌纤维素为模板制备碳化硅纳米线

    Institute of Scientific and Technical Information of China (English)

    温丽霞; 马拥军

    2012-01-01

    以碳化细菌纤维素为模板和碳源,通过气相渗硅法制备碳化硅纳米线。x射线衍射和扫描电镜(SEM)研究了碳化硅样品的结构与形貌,结果表明所得碳化硅都是纯立方相结构,并且粒度随温度的升高而增大。碳化硅纳米线表面光滑,长度达到微米级。%SiC nanowires were synthesized by the infiltration process of reactive vapor Si, using carbona- ted bacterial cellulose as carbon template and a reactant. XRD and SEM were used to study the phase and morphology of the silicon carbide. The results show that silicon carbide is pure cubic phase and the parti- cle sizes are increasing with the temperature increasing. The surface of SiC nanowires is smooth and the length reaches a micron level.

  7. Atomic Scale Interface Manipulation, Structural Engineering, and Their Impact on Ultrathin Carbon Films in Controlling Wear, Friction, and Corrosion.

    Science.gov (United States)

    Dwivedi, Neeraj; Yeo, Reuben J; Yak, Leonard J K; Satyanarayana, Nalam; Dhand, Chetna; Bhat, Thirumaleshwara N; Zhang, Zheng; Tripathy, Sudhiranjan; Bhatia, Charanjit S

    2016-07-13

    Reducing friction, wear, and corrosion of diverse materials/devices using systems. Here, we present a novel approach based on atomic scale interface manipulation to engineer and control the friction, wear, corrosion, and structural characteristics of 0.7-1.7 nm carbon-based films on CoCrPt:oxide-based magnetic media. We demonstrate that when an atomically thin (∼0.5 nm) chromium nitride (CrNx) layer is sandwiched between the magnetic media and an ultrathin carbon overlayer (1.2 nm), it modifies the film-substrate interface, creates various types of interfacial bonding, increases the interfacial adhesion, and tunes the structure of carbon in terms of its sp(3) bonding. These contribute to its remarkable functional properties, such as stable and lowest coefficient of friction (∼0.15-0.2), highest wear resistance and better corrosion resistance despite being only ∼1.7 nm thick, surpassing those of ∼2.7 nm thick current commercial carbon overcoat (COC) and other overcoats in this work. While this approach has direct implications for advancing current magnetic storage technology with its ultralow thickness, it can also be applied to advance the protective and barrier capabilities of other ultrathin materials for associated technologies. PMID:27267790

  8. Electrical current flow at conductive nanowires formed in GaN thin films by a dislocation template technique

    Science.gov (United States)

    Amma, Shin-ichi; Tokumoto, Yuki; Edagawa, Keiichi; Shibata, Naoya; Mizoguchi, Teruyasu; Yamamoto, Takahisa; Ikuhara, Yuichi

    2010-05-01

    Conductive nanowires were fabricated in GaN thin film by selectively doping of Al along threading dislocations. Electrical current flow localized at the nanowires was directly measured by a contact mode atomic force microscope. The current flow at the nanowires was considered to be Frenkel-Poole emission mode, suggesting the existence of the deep acceptor level along the nanowires as a possible cause of the current flow. The results obtained in this study show the possibility for fabricating nanowires using pipe-diffusion at dislocations in solid thin films.

  9. Organic electrochemical transistors based on a dielectrophoretically aligned nanowire array

    Directory of Open Access Journals (Sweden)

    Choi WooSeok

    2011-01-01

    Full Text Available Abstract In this study, we synthesized an organic electrochemical transistor (OECT using dielectrophoresis of a carbon nanotube-Nafion (CNT-Nafion suspension. Dielectrophoretically aligned nanowires formed a one-dimensional submicron bundle between triangular electrodes. The CNT-Nafion composite nanowire bundles showed p-type semiconductor characteristics. The drain-source current decreased with increasing gate voltage. The nanowire bundles showed potential as pH sensor because the drain-source current ratio varied linearly according to the gate voltage in pH buffers.

  10. Elastic properties and electron transport in InAs nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Migunov, Vadim

    2013-02-22

    The electron transport and elastic properties of InAs nanowires grown by chemical vapor deposition on InAs (001) substrate were studied experimentally, in-situ in a transmission electron microscope (TEM). A TEM holder allowing the measurement of a nanoforce while simultaneous imaging nanowire bending was used. Diffraction images from local areas of the wire were recorded to correlate elastic properties with the atomic structure of the nanowires. Another TEM holder allowing the application of electrical bias between the nanowire and an apex of a metallic needle while simultaneous imaging the nanowire in TEM or performing electron holography was used to detect mechanical vibrations in mechanical study or holographical observation of the nanowire inner potential in the electron transport studies. The combination of the scanning probe methods with TEM allows to correlate the measured electric and elastic properties of the nanowires with direct identification of their atomic structure. It was found that the nanowires have different atomic structures and different stacking fault defect densities that impacts critically on the elastic properties and electric transport. The unique methods, that were applied in this work, allowed to obtain dependencies of resistivity and Young's modulus of left angle 111 right angle -oriented InAs nanowires on defect density and diameter. It was found that the higher is the defect density the higher are the resistivity and the Young's modulus. Regarding the resistivity, it was deduced that the stacking faults increase the scattering of the electrons in the nanowire. These findings are consistent with the literature, however, the effect described by the other groups is not so pronounced. This difference can be attributed to the significant incompleteness of the physical models used for the data analysis. Regarding the elastic modulus, there are several mechanisms affecting the elasticity of the nanowires discussed in the thesis. It

  11. Ab initio vibrations in nonequilibrium nanowires

    International Nuclear Information System (INIS)

    We review recent results on electronic and thermal transport in two different quasi one-dimensional systems: Silicon nanowires (SiNW) and atomic gold chains. For SiNW's we compute the ballistic electronic and thermal transport properties on equal footing, allowing us to make quantitative predictions for the thermoelectric properties, while for the atomic gold chains we evaluate microscopically the damping of the vibrations, due to the coupling of the chain atoms to the modes in the bulk contacts. Both approaches are based on the combination of density-functional theory, and nonequilibrium Green's functions.

  12. Field Ionization of Cold Atoms near the Wall of a Single Carbon Nanotube

    International Nuclear Information System (INIS)

    We observe the capture and field ionization of individual atoms near the side wall of a single suspended nanotube. Extremely large cross sections for ionization from an atomic beam are observed at modest voltages due to the nanotube's small radius and extended length. The effects of the field strength on both the atomic capture and the ionization process are clearly distinguished in the data, as are prompt and delayed ionizations related to the locations at which they occur. Efficient and sensitive neutral atom detectors can be based on the nanotube capture and wall ionization processes.

  13. Field Ionization of Cold Atoms near the Wall of a Single Carbon Nanotube

    CERN Document Server

    Goodsell, Anne; Golovchenko, J A; Hau, Lene Vestergaard; 10.1103/PhysRevLett.104.133002

    2010-01-01

    We observe the capture and field ionization of individual atoms near the side wall of a single suspended nanotube. Extremely large cross sections for ionization from an atomic beam are observed at modest voltages due to the nanotube's small radius and extended length. The effects of the field strength on both the atomic capture and the ionization process are clearly distinguished in the data, as are prompt and delayed ionizations related to the locations at which they occur. Efficient and sensitive neutral atom detectors can be based on the nanotube capture and wall ionization processes.

  14. Chemisorption of single fluorine atoms on the surface of zigzag single-walled carbon nanotubes: A model calculation

    Energy Technology Data Exchange (ETDEWEB)

    Margulis, Vl.A. [Department of Physics, N.P. Ogarev Mordovian State University, Saransk 430000 (Russian Federation)]. E-mail: 612033@inbox.ru; Muryumin, E.E. [Department of Chemistry, N.P. Ogarev Mordovian State University, Saransk 430000 (Russian Federation)

    2007-03-01

    We report a model calculation of the chemisorption energies {delta}E{sub ads} of single fluorine atoms on the outer surface of zigzag single-walled carbon nanotubes (Z-SWCNTs) (p,0) with p ranging from 11 to 21. A simplified model based on an effective-mass theory is adopted to describe the electronic structure of the nanotubes. Chemisorption is treated within the Anderson-Newns approach, which takes account of Coulomb interaction between adsorbate electrons. Considering adsorption of an adatom directly on top of a surface carbon atom, we find that in the case of a fluorine atom bonded to the sidewall of the nanotubes, the absolute values of {delta}E{sub ads} are in the range 4.3-5.5eV for Z-SWCNTs with typical diameters of 0.86-1.66nm, larger {delta}E{sub ads} values being associated with semiconducting tubes. For the latter ones, {delta}E{sub ads} decreases rather significantly as the radius R of the tubes increases, tending towards the ''infinite'' radius graphene case, whereas for metallic tubes {delta}E{sub ads} slightly increases with increasing R. The localized acceptor states induced by a fluorine atom in the band gap of the semiconducting tubes are found to be responsible for such difference in the behaviour of {delta}E{sub ads} for the two above-mentioned types of tubes. The results obtained shed light on the possible mechanism of the atomic fluorine adsorption-induced hole-doping of the semiconducting tubes, which might significantly affect the transport properties of these tubes.

  15. Synthesis and Photoluminescence Property of Silicon Carbide Nanowires Via Carbothermic Reduction of Silica

    OpenAIRE

    Luo Xiaogang; Ma Wenhui; Zhou Yang; Liu Dachun; Yang Bin; Dai Yongnian

    2009-01-01

    Abstract Silicon carbide nanowires have been synthesized at 1400 °C by carbothermic reduction of silica with bamboo carbon under normal atmosphere pressure without metallic catalyst. X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy and Fourier transformed infrared spectroscopy were used to characterize the silicon carbide nanowires. The results show that the silicon carbide nanowires have a core–shell structure and gr...

  16. Nanowires for energy generation

    International Nuclear Information System (INIS)

    As a result of their morphology, nanowires bring new properties and the promise of performance for a range of electronic devices. This review looks into the properties of nanowires and the multiple ways in which they have been exploited for energy generation, from photovoltaics to piezoelectric generators. (paper)

  17. Nanowire Photovoltaic Devices

    Science.gov (United States)

    Forbes, David

    2015-01-01

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

  18. Metallic nanowire networks

    Science.gov (United States)

    Song, Yujiang; Shelnutt, John A.

    2012-11-06

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

  19. 碳泡沫衬底上氮化铝纳米线的生长及其光致发光特性研究%Growth and photoluminescence character research of aluminum nitride nanowires upon carbon foam substrate

    Institute of Scientific and Technical Information of China (English)

    程赛; 吕惠民; 石振海; 崔静雅

    2012-01-01

    To simplify preparation process of A1N/C composite foam, A1N nanomaterials are prepared via double decomposition reaction and then 800 °C annealing process to recrystallize hexagonal A1N (h-A1N) nanowires on carbon foam substrate. Fore the morphology characterization it follows that, h-A1N nanowires with straight cylindrical morphology grow along the [001]direction on carbon micro- spheres surface and are about 50 nm in diameter and several micrometers in length. Meanwhile, the growth mechanism of nanowire is interpreted as vapor-liquid-solid(VLS) process. The photoluminescence(PL) spectrum of as-prepared sample is also researched, and the results show that a sharp photoluminescence peak appears at 423 nm and shifts toward the red side with temperature increasing. The peak is attributed to the transition luminescence, owing to the substitution of C for N impurity energy level. The sample has good PL character in purple light band and is potential to be used in the photodetector field.%为了简化A1N/C复合泡沫材料的制备流程,本文采用复分解反应法制备A1N纳米材料,并通过800°C退火处理使其在碳泡沫衬底上重结晶为六方相A1N纳米线.通过形貌表征测试,纳米线为表面光滑的长直形圆柱体,直径约50nm,长度10μm以上,在碳微球表面沿[001]方向生长.同时,采用VLS生长机理对纳米线的生长进行了解释.对样品光致发光谱的研究表明。中心波长423nm处存在一尖锐发光峰且随温度升高发生明显的红移现象,系C替N杂质能级跃迁发光所致.样品在紫光波段具有良好的光致发光特性,有望应用于光探测器领域.

  20. Highly ordered ultralong magnetic nanowires wrapped in stacked graphene layers

    Directory of Open Access Journals (Sweden)

    Abdel-Aziz El Mel

    2012-12-01

    Full Text Available We report on the synthesis and magnetic characterization of ultralong (1 cm arrays of highly ordered coaxial nanowires with nickel cores and graphene stacking shells (also known as metal-filled carbon nanotubes. Carbon-containing nickel nanowires are first grown on a nanograted surface by magnetron sputtering. Then, a post-annealing treatment favors the metal-catalyzed crystallization of carbon into stacked graphene layers rolled around the nickel cores. The observed uniaxial magnetic anisotropy field oriented along the nanowire axis is an indication that the shape anisotropy dominates the dipolar coupling between the wires. We further show that the thermal treatment induces a decrease in the coercivity of the nanowire arrays. This reflects an enhancement of the quality of the nickel nanowires after annealing attributed to a decrease of the roughness of the nickel surface and to a reduction of the defect density. This new type of graphene–ferromagnetic-metal nanowire appears to be an interesting building block for spintronic applications.

  1. Semiconductor nanowire lasers

    Science.gov (United States)

    Eaton, Samuel W.; Fu, Anthony; Wong, Andrew B.; Ning, Cun-Zheng; Yang, Peidong

    2016-06-01

    The discovery and continued development of the laser has revolutionized both science and industry. The advent of miniaturized, semiconductor lasers has made this technology an integral part of everyday life. Exciting research continues with a new focus on nanowire lasers because of their great potential in the field of optoelectronics. In this Review, we explore the latest advancements in the development of nanowire lasers and offer our perspective on future improvements and trends. We discuss fundamental material considerations and the latest, most effective materials for nanowire lasers. A discussion of novel cavity designs and amplification methods is followed by some of the latest work on surface plasmon polariton nanowire lasers. Finally, exciting new reports of electrically pumped nanowire lasers with the potential for integrated optoelectronic applications are described.

  2. Printing nanotube/nanowire for flexible microsystems

    Science.gov (United States)

    Tortorich, Ryan P.; Choi, Jin-Woo

    2014-04-01

    Printing has become an emerging manufacturing technology for mechanics, electronics, and consumer products. Additionally, both nanotubes and nanowires have recently been used as materials for sensors and electrodes due to their unique electrical and mechanical properties. Printed electrodes and conductive traces particularly offer versatility of fabricating low-cost, disposable, and flexible electrical devices and microsystems. While various printing methods such as screen printing have been conventional methods for printing conductive traces and electrodes, inkjet printing has recently attracted great attention due to its unique advantages including no template requirement, rapid printing at low cost, on-demand printing capability, and precise control of the printed material. Computer generated conductive traces or electrode patterns can simply be printed on a thin film substrate with proper conductive ink consisting of nanotubes or nanowires. However, in order to develop nanotube or nanowire ink, there are a few challenges that need to be addressed. The most difficult obstacle to overcome is that of nanotube/nanowire dispersion within a solution. Other challenges include adjusting surface tension and controlling viscosity of the ink as well as treating the surface of the printing substrate. In an attempt to pave the way for nanomaterial inkjet printing, we present a method for preparing carbon nanotube ink as well as its printing technique. A fully printed electrochemical sensor using inkjet-printed carbon nanotube electrodes is also demonstrated as an example of the possibilities for this technology.

  3. Effects of surface atomistic modification on mechanical properties of gold nanowires

    Science.gov (United States)

    Sun, Xiao-Yu; Xu, Yuanjie; Wang, Gang-Feng; Gu, Yuantong; Feng, Xi-Qiao

    2015-09-01

    Modulation of the physical and mechanical properties of nanowires is a challenging issue for their technological applications. In this paper, we investigate the effects of surface modification on the mechanical properties of gold nanowires by performing molecular dynamics simulations. It is found that by modifying a small density of silver atoms to the surface of a gold nanowire, the residual surface stress state can be altered, rendering a great improvement of its plastic yield strength. This finding is in good agreement with experimental measurements. The underlying physical mechanisms are analyzed by a core-shell nanowire model. The results are helpful for the design and optimization of advanced nanomaterial with superior mechanical properties.

  4. Computational design of organometallic oligomers featuring 1,3-metal-carbon bonding and planar tetracoordinate carbon atoms.

    Science.gov (United States)

    Zhao, Xue-Feng; Yuan, Cai-Xia; Wang, Xiang; Li, Jia-Jia; Wu, Yan-Bo; Wang, Xiaotai

    2016-01-15

    Density functional theory computations (B3LYP) have been used to explore the chemistry of titanium-aromatic carbon "edge complexes" with 1,3-metal-carbon (1,3-MC) bonding between Ti and planar tetracoordinate Cβ . The titanium-coordinated, end-capping chlorides are replaced with OH or SH groups to afford two series of difunctional monomers that can undergo condensation to form oxide- and sulfide-bridged oligomers. The sulfide-linked oligomers have less molecular strain and are more exergonic than the corresponding oxide-linked oligomers. The HOMO-LUMO gap of the oligomers varies with their composition and decreases with growing oligomer chain. This theoretical study is intended to enrich 1,3-MC bonding and planar tetracoordinate carbon chemistry and provide interesting ideas to experimentalists. Organometallic complexes with the TiE2 (E = OH and SH) decoration on the edge of aromatic hydrocarbons have been computationally designed, which feature 1,3-metal-carbon (1,3-MC) bonding between titanium and planar tetracoordinate β-carbon. Condensation of these difunctional monomers by eliminating small molecules (H2O and H2S) produce chain-like oligomers. The HOMO-LUMO gaps of the oligomers decreases with growing oligomer chain, a trend that suggests possible semiconductor properties for oligomers with longer chains. PMID:26399226

  5. Erosion of Carbon-based spacecraft structures in LEO by Atomic Oxygen

    DEFF Research Database (Denmark)

    Jørgensen, John Leif

    1998-01-01

    Atomic oxygen is constantly generated on the topside of the atmosphere by ionizing radiation. The ionizing solar radiation, UV and particles, will on impact dissociate molecular oxygen to atomic oxygen. However, due to the ratio between the UV and the particle flux from the sun, and due to...... comparable cross sections for the reactions, the UV generation largely dominates. Atomic oxygen is very reactive, and will enter into chemical reactions with most materials. This is especially true for earth orbiting spacecraft structures, as the orbital velocity corresponds to a kinetic energy released at...

  6. Low-Power Nanowire Circuits and Transistors

    OpenAIRE

    Dey, Anil

    2013-01-01

    This thesis explores several novel material systems and innovative device concepts enabled by nanowire technology. State-of-the-art fabrication techniques such as electron beam lithography and atomic layer deposition are utilized to achieve high control and quality in the device fabrication. The devices in this thesis are based on two main types of design geometries, lateral and vertical, each of which have strengths and weaknesses. The first part of the thesis describes the goals of future m...

  7. Nanowires and nanobelts, v.2 nanowires and nanobelts of functional materials

    CERN Document Server

    Wang, Zhong Lin

    2010-01-01

    Nanowires, nanobelts, nanoribbons, nanorods ..., are a new class of quasi-one-dimensional materials that have been attracting a great research interest in the last few years. These non-carbon based materials have been demonstrated to exhibit superior electrical, optical, mechanical and thermal properties, and can be used as fundamental building blocks for nano-scale science and technology, ranging from chemical and biological sensors, field effect transistors to logic circuits. Nanocircuits built using semiconductor nanowires demonstrated were declared a ""breakthrough in science"" by Science

  8. La2−xSrxCuO4 superconductor nanowire devices

    International Nuclear Information System (INIS)

    Highlights: • We grew La2−xSrxCuO4 (LSCO) films using ALL-MBE. • LSCO films were characterized by Atomic Force Microscopy and mutual inductance measurements post-growth. • Single nanowire LSCO devices were fabricated using high-resolution electron beam lithography. • Electrical transport measurements were used to characterize LSCO nanowire properties. - Abstract: La2−xSrxCuO4 nanowire devices have been fabricated and characterized using electrical transport measurements. Nanowires with widths down to 80 nm are patterned using high-resolution electron beam lithography. However, the narrowest nanowires show incomplete superconducting transitions with some residual resistance at T = 4 K. Here, we report on the refinement of the fabrication process to achieve narrower nanowire devices with complete superconducting transitions, opening the path to the study of novel physics arising from dimension-limited superconductivity on the nanoscale

  9. Effects of surface atomistic modification on mechanical properties of gold nanowires

    International Nuclear Information System (INIS)

    Highlights: • Molecular dynamics simulations of surface modification effect of Au nanowires. • Surface modification can greatly affect the mechanical properties of nanowires. • Core–shell model is used to elucidate the effect of residual surface stress. - Abstract: Modulation of the physical and mechanical properties of nanowires is a challenging issue for their technological applications. In this paper, we investigate the effects of surface modification on the mechanical properties of gold nanowires by performing molecular dynamics simulations. It is found that by modifying a small density of silver atoms to the surface of a gold nanowire, the residual surface stress state can be altered, rendering a great improvement of its plastic yield strength. This finding is in good agreement with experimental measurements. The underlying physical mechanisms are analyzed by a core–shell nanowire model. The results are helpful for the design and optimization of advanced nanomaterial with superior mechanical properties

  10. Cold welding of copper nanowires with single-crystalline and twinned structures: A comparison study

    Science.gov (United States)

    Huang, Rao; Shao, Gui-Fang; Wen, Yu-Hua

    2016-09-01

    In this article, molecular simulations were adopted to explore the cold welding processes of copper nanowires with both single-crystalline and fivefold twinned structures. It was verified that the twinned nanowires exhibited enhanced strength but lowered elastic limit and ductility. Both nanowires could be successfully welded through rather small loadings, although their stress-strain responses toward compression were different. Meanwhile, more stress was accumulated in the twinned nanowire due to repulsive force of the twin boundaries against the nucleation and motions of dislocations. Moreover, by characterizing the structure evolutions in the welding process, it can be ascertained that perfect atomic order was finally built at the weld region in both nanowires. This comparison study will be of great importance to future mechanical processing of metallic nanowires.

  11. The formation of pentagonal Ni nanowires: dependence on the stretching direction and the temperature

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Mochales, P. [Departamento de Fisica de la Materia Condensada, Facultad de Ciencias, Universidad Autonoma de Madrid, c/Francisco Tomas y Valiente 7, Cantoblanco, 28049 Madrid (Spain); Paredes, R. [Centro de Fisica, Instituto Venezolano de Investigaciones Cientificas, Apto. 20632, Caracas 1020A (Venezuela); Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, c/Sor Juana Ines de la Cruz 3, Cantoblanco, 28049 Madrid (Spain); Pelaez, S.; Serena, P.A. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, c/Sor Juana Ines de la Cruz 3, Cantoblanco, 28049 Madrid (Spain)

    2008-06-15

    We have constructed computational minimum cross-section histograms that statistically unveil the presence of preferred configuration during the breakage of Ni nanowires. The computed histograms showed strong dependence on the nanowire stretching direction. For the[100] and[110] stretching directions we have observed a very large peak associated to a minimum cross-section of 5 atoms. We have confirmed that the configurations that contribute to this peak are staggered pentagonal nanowires. We have found that the formation of these nanowires is enhanced by increasing the temperature up to 550 K. At higher temperatures, the formation of pentagonal nanowires declines due to the competence against the nanowire melting processes. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Effects of surface atomistic modification on mechanical properties of gold nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Xiao-Yu [AML and CNMM, Department of Engineering Mechanics, Tsinghua University, Beijing 100084 (China); Department of Engineering Mechanics, School of Civil Engineering, Wuhan University, Wuhan 430072 (China); Xu, Yuanjie [Department of Engineering Mechanics, School of Civil Engineering, Wuhan University, Wuhan 430072 (China); Wang, Gang-Feng [Department of Engineering Mechanics, Xi' an Jiaotong University, Xi' an 710049 (China); Gu, Yuantong [School of Chemistry, Physics, and Mechanical Engineering, Queensland University of Technology, Brisbane 4001 (Australia); Feng, Xi-Qiao, E-mail: fengxq@tsinghua.edu.cn [AML and CNMM, Department of Engineering Mechanics, Tsinghua University, Beijing 100084 (China)

    2015-09-18

    Highlights: • Molecular dynamics simulations of surface modification effect of Au nanowires. • Surface modification can greatly affect the mechanical properties of nanowires. • Core–shell model is used to elucidate the effect of residual surface stress. - Abstract: Modulation of the physical and mechanical properties of nanowires is a challenging issue for their technological applications. In this paper, we investigate the effects of surface modification on the mechanical properties of gold nanowires by performing molecular dynamics simulations. It is found that by modifying a small density of silver atoms to the surface of a gold nanowire, the residual surface stress state can be altered, rendering a great improvement of its plastic yield strength. This finding is in good agreement with experimental measurements. The underlying physical mechanisms are analyzed by a core–shell nanowire model. The results are helpful for the design and optimization of advanced nanomaterial with superior mechanical properties.

  13. Magnetization reversal in permalloy ferromagnetic nanowires investigated with magnetoresistance measurements

    Science.gov (United States)

    Oliveira, A. B.; Rezende, S. M.; Azevedo, A.

    2008-07-01

    The magnetization reversal process in single Permalloy (Ni81Fe19) nanowires has been investigated by magnetoresistance measurements as a function of the angle between the applied field and the wire direction. The Permalloy nanostructures fabricated on an ultrathin film by atomic force microscopy consist of two large rectangular pads connected by a nanowire with the shape of a long thin narrow tape. For each field direction in the plane of the film the dependence of the magnetoresistance on the field value exhibits two main contributions: one from the pads and one from the nanowire. The contribution from the pads is due to a usual anisotropic magnetoresistance characteristic of coherent magnetization rotation, whereas the contribution from the nanowire is an abrupt transition at the switching field. The dependence of the switching field on the in-plane field angle is quantitatively described by a model of nucleation field with the buckling magnetization rotation mode.

  14. Preparation and Characterization of Amorphous Silicon Oxide Nanowires

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Large-scale amorphous silicon nanowires (SiNWs) with a diameter about 100 nm and a length of dozens of micrometers on silicon wafers were synthesized by thermal evaporation of silicon monoxide (SiO).Scanning electron microscope (SEM) and transmission electron microscope (TEM) observations show that the silicon nanowires are smooth.Selected area electron diffraction (SAED) shows that the silicon nanowires are amorphous and energy-dispersive X-ray spectroscopy (EDS) indicates that the nanowires have the composition of Si and O elements in an atomic ratio of 1:2, their composition approximates that of SiO2.SiO is considered to be used as a Si sources to produce SiNWs.We conclude that the growth mechanism is closely related to the defect structure and silicon monoxide followed by growth through an oxide-assisted vapor-solid reaction.

  15. Hydrogen passivation effects on carbon dangling bond defects accompanying a nearby hydrogen atom in p-type Cd diamond

    Energy Technology Data Exchange (ETDEWEB)

    Mizuochi, N. [Graduate School of Library, Information and Media Studies, University of Tsukuba, 1-2 Kasuga, Tsukuba-City, Ibaraki 305-8550 (Japan) and Diamond Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan) and CREST JST - Japan Science and Technology (Japan)]. E-mail: mizuochi@slis.tsukuba.ac.jp; Ogura, M. [Diamond Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); CREST JST (Japan Science and Technology) (Japan); Isoya, J. [Graduate School of Library, Information and Media Studies, University of Tsukuba, 1-2 Kasuga, Tsukuba-City, Ibaraki 305-8550 (Japan); Diamond Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Okushi, H. [Diamond Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); CREST JST (Japan Science and Technology) (Japan); Yamasaki, S. [Diamond Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); CREST JST (Japan Science and Technology) (Japan); Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, 305-8577 (Japan)

    2006-04-01

    Hydrogen (deuterium) passivation effects on carbon dangling bond defects accompanying a nearby hydrogen atom (H1') in boron-doped Cd homoepitaxial diamond films were investigated by electron paramagnetic resonance (EPR). Deuterium was incorporated into the films using microwave deuterium plasma at 673 K for 22 h. Incorporation of deuterium was confirmed by the passivation of boron acceptors. From the comparison of the EPR signal intensity before and after the deuterium plasma exposure, it was revealed that H1' could not be passivated by the present condition. From these, the high stability of H1' was indicated.

  16. Surface potential investigation on single wall carbon nanotubes by Kelvin probe force microscopy and atomic force microscope potentiometry

    International Nuclear Information System (INIS)

    Surface potentials of single wall carbon nanotubes (SWNTs) connecting two metallic electrodes have been investigated by both Kelvin probe force microscopy (KFM) and atomic force microscope potentiometry (AFMP). By comparing the surface potential measurements obtained by both methods, we also studied the major factors affecting the potential measurements of the SWNTs, such as the surroundings, stray electric fields, and the effect of the AFM tip size, which can be larger than the SWNT diameter. In this study, we used KFM based on non-contact AFM and AFMP using the point-by-point contact mode in which the AFM tip worked as a voltage probe

  17. Use of dielectrophoresis in the fabrication of an atomic force microscope tip with a carbon nanotube: experimental investigation

    International Nuclear Information System (INIS)

    We have developed a method for fabricating a carbon nanotube (CNT) tip for an atomic force microscope (AFM). To attach a CNT to the tip apex, we used dielectrophoresis (DEP) with a non-uniform electric field. After inserting a drop of CNT solution and applying an AC electric field between a metal-coated AFM tip and an electrode plate, CNTs were deposited directly on the tip so that they protruded from the tip. We fabricated tips with individual multi-walled carbon nanotubes and found the experimental conditions that gave high fabrication yields. From AFM measurements of the nanoscale anodized aluminium oxide (AAO) structure, we have shown that a CNT tip assembled using DEP can produce high-resolution images and have a good wear resistance

  18. Investigation of Nucleation Mechanism and Tapering Observed in ZnO Nanowire Growth by Carbothermal Reduction Technique

    Directory of Open Access Journals (Sweden)

    Oye Michael

    2011-01-01

    Full Text Available Abstract ZnO nanowire nucleation mechanism and initial stages of nanowire growth using the carbothermal reduction technique are studied confirming the involvement of the catalyst at the tip in the growth process. Role of the Au catalyst is further confirmed when the tapering observed in the nanowires can be explained by the change in the shape of the catalyst causing a variation of the contact area at the liquid–solid interface of the nanowires. The rate of decrease in nanowire diameter with length on the average is found to be 0.36 nm/s and this rate is larger near the base. Variation in the ZnO nanowire diameter with length is further explained on the basis of the rate at which Zn atoms are supplied as well as the droplet stability at the high flow rates and temperature. Further, saw-tooth faceting is noticed in tapered nanowires, and the formation is analyzed crystallographically.

  19. Operando atomic structure and active sites of TiO2(110)-supported gold nanoparticles during carbon monoxide oxidation.

    Science.gov (United States)

    Saint-Lager, Marie-Claire; Laoufi, Issam; Bailly, Aude

    2013-01-01

    It is well known that gold nanoparticles supported on TiO2 act as a catalyst for CO oxidation, even below room temperature. Despite extensive studies, the origin of this catalytic activity remains under debate. Indeed, when the particle size decreases, many changes may occur; thus modifying the nanoparticles' electronic properties and consequently their catalytic performances. Thanks to a state-of-the-art home-developed setup, model catalysts can be prepared in ultra-high vacuum and their morphology then studied in operando conditions by Grazing Incidence Small Angle X-ray Scattering, as well as their atomic structure by Grazing Incidence X-ray Diffraction as a function of their catalytic activity. We previously reported on the existence of a catalytic activity maximum observed for three-dimensional gold nanoparticles with a diameter of 2-3 nm and a height of 6-7 atomic planes. In the present work we correlate this size dependence of the catalytic activity to the nanoparticles' atomic structure. We show that even when their size decreases below the optimum diameter, the gold nanoparticles keep the face-centered cubic structure characteristic of bulk gold. Nevertheless, for these smallest nanoparticles, the lattice parameter presents anisotropic strains with a larger contraction in the direction perpendicular to the surface. Moreover a careful analysis of the atomic-scale morphology around the catalytic activity maximum tends to evidence the role of sites with a specific geometry at the interface between the nanoparticles and the substrate. This argues for models where atoms at the interface periphery act as catalytically active sites for carbon monoxide oxidation. PMID:24015583

  20. Fabricating nanoscale DNA patterns with gold nanowires.

    Science.gov (United States)

    Chen, Yulin; Kung, Sheng-Chin; Taggart, David K; Halpern, Aaron R; Penner, Reginald M; Corn, Robert M

    2010-04-15

    Surface patterns of single-stranded DNA (ssDNA) consisting of nanoscale lines as thin as 40 nm were fabricated on polymer substrates for nanotechnology and bioaffinity sensing applications. Large scale arrays (with areas up to 4 cm(2)) of ssDNA "nanolines" were created on streptavidin-coated polymer (PDMS) surfaces by transferring biotinylated ssDNA from a master pattern of gold nanowires attached to a glass substrate. The gold nano-wires were first formed on the glass substrate by the process of lithographically patterned nanowire electrodeposition (LPNE), and then "inked" with biotinylated ssDNA by hybridization adsorption to a thiol-modified ssDNA monolayer attached to the gold nanowires. The transferred ssDNA nanolines were capable of hybridizing with ssDNA from solution to form double-stranded DNA (dsDNA) patterns; a combination of fluorescence and atomic force microscopy (AFM) measurements were used to characterize the dsDNA nanoline arrays. To demonstrate the utility of these surfaces for biosensing, optical diffraction measurements of the hybridization adsorption of DNA-coated gold nanoparticles onto the ssDNA nanoline arrays were used to detect a specific target sequence of unlabeled ssDNA in solution. PMID:20337428

  1. Silicon nanowire hybrid photovoltaics

    KAUST Repository

    Garnett, Erik C.

    2010-06-01

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

  2. Programmability of nanowire networks

    Science.gov (United States)

    Bellew, A. T.; Bell, A. P.; McCarthy, E. K.; Fairfield, J. A.; Boland, J. J.

    2014-07-01

    Electrical connectivity in networks of nanoscale junctions must be better understood if nanowire devices are to be scaled up from single wires to functional material systems. We show that the natural connectivity behaviour found in random nanowire networks presents a new paradigm for creating multi-functional, programmable materials. In devices made from networks of Ni/NiO core-shell nanowires at different length scales, we discover the emergence of distinct behavioural regimes when networks are electrically stressed. We show that a small network, with few nanowire-nanowire junctions, acts as a unipolar resistive switch, demonstrating very high ON/OFF current ratios (>105). However, large networks of nanowires distribute an applied bias across a large number of junctions, and thus respond not by switching but instead by evolving connectivity. We demonstrate that these emergent properties lead to fault-tolerant materials whose resistance may be tuned, and which are capable of adaptively reconfiguring under stress. By combining these two behavioural regimes, we demonstrate that the same nanowire network may be programmed to act both as a metallic interconnect, and a resistive switch device with high ON/OFF ratio. These results enable the fabrication of programmable, multi-functional materials from random nanowire networks.Electrical connectivity in networks of nanoscale junctions must be better understood if nanowire devices are to be scaled up from single wires to functional material systems. We show that the natural connectivity behaviour found in random nanowire networks presents a new paradigm for creating multi-functional, programmable materials. In devices made from networks of Ni/NiO core-shell nanowires at different length scales, we discover the emergence of distinct behavioural regimes when networks are electrically stressed. We show that a small network, with few nanowire-nanowire junctions, acts as a unipolar resistive switch, demonstrating very high ON

  3. Ab initio simulations on rutile-based titania nanowires

    Science.gov (United States)

    Zhukovskii, Yu F.; Evarestov, R. A.

    2012-08-01

    The rod symmetry groups for monoperiodic (1D) nanostructures have been applied for construction of models for bulk-like TiO2 nanowires (NWs) cut from a rutile-based 3D crystal along the chosen [001] and [110] directions of crystallographic axes. In this study, we have considered nanowires described by both the Ti-atom centered rotation axes as well as the hollow site centered axes passing through the interstitial positions between the Ti and O atoms closest to the axes. The most stable [001]-oriented TiO2 NWs with rhombic cross sections are found to display the energetically preferable {110} facets only while the nanowires with quasi-square sections across the [110] axis are formed by the alternating { 1bar 10 } and {001} facets. For simulations on rutile-based nanowires possessing different diameters for each NW type, we have performed large-scale ab initio Density Functional Theory (DFT) and hybrid DFT-Hartree Fock (DFT-HF) calculations with total geometry optimization within the Generalized Gradient Approximation (GGA) in the form of the Perdew-Becke-Ernzenhof (PBE) exchange-correlation functionals (PBE and PBE0, respectively), using the formalism of linear combination of localized atomic functions (LCAO). We have simulated both structural and electronic properties of TiO2 NWs depending both on orientation and position of symmetry axes as well as on diameter and morphology of nanowires.

  4. Partially oxidized atomic cobalt layers for carbon dioxide electroreduction to liquid fuel

    Science.gov (United States)

    Gao, Shan; Lin, Yue; Jiao, Xingchen; Sun, Yongfu; Luo, Qiquan; Zhang, Wenhua; Li, Dianqi; Yang, Jinlong; Xie, Yi

    2016-01-01

    Electroreduction of CO2 into useful fuels, especially if driven by renewable energy, represents a potentially ‘clean’ strategy for replacing fossil feedstocks and dealing with increasing CO2 emissions and their adverse effects on climate. The critical bottleneck lies in activating CO2 into the CO2•- radical anion or other intermediates that can be converted further, as the activation usually requires impractically high overpotentials. Recently, electrocatalysts based on oxide-derived metal nanostructures have been shown to enable CO2 reduction at low overpotentials. However, it remains unclear how the electrocatalytic activity of these metals is influenced by their native oxides, mainly because microstructural features such as interfaces and defects influence CO2 reduction activity yet are difficult to control. To evaluate the role of the two different catalytic sites, here we fabricate two kinds of four-atom-thick layers: pure cobalt metal, and co-existing domains of cobalt metal and cobalt oxide. Cobalt mainly produces formate (HCOO-) during CO2 electroreduction; we find that surface cobalt atoms of the atomically thin layers have higher intrinsic activity and selectivity towards formate production, at lower overpotentials, than do surface cobalt atoms on bulk samples. Partial oxidation of the atomic layers further increases their intrinsic activity, allowing us to realize stable current densities of about 10 milliamperes per square centimetre over 40 hours, with approximately 90 per cent formate selectivity at an overpotential of only 0.24 volts, which outperforms previously reported metal or metal oxide electrodes evaluated under comparable conditions. The correct morphology and oxidation state can thus transform a material from one considered nearly non-catalytic for the CO2 electroreduction reaction into an active catalyst. These findings point to new opportunities for manipulating and improving the CO2 electroreduction properties of metal systems

  5. Negative ion productions in high velocity collision between small carbon clusters and Helium atom target

    International Nuclear Information System (INIS)

    We measured absolute double capture cross section of Cn+ ions (n=1,5) colliding, at 2.3 and 2.6 a.u velocities, with an Helium target atom and the branching ratios of fragmentation of the so formed electronically excited anions Cn−*. We also measured absolute cross section for the electronic attachment on neutral Cn clusters colliding at same velocities with He atom. This is to our knowledge the first measurement of neutral-neutral charge exchange in high velocity collision.

  6. Characterization of atomic structure of oxide films on carbon steel in simulated concrete pore solutions using EELS

    International Nuclear Information System (INIS)

    The atomic structure of oxide films formed on carbon steel that are exposed to highly alkaline simulated concrete pore solutions was investigated using Electron Energy Loss Spectroscopy (EELS). In particular, the effect of chloride exposure on film structure was studied in two types of simulated pore solutions: saturated calcium hydroxide (CH) and a solution prepared to represent typical concrete pore solutions (CP). It was shown that the films that form on carbon steel in simulated concrete pore solutions contained three indistinct layers. The inner oxide film had a structure similar to that of FeIIO, which is known to be unstable in the presence of chlorides. The outer oxide film mainly resembled Fe3O4 (FeIIO·Fe2IIIO3) in the CH solution and α-Fe2IIIO3/Fe3O4 in the CP solution. The composition of the transition layer between the inner and outer layers of the oxide film was mainly composed of Fe3O4 (FeIIO·Fe2IIIO3). In the presence of chloride, the relative amount of the FeIII/FeII increased, confirming that chlorides induce valence state transformation of oxides from FeII to FeIII, and the difference between the atomic structures of oxide film layers diminished.

  7. Carbon Dioxide Activation by Scandium Atoms and Scandium Monoxide Molecules: Formation and Spectroscopic Characterization of ScCO3 and OCScCO3 in Solid Neon.

    Science.gov (United States)

    Zhang, Qingnan; Qu, Hui; Chen, Mohua; Zhou, Mingfei

    2016-01-28

    The reactions of carbon dioxide with scandium monoxide molecules and scandium atoms are investigated using matrix isolation infrared spectroscopy in solid neon. The species formed are identified by the effects of isotopic substitution on their infrared spectra as well as density functional calculations. The results show that the ground state ScO molecule reacts with carbon dioxide to form the carbonate complex ScCO3 spontaneously on annealing. The ground state Sc atom reacts with two carbon dioxide molecules to give the carbonate carbonyl complex OCScCO3 via the previously reported OScCO insertion intermediate on annealing. The observation of these spontaneous reactions is consistent with theoretical predictions that both the Sc + 2CO2 → OCScCO3 and ScO + CO2 → ScCO3 reactions are thermodynamically exothermic and are kinetically facile, requiring little or no activation energy. PMID:26738558

  8. Nanowelding configuration between carbon nanotubes in axial direction

    International Nuclear Information System (INIS)

    Highlights: ► Nanowelding process could be accomplished at a lower temperature than the melting point of the bulk solder. ► CNTs are connected with solder joints of nodule shape. ► Some silver atoms are captured and dragged into carbon nanotube to form the core filling structures of nanowires. ► Some silver atoms diffuse along the outer walls of SWNTs with the dominant mechanism of capillary wetting. - Abstract: Interconnect technology of carbon nanotubes (CNTs) is essential for functional devices. However, difficulty in the fabrication of the interface between carbon nanotube (CNT) and CNT in axial direction, hindered the quality of connection and practical applications of electrical devices. Also, investigation of dynamic evolution of connection configuration about nanowelding is still lacking. In order to analyze the nanowelding configuration between CNTs in axial direction, the different connection cases are investigated using molecular dynamics simulation. Simulation results show that the nanowelding process could be accomplished at a lower temperature than the melting point of the bulk solder and the CNTs are connected with solder joints of nodule shape. It is also found that metal atoms are captured and dragged into nanotube to form the core filling structures of nanowires during nanowelding. Also, the connection configuration shows that Ag atoms diffuse along the outer walls of SWNTs with the dominant mechanism of capillary wetting, which would increase the contact length to improve the mechanical strength.

  9. Biofunctionalized Magnetic Nanowires

    KAUST Repository

    Kosel, Jurgen

    2013-12-19

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

  10. Scaling Law in Carbon Nanotube Electromechanical Devices

    Science.gov (United States)

    Lefèvre, R.; Goffman, M. F.; Derycke, V.; Miko, C.; Forró, L.; Bourgoin, J. P.; Hesto, P.

    2005-10-01

    We report a method for probing electromechanical properties of multiwalled carbon nanotubes (CNTs). This method is based on atomic force microscopy measurements on a doubly clamped suspended CNT electrostatically deflected by a gate electrode. We measure the maximum deflection as a function of the applied gate voltage. Data from different CNTs scale into an universal curve within the experimental accuracy, in agreement with a continuum model prediction. This method and the general validity of the scaling law constitute a very useful tool for designing actuators and in general conducting nanowire-based nanoelectromechanical systems.

  11. 3D scaffolds from vertically aligned carbon nanotubes/poly(methyl methacrylate) composites via atom transfer radical polymerization

    International Nuclear Information System (INIS)

    Vertically aligned carbon nanotubes (VACNTs) synthesized by Thermal Chemical Vapour Deposition (TCVD) were modified using an Ar:O2 (97:3) plasma to generate oxygen-containing functional groups on the surface for subsequent modification. X-ray photo-emission spectroscopy (XPS) and micro-Raman analyses confirmed the grafting of those functional groups onto the surface of the nanotubes as well as the removal of amorphous carbon produced and deposited on the VACNT forests during the CVD process. The plasma treated VACNT forests were further modified with 2-bromo-2-methylpropionyl bromide, an atom transfer radical polymerization (ATRP) initiator, to grow poly(methyl methacrylate) (PMMA) chains from the forests via ATRP. Scanning transmission electron microscopy (STEM) of the ensuing VACNT/PMMA composites confirmed the coating of the nanotube forests with the PMMA polymer. 3D scaffolds of polymeric composites with honeycomb like structure were then obtained. Compressive tests have shown that the VACNT/PMMA composite has higher compressive strength than the pristine forest. - Highlights: • Vertically aligned carbon nanotubes (VACNTs) were synthesized and plasma modified. • X-ray photo-emission and Raman spectroscopies confirmed the VACNTs modification. • Poly(methyl methacrylate) chains were grown via ATRP from the VACNTs. • STEM of the VACNT/PMMA composites confirmed that PMMA surrounds the nanotubes. • VACNT/PMMA composite has higher compressive strength compared to the pristine forest

  12. 3D scaffolds from vertically aligned carbon nanotubes/poly(methyl methacrylate) composites via atom transfer radical polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Tebikachew, Behabtu; Magina, Sandra [CICECO, Department of Chemistry, University of Aveiro (Portugal); Mata, Diogo; Oliveira, Filipe J.; Silva, Rui F. [CICECO, Department of Materials and Ceramic Engineering, University of Aveiro (Portugal); Barros-Timmons, Ana, E-mail: anabarros@ua.pt [CICECO, Department of Chemistry, University of Aveiro (Portugal)

    2015-01-15

    Vertically aligned carbon nanotubes (VACNTs) synthesized by Thermal Chemical Vapour Deposition (TCVD) were modified using an Ar:O{sub 2} (97:3) plasma to generate oxygen-containing functional groups on the surface for subsequent modification. X-ray photo-emission spectroscopy (XPS) and micro-Raman analyses confirmed the grafting of those functional groups onto the surface of the nanotubes as well as the removal of amorphous carbon produced and deposited on the VACNT forests during the CVD process. The plasma treated VACNT forests were further modified with 2-bromo-2-methylpropionyl bromide, an atom transfer radical polymerization (ATRP) initiator, to grow poly(methyl methacrylate) (PMMA) chains from the forests via ATRP. Scanning transmission electron microscopy (STEM) of the ensuing VACNT/PMMA composites confirmed the coating of the nanotube forests with the PMMA polymer. 3D scaffolds of polymeric composites with honeycomb like structure were then obtained. Compressive tests have shown that the VACNT/PMMA composite has higher compressive strength than the pristine forest. - Highlights: • Vertically aligned carbon nanotubes (VACNTs) were synthesized and plasma modified. • X-ray photo-emission and Raman spectroscopies confirmed the VACNTs modification. • Poly(methyl methacrylate) chains were grown via ATRP from the VACNTs. • STEM of the VACNT/PMMA composites confirmed that PMMA surrounds the nanotubes. • VACNT/PMMA composite has higher compressive strength compared to the pristine forest.

  13. Nanowire structures and electrical devices

    Science.gov (United States)

    Bezryadin, Alexey; Remeika, Mikas

    2010-07-06

    The present invention provides structures and devices comprising conductive segments and conductance constricting segments of a nanowire, such as metallic, superconducting or semiconducting nanowire. The present invention provides structures and devices comprising conductive nanowire segments and conductance constricting nanowire segments having accurately selected phases including crystalline and amorphous states, compositions, morphologies and physical dimensions, including selected cross sectional dimensions, shapes and lengths along the length of a nanowire. Further, the present invention provides methods of processing nanowires capable of patterning a nanowire to form a plurality of conductance constricting segments having selected positions along the length of a nanowire, including conductance constricting segments having reduced cross sectional dimensions and conductance constricting segments comprising one or more insulating materials such as metal oxides.

  14. Novel carbon nanostructures

    International Nuclear Information System (INIS)

    The discovery of carbon nanotubes in 1991 opened up a challenging new area of research, because they are expected to be ideal building blocks for nanoscale applications due to their extraordinary mechanical and electronic properties. Various production methods have been developed, however precise control of nanotube morphology (e.g. length, diameter) has yet to be realised, a fact which has delayed industrial exploitation. Thus a comprehensive understanding of nanotube growth is essential, and this thesis is concerned with this important problem, i.e. the controlled production of novel carbon nanomaterials. Chapter 1 surveys production methods for fullerenes, carbon nanotubes and other carbon-based materials, such as fibres, particles etc. The sophisticated tools required for this work, e.g. high resolution transmission electron microscopy (HRTEM), high resolution electron energy loss spectroscopy (HREELS), etc. are reviewed in Chapter 2. Chapter 3 describes a novel approach to carbon nanotubes, using laser etching techniques, which generates aligned tubes of uniform diameter and length. The mode of catalyst preparation, as well as the nature of the precursor, play crucial roles in this process. The preparation of modified carbon nanotubes by the pyrolysis of metallocene, e.g. ferrocene in conjunction with various hydrocarbons, is discussed in Chapter 4. Superconducting interference device measurements (SQUID) show that Fe-filled carbon nanotubes exhibit enhanced coercivities in the 430-1070 Oe range, i.e. greater than those reported for Ni and Co nanowires. Carbon nanotubes can be also modified by replacing atoms of the carbon network with nitrogen, boron or both. The creation of large arrays of nitrogen-doped carbon nanotubes, for example CNx nanofibres, as well as the formation of BxCyNz onions is described in Chapter 5. Electron irradiation of these onions generates pure carbon onions. Finally (Chapter 6), the catalytic behaviour of metal particles in different

  15. CNTs/mesostructured silica core-shell nanowires via interfacial surfactant templating

    Institute of Scientific and Technical Information of China (English)

    ZHANG Lei; QIAO ShiZhang; YAN ZiFeng; ZHENG HuaJun; LI Li; DING RongGang; LU GaoQing(Max)

    2009-01-01

    Carbon nanotubes (CNTs)/mesostructured silica core-shell nanowires with a carbon nanotube core and controllable highly ordered periodic mesoporous silica shell are syntheiszed via the interfacial surfac-tant template. The core-shell nanowires are characterized by transmission electron microscope (TEM), X-ray diffraction pattern (XRD) and nitrogen sorption/desorption. The results indicate that the core-shell nanowires have highly ordered periodic mesoporous silica shell (space group p6mm), high BET sur-face area and narrow pore size distribution. Moreover, the morphology of core-shell nanowires can be controlled by the pH value. The core-shell nanowires have promising applications in biosensors, nanoprobes and energy storage due to their good dispersibility in polar solvents.

  16. The Effect of Kinetic Energy on the Reactions of Nucleogenic Carbon Atoms with Hydrocarbons

    International Nuclear Information System (INIS)

    The basic technique for studying the effect of kinetic energy on reactions of C atoms produced by nuclear transformation involves the well-known method of moderation with inert gases. However, this can be combined with other techniques such as (1) the use of scavengers to detect processes involving long- lived radicals, (2) degradative studies that serve to fix the position occupied by the labelled atom, (3) double tracer studies in which a reactant is partially labelled with deuterium and the isotopic composition of the labelled products is determined in order to establish the origin of the hydrogen which they contain. In this paper new results on product yields in two systems, neon-ethylene and neon-ethane, will be presented, and the relation of these results to other work involving degradative studies and double tracer experiments will be discussed. The discussion of the neon-ethylene results is in terms of the two previously postulated insertion mechanisms, insertion of the C atom into the C = C and into the C-H bonds to give C-C2H4 adducts, As neon concentration is increased no product is eliminated, but the relative yields of products are altered markedly. Those products such as acetylene and vinyl acetylene which can be formed from the initial C-C2H4 adducts via processes with a high energy requirement decrease in importance, and the yields of products formed in low energy processes, such as C5 compounds, increase. The ethane pattern is similar. Degradative studies have already shown that the intramolecular C11 distribution in allene and methyl- acetylene formed from ethylene is affected by neon moderation. These results imply both participation of the C = C and C-H bonds in formation of these products, and a dependence of the ratio of attack at the two bond types on the kinetic energy of the reacting C atom. Other work involving double tracer studies on acetylene formation from single molecules such as CH2CD2, CH3CH2D, CD9CDH2 and from various mixtures of

  17. The elastic properties and energy characteristics of Au nanowires: an atomistic simulation study

    Institute of Scientific and Technical Information of China (English)

    Liu Shan-Shan; Wen Yu-Hua; Zhu Zi-Zhong

    2008-01-01

    This paper have performed molecular static calculations with the quantum corrected Sutten-Cben type many body potential to study size effects on the elastic modulus of Au nanowires with [100], [110] and [111] crystallographic directions, and to explore the preferential growth orientation of Au nanowires. The main focus of this work is the size effects on their surface characteristics. Using the common neighbour analysis, this paper deduces that surface region approximately consists of two layer atoms. Further, it extracts the elastic modulus of surface, and calculate surface energy of nanowire. The results show that for all three directions the Young's modulus of nanowire increases as the diameter increases. Similar trend has been observed for the Young's modulus of surface. However, the atomic average potential energy of nanowire shows an opposite change. Both the potential and surface energy of [110] nanowire are the lowest among all three orientational nanowires, which helps to explain why Au nanowires possess a [110] preferred orientation during the experimental growth proceeds.

  18. Effect of size on fracture and tensile manipulation of gold nanowires

    International Nuclear Information System (INIS)

    The fracture of metallic nanowires has attracted much attention owing to its reliability of application in nanoelectromechanical system. In this paper, we studied the fracture of [100] single-crystal gold nanowire subjected to uniaxial tension. The statistical breaking position distributions showed that the size effects had dominated the deformation and fracture of nanowires, and the quasi-static tensile deformations are insensitive to the styles of tensile rates. Furthermore, it was observed that the small-sized nanowire broke in the middle with disordered crystalline structure; for the middle-sized nanowire, although slippage plane had maintained the lattice degree, the fracture also happened in the middle due to symmetric tension; for the large-sized nanowire, the slippage was destroyed by symmetric tension, which induced the broken neck at one end of the nanowire. When the nanowire width is less than 5a (“a” means lattice constant, 0.408 nm for gold), the mechanical strength is relatively strong with obvious uncertainty, which can be attributed to the surface atom effect; when the width is larger than 5a, the influence of size on the mechanical property is more obvious at the constant strain rate than that at the absolute rate. Finally, the mechanical strength of the nanowire decreases with the size increasing

  19. Thermal stability of comp ound stucture of silicon nanowire encapsulated in carb on nanotub es%碳纳米管包裹的硅纳米线复合结构的热稳定性研究∗

    Institute of Scientific and Technical Information of China (English)

    卢顺顺; 张晋敏; 郭笑天; 高廷红; 田泽安; 何帆; 贺晓金; 吴宏仙; 谢泉

    2016-01-01

    To guide the experiment research, the thermal stability of composite silicon nanowire encapsulated in carbon nanotubes is investigated by computer simulation. The cubic-diamond-structured silicon nanowires with the same diameter and [111] orientationt are filled in some armchaired single-walled carbon nanotubes. The heat process of compound structure of silicon nanowire encapsulated in carbon nanotubes is simulated by classical molecular dynamic method. Through the visualization and energy analysis method, the thermal stability of composite structure is studied. The changes in the thermal stability of silicon nanowires and carbon nanotubes are explained by the relationship between carbon nanotube space constraint and van der Waals force. It is found that the diameter of the carbon nanotubes is closely related to the thermal stability of silicon nanowires inside. When the nanotube diameter is small, thermal stability of silicon nanowires increases;when the nanotube diameter increases up to a certain size, the thermal stability of silicon nanowires will suddenly drop significantly: until the distance between silicon nanowires and the wall of carbon nanotube is greater than 1 nm, the thermal stability of silicon nanowires will be restored. On the other hand, silicon nanowires filled into the carbon nanotubes have an effect of reducing the thermal stability of carbon nanotubes.

  20. Nanowire field effect transistors principles and applications

    CERN Document Server

    Jeong, Yoon-Ha

    2014-01-01

    Nanowire Field Effect Transistor: Basic Principles and Applications” places an emphasis on the application aspects of nanowire field effect transistors (NWFET). Device physics and electronics are discussed in a compact manner, together with the p-n junction diode and MOSFET, the former as an essential element in NWFET and the latter as a general background of the FET. During this discussion, the photo-diode, solar cell, LED, LD, DRAM, flash EEPROM and sensors are highlighted to pave the way for similar applications of NWFET. Modeling is discussed in close analogy and comparison with MOSFETs. Contributors focus on processing, electrostatic discharge (ESD) and application of NWFET. This includes coverage of solar and memory cells, biological and chemical sensors, displays and atomic scale light emitting diodes. Appropriate for scientists and engineers interested in acquiring a working knowledge of NWFET as well as graduate students specializing in this subject.

  1. Epitaxy of semiconductor-superconductor nanowires

    DEFF Research Database (Denmark)

    Krogstrup, P.; Ziino, N.L.B.; Chang, W.;

    2015-01-01

    Controlling the properties of semiconductor/metal interfaces is a powerful method for designing functionality and improving the performance of electrical devices. Recently semiconductor/superconductor hybrids have appeared as an important example where the atomic scale uniformity of the interface...... plays a key role in determining the quality of the induced superconducting gap. Here we present epitaxial growth of semiconductor-metal core-shell nanowires by molecular beam epitaxy, a method that provides a conceptually new route to controlled electrical contacting of nanostructures and the design of...... devices for specialized applications such as topological and gate-controlled superconducting electronics. Our materials of choice, InAs/Al grown with epitaxially matched single-plane interfaces, and alternative semiconductor/metal combinations allowing epitaxial interface matching in nanowires are...

  2. Strain Rate Induced Amorphization in Metallic Nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Y.; Cagin, T.; Goddard, W.A. III [Materials and Process Simulation Center, California Institute of Technology, Pasadena, California 91125 (United States); Ikeda, H.; Samwer, K.; Johnson, W.L. [Keck Laboratory of Engineering Materials, California Institute of Technology, Pasadena, California 91125 (United States)

    1999-04-01

    Using molecular dynamics simulations with a many-body force field, we studied the deformation of single crystal Ni and NiCu random alloy nanowires subjected to uniform strain rates but kept at 300thinspthinspK. For all strain rates, the Ni nanowire is elastic up to 7.5{percent} strain with a yield stress of 5.5thinspthinspGPa, far above that of bulk Ni. At high strain rates, we find that for both systems the crystalline phase transforms continuously to an amorphous phase, exhibiting a dramatic change in atomic short-range order and a near vanishing of the tetragonal shear elastic constant perpendicular to the tensile direction. This amorphization which occurs directly from the homogeneous, elastically deformed system with no chemical or structural inhomogeneities exhibits a new mode of amorphization. {copyright} {ital 1999} {ital The American Physical Society}

  3. Highly Robust Silver Nanowire Network for Transparent Electrode.

    Science.gov (United States)

    Song, Tze-Bin; Rim, You Seung; Liu, Fengmin; Bob, Brion; Ye, Shenglin; Hsieh, Yao-Tsung; Yang, Yang

    2015-11-11

    Solution-processed silver nanowire networks are one of the promising candidates to replace a traditional indium tin oxide as next-generation transparent and flexible electrodes due to their ease of processing, moderate flexibility, high transparency, and low sheet resistance. To date, however, high stability of the nanowire networks remains a major challenge because the long-term usages of these electrodes are limited by their poor thermal and chemical stabilities. Existing methods for addressing this challenge mainly focus on protecting the nanowire network with additional layers that require vacuum processes, which can lead to an increment in manufacturing cost. Here, we report a straightforward strategy of a sol-gel processing as a fast and robust way to improve the stabilities of silver nanowires. Compared with reported nanoparticles embedded in nanowire networks, better thermal and chemical stabilities are achieved via sol-gel coating of TiO2 over the silver nanowire networks. The conformal surface coverage suppressed surface diffusion of silver atoms and prevented chemical corrosion from the environment. These results highlight the important role of the functional layer in providing better thermal and chemical stabilities along with improved electrical properties and mechanical robustness. The silver nanowire/TiO2 composite electrodes were applied as the source and drain electrodes for In2O3 thin-film transistors (TFTs) and the devices exhibited improved electrical performance annealed at 300 °C without the degradation of the electrodes. These key findings not only demonstrated a general and effective method to improve the thermal and chemical stabilities of metal nanowire networks but also provided a basic guideline toward rational design of highly efficient and robust composite electrodes. PMID:26488682

  4. Dimensional effects in semiconductor nanowires; Dimensionseffekte in Halbleiternanodraehten

    Energy Technology Data Exchange (ETDEWEB)

    Stichtenoth, Daniel

    2008-06-23

    Nanomaterials show new physical properties, which are determined by their size and morphology. These new properties can be ascribed to the higher surface to volume ratio, to quantum size effects or to a form anisotropy. They may enable new technologies. The nanowires studied in this work have a diameter of 4 to 400 nm and a length up to 100 {mu}m. The semiconductor material used is mainly zinc oxide (ZnO), zinc sulfide (ZnS) and gallium arsenide (GaAs). All nanowires were synthesized according to the vapor liquid solid mechanism, which was originally postulated for the growth of silicon whiskers. Respective modifications for the growth of compound semiconductor nanowires are discussed. Detailed luminescence studies on ZnO nanowires with different diameters show pronounced size effects which can be attributed to the origins given above. Similar to bulk material, a tuning of the material properties is often essential for a further functionalization of the nanowires. This is typical realized by doping the source material. It becomes apparent, that a controlled doping of nanowires during the growth process is not successful. Here an alternative method is chosen: the doping after the growth by ion implantation. However, the doping by ion implantation goes always along with the creation of crystal defects. The defects have to be annihilated in order to reach an activation of th introduced dopants. At high ion fluences and ion masses the sputtering of surface atoms becomes more important. This results in a characteristic change in the morphology of the nanowires. In detail, the doping of ZnO and ZnS nanowires with color centers (manganese and rare earth elements) is demonstrated. Especially, the intra 3d luminescence of manganese implanted ZnS nanostructures shows a strong dependence of the nanowire diameter and morphology. This dependence can be described by expanding Foersters model (which describes an energy transfer to the color centers) by a dimensional parameter

  5. Novel nanotubes and encapsulated nanowires

    International Nuclear Information System (INIS)

    Carbon nanotubes, with or without encapsulated material, generated by arcdischarge and electrolytic techniques have been studied. Microcrystals of refractory carbides (i.e. NbC, TaC, MoC), contained in nanotubes and polyhedral particles, produced by arcing electrodes of graphite/metal mixtures, were analysed by high resolution transmission electron microscopy (HRTEM) and X-ray powder diffraction. Encapsulation of MoC was found to give rise to an unusual stable form, namely face-centered-cubic MoC. SQUID measurements indicate that the encapsulated carbides exhibit superconducting transitions at about 10-12 K, thus they differ from carbon nanotubes/nanoparticles which do not superconduct. Four-probe and microwave (contactless) conductivity measurements indicate that most of the analysed samples behave as semiconductors. However, metallic transport was observed in specimens containing single conglomerated carbon nanotube bundles and boron-doped carbon nanotubes. Novel metallic βSn nanowires were produced by electrolysis of graphite electrodes immersed in molten LiCl/SnCl2 mixtures. Prolonged electron irradiation of these nanowiresleads to axial growth and to dynamic transformations. These observations suggest ways in which materials may be modified by microencapsulation and irradiation. (orig.)

  6. The effect of deposition energy of energetic atoms on the growth and structure of ultrathin amorphous carbon films studied by molecular dynamics simulations

    KAUST Repository

    Wang, N

    2014-05-16

    The growth and structure of ultrathin amorphous carbon films was investigated by molecular dynamics simulations. The second-generation reactive-empirical-bond-order potential was used to model atomic interactions. Films with different structures were simulated by varying the deposition energy of carbon atoms in the range of 1-120 eV. Intrinsic film characteristics (e.g. density and internal stress) were determined after the system reached equilibrium. Short- and intermediate-range carbon atom ordering is examined in the context of atomic hybridization and ring connectivity simulation results. It is shown that relatively high deposition energy (i.e., 80 eV) yields a multilayer film structure consisting of an intermixing layer, bulk film and surface layer, consistent with the classical subplantation model. The highest film density (3.3 g cm-3), sp3 fraction (∼43%), and intermediate-range carbon atom ordering correspond to a deposition energy of ∼80 eV, which is in good agreement with experimental findings. © 2014 IOP Publishing Ltd.

  7. Effects of carbon coating on interaction of hydrogen atoms and molecules with palladium surface and on permeation of hydrogen through palladium membranes

    Energy Technology Data Exchange (ETDEWEB)

    Doroshin, A.Yu.; Livshits, A.I.; Samartsev, A.A.

    1985-08-01

    Studies were conducted on the interaction and permeation of hydrogen atoms and molecules with carbon-coated and uncoated 20 ..mu..-thick palladium films, since such studies may contribute to a better understanding of heterogeneous catalysis involving hydrogen. The data showed that carbonization of the palladium surface markedly decreases the rate of dissociative diffusion of hydrogen molecules and that, in distinction to noncoated surfaces, the rate constants show a strong dependence on the temperature of palladium. As a result of passivation by carbon, the permeability of palladium membranes to hydrogen shows a pronounced drop at low hydrogen pressures. Concomitantly, the probability of diffusion of hydrogen atoms striking the surface remains high (ca. 10/sup -2/) and is unaffected by the temperature of the metal. In view of this, the membranes show high selectivity for hydrogen atoms vis-a-vis hydrogen molecules. The putative mechanism proposed to account for this selectivity assumes that chemically active hydrogen atoms bind more strongly to the surface, and that their desorption into the gas phase is virtually an impossibility. Migrating on the surface, such atoms are more likely to encounter active sites and diffuse into the metal rather than encounter other hydrogen atoms and recombine to yield hydrogen molecules. 29 references, 3 figures.

  8. Pressure Effects on the Atomic and Electronic Structure of Aligned Small Diameter Carbon Nanotubes

    OpenAIRE

    Saxena, Sumit; Trevor A. Tyson

    2008-01-01

    Density functional methods have been used to calculate the electronic properties of aligned smalldiameter single-walled carbon nanotubes under hydrostatic pressures. Abrupt pressure induced semiconductor-metal and metal-semiconductor transitions concomitant with changes in structure are observed. Novel and unexpected unit cell nanotube cross-sections are found. These tubes are observed to form interlinking structures at very high pressures. The large changes in electronic structure and the ab...

  9. Adsorption of glycine on diamond (001): Role of bond angle of carbon atoms

    Science.gov (United States)

    Li, Lin; Xu, Jing; Xu, Li-Fang; Lian, Chao-Sheng; Li, Jun-Jie; Wang, Jian-Tao; Gu, Chang-Zhi

    2015-05-01

    The adsorption behaviors of glycine on diamond (001) are systematically investigated by first-principles calculations. We have considered all possible adsorption configurations without a surface dangling bond and give a quantitative analysis for the relationship between the deviation of carbon bond angle and adsorption energy. We found that a smaller distortion of carbon covalent bond angle results in a more stable adsorption structure, and the most stable adsorption has a benzene-ring-like structure with the highest adsorption energy of 5.11 eV per molecule and the minimum distortion of carbon covalent bond angle. Project supported by the National Natural Science Foundation of China (Grant Nos. 51272278, 91323304, 10774177, and 11374341), the National Basic Research Program of China (Grand No. 2009CB930502), the Knowledge Innovation Project of Chinese Academy of Sciences (Grand No. KJCX2-EW-W02), the Fundamental Research Funds for the Central Universities of Ministry of Education of China, and the Research Funds of Renmin University of China.

  10. Determination of cadmium and lead in urine by flame atomic absorption spectrometry after activated carbon enrichment

    International Nuclear Information System (INIS)

    In this study, ammonium pyrrolidine dithiocarbamate was used as a complexing agent in the enrichment step for the determination of cadmium and lead in urine. The recoveries were above 90% and the factors effecting recoveries, such as sample preparation, pH, amount of activated carbon, complexing reagent and the contact time, were studied. The interference effects from matrix components were compared after activated carbon enrichment. The calibration graphs were rectilinear for a range 1.2-80 μ l -1 and 1.6-53 μ l -1 for cadmium and lead, respectively. The relative standard deviations of the measurements (n=9) at concentration of 20 μ l -1 were 3% for cadmium and lead. Detection limits, defined as 3 s of blanks were 1.2 μ l -1 for cadmium and 1.6 μ l -1 for lead. The untreated urine (300 ml) was adjusted to pH 6 and 4 ml of 2% APDC solution were added to complex the metals. The mixture was stirred with 500 mg activated carbon for 40 min and next was filtered. The metals were leached with nitric acid. (author). 28 refs, 4 figs, 3 tabs

  11. CH/pi interaction between benzene and hydrocarbons having six carbon atoms in their binary liquid mixtures.

    Science.gov (United States)

    Kasahara, Yasutoshi; Suzuki, Yuji; Kabasawa, Aino; Minami, Hideyuki; Matsuzawa, Hideyo; Iwahashi, Makio

    2010-01-01

    Molecular interactions between benzene and hydrocarbons having six carbon atoms, such as hexane, cyclohexane and 1-hexene in their binary liquid mixtures were studied through the measurements of density, viscosity, self-diffusion coefficient, (13)C NMR spin-lattice relaxation time and (1)H NMR chemical shift. CH/pi attraction between hexane and benzene in their binary mixture was observed in a relatively benzene rich region, whereas a special attractive interaction was not observed between cyclohexane and benzene. On the other hand, 1-hexene and benzene in their binary mixtures were characteristic in their self-diffusion coefficient behaviors: 1-hexene more strongly attract benzene not only by the CH/pi attraction but also probably by the p/p interaction between the double bond in 1-hexene and the p-electron in benzene ring. PMID:20032596

  12. Application of multiwalled carbon nanotubes treated by potassium permanganate for determination of trace cadmium prior to flame atomic absorption spectrometry

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this study we investigated the enrichment ability of oxidized multiwalled carbon nanotubes (MWCNTs) and established a new method for the determination of trace cadmium in environment with flame atomic absorption spectrometry. The MWCNTs were oxidized by potassium permanganate under appropriate conditions before use as preconcentration packing. Parameters influencing the recoveries of target analytes were optimized. Under optimal conditions, the target analyte exhibited a good linearity (R2=0.9992)over the concentration range 0.5-50 ng/ml. The detection limit and precision of the proposed method were 0.15 ng/ml and 2.06%,respectively. The proposed method was applied to the determination of cadmium in real-world environmental samples and the recoveries were in the range of 91.3%-108.0%. All these experimental results indicated that this new procedure could be applied to the determination of trace cadmium in environmental waters.

  13. Electronic structure effects on stability and quantum conductance in 2D gold nanowires

    International Nuclear Information System (INIS)

    In this study, we have investigated the stability and conductivity of unsupported, two-dimensional infinite gold nanowires using ab initio density functional theory (DFT). Two-dimensional ribbon-like nanowires with 1–5 rows of gold atoms in the non-periodic direction and with different possible structures have been considered. The nanowires with >2 rows of atoms exhibit dimerization, similar to finite wires, along the non-periodic direction. Our results show that in these zero thickness nanowires, the parallelogram motif is the most stable. A comparison between parallelogram- and rectangular-shaped nanowires of increasing width indicates that zero thickness (111) oriented wires have a higher stability over (100). A detailed analysis of the electronic structure, reveals that the (111) oriented structures show increased delocalization of s and p electrons in addition to a stronger delocalization of the d electrons and hence are the most stable. The density of states show that the nanowires are metallic and conducting except for the double zigzag structure, which is semiconducting. Conductance calculations show transmission for a wide range of energies in all the stable nanowires with more than two rows of atoms. The conductance channels are not purely s and have strong contributions from the d levels, and weak contributions from the p levels.

  14. Molecular dynamics simulation for the influence of incident angles of energetic carbon atoms on the structure and properties of diamond-like carbon films

    International Nuclear Information System (INIS)

    The influence of incident angles of energetic carbon atoms (0–60°) on the structure and properties of diamond-like carbon (DLC) films was investigated by the molecular dynamics simulation using a Tersoff interatomic potential. The present simulation revealed that as the incident angles increased from 0 to 60°, the surface roughness of DLC films increased and the more porous structure was generated. Along the growth direction of DLC films, the whole system could be divided into four regions including substrate region, transition region, stable region and surface region except the case at the incident angle of 60°. When the incident angle was 45°, the residual stress was significantly reduced by 12% with little deterioration of mechanical behavior. The further structure analysis using both the bond angles and bond length distributions indicated that the compressive stress reduction mainly resulted from the relaxation of highly distorted C–C bond length. - Highlights: • The dependence of films properties on different incident angles was investigated. • The change of incident angles reduced the stress without obvious damage of density. • The stress reduction attributed to the relaxation of highly distorted bond length

  15. Atomic Physics with the Goddard High Resolution Spectrograph on the Hubble Space Telescope. V. Oscillator Strengths for Neutral Carbon Lines below 1200 Angstrom

    OpenAIRE

    Federman, S. R.; Zsargo, J.

    2001-01-01

    We analyzed high resolution spectra of interstellar neutral carbon absorption toward $\\lambda$ Ori, 1 Sco, and $\\delta$ Sco that were obtained with the Goddard High Resolution Spectrograph on the Hubble Space Telescope. Several multiplets were detected within the wavelength interval 1150 to 1200 A, where most neutral carbon lines have ill-defined oscillator strength; multiplets at longer wavelengths with well-defined atomic parameters were also seen. We extracted accurate column densities and...

  16. Metals on graphene and carbon nanotube surfaces: From mobile atoms to atomtronics to bulk metals to clusters and catalysts

    KAUST Repository

    Sarkar, Santanu C.

    2014-01-14

    In this Perspective, we present an overview of recent fundamental studies on the nature of the interaction between individual metal atoms and metal clusters and the conjugated surfaces of graphene and carbon nanotube with a particular focus on the electronic structure and chemical bonding at the metal-graphene interface. We discuss the relevance of organometallic complexes of graphitic materials to the development of a fundamental understanding of these interactions and their application in atomtronics as atomic interconnects, high mobility organometallic transistor devices, high-frequency electronic devices, organometallic catalysis (hydrogen fuel generation by photocatalytic water splitting, fuel cells, hydrogenation), spintronics, memory devices, and the next generation energy devices. We touch on chemical vapor deposition (CVD) graphene grown on metals, the reactivity of its surface, and its use as a template for asymmetric graphene functionalization chemistry (ultrathin Janus discs). We highlight some of the latest advances in understanding the nature of interactions between metals and graphene surfaces from the standpoint of metal overlayers deposited on graphene and SWNT thin films. Finally, we comment on the major challenges facing the field and the opportunities for technological applications. © 2013 American Chemical Society.

  17. How surface reparation prevents catalytic oxidation of carbon monoxide on atomic gold at defective magnesium oxide surfaces.

    Science.gov (United States)

    Töpfer, Kai; Tremblay, Jean Christophe

    2016-07-21

    In this contribution, we study using first principles the co-adsorption and catalytic behaviors of CO and O2 on a single gold atom deposited at defective magnesium oxide surfaces. Using cluster models and point charge embedding within a density functional theory framework, we simulate the CO oxidation reaction for Au1 on differently charged oxygen vacancies of MgO(001) to rationalize its experimentally observed lack of catalytic activity. Our results show that: (1) co-adsorption is weakly supported at F(0) and F(2+) defects but not at F(1+) sites, (2) electron redistribution from the F(0) vacancy via the Au1 cluster to the adsorbed molecular oxygen weakens the O2 bond, as required for a sustainable catalytic cycle, (3) a metastable carbonate intermediate can form on defects of the F(0) type, (4) only a small activation barrier exists for the highly favorable dissociation of CO2 from F(0), and (5) the moderate adsorption energy of the gold atom on the F(0) defect cannot prevent insertion of molecular oxygen inside the defect. Due to the lack of protection of the color centers, the surface becomes invariably repaired by the surrounding oxygen and the catalytic cycle is irreversibly broken in the first oxidation step. PMID:27345190

  18. The Novel Semiconductor Nanowire Heterostructures

    Institute of Scientific and Technical Information of China (English)

    J.Q.Hu; Y.Bando; J.H.Zhan; D.Golberg

    2007-01-01

    1 Results If one-dimensional heterostructures with a well-defined compositional profile along the wire radial or axial direction can be realized within semiconductor nanowires, new nano-electronic devices,such as nano-waveguide and nano-capcipator, might be obtained. Here,we report the novel semiconducting nanowire heterostructures:(1) Si/ZnS side-to-side biaxial nanowires and ZnS/Si/ZnS sandwich-like triaxial nanowires[1],(2) Ga-Mg3N2 and Ga-ZnS metal-semiconductor nanowire heterojunctions[2-3]and (3) ...

  19. Nanowire mesh solar fuels generator

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-05-24

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

  20. Hetero-atom doped carbon nanotubes for dye degradation and oxygen reduction reaction

    International Nuclear Information System (INIS)

    We report the synthesis of nitrogen doped vertically aligned multi-walled (MWNCNTs) carbon nanotubes by pyrolysis and its catalytic performance for degradation of methylene blue (MB) dye & oxygen reduction reaction (ORR). The degradation of MB was monitored spectrophotometrically with time. Kinetic studies show the degradation of MB follows a first order kinetic with rate constant k=0.0178 min−1. The present rate constant is better than that reported for various supported/non-supported semiconducting nanomaterials. Further ORR performance in alkaline media makes MWNCNTs a promising cost-effective, fuel crossover tolerance, metal-free, eco-friendly cathode catalyst for direct alcohol fuel cell

  1. Extraordinarily high conductivity of flexible adhesive films by hybrids of silver nanoparticle-nanowires.

    Science.gov (United States)

    Ajmal, C Muhammed; Menamparambath, Mini Mol; Choi, Hyouk Ryeol; Baik, Seunghyun

    2016-06-01

    Highly conductive flexible adhesive (CFA) film was developed using micro-sized silver flakes (primary fillers), hybrids of silver nanoparticle-nanowires (secondary fillers) and nitrile butadiene rubber. The hybrids of silver nanoparticle-nanowires were synthesized by decorating silver nanowires with silver nanoparticle clusters using bifunctional cysteamine as a linker. The dispersion in ethanol was excellent for several months. Silver nanowires constructed electrical networks between the micro-scale silver flakes. The low-temperature surface sintering of silver nanoparticles enabled effective joining of silver nanowires to silver flakes. The hybrids of silver nanoparticle-nanowires provided a greater maximum conductivity (54 390 S cm(-1)) than pure silver nanowires, pure multiwalled carbon nanotubes, and multiwalled carbon nanotubes decorated with silver nanoparticles in nitrile butadiene rubber matrix. The resistance change was smallest upon bending when the hybrids of silver nanoparticle-nanowires were employed. The adhesion of the film on polyethylene terephthalate substrate was excellent. Light emitting diodes were successfully wired to the CFA circuit patterned by the screen printing method for application demonstration. PMID:27109551

  2. Extraordinarily high conductivity of flexible adhesive films by hybrids of silver nanoparticle–nanowires

    Science.gov (United States)

    Muhammed Ajmal, C.; Mol Menamparambath, Mini; Ryeol Choi, Hyouk; Baik, Seunghyun

    2016-06-01

    Highly conductive flexible adhesive (CFA) film was developed using micro-sized silver flakes (primary fillers), hybrids of silver nanoparticle–nanowires (secondary fillers) and nitrile butadiene rubber. The hybrids of silver nanoparticle–nanowires were synthesized by decorating silver nanowires with silver nanoparticle clusters using bifunctional cysteamine as a linker. The dispersion in ethanol was excellent for several months. Silver nanowires constructed electrical networks between the micro-scale silver flakes. The low-temperature surface sintering of silver nanoparticles enabled effective joining of silver nanowires to silver flakes. The hybrids of silver nanoparticle–nanowires provided a greater maximum conductivity (54 390 S cm‑1) than pure silver nanowires, pure multiwalled carbon nanotubes, and multiwalled carbon nanotubes decorated with silver nanoparticles in nitrile butadiene rubber matrix. The resistance change was smallest upon bending when the hybrids of silver nanoparticle–nanowires were employed. The adhesion of the film on polyethylene terephthalate substrate was excellent. Light emitting diodes were successfully wired to the CFA circuit patterned by the screen printing method for application demonstration.

  3. Influence of Different Defects in Vertically Aligned Carbon Nanotubes on TiO2 Nanoparticle Formation through Atomic Layer Deposition.

    Science.gov (United States)

    Acauan, Luiz; Dias, Anna C; Pereira, Marcelo B; Horowitz, Flavio; Bergmann, Carlos P

    2016-06-29

    The chemical inertness of carbon nanotubes (CNT) requires some degree of "defect engineering" for controlled deposition of metal oxides through atomic layer deposition (ALD). The type, quantity, and distribution of such defects rules the deposition rate and defines the growth behavior. In this work, we employed ALD to grow titanium oxide (TiO2) on vertically aligned carbon nanotubes (VACNT). The effects of nitrogen doping and oxygen plasma pretreatment of the CNT on the morphology and total amount of TiO2 were systematically studied using transmission electron microscopy, Raman spectroscopy, and thermogravimetric analysis. The induced chemical changes for each functionalization route were identified by X-ray photoelectron and Raman spectroscopies. The TiO2 mass fraction deposited with the same number of cycles for the pristine CNT, nitrogen-doped CNT, and plasma-treated CNT were 8, 47, and 80%, respectively. We demonstrate that TiO2 nucleation is dependent mainly on surface incorporation of heteroatoms and their distribution rather than structural defects that govern the growth behavior. Therefore, selecting the best way to functionalize CNT will allow us to tailor TiO2 distribution and hence fabricate complex heterostructures. PMID:27269125

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

    KAUST Repository

    Chan, Candace K.

    2010-03-23

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

  5. Tracing H2 column density with atomic carbon (CI) and CO isotopologues

    CERN Document Server

    Lo, N; Jones, P A; Bronfman, L; Cortes, P C; Simon, R; Lowe, V; Fissel, L; Novak, G

    2014-01-01

    We present first results of neutral carbon ([CI], 3P1 - 3P0 at 492 GHz) and carbon monoxide (13CO, J = 1 - 0) mapping in the Vela Molecular Ridge cloud C (VMR-C) and G333 giant molecular cloud complexes with the NANTEN2 and Mopra telescopes. For the four regions mapped in this work, we find that [CI] has very similar spectral emission profiles to 13CO, with comparable line widths. We find that [CI] has opacity of 0.1 - 1.3 across the mapped region while the [CI]/13CO peak brightness temperature ratio is between 0.2 to 0.8. The [CI] column density is an order of magnitude lower than that of 13CO. The H2 column density derived from [CI] is comparable to values obtained from 12CO. Our maps show CI is preferentially detected in gas with low temperatures (below 20 K), which possibly explains the comparable H2 column density calculated from both tracers (both CI and 12CO underestimate column density), as a significant amount of the CI in the warmer gas is likely in the higher energy state transition ([CI], 3P2 - 3P...

  6. TRACING H2 COLUMN DENSITY WITH ATOMIC CARBON (C I) AND CO ISOTOPOLOGS

    International Nuclear Information System (INIS)

    We present the first results of neutral carbon ([C I] 3 P 1-3 P 0 at 492 GHz) and carbon monoxide (13CO, J = 1-0) mapping in the Vela Molecular Ridge cloud C (VMR-C) and the G333 giant molecular cloud complexes with the NANTEN2 and Mopra telescopes. For the four regions mapped in this work, we find that [C I] has very similar spectral emission profiles to 13CO, with comparable line widths. We find that [C I] has an opacity of 0.1-1.3 across the mapped region while the [C I]/13CO peak brightness temperature ratio is between 0.2 and 0.8. The [C I] column density is an order of magnitude lower than that of 13CO. The H2 column density derived from [C I] is comparable to values obtained from 12CO. Our maps show that C I is preferentially detected in gas with low temperatures (below 20 K), which possibly explains the comparable H2 column density calculated from both tracers (both C I and 12CO underestimate column density), as a significant amount of the C I in the warmer gas is likely in the higher energy state transition ([C I] 3 P 2-3 P 1 at 810 GHz), and thus it is likely that observations of both the above [C I] transitions are needed in order to recover the total H2 column density

  7. A New One-dimensional Quantum Material - Ta2Pd3Se8 Atomic Chain

    Science.gov (United States)

    Liu, Xue; Liu, Jinyu; Hu, Jin; Yue, Chunlei; Mao, Zhiqiang; Wei, Jiang; Antipina, Liubov; Sorokin, Pavel; Sanchez, Ana

    Since the discovery of carbon nanotube, there has been a persistent effort to search for other one dimensional (1D) quantum systems. However, only a few examples have been found. We report a new 1D example - semiconducting Ta2Pd3Se8. We demonstrate that the Ta2Pd3Se8 nanowire as thin as 1.3nm can be easily obtained by applying simple mechanical exfoliation from its bulk counterpart. High resolution TEM shows an intrinsic 1D chain-like crystalline morphology on these nano wires, indicating weak bonding between these atomic chains. Theoretical calculation shows a direct bandgap structure, which evolves from 0.53eV in the bulk to 1.04eV in single atomic chain. The field effect transistor based on Ta2Pd3Se8 nanowire achieved a promising performance with 104On/Off ratio and 80 cm2V-1s-1 mobility. Low temperature transport study reflects two different mechanisms, variable range hopping and thermal activation, which dominate the transport properties at different temperature regimes. Ta2Pd3Se8 nanowire provides an intrinsic 1D material system for the study low dimensional condensed matter physics.

  8. Diagnostics of Carbon Nanotube Formation in a Laser Produced Plume: An Investigation of the Metal Catalyst by Laser Ablation Atomic Fluorescence Spectroscopy

    Science.gov (United States)

    deBoer, Gary; Scott, Carl

    2003-01-01

    Carbon nanotubes, elongated molecular tubes with diameters of nanometers and lengths in microns, hold great promise for material science. Hopes for super strong light-weight material to be used in spacecraft design is the driving force behind nanotube work at JSC. The molecular nature of these materials requires the appropriate tools for investigation of their structure, properties, and formation. The mechanism of nanotube formation is of particular interest because it may hold keys to controlling the formation of different types of nanotubes and allow them to be produced in much greater quantities at less cost than is currently available. This summer's work involved the interpretation of data taken last summer and analyzed over the academic year. The work involved diagnostic studies of carbon nanotube formation processes occurring in a laser-produced plume. Laser ablation of metal doped graphite to produce a plasma plume in which carbon nanotubes self assemble is one method of making carbon nanotube. The laser ablation method is amenable to applying the techniques of laser spectroscopy, a powerful tool for probing the energies and dynamics of atomic and molecular species. The experimental work performed last summer involved probing one of the metal catalysts, nickel, by laser induced fluorescence. The nickel atom was studied as a function of oven temperature, probe laser wavelength, time after ablation, and position in the laser produced plume. This data along with previously obtained data on carbon was analyzed over the academic year. Interpretations of the data were developed this summer along with discussions of future work. The temperature of the oven in which the target is ablated greatly influences the amount of material ablated and the propagation of the plume. The ablation conditions and the time scale of atomic and molecular lifetimes suggest that initial ablation of the metal doped carbon target results in atomic and small molecular species. The metal

  9. Atomic structure of carbon-induced Si(001)c(4x4) reconstruction as a Si-Si homodimer and C-Si heterodimer network

    International Nuclear Information System (INIS)

    A combination of low-energy electron diffraction, x-ray and ultraviolet photoelectron spectroscopy, and scanning-tunneling microscopy studies, in conjunction with ab initio calculations leads us to suggest a model for the carbon (C)-induced Si(001)c(4x4) atomic structure. This surface superstructure is obtained in a defined range of C2H4 exposures at 600 deg. C. Experimental probes show that the c(4x4) superstructure involves C atoms in both surface and subsurface sites. This is reflected in well-marked features in photoemission valence- and core-level spectra. Surface carbon atoms are stabilized in Si-C heterodimers, with a surface density of about 0.25 monolayer (ML) [i.e., two C atoms per c(4x4) unit cell of eight atoms]. In the subsurface region, carbon atoms substitute for Si atoms in well-defined sites of the third or fourth layers of the Si substrate. The subsurface C density increases with C2H4 exposure time up to a limit value of about 0.5 ML, within the c(4x4) surface structure. Further exposure disrupts the c(4x4) reconstruction and leads to a (2x1) low-energy electron diffraction pattern. Interaction with atomic hydrogen shows that the surface contains a mixture of heterodimers (Si-C) and homodimers (Si-Si), with an 1:1 proportion. These assignments are supported by first-principle calculations, which yield valence band and core level states in fairly good agreement with the experiment. Furthermore, total energy calculations strongly favor C incorporation in surface Si-C dimers and in third and fourth layer sites, and rule out C incorporation in sites of the second Si layer. The most stable c(4x4) surface configuration, suggested by our calculations, consists of alternate Si-C and Si-Si dimer lines. In such a configuration, surface carbon atoms in Si-C dimers induce a surface stress that leads to charge redistribution and atomic relaxation of the adjacent Si-Si dimers, consistent with scanning-tunneling microscopy images. Additional C atoms (in excess

  10. AFM characterization and electrochemical property of Ag nanowires by modified AAO template method

    International Nuclear Information System (INIS)

    Ag nanowires as electrode materials were prepared from modified anodic aluminum oxide (AAO) template method by using dextrose as reductive, and the process of Ag nanowires growth was monitored by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The structure and electrochemical properties of Ag nanowires were characterized by X-ray diffraction (XRD), UV-vis absorption spectra and cyclic voltammograms (CV) measurements. The results show that Ag nanowires prepared from AAO possessed typical face centered cubic structure with average diameter of 60 nm. Furthermore, the CV characterization reveals that Ag nanowires featured a pair of asymmetrical redox peaks with the position near 0.5 V and the microstructure was maintained in electrochemical reaction

  11. Direct growth of oxide nanowires on CuOx thin film

    International Nuclear Information System (INIS)

    Oxide nanowires were directly grown on a CuOx thin film deposited by plasma-enhanced atomic layer deposition without additional metal catalysts. Oxide nanowires would exhibit metal–catalyst-free growth on the CuOx thin film with oxide materials diffused on the top. Through a focused ion beam and transmission electron microscopy, we could verify that SnO2 and ZnO nanowires were grown as single-crystalline structures just above the CuOx thin film. Bottom-gate structural SnO2 and ZnO nanowire transistors exhibited mobilities of 135.2 and 237.6 cm2 V−1 s−1, respectively. We anticipate that a variety of large-area and high-density oxide nanowires can be grown at low cost by using the CuOx thin film. (paper)

  12. Direct growth of oxide nanowires on CuOx thin film.

    Science.gov (United States)

    Kim, Hwansoo; Lee, Byung Kook; An, Ki-Seok; Ju, Sanghyun

    2012-02-01

    Oxide nanowires were directly grown on a CuO(x) thin film deposited by plasma-enhanced atomic layer deposition without additional metal catalysts. Oxide nanowires would exhibit metal-catalyst-free growth on the CuO(x) thin film with oxide materials diffused on the top. Through a focused ion beam and transmission electron microscopy, we could verify that SnO(2) and ZnO nanowires were grown as single-crystalline structures just above the CuO(x) thin film. Bottom-gate structural SnO(2) and ZnO nanowire transistors exhibited mobilities of 135.2 and 237.6 cm(2) V(-1) s(-1), respectively. We anticipate that a variety of large-area and high-density oxide nanowires can be grown at low cost by using the CuO(x) thin film. PMID:22214566

  13. Low-Temperature Selective Growth of Tungsten Oxide Nanowires by Controlled Nanoscale Stress Induction

    Science.gov (United States)

    Na, Hyungjoo; Eun, Youngkee; Kim, Min-Ook; Choi, Jungwook; Kim, Jongbaeg

    2015-12-01

    We report a unique approach for the patterned growth of single-crystalline tungsten oxide (WOx) nanowires based on localized stress-induction. Ions implanted into the desired growth area of WOx thin films lead to a local increase in the compressive stress, leading to the growth of nanowire at lower temperatures (600 °C vs. 750-900 °C) than for equivalent non-implanted samples. Nanowires were successfully grown on the microscale patterns using wafer-level ion implantation and on the nanometer scale patterns using a focused ion beam (FIB). Experimental results show that nanowire growth is influenced by a number of factors including the dose of the implanted ions and their atomic radius. The implanted-ion-assisted, stress-induced method proposed here for the patterned growth of WOx nanowires is simpler than alternative approaches and enhances the compatibility of the process by reducing the growth temperature.

  14. Self-organized patterns along sidewalls of iron silicide nanowires on Si(110) and their origin

    International Nuclear Information System (INIS)

    Iron silicide (cubic FeSi2) nanowires have been grown on Si(110) by reactive deposition epitaxy and investigated by scanning tunneling microscopy and scanning/transmission electron microscopy. On an otherwise uniform nanowire, a semi-periodic pattern along the edges of FeSi2 nanowires has been discovered. The origin of such growth patterns has been traced to initial growth of silicide nanodots with a pyramidal Si base at the chevron-like atomic arrangement of a clean reconstructed Si(110) surface. The pyramidal base evolves into a comb-like structure along the edges of the nanowires. This causes the semi-periodic structure of the iron silicide nanowires along their edges

  15. Self-organized patterns along sidewalls of iron silicide nanowires on Si(110) and their origin

    Energy Technology Data Exchange (ETDEWEB)

    Das, Debolina; Mahato, J. C.; Bisi, Bhaskar; Dev, B. N., E-mail: msbnd@iacs.res.in [Department of Materials Science, Indian Association for the Cultivation of Science, Kolkata 700032 (India); Satpati, B. [Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India)

    2014-11-10

    Iron silicide (cubic FeSi{sub 2}) nanowires have been grown on Si(110) by reactive deposition epitaxy and investigated by scanning tunneling microscopy and scanning/transmission electron microscopy. On an otherwise uniform nanowire, a semi-periodic pattern along the edges of FeSi{sub 2} nanowires has been discovered. The origin of such growth patterns has been traced to initial growth of silicide nanodots with a pyramidal Si base at the chevron-like atomic arrangement of a clean reconstructed Si(110) surface. The pyramidal base evolves into a comb-like structure along the edges of the nanowires. This causes the semi-periodic structure of the iron silicide nanowires along their edges.

  16. Single-nanowire photoelectrochemistry

    Science.gov (United States)

    Su, Yude; Liu, Chong; Brittman, Sarah; Tang, Jinyao; Fu, Anthony; Kornienko, Nikolay; Kong, Qiao; Yang, Peidong

    2016-07-01

    Photoelectrochemistry is one of several promising approaches for the realization of efficient solar-to-fuel conversion. Recent work has shown that photoelectrodes made of semiconductor nano-/microwire arrays can have better photoelectrochemical performance than their planar counterparts because of their unique properties, such as high surface area. Although considerable research effort has focused on studying wire arrays, the inhomogeneity in the geometry, doping, defects and catalyst loading present in such arrays can obscure the link between these properties and the photoelectrochemical performance of the wires, and correlating performance with the specific properties of individual wires is difficult because of ensemble averaging. Here, we show that a single-nanowire-based photoelectrode platform can be used to reliably probe the current–voltage (I–V) characteristics of individual nanowires. We find that the photovoltage output of ensemble array samples can be limited by poorly performing individual wires, which highlights the importance of improving nanowire homogeneity within an array. Furthermore, the platform allows the flux of photogenerated electrons to be quantified as a function of the lengths and diameters of individual nanowires, and we find that the flux over the entire nanowire surface (7–30 electrons nm–2 s–1) is significantly reduced as compared with that of a planar analogue (∼1,200 electrons nm–2 s–1). Such characterization of the photogenerated carrier flux at the semiconductor/electrolyte interface is essential for designing nanowire photoelectrodes that match the activity of their loaded electrocatalysts.

  17. La{sub 2−x}Sr{sub x}CuO{sub 4} superconductor nanowire devices

    Energy Technology Data Exchange (ETDEWEB)

    Litombe, N.E. [Harvard University, Cambridge, MA 02138 (United States); Brookhaven National Laboratory, Upton, NY 11973 (United States); Bollinger, A.T. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Hoffman, J.E. [Harvard University, Cambridge, MA 02138 (United States); Božović, I., E-mail: bozovic@bnl.gov [Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2014-11-15

    Highlights: • We grew La{sub 2−x}Sr{sub x}CuO{sub 4} (LSCO) films using ALL-MBE. • LSCO films were characterized by Atomic Force Microscopy and mutual inductance measurements post-growth. • Single nanowire LSCO devices were fabricated using high-resolution electron beam lithography. • Electrical transport measurements were used to characterize LSCO nanowire properties. - Abstract: La{sub 2−x}Sr{sub x}CuO{sub 4} nanowire devices have been fabricated and characterized using electrical transport measurements. Nanowires with widths down to 80 nm are patterned using high-resolution electron beam lithography. However, the narrowest nanowires show incomplete superconducting transitions with some residual resistance at T = 4 K. Here, we report on the refinement of the fabrication process to achieve narrower nanowire devices with complete superconducting transitions, opening the path to the study of novel physics arising from dimension-limited superconductivity on the nanoscale.

  18. AFM-based manipulation of InAs nanowires

    International Nuclear Information System (INIS)

    A controlled method of manipulation of nanowires was found using the tip of an Atomic Force Microscope (AFM). Manipulation is done in the 'Retrace Lift' mode, where feedback is turned off for the reverse scan and the tip follows a nominal path. The effective manipulation force during the reverse scan can be changed by varying an offset in the height of the tip over the surface. Using this method, we have studied InAs nanowires on different substrates. We have also investigated interactions between wires and with gold features patterned onto the substrates

  19. Indium tin oxide nanowires grown by one-step thermal evaporation-deposition process at low temperature.

    Science.gov (United States)

    Dong, Haibo; Zhang, Xiaoxian; Niu, Zhiqiang; Zhao, Duan; Li, Jinzhu; Cai, Le; Zhou, Weiya; Xie, Sishen

    2013-02-01

    Indium tin oxide (ITO), as one of the most important transparent conducting oxide, is widely used in electro-optical field. We have developed a simple one-step method to synthesize ITO nanowires at low temperature of 600 degrees C. In detail, mixtures of InN nanowires and SnO powder, with the molar ratio of 10:1, have been used as precursors for the thermal evaporation-deposition of ITO nanowires on silicon/quartz slices. During the growth process, the evaporation temperature is maintained at 600 degrees C, which favors the decomposition of InN and oxidation of In, with a limited incorporation of Sn in the resulting compound (In:Sn approximately 11:1 in atomic ratio). As far as we know, this is the lowest growth temperature reported on the thermal deposition of ITO nanowires. The diameters of the nanowires are about 120 nm and the lengths are up to tens of micrometers. XRD characterization indicates the high crystallization of the nanowires. HRTEM results show the nanowires grow along the [200] direction. The transmittance of the nanowire film on quartz slice is more than 75% in the visible region. Based on photolithography and lift-off techniques, four-terminal measurement was utilized to test the resistivity of individual nanowire (6.11 x 10(-4) omega x cm). The high crystallization quality, good transmittance and low resistivity make as-grown ITO nanowires a promising candidate as transparent electrodes of nanoscale devices. PMID:23646624

  20. Ru-decorated Pt nanoparticles on N-doped multi-walled carbon nanotubes by atomic layer deposition for direct methanol fuel cells

    DEFF Research Database (Denmark)

    Johansson, Anne-Charlotte Elisabeth Birgitta; Yang, R.B.; Haugshøj, K.B.;

    2013-01-01

    We present atomic layer deposition (ALD) as a new method for the preparation of highly dispersed Ru-decorated Pt nanoparticles for use as catalyst in direct methanol fuel cells (DMFCs). The nanoparticles were deposited onto N-doped multi-walled carbon nanotubes (MWCNTs) at 250 °C using trimethyl...... controlled size and composition can be deposited, with up-scaling prospects....